tcp_input.c revision b138338056fc423c61a583d45f8aa64cfad87131
1/* 2 * INET An implementation of the TCP/IP protocol suite for the LINUX 3 * operating system. INET is implemented using the BSD Socket 4 * interface as the means of communication with the user level. 5 * 6 * Implementation of the Transmission Control Protocol(TCP). 7 * 8 * Authors: Ross Biro 9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 10 * Mark Evans, <evansmp@uhura.aston.ac.uk> 11 * Corey Minyard <wf-rch!minyard@relay.EU.net> 12 * Florian La Roche, <flla@stud.uni-sb.de> 13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> 14 * Linus Torvalds, <torvalds@cs.helsinki.fi> 15 * Alan Cox, <gw4pts@gw4pts.ampr.org> 16 * Matthew Dillon, <dillon@apollo.west.oic.com> 17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 18 * Jorge Cwik, <jorge@laser.satlink.net> 19 */ 20 21/* 22 * Changes: 23 * Pedro Roque : Fast Retransmit/Recovery. 24 * Two receive queues. 25 * Retransmit queue handled by TCP. 26 * Better retransmit timer handling. 27 * New congestion avoidance. 28 * Header prediction. 29 * Variable renaming. 30 * 31 * Eric : Fast Retransmit. 32 * Randy Scott : MSS option defines. 33 * Eric Schenk : Fixes to slow start algorithm. 34 * Eric Schenk : Yet another double ACK bug. 35 * Eric Schenk : Delayed ACK bug fixes. 36 * Eric Schenk : Floyd style fast retrans war avoidance. 37 * David S. Miller : Don't allow zero congestion window. 38 * Eric Schenk : Fix retransmitter so that it sends 39 * next packet on ack of previous packet. 40 * Andi Kleen : Moved open_request checking here 41 * and process RSTs for open_requests. 42 * Andi Kleen : Better prune_queue, and other fixes. 43 * Andrey Savochkin: Fix RTT measurements in the presence of 44 * timestamps. 45 * Andrey Savochkin: Check sequence numbers correctly when 46 * removing SACKs due to in sequence incoming 47 * data segments. 48 * Andi Kleen: Make sure we never ack data there is not 49 * enough room for. Also make this condition 50 * a fatal error if it might still happen. 51 * Andi Kleen: Add tcp_measure_rcv_mss to make 52 * connections with MSS<min(MTU,ann. MSS) 53 * work without delayed acks. 54 * Andi Kleen: Process packets with PSH set in the 55 * fast path. 56 * J Hadi Salim: ECN support 57 * Andrei Gurtov, 58 * Pasi Sarolahti, 59 * Panu Kuhlberg: Experimental audit of TCP (re)transmission 60 * engine. Lots of bugs are found. 61 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs 62 */ 63 64#include <linux/mm.h> 65#include <linux/module.h> 66#include <linux/sysctl.h> 67#include <linux/kernel.h> 68#include <net/dst.h> 69#include <net/tcp.h> 70#include <net/inet_common.h> 71#include <linux/ipsec.h> 72#include <asm/unaligned.h> 73#include <net/netdma.h> 74 75int sysctl_tcp_timestamps __read_mostly = 1; 76int sysctl_tcp_window_scaling __read_mostly = 1; 77int sysctl_tcp_sack __read_mostly = 1; 78int sysctl_tcp_fack __read_mostly = 1; 79int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH; 80int sysctl_tcp_ecn __read_mostly = 2; 81int sysctl_tcp_dsack __read_mostly = 1; 82int sysctl_tcp_app_win __read_mostly = 31; 83int sysctl_tcp_adv_win_scale __read_mostly = 2; 84 85int sysctl_tcp_stdurg __read_mostly; 86int sysctl_tcp_rfc1337 __read_mostly; 87int sysctl_tcp_max_orphans __read_mostly = NR_FILE; 88int sysctl_tcp_frto __read_mostly = 2; 89int sysctl_tcp_frto_response __read_mostly; 90int sysctl_tcp_nometrics_save __read_mostly; 91 92int sysctl_tcp_thin_dupack __read_mostly; 93 94int sysctl_tcp_moderate_rcvbuf __read_mostly = 1; 95int sysctl_tcp_abc __read_mostly; 96 97#define FLAG_DATA 0x01 /* Incoming frame contained data. */ 98#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ 99#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ 100#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ 101#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ 102#define FLAG_DATA_SACKED 0x20 /* New SACK. */ 103#define FLAG_ECE 0x40 /* ECE in this ACK */ 104#define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */ 105#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ 106#define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */ 107#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */ 108#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */ 109#define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */ 110#define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */ 111 112#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) 113#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) 114#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) 115#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) 116#define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED) 117 118#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) 119#define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH)) 120 121/* Adapt the MSS value used to make delayed ack decision to the 122 * real world. 123 */ 124static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) 125{ 126 struct inet_connection_sock *icsk = inet_csk(sk); 127 const unsigned int lss = icsk->icsk_ack.last_seg_size; 128 unsigned int len; 129 130 icsk->icsk_ack.last_seg_size = 0; 131 132 /* skb->len may jitter because of SACKs, even if peer 133 * sends good full-sized frames. 134 */ 135 len = skb_shinfo(skb)->gso_size ? : skb->len; 136 if (len >= icsk->icsk_ack.rcv_mss) { 137 icsk->icsk_ack.rcv_mss = len; 138 } else { 139 /* Otherwise, we make more careful check taking into account, 140 * that SACKs block is variable. 141 * 142 * "len" is invariant segment length, including TCP header. 143 */ 144 len += skb->data - skb_transport_header(skb); 145 if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) || 146 /* If PSH is not set, packet should be 147 * full sized, provided peer TCP is not badly broken. 148 * This observation (if it is correct 8)) allows 149 * to handle super-low mtu links fairly. 150 */ 151 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && 152 !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) { 153 /* Subtract also invariant (if peer is RFC compliant), 154 * tcp header plus fixed timestamp option length. 155 * Resulting "len" is MSS free of SACK jitter. 156 */ 157 len -= tcp_sk(sk)->tcp_header_len; 158 icsk->icsk_ack.last_seg_size = len; 159 if (len == lss) { 160 icsk->icsk_ack.rcv_mss = len; 161 return; 162 } 163 } 164 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) 165 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; 166 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; 167 } 168} 169 170static void tcp_incr_quickack(struct sock *sk) 171{ 172 struct inet_connection_sock *icsk = inet_csk(sk); 173 unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); 174 175 if (quickacks == 0) 176 quickacks = 2; 177 if (quickacks > icsk->icsk_ack.quick) 178 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS); 179} 180 181void tcp_enter_quickack_mode(struct sock *sk) 182{ 183 struct inet_connection_sock *icsk = inet_csk(sk); 184 tcp_incr_quickack(sk); 185 icsk->icsk_ack.pingpong = 0; 186 icsk->icsk_ack.ato = TCP_ATO_MIN; 187} 188 189/* Send ACKs quickly, if "quick" count is not exhausted 190 * and the session is not interactive. 191 */ 192 193static inline int tcp_in_quickack_mode(const struct sock *sk) 194{ 195 const struct inet_connection_sock *icsk = inet_csk(sk); 196 return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong; 197} 198 199static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp) 200{ 201 if (tp->ecn_flags & TCP_ECN_OK) 202 tp->ecn_flags |= TCP_ECN_QUEUE_CWR; 203} 204 205static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, struct sk_buff *skb) 206{ 207 if (tcp_hdr(skb)->cwr) 208 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; 209} 210 211static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp) 212{ 213 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; 214} 215 216static inline void TCP_ECN_check_ce(struct tcp_sock *tp, struct sk_buff *skb) 217{ 218 if (tp->ecn_flags & TCP_ECN_OK) { 219 if (INET_ECN_is_ce(TCP_SKB_CB(skb)->flags)) 220 tp->ecn_flags |= TCP_ECN_DEMAND_CWR; 221 /* Funny extension: if ECT is not set on a segment, 222 * it is surely retransmit. It is not in ECN RFC, 223 * but Linux follows this rule. */ 224 else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb)->flags))) 225 tcp_enter_quickack_mode((struct sock *)tp); 226 } 227} 228 229static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, struct tcphdr *th) 230{ 231 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr)) 232 tp->ecn_flags &= ~TCP_ECN_OK; 233} 234 235static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, struct tcphdr *th) 236{ 237 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr)) 238 tp->ecn_flags &= ~TCP_ECN_OK; 239} 240 241static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock *tp, struct tcphdr *th) 242{ 243 if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK)) 244 return 1; 245 return 0; 246} 247 248/* Buffer size and advertised window tuning. 249 * 250 * 1. Tuning sk->sk_sndbuf, when connection enters established state. 251 */ 252 253static void tcp_fixup_sndbuf(struct sock *sk) 254{ 255 int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 + 256 sizeof(struct sk_buff); 257 258 if (sk->sk_sndbuf < 3 * sndmem) 259 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]); 260} 261 262/* 2. Tuning advertised window (window_clamp, rcv_ssthresh) 263 * 264 * All tcp_full_space() is split to two parts: "network" buffer, allocated 265 * forward and advertised in receiver window (tp->rcv_wnd) and 266 * "application buffer", required to isolate scheduling/application 267 * latencies from network. 268 * window_clamp is maximal advertised window. It can be less than 269 * tcp_full_space(), in this case tcp_full_space() - window_clamp 270 * is reserved for "application" buffer. The less window_clamp is 271 * the smoother our behaviour from viewpoint of network, but the lower 272 * throughput and the higher sensitivity of the connection to losses. 8) 273 * 274 * rcv_ssthresh is more strict window_clamp used at "slow start" 275 * phase to predict further behaviour of this connection. 276 * It is used for two goals: 277 * - to enforce header prediction at sender, even when application 278 * requires some significant "application buffer". It is check #1. 279 * - to prevent pruning of receive queue because of misprediction 280 * of receiver window. Check #2. 281 * 282 * The scheme does not work when sender sends good segments opening 283 * window and then starts to feed us spaghetti. But it should work 284 * in common situations. Otherwise, we have to rely on queue collapsing. 285 */ 286 287/* Slow part of check#2. */ 288static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb) 289{ 290 struct tcp_sock *tp = tcp_sk(sk); 291 /* Optimize this! */ 292 int truesize = tcp_win_from_space(skb->truesize) >> 1; 293 int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1; 294 295 while (tp->rcv_ssthresh <= window) { 296 if (truesize <= skb->len) 297 return 2 * inet_csk(sk)->icsk_ack.rcv_mss; 298 299 truesize >>= 1; 300 window >>= 1; 301 } 302 return 0; 303} 304 305static void tcp_grow_window(struct sock *sk, struct sk_buff *skb) 306{ 307 struct tcp_sock *tp = tcp_sk(sk); 308 309 /* Check #1 */ 310 if (tp->rcv_ssthresh < tp->window_clamp && 311 (int)tp->rcv_ssthresh < tcp_space(sk) && 312 !tcp_memory_pressure) { 313 int incr; 314 315 /* Check #2. Increase window, if skb with such overhead 316 * will fit to rcvbuf in future. 317 */ 318 if (tcp_win_from_space(skb->truesize) <= skb->len) 319 incr = 2 * tp->advmss; 320 else 321 incr = __tcp_grow_window(sk, skb); 322 323 if (incr) { 324 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, 325 tp->window_clamp); 326 inet_csk(sk)->icsk_ack.quick |= 1; 327 } 328 } 329} 330 331/* 3. Tuning rcvbuf, when connection enters established state. */ 332 333static void tcp_fixup_rcvbuf(struct sock *sk) 334{ 335 struct tcp_sock *tp = tcp_sk(sk); 336 int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); 337 338 /* Try to select rcvbuf so that 4 mss-sized segments 339 * will fit to window and corresponding skbs will fit to our rcvbuf. 340 * (was 3; 4 is minimum to allow fast retransmit to work.) 341 */ 342 while (tcp_win_from_space(rcvmem) < tp->advmss) 343 rcvmem += 128; 344 if (sk->sk_rcvbuf < 4 * rcvmem) 345 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]); 346} 347 348/* 4. Try to fixup all. It is made immediately after connection enters 349 * established state. 350 */ 351static void tcp_init_buffer_space(struct sock *sk) 352{ 353 struct tcp_sock *tp = tcp_sk(sk); 354 int maxwin; 355 356 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) 357 tcp_fixup_rcvbuf(sk); 358 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) 359 tcp_fixup_sndbuf(sk); 360 361 tp->rcvq_space.space = tp->rcv_wnd; 362 363 maxwin = tcp_full_space(sk); 364 365 if (tp->window_clamp >= maxwin) { 366 tp->window_clamp = maxwin; 367 368 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) 369 tp->window_clamp = max(maxwin - 370 (maxwin >> sysctl_tcp_app_win), 371 4 * tp->advmss); 372 } 373 374 /* Force reservation of one segment. */ 375 if (sysctl_tcp_app_win && 376 tp->window_clamp > 2 * tp->advmss && 377 tp->window_clamp + tp->advmss > maxwin) 378 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); 379 380 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); 381 tp->snd_cwnd_stamp = tcp_time_stamp; 382} 383 384/* 5. Recalculate window clamp after socket hit its memory bounds. */ 385static void tcp_clamp_window(struct sock *sk) 386{ 387 struct tcp_sock *tp = tcp_sk(sk); 388 struct inet_connection_sock *icsk = inet_csk(sk); 389 390 icsk->icsk_ack.quick = 0; 391 392 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && 393 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && 394 !tcp_memory_pressure && 395 atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) { 396 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), 397 sysctl_tcp_rmem[2]); 398 } 399 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) 400 tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss); 401} 402 403/* Initialize RCV_MSS value. 404 * RCV_MSS is an our guess about MSS used by the peer. 405 * We haven't any direct information about the MSS. 406 * It's better to underestimate the RCV_MSS rather than overestimate. 407 * Overestimations make us ACKing less frequently than needed. 408 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). 409 */ 410void tcp_initialize_rcv_mss(struct sock *sk) 411{ 412 struct tcp_sock *tp = tcp_sk(sk); 413 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); 414 415 hint = min(hint, tp->rcv_wnd / 2); 416 hint = min(hint, TCP_MSS_DEFAULT); 417 hint = max(hint, TCP_MIN_MSS); 418 419 inet_csk(sk)->icsk_ack.rcv_mss = hint; 420} 421 422/* Receiver "autotuning" code. 423 * 424 * The algorithm for RTT estimation w/o timestamps is based on 425 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. 426 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps> 427 * 428 * More detail on this code can be found at 429 * <http://www.psc.edu/~jheffner/senior_thesis.ps>, 430 * though this reference is out of date. A new paper 431 * is pending. 432 */ 433static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) 434{ 435 u32 new_sample = tp->rcv_rtt_est.rtt; 436 long m = sample; 437 438 if (m == 0) 439 m = 1; 440 441 if (new_sample != 0) { 442 /* If we sample in larger samples in the non-timestamp 443 * case, we could grossly overestimate the RTT especially 444 * with chatty applications or bulk transfer apps which 445 * are stalled on filesystem I/O. 446 * 447 * Also, since we are only going for a minimum in the 448 * non-timestamp case, we do not smooth things out 449 * else with timestamps disabled convergence takes too 450 * long. 451 */ 452 if (!win_dep) { 453 m -= (new_sample >> 3); 454 new_sample += m; 455 } else if (m < new_sample) 456 new_sample = m << 3; 457 } else { 458 /* No previous measure. */ 459 new_sample = m << 3; 460 } 461 462 if (tp->rcv_rtt_est.rtt != new_sample) 463 tp->rcv_rtt_est.rtt = new_sample; 464} 465 466static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) 467{ 468 if (tp->rcv_rtt_est.time == 0) 469 goto new_measure; 470 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) 471 return; 472 tcp_rcv_rtt_update(tp, jiffies - tp->rcv_rtt_est.time, 1); 473 474new_measure: 475 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; 476 tp->rcv_rtt_est.time = tcp_time_stamp; 477} 478 479static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, 480 const struct sk_buff *skb) 481{ 482 struct tcp_sock *tp = tcp_sk(sk); 483 if (tp->rx_opt.rcv_tsecr && 484 (TCP_SKB_CB(skb)->end_seq - 485 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) 486 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); 487} 488 489/* 490 * This function should be called every time data is copied to user space. 491 * It calculates the appropriate TCP receive buffer space. 492 */ 493void tcp_rcv_space_adjust(struct sock *sk) 494{ 495 struct tcp_sock *tp = tcp_sk(sk); 496 int time; 497 int space; 498 499 if (tp->rcvq_space.time == 0) 500 goto new_measure; 501 502 time = tcp_time_stamp - tp->rcvq_space.time; 503 if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0) 504 return; 505 506 space = 2 * (tp->copied_seq - tp->rcvq_space.seq); 507 508 space = max(tp->rcvq_space.space, space); 509 510 if (tp->rcvq_space.space != space) { 511 int rcvmem; 512 513 tp->rcvq_space.space = space; 514 515 if (sysctl_tcp_moderate_rcvbuf && 516 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { 517 int new_clamp = space; 518 519 /* Receive space grows, normalize in order to 520 * take into account packet headers and sk_buff 521 * structure overhead. 522 */ 523 space /= tp->advmss; 524 if (!space) 525 space = 1; 526 rcvmem = (tp->advmss + MAX_TCP_HEADER + 527 16 + sizeof(struct sk_buff)); 528 while (tcp_win_from_space(rcvmem) < tp->advmss) 529 rcvmem += 128; 530 space *= rcvmem; 531 space = min(space, sysctl_tcp_rmem[2]); 532 if (space > sk->sk_rcvbuf) { 533 sk->sk_rcvbuf = space; 534 535 /* Make the window clamp follow along. */ 536 tp->window_clamp = new_clamp; 537 } 538 } 539 } 540 541new_measure: 542 tp->rcvq_space.seq = tp->copied_seq; 543 tp->rcvq_space.time = tcp_time_stamp; 544} 545 546/* There is something which you must keep in mind when you analyze the 547 * behavior of the tp->ato delayed ack timeout interval. When a 548 * connection starts up, we want to ack as quickly as possible. The 549 * problem is that "good" TCP's do slow start at the beginning of data 550 * transmission. The means that until we send the first few ACK's the 551 * sender will sit on his end and only queue most of his data, because 552 * he can only send snd_cwnd unacked packets at any given time. For 553 * each ACK we send, he increments snd_cwnd and transmits more of his 554 * queue. -DaveM 555 */ 556static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) 557{ 558 struct tcp_sock *tp = tcp_sk(sk); 559 struct inet_connection_sock *icsk = inet_csk(sk); 560 u32 now; 561 562 inet_csk_schedule_ack(sk); 563 564 tcp_measure_rcv_mss(sk, skb); 565 566 tcp_rcv_rtt_measure(tp); 567 568 now = tcp_time_stamp; 569 570 if (!icsk->icsk_ack.ato) { 571 /* The _first_ data packet received, initialize 572 * delayed ACK engine. 573 */ 574 tcp_incr_quickack(sk); 575 icsk->icsk_ack.ato = TCP_ATO_MIN; 576 } else { 577 int m = now - icsk->icsk_ack.lrcvtime; 578 579 if (m <= TCP_ATO_MIN / 2) { 580 /* The fastest case is the first. */ 581 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; 582 } else if (m < icsk->icsk_ack.ato) { 583 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; 584 if (icsk->icsk_ack.ato > icsk->icsk_rto) 585 icsk->icsk_ack.ato = icsk->icsk_rto; 586 } else if (m > icsk->icsk_rto) { 587 /* Too long gap. Apparently sender failed to 588 * restart window, so that we send ACKs quickly. 589 */ 590 tcp_incr_quickack(sk); 591 sk_mem_reclaim(sk); 592 } 593 } 594 icsk->icsk_ack.lrcvtime = now; 595 596 TCP_ECN_check_ce(tp, skb); 597 598 if (skb->len >= 128) 599 tcp_grow_window(sk, skb); 600} 601 602/* Called to compute a smoothed rtt estimate. The data fed to this 603 * routine either comes from timestamps, or from segments that were 604 * known _not_ to have been retransmitted [see Karn/Partridge 605 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 606 * piece by Van Jacobson. 607 * NOTE: the next three routines used to be one big routine. 608 * To save cycles in the RFC 1323 implementation it was better to break 609 * it up into three procedures. -- erics 610 */ 611static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) 612{ 613 struct tcp_sock *tp = tcp_sk(sk); 614 long m = mrtt; /* RTT */ 615 616 /* The following amusing code comes from Jacobson's 617 * article in SIGCOMM '88. Note that rtt and mdev 618 * are scaled versions of rtt and mean deviation. 619 * This is designed to be as fast as possible 620 * m stands for "measurement". 621 * 622 * On a 1990 paper the rto value is changed to: 623 * RTO = rtt + 4 * mdev 624 * 625 * Funny. This algorithm seems to be very broken. 626 * These formulae increase RTO, when it should be decreased, increase 627 * too slowly, when it should be increased quickly, decrease too quickly 628 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely 629 * does not matter how to _calculate_ it. Seems, it was trap 630 * that VJ failed to avoid. 8) 631 */ 632 if (m == 0) 633 m = 1; 634 if (tp->srtt != 0) { 635 m -= (tp->srtt >> 3); /* m is now error in rtt est */ 636 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ 637 if (m < 0) { 638 m = -m; /* m is now abs(error) */ 639 m -= (tp->mdev >> 2); /* similar update on mdev */ 640 /* This is similar to one of Eifel findings. 641 * Eifel blocks mdev updates when rtt decreases. 642 * This solution is a bit different: we use finer gain 643 * for mdev in this case (alpha*beta). 644 * Like Eifel it also prevents growth of rto, 645 * but also it limits too fast rto decreases, 646 * happening in pure Eifel. 647 */ 648 if (m > 0) 649 m >>= 3; 650 } else { 651 m -= (tp->mdev >> 2); /* similar update on mdev */ 652 } 653 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ 654 if (tp->mdev > tp->mdev_max) { 655 tp->mdev_max = tp->mdev; 656 if (tp->mdev_max > tp->rttvar) 657 tp->rttvar = tp->mdev_max; 658 } 659 if (after(tp->snd_una, tp->rtt_seq)) { 660 if (tp->mdev_max < tp->rttvar) 661 tp->rttvar -= (tp->rttvar - tp->mdev_max) >> 2; 662 tp->rtt_seq = tp->snd_nxt; 663 tp->mdev_max = tcp_rto_min(sk); 664 } 665 } else { 666 /* no previous measure. */ 667 tp->srtt = m << 3; /* take the measured time to be rtt */ 668 tp->mdev = m << 1; /* make sure rto = 3*rtt */ 669 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); 670 tp->rtt_seq = tp->snd_nxt; 671 } 672} 673 674/* Calculate rto without backoff. This is the second half of Van Jacobson's 675 * routine referred to above. 676 */ 677static inline void tcp_set_rto(struct sock *sk) 678{ 679 const struct tcp_sock *tp = tcp_sk(sk); 680 /* Old crap is replaced with new one. 8) 681 * 682 * More seriously: 683 * 1. If rtt variance happened to be less 50msec, it is hallucination. 684 * It cannot be less due to utterly erratic ACK generation made 685 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ 686 * to do with delayed acks, because at cwnd>2 true delack timeout 687 * is invisible. Actually, Linux-2.4 also generates erratic 688 * ACKs in some circumstances. 689 */ 690 inet_csk(sk)->icsk_rto = __tcp_set_rto(tp); 691 692 /* 2. Fixups made earlier cannot be right. 693 * If we do not estimate RTO correctly without them, 694 * all the algo is pure shit and should be replaced 695 * with correct one. It is exactly, which we pretend to do. 696 */ 697 698 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo 699 * guarantees that rto is higher. 700 */ 701 tcp_bound_rto(sk); 702} 703 704/* Save metrics learned by this TCP session. 705 This function is called only, when TCP finishes successfully 706 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. 707 */ 708void tcp_update_metrics(struct sock *sk) 709{ 710 struct tcp_sock *tp = tcp_sk(sk); 711 struct dst_entry *dst = __sk_dst_get(sk); 712 713 if (sysctl_tcp_nometrics_save) 714 return; 715 716 dst_confirm(dst); 717 718 if (dst && (dst->flags & DST_HOST)) { 719 const struct inet_connection_sock *icsk = inet_csk(sk); 720 int m; 721 unsigned long rtt; 722 723 if (icsk->icsk_backoff || !tp->srtt) { 724 /* This session failed to estimate rtt. Why? 725 * Probably, no packets returned in time. 726 * Reset our results. 727 */ 728 if (!(dst_metric_locked(dst, RTAX_RTT))) 729 dst->metrics[RTAX_RTT - 1] = 0; 730 return; 731 } 732 733 rtt = dst_metric_rtt(dst, RTAX_RTT); 734 m = rtt - tp->srtt; 735 736 /* If newly calculated rtt larger than stored one, 737 * store new one. Otherwise, use EWMA. Remember, 738 * rtt overestimation is always better than underestimation. 739 */ 740 if (!(dst_metric_locked(dst, RTAX_RTT))) { 741 if (m <= 0) 742 set_dst_metric_rtt(dst, RTAX_RTT, tp->srtt); 743 else 744 set_dst_metric_rtt(dst, RTAX_RTT, rtt - (m >> 3)); 745 } 746 747 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { 748 unsigned long var; 749 if (m < 0) 750 m = -m; 751 752 /* Scale deviation to rttvar fixed point */ 753 m >>= 1; 754 if (m < tp->mdev) 755 m = tp->mdev; 756 757 var = dst_metric_rtt(dst, RTAX_RTTVAR); 758 if (m >= var) 759 var = m; 760 else 761 var -= (var - m) >> 2; 762 763 set_dst_metric_rtt(dst, RTAX_RTTVAR, var); 764 } 765 766 if (tcp_in_initial_slowstart(tp)) { 767 /* Slow start still did not finish. */ 768 if (dst_metric(dst, RTAX_SSTHRESH) && 769 !dst_metric_locked(dst, RTAX_SSTHRESH) && 770 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) 771 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1; 772 if (!dst_metric_locked(dst, RTAX_CWND) && 773 tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) 774 dst->metrics[RTAX_CWND - 1] = tp->snd_cwnd; 775 } else if (tp->snd_cwnd > tp->snd_ssthresh && 776 icsk->icsk_ca_state == TCP_CA_Open) { 777 /* Cong. avoidance phase, cwnd is reliable. */ 778 if (!dst_metric_locked(dst, RTAX_SSTHRESH)) 779 dst->metrics[RTAX_SSTHRESH-1] = 780 max(tp->snd_cwnd >> 1, tp->snd_ssthresh); 781 if (!dst_metric_locked(dst, RTAX_CWND)) 782 dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_cwnd) >> 1; 783 } else { 784 /* Else slow start did not finish, cwnd is non-sense, 785 ssthresh may be also invalid. 786 */ 787 if (!dst_metric_locked(dst, RTAX_CWND)) 788 dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_ssthresh) >> 1; 789 if (dst_metric(dst, RTAX_SSTHRESH) && 790 !dst_metric_locked(dst, RTAX_SSTHRESH) && 791 tp->snd_ssthresh > dst_metric(dst, RTAX_SSTHRESH)) 792 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh; 793 } 794 795 if (!dst_metric_locked(dst, RTAX_REORDERING)) { 796 if (dst_metric(dst, RTAX_REORDERING) < tp->reordering && 797 tp->reordering != sysctl_tcp_reordering) 798 dst->metrics[RTAX_REORDERING-1] = tp->reordering; 799 } 800 } 801} 802 803/* Numbers are taken from RFC3390. 804 * 805 * John Heffner states: 806 * 807 * The RFC specifies a window of no more than 4380 bytes 808 * unless 2*MSS > 4380. Reading the pseudocode in the RFC 809 * is a bit misleading because they use a clamp at 4380 bytes 810 * rather than use a multiplier in the relevant range. 811 */ 812__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst) 813{ 814 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); 815 816 if (!cwnd) { 817 if (tp->mss_cache > 1460) 818 cwnd = 2; 819 else 820 cwnd = (tp->mss_cache > 1095) ? 3 : 4; 821 } 822 return min_t(__u32, cwnd, tp->snd_cwnd_clamp); 823} 824 825/* Set slow start threshold and cwnd not falling to slow start */ 826void tcp_enter_cwr(struct sock *sk, const int set_ssthresh) 827{ 828 struct tcp_sock *tp = tcp_sk(sk); 829 const struct inet_connection_sock *icsk = inet_csk(sk); 830 831 tp->prior_ssthresh = 0; 832 tp->bytes_acked = 0; 833 if (icsk->icsk_ca_state < TCP_CA_CWR) { 834 tp->undo_marker = 0; 835 if (set_ssthresh) 836 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 837 tp->snd_cwnd = min(tp->snd_cwnd, 838 tcp_packets_in_flight(tp) + 1U); 839 tp->snd_cwnd_cnt = 0; 840 tp->high_seq = tp->snd_nxt; 841 tp->snd_cwnd_stamp = tcp_time_stamp; 842 TCP_ECN_queue_cwr(tp); 843 844 tcp_set_ca_state(sk, TCP_CA_CWR); 845 } 846} 847 848/* 849 * Packet counting of FACK is based on in-order assumptions, therefore TCP 850 * disables it when reordering is detected 851 */ 852static void tcp_disable_fack(struct tcp_sock *tp) 853{ 854 /* RFC3517 uses different metric in lost marker => reset on change */ 855 if (tcp_is_fack(tp)) 856 tp->lost_skb_hint = NULL; 857 tp->rx_opt.sack_ok &= ~2; 858} 859 860/* Take a notice that peer is sending D-SACKs */ 861static void tcp_dsack_seen(struct tcp_sock *tp) 862{ 863 tp->rx_opt.sack_ok |= 4; 864} 865 866/* Initialize metrics on socket. */ 867 868static void tcp_init_metrics(struct sock *sk) 869{ 870 struct tcp_sock *tp = tcp_sk(sk); 871 struct dst_entry *dst = __sk_dst_get(sk); 872 873 if (dst == NULL) 874 goto reset; 875 876 dst_confirm(dst); 877 878 if (dst_metric_locked(dst, RTAX_CWND)) 879 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); 880 if (dst_metric(dst, RTAX_SSTHRESH)) { 881 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); 882 if (tp->snd_ssthresh > tp->snd_cwnd_clamp) 883 tp->snd_ssthresh = tp->snd_cwnd_clamp; 884 } 885 if (dst_metric(dst, RTAX_REORDERING) && 886 tp->reordering != dst_metric(dst, RTAX_REORDERING)) { 887 tcp_disable_fack(tp); 888 tp->reordering = dst_metric(dst, RTAX_REORDERING); 889 } 890 891 if (dst_metric(dst, RTAX_RTT) == 0) 892 goto reset; 893 894 if (!tp->srtt && dst_metric_rtt(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3)) 895 goto reset; 896 897 /* Initial rtt is determined from SYN,SYN-ACK. 898 * The segment is small and rtt may appear much 899 * less than real one. Use per-dst memory 900 * to make it more realistic. 901 * 902 * A bit of theory. RTT is time passed after "normal" sized packet 903 * is sent until it is ACKed. In normal circumstances sending small 904 * packets force peer to delay ACKs and calculation is correct too. 905 * The algorithm is adaptive and, provided we follow specs, it 906 * NEVER underestimate RTT. BUT! If peer tries to make some clever 907 * tricks sort of "quick acks" for time long enough to decrease RTT 908 * to low value, and then abruptly stops to do it and starts to delay 909 * ACKs, wait for troubles. 910 */ 911 if (dst_metric_rtt(dst, RTAX_RTT) > tp->srtt) { 912 tp->srtt = dst_metric_rtt(dst, RTAX_RTT); 913 tp->rtt_seq = tp->snd_nxt; 914 } 915 if (dst_metric_rtt(dst, RTAX_RTTVAR) > tp->mdev) { 916 tp->mdev = dst_metric_rtt(dst, RTAX_RTTVAR); 917 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); 918 } 919 tcp_set_rto(sk); 920 if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp) 921 goto reset; 922 923cwnd: 924 tp->snd_cwnd = tcp_init_cwnd(tp, dst); 925 tp->snd_cwnd_stamp = tcp_time_stamp; 926 return; 927 928reset: 929 /* Play conservative. If timestamps are not 930 * supported, TCP will fail to recalculate correct 931 * rtt, if initial rto is too small. FORGET ALL AND RESET! 932 */ 933 if (!tp->rx_opt.saw_tstamp && tp->srtt) { 934 tp->srtt = 0; 935 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT; 936 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; 937 } 938 goto cwnd; 939} 940 941static void tcp_update_reordering(struct sock *sk, const int metric, 942 const int ts) 943{ 944 struct tcp_sock *tp = tcp_sk(sk); 945 if (metric > tp->reordering) { 946 int mib_idx; 947 948 tp->reordering = min(TCP_MAX_REORDERING, metric); 949 950 /* This exciting event is worth to be remembered. 8) */ 951 if (ts) 952 mib_idx = LINUX_MIB_TCPTSREORDER; 953 else if (tcp_is_reno(tp)) 954 mib_idx = LINUX_MIB_TCPRENOREORDER; 955 else if (tcp_is_fack(tp)) 956 mib_idx = LINUX_MIB_TCPFACKREORDER; 957 else 958 mib_idx = LINUX_MIB_TCPSACKREORDER; 959 960 NET_INC_STATS_BH(sock_net(sk), mib_idx); 961#if FASTRETRANS_DEBUG > 1 962 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", 963 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, 964 tp->reordering, 965 tp->fackets_out, 966 tp->sacked_out, 967 tp->undo_marker ? tp->undo_retrans : 0); 968#endif 969 tcp_disable_fack(tp); 970 } 971} 972 973/* This must be called before lost_out is incremented */ 974static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) 975{ 976 if ((tp->retransmit_skb_hint == NULL) || 977 before(TCP_SKB_CB(skb)->seq, 978 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) 979 tp->retransmit_skb_hint = skb; 980 981 if (!tp->lost_out || 982 after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high)) 983 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; 984} 985 986static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb) 987{ 988 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { 989 tcp_verify_retransmit_hint(tp, skb); 990 991 tp->lost_out += tcp_skb_pcount(skb); 992 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 993 } 994} 995 996static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, 997 struct sk_buff *skb) 998{ 999 tcp_verify_retransmit_hint(tp, skb); 1000 1001 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { 1002 tp->lost_out += tcp_skb_pcount(skb); 1003 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1004 } 1005} 1006 1007/* This procedure tags the retransmission queue when SACKs arrive. 1008 * 1009 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). 1010 * Packets in queue with these bits set are counted in variables 1011 * sacked_out, retrans_out and lost_out, correspondingly. 1012 * 1013 * Valid combinations are: 1014 * Tag InFlight Description 1015 * 0 1 - orig segment is in flight. 1016 * S 0 - nothing flies, orig reached receiver. 1017 * L 0 - nothing flies, orig lost by net. 1018 * R 2 - both orig and retransmit are in flight. 1019 * L|R 1 - orig is lost, retransmit is in flight. 1020 * S|R 1 - orig reached receiver, retrans is still in flight. 1021 * (L|S|R is logically valid, it could occur when L|R is sacked, 1022 * but it is equivalent to plain S and code short-curcuits it to S. 1023 * L|S is logically invalid, it would mean -1 packet in flight 8)) 1024 * 1025 * These 6 states form finite state machine, controlled by the following events: 1026 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) 1027 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) 1028 * 3. Loss detection event of one of three flavors: 1029 * A. Scoreboard estimator decided the packet is lost. 1030 * A'. Reno "three dupacks" marks head of queue lost. 1031 * A''. Its FACK modfication, head until snd.fack is lost. 1032 * B. SACK arrives sacking data transmitted after never retransmitted 1033 * hole was sent out. 1034 * C. SACK arrives sacking SND.NXT at the moment, when the 1035 * segment was retransmitted. 1036 * 4. D-SACK added new rule: D-SACK changes any tag to S. 1037 * 1038 * It is pleasant to note, that state diagram turns out to be commutative, 1039 * so that we are allowed not to be bothered by order of our actions, 1040 * when multiple events arrive simultaneously. (see the function below). 1041 * 1042 * Reordering detection. 1043 * -------------------- 1044 * Reordering metric is maximal distance, which a packet can be displaced 1045 * in packet stream. With SACKs we can estimate it: 1046 * 1047 * 1. SACK fills old hole and the corresponding segment was not 1048 * ever retransmitted -> reordering. Alas, we cannot use it 1049 * when segment was retransmitted. 1050 * 2. The last flaw is solved with D-SACK. D-SACK arrives 1051 * for retransmitted and already SACKed segment -> reordering.. 1052 * Both of these heuristics are not used in Loss state, when we cannot 1053 * account for retransmits accurately. 1054 * 1055 * SACK block validation. 1056 * ---------------------- 1057 * 1058 * SACK block range validation checks that the received SACK block fits to 1059 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT. 1060 * Note that SND.UNA is not included to the range though being valid because 1061 * it means that the receiver is rather inconsistent with itself reporting 1062 * SACK reneging when it should advance SND.UNA. Such SACK block this is 1063 * perfectly valid, however, in light of RFC2018 which explicitly states 1064 * that "SACK block MUST reflect the newest segment. Even if the newest 1065 * segment is going to be discarded ...", not that it looks very clever 1066 * in case of head skb. Due to potentional receiver driven attacks, we 1067 * choose to avoid immediate execution of a walk in write queue due to 1068 * reneging and defer head skb's loss recovery to standard loss recovery 1069 * procedure that will eventually trigger (nothing forbids us doing this). 1070 * 1071 * Implements also blockage to start_seq wrap-around. Problem lies in the 1072 * fact that though start_seq (s) is before end_seq (i.e., not reversed), 1073 * there's no guarantee that it will be before snd_nxt (n). The problem 1074 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt 1075 * wrap (s_w): 1076 * 1077 * <- outs wnd -> <- wrapzone -> 1078 * u e n u_w e_w s n_w 1079 * | | | | | | | 1080 * |<------------+------+----- TCP seqno space --------------+---------->| 1081 * ...-- <2^31 ->| |<--------... 1082 * ...---- >2^31 ------>| |<--------... 1083 * 1084 * Current code wouldn't be vulnerable but it's better still to discard such 1085 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat 1086 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in 1087 * snd_nxt wrap -> snd_una region will then become "well defined", i.e., 1088 * equal to the ideal case (infinite seqno space without wrap caused issues). 1089 * 1090 * With D-SACK the lower bound is extended to cover sequence space below 1091 * SND.UNA down to undo_marker, which is the last point of interest. Yet 1092 * again, D-SACK block must not to go across snd_una (for the same reason as 1093 * for the normal SACK blocks, explained above). But there all simplicity 1094 * ends, TCP might receive valid D-SACKs below that. As long as they reside 1095 * fully below undo_marker they do not affect behavior in anyway and can 1096 * therefore be safely ignored. In rare cases (which are more or less 1097 * theoretical ones), the D-SACK will nicely cross that boundary due to skb 1098 * fragmentation and packet reordering past skb's retransmission. To consider 1099 * them correctly, the acceptable range must be extended even more though 1100 * the exact amount is rather hard to quantify. However, tp->max_window can 1101 * be used as an exaggerated estimate. 1102 */ 1103static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack, 1104 u32 start_seq, u32 end_seq) 1105{ 1106 /* Too far in future, or reversed (interpretation is ambiguous) */ 1107 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq)) 1108 return 0; 1109 1110 /* Nasty start_seq wrap-around check (see comments above) */ 1111 if (!before(start_seq, tp->snd_nxt)) 1112 return 0; 1113 1114 /* In outstanding window? ...This is valid exit for D-SACKs too. 1115 * start_seq == snd_una is non-sensical (see comments above) 1116 */ 1117 if (after(start_seq, tp->snd_una)) 1118 return 1; 1119 1120 if (!is_dsack || !tp->undo_marker) 1121 return 0; 1122 1123 /* ...Then it's D-SACK, and must reside below snd_una completely */ 1124 if (!after(end_seq, tp->snd_una)) 1125 return 0; 1126 1127 if (!before(start_seq, tp->undo_marker)) 1128 return 1; 1129 1130 /* Too old */ 1131 if (!after(end_seq, tp->undo_marker)) 1132 return 0; 1133 1134 /* Undo_marker boundary crossing (overestimates a lot). Known already: 1135 * start_seq < undo_marker and end_seq >= undo_marker. 1136 */ 1137 return !before(start_seq, end_seq - tp->max_window); 1138} 1139 1140/* Check for lost retransmit. This superb idea is borrowed from "ratehalving". 1141 * Event "C". Later note: FACK people cheated me again 8), we have to account 1142 * for reordering! Ugly, but should help. 1143 * 1144 * Search retransmitted skbs from write_queue that were sent when snd_nxt was 1145 * less than what is now known to be received by the other end (derived from 1146 * highest SACK block). Also calculate the lowest snd_nxt among the remaining 1147 * retransmitted skbs to avoid some costly processing per ACKs. 1148 */ 1149static void tcp_mark_lost_retrans(struct sock *sk) 1150{ 1151 const struct inet_connection_sock *icsk = inet_csk(sk); 1152 struct tcp_sock *tp = tcp_sk(sk); 1153 struct sk_buff *skb; 1154 int cnt = 0; 1155 u32 new_low_seq = tp->snd_nxt; 1156 u32 received_upto = tcp_highest_sack_seq(tp); 1157 1158 if (!tcp_is_fack(tp) || !tp->retrans_out || 1159 !after(received_upto, tp->lost_retrans_low) || 1160 icsk->icsk_ca_state != TCP_CA_Recovery) 1161 return; 1162 1163 tcp_for_write_queue(skb, sk) { 1164 u32 ack_seq = TCP_SKB_CB(skb)->ack_seq; 1165 1166 if (skb == tcp_send_head(sk)) 1167 break; 1168 if (cnt == tp->retrans_out) 1169 break; 1170 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1171 continue; 1172 1173 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) 1174 continue; 1175 1176 /* TODO: We would like to get rid of tcp_is_fack(tp) only 1177 * constraint here (see above) but figuring out that at 1178 * least tp->reordering SACK blocks reside between ack_seq 1179 * and received_upto is not easy task to do cheaply with 1180 * the available datastructures. 1181 * 1182 * Whether FACK should check here for tp->reordering segs 1183 * in-between one could argue for either way (it would be 1184 * rather simple to implement as we could count fack_count 1185 * during the walk and do tp->fackets_out - fack_count). 1186 */ 1187 if (after(received_upto, ack_seq)) { 1188 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1189 tp->retrans_out -= tcp_skb_pcount(skb); 1190 1191 tcp_skb_mark_lost_uncond_verify(tp, skb); 1192 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT); 1193 } else { 1194 if (before(ack_seq, new_low_seq)) 1195 new_low_seq = ack_seq; 1196 cnt += tcp_skb_pcount(skb); 1197 } 1198 } 1199 1200 if (tp->retrans_out) 1201 tp->lost_retrans_low = new_low_seq; 1202} 1203 1204static int tcp_check_dsack(struct sock *sk, struct sk_buff *ack_skb, 1205 struct tcp_sack_block_wire *sp, int num_sacks, 1206 u32 prior_snd_una) 1207{ 1208 struct tcp_sock *tp = tcp_sk(sk); 1209 u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq); 1210 u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq); 1211 int dup_sack = 0; 1212 1213 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) { 1214 dup_sack = 1; 1215 tcp_dsack_seen(tp); 1216 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV); 1217 } else if (num_sacks > 1) { 1218 u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq); 1219 u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq); 1220 1221 if (!after(end_seq_0, end_seq_1) && 1222 !before(start_seq_0, start_seq_1)) { 1223 dup_sack = 1; 1224 tcp_dsack_seen(tp); 1225 NET_INC_STATS_BH(sock_net(sk), 1226 LINUX_MIB_TCPDSACKOFORECV); 1227 } 1228 } 1229 1230 /* D-SACK for already forgotten data... Do dumb counting. */ 1231 if (dup_sack && 1232 !after(end_seq_0, prior_snd_una) && 1233 after(end_seq_0, tp->undo_marker)) 1234 tp->undo_retrans--; 1235 1236 return dup_sack; 1237} 1238 1239struct tcp_sacktag_state { 1240 int reord; 1241 int fack_count; 1242 int flag; 1243}; 1244 1245/* Check if skb is fully within the SACK block. In presence of GSO skbs, 1246 * the incoming SACK may not exactly match but we can find smaller MSS 1247 * aligned portion of it that matches. Therefore we might need to fragment 1248 * which may fail and creates some hassle (caller must handle error case 1249 * returns). 1250 * 1251 * FIXME: this could be merged to shift decision code 1252 */ 1253static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, 1254 u32 start_seq, u32 end_seq) 1255{ 1256 int in_sack, err; 1257 unsigned int pkt_len; 1258 unsigned int mss; 1259 1260 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && 1261 !before(end_seq, TCP_SKB_CB(skb)->end_seq); 1262 1263 if (tcp_skb_pcount(skb) > 1 && !in_sack && 1264 after(TCP_SKB_CB(skb)->end_seq, start_seq)) { 1265 mss = tcp_skb_mss(skb); 1266 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); 1267 1268 if (!in_sack) { 1269 pkt_len = start_seq - TCP_SKB_CB(skb)->seq; 1270 if (pkt_len < mss) 1271 pkt_len = mss; 1272 } else { 1273 pkt_len = end_seq - TCP_SKB_CB(skb)->seq; 1274 if (pkt_len < mss) 1275 return -EINVAL; 1276 } 1277 1278 /* Round if necessary so that SACKs cover only full MSSes 1279 * and/or the remaining small portion (if present) 1280 */ 1281 if (pkt_len > mss) { 1282 unsigned int new_len = (pkt_len / mss) * mss; 1283 if (!in_sack && new_len < pkt_len) { 1284 new_len += mss; 1285 if (new_len > skb->len) 1286 return 0; 1287 } 1288 pkt_len = new_len; 1289 } 1290 err = tcp_fragment(sk, skb, pkt_len, mss); 1291 if (err < 0) 1292 return err; 1293 } 1294 1295 return in_sack; 1296} 1297 1298static u8 tcp_sacktag_one(struct sk_buff *skb, struct sock *sk, 1299 struct tcp_sacktag_state *state, 1300 int dup_sack, int pcount) 1301{ 1302 struct tcp_sock *tp = tcp_sk(sk); 1303 u8 sacked = TCP_SKB_CB(skb)->sacked; 1304 int fack_count = state->fack_count; 1305 1306 /* Account D-SACK for retransmitted packet. */ 1307 if (dup_sack && (sacked & TCPCB_RETRANS)) { 1308 if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) 1309 tp->undo_retrans--; 1310 if (sacked & TCPCB_SACKED_ACKED) 1311 state->reord = min(fack_count, state->reord); 1312 } 1313 1314 /* Nothing to do; acked frame is about to be dropped (was ACKed). */ 1315 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1316 return sacked; 1317 1318 if (!(sacked & TCPCB_SACKED_ACKED)) { 1319 if (sacked & TCPCB_SACKED_RETRANS) { 1320 /* If the segment is not tagged as lost, 1321 * we do not clear RETRANS, believing 1322 * that retransmission is still in flight. 1323 */ 1324 if (sacked & TCPCB_LOST) { 1325 sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); 1326 tp->lost_out -= pcount; 1327 tp->retrans_out -= pcount; 1328 } 1329 } else { 1330 if (!(sacked & TCPCB_RETRANS)) { 1331 /* New sack for not retransmitted frame, 1332 * which was in hole. It is reordering. 1333 */ 1334 if (before(TCP_SKB_CB(skb)->seq, 1335 tcp_highest_sack_seq(tp))) 1336 state->reord = min(fack_count, 1337 state->reord); 1338 1339 /* SACK enhanced F-RTO (RFC4138; Appendix B) */ 1340 if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark)) 1341 state->flag |= FLAG_ONLY_ORIG_SACKED; 1342 } 1343 1344 if (sacked & TCPCB_LOST) { 1345 sacked &= ~TCPCB_LOST; 1346 tp->lost_out -= pcount; 1347 } 1348 } 1349 1350 sacked |= TCPCB_SACKED_ACKED; 1351 state->flag |= FLAG_DATA_SACKED; 1352 tp->sacked_out += pcount; 1353 1354 fack_count += pcount; 1355 1356 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */ 1357 if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) && 1358 before(TCP_SKB_CB(skb)->seq, 1359 TCP_SKB_CB(tp->lost_skb_hint)->seq)) 1360 tp->lost_cnt_hint += pcount; 1361 1362 if (fack_count > tp->fackets_out) 1363 tp->fackets_out = fack_count; 1364 } 1365 1366 /* D-SACK. We can detect redundant retransmission in S|R and plain R 1367 * frames and clear it. undo_retrans is decreased above, L|R frames 1368 * are accounted above as well. 1369 */ 1370 if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) { 1371 sacked &= ~TCPCB_SACKED_RETRANS; 1372 tp->retrans_out -= pcount; 1373 } 1374 1375 return sacked; 1376} 1377 1378static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb, 1379 struct tcp_sacktag_state *state, 1380 unsigned int pcount, int shifted, int mss, 1381 int dup_sack) 1382{ 1383 struct tcp_sock *tp = tcp_sk(sk); 1384 struct sk_buff *prev = tcp_write_queue_prev(sk, skb); 1385 1386 BUG_ON(!pcount); 1387 1388 /* Tweak before seqno plays */ 1389 if (!tcp_is_fack(tp) && tcp_is_sack(tp) && tp->lost_skb_hint && 1390 !before(TCP_SKB_CB(tp->lost_skb_hint)->seq, TCP_SKB_CB(skb)->seq)) 1391 tp->lost_cnt_hint += pcount; 1392 1393 TCP_SKB_CB(prev)->end_seq += shifted; 1394 TCP_SKB_CB(skb)->seq += shifted; 1395 1396 skb_shinfo(prev)->gso_segs += pcount; 1397 BUG_ON(skb_shinfo(skb)->gso_segs < pcount); 1398 skb_shinfo(skb)->gso_segs -= pcount; 1399 1400 /* When we're adding to gso_segs == 1, gso_size will be zero, 1401 * in theory this shouldn't be necessary but as long as DSACK 1402 * code can come after this skb later on it's better to keep 1403 * setting gso_size to something. 1404 */ 1405 if (!skb_shinfo(prev)->gso_size) { 1406 skb_shinfo(prev)->gso_size = mss; 1407 skb_shinfo(prev)->gso_type = sk->sk_gso_type; 1408 } 1409 1410 /* CHECKME: To clear or not to clear? Mimics normal skb currently */ 1411 if (skb_shinfo(skb)->gso_segs <= 1) { 1412 skb_shinfo(skb)->gso_size = 0; 1413 skb_shinfo(skb)->gso_type = 0; 1414 } 1415 1416 /* We discard results */ 1417 tcp_sacktag_one(skb, sk, state, dup_sack, pcount); 1418 1419 /* Difference in this won't matter, both ACKed by the same cumul. ACK */ 1420 TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS); 1421 1422 if (skb->len > 0) { 1423 BUG_ON(!tcp_skb_pcount(skb)); 1424 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED); 1425 return 0; 1426 } 1427 1428 /* Whole SKB was eaten :-) */ 1429 1430 if (skb == tp->retransmit_skb_hint) 1431 tp->retransmit_skb_hint = prev; 1432 if (skb == tp->scoreboard_skb_hint) 1433 tp->scoreboard_skb_hint = prev; 1434 if (skb == tp->lost_skb_hint) { 1435 tp->lost_skb_hint = prev; 1436 tp->lost_cnt_hint -= tcp_skb_pcount(prev); 1437 } 1438 1439 TCP_SKB_CB(skb)->flags |= TCP_SKB_CB(prev)->flags; 1440 if (skb == tcp_highest_sack(sk)) 1441 tcp_advance_highest_sack(sk, skb); 1442 1443 tcp_unlink_write_queue(skb, sk); 1444 sk_wmem_free_skb(sk, skb); 1445 1446 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED); 1447 1448 return 1; 1449} 1450 1451/* I wish gso_size would have a bit more sane initialization than 1452 * something-or-zero which complicates things 1453 */ 1454static int tcp_skb_seglen(struct sk_buff *skb) 1455{ 1456 return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb); 1457} 1458 1459/* Shifting pages past head area doesn't work */ 1460static int skb_can_shift(struct sk_buff *skb) 1461{ 1462 return !skb_headlen(skb) && skb_is_nonlinear(skb); 1463} 1464 1465/* Try collapsing SACK blocks spanning across multiple skbs to a single 1466 * skb. 1467 */ 1468static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb, 1469 struct tcp_sacktag_state *state, 1470 u32 start_seq, u32 end_seq, 1471 int dup_sack) 1472{ 1473 struct tcp_sock *tp = tcp_sk(sk); 1474 struct sk_buff *prev; 1475 int mss; 1476 int pcount = 0; 1477 int len; 1478 int in_sack; 1479 1480 if (!sk_can_gso(sk)) 1481 goto fallback; 1482 1483 /* Normally R but no L won't result in plain S */ 1484 if (!dup_sack && 1485 (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS) 1486 goto fallback; 1487 if (!skb_can_shift(skb)) 1488 goto fallback; 1489 /* This frame is about to be dropped (was ACKed). */ 1490 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1491 goto fallback; 1492 1493 /* Can only happen with delayed DSACK + discard craziness */ 1494 if (unlikely(skb == tcp_write_queue_head(sk))) 1495 goto fallback; 1496 prev = tcp_write_queue_prev(sk, skb); 1497 1498 if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) 1499 goto fallback; 1500 1501 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && 1502 !before(end_seq, TCP_SKB_CB(skb)->end_seq); 1503 1504 if (in_sack) { 1505 len = skb->len; 1506 pcount = tcp_skb_pcount(skb); 1507 mss = tcp_skb_seglen(skb); 1508 1509 /* TODO: Fix DSACKs to not fragment already SACKed and we can 1510 * drop this restriction as unnecessary 1511 */ 1512 if (mss != tcp_skb_seglen(prev)) 1513 goto fallback; 1514 } else { 1515 if (!after(TCP_SKB_CB(skb)->end_seq, start_seq)) 1516 goto noop; 1517 /* CHECKME: This is non-MSS split case only?, this will 1518 * cause skipped skbs due to advancing loop btw, original 1519 * has that feature too 1520 */ 1521 if (tcp_skb_pcount(skb) <= 1) 1522 goto noop; 1523 1524 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); 1525 if (!in_sack) { 1526 /* TODO: head merge to next could be attempted here 1527 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)), 1528 * though it might not be worth of the additional hassle 1529 * 1530 * ...we can probably just fallback to what was done 1531 * previously. We could try merging non-SACKed ones 1532 * as well but it probably isn't going to buy off 1533 * because later SACKs might again split them, and 1534 * it would make skb timestamp tracking considerably 1535 * harder problem. 1536 */ 1537 goto fallback; 1538 } 1539 1540 len = end_seq - TCP_SKB_CB(skb)->seq; 1541 BUG_ON(len < 0); 1542 BUG_ON(len > skb->len); 1543 1544 /* MSS boundaries should be honoured or else pcount will 1545 * severely break even though it makes things bit trickier. 1546 * Optimize common case to avoid most of the divides 1547 */ 1548 mss = tcp_skb_mss(skb); 1549 1550 /* TODO: Fix DSACKs to not fragment already SACKed and we can 1551 * drop this restriction as unnecessary 1552 */ 1553 if (mss != tcp_skb_seglen(prev)) 1554 goto fallback; 1555 1556 if (len == mss) { 1557 pcount = 1; 1558 } else if (len < mss) { 1559 goto noop; 1560 } else { 1561 pcount = len / mss; 1562 len = pcount * mss; 1563 } 1564 } 1565 1566 if (!skb_shift(prev, skb, len)) 1567 goto fallback; 1568 if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack)) 1569 goto out; 1570 1571 /* Hole filled allows collapsing with the next as well, this is very 1572 * useful when hole on every nth skb pattern happens 1573 */ 1574 if (prev == tcp_write_queue_tail(sk)) 1575 goto out; 1576 skb = tcp_write_queue_next(sk, prev); 1577 1578 if (!skb_can_shift(skb) || 1579 (skb == tcp_send_head(sk)) || 1580 ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) || 1581 (mss != tcp_skb_seglen(skb))) 1582 goto out; 1583 1584 len = skb->len; 1585 if (skb_shift(prev, skb, len)) { 1586 pcount += tcp_skb_pcount(skb); 1587 tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0); 1588 } 1589 1590out: 1591 state->fack_count += pcount; 1592 return prev; 1593 1594noop: 1595 return skb; 1596 1597fallback: 1598 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK); 1599 return NULL; 1600} 1601 1602static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, 1603 struct tcp_sack_block *next_dup, 1604 struct tcp_sacktag_state *state, 1605 u32 start_seq, u32 end_seq, 1606 int dup_sack_in) 1607{ 1608 struct tcp_sock *tp = tcp_sk(sk); 1609 struct sk_buff *tmp; 1610 1611 tcp_for_write_queue_from(skb, sk) { 1612 int in_sack = 0; 1613 int dup_sack = dup_sack_in; 1614 1615 if (skb == tcp_send_head(sk)) 1616 break; 1617 1618 /* queue is in-order => we can short-circuit the walk early */ 1619 if (!before(TCP_SKB_CB(skb)->seq, end_seq)) 1620 break; 1621 1622 if ((next_dup != NULL) && 1623 before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) { 1624 in_sack = tcp_match_skb_to_sack(sk, skb, 1625 next_dup->start_seq, 1626 next_dup->end_seq); 1627 if (in_sack > 0) 1628 dup_sack = 1; 1629 } 1630 1631 /* skb reference here is a bit tricky to get right, since 1632 * shifting can eat and free both this skb and the next, 1633 * so not even _safe variant of the loop is enough. 1634 */ 1635 if (in_sack <= 0) { 1636 tmp = tcp_shift_skb_data(sk, skb, state, 1637 start_seq, end_seq, dup_sack); 1638 if (tmp != NULL) { 1639 if (tmp != skb) { 1640 skb = tmp; 1641 continue; 1642 } 1643 1644 in_sack = 0; 1645 } else { 1646 in_sack = tcp_match_skb_to_sack(sk, skb, 1647 start_seq, 1648 end_seq); 1649 } 1650 } 1651 1652 if (unlikely(in_sack < 0)) 1653 break; 1654 1655 if (in_sack) { 1656 TCP_SKB_CB(skb)->sacked = tcp_sacktag_one(skb, sk, 1657 state, 1658 dup_sack, 1659 tcp_skb_pcount(skb)); 1660 1661 if (!before(TCP_SKB_CB(skb)->seq, 1662 tcp_highest_sack_seq(tp))) 1663 tcp_advance_highest_sack(sk, skb); 1664 } 1665 1666 state->fack_count += tcp_skb_pcount(skb); 1667 } 1668 return skb; 1669} 1670 1671/* Avoid all extra work that is being done by sacktag while walking in 1672 * a normal way 1673 */ 1674static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, 1675 struct tcp_sacktag_state *state, 1676 u32 skip_to_seq) 1677{ 1678 tcp_for_write_queue_from(skb, sk) { 1679 if (skb == tcp_send_head(sk)) 1680 break; 1681 1682 if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq)) 1683 break; 1684 1685 state->fack_count += tcp_skb_pcount(skb); 1686 } 1687 return skb; 1688} 1689 1690static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb, 1691 struct sock *sk, 1692 struct tcp_sack_block *next_dup, 1693 struct tcp_sacktag_state *state, 1694 u32 skip_to_seq) 1695{ 1696 if (next_dup == NULL) 1697 return skb; 1698 1699 if (before(next_dup->start_seq, skip_to_seq)) { 1700 skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq); 1701 skb = tcp_sacktag_walk(skb, sk, NULL, state, 1702 next_dup->start_seq, next_dup->end_seq, 1703 1); 1704 } 1705 1706 return skb; 1707} 1708 1709static int tcp_sack_cache_ok(struct tcp_sock *tp, struct tcp_sack_block *cache) 1710{ 1711 return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); 1712} 1713 1714static int 1715tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 1716 u32 prior_snd_una) 1717{ 1718 const struct inet_connection_sock *icsk = inet_csk(sk); 1719 struct tcp_sock *tp = tcp_sk(sk); 1720 unsigned char *ptr = (skb_transport_header(ack_skb) + 1721 TCP_SKB_CB(ack_skb)->sacked); 1722 struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2); 1723 struct tcp_sack_block sp[TCP_NUM_SACKS]; 1724 struct tcp_sack_block *cache; 1725 struct tcp_sacktag_state state; 1726 struct sk_buff *skb; 1727 int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3); 1728 int used_sacks; 1729 int found_dup_sack = 0; 1730 int i, j; 1731 int first_sack_index; 1732 1733 state.flag = 0; 1734 state.reord = tp->packets_out; 1735 1736 if (!tp->sacked_out) { 1737 if (WARN_ON(tp->fackets_out)) 1738 tp->fackets_out = 0; 1739 tcp_highest_sack_reset(sk); 1740 } 1741 1742 found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire, 1743 num_sacks, prior_snd_una); 1744 if (found_dup_sack) 1745 state.flag |= FLAG_DSACKING_ACK; 1746 1747 /* Eliminate too old ACKs, but take into 1748 * account more or less fresh ones, they can 1749 * contain valid SACK info. 1750 */ 1751 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) 1752 return 0; 1753 1754 if (!tp->packets_out) 1755 goto out; 1756 1757 used_sacks = 0; 1758 first_sack_index = 0; 1759 for (i = 0; i < num_sacks; i++) { 1760 int dup_sack = !i && found_dup_sack; 1761 1762 sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq); 1763 sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq); 1764 1765 if (!tcp_is_sackblock_valid(tp, dup_sack, 1766 sp[used_sacks].start_seq, 1767 sp[used_sacks].end_seq)) { 1768 int mib_idx; 1769 1770 if (dup_sack) { 1771 if (!tp->undo_marker) 1772 mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO; 1773 else 1774 mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD; 1775 } else { 1776 /* Don't count olds caused by ACK reordering */ 1777 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) && 1778 !after(sp[used_sacks].end_seq, tp->snd_una)) 1779 continue; 1780 mib_idx = LINUX_MIB_TCPSACKDISCARD; 1781 } 1782 1783 NET_INC_STATS_BH(sock_net(sk), mib_idx); 1784 if (i == 0) 1785 first_sack_index = -1; 1786 continue; 1787 } 1788 1789 /* Ignore very old stuff early */ 1790 if (!after(sp[used_sacks].end_seq, prior_snd_una)) 1791 continue; 1792 1793 used_sacks++; 1794 } 1795 1796 /* order SACK blocks to allow in order walk of the retrans queue */ 1797 for (i = used_sacks - 1; i > 0; i--) { 1798 for (j = 0; j < i; j++) { 1799 if (after(sp[j].start_seq, sp[j + 1].start_seq)) { 1800 swap(sp[j], sp[j + 1]); 1801 1802 /* Track where the first SACK block goes to */ 1803 if (j == first_sack_index) 1804 first_sack_index = j + 1; 1805 } 1806 } 1807 } 1808 1809 skb = tcp_write_queue_head(sk); 1810 state.fack_count = 0; 1811 i = 0; 1812 1813 if (!tp->sacked_out) { 1814 /* It's already past, so skip checking against it */ 1815 cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); 1816 } else { 1817 cache = tp->recv_sack_cache; 1818 /* Skip empty blocks in at head of the cache */ 1819 while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq && 1820 !cache->end_seq) 1821 cache++; 1822 } 1823 1824 while (i < used_sacks) { 1825 u32 start_seq = sp[i].start_seq; 1826 u32 end_seq = sp[i].end_seq; 1827 int dup_sack = (found_dup_sack && (i == first_sack_index)); 1828 struct tcp_sack_block *next_dup = NULL; 1829 1830 if (found_dup_sack && ((i + 1) == first_sack_index)) 1831 next_dup = &sp[i + 1]; 1832 1833 /* Event "B" in the comment above. */ 1834 if (after(end_seq, tp->high_seq)) 1835 state.flag |= FLAG_DATA_LOST; 1836 1837 /* Skip too early cached blocks */ 1838 while (tcp_sack_cache_ok(tp, cache) && 1839 !before(start_seq, cache->end_seq)) 1840 cache++; 1841 1842 /* Can skip some work by looking recv_sack_cache? */ 1843 if (tcp_sack_cache_ok(tp, cache) && !dup_sack && 1844 after(end_seq, cache->start_seq)) { 1845 1846 /* Head todo? */ 1847 if (before(start_seq, cache->start_seq)) { 1848 skb = tcp_sacktag_skip(skb, sk, &state, 1849 start_seq); 1850 skb = tcp_sacktag_walk(skb, sk, next_dup, 1851 &state, 1852 start_seq, 1853 cache->start_seq, 1854 dup_sack); 1855 } 1856 1857 /* Rest of the block already fully processed? */ 1858 if (!after(end_seq, cache->end_seq)) 1859 goto advance_sp; 1860 1861 skb = tcp_maybe_skipping_dsack(skb, sk, next_dup, 1862 &state, 1863 cache->end_seq); 1864 1865 /* ...tail remains todo... */ 1866 if (tcp_highest_sack_seq(tp) == cache->end_seq) { 1867 /* ...but better entrypoint exists! */ 1868 skb = tcp_highest_sack(sk); 1869 if (skb == NULL) 1870 break; 1871 state.fack_count = tp->fackets_out; 1872 cache++; 1873 goto walk; 1874 } 1875 1876 skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq); 1877 /* Check overlap against next cached too (past this one already) */ 1878 cache++; 1879 continue; 1880 } 1881 1882 if (!before(start_seq, tcp_highest_sack_seq(tp))) { 1883 skb = tcp_highest_sack(sk); 1884 if (skb == NULL) 1885 break; 1886 state.fack_count = tp->fackets_out; 1887 } 1888 skb = tcp_sacktag_skip(skb, sk, &state, start_seq); 1889 1890walk: 1891 skb = tcp_sacktag_walk(skb, sk, next_dup, &state, 1892 start_seq, end_seq, dup_sack); 1893 1894advance_sp: 1895 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct 1896 * due to in-order walk 1897 */ 1898 if (after(end_seq, tp->frto_highmark)) 1899 state.flag &= ~FLAG_ONLY_ORIG_SACKED; 1900 1901 i++; 1902 } 1903 1904 /* Clear the head of the cache sack blocks so we can skip it next time */ 1905 for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) { 1906 tp->recv_sack_cache[i].start_seq = 0; 1907 tp->recv_sack_cache[i].end_seq = 0; 1908 } 1909 for (j = 0; j < used_sacks; j++) 1910 tp->recv_sack_cache[i++] = sp[j]; 1911 1912 tcp_mark_lost_retrans(sk); 1913 1914 tcp_verify_left_out(tp); 1915 1916 if ((state.reord < tp->fackets_out) && 1917 ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) && 1918 (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark))) 1919 tcp_update_reordering(sk, tp->fackets_out - state.reord, 0); 1920 1921out: 1922 1923#if FASTRETRANS_DEBUG > 0 1924 WARN_ON((int)tp->sacked_out < 0); 1925 WARN_ON((int)tp->lost_out < 0); 1926 WARN_ON((int)tp->retrans_out < 0); 1927 WARN_ON((int)tcp_packets_in_flight(tp) < 0); 1928#endif 1929 return state.flag; 1930} 1931 1932/* Limits sacked_out so that sum with lost_out isn't ever larger than 1933 * packets_out. Returns zero if sacked_out adjustement wasn't necessary. 1934 */ 1935static int tcp_limit_reno_sacked(struct tcp_sock *tp) 1936{ 1937 u32 holes; 1938 1939 holes = max(tp->lost_out, 1U); 1940 holes = min(holes, tp->packets_out); 1941 1942 if ((tp->sacked_out + holes) > tp->packets_out) { 1943 tp->sacked_out = tp->packets_out - holes; 1944 return 1; 1945 } 1946 return 0; 1947} 1948 1949/* If we receive more dupacks than we expected counting segments 1950 * in assumption of absent reordering, interpret this as reordering. 1951 * The only another reason could be bug in receiver TCP. 1952 */ 1953static void tcp_check_reno_reordering(struct sock *sk, const int addend) 1954{ 1955 struct tcp_sock *tp = tcp_sk(sk); 1956 if (tcp_limit_reno_sacked(tp)) 1957 tcp_update_reordering(sk, tp->packets_out + addend, 0); 1958} 1959 1960/* Emulate SACKs for SACKless connection: account for a new dupack. */ 1961 1962static void tcp_add_reno_sack(struct sock *sk) 1963{ 1964 struct tcp_sock *tp = tcp_sk(sk); 1965 tp->sacked_out++; 1966 tcp_check_reno_reordering(sk, 0); 1967 tcp_verify_left_out(tp); 1968} 1969 1970/* Account for ACK, ACKing some data in Reno Recovery phase. */ 1971 1972static void tcp_remove_reno_sacks(struct sock *sk, int acked) 1973{ 1974 struct tcp_sock *tp = tcp_sk(sk); 1975 1976 if (acked > 0) { 1977 /* One ACK acked hole. The rest eat duplicate ACKs. */ 1978 if (acked - 1 >= tp->sacked_out) 1979 tp->sacked_out = 0; 1980 else 1981 tp->sacked_out -= acked - 1; 1982 } 1983 tcp_check_reno_reordering(sk, acked); 1984 tcp_verify_left_out(tp); 1985} 1986 1987static inline void tcp_reset_reno_sack(struct tcp_sock *tp) 1988{ 1989 tp->sacked_out = 0; 1990} 1991 1992static int tcp_is_sackfrto(const struct tcp_sock *tp) 1993{ 1994 return (sysctl_tcp_frto == 0x2) && !tcp_is_reno(tp); 1995} 1996 1997/* F-RTO can only be used if TCP has never retransmitted anything other than 1998 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here) 1999 */ 2000int tcp_use_frto(struct sock *sk) 2001{ 2002 const struct tcp_sock *tp = tcp_sk(sk); 2003 const struct inet_connection_sock *icsk = inet_csk(sk); 2004 struct sk_buff *skb; 2005 2006 if (!sysctl_tcp_frto) 2007 return 0; 2008 2009 /* MTU probe and F-RTO won't really play nicely along currently */ 2010 if (icsk->icsk_mtup.probe_size) 2011 return 0; 2012 2013 if (tcp_is_sackfrto(tp)) 2014 return 1; 2015 2016 /* Avoid expensive walking of rexmit queue if possible */ 2017 if (tp->retrans_out > 1) 2018 return 0; 2019 2020 skb = tcp_write_queue_head(sk); 2021 if (tcp_skb_is_last(sk, skb)) 2022 return 1; 2023 skb = tcp_write_queue_next(sk, skb); /* Skips head */ 2024 tcp_for_write_queue_from(skb, sk) { 2025 if (skb == tcp_send_head(sk)) 2026 break; 2027 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2028 return 0; 2029 /* Short-circuit when first non-SACKed skb has been checked */ 2030 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 2031 break; 2032 } 2033 return 1; 2034} 2035 2036/* RTO occurred, but do not yet enter Loss state. Instead, defer RTO 2037 * recovery a bit and use heuristics in tcp_process_frto() to detect if 2038 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to 2039 * keep retrans_out counting accurate (with SACK F-RTO, other than head 2040 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS 2041 * bits are handled if the Loss state is really to be entered (in 2042 * tcp_enter_frto_loss). 2043 * 2044 * Do like tcp_enter_loss() would; when RTO expires the second time it 2045 * does: 2046 * "Reduce ssthresh if it has not yet been made inside this window." 2047 */ 2048void tcp_enter_frto(struct sock *sk) 2049{ 2050 const struct inet_connection_sock *icsk = inet_csk(sk); 2051 struct tcp_sock *tp = tcp_sk(sk); 2052 struct sk_buff *skb; 2053 2054 if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) || 2055 tp->snd_una == tp->high_seq || 2056 ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) && 2057 !icsk->icsk_retransmits)) { 2058 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2059 /* Our state is too optimistic in ssthresh() call because cwnd 2060 * is not reduced until tcp_enter_frto_loss() when previous F-RTO 2061 * recovery has not yet completed. Pattern would be this: RTO, 2062 * Cumulative ACK, RTO (2xRTO for the same segment does not end 2063 * up here twice). 2064 * RFC4138 should be more specific on what to do, even though 2065 * RTO is quite unlikely to occur after the first Cumulative ACK 2066 * due to back-off and complexity of triggering events ... 2067 */ 2068 if (tp->frto_counter) { 2069 u32 stored_cwnd; 2070 stored_cwnd = tp->snd_cwnd; 2071 tp->snd_cwnd = 2; 2072 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2073 tp->snd_cwnd = stored_cwnd; 2074 } else { 2075 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2076 } 2077 /* ... in theory, cong.control module could do "any tricks" in 2078 * ssthresh(), which means that ca_state, lost bits and lost_out 2079 * counter would have to be faked before the call occurs. We 2080 * consider that too expensive, unlikely and hacky, so modules 2081 * using these in ssthresh() must deal these incompatibility 2082 * issues if they receives CA_EVENT_FRTO and frto_counter != 0 2083 */ 2084 tcp_ca_event(sk, CA_EVENT_FRTO); 2085 } 2086 2087 tp->undo_marker = tp->snd_una; 2088 tp->undo_retrans = 0; 2089 2090 skb = tcp_write_queue_head(sk); 2091 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2092 tp->undo_marker = 0; 2093 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 2094 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 2095 tp->retrans_out -= tcp_skb_pcount(skb); 2096 } 2097 tcp_verify_left_out(tp); 2098 2099 /* Too bad if TCP was application limited */ 2100 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1); 2101 2102 /* Earlier loss recovery underway (see RFC4138; Appendix B). 2103 * The last condition is necessary at least in tp->frto_counter case. 2104 */ 2105 if (tcp_is_sackfrto(tp) && (tp->frto_counter || 2106 ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) && 2107 after(tp->high_seq, tp->snd_una)) { 2108 tp->frto_highmark = tp->high_seq; 2109 } else { 2110 tp->frto_highmark = tp->snd_nxt; 2111 } 2112 tcp_set_ca_state(sk, TCP_CA_Disorder); 2113 tp->high_seq = tp->snd_nxt; 2114 tp->frto_counter = 1; 2115} 2116 2117/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO, 2118 * which indicates that we should follow the traditional RTO recovery, 2119 * i.e. mark everything lost and do go-back-N retransmission. 2120 */ 2121static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag) 2122{ 2123 struct tcp_sock *tp = tcp_sk(sk); 2124 struct sk_buff *skb; 2125 2126 tp->lost_out = 0; 2127 tp->retrans_out = 0; 2128 if (tcp_is_reno(tp)) 2129 tcp_reset_reno_sack(tp); 2130 2131 tcp_for_write_queue(skb, sk) { 2132 if (skb == tcp_send_head(sk)) 2133 break; 2134 2135 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 2136 /* 2137 * Count the retransmission made on RTO correctly (only when 2138 * waiting for the first ACK and did not get it)... 2139 */ 2140 if ((tp->frto_counter == 1) && !(flag & FLAG_DATA_ACKED)) { 2141 /* For some reason this R-bit might get cleared? */ 2142 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) 2143 tp->retrans_out += tcp_skb_pcount(skb); 2144 /* ...enter this if branch just for the first segment */ 2145 flag |= FLAG_DATA_ACKED; 2146 } else { 2147 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2148 tp->undo_marker = 0; 2149 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 2150 } 2151 2152 /* Marking forward transmissions that were made after RTO lost 2153 * can cause unnecessary retransmissions in some scenarios, 2154 * SACK blocks will mitigate that in some but not in all cases. 2155 * We used to not mark them but it was causing break-ups with 2156 * receivers that do only in-order receival. 2157 * 2158 * TODO: we could detect presence of such receiver and select 2159 * different behavior per flow. 2160 */ 2161 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 2162 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 2163 tp->lost_out += tcp_skb_pcount(skb); 2164 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; 2165 } 2166 } 2167 tcp_verify_left_out(tp); 2168 2169 tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments; 2170 tp->snd_cwnd_cnt = 0; 2171 tp->snd_cwnd_stamp = tcp_time_stamp; 2172 tp->frto_counter = 0; 2173 tp->bytes_acked = 0; 2174 2175 tp->reordering = min_t(unsigned int, tp->reordering, 2176 sysctl_tcp_reordering); 2177 tcp_set_ca_state(sk, TCP_CA_Loss); 2178 tp->high_seq = tp->snd_nxt; 2179 TCP_ECN_queue_cwr(tp); 2180 2181 tcp_clear_all_retrans_hints(tp); 2182} 2183 2184static void tcp_clear_retrans_partial(struct tcp_sock *tp) 2185{ 2186 tp->retrans_out = 0; 2187 tp->lost_out = 0; 2188 2189 tp->undo_marker = 0; 2190 tp->undo_retrans = 0; 2191} 2192 2193void tcp_clear_retrans(struct tcp_sock *tp) 2194{ 2195 tcp_clear_retrans_partial(tp); 2196 2197 tp->fackets_out = 0; 2198 tp->sacked_out = 0; 2199} 2200 2201/* Enter Loss state. If "how" is not zero, forget all SACK information 2202 * and reset tags completely, otherwise preserve SACKs. If receiver 2203 * dropped its ofo queue, we will know this due to reneging detection. 2204 */ 2205void tcp_enter_loss(struct sock *sk, int how) 2206{ 2207 const struct inet_connection_sock *icsk = inet_csk(sk); 2208 struct tcp_sock *tp = tcp_sk(sk); 2209 struct sk_buff *skb; 2210 2211 /* Reduce ssthresh if it has not yet been made inside this window. */ 2212 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq || 2213 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { 2214 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2215 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2216 tcp_ca_event(sk, CA_EVENT_LOSS); 2217 } 2218 tp->snd_cwnd = 1; 2219 tp->snd_cwnd_cnt = 0; 2220 tp->snd_cwnd_stamp = tcp_time_stamp; 2221 2222 tp->bytes_acked = 0; 2223 tcp_clear_retrans_partial(tp); 2224 2225 if (tcp_is_reno(tp)) 2226 tcp_reset_reno_sack(tp); 2227 2228 if (!how) { 2229 /* Push undo marker, if it was plain RTO and nothing 2230 * was retransmitted. */ 2231 tp->undo_marker = tp->snd_una; 2232 } else { 2233 tp->sacked_out = 0; 2234 tp->fackets_out = 0; 2235 } 2236 tcp_clear_all_retrans_hints(tp); 2237 2238 tcp_for_write_queue(skb, sk) { 2239 if (skb == tcp_send_head(sk)) 2240 break; 2241 2242 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2243 tp->undo_marker = 0; 2244 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; 2245 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { 2246 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; 2247 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 2248 tp->lost_out += tcp_skb_pcount(skb); 2249 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; 2250 } 2251 } 2252 tcp_verify_left_out(tp); 2253 2254 tp->reordering = min_t(unsigned int, tp->reordering, 2255 sysctl_tcp_reordering); 2256 tcp_set_ca_state(sk, TCP_CA_Loss); 2257 tp->high_seq = tp->snd_nxt; 2258 TCP_ECN_queue_cwr(tp); 2259 /* Abort F-RTO algorithm if one is in progress */ 2260 tp->frto_counter = 0; 2261} 2262 2263/* If ACK arrived pointing to a remembered SACK, it means that our 2264 * remembered SACKs do not reflect real state of receiver i.e. 2265 * receiver _host_ is heavily congested (or buggy). 2266 * 2267 * Do processing similar to RTO timeout. 2268 */ 2269static int tcp_check_sack_reneging(struct sock *sk, int flag) 2270{ 2271 if (flag & FLAG_SACK_RENEGING) { 2272 struct inet_connection_sock *icsk = inet_csk(sk); 2273 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSACKRENEGING); 2274 2275 tcp_enter_loss(sk, 1); 2276 icsk->icsk_retransmits++; 2277 tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); 2278 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 2279 icsk->icsk_rto, TCP_RTO_MAX); 2280 return 1; 2281 } 2282 return 0; 2283} 2284 2285static inline int tcp_fackets_out(struct tcp_sock *tp) 2286{ 2287 return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out; 2288} 2289 2290/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs 2291 * counter when SACK is enabled (without SACK, sacked_out is used for 2292 * that purpose). 2293 * 2294 * Instead, with FACK TCP uses fackets_out that includes both SACKed 2295 * segments up to the highest received SACK block so far and holes in 2296 * between them. 2297 * 2298 * With reordering, holes may still be in flight, so RFC3517 recovery 2299 * uses pure sacked_out (total number of SACKed segments) even though 2300 * it violates the RFC that uses duplicate ACKs, often these are equal 2301 * but when e.g. out-of-window ACKs or packet duplication occurs, 2302 * they differ. Since neither occurs due to loss, TCP should really 2303 * ignore them. 2304 */ 2305static inline int tcp_dupack_heuristics(struct tcp_sock *tp) 2306{ 2307 return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1; 2308} 2309 2310static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb) 2311{ 2312 return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto); 2313} 2314 2315static inline int tcp_head_timedout(struct sock *sk) 2316{ 2317 struct tcp_sock *tp = tcp_sk(sk); 2318 2319 return tp->packets_out && 2320 tcp_skb_timedout(sk, tcp_write_queue_head(sk)); 2321} 2322 2323/* Linux NewReno/SACK/FACK/ECN state machine. 2324 * -------------------------------------- 2325 * 2326 * "Open" Normal state, no dubious events, fast path. 2327 * "Disorder" In all the respects it is "Open", 2328 * but requires a bit more attention. It is entered when 2329 * we see some SACKs or dupacks. It is split of "Open" 2330 * mainly to move some processing from fast path to slow one. 2331 * "CWR" CWND was reduced due to some Congestion Notification event. 2332 * It can be ECN, ICMP source quench, local device congestion. 2333 * "Recovery" CWND was reduced, we are fast-retransmitting. 2334 * "Loss" CWND was reduced due to RTO timeout or SACK reneging. 2335 * 2336 * tcp_fastretrans_alert() is entered: 2337 * - each incoming ACK, if state is not "Open" 2338 * - when arrived ACK is unusual, namely: 2339 * * SACK 2340 * * Duplicate ACK. 2341 * * ECN ECE. 2342 * 2343 * Counting packets in flight is pretty simple. 2344 * 2345 * in_flight = packets_out - left_out + retrans_out 2346 * 2347 * packets_out is SND.NXT-SND.UNA counted in packets. 2348 * 2349 * retrans_out is number of retransmitted segments. 2350 * 2351 * left_out is number of segments left network, but not ACKed yet. 2352 * 2353 * left_out = sacked_out + lost_out 2354 * 2355 * sacked_out: Packets, which arrived to receiver out of order 2356 * and hence not ACKed. With SACKs this number is simply 2357 * amount of SACKed data. Even without SACKs 2358 * it is easy to give pretty reliable estimate of this number, 2359 * counting duplicate ACKs. 2360 * 2361 * lost_out: Packets lost by network. TCP has no explicit 2362 * "loss notification" feedback from network (for now). 2363 * It means that this number can be only _guessed_. 2364 * Actually, it is the heuristics to predict lossage that 2365 * distinguishes different algorithms. 2366 * 2367 * F.e. after RTO, when all the queue is considered as lost, 2368 * lost_out = packets_out and in_flight = retrans_out. 2369 * 2370 * Essentially, we have now two algorithms counting 2371 * lost packets. 2372 * 2373 * FACK: It is the simplest heuristics. As soon as we decided 2374 * that something is lost, we decide that _all_ not SACKed 2375 * packets until the most forward SACK are lost. I.e. 2376 * lost_out = fackets_out - sacked_out and left_out = fackets_out. 2377 * It is absolutely correct estimate, if network does not reorder 2378 * packets. And it loses any connection to reality when reordering 2379 * takes place. We use FACK by default until reordering 2380 * is suspected on the path to this destination. 2381 * 2382 * NewReno: when Recovery is entered, we assume that one segment 2383 * is lost (classic Reno). While we are in Recovery and 2384 * a partial ACK arrives, we assume that one more packet 2385 * is lost (NewReno). This heuristics are the same in NewReno 2386 * and SACK. 2387 * 2388 * Imagine, that's all! Forget about all this shamanism about CWND inflation 2389 * deflation etc. CWND is real congestion window, never inflated, changes 2390 * only according to classic VJ rules. 2391 * 2392 * Really tricky (and requiring careful tuning) part of algorithm 2393 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). 2394 * The first determines the moment _when_ we should reduce CWND and, 2395 * hence, slow down forward transmission. In fact, it determines the moment 2396 * when we decide that hole is caused by loss, rather than by a reorder. 2397 * 2398 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill 2399 * holes, caused by lost packets. 2400 * 2401 * And the most logically complicated part of algorithm is undo 2402 * heuristics. We detect false retransmits due to both too early 2403 * fast retransmit (reordering) and underestimated RTO, analyzing 2404 * timestamps and D-SACKs. When we detect that some segments were 2405 * retransmitted by mistake and CWND reduction was wrong, we undo 2406 * window reduction and abort recovery phase. This logic is hidden 2407 * inside several functions named tcp_try_undo_<something>. 2408 */ 2409 2410/* This function decides, when we should leave Disordered state 2411 * and enter Recovery phase, reducing congestion window. 2412 * 2413 * Main question: may we further continue forward transmission 2414 * with the same cwnd? 2415 */ 2416static int tcp_time_to_recover(struct sock *sk) 2417{ 2418 struct tcp_sock *tp = tcp_sk(sk); 2419 __u32 packets_out; 2420 2421 /* Do not perform any recovery during F-RTO algorithm */ 2422 if (tp->frto_counter) 2423 return 0; 2424 2425 /* Trick#1: The loss is proven. */ 2426 if (tp->lost_out) 2427 return 1; 2428 2429 /* Not-A-Trick#2 : Classic rule... */ 2430 if (tcp_dupack_heuristics(tp) > tp->reordering) 2431 return 1; 2432 2433 /* Trick#3 : when we use RFC2988 timer restart, fast 2434 * retransmit can be triggered by timeout of queue head. 2435 */ 2436 if (tcp_is_fack(tp) && tcp_head_timedout(sk)) 2437 return 1; 2438 2439 /* Trick#4: It is still not OK... But will it be useful to delay 2440 * recovery more? 2441 */ 2442 packets_out = tp->packets_out; 2443 if (packets_out <= tp->reordering && 2444 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && 2445 !tcp_may_send_now(sk)) { 2446 /* We have nothing to send. This connection is limited 2447 * either by receiver window or by application. 2448 */ 2449 return 1; 2450 } 2451 2452 /* If a thin stream is detected, retransmit after first 2453 * received dupack. Employ only if SACK is supported in order 2454 * to avoid possible corner-case series of spurious retransmissions 2455 * Use only if there are no unsent data. 2456 */ 2457 if ((tp->thin_dupack || sysctl_tcp_thin_dupack) && 2458 tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 && 2459 tcp_is_sack(tp) && !tcp_send_head(sk)) 2460 return 1; 2461 2462 return 0; 2463} 2464 2465/* New heuristics: it is possible only after we switched to restart timer 2466 * each time when something is ACKed. Hence, we can detect timed out packets 2467 * during fast retransmit without falling to slow start. 2468 * 2469 * Usefulness of this as is very questionable, since we should know which of 2470 * the segments is the next to timeout which is relatively expensive to find 2471 * in general case unless we add some data structure just for that. The 2472 * current approach certainly won't find the right one too often and when it 2473 * finally does find _something_ it usually marks large part of the window 2474 * right away (because a retransmission with a larger timestamp blocks the 2475 * loop from advancing). -ij 2476 */ 2477static void tcp_timeout_skbs(struct sock *sk) 2478{ 2479 struct tcp_sock *tp = tcp_sk(sk); 2480 struct sk_buff *skb; 2481 2482 if (!tcp_is_fack(tp) || !tcp_head_timedout(sk)) 2483 return; 2484 2485 skb = tp->scoreboard_skb_hint; 2486 if (tp->scoreboard_skb_hint == NULL) 2487 skb = tcp_write_queue_head(sk); 2488 2489 tcp_for_write_queue_from(skb, sk) { 2490 if (skb == tcp_send_head(sk)) 2491 break; 2492 if (!tcp_skb_timedout(sk, skb)) 2493 break; 2494 2495 tcp_skb_mark_lost(tp, skb); 2496 } 2497 2498 tp->scoreboard_skb_hint = skb; 2499 2500 tcp_verify_left_out(tp); 2501} 2502 2503/* Mark head of queue up as lost. With RFC3517 SACK, the packets is 2504 * is against sacked "cnt", otherwise it's against facked "cnt" 2505 */ 2506static void tcp_mark_head_lost(struct sock *sk, int packets) 2507{ 2508 struct tcp_sock *tp = tcp_sk(sk); 2509 struct sk_buff *skb; 2510 int cnt, oldcnt; 2511 int err; 2512 unsigned int mss; 2513 2514 if (packets == 0) 2515 return; 2516 2517 WARN_ON(packets > tp->packets_out); 2518 if (tp->lost_skb_hint) { 2519 skb = tp->lost_skb_hint; 2520 cnt = tp->lost_cnt_hint; 2521 } else { 2522 skb = tcp_write_queue_head(sk); 2523 cnt = 0; 2524 } 2525 2526 tcp_for_write_queue_from(skb, sk) { 2527 if (skb == tcp_send_head(sk)) 2528 break; 2529 /* TODO: do this better */ 2530 /* this is not the most efficient way to do this... */ 2531 tp->lost_skb_hint = skb; 2532 tp->lost_cnt_hint = cnt; 2533 2534 if (after(TCP_SKB_CB(skb)->end_seq, tp->high_seq)) 2535 break; 2536 2537 oldcnt = cnt; 2538 if (tcp_is_fack(tp) || tcp_is_reno(tp) || 2539 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 2540 cnt += tcp_skb_pcount(skb); 2541 2542 if (cnt > packets) { 2543 if (tcp_is_sack(tp) || (oldcnt >= packets)) 2544 break; 2545 2546 mss = skb_shinfo(skb)->gso_size; 2547 err = tcp_fragment(sk, skb, (packets - oldcnt) * mss, mss); 2548 if (err < 0) 2549 break; 2550 cnt = packets; 2551 } 2552 2553 tcp_skb_mark_lost(tp, skb); 2554 } 2555 tcp_verify_left_out(tp); 2556} 2557 2558/* Account newly detected lost packet(s) */ 2559 2560static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit) 2561{ 2562 struct tcp_sock *tp = tcp_sk(sk); 2563 2564 if (tcp_is_reno(tp)) { 2565 tcp_mark_head_lost(sk, 1); 2566 } else if (tcp_is_fack(tp)) { 2567 int lost = tp->fackets_out - tp->reordering; 2568 if (lost <= 0) 2569 lost = 1; 2570 tcp_mark_head_lost(sk, lost); 2571 } else { 2572 int sacked_upto = tp->sacked_out - tp->reordering; 2573 if (sacked_upto < fast_rexmit) 2574 sacked_upto = fast_rexmit; 2575 tcp_mark_head_lost(sk, sacked_upto); 2576 } 2577 2578 tcp_timeout_skbs(sk); 2579} 2580 2581/* CWND moderation, preventing bursts due to too big ACKs 2582 * in dubious situations. 2583 */ 2584static inline void tcp_moderate_cwnd(struct tcp_sock *tp) 2585{ 2586 tp->snd_cwnd = min(tp->snd_cwnd, 2587 tcp_packets_in_flight(tp) + tcp_max_burst(tp)); 2588 tp->snd_cwnd_stamp = tcp_time_stamp; 2589} 2590 2591/* Lower bound on congestion window is slow start threshold 2592 * unless congestion avoidance choice decides to overide it. 2593 */ 2594static inline u32 tcp_cwnd_min(const struct sock *sk) 2595{ 2596 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; 2597 2598 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh; 2599} 2600 2601/* Decrease cwnd each second ack. */ 2602static void tcp_cwnd_down(struct sock *sk, int flag) 2603{ 2604 struct tcp_sock *tp = tcp_sk(sk); 2605 int decr = tp->snd_cwnd_cnt + 1; 2606 2607 if ((flag & (FLAG_ANY_PROGRESS | FLAG_DSACKING_ACK)) || 2608 (tcp_is_reno(tp) && !(flag & FLAG_NOT_DUP))) { 2609 tp->snd_cwnd_cnt = decr & 1; 2610 decr >>= 1; 2611 2612 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk)) 2613 tp->snd_cwnd -= decr; 2614 2615 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1); 2616 tp->snd_cwnd_stamp = tcp_time_stamp; 2617 } 2618} 2619 2620/* Nothing was retransmitted or returned timestamp is less 2621 * than timestamp of the first retransmission. 2622 */ 2623static inline int tcp_packet_delayed(struct tcp_sock *tp) 2624{ 2625 return !tp->retrans_stamp || 2626 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 2627 before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp)); 2628} 2629 2630/* Undo procedures. */ 2631 2632#if FASTRETRANS_DEBUG > 1 2633static void DBGUNDO(struct sock *sk, const char *msg) 2634{ 2635 struct tcp_sock *tp = tcp_sk(sk); 2636 struct inet_sock *inet = inet_sk(sk); 2637 2638 if (sk->sk_family == AF_INET) { 2639 printk(KERN_DEBUG "Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n", 2640 msg, 2641 &inet->daddr, ntohs(inet->dport), 2642 tp->snd_cwnd, tcp_left_out(tp), 2643 tp->snd_ssthresh, tp->prior_ssthresh, 2644 tp->packets_out); 2645 } 2646#if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) 2647 else if (sk->sk_family == AF_INET6) { 2648 struct ipv6_pinfo *np = inet6_sk(sk); 2649 printk(KERN_DEBUG "Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n", 2650 msg, 2651 &np->daddr, ntohs(inet->dport), 2652 tp->snd_cwnd, tcp_left_out(tp), 2653 tp->snd_ssthresh, tp->prior_ssthresh, 2654 tp->packets_out); 2655 } 2656#endif 2657} 2658#else 2659#define DBGUNDO(x...) do { } while (0) 2660#endif 2661 2662static void tcp_undo_cwr(struct sock *sk, const int undo) 2663{ 2664 struct tcp_sock *tp = tcp_sk(sk); 2665 2666 if (tp->prior_ssthresh) { 2667 const struct inet_connection_sock *icsk = inet_csk(sk); 2668 2669 if (icsk->icsk_ca_ops->undo_cwnd) 2670 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); 2671 else 2672 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1); 2673 2674 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) { 2675 tp->snd_ssthresh = tp->prior_ssthresh; 2676 TCP_ECN_withdraw_cwr(tp); 2677 } 2678 } else { 2679 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); 2680 } 2681 tcp_moderate_cwnd(tp); 2682 tp->snd_cwnd_stamp = tcp_time_stamp; 2683} 2684 2685static inline int tcp_may_undo(struct tcp_sock *tp) 2686{ 2687 return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp)); 2688} 2689 2690/* People celebrate: "We love our President!" */ 2691static int tcp_try_undo_recovery(struct sock *sk) 2692{ 2693 struct tcp_sock *tp = tcp_sk(sk); 2694 2695 if (tcp_may_undo(tp)) { 2696 int mib_idx; 2697 2698 /* Happy end! We did not retransmit anything 2699 * or our original transmission succeeded. 2700 */ 2701 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); 2702 tcp_undo_cwr(sk, 1); 2703 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) 2704 mib_idx = LINUX_MIB_TCPLOSSUNDO; 2705 else 2706 mib_idx = LINUX_MIB_TCPFULLUNDO; 2707 2708 NET_INC_STATS_BH(sock_net(sk), mib_idx); 2709 tp->undo_marker = 0; 2710 } 2711 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) { 2712 /* Hold old state until something *above* high_seq 2713 * is ACKed. For Reno it is MUST to prevent false 2714 * fast retransmits (RFC2582). SACK TCP is safe. */ 2715 tcp_moderate_cwnd(tp); 2716 return 1; 2717 } 2718 tcp_set_ca_state(sk, TCP_CA_Open); 2719 return 0; 2720} 2721 2722/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ 2723static void tcp_try_undo_dsack(struct sock *sk) 2724{ 2725 struct tcp_sock *tp = tcp_sk(sk); 2726 2727 if (tp->undo_marker && !tp->undo_retrans) { 2728 DBGUNDO(sk, "D-SACK"); 2729 tcp_undo_cwr(sk, 1); 2730 tp->undo_marker = 0; 2731 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO); 2732 } 2733} 2734 2735/* We can clear retrans_stamp when there are no retransmissions in the 2736 * window. It would seem that it is trivially available for us in 2737 * tp->retrans_out, however, that kind of assumptions doesn't consider 2738 * what will happen if errors occur when sending retransmission for the 2739 * second time. ...It could the that such segment has only 2740 * TCPCB_EVER_RETRANS set at the present time. It seems that checking 2741 * the head skb is enough except for some reneging corner cases that 2742 * are not worth the effort. 2743 * 2744 * Main reason for all this complexity is the fact that connection dying 2745 * time now depends on the validity of the retrans_stamp, in particular, 2746 * that successive retransmissions of a segment must not advance 2747 * retrans_stamp under any conditions. 2748 */ 2749static int tcp_any_retrans_done(struct sock *sk) 2750{ 2751 struct tcp_sock *tp = tcp_sk(sk); 2752 struct sk_buff *skb; 2753 2754 if (tp->retrans_out) 2755 return 1; 2756 2757 skb = tcp_write_queue_head(sk); 2758 if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS)) 2759 return 1; 2760 2761 return 0; 2762} 2763 2764/* Undo during fast recovery after partial ACK. */ 2765 2766static int tcp_try_undo_partial(struct sock *sk, int acked) 2767{ 2768 struct tcp_sock *tp = tcp_sk(sk); 2769 /* Partial ACK arrived. Force Hoe's retransmit. */ 2770 int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering); 2771 2772 if (tcp_may_undo(tp)) { 2773 /* Plain luck! Hole if filled with delayed 2774 * packet, rather than with a retransmit. 2775 */ 2776 if (!tcp_any_retrans_done(sk)) 2777 tp->retrans_stamp = 0; 2778 2779 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1); 2780 2781 DBGUNDO(sk, "Hoe"); 2782 tcp_undo_cwr(sk, 0); 2783 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO); 2784 2785 /* So... Do not make Hoe's retransmit yet. 2786 * If the first packet was delayed, the rest 2787 * ones are most probably delayed as well. 2788 */ 2789 failed = 0; 2790 } 2791 return failed; 2792} 2793 2794/* Undo during loss recovery after partial ACK. */ 2795static int tcp_try_undo_loss(struct sock *sk) 2796{ 2797 struct tcp_sock *tp = tcp_sk(sk); 2798 2799 if (tcp_may_undo(tp)) { 2800 struct sk_buff *skb; 2801 tcp_for_write_queue(skb, sk) { 2802 if (skb == tcp_send_head(sk)) 2803 break; 2804 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 2805 } 2806 2807 tcp_clear_all_retrans_hints(tp); 2808 2809 DBGUNDO(sk, "partial loss"); 2810 tp->lost_out = 0; 2811 tcp_undo_cwr(sk, 1); 2812 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO); 2813 inet_csk(sk)->icsk_retransmits = 0; 2814 tp->undo_marker = 0; 2815 if (tcp_is_sack(tp)) 2816 tcp_set_ca_state(sk, TCP_CA_Open); 2817 return 1; 2818 } 2819 return 0; 2820} 2821 2822static inline void tcp_complete_cwr(struct sock *sk) 2823{ 2824 struct tcp_sock *tp = tcp_sk(sk); 2825 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 2826 tp->snd_cwnd_stamp = tcp_time_stamp; 2827 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); 2828} 2829 2830static void tcp_try_keep_open(struct sock *sk) 2831{ 2832 struct tcp_sock *tp = tcp_sk(sk); 2833 int state = TCP_CA_Open; 2834 2835 if (tcp_left_out(tp) || tcp_any_retrans_done(sk) || tp->undo_marker) 2836 state = TCP_CA_Disorder; 2837 2838 if (inet_csk(sk)->icsk_ca_state != state) { 2839 tcp_set_ca_state(sk, state); 2840 tp->high_seq = tp->snd_nxt; 2841 } 2842} 2843 2844static void tcp_try_to_open(struct sock *sk, int flag) 2845{ 2846 struct tcp_sock *tp = tcp_sk(sk); 2847 2848 tcp_verify_left_out(tp); 2849 2850 if (!tp->frto_counter && !tcp_any_retrans_done(sk)) 2851 tp->retrans_stamp = 0; 2852 2853 if (flag & FLAG_ECE) 2854 tcp_enter_cwr(sk, 1); 2855 2856 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { 2857 tcp_try_keep_open(sk); 2858 tcp_moderate_cwnd(tp); 2859 } else { 2860 tcp_cwnd_down(sk, flag); 2861 } 2862} 2863 2864static void tcp_mtup_probe_failed(struct sock *sk) 2865{ 2866 struct inet_connection_sock *icsk = inet_csk(sk); 2867 2868 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; 2869 icsk->icsk_mtup.probe_size = 0; 2870} 2871 2872static void tcp_mtup_probe_success(struct sock *sk) 2873{ 2874 struct tcp_sock *tp = tcp_sk(sk); 2875 struct inet_connection_sock *icsk = inet_csk(sk); 2876 2877 /* FIXME: breaks with very large cwnd */ 2878 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2879 tp->snd_cwnd = tp->snd_cwnd * 2880 tcp_mss_to_mtu(sk, tp->mss_cache) / 2881 icsk->icsk_mtup.probe_size; 2882 tp->snd_cwnd_cnt = 0; 2883 tp->snd_cwnd_stamp = tcp_time_stamp; 2884 tp->rcv_ssthresh = tcp_current_ssthresh(sk); 2885 2886 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; 2887 icsk->icsk_mtup.probe_size = 0; 2888 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 2889} 2890 2891/* Do a simple retransmit without using the backoff mechanisms in 2892 * tcp_timer. This is used for path mtu discovery. 2893 * The socket is already locked here. 2894 */ 2895void tcp_simple_retransmit(struct sock *sk) 2896{ 2897 const struct inet_connection_sock *icsk = inet_csk(sk); 2898 struct tcp_sock *tp = tcp_sk(sk); 2899 struct sk_buff *skb; 2900 unsigned int mss = tcp_current_mss(sk); 2901 u32 prior_lost = tp->lost_out; 2902 2903 tcp_for_write_queue(skb, sk) { 2904 if (skb == tcp_send_head(sk)) 2905 break; 2906 if (tcp_skb_seglen(skb) > mss && 2907 !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 2908 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 2909 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 2910 tp->retrans_out -= tcp_skb_pcount(skb); 2911 } 2912 tcp_skb_mark_lost_uncond_verify(tp, skb); 2913 } 2914 } 2915 2916 tcp_clear_retrans_hints_partial(tp); 2917 2918 if (prior_lost == tp->lost_out) 2919 return; 2920 2921 if (tcp_is_reno(tp)) 2922 tcp_limit_reno_sacked(tp); 2923 2924 tcp_verify_left_out(tp); 2925 2926 /* Don't muck with the congestion window here. 2927 * Reason is that we do not increase amount of _data_ 2928 * in network, but units changed and effective 2929 * cwnd/ssthresh really reduced now. 2930 */ 2931 if (icsk->icsk_ca_state != TCP_CA_Loss) { 2932 tp->high_seq = tp->snd_nxt; 2933 tp->snd_ssthresh = tcp_current_ssthresh(sk); 2934 tp->prior_ssthresh = 0; 2935 tp->undo_marker = 0; 2936 tcp_set_ca_state(sk, TCP_CA_Loss); 2937 } 2938 tcp_xmit_retransmit_queue(sk); 2939} 2940 2941/* Process an event, which can update packets-in-flight not trivially. 2942 * Main goal of this function is to calculate new estimate for left_out, 2943 * taking into account both packets sitting in receiver's buffer and 2944 * packets lost by network. 2945 * 2946 * Besides that it does CWND reduction, when packet loss is detected 2947 * and changes state of machine. 2948 * 2949 * It does _not_ decide what to send, it is made in function 2950 * tcp_xmit_retransmit_queue(). 2951 */ 2952static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag) 2953{ 2954 struct inet_connection_sock *icsk = inet_csk(sk); 2955 struct tcp_sock *tp = tcp_sk(sk); 2956 int is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP)); 2957 int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) && 2958 (tcp_fackets_out(tp) > tp->reordering)); 2959 int fast_rexmit = 0, mib_idx; 2960 2961 if (WARN_ON(!tp->packets_out && tp->sacked_out)) 2962 tp->sacked_out = 0; 2963 if (WARN_ON(!tp->sacked_out && tp->fackets_out)) 2964 tp->fackets_out = 0; 2965 2966 /* Now state machine starts. 2967 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ 2968 if (flag & FLAG_ECE) 2969 tp->prior_ssthresh = 0; 2970 2971 /* B. In all the states check for reneging SACKs. */ 2972 if (tcp_check_sack_reneging(sk, flag)) 2973 return; 2974 2975 /* C. Process data loss notification, provided it is valid. */ 2976 if (tcp_is_fack(tp) && (flag & FLAG_DATA_LOST) && 2977 before(tp->snd_una, tp->high_seq) && 2978 icsk->icsk_ca_state != TCP_CA_Open && 2979 tp->fackets_out > tp->reordering) { 2980 tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering); 2981 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSS); 2982 } 2983 2984 /* D. Check consistency of the current state. */ 2985 tcp_verify_left_out(tp); 2986 2987 /* E. Check state exit conditions. State can be terminated 2988 * when high_seq is ACKed. */ 2989 if (icsk->icsk_ca_state == TCP_CA_Open) { 2990 WARN_ON(tp->retrans_out != 0); 2991 tp->retrans_stamp = 0; 2992 } else if (!before(tp->snd_una, tp->high_seq)) { 2993 switch (icsk->icsk_ca_state) { 2994 case TCP_CA_Loss: 2995 icsk->icsk_retransmits = 0; 2996 if (tcp_try_undo_recovery(sk)) 2997 return; 2998 break; 2999 3000 case TCP_CA_CWR: 3001 /* CWR is to be held something *above* high_seq 3002 * is ACKed for CWR bit to reach receiver. */ 3003 if (tp->snd_una != tp->high_seq) { 3004 tcp_complete_cwr(sk); 3005 tcp_set_ca_state(sk, TCP_CA_Open); 3006 } 3007 break; 3008 3009 case TCP_CA_Disorder: 3010 tcp_try_undo_dsack(sk); 3011 if (!tp->undo_marker || 3012 /* For SACK case do not Open to allow to undo 3013 * catching for all duplicate ACKs. */ 3014 tcp_is_reno(tp) || tp->snd_una != tp->high_seq) { 3015 tp->undo_marker = 0; 3016 tcp_set_ca_state(sk, TCP_CA_Open); 3017 } 3018 break; 3019 3020 case TCP_CA_Recovery: 3021 if (tcp_is_reno(tp)) 3022 tcp_reset_reno_sack(tp); 3023 if (tcp_try_undo_recovery(sk)) 3024 return; 3025 tcp_complete_cwr(sk); 3026 break; 3027 } 3028 } 3029 3030 /* F. Process state. */ 3031 switch (icsk->icsk_ca_state) { 3032 case TCP_CA_Recovery: 3033 if (!(flag & FLAG_SND_UNA_ADVANCED)) { 3034 if (tcp_is_reno(tp) && is_dupack) 3035 tcp_add_reno_sack(sk); 3036 } else 3037 do_lost = tcp_try_undo_partial(sk, pkts_acked); 3038 break; 3039 case TCP_CA_Loss: 3040 if (flag & FLAG_DATA_ACKED) 3041 icsk->icsk_retransmits = 0; 3042 if (tcp_is_reno(tp) && flag & FLAG_SND_UNA_ADVANCED) 3043 tcp_reset_reno_sack(tp); 3044 if (!tcp_try_undo_loss(sk)) { 3045 tcp_moderate_cwnd(tp); 3046 tcp_xmit_retransmit_queue(sk); 3047 return; 3048 } 3049 if (icsk->icsk_ca_state != TCP_CA_Open) 3050 return; 3051 /* Loss is undone; fall through to processing in Open state. */ 3052 default: 3053 if (tcp_is_reno(tp)) { 3054 if (flag & FLAG_SND_UNA_ADVANCED) 3055 tcp_reset_reno_sack(tp); 3056 if (is_dupack) 3057 tcp_add_reno_sack(sk); 3058 } 3059 3060 if (icsk->icsk_ca_state == TCP_CA_Disorder) 3061 tcp_try_undo_dsack(sk); 3062 3063 if (!tcp_time_to_recover(sk)) { 3064 tcp_try_to_open(sk, flag); 3065 return; 3066 } 3067 3068 /* MTU probe failure: don't reduce cwnd */ 3069 if (icsk->icsk_ca_state < TCP_CA_CWR && 3070 icsk->icsk_mtup.probe_size && 3071 tp->snd_una == tp->mtu_probe.probe_seq_start) { 3072 tcp_mtup_probe_failed(sk); 3073 /* Restores the reduction we did in tcp_mtup_probe() */ 3074 tp->snd_cwnd++; 3075 tcp_simple_retransmit(sk); 3076 return; 3077 } 3078 3079 /* Otherwise enter Recovery state */ 3080 3081 if (tcp_is_reno(tp)) 3082 mib_idx = LINUX_MIB_TCPRENORECOVERY; 3083 else 3084 mib_idx = LINUX_MIB_TCPSACKRECOVERY; 3085 3086 NET_INC_STATS_BH(sock_net(sk), mib_idx); 3087 3088 tp->high_seq = tp->snd_nxt; 3089 tp->prior_ssthresh = 0; 3090 tp->undo_marker = tp->snd_una; 3091 tp->undo_retrans = tp->retrans_out; 3092 3093 if (icsk->icsk_ca_state < TCP_CA_CWR) { 3094 if (!(flag & FLAG_ECE)) 3095 tp->prior_ssthresh = tcp_current_ssthresh(sk); 3096 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 3097 TCP_ECN_queue_cwr(tp); 3098 } 3099 3100 tp->bytes_acked = 0; 3101 tp->snd_cwnd_cnt = 0; 3102 tcp_set_ca_state(sk, TCP_CA_Recovery); 3103 fast_rexmit = 1; 3104 } 3105 3106 if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk))) 3107 tcp_update_scoreboard(sk, fast_rexmit); 3108 tcp_cwnd_down(sk, flag); 3109 tcp_xmit_retransmit_queue(sk); 3110} 3111 3112static void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt) 3113{ 3114 tcp_rtt_estimator(sk, seq_rtt); 3115 tcp_set_rto(sk); 3116 inet_csk(sk)->icsk_backoff = 0; 3117} 3118 3119/* Read draft-ietf-tcplw-high-performance before mucking 3120 * with this code. (Supersedes RFC1323) 3121 */ 3122static void tcp_ack_saw_tstamp(struct sock *sk, int flag) 3123{ 3124 /* RTTM Rule: A TSecr value received in a segment is used to 3125 * update the averaged RTT measurement only if the segment 3126 * acknowledges some new data, i.e., only if it advances the 3127 * left edge of the send window. 3128 * 3129 * See draft-ietf-tcplw-high-performance-00, section 3.3. 3130 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> 3131 * 3132 * Changed: reset backoff as soon as we see the first valid sample. 3133 * If we do not, we get strongly overestimated rto. With timestamps 3134 * samples are accepted even from very old segments: f.e., when rtt=1 3135 * increases to 8, we retransmit 5 times and after 8 seconds delayed 3136 * answer arrives rto becomes 120 seconds! If at least one of segments 3137 * in window is lost... Voila. --ANK (010210) 3138 */ 3139 struct tcp_sock *tp = tcp_sk(sk); 3140 3141 tcp_valid_rtt_meas(sk, tcp_time_stamp - tp->rx_opt.rcv_tsecr); 3142} 3143 3144static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag) 3145{ 3146 /* We don't have a timestamp. Can only use 3147 * packets that are not retransmitted to determine 3148 * rtt estimates. Also, we must not reset the 3149 * backoff for rto until we get a non-retransmitted 3150 * packet. This allows us to deal with a situation 3151 * where the network delay has increased suddenly. 3152 * I.e. Karn's algorithm. (SIGCOMM '87, p5.) 3153 */ 3154 3155 if (flag & FLAG_RETRANS_DATA_ACKED) 3156 return; 3157 3158 tcp_valid_rtt_meas(sk, seq_rtt); 3159} 3160 3161static inline void tcp_ack_update_rtt(struct sock *sk, const int flag, 3162 const s32 seq_rtt) 3163{ 3164 const struct tcp_sock *tp = tcp_sk(sk); 3165 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ 3166 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) 3167 tcp_ack_saw_tstamp(sk, flag); 3168 else if (seq_rtt >= 0) 3169 tcp_ack_no_tstamp(sk, seq_rtt, flag); 3170} 3171 3172static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) 3173{ 3174 const struct inet_connection_sock *icsk = inet_csk(sk); 3175 icsk->icsk_ca_ops->cong_avoid(sk, ack, in_flight); 3176 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp; 3177} 3178 3179/* Restart timer after forward progress on connection. 3180 * RFC2988 recommends to restart timer to now+rto. 3181 */ 3182static void tcp_rearm_rto(struct sock *sk) 3183{ 3184 struct tcp_sock *tp = tcp_sk(sk); 3185 3186 if (!tp->packets_out) { 3187 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); 3188 } else { 3189 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 3190 inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 3191 } 3192} 3193 3194/* If we get here, the whole TSO packet has not been acked. */ 3195static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb) 3196{ 3197 struct tcp_sock *tp = tcp_sk(sk); 3198 u32 packets_acked; 3199 3200 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)); 3201 3202 packets_acked = tcp_skb_pcount(skb); 3203 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) 3204 return 0; 3205 packets_acked -= tcp_skb_pcount(skb); 3206 3207 if (packets_acked) { 3208 BUG_ON(tcp_skb_pcount(skb) == 0); 3209 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)); 3210 } 3211 3212 return packets_acked; 3213} 3214 3215/* Remove acknowledged frames from the retransmission queue. If our packet 3216 * is before the ack sequence we can discard it as it's confirmed to have 3217 * arrived at the other end. 3218 */ 3219static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets, 3220 u32 prior_snd_una) 3221{ 3222 struct tcp_sock *tp = tcp_sk(sk); 3223 const struct inet_connection_sock *icsk = inet_csk(sk); 3224 struct sk_buff *skb; 3225 u32 now = tcp_time_stamp; 3226 int fully_acked = 1; 3227 int flag = 0; 3228 u32 pkts_acked = 0; 3229 u32 reord = tp->packets_out; 3230 u32 prior_sacked = tp->sacked_out; 3231 s32 seq_rtt = -1; 3232 s32 ca_seq_rtt = -1; 3233 ktime_t last_ackt = net_invalid_timestamp(); 3234 3235 while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) { 3236 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 3237 u32 acked_pcount; 3238 u8 sacked = scb->sacked; 3239 3240 /* Determine how many packets and what bytes were acked, tso and else */ 3241 if (after(scb->end_seq, tp->snd_una)) { 3242 if (tcp_skb_pcount(skb) == 1 || 3243 !after(tp->snd_una, scb->seq)) 3244 break; 3245 3246 acked_pcount = tcp_tso_acked(sk, skb); 3247 if (!acked_pcount) 3248 break; 3249 3250 fully_acked = 0; 3251 } else { 3252 acked_pcount = tcp_skb_pcount(skb); 3253 } 3254 3255 if (sacked & TCPCB_RETRANS) { 3256 if (sacked & TCPCB_SACKED_RETRANS) 3257 tp->retrans_out -= acked_pcount; 3258 flag |= FLAG_RETRANS_DATA_ACKED; 3259 ca_seq_rtt = -1; 3260 seq_rtt = -1; 3261 if ((flag & FLAG_DATA_ACKED) || (acked_pcount > 1)) 3262 flag |= FLAG_NONHEAD_RETRANS_ACKED; 3263 } else { 3264 ca_seq_rtt = now - scb->when; 3265 last_ackt = skb->tstamp; 3266 if (seq_rtt < 0) { 3267 seq_rtt = ca_seq_rtt; 3268 } 3269 if (!(sacked & TCPCB_SACKED_ACKED)) 3270 reord = min(pkts_acked, reord); 3271 } 3272 3273 if (sacked & TCPCB_SACKED_ACKED) 3274 tp->sacked_out -= acked_pcount; 3275 if (sacked & TCPCB_LOST) 3276 tp->lost_out -= acked_pcount; 3277 3278 tp->packets_out -= acked_pcount; 3279 pkts_acked += acked_pcount; 3280 3281 /* Initial outgoing SYN's get put onto the write_queue 3282 * just like anything else we transmit. It is not 3283 * true data, and if we misinform our callers that 3284 * this ACK acks real data, we will erroneously exit 3285 * connection startup slow start one packet too 3286 * quickly. This is severely frowned upon behavior. 3287 */ 3288 if (!(scb->flags & TCPCB_FLAG_SYN)) { 3289 flag |= FLAG_DATA_ACKED; 3290 } else { 3291 flag |= FLAG_SYN_ACKED; 3292 tp->retrans_stamp = 0; 3293 } 3294 3295 if (!fully_acked) 3296 break; 3297 3298 tcp_unlink_write_queue(skb, sk); 3299 sk_wmem_free_skb(sk, skb); 3300 tp->scoreboard_skb_hint = NULL; 3301 if (skb == tp->retransmit_skb_hint) 3302 tp->retransmit_skb_hint = NULL; 3303 if (skb == tp->lost_skb_hint) 3304 tp->lost_skb_hint = NULL; 3305 } 3306 3307 if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una))) 3308 tp->snd_up = tp->snd_una; 3309 3310 if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 3311 flag |= FLAG_SACK_RENEGING; 3312 3313 if (flag & FLAG_ACKED) { 3314 const struct tcp_congestion_ops *ca_ops 3315 = inet_csk(sk)->icsk_ca_ops; 3316 3317 if (unlikely(icsk->icsk_mtup.probe_size && 3318 !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) { 3319 tcp_mtup_probe_success(sk); 3320 } 3321 3322 tcp_ack_update_rtt(sk, flag, seq_rtt); 3323 tcp_rearm_rto(sk); 3324 3325 if (tcp_is_reno(tp)) { 3326 tcp_remove_reno_sacks(sk, pkts_acked); 3327 } else { 3328 int delta; 3329 3330 /* Non-retransmitted hole got filled? That's reordering */ 3331 if (reord < prior_fackets) 3332 tcp_update_reordering(sk, tp->fackets_out - reord, 0); 3333 3334 delta = tcp_is_fack(tp) ? pkts_acked : 3335 prior_sacked - tp->sacked_out; 3336 tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta); 3337 } 3338 3339 tp->fackets_out -= min(pkts_acked, tp->fackets_out); 3340 3341 if (ca_ops->pkts_acked) { 3342 s32 rtt_us = -1; 3343 3344 /* Is the ACK triggering packet unambiguous? */ 3345 if (!(flag & FLAG_RETRANS_DATA_ACKED)) { 3346 /* High resolution needed and available? */ 3347 if (ca_ops->flags & TCP_CONG_RTT_STAMP && 3348 !ktime_equal(last_ackt, 3349 net_invalid_timestamp())) 3350 rtt_us = ktime_us_delta(ktime_get_real(), 3351 last_ackt); 3352 else if (ca_seq_rtt > 0) 3353 rtt_us = jiffies_to_usecs(ca_seq_rtt); 3354 } 3355 3356 ca_ops->pkts_acked(sk, pkts_acked, rtt_us); 3357 } 3358 } 3359 3360#if FASTRETRANS_DEBUG > 0 3361 WARN_ON((int)tp->sacked_out < 0); 3362 WARN_ON((int)tp->lost_out < 0); 3363 WARN_ON((int)tp->retrans_out < 0); 3364 if (!tp->packets_out && tcp_is_sack(tp)) { 3365 icsk = inet_csk(sk); 3366 if (tp->lost_out) { 3367 printk(KERN_DEBUG "Leak l=%u %d\n", 3368 tp->lost_out, icsk->icsk_ca_state); 3369 tp->lost_out = 0; 3370 } 3371 if (tp->sacked_out) { 3372 printk(KERN_DEBUG "Leak s=%u %d\n", 3373 tp->sacked_out, icsk->icsk_ca_state); 3374 tp->sacked_out = 0; 3375 } 3376 if (tp->retrans_out) { 3377 printk(KERN_DEBUG "Leak r=%u %d\n", 3378 tp->retrans_out, icsk->icsk_ca_state); 3379 tp->retrans_out = 0; 3380 } 3381 } 3382#endif 3383 return flag; 3384} 3385 3386static void tcp_ack_probe(struct sock *sk) 3387{ 3388 const struct tcp_sock *tp = tcp_sk(sk); 3389 struct inet_connection_sock *icsk = inet_csk(sk); 3390 3391 /* Was it a usable window open? */ 3392 3393 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) { 3394 icsk->icsk_backoff = 0; 3395 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0); 3396 /* Socket must be waked up by subsequent tcp_data_snd_check(). 3397 * This function is not for random using! 3398 */ 3399 } else { 3400 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 3401 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), 3402 TCP_RTO_MAX); 3403 } 3404} 3405 3406static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag) 3407{ 3408 return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || 3409 inet_csk(sk)->icsk_ca_state != TCP_CA_Open); 3410} 3411 3412static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag) 3413{ 3414 const struct tcp_sock *tp = tcp_sk(sk); 3415 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) && 3416 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR)); 3417} 3418 3419/* Check that window update is acceptable. 3420 * The function assumes that snd_una<=ack<=snd_next. 3421 */ 3422static inline int tcp_may_update_window(const struct tcp_sock *tp, 3423 const u32 ack, const u32 ack_seq, 3424 const u32 nwin) 3425{ 3426 return (after(ack, tp->snd_una) || 3427 after(ack_seq, tp->snd_wl1) || 3428 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd)); 3429} 3430 3431/* Update our send window. 3432 * 3433 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 3434 * and in FreeBSD. NetBSD's one is even worse.) is wrong. 3435 */ 3436static int tcp_ack_update_window(struct sock *sk, struct sk_buff *skb, u32 ack, 3437 u32 ack_seq) 3438{ 3439 struct tcp_sock *tp = tcp_sk(sk); 3440 int flag = 0; 3441 u32 nwin = ntohs(tcp_hdr(skb)->window); 3442 3443 if (likely(!tcp_hdr(skb)->syn)) 3444 nwin <<= tp->rx_opt.snd_wscale; 3445 3446 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { 3447 flag |= FLAG_WIN_UPDATE; 3448 tcp_update_wl(tp, ack_seq); 3449 3450 if (tp->snd_wnd != nwin) { 3451 tp->snd_wnd = nwin; 3452 3453 /* Note, it is the only place, where 3454 * fast path is recovered for sending TCP. 3455 */ 3456 tp->pred_flags = 0; 3457 tcp_fast_path_check(sk); 3458 3459 if (nwin > tp->max_window) { 3460 tp->max_window = nwin; 3461 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie); 3462 } 3463 } 3464 } 3465 3466 tp->snd_una = ack; 3467 3468 return flag; 3469} 3470 3471/* A very conservative spurious RTO response algorithm: reduce cwnd and 3472 * continue in congestion avoidance. 3473 */ 3474static void tcp_conservative_spur_to_response(struct tcp_sock *tp) 3475{ 3476 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 3477 tp->snd_cwnd_cnt = 0; 3478 tp->bytes_acked = 0; 3479 TCP_ECN_queue_cwr(tp); 3480 tcp_moderate_cwnd(tp); 3481} 3482 3483/* A conservative spurious RTO response algorithm: reduce cwnd using 3484 * rate halving and continue in congestion avoidance. 3485 */ 3486static void tcp_ratehalving_spur_to_response(struct sock *sk) 3487{ 3488 tcp_enter_cwr(sk, 0); 3489} 3490 3491static void tcp_undo_spur_to_response(struct sock *sk, int flag) 3492{ 3493 if (flag & FLAG_ECE) 3494 tcp_ratehalving_spur_to_response(sk); 3495 else 3496 tcp_undo_cwr(sk, 1); 3497} 3498 3499/* F-RTO spurious RTO detection algorithm (RFC4138) 3500 * 3501 * F-RTO affects during two new ACKs following RTO (well, almost, see inline 3502 * comments). State (ACK number) is kept in frto_counter. When ACK advances 3503 * window (but not to or beyond highest sequence sent before RTO): 3504 * On First ACK, send two new segments out. 3505 * On Second ACK, RTO was likely spurious. Do spurious response (response 3506 * algorithm is not part of the F-RTO detection algorithm 3507 * given in RFC4138 but can be selected separately). 3508 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss 3509 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding 3510 * of Nagle, this is done using frto_counter states 2 and 3, when a new data 3511 * segment of any size sent during F-RTO, state 2 is upgraded to 3. 3512 * 3513 * Rationale: if the RTO was spurious, new ACKs should arrive from the 3514 * original window even after we transmit two new data segments. 3515 * 3516 * SACK version: 3517 * on first step, wait until first cumulative ACK arrives, then move to 3518 * the second step. In second step, the next ACK decides. 3519 * 3520 * F-RTO is implemented (mainly) in four functions: 3521 * - tcp_use_frto() is used to determine if TCP is can use F-RTO 3522 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is 3523 * called when tcp_use_frto() showed green light 3524 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm 3525 * - tcp_enter_frto_loss() is called if there is not enough evidence 3526 * to prove that the RTO is indeed spurious. It transfers the control 3527 * from F-RTO to the conventional RTO recovery 3528 */ 3529static int tcp_process_frto(struct sock *sk, int flag) 3530{ 3531 struct tcp_sock *tp = tcp_sk(sk); 3532 3533 tcp_verify_left_out(tp); 3534 3535 /* Duplicate the behavior from Loss state (fastretrans_alert) */ 3536 if (flag & FLAG_DATA_ACKED) 3537 inet_csk(sk)->icsk_retransmits = 0; 3538 3539 if ((flag & FLAG_NONHEAD_RETRANS_ACKED) || 3540 ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED))) 3541 tp->undo_marker = 0; 3542 3543 if (!before(tp->snd_una, tp->frto_highmark)) { 3544 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag); 3545 return 1; 3546 } 3547 3548 if (!tcp_is_sackfrto(tp)) { 3549 /* RFC4138 shortcoming in step 2; should also have case c): 3550 * ACK isn't duplicate nor advances window, e.g., opposite dir 3551 * data, winupdate 3552 */ 3553 if (!(flag & FLAG_ANY_PROGRESS) && (flag & FLAG_NOT_DUP)) 3554 return 1; 3555 3556 if (!(flag & FLAG_DATA_ACKED)) { 3557 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3), 3558 flag); 3559 return 1; 3560 } 3561 } else { 3562 if (!(flag & FLAG_DATA_ACKED) && (tp->frto_counter == 1)) { 3563 /* Prevent sending of new data. */ 3564 tp->snd_cwnd = min(tp->snd_cwnd, 3565 tcp_packets_in_flight(tp)); 3566 return 1; 3567 } 3568 3569 if ((tp->frto_counter >= 2) && 3570 (!(flag & FLAG_FORWARD_PROGRESS) || 3571 ((flag & FLAG_DATA_SACKED) && 3572 !(flag & FLAG_ONLY_ORIG_SACKED)))) { 3573 /* RFC4138 shortcoming (see comment above) */ 3574 if (!(flag & FLAG_FORWARD_PROGRESS) && 3575 (flag & FLAG_NOT_DUP)) 3576 return 1; 3577 3578 tcp_enter_frto_loss(sk, 3, flag); 3579 return 1; 3580 } 3581 } 3582 3583 if (tp->frto_counter == 1) { 3584 /* tcp_may_send_now needs to see updated state */ 3585 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; 3586 tp->frto_counter = 2; 3587 3588 if (!tcp_may_send_now(sk)) 3589 tcp_enter_frto_loss(sk, 2, flag); 3590 3591 return 1; 3592 } else { 3593 switch (sysctl_tcp_frto_response) { 3594 case 2: 3595 tcp_undo_spur_to_response(sk, flag); 3596 break; 3597 case 1: 3598 tcp_conservative_spur_to_response(tp); 3599 break; 3600 default: 3601 tcp_ratehalving_spur_to_response(sk); 3602 break; 3603 } 3604 tp->frto_counter = 0; 3605 tp->undo_marker = 0; 3606 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSPURIOUSRTOS); 3607 } 3608 return 0; 3609} 3610 3611/* This routine deals with incoming acks, but not outgoing ones. */ 3612static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) 3613{ 3614 struct inet_connection_sock *icsk = inet_csk(sk); 3615 struct tcp_sock *tp = tcp_sk(sk); 3616 u32 prior_snd_una = tp->snd_una; 3617 u32 ack_seq = TCP_SKB_CB(skb)->seq; 3618 u32 ack = TCP_SKB_CB(skb)->ack_seq; 3619 u32 prior_in_flight; 3620 u32 prior_fackets; 3621 int prior_packets; 3622 int frto_cwnd = 0; 3623 3624 /* If the ack is older than previous acks 3625 * then we can probably ignore it. 3626 */ 3627 if (before(ack, prior_snd_una)) 3628 goto old_ack; 3629 3630 /* If the ack includes data we haven't sent yet, discard 3631 * this segment (RFC793 Section 3.9). 3632 */ 3633 if (after(ack, tp->snd_nxt)) 3634 goto invalid_ack; 3635 3636 if (after(ack, prior_snd_una)) 3637 flag |= FLAG_SND_UNA_ADVANCED; 3638 3639 if (sysctl_tcp_abc) { 3640 if (icsk->icsk_ca_state < TCP_CA_CWR) 3641 tp->bytes_acked += ack - prior_snd_una; 3642 else if (icsk->icsk_ca_state == TCP_CA_Loss) 3643 /* we assume just one segment left network */ 3644 tp->bytes_acked += min(ack - prior_snd_una, 3645 tp->mss_cache); 3646 } 3647 3648 prior_fackets = tp->fackets_out; 3649 prior_in_flight = tcp_packets_in_flight(tp); 3650 3651 if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) { 3652 /* Window is constant, pure forward advance. 3653 * No more checks are required. 3654 * Note, we use the fact that SND.UNA>=SND.WL2. 3655 */ 3656 tcp_update_wl(tp, ack_seq); 3657 tp->snd_una = ack; 3658 flag |= FLAG_WIN_UPDATE; 3659 3660 tcp_ca_event(sk, CA_EVENT_FAST_ACK); 3661 3662 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS); 3663 } else { 3664 if (ack_seq != TCP_SKB_CB(skb)->end_seq) 3665 flag |= FLAG_DATA; 3666 else 3667 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPUREACKS); 3668 3669 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq); 3670 3671 if (TCP_SKB_CB(skb)->sacked) 3672 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); 3673 3674 if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) 3675 flag |= FLAG_ECE; 3676 3677 tcp_ca_event(sk, CA_EVENT_SLOW_ACK); 3678 } 3679 3680 /* We passed data and got it acked, remove any soft error 3681 * log. Something worked... 3682 */ 3683 sk->sk_err_soft = 0; 3684 icsk->icsk_probes_out = 0; 3685 tp->rcv_tstamp = tcp_time_stamp; 3686 prior_packets = tp->packets_out; 3687 if (!prior_packets) 3688 goto no_queue; 3689 3690 /* See if we can take anything off of the retransmit queue. */ 3691 flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una); 3692 3693 if (tp->frto_counter) 3694 frto_cwnd = tcp_process_frto(sk, flag); 3695 /* Guarantee sacktag reordering detection against wrap-arounds */ 3696 if (before(tp->frto_highmark, tp->snd_una)) 3697 tp->frto_highmark = 0; 3698 3699 if (tcp_ack_is_dubious(sk, flag)) { 3700 /* Advance CWND, if state allows this. */ 3701 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd && 3702 tcp_may_raise_cwnd(sk, flag)) 3703 tcp_cong_avoid(sk, ack, prior_in_flight); 3704 tcp_fastretrans_alert(sk, prior_packets - tp->packets_out, 3705 flag); 3706 } else { 3707 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd) 3708 tcp_cong_avoid(sk, ack, prior_in_flight); 3709 } 3710 3711 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) 3712 dst_confirm(sk->sk_dst_cache); 3713 3714 return 1; 3715 3716no_queue: 3717 /* If this ack opens up a zero window, clear backoff. It was 3718 * being used to time the probes, and is probably far higher than 3719 * it needs to be for normal retransmission. 3720 */ 3721 if (tcp_send_head(sk)) 3722 tcp_ack_probe(sk); 3723 return 1; 3724 3725invalid_ack: 3726 SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt); 3727 return -1; 3728 3729old_ack: 3730 if (TCP_SKB_CB(skb)->sacked) { 3731 tcp_sacktag_write_queue(sk, skb, prior_snd_una); 3732 if (icsk->icsk_ca_state == TCP_CA_Open) 3733 tcp_try_keep_open(sk); 3734 } 3735 3736 SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt); 3737 return 0; 3738} 3739 3740/* Look for tcp options. Normally only called on SYN and SYNACK packets. 3741 * But, this can also be called on packets in the established flow when 3742 * the fast version below fails. 3743 */ 3744void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, 3745 u8 **hvpp, int estab) 3746{ 3747 unsigned char *ptr; 3748 struct tcphdr *th = tcp_hdr(skb); 3749 int length = (th->doff * 4) - sizeof(struct tcphdr); 3750 3751 ptr = (unsigned char *)(th + 1); 3752 opt_rx->saw_tstamp = 0; 3753 3754 while (length > 0) { 3755 int opcode = *ptr++; 3756 int opsize; 3757 3758 switch (opcode) { 3759 case TCPOPT_EOL: 3760 return; 3761 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ 3762 length--; 3763 continue; 3764 default: 3765 opsize = *ptr++; 3766 if (opsize < 2) /* "silly options" */ 3767 return; 3768 if (opsize > length) 3769 return; /* don't parse partial options */ 3770 switch (opcode) { 3771 case TCPOPT_MSS: 3772 if (opsize == TCPOLEN_MSS && th->syn && !estab) { 3773 u16 in_mss = get_unaligned_be16(ptr); 3774 if (in_mss) { 3775 if (opt_rx->user_mss && 3776 opt_rx->user_mss < in_mss) 3777 in_mss = opt_rx->user_mss; 3778 opt_rx->mss_clamp = in_mss; 3779 } 3780 } 3781 break; 3782 case TCPOPT_WINDOW: 3783 if (opsize == TCPOLEN_WINDOW && th->syn && 3784 !estab && sysctl_tcp_window_scaling) { 3785 __u8 snd_wscale = *(__u8 *)ptr; 3786 opt_rx->wscale_ok = 1; 3787 if (snd_wscale > 14) { 3788 if (net_ratelimit()) 3789 printk(KERN_INFO "tcp_parse_options: Illegal window " 3790 "scaling value %d >14 received.\n", 3791 snd_wscale); 3792 snd_wscale = 14; 3793 } 3794 opt_rx->snd_wscale = snd_wscale; 3795 } 3796 break; 3797 case TCPOPT_TIMESTAMP: 3798 if ((opsize == TCPOLEN_TIMESTAMP) && 3799 ((estab && opt_rx->tstamp_ok) || 3800 (!estab && sysctl_tcp_timestamps))) { 3801 opt_rx->saw_tstamp = 1; 3802 opt_rx->rcv_tsval = get_unaligned_be32(ptr); 3803 opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4); 3804 } 3805 break; 3806 case TCPOPT_SACK_PERM: 3807 if (opsize == TCPOLEN_SACK_PERM && th->syn && 3808 !estab && sysctl_tcp_sack) { 3809 opt_rx->sack_ok = 1; 3810 tcp_sack_reset(opt_rx); 3811 } 3812 break; 3813 3814 case TCPOPT_SACK: 3815 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && 3816 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && 3817 opt_rx->sack_ok) { 3818 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; 3819 } 3820 break; 3821#ifdef CONFIG_TCP_MD5SIG 3822 case TCPOPT_MD5SIG: 3823 /* 3824 * The MD5 Hash has already been 3825 * checked (see tcp_v{4,6}_do_rcv()). 3826 */ 3827 break; 3828#endif 3829 case TCPOPT_COOKIE: 3830 /* This option is variable length. 3831 */ 3832 switch (opsize) { 3833 case TCPOLEN_COOKIE_BASE: 3834 /* not yet implemented */ 3835 break; 3836 case TCPOLEN_COOKIE_PAIR: 3837 /* not yet implemented */ 3838 break; 3839 case TCPOLEN_COOKIE_MIN+0: 3840 case TCPOLEN_COOKIE_MIN+2: 3841 case TCPOLEN_COOKIE_MIN+4: 3842 case TCPOLEN_COOKIE_MIN+6: 3843 case TCPOLEN_COOKIE_MAX: 3844 /* 16-bit multiple */ 3845 opt_rx->cookie_plus = opsize; 3846 *hvpp = ptr; 3847 default: 3848 /* ignore option */ 3849 break; 3850 }; 3851 break; 3852 }; 3853 3854 ptr += opsize-2; 3855 length -= opsize; 3856 } 3857 } 3858} 3859 3860static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, struct tcphdr *th) 3861{ 3862 __be32 *ptr = (__be32 *)(th + 1); 3863 3864 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) 3865 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { 3866 tp->rx_opt.saw_tstamp = 1; 3867 ++ptr; 3868 tp->rx_opt.rcv_tsval = ntohl(*ptr); 3869 ++ptr; 3870 tp->rx_opt.rcv_tsecr = ntohl(*ptr); 3871 return 1; 3872 } 3873 return 0; 3874} 3875 3876/* Fast parse options. This hopes to only see timestamps. 3877 * If it is wrong it falls back on tcp_parse_options(). 3878 */ 3879static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th, 3880 struct tcp_sock *tp, u8 **hvpp) 3881{ 3882 /* In the spirit of fast parsing, compare doff directly to constant 3883 * values. Because equality is used, short doff can be ignored here. 3884 */ 3885 if (th->doff == (sizeof(*th) / 4)) { 3886 tp->rx_opt.saw_tstamp = 0; 3887 return 0; 3888 } else if (tp->rx_opt.tstamp_ok && 3889 th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) { 3890 if (tcp_parse_aligned_timestamp(tp, th)) 3891 return 1; 3892 } 3893 tcp_parse_options(skb, &tp->rx_opt, hvpp, 1); 3894 return 1; 3895} 3896 3897#ifdef CONFIG_TCP_MD5SIG 3898/* 3899 * Parse MD5 Signature option 3900 */ 3901u8 *tcp_parse_md5sig_option(struct tcphdr *th) 3902{ 3903 int length = (th->doff << 2) - sizeof (*th); 3904 u8 *ptr = (u8*)(th + 1); 3905 3906 /* If the TCP option is too short, we can short cut */ 3907 if (length < TCPOLEN_MD5SIG) 3908 return NULL; 3909 3910 while (length > 0) { 3911 int opcode = *ptr++; 3912 int opsize; 3913 3914 switch(opcode) { 3915 case TCPOPT_EOL: 3916 return NULL; 3917 case TCPOPT_NOP: 3918 length--; 3919 continue; 3920 default: 3921 opsize = *ptr++; 3922 if (opsize < 2 || opsize > length) 3923 return NULL; 3924 if (opcode == TCPOPT_MD5SIG) 3925 return ptr; 3926 } 3927 ptr += opsize - 2; 3928 length -= opsize; 3929 } 3930 return NULL; 3931} 3932#endif 3933 3934static inline void tcp_store_ts_recent(struct tcp_sock *tp) 3935{ 3936 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; 3937 tp->rx_opt.ts_recent_stamp = get_seconds(); 3938} 3939 3940static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) 3941{ 3942 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { 3943 /* PAWS bug workaround wrt. ACK frames, the PAWS discard 3944 * extra check below makes sure this can only happen 3945 * for pure ACK frames. -DaveM 3946 * 3947 * Not only, also it occurs for expired timestamps. 3948 */ 3949 3950 if (tcp_paws_check(&tp->rx_opt, 0)) 3951 tcp_store_ts_recent(tp); 3952 } 3953} 3954 3955/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM 3956 * 3957 * It is not fatal. If this ACK does _not_ change critical state (seqs, window) 3958 * it can pass through stack. So, the following predicate verifies that 3959 * this segment is not used for anything but congestion avoidance or 3960 * fast retransmit. Moreover, we even are able to eliminate most of such 3961 * second order effects, if we apply some small "replay" window (~RTO) 3962 * to timestamp space. 3963 * 3964 * All these measures still do not guarantee that we reject wrapped ACKs 3965 * on networks with high bandwidth, when sequence space is recycled fastly, 3966 * but it guarantees that such events will be very rare and do not affect 3967 * connection seriously. This doesn't look nice, but alas, PAWS is really 3968 * buggy extension. 3969 * 3970 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC 3971 * states that events when retransmit arrives after original data are rare. 3972 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is 3973 * the biggest problem on large power networks even with minor reordering. 3974 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe 3975 * up to bandwidth of 18Gigabit/sec. 8) ] 3976 */ 3977 3978static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb) 3979{ 3980 struct tcp_sock *tp = tcp_sk(sk); 3981 struct tcphdr *th = tcp_hdr(skb); 3982 u32 seq = TCP_SKB_CB(skb)->seq; 3983 u32 ack = TCP_SKB_CB(skb)->ack_seq; 3984 3985 return (/* 1. Pure ACK with correct sequence number. */ 3986 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && 3987 3988 /* 2. ... and duplicate ACK. */ 3989 ack == tp->snd_una && 3990 3991 /* 3. ... and does not update window. */ 3992 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && 3993 3994 /* 4. ... and sits in replay window. */ 3995 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ); 3996} 3997 3998static inline int tcp_paws_discard(const struct sock *sk, 3999 const struct sk_buff *skb) 4000{ 4001 const struct tcp_sock *tp = tcp_sk(sk); 4002 4003 return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) && 4004 !tcp_disordered_ack(sk, skb); 4005} 4006 4007/* Check segment sequence number for validity. 4008 * 4009 * Segment controls are considered valid, if the segment 4010 * fits to the window after truncation to the window. Acceptability 4011 * of data (and SYN, FIN, of course) is checked separately. 4012 * See tcp_data_queue(), for example. 4013 * 4014 * Also, controls (RST is main one) are accepted using RCV.WUP instead 4015 * of RCV.NXT. Peer still did not advance his SND.UNA when we 4016 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. 4017 * (borrowed from freebsd) 4018 */ 4019 4020static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq) 4021{ 4022 return !before(end_seq, tp->rcv_wup) && 4023 !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); 4024} 4025 4026/* When we get a reset we do this. */ 4027static void tcp_reset(struct sock *sk) 4028{ 4029 /* We want the right error as BSD sees it (and indeed as we do). */ 4030 switch (sk->sk_state) { 4031 case TCP_SYN_SENT: 4032 sk->sk_err = ECONNREFUSED; 4033 break; 4034 case TCP_CLOSE_WAIT: 4035 sk->sk_err = EPIPE; 4036 break; 4037 case TCP_CLOSE: 4038 return; 4039 default: 4040 sk->sk_err = ECONNRESET; 4041 } 4042 4043 if (!sock_flag(sk, SOCK_DEAD)) 4044 sk->sk_error_report(sk); 4045 4046 tcp_done(sk); 4047} 4048 4049/* 4050 * Process the FIN bit. This now behaves as it is supposed to work 4051 * and the FIN takes effect when it is validly part of sequence 4052 * space. Not before when we get holes. 4053 * 4054 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT 4055 * (and thence onto LAST-ACK and finally, CLOSE, we never enter 4056 * TIME-WAIT) 4057 * 4058 * If we are in FINWAIT-1, a received FIN indicates simultaneous 4059 * close and we go into CLOSING (and later onto TIME-WAIT) 4060 * 4061 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. 4062 */ 4063static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th) 4064{ 4065 struct tcp_sock *tp = tcp_sk(sk); 4066 4067 inet_csk_schedule_ack(sk); 4068 4069 sk->sk_shutdown |= RCV_SHUTDOWN; 4070 sock_set_flag(sk, SOCK_DONE); 4071 4072 switch (sk->sk_state) { 4073 case TCP_SYN_RECV: 4074 case TCP_ESTABLISHED: 4075 /* Move to CLOSE_WAIT */ 4076 tcp_set_state(sk, TCP_CLOSE_WAIT); 4077 inet_csk(sk)->icsk_ack.pingpong = 1; 4078 break; 4079 4080 case TCP_CLOSE_WAIT: 4081 case TCP_CLOSING: 4082 /* Received a retransmission of the FIN, do 4083 * nothing. 4084 */ 4085 break; 4086 case TCP_LAST_ACK: 4087 /* RFC793: Remain in the LAST-ACK state. */ 4088 break; 4089 4090 case TCP_FIN_WAIT1: 4091 /* This case occurs when a simultaneous close 4092 * happens, we must ack the received FIN and 4093 * enter the CLOSING state. 4094 */ 4095 tcp_send_ack(sk); 4096 tcp_set_state(sk, TCP_CLOSING); 4097 break; 4098 case TCP_FIN_WAIT2: 4099 /* Received a FIN -- send ACK and enter TIME_WAIT. */ 4100 tcp_send_ack(sk); 4101 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 4102 break; 4103 default: 4104 /* Only TCP_LISTEN and TCP_CLOSE are left, in these 4105 * cases we should never reach this piece of code. 4106 */ 4107 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n", 4108 __func__, sk->sk_state); 4109 break; 4110 } 4111 4112 /* It _is_ possible, that we have something out-of-order _after_ FIN. 4113 * Probably, we should reset in this case. For now drop them. 4114 */ 4115 __skb_queue_purge(&tp->out_of_order_queue); 4116 if (tcp_is_sack(tp)) 4117 tcp_sack_reset(&tp->rx_opt); 4118 sk_mem_reclaim(sk); 4119 4120 if (!sock_flag(sk, SOCK_DEAD)) { 4121 sk->sk_state_change(sk); 4122 4123 /* Do not send POLL_HUP for half duplex close. */ 4124 if (sk->sk_shutdown == SHUTDOWN_MASK || 4125 sk->sk_state == TCP_CLOSE) 4126 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP); 4127 else 4128 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); 4129 } 4130} 4131 4132static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, 4133 u32 end_seq) 4134{ 4135 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { 4136 if (before(seq, sp->start_seq)) 4137 sp->start_seq = seq; 4138 if (after(end_seq, sp->end_seq)) 4139 sp->end_seq = end_seq; 4140 return 1; 4141 } 4142 return 0; 4143} 4144 4145static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq) 4146{ 4147 struct tcp_sock *tp = tcp_sk(sk); 4148 4149 if (tcp_is_sack(tp) && sysctl_tcp_dsack) { 4150 int mib_idx; 4151 4152 if (before(seq, tp->rcv_nxt)) 4153 mib_idx = LINUX_MIB_TCPDSACKOLDSENT; 4154 else 4155 mib_idx = LINUX_MIB_TCPDSACKOFOSENT; 4156 4157 NET_INC_STATS_BH(sock_net(sk), mib_idx); 4158 4159 tp->rx_opt.dsack = 1; 4160 tp->duplicate_sack[0].start_seq = seq; 4161 tp->duplicate_sack[0].end_seq = end_seq; 4162 } 4163} 4164 4165static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq) 4166{ 4167 struct tcp_sock *tp = tcp_sk(sk); 4168 4169 if (!tp->rx_opt.dsack) 4170 tcp_dsack_set(sk, seq, end_seq); 4171 else 4172 tcp_sack_extend(tp->duplicate_sack, seq, end_seq); 4173} 4174 4175static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb) 4176{ 4177 struct tcp_sock *tp = tcp_sk(sk); 4178 4179 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 4180 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4181 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); 4182 tcp_enter_quickack_mode(sk); 4183 4184 if (tcp_is_sack(tp) && sysctl_tcp_dsack) { 4185 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 4186 4187 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) 4188 end_seq = tp->rcv_nxt; 4189 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq); 4190 } 4191 } 4192 4193 tcp_send_ack(sk); 4194} 4195 4196/* These routines update the SACK block as out-of-order packets arrive or 4197 * in-order packets close up the sequence space. 4198 */ 4199static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) 4200{ 4201 int this_sack; 4202 struct tcp_sack_block *sp = &tp->selective_acks[0]; 4203 struct tcp_sack_block *swalk = sp + 1; 4204 4205 /* See if the recent change to the first SACK eats into 4206 * or hits the sequence space of other SACK blocks, if so coalesce. 4207 */ 4208 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) { 4209 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { 4210 int i; 4211 4212 /* Zap SWALK, by moving every further SACK up by one slot. 4213 * Decrease num_sacks. 4214 */ 4215 tp->rx_opt.num_sacks--; 4216 for (i = this_sack; i < tp->rx_opt.num_sacks; i++) 4217 sp[i] = sp[i + 1]; 4218 continue; 4219 } 4220 this_sack++, swalk++; 4221 } 4222} 4223 4224static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) 4225{ 4226 struct tcp_sock *tp = tcp_sk(sk); 4227 struct tcp_sack_block *sp = &tp->selective_acks[0]; 4228 int cur_sacks = tp->rx_opt.num_sacks; 4229 int this_sack; 4230 4231 if (!cur_sacks) 4232 goto new_sack; 4233 4234 for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) { 4235 if (tcp_sack_extend(sp, seq, end_seq)) { 4236 /* Rotate this_sack to the first one. */ 4237 for (; this_sack > 0; this_sack--, sp--) 4238 swap(*sp, *(sp - 1)); 4239 if (cur_sacks > 1) 4240 tcp_sack_maybe_coalesce(tp); 4241 return; 4242 } 4243 } 4244 4245 /* Could not find an adjacent existing SACK, build a new one, 4246 * put it at the front, and shift everyone else down. We 4247 * always know there is at least one SACK present already here. 4248 * 4249 * If the sack array is full, forget about the last one. 4250 */ 4251 if (this_sack >= TCP_NUM_SACKS) { 4252 this_sack--; 4253 tp->rx_opt.num_sacks--; 4254 sp--; 4255 } 4256 for (; this_sack > 0; this_sack--, sp--) 4257 *sp = *(sp - 1); 4258 4259new_sack: 4260 /* Build the new head SACK, and we're done. */ 4261 sp->start_seq = seq; 4262 sp->end_seq = end_seq; 4263 tp->rx_opt.num_sacks++; 4264} 4265 4266/* RCV.NXT advances, some SACKs should be eaten. */ 4267 4268static void tcp_sack_remove(struct tcp_sock *tp) 4269{ 4270 struct tcp_sack_block *sp = &tp->selective_acks[0]; 4271 int num_sacks = tp->rx_opt.num_sacks; 4272 int this_sack; 4273 4274 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ 4275 if (skb_queue_empty(&tp->out_of_order_queue)) { 4276 tp->rx_opt.num_sacks = 0; 4277 return; 4278 } 4279 4280 for (this_sack = 0; this_sack < num_sacks;) { 4281 /* Check if the start of the sack is covered by RCV.NXT. */ 4282 if (!before(tp->rcv_nxt, sp->start_seq)) { 4283 int i; 4284 4285 /* RCV.NXT must cover all the block! */ 4286 WARN_ON(before(tp->rcv_nxt, sp->end_seq)); 4287 4288 /* Zap this SACK, by moving forward any other SACKS. */ 4289 for (i=this_sack+1; i < num_sacks; i++) 4290 tp->selective_acks[i-1] = tp->selective_acks[i]; 4291 num_sacks--; 4292 continue; 4293 } 4294 this_sack++; 4295 sp++; 4296 } 4297 tp->rx_opt.num_sacks = num_sacks; 4298} 4299 4300/* This one checks to see if we can put data from the 4301 * out_of_order queue into the receive_queue. 4302 */ 4303static void tcp_ofo_queue(struct sock *sk) 4304{ 4305 struct tcp_sock *tp = tcp_sk(sk); 4306 __u32 dsack_high = tp->rcv_nxt; 4307 struct sk_buff *skb; 4308 4309 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { 4310 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 4311 break; 4312 4313 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { 4314 __u32 dsack = dsack_high; 4315 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) 4316 dsack_high = TCP_SKB_CB(skb)->end_seq; 4317 tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack); 4318 } 4319 4320 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 4321 SOCK_DEBUG(sk, "ofo packet was already received\n"); 4322 __skb_unlink(skb, &tp->out_of_order_queue); 4323 __kfree_skb(skb); 4324 continue; 4325 } 4326 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", 4327 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 4328 TCP_SKB_CB(skb)->end_seq); 4329 4330 __skb_unlink(skb, &tp->out_of_order_queue); 4331 __skb_queue_tail(&sk->sk_receive_queue, skb); 4332 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4333 if (tcp_hdr(skb)->fin) 4334 tcp_fin(skb, sk, tcp_hdr(skb)); 4335 } 4336} 4337 4338static int tcp_prune_ofo_queue(struct sock *sk); 4339static int tcp_prune_queue(struct sock *sk); 4340 4341static inline int tcp_try_rmem_schedule(struct sock *sk, unsigned int size) 4342{ 4343 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || 4344 !sk_rmem_schedule(sk, size)) { 4345 4346 if (tcp_prune_queue(sk) < 0) 4347 return -1; 4348 4349 if (!sk_rmem_schedule(sk, size)) { 4350 if (!tcp_prune_ofo_queue(sk)) 4351 return -1; 4352 4353 if (!sk_rmem_schedule(sk, size)) 4354 return -1; 4355 } 4356 } 4357 return 0; 4358} 4359 4360static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) 4361{ 4362 struct tcphdr *th = tcp_hdr(skb); 4363 struct tcp_sock *tp = tcp_sk(sk); 4364 int eaten = -1; 4365 4366 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) 4367 goto drop; 4368 4369 __skb_pull(skb, th->doff * 4); 4370 4371 TCP_ECN_accept_cwr(tp, skb); 4372 4373 tp->rx_opt.dsack = 0; 4374 4375 /* Queue data for delivery to the user. 4376 * Packets in sequence go to the receive queue. 4377 * Out of sequence packets to the out_of_order_queue. 4378 */ 4379 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { 4380 if (tcp_receive_window(tp) == 0) 4381 goto out_of_window; 4382 4383 /* Ok. In sequence. In window. */ 4384 if (tp->ucopy.task == current && 4385 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && 4386 sock_owned_by_user(sk) && !tp->urg_data) { 4387 int chunk = min_t(unsigned int, skb->len, 4388 tp->ucopy.len); 4389 4390 __set_current_state(TASK_RUNNING); 4391 4392 local_bh_enable(); 4393 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { 4394 tp->ucopy.len -= chunk; 4395 tp->copied_seq += chunk; 4396 eaten = (chunk == skb->len && !th->fin); 4397 tcp_rcv_space_adjust(sk); 4398 } 4399 local_bh_disable(); 4400 } 4401 4402 if (eaten <= 0) { 4403queue_and_out: 4404 if (eaten < 0 && 4405 tcp_try_rmem_schedule(sk, skb->truesize)) 4406 goto drop; 4407 4408 skb_set_owner_r(skb, sk); 4409 __skb_queue_tail(&sk->sk_receive_queue, skb); 4410 } 4411 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4412 if (skb->len) 4413 tcp_event_data_recv(sk, skb); 4414 if (th->fin) 4415 tcp_fin(skb, sk, th); 4416 4417 if (!skb_queue_empty(&tp->out_of_order_queue)) { 4418 tcp_ofo_queue(sk); 4419 4420 /* RFC2581. 4.2. SHOULD send immediate ACK, when 4421 * gap in queue is filled. 4422 */ 4423 if (skb_queue_empty(&tp->out_of_order_queue)) 4424 inet_csk(sk)->icsk_ack.pingpong = 0; 4425 } 4426 4427 if (tp->rx_opt.num_sacks) 4428 tcp_sack_remove(tp); 4429 4430 tcp_fast_path_check(sk); 4431 4432 if (eaten > 0) 4433 __kfree_skb(skb); 4434 else if (!sock_flag(sk, SOCK_DEAD)) 4435 sk->sk_data_ready(sk, 0); 4436 return; 4437 } 4438 4439 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 4440 /* A retransmit, 2nd most common case. Force an immediate ack. */ 4441 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); 4442 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 4443 4444out_of_window: 4445 tcp_enter_quickack_mode(sk); 4446 inet_csk_schedule_ack(sk); 4447drop: 4448 __kfree_skb(skb); 4449 return; 4450 } 4451 4452 /* Out of window. F.e. zero window probe. */ 4453 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) 4454 goto out_of_window; 4455 4456 tcp_enter_quickack_mode(sk); 4457 4458 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4459 /* Partial packet, seq < rcv_next < end_seq */ 4460 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", 4461 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 4462 TCP_SKB_CB(skb)->end_seq); 4463 4464 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); 4465 4466 /* If window is closed, drop tail of packet. But after 4467 * remembering D-SACK for its head made in previous line. 4468 */ 4469 if (!tcp_receive_window(tp)) 4470 goto out_of_window; 4471 goto queue_and_out; 4472 } 4473 4474 TCP_ECN_check_ce(tp, skb); 4475 4476 if (tcp_try_rmem_schedule(sk, skb->truesize)) 4477 goto drop; 4478 4479 /* Disable header prediction. */ 4480 tp->pred_flags = 0; 4481 inet_csk_schedule_ack(sk); 4482 4483 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", 4484 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 4485 4486 skb_set_owner_r(skb, sk); 4487 4488 if (!skb_peek(&tp->out_of_order_queue)) { 4489 /* Initial out of order segment, build 1 SACK. */ 4490 if (tcp_is_sack(tp)) { 4491 tp->rx_opt.num_sacks = 1; 4492 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; 4493 tp->selective_acks[0].end_seq = 4494 TCP_SKB_CB(skb)->end_seq; 4495 } 4496 __skb_queue_head(&tp->out_of_order_queue, skb); 4497 } else { 4498 struct sk_buff *skb1 = skb_peek_tail(&tp->out_of_order_queue); 4499 u32 seq = TCP_SKB_CB(skb)->seq; 4500 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 4501 4502 if (seq == TCP_SKB_CB(skb1)->end_seq) { 4503 __skb_queue_after(&tp->out_of_order_queue, skb1, skb); 4504 4505 if (!tp->rx_opt.num_sacks || 4506 tp->selective_acks[0].end_seq != seq) 4507 goto add_sack; 4508 4509 /* Common case: data arrive in order after hole. */ 4510 tp->selective_acks[0].end_seq = end_seq; 4511 return; 4512 } 4513 4514 /* Find place to insert this segment. */ 4515 while (1) { 4516 if (!after(TCP_SKB_CB(skb1)->seq, seq)) 4517 break; 4518 if (skb_queue_is_first(&tp->out_of_order_queue, skb1)) { 4519 skb1 = NULL; 4520 break; 4521 } 4522 skb1 = skb_queue_prev(&tp->out_of_order_queue, skb1); 4523 } 4524 4525 /* Do skb overlap to previous one? */ 4526 if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) { 4527 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 4528 /* All the bits are present. Drop. */ 4529 __kfree_skb(skb); 4530 tcp_dsack_set(sk, seq, end_seq); 4531 goto add_sack; 4532 } 4533 if (after(seq, TCP_SKB_CB(skb1)->seq)) { 4534 /* Partial overlap. */ 4535 tcp_dsack_set(sk, seq, 4536 TCP_SKB_CB(skb1)->end_seq); 4537 } else { 4538 if (skb_queue_is_first(&tp->out_of_order_queue, 4539 skb1)) 4540 skb1 = NULL; 4541 else 4542 skb1 = skb_queue_prev( 4543 &tp->out_of_order_queue, 4544 skb1); 4545 } 4546 } 4547 if (!skb1) 4548 __skb_queue_head(&tp->out_of_order_queue, skb); 4549 else 4550 __skb_queue_after(&tp->out_of_order_queue, skb1, skb); 4551 4552 /* And clean segments covered by new one as whole. */ 4553 while (!skb_queue_is_last(&tp->out_of_order_queue, skb)) { 4554 skb1 = skb_queue_next(&tp->out_of_order_queue, skb); 4555 4556 if (!after(end_seq, TCP_SKB_CB(skb1)->seq)) 4557 break; 4558 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 4559 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, 4560 end_seq); 4561 break; 4562 } 4563 __skb_unlink(skb1, &tp->out_of_order_queue); 4564 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, 4565 TCP_SKB_CB(skb1)->end_seq); 4566 __kfree_skb(skb1); 4567 } 4568 4569add_sack: 4570 if (tcp_is_sack(tp)) 4571 tcp_sack_new_ofo_skb(sk, seq, end_seq); 4572 } 4573} 4574 4575static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb, 4576 struct sk_buff_head *list) 4577{ 4578 struct sk_buff *next = NULL; 4579 4580 if (!skb_queue_is_last(list, skb)) 4581 next = skb_queue_next(list, skb); 4582 4583 __skb_unlink(skb, list); 4584 __kfree_skb(skb); 4585 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED); 4586 4587 return next; 4588} 4589 4590/* Collapse contiguous sequence of skbs head..tail with 4591 * sequence numbers start..end. 4592 * 4593 * If tail is NULL, this means until the end of the list. 4594 * 4595 * Segments with FIN/SYN are not collapsed (only because this 4596 * simplifies code) 4597 */ 4598static void 4599tcp_collapse(struct sock *sk, struct sk_buff_head *list, 4600 struct sk_buff *head, struct sk_buff *tail, 4601 u32 start, u32 end) 4602{ 4603 struct sk_buff *skb, *n; 4604 bool end_of_skbs; 4605 4606 /* First, check that queue is collapsible and find 4607 * the point where collapsing can be useful. */ 4608 skb = head; 4609restart: 4610 end_of_skbs = true; 4611 skb_queue_walk_from_safe(list, skb, n) { 4612 if (skb == tail) 4613 break; 4614 /* No new bits? It is possible on ofo queue. */ 4615 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 4616 skb = tcp_collapse_one(sk, skb, list); 4617 if (!skb) 4618 break; 4619 goto restart; 4620 } 4621 4622 /* The first skb to collapse is: 4623 * - not SYN/FIN and 4624 * - bloated or contains data before "start" or 4625 * overlaps to the next one. 4626 */ 4627 if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin && 4628 (tcp_win_from_space(skb->truesize) > skb->len || 4629 before(TCP_SKB_CB(skb)->seq, start))) { 4630 end_of_skbs = false; 4631 break; 4632 } 4633 4634 if (!skb_queue_is_last(list, skb)) { 4635 struct sk_buff *next = skb_queue_next(list, skb); 4636 if (next != tail && 4637 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(next)->seq) { 4638 end_of_skbs = false; 4639 break; 4640 } 4641 } 4642 4643 /* Decided to skip this, advance start seq. */ 4644 start = TCP_SKB_CB(skb)->end_seq; 4645 } 4646 if (end_of_skbs || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin) 4647 return; 4648 4649 while (before(start, end)) { 4650 struct sk_buff *nskb; 4651 unsigned int header = skb_headroom(skb); 4652 int copy = SKB_MAX_ORDER(header, 0); 4653 4654 /* Too big header? This can happen with IPv6. */ 4655 if (copy < 0) 4656 return; 4657 if (end - start < copy) 4658 copy = end - start; 4659 nskb = alloc_skb(copy + header, GFP_ATOMIC); 4660 if (!nskb) 4661 return; 4662 4663 skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head); 4664 skb_set_network_header(nskb, (skb_network_header(skb) - 4665 skb->head)); 4666 skb_set_transport_header(nskb, (skb_transport_header(skb) - 4667 skb->head)); 4668 skb_reserve(nskb, header); 4669 memcpy(nskb->head, skb->head, header); 4670 memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); 4671 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; 4672 __skb_queue_before(list, skb, nskb); 4673 skb_set_owner_r(nskb, sk); 4674 4675 /* Copy data, releasing collapsed skbs. */ 4676 while (copy > 0) { 4677 int offset = start - TCP_SKB_CB(skb)->seq; 4678 int size = TCP_SKB_CB(skb)->end_seq - start; 4679 4680 BUG_ON(offset < 0); 4681 if (size > 0) { 4682 size = min(copy, size); 4683 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) 4684 BUG(); 4685 TCP_SKB_CB(nskb)->end_seq += size; 4686 copy -= size; 4687 start += size; 4688 } 4689 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 4690 skb = tcp_collapse_one(sk, skb, list); 4691 if (!skb || 4692 skb == tail || 4693 tcp_hdr(skb)->syn || 4694 tcp_hdr(skb)->fin) 4695 return; 4696 } 4697 } 4698 } 4699} 4700 4701/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs 4702 * and tcp_collapse() them until all the queue is collapsed. 4703 */ 4704static void tcp_collapse_ofo_queue(struct sock *sk) 4705{ 4706 struct tcp_sock *tp = tcp_sk(sk); 4707 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); 4708 struct sk_buff *head; 4709 u32 start, end; 4710 4711 if (skb == NULL) 4712 return; 4713 4714 start = TCP_SKB_CB(skb)->seq; 4715 end = TCP_SKB_CB(skb)->end_seq; 4716 head = skb; 4717 4718 for (;;) { 4719 struct sk_buff *next = NULL; 4720 4721 if (!skb_queue_is_last(&tp->out_of_order_queue, skb)) 4722 next = skb_queue_next(&tp->out_of_order_queue, skb); 4723 skb = next; 4724 4725 /* Segment is terminated when we see gap or when 4726 * we are at the end of all the queue. */ 4727 if (!skb || 4728 after(TCP_SKB_CB(skb)->seq, end) || 4729 before(TCP_SKB_CB(skb)->end_seq, start)) { 4730 tcp_collapse(sk, &tp->out_of_order_queue, 4731 head, skb, start, end); 4732 head = skb; 4733 if (!skb) 4734 break; 4735 /* Start new segment */ 4736 start = TCP_SKB_CB(skb)->seq; 4737 end = TCP_SKB_CB(skb)->end_seq; 4738 } else { 4739 if (before(TCP_SKB_CB(skb)->seq, start)) 4740 start = TCP_SKB_CB(skb)->seq; 4741 if (after(TCP_SKB_CB(skb)->end_seq, end)) 4742 end = TCP_SKB_CB(skb)->end_seq; 4743 } 4744 } 4745} 4746 4747/* 4748 * Purge the out-of-order queue. 4749 * Return true if queue was pruned. 4750 */ 4751static int tcp_prune_ofo_queue(struct sock *sk) 4752{ 4753 struct tcp_sock *tp = tcp_sk(sk); 4754 int res = 0; 4755 4756 if (!skb_queue_empty(&tp->out_of_order_queue)) { 4757 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_OFOPRUNED); 4758 __skb_queue_purge(&tp->out_of_order_queue); 4759 4760 /* Reset SACK state. A conforming SACK implementation will 4761 * do the same at a timeout based retransmit. When a connection 4762 * is in a sad state like this, we care only about integrity 4763 * of the connection not performance. 4764 */ 4765 if (tp->rx_opt.sack_ok) 4766 tcp_sack_reset(&tp->rx_opt); 4767 sk_mem_reclaim(sk); 4768 res = 1; 4769 } 4770 return res; 4771} 4772 4773/* Reduce allocated memory if we can, trying to get 4774 * the socket within its memory limits again. 4775 * 4776 * Return less than zero if we should start dropping frames 4777 * until the socket owning process reads some of the data 4778 * to stabilize the situation. 4779 */ 4780static int tcp_prune_queue(struct sock *sk) 4781{ 4782 struct tcp_sock *tp = tcp_sk(sk); 4783 4784 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); 4785 4786 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PRUNECALLED); 4787 4788 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) 4789 tcp_clamp_window(sk); 4790 else if (tcp_memory_pressure) 4791 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); 4792 4793 tcp_collapse_ofo_queue(sk); 4794 if (!skb_queue_empty(&sk->sk_receive_queue)) 4795 tcp_collapse(sk, &sk->sk_receive_queue, 4796 skb_peek(&sk->sk_receive_queue), 4797 NULL, 4798 tp->copied_seq, tp->rcv_nxt); 4799 sk_mem_reclaim(sk); 4800 4801 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 4802 return 0; 4803 4804 /* Collapsing did not help, destructive actions follow. 4805 * This must not ever occur. */ 4806 4807 tcp_prune_ofo_queue(sk); 4808 4809 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 4810 return 0; 4811 4812 /* If we are really being abused, tell the caller to silently 4813 * drop receive data on the floor. It will get retransmitted 4814 * and hopefully then we'll have sufficient space. 4815 */ 4816 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_RCVPRUNED); 4817 4818 /* Massive buffer overcommit. */ 4819 tp->pred_flags = 0; 4820 return -1; 4821} 4822 4823/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. 4824 * As additional protections, we do not touch cwnd in retransmission phases, 4825 * and if application hit its sndbuf limit recently. 4826 */ 4827void tcp_cwnd_application_limited(struct sock *sk) 4828{ 4829 struct tcp_sock *tp = tcp_sk(sk); 4830 4831 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && 4832 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { 4833 /* Limited by application or receiver window. */ 4834 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); 4835 u32 win_used = max(tp->snd_cwnd_used, init_win); 4836 if (win_used < tp->snd_cwnd) { 4837 tp->snd_ssthresh = tcp_current_ssthresh(sk); 4838 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; 4839 } 4840 tp->snd_cwnd_used = 0; 4841 } 4842 tp->snd_cwnd_stamp = tcp_time_stamp; 4843} 4844 4845static int tcp_should_expand_sndbuf(struct sock *sk) 4846{ 4847 struct tcp_sock *tp = tcp_sk(sk); 4848 4849 /* If the user specified a specific send buffer setting, do 4850 * not modify it. 4851 */ 4852 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) 4853 return 0; 4854 4855 /* If we are under global TCP memory pressure, do not expand. */ 4856 if (tcp_memory_pressure) 4857 return 0; 4858 4859 /* If we are under soft global TCP memory pressure, do not expand. */ 4860 if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0]) 4861 return 0; 4862 4863 /* If we filled the congestion window, do not expand. */ 4864 if (tp->packets_out >= tp->snd_cwnd) 4865 return 0; 4866 4867 return 1; 4868} 4869 4870/* When incoming ACK allowed to free some skb from write_queue, 4871 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket 4872 * on the exit from tcp input handler. 4873 * 4874 * PROBLEM: sndbuf expansion does not work well with largesend. 4875 */ 4876static void tcp_new_space(struct sock *sk) 4877{ 4878 struct tcp_sock *tp = tcp_sk(sk); 4879 4880 if (tcp_should_expand_sndbuf(sk)) { 4881 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + 4882 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); 4883 int demanded = max_t(unsigned int, tp->snd_cwnd, 4884 tp->reordering + 1); 4885 sndmem *= 2 * demanded; 4886 if (sndmem > sk->sk_sndbuf) 4887 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); 4888 tp->snd_cwnd_stamp = tcp_time_stamp; 4889 } 4890 4891 sk->sk_write_space(sk); 4892} 4893 4894static void tcp_check_space(struct sock *sk) 4895{ 4896 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { 4897 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); 4898 if (sk->sk_socket && 4899 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) 4900 tcp_new_space(sk); 4901 } 4902} 4903 4904static inline void tcp_data_snd_check(struct sock *sk) 4905{ 4906 tcp_push_pending_frames(sk); 4907 tcp_check_space(sk); 4908} 4909 4910/* 4911 * Check if sending an ack is needed. 4912 */ 4913static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) 4914{ 4915 struct tcp_sock *tp = tcp_sk(sk); 4916 4917 /* More than one full frame received... */ 4918 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss && 4919 /* ... and right edge of window advances far enough. 4920 * (tcp_recvmsg() will send ACK otherwise). Or... 4921 */ 4922 __tcp_select_window(sk) >= tp->rcv_wnd) || 4923 /* We ACK each frame or... */ 4924 tcp_in_quickack_mode(sk) || 4925 /* We have out of order data. */ 4926 (ofo_possible && skb_peek(&tp->out_of_order_queue))) { 4927 /* Then ack it now */ 4928 tcp_send_ack(sk); 4929 } else { 4930 /* Else, send delayed ack. */ 4931 tcp_send_delayed_ack(sk); 4932 } 4933} 4934 4935static inline void tcp_ack_snd_check(struct sock *sk) 4936{ 4937 if (!inet_csk_ack_scheduled(sk)) { 4938 /* We sent a data segment already. */ 4939 return; 4940 } 4941 __tcp_ack_snd_check(sk, 1); 4942} 4943 4944/* 4945 * This routine is only called when we have urgent data 4946 * signaled. Its the 'slow' part of tcp_urg. It could be 4947 * moved inline now as tcp_urg is only called from one 4948 * place. We handle URGent data wrong. We have to - as 4949 * BSD still doesn't use the correction from RFC961. 4950 * For 1003.1g we should support a new option TCP_STDURG to permit 4951 * either form (or just set the sysctl tcp_stdurg). 4952 */ 4953 4954static void tcp_check_urg(struct sock *sk, struct tcphdr *th) 4955{ 4956 struct tcp_sock *tp = tcp_sk(sk); 4957 u32 ptr = ntohs(th->urg_ptr); 4958 4959 if (ptr && !sysctl_tcp_stdurg) 4960 ptr--; 4961 ptr += ntohl(th->seq); 4962 4963 /* Ignore urgent data that we've already seen and read. */ 4964 if (after(tp->copied_seq, ptr)) 4965 return; 4966 4967 /* Do not replay urg ptr. 4968 * 4969 * NOTE: interesting situation not covered by specs. 4970 * Misbehaving sender may send urg ptr, pointing to segment, 4971 * which we already have in ofo queue. We are not able to fetch 4972 * such data and will stay in TCP_URG_NOTYET until will be eaten 4973 * by recvmsg(). Seems, we are not obliged to handle such wicked 4974 * situations. But it is worth to think about possibility of some 4975 * DoSes using some hypothetical application level deadlock. 4976 */ 4977 if (before(ptr, tp->rcv_nxt)) 4978 return; 4979 4980 /* Do we already have a newer (or duplicate) urgent pointer? */ 4981 if (tp->urg_data && !after(ptr, tp->urg_seq)) 4982 return; 4983 4984 /* Tell the world about our new urgent pointer. */ 4985 sk_send_sigurg(sk); 4986 4987 /* We may be adding urgent data when the last byte read was 4988 * urgent. To do this requires some care. We cannot just ignore 4989 * tp->copied_seq since we would read the last urgent byte again 4990 * as data, nor can we alter copied_seq until this data arrives 4991 * or we break the semantics of SIOCATMARK (and thus sockatmark()) 4992 * 4993 * NOTE. Double Dutch. Rendering to plain English: author of comment 4994 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); 4995 * and expect that both A and B disappear from stream. This is _wrong_. 4996 * Though this happens in BSD with high probability, this is occasional. 4997 * Any application relying on this is buggy. Note also, that fix "works" 4998 * only in this artificial test. Insert some normal data between A and B and we will 4999 * decline of BSD again. Verdict: it is better to remove to trap 5000 * buggy users. 5001 */ 5002 if (tp->urg_seq == tp->copied_seq && tp->urg_data && 5003 !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) { 5004 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); 5005 tp->copied_seq++; 5006 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { 5007 __skb_unlink(skb, &sk->sk_receive_queue); 5008 __kfree_skb(skb); 5009 } 5010 } 5011 5012 tp->urg_data = TCP_URG_NOTYET; 5013 tp->urg_seq = ptr; 5014 5015 /* Disable header prediction. */ 5016 tp->pred_flags = 0; 5017} 5018 5019/* This is the 'fast' part of urgent handling. */ 5020static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th) 5021{ 5022 struct tcp_sock *tp = tcp_sk(sk); 5023 5024 /* Check if we get a new urgent pointer - normally not. */ 5025 if (th->urg) 5026 tcp_check_urg(sk, th); 5027 5028 /* Do we wait for any urgent data? - normally not... */ 5029 if (tp->urg_data == TCP_URG_NOTYET) { 5030 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - 5031 th->syn; 5032 5033 /* Is the urgent pointer pointing into this packet? */ 5034 if (ptr < skb->len) { 5035 u8 tmp; 5036 if (skb_copy_bits(skb, ptr, &tmp, 1)) 5037 BUG(); 5038 tp->urg_data = TCP_URG_VALID | tmp; 5039 if (!sock_flag(sk, SOCK_DEAD)) 5040 sk->sk_data_ready(sk, 0); 5041 } 5042 } 5043} 5044 5045static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) 5046{ 5047 struct tcp_sock *tp = tcp_sk(sk); 5048 int chunk = skb->len - hlen; 5049 int err; 5050 5051 local_bh_enable(); 5052 if (skb_csum_unnecessary(skb)) 5053 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); 5054 else 5055 err = skb_copy_and_csum_datagram_iovec(skb, hlen, 5056 tp->ucopy.iov); 5057 5058 if (!err) { 5059 tp->ucopy.len -= chunk; 5060 tp->copied_seq += chunk; 5061 tcp_rcv_space_adjust(sk); 5062 } 5063 5064 local_bh_disable(); 5065 return err; 5066} 5067 5068static __sum16 __tcp_checksum_complete_user(struct sock *sk, 5069 struct sk_buff *skb) 5070{ 5071 __sum16 result; 5072 5073 if (sock_owned_by_user(sk)) { 5074 local_bh_enable(); 5075 result = __tcp_checksum_complete(skb); 5076 local_bh_disable(); 5077 } else { 5078 result = __tcp_checksum_complete(skb); 5079 } 5080 return result; 5081} 5082 5083static inline int tcp_checksum_complete_user(struct sock *sk, 5084 struct sk_buff *skb) 5085{ 5086 return !skb_csum_unnecessary(skb) && 5087 __tcp_checksum_complete_user(sk, skb); 5088} 5089 5090#ifdef CONFIG_NET_DMA 5091static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, 5092 int hlen) 5093{ 5094 struct tcp_sock *tp = tcp_sk(sk); 5095 int chunk = skb->len - hlen; 5096 int dma_cookie; 5097 int copied_early = 0; 5098 5099 if (tp->ucopy.wakeup) 5100 return 0; 5101 5102 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list) 5103 tp->ucopy.dma_chan = dma_find_channel(DMA_MEMCPY); 5104 5105 if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) { 5106 5107 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan, 5108 skb, hlen, 5109 tp->ucopy.iov, chunk, 5110 tp->ucopy.pinned_list); 5111 5112 if (dma_cookie < 0) 5113 goto out; 5114 5115 tp->ucopy.dma_cookie = dma_cookie; 5116 copied_early = 1; 5117 5118 tp->ucopy.len -= chunk; 5119 tp->copied_seq += chunk; 5120 tcp_rcv_space_adjust(sk); 5121 5122 if ((tp->ucopy.len == 0) || 5123 (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) || 5124 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) { 5125 tp->ucopy.wakeup = 1; 5126 sk->sk_data_ready(sk, 0); 5127 } 5128 } else if (chunk > 0) { 5129 tp->ucopy.wakeup = 1; 5130 sk->sk_data_ready(sk, 0); 5131 } 5132out: 5133 return copied_early; 5134} 5135#endif /* CONFIG_NET_DMA */ 5136 5137/* Does PAWS and seqno based validation of an incoming segment, flags will 5138 * play significant role here. 5139 */ 5140static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, 5141 struct tcphdr *th, int syn_inerr) 5142{ 5143 u8 *hash_location; 5144 struct tcp_sock *tp = tcp_sk(sk); 5145 5146 /* RFC1323: H1. Apply PAWS check first. */ 5147 if (tcp_fast_parse_options(skb, th, tp, &hash_location) && 5148 tp->rx_opt.saw_tstamp && 5149 tcp_paws_discard(sk, skb)) { 5150 if (!th->rst) { 5151 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED); 5152 tcp_send_dupack(sk, skb); 5153 goto discard; 5154 } 5155 /* Reset is accepted even if it did not pass PAWS. */ 5156 } 5157 5158 /* Step 1: check sequence number */ 5159 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { 5160 /* RFC793, page 37: "In all states except SYN-SENT, all reset 5161 * (RST) segments are validated by checking their SEQ-fields." 5162 * And page 69: "If an incoming segment is not acceptable, 5163 * an acknowledgment should be sent in reply (unless the RST 5164 * bit is set, if so drop the segment and return)". 5165 */ 5166 if (!th->rst) 5167 tcp_send_dupack(sk, skb); 5168 goto discard; 5169 } 5170 5171 /* Step 2: check RST bit */ 5172 if (th->rst) { 5173 tcp_reset(sk); 5174 goto discard; 5175 } 5176 5177 /* ts_recent update must be made after we are sure that the packet 5178 * is in window. 5179 */ 5180 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 5181 5182 /* step 3: check security and precedence [ignored] */ 5183 5184 /* step 4: Check for a SYN in window. */ 5185 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 5186 if (syn_inerr) 5187 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); 5188 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN); 5189 tcp_reset(sk); 5190 return -1; 5191 } 5192 5193 return 1; 5194 5195discard: 5196 __kfree_skb(skb); 5197 return 0; 5198} 5199 5200/* 5201 * TCP receive function for the ESTABLISHED state. 5202 * 5203 * It is split into a fast path and a slow path. The fast path is 5204 * disabled when: 5205 * - A zero window was announced from us - zero window probing 5206 * is only handled properly in the slow path. 5207 * - Out of order segments arrived. 5208 * - Urgent data is expected. 5209 * - There is no buffer space left 5210 * - Unexpected TCP flags/window values/header lengths are received 5211 * (detected by checking the TCP header against pred_flags) 5212 * - Data is sent in both directions. Fast path only supports pure senders 5213 * or pure receivers (this means either the sequence number or the ack 5214 * value must stay constant) 5215 * - Unexpected TCP option. 5216 * 5217 * When these conditions are not satisfied it drops into a standard 5218 * receive procedure patterned after RFC793 to handle all cases. 5219 * The first three cases are guaranteed by proper pred_flags setting, 5220 * the rest is checked inline. Fast processing is turned on in 5221 * tcp_data_queue when everything is OK. 5222 */ 5223int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, 5224 struct tcphdr *th, unsigned len) 5225{ 5226 struct tcp_sock *tp = tcp_sk(sk); 5227 int res; 5228 5229 /* 5230 * Header prediction. 5231 * The code loosely follows the one in the famous 5232 * "30 instruction TCP receive" Van Jacobson mail. 5233 * 5234 * Van's trick is to deposit buffers into socket queue 5235 * on a device interrupt, to call tcp_recv function 5236 * on the receive process context and checksum and copy 5237 * the buffer to user space. smart... 5238 * 5239 * Our current scheme is not silly either but we take the 5240 * extra cost of the net_bh soft interrupt processing... 5241 * We do checksum and copy also but from device to kernel. 5242 */ 5243 5244 tp->rx_opt.saw_tstamp = 0; 5245 5246 /* pred_flags is 0xS?10 << 16 + snd_wnd 5247 * if header_prediction is to be made 5248 * 'S' will always be tp->tcp_header_len >> 2 5249 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to 5250 * turn it off (when there are holes in the receive 5251 * space for instance) 5252 * PSH flag is ignored. 5253 */ 5254 5255 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && 5256 TCP_SKB_CB(skb)->seq == tp->rcv_nxt && 5257 !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) { 5258 int tcp_header_len = tp->tcp_header_len; 5259 5260 /* Timestamp header prediction: tcp_header_len 5261 * is automatically equal to th->doff*4 due to pred_flags 5262 * match. 5263 */ 5264 5265 /* Check timestamp */ 5266 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { 5267 /* No? Slow path! */ 5268 if (!tcp_parse_aligned_timestamp(tp, th)) 5269 goto slow_path; 5270 5271 /* If PAWS failed, check it more carefully in slow path */ 5272 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) 5273 goto slow_path; 5274 5275 /* DO NOT update ts_recent here, if checksum fails 5276 * and timestamp was corrupted part, it will result 5277 * in a hung connection since we will drop all 5278 * future packets due to the PAWS test. 5279 */ 5280 } 5281 5282 if (len <= tcp_header_len) { 5283 /* Bulk data transfer: sender */ 5284 if (len == tcp_header_len) { 5285 /* Predicted packet is in window by definition. 5286 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 5287 * Hence, check seq<=rcv_wup reduces to: 5288 */ 5289 if (tcp_header_len == 5290 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 5291 tp->rcv_nxt == tp->rcv_wup) 5292 tcp_store_ts_recent(tp); 5293 5294 /* We know that such packets are checksummed 5295 * on entry. 5296 */ 5297 tcp_ack(sk, skb, 0); 5298 __kfree_skb(skb); 5299 tcp_data_snd_check(sk); 5300 return 0; 5301 } else { /* Header too small */ 5302 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); 5303 goto discard; 5304 } 5305 } else { 5306 int eaten = 0; 5307 int copied_early = 0; 5308 5309 if (tp->copied_seq == tp->rcv_nxt && 5310 len - tcp_header_len <= tp->ucopy.len) { 5311#ifdef CONFIG_NET_DMA 5312 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) { 5313 copied_early = 1; 5314 eaten = 1; 5315 } 5316#endif 5317 if (tp->ucopy.task == current && 5318 sock_owned_by_user(sk) && !copied_early) { 5319 __set_current_state(TASK_RUNNING); 5320 5321 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) 5322 eaten = 1; 5323 } 5324 if (eaten) { 5325 /* Predicted packet is in window by definition. 5326 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 5327 * Hence, check seq<=rcv_wup reduces to: 5328 */ 5329 if (tcp_header_len == 5330 (sizeof(struct tcphdr) + 5331 TCPOLEN_TSTAMP_ALIGNED) && 5332 tp->rcv_nxt == tp->rcv_wup) 5333 tcp_store_ts_recent(tp); 5334 5335 tcp_rcv_rtt_measure_ts(sk, skb); 5336 5337 __skb_pull(skb, tcp_header_len); 5338 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 5339 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITSTOUSER); 5340 } 5341 if (copied_early) 5342 tcp_cleanup_rbuf(sk, skb->len); 5343 } 5344 if (!eaten) { 5345 if (tcp_checksum_complete_user(sk, skb)) 5346 goto csum_error; 5347 5348 /* Predicted packet is in window by definition. 5349 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 5350 * Hence, check seq<=rcv_wup reduces to: 5351 */ 5352 if (tcp_header_len == 5353 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 5354 tp->rcv_nxt == tp->rcv_wup) 5355 tcp_store_ts_recent(tp); 5356 5357 tcp_rcv_rtt_measure_ts(sk, skb); 5358 5359 if ((int)skb->truesize > sk->sk_forward_alloc) 5360 goto step5; 5361 5362 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS); 5363 5364 /* Bulk data transfer: receiver */ 5365 __skb_pull(skb, tcp_header_len); 5366 __skb_queue_tail(&sk->sk_receive_queue, skb); 5367 skb_set_owner_r(skb, sk); 5368 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 5369 } 5370 5371 tcp_event_data_recv(sk, skb); 5372 5373 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { 5374 /* Well, only one small jumplet in fast path... */ 5375 tcp_ack(sk, skb, FLAG_DATA); 5376 tcp_data_snd_check(sk); 5377 if (!inet_csk_ack_scheduled(sk)) 5378 goto no_ack; 5379 } 5380 5381 if (!copied_early || tp->rcv_nxt != tp->rcv_wup) 5382 __tcp_ack_snd_check(sk, 0); 5383no_ack: 5384#ifdef CONFIG_NET_DMA 5385 if (copied_early) 5386 __skb_queue_tail(&sk->sk_async_wait_queue, skb); 5387 else 5388#endif 5389 if (eaten) 5390 __kfree_skb(skb); 5391 else 5392 sk->sk_data_ready(sk, 0); 5393 return 0; 5394 } 5395 } 5396 5397slow_path: 5398 if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb)) 5399 goto csum_error; 5400 5401 /* 5402 * Standard slow path. 5403 */ 5404 5405 res = tcp_validate_incoming(sk, skb, th, 1); 5406 if (res <= 0) 5407 return -res; 5408 5409step5: 5410 if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0) 5411 goto discard; 5412 5413 tcp_rcv_rtt_measure_ts(sk, skb); 5414 5415 /* Process urgent data. */ 5416 tcp_urg(sk, skb, th); 5417 5418 /* step 7: process the segment text */ 5419 tcp_data_queue(sk, skb); 5420 5421 tcp_data_snd_check(sk); 5422 tcp_ack_snd_check(sk); 5423 return 0; 5424 5425csum_error: 5426 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); 5427 5428discard: 5429 __kfree_skb(skb); 5430 return 0; 5431} 5432 5433static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 5434 struct tcphdr *th, unsigned len) 5435{ 5436 u8 *hash_location; 5437 struct inet_connection_sock *icsk = inet_csk(sk); 5438 struct tcp_sock *tp = tcp_sk(sk); 5439 struct tcp_cookie_values *cvp = tp->cookie_values; 5440 int saved_clamp = tp->rx_opt.mss_clamp; 5441 5442 tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0); 5443 5444 if (th->ack) { 5445 /* rfc793: 5446 * "If the state is SYN-SENT then 5447 * first check the ACK bit 5448 * If the ACK bit is set 5449 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send 5450 * a reset (unless the RST bit is set, if so drop 5451 * the segment and return)" 5452 * 5453 * We do not send data with SYN, so that RFC-correct 5454 * test reduces to: 5455 */ 5456 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt) 5457 goto reset_and_undo; 5458 5459 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 5460 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, 5461 tcp_time_stamp)) { 5462 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSACTIVEREJECTED); 5463 goto reset_and_undo; 5464 } 5465 5466 /* Now ACK is acceptable. 5467 * 5468 * "If the RST bit is set 5469 * If the ACK was acceptable then signal the user "error: 5470 * connection reset", drop the segment, enter CLOSED state, 5471 * delete TCB, and return." 5472 */ 5473 5474 if (th->rst) { 5475 tcp_reset(sk); 5476 goto discard; 5477 } 5478 5479 /* rfc793: 5480 * "fifth, if neither of the SYN or RST bits is set then 5481 * drop the segment and return." 5482 * 5483 * See note below! 5484 * --ANK(990513) 5485 */ 5486 if (!th->syn) 5487 goto discard_and_undo; 5488 5489 /* rfc793: 5490 * "If the SYN bit is on ... 5491 * are acceptable then ... 5492 * (our SYN has been ACKed), change the connection 5493 * state to ESTABLISHED..." 5494 */ 5495 5496 TCP_ECN_rcv_synack(tp, th); 5497 5498 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 5499 tcp_ack(sk, skb, FLAG_SLOWPATH); 5500 5501 /* Ok.. it's good. Set up sequence numbers and 5502 * move to established. 5503 */ 5504 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 5505 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 5506 5507 /* RFC1323: The window in SYN & SYN/ACK segments is 5508 * never scaled. 5509 */ 5510 tp->snd_wnd = ntohs(th->window); 5511 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); 5512 5513 if (!tp->rx_opt.wscale_ok) { 5514 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; 5515 tp->window_clamp = min(tp->window_clamp, 65535U); 5516 } 5517 5518 if (tp->rx_opt.saw_tstamp) { 5519 tp->rx_opt.tstamp_ok = 1; 5520 tp->tcp_header_len = 5521 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 5522 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 5523 tcp_store_ts_recent(tp); 5524 } else { 5525 tp->tcp_header_len = sizeof(struct tcphdr); 5526 } 5527 5528 if (tcp_is_sack(tp) && sysctl_tcp_fack) 5529 tcp_enable_fack(tp); 5530 5531 tcp_mtup_init(sk); 5532 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 5533 tcp_initialize_rcv_mss(sk); 5534 5535 /* Remember, tcp_poll() does not lock socket! 5536 * Change state from SYN-SENT only after copied_seq 5537 * is initialized. */ 5538 tp->copied_seq = tp->rcv_nxt; 5539 5540 if (cvp != NULL && 5541 cvp->cookie_pair_size > 0 && 5542 tp->rx_opt.cookie_plus > 0) { 5543 int cookie_size = tp->rx_opt.cookie_plus 5544 - TCPOLEN_COOKIE_BASE; 5545 int cookie_pair_size = cookie_size 5546 + cvp->cookie_desired; 5547 5548 /* A cookie extension option was sent and returned. 5549 * Note that each incoming SYNACK replaces the 5550 * Responder cookie. The initial exchange is most 5551 * fragile, as protection against spoofing relies 5552 * entirely upon the sequence and timestamp (above). 5553 * This replacement strategy allows the correct pair to 5554 * pass through, while any others will be filtered via 5555 * Responder verification later. 5556 */ 5557 if (sizeof(cvp->cookie_pair) >= cookie_pair_size) { 5558 memcpy(&cvp->cookie_pair[cvp->cookie_desired], 5559 hash_location, cookie_size); 5560 cvp->cookie_pair_size = cookie_pair_size; 5561 } 5562 } 5563 5564 smp_mb(); 5565 tcp_set_state(sk, TCP_ESTABLISHED); 5566 5567 security_inet_conn_established(sk, skb); 5568 5569 /* Make sure socket is routed, for correct metrics. */ 5570 icsk->icsk_af_ops->rebuild_header(sk); 5571 5572 tcp_init_metrics(sk); 5573 5574 tcp_init_congestion_control(sk); 5575 5576 /* Prevent spurious tcp_cwnd_restart() on first data 5577 * packet. 5578 */ 5579 tp->lsndtime = tcp_time_stamp; 5580 5581 tcp_init_buffer_space(sk); 5582 5583 if (sock_flag(sk, SOCK_KEEPOPEN)) 5584 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); 5585 5586 if (!tp->rx_opt.snd_wscale) 5587 __tcp_fast_path_on(tp, tp->snd_wnd); 5588 else 5589 tp->pred_flags = 0; 5590 5591 if (!sock_flag(sk, SOCK_DEAD)) { 5592 sk->sk_state_change(sk); 5593 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT); 5594 } 5595 5596 if (sk->sk_write_pending || 5597 icsk->icsk_accept_queue.rskq_defer_accept || 5598 icsk->icsk_ack.pingpong) { 5599 /* Save one ACK. Data will be ready after 5600 * several ticks, if write_pending is set. 5601 * 5602 * It may be deleted, but with this feature tcpdumps 5603 * look so _wonderfully_ clever, that I was not able 5604 * to stand against the temptation 8) --ANK 5605 */ 5606 inet_csk_schedule_ack(sk); 5607 icsk->icsk_ack.lrcvtime = tcp_time_stamp; 5608 icsk->icsk_ack.ato = TCP_ATO_MIN; 5609 tcp_incr_quickack(sk); 5610 tcp_enter_quickack_mode(sk); 5611 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 5612 TCP_DELACK_MAX, TCP_RTO_MAX); 5613 5614discard: 5615 __kfree_skb(skb); 5616 return 0; 5617 } else { 5618 tcp_send_ack(sk); 5619 } 5620 return -1; 5621 } 5622 5623 /* No ACK in the segment */ 5624 5625 if (th->rst) { 5626 /* rfc793: 5627 * "If the RST bit is set 5628 * 5629 * Otherwise (no ACK) drop the segment and return." 5630 */ 5631 5632 goto discard_and_undo; 5633 } 5634 5635 /* PAWS check. */ 5636 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && 5637 tcp_paws_reject(&tp->rx_opt, 0)) 5638 goto discard_and_undo; 5639 5640 if (th->syn) { 5641 /* We see SYN without ACK. It is attempt of 5642 * simultaneous connect with crossed SYNs. 5643 * Particularly, it can be connect to self. 5644 */ 5645 tcp_set_state(sk, TCP_SYN_RECV); 5646 5647 if (tp->rx_opt.saw_tstamp) { 5648 tp->rx_opt.tstamp_ok = 1; 5649 tcp_store_ts_recent(tp); 5650 tp->tcp_header_len = 5651 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 5652 } else { 5653 tp->tcp_header_len = sizeof(struct tcphdr); 5654 } 5655 5656 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 5657 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 5658 5659 /* RFC1323: The window in SYN & SYN/ACK segments is 5660 * never scaled. 5661 */ 5662 tp->snd_wnd = ntohs(th->window); 5663 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 5664 tp->max_window = tp->snd_wnd; 5665 5666 TCP_ECN_rcv_syn(tp, th); 5667 5668 tcp_mtup_init(sk); 5669 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 5670 tcp_initialize_rcv_mss(sk); 5671 5672 tcp_send_synack(sk); 5673#if 0 5674 /* Note, we could accept data and URG from this segment. 5675 * There are no obstacles to make this. 5676 * 5677 * However, if we ignore data in ACKless segments sometimes, 5678 * we have no reasons to accept it sometimes. 5679 * Also, seems the code doing it in step6 of tcp_rcv_state_process 5680 * is not flawless. So, discard packet for sanity. 5681 * Uncomment this return to process the data. 5682 */ 5683 return -1; 5684#else 5685 goto discard; 5686#endif 5687 } 5688 /* "fifth, if neither of the SYN or RST bits is set then 5689 * drop the segment and return." 5690 */ 5691 5692discard_and_undo: 5693 tcp_clear_options(&tp->rx_opt); 5694 tp->rx_opt.mss_clamp = saved_clamp; 5695 goto discard; 5696 5697reset_and_undo: 5698 tcp_clear_options(&tp->rx_opt); 5699 tp->rx_opt.mss_clamp = saved_clamp; 5700 return 1; 5701} 5702 5703/* 5704 * This function implements the receiving procedure of RFC 793 for 5705 * all states except ESTABLISHED and TIME_WAIT. 5706 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be 5707 * address independent. 5708 */ 5709 5710int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, 5711 struct tcphdr *th, unsigned len) 5712{ 5713 struct tcp_sock *tp = tcp_sk(sk); 5714 struct inet_connection_sock *icsk = inet_csk(sk); 5715 int queued = 0; 5716 int res; 5717 5718 tp->rx_opt.saw_tstamp = 0; 5719 5720 switch (sk->sk_state) { 5721 case TCP_CLOSE: 5722 goto discard; 5723 5724 case TCP_LISTEN: 5725 if (th->ack) 5726 return 1; 5727 5728 if (th->rst) 5729 goto discard; 5730 5731 if (th->syn) { 5732 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0) 5733 return 1; 5734 5735 /* Now we have several options: In theory there is 5736 * nothing else in the frame. KA9Q has an option to 5737 * send data with the syn, BSD accepts data with the 5738 * syn up to the [to be] advertised window and 5739 * Solaris 2.1 gives you a protocol error. For now 5740 * we just ignore it, that fits the spec precisely 5741 * and avoids incompatibilities. It would be nice in 5742 * future to drop through and process the data. 5743 * 5744 * Now that TTCP is starting to be used we ought to 5745 * queue this data. 5746 * But, this leaves one open to an easy denial of 5747 * service attack, and SYN cookies can't defend 5748 * against this problem. So, we drop the data 5749 * in the interest of security over speed unless 5750 * it's still in use. 5751 */ 5752 kfree_skb(skb); 5753 return 0; 5754 } 5755 goto discard; 5756 5757 case TCP_SYN_SENT: 5758 queued = tcp_rcv_synsent_state_process(sk, skb, th, len); 5759 if (queued >= 0) 5760 return queued; 5761 5762 /* Do step6 onward by hand. */ 5763 tcp_urg(sk, skb, th); 5764 __kfree_skb(skb); 5765 tcp_data_snd_check(sk); 5766 return 0; 5767 } 5768 5769 res = tcp_validate_incoming(sk, skb, th, 0); 5770 if (res <= 0) 5771 return -res; 5772 5773 /* step 5: check the ACK field */ 5774 if (th->ack) { 5775 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH) > 0; 5776 5777 switch (sk->sk_state) { 5778 case TCP_SYN_RECV: 5779 if (acceptable) { 5780 tp->copied_seq = tp->rcv_nxt; 5781 smp_mb(); 5782 tcp_set_state(sk, TCP_ESTABLISHED); 5783 sk->sk_state_change(sk); 5784 5785 /* Note, that this wakeup is only for marginal 5786 * crossed SYN case. Passively open sockets 5787 * are not waked up, because sk->sk_sleep == 5788 * NULL and sk->sk_socket == NULL. 5789 */ 5790 if (sk->sk_socket) 5791 sk_wake_async(sk, 5792 SOCK_WAKE_IO, POLL_OUT); 5793 5794 tp->snd_una = TCP_SKB_CB(skb)->ack_seq; 5795 tp->snd_wnd = ntohs(th->window) << 5796 tp->rx_opt.snd_wscale; 5797 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); 5798 5799 /* tcp_ack considers this ACK as duplicate 5800 * and does not calculate rtt. 5801 * Force it here. 5802 */ 5803 tcp_ack_update_rtt(sk, 0, 0); 5804 5805 if (tp->rx_opt.tstamp_ok) 5806 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 5807 5808 /* Make sure socket is routed, for 5809 * correct metrics. 5810 */ 5811 icsk->icsk_af_ops->rebuild_header(sk); 5812 5813 tcp_init_metrics(sk); 5814 5815 tcp_init_congestion_control(sk); 5816 5817 /* Prevent spurious tcp_cwnd_restart() on 5818 * first data packet. 5819 */ 5820 tp->lsndtime = tcp_time_stamp; 5821 5822 tcp_mtup_init(sk); 5823 tcp_initialize_rcv_mss(sk); 5824 tcp_init_buffer_space(sk); 5825 tcp_fast_path_on(tp); 5826 } else { 5827 return 1; 5828 } 5829 break; 5830 5831 case TCP_FIN_WAIT1: 5832 if (tp->snd_una == tp->write_seq) { 5833 tcp_set_state(sk, TCP_FIN_WAIT2); 5834 sk->sk_shutdown |= SEND_SHUTDOWN; 5835 dst_confirm(sk->sk_dst_cache); 5836 5837 if (!sock_flag(sk, SOCK_DEAD)) 5838 /* Wake up lingering close() */ 5839 sk->sk_state_change(sk); 5840 else { 5841 int tmo; 5842 5843 if (tp->linger2 < 0 || 5844 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 5845 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { 5846 tcp_done(sk); 5847 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA); 5848 return 1; 5849 } 5850 5851 tmo = tcp_fin_time(sk); 5852 if (tmo > TCP_TIMEWAIT_LEN) { 5853 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); 5854 } else if (th->fin || sock_owned_by_user(sk)) { 5855 /* Bad case. We could lose such FIN otherwise. 5856 * It is not a big problem, but it looks confusing 5857 * and not so rare event. We still can lose it now, 5858 * if it spins in bh_lock_sock(), but it is really 5859 * marginal case. 5860 */ 5861 inet_csk_reset_keepalive_timer(sk, tmo); 5862 } else { 5863 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 5864 goto discard; 5865 } 5866 } 5867 } 5868 break; 5869 5870 case TCP_CLOSING: 5871 if (tp->snd_una == tp->write_seq) { 5872 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 5873 goto discard; 5874 } 5875 break; 5876 5877 case TCP_LAST_ACK: 5878 if (tp->snd_una == tp->write_seq) { 5879 tcp_update_metrics(sk); 5880 tcp_done(sk); 5881 goto discard; 5882 } 5883 break; 5884 } 5885 } else 5886 goto discard; 5887 5888 /* step 6: check the URG bit */ 5889 tcp_urg(sk, skb, th); 5890 5891 /* step 7: process the segment text */ 5892 switch (sk->sk_state) { 5893 case TCP_CLOSE_WAIT: 5894 case TCP_CLOSING: 5895 case TCP_LAST_ACK: 5896 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 5897 break; 5898 case TCP_FIN_WAIT1: 5899 case TCP_FIN_WAIT2: 5900 /* RFC 793 says to queue data in these states, 5901 * RFC 1122 says we MUST send a reset. 5902 * BSD 4.4 also does reset. 5903 */ 5904 if (sk->sk_shutdown & RCV_SHUTDOWN) { 5905 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 5906 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { 5907 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA); 5908 tcp_reset(sk); 5909 return 1; 5910 } 5911 } 5912 /* Fall through */ 5913 case TCP_ESTABLISHED: 5914 tcp_data_queue(sk, skb); 5915 queued = 1; 5916 break; 5917 } 5918 5919 /* tcp_data could move socket to TIME-WAIT */ 5920 if (sk->sk_state != TCP_CLOSE) { 5921 tcp_data_snd_check(sk); 5922 tcp_ack_snd_check(sk); 5923 } 5924 5925 if (!queued) { 5926discard: 5927 __kfree_skb(skb); 5928 } 5929 return 0; 5930} 5931 5932EXPORT_SYMBOL(sysctl_tcp_ecn); 5933EXPORT_SYMBOL(sysctl_tcp_reordering); 5934EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); 5935EXPORT_SYMBOL(tcp_parse_options); 5936#ifdef CONFIG_TCP_MD5SIG 5937EXPORT_SYMBOL(tcp_parse_md5sig_option); 5938#endif 5939EXPORT_SYMBOL(tcp_rcv_established); 5940EXPORT_SYMBOL(tcp_rcv_state_process); 5941EXPORT_SYMBOL(tcp_initialize_rcv_mss); 5942