tcp_input.c revision 3ccd3130b3f681a4aef6392327256786b3b6aa04
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 * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $ 9 * 10 * Authors: Ross Biro 11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 12 * Mark Evans, <evansmp@uhura.aston.ac.uk> 13 * Corey Minyard <wf-rch!minyard@relay.EU.net> 14 * Florian La Roche, <flla@stud.uni-sb.de> 15 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> 16 * Linus Torvalds, <torvalds@cs.helsinki.fi> 17 * Alan Cox, <gw4pts@gw4pts.ampr.org> 18 * Matthew Dillon, <dillon@apollo.west.oic.com> 19 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 20 * Jorge Cwik, <jorge@laser.satlink.net> 21 */ 22 23/* 24 * Changes: 25 * Pedro Roque : Fast Retransmit/Recovery. 26 * Two receive queues. 27 * Retransmit queue handled by TCP. 28 * Better retransmit timer handling. 29 * New congestion avoidance. 30 * Header prediction. 31 * Variable renaming. 32 * 33 * Eric : Fast Retransmit. 34 * Randy Scott : MSS option defines. 35 * Eric Schenk : Fixes to slow start algorithm. 36 * Eric Schenk : Yet another double ACK bug. 37 * Eric Schenk : Delayed ACK bug fixes. 38 * Eric Schenk : Floyd style fast retrans war avoidance. 39 * David S. Miller : Don't allow zero congestion window. 40 * Eric Schenk : Fix retransmitter so that it sends 41 * next packet on ack of previous packet. 42 * Andi Kleen : Moved open_request checking here 43 * and process RSTs for open_requests. 44 * Andi Kleen : Better prune_queue, and other fixes. 45 * Andrey Savochkin: Fix RTT measurements in the presence of 46 * timestamps. 47 * Andrey Savochkin: Check sequence numbers correctly when 48 * removing SACKs due to in sequence incoming 49 * data segments. 50 * Andi Kleen: Make sure we never ack data there is not 51 * enough room for. Also make this condition 52 * a fatal error if it might still happen. 53 * Andi Kleen: Add tcp_measure_rcv_mss to make 54 * connections with MSS<min(MTU,ann. MSS) 55 * work without delayed acks. 56 * Andi Kleen: Process packets with PSH set in the 57 * fast path. 58 * J Hadi Salim: ECN support 59 * Andrei Gurtov, 60 * Pasi Sarolahti, 61 * Panu Kuhlberg: Experimental audit of TCP (re)transmission 62 * engine. Lots of bugs are found. 63 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs 64 */ 65 66#include <linux/mm.h> 67#include <linux/module.h> 68#include <linux/sysctl.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; 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_moderate_rcvbuf __read_mostly = 1; 93int sysctl_tcp_abc __read_mostly; 94 95#define FLAG_DATA 0x01 /* Incoming frame contained data. */ 96#define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ 97#define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ 98#define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ 99#define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ 100#define FLAG_DATA_SACKED 0x20 /* New SACK. */ 101#define FLAG_ECE 0x40 /* ECE in this ACK */ 102#define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */ 103#define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ 104#define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */ 105#define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */ 106#define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */ 107#define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */ 108 109#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) 110#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) 111#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) 112#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) 113#define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED) 114 115#define IsSackFrto() (sysctl_tcp_frto == 0x2) 116 117#define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) 118#define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH)) 119 120/* Adapt the MSS value used to make delayed ack decision to the 121 * real world. 122 */ 123static void tcp_measure_rcv_mss(struct sock *sk, 124 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_MIN_RCVMSS + 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, 306 struct sk_buff *skb) 307{ 308 struct tcp_sock *tp = tcp_sk(sk); 309 310 /* Check #1 */ 311 if (tp->rcv_ssthresh < tp->window_clamp && 312 (int)tp->rcv_ssthresh < tcp_space(sk) && 313 !tcp_memory_pressure) { 314 int incr; 315 316 /* Check #2. Increase window, if skb with such overhead 317 * will fit to rcvbuf in future. 318 */ 319 if (tcp_win_from_space(skb->truesize) <= skb->len) 320 incr = 2*tp->advmss; 321 else 322 incr = __tcp_grow_window(sk, skb); 323 324 if (incr) { 325 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, 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} 402 403 404/* Initialize RCV_MSS value. 405 * RCV_MSS is an our guess about MSS used by the peer. 406 * We haven't any direct information about the MSS. 407 * It's better to underestimate the RCV_MSS rather than overestimate. 408 * Overestimations make us ACKing less frequently than needed. 409 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). 410 */ 411void tcp_initialize_rcv_mss(struct sock *sk) 412{ 413 struct tcp_sock *tp = tcp_sk(sk); 414 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); 415 416 hint = min(hint, tp->rcv_wnd/2); 417 hint = min(hint, TCP_MIN_RCVMSS); 418 hint = max(hint, TCP_MIN_MSS); 419 420 inet_csk(sk)->icsk_ack.rcv_mss = hint; 421} 422 423/* Receiver "autotuning" code. 424 * 425 * The algorithm for RTT estimation w/o timestamps is based on 426 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. 427 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps> 428 * 429 * More detail on this code can be found at 430 * <http://www.psc.edu/~jheffner/senior_thesis.ps>, 431 * though this reference is out of date. A new paper 432 * is pending. 433 */ 434static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) 435{ 436 u32 new_sample = tp->rcv_rtt_est.rtt; 437 long m = sample; 438 439 if (m == 0) 440 m = 1; 441 442 if (new_sample != 0) { 443 /* If we sample in larger samples in the non-timestamp 444 * case, we could grossly overestimate the RTT especially 445 * with chatty applications or bulk transfer apps which 446 * are stalled on filesystem I/O. 447 * 448 * Also, since we are only going for a minimum in the 449 * non-timestamp case, we do not smooth things out 450 * else with timestamps disabled convergence takes too 451 * long. 452 */ 453 if (!win_dep) { 454 m -= (new_sample >> 3); 455 new_sample += m; 456 } else if (m < new_sample) 457 new_sample = m << 3; 458 } else { 459 /* No previous measure. */ 460 new_sample = m << 3; 461 } 462 463 if (tp->rcv_rtt_est.rtt != new_sample) 464 tp->rcv_rtt_est.rtt = new_sample; 465} 466 467static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) 468{ 469 if (tp->rcv_rtt_est.time == 0) 470 goto new_measure; 471 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) 472 return; 473 tcp_rcv_rtt_update(tp, 474 jiffies - tp->rcv_rtt_est.time, 475 1); 476 477new_measure: 478 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; 479 tp->rcv_rtt_est.time = tcp_time_stamp; 480} 481 482static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb) 483{ 484 struct tcp_sock *tp = tcp_sk(sk); 485 if (tp->rx_opt.rcv_tsecr && 486 (TCP_SKB_CB(skb)->end_seq - 487 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) 488 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); 489} 490 491/* 492 * This function should be called every time data is copied to user space. 493 * It calculates the appropriate TCP receive buffer space. 494 */ 495void tcp_rcv_space_adjust(struct sock *sk) 496{ 497 struct tcp_sock *tp = tcp_sk(sk); 498 int time; 499 int space; 500 501 if (tp->rcvq_space.time == 0) 502 goto new_measure; 503 504 time = tcp_time_stamp - tp->rcvq_space.time; 505 if (time < (tp->rcv_rtt_est.rtt >> 3) || 506 tp->rcv_rtt_est.rtt == 0) 507 return; 508 509 space = 2 * (tp->copied_seq - tp->rcvq_space.seq); 510 511 space = max(tp->rcvq_space.space, space); 512 513 if (tp->rcvq_space.space != space) { 514 int rcvmem; 515 516 tp->rcvq_space.space = space; 517 518 if (sysctl_tcp_moderate_rcvbuf && 519 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { 520 int new_clamp = space; 521 522 /* Receive space grows, normalize in order to 523 * take into account packet headers and sk_buff 524 * structure overhead. 525 */ 526 space /= tp->advmss; 527 if (!space) 528 space = 1; 529 rcvmem = (tp->advmss + MAX_TCP_HEADER + 530 16 + sizeof(struct sk_buff)); 531 while (tcp_win_from_space(rcvmem) < tp->advmss) 532 rcvmem += 128; 533 space *= rcvmem; 534 space = min(space, sysctl_tcp_rmem[2]); 535 if (space > sk->sk_rcvbuf) { 536 sk->sk_rcvbuf = space; 537 538 /* Make the window clamp follow along. */ 539 tp->window_clamp = new_clamp; 540 } 541 } 542 } 543 544new_measure: 545 tp->rcvq_space.seq = tp->copied_seq; 546 tp->rcvq_space.time = tcp_time_stamp; 547} 548 549/* There is something which you must keep in mind when you analyze the 550 * behavior of the tp->ato delayed ack timeout interval. When a 551 * connection starts up, we want to ack as quickly as possible. The 552 * problem is that "good" TCP's do slow start at the beginning of data 553 * transmission. The means that until we send the first few ACK's the 554 * sender will sit on his end and only queue most of his data, because 555 * he can only send snd_cwnd unacked packets at any given time. For 556 * each ACK we send, he increments snd_cwnd and transmits more of his 557 * queue. -DaveM 558 */ 559static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) 560{ 561 struct tcp_sock *tp = tcp_sk(sk); 562 struct inet_connection_sock *icsk = inet_csk(sk); 563 u32 now; 564 565 inet_csk_schedule_ack(sk); 566 567 tcp_measure_rcv_mss(sk, skb); 568 569 tcp_rcv_rtt_measure(tp); 570 571 now = tcp_time_stamp; 572 573 if (!icsk->icsk_ack.ato) { 574 /* The _first_ data packet received, initialize 575 * delayed ACK engine. 576 */ 577 tcp_incr_quickack(sk); 578 icsk->icsk_ack.ato = TCP_ATO_MIN; 579 } else { 580 int m = now - icsk->icsk_ack.lrcvtime; 581 582 if (m <= TCP_ATO_MIN/2) { 583 /* The fastest case is the first. */ 584 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; 585 } else if (m < icsk->icsk_ack.ato) { 586 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; 587 if (icsk->icsk_ack.ato > icsk->icsk_rto) 588 icsk->icsk_ack.ato = icsk->icsk_rto; 589 } else if (m > icsk->icsk_rto) { 590 /* Too long gap. Apparently sender failed to 591 * restart window, so that we send ACKs quickly. 592 */ 593 tcp_incr_quickack(sk); 594 sk_mem_reclaim(sk); 595 } 596 } 597 icsk->icsk_ack.lrcvtime = now; 598 599 TCP_ECN_check_ce(tp, skb); 600 601 if (skb->len >= 128) 602 tcp_grow_window(sk, skb); 603} 604 605static u32 tcp_rto_min(struct sock *sk) 606{ 607 struct dst_entry *dst = __sk_dst_get(sk); 608 u32 rto_min = TCP_RTO_MIN; 609 610 if (dst && dst_metric_locked(dst, RTAX_RTO_MIN)) 611 rto_min = dst->metrics[RTAX_RTO_MIN-1]; 612 return rto_min; 613} 614 615/* Called to compute a smoothed rtt estimate. The data fed to this 616 * routine either comes from timestamps, or from segments that were 617 * known _not_ to have been retransmitted [see Karn/Partridge 618 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 619 * piece by Van Jacobson. 620 * NOTE: the next three routines used to be one big routine. 621 * To save cycles in the RFC 1323 implementation it was better to break 622 * it up into three procedures. -- erics 623 */ 624static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) 625{ 626 struct tcp_sock *tp = tcp_sk(sk); 627 long m = mrtt; /* RTT */ 628 629 /* The following amusing code comes from Jacobson's 630 * article in SIGCOMM '88. Note that rtt and mdev 631 * are scaled versions of rtt and mean deviation. 632 * This is designed to be as fast as possible 633 * m stands for "measurement". 634 * 635 * On a 1990 paper the rto value is changed to: 636 * RTO = rtt + 4 * mdev 637 * 638 * Funny. This algorithm seems to be very broken. 639 * These formulae increase RTO, when it should be decreased, increase 640 * too slowly, when it should be increased quickly, decrease too quickly 641 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely 642 * does not matter how to _calculate_ it. Seems, it was trap 643 * that VJ failed to avoid. 8) 644 */ 645 if (m == 0) 646 m = 1; 647 if (tp->srtt != 0) { 648 m -= (tp->srtt >> 3); /* m is now error in rtt est */ 649 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ 650 if (m < 0) { 651 m = -m; /* m is now abs(error) */ 652 m -= (tp->mdev >> 2); /* similar update on mdev */ 653 /* This is similar to one of Eifel findings. 654 * Eifel blocks mdev updates when rtt decreases. 655 * This solution is a bit different: we use finer gain 656 * for mdev in this case (alpha*beta). 657 * Like Eifel it also prevents growth of rto, 658 * but also it limits too fast rto decreases, 659 * happening in pure Eifel. 660 */ 661 if (m > 0) 662 m >>= 3; 663 } else { 664 m -= (tp->mdev >> 2); /* similar update on mdev */ 665 } 666 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ 667 if (tp->mdev > tp->mdev_max) { 668 tp->mdev_max = tp->mdev; 669 if (tp->mdev_max > tp->rttvar) 670 tp->rttvar = tp->mdev_max; 671 } 672 if (after(tp->snd_una, tp->rtt_seq)) { 673 if (tp->mdev_max < tp->rttvar) 674 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2; 675 tp->rtt_seq = tp->snd_nxt; 676 tp->mdev_max = tcp_rto_min(sk); 677 } 678 } else { 679 /* no previous measure. */ 680 tp->srtt = m<<3; /* take the measured time to be rtt */ 681 tp->mdev = m<<1; /* make sure rto = 3*rtt */ 682 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); 683 tp->rtt_seq = tp->snd_nxt; 684 } 685} 686 687/* Calculate rto without backoff. This is the second half of Van Jacobson's 688 * routine referred to above. 689 */ 690static inline void tcp_set_rto(struct sock *sk) 691{ 692 const struct tcp_sock *tp = tcp_sk(sk); 693 /* Old crap is replaced with new one. 8) 694 * 695 * More seriously: 696 * 1. If rtt variance happened to be less 50msec, it is hallucination. 697 * It cannot be less due to utterly erratic ACK generation made 698 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ 699 * to do with delayed acks, because at cwnd>2 true delack timeout 700 * is invisible. Actually, Linux-2.4 also generates erratic 701 * ACKs in some circumstances. 702 */ 703 inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar; 704 705 /* 2. Fixups made earlier cannot be right. 706 * If we do not estimate RTO correctly without them, 707 * all the algo is pure shit and should be replaced 708 * with correct one. It is exactly, which we pretend to do. 709 */ 710} 711 712/* NOTE: clamping at TCP_RTO_MIN is not required, current algo 713 * guarantees that rto is higher. 714 */ 715static inline void tcp_bound_rto(struct sock *sk) 716{ 717 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX) 718 inet_csk(sk)->icsk_rto = TCP_RTO_MAX; 719} 720 721/* Save metrics learned by this TCP session. 722 This function is called only, when TCP finishes successfully 723 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. 724 */ 725void tcp_update_metrics(struct sock *sk) 726{ 727 struct tcp_sock *tp = tcp_sk(sk); 728 struct dst_entry *dst = __sk_dst_get(sk); 729 730 if (sysctl_tcp_nometrics_save) 731 return; 732 733 dst_confirm(dst); 734 735 if (dst && (dst->flags&DST_HOST)) { 736 const struct inet_connection_sock *icsk = inet_csk(sk); 737 int m; 738 739 if (icsk->icsk_backoff || !tp->srtt) { 740 /* This session failed to estimate rtt. Why? 741 * Probably, no packets returned in time. 742 * Reset our results. 743 */ 744 if (!(dst_metric_locked(dst, RTAX_RTT))) 745 dst->metrics[RTAX_RTT-1] = 0; 746 return; 747 } 748 749 m = dst_metric(dst, RTAX_RTT) - tp->srtt; 750 751 /* If newly calculated rtt larger than stored one, 752 * store new one. Otherwise, use EWMA. Remember, 753 * rtt overestimation is always better than underestimation. 754 */ 755 if (!(dst_metric_locked(dst, RTAX_RTT))) { 756 if (m <= 0) 757 dst->metrics[RTAX_RTT-1] = tp->srtt; 758 else 759 dst->metrics[RTAX_RTT-1] -= (m>>3); 760 } 761 762 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { 763 if (m < 0) 764 m = -m; 765 766 /* Scale deviation to rttvar fixed point */ 767 m >>= 1; 768 if (m < tp->mdev) 769 m = tp->mdev; 770 771 if (m >= dst_metric(dst, RTAX_RTTVAR)) 772 dst->metrics[RTAX_RTTVAR-1] = m; 773 else 774 dst->metrics[RTAX_RTTVAR-1] -= 775 (dst->metrics[RTAX_RTTVAR-1] - m)>>2; 776 } 777 778 if (tp->snd_ssthresh >= 0xFFFF) { 779 /* Slow start still did not finish. */ 780 if (dst_metric(dst, RTAX_SSTHRESH) && 781 !dst_metric_locked(dst, RTAX_SSTHRESH) && 782 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) 783 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1; 784 if (!dst_metric_locked(dst, RTAX_CWND) && 785 tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) 786 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd; 787 } else if (tp->snd_cwnd > tp->snd_ssthresh && 788 icsk->icsk_ca_state == TCP_CA_Open) { 789 /* Cong. avoidance phase, cwnd is reliable. */ 790 if (!dst_metric_locked(dst, RTAX_SSTHRESH)) 791 dst->metrics[RTAX_SSTHRESH-1] = 792 max(tp->snd_cwnd >> 1, tp->snd_ssthresh); 793 if (!dst_metric_locked(dst, RTAX_CWND)) 794 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1; 795 } else { 796 /* Else slow start did not finish, cwnd is non-sense, 797 ssthresh may be also invalid. 798 */ 799 if (!dst_metric_locked(dst, RTAX_CWND)) 800 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1; 801 if (dst->metrics[RTAX_SSTHRESH-1] && 802 !dst_metric_locked(dst, RTAX_SSTHRESH) && 803 tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1]) 804 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh; 805 } 806 807 if (!dst_metric_locked(dst, RTAX_REORDERING)) { 808 if (dst->metrics[RTAX_REORDERING-1] < tp->reordering && 809 tp->reordering != sysctl_tcp_reordering) 810 dst->metrics[RTAX_REORDERING-1] = tp->reordering; 811 } 812 } 813} 814 815/* Numbers are taken from RFC3390. 816 * 817 * John Heffner states: 818 * 819 * The RFC specifies a window of no more than 4380 bytes 820 * unless 2*MSS > 4380. Reading the pseudocode in the RFC 821 * is a bit misleading because they use a clamp at 4380 bytes 822 * rather than use a multiplier in the relevant range. 823 */ 824__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst) 825{ 826 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); 827 828 if (!cwnd) { 829 if (tp->mss_cache > 1460) 830 cwnd = 2; 831 else 832 cwnd = (tp->mss_cache > 1095) ? 3 : 4; 833 } 834 return min_t(__u32, cwnd, tp->snd_cwnd_clamp); 835} 836 837/* Set slow start threshold and cwnd not falling to slow start */ 838void tcp_enter_cwr(struct sock *sk, const int set_ssthresh) 839{ 840 struct tcp_sock *tp = tcp_sk(sk); 841 const struct inet_connection_sock *icsk = inet_csk(sk); 842 843 tp->prior_ssthresh = 0; 844 tp->bytes_acked = 0; 845 if (icsk->icsk_ca_state < TCP_CA_CWR) { 846 tp->undo_marker = 0; 847 if (set_ssthresh) 848 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 849 tp->snd_cwnd = min(tp->snd_cwnd, 850 tcp_packets_in_flight(tp) + 1U); 851 tp->snd_cwnd_cnt = 0; 852 tp->high_seq = tp->snd_nxt; 853 tp->snd_cwnd_stamp = tcp_time_stamp; 854 TCP_ECN_queue_cwr(tp); 855 856 tcp_set_ca_state(sk, TCP_CA_CWR); 857 } 858} 859 860/* 861 * Packet counting of FACK is based on in-order assumptions, therefore TCP 862 * disables it when reordering is detected 863 */ 864static void tcp_disable_fack(struct tcp_sock *tp) 865{ 866 /* RFC3517 uses different metric in lost marker => reset on change */ 867 if (tcp_is_fack(tp)) 868 tp->lost_skb_hint = NULL; 869 tp->rx_opt.sack_ok &= ~2; 870} 871 872/* Take a notice that peer is sending D-SACKs */ 873static void tcp_dsack_seen(struct tcp_sock *tp) 874{ 875 tp->rx_opt.sack_ok |= 4; 876} 877 878/* Initialize metrics on socket. */ 879 880static void tcp_init_metrics(struct sock *sk) 881{ 882 struct tcp_sock *tp = tcp_sk(sk); 883 struct dst_entry *dst = __sk_dst_get(sk); 884 885 if (dst == NULL) 886 goto reset; 887 888 dst_confirm(dst); 889 890 if (dst_metric_locked(dst, RTAX_CWND)) 891 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); 892 if (dst_metric(dst, RTAX_SSTHRESH)) { 893 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); 894 if (tp->snd_ssthresh > tp->snd_cwnd_clamp) 895 tp->snd_ssthresh = tp->snd_cwnd_clamp; 896 } 897 if (dst_metric(dst, RTAX_REORDERING) && 898 tp->reordering != dst_metric(dst, RTAX_REORDERING)) { 899 tcp_disable_fack(tp); 900 tp->reordering = dst_metric(dst, RTAX_REORDERING); 901 } 902 903 if (dst_metric(dst, RTAX_RTT) == 0) 904 goto reset; 905 906 if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3)) 907 goto reset; 908 909 /* Initial rtt is determined from SYN,SYN-ACK. 910 * The segment is small and rtt may appear much 911 * less than real one. Use per-dst memory 912 * to make it more realistic. 913 * 914 * A bit of theory. RTT is time passed after "normal" sized packet 915 * is sent until it is ACKed. In normal circumstances sending small 916 * packets force peer to delay ACKs and calculation is correct too. 917 * The algorithm is adaptive and, provided we follow specs, it 918 * NEVER underestimate RTT. BUT! If peer tries to make some clever 919 * tricks sort of "quick acks" for time long enough to decrease RTT 920 * to low value, and then abruptly stops to do it and starts to delay 921 * ACKs, wait for troubles. 922 */ 923 if (dst_metric(dst, RTAX_RTT) > tp->srtt) { 924 tp->srtt = dst_metric(dst, RTAX_RTT); 925 tp->rtt_seq = tp->snd_nxt; 926 } 927 if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) { 928 tp->mdev = dst_metric(dst, RTAX_RTTVAR); 929 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); 930 } 931 tcp_set_rto(sk); 932 tcp_bound_rto(sk); 933 if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp) 934 goto reset; 935 tp->snd_cwnd = tcp_init_cwnd(tp, dst); 936 tp->snd_cwnd_stamp = tcp_time_stamp; 937 return; 938 939reset: 940 /* Play conservative. If timestamps are not 941 * supported, TCP will fail to recalculate correct 942 * rtt, if initial rto is too small. FORGET ALL AND RESET! 943 */ 944 if (!tp->rx_opt.saw_tstamp && tp->srtt) { 945 tp->srtt = 0; 946 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT; 947 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; 948 } 949} 950 951static void tcp_update_reordering(struct sock *sk, const int metric, 952 const int ts) 953{ 954 struct tcp_sock *tp = tcp_sk(sk); 955 if (metric > tp->reordering) { 956 tp->reordering = min(TCP_MAX_REORDERING, metric); 957 958 /* This exciting event is worth to be remembered. 8) */ 959 if (ts) 960 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER); 961 else if (tcp_is_reno(tp)) 962 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER); 963 else if (tcp_is_fack(tp)) 964 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER); 965 else 966 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER); 967#if FASTRETRANS_DEBUG > 1 968 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", 969 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, 970 tp->reordering, 971 tp->fackets_out, 972 tp->sacked_out, 973 tp->undo_marker ? tp->undo_retrans : 0); 974#endif 975 tcp_disable_fack(tp); 976 } 977} 978 979/* This procedure tags the retransmission queue when SACKs arrive. 980 * 981 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). 982 * Packets in queue with these bits set are counted in variables 983 * sacked_out, retrans_out and lost_out, correspondingly. 984 * 985 * Valid combinations are: 986 * Tag InFlight Description 987 * 0 1 - orig segment is in flight. 988 * S 0 - nothing flies, orig reached receiver. 989 * L 0 - nothing flies, orig lost by net. 990 * R 2 - both orig and retransmit are in flight. 991 * L|R 1 - orig is lost, retransmit is in flight. 992 * S|R 1 - orig reached receiver, retrans is still in flight. 993 * (L|S|R is logically valid, it could occur when L|R is sacked, 994 * but it is equivalent to plain S and code short-curcuits it to S. 995 * L|S is logically invalid, it would mean -1 packet in flight 8)) 996 * 997 * These 6 states form finite state machine, controlled by the following events: 998 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) 999 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) 1000 * 3. Loss detection event of one of three flavors: 1001 * A. Scoreboard estimator decided the packet is lost. 1002 * A'. Reno "three dupacks" marks head of queue lost. 1003 * A''. Its FACK modfication, head until snd.fack is lost. 1004 * B. SACK arrives sacking data transmitted after never retransmitted 1005 * hole was sent out. 1006 * C. SACK arrives sacking SND.NXT at the moment, when the 1007 * segment was retransmitted. 1008 * 4. D-SACK added new rule: D-SACK changes any tag to S. 1009 * 1010 * It is pleasant to note, that state diagram turns out to be commutative, 1011 * so that we are allowed not to be bothered by order of our actions, 1012 * when multiple events arrive simultaneously. (see the function below). 1013 * 1014 * Reordering detection. 1015 * -------------------- 1016 * Reordering metric is maximal distance, which a packet can be displaced 1017 * in packet stream. With SACKs we can estimate it: 1018 * 1019 * 1. SACK fills old hole and the corresponding segment was not 1020 * ever retransmitted -> reordering. Alas, we cannot use it 1021 * when segment was retransmitted. 1022 * 2. The last flaw is solved with D-SACK. D-SACK arrives 1023 * for retransmitted and already SACKed segment -> reordering.. 1024 * Both of these heuristics are not used in Loss state, when we cannot 1025 * account for retransmits accurately. 1026 * 1027 * SACK block validation. 1028 * ---------------------- 1029 * 1030 * SACK block range validation checks that the received SACK block fits to 1031 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT. 1032 * Note that SND.UNA is not included to the range though being valid because 1033 * it means that the receiver is rather inconsistent with itself reporting 1034 * SACK reneging when it should advance SND.UNA. Such SACK block this is 1035 * perfectly valid, however, in light of RFC2018 which explicitly states 1036 * that "SACK block MUST reflect the newest segment. Even if the newest 1037 * segment is going to be discarded ...", not that it looks very clever 1038 * in case of head skb. Due to potentional receiver driven attacks, we 1039 * choose to avoid immediate execution of a walk in write queue due to 1040 * reneging and defer head skb's loss recovery to standard loss recovery 1041 * procedure that will eventually trigger (nothing forbids us doing this). 1042 * 1043 * Implements also blockage to start_seq wrap-around. Problem lies in the 1044 * fact that though start_seq (s) is before end_seq (i.e., not reversed), 1045 * there's no guarantee that it will be before snd_nxt (n). The problem 1046 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt 1047 * wrap (s_w): 1048 * 1049 * <- outs wnd -> <- wrapzone -> 1050 * u e n u_w e_w s n_w 1051 * | | | | | | | 1052 * |<------------+------+----- TCP seqno space --------------+---------->| 1053 * ...-- <2^31 ->| |<--------... 1054 * ...---- >2^31 ------>| |<--------... 1055 * 1056 * Current code wouldn't be vulnerable but it's better still to discard such 1057 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat 1058 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in 1059 * snd_nxt wrap -> snd_una region will then become "well defined", i.e., 1060 * equal to the ideal case (infinite seqno space without wrap caused issues). 1061 * 1062 * With D-SACK the lower bound is extended to cover sequence space below 1063 * SND.UNA down to undo_marker, which is the last point of interest. Yet 1064 * again, D-SACK block must not to go across snd_una (for the same reason as 1065 * for the normal SACK blocks, explained above). But there all simplicity 1066 * ends, TCP might receive valid D-SACKs below that. As long as they reside 1067 * fully below undo_marker they do not affect behavior in anyway and can 1068 * therefore be safely ignored. In rare cases (which are more or less 1069 * theoretical ones), the D-SACK will nicely cross that boundary due to skb 1070 * fragmentation and packet reordering past skb's retransmission. To consider 1071 * them correctly, the acceptable range must be extended even more though 1072 * the exact amount is rather hard to quantify. However, tp->max_window can 1073 * be used as an exaggerated estimate. 1074 */ 1075static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack, 1076 u32 start_seq, u32 end_seq) 1077{ 1078 /* Too far in future, or reversed (interpretation is ambiguous) */ 1079 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq)) 1080 return 0; 1081 1082 /* Nasty start_seq wrap-around check (see comments above) */ 1083 if (!before(start_seq, tp->snd_nxt)) 1084 return 0; 1085 1086 /* In outstanding window? ...This is valid exit for D-SACKs too. 1087 * start_seq == snd_una is non-sensical (see comments above) 1088 */ 1089 if (after(start_seq, tp->snd_una)) 1090 return 1; 1091 1092 if (!is_dsack || !tp->undo_marker) 1093 return 0; 1094 1095 /* ...Then it's D-SACK, and must reside below snd_una completely */ 1096 if (!after(end_seq, tp->snd_una)) 1097 return 0; 1098 1099 if (!before(start_seq, tp->undo_marker)) 1100 return 1; 1101 1102 /* Too old */ 1103 if (!after(end_seq, tp->undo_marker)) 1104 return 0; 1105 1106 /* Undo_marker boundary crossing (overestimates a lot). Known already: 1107 * start_seq < undo_marker and end_seq >= undo_marker. 1108 */ 1109 return !before(start_seq, end_seq - tp->max_window); 1110} 1111 1112/* Check for lost retransmit. This superb idea is borrowed from "ratehalving". 1113 * Event "C". Later note: FACK people cheated me again 8), we have to account 1114 * for reordering! Ugly, but should help. 1115 * 1116 * Search retransmitted skbs from write_queue that were sent when snd_nxt was 1117 * less than what is now known to be received by the other end (derived from 1118 * highest SACK block). Also calculate the lowest snd_nxt among the remaining 1119 * retransmitted skbs to avoid some costly processing per ACKs. 1120 */ 1121static void tcp_mark_lost_retrans(struct sock *sk) 1122{ 1123 const struct inet_connection_sock *icsk = inet_csk(sk); 1124 struct tcp_sock *tp = tcp_sk(sk); 1125 struct sk_buff *skb; 1126 int cnt = 0; 1127 u32 new_low_seq = tp->snd_nxt; 1128 u32 received_upto = tcp_highest_sack_seq(tp); 1129 1130 if (!tcp_is_fack(tp) || !tp->retrans_out || 1131 !after(received_upto, tp->lost_retrans_low) || 1132 icsk->icsk_ca_state != TCP_CA_Recovery) 1133 return; 1134 1135 tcp_for_write_queue(skb, sk) { 1136 u32 ack_seq = TCP_SKB_CB(skb)->ack_seq; 1137 1138 if (skb == tcp_send_head(sk)) 1139 break; 1140 if (cnt == tp->retrans_out) 1141 break; 1142 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1143 continue; 1144 1145 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) 1146 continue; 1147 1148 if (after(received_upto, ack_seq) && 1149 (tcp_is_fack(tp) || 1150 !before(received_upto, 1151 ack_seq + tp->reordering * tp->mss_cache))) { 1152 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1153 tp->retrans_out -= tcp_skb_pcount(skb); 1154 1155 /* clear lost hint */ 1156 tp->retransmit_skb_hint = NULL; 1157 1158 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { 1159 tp->lost_out += tcp_skb_pcount(skb); 1160 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1161 } 1162 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT); 1163 } else { 1164 if (before(ack_seq, new_low_seq)) 1165 new_low_seq = ack_seq; 1166 cnt += tcp_skb_pcount(skb); 1167 } 1168 } 1169 1170 if (tp->retrans_out) 1171 tp->lost_retrans_low = new_low_seq; 1172} 1173 1174static int tcp_check_dsack(struct tcp_sock *tp, struct sk_buff *ack_skb, 1175 struct tcp_sack_block_wire *sp, int num_sacks, 1176 u32 prior_snd_una) 1177{ 1178 u32 start_seq_0 = ntohl(get_unaligned(&sp[0].start_seq)); 1179 u32 end_seq_0 = ntohl(get_unaligned(&sp[0].end_seq)); 1180 int dup_sack = 0; 1181 1182 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) { 1183 dup_sack = 1; 1184 tcp_dsack_seen(tp); 1185 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV); 1186 } else if (num_sacks > 1) { 1187 u32 end_seq_1 = ntohl(get_unaligned(&sp[1].end_seq)); 1188 u32 start_seq_1 = ntohl(get_unaligned(&sp[1].start_seq)); 1189 1190 if (!after(end_seq_0, end_seq_1) && 1191 !before(start_seq_0, start_seq_1)) { 1192 dup_sack = 1; 1193 tcp_dsack_seen(tp); 1194 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV); 1195 } 1196 } 1197 1198 /* D-SACK for already forgotten data... Do dumb counting. */ 1199 if (dup_sack && 1200 !after(end_seq_0, prior_snd_una) && 1201 after(end_seq_0, tp->undo_marker)) 1202 tp->undo_retrans--; 1203 1204 return dup_sack; 1205} 1206 1207/* Check if skb is fully within the SACK block. In presence of GSO skbs, 1208 * the incoming SACK may not exactly match but we can find smaller MSS 1209 * aligned portion of it that matches. Therefore we might need to fragment 1210 * which may fail and creates some hassle (caller must handle error case 1211 * returns). 1212 */ 1213static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, 1214 u32 start_seq, u32 end_seq) 1215{ 1216 int in_sack, err; 1217 unsigned int pkt_len; 1218 1219 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && 1220 !before(end_seq, TCP_SKB_CB(skb)->end_seq); 1221 1222 if (tcp_skb_pcount(skb) > 1 && !in_sack && 1223 after(TCP_SKB_CB(skb)->end_seq, start_seq)) { 1224 1225 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); 1226 1227 if (!in_sack) 1228 pkt_len = start_seq - TCP_SKB_CB(skb)->seq; 1229 else 1230 pkt_len = end_seq - TCP_SKB_CB(skb)->seq; 1231 err = tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size); 1232 if (err < 0) 1233 return err; 1234 } 1235 1236 return in_sack; 1237} 1238 1239static int tcp_sacktag_one(struct sk_buff *skb, struct sock *sk, 1240 int *reord, int dup_sack, int fack_count) 1241{ 1242 struct tcp_sock *tp = tcp_sk(sk); 1243 u8 sacked = TCP_SKB_CB(skb)->sacked; 1244 int flag = 0; 1245 1246 /* Account D-SACK for retransmitted packet. */ 1247 if (dup_sack && (sacked & TCPCB_RETRANS)) { 1248 if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) 1249 tp->undo_retrans--; 1250 if (sacked & TCPCB_SACKED_ACKED) 1251 *reord = min(fack_count, *reord); 1252 } 1253 1254 /* Nothing to do; acked frame is about to be dropped (was ACKed). */ 1255 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1256 return flag; 1257 1258 if (!(sacked & TCPCB_SACKED_ACKED)) { 1259 if (sacked & TCPCB_SACKED_RETRANS) { 1260 /* If the segment is not tagged as lost, 1261 * we do not clear RETRANS, believing 1262 * that retransmission is still in flight. 1263 */ 1264 if (sacked & TCPCB_LOST) { 1265 TCP_SKB_CB(skb)->sacked &= 1266 ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); 1267 tp->lost_out -= tcp_skb_pcount(skb); 1268 tp->retrans_out -= tcp_skb_pcount(skb); 1269 1270 /* clear lost hint */ 1271 tp->retransmit_skb_hint = NULL; 1272 } 1273 } else { 1274 if (!(sacked & TCPCB_RETRANS)) { 1275 /* New sack for not retransmitted frame, 1276 * which was in hole. It is reordering. 1277 */ 1278 if (before(TCP_SKB_CB(skb)->seq, 1279 tcp_highest_sack_seq(tp))) 1280 *reord = min(fack_count, *reord); 1281 1282 /* SACK enhanced F-RTO (RFC4138; Appendix B) */ 1283 if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark)) 1284 flag |= FLAG_ONLY_ORIG_SACKED; 1285 } 1286 1287 if (sacked & TCPCB_LOST) { 1288 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 1289 tp->lost_out -= tcp_skb_pcount(skb); 1290 1291 /* clear lost hint */ 1292 tp->retransmit_skb_hint = NULL; 1293 } 1294 } 1295 1296 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED; 1297 flag |= FLAG_DATA_SACKED; 1298 tp->sacked_out += tcp_skb_pcount(skb); 1299 1300 fack_count += tcp_skb_pcount(skb); 1301 1302 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */ 1303 if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) && 1304 before(TCP_SKB_CB(skb)->seq, 1305 TCP_SKB_CB(tp->lost_skb_hint)->seq)) 1306 tp->lost_cnt_hint += tcp_skb_pcount(skb); 1307 1308 if (fack_count > tp->fackets_out) 1309 tp->fackets_out = fack_count; 1310 1311 if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp))) 1312 tcp_advance_highest_sack(sk, skb); 1313 } 1314 1315 /* D-SACK. We can detect redundant retransmission in S|R and plain R 1316 * frames and clear it. undo_retrans is decreased above, L|R frames 1317 * are accounted above as well. 1318 */ 1319 if (dup_sack && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) { 1320 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1321 tp->retrans_out -= tcp_skb_pcount(skb); 1322 tp->retransmit_skb_hint = NULL; 1323 } 1324 1325 return flag; 1326} 1327 1328static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, 1329 struct tcp_sack_block *next_dup, 1330 u32 start_seq, u32 end_seq, 1331 int dup_sack_in, int *fack_count, 1332 int *reord, int *flag) 1333{ 1334 tcp_for_write_queue_from(skb, sk) { 1335 int in_sack = 0; 1336 int dup_sack = dup_sack_in; 1337 1338 if (skb == tcp_send_head(sk)) 1339 break; 1340 1341 /* queue is in-order => we can short-circuit the walk early */ 1342 if (!before(TCP_SKB_CB(skb)->seq, end_seq)) 1343 break; 1344 1345 if ((next_dup != NULL) && 1346 before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) { 1347 in_sack = tcp_match_skb_to_sack(sk, skb, 1348 next_dup->start_seq, 1349 next_dup->end_seq); 1350 if (in_sack > 0) 1351 dup_sack = 1; 1352 } 1353 1354 if (in_sack <= 0) 1355 in_sack = tcp_match_skb_to_sack(sk, skb, start_seq, end_seq); 1356 if (unlikely(in_sack < 0)) 1357 break; 1358 1359 if (in_sack) 1360 *flag |= tcp_sacktag_one(skb, sk, reord, dup_sack, *fack_count); 1361 1362 *fack_count += tcp_skb_pcount(skb); 1363 } 1364 return skb; 1365} 1366 1367/* Avoid all extra work that is being done by sacktag while walking in 1368 * a normal way 1369 */ 1370static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, 1371 u32 skip_to_seq) 1372{ 1373 tcp_for_write_queue_from(skb, sk) { 1374 if (skb == tcp_send_head(sk)) 1375 break; 1376 1377 if (!before(TCP_SKB_CB(skb)->end_seq, skip_to_seq)) 1378 break; 1379 } 1380 return skb; 1381} 1382 1383static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb, 1384 struct sock *sk, 1385 struct tcp_sack_block *next_dup, 1386 u32 skip_to_seq, 1387 int *fack_count, int *reord, 1388 int *flag) 1389{ 1390 if (next_dup == NULL) 1391 return skb; 1392 1393 if (before(next_dup->start_seq, skip_to_seq)) { 1394 skb = tcp_sacktag_skip(skb, sk, next_dup->start_seq); 1395 tcp_sacktag_walk(skb, sk, NULL, 1396 next_dup->start_seq, next_dup->end_seq, 1397 1, fack_count, reord, flag); 1398 } 1399 1400 return skb; 1401} 1402 1403static int tcp_sack_cache_ok(struct tcp_sock *tp, struct tcp_sack_block *cache) 1404{ 1405 return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); 1406} 1407 1408static int 1409tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una) 1410{ 1411 const struct inet_connection_sock *icsk = inet_csk(sk); 1412 struct tcp_sock *tp = tcp_sk(sk); 1413 unsigned char *ptr = (skb_transport_header(ack_skb) + 1414 TCP_SKB_CB(ack_skb)->sacked); 1415 struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2); 1416 struct tcp_sack_block sp[4]; 1417 struct tcp_sack_block *cache; 1418 struct sk_buff *skb; 1419 int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3; 1420 int used_sacks; 1421 int reord = tp->packets_out; 1422 int flag = 0; 1423 int found_dup_sack = 0; 1424 int fack_count; 1425 int i, j; 1426 int first_sack_index; 1427 1428 if (!tp->sacked_out) { 1429 if (WARN_ON(tp->fackets_out)) 1430 tp->fackets_out = 0; 1431 tcp_highest_sack_reset(sk); 1432 } 1433 1434 found_dup_sack = tcp_check_dsack(tp, ack_skb, sp_wire, 1435 num_sacks, prior_snd_una); 1436 if (found_dup_sack) 1437 flag |= FLAG_DSACKING_ACK; 1438 1439 /* Eliminate too old ACKs, but take into 1440 * account more or less fresh ones, they can 1441 * contain valid SACK info. 1442 */ 1443 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) 1444 return 0; 1445 1446 if (!tp->packets_out) 1447 goto out; 1448 1449 used_sacks = 0; 1450 first_sack_index = 0; 1451 for (i = 0; i < num_sacks; i++) { 1452 int dup_sack = !i && found_dup_sack; 1453 1454 sp[used_sacks].start_seq = ntohl(get_unaligned(&sp_wire[i].start_seq)); 1455 sp[used_sacks].end_seq = ntohl(get_unaligned(&sp_wire[i].end_seq)); 1456 1457 if (!tcp_is_sackblock_valid(tp, dup_sack, 1458 sp[used_sacks].start_seq, 1459 sp[used_sacks].end_seq)) { 1460 if (dup_sack) { 1461 if (!tp->undo_marker) 1462 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDNOUNDO); 1463 else 1464 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKIGNOREDOLD); 1465 } else { 1466 /* Don't count olds caused by ACK reordering */ 1467 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) && 1468 !after(sp[used_sacks].end_seq, tp->snd_una)) 1469 continue; 1470 NET_INC_STATS_BH(LINUX_MIB_TCPSACKDISCARD); 1471 } 1472 if (i == 0) 1473 first_sack_index = -1; 1474 continue; 1475 } 1476 1477 /* Ignore very old stuff early */ 1478 if (!after(sp[used_sacks].end_seq, prior_snd_una)) 1479 continue; 1480 1481 used_sacks++; 1482 } 1483 1484 /* order SACK blocks to allow in order walk of the retrans queue */ 1485 for (i = used_sacks - 1; i > 0; i--) { 1486 for (j = 0; j < i; j++){ 1487 if (after(sp[j].start_seq, sp[j+1].start_seq)) { 1488 struct tcp_sack_block tmp; 1489 1490 tmp = sp[j]; 1491 sp[j] = sp[j+1]; 1492 sp[j+1] = tmp; 1493 1494 /* Track where the first SACK block goes to */ 1495 if (j == first_sack_index) 1496 first_sack_index = j+1; 1497 } 1498 } 1499 } 1500 1501 skb = tcp_write_queue_head(sk); 1502 fack_count = 0; 1503 i = 0; 1504 1505 if (!tp->sacked_out) { 1506 /* It's already past, so skip checking against it */ 1507 cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); 1508 } else { 1509 cache = tp->recv_sack_cache; 1510 /* Skip empty blocks in at head of the cache */ 1511 while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq && 1512 !cache->end_seq) 1513 cache++; 1514 } 1515 1516 while (i < used_sacks) { 1517 u32 start_seq = sp[i].start_seq; 1518 u32 end_seq = sp[i].end_seq; 1519 int dup_sack = (found_dup_sack && (i == first_sack_index)); 1520 struct tcp_sack_block *next_dup = NULL; 1521 1522 if (found_dup_sack && ((i + 1) == first_sack_index)) 1523 next_dup = &sp[i + 1]; 1524 1525 /* Event "B" in the comment above. */ 1526 if (after(end_seq, tp->high_seq)) 1527 flag |= FLAG_DATA_LOST; 1528 1529 /* Skip too early cached blocks */ 1530 while (tcp_sack_cache_ok(tp, cache) && 1531 !before(start_seq, cache->end_seq)) 1532 cache++; 1533 1534 /* Can skip some work by looking recv_sack_cache? */ 1535 if (tcp_sack_cache_ok(tp, cache) && !dup_sack && 1536 after(end_seq, cache->start_seq)) { 1537 1538 /* Head todo? */ 1539 if (before(start_seq, cache->start_seq)) { 1540 skb = tcp_sacktag_skip(skb, sk, start_seq); 1541 skb = tcp_sacktag_walk(skb, sk, next_dup, start_seq, 1542 cache->start_seq, dup_sack, 1543 &fack_count, &reord, &flag); 1544 } 1545 1546 /* Rest of the block already fully processed? */ 1547 if (!after(end_seq, cache->end_seq)) 1548 goto advance_sp; 1549 1550 skb = tcp_maybe_skipping_dsack(skb, sk, next_dup, cache->end_seq, 1551 &fack_count, &reord, &flag); 1552 1553 /* ...tail remains todo... */ 1554 if (tcp_highest_sack_seq(tp) == cache->end_seq) { 1555 /* ...but better entrypoint exists! */ 1556 skb = tcp_highest_sack(sk); 1557 if (skb == NULL) 1558 break; 1559 fack_count = tp->fackets_out; 1560 cache++; 1561 goto walk; 1562 } 1563 1564 skb = tcp_sacktag_skip(skb, sk, cache->end_seq); 1565 /* Check overlap against next cached too (past this one already) */ 1566 cache++; 1567 continue; 1568 } 1569 1570 if (!before(start_seq, tcp_highest_sack_seq(tp))) { 1571 skb = tcp_highest_sack(sk); 1572 if (skb == NULL) 1573 break; 1574 fack_count = tp->fackets_out; 1575 } 1576 skb = tcp_sacktag_skip(skb, sk, start_seq); 1577 1578walk: 1579 skb = tcp_sacktag_walk(skb, sk, next_dup, start_seq, end_seq, 1580 dup_sack, &fack_count, &reord, &flag); 1581 1582advance_sp: 1583 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct 1584 * due to in-order walk 1585 */ 1586 if (after(end_seq, tp->frto_highmark)) 1587 flag &= ~FLAG_ONLY_ORIG_SACKED; 1588 1589 i++; 1590 } 1591 1592 /* Clear the head of the cache sack blocks so we can skip it next time */ 1593 for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) { 1594 tp->recv_sack_cache[i].start_seq = 0; 1595 tp->recv_sack_cache[i].end_seq = 0; 1596 } 1597 for (j = 0; j < used_sacks; j++) 1598 tp->recv_sack_cache[i++] = sp[j]; 1599 1600 tcp_mark_lost_retrans(sk); 1601 1602 tcp_verify_left_out(tp); 1603 1604 if ((reord < tp->fackets_out) && 1605 ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) && 1606 (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark))) 1607 tcp_update_reordering(sk, tp->fackets_out - reord, 0); 1608 1609out: 1610 1611#if FASTRETRANS_DEBUG > 0 1612 BUG_TRAP((int)tp->sacked_out >= 0); 1613 BUG_TRAP((int)tp->lost_out >= 0); 1614 BUG_TRAP((int)tp->retrans_out >= 0); 1615 BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0); 1616#endif 1617 return flag; 1618} 1619 1620/* If we receive more dupacks than we expected counting segments 1621 * in assumption of absent reordering, interpret this as reordering. 1622 * The only another reason could be bug in receiver TCP. 1623 */ 1624static void tcp_check_reno_reordering(struct sock *sk, const int addend) 1625{ 1626 struct tcp_sock *tp = tcp_sk(sk); 1627 u32 holes; 1628 1629 holes = max(tp->lost_out, 1U); 1630 holes = min(holes, tp->packets_out); 1631 1632 if ((tp->sacked_out + holes) > tp->packets_out) { 1633 tp->sacked_out = tp->packets_out - holes; 1634 tcp_update_reordering(sk, tp->packets_out + addend, 0); 1635 } 1636} 1637 1638/* Emulate SACKs for SACKless connection: account for a new dupack. */ 1639 1640static void tcp_add_reno_sack(struct sock *sk) 1641{ 1642 struct tcp_sock *tp = tcp_sk(sk); 1643 tp->sacked_out++; 1644 tcp_check_reno_reordering(sk, 0); 1645 tcp_verify_left_out(tp); 1646} 1647 1648/* Account for ACK, ACKing some data in Reno Recovery phase. */ 1649 1650static void tcp_remove_reno_sacks(struct sock *sk, int acked) 1651{ 1652 struct tcp_sock *tp = tcp_sk(sk); 1653 1654 if (acked > 0) { 1655 /* One ACK acked hole. The rest eat duplicate ACKs. */ 1656 if (acked-1 >= tp->sacked_out) 1657 tp->sacked_out = 0; 1658 else 1659 tp->sacked_out -= acked-1; 1660 } 1661 tcp_check_reno_reordering(sk, acked); 1662 tcp_verify_left_out(tp); 1663} 1664 1665static inline void tcp_reset_reno_sack(struct tcp_sock *tp) 1666{ 1667 tp->sacked_out = 0; 1668} 1669 1670/* F-RTO can only be used if TCP has never retransmitted anything other than 1671 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here) 1672 */ 1673int tcp_use_frto(struct sock *sk) 1674{ 1675 const struct tcp_sock *tp = tcp_sk(sk); 1676 struct sk_buff *skb; 1677 1678 if (!sysctl_tcp_frto) 1679 return 0; 1680 1681 if (IsSackFrto()) 1682 return 1; 1683 1684 /* Avoid expensive walking of rexmit queue if possible */ 1685 if (tp->retrans_out > 1) 1686 return 0; 1687 1688 skb = tcp_write_queue_head(sk); 1689 skb = tcp_write_queue_next(sk, skb); /* Skips head */ 1690 tcp_for_write_queue_from(skb, sk) { 1691 if (skb == tcp_send_head(sk)) 1692 break; 1693 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS) 1694 return 0; 1695 /* Short-circuit when first non-SACKed skb has been checked */ 1696 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) 1697 break; 1698 } 1699 return 1; 1700} 1701 1702/* RTO occurred, but do not yet enter Loss state. Instead, defer RTO 1703 * recovery a bit and use heuristics in tcp_process_frto() to detect if 1704 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to 1705 * keep retrans_out counting accurate (with SACK F-RTO, other than head 1706 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS 1707 * bits are handled if the Loss state is really to be entered (in 1708 * tcp_enter_frto_loss). 1709 * 1710 * Do like tcp_enter_loss() would; when RTO expires the second time it 1711 * does: 1712 * "Reduce ssthresh if it has not yet been made inside this window." 1713 */ 1714void tcp_enter_frto(struct sock *sk) 1715{ 1716 const struct inet_connection_sock *icsk = inet_csk(sk); 1717 struct tcp_sock *tp = tcp_sk(sk); 1718 struct sk_buff *skb; 1719 1720 if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) || 1721 tp->snd_una == tp->high_seq || 1722 ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) && 1723 !icsk->icsk_retransmits)) { 1724 tp->prior_ssthresh = tcp_current_ssthresh(sk); 1725 /* Our state is too optimistic in ssthresh() call because cwnd 1726 * is not reduced until tcp_enter_frto_loss() when previous F-RTO 1727 * recovery has not yet completed. Pattern would be this: RTO, 1728 * Cumulative ACK, RTO (2xRTO for the same segment does not end 1729 * up here twice). 1730 * RFC4138 should be more specific on what to do, even though 1731 * RTO is quite unlikely to occur after the first Cumulative ACK 1732 * due to back-off and complexity of triggering events ... 1733 */ 1734 if (tp->frto_counter) { 1735 u32 stored_cwnd; 1736 stored_cwnd = tp->snd_cwnd; 1737 tp->snd_cwnd = 2; 1738 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 1739 tp->snd_cwnd = stored_cwnd; 1740 } else { 1741 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 1742 } 1743 /* ... in theory, cong.control module could do "any tricks" in 1744 * ssthresh(), which means that ca_state, lost bits and lost_out 1745 * counter would have to be faked before the call occurs. We 1746 * consider that too expensive, unlikely and hacky, so modules 1747 * using these in ssthresh() must deal these incompatibility 1748 * issues if they receives CA_EVENT_FRTO and frto_counter != 0 1749 */ 1750 tcp_ca_event(sk, CA_EVENT_FRTO); 1751 } 1752 1753 tp->undo_marker = tp->snd_una; 1754 tp->undo_retrans = 0; 1755 1756 skb = tcp_write_queue_head(sk); 1757 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 1758 tp->undo_marker = 0; 1759 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 1760 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1761 tp->retrans_out -= tcp_skb_pcount(skb); 1762 } 1763 tcp_verify_left_out(tp); 1764 1765 /* Too bad if TCP was application limited */ 1766 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1); 1767 1768 /* Earlier loss recovery underway (see RFC4138; Appendix B). 1769 * The last condition is necessary at least in tp->frto_counter case. 1770 */ 1771 if (IsSackFrto() && (tp->frto_counter || 1772 ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) && 1773 after(tp->high_seq, tp->snd_una)) { 1774 tp->frto_highmark = tp->high_seq; 1775 } else { 1776 tp->frto_highmark = tp->snd_nxt; 1777 } 1778 tcp_set_ca_state(sk, TCP_CA_Disorder); 1779 tp->high_seq = tp->snd_nxt; 1780 tp->frto_counter = 1; 1781} 1782 1783/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO, 1784 * which indicates that we should follow the traditional RTO recovery, 1785 * i.e. mark everything lost and do go-back-N retransmission. 1786 */ 1787static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag) 1788{ 1789 struct tcp_sock *tp = tcp_sk(sk); 1790 struct sk_buff *skb; 1791 1792 tp->lost_out = 0; 1793 tp->retrans_out = 0; 1794 if (tcp_is_reno(tp)) 1795 tcp_reset_reno_sack(tp); 1796 1797 tcp_for_write_queue(skb, sk) { 1798 if (skb == tcp_send_head(sk)) 1799 break; 1800 1801 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 1802 /* 1803 * Count the retransmission made on RTO correctly (only when 1804 * waiting for the first ACK and did not get it)... 1805 */ 1806 if ((tp->frto_counter == 1) && !(flag&FLAG_DATA_ACKED)) { 1807 /* For some reason this R-bit might get cleared? */ 1808 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) 1809 tp->retrans_out += tcp_skb_pcount(skb); 1810 /* ...enter this if branch just for the first segment */ 1811 flag |= FLAG_DATA_ACKED; 1812 } else { 1813 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 1814 tp->undo_marker = 0; 1815 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1816 } 1817 1818 /* Don't lost mark skbs that were fwd transmitted after RTO */ 1819 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) && 1820 !after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark)) { 1821 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1822 tp->lost_out += tcp_skb_pcount(skb); 1823 } 1824 } 1825 tcp_verify_left_out(tp); 1826 1827 tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments; 1828 tp->snd_cwnd_cnt = 0; 1829 tp->snd_cwnd_stamp = tcp_time_stamp; 1830 tp->frto_counter = 0; 1831 tp->bytes_acked = 0; 1832 1833 tp->reordering = min_t(unsigned int, tp->reordering, 1834 sysctl_tcp_reordering); 1835 tcp_set_ca_state(sk, TCP_CA_Loss); 1836 tp->high_seq = tp->frto_highmark; 1837 TCP_ECN_queue_cwr(tp); 1838 1839 tcp_clear_retrans_hints_partial(tp); 1840} 1841 1842static void tcp_clear_retrans_partial(struct tcp_sock *tp) 1843{ 1844 tp->retrans_out = 0; 1845 tp->lost_out = 0; 1846 1847 tp->undo_marker = 0; 1848 tp->undo_retrans = 0; 1849} 1850 1851void tcp_clear_retrans(struct tcp_sock *tp) 1852{ 1853 tcp_clear_retrans_partial(tp); 1854 1855 tp->fackets_out = 0; 1856 tp->sacked_out = 0; 1857} 1858 1859/* Enter Loss state. If "how" is not zero, forget all SACK information 1860 * and reset tags completely, otherwise preserve SACKs. If receiver 1861 * dropped its ofo queue, we will know this due to reneging detection. 1862 */ 1863void tcp_enter_loss(struct sock *sk, int how) 1864{ 1865 const struct inet_connection_sock *icsk = inet_csk(sk); 1866 struct tcp_sock *tp = tcp_sk(sk); 1867 struct sk_buff *skb; 1868 1869 /* Reduce ssthresh if it has not yet been made inside this window. */ 1870 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq || 1871 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { 1872 tp->prior_ssthresh = tcp_current_ssthresh(sk); 1873 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 1874 tcp_ca_event(sk, CA_EVENT_LOSS); 1875 } 1876 tp->snd_cwnd = 1; 1877 tp->snd_cwnd_cnt = 0; 1878 tp->snd_cwnd_stamp = tcp_time_stamp; 1879 1880 tp->bytes_acked = 0; 1881 tcp_clear_retrans_partial(tp); 1882 1883 if (tcp_is_reno(tp)) 1884 tcp_reset_reno_sack(tp); 1885 1886 if (!how) { 1887 /* Push undo marker, if it was plain RTO and nothing 1888 * was retransmitted. */ 1889 tp->undo_marker = tp->snd_una; 1890 tcp_clear_retrans_hints_partial(tp); 1891 } else { 1892 tp->sacked_out = 0; 1893 tp->fackets_out = 0; 1894 tcp_clear_all_retrans_hints(tp); 1895 } 1896 1897 tcp_for_write_queue(skb, sk) { 1898 if (skb == tcp_send_head(sk)) 1899 break; 1900 1901 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS) 1902 tp->undo_marker = 0; 1903 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; 1904 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { 1905 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; 1906 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1907 tp->lost_out += tcp_skb_pcount(skb); 1908 } 1909 } 1910 tcp_verify_left_out(tp); 1911 1912 tp->reordering = min_t(unsigned int, tp->reordering, 1913 sysctl_tcp_reordering); 1914 tcp_set_ca_state(sk, TCP_CA_Loss); 1915 tp->high_seq = tp->snd_nxt; 1916 TCP_ECN_queue_cwr(tp); 1917 /* Abort F-RTO algorithm if one is in progress */ 1918 tp->frto_counter = 0; 1919} 1920 1921static int tcp_check_sack_reneging(struct sock *sk) 1922{ 1923 struct sk_buff *skb; 1924 1925 /* If ACK arrived pointing to a remembered SACK, 1926 * it means that our remembered SACKs do not reflect 1927 * real state of receiver i.e. 1928 * receiver _host_ is heavily congested (or buggy). 1929 * Do processing similar to RTO timeout. 1930 */ 1931 if ((skb = tcp_write_queue_head(sk)) != NULL && 1932 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 1933 struct inet_connection_sock *icsk = inet_csk(sk); 1934 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING); 1935 1936 tcp_enter_loss(sk, 1); 1937 icsk->icsk_retransmits++; 1938 tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); 1939 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 1940 icsk->icsk_rto, TCP_RTO_MAX); 1941 return 1; 1942 } 1943 return 0; 1944} 1945 1946static inline int tcp_fackets_out(struct tcp_sock *tp) 1947{ 1948 return tcp_is_reno(tp) ? tp->sacked_out+1 : tp->fackets_out; 1949} 1950 1951/* Heurestics to calculate number of duplicate ACKs. There's no dupACKs 1952 * counter when SACK is enabled (without SACK, sacked_out is used for 1953 * that purpose). 1954 * 1955 * Instead, with FACK TCP uses fackets_out that includes both SACKed 1956 * segments up to the highest received SACK block so far and holes in 1957 * between them. 1958 * 1959 * With reordering, holes may still be in flight, so RFC3517 recovery 1960 * uses pure sacked_out (total number of SACKed segments) even though 1961 * it violates the RFC that uses duplicate ACKs, often these are equal 1962 * but when e.g. out-of-window ACKs or packet duplication occurs, 1963 * they differ. Since neither occurs due to loss, TCP should really 1964 * ignore them. 1965 */ 1966static inline int tcp_dupack_heurestics(struct tcp_sock *tp) 1967{ 1968 return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1; 1969} 1970 1971static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb) 1972{ 1973 return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto); 1974} 1975 1976static inline int tcp_head_timedout(struct sock *sk) 1977{ 1978 struct tcp_sock *tp = tcp_sk(sk); 1979 1980 return tp->packets_out && 1981 tcp_skb_timedout(sk, tcp_write_queue_head(sk)); 1982} 1983 1984/* Linux NewReno/SACK/FACK/ECN state machine. 1985 * -------------------------------------- 1986 * 1987 * "Open" Normal state, no dubious events, fast path. 1988 * "Disorder" In all the respects it is "Open", 1989 * but requires a bit more attention. It is entered when 1990 * we see some SACKs or dupacks. It is split of "Open" 1991 * mainly to move some processing from fast path to slow one. 1992 * "CWR" CWND was reduced due to some Congestion Notification event. 1993 * It can be ECN, ICMP source quench, local device congestion. 1994 * "Recovery" CWND was reduced, we are fast-retransmitting. 1995 * "Loss" CWND was reduced due to RTO timeout or SACK reneging. 1996 * 1997 * tcp_fastretrans_alert() is entered: 1998 * - each incoming ACK, if state is not "Open" 1999 * - when arrived ACK is unusual, namely: 2000 * * SACK 2001 * * Duplicate ACK. 2002 * * ECN ECE. 2003 * 2004 * Counting packets in flight is pretty simple. 2005 * 2006 * in_flight = packets_out - left_out + retrans_out 2007 * 2008 * packets_out is SND.NXT-SND.UNA counted in packets. 2009 * 2010 * retrans_out is number of retransmitted segments. 2011 * 2012 * left_out is number of segments left network, but not ACKed yet. 2013 * 2014 * left_out = sacked_out + lost_out 2015 * 2016 * sacked_out: Packets, which arrived to receiver out of order 2017 * and hence not ACKed. With SACKs this number is simply 2018 * amount of SACKed data. Even without SACKs 2019 * it is easy to give pretty reliable estimate of this number, 2020 * counting duplicate ACKs. 2021 * 2022 * lost_out: Packets lost by network. TCP has no explicit 2023 * "loss notification" feedback from network (for now). 2024 * It means that this number can be only _guessed_. 2025 * Actually, it is the heuristics to predict lossage that 2026 * distinguishes different algorithms. 2027 * 2028 * F.e. after RTO, when all the queue is considered as lost, 2029 * lost_out = packets_out and in_flight = retrans_out. 2030 * 2031 * Essentially, we have now two algorithms counting 2032 * lost packets. 2033 * 2034 * FACK: It is the simplest heuristics. As soon as we decided 2035 * that something is lost, we decide that _all_ not SACKed 2036 * packets until the most forward SACK are lost. I.e. 2037 * lost_out = fackets_out - sacked_out and left_out = fackets_out. 2038 * It is absolutely correct estimate, if network does not reorder 2039 * packets. And it loses any connection to reality when reordering 2040 * takes place. We use FACK by default until reordering 2041 * is suspected on the path to this destination. 2042 * 2043 * NewReno: when Recovery is entered, we assume that one segment 2044 * is lost (classic Reno). While we are in Recovery and 2045 * a partial ACK arrives, we assume that one more packet 2046 * is lost (NewReno). This heuristics are the same in NewReno 2047 * and SACK. 2048 * 2049 * Imagine, that's all! Forget about all this shamanism about CWND inflation 2050 * deflation etc. CWND is real congestion window, never inflated, changes 2051 * only according to classic VJ rules. 2052 * 2053 * Really tricky (and requiring careful tuning) part of algorithm 2054 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). 2055 * The first determines the moment _when_ we should reduce CWND and, 2056 * hence, slow down forward transmission. In fact, it determines the moment 2057 * when we decide that hole is caused by loss, rather than by a reorder. 2058 * 2059 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill 2060 * holes, caused by lost packets. 2061 * 2062 * And the most logically complicated part of algorithm is undo 2063 * heuristics. We detect false retransmits due to both too early 2064 * fast retransmit (reordering) and underestimated RTO, analyzing 2065 * timestamps and D-SACKs. When we detect that some segments were 2066 * retransmitted by mistake and CWND reduction was wrong, we undo 2067 * window reduction and abort recovery phase. This logic is hidden 2068 * inside several functions named tcp_try_undo_<something>. 2069 */ 2070 2071/* This function decides, when we should leave Disordered state 2072 * and enter Recovery phase, reducing congestion window. 2073 * 2074 * Main question: may we further continue forward transmission 2075 * with the same cwnd? 2076 */ 2077static int tcp_time_to_recover(struct sock *sk) 2078{ 2079 struct tcp_sock *tp = tcp_sk(sk); 2080 __u32 packets_out; 2081 2082 /* Do not perform any recovery during F-RTO algorithm */ 2083 if (tp->frto_counter) 2084 return 0; 2085 2086 /* Trick#1: The loss is proven. */ 2087 if (tp->lost_out) 2088 return 1; 2089 2090 /* Not-A-Trick#2 : Classic rule... */ 2091 if (tcp_dupack_heurestics(tp) > tp->reordering) 2092 return 1; 2093 2094 /* Trick#3 : when we use RFC2988 timer restart, fast 2095 * retransmit can be triggered by timeout of queue head. 2096 */ 2097 if (tcp_is_fack(tp) && tcp_head_timedout(sk)) 2098 return 1; 2099 2100 /* Trick#4: It is still not OK... But will it be useful to delay 2101 * recovery more? 2102 */ 2103 packets_out = tp->packets_out; 2104 if (packets_out <= tp->reordering && 2105 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && 2106 !tcp_may_send_now(sk)) { 2107 /* We have nothing to send. This connection is limited 2108 * either by receiver window or by application. 2109 */ 2110 return 1; 2111 } 2112 2113 return 0; 2114} 2115 2116/* RFC: This is from the original, I doubt that this is necessary at all: 2117 * clear xmit_retrans hint if seq of this skb is beyond hint. How could we 2118 * retransmitted past LOST markings in the first place? I'm not fully sure 2119 * about undo and end of connection cases, which can cause R without L? 2120 */ 2121static void tcp_verify_retransmit_hint(struct tcp_sock *tp, 2122 struct sk_buff *skb) 2123{ 2124 if ((tp->retransmit_skb_hint != NULL) && 2125 before(TCP_SKB_CB(skb)->seq, 2126 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) 2127 tp->retransmit_skb_hint = NULL; 2128} 2129 2130/* Mark head of queue up as lost. With RFC3517 SACK, the packets is 2131 * is against sacked "cnt", otherwise it's against facked "cnt" 2132 */ 2133static void tcp_mark_head_lost(struct sock *sk, int packets, int fast_rexmit) 2134{ 2135 struct tcp_sock *tp = tcp_sk(sk); 2136 struct sk_buff *skb; 2137 int cnt; 2138 2139 BUG_TRAP(packets <= tp->packets_out); 2140 if (tp->lost_skb_hint) { 2141 skb = tp->lost_skb_hint; 2142 cnt = tp->lost_cnt_hint; 2143 } else { 2144 skb = tcp_write_queue_head(sk); 2145 cnt = 0; 2146 } 2147 2148 tcp_for_write_queue_from(skb, sk) { 2149 if (skb == tcp_send_head(sk)) 2150 break; 2151 /* TODO: do this better */ 2152 /* this is not the most efficient way to do this... */ 2153 tp->lost_skb_hint = skb; 2154 tp->lost_cnt_hint = cnt; 2155 2156 if (tcp_is_fack(tp) || 2157 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 2158 cnt += tcp_skb_pcount(skb); 2159 2160 if (((!fast_rexmit || (tp->lost_out > 0)) && (cnt > packets)) || 2161 after(TCP_SKB_CB(skb)->end_seq, tp->high_seq)) 2162 break; 2163 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_SACKED_ACKED|TCPCB_LOST))) { 2164 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 2165 tp->lost_out += tcp_skb_pcount(skb); 2166 tcp_verify_retransmit_hint(tp, skb); 2167 } 2168 } 2169 tcp_verify_left_out(tp); 2170} 2171 2172/* Account newly detected lost packet(s) */ 2173 2174static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit) 2175{ 2176 struct tcp_sock *tp = tcp_sk(sk); 2177 2178 if (tcp_is_reno(tp)) { 2179 tcp_mark_head_lost(sk, 1, fast_rexmit); 2180 } else if (tcp_is_fack(tp)) { 2181 int lost = tp->fackets_out - tp->reordering; 2182 if (lost <= 0) 2183 lost = 1; 2184 tcp_mark_head_lost(sk, lost, fast_rexmit); 2185 } else { 2186 int sacked_upto = tp->sacked_out - tp->reordering; 2187 if (sacked_upto < 0) 2188 sacked_upto = 0; 2189 tcp_mark_head_lost(sk, sacked_upto, fast_rexmit); 2190 } 2191 2192 /* New heuristics: it is possible only after we switched 2193 * to restart timer each time when something is ACKed. 2194 * Hence, we can detect timed out packets during fast 2195 * retransmit without falling to slow start. 2196 */ 2197 if (tcp_is_fack(tp) && tcp_head_timedout(sk)) { 2198 struct sk_buff *skb; 2199 2200 skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint 2201 : tcp_write_queue_head(sk); 2202 2203 tcp_for_write_queue_from(skb, sk) { 2204 if (skb == tcp_send_head(sk)) 2205 break; 2206 if (!tcp_skb_timedout(sk, skb)) 2207 break; 2208 2209 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_SACKED_ACKED|TCPCB_LOST))) { 2210 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 2211 tp->lost_out += tcp_skb_pcount(skb); 2212 tcp_verify_retransmit_hint(tp, skb); 2213 } 2214 } 2215 2216 tp->scoreboard_skb_hint = skb; 2217 2218 tcp_verify_left_out(tp); 2219 } 2220} 2221 2222/* CWND moderation, preventing bursts due to too big ACKs 2223 * in dubious situations. 2224 */ 2225static inline void tcp_moderate_cwnd(struct tcp_sock *tp) 2226{ 2227 tp->snd_cwnd = min(tp->snd_cwnd, 2228 tcp_packets_in_flight(tp)+tcp_max_burst(tp)); 2229 tp->snd_cwnd_stamp = tcp_time_stamp; 2230} 2231 2232/* Lower bound on congestion window is slow start threshold 2233 * unless congestion avoidance choice decides to overide it. 2234 */ 2235static inline u32 tcp_cwnd_min(const struct sock *sk) 2236{ 2237 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; 2238 2239 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh; 2240} 2241 2242/* Decrease cwnd each second ack. */ 2243static void tcp_cwnd_down(struct sock *sk, int flag) 2244{ 2245 struct tcp_sock *tp = tcp_sk(sk); 2246 int decr = tp->snd_cwnd_cnt + 1; 2247 2248 if ((flag&(FLAG_ANY_PROGRESS|FLAG_DSACKING_ACK)) || 2249 (tcp_is_reno(tp) && !(flag&FLAG_NOT_DUP))) { 2250 tp->snd_cwnd_cnt = decr&1; 2251 decr >>= 1; 2252 2253 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk)) 2254 tp->snd_cwnd -= decr; 2255 2256 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1); 2257 tp->snd_cwnd_stamp = tcp_time_stamp; 2258 } 2259} 2260 2261/* Nothing was retransmitted or returned timestamp is less 2262 * than timestamp of the first retransmission. 2263 */ 2264static inline int tcp_packet_delayed(struct tcp_sock *tp) 2265{ 2266 return !tp->retrans_stamp || 2267 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 2268 (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0); 2269} 2270 2271/* Undo procedures. */ 2272 2273#if FASTRETRANS_DEBUG > 1 2274static void DBGUNDO(struct sock *sk, const char *msg) 2275{ 2276 struct tcp_sock *tp = tcp_sk(sk); 2277 struct inet_sock *inet = inet_sk(sk); 2278 2279 printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n", 2280 msg, 2281 NIPQUAD(inet->daddr), ntohs(inet->dport), 2282 tp->snd_cwnd, tcp_left_out(tp), 2283 tp->snd_ssthresh, tp->prior_ssthresh, 2284 tp->packets_out); 2285} 2286#else 2287#define DBGUNDO(x...) do { } while (0) 2288#endif 2289 2290static void tcp_undo_cwr(struct sock *sk, const int undo) 2291{ 2292 struct tcp_sock *tp = tcp_sk(sk); 2293 2294 if (tp->prior_ssthresh) { 2295 const struct inet_connection_sock *icsk = inet_csk(sk); 2296 2297 if (icsk->icsk_ca_ops->undo_cwnd) 2298 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); 2299 else 2300 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1); 2301 2302 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) { 2303 tp->snd_ssthresh = tp->prior_ssthresh; 2304 TCP_ECN_withdraw_cwr(tp); 2305 } 2306 } else { 2307 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); 2308 } 2309 tcp_moderate_cwnd(tp); 2310 tp->snd_cwnd_stamp = tcp_time_stamp; 2311 2312 /* There is something screwy going on with the retrans hints after 2313 an undo */ 2314 tcp_clear_all_retrans_hints(tp); 2315} 2316 2317static inline int tcp_may_undo(struct tcp_sock *tp) 2318{ 2319 return tp->undo_marker && 2320 (!tp->undo_retrans || tcp_packet_delayed(tp)); 2321} 2322 2323/* People celebrate: "We love our President!" */ 2324static int tcp_try_undo_recovery(struct sock *sk) 2325{ 2326 struct tcp_sock *tp = tcp_sk(sk); 2327 2328 if (tcp_may_undo(tp)) { 2329 /* Happy end! We did not retransmit anything 2330 * or our original transmission succeeded. 2331 */ 2332 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); 2333 tcp_undo_cwr(sk, 1); 2334 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) 2335 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); 2336 else 2337 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO); 2338 tp->undo_marker = 0; 2339 } 2340 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) { 2341 /* Hold old state until something *above* high_seq 2342 * is ACKed. For Reno it is MUST to prevent false 2343 * fast retransmits (RFC2582). SACK TCP is safe. */ 2344 tcp_moderate_cwnd(tp); 2345 return 1; 2346 } 2347 tcp_set_ca_state(sk, TCP_CA_Open); 2348 return 0; 2349} 2350 2351/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ 2352static void tcp_try_undo_dsack(struct sock *sk) 2353{ 2354 struct tcp_sock *tp = tcp_sk(sk); 2355 2356 if (tp->undo_marker && !tp->undo_retrans) { 2357 DBGUNDO(sk, "D-SACK"); 2358 tcp_undo_cwr(sk, 1); 2359 tp->undo_marker = 0; 2360 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO); 2361 } 2362} 2363 2364/* Undo during fast recovery after partial ACK. */ 2365 2366static int tcp_try_undo_partial(struct sock *sk, int acked) 2367{ 2368 struct tcp_sock *tp = tcp_sk(sk); 2369 /* Partial ACK arrived. Force Hoe's retransmit. */ 2370 int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering); 2371 2372 if (tcp_may_undo(tp)) { 2373 /* Plain luck! Hole if filled with delayed 2374 * packet, rather than with a retransmit. 2375 */ 2376 if (tp->retrans_out == 0) 2377 tp->retrans_stamp = 0; 2378 2379 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1); 2380 2381 DBGUNDO(sk, "Hoe"); 2382 tcp_undo_cwr(sk, 0); 2383 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO); 2384 2385 /* So... Do not make Hoe's retransmit yet. 2386 * If the first packet was delayed, the rest 2387 * ones are most probably delayed as well. 2388 */ 2389 failed = 0; 2390 } 2391 return failed; 2392} 2393 2394/* Undo during loss recovery after partial ACK. */ 2395static int tcp_try_undo_loss(struct sock *sk) 2396{ 2397 struct tcp_sock *tp = tcp_sk(sk); 2398 2399 if (tcp_may_undo(tp)) { 2400 struct sk_buff *skb; 2401 tcp_for_write_queue(skb, sk) { 2402 if (skb == tcp_send_head(sk)) 2403 break; 2404 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 2405 } 2406 2407 tcp_clear_all_retrans_hints(tp); 2408 2409 DBGUNDO(sk, "partial loss"); 2410 tp->lost_out = 0; 2411 tcp_undo_cwr(sk, 1); 2412 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); 2413 inet_csk(sk)->icsk_retransmits = 0; 2414 tp->undo_marker = 0; 2415 if (tcp_is_sack(tp)) 2416 tcp_set_ca_state(sk, TCP_CA_Open); 2417 return 1; 2418 } 2419 return 0; 2420} 2421 2422static inline void tcp_complete_cwr(struct sock *sk) 2423{ 2424 struct tcp_sock *tp = tcp_sk(sk); 2425 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 2426 tp->snd_cwnd_stamp = tcp_time_stamp; 2427 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); 2428} 2429 2430static void tcp_try_to_open(struct sock *sk, int flag) 2431{ 2432 struct tcp_sock *tp = tcp_sk(sk); 2433 2434 tcp_verify_left_out(tp); 2435 2436 if (tp->retrans_out == 0) 2437 tp->retrans_stamp = 0; 2438 2439 if (flag&FLAG_ECE) 2440 tcp_enter_cwr(sk, 1); 2441 2442 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { 2443 int state = TCP_CA_Open; 2444 2445 if (tcp_left_out(tp) || tp->retrans_out || tp->undo_marker) 2446 state = TCP_CA_Disorder; 2447 2448 if (inet_csk(sk)->icsk_ca_state != state) { 2449 tcp_set_ca_state(sk, state); 2450 tp->high_seq = tp->snd_nxt; 2451 } 2452 tcp_moderate_cwnd(tp); 2453 } else { 2454 tcp_cwnd_down(sk, flag); 2455 } 2456} 2457 2458static void tcp_mtup_probe_failed(struct sock *sk) 2459{ 2460 struct inet_connection_sock *icsk = inet_csk(sk); 2461 2462 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; 2463 icsk->icsk_mtup.probe_size = 0; 2464} 2465 2466static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb) 2467{ 2468 struct tcp_sock *tp = tcp_sk(sk); 2469 struct inet_connection_sock *icsk = inet_csk(sk); 2470 2471 /* FIXME: breaks with very large cwnd */ 2472 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2473 tp->snd_cwnd = tp->snd_cwnd * 2474 tcp_mss_to_mtu(sk, tp->mss_cache) / 2475 icsk->icsk_mtup.probe_size; 2476 tp->snd_cwnd_cnt = 0; 2477 tp->snd_cwnd_stamp = tcp_time_stamp; 2478 tp->rcv_ssthresh = tcp_current_ssthresh(sk); 2479 2480 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; 2481 icsk->icsk_mtup.probe_size = 0; 2482 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 2483} 2484 2485 2486/* Process an event, which can update packets-in-flight not trivially. 2487 * Main goal of this function is to calculate new estimate for left_out, 2488 * taking into account both packets sitting in receiver's buffer and 2489 * packets lost by network. 2490 * 2491 * Besides that it does CWND reduction, when packet loss is detected 2492 * and changes state of machine. 2493 * 2494 * It does _not_ decide what to send, it is made in function 2495 * tcp_xmit_retransmit_queue(). 2496 */ 2497static void 2498tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag) 2499{ 2500 struct inet_connection_sock *icsk = inet_csk(sk); 2501 struct tcp_sock *tp = tcp_sk(sk); 2502 int is_dupack = !(flag&(FLAG_SND_UNA_ADVANCED|FLAG_NOT_DUP)); 2503 int do_lost = is_dupack || ((flag&FLAG_DATA_SACKED) && 2504 (tcp_fackets_out(tp) > tp->reordering)); 2505 int fast_rexmit = 0; 2506 2507 if (WARN_ON(!tp->packets_out && tp->sacked_out)) 2508 tp->sacked_out = 0; 2509 if (WARN_ON(!tp->sacked_out && tp->fackets_out)) 2510 tp->fackets_out = 0; 2511 2512 /* Now state machine starts. 2513 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ 2514 if (flag&FLAG_ECE) 2515 tp->prior_ssthresh = 0; 2516 2517 /* B. In all the states check for reneging SACKs. */ 2518 if (tp->sacked_out && tcp_check_sack_reneging(sk)) 2519 return; 2520 2521 /* C. Process data loss notification, provided it is valid. */ 2522 if (tcp_is_fack(tp) && (flag & FLAG_DATA_LOST) && 2523 before(tp->snd_una, tp->high_seq) && 2524 icsk->icsk_ca_state != TCP_CA_Open && 2525 tp->fackets_out > tp->reordering) { 2526 tcp_mark_head_lost(sk, tp->fackets_out-tp->reordering, 0); 2527 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS); 2528 } 2529 2530 /* D. Check consistency of the current state. */ 2531 tcp_verify_left_out(tp); 2532 2533 /* E. Check state exit conditions. State can be terminated 2534 * when high_seq is ACKed. */ 2535 if (icsk->icsk_ca_state == TCP_CA_Open) { 2536 BUG_TRAP(tp->retrans_out == 0); 2537 tp->retrans_stamp = 0; 2538 } else if (!before(tp->snd_una, tp->high_seq)) { 2539 switch (icsk->icsk_ca_state) { 2540 case TCP_CA_Loss: 2541 icsk->icsk_retransmits = 0; 2542 if (tcp_try_undo_recovery(sk)) 2543 return; 2544 break; 2545 2546 case TCP_CA_CWR: 2547 /* CWR is to be held something *above* high_seq 2548 * is ACKed for CWR bit to reach receiver. */ 2549 if (tp->snd_una != tp->high_seq) { 2550 tcp_complete_cwr(sk); 2551 tcp_set_ca_state(sk, TCP_CA_Open); 2552 } 2553 break; 2554 2555 case TCP_CA_Disorder: 2556 tcp_try_undo_dsack(sk); 2557 if (!tp->undo_marker || 2558 /* For SACK case do not Open to allow to undo 2559 * catching for all duplicate ACKs. */ 2560 tcp_is_reno(tp) || tp->snd_una != tp->high_seq) { 2561 tp->undo_marker = 0; 2562 tcp_set_ca_state(sk, TCP_CA_Open); 2563 } 2564 break; 2565 2566 case TCP_CA_Recovery: 2567 if (tcp_is_reno(tp)) 2568 tcp_reset_reno_sack(tp); 2569 if (tcp_try_undo_recovery(sk)) 2570 return; 2571 tcp_complete_cwr(sk); 2572 break; 2573 } 2574 } 2575 2576 /* F. Process state. */ 2577 switch (icsk->icsk_ca_state) { 2578 case TCP_CA_Recovery: 2579 if (!(flag & FLAG_SND_UNA_ADVANCED)) { 2580 if (tcp_is_reno(tp) && is_dupack) 2581 tcp_add_reno_sack(sk); 2582 } else 2583 do_lost = tcp_try_undo_partial(sk, pkts_acked); 2584 break; 2585 case TCP_CA_Loss: 2586 if (flag&FLAG_DATA_ACKED) 2587 icsk->icsk_retransmits = 0; 2588 if (!tcp_try_undo_loss(sk)) { 2589 tcp_moderate_cwnd(tp); 2590 tcp_xmit_retransmit_queue(sk); 2591 return; 2592 } 2593 if (icsk->icsk_ca_state != TCP_CA_Open) 2594 return; 2595 /* Loss is undone; fall through to processing in Open state. */ 2596 default: 2597 if (tcp_is_reno(tp)) { 2598 if (flag & FLAG_SND_UNA_ADVANCED) 2599 tcp_reset_reno_sack(tp); 2600 if (is_dupack) 2601 tcp_add_reno_sack(sk); 2602 } 2603 2604 if (icsk->icsk_ca_state == TCP_CA_Disorder) 2605 tcp_try_undo_dsack(sk); 2606 2607 if (!tcp_time_to_recover(sk)) { 2608 tcp_try_to_open(sk, flag); 2609 return; 2610 } 2611 2612 /* MTU probe failure: don't reduce cwnd */ 2613 if (icsk->icsk_ca_state < TCP_CA_CWR && 2614 icsk->icsk_mtup.probe_size && 2615 tp->snd_una == tp->mtu_probe.probe_seq_start) { 2616 tcp_mtup_probe_failed(sk); 2617 /* Restores the reduction we did in tcp_mtup_probe() */ 2618 tp->snd_cwnd++; 2619 tcp_simple_retransmit(sk); 2620 return; 2621 } 2622 2623 /* Otherwise enter Recovery state */ 2624 2625 if (tcp_is_reno(tp)) 2626 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY); 2627 else 2628 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY); 2629 2630 tp->high_seq = tp->snd_nxt; 2631 tp->prior_ssthresh = 0; 2632 tp->undo_marker = tp->snd_una; 2633 tp->undo_retrans = tp->retrans_out; 2634 2635 if (icsk->icsk_ca_state < TCP_CA_CWR) { 2636 if (!(flag&FLAG_ECE)) 2637 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2638 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2639 TCP_ECN_queue_cwr(tp); 2640 } 2641 2642 tp->bytes_acked = 0; 2643 tp->snd_cwnd_cnt = 0; 2644 tcp_set_ca_state(sk, TCP_CA_Recovery); 2645 fast_rexmit = 1; 2646 } 2647 2648 if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk))) 2649 tcp_update_scoreboard(sk, fast_rexmit); 2650 tcp_cwnd_down(sk, flag); 2651 tcp_xmit_retransmit_queue(sk); 2652} 2653 2654/* Read draft-ietf-tcplw-high-performance before mucking 2655 * with this code. (Supersedes RFC1323) 2656 */ 2657static void tcp_ack_saw_tstamp(struct sock *sk, int flag) 2658{ 2659 /* RTTM Rule: A TSecr value received in a segment is used to 2660 * update the averaged RTT measurement only if the segment 2661 * acknowledges some new data, i.e., only if it advances the 2662 * left edge of the send window. 2663 * 2664 * See draft-ietf-tcplw-high-performance-00, section 3.3. 2665 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> 2666 * 2667 * Changed: reset backoff as soon as we see the first valid sample. 2668 * If we do not, we get strongly overestimated rto. With timestamps 2669 * samples are accepted even from very old segments: f.e., when rtt=1 2670 * increases to 8, we retransmit 5 times and after 8 seconds delayed 2671 * answer arrives rto becomes 120 seconds! If at least one of segments 2672 * in window is lost... Voila. --ANK (010210) 2673 */ 2674 struct tcp_sock *tp = tcp_sk(sk); 2675 const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr; 2676 tcp_rtt_estimator(sk, seq_rtt); 2677 tcp_set_rto(sk); 2678 inet_csk(sk)->icsk_backoff = 0; 2679 tcp_bound_rto(sk); 2680} 2681 2682static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag) 2683{ 2684 /* We don't have a timestamp. Can only use 2685 * packets that are not retransmitted to determine 2686 * rtt estimates. Also, we must not reset the 2687 * backoff for rto until we get a non-retransmitted 2688 * packet. This allows us to deal with a situation 2689 * where the network delay has increased suddenly. 2690 * I.e. Karn's algorithm. (SIGCOMM '87, p5.) 2691 */ 2692 2693 if (flag & FLAG_RETRANS_DATA_ACKED) 2694 return; 2695 2696 tcp_rtt_estimator(sk, seq_rtt); 2697 tcp_set_rto(sk); 2698 inet_csk(sk)->icsk_backoff = 0; 2699 tcp_bound_rto(sk); 2700} 2701 2702static inline void tcp_ack_update_rtt(struct sock *sk, const int flag, 2703 const s32 seq_rtt) 2704{ 2705 const struct tcp_sock *tp = tcp_sk(sk); 2706 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ 2707 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) 2708 tcp_ack_saw_tstamp(sk, flag); 2709 else if (seq_rtt >= 0) 2710 tcp_ack_no_tstamp(sk, seq_rtt, flag); 2711} 2712 2713static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) 2714{ 2715 const struct inet_connection_sock *icsk = inet_csk(sk); 2716 icsk->icsk_ca_ops->cong_avoid(sk, ack, in_flight); 2717 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp; 2718} 2719 2720/* Restart timer after forward progress on connection. 2721 * RFC2988 recommends to restart timer to now+rto. 2722 */ 2723static void tcp_rearm_rto(struct sock *sk) 2724{ 2725 struct tcp_sock *tp = tcp_sk(sk); 2726 2727 if (!tp->packets_out) { 2728 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); 2729 } else { 2730 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 2731 } 2732} 2733 2734/* If we get here, the whole TSO packet has not been acked. */ 2735static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb) 2736{ 2737 struct tcp_sock *tp = tcp_sk(sk); 2738 u32 packets_acked; 2739 2740 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)); 2741 2742 packets_acked = tcp_skb_pcount(skb); 2743 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) 2744 return 0; 2745 packets_acked -= tcp_skb_pcount(skb); 2746 2747 if (packets_acked) { 2748 BUG_ON(tcp_skb_pcount(skb) == 0); 2749 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)); 2750 } 2751 2752 return packets_acked; 2753} 2754 2755/* Remove acknowledged frames from the retransmission queue. If our packet 2756 * is before the ack sequence we can discard it as it's confirmed to have 2757 * arrived at the other end. 2758 */ 2759static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets) 2760{ 2761 struct tcp_sock *tp = tcp_sk(sk); 2762 const struct inet_connection_sock *icsk = inet_csk(sk); 2763 struct sk_buff *skb; 2764 u32 now = tcp_time_stamp; 2765 int fully_acked = 1; 2766 int flag = 0; 2767 u32 pkts_acked = 0; 2768 u32 reord = tp->packets_out; 2769 s32 seq_rtt = -1; 2770 s32 ca_seq_rtt = -1; 2771 ktime_t last_ackt = net_invalid_timestamp(); 2772 2773 while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) { 2774 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 2775 u32 end_seq; 2776 u32 acked_pcount; 2777 u8 sacked = scb->sacked; 2778 2779 /* Determine how many packets and what bytes were acked, tso and else */ 2780 if (after(scb->end_seq, tp->snd_una)) { 2781 if (tcp_skb_pcount(skb) == 1 || 2782 !after(tp->snd_una, scb->seq)) 2783 break; 2784 2785 acked_pcount = tcp_tso_acked(sk, skb); 2786 if (!acked_pcount) 2787 break; 2788 2789 fully_acked = 0; 2790 end_seq = tp->snd_una; 2791 } else { 2792 acked_pcount = tcp_skb_pcount(skb); 2793 end_seq = scb->end_seq; 2794 } 2795 2796 /* MTU probing checks */ 2797 if (fully_acked && icsk->icsk_mtup.probe_size && 2798 !after(tp->mtu_probe.probe_seq_end, scb->end_seq)) { 2799 tcp_mtup_probe_success(sk, skb); 2800 } 2801 2802 if (sacked & TCPCB_RETRANS) { 2803 if (sacked & TCPCB_SACKED_RETRANS) 2804 tp->retrans_out -= acked_pcount; 2805 flag |= FLAG_RETRANS_DATA_ACKED; 2806 ca_seq_rtt = -1; 2807 seq_rtt = -1; 2808 if ((flag & FLAG_DATA_ACKED) || 2809 (acked_pcount > 1)) 2810 flag |= FLAG_NONHEAD_RETRANS_ACKED; 2811 } else { 2812 ca_seq_rtt = now - scb->when; 2813 last_ackt = skb->tstamp; 2814 if (seq_rtt < 0) { 2815 seq_rtt = ca_seq_rtt; 2816 } 2817 if (!(sacked & TCPCB_SACKED_ACKED)) 2818 reord = min(pkts_acked, reord); 2819 } 2820 2821 if (sacked & TCPCB_SACKED_ACKED) 2822 tp->sacked_out -= acked_pcount; 2823 if (sacked & TCPCB_LOST) 2824 tp->lost_out -= acked_pcount; 2825 2826 if (unlikely((sacked & TCPCB_URG) && tp->urg_mode && 2827 !before(end_seq, tp->snd_up))) 2828 tp->urg_mode = 0; 2829 2830 tp->packets_out -= acked_pcount; 2831 pkts_acked += acked_pcount; 2832 2833 /* Initial outgoing SYN's get put onto the write_queue 2834 * just like anything else we transmit. It is not 2835 * true data, and if we misinform our callers that 2836 * this ACK acks real data, we will erroneously exit 2837 * connection startup slow start one packet too 2838 * quickly. This is severely frowned upon behavior. 2839 */ 2840 if (!(scb->flags & TCPCB_FLAG_SYN)) { 2841 flag |= FLAG_DATA_ACKED; 2842 } else { 2843 flag |= FLAG_SYN_ACKED; 2844 tp->retrans_stamp = 0; 2845 } 2846 2847 if (!fully_acked) 2848 break; 2849 2850 tcp_unlink_write_queue(skb, sk); 2851 sk_wmem_free_skb(sk, skb); 2852 tcp_clear_all_retrans_hints(tp); 2853 } 2854 2855 if (flag & FLAG_ACKED) { 2856 const struct tcp_congestion_ops *ca_ops 2857 = inet_csk(sk)->icsk_ca_ops; 2858 2859 tcp_ack_update_rtt(sk, flag, seq_rtt); 2860 tcp_rearm_rto(sk); 2861 2862 if (tcp_is_reno(tp)) { 2863 tcp_remove_reno_sacks(sk, pkts_acked); 2864 } else { 2865 /* Non-retransmitted hole got filled? That's reordering */ 2866 if (reord < prior_fackets) 2867 tcp_update_reordering(sk, tp->fackets_out - reord, 0); 2868 } 2869 2870 tp->fackets_out -= min(pkts_acked, tp->fackets_out); 2871 2872 if (ca_ops->pkts_acked) { 2873 s32 rtt_us = -1; 2874 2875 /* Is the ACK triggering packet unambiguous? */ 2876 if (!(flag & FLAG_RETRANS_DATA_ACKED)) { 2877 /* High resolution needed and available? */ 2878 if (ca_ops->flags & TCP_CONG_RTT_STAMP && 2879 !ktime_equal(last_ackt, 2880 net_invalid_timestamp())) 2881 rtt_us = ktime_us_delta(ktime_get_real(), 2882 last_ackt); 2883 else if (ca_seq_rtt > 0) 2884 rtt_us = jiffies_to_usecs(ca_seq_rtt); 2885 } 2886 2887 ca_ops->pkts_acked(sk, pkts_acked, rtt_us); 2888 } 2889 } 2890 2891#if FASTRETRANS_DEBUG > 0 2892 BUG_TRAP((int)tp->sacked_out >= 0); 2893 BUG_TRAP((int)tp->lost_out >= 0); 2894 BUG_TRAP((int)tp->retrans_out >= 0); 2895 if (!tp->packets_out && tcp_is_sack(tp)) { 2896 icsk = inet_csk(sk); 2897 if (tp->lost_out) { 2898 printk(KERN_DEBUG "Leak l=%u %d\n", 2899 tp->lost_out, icsk->icsk_ca_state); 2900 tp->lost_out = 0; 2901 } 2902 if (tp->sacked_out) { 2903 printk(KERN_DEBUG "Leak s=%u %d\n", 2904 tp->sacked_out, icsk->icsk_ca_state); 2905 tp->sacked_out = 0; 2906 } 2907 if (tp->retrans_out) { 2908 printk(KERN_DEBUG "Leak r=%u %d\n", 2909 tp->retrans_out, icsk->icsk_ca_state); 2910 tp->retrans_out = 0; 2911 } 2912 } 2913#endif 2914 return flag; 2915} 2916 2917static void tcp_ack_probe(struct sock *sk) 2918{ 2919 const struct tcp_sock *tp = tcp_sk(sk); 2920 struct inet_connection_sock *icsk = inet_csk(sk); 2921 2922 /* Was it a usable window open? */ 2923 2924 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, 2925 tp->snd_una + tp->snd_wnd)) { 2926 icsk->icsk_backoff = 0; 2927 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0); 2928 /* Socket must be waked up by subsequent tcp_data_snd_check(). 2929 * This function is not for random using! 2930 */ 2931 } else { 2932 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 2933 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), 2934 TCP_RTO_MAX); 2935 } 2936} 2937 2938static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag) 2939{ 2940 return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || 2941 inet_csk(sk)->icsk_ca_state != TCP_CA_Open); 2942} 2943 2944static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag) 2945{ 2946 const struct tcp_sock *tp = tcp_sk(sk); 2947 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) && 2948 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR)); 2949} 2950 2951/* Check that window update is acceptable. 2952 * The function assumes that snd_una<=ack<=snd_next. 2953 */ 2954static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack, 2955 const u32 ack_seq, const u32 nwin) 2956{ 2957 return (after(ack, tp->snd_una) || 2958 after(ack_seq, tp->snd_wl1) || 2959 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd)); 2960} 2961 2962/* Update our send window. 2963 * 2964 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 2965 * and in FreeBSD. NetBSD's one is even worse.) is wrong. 2966 */ 2967static int tcp_ack_update_window(struct sock *sk, struct sk_buff *skb, u32 ack, 2968 u32 ack_seq) 2969{ 2970 struct tcp_sock *tp = tcp_sk(sk); 2971 int flag = 0; 2972 u32 nwin = ntohs(tcp_hdr(skb)->window); 2973 2974 if (likely(!tcp_hdr(skb)->syn)) 2975 nwin <<= tp->rx_opt.snd_wscale; 2976 2977 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { 2978 flag |= FLAG_WIN_UPDATE; 2979 tcp_update_wl(tp, ack, ack_seq); 2980 2981 if (tp->snd_wnd != nwin) { 2982 tp->snd_wnd = nwin; 2983 2984 /* Note, it is the only place, where 2985 * fast path is recovered for sending TCP. 2986 */ 2987 tp->pred_flags = 0; 2988 tcp_fast_path_check(sk); 2989 2990 if (nwin > tp->max_window) { 2991 tp->max_window = nwin; 2992 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie); 2993 } 2994 } 2995 } 2996 2997 tp->snd_una = ack; 2998 2999 return flag; 3000} 3001 3002/* A very conservative spurious RTO response algorithm: reduce cwnd and 3003 * continue in congestion avoidance. 3004 */ 3005static void tcp_conservative_spur_to_response(struct tcp_sock *tp) 3006{ 3007 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 3008 tp->snd_cwnd_cnt = 0; 3009 tp->bytes_acked = 0; 3010 TCP_ECN_queue_cwr(tp); 3011 tcp_moderate_cwnd(tp); 3012} 3013 3014/* A conservative spurious RTO response algorithm: reduce cwnd using 3015 * rate halving and continue in congestion avoidance. 3016 */ 3017static void tcp_ratehalving_spur_to_response(struct sock *sk) 3018{ 3019 tcp_enter_cwr(sk, 0); 3020} 3021 3022static void tcp_undo_spur_to_response(struct sock *sk, int flag) 3023{ 3024 if (flag&FLAG_ECE) 3025 tcp_ratehalving_spur_to_response(sk); 3026 else 3027 tcp_undo_cwr(sk, 1); 3028} 3029 3030/* F-RTO spurious RTO detection algorithm (RFC4138) 3031 * 3032 * F-RTO affects during two new ACKs following RTO (well, almost, see inline 3033 * comments). State (ACK number) is kept in frto_counter. When ACK advances 3034 * window (but not to or beyond highest sequence sent before RTO): 3035 * On First ACK, send two new segments out. 3036 * On Second ACK, RTO was likely spurious. Do spurious response (response 3037 * algorithm is not part of the F-RTO detection algorithm 3038 * given in RFC4138 but can be selected separately). 3039 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss 3040 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding 3041 * of Nagle, this is done using frto_counter states 2 and 3, when a new data 3042 * segment of any size sent during F-RTO, state 2 is upgraded to 3. 3043 * 3044 * Rationale: if the RTO was spurious, new ACKs should arrive from the 3045 * original window even after we transmit two new data segments. 3046 * 3047 * SACK version: 3048 * on first step, wait until first cumulative ACK arrives, then move to 3049 * the second step. In second step, the next ACK decides. 3050 * 3051 * F-RTO is implemented (mainly) in four functions: 3052 * - tcp_use_frto() is used to determine if TCP is can use F-RTO 3053 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is 3054 * called when tcp_use_frto() showed green light 3055 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm 3056 * - tcp_enter_frto_loss() is called if there is not enough evidence 3057 * to prove that the RTO is indeed spurious. It transfers the control 3058 * from F-RTO to the conventional RTO recovery 3059 */ 3060static int tcp_process_frto(struct sock *sk, int flag) 3061{ 3062 struct tcp_sock *tp = tcp_sk(sk); 3063 3064 tcp_verify_left_out(tp); 3065 3066 /* Duplicate the behavior from Loss state (fastretrans_alert) */ 3067 if (flag&FLAG_DATA_ACKED) 3068 inet_csk(sk)->icsk_retransmits = 0; 3069 3070 if ((flag & FLAG_NONHEAD_RETRANS_ACKED) || 3071 ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED))) 3072 tp->undo_marker = 0; 3073 3074 if (!before(tp->snd_una, tp->frto_highmark)) { 3075 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag); 3076 return 1; 3077 } 3078 3079 if (!IsSackFrto() || tcp_is_reno(tp)) { 3080 /* RFC4138 shortcoming in step 2; should also have case c): 3081 * ACK isn't duplicate nor advances window, e.g., opposite dir 3082 * data, winupdate 3083 */ 3084 if (!(flag&FLAG_ANY_PROGRESS) && (flag&FLAG_NOT_DUP)) 3085 return 1; 3086 3087 if (!(flag&FLAG_DATA_ACKED)) { 3088 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3), 3089 flag); 3090 return 1; 3091 } 3092 } else { 3093 if (!(flag&FLAG_DATA_ACKED) && (tp->frto_counter == 1)) { 3094 /* Prevent sending of new data. */ 3095 tp->snd_cwnd = min(tp->snd_cwnd, 3096 tcp_packets_in_flight(tp)); 3097 return 1; 3098 } 3099 3100 if ((tp->frto_counter >= 2) && 3101 (!(flag&FLAG_FORWARD_PROGRESS) || 3102 ((flag&FLAG_DATA_SACKED) && !(flag&FLAG_ONLY_ORIG_SACKED)))) { 3103 /* RFC4138 shortcoming (see comment above) */ 3104 if (!(flag&FLAG_FORWARD_PROGRESS) && (flag&FLAG_NOT_DUP)) 3105 return 1; 3106 3107 tcp_enter_frto_loss(sk, 3, flag); 3108 return 1; 3109 } 3110 } 3111 3112 if (tp->frto_counter == 1) { 3113 /* tcp_may_send_now needs to see updated state */ 3114 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; 3115 tp->frto_counter = 2; 3116 3117 if (!tcp_may_send_now(sk)) 3118 tcp_enter_frto_loss(sk, 2, flag); 3119 3120 return 1; 3121 } else { 3122 switch (sysctl_tcp_frto_response) { 3123 case 2: 3124 tcp_undo_spur_to_response(sk, flag); 3125 break; 3126 case 1: 3127 tcp_conservative_spur_to_response(tp); 3128 break; 3129 default: 3130 tcp_ratehalving_spur_to_response(sk); 3131 break; 3132 } 3133 tp->frto_counter = 0; 3134 tp->undo_marker = 0; 3135 NET_INC_STATS_BH(LINUX_MIB_TCPSPURIOUSRTOS); 3136 } 3137 return 0; 3138} 3139 3140/* This routine deals with incoming acks, but not outgoing ones. */ 3141static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) 3142{ 3143 struct inet_connection_sock *icsk = inet_csk(sk); 3144 struct tcp_sock *tp = tcp_sk(sk); 3145 u32 prior_snd_una = tp->snd_una; 3146 u32 ack_seq = TCP_SKB_CB(skb)->seq; 3147 u32 ack = TCP_SKB_CB(skb)->ack_seq; 3148 u32 prior_in_flight; 3149 u32 prior_fackets; 3150 int prior_packets; 3151 int frto_cwnd = 0; 3152 3153 /* If the ack is newer than sent or older than previous acks 3154 * then we can probably ignore it. 3155 */ 3156 if (after(ack, tp->snd_nxt)) 3157 goto uninteresting_ack; 3158 3159 if (before(ack, prior_snd_una)) 3160 goto old_ack; 3161 3162 if (after(ack, prior_snd_una)) 3163 flag |= FLAG_SND_UNA_ADVANCED; 3164 3165 if (sysctl_tcp_abc) { 3166 if (icsk->icsk_ca_state < TCP_CA_CWR) 3167 tp->bytes_acked += ack - prior_snd_una; 3168 else if (icsk->icsk_ca_state == TCP_CA_Loss) 3169 /* we assume just one segment left network */ 3170 tp->bytes_acked += min(ack - prior_snd_una, tp->mss_cache); 3171 } 3172 3173 prior_fackets = tp->fackets_out; 3174 prior_in_flight = tcp_packets_in_flight(tp); 3175 3176 if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) { 3177 /* Window is constant, pure forward advance. 3178 * No more checks are required. 3179 * Note, we use the fact that SND.UNA>=SND.WL2. 3180 */ 3181 tcp_update_wl(tp, ack, ack_seq); 3182 tp->snd_una = ack; 3183 flag |= FLAG_WIN_UPDATE; 3184 3185 tcp_ca_event(sk, CA_EVENT_FAST_ACK); 3186 3187 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS); 3188 } else { 3189 if (ack_seq != TCP_SKB_CB(skb)->end_seq) 3190 flag |= FLAG_DATA; 3191 else 3192 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS); 3193 3194 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq); 3195 3196 if (TCP_SKB_CB(skb)->sacked) 3197 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); 3198 3199 if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) 3200 flag |= FLAG_ECE; 3201 3202 tcp_ca_event(sk, CA_EVENT_SLOW_ACK); 3203 } 3204 3205 /* We passed data and got it acked, remove any soft error 3206 * log. Something worked... 3207 */ 3208 sk->sk_err_soft = 0; 3209 tp->rcv_tstamp = tcp_time_stamp; 3210 prior_packets = tp->packets_out; 3211 if (!prior_packets) 3212 goto no_queue; 3213 3214 /* See if we can take anything off of the retransmit queue. */ 3215 flag |= tcp_clean_rtx_queue(sk, prior_fackets); 3216 3217 if (tp->frto_counter) 3218 frto_cwnd = tcp_process_frto(sk, flag); 3219 /* Guarantee sacktag reordering detection against wrap-arounds */ 3220 if (before(tp->frto_highmark, tp->snd_una)) 3221 tp->frto_highmark = 0; 3222 3223 if (tcp_ack_is_dubious(sk, flag)) { 3224 /* Advance CWND, if state allows this. */ 3225 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd && 3226 tcp_may_raise_cwnd(sk, flag)) 3227 tcp_cong_avoid(sk, ack, prior_in_flight); 3228 tcp_fastretrans_alert(sk, prior_packets - tp->packets_out, flag); 3229 } else { 3230 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd) 3231 tcp_cong_avoid(sk, ack, prior_in_flight); 3232 } 3233 3234 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP)) 3235 dst_confirm(sk->sk_dst_cache); 3236 3237 return 1; 3238 3239no_queue: 3240 icsk->icsk_probes_out = 0; 3241 3242 /* If this ack opens up a zero window, clear backoff. It was 3243 * being used to time the probes, and is probably far higher than 3244 * it needs to be for normal retransmission. 3245 */ 3246 if (tcp_send_head(sk)) 3247 tcp_ack_probe(sk); 3248 return 1; 3249 3250old_ack: 3251 if (TCP_SKB_CB(skb)->sacked) 3252 tcp_sacktag_write_queue(sk, skb, prior_snd_una); 3253 3254uninteresting_ack: 3255 SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt); 3256 return 0; 3257} 3258 3259 3260/* Look for tcp options. Normally only called on SYN and SYNACK packets. 3261 * But, this can also be called on packets in the established flow when 3262 * the fast version below fails. 3263 */ 3264void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab) 3265{ 3266 unsigned char *ptr; 3267 struct tcphdr *th = tcp_hdr(skb); 3268 int length=(th->doff*4)-sizeof(struct tcphdr); 3269 3270 ptr = (unsigned char *)(th + 1); 3271 opt_rx->saw_tstamp = 0; 3272 3273 while (length > 0) { 3274 int opcode=*ptr++; 3275 int opsize; 3276 3277 switch (opcode) { 3278 case TCPOPT_EOL: 3279 return; 3280 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ 3281 length--; 3282 continue; 3283 default: 3284 opsize=*ptr++; 3285 if (opsize < 2) /* "silly options" */ 3286 return; 3287 if (opsize > length) 3288 return; /* don't parse partial options */ 3289 switch (opcode) { 3290 case TCPOPT_MSS: 3291 if (opsize==TCPOLEN_MSS && th->syn && !estab) { 3292 u16 in_mss = ntohs(get_unaligned((__be16 *)ptr)); 3293 if (in_mss) { 3294 if (opt_rx->user_mss && opt_rx->user_mss < in_mss) 3295 in_mss = opt_rx->user_mss; 3296 opt_rx->mss_clamp = in_mss; 3297 } 3298 } 3299 break; 3300 case TCPOPT_WINDOW: 3301 if (opsize==TCPOLEN_WINDOW && th->syn && !estab) 3302 if (sysctl_tcp_window_scaling) { 3303 __u8 snd_wscale = *(__u8 *) ptr; 3304 opt_rx->wscale_ok = 1; 3305 if (snd_wscale > 14) { 3306 if (net_ratelimit()) 3307 printk(KERN_INFO "tcp_parse_options: Illegal window " 3308 "scaling value %d >14 received.\n", 3309 snd_wscale); 3310 snd_wscale = 14; 3311 } 3312 opt_rx->snd_wscale = snd_wscale; 3313 } 3314 break; 3315 case TCPOPT_TIMESTAMP: 3316 if (opsize==TCPOLEN_TIMESTAMP) { 3317 if ((estab && opt_rx->tstamp_ok) || 3318 (!estab && sysctl_tcp_timestamps)) { 3319 opt_rx->saw_tstamp = 1; 3320 opt_rx->rcv_tsval = ntohl(get_unaligned((__be32 *)ptr)); 3321 opt_rx->rcv_tsecr = ntohl(get_unaligned((__be32 *)(ptr+4))); 3322 } 3323 } 3324 break; 3325 case TCPOPT_SACK_PERM: 3326 if (opsize==TCPOLEN_SACK_PERM && th->syn && !estab) { 3327 if (sysctl_tcp_sack) { 3328 opt_rx->sack_ok = 1; 3329 tcp_sack_reset(opt_rx); 3330 } 3331 } 3332 break; 3333 3334 case TCPOPT_SACK: 3335 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && 3336 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && 3337 opt_rx->sack_ok) { 3338 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; 3339 } 3340 break; 3341#ifdef CONFIG_TCP_MD5SIG 3342 case TCPOPT_MD5SIG: 3343 /* 3344 * The MD5 Hash has already been 3345 * checked (see tcp_v{4,6}_do_rcv()). 3346 */ 3347 break; 3348#endif 3349 } 3350 3351 ptr+=opsize-2; 3352 length-=opsize; 3353 } 3354 } 3355} 3356 3357/* Fast parse options. This hopes to only see timestamps. 3358 * If it is wrong it falls back on tcp_parse_options(). 3359 */ 3360static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th, 3361 struct tcp_sock *tp) 3362{ 3363 if (th->doff == sizeof(struct tcphdr)>>2) { 3364 tp->rx_opt.saw_tstamp = 0; 3365 return 0; 3366 } else if (tp->rx_opt.tstamp_ok && 3367 th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) { 3368 __be32 *ptr = (__be32 *)(th + 1); 3369 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) 3370 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { 3371 tp->rx_opt.saw_tstamp = 1; 3372 ++ptr; 3373 tp->rx_opt.rcv_tsval = ntohl(*ptr); 3374 ++ptr; 3375 tp->rx_opt.rcv_tsecr = ntohl(*ptr); 3376 return 1; 3377 } 3378 } 3379 tcp_parse_options(skb, &tp->rx_opt, 1); 3380 return 1; 3381} 3382 3383static inline void tcp_store_ts_recent(struct tcp_sock *tp) 3384{ 3385 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; 3386 tp->rx_opt.ts_recent_stamp = get_seconds(); 3387} 3388 3389static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) 3390{ 3391 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { 3392 /* PAWS bug workaround wrt. ACK frames, the PAWS discard 3393 * extra check below makes sure this can only happen 3394 * for pure ACK frames. -DaveM 3395 * 3396 * Not only, also it occurs for expired timestamps. 3397 */ 3398 3399 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 || 3400 get_seconds() >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS) 3401 tcp_store_ts_recent(tp); 3402 } 3403} 3404 3405/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM 3406 * 3407 * It is not fatal. If this ACK does _not_ change critical state (seqs, window) 3408 * it can pass through stack. So, the following predicate verifies that 3409 * this segment is not used for anything but congestion avoidance or 3410 * fast retransmit. Moreover, we even are able to eliminate most of such 3411 * second order effects, if we apply some small "replay" window (~RTO) 3412 * to timestamp space. 3413 * 3414 * All these measures still do not guarantee that we reject wrapped ACKs 3415 * on networks with high bandwidth, when sequence space is recycled fastly, 3416 * but it guarantees that such events will be very rare and do not affect 3417 * connection seriously. This doesn't look nice, but alas, PAWS is really 3418 * buggy extension. 3419 * 3420 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC 3421 * states that events when retransmit arrives after original data are rare. 3422 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is 3423 * the biggest problem on large power networks even with minor reordering. 3424 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe 3425 * up to bandwidth of 18Gigabit/sec. 8) ] 3426 */ 3427 3428static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb) 3429{ 3430 struct tcp_sock *tp = tcp_sk(sk); 3431 struct tcphdr *th = tcp_hdr(skb); 3432 u32 seq = TCP_SKB_CB(skb)->seq; 3433 u32 ack = TCP_SKB_CB(skb)->ack_seq; 3434 3435 return (/* 1. Pure ACK with correct sequence number. */ 3436 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && 3437 3438 /* 2. ... and duplicate ACK. */ 3439 ack == tp->snd_una && 3440 3441 /* 3. ... and does not update window. */ 3442 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && 3443 3444 /* 4. ... and sits in replay window. */ 3445 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ); 3446} 3447 3448static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb) 3449{ 3450 const struct tcp_sock *tp = tcp_sk(sk); 3451 return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW && 3452 get_seconds() < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS && 3453 !tcp_disordered_ack(sk, skb)); 3454} 3455 3456/* Check segment sequence number for validity. 3457 * 3458 * Segment controls are considered valid, if the segment 3459 * fits to the window after truncation to the window. Acceptability 3460 * of data (and SYN, FIN, of course) is checked separately. 3461 * See tcp_data_queue(), for example. 3462 * 3463 * Also, controls (RST is main one) are accepted using RCV.WUP instead 3464 * of RCV.NXT. Peer still did not advance his SND.UNA when we 3465 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. 3466 * (borrowed from freebsd) 3467 */ 3468 3469static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq) 3470{ 3471 return !before(end_seq, tp->rcv_wup) && 3472 !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); 3473} 3474 3475/* When we get a reset we do this. */ 3476static void tcp_reset(struct sock *sk) 3477{ 3478 /* We want the right error as BSD sees it (and indeed as we do). */ 3479 switch (sk->sk_state) { 3480 case TCP_SYN_SENT: 3481 sk->sk_err = ECONNREFUSED; 3482 break; 3483 case TCP_CLOSE_WAIT: 3484 sk->sk_err = EPIPE; 3485 break; 3486 case TCP_CLOSE: 3487 return; 3488 default: 3489 sk->sk_err = ECONNRESET; 3490 } 3491 3492 if (!sock_flag(sk, SOCK_DEAD)) 3493 sk->sk_error_report(sk); 3494 3495 tcp_done(sk); 3496} 3497 3498/* 3499 * Process the FIN bit. This now behaves as it is supposed to work 3500 * and the FIN takes effect when it is validly part of sequence 3501 * space. Not before when we get holes. 3502 * 3503 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT 3504 * (and thence onto LAST-ACK and finally, CLOSE, we never enter 3505 * TIME-WAIT) 3506 * 3507 * If we are in FINWAIT-1, a received FIN indicates simultaneous 3508 * close and we go into CLOSING (and later onto TIME-WAIT) 3509 * 3510 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. 3511 */ 3512static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th) 3513{ 3514 struct tcp_sock *tp = tcp_sk(sk); 3515 3516 inet_csk_schedule_ack(sk); 3517 3518 sk->sk_shutdown |= RCV_SHUTDOWN; 3519 sock_set_flag(sk, SOCK_DONE); 3520 3521 switch (sk->sk_state) { 3522 case TCP_SYN_RECV: 3523 case TCP_ESTABLISHED: 3524 /* Move to CLOSE_WAIT */ 3525 tcp_set_state(sk, TCP_CLOSE_WAIT); 3526 inet_csk(sk)->icsk_ack.pingpong = 1; 3527 break; 3528 3529 case TCP_CLOSE_WAIT: 3530 case TCP_CLOSING: 3531 /* Received a retransmission of the FIN, do 3532 * nothing. 3533 */ 3534 break; 3535 case TCP_LAST_ACK: 3536 /* RFC793: Remain in the LAST-ACK state. */ 3537 break; 3538 3539 case TCP_FIN_WAIT1: 3540 /* This case occurs when a simultaneous close 3541 * happens, we must ack the received FIN and 3542 * enter the CLOSING state. 3543 */ 3544 tcp_send_ack(sk); 3545 tcp_set_state(sk, TCP_CLOSING); 3546 break; 3547 case TCP_FIN_WAIT2: 3548 /* Received a FIN -- send ACK and enter TIME_WAIT. */ 3549 tcp_send_ack(sk); 3550 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 3551 break; 3552 default: 3553 /* Only TCP_LISTEN and TCP_CLOSE are left, in these 3554 * cases we should never reach this piece of code. 3555 */ 3556 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n", 3557 __FUNCTION__, sk->sk_state); 3558 break; 3559 } 3560 3561 /* It _is_ possible, that we have something out-of-order _after_ FIN. 3562 * Probably, we should reset in this case. For now drop them. 3563 */ 3564 __skb_queue_purge(&tp->out_of_order_queue); 3565 if (tcp_is_sack(tp)) 3566 tcp_sack_reset(&tp->rx_opt); 3567 sk_mem_reclaim(sk); 3568 3569 if (!sock_flag(sk, SOCK_DEAD)) { 3570 sk->sk_state_change(sk); 3571 3572 /* Do not send POLL_HUP for half duplex close. */ 3573 if (sk->sk_shutdown == SHUTDOWN_MASK || 3574 sk->sk_state == TCP_CLOSE) 3575 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP); 3576 else 3577 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); 3578 } 3579} 3580 3581static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq) 3582{ 3583 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { 3584 if (before(seq, sp->start_seq)) 3585 sp->start_seq = seq; 3586 if (after(end_seq, sp->end_seq)) 3587 sp->end_seq = end_seq; 3588 return 1; 3589 } 3590 return 0; 3591} 3592 3593static void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq) 3594{ 3595 if (tcp_is_sack(tp) && sysctl_tcp_dsack) { 3596 if (before(seq, tp->rcv_nxt)) 3597 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT); 3598 else 3599 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT); 3600 3601 tp->rx_opt.dsack = 1; 3602 tp->duplicate_sack[0].start_seq = seq; 3603 tp->duplicate_sack[0].end_seq = end_seq; 3604 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok); 3605 } 3606} 3607 3608static void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq) 3609{ 3610 if (!tp->rx_opt.dsack) 3611 tcp_dsack_set(tp, seq, end_seq); 3612 else 3613 tcp_sack_extend(tp->duplicate_sack, seq, end_seq); 3614} 3615 3616static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb) 3617{ 3618 struct tcp_sock *tp = tcp_sk(sk); 3619 3620 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 3621 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 3622 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); 3623 tcp_enter_quickack_mode(sk); 3624 3625 if (tcp_is_sack(tp) && sysctl_tcp_dsack) { 3626 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 3627 3628 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) 3629 end_seq = tp->rcv_nxt; 3630 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq); 3631 } 3632 } 3633 3634 tcp_send_ack(sk); 3635} 3636 3637/* These routines update the SACK block as out-of-order packets arrive or 3638 * in-order packets close up the sequence space. 3639 */ 3640static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) 3641{ 3642 int this_sack; 3643 struct tcp_sack_block *sp = &tp->selective_acks[0]; 3644 struct tcp_sack_block *swalk = sp+1; 3645 3646 /* See if the recent change to the first SACK eats into 3647 * or hits the sequence space of other SACK blocks, if so coalesce. 3648 */ 3649 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) { 3650 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { 3651 int i; 3652 3653 /* Zap SWALK, by moving every further SACK up by one slot. 3654 * Decrease num_sacks. 3655 */ 3656 tp->rx_opt.num_sacks--; 3657 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); 3658 for (i=this_sack; i < tp->rx_opt.num_sacks; i++) 3659 sp[i] = sp[i+1]; 3660 continue; 3661 } 3662 this_sack++, swalk++; 3663 } 3664} 3665 3666static inline void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2) 3667{ 3668 __u32 tmp; 3669 3670 tmp = sack1->start_seq; 3671 sack1->start_seq = sack2->start_seq; 3672 sack2->start_seq = tmp; 3673 3674 tmp = sack1->end_seq; 3675 sack1->end_seq = sack2->end_seq; 3676 sack2->end_seq = tmp; 3677} 3678 3679static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) 3680{ 3681 struct tcp_sock *tp = tcp_sk(sk); 3682 struct tcp_sack_block *sp = &tp->selective_acks[0]; 3683 int cur_sacks = tp->rx_opt.num_sacks; 3684 int this_sack; 3685 3686 if (!cur_sacks) 3687 goto new_sack; 3688 3689 for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) { 3690 if (tcp_sack_extend(sp, seq, end_seq)) { 3691 /* Rotate this_sack to the first one. */ 3692 for (; this_sack>0; this_sack--, sp--) 3693 tcp_sack_swap(sp, sp-1); 3694 if (cur_sacks > 1) 3695 tcp_sack_maybe_coalesce(tp); 3696 return; 3697 } 3698 } 3699 3700 /* Could not find an adjacent existing SACK, build a new one, 3701 * put it at the front, and shift everyone else down. We 3702 * always know there is at least one SACK present already here. 3703 * 3704 * If the sack array is full, forget about the last one. 3705 */ 3706 if (this_sack >= 4) { 3707 this_sack--; 3708 tp->rx_opt.num_sacks--; 3709 sp--; 3710 } 3711 for (; this_sack > 0; this_sack--, sp--) 3712 *sp = *(sp-1); 3713 3714new_sack: 3715 /* Build the new head SACK, and we're done. */ 3716 sp->start_seq = seq; 3717 sp->end_seq = end_seq; 3718 tp->rx_opt.num_sacks++; 3719 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); 3720} 3721 3722/* RCV.NXT advances, some SACKs should be eaten. */ 3723 3724static void tcp_sack_remove(struct tcp_sock *tp) 3725{ 3726 struct tcp_sack_block *sp = &tp->selective_acks[0]; 3727 int num_sacks = tp->rx_opt.num_sacks; 3728 int this_sack; 3729 3730 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ 3731 if (skb_queue_empty(&tp->out_of_order_queue)) { 3732 tp->rx_opt.num_sacks = 0; 3733 tp->rx_opt.eff_sacks = tp->rx_opt.dsack; 3734 return; 3735 } 3736 3737 for (this_sack = 0; this_sack < num_sacks; ) { 3738 /* Check if the start of the sack is covered by RCV.NXT. */ 3739 if (!before(tp->rcv_nxt, sp->start_seq)) { 3740 int i; 3741 3742 /* RCV.NXT must cover all the block! */ 3743 BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq)); 3744 3745 /* Zap this SACK, by moving forward any other SACKS. */ 3746 for (i=this_sack+1; i < num_sacks; i++) 3747 tp->selective_acks[i-1] = tp->selective_acks[i]; 3748 num_sacks--; 3749 continue; 3750 } 3751 this_sack++; 3752 sp++; 3753 } 3754 if (num_sacks != tp->rx_opt.num_sacks) { 3755 tp->rx_opt.num_sacks = num_sacks; 3756 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); 3757 } 3758} 3759 3760/* This one checks to see if we can put data from the 3761 * out_of_order queue into the receive_queue. 3762 */ 3763static void tcp_ofo_queue(struct sock *sk) 3764{ 3765 struct tcp_sock *tp = tcp_sk(sk); 3766 __u32 dsack_high = tp->rcv_nxt; 3767 struct sk_buff *skb; 3768 3769 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { 3770 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 3771 break; 3772 3773 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { 3774 __u32 dsack = dsack_high; 3775 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) 3776 dsack_high = TCP_SKB_CB(skb)->end_seq; 3777 tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack); 3778 } 3779 3780 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 3781 SOCK_DEBUG(sk, "ofo packet was already received \n"); 3782 __skb_unlink(skb, &tp->out_of_order_queue); 3783 __kfree_skb(skb); 3784 continue; 3785 } 3786 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", 3787 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 3788 TCP_SKB_CB(skb)->end_seq); 3789 3790 __skb_unlink(skb, &tp->out_of_order_queue); 3791 __skb_queue_tail(&sk->sk_receive_queue, skb); 3792 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 3793 if (tcp_hdr(skb)->fin) 3794 tcp_fin(skb, sk, tcp_hdr(skb)); 3795 } 3796} 3797 3798static int tcp_prune_queue(struct sock *sk); 3799 3800static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) 3801{ 3802 struct tcphdr *th = tcp_hdr(skb); 3803 struct tcp_sock *tp = tcp_sk(sk); 3804 int eaten = -1; 3805 3806 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) 3807 goto drop; 3808 3809 __skb_pull(skb, th->doff*4); 3810 3811 TCP_ECN_accept_cwr(tp, skb); 3812 3813 if (tp->rx_opt.dsack) { 3814 tp->rx_opt.dsack = 0; 3815 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks, 3816 4 - tp->rx_opt.tstamp_ok); 3817 } 3818 3819 /* Queue data for delivery to the user. 3820 * Packets in sequence go to the receive queue. 3821 * Out of sequence packets to the out_of_order_queue. 3822 */ 3823 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { 3824 if (tcp_receive_window(tp) == 0) 3825 goto out_of_window; 3826 3827 /* Ok. In sequence. In window. */ 3828 if (tp->ucopy.task == current && 3829 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && 3830 sock_owned_by_user(sk) && !tp->urg_data) { 3831 int chunk = min_t(unsigned int, skb->len, 3832 tp->ucopy.len); 3833 3834 __set_current_state(TASK_RUNNING); 3835 3836 local_bh_enable(); 3837 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { 3838 tp->ucopy.len -= chunk; 3839 tp->copied_seq += chunk; 3840 eaten = (chunk == skb->len && !th->fin); 3841 tcp_rcv_space_adjust(sk); 3842 } 3843 local_bh_disable(); 3844 } 3845 3846 if (eaten <= 0) { 3847queue_and_out: 3848 if (eaten < 0 && 3849 (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || 3850 !sk_rmem_schedule(sk, skb->truesize))) { 3851 if (tcp_prune_queue(sk) < 0 || 3852 !sk_rmem_schedule(sk, skb->truesize)) 3853 goto drop; 3854 } 3855 skb_set_owner_r(skb, sk); 3856 __skb_queue_tail(&sk->sk_receive_queue, skb); 3857 } 3858 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 3859 if (skb->len) 3860 tcp_event_data_recv(sk, skb); 3861 if (th->fin) 3862 tcp_fin(skb, sk, th); 3863 3864 if (!skb_queue_empty(&tp->out_of_order_queue)) { 3865 tcp_ofo_queue(sk); 3866 3867 /* RFC2581. 4.2. SHOULD send immediate ACK, when 3868 * gap in queue is filled. 3869 */ 3870 if (skb_queue_empty(&tp->out_of_order_queue)) 3871 inet_csk(sk)->icsk_ack.pingpong = 0; 3872 } 3873 3874 if (tp->rx_opt.num_sacks) 3875 tcp_sack_remove(tp); 3876 3877 tcp_fast_path_check(sk); 3878 3879 if (eaten > 0) 3880 __kfree_skb(skb); 3881 else if (!sock_flag(sk, SOCK_DEAD)) 3882 sk->sk_data_ready(sk, 0); 3883 return; 3884 } 3885 3886 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 3887 /* A retransmit, 2nd most common case. Force an immediate ack. */ 3888 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); 3889 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 3890 3891out_of_window: 3892 tcp_enter_quickack_mode(sk); 3893 inet_csk_schedule_ack(sk); 3894drop: 3895 __kfree_skb(skb); 3896 return; 3897 } 3898 3899 /* Out of window. F.e. zero window probe. */ 3900 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) 3901 goto out_of_window; 3902 3903 tcp_enter_quickack_mode(sk); 3904 3905 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 3906 /* Partial packet, seq < rcv_next < end_seq */ 3907 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", 3908 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 3909 TCP_SKB_CB(skb)->end_seq); 3910 3911 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); 3912 3913 /* If window is closed, drop tail of packet. But after 3914 * remembering D-SACK for its head made in previous line. 3915 */ 3916 if (!tcp_receive_window(tp)) 3917 goto out_of_window; 3918 goto queue_and_out; 3919 } 3920 3921 TCP_ECN_check_ce(tp, skb); 3922 3923 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || 3924 !sk_rmem_schedule(sk, skb->truesize)) { 3925 if (tcp_prune_queue(sk) < 0 || 3926 !sk_rmem_schedule(sk, skb->truesize)) 3927 goto drop; 3928 } 3929 3930 /* Disable header prediction. */ 3931 tp->pred_flags = 0; 3932 inet_csk_schedule_ack(sk); 3933 3934 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", 3935 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 3936 3937 skb_set_owner_r(skb, sk); 3938 3939 if (!skb_peek(&tp->out_of_order_queue)) { 3940 /* Initial out of order segment, build 1 SACK. */ 3941 if (tcp_is_sack(tp)) { 3942 tp->rx_opt.num_sacks = 1; 3943 tp->rx_opt.dsack = 0; 3944 tp->rx_opt.eff_sacks = 1; 3945 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; 3946 tp->selective_acks[0].end_seq = 3947 TCP_SKB_CB(skb)->end_seq; 3948 } 3949 __skb_queue_head(&tp->out_of_order_queue,skb); 3950 } else { 3951 struct sk_buff *skb1 = tp->out_of_order_queue.prev; 3952 u32 seq = TCP_SKB_CB(skb)->seq; 3953 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 3954 3955 if (seq == TCP_SKB_CB(skb1)->end_seq) { 3956 __skb_append(skb1, skb, &tp->out_of_order_queue); 3957 3958 if (!tp->rx_opt.num_sacks || 3959 tp->selective_acks[0].end_seq != seq) 3960 goto add_sack; 3961 3962 /* Common case: data arrive in order after hole. */ 3963 tp->selective_acks[0].end_seq = end_seq; 3964 return; 3965 } 3966 3967 /* Find place to insert this segment. */ 3968 do { 3969 if (!after(TCP_SKB_CB(skb1)->seq, seq)) 3970 break; 3971 } while ((skb1 = skb1->prev) != 3972 (struct sk_buff*)&tp->out_of_order_queue); 3973 3974 /* Do skb overlap to previous one? */ 3975 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue && 3976 before(seq, TCP_SKB_CB(skb1)->end_seq)) { 3977 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 3978 /* All the bits are present. Drop. */ 3979 __kfree_skb(skb); 3980 tcp_dsack_set(tp, seq, end_seq); 3981 goto add_sack; 3982 } 3983 if (after(seq, TCP_SKB_CB(skb1)->seq)) { 3984 /* Partial overlap. */ 3985 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq); 3986 } else { 3987 skb1 = skb1->prev; 3988 } 3989 } 3990 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue); 3991 3992 /* And clean segments covered by new one as whole. */ 3993 while ((skb1 = skb->next) != 3994 (struct sk_buff*)&tp->out_of_order_queue && 3995 after(end_seq, TCP_SKB_CB(skb1)->seq)) { 3996 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 3997 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq); 3998 break; 3999 } 4000 __skb_unlink(skb1, &tp->out_of_order_queue); 4001 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq); 4002 __kfree_skb(skb1); 4003 } 4004 4005add_sack: 4006 if (tcp_is_sack(tp)) 4007 tcp_sack_new_ofo_skb(sk, seq, end_seq); 4008 } 4009} 4010 4011/* Collapse contiguous sequence of skbs head..tail with 4012 * sequence numbers start..end. 4013 * Segments with FIN/SYN are not collapsed (only because this 4014 * simplifies code) 4015 */ 4016static void 4017tcp_collapse(struct sock *sk, struct sk_buff_head *list, 4018 struct sk_buff *head, struct sk_buff *tail, 4019 u32 start, u32 end) 4020{ 4021 struct sk_buff *skb; 4022 4023 /* First, check that queue is collapsible and find 4024 * the point where collapsing can be useful. */ 4025 for (skb = head; skb != tail; ) { 4026 /* No new bits? It is possible on ofo queue. */ 4027 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 4028 struct sk_buff *next = skb->next; 4029 __skb_unlink(skb, list); 4030 __kfree_skb(skb); 4031 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); 4032 skb = next; 4033 continue; 4034 } 4035 4036 /* The first skb to collapse is: 4037 * - not SYN/FIN and 4038 * - bloated or contains data before "start" or 4039 * overlaps to the next one. 4040 */ 4041 if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin && 4042 (tcp_win_from_space(skb->truesize) > skb->len || 4043 before(TCP_SKB_CB(skb)->seq, start) || 4044 (skb->next != tail && 4045 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq))) 4046 break; 4047 4048 /* Decided to skip this, advance start seq. */ 4049 start = TCP_SKB_CB(skb)->end_seq; 4050 skb = skb->next; 4051 } 4052 if (skb == tail || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin) 4053 return; 4054 4055 while (before(start, end)) { 4056 struct sk_buff *nskb; 4057 unsigned int header = skb_headroom(skb); 4058 int copy = SKB_MAX_ORDER(header, 0); 4059 4060 /* Too big header? This can happen with IPv6. */ 4061 if (copy < 0) 4062 return; 4063 if (end-start < copy) 4064 copy = end-start; 4065 nskb = alloc_skb(copy+header, GFP_ATOMIC); 4066 if (!nskb) 4067 return; 4068 4069 skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head); 4070 skb_set_network_header(nskb, (skb_network_header(skb) - 4071 skb->head)); 4072 skb_set_transport_header(nskb, (skb_transport_header(skb) - 4073 skb->head)); 4074 skb_reserve(nskb, header); 4075 memcpy(nskb->head, skb->head, header); 4076 memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); 4077 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; 4078 __skb_insert(nskb, skb->prev, skb, list); 4079 skb_set_owner_r(nskb, sk); 4080 4081 /* Copy data, releasing collapsed skbs. */ 4082 while (copy > 0) { 4083 int offset = start - TCP_SKB_CB(skb)->seq; 4084 int size = TCP_SKB_CB(skb)->end_seq - start; 4085 4086 BUG_ON(offset < 0); 4087 if (size > 0) { 4088 size = min(copy, size); 4089 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) 4090 BUG(); 4091 TCP_SKB_CB(nskb)->end_seq += size; 4092 copy -= size; 4093 start += size; 4094 } 4095 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 4096 struct sk_buff *next = skb->next; 4097 __skb_unlink(skb, list); 4098 __kfree_skb(skb); 4099 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); 4100 skb = next; 4101 if (skb == tail || 4102 tcp_hdr(skb)->syn || 4103 tcp_hdr(skb)->fin) 4104 return; 4105 } 4106 } 4107 } 4108} 4109 4110/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs 4111 * and tcp_collapse() them until all the queue is collapsed. 4112 */ 4113static void tcp_collapse_ofo_queue(struct sock *sk) 4114{ 4115 struct tcp_sock *tp = tcp_sk(sk); 4116 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); 4117 struct sk_buff *head; 4118 u32 start, end; 4119 4120 if (skb == NULL) 4121 return; 4122 4123 start = TCP_SKB_CB(skb)->seq; 4124 end = TCP_SKB_CB(skb)->end_seq; 4125 head = skb; 4126 4127 for (;;) { 4128 skb = skb->next; 4129 4130 /* Segment is terminated when we see gap or when 4131 * we are at the end of all the queue. */ 4132 if (skb == (struct sk_buff *)&tp->out_of_order_queue || 4133 after(TCP_SKB_CB(skb)->seq, end) || 4134 before(TCP_SKB_CB(skb)->end_seq, start)) { 4135 tcp_collapse(sk, &tp->out_of_order_queue, 4136 head, skb, start, end); 4137 head = skb; 4138 if (skb == (struct sk_buff *)&tp->out_of_order_queue) 4139 break; 4140 /* Start new segment */ 4141 start = TCP_SKB_CB(skb)->seq; 4142 end = TCP_SKB_CB(skb)->end_seq; 4143 } else { 4144 if (before(TCP_SKB_CB(skb)->seq, start)) 4145 start = TCP_SKB_CB(skb)->seq; 4146 if (after(TCP_SKB_CB(skb)->end_seq, end)) 4147 end = TCP_SKB_CB(skb)->end_seq; 4148 } 4149 } 4150} 4151 4152/* Reduce allocated memory if we can, trying to get 4153 * the socket within its memory limits again. 4154 * 4155 * Return less than zero if we should start dropping frames 4156 * until the socket owning process reads some of the data 4157 * to stabilize the situation. 4158 */ 4159static int tcp_prune_queue(struct sock *sk) 4160{ 4161 struct tcp_sock *tp = tcp_sk(sk); 4162 4163 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); 4164 4165 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED); 4166 4167 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) 4168 tcp_clamp_window(sk); 4169 else if (tcp_memory_pressure) 4170 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); 4171 4172 tcp_collapse_ofo_queue(sk); 4173 tcp_collapse(sk, &sk->sk_receive_queue, 4174 sk->sk_receive_queue.next, 4175 (struct sk_buff*)&sk->sk_receive_queue, 4176 tp->copied_seq, tp->rcv_nxt); 4177 sk_mem_reclaim(sk); 4178 4179 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 4180 return 0; 4181 4182 /* Collapsing did not help, destructive actions follow. 4183 * This must not ever occur. */ 4184 4185 /* First, purge the out_of_order queue. */ 4186 if (!skb_queue_empty(&tp->out_of_order_queue)) { 4187 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED); 4188 __skb_queue_purge(&tp->out_of_order_queue); 4189 4190 /* Reset SACK state. A conforming SACK implementation will 4191 * do the same at a timeout based retransmit. When a connection 4192 * is in a sad state like this, we care only about integrity 4193 * of the connection not performance. 4194 */ 4195 if (tcp_is_sack(tp)) 4196 tcp_sack_reset(&tp->rx_opt); 4197 sk_mem_reclaim(sk); 4198 } 4199 4200 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 4201 return 0; 4202 4203 /* If we are really being abused, tell the caller to silently 4204 * drop receive data on the floor. It will get retransmitted 4205 * and hopefully then we'll have sufficient space. 4206 */ 4207 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED); 4208 4209 /* Massive buffer overcommit. */ 4210 tp->pred_flags = 0; 4211 return -1; 4212} 4213 4214 4215/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. 4216 * As additional protections, we do not touch cwnd in retransmission phases, 4217 * and if application hit its sndbuf limit recently. 4218 */ 4219void tcp_cwnd_application_limited(struct sock *sk) 4220{ 4221 struct tcp_sock *tp = tcp_sk(sk); 4222 4223 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && 4224 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { 4225 /* Limited by application or receiver window. */ 4226 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); 4227 u32 win_used = max(tp->snd_cwnd_used, init_win); 4228 if (win_used < tp->snd_cwnd) { 4229 tp->snd_ssthresh = tcp_current_ssthresh(sk); 4230 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; 4231 } 4232 tp->snd_cwnd_used = 0; 4233 } 4234 tp->snd_cwnd_stamp = tcp_time_stamp; 4235} 4236 4237static int tcp_should_expand_sndbuf(struct sock *sk) 4238{ 4239 struct tcp_sock *tp = tcp_sk(sk); 4240 4241 /* If the user specified a specific send buffer setting, do 4242 * not modify it. 4243 */ 4244 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) 4245 return 0; 4246 4247 /* If we are under global TCP memory pressure, do not expand. */ 4248 if (tcp_memory_pressure) 4249 return 0; 4250 4251 /* If we are under soft global TCP memory pressure, do not expand. */ 4252 if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0]) 4253 return 0; 4254 4255 /* If we filled the congestion window, do not expand. */ 4256 if (tp->packets_out >= tp->snd_cwnd) 4257 return 0; 4258 4259 return 1; 4260} 4261 4262/* When incoming ACK allowed to free some skb from write_queue, 4263 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket 4264 * on the exit from tcp input handler. 4265 * 4266 * PROBLEM: sndbuf expansion does not work well with largesend. 4267 */ 4268static void tcp_new_space(struct sock *sk) 4269{ 4270 struct tcp_sock *tp = tcp_sk(sk); 4271 4272 if (tcp_should_expand_sndbuf(sk)) { 4273 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + 4274 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff), 4275 demanded = max_t(unsigned int, tp->snd_cwnd, 4276 tp->reordering + 1); 4277 sndmem *= 2*demanded; 4278 if (sndmem > sk->sk_sndbuf) 4279 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); 4280 tp->snd_cwnd_stamp = tcp_time_stamp; 4281 } 4282 4283 sk->sk_write_space(sk); 4284} 4285 4286static void tcp_check_space(struct sock *sk) 4287{ 4288 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { 4289 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); 4290 if (sk->sk_socket && 4291 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) 4292 tcp_new_space(sk); 4293 } 4294} 4295 4296static inline void tcp_data_snd_check(struct sock *sk) 4297{ 4298 tcp_push_pending_frames(sk); 4299 tcp_check_space(sk); 4300} 4301 4302/* 4303 * Check if sending an ack is needed. 4304 */ 4305static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) 4306{ 4307 struct tcp_sock *tp = tcp_sk(sk); 4308 4309 /* More than one full frame received... */ 4310 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss 4311 /* ... and right edge of window advances far enough. 4312 * (tcp_recvmsg() will send ACK otherwise). Or... 4313 */ 4314 && __tcp_select_window(sk) >= tp->rcv_wnd) || 4315 /* We ACK each frame or... */ 4316 tcp_in_quickack_mode(sk) || 4317 /* We have out of order data. */ 4318 (ofo_possible && 4319 skb_peek(&tp->out_of_order_queue))) { 4320 /* Then ack it now */ 4321 tcp_send_ack(sk); 4322 } else { 4323 /* Else, send delayed ack. */ 4324 tcp_send_delayed_ack(sk); 4325 } 4326} 4327 4328static inline void tcp_ack_snd_check(struct sock *sk) 4329{ 4330 if (!inet_csk_ack_scheduled(sk)) { 4331 /* We sent a data segment already. */ 4332 return; 4333 } 4334 __tcp_ack_snd_check(sk, 1); 4335} 4336 4337/* 4338 * This routine is only called when we have urgent data 4339 * signaled. Its the 'slow' part of tcp_urg. It could be 4340 * moved inline now as tcp_urg is only called from one 4341 * place. We handle URGent data wrong. We have to - as 4342 * BSD still doesn't use the correction from RFC961. 4343 * For 1003.1g we should support a new option TCP_STDURG to permit 4344 * either form (or just set the sysctl tcp_stdurg). 4345 */ 4346 4347static void tcp_check_urg(struct sock * sk, struct tcphdr * th) 4348{ 4349 struct tcp_sock *tp = tcp_sk(sk); 4350 u32 ptr = ntohs(th->urg_ptr); 4351 4352 if (ptr && !sysctl_tcp_stdurg) 4353 ptr--; 4354 ptr += ntohl(th->seq); 4355 4356 /* Ignore urgent data that we've already seen and read. */ 4357 if (after(tp->copied_seq, ptr)) 4358 return; 4359 4360 /* Do not replay urg ptr. 4361 * 4362 * NOTE: interesting situation not covered by specs. 4363 * Misbehaving sender may send urg ptr, pointing to segment, 4364 * which we already have in ofo queue. We are not able to fetch 4365 * such data and will stay in TCP_URG_NOTYET until will be eaten 4366 * by recvmsg(). Seems, we are not obliged to handle such wicked 4367 * situations. But it is worth to think about possibility of some 4368 * DoSes using some hypothetical application level deadlock. 4369 */ 4370 if (before(ptr, tp->rcv_nxt)) 4371 return; 4372 4373 /* Do we already have a newer (or duplicate) urgent pointer? */ 4374 if (tp->urg_data && !after(ptr, tp->urg_seq)) 4375 return; 4376 4377 /* Tell the world about our new urgent pointer. */ 4378 sk_send_sigurg(sk); 4379 4380 /* We may be adding urgent data when the last byte read was 4381 * urgent. To do this requires some care. We cannot just ignore 4382 * tp->copied_seq since we would read the last urgent byte again 4383 * as data, nor can we alter copied_seq until this data arrives 4384 * or we break the semantics of SIOCATMARK (and thus sockatmark()) 4385 * 4386 * NOTE. Double Dutch. Rendering to plain English: author of comment 4387 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); 4388 * and expect that both A and B disappear from stream. This is _wrong_. 4389 * Though this happens in BSD with high probability, this is occasional. 4390 * Any application relying on this is buggy. Note also, that fix "works" 4391 * only in this artificial test. Insert some normal data between A and B and we will 4392 * decline of BSD again. Verdict: it is better to remove to trap 4393 * buggy users. 4394 */ 4395 if (tp->urg_seq == tp->copied_seq && tp->urg_data && 4396 !sock_flag(sk, SOCK_URGINLINE) && 4397 tp->copied_seq != tp->rcv_nxt) { 4398 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); 4399 tp->copied_seq++; 4400 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { 4401 __skb_unlink(skb, &sk->sk_receive_queue); 4402 __kfree_skb(skb); 4403 } 4404 } 4405 4406 tp->urg_data = TCP_URG_NOTYET; 4407 tp->urg_seq = ptr; 4408 4409 /* Disable header prediction. */ 4410 tp->pred_flags = 0; 4411} 4412 4413/* This is the 'fast' part of urgent handling. */ 4414static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th) 4415{ 4416 struct tcp_sock *tp = tcp_sk(sk); 4417 4418 /* Check if we get a new urgent pointer - normally not. */ 4419 if (th->urg) 4420 tcp_check_urg(sk,th); 4421 4422 /* Do we wait for any urgent data? - normally not... */ 4423 if (tp->urg_data == TCP_URG_NOTYET) { 4424 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - 4425 th->syn; 4426 4427 /* Is the urgent pointer pointing into this packet? */ 4428 if (ptr < skb->len) { 4429 u8 tmp; 4430 if (skb_copy_bits(skb, ptr, &tmp, 1)) 4431 BUG(); 4432 tp->urg_data = TCP_URG_VALID | tmp; 4433 if (!sock_flag(sk, SOCK_DEAD)) 4434 sk->sk_data_ready(sk, 0); 4435 } 4436 } 4437} 4438 4439static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) 4440{ 4441 struct tcp_sock *tp = tcp_sk(sk); 4442 int chunk = skb->len - hlen; 4443 int err; 4444 4445 local_bh_enable(); 4446 if (skb_csum_unnecessary(skb)) 4447 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); 4448 else 4449 err = skb_copy_and_csum_datagram_iovec(skb, hlen, 4450 tp->ucopy.iov); 4451 4452 if (!err) { 4453 tp->ucopy.len -= chunk; 4454 tp->copied_seq += chunk; 4455 tcp_rcv_space_adjust(sk); 4456 } 4457 4458 local_bh_disable(); 4459 return err; 4460} 4461 4462static __sum16 __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) 4463{ 4464 __sum16 result; 4465 4466 if (sock_owned_by_user(sk)) { 4467 local_bh_enable(); 4468 result = __tcp_checksum_complete(skb); 4469 local_bh_disable(); 4470 } else { 4471 result = __tcp_checksum_complete(skb); 4472 } 4473 return result; 4474} 4475 4476static inline int tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) 4477{ 4478 return !skb_csum_unnecessary(skb) && 4479 __tcp_checksum_complete_user(sk, skb); 4480} 4481 4482#ifdef CONFIG_NET_DMA 4483static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, int hlen) 4484{ 4485 struct tcp_sock *tp = tcp_sk(sk); 4486 int chunk = skb->len - hlen; 4487 int dma_cookie; 4488 int copied_early = 0; 4489 4490 if (tp->ucopy.wakeup) 4491 return 0; 4492 4493 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list) 4494 tp->ucopy.dma_chan = get_softnet_dma(); 4495 4496 if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) { 4497 4498 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan, 4499 skb, hlen, tp->ucopy.iov, chunk, tp->ucopy.pinned_list); 4500 4501 if (dma_cookie < 0) 4502 goto out; 4503 4504 tp->ucopy.dma_cookie = dma_cookie; 4505 copied_early = 1; 4506 4507 tp->ucopy.len -= chunk; 4508 tp->copied_seq += chunk; 4509 tcp_rcv_space_adjust(sk); 4510 4511 if ((tp->ucopy.len == 0) || 4512 (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) || 4513 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) { 4514 tp->ucopy.wakeup = 1; 4515 sk->sk_data_ready(sk, 0); 4516 } 4517 } else if (chunk > 0) { 4518 tp->ucopy.wakeup = 1; 4519 sk->sk_data_ready(sk, 0); 4520 } 4521out: 4522 return copied_early; 4523} 4524#endif /* CONFIG_NET_DMA */ 4525 4526/* 4527 * TCP receive function for the ESTABLISHED state. 4528 * 4529 * It is split into a fast path and a slow path. The fast path is 4530 * disabled when: 4531 * - A zero window was announced from us - zero window probing 4532 * is only handled properly in the slow path. 4533 * - Out of order segments arrived. 4534 * - Urgent data is expected. 4535 * - There is no buffer space left 4536 * - Unexpected TCP flags/window values/header lengths are received 4537 * (detected by checking the TCP header against pred_flags) 4538 * - Data is sent in both directions. Fast path only supports pure senders 4539 * or pure receivers (this means either the sequence number or the ack 4540 * value must stay constant) 4541 * - Unexpected TCP option. 4542 * 4543 * When these conditions are not satisfied it drops into a standard 4544 * receive procedure patterned after RFC793 to handle all cases. 4545 * The first three cases are guaranteed by proper pred_flags setting, 4546 * the rest is checked inline. Fast processing is turned on in 4547 * tcp_data_queue when everything is OK. 4548 */ 4549int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, 4550 struct tcphdr *th, unsigned len) 4551{ 4552 struct tcp_sock *tp = tcp_sk(sk); 4553 4554 /* 4555 * Header prediction. 4556 * The code loosely follows the one in the famous 4557 * "30 instruction TCP receive" Van Jacobson mail. 4558 * 4559 * Van's trick is to deposit buffers into socket queue 4560 * on a device interrupt, to call tcp_recv function 4561 * on the receive process context and checksum and copy 4562 * the buffer to user space. smart... 4563 * 4564 * Our current scheme is not silly either but we take the 4565 * extra cost of the net_bh soft interrupt processing... 4566 * We do checksum and copy also but from device to kernel. 4567 */ 4568 4569 tp->rx_opt.saw_tstamp = 0; 4570 4571 /* pred_flags is 0xS?10 << 16 + snd_wnd 4572 * if header_prediction is to be made 4573 * 'S' will always be tp->tcp_header_len >> 2 4574 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to 4575 * turn it off (when there are holes in the receive 4576 * space for instance) 4577 * PSH flag is ignored. 4578 */ 4579 4580 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && 4581 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { 4582 int tcp_header_len = tp->tcp_header_len; 4583 4584 /* Timestamp header prediction: tcp_header_len 4585 * is automatically equal to th->doff*4 due to pred_flags 4586 * match. 4587 */ 4588 4589 /* Check timestamp */ 4590 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { 4591 __be32 *ptr = (__be32 *)(th + 1); 4592 4593 /* No? Slow path! */ 4594 if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) 4595 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) 4596 goto slow_path; 4597 4598 tp->rx_opt.saw_tstamp = 1; 4599 ++ptr; 4600 tp->rx_opt.rcv_tsval = ntohl(*ptr); 4601 ++ptr; 4602 tp->rx_opt.rcv_tsecr = ntohl(*ptr); 4603 4604 /* If PAWS failed, check it more carefully in slow path */ 4605 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) 4606 goto slow_path; 4607 4608 /* DO NOT update ts_recent here, if checksum fails 4609 * and timestamp was corrupted part, it will result 4610 * in a hung connection since we will drop all 4611 * future packets due to the PAWS test. 4612 */ 4613 } 4614 4615 if (len <= tcp_header_len) { 4616 /* Bulk data transfer: sender */ 4617 if (len == tcp_header_len) { 4618 /* Predicted packet is in window by definition. 4619 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 4620 * Hence, check seq<=rcv_wup reduces to: 4621 */ 4622 if (tcp_header_len == 4623 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 4624 tp->rcv_nxt == tp->rcv_wup) 4625 tcp_store_ts_recent(tp); 4626 4627 /* We know that such packets are checksummed 4628 * on entry. 4629 */ 4630 tcp_ack(sk, skb, 0); 4631 __kfree_skb(skb); 4632 tcp_data_snd_check(sk); 4633 return 0; 4634 } else { /* Header too small */ 4635 TCP_INC_STATS_BH(TCP_MIB_INERRS); 4636 goto discard; 4637 } 4638 } else { 4639 int eaten = 0; 4640 int copied_early = 0; 4641 4642 if (tp->copied_seq == tp->rcv_nxt && 4643 len - tcp_header_len <= tp->ucopy.len) { 4644#ifdef CONFIG_NET_DMA 4645 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) { 4646 copied_early = 1; 4647 eaten = 1; 4648 } 4649#endif 4650 if (tp->ucopy.task == current && sock_owned_by_user(sk) && !copied_early) { 4651 __set_current_state(TASK_RUNNING); 4652 4653 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) 4654 eaten = 1; 4655 } 4656 if (eaten) { 4657 /* Predicted packet is in window by definition. 4658 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 4659 * Hence, check seq<=rcv_wup reduces to: 4660 */ 4661 if (tcp_header_len == 4662 (sizeof(struct tcphdr) + 4663 TCPOLEN_TSTAMP_ALIGNED) && 4664 tp->rcv_nxt == tp->rcv_wup) 4665 tcp_store_ts_recent(tp); 4666 4667 tcp_rcv_rtt_measure_ts(sk, skb); 4668 4669 __skb_pull(skb, tcp_header_len); 4670 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4671 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER); 4672 } 4673 if (copied_early) 4674 tcp_cleanup_rbuf(sk, skb->len); 4675 } 4676 if (!eaten) { 4677 if (tcp_checksum_complete_user(sk, skb)) 4678 goto csum_error; 4679 4680 /* Predicted packet is in window by definition. 4681 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 4682 * Hence, check seq<=rcv_wup reduces to: 4683 */ 4684 if (tcp_header_len == 4685 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 4686 tp->rcv_nxt == tp->rcv_wup) 4687 tcp_store_ts_recent(tp); 4688 4689 tcp_rcv_rtt_measure_ts(sk, skb); 4690 4691 if ((int)skb->truesize > sk->sk_forward_alloc) 4692 goto step5; 4693 4694 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS); 4695 4696 /* Bulk data transfer: receiver */ 4697 __skb_pull(skb,tcp_header_len); 4698 __skb_queue_tail(&sk->sk_receive_queue, skb); 4699 skb_set_owner_r(skb, sk); 4700 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4701 } 4702 4703 tcp_event_data_recv(sk, skb); 4704 4705 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { 4706 /* Well, only one small jumplet in fast path... */ 4707 tcp_ack(sk, skb, FLAG_DATA); 4708 tcp_data_snd_check(sk); 4709 if (!inet_csk_ack_scheduled(sk)) 4710 goto no_ack; 4711 } 4712 4713 __tcp_ack_snd_check(sk, 0); 4714no_ack: 4715#ifdef CONFIG_NET_DMA 4716 if (copied_early) 4717 __skb_queue_tail(&sk->sk_async_wait_queue, skb); 4718 else 4719#endif 4720 if (eaten) 4721 __kfree_skb(skb); 4722 else 4723 sk->sk_data_ready(sk, 0); 4724 return 0; 4725 } 4726 } 4727 4728slow_path: 4729 if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb)) 4730 goto csum_error; 4731 4732 /* 4733 * RFC1323: H1. Apply PAWS check first. 4734 */ 4735 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && 4736 tcp_paws_discard(sk, skb)) { 4737 if (!th->rst) { 4738 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); 4739 tcp_send_dupack(sk, skb); 4740 goto discard; 4741 } 4742 /* Resets are accepted even if PAWS failed. 4743 4744 ts_recent update must be made after we are sure 4745 that the packet is in window. 4746 */ 4747 } 4748 4749 /* 4750 * Standard slow path. 4751 */ 4752 4753 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { 4754 /* RFC793, page 37: "In all states except SYN-SENT, all reset 4755 * (RST) segments are validated by checking their SEQ-fields." 4756 * And page 69: "If an incoming segment is not acceptable, 4757 * an acknowledgment should be sent in reply (unless the RST bit 4758 * is set, if so drop the segment and return)". 4759 */ 4760 if (!th->rst) 4761 tcp_send_dupack(sk, skb); 4762 goto discard; 4763 } 4764 4765 if (th->rst) { 4766 tcp_reset(sk); 4767 goto discard; 4768 } 4769 4770 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 4771 4772 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4773 TCP_INC_STATS_BH(TCP_MIB_INERRS); 4774 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); 4775 tcp_reset(sk); 4776 return 1; 4777 } 4778 4779step5: 4780 if (th->ack) 4781 tcp_ack(sk, skb, FLAG_SLOWPATH); 4782 4783 tcp_rcv_rtt_measure_ts(sk, skb); 4784 4785 /* Process urgent data. */ 4786 tcp_urg(sk, skb, th); 4787 4788 /* step 7: process the segment text */ 4789 tcp_data_queue(sk, skb); 4790 4791 tcp_data_snd_check(sk); 4792 tcp_ack_snd_check(sk); 4793 return 0; 4794 4795csum_error: 4796 TCP_INC_STATS_BH(TCP_MIB_INERRS); 4797 4798discard: 4799 __kfree_skb(skb); 4800 return 0; 4801} 4802 4803static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 4804 struct tcphdr *th, unsigned len) 4805{ 4806 struct tcp_sock *tp = tcp_sk(sk); 4807 struct inet_connection_sock *icsk = inet_csk(sk); 4808 int saved_clamp = tp->rx_opt.mss_clamp; 4809 4810 tcp_parse_options(skb, &tp->rx_opt, 0); 4811 4812 if (th->ack) { 4813 /* rfc793: 4814 * "If the state is SYN-SENT then 4815 * first check the ACK bit 4816 * If the ACK bit is set 4817 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send 4818 * a reset (unless the RST bit is set, if so drop 4819 * the segment and return)" 4820 * 4821 * We do not send data with SYN, so that RFC-correct 4822 * test reduces to: 4823 */ 4824 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt) 4825 goto reset_and_undo; 4826 4827 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 4828 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, 4829 tcp_time_stamp)) { 4830 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED); 4831 goto reset_and_undo; 4832 } 4833 4834 /* Now ACK is acceptable. 4835 * 4836 * "If the RST bit is set 4837 * If the ACK was acceptable then signal the user "error: 4838 * connection reset", drop the segment, enter CLOSED state, 4839 * delete TCB, and return." 4840 */ 4841 4842 if (th->rst) { 4843 tcp_reset(sk); 4844 goto discard; 4845 } 4846 4847 /* rfc793: 4848 * "fifth, if neither of the SYN or RST bits is set then 4849 * drop the segment and return." 4850 * 4851 * See note below! 4852 * --ANK(990513) 4853 */ 4854 if (!th->syn) 4855 goto discard_and_undo; 4856 4857 /* rfc793: 4858 * "If the SYN bit is on ... 4859 * are acceptable then ... 4860 * (our SYN has been ACKed), change the connection 4861 * state to ESTABLISHED..." 4862 */ 4863 4864 TCP_ECN_rcv_synack(tp, th); 4865 4866 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 4867 tcp_ack(sk, skb, FLAG_SLOWPATH); 4868 4869 /* Ok.. it's good. Set up sequence numbers and 4870 * move to established. 4871 */ 4872 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 4873 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 4874 4875 /* RFC1323: The window in SYN & SYN/ACK segments is 4876 * never scaled. 4877 */ 4878 tp->snd_wnd = ntohs(th->window); 4879 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq); 4880 4881 if (!tp->rx_opt.wscale_ok) { 4882 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; 4883 tp->window_clamp = min(tp->window_clamp, 65535U); 4884 } 4885 4886 if (tp->rx_opt.saw_tstamp) { 4887 tp->rx_opt.tstamp_ok = 1; 4888 tp->tcp_header_len = 4889 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 4890 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 4891 tcp_store_ts_recent(tp); 4892 } else { 4893 tp->tcp_header_len = sizeof(struct tcphdr); 4894 } 4895 4896 if (tcp_is_sack(tp) && sysctl_tcp_fack) 4897 tcp_enable_fack(tp); 4898 4899 tcp_mtup_init(sk); 4900 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 4901 tcp_initialize_rcv_mss(sk); 4902 4903 /* Remember, tcp_poll() does not lock socket! 4904 * Change state from SYN-SENT only after copied_seq 4905 * is initialized. */ 4906 tp->copied_seq = tp->rcv_nxt; 4907 smp_mb(); 4908 tcp_set_state(sk, TCP_ESTABLISHED); 4909 4910 security_inet_conn_established(sk, skb); 4911 4912 /* Make sure socket is routed, for correct metrics. */ 4913 icsk->icsk_af_ops->rebuild_header(sk); 4914 4915 tcp_init_metrics(sk); 4916 4917 tcp_init_congestion_control(sk); 4918 4919 /* Prevent spurious tcp_cwnd_restart() on first data 4920 * packet. 4921 */ 4922 tp->lsndtime = tcp_time_stamp; 4923 4924 tcp_init_buffer_space(sk); 4925 4926 if (sock_flag(sk, SOCK_KEEPOPEN)) 4927 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); 4928 4929 if (!tp->rx_opt.snd_wscale) 4930 __tcp_fast_path_on(tp, tp->snd_wnd); 4931 else 4932 tp->pred_flags = 0; 4933 4934 if (!sock_flag(sk, SOCK_DEAD)) { 4935 sk->sk_state_change(sk); 4936 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT); 4937 } 4938 4939 if (sk->sk_write_pending || 4940 icsk->icsk_accept_queue.rskq_defer_accept || 4941 icsk->icsk_ack.pingpong) { 4942 /* Save one ACK. Data will be ready after 4943 * several ticks, if write_pending is set. 4944 * 4945 * It may be deleted, but with this feature tcpdumps 4946 * look so _wonderfully_ clever, that I was not able 4947 * to stand against the temptation 8) --ANK 4948 */ 4949 inet_csk_schedule_ack(sk); 4950 icsk->icsk_ack.lrcvtime = tcp_time_stamp; 4951 icsk->icsk_ack.ato = TCP_ATO_MIN; 4952 tcp_incr_quickack(sk); 4953 tcp_enter_quickack_mode(sk); 4954 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 4955 TCP_DELACK_MAX, TCP_RTO_MAX); 4956 4957discard: 4958 __kfree_skb(skb); 4959 return 0; 4960 } else { 4961 tcp_send_ack(sk); 4962 } 4963 return -1; 4964 } 4965 4966 /* No ACK in the segment */ 4967 4968 if (th->rst) { 4969 /* rfc793: 4970 * "If the RST bit is set 4971 * 4972 * Otherwise (no ACK) drop the segment and return." 4973 */ 4974 4975 goto discard_and_undo; 4976 } 4977 4978 /* PAWS check. */ 4979 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0)) 4980 goto discard_and_undo; 4981 4982 if (th->syn) { 4983 /* We see SYN without ACK. It is attempt of 4984 * simultaneous connect with crossed SYNs. 4985 * Particularly, it can be connect to self. 4986 */ 4987 tcp_set_state(sk, TCP_SYN_RECV); 4988 4989 if (tp->rx_opt.saw_tstamp) { 4990 tp->rx_opt.tstamp_ok = 1; 4991 tcp_store_ts_recent(tp); 4992 tp->tcp_header_len = 4993 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 4994 } else { 4995 tp->tcp_header_len = sizeof(struct tcphdr); 4996 } 4997 4998 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 4999 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 5000 5001 /* RFC1323: The window in SYN & SYN/ACK segments is 5002 * never scaled. 5003 */ 5004 tp->snd_wnd = ntohs(th->window); 5005 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 5006 tp->max_window = tp->snd_wnd; 5007 5008 TCP_ECN_rcv_syn(tp, th); 5009 5010 tcp_mtup_init(sk); 5011 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 5012 tcp_initialize_rcv_mss(sk); 5013 5014 5015 tcp_send_synack(sk); 5016#if 0 5017 /* Note, we could accept data and URG from this segment. 5018 * There are no obstacles to make this. 5019 * 5020 * However, if we ignore data in ACKless segments sometimes, 5021 * we have no reasons to accept it sometimes. 5022 * Also, seems the code doing it in step6 of tcp_rcv_state_process 5023 * is not flawless. So, discard packet for sanity. 5024 * Uncomment this return to process the data. 5025 */ 5026 return -1; 5027#else 5028 goto discard; 5029#endif 5030 } 5031 /* "fifth, if neither of the SYN or RST bits is set then 5032 * drop the segment and return." 5033 */ 5034 5035discard_and_undo: 5036 tcp_clear_options(&tp->rx_opt); 5037 tp->rx_opt.mss_clamp = saved_clamp; 5038 goto discard; 5039 5040reset_and_undo: 5041 tcp_clear_options(&tp->rx_opt); 5042 tp->rx_opt.mss_clamp = saved_clamp; 5043 return 1; 5044} 5045 5046 5047/* 5048 * This function implements the receiving procedure of RFC 793 for 5049 * all states except ESTABLISHED and TIME_WAIT. 5050 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be 5051 * address independent. 5052 */ 5053 5054int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, 5055 struct tcphdr *th, unsigned len) 5056{ 5057 struct tcp_sock *tp = tcp_sk(sk); 5058 struct inet_connection_sock *icsk = inet_csk(sk); 5059 int queued = 0; 5060 5061 tp->rx_opt.saw_tstamp = 0; 5062 5063 switch (sk->sk_state) { 5064 case TCP_CLOSE: 5065 goto discard; 5066 5067 case TCP_LISTEN: 5068 if (th->ack) 5069 return 1; 5070 5071 if (th->rst) 5072 goto discard; 5073 5074 if (th->syn) { 5075 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0) 5076 return 1; 5077 5078 /* Now we have several options: In theory there is 5079 * nothing else in the frame. KA9Q has an option to 5080 * send data with the syn, BSD accepts data with the 5081 * syn up to the [to be] advertised window and 5082 * Solaris 2.1 gives you a protocol error. For now 5083 * we just ignore it, that fits the spec precisely 5084 * and avoids incompatibilities. It would be nice in 5085 * future to drop through and process the data. 5086 * 5087 * Now that TTCP is starting to be used we ought to 5088 * queue this data. 5089 * But, this leaves one open to an easy denial of 5090 * service attack, and SYN cookies can't defend 5091 * against this problem. So, we drop the data 5092 * in the interest of security over speed unless 5093 * it's still in use. 5094 */ 5095 kfree_skb(skb); 5096 return 0; 5097 } 5098 goto discard; 5099 5100 case TCP_SYN_SENT: 5101 queued = tcp_rcv_synsent_state_process(sk, skb, th, len); 5102 if (queued >= 0) 5103 return queued; 5104 5105 /* Do step6 onward by hand. */ 5106 tcp_urg(sk, skb, th); 5107 __kfree_skb(skb); 5108 tcp_data_snd_check(sk); 5109 return 0; 5110 } 5111 5112 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && 5113 tcp_paws_discard(sk, skb)) { 5114 if (!th->rst) { 5115 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); 5116 tcp_send_dupack(sk, skb); 5117 goto discard; 5118 } 5119 /* Reset is accepted even if it did not pass PAWS. */ 5120 } 5121 5122 /* step 1: check sequence number */ 5123 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { 5124 if (!th->rst) 5125 tcp_send_dupack(sk, skb); 5126 goto discard; 5127 } 5128 5129 /* step 2: check RST bit */ 5130 if (th->rst) { 5131 tcp_reset(sk); 5132 goto discard; 5133 } 5134 5135 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 5136 5137 /* step 3: check security and precedence [ignored] */ 5138 5139 /* step 4: 5140 * 5141 * Check for a SYN in window. 5142 */ 5143 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 5144 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); 5145 tcp_reset(sk); 5146 return 1; 5147 } 5148 5149 /* step 5: check the ACK field */ 5150 if (th->ack) { 5151 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH); 5152 5153 switch (sk->sk_state) { 5154 case TCP_SYN_RECV: 5155 if (acceptable) { 5156 tp->copied_seq = tp->rcv_nxt; 5157 smp_mb(); 5158 tcp_set_state(sk, TCP_ESTABLISHED); 5159 sk->sk_state_change(sk); 5160 5161 /* Note, that this wakeup is only for marginal 5162 * crossed SYN case. Passively open sockets 5163 * are not waked up, because sk->sk_sleep == 5164 * NULL and sk->sk_socket == NULL. 5165 */ 5166 if (sk->sk_socket) 5167 sk_wake_async(sk, 5168 SOCK_WAKE_IO, POLL_OUT); 5169 5170 tp->snd_una = TCP_SKB_CB(skb)->ack_seq; 5171 tp->snd_wnd = ntohs(th->window) << 5172 tp->rx_opt.snd_wscale; 5173 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, 5174 TCP_SKB_CB(skb)->seq); 5175 5176 /* tcp_ack considers this ACK as duplicate 5177 * and does not calculate rtt. 5178 * Fix it at least with timestamps. 5179 */ 5180 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 5181 !tp->srtt) 5182 tcp_ack_saw_tstamp(sk, 0); 5183 5184 if (tp->rx_opt.tstamp_ok) 5185 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 5186 5187 /* Make sure socket is routed, for 5188 * correct metrics. 5189 */ 5190 icsk->icsk_af_ops->rebuild_header(sk); 5191 5192 tcp_init_metrics(sk); 5193 5194 tcp_init_congestion_control(sk); 5195 5196 /* Prevent spurious tcp_cwnd_restart() on 5197 * first data packet. 5198 */ 5199 tp->lsndtime = tcp_time_stamp; 5200 5201 tcp_mtup_init(sk); 5202 tcp_initialize_rcv_mss(sk); 5203 tcp_init_buffer_space(sk); 5204 tcp_fast_path_on(tp); 5205 } else { 5206 return 1; 5207 } 5208 break; 5209 5210 case TCP_FIN_WAIT1: 5211 if (tp->snd_una == tp->write_seq) { 5212 tcp_set_state(sk, TCP_FIN_WAIT2); 5213 sk->sk_shutdown |= SEND_SHUTDOWN; 5214 dst_confirm(sk->sk_dst_cache); 5215 5216 if (!sock_flag(sk, SOCK_DEAD)) 5217 /* Wake up lingering close() */ 5218 sk->sk_state_change(sk); 5219 else { 5220 int tmo; 5221 5222 if (tp->linger2 < 0 || 5223 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 5224 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { 5225 tcp_done(sk); 5226 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); 5227 return 1; 5228 } 5229 5230 tmo = tcp_fin_time(sk); 5231 if (tmo > TCP_TIMEWAIT_LEN) { 5232 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); 5233 } else if (th->fin || sock_owned_by_user(sk)) { 5234 /* Bad case. We could lose such FIN otherwise. 5235 * It is not a big problem, but it looks confusing 5236 * and not so rare event. We still can lose it now, 5237 * if it spins in bh_lock_sock(), but it is really 5238 * marginal case. 5239 */ 5240 inet_csk_reset_keepalive_timer(sk, tmo); 5241 } else { 5242 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 5243 goto discard; 5244 } 5245 } 5246 } 5247 break; 5248 5249 case TCP_CLOSING: 5250 if (tp->snd_una == tp->write_seq) { 5251 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 5252 goto discard; 5253 } 5254 break; 5255 5256 case TCP_LAST_ACK: 5257 if (tp->snd_una == tp->write_seq) { 5258 tcp_update_metrics(sk); 5259 tcp_done(sk); 5260 goto discard; 5261 } 5262 break; 5263 } 5264 } else 5265 goto discard; 5266 5267 /* step 6: check the URG bit */ 5268 tcp_urg(sk, skb, th); 5269 5270 /* step 7: process the segment text */ 5271 switch (sk->sk_state) { 5272 case TCP_CLOSE_WAIT: 5273 case TCP_CLOSING: 5274 case TCP_LAST_ACK: 5275 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 5276 break; 5277 case TCP_FIN_WAIT1: 5278 case TCP_FIN_WAIT2: 5279 /* RFC 793 says to queue data in these states, 5280 * RFC 1122 says we MUST send a reset. 5281 * BSD 4.4 also does reset. 5282 */ 5283 if (sk->sk_shutdown & RCV_SHUTDOWN) { 5284 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 5285 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { 5286 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); 5287 tcp_reset(sk); 5288 return 1; 5289 } 5290 } 5291 /* Fall through */ 5292 case TCP_ESTABLISHED: 5293 tcp_data_queue(sk, skb); 5294 queued = 1; 5295 break; 5296 } 5297 5298 /* tcp_data could move socket to TIME-WAIT */ 5299 if (sk->sk_state != TCP_CLOSE) { 5300 tcp_data_snd_check(sk); 5301 tcp_ack_snd_check(sk); 5302 } 5303 5304 if (!queued) { 5305discard: 5306 __kfree_skb(skb); 5307 } 5308 return 0; 5309} 5310 5311EXPORT_SYMBOL(sysctl_tcp_ecn); 5312EXPORT_SYMBOL(sysctl_tcp_reordering); 5313EXPORT_SYMBOL(tcp_parse_options); 5314EXPORT_SYMBOL(tcp_rcv_established); 5315EXPORT_SYMBOL(tcp_rcv_state_process); 5316EXPORT_SYMBOL(tcp_initialize_rcv_mss); 5317