tcp_input.c revision 31713c333ddbb66d694829082620b69b71c4b09a
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; 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 */ 105 106#define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) 107#define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) 108#define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) 109#define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) 110 111#define IsReno(tp) ((tp)->rx_opt.sack_ok == 0) 112#define IsFack(tp) ((tp)->rx_opt.sack_ok & 2) 113#define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4) 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) 118 119/* Adapt the MSS value used to make delayed ack decision to the 120 * real world. 121 */ 122static void tcp_measure_rcv_mss(struct sock *sk, 123 const struct sk_buff *skb) 124{ 125 struct inet_connection_sock *icsk = inet_csk(sk); 126 const unsigned int lss = icsk->icsk_ack.last_seg_size; 127 unsigned int len; 128 129 icsk->icsk_ack.last_seg_size = 0; 130 131 /* skb->len may jitter because of SACKs, even if peer 132 * sends good full-sized frames. 133 */ 134 len = skb_shinfo(skb)->gso_size ?: skb->len; 135 if (len >= icsk->icsk_ack.rcv_mss) { 136 icsk->icsk_ack.rcv_mss = len; 137 } else { 138 /* Otherwise, we make more careful check taking into account, 139 * that SACKs block is variable. 140 * 141 * "len" is invariant segment length, including TCP header. 142 */ 143 len += skb->data - skb->h.raw; 144 if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) || 145 /* If PSH is not set, packet should be 146 * full sized, provided peer TCP is not badly broken. 147 * This observation (if it is correct 8)) allows 148 * to handle super-low mtu links fairly. 149 */ 150 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && 151 !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) { 152 /* Subtract also invariant (if peer is RFC compliant), 153 * tcp header plus fixed timestamp option length. 154 * Resulting "len" is MSS free of SACK jitter. 155 */ 156 len -= tcp_sk(sk)->tcp_header_len; 157 icsk->icsk_ack.last_seg_size = len; 158 if (len == lss) { 159 icsk->icsk_ack.rcv_mss = len; 160 return; 161 } 162 } 163 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) 164 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; 165 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; 166 } 167} 168 169static void tcp_incr_quickack(struct sock *sk) 170{ 171 struct inet_connection_sock *icsk = inet_csk(sk); 172 unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); 173 174 if (quickacks==0) 175 quickacks=2; 176 if (quickacks > icsk->icsk_ack.quick) 177 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS); 178} 179 180void tcp_enter_quickack_mode(struct sock *sk) 181{ 182 struct inet_connection_sock *icsk = inet_csk(sk); 183 tcp_incr_quickack(sk); 184 icsk->icsk_ack.pingpong = 0; 185 icsk->icsk_ack.ato = TCP_ATO_MIN; 186} 187 188/* Send ACKs quickly, if "quick" count is not exhausted 189 * and the session is not interactive. 190 */ 191 192static inline int tcp_in_quickack_mode(const struct sock *sk) 193{ 194 const struct inet_connection_sock *icsk = inet_csk(sk); 195 return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong; 196} 197 198/* Buffer size and advertised window tuning. 199 * 200 * 1. Tuning sk->sk_sndbuf, when connection enters established state. 201 */ 202 203static void tcp_fixup_sndbuf(struct sock *sk) 204{ 205 int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 + 206 sizeof(struct sk_buff); 207 208 if (sk->sk_sndbuf < 3 * sndmem) 209 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]); 210} 211 212/* 2. Tuning advertised window (window_clamp, rcv_ssthresh) 213 * 214 * All tcp_full_space() is split to two parts: "network" buffer, allocated 215 * forward and advertised in receiver window (tp->rcv_wnd) and 216 * "application buffer", required to isolate scheduling/application 217 * latencies from network. 218 * window_clamp is maximal advertised window. It can be less than 219 * tcp_full_space(), in this case tcp_full_space() - window_clamp 220 * is reserved for "application" buffer. The less window_clamp is 221 * the smoother our behaviour from viewpoint of network, but the lower 222 * throughput and the higher sensitivity of the connection to losses. 8) 223 * 224 * rcv_ssthresh is more strict window_clamp used at "slow start" 225 * phase to predict further behaviour of this connection. 226 * It is used for two goals: 227 * - to enforce header prediction at sender, even when application 228 * requires some significant "application buffer". It is check #1. 229 * - to prevent pruning of receive queue because of misprediction 230 * of receiver window. Check #2. 231 * 232 * The scheme does not work when sender sends good segments opening 233 * window and then starts to feed us spaghetti. But it should work 234 * in common situations. Otherwise, we have to rely on queue collapsing. 235 */ 236 237/* Slow part of check#2. */ 238static int __tcp_grow_window(const struct sock *sk, struct tcp_sock *tp, 239 const struct sk_buff *skb) 240{ 241 /* Optimize this! */ 242 int truesize = tcp_win_from_space(skb->truesize)/2; 243 int window = tcp_win_from_space(sysctl_tcp_rmem[2])/2; 244 245 while (tp->rcv_ssthresh <= window) { 246 if (truesize <= skb->len) 247 return 2 * inet_csk(sk)->icsk_ack.rcv_mss; 248 249 truesize >>= 1; 250 window >>= 1; 251 } 252 return 0; 253} 254 255static void tcp_grow_window(struct sock *sk, struct tcp_sock *tp, 256 struct sk_buff *skb) 257{ 258 /* Check #1 */ 259 if (tp->rcv_ssthresh < tp->window_clamp && 260 (int)tp->rcv_ssthresh < tcp_space(sk) && 261 !tcp_memory_pressure) { 262 int incr; 263 264 /* Check #2. Increase window, if skb with such overhead 265 * will fit to rcvbuf in future. 266 */ 267 if (tcp_win_from_space(skb->truesize) <= skb->len) 268 incr = 2*tp->advmss; 269 else 270 incr = __tcp_grow_window(sk, tp, skb); 271 272 if (incr) { 273 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp); 274 inet_csk(sk)->icsk_ack.quick |= 1; 275 } 276 } 277} 278 279/* 3. Tuning rcvbuf, when connection enters established state. */ 280 281static void tcp_fixup_rcvbuf(struct sock *sk) 282{ 283 struct tcp_sock *tp = tcp_sk(sk); 284 int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); 285 286 /* Try to select rcvbuf so that 4 mss-sized segments 287 * will fit to window and corresponding skbs will fit to our rcvbuf. 288 * (was 3; 4 is minimum to allow fast retransmit to work.) 289 */ 290 while (tcp_win_from_space(rcvmem) < tp->advmss) 291 rcvmem += 128; 292 if (sk->sk_rcvbuf < 4 * rcvmem) 293 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]); 294} 295 296/* 4. Try to fixup all. It is made immediately after connection enters 297 * established state. 298 */ 299static void tcp_init_buffer_space(struct sock *sk) 300{ 301 struct tcp_sock *tp = tcp_sk(sk); 302 int maxwin; 303 304 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) 305 tcp_fixup_rcvbuf(sk); 306 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) 307 tcp_fixup_sndbuf(sk); 308 309 tp->rcvq_space.space = tp->rcv_wnd; 310 311 maxwin = tcp_full_space(sk); 312 313 if (tp->window_clamp >= maxwin) { 314 tp->window_clamp = maxwin; 315 316 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) 317 tp->window_clamp = max(maxwin - 318 (maxwin >> sysctl_tcp_app_win), 319 4 * tp->advmss); 320 } 321 322 /* Force reservation of one segment. */ 323 if (sysctl_tcp_app_win && 324 tp->window_clamp > 2 * tp->advmss && 325 tp->window_clamp + tp->advmss > maxwin) 326 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); 327 328 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); 329 tp->snd_cwnd_stamp = tcp_time_stamp; 330} 331 332/* 5. Recalculate window clamp after socket hit its memory bounds. */ 333static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp) 334{ 335 struct inet_connection_sock *icsk = inet_csk(sk); 336 337 icsk->icsk_ack.quick = 0; 338 339 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && 340 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && 341 !tcp_memory_pressure && 342 atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) { 343 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), 344 sysctl_tcp_rmem[2]); 345 } 346 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) 347 tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss); 348} 349 350 351/* Initialize RCV_MSS value. 352 * RCV_MSS is an our guess about MSS used by the peer. 353 * We haven't any direct information about the MSS. 354 * It's better to underestimate the RCV_MSS rather than overestimate. 355 * Overestimations make us ACKing less frequently than needed. 356 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). 357 */ 358void tcp_initialize_rcv_mss(struct sock *sk) 359{ 360 struct tcp_sock *tp = tcp_sk(sk); 361 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); 362 363 hint = min(hint, tp->rcv_wnd/2); 364 hint = min(hint, TCP_MIN_RCVMSS); 365 hint = max(hint, TCP_MIN_MSS); 366 367 inet_csk(sk)->icsk_ack.rcv_mss = hint; 368} 369 370/* Receiver "autotuning" code. 371 * 372 * The algorithm for RTT estimation w/o timestamps is based on 373 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. 374 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps> 375 * 376 * More detail on this code can be found at 377 * <http://www.psc.edu/~jheffner/senior_thesis.ps>, 378 * though this reference is out of date. A new paper 379 * is pending. 380 */ 381static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) 382{ 383 u32 new_sample = tp->rcv_rtt_est.rtt; 384 long m = sample; 385 386 if (m == 0) 387 m = 1; 388 389 if (new_sample != 0) { 390 /* If we sample in larger samples in the non-timestamp 391 * case, we could grossly overestimate the RTT especially 392 * with chatty applications or bulk transfer apps which 393 * are stalled on filesystem I/O. 394 * 395 * Also, since we are only going for a minimum in the 396 * non-timestamp case, we do not smooth things out 397 * else with timestamps disabled convergence takes too 398 * long. 399 */ 400 if (!win_dep) { 401 m -= (new_sample >> 3); 402 new_sample += m; 403 } else if (m < new_sample) 404 new_sample = m << 3; 405 } else { 406 /* No previous measure. */ 407 new_sample = m << 3; 408 } 409 410 if (tp->rcv_rtt_est.rtt != new_sample) 411 tp->rcv_rtt_est.rtt = new_sample; 412} 413 414static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) 415{ 416 if (tp->rcv_rtt_est.time == 0) 417 goto new_measure; 418 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) 419 return; 420 tcp_rcv_rtt_update(tp, 421 jiffies - tp->rcv_rtt_est.time, 422 1); 423 424new_measure: 425 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; 426 tp->rcv_rtt_est.time = tcp_time_stamp; 427} 428 429static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb) 430{ 431 struct tcp_sock *tp = tcp_sk(sk); 432 if (tp->rx_opt.rcv_tsecr && 433 (TCP_SKB_CB(skb)->end_seq - 434 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) 435 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); 436} 437 438/* 439 * This function should be called every time data is copied to user space. 440 * It calculates the appropriate TCP receive buffer space. 441 */ 442void tcp_rcv_space_adjust(struct sock *sk) 443{ 444 struct tcp_sock *tp = tcp_sk(sk); 445 int time; 446 int space; 447 448 if (tp->rcvq_space.time == 0) 449 goto new_measure; 450 451 time = tcp_time_stamp - tp->rcvq_space.time; 452 if (time < (tp->rcv_rtt_est.rtt >> 3) || 453 tp->rcv_rtt_est.rtt == 0) 454 return; 455 456 space = 2 * (tp->copied_seq - tp->rcvq_space.seq); 457 458 space = max(tp->rcvq_space.space, space); 459 460 if (tp->rcvq_space.space != space) { 461 int rcvmem; 462 463 tp->rcvq_space.space = space; 464 465 if (sysctl_tcp_moderate_rcvbuf && 466 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { 467 int new_clamp = space; 468 469 /* Receive space grows, normalize in order to 470 * take into account packet headers and sk_buff 471 * structure overhead. 472 */ 473 space /= tp->advmss; 474 if (!space) 475 space = 1; 476 rcvmem = (tp->advmss + MAX_TCP_HEADER + 477 16 + sizeof(struct sk_buff)); 478 while (tcp_win_from_space(rcvmem) < tp->advmss) 479 rcvmem += 128; 480 space *= rcvmem; 481 space = min(space, sysctl_tcp_rmem[2]); 482 if (space > sk->sk_rcvbuf) { 483 sk->sk_rcvbuf = space; 484 485 /* Make the window clamp follow along. */ 486 tp->window_clamp = new_clamp; 487 } 488 } 489 } 490 491new_measure: 492 tp->rcvq_space.seq = tp->copied_seq; 493 tp->rcvq_space.time = tcp_time_stamp; 494} 495 496/* There is something which you must keep in mind when you analyze the 497 * behavior of the tp->ato delayed ack timeout interval. When a 498 * connection starts up, we want to ack as quickly as possible. The 499 * problem is that "good" TCP's do slow start at the beginning of data 500 * transmission. The means that until we send the first few ACK's the 501 * sender will sit on his end and only queue most of his data, because 502 * he can only send snd_cwnd unacked packets at any given time. For 503 * each ACK we send, he increments snd_cwnd and transmits more of his 504 * queue. -DaveM 505 */ 506static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb) 507{ 508 struct inet_connection_sock *icsk = inet_csk(sk); 509 u32 now; 510 511 inet_csk_schedule_ack(sk); 512 513 tcp_measure_rcv_mss(sk, skb); 514 515 tcp_rcv_rtt_measure(tp); 516 517 now = tcp_time_stamp; 518 519 if (!icsk->icsk_ack.ato) { 520 /* The _first_ data packet received, initialize 521 * delayed ACK engine. 522 */ 523 tcp_incr_quickack(sk); 524 icsk->icsk_ack.ato = TCP_ATO_MIN; 525 } else { 526 int m = now - icsk->icsk_ack.lrcvtime; 527 528 if (m <= TCP_ATO_MIN/2) { 529 /* The fastest case is the first. */ 530 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; 531 } else if (m < icsk->icsk_ack.ato) { 532 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; 533 if (icsk->icsk_ack.ato > icsk->icsk_rto) 534 icsk->icsk_ack.ato = icsk->icsk_rto; 535 } else if (m > icsk->icsk_rto) { 536 /* Too long gap. Apparently sender failed to 537 * restart window, so that we send ACKs quickly. 538 */ 539 tcp_incr_quickack(sk); 540 sk_stream_mem_reclaim(sk); 541 } 542 } 543 icsk->icsk_ack.lrcvtime = now; 544 545 TCP_ECN_check_ce(tp, skb); 546 547 if (skb->len >= 128) 548 tcp_grow_window(sk, tp, skb); 549} 550 551/* Called to compute a smoothed rtt estimate. The data fed to this 552 * routine either comes from timestamps, or from segments that were 553 * known _not_ to have been retransmitted [see Karn/Partridge 554 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 555 * piece by Van Jacobson. 556 * NOTE: the next three routines used to be one big routine. 557 * To save cycles in the RFC 1323 implementation it was better to break 558 * it up into three procedures. -- erics 559 */ 560static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) 561{ 562 struct tcp_sock *tp = tcp_sk(sk); 563 long m = mrtt; /* RTT */ 564 565 /* The following amusing code comes from Jacobson's 566 * article in SIGCOMM '88. Note that rtt and mdev 567 * are scaled versions of rtt and mean deviation. 568 * This is designed to be as fast as possible 569 * m stands for "measurement". 570 * 571 * On a 1990 paper the rto value is changed to: 572 * RTO = rtt + 4 * mdev 573 * 574 * Funny. This algorithm seems to be very broken. 575 * These formulae increase RTO, when it should be decreased, increase 576 * too slowly, when it should be increased quickly, decrease too quickly 577 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely 578 * does not matter how to _calculate_ it. Seems, it was trap 579 * that VJ failed to avoid. 8) 580 */ 581 if (m == 0) 582 m = 1; 583 if (tp->srtt != 0) { 584 m -= (tp->srtt >> 3); /* m is now error in rtt est */ 585 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ 586 if (m < 0) { 587 m = -m; /* m is now abs(error) */ 588 m -= (tp->mdev >> 2); /* similar update on mdev */ 589 /* This is similar to one of Eifel findings. 590 * Eifel blocks mdev updates when rtt decreases. 591 * This solution is a bit different: we use finer gain 592 * for mdev in this case (alpha*beta). 593 * Like Eifel it also prevents growth of rto, 594 * but also it limits too fast rto decreases, 595 * happening in pure Eifel. 596 */ 597 if (m > 0) 598 m >>= 3; 599 } else { 600 m -= (tp->mdev >> 2); /* similar update on mdev */ 601 } 602 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ 603 if (tp->mdev > tp->mdev_max) { 604 tp->mdev_max = tp->mdev; 605 if (tp->mdev_max > tp->rttvar) 606 tp->rttvar = tp->mdev_max; 607 } 608 if (after(tp->snd_una, tp->rtt_seq)) { 609 if (tp->mdev_max < tp->rttvar) 610 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2; 611 tp->rtt_seq = tp->snd_nxt; 612 tp->mdev_max = TCP_RTO_MIN; 613 } 614 } else { 615 /* no previous measure. */ 616 tp->srtt = m<<3; /* take the measured time to be rtt */ 617 tp->mdev = m<<1; /* make sure rto = 3*rtt */ 618 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); 619 tp->rtt_seq = tp->snd_nxt; 620 } 621} 622 623/* Calculate rto without backoff. This is the second half of Van Jacobson's 624 * routine referred to above. 625 */ 626static inline void tcp_set_rto(struct sock *sk) 627{ 628 const struct tcp_sock *tp = tcp_sk(sk); 629 /* Old crap is replaced with new one. 8) 630 * 631 * More seriously: 632 * 1. If rtt variance happened to be less 50msec, it is hallucination. 633 * It cannot be less due to utterly erratic ACK generation made 634 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ 635 * to do with delayed acks, because at cwnd>2 true delack timeout 636 * is invisible. Actually, Linux-2.4 also generates erratic 637 * ACKs in some circumstances. 638 */ 639 inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar; 640 641 /* 2. Fixups made earlier cannot be right. 642 * If we do not estimate RTO correctly without them, 643 * all the algo is pure shit and should be replaced 644 * with correct one. It is exactly, which we pretend to do. 645 */ 646} 647 648/* NOTE: clamping at TCP_RTO_MIN is not required, current algo 649 * guarantees that rto is higher. 650 */ 651static inline void tcp_bound_rto(struct sock *sk) 652{ 653 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX) 654 inet_csk(sk)->icsk_rto = TCP_RTO_MAX; 655} 656 657/* Save metrics learned by this TCP session. 658 This function is called only, when TCP finishes successfully 659 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. 660 */ 661void tcp_update_metrics(struct sock *sk) 662{ 663 struct tcp_sock *tp = tcp_sk(sk); 664 struct dst_entry *dst = __sk_dst_get(sk); 665 666 if (sysctl_tcp_nometrics_save) 667 return; 668 669 dst_confirm(dst); 670 671 if (dst && (dst->flags&DST_HOST)) { 672 const struct inet_connection_sock *icsk = inet_csk(sk); 673 int m; 674 675 if (icsk->icsk_backoff || !tp->srtt) { 676 /* This session failed to estimate rtt. Why? 677 * Probably, no packets returned in time. 678 * Reset our results. 679 */ 680 if (!(dst_metric_locked(dst, RTAX_RTT))) 681 dst->metrics[RTAX_RTT-1] = 0; 682 return; 683 } 684 685 m = dst_metric(dst, RTAX_RTT) - tp->srtt; 686 687 /* If newly calculated rtt larger than stored one, 688 * store new one. Otherwise, use EWMA. Remember, 689 * rtt overestimation is always better than underestimation. 690 */ 691 if (!(dst_metric_locked(dst, RTAX_RTT))) { 692 if (m <= 0) 693 dst->metrics[RTAX_RTT-1] = tp->srtt; 694 else 695 dst->metrics[RTAX_RTT-1] -= (m>>3); 696 } 697 698 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { 699 if (m < 0) 700 m = -m; 701 702 /* Scale deviation to rttvar fixed point */ 703 m >>= 1; 704 if (m < tp->mdev) 705 m = tp->mdev; 706 707 if (m >= dst_metric(dst, RTAX_RTTVAR)) 708 dst->metrics[RTAX_RTTVAR-1] = m; 709 else 710 dst->metrics[RTAX_RTTVAR-1] -= 711 (dst->metrics[RTAX_RTTVAR-1] - m)>>2; 712 } 713 714 if (tp->snd_ssthresh >= 0xFFFF) { 715 /* Slow start still did not finish. */ 716 if (dst_metric(dst, RTAX_SSTHRESH) && 717 !dst_metric_locked(dst, RTAX_SSTHRESH) && 718 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) 719 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1; 720 if (!dst_metric_locked(dst, RTAX_CWND) && 721 tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) 722 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd; 723 } else if (tp->snd_cwnd > tp->snd_ssthresh && 724 icsk->icsk_ca_state == TCP_CA_Open) { 725 /* Cong. avoidance phase, cwnd is reliable. */ 726 if (!dst_metric_locked(dst, RTAX_SSTHRESH)) 727 dst->metrics[RTAX_SSTHRESH-1] = 728 max(tp->snd_cwnd >> 1, tp->snd_ssthresh); 729 if (!dst_metric_locked(dst, RTAX_CWND)) 730 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1; 731 } else { 732 /* Else slow start did not finish, cwnd is non-sense, 733 ssthresh may be also invalid. 734 */ 735 if (!dst_metric_locked(dst, RTAX_CWND)) 736 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1; 737 if (dst->metrics[RTAX_SSTHRESH-1] && 738 !dst_metric_locked(dst, RTAX_SSTHRESH) && 739 tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1]) 740 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh; 741 } 742 743 if (!dst_metric_locked(dst, RTAX_REORDERING)) { 744 if (dst->metrics[RTAX_REORDERING-1] < tp->reordering && 745 tp->reordering != sysctl_tcp_reordering) 746 dst->metrics[RTAX_REORDERING-1] = tp->reordering; 747 } 748 } 749} 750 751/* Numbers are taken from RFC2414. */ 752__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst) 753{ 754 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); 755 756 if (!cwnd) { 757 if (tp->mss_cache > 1460) 758 cwnd = 2; 759 else 760 cwnd = (tp->mss_cache > 1095) ? 3 : 4; 761 } 762 return min_t(__u32, cwnd, tp->snd_cwnd_clamp); 763} 764 765/* Set slow start threshold and cwnd not falling to slow start */ 766void tcp_enter_cwr(struct sock *sk, const int set_ssthresh) 767{ 768 struct tcp_sock *tp = tcp_sk(sk); 769 const struct inet_connection_sock *icsk = inet_csk(sk); 770 771 tp->prior_ssthresh = 0; 772 tp->bytes_acked = 0; 773 if (icsk->icsk_ca_state < TCP_CA_CWR) { 774 tp->undo_marker = 0; 775 if (set_ssthresh) 776 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 777 tp->snd_cwnd = min(tp->snd_cwnd, 778 tcp_packets_in_flight(tp) + 1U); 779 tp->snd_cwnd_cnt = 0; 780 tp->high_seq = tp->snd_nxt; 781 tp->snd_cwnd_stamp = tcp_time_stamp; 782 TCP_ECN_queue_cwr(tp); 783 784 tcp_set_ca_state(sk, TCP_CA_CWR); 785 } 786} 787 788/* Initialize metrics on socket. */ 789 790static void tcp_init_metrics(struct sock *sk) 791{ 792 struct tcp_sock *tp = tcp_sk(sk); 793 struct dst_entry *dst = __sk_dst_get(sk); 794 795 if (dst == NULL) 796 goto reset; 797 798 dst_confirm(dst); 799 800 if (dst_metric_locked(dst, RTAX_CWND)) 801 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); 802 if (dst_metric(dst, RTAX_SSTHRESH)) { 803 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); 804 if (tp->snd_ssthresh > tp->snd_cwnd_clamp) 805 tp->snd_ssthresh = tp->snd_cwnd_clamp; 806 } 807 if (dst_metric(dst, RTAX_REORDERING) && 808 tp->reordering != dst_metric(dst, RTAX_REORDERING)) { 809 tp->rx_opt.sack_ok &= ~2; 810 tp->reordering = dst_metric(dst, RTAX_REORDERING); 811 } 812 813 if (dst_metric(dst, RTAX_RTT) == 0) 814 goto reset; 815 816 if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3)) 817 goto reset; 818 819 /* Initial rtt is determined from SYN,SYN-ACK. 820 * The segment is small and rtt may appear much 821 * less than real one. Use per-dst memory 822 * to make it more realistic. 823 * 824 * A bit of theory. RTT is time passed after "normal" sized packet 825 * is sent until it is ACKed. In normal circumstances sending small 826 * packets force peer to delay ACKs and calculation is correct too. 827 * The algorithm is adaptive and, provided we follow specs, it 828 * NEVER underestimate RTT. BUT! If peer tries to make some clever 829 * tricks sort of "quick acks" for time long enough to decrease RTT 830 * to low value, and then abruptly stops to do it and starts to delay 831 * ACKs, wait for troubles. 832 */ 833 if (dst_metric(dst, RTAX_RTT) > tp->srtt) { 834 tp->srtt = dst_metric(dst, RTAX_RTT); 835 tp->rtt_seq = tp->snd_nxt; 836 } 837 if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) { 838 tp->mdev = dst_metric(dst, RTAX_RTTVAR); 839 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); 840 } 841 tcp_set_rto(sk); 842 tcp_bound_rto(sk); 843 if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp) 844 goto reset; 845 tp->snd_cwnd = tcp_init_cwnd(tp, dst); 846 tp->snd_cwnd_stamp = tcp_time_stamp; 847 return; 848 849reset: 850 /* Play conservative. If timestamps are not 851 * supported, TCP will fail to recalculate correct 852 * rtt, if initial rto is too small. FORGET ALL AND RESET! 853 */ 854 if (!tp->rx_opt.saw_tstamp && tp->srtt) { 855 tp->srtt = 0; 856 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT; 857 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; 858 } 859} 860 861static void tcp_update_reordering(struct sock *sk, const int metric, 862 const int ts) 863{ 864 struct tcp_sock *tp = tcp_sk(sk); 865 if (metric > tp->reordering) { 866 tp->reordering = min(TCP_MAX_REORDERING, metric); 867 868 /* This exciting event is worth to be remembered. 8) */ 869 if (ts) 870 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER); 871 else if (IsReno(tp)) 872 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER); 873 else if (IsFack(tp)) 874 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER); 875 else 876 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER); 877#if FASTRETRANS_DEBUG > 1 878 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", 879 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, 880 tp->reordering, 881 tp->fackets_out, 882 tp->sacked_out, 883 tp->undo_marker ? tp->undo_retrans : 0); 884#endif 885 /* Disable FACK yet. */ 886 tp->rx_opt.sack_ok &= ~2; 887 } 888} 889 890/* This procedure tags the retransmission queue when SACKs arrive. 891 * 892 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). 893 * Packets in queue with these bits set are counted in variables 894 * sacked_out, retrans_out and lost_out, correspondingly. 895 * 896 * Valid combinations are: 897 * Tag InFlight Description 898 * 0 1 - orig segment is in flight. 899 * S 0 - nothing flies, orig reached receiver. 900 * L 0 - nothing flies, orig lost by net. 901 * R 2 - both orig and retransmit are in flight. 902 * L|R 1 - orig is lost, retransmit is in flight. 903 * S|R 1 - orig reached receiver, retrans is still in flight. 904 * (L|S|R is logically valid, it could occur when L|R is sacked, 905 * but it is equivalent to plain S and code short-curcuits it to S. 906 * L|S is logically invalid, it would mean -1 packet in flight 8)) 907 * 908 * These 6 states form finite state machine, controlled by the following events: 909 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) 910 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) 911 * 3. Loss detection event of one of three flavors: 912 * A. Scoreboard estimator decided the packet is lost. 913 * A'. Reno "three dupacks" marks head of queue lost. 914 * A''. Its FACK modfication, head until snd.fack is lost. 915 * B. SACK arrives sacking data transmitted after never retransmitted 916 * hole was sent out. 917 * C. SACK arrives sacking SND.NXT at the moment, when the 918 * segment was retransmitted. 919 * 4. D-SACK added new rule: D-SACK changes any tag to S. 920 * 921 * It is pleasant to note, that state diagram turns out to be commutative, 922 * so that we are allowed not to be bothered by order of our actions, 923 * when multiple events arrive simultaneously. (see the function below). 924 * 925 * Reordering detection. 926 * -------------------- 927 * Reordering metric is maximal distance, which a packet can be displaced 928 * in packet stream. With SACKs we can estimate it: 929 * 930 * 1. SACK fills old hole and the corresponding segment was not 931 * ever retransmitted -> reordering. Alas, we cannot use it 932 * when segment was retransmitted. 933 * 2. The last flaw is solved with D-SACK. D-SACK arrives 934 * for retransmitted and already SACKed segment -> reordering.. 935 * Both of these heuristics are not used in Loss state, when we cannot 936 * account for retransmits accurately. 937 */ 938static int 939tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una) 940{ 941 const struct inet_connection_sock *icsk = inet_csk(sk); 942 struct tcp_sock *tp = tcp_sk(sk); 943 unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked; 944 struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2); 945 struct sk_buff *cached_skb; 946 int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3; 947 int reord = tp->packets_out; 948 int prior_fackets; 949 u32 lost_retrans = 0; 950 int flag = 0; 951 int dup_sack = 0; 952 int cached_fack_count; 953 int i; 954 int first_sack_index; 955 956 if (!tp->sacked_out) 957 tp->fackets_out = 0; 958 prior_fackets = tp->fackets_out; 959 960 /* Check for D-SACK. */ 961 if (before(ntohl(sp[0].start_seq), TCP_SKB_CB(ack_skb)->ack_seq)) { 962 dup_sack = 1; 963 tp->rx_opt.sack_ok |= 4; 964 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV); 965 } else if (num_sacks > 1 && 966 !after(ntohl(sp[0].end_seq), ntohl(sp[1].end_seq)) && 967 !before(ntohl(sp[0].start_seq), ntohl(sp[1].start_seq))) { 968 dup_sack = 1; 969 tp->rx_opt.sack_ok |= 4; 970 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV); 971 } 972 973 /* D-SACK for already forgotten data... 974 * Do dumb counting. */ 975 if (dup_sack && 976 !after(ntohl(sp[0].end_seq), prior_snd_una) && 977 after(ntohl(sp[0].end_seq), tp->undo_marker)) 978 tp->undo_retrans--; 979 980 /* Eliminate too old ACKs, but take into 981 * account more or less fresh ones, they can 982 * contain valid SACK info. 983 */ 984 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) 985 return 0; 986 987 /* SACK fastpath: 988 * if the only SACK change is the increase of the end_seq of 989 * the first block then only apply that SACK block 990 * and use retrans queue hinting otherwise slowpath */ 991 flag = 1; 992 for (i = 0; i < num_sacks; i++) { 993 __be32 start_seq = sp[i].start_seq; 994 __be32 end_seq = sp[i].end_seq; 995 996 if (i == 0) { 997 if (tp->recv_sack_cache[i].start_seq != start_seq) 998 flag = 0; 999 } else { 1000 if ((tp->recv_sack_cache[i].start_seq != start_seq) || 1001 (tp->recv_sack_cache[i].end_seq != end_seq)) 1002 flag = 0; 1003 } 1004 tp->recv_sack_cache[i].start_seq = start_seq; 1005 tp->recv_sack_cache[i].end_seq = end_seq; 1006 } 1007 /* Clear the rest of the cache sack blocks so they won't match mistakenly. */ 1008 for (; i < ARRAY_SIZE(tp->recv_sack_cache); i++) { 1009 tp->recv_sack_cache[i].start_seq = 0; 1010 tp->recv_sack_cache[i].end_seq = 0; 1011 } 1012 1013 first_sack_index = 0; 1014 if (flag) 1015 num_sacks = 1; 1016 else { 1017 int j; 1018 tp->fastpath_skb_hint = NULL; 1019 1020 /* order SACK blocks to allow in order walk of the retrans queue */ 1021 for (i = num_sacks-1; i > 0; i--) { 1022 for (j = 0; j < i; j++){ 1023 if (after(ntohl(sp[j].start_seq), 1024 ntohl(sp[j+1].start_seq))){ 1025 struct tcp_sack_block_wire tmp; 1026 1027 tmp = sp[j]; 1028 sp[j] = sp[j+1]; 1029 sp[j+1] = tmp; 1030 1031 /* Track where the first SACK block goes to */ 1032 if (j == first_sack_index) 1033 first_sack_index = j+1; 1034 } 1035 1036 } 1037 } 1038 } 1039 1040 /* clear flag as used for different purpose in following code */ 1041 flag = 0; 1042 1043 /* Use SACK fastpath hint if valid */ 1044 cached_skb = tp->fastpath_skb_hint; 1045 cached_fack_count = tp->fastpath_cnt_hint; 1046 if (!cached_skb) { 1047 cached_skb = tcp_write_queue_head(sk); 1048 cached_fack_count = 0; 1049 } 1050 1051 for (i=0; i<num_sacks; i++, sp++) { 1052 struct sk_buff *skb; 1053 __u32 start_seq = ntohl(sp->start_seq); 1054 __u32 end_seq = ntohl(sp->end_seq); 1055 int fack_count; 1056 1057 skb = cached_skb; 1058 fack_count = cached_fack_count; 1059 1060 /* Event "B" in the comment above. */ 1061 if (after(end_seq, tp->high_seq)) 1062 flag |= FLAG_DATA_LOST; 1063 1064 tcp_for_write_queue_from(skb, sk) { 1065 int in_sack, pcount; 1066 u8 sacked; 1067 1068 if (skb == tcp_send_head(sk)) 1069 break; 1070 1071 cached_skb = skb; 1072 cached_fack_count = fack_count; 1073 if (i == first_sack_index) { 1074 tp->fastpath_skb_hint = skb; 1075 tp->fastpath_cnt_hint = fack_count; 1076 } 1077 1078 /* The retransmission queue is always in order, so 1079 * we can short-circuit the walk early. 1080 */ 1081 if (!before(TCP_SKB_CB(skb)->seq, end_seq)) 1082 break; 1083 1084 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && 1085 !before(end_seq, TCP_SKB_CB(skb)->end_seq); 1086 1087 pcount = tcp_skb_pcount(skb); 1088 1089 if (pcount > 1 && !in_sack && 1090 after(TCP_SKB_CB(skb)->end_seq, start_seq)) { 1091 unsigned int pkt_len; 1092 1093 in_sack = !after(start_seq, 1094 TCP_SKB_CB(skb)->seq); 1095 1096 if (!in_sack) 1097 pkt_len = (start_seq - 1098 TCP_SKB_CB(skb)->seq); 1099 else 1100 pkt_len = (end_seq - 1101 TCP_SKB_CB(skb)->seq); 1102 if (tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size)) 1103 break; 1104 pcount = tcp_skb_pcount(skb); 1105 } 1106 1107 fack_count += pcount; 1108 1109 sacked = TCP_SKB_CB(skb)->sacked; 1110 1111 /* Account D-SACK for retransmitted packet. */ 1112 if ((dup_sack && in_sack) && 1113 (sacked & TCPCB_RETRANS) && 1114 after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) 1115 tp->undo_retrans--; 1116 1117 /* The frame is ACKed. */ 1118 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) { 1119 if (sacked&TCPCB_RETRANS) { 1120 if ((dup_sack && in_sack) && 1121 (sacked&TCPCB_SACKED_ACKED)) 1122 reord = min(fack_count, reord); 1123 } else { 1124 /* If it was in a hole, we detected reordering. */ 1125 if (fack_count < prior_fackets && 1126 !(sacked&TCPCB_SACKED_ACKED)) 1127 reord = min(fack_count, reord); 1128 } 1129 1130 /* Nothing to do; acked frame is about to be dropped. */ 1131 continue; 1132 } 1133 1134 if ((sacked&TCPCB_SACKED_RETRANS) && 1135 after(end_seq, TCP_SKB_CB(skb)->ack_seq) && 1136 (!lost_retrans || after(end_seq, lost_retrans))) 1137 lost_retrans = end_seq; 1138 1139 if (!in_sack) 1140 continue; 1141 1142 if (!(sacked&TCPCB_SACKED_ACKED)) { 1143 if (sacked & TCPCB_SACKED_RETRANS) { 1144 /* If the segment is not tagged as lost, 1145 * we do not clear RETRANS, believing 1146 * that retransmission is still in flight. 1147 */ 1148 if (sacked & TCPCB_LOST) { 1149 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); 1150 tp->lost_out -= tcp_skb_pcount(skb); 1151 tp->retrans_out -= tcp_skb_pcount(skb); 1152 1153 /* clear lost hint */ 1154 tp->retransmit_skb_hint = NULL; 1155 } 1156 } else { 1157 /* New sack for not retransmitted frame, 1158 * which was in hole. It is reordering. 1159 */ 1160 if (!(sacked & TCPCB_RETRANS) && 1161 fack_count < prior_fackets) 1162 reord = min(fack_count, reord); 1163 1164 if (sacked & TCPCB_LOST) { 1165 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 1166 tp->lost_out -= tcp_skb_pcount(skb); 1167 1168 /* clear lost hint */ 1169 tp->retransmit_skb_hint = NULL; 1170 } 1171 /* SACK enhanced F-RTO detection. 1172 * Set flag if and only if non-rexmitted 1173 * segments below frto_highmark are 1174 * SACKed (RFC4138; Appendix B). 1175 * Clearing correct due to in-order walk 1176 */ 1177 if (after(end_seq, tp->frto_highmark)) { 1178 flag &= ~FLAG_ONLY_ORIG_SACKED; 1179 } else { 1180 if (!(sacked & TCPCB_RETRANS)) 1181 flag |= FLAG_ONLY_ORIG_SACKED; 1182 } 1183 } 1184 1185 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED; 1186 flag |= FLAG_DATA_SACKED; 1187 tp->sacked_out += tcp_skb_pcount(skb); 1188 1189 if (fack_count > tp->fackets_out) 1190 tp->fackets_out = fack_count; 1191 } else { 1192 if (dup_sack && (sacked&TCPCB_RETRANS)) 1193 reord = min(fack_count, reord); 1194 } 1195 1196 /* D-SACK. We can detect redundant retransmission 1197 * in S|R and plain R frames and clear it. 1198 * undo_retrans is decreased above, L|R frames 1199 * are accounted above as well. 1200 */ 1201 if (dup_sack && 1202 (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) { 1203 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1204 tp->retrans_out -= tcp_skb_pcount(skb); 1205 tp->retransmit_skb_hint = NULL; 1206 } 1207 } 1208 } 1209 1210 /* Check for lost retransmit. This superb idea is 1211 * borrowed from "ratehalving". Event "C". 1212 * Later note: FACK people cheated me again 8), 1213 * we have to account for reordering! Ugly, 1214 * but should help. 1215 */ 1216 if (lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) { 1217 struct sk_buff *skb; 1218 1219 tcp_for_write_queue(skb, sk) { 1220 if (skb == tcp_send_head(sk)) 1221 break; 1222 if (after(TCP_SKB_CB(skb)->seq, lost_retrans)) 1223 break; 1224 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1225 continue; 1226 if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) && 1227 after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) && 1228 (IsFack(tp) || 1229 !before(lost_retrans, 1230 TCP_SKB_CB(skb)->ack_seq + tp->reordering * 1231 tp->mss_cache))) { 1232 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1233 tp->retrans_out -= tcp_skb_pcount(skb); 1234 1235 /* clear lost hint */ 1236 tp->retransmit_skb_hint = NULL; 1237 1238 if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) { 1239 tp->lost_out += tcp_skb_pcount(skb); 1240 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1241 flag |= FLAG_DATA_SACKED; 1242 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT); 1243 } 1244 } 1245 } 1246 } 1247 1248 tp->left_out = tp->sacked_out + tp->lost_out; 1249 1250 if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss && 1251 (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark))) 1252 tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0); 1253 1254#if FASTRETRANS_DEBUG > 0 1255 BUG_TRAP((int)tp->sacked_out >= 0); 1256 BUG_TRAP((int)tp->lost_out >= 0); 1257 BUG_TRAP((int)tp->retrans_out >= 0); 1258 BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0); 1259#endif 1260 return flag; 1261} 1262 1263/* F-RTO can only be used if these conditions are satisfied: 1264 * - there must be some unsent new data 1265 * - the advertised window should allow sending it 1266 * - TCP has never retransmitted anything other than head (SACK enhanced 1267 * variant from Appendix B of RFC4138 is more robust here) 1268 */ 1269int tcp_use_frto(struct sock *sk) 1270{ 1271 const struct tcp_sock *tp = tcp_sk(sk); 1272 struct sk_buff *skb; 1273 1274 if (!sysctl_tcp_frto || !tcp_send_head(sk) || 1275 after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, 1276 tp->snd_una + tp->snd_wnd)) 1277 return 0; 1278 1279 if (IsSackFrto()) 1280 return 1; 1281 1282 /* Avoid expensive walking of rexmit queue if possible */ 1283 if (tp->retrans_out > 1) 1284 return 0; 1285 1286 skb = tcp_write_queue_head(sk); 1287 skb = tcp_write_queue_next(sk, skb); /* Skips head */ 1288 tcp_for_write_queue_from(skb, sk) { 1289 if (skb == tcp_send_head(sk)) 1290 break; 1291 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS) 1292 return 0; 1293 /* Short-circuit when first non-SACKed skb has been checked */ 1294 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) 1295 break; 1296 } 1297 return 1; 1298} 1299 1300/* RTO occurred, but do not yet enter Loss state. Instead, defer RTO 1301 * recovery a bit and use heuristics in tcp_process_frto() to detect if 1302 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to 1303 * keep retrans_out counting accurate (with SACK F-RTO, other than head 1304 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS 1305 * bits are handled if the Loss state is really to be entered (in 1306 * tcp_enter_frto_loss). 1307 * 1308 * Do like tcp_enter_loss() would; when RTO expires the second time it 1309 * does: 1310 * "Reduce ssthresh if it has not yet been made inside this window." 1311 */ 1312void tcp_enter_frto(struct sock *sk) 1313{ 1314 const struct inet_connection_sock *icsk = inet_csk(sk); 1315 struct tcp_sock *tp = tcp_sk(sk); 1316 struct sk_buff *skb; 1317 1318 if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) || 1319 tp->snd_una == tp->high_seq || 1320 ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) && 1321 !icsk->icsk_retransmits)) { 1322 tp->prior_ssthresh = tcp_current_ssthresh(sk); 1323 /* Our state is too optimistic in ssthresh() call because cwnd 1324 * is not reduced until tcp_enter_frto_loss() when previous FRTO 1325 * recovery has not yet completed. Pattern would be this: RTO, 1326 * Cumulative ACK, RTO (2xRTO for the same segment does not end 1327 * up here twice). 1328 * RFC4138 should be more specific on what to do, even though 1329 * RTO is quite unlikely to occur after the first Cumulative ACK 1330 * due to back-off and complexity of triggering events ... 1331 */ 1332 if (tp->frto_counter) { 1333 u32 stored_cwnd; 1334 stored_cwnd = tp->snd_cwnd; 1335 tp->snd_cwnd = 2; 1336 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 1337 tp->snd_cwnd = stored_cwnd; 1338 } else { 1339 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 1340 } 1341 /* ... in theory, cong.control module could do "any tricks" in 1342 * ssthresh(), which means that ca_state, lost bits and lost_out 1343 * counter would have to be faked before the call occurs. We 1344 * consider that too expensive, unlikely and hacky, so modules 1345 * using these in ssthresh() must deal these incompatibility 1346 * issues if they receives CA_EVENT_FRTO and frto_counter != 0 1347 */ 1348 tcp_ca_event(sk, CA_EVENT_FRTO); 1349 } 1350 1351 tp->undo_marker = tp->snd_una; 1352 tp->undo_retrans = 0; 1353 1354 skb = tcp_write_queue_head(sk); 1355 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 1356 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1357 tp->retrans_out -= tcp_skb_pcount(skb); 1358 } 1359 tcp_sync_left_out(tp); 1360 1361 /* Earlier loss recovery underway (see RFC4138; Appendix B). 1362 * The last condition is necessary at least in tp->frto_counter case. 1363 */ 1364 if (IsSackFrto() && (tp->frto_counter || 1365 ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) && 1366 after(tp->high_seq, tp->snd_una)) { 1367 tp->frto_highmark = tp->high_seq; 1368 } else { 1369 tp->frto_highmark = tp->snd_nxt; 1370 } 1371 tcp_set_ca_state(sk, TCP_CA_Disorder); 1372 tp->high_seq = tp->snd_nxt; 1373 tp->frto_counter = 1; 1374} 1375 1376/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO, 1377 * which indicates that we should follow the traditional RTO recovery, 1378 * i.e. mark everything lost and do go-back-N retransmission. 1379 */ 1380static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag) 1381{ 1382 struct tcp_sock *tp = tcp_sk(sk); 1383 struct sk_buff *skb; 1384 int cnt = 0; 1385 1386 tp->sacked_out = 0; 1387 tp->lost_out = 0; 1388 tp->fackets_out = 0; 1389 tp->retrans_out = 0; 1390 1391 tcp_for_write_queue(skb, sk) { 1392 if (skb == tcp_send_head(sk)) 1393 break; 1394 cnt += tcp_skb_pcount(skb); 1395 /* 1396 * Count the retransmission made on RTO correctly (only when 1397 * waiting for the first ACK and did not get it)... 1398 */ 1399 if ((tp->frto_counter == 1) && !(flag&FLAG_DATA_ACKED)) { 1400 tp->retrans_out += tcp_skb_pcount(skb); 1401 /* ...enter this if branch just for the first segment */ 1402 flag |= FLAG_DATA_ACKED; 1403 } else { 1404 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); 1405 } 1406 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) { 1407 1408 /* Do not mark those segments lost that were 1409 * forward transmitted after RTO 1410 */ 1411 if (!after(TCP_SKB_CB(skb)->end_seq, 1412 tp->frto_highmark)) { 1413 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1414 tp->lost_out += tcp_skb_pcount(skb); 1415 } 1416 } else { 1417 tp->sacked_out += tcp_skb_pcount(skb); 1418 tp->fackets_out = cnt; 1419 } 1420 } 1421 tcp_sync_left_out(tp); 1422 1423 tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments; 1424 tp->snd_cwnd_cnt = 0; 1425 tp->snd_cwnd_stamp = tcp_time_stamp; 1426 tp->undo_marker = 0; 1427 tp->frto_counter = 0; 1428 1429 tp->reordering = min_t(unsigned int, tp->reordering, 1430 sysctl_tcp_reordering); 1431 tcp_set_ca_state(sk, TCP_CA_Loss); 1432 tp->high_seq = tp->frto_highmark; 1433 TCP_ECN_queue_cwr(tp); 1434 1435 clear_all_retrans_hints(tp); 1436} 1437 1438void tcp_clear_retrans(struct tcp_sock *tp) 1439{ 1440 tp->left_out = 0; 1441 tp->retrans_out = 0; 1442 1443 tp->fackets_out = 0; 1444 tp->sacked_out = 0; 1445 tp->lost_out = 0; 1446 1447 tp->undo_marker = 0; 1448 tp->undo_retrans = 0; 1449} 1450 1451/* Enter Loss state. If "how" is not zero, forget all SACK information 1452 * and reset tags completely, otherwise preserve SACKs. If receiver 1453 * dropped its ofo queue, we will know this due to reneging detection. 1454 */ 1455void tcp_enter_loss(struct sock *sk, int how) 1456{ 1457 const struct inet_connection_sock *icsk = inet_csk(sk); 1458 struct tcp_sock *tp = tcp_sk(sk); 1459 struct sk_buff *skb; 1460 int cnt = 0; 1461 1462 /* Reduce ssthresh if it has not yet been made inside this window. */ 1463 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq || 1464 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { 1465 tp->prior_ssthresh = tcp_current_ssthresh(sk); 1466 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 1467 tcp_ca_event(sk, CA_EVENT_LOSS); 1468 } 1469 tp->snd_cwnd = 1; 1470 tp->snd_cwnd_cnt = 0; 1471 tp->snd_cwnd_stamp = tcp_time_stamp; 1472 1473 tp->bytes_acked = 0; 1474 tcp_clear_retrans(tp); 1475 1476 /* Push undo marker, if it was plain RTO and nothing 1477 * was retransmitted. */ 1478 if (!how) 1479 tp->undo_marker = tp->snd_una; 1480 1481 tcp_for_write_queue(skb, sk) { 1482 if (skb == tcp_send_head(sk)) 1483 break; 1484 cnt += tcp_skb_pcount(skb); 1485 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS) 1486 tp->undo_marker = 0; 1487 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; 1488 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { 1489 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; 1490 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1491 tp->lost_out += tcp_skb_pcount(skb); 1492 } else { 1493 tp->sacked_out += tcp_skb_pcount(skb); 1494 tp->fackets_out = cnt; 1495 } 1496 } 1497 tcp_sync_left_out(tp); 1498 1499 tp->reordering = min_t(unsigned int, tp->reordering, 1500 sysctl_tcp_reordering); 1501 tcp_set_ca_state(sk, TCP_CA_Loss); 1502 tp->high_seq = tp->snd_nxt; 1503 TCP_ECN_queue_cwr(tp); 1504 1505 clear_all_retrans_hints(tp); 1506} 1507 1508static int tcp_check_sack_reneging(struct sock *sk) 1509{ 1510 struct sk_buff *skb; 1511 1512 /* If ACK arrived pointing to a remembered SACK, 1513 * it means that our remembered SACKs do not reflect 1514 * real state of receiver i.e. 1515 * receiver _host_ is heavily congested (or buggy). 1516 * Do processing similar to RTO timeout. 1517 */ 1518 if ((skb = tcp_write_queue_head(sk)) != NULL && 1519 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 1520 struct inet_connection_sock *icsk = inet_csk(sk); 1521 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING); 1522 1523 tcp_enter_loss(sk, 1); 1524 icsk->icsk_retransmits++; 1525 tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); 1526 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 1527 icsk->icsk_rto, TCP_RTO_MAX); 1528 return 1; 1529 } 1530 return 0; 1531} 1532 1533static inline int tcp_fackets_out(struct tcp_sock *tp) 1534{ 1535 return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out; 1536} 1537 1538static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb) 1539{ 1540 return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto); 1541} 1542 1543static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp) 1544{ 1545 return tp->packets_out && 1546 tcp_skb_timedout(sk, tcp_write_queue_head(sk)); 1547} 1548 1549/* Linux NewReno/SACK/FACK/ECN state machine. 1550 * -------------------------------------- 1551 * 1552 * "Open" Normal state, no dubious events, fast path. 1553 * "Disorder" In all the respects it is "Open", 1554 * but requires a bit more attention. It is entered when 1555 * we see some SACKs or dupacks. It is split of "Open" 1556 * mainly to move some processing from fast path to slow one. 1557 * "CWR" CWND was reduced due to some Congestion Notification event. 1558 * It can be ECN, ICMP source quench, local device congestion. 1559 * "Recovery" CWND was reduced, we are fast-retransmitting. 1560 * "Loss" CWND was reduced due to RTO timeout or SACK reneging. 1561 * 1562 * tcp_fastretrans_alert() is entered: 1563 * - each incoming ACK, if state is not "Open" 1564 * - when arrived ACK is unusual, namely: 1565 * * SACK 1566 * * Duplicate ACK. 1567 * * ECN ECE. 1568 * 1569 * Counting packets in flight is pretty simple. 1570 * 1571 * in_flight = packets_out - left_out + retrans_out 1572 * 1573 * packets_out is SND.NXT-SND.UNA counted in packets. 1574 * 1575 * retrans_out is number of retransmitted segments. 1576 * 1577 * left_out is number of segments left network, but not ACKed yet. 1578 * 1579 * left_out = sacked_out + lost_out 1580 * 1581 * sacked_out: Packets, which arrived to receiver out of order 1582 * and hence not ACKed. With SACKs this number is simply 1583 * amount of SACKed data. Even without SACKs 1584 * it is easy to give pretty reliable estimate of this number, 1585 * counting duplicate ACKs. 1586 * 1587 * lost_out: Packets lost by network. TCP has no explicit 1588 * "loss notification" feedback from network (for now). 1589 * It means that this number can be only _guessed_. 1590 * Actually, it is the heuristics to predict lossage that 1591 * distinguishes different algorithms. 1592 * 1593 * F.e. after RTO, when all the queue is considered as lost, 1594 * lost_out = packets_out and in_flight = retrans_out. 1595 * 1596 * Essentially, we have now two algorithms counting 1597 * lost packets. 1598 * 1599 * FACK: It is the simplest heuristics. As soon as we decided 1600 * that something is lost, we decide that _all_ not SACKed 1601 * packets until the most forward SACK are lost. I.e. 1602 * lost_out = fackets_out - sacked_out and left_out = fackets_out. 1603 * It is absolutely correct estimate, if network does not reorder 1604 * packets. And it loses any connection to reality when reordering 1605 * takes place. We use FACK by default until reordering 1606 * is suspected on the path to this destination. 1607 * 1608 * NewReno: when Recovery is entered, we assume that one segment 1609 * is lost (classic Reno). While we are in Recovery and 1610 * a partial ACK arrives, we assume that one more packet 1611 * is lost (NewReno). This heuristics are the same in NewReno 1612 * and SACK. 1613 * 1614 * Imagine, that's all! Forget about all this shamanism about CWND inflation 1615 * deflation etc. CWND is real congestion window, never inflated, changes 1616 * only according to classic VJ rules. 1617 * 1618 * Really tricky (and requiring careful tuning) part of algorithm 1619 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). 1620 * The first determines the moment _when_ we should reduce CWND and, 1621 * hence, slow down forward transmission. In fact, it determines the moment 1622 * when we decide that hole is caused by loss, rather than by a reorder. 1623 * 1624 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill 1625 * holes, caused by lost packets. 1626 * 1627 * And the most logically complicated part of algorithm is undo 1628 * heuristics. We detect false retransmits due to both too early 1629 * fast retransmit (reordering) and underestimated RTO, analyzing 1630 * timestamps and D-SACKs. When we detect that some segments were 1631 * retransmitted by mistake and CWND reduction was wrong, we undo 1632 * window reduction and abort recovery phase. This logic is hidden 1633 * inside several functions named tcp_try_undo_<something>. 1634 */ 1635 1636/* This function decides, when we should leave Disordered state 1637 * and enter Recovery phase, reducing congestion window. 1638 * 1639 * Main question: may we further continue forward transmission 1640 * with the same cwnd? 1641 */ 1642static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp) 1643{ 1644 __u32 packets_out; 1645 1646 /* Do not perform any recovery during FRTO algorithm */ 1647 if (tp->frto_counter) 1648 return 0; 1649 1650 /* Trick#1: The loss is proven. */ 1651 if (tp->lost_out) 1652 return 1; 1653 1654 /* Not-A-Trick#2 : Classic rule... */ 1655 if (tcp_fackets_out(tp) > tp->reordering) 1656 return 1; 1657 1658 /* Trick#3 : when we use RFC2988 timer restart, fast 1659 * retransmit can be triggered by timeout of queue head. 1660 */ 1661 if (tcp_head_timedout(sk, tp)) 1662 return 1; 1663 1664 /* Trick#4: It is still not OK... But will it be useful to delay 1665 * recovery more? 1666 */ 1667 packets_out = tp->packets_out; 1668 if (packets_out <= tp->reordering && 1669 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && 1670 !tcp_may_send_now(sk, tp)) { 1671 /* We have nothing to send. This connection is limited 1672 * either by receiver window or by application. 1673 */ 1674 return 1; 1675 } 1676 1677 return 0; 1678} 1679 1680/* If we receive more dupacks than we expected counting segments 1681 * in assumption of absent reordering, interpret this as reordering. 1682 * The only another reason could be bug in receiver TCP. 1683 */ 1684static void tcp_check_reno_reordering(struct sock *sk, const int addend) 1685{ 1686 struct tcp_sock *tp = tcp_sk(sk); 1687 u32 holes; 1688 1689 holes = max(tp->lost_out, 1U); 1690 holes = min(holes, tp->packets_out); 1691 1692 if ((tp->sacked_out + holes) > tp->packets_out) { 1693 tp->sacked_out = tp->packets_out - holes; 1694 tcp_update_reordering(sk, tp->packets_out + addend, 0); 1695 } 1696} 1697 1698/* Emulate SACKs for SACKless connection: account for a new dupack. */ 1699 1700static void tcp_add_reno_sack(struct sock *sk) 1701{ 1702 struct tcp_sock *tp = tcp_sk(sk); 1703 tp->sacked_out++; 1704 tcp_check_reno_reordering(sk, 0); 1705 tcp_sync_left_out(tp); 1706} 1707 1708/* Account for ACK, ACKing some data in Reno Recovery phase. */ 1709 1710static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked) 1711{ 1712 if (acked > 0) { 1713 /* One ACK acked hole. The rest eat duplicate ACKs. */ 1714 if (acked-1 >= tp->sacked_out) 1715 tp->sacked_out = 0; 1716 else 1717 tp->sacked_out -= acked-1; 1718 } 1719 tcp_check_reno_reordering(sk, acked); 1720 tcp_sync_left_out(tp); 1721} 1722 1723static inline void tcp_reset_reno_sack(struct tcp_sock *tp) 1724{ 1725 tp->sacked_out = 0; 1726 tp->left_out = tp->lost_out; 1727} 1728 1729/* Mark head of queue up as lost. */ 1730static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp, 1731 int packets, u32 high_seq) 1732{ 1733 struct sk_buff *skb; 1734 int cnt; 1735 1736 BUG_TRAP(packets <= tp->packets_out); 1737 if (tp->lost_skb_hint) { 1738 skb = tp->lost_skb_hint; 1739 cnt = tp->lost_cnt_hint; 1740 } else { 1741 skb = tcp_write_queue_head(sk); 1742 cnt = 0; 1743 } 1744 1745 tcp_for_write_queue_from(skb, sk) { 1746 if (skb == tcp_send_head(sk)) 1747 break; 1748 /* TODO: do this better */ 1749 /* this is not the most efficient way to do this... */ 1750 tp->lost_skb_hint = skb; 1751 tp->lost_cnt_hint = cnt; 1752 cnt += tcp_skb_pcount(skb); 1753 if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, high_seq)) 1754 break; 1755 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) { 1756 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1757 tp->lost_out += tcp_skb_pcount(skb); 1758 1759 /* clear xmit_retransmit_queue hints 1760 * if this is beyond hint */ 1761 if (tp->retransmit_skb_hint != NULL && 1762 before(TCP_SKB_CB(skb)->seq, 1763 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) 1764 tp->retransmit_skb_hint = NULL; 1765 1766 } 1767 } 1768 tcp_sync_left_out(tp); 1769} 1770 1771/* Account newly detected lost packet(s) */ 1772 1773static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp) 1774{ 1775 if (IsFack(tp)) { 1776 int lost = tp->fackets_out - tp->reordering; 1777 if (lost <= 0) 1778 lost = 1; 1779 tcp_mark_head_lost(sk, tp, lost, tp->high_seq); 1780 } else { 1781 tcp_mark_head_lost(sk, tp, 1, tp->high_seq); 1782 } 1783 1784 /* New heuristics: it is possible only after we switched 1785 * to restart timer each time when something is ACKed. 1786 * Hence, we can detect timed out packets during fast 1787 * retransmit without falling to slow start. 1788 */ 1789 if (!IsReno(tp) && tcp_head_timedout(sk, tp)) { 1790 struct sk_buff *skb; 1791 1792 skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint 1793 : tcp_write_queue_head(sk); 1794 1795 tcp_for_write_queue_from(skb, sk) { 1796 if (skb == tcp_send_head(sk)) 1797 break; 1798 if (!tcp_skb_timedout(sk, skb)) 1799 break; 1800 1801 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) { 1802 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1803 tp->lost_out += tcp_skb_pcount(skb); 1804 1805 /* clear xmit_retrans hint */ 1806 if (tp->retransmit_skb_hint && 1807 before(TCP_SKB_CB(skb)->seq, 1808 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) 1809 1810 tp->retransmit_skb_hint = NULL; 1811 } 1812 } 1813 1814 tp->scoreboard_skb_hint = skb; 1815 1816 tcp_sync_left_out(tp); 1817 } 1818} 1819 1820/* CWND moderation, preventing bursts due to too big ACKs 1821 * in dubious situations. 1822 */ 1823static inline void tcp_moderate_cwnd(struct tcp_sock *tp) 1824{ 1825 tp->snd_cwnd = min(tp->snd_cwnd, 1826 tcp_packets_in_flight(tp)+tcp_max_burst(tp)); 1827 tp->snd_cwnd_stamp = tcp_time_stamp; 1828} 1829 1830/* Lower bound on congestion window is slow start threshold 1831 * unless congestion avoidance choice decides to overide it. 1832 */ 1833static inline u32 tcp_cwnd_min(const struct sock *sk) 1834{ 1835 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; 1836 1837 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh; 1838} 1839 1840/* Decrease cwnd each second ack. */ 1841static void tcp_cwnd_down(struct sock *sk) 1842{ 1843 struct tcp_sock *tp = tcp_sk(sk); 1844 int decr = tp->snd_cwnd_cnt + 1; 1845 1846 tp->snd_cwnd_cnt = decr&1; 1847 decr >>= 1; 1848 1849 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk)) 1850 tp->snd_cwnd -= decr; 1851 1852 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1); 1853 tp->snd_cwnd_stamp = tcp_time_stamp; 1854} 1855 1856/* Nothing was retransmitted or returned timestamp is less 1857 * than timestamp of the first retransmission. 1858 */ 1859static inline int tcp_packet_delayed(struct tcp_sock *tp) 1860{ 1861 return !tp->retrans_stamp || 1862 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 1863 (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0); 1864} 1865 1866/* Undo procedures. */ 1867 1868#if FASTRETRANS_DEBUG > 1 1869static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg) 1870{ 1871 struct inet_sock *inet = inet_sk(sk); 1872 printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n", 1873 msg, 1874 NIPQUAD(inet->daddr), ntohs(inet->dport), 1875 tp->snd_cwnd, tp->left_out, 1876 tp->snd_ssthresh, tp->prior_ssthresh, 1877 tp->packets_out); 1878} 1879#else 1880#define DBGUNDO(x...) do { } while (0) 1881#endif 1882 1883static void tcp_undo_cwr(struct sock *sk, const int undo) 1884{ 1885 struct tcp_sock *tp = tcp_sk(sk); 1886 1887 if (tp->prior_ssthresh) { 1888 const struct inet_connection_sock *icsk = inet_csk(sk); 1889 1890 if (icsk->icsk_ca_ops->undo_cwnd) 1891 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); 1892 else 1893 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1); 1894 1895 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) { 1896 tp->snd_ssthresh = tp->prior_ssthresh; 1897 TCP_ECN_withdraw_cwr(tp); 1898 } 1899 } else { 1900 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); 1901 } 1902 tcp_moderate_cwnd(tp); 1903 tp->snd_cwnd_stamp = tcp_time_stamp; 1904 1905 /* There is something screwy going on with the retrans hints after 1906 an undo */ 1907 clear_all_retrans_hints(tp); 1908} 1909 1910static inline int tcp_may_undo(struct tcp_sock *tp) 1911{ 1912 return tp->undo_marker && 1913 (!tp->undo_retrans || tcp_packet_delayed(tp)); 1914} 1915 1916/* People celebrate: "We love our President!" */ 1917static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp) 1918{ 1919 if (tcp_may_undo(tp)) { 1920 /* Happy end! We did not retransmit anything 1921 * or our original transmission succeeded. 1922 */ 1923 DBGUNDO(sk, tp, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); 1924 tcp_undo_cwr(sk, 1); 1925 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) 1926 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); 1927 else 1928 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO); 1929 tp->undo_marker = 0; 1930 } 1931 if (tp->snd_una == tp->high_seq && IsReno(tp)) { 1932 /* Hold old state until something *above* high_seq 1933 * is ACKed. For Reno it is MUST to prevent false 1934 * fast retransmits (RFC2582). SACK TCP is safe. */ 1935 tcp_moderate_cwnd(tp); 1936 return 1; 1937 } 1938 tcp_set_ca_state(sk, TCP_CA_Open); 1939 return 0; 1940} 1941 1942/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ 1943static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp) 1944{ 1945 if (tp->undo_marker && !tp->undo_retrans) { 1946 DBGUNDO(sk, tp, "D-SACK"); 1947 tcp_undo_cwr(sk, 1); 1948 tp->undo_marker = 0; 1949 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO); 1950 } 1951} 1952 1953/* Undo during fast recovery after partial ACK. */ 1954 1955static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp, 1956 int acked) 1957{ 1958 /* Partial ACK arrived. Force Hoe's retransmit. */ 1959 int failed = IsReno(tp) || tp->fackets_out>tp->reordering; 1960 1961 if (tcp_may_undo(tp)) { 1962 /* Plain luck! Hole if filled with delayed 1963 * packet, rather than with a retransmit. 1964 */ 1965 if (tp->retrans_out == 0) 1966 tp->retrans_stamp = 0; 1967 1968 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1); 1969 1970 DBGUNDO(sk, tp, "Hoe"); 1971 tcp_undo_cwr(sk, 0); 1972 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO); 1973 1974 /* So... Do not make Hoe's retransmit yet. 1975 * If the first packet was delayed, the rest 1976 * ones are most probably delayed as well. 1977 */ 1978 failed = 0; 1979 } 1980 return failed; 1981} 1982 1983/* Undo during loss recovery after partial ACK. */ 1984static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp) 1985{ 1986 if (tcp_may_undo(tp)) { 1987 struct sk_buff *skb; 1988 tcp_for_write_queue(skb, sk) { 1989 if (skb == tcp_send_head(sk)) 1990 break; 1991 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 1992 } 1993 1994 clear_all_retrans_hints(tp); 1995 1996 DBGUNDO(sk, tp, "partial loss"); 1997 tp->lost_out = 0; 1998 tp->left_out = tp->sacked_out; 1999 tcp_undo_cwr(sk, 1); 2000 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); 2001 inet_csk(sk)->icsk_retransmits = 0; 2002 tp->undo_marker = 0; 2003 if (!IsReno(tp)) 2004 tcp_set_ca_state(sk, TCP_CA_Open); 2005 return 1; 2006 } 2007 return 0; 2008} 2009 2010static inline void tcp_complete_cwr(struct sock *sk) 2011{ 2012 struct tcp_sock *tp = tcp_sk(sk); 2013 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 2014 tp->snd_cwnd_stamp = tcp_time_stamp; 2015 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); 2016} 2017 2018static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag) 2019{ 2020 tp->left_out = tp->sacked_out; 2021 2022 if (tp->retrans_out == 0) 2023 tp->retrans_stamp = 0; 2024 2025 if (flag&FLAG_ECE) 2026 tcp_enter_cwr(sk, 1); 2027 2028 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { 2029 int state = TCP_CA_Open; 2030 2031 if (tp->left_out || tp->retrans_out || tp->undo_marker) 2032 state = TCP_CA_Disorder; 2033 2034 if (inet_csk(sk)->icsk_ca_state != state) { 2035 tcp_set_ca_state(sk, state); 2036 tp->high_seq = tp->snd_nxt; 2037 } 2038 tcp_moderate_cwnd(tp); 2039 } else { 2040 tcp_cwnd_down(sk); 2041 } 2042} 2043 2044static void tcp_mtup_probe_failed(struct sock *sk) 2045{ 2046 struct inet_connection_sock *icsk = inet_csk(sk); 2047 2048 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; 2049 icsk->icsk_mtup.probe_size = 0; 2050} 2051 2052static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb) 2053{ 2054 struct tcp_sock *tp = tcp_sk(sk); 2055 struct inet_connection_sock *icsk = inet_csk(sk); 2056 2057 /* FIXME: breaks with very large cwnd */ 2058 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2059 tp->snd_cwnd = tp->snd_cwnd * 2060 tcp_mss_to_mtu(sk, tp->mss_cache) / 2061 icsk->icsk_mtup.probe_size; 2062 tp->snd_cwnd_cnt = 0; 2063 tp->snd_cwnd_stamp = tcp_time_stamp; 2064 tp->rcv_ssthresh = tcp_current_ssthresh(sk); 2065 2066 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; 2067 icsk->icsk_mtup.probe_size = 0; 2068 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 2069} 2070 2071 2072/* Process an event, which can update packets-in-flight not trivially. 2073 * Main goal of this function is to calculate new estimate for left_out, 2074 * taking into account both packets sitting in receiver's buffer and 2075 * packets lost by network. 2076 * 2077 * Besides that it does CWND reduction, when packet loss is detected 2078 * and changes state of machine. 2079 * 2080 * It does _not_ decide what to send, it is made in function 2081 * tcp_xmit_retransmit_queue(). 2082 */ 2083static void 2084tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una, 2085 int prior_packets, int flag) 2086{ 2087 struct inet_connection_sock *icsk = inet_csk(sk); 2088 struct tcp_sock *tp = tcp_sk(sk); 2089 int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP)); 2090 2091 /* Some technical things: 2092 * 1. Reno does not count dupacks (sacked_out) automatically. */ 2093 if (!tp->packets_out) 2094 tp->sacked_out = 0; 2095 /* 2. SACK counts snd_fack in packets inaccurately. */ 2096 if (tp->sacked_out == 0) 2097 tp->fackets_out = 0; 2098 2099 /* Now state machine starts. 2100 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ 2101 if (flag&FLAG_ECE) 2102 tp->prior_ssthresh = 0; 2103 2104 /* B. In all the states check for reneging SACKs. */ 2105 if (tp->sacked_out && tcp_check_sack_reneging(sk)) 2106 return; 2107 2108 /* C. Process data loss notification, provided it is valid. */ 2109 if ((flag&FLAG_DATA_LOST) && 2110 before(tp->snd_una, tp->high_seq) && 2111 icsk->icsk_ca_state != TCP_CA_Open && 2112 tp->fackets_out > tp->reordering) { 2113 tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq); 2114 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS); 2115 } 2116 2117 /* D. Synchronize left_out to current state. */ 2118 tcp_sync_left_out(tp); 2119 2120 /* E. Check state exit conditions. State can be terminated 2121 * when high_seq is ACKed. */ 2122 if (icsk->icsk_ca_state == TCP_CA_Open) { 2123 BUG_TRAP(tp->retrans_out == 0); 2124 tp->retrans_stamp = 0; 2125 } else if (!before(tp->snd_una, tp->high_seq)) { 2126 switch (icsk->icsk_ca_state) { 2127 case TCP_CA_Loss: 2128 icsk->icsk_retransmits = 0; 2129 if (tcp_try_undo_recovery(sk, tp)) 2130 return; 2131 break; 2132 2133 case TCP_CA_CWR: 2134 /* CWR is to be held something *above* high_seq 2135 * is ACKed for CWR bit to reach receiver. */ 2136 if (tp->snd_una != tp->high_seq) { 2137 tcp_complete_cwr(sk); 2138 tcp_set_ca_state(sk, TCP_CA_Open); 2139 } 2140 break; 2141 2142 case TCP_CA_Disorder: 2143 tcp_try_undo_dsack(sk, tp); 2144 if (!tp->undo_marker || 2145 /* For SACK case do not Open to allow to undo 2146 * catching for all duplicate ACKs. */ 2147 IsReno(tp) || tp->snd_una != tp->high_seq) { 2148 tp->undo_marker = 0; 2149 tcp_set_ca_state(sk, TCP_CA_Open); 2150 } 2151 break; 2152 2153 case TCP_CA_Recovery: 2154 if (IsReno(tp)) 2155 tcp_reset_reno_sack(tp); 2156 if (tcp_try_undo_recovery(sk, tp)) 2157 return; 2158 tcp_complete_cwr(sk); 2159 break; 2160 } 2161 } 2162 2163 /* F. Process state. */ 2164 switch (icsk->icsk_ca_state) { 2165 case TCP_CA_Recovery: 2166 if (prior_snd_una == tp->snd_una) { 2167 if (IsReno(tp) && is_dupack) 2168 tcp_add_reno_sack(sk); 2169 } else { 2170 int acked = prior_packets - tp->packets_out; 2171 if (IsReno(tp)) 2172 tcp_remove_reno_sacks(sk, tp, acked); 2173 is_dupack = tcp_try_undo_partial(sk, tp, acked); 2174 } 2175 break; 2176 case TCP_CA_Loss: 2177 if (flag&FLAG_DATA_ACKED) 2178 icsk->icsk_retransmits = 0; 2179 if (!tcp_try_undo_loss(sk, tp)) { 2180 tcp_moderate_cwnd(tp); 2181 tcp_xmit_retransmit_queue(sk); 2182 return; 2183 } 2184 if (icsk->icsk_ca_state != TCP_CA_Open) 2185 return; 2186 /* Loss is undone; fall through to processing in Open state. */ 2187 default: 2188 if (IsReno(tp)) { 2189 if (tp->snd_una != prior_snd_una) 2190 tcp_reset_reno_sack(tp); 2191 if (is_dupack) 2192 tcp_add_reno_sack(sk); 2193 } 2194 2195 if (icsk->icsk_ca_state == TCP_CA_Disorder) 2196 tcp_try_undo_dsack(sk, tp); 2197 2198 if (!tcp_time_to_recover(sk, tp)) { 2199 tcp_try_to_open(sk, tp, flag); 2200 return; 2201 } 2202 2203 /* MTU probe failure: don't reduce cwnd */ 2204 if (icsk->icsk_ca_state < TCP_CA_CWR && 2205 icsk->icsk_mtup.probe_size && 2206 tp->snd_una == tp->mtu_probe.probe_seq_start) { 2207 tcp_mtup_probe_failed(sk); 2208 /* Restores the reduction we did in tcp_mtup_probe() */ 2209 tp->snd_cwnd++; 2210 tcp_simple_retransmit(sk); 2211 return; 2212 } 2213 2214 /* Otherwise enter Recovery state */ 2215 2216 if (IsReno(tp)) 2217 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY); 2218 else 2219 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY); 2220 2221 tp->high_seq = tp->snd_nxt; 2222 tp->prior_ssthresh = 0; 2223 tp->undo_marker = tp->snd_una; 2224 tp->undo_retrans = tp->retrans_out; 2225 2226 if (icsk->icsk_ca_state < TCP_CA_CWR) { 2227 if (!(flag&FLAG_ECE)) 2228 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2229 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2230 TCP_ECN_queue_cwr(tp); 2231 } 2232 2233 tp->bytes_acked = 0; 2234 tp->snd_cwnd_cnt = 0; 2235 tcp_set_ca_state(sk, TCP_CA_Recovery); 2236 } 2237 2238 if (is_dupack || tcp_head_timedout(sk, tp)) 2239 tcp_update_scoreboard(sk, tp); 2240 tcp_cwnd_down(sk); 2241 tcp_xmit_retransmit_queue(sk); 2242} 2243 2244/* Read draft-ietf-tcplw-high-performance before mucking 2245 * with this code. (Supersedes RFC1323) 2246 */ 2247static void tcp_ack_saw_tstamp(struct sock *sk, int flag) 2248{ 2249 /* RTTM Rule: A TSecr value received in a segment is used to 2250 * update the averaged RTT measurement only if the segment 2251 * acknowledges some new data, i.e., only if it advances the 2252 * left edge of the send window. 2253 * 2254 * See draft-ietf-tcplw-high-performance-00, section 3.3. 2255 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> 2256 * 2257 * Changed: reset backoff as soon as we see the first valid sample. 2258 * If we do not, we get strongly overestimated rto. With timestamps 2259 * samples are accepted even from very old segments: f.e., when rtt=1 2260 * increases to 8, we retransmit 5 times and after 8 seconds delayed 2261 * answer arrives rto becomes 120 seconds! If at least one of segments 2262 * in window is lost... Voila. --ANK (010210) 2263 */ 2264 struct tcp_sock *tp = tcp_sk(sk); 2265 const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr; 2266 tcp_rtt_estimator(sk, seq_rtt); 2267 tcp_set_rto(sk); 2268 inet_csk(sk)->icsk_backoff = 0; 2269 tcp_bound_rto(sk); 2270} 2271 2272static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag) 2273{ 2274 /* We don't have a timestamp. Can only use 2275 * packets that are not retransmitted to determine 2276 * rtt estimates. Also, we must not reset the 2277 * backoff for rto until we get a non-retransmitted 2278 * packet. This allows us to deal with a situation 2279 * where the network delay has increased suddenly. 2280 * I.e. Karn's algorithm. (SIGCOMM '87, p5.) 2281 */ 2282 2283 if (flag & FLAG_RETRANS_DATA_ACKED) 2284 return; 2285 2286 tcp_rtt_estimator(sk, seq_rtt); 2287 tcp_set_rto(sk); 2288 inet_csk(sk)->icsk_backoff = 0; 2289 tcp_bound_rto(sk); 2290} 2291 2292static inline void tcp_ack_update_rtt(struct sock *sk, const int flag, 2293 const s32 seq_rtt) 2294{ 2295 const struct tcp_sock *tp = tcp_sk(sk); 2296 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ 2297 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) 2298 tcp_ack_saw_tstamp(sk, flag); 2299 else if (seq_rtt >= 0) 2300 tcp_ack_no_tstamp(sk, seq_rtt, flag); 2301} 2302 2303static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt, 2304 u32 in_flight, int good) 2305{ 2306 const struct inet_connection_sock *icsk = inet_csk(sk); 2307 icsk->icsk_ca_ops->cong_avoid(sk, ack, rtt, in_flight, good); 2308 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp; 2309} 2310 2311/* Restart timer after forward progress on connection. 2312 * RFC2988 recommends to restart timer to now+rto. 2313 */ 2314 2315static void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp) 2316{ 2317 if (!tp->packets_out) { 2318 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); 2319 } else { 2320 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 2321 } 2322} 2323 2324static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb, 2325 __u32 now, __s32 *seq_rtt) 2326{ 2327 struct tcp_sock *tp = tcp_sk(sk); 2328 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 2329 __u32 seq = tp->snd_una; 2330 __u32 packets_acked; 2331 int acked = 0; 2332 2333 /* If we get here, the whole TSO packet has not been 2334 * acked. 2335 */ 2336 BUG_ON(!after(scb->end_seq, seq)); 2337 2338 packets_acked = tcp_skb_pcount(skb); 2339 if (tcp_trim_head(sk, skb, seq - scb->seq)) 2340 return 0; 2341 packets_acked -= tcp_skb_pcount(skb); 2342 2343 if (packets_acked) { 2344 __u8 sacked = scb->sacked; 2345 2346 acked |= FLAG_DATA_ACKED; 2347 if (sacked) { 2348 if (sacked & TCPCB_RETRANS) { 2349 if (sacked & TCPCB_SACKED_RETRANS) 2350 tp->retrans_out -= packets_acked; 2351 acked |= FLAG_RETRANS_DATA_ACKED; 2352 *seq_rtt = -1; 2353 } else if (*seq_rtt < 0) 2354 *seq_rtt = now - scb->when; 2355 if (sacked & TCPCB_SACKED_ACKED) 2356 tp->sacked_out -= packets_acked; 2357 if (sacked & TCPCB_LOST) 2358 tp->lost_out -= packets_acked; 2359 if (sacked & TCPCB_URG) { 2360 if (tp->urg_mode && 2361 !before(seq, tp->snd_up)) 2362 tp->urg_mode = 0; 2363 } 2364 } else if (*seq_rtt < 0) 2365 *seq_rtt = now - scb->when; 2366 2367 if (tp->fackets_out) { 2368 __u32 dval = min(tp->fackets_out, packets_acked); 2369 tp->fackets_out -= dval; 2370 } 2371 tp->packets_out -= packets_acked; 2372 2373 BUG_ON(tcp_skb_pcount(skb) == 0); 2374 BUG_ON(!before(scb->seq, scb->end_seq)); 2375 } 2376 2377 return acked; 2378} 2379 2380static u32 tcp_usrtt(struct timeval *tv) 2381{ 2382 struct timeval now; 2383 2384 do_gettimeofday(&now); 2385 return (now.tv_sec - tv->tv_sec) * 1000000 + (now.tv_usec - tv->tv_usec); 2386} 2387 2388/* Remove acknowledged frames from the retransmission queue. */ 2389static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p) 2390{ 2391 struct tcp_sock *tp = tcp_sk(sk); 2392 const struct inet_connection_sock *icsk = inet_csk(sk); 2393 struct sk_buff *skb; 2394 __u32 now = tcp_time_stamp; 2395 int acked = 0; 2396 __s32 seq_rtt = -1; 2397 u32 pkts_acked = 0; 2398 void (*rtt_sample)(struct sock *sk, u32 usrtt) 2399 = icsk->icsk_ca_ops->rtt_sample; 2400 struct timeval tv = { .tv_sec = 0, .tv_usec = 0 }; 2401 2402 while ((skb = tcp_write_queue_head(sk)) && 2403 skb != tcp_send_head(sk)) { 2404 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 2405 __u8 sacked = scb->sacked; 2406 2407 /* If our packet is before the ack sequence we can 2408 * discard it as it's confirmed to have arrived at 2409 * the other end. 2410 */ 2411 if (after(scb->end_seq, tp->snd_una)) { 2412 if (tcp_skb_pcount(skb) > 1 && 2413 after(tp->snd_una, scb->seq)) 2414 acked |= tcp_tso_acked(sk, skb, 2415 now, &seq_rtt); 2416 break; 2417 } 2418 2419 /* Initial outgoing SYN's get put onto the write_queue 2420 * just like anything else we transmit. It is not 2421 * true data, and if we misinform our callers that 2422 * this ACK acks real data, we will erroneously exit 2423 * connection startup slow start one packet too 2424 * quickly. This is severely frowned upon behavior. 2425 */ 2426 if (!(scb->flags & TCPCB_FLAG_SYN)) { 2427 acked |= FLAG_DATA_ACKED; 2428 ++pkts_acked; 2429 } else { 2430 acked |= FLAG_SYN_ACKED; 2431 tp->retrans_stamp = 0; 2432 } 2433 2434 /* MTU probing checks */ 2435 if (icsk->icsk_mtup.probe_size) { 2436 if (!after(tp->mtu_probe.probe_seq_end, TCP_SKB_CB(skb)->end_seq)) { 2437 tcp_mtup_probe_success(sk, skb); 2438 } 2439 } 2440 2441 if (sacked) { 2442 if (sacked & TCPCB_RETRANS) { 2443 if (sacked & TCPCB_SACKED_RETRANS) 2444 tp->retrans_out -= tcp_skb_pcount(skb); 2445 acked |= FLAG_RETRANS_DATA_ACKED; 2446 seq_rtt = -1; 2447 } else if (seq_rtt < 0) { 2448 seq_rtt = now - scb->when; 2449 skb_get_timestamp(skb, &tv); 2450 } 2451 if (sacked & TCPCB_SACKED_ACKED) 2452 tp->sacked_out -= tcp_skb_pcount(skb); 2453 if (sacked & TCPCB_LOST) 2454 tp->lost_out -= tcp_skb_pcount(skb); 2455 if (sacked & TCPCB_URG) { 2456 if (tp->urg_mode && 2457 !before(scb->end_seq, tp->snd_up)) 2458 tp->urg_mode = 0; 2459 } 2460 } else if (seq_rtt < 0) { 2461 seq_rtt = now - scb->when; 2462 skb_get_timestamp(skb, &tv); 2463 } 2464 tcp_dec_pcount_approx(&tp->fackets_out, skb); 2465 tcp_packets_out_dec(tp, skb); 2466 tcp_unlink_write_queue(skb, sk); 2467 sk_stream_free_skb(sk, skb); 2468 clear_all_retrans_hints(tp); 2469 } 2470 2471 if (acked&FLAG_ACKED) { 2472 tcp_ack_update_rtt(sk, acked, seq_rtt); 2473 tcp_ack_packets_out(sk, tp); 2474 if (rtt_sample && !(acked & FLAG_RETRANS_DATA_ACKED)) 2475 (*rtt_sample)(sk, tcp_usrtt(&tv)); 2476 2477 if (icsk->icsk_ca_ops->pkts_acked) 2478 icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked); 2479 } 2480 2481#if FASTRETRANS_DEBUG > 0 2482 BUG_TRAP((int)tp->sacked_out >= 0); 2483 BUG_TRAP((int)tp->lost_out >= 0); 2484 BUG_TRAP((int)tp->retrans_out >= 0); 2485 if (!tp->packets_out && tp->rx_opt.sack_ok) { 2486 const struct inet_connection_sock *icsk = inet_csk(sk); 2487 if (tp->lost_out) { 2488 printk(KERN_DEBUG "Leak l=%u %d\n", 2489 tp->lost_out, icsk->icsk_ca_state); 2490 tp->lost_out = 0; 2491 } 2492 if (tp->sacked_out) { 2493 printk(KERN_DEBUG "Leak s=%u %d\n", 2494 tp->sacked_out, icsk->icsk_ca_state); 2495 tp->sacked_out = 0; 2496 } 2497 if (tp->retrans_out) { 2498 printk(KERN_DEBUG "Leak r=%u %d\n", 2499 tp->retrans_out, icsk->icsk_ca_state); 2500 tp->retrans_out = 0; 2501 } 2502 } 2503#endif 2504 *seq_rtt_p = seq_rtt; 2505 return acked; 2506} 2507 2508static void tcp_ack_probe(struct sock *sk) 2509{ 2510 const struct tcp_sock *tp = tcp_sk(sk); 2511 struct inet_connection_sock *icsk = inet_csk(sk); 2512 2513 /* Was it a usable window open? */ 2514 2515 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, 2516 tp->snd_una + tp->snd_wnd)) { 2517 icsk->icsk_backoff = 0; 2518 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0); 2519 /* Socket must be waked up by subsequent tcp_data_snd_check(). 2520 * This function is not for random using! 2521 */ 2522 } else { 2523 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 2524 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), 2525 TCP_RTO_MAX); 2526 } 2527} 2528 2529static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag) 2530{ 2531 return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || 2532 inet_csk(sk)->icsk_ca_state != TCP_CA_Open); 2533} 2534 2535static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag) 2536{ 2537 const struct tcp_sock *tp = tcp_sk(sk); 2538 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) && 2539 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR)); 2540} 2541 2542/* Check that window update is acceptable. 2543 * The function assumes that snd_una<=ack<=snd_next. 2544 */ 2545static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack, 2546 const u32 ack_seq, const u32 nwin) 2547{ 2548 return (after(ack, tp->snd_una) || 2549 after(ack_seq, tp->snd_wl1) || 2550 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd)); 2551} 2552 2553/* Update our send window. 2554 * 2555 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 2556 * and in FreeBSD. NetBSD's one is even worse.) is wrong. 2557 */ 2558static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp, 2559 struct sk_buff *skb, u32 ack, u32 ack_seq) 2560{ 2561 int flag = 0; 2562 u32 nwin = ntohs(skb->h.th->window); 2563 2564 if (likely(!skb->h.th->syn)) 2565 nwin <<= tp->rx_opt.snd_wscale; 2566 2567 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { 2568 flag |= FLAG_WIN_UPDATE; 2569 tcp_update_wl(tp, ack, ack_seq); 2570 2571 if (tp->snd_wnd != nwin) { 2572 tp->snd_wnd = nwin; 2573 2574 /* Note, it is the only place, where 2575 * fast path is recovered for sending TCP. 2576 */ 2577 tp->pred_flags = 0; 2578 tcp_fast_path_check(sk, tp); 2579 2580 if (nwin > tp->max_window) { 2581 tp->max_window = nwin; 2582 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie); 2583 } 2584 } 2585 } 2586 2587 tp->snd_una = ack; 2588 2589 return flag; 2590} 2591 2592/* A very conservative spurious RTO response algorithm: reduce cwnd and 2593 * continue in congestion avoidance. 2594 */ 2595static void tcp_conservative_spur_to_response(struct tcp_sock *tp) 2596{ 2597 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 2598 tp->snd_cwnd_cnt = 0; 2599 tcp_moderate_cwnd(tp); 2600} 2601 2602/* A conservative spurious RTO response algorithm: reduce cwnd using 2603 * rate halving and continue in congestion avoidance. 2604 */ 2605static void tcp_ratehalving_spur_to_response(struct sock *sk) 2606{ 2607 tcp_enter_cwr(sk, 0); 2608} 2609 2610static void tcp_undo_spur_to_response(struct sock *sk, int flag) 2611{ 2612 if (flag&FLAG_ECE) 2613 tcp_ratehalving_spur_to_response(sk); 2614 else 2615 tcp_undo_cwr(sk, 1); 2616} 2617 2618/* F-RTO spurious RTO detection algorithm (RFC4138) 2619 * 2620 * F-RTO affects during two new ACKs following RTO (well, almost, see inline 2621 * comments). State (ACK number) is kept in frto_counter. When ACK advances 2622 * window (but not to or beyond highest sequence sent before RTO): 2623 * On First ACK, send two new segments out. 2624 * On Second ACK, RTO was likely spurious. Do spurious response (response 2625 * algorithm is not part of the F-RTO detection algorithm 2626 * given in RFC4138 but can be selected separately). 2627 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss 2628 * and TCP falls back to conventional RTO recovery. 2629 * 2630 * Rationale: if the RTO was spurious, new ACKs should arrive from the 2631 * original window even after we transmit two new data segments. 2632 * 2633 * SACK version: 2634 * on first step, wait until first cumulative ACK arrives, then move to 2635 * the second step. In second step, the next ACK decides. 2636 * 2637 * F-RTO is implemented (mainly) in four functions: 2638 * - tcp_use_frto() is used to determine if TCP is can use F-RTO 2639 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is 2640 * called when tcp_use_frto() showed green light 2641 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm 2642 * - tcp_enter_frto_loss() is called if there is not enough evidence 2643 * to prove that the RTO is indeed spurious. It transfers the control 2644 * from F-RTO to the conventional RTO recovery 2645 */ 2646static int tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag) 2647{ 2648 struct tcp_sock *tp = tcp_sk(sk); 2649 2650 tcp_sync_left_out(tp); 2651 2652 /* Duplicate the behavior from Loss state (fastretrans_alert) */ 2653 if (flag&FLAG_DATA_ACKED) 2654 inet_csk(sk)->icsk_retransmits = 0; 2655 2656 if (!before(tp->snd_una, tp->frto_highmark)) { 2657 tcp_enter_frto_loss(sk, tp->frto_counter + 1, flag); 2658 return 1; 2659 } 2660 2661 if (!IsSackFrto() || IsReno(tp)) { 2662 /* RFC4138 shortcoming in step 2; should also have case c): 2663 * ACK isn't duplicate nor advances window, e.g., opposite dir 2664 * data, winupdate 2665 */ 2666 if ((tp->snd_una == prior_snd_una) && (flag&FLAG_NOT_DUP) && 2667 !(flag&FLAG_FORWARD_PROGRESS)) 2668 return 1; 2669 2670 if (!(flag&FLAG_DATA_ACKED)) { 2671 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3), 2672 flag); 2673 return 1; 2674 } 2675 } else { 2676 if (!(flag&FLAG_DATA_ACKED) && (tp->frto_counter == 1)) { 2677 /* Prevent sending of new data. */ 2678 tp->snd_cwnd = min(tp->snd_cwnd, 2679 tcp_packets_in_flight(tp)); 2680 return 1; 2681 } 2682 2683 if ((tp->frto_counter == 2) && 2684 (!(flag&FLAG_FORWARD_PROGRESS) || 2685 ((flag&FLAG_DATA_SACKED) && !(flag&FLAG_ONLY_ORIG_SACKED)))) { 2686 /* RFC4138 shortcoming (see comment above) */ 2687 if (!(flag&FLAG_FORWARD_PROGRESS) && (flag&FLAG_NOT_DUP)) 2688 return 1; 2689 2690 tcp_enter_frto_loss(sk, 3, flag); 2691 return 1; 2692 } 2693 } 2694 2695 if (tp->frto_counter == 1) { 2696 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; 2697 tp->frto_counter = 2; 2698 return 1; 2699 } else /* frto_counter == 2 */ { 2700 switch (sysctl_tcp_frto_response) { 2701 case 2: 2702 tcp_undo_spur_to_response(sk, flag); 2703 break; 2704 case 1: 2705 tcp_conservative_spur_to_response(tp); 2706 break; 2707 default: 2708 tcp_ratehalving_spur_to_response(sk); 2709 break; 2710 }; 2711 tp->frto_counter = 0; 2712 } 2713 return 0; 2714} 2715 2716/* This routine deals with incoming acks, but not outgoing ones. */ 2717static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) 2718{ 2719 struct inet_connection_sock *icsk = inet_csk(sk); 2720 struct tcp_sock *tp = tcp_sk(sk); 2721 u32 prior_snd_una = tp->snd_una; 2722 u32 ack_seq = TCP_SKB_CB(skb)->seq; 2723 u32 ack = TCP_SKB_CB(skb)->ack_seq; 2724 u32 prior_in_flight; 2725 s32 seq_rtt; 2726 int prior_packets; 2727 int frto_cwnd = 0; 2728 2729 /* If the ack is newer than sent or older than previous acks 2730 * then we can probably ignore it. 2731 */ 2732 if (after(ack, tp->snd_nxt)) 2733 goto uninteresting_ack; 2734 2735 if (before(ack, prior_snd_una)) 2736 goto old_ack; 2737 2738 if (sysctl_tcp_abc) { 2739 if (icsk->icsk_ca_state < TCP_CA_CWR) 2740 tp->bytes_acked += ack - prior_snd_una; 2741 else if (icsk->icsk_ca_state == TCP_CA_Loss) 2742 /* we assume just one segment left network */ 2743 tp->bytes_acked += min(ack - prior_snd_una, tp->mss_cache); 2744 } 2745 2746 if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) { 2747 /* Window is constant, pure forward advance. 2748 * No more checks are required. 2749 * Note, we use the fact that SND.UNA>=SND.WL2. 2750 */ 2751 tcp_update_wl(tp, ack, ack_seq); 2752 tp->snd_una = ack; 2753 flag |= FLAG_WIN_UPDATE; 2754 2755 tcp_ca_event(sk, CA_EVENT_FAST_ACK); 2756 2757 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS); 2758 } else { 2759 if (ack_seq != TCP_SKB_CB(skb)->end_seq) 2760 flag |= FLAG_DATA; 2761 else 2762 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS); 2763 2764 flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq); 2765 2766 if (TCP_SKB_CB(skb)->sacked) 2767 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); 2768 2769 if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th)) 2770 flag |= FLAG_ECE; 2771 2772 tcp_ca_event(sk, CA_EVENT_SLOW_ACK); 2773 } 2774 2775 /* We passed data and got it acked, remove any soft error 2776 * log. Something worked... 2777 */ 2778 sk->sk_err_soft = 0; 2779 tp->rcv_tstamp = tcp_time_stamp; 2780 prior_packets = tp->packets_out; 2781 if (!prior_packets) 2782 goto no_queue; 2783 2784 prior_in_flight = tcp_packets_in_flight(tp); 2785 2786 /* See if we can take anything off of the retransmit queue. */ 2787 flag |= tcp_clean_rtx_queue(sk, &seq_rtt); 2788 2789 if (tp->frto_counter) 2790 frto_cwnd = tcp_process_frto(sk, prior_snd_una, flag); 2791 2792 if (tcp_ack_is_dubious(sk, flag)) { 2793 /* Advance CWND, if state allows this. */ 2794 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd && 2795 tcp_may_raise_cwnd(sk, flag)) 2796 tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 0); 2797 tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag); 2798 } else { 2799 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd) 2800 tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1); 2801 } 2802 2803 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP)) 2804 dst_confirm(sk->sk_dst_cache); 2805 2806 return 1; 2807 2808no_queue: 2809 icsk->icsk_probes_out = 0; 2810 2811 /* If this ack opens up a zero window, clear backoff. It was 2812 * being used to time the probes, and is probably far higher than 2813 * it needs to be for normal retransmission. 2814 */ 2815 if (tcp_send_head(sk)) 2816 tcp_ack_probe(sk); 2817 return 1; 2818 2819old_ack: 2820 if (TCP_SKB_CB(skb)->sacked) 2821 tcp_sacktag_write_queue(sk, skb, prior_snd_una); 2822 2823uninteresting_ack: 2824 SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt); 2825 return 0; 2826} 2827 2828 2829/* Look for tcp options. Normally only called on SYN and SYNACK packets. 2830 * But, this can also be called on packets in the established flow when 2831 * the fast version below fails. 2832 */ 2833void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab) 2834{ 2835 unsigned char *ptr; 2836 struct tcphdr *th = skb->h.th; 2837 int length=(th->doff*4)-sizeof(struct tcphdr); 2838 2839 ptr = (unsigned char *)(th + 1); 2840 opt_rx->saw_tstamp = 0; 2841 2842 while (length > 0) { 2843 int opcode=*ptr++; 2844 int opsize; 2845 2846 switch (opcode) { 2847 case TCPOPT_EOL: 2848 return; 2849 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ 2850 length--; 2851 continue; 2852 default: 2853 opsize=*ptr++; 2854 if (opsize < 2) /* "silly options" */ 2855 return; 2856 if (opsize > length) 2857 return; /* don't parse partial options */ 2858 switch (opcode) { 2859 case TCPOPT_MSS: 2860 if (opsize==TCPOLEN_MSS && th->syn && !estab) { 2861 u16 in_mss = ntohs(get_unaligned((__be16 *)ptr)); 2862 if (in_mss) { 2863 if (opt_rx->user_mss && opt_rx->user_mss < in_mss) 2864 in_mss = opt_rx->user_mss; 2865 opt_rx->mss_clamp = in_mss; 2866 } 2867 } 2868 break; 2869 case TCPOPT_WINDOW: 2870 if (opsize==TCPOLEN_WINDOW && th->syn && !estab) 2871 if (sysctl_tcp_window_scaling) { 2872 __u8 snd_wscale = *(__u8 *) ptr; 2873 opt_rx->wscale_ok = 1; 2874 if (snd_wscale > 14) { 2875 if (net_ratelimit()) 2876 printk(KERN_INFO "tcp_parse_options: Illegal window " 2877 "scaling value %d >14 received.\n", 2878 snd_wscale); 2879 snd_wscale = 14; 2880 } 2881 opt_rx->snd_wscale = snd_wscale; 2882 } 2883 break; 2884 case TCPOPT_TIMESTAMP: 2885 if (opsize==TCPOLEN_TIMESTAMP) { 2886 if ((estab && opt_rx->tstamp_ok) || 2887 (!estab && sysctl_tcp_timestamps)) { 2888 opt_rx->saw_tstamp = 1; 2889 opt_rx->rcv_tsval = ntohl(get_unaligned((__be32 *)ptr)); 2890 opt_rx->rcv_tsecr = ntohl(get_unaligned((__be32 *)(ptr+4))); 2891 } 2892 } 2893 break; 2894 case TCPOPT_SACK_PERM: 2895 if (opsize==TCPOLEN_SACK_PERM && th->syn && !estab) { 2896 if (sysctl_tcp_sack) { 2897 opt_rx->sack_ok = 1; 2898 tcp_sack_reset(opt_rx); 2899 } 2900 } 2901 break; 2902 2903 case TCPOPT_SACK: 2904 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && 2905 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && 2906 opt_rx->sack_ok) { 2907 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; 2908 } 2909#ifdef CONFIG_TCP_MD5SIG 2910 case TCPOPT_MD5SIG: 2911 /* 2912 * The MD5 Hash has already been 2913 * checked (see tcp_v{4,6}_do_rcv()). 2914 */ 2915 break; 2916#endif 2917 }; 2918 ptr+=opsize-2; 2919 length-=opsize; 2920 }; 2921 } 2922} 2923 2924/* Fast parse options. This hopes to only see timestamps. 2925 * If it is wrong it falls back on tcp_parse_options(). 2926 */ 2927static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th, 2928 struct tcp_sock *tp) 2929{ 2930 if (th->doff == sizeof(struct tcphdr)>>2) { 2931 tp->rx_opt.saw_tstamp = 0; 2932 return 0; 2933 } else if (tp->rx_opt.tstamp_ok && 2934 th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) { 2935 __be32 *ptr = (__be32 *)(th + 1); 2936 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) 2937 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { 2938 tp->rx_opt.saw_tstamp = 1; 2939 ++ptr; 2940 tp->rx_opt.rcv_tsval = ntohl(*ptr); 2941 ++ptr; 2942 tp->rx_opt.rcv_tsecr = ntohl(*ptr); 2943 return 1; 2944 } 2945 } 2946 tcp_parse_options(skb, &tp->rx_opt, 1); 2947 return 1; 2948} 2949 2950static inline void tcp_store_ts_recent(struct tcp_sock *tp) 2951{ 2952 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; 2953 tp->rx_opt.ts_recent_stamp = get_seconds(); 2954} 2955 2956static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) 2957{ 2958 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { 2959 /* PAWS bug workaround wrt. ACK frames, the PAWS discard 2960 * extra check below makes sure this can only happen 2961 * for pure ACK frames. -DaveM 2962 * 2963 * Not only, also it occurs for expired timestamps. 2964 */ 2965 2966 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 || 2967 get_seconds() >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS) 2968 tcp_store_ts_recent(tp); 2969 } 2970} 2971 2972/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM 2973 * 2974 * It is not fatal. If this ACK does _not_ change critical state (seqs, window) 2975 * it can pass through stack. So, the following predicate verifies that 2976 * this segment is not used for anything but congestion avoidance or 2977 * fast retransmit. Moreover, we even are able to eliminate most of such 2978 * second order effects, if we apply some small "replay" window (~RTO) 2979 * to timestamp space. 2980 * 2981 * All these measures still do not guarantee that we reject wrapped ACKs 2982 * on networks with high bandwidth, when sequence space is recycled fastly, 2983 * but it guarantees that such events will be very rare and do not affect 2984 * connection seriously. This doesn't look nice, but alas, PAWS is really 2985 * buggy extension. 2986 * 2987 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC 2988 * states that events when retransmit arrives after original data are rare. 2989 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is 2990 * the biggest problem on large power networks even with minor reordering. 2991 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe 2992 * up to bandwidth of 18Gigabit/sec. 8) ] 2993 */ 2994 2995static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb) 2996{ 2997 struct tcp_sock *tp = tcp_sk(sk); 2998 struct tcphdr *th = skb->h.th; 2999 u32 seq = TCP_SKB_CB(skb)->seq; 3000 u32 ack = TCP_SKB_CB(skb)->ack_seq; 3001 3002 return (/* 1. Pure ACK with correct sequence number. */ 3003 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && 3004 3005 /* 2. ... and duplicate ACK. */ 3006 ack == tp->snd_una && 3007 3008 /* 3. ... and does not update window. */ 3009 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && 3010 3011 /* 4. ... and sits in replay window. */ 3012 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ); 3013} 3014 3015static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb) 3016{ 3017 const struct tcp_sock *tp = tcp_sk(sk); 3018 return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW && 3019 get_seconds() < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS && 3020 !tcp_disordered_ack(sk, skb)); 3021} 3022 3023/* Check segment sequence number for validity. 3024 * 3025 * Segment controls are considered valid, if the segment 3026 * fits to the window after truncation to the window. Acceptability 3027 * of data (and SYN, FIN, of course) is checked separately. 3028 * See tcp_data_queue(), for example. 3029 * 3030 * Also, controls (RST is main one) are accepted using RCV.WUP instead 3031 * of RCV.NXT. Peer still did not advance his SND.UNA when we 3032 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. 3033 * (borrowed from freebsd) 3034 */ 3035 3036static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq) 3037{ 3038 return !before(end_seq, tp->rcv_wup) && 3039 !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); 3040} 3041 3042/* When we get a reset we do this. */ 3043static void tcp_reset(struct sock *sk) 3044{ 3045 /* We want the right error as BSD sees it (and indeed as we do). */ 3046 switch (sk->sk_state) { 3047 case TCP_SYN_SENT: 3048 sk->sk_err = ECONNREFUSED; 3049 break; 3050 case TCP_CLOSE_WAIT: 3051 sk->sk_err = EPIPE; 3052 break; 3053 case TCP_CLOSE: 3054 return; 3055 default: 3056 sk->sk_err = ECONNRESET; 3057 } 3058 3059 if (!sock_flag(sk, SOCK_DEAD)) 3060 sk->sk_error_report(sk); 3061 3062 tcp_done(sk); 3063} 3064 3065/* 3066 * Process the FIN bit. This now behaves as it is supposed to work 3067 * and the FIN takes effect when it is validly part of sequence 3068 * space. Not before when we get holes. 3069 * 3070 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT 3071 * (and thence onto LAST-ACK and finally, CLOSE, we never enter 3072 * TIME-WAIT) 3073 * 3074 * If we are in FINWAIT-1, a received FIN indicates simultaneous 3075 * close and we go into CLOSING (and later onto TIME-WAIT) 3076 * 3077 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. 3078 */ 3079static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th) 3080{ 3081 struct tcp_sock *tp = tcp_sk(sk); 3082 3083 inet_csk_schedule_ack(sk); 3084 3085 sk->sk_shutdown |= RCV_SHUTDOWN; 3086 sock_set_flag(sk, SOCK_DONE); 3087 3088 switch (sk->sk_state) { 3089 case TCP_SYN_RECV: 3090 case TCP_ESTABLISHED: 3091 /* Move to CLOSE_WAIT */ 3092 tcp_set_state(sk, TCP_CLOSE_WAIT); 3093 inet_csk(sk)->icsk_ack.pingpong = 1; 3094 break; 3095 3096 case TCP_CLOSE_WAIT: 3097 case TCP_CLOSING: 3098 /* Received a retransmission of the FIN, do 3099 * nothing. 3100 */ 3101 break; 3102 case TCP_LAST_ACK: 3103 /* RFC793: Remain in the LAST-ACK state. */ 3104 break; 3105 3106 case TCP_FIN_WAIT1: 3107 /* This case occurs when a simultaneous close 3108 * happens, we must ack the received FIN and 3109 * enter the CLOSING state. 3110 */ 3111 tcp_send_ack(sk); 3112 tcp_set_state(sk, TCP_CLOSING); 3113 break; 3114 case TCP_FIN_WAIT2: 3115 /* Received a FIN -- send ACK and enter TIME_WAIT. */ 3116 tcp_send_ack(sk); 3117 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 3118 break; 3119 default: 3120 /* Only TCP_LISTEN and TCP_CLOSE are left, in these 3121 * cases we should never reach this piece of code. 3122 */ 3123 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n", 3124 __FUNCTION__, sk->sk_state); 3125 break; 3126 }; 3127 3128 /* It _is_ possible, that we have something out-of-order _after_ FIN. 3129 * Probably, we should reset in this case. For now drop them. 3130 */ 3131 __skb_queue_purge(&tp->out_of_order_queue); 3132 if (tp->rx_opt.sack_ok) 3133 tcp_sack_reset(&tp->rx_opt); 3134 sk_stream_mem_reclaim(sk); 3135 3136 if (!sock_flag(sk, SOCK_DEAD)) { 3137 sk->sk_state_change(sk); 3138 3139 /* Do not send POLL_HUP for half duplex close. */ 3140 if (sk->sk_shutdown == SHUTDOWN_MASK || 3141 sk->sk_state == TCP_CLOSE) 3142 sk_wake_async(sk, 1, POLL_HUP); 3143 else 3144 sk_wake_async(sk, 1, POLL_IN); 3145 } 3146} 3147 3148static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq) 3149{ 3150 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { 3151 if (before(seq, sp->start_seq)) 3152 sp->start_seq = seq; 3153 if (after(end_seq, sp->end_seq)) 3154 sp->end_seq = end_seq; 3155 return 1; 3156 } 3157 return 0; 3158} 3159 3160static void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq) 3161{ 3162 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) { 3163 if (before(seq, tp->rcv_nxt)) 3164 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT); 3165 else 3166 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT); 3167 3168 tp->rx_opt.dsack = 1; 3169 tp->duplicate_sack[0].start_seq = seq; 3170 tp->duplicate_sack[0].end_seq = end_seq; 3171 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok); 3172 } 3173} 3174 3175static void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq) 3176{ 3177 if (!tp->rx_opt.dsack) 3178 tcp_dsack_set(tp, seq, end_seq); 3179 else 3180 tcp_sack_extend(tp->duplicate_sack, seq, end_seq); 3181} 3182 3183static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb) 3184{ 3185 struct tcp_sock *tp = tcp_sk(sk); 3186 3187 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 3188 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 3189 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); 3190 tcp_enter_quickack_mode(sk); 3191 3192 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) { 3193 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 3194 3195 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) 3196 end_seq = tp->rcv_nxt; 3197 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq); 3198 } 3199 } 3200 3201 tcp_send_ack(sk); 3202} 3203 3204/* These routines update the SACK block as out-of-order packets arrive or 3205 * in-order packets close up the sequence space. 3206 */ 3207static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) 3208{ 3209 int this_sack; 3210 struct tcp_sack_block *sp = &tp->selective_acks[0]; 3211 struct tcp_sack_block *swalk = sp+1; 3212 3213 /* See if the recent change to the first SACK eats into 3214 * or hits the sequence space of other SACK blocks, if so coalesce. 3215 */ 3216 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) { 3217 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { 3218 int i; 3219 3220 /* Zap SWALK, by moving every further SACK up by one slot. 3221 * Decrease num_sacks. 3222 */ 3223 tp->rx_opt.num_sacks--; 3224 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); 3225 for (i=this_sack; i < tp->rx_opt.num_sacks; i++) 3226 sp[i] = sp[i+1]; 3227 continue; 3228 } 3229 this_sack++, swalk++; 3230 } 3231} 3232 3233static inline void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2) 3234{ 3235 __u32 tmp; 3236 3237 tmp = sack1->start_seq; 3238 sack1->start_seq = sack2->start_seq; 3239 sack2->start_seq = tmp; 3240 3241 tmp = sack1->end_seq; 3242 sack1->end_seq = sack2->end_seq; 3243 sack2->end_seq = tmp; 3244} 3245 3246static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) 3247{ 3248 struct tcp_sock *tp = tcp_sk(sk); 3249 struct tcp_sack_block *sp = &tp->selective_acks[0]; 3250 int cur_sacks = tp->rx_opt.num_sacks; 3251 int this_sack; 3252 3253 if (!cur_sacks) 3254 goto new_sack; 3255 3256 for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) { 3257 if (tcp_sack_extend(sp, seq, end_seq)) { 3258 /* Rotate this_sack to the first one. */ 3259 for (; this_sack>0; this_sack--, sp--) 3260 tcp_sack_swap(sp, sp-1); 3261 if (cur_sacks > 1) 3262 tcp_sack_maybe_coalesce(tp); 3263 return; 3264 } 3265 } 3266 3267 /* Could not find an adjacent existing SACK, build a new one, 3268 * put it at the front, and shift everyone else down. We 3269 * always know there is at least one SACK present already here. 3270 * 3271 * If the sack array is full, forget about the last one. 3272 */ 3273 if (this_sack >= 4) { 3274 this_sack--; 3275 tp->rx_opt.num_sacks--; 3276 sp--; 3277 } 3278 for (; this_sack > 0; this_sack--, sp--) 3279 *sp = *(sp-1); 3280 3281new_sack: 3282 /* Build the new head SACK, and we're done. */ 3283 sp->start_seq = seq; 3284 sp->end_seq = end_seq; 3285 tp->rx_opt.num_sacks++; 3286 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); 3287} 3288 3289/* RCV.NXT advances, some SACKs should be eaten. */ 3290 3291static void tcp_sack_remove(struct tcp_sock *tp) 3292{ 3293 struct tcp_sack_block *sp = &tp->selective_acks[0]; 3294 int num_sacks = tp->rx_opt.num_sacks; 3295 int this_sack; 3296 3297 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ 3298 if (skb_queue_empty(&tp->out_of_order_queue)) { 3299 tp->rx_opt.num_sacks = 0; 3300 tp->rx_opt.eff_sacks = tp->rx_opt.dsack; 3301 return; 3302 } 3303 3304 for (this_sack = 0; this_sack < num_sacks; ) { 3305 /* Check if the start of the sack is covered by RCV.NXT. */ 3306 if (!before(tp->rcv_nxt, sp->start_seq)) { 3307 int i; 3308 3309 /* RCV.NXT must cover all the block! */ 3310 BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq)); 3311 3312 /* Zap this SACK, by moving forward any other SACKS. */ 3313 for (i=this_sack+1; i < num_sacks; i++) 3314 tp->selective_acks[i-1] = tp->selective_acks[i]; 3315 num_sacks--; 3316 continue; 3317 } 3318 this_sack++; 3319 sp++; 3320 } 3321 if (num_sacks != tp->rx_opt.num_sacks) { 3322 tp->rx_opt.num_sacks = num_sacks; 3323 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); 3324 } 3325} 3326 3327/* This one checks to see if we can put data from the 3328 * out_of_order queue into the receive_queue. 3329 */ 3330static void tcp_ofo_queue(struct sock *sk) 3331{ 3332 struct tcp_sock *tp = tcp_sk(sk); 3333 __u32 dsack_high = tp->rcv_nxt; 3334 struct sk_buff *skb; 3335 3336 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { 3337 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 3338 break; 3339 3340 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { 3341 __u32 dsack = dsack_high; 3342 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) 3343 dsack_high = TCP_SKB_CB(skb)->end_seq; 3344 tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack); 3345 } 3346 3347 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 3348 SOCK_DEBUG(sk, "ofo packet was already received \n"); 3349 __skb_unlink(skb, &tp->out_of_order_queue); 3350 __kfree_skb(skb); 3351 continue; 3352 } 3353 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", 3354 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 3355 TCP_SKB_CB(skb)->end_seq); 3356 3357 __skb_unlink(skb, &tp->out_of_order_queue); 3358 __skb_queue_tail(&sk->sk_receive_queue, skb); 3359 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 3360 if (skb->h.th->fin) 3361 tcp_fin(skb, sk, skb->h.th); 3362 } 3363} 3364 3365static int tcp_prune_queue(struct sock *sk); 3366 3367static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) 3368{ 3369 struct tcphdr *th = skb->h.th; 3370 struct tcp_sock *tp = tcp_sk(sk); 3371 int eaten = -1; 3372 3373 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) 3374 goto drop; 3375 3376 __skb_pull(skb, th->doff*4); 3377 3378 TCP_ECN_accept_cwr(tp, skb); 3379 3380 if (tp->rx_opt.dsack) { 3381 tp->rx_opt.dsack = 0; 3382 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks, 3383 4 - tp->rx_opt.tstamp_ok); 3384 } 3385 3386 /* Queue data for delivery to the user. 3387 * Packets in sequence go to the receive queue. 3388 * Out of sequence packets to the out_of_order_queue. 3389 */ 3390 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { 3391 if (tcp_receive_window(tp) == 0) 3392 goto out_of_window; 3393 3394 /* Ok. In sequence. In window. */ 3395 if (tp->ucopy.task == current && 3396 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && 3397 sock_owned_by_user(sk) && !tp->urg_data) { 3398 int chunk = min_t(unsigned int, skb->len, 3399 tp->ucopy.len); 3400 3401 __set_current_state(TASK_RUNNING); 3402 3403 local_bh_enable(); 3404 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { 3405 tp->ucopy.len -= chunk; 3406 tp->copied_seq += chunk; 3407 eaten = (chunk == skb->len && !th->fin); 3408 tcp_rcv_space_adjust(sk); 3409 } 3410 local_bh_disable(); 3411 } 3412 3413 if (eaten <= 0) { 3414queue_and_out: 3415 if (eaten < 0 && 3416 (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || 3417 !sk_stream_rmem_schedule(sk, skb))) { 3418 if (tcp_prune_queue(sk) < 0 || 3419 !sk_stream_rmem_schedule(sk, skb)) 3420 goto drop; 3421 } 3422 sk_stream_set_owner_r(skb, sk); 3423 __skb_queue_tail(&sk->sk_receive_queue, skb); 3424 } 3425 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 3426 if (skb->len) 3427 tcp_event_data_recv(sk, tp, skb); 3428 if (th->fin) 3429 tcp_fin(skb, sk, th); 3430 3431 if (!skb_queue_empty(&tp->out_of_order_queue)) { 3432 tcp_ofo_queue(sk); 3433 3434 /* RFC2581. 4.2. SHOULD send immediate ACK, when 3435 * gap in queue is filled. 3436 */ 3437 if (skb_queue_empty(&tp->out_of_order_queue)) 3438 inet_csk(sk)->icsk_ack.pingpong = 0; 3439 } 3440 3441 if (tp->rx_opt.num_sacks) 3442 tcp_sack_remove(tp); 3443 3444 tcp_fast_path_check(sk, tp); 3445 3446 if (eaten > 0) 3447 __kfree_skb(skb); 3448 else if (!sock_flag(sk, SOCK_DEAD)) 3449 sk->sk_data_ready(sk, 0); 3450 return; 3451 } 3452 3453 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 3454 /* A retransmit, 2nd most common case. Force an immediate ack. */ 3455 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); 3456 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 3457 3458out_of_window: 3459 tcp_enter_quickack_mode(sk); 3460 inet_csk_schedule_ack(sk); 3461drop: 3462 __kfree_skb(skb); 3463 return; 3464 } 3465 3466 /* Out of window. F.e. zero window probe. */ 3467 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) 3468 goto out_of_window; 3469 3470 tcp_enter_quickack_mode(sk); 3471 3472 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 3473 /* Partial packet, seq < rcv_next < end_seq */ 3474 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", 3475 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 3476 TCP_SKB_CB(skb)->end_seq); 3477 3478 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); 3479 3480 /* If window is closed, drop tail of packet. But after 3481 * remembering D-SACK for its head made in previous line. 3482 */ 3483 if (!tcp_receive_window(tp)) 3484 goto out_of_window; 3485 goto queue_and_out; 3486 } 3487 3488 TCP_ECN_check_ce(tp, skb); 3489 3490 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || 3491 !sk_stream_rmem_schedule(sk, skb)) { 3492 if (tcp_prune_queue(sk) < 0 || 3493 !sk_stream_rmem_schedule(sk, skb)) 3494 goto drop; 3495 } 3496 3497 /* Disable header prediction. */ 3498 tp->pred_flags = 0; 3499 inet_csk_schedule_ack(sk); 3500 3501 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", 3502 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 3503 3504 sk_stream_set_owner_r(skb, sk); 3505 3506 if (!skb_peek(&tp->out_of_order_queue)) { 3507 /* Initial out of order segment, build 1 SACK. */ 3508 if (tp->rx_opt.sack_ok) { 3509 tp->rx_opt.num_sacks = 1; 3510 tp->rx_opt.dsack = 0; 3511 tp->rx_opt.eff_sacks = 1; 3512 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; 3513 tp->selective_acks[0].end_seq = 3514 TCP_SKB_CB(skb)->end_seq; 3515 } 3516 __skb_queue_head(&tp->out_of_order_queue,skb); 3517 } else { 3518 struct sk_buff *skb1 = tp->out_of_order_queue.prev; 3519 u32 seq = TCP_SKB_CB(skb)->seq; 3520 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 3521 3522 if (seq == TCP_SKB_CB(skb1)->end_seq) { 3523 __skb_append(skb1, skb, &tp->out_of_order_queue); 3524 3525 if (!tp->rx_opt.num_sacks || 3526 tp->selective_acks[0].end_seq != seq) 3527 goto add_sack; 3528 3529 /* Common case: data arrive in order after hole. */ 3530 tp->selective_acks[0].end_seq = end_seq; 3531 return; 3532 } 3533 3534 /* Find place to insert this segment. */ 3535 do { 3536 if (!after(TCP_SKB_CB(skb1)->seq, seq)) 3537 break; 3538 } while ((skb1 = skb1->prev) != 3539 (struct sk_buff*)&tp->out_of_order_queue); 3540 3541 /* Do skb overlap to previous one? */ 3542 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue && 3543 before(seq, TCP_SKB_CB(skb1)->end_seq)) { 3544 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 3545 /* All the bits are present. Drop. */ 3546 __kfree_skb(skb); 3547 tcp_dsack_set(tp, seq, end_seq); 3548 goto add_sack; 3549 } 3550 if (after(seq, TCP_SKB_CB(skb1)->seq)) { 3551 /* Partial overlap. */ 3552 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq); 3553 } else { 3554 skb1 = skb1->prev; 3555 } 3556 } 3557 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue); 3558 3559 /* And clean segments covered by new one as whole. */ 3560 while ((skb1 = skb->next) != 3561 (struct sk_buff*)&tp->out_of_order_queue && 3562 after(end_seq, TCP_SKB_CB(skb1)->seq)) { 3563 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 3564 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq); 3565 break; 3566 } 3567 __skb_unlink(skb1, &tp->out_of_order_queue); 3568 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq); 3569 __kfree_skb(skb1); 3570 } 3571 3572add_sack: 3573 if (tp->rx_opt.sack_ok) 3574 tcp_sack_new_ofo_skb(sk, seq, end_seq); 3575 } 3576} 3577 3578/* Collapse contiguous sequence of skbs head..tail with 3579 * sequence numbers start..end. 3580 * Segments with FIN/SYN are not collapsed (only because this 3581 * simplifies code) 3582 */ 3583static void 3584tcp_collapse(struct sock *sk, struct sk_buff_head *list, 3585 struct sk_buff *head, struct sk_buff *tail, 3586 u32 start, u32 end) 3587{ 3588 struct sk_buff *skb; 3589 3590 /* First, check that queue is collapsible and find 3591 * the point where collapsing can be useful. */ 3592 for (skb = head; skb != tail; ) { 3593 /* No new bits? It is possible on ofo queue. */ 3594 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 3595 struct sk_buff *next = skb->next; 3596 __skb_unlink(skb, list); 3597 __kfree_skb(skb); 3598 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); 3599 skb = next; 3600 continue; 3601 } 3602 3603 /* The first skb to collapse is: 3604 * - not SYN/FIN and 3605 * - bloated or contains data before "start" or 3606 * overlaps to the next one. 3607 */ 3608 if (!skb->h.th->syn && !skb->h.th->fin && 3609 (tcp_win_from_space(skb->truesize) > skb->len || 3610 before(TCP_SKB_CB(skb)->seq, start) || 3611 (skb->next != tail && 3612 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq))) 3613 break; 3614 3615 /* Decided to skip this, advance start seq. */ 3616 start = TCP_SKB_CB(skb)->end_seq; 3617 skb = skb->next; 3618 } 3619 if (skb == tail || skb->h.th->syn || skb->h.th->fin) 3620 return; 3621 3622 while (before(start, end)) { 3623 struct sk_buff *nskb; 3624 int header = skb_headroom(skb); 3625 int copy = SKB_MAX_ORDER(header, 0); 3626 3627 /* Too big header? This can happen with IPv6. */ 3628 if (copy < 0) 3629 return; 3630 if (end-start < copy) 3631 copy = end-start; 3632 nskb = alloc_skb(copy+header, GFP_ATOMIC); 3633 if (!nskb) 3634 return; 3635 3636 skb_set_mac_header(nskb, skb->mac.raw - skb->head); 3637 nskb->nh.raw = nskb->data + (skb->nh.raw - skb->head); 3638 nskb->h.raw = nskb->data + (skb->h.raw - skb->head); 3639 3640 skb_reserve(nskb, header); 3641 memcpy(nskb->head, skb->head, header); 3642 memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); 3643 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; 3644 __skb_insert(nskb, skb->prev, skb, list); 3645 sk_stream_set_owner_r(nskb, sk); 3646 3647 /* Copy data, releasing collapsed skbs. */ 3648 while (copy > 0) { 3649 int offset = start - TCP_SKB_CB(skb)->seq; 3650 int size = TCP_SKB_CB(skb)->end_seq - start; 3651 3652 BUG_ON(offset < 0); 3653 if (size > 0) { 3654 size = min(copy, size); 3655 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) 3656 BUG(); 3657 TCP_SKB_CB(nskb)->end_seq += size; 3658 copy -= size; 3659 start += size; 3660 } 3661 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 3662 struct sk_buff *next = skb->next; 3663 __skb_unlink(skb, list); 3664 __kfree_skb(skb); 3665 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); 3666 skb = next; 3667 if (skb == tail || skb->h.th->syn || skb->h.th->fin) 3668 return; 3669 } 3670 } 3671 } 3672} 3673 3674/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs 3675 * and tcp_collapse() them until all the queue is collapsed. 3676 */ 3677static void tcp_collapse_ofo_queue(struct sock *sk) 3678{ 3679 struct tcp_sock *tp = tcp_sk(sk); 3680 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); 3681 struct sk_buff *head; 3682 u32 start, end; 3683 3684 if (skb == NULL) 3685 return; 3686 3687 start = TCP_SKB_CB(skb)->seq; 3688 end = TCP_SKB_CB(skb)->end_seq; 3689 head = skb; 3690 3691 for (;;) { 3692 skb = skb->next; 3693 3694 /* Segment is terminated when we see gap or when 3695 * we are at the end of all the queue. */ 3696 if (skb == (struct sk_buff *)&tp->out_of_order_queue || 3697 after(TCP_SKB_CB(skb)->seq, end) || 3698 before(TCP_SKB_CB(skb)->end_seq, start)) { 3699 tcp_collapse(sk, &tp->out_of_order_queue, 3700 head, skb, start, end); 3701 head = skb; 3702 if (skb == (struct sk_buff *)&tp->out_of_order_queue) 3703 break; 3704 /* Start new segment */ 3705 start = TCP_SKB_CB(skb)->seq; 3706 end = TCP_SKB_CB(skb)->end_seq; 3707 } else { 3708 if (before(TCP_SKB_CB(skb)->seq, start)) 3709 start = TCP_SKB_CB(skb)->seq; 3710 if (after(TCP_SKB_CB(skb)->end_seq, end)) 3711 end = TCP_SKB_CB(skb)->end_seq; 3712 } 3713 } 3714} 3715 3716/* Reduce allocated memory if we can, trying to get 3717 * the socket within its memory limits again. 3718 * 3719 * Return less than zero if we should start dropping frames 3720 * until the socket owning process reads some of the data 3721 * to stabilize the situation. 3722 */ 3723static int tcp_prune_queue(struct sock *sk) 3724{ 3725 struct tcp_sock *tp = tcp_sk(sk); 3726 3727 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); 3728 3729 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED); 3730 3731 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) 3732 tcp_clamp_window(sk, tp); 3733 else if (tcp_memory_pressure) 3734 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); 3735 3736 tcp_collapse_ofo_queue(sk); 3737 tcp_collapse(sk, &sk->sk_receive_queue, 3738 sk->sk_receive_queue.next, 3739 (struct sk_buff*)&sk->sk_receive_queue, 3740 tp->copied_seq, tp->rcv_nxt); 3741 sk_stream_mem_reclaim(sk); 3742 3743 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 3744 return 0; 3745 3746 /* Collapsing did not help, destructive actions follow. 3747 * This must not ever occur. */ 3748 3749 /* First, purge the out_of_order queue. */ 3750 if (!skb_queue_empty(&tp->out_of_order_queue)) { 3751 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED); 3752 __skb_queue_purge(&tp->out_of_order_queue); 3753 3754 /* Reset SACK state. A conforming SACK implementation will 3755 * do the same at a timeout based retransmit. When a connection 3756 * is in a sad state like this, we care only about integrity 3757 * of the connection not performance. 3758 */ 3759 if (tp->rx_opt.sack_ok) 3760 tcp_sack_reset(&tp->rx_opt); 3761 sk_stream_mem_reclaim(sk); 3762 } 3763 3764 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 3765 return 0; 3766 3767 /* If we are really being abused, tell the caller to silently 3768 * drop receive data on the floor. It will get retransmitted 3769 * and hopefully then we'll have sufficient space. 3770 */ 3771 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED); 3772 3773 /* Massive buffer overcommit. */ 3774 tp->pred_flags = 0; 3775 return -1; 3776} 3777 3778 3779/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. 3780 * As additional protections, we do not touch cwnd in retransmission phases, 3781 * and if application hit its sndbuf limit recently. 3782 */ 3783void tcp_cwnd_application_limited(struct sock *sk) 3784{ 3785 struct tcp_sock *tp = tcp_sk(sk); 3786 3787 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && 3788 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { 3789 /* Limited by application or receiver window. */ 3790 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); 3791 u32 win_used = max(tp->snd_cwnd_used, init_win); 3792 if (win_used < tp->snd_cwnd) { 3793 tp->snd_ssthresh = tcp_current_ssthresh(sk); 3794 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; 3795 } 3796 tp->snd_cwnd_used = 0; 3797 } 3798 tp->snd_cwnd_stamp = tcp_time_stamp; 3799} 3800 3801static int tcp_should_expand_sndbuf(struct sock *sk, struct tcp_sock *tp) 3802{ 3803 /* If the user specified a specific send buffer setting, do 3804 * not modify it. 3805 */ 3806 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) 3807 return 0; 3808 3809 /* If we are under global TCP memory pressure, do not expand. */ 3810 if (tcp_memory_pressure) 3811 return 0; 3812 3813 /* If we are under soft global TCP memory pressure, do not expand. */ 3814 if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0]) 3815 return 0; 3816 3817 /* If we filled the congestion window, do not expand. */ 3818 if (tp->packets_out >= tp->snd_cwnd) 3819 return 0; 3820 3821 return 1; 3822} 3823 3824/* When incoming ACK allowed to free some skb from write_queue, 3825 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket 3826 * on the exit from tcp input handler. 3827 * 3828 * PROBLEM: sndbuf expansion does not work well with largesend. 3829 */ 3830static void tcp_new_space(struct sock *sk) 3831{ 3832 struct tcp_sock *tp = tcp_sk(sk); 3833 3834 if (tcp_should_expand_sndbuf(sk, tp)) { 3835 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + 3836 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff), 3837 demanded = max_t(unsigned int, tp->snd_cwnd, 3838 tp->reordering + 1); 3839 sndmem *= 2*demanded; 3840 if (sndmem > sk->sk_sndbuf) 3841 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); 3842 tp->snd_cwnd_stamp = tcp_time_stamp; 3843 } 3844 3845 sk->sk_write_space(sk); 3846} 3847 3848static void tcp_check_space(struct sock *sk) 3849{ 3850 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { 3851 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); 3852 if (sk->sk_socket && 3853 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) 3854 tcp_new_space(sk); 3855 } 3856} 3857 3858static inline void tcp_data_snd_check(struct sock *sk, struct tcp_sock *tp) 3859{ 3860 tcp_push_pending_frames(sk, tp); 3861 tcp_check_space(sk); 3862} 3863 3864/* 3865 * Check if sending an ack is needed. 3866 */ 3867static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) 3868{ 3869 struct tcp_sock *tp = tcp_sk(sk); 3870 3871 /* More than one full frame received... */ 3872 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss 3873 /* ... and right edge of window advances far enough. 3874 * (tcp_recvmsg() will send ACK otherwise). Or... 3875 */ 3876 && __tcp_select_window(sk) >= tp->rcv_wnd) || 3877 /* We ACK each frame or... */ 3878 tcp_in_quickack_mode(sk) || 3879 /* We have out of order data. */ 3880 (ofo_possible && 3881 skb_peek(&tp->out_of_order_queue))) { 3882 /* Then ack it now */ 3883 tcp_send_ack(sk); 3884 } else { 3885 /* Else, send delayed ack. */ 3886 tcp_send_delayed_ack(sk); 3887 } 3888} 3889 3890static inline void tcp_ack_snd_check(struct sock *sk) 3891{ 3892 if (!inet_csk_ack_scheduled(sk)) { 3893 /* We sent a data segment already. */ 3894 return; 3895 } 3896 __tcp_ack_snd_check(sk, 1); 3897} 3898 3899/* 3900 * This routine is only called when we have urgent data 3901 * signaled. Its the 'slow' part of tcp_urg. It could be 3902 * moved inline now as tcp_urg is only called from one 3903 * place. We handle URGent data wrong. We have to - as 3904 * BSD still doesn't use the correction from RFC961. 3905 * For 1003.1g we should support a new option TCP_STDURG to permit 3906 * either form (or just set the sysctl tcp_stdurg). 3907 */ 3908 3909static void tcp_check_urg(struct sock * sk, struct tcphdr * th) 3910{ 3911 struct tcp_sock *tp = tcp_sk(sk); 3912 u32 ptr = ntohs(th->urg_ptr); 3913 3914 if (ptr && !sysctl_tcp_stdurg) 3915 ptr--; 3916 ptr += ntohl(th->seq); 3917 3918 /* Ignore urgent data that we've already seen and read. */ 3919 if (after(tp->copied_seq, ptr)) 3920 return; 3921 3922 /* Do not replay urg ptr. 3923 * 3924 * NOTE: interesting situation not covered by specs. 3925 * Misbehaving sender may send urg ptr, pointing to segment, 3926 * which we already have in ofo queue. We are not able to fetch 3927 * such data and will stay in TCP_URG_NOTYET until will be eaten 3928 * by recvmsg(). Seems, we are not obliged to handle such wicked 3929 * situations. But it is worth to think about possibility of some 3930 * DoSes using some hypothetical application level deadlock. 3931 */ 3932 if (before(ptr, tp->rcv_nxt)) 3933 return; 3934 3935 /* Do we already have a newer (or duplicate) urgent pointer? */ 3936 if (tp->urg_data && !after(ptr, tp->urg_seq)) 3937 return; 3938 3939 /* Tell the world about our new urgent pointer. */ 3940 sk_send_sigurg(sk); 3941 3942 /* We may be adding urgent data when the last byte read was 3943 * urgent. To do this requires some care. We cannot just ignore 3944 * tp->copied_seq since we would read the last urgent byte again 3945 * as data, nor can we alter copied_seq until this data arrives 3946 * or we break the semantics of SIOCATMARK (and thus sockatmark()) 3947 * 3948 * NOTE. Double Dutch. Rendering to plain English: author of comment 3949 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); 3950 * and expect that both A and B disappear from stream. This is _wrong_. 3951 * Though this happens in BSD with high probability, this is occasional. 3952 * Any application relying on this is buggy. Note also, that fix "works" 3953 * only in this artificial test. Insert some normal data between A and B and we will 3954 * decline of BSD again. Verdict: it is better to remove to trap 3955 * buggy users. 3956 */ 3957 if (tp->urg_seq == tp->copied_seq && tp->urg_data && 3958 !sock_flag(sk, SOCK_URGINLINE) && 3959 tp->copied_seq != tp->rcv_nxt) { 3960 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); 3961 tp->copied_seq++; 3962 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { 3963 __skb_unlink(skb, &sk->sk_receive_queue); 3964 __kfree_skb(skb); 3965 } 3966 } 3967 3968 tp->urg_data = TCP_URG_NOTYET; 3969 tp->urg_seq = ptr; 3970 3971 /* Disable header prediction. */ 3972 tp->pred_flags = 0; 3973} 3974 3975/* This is the 'fast' part of urgent handling. */ 3976static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th) 3977{ 3978 struct tcp_sock *tp = tcp_sk(sk); 3979 3980 /* Check if we get a new urgent pointer - normally not. */ 3981 if (th->urg) 3982 tcp_check_urg(sk,th); 3983 3984 /* Do we wait for any urgent data? - normally not... */ 3985 if (tp->urg_data == TCP_URG_NOTYET) { 3986 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - 3987 th->syn; 3988 3989 /* Is the urgent pointer pointing into this packet? */ 3990 if (ptr < skb->len) { 3991 u8 tmp; 3992 if (skb_copy_bits(skb, ptr, &tmp, 1)) 3993 BUG(); 3994 tp->urg_data = TCP_URG_VALID | tmp; 3995 if (!sock_flag(sk, SOCK_DEAD)) 3996 sk->sk_data_ready(sk, 0); 3997 } 3998 } 3999} 4000 4001static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) 4002{ 4003 struct tcp_sock *tp = tcp_sk(sk); 4004 int chunk = skb->len - hlen; 4005 int err; 4006 4007 local_bh_enable(); 4008 if (skb->ip_summed==CHECKSUM_UNNECESSARY) 4009 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); 4010 else 4011 err = skb_copy_and_csum_datagram_iovec(skb, hlen, 4012 tp->ucopy.iov); 4013 4014 if (!err) { 4015 tp->ucopy.len -= chunk; 4016 tp->copied_seq += chunk; 4017 tcp_rcv_space_adjust(sk); 4018 } 4019 4020 local_bh_disable(); 4021 return err; 4022} 4023 4024static __sum16 __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) 4025{ 4026 __sum16 result; 4027 4028 if (sock_owned_by_user(sk)) { 4029 local_bh_enable(); 4030 result = __tcp_checksum_complete(skb); 4031 local_bh_disable(); 4032 } else { 4033 result = __tcp_checksum_complete(skb); 4034 } 4035 return result; 4036} 4037 4038static inline int tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) 4039{ 4040 return skb->ip_summed != CHECKSUM_UNNECESSARY && 4041 __tcp_checksum_complete_user(sk, skb); 4042} 4043 4044#ifdef CONFIG_NET_DMA 4045static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, int hlen) 4046{ 4047 struct tcp_sock *tp = tcp_sk(sk); 4048 int chunk = skb->len - hlen; 4049 int dma_cookie; 4050 int copied_early = 0; 4051 4052 if (tp->ucopy.wakeup) 4053 return 0; 4054 4055 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list) 4056 tp->ucopy.dma_chan = get_softnet_dma(); 4057 4058 if (tp->ucopy.dma_chan && skb->ip_summed == CHECKSUM_UNNECESSARY) { 4059 4060 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan, 4061 skb, hlen, tp->ucopy.iov, chunk, tp->ucopy.pinned_list); 4062 4063 if (dma_cookie < 0) 4064 goto out; 4065 4066 tp->ucopy.dma_cookie = dma_cookie; 4067 copied_early = 1; 4068 4069 tp->ucopy.len -= chunk; 4070 tp->copied_seq += chunk; 4071 tcp_rcv_space_adjust(sk); 4072 4073 if ((tp->ucopy.len == 0) || 4074 (tcp_flag_word(skb->h.th) & TCP_FLAG_PSH) || 4075 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) { 4076 tp->ucopy.wakeup = 1; 4077 sk->sk_data_ready(sk, 0); 4078 } 4079 } else if (chunk > 0) { 4080 tp->ucopy.wakeup = 1; 4081 sk->sk_data_ready(sk, 0); 4082 } 4083out: 4084 return copied_early; 4085} 4086#endif /* CONFIG_NET_DMA */ 4087 4088/* 4089 * TCP receive function for the ESTABLISHED state. 4090 * 4091 * It is split into a fast path and a slow path. The fast path is 4092 * disabled when: 4093 * - A zero window was announced from us - zero window probing 4094 * is only handled properly in the slow path. 4095 * - Out of order segments arrived. 4096 * - Urgent data is expected. 4097 * - There is no buffer space left 4098 * - Unexpected TCP flags/window values/header lengths are received 4099 * (detected by checking the TCP header against pred_flags) 4100 * - Data is sent in both directions. Fast path only supports pure senders 4101 * or pure receivers (this means either the sequence number or the ack 4102 * value must stay constant) 4103 * - Unexpected TCP option. 4104 * 4105 * When these conditions are not satisfied it drops into a standard 4106 * receive procedure patterned after RFC793 to handle all cases. 4107 * The first three cases are guaranteed by proper pred_flags setting, 4108 * the rest is checked inline. Fast processing is turned on in 4109 * tcp_data_queue when everything is OK. 4110 */ 4111int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, 4112 struct tcphdr *th, unsigned len) 4113{ 4114 struct tcp_sock *tp = tcp_sk(sk); 4115 4116 /* 4117 * Header prediction. 4118 * The code loosely follows the one in the famous 4119 * "30 instruction TCP receive" Van Jacobson mail. 4120 * 4121 * Van's trick is to deposit buffers into socket queue 4122 * on a device interrupt, to call tcp_recv function 4123 * on the receive process context and checksum and copy 4124 * the buffer to user space. smart... 4125 * 4126 * Our current scheme is not silly either but we take the 4127 * extra cost of the net_bh soft interrupt processing... 4128 * We do checksum and copy also but from device to kernel. 4129 */ 4130 4131 tp->rx_opt.saw_tstamp = 0; 4132 4133 /* pred_flags is 0xS?10 << 16 + snd_wnd 4134 * if header_prediction is to be made 4135 * 'S' will always be tp->tcp_header_len >> 2 4136 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to 4137 * turn it off (when there are holes in the receive 4138 * space for instance) 4139 * PSH flag is ignored. 4140 */ 4141 4142 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && 4143 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { 4144 int tcp_header_len = tp->tcp_header_len; 4145 4146 /* Timestamp header prediction: tcp_header_len 4147 * is automatically equal to th->doff*4 due to pred_flags 4148 * match. 4149 */ 4150 4151 /* Check timestamp */ 4152 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { 4153 __be32 *ptr = (__be32 *)(th + 1); 4154 4155 /* No? Slow path! */ 4156 if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) 4157 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) 4158 goto slow_path; 4159 4160 tp->rx_opt.saw_tstamp = 1; 4161 ++ptr; 4162 tp->rx_opt.rcv_tsval = ntohl(*ptr); 4163 ++ptr; 4164 tp->rx_opt.rcv_tsecr = ntohl(*ptr); 4165 4166 /* If PAWS failed, check it more carefully in slow path */ 4167 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) 4168 goto slow_path; 4169 4170 /* DO NOT update ts_recent here, if checksum fails 4171 * and timestamp was corrupted part, it will result 4172 * in a hung connection since we will drop all 4173 * future packets due to the PAWS test. 4174 */ 4175 } 4176 4177 if (len <= tcp_header_len) { 4178 /* Bulk data transfer: sender */ 4179 if (len == tcp_header_len) { 4180 /* Predicted packet is in window by definition. 4181 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 4182 * Hence, check seq<=rcv_wup reduces to: 4183 */ 4184 if (tcp_header_len == 4185 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 4186 tp->rcv_nxt == tp->rcv_wup) 4187 tcp_store_ts_recent(tp); 4188 4189 /* We know that such packets are checksummed 4190 * on entry. 4191 */ 4192 tcp_ack(sk, skb, 0); 4193 __kfree_skb(skb); 4194 tcp_data_snd_check(sk, tp); 4195 return 0; 4196 } else { /* Header too small */ 4197 TCP_INC_STATS_BH(TCP_MIB_INERRS); 4198 goto discard; 4199 } 4200 } else { 4201 int eaten = 0; 4202 int copied_early = 0; 4203 4204 if (tp->copied_seq == tp->rcv_nxt && 4205 len - tcp_header_len <= tp->ucopy.len) { 4206#ifdef CONFIG_NET_DMA 4207 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) { 4208 copied_early = 1; 4209 eaten = 1; 4210 } 4211#endif 4212 if (tp->ucopy.task == current && sock_owned_by_user(sk) && !copied_early) { 4213 __set_current_state(TASK_RUNNING); 4214 4215 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) 4216 eaten = 1; 4217 } 4218 if (eaten) { 4219 /* Predicted packet is in window by definition. 4220 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 4221 * Hence, check seq<=rcv_wup reduces to: 4222 */ 4223 if (tcp_header_len == 4224 (sizeof(struct tcphdr) + 4225 TCPOLEN_TSTAMP_ALIGNED) && 4226 tp->rcv_nxt == tp->rcv_wup) 4227 tcp_store_ts_recent(tp); 4228 4229 tcp_rcv_rtt_measure_ts(sk, skb); 4230 4231 __skb_pull(skb, tcp_header_len); 4232 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4233 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER); 4234 } 4235 if (copied_early) 4236 tcp_cleanup_rbuf(sk, skb->len); 4237 } 4238 if (!eaten) { 4239 if (tcp_checksum_complete_user(sk, skb)) 4240 goto csum_error; 4241 4242 /* Predicted packet is in window by definition. 4243 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 4244 * Hence, check seq<=rcv_wup reduces to: 4245 */ 4246 if (tcp_header_len == 4247 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 4248 tp->rcv_nxt == tp->rcv_wup) 4249 tcp_store_ts_recent(tp); 4250 4251 tcp_rcv_rtt_measure_ts(sk, skb); 4252 4253 if ((int)skb->truesize > sk->sk_forward_alloc) 4254 goto step5; 4255 4256 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS); 4257 4258 /* Bulk data transfer: receiver */ 4259 __skb_pull(skb,tcp_header_len); 4260 __skb_queue_tail(&sk->sk_receive_queue, skb); 4261 sk_stream_set_owner_r(skb, sk); 4262 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4263 } 4264 4265 tcp_event_data_recv(sk, tp, skb); 4266 4267 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { 4268 /* Well, only one small jumplet in fast path... */ 4269 tcp_ack(sk, skb, FLAG_DATA); 4270 tcp_data_snd_check(sk, tp); 4271 if (!inet_csk_ack_scheduled(sk)) 4272 goto no_ack; 4273 } 4274 4275 __tcp_ack_snd_check(sk, 0); 4276no_ack: 4277#ifdef CONFIG_NET_DMA 4278 if (copied_early) 4279 __skb_queue_tail(&sk->sk_async_wait_queue, skb); 4280 else 4281#endif 4282 if (eaten) 4283 __kfree_skb(skb); 4284 else 4285 sk->sk_data_ready(sk, 0); 4286 return 0; 4287 } 4288 } 4289 4290slow_path: 4291 if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb)) 4292 goto csum_error; 4293 4294 /* 4295 * RFC1323: H1. Apply PAWS check first. 4296 */ 4297 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && 4298 tcp_paws_discard(sk, skb)) { 4299 if (!th->rst) { 4300 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); 4301 tcp_send_dupack(sk, skb); 4302 goto discard; 4303 } 4304 /* Resets are accepted even if PAWS failed. 4305 4306 ts_recent update must be made after we are sure 4307 that the packet is in window. 4308 */ 4309 } 4310 4311 /* 4312 * Standard slow path. 4313 */ 4314 4315 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { 4316 /* RFC793, page 37: "In all states except SYN-SENT, all reset 4317 * (RST) segments are validated by checking their SEQ-fields." 4318 * And page 69: "If an incoming segment is not acceptable, 4319 * an acknowledgment should be sent in reply (unless the RST bit 4320 * is set, if so drop the segment and return)". 4321 */ 4322 if (!th->rst) 4323 tcp_send_dupack(sk, skb); 4324 goto discard; 4325 } 4326 4327 if (th->rst) { 4328 tcp_reset(sk); 4329 goto discard; 4330 } 4331 4332 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 4333 4334 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4335 TCP_INC_STATS_BH(TCP_MIB_INERRS); 4336 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); 4337 tcp_reset(sk); 4338 return 1; 4339 } 4340 4341step5: 4342 if (th->ack) 4343 tcp_ack(sk, skb, FLAG_SLOWPATH); 4344 4345 tcp_rcv_rtt_measure_ts(sk, skb); 4346 4347 /* Process urgent data. */ 4348 tcp_urg(sk, skb, th); 4349 4350 /* step 7: process the segment text */ 4351 tcp_data_queue(sk, skb); 4352 4353 tcp_data_snd_check(sk, tp); 4354 tcp_ack_snd_check(sk); 4355 return 0; 4356 4357csum_error: 4358 TCP_INC_STATS_BH(TCP_MIB_INERRS); 4359 4360discard: 4361 __kfree_skb(skb); 4362 return 0; 4363} 4364 4365static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 4366 struct tcphdr *th, unsigned len) 4367{ 4368 struct tcp_sock *tp = tcp_sk(sk); 4369 struct inet_connection_sock *icsk = inet_csk(sk); 4370 int saved_clamp = tp->rx_opt.mss_clamp; 4371 4372 tcp_parse_options(skb, &tp->rx_opt, 0); 4373 4374 if (th->ack) { 4375 /* rfc793: 4376 * "If the state is SYN-SENT then 4377 * first check the ACK bit 4378 * If the ACK bit is set 4379 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send 4380 * a reset (unless the RST bit is set, if so drop 4381 * the segment and return)" 4382 * 4383 * We do not send data with SYN, so that RFC-correct 4384 * test reduces to: 4385 */ 4386 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt) 4387 goto reset_and_undo; 4388 4389 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 4390 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, 4391 tcp_time_stamp)) { 4392 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED); 4393 goto reset_and_undo; 4394 } 4395 4396 /* Now ACK is acceptable. 4397 * 4398 * "If the RST bit is set 4399 * If the ACK was acceptable then signal the user "error: 4400 * connection reset", drop the segment, enter CLOSED state, 4401 * delete TCB, and return." 4402 */ 4403 4404 if (th->rst) { 4405 tcp_reset(sk); 4406 goto discard; 4407 } 4408 4409 /* rfc793: 4410 * "fifth, if neither of the SYN or RST bits is set then 4411 * drop the segment and return." 4412 * 4413 * See note below! 4414 * --ANK(990513) 4415 */ 4416 if (!th->syn) 4417 goto discard_and_undo; 4418 4419 /* rfc793: 4420 * "If the SYN bit is on ... 4421 * are acceptable then ... 4422 * (our SYN has been ACKed), change the connection 4423 * state to ESTABLISHED..." 4424 */ 4425 4426 TCP_ECN_rcv_synack(tp, th); 4427 4428 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 4429 tcp_ack(sk, skb, FLAG_SLOWPATH); 4430 4431 /* Ok.. it's good. Set up sequence numbers and 4432 * move to established. 4433 */ 4434 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 4435 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 4436 4437 /* RFC1323: The window in SYN & SYN/ACK segments is 4438 * never scaled. 4439 */ 4440 tp->snd_wnd = ntohs(th->window); 4441 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq); 4442 4443 if (!tp->rx_opt.wscale_ok) { 4444 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; 4445 tp->window_clamp = min(tp->window_clamp, 65535U); 4446 } 4447 4448 if (tp->rx_opt.saw_tstamp) { 4449 tp->rx_opt.tstamp_ok = 1; 4450 tp->tcp_header_len = 4451 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 4452 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 4453 tcp_store_ts_recent(tp); 4454 } else { 4455 tp->tcp_header_len = sizeof(struct tcphdr); 4456 } 4457 4458 if (tp->rx_opt.sack_ok && sysctl_tcp_fack) 4459 tp->rx_opt.sack_ok |= 2; 4460 4461 tcp_mtup_init(sk); 4462 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 4463 tcp_initialize_rcv_mss(sk); 4464 4465 /* Remember, tcp_poll() does not lock socket! 4466 * Change state from SYN-SENT only after copied_seq 4467 * is initialized. */ 4468 tp->copied_seq = tp->rcv_nxt; 4469 smp_mb(); 4470 tcp_set_state(sk, TCP_ESTABLISHED); 4471 4472 security_inet_conn_established(sk, skb); 4473 4474 /* Make sure socket is routed, for correct metrics. */ 4475 icsk->icsk_af_ops->rebuild_header(sk); 4476 4477 tcp_init_metrics(sk); 4478 4479 tcp_init_congestion_control(sk); 4480 4481 /* Prevent spurious tcp_cwnd_restart() on first data 4482 * packet. 4483 */ 4484 tp->lsndtime = tcp_time_stamp; 4485 4486 tcp_init_buffer_space(sk); 4487 4488 if (sock_flag(sk, SOCK_KEEPOPEN)) 4489 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); 4490 4491 if (!tp->rx_opt.snd_wscale) 4492 __tcp_fast_path_on(tp, tp->snd_wnd); 4493 else 4494 tp->pred_flags = 0; 4495 4496 if (!sock_flag(sk, SOCK_DEAD)) { 4497 sk->sk_state_change(sk); 4498 sk_wake_async(sk, 0, POLL_OUT); 4499 } 4500 4501 if (sk->sk_write_pending || 4502 icsk->icsk_accept_queue.rskq_defer_accept || 4503 icsk->icsk_ack.pingpong) { 4504 /* Save one ACK. Data will be ready after 4505 * several ticks, if write_pending is set. 4506 * 4507 * It may be deleted, but with this feature tcpdumps 4508 * look so _wonderfully_ clever, that I was not able 4509 * to stand against the temptation 8) --ANK 4510 */ 4511 inet_csk_schedule_ack(sk); 4512 icsk->icsk_ack.lrcvtime = tcp_time_stamp; 4513 icsk->icsk_ack.ato = TCP_ATO_MIN; 4514 tcp_incr_quickack(sk); 4515 tcp_enter_quickack_mode(sk); 4516 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 4517 TCP_DELACK_MAX, TCP_RTO_MAX); 4518 4519discard: 4520 __kfree_skb(skb); 4521 return 0; 4522 } else { 4523 tcp_send_ack(sk); 4524 } 4525 return -1; 4526 } 4527 4528 /* No ACK in the segment */ 4529 4530 if (th->rst) { 4531 /* rfc793: 4532 * "If the RST bit is set 4533 * 4534 * Otherwise (no ACK) drop the segment and return." 4535 */ 4536 4537 goto discard_and_undo; 4538 } 4539 4540 /* PAWS check. */ 4541 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0)) 4542 goto discard_and_undo; 4543 4544 if (th->syn) { 4545 /* We see SYN without ACK. It is attempt of 4546 * simultaneous connect with crossed SYNs. 4547 * Particularly, it can be connect to self. 4548 */ 4549 tcp_set_state(sk, TCP_SYN_RECV); 4550 4551 if (tp->rx_opt.saw_tstamp) { 4552 tp->rx_opt.tstamp_ok = 1; 4553 tcp_store_ts_recent(tp); 4554 tp->tcp_header_len = 4555 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 4556 } else { 4557 tp->tcp_header_len = sizeof(struct tcphdr); 4558 } 4559 4560 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 4561 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 4562 4563 /* RFC1323: The window in SYN & SYN/ACK segments is 4564 * never scaled. 4565 */ 4566 tp->snd_wnd = ntohs(th->window); 4567 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 4568 tp->max_window = tp->snd_wnd; 4569 4570 TCP_ECN_rcv_syn(tp, th); 4571 4572 tcp_mtup_init(sk); 4573 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 4574 tcp_initialize_rcv_mss(sk); 4575 4576 4577 tcp_send_synack(sk); 4578#if 0 4579 /* Note, we could accept data and URG from this segment. 4580 * There are no obstacles to make this. 4581 * 4582 * However, if we ignore data in ACKless segments sometimes, 4583 * we have no reasons to accept it sometimes. 4584 * Also, seems the code doing it in step6 of tcp_rcv_state_process 4585 * is not flawless. So, discard packet for sanity. 4586 * Uncomment this return to process the data. 4587 */ 4588 return -1; 4589#else 4590 goto discard; 4591#endif 4592 } 4593 /* "fifth, if neither of the SYN or RST bits is set then 4594 * drop the segment and return." 4595 */ 4596 4597discard_and_undo: 4598 tcp_clear_options(&tp->rx_opt); 4599 tp->rx_opt.mss_clamp = saved_clamp; 4600 goto discard; 4601 4602reset_and_undo: 4603 tcp_clear_options(&tp->rx_opt); 4604 tp->rx_opt.mss_clamp = saved_clamp; 4605 return 1; 4606} 4607 4608 4609/* 4610 * This function implements the receiving procedure of RFC 793 for 4611 * all states except ESTABLISHED and TIME_WAIT. 4612 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be 4613 * address independent. 4614 */ 4615 4616int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, 4617 struct tcphdr *th, unsigned len) 4618{ 4619 struct tcp_sock *tp = tcp_sk(sk); 4620 struct inet_connection_sock *icsk = inet_csk(sk); 4621 int queued = 0; 4622 4623 tp->rx_opt.saw_tstamp = 0; 4624 4625 switch (sk->sk_state) { 4626 case TCP_CLOSE: 4627 goto discard; 4628 4629 case TCP_LISTEN: 4630 if (th->ack) 4631 return 1; 4632 4633 if (th->rst) 4634 goto discard; 4635 4636 if (th->syn) { 4637 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0) 4638 return 1; 4639 4640 /* Now we have several options: In theory there is 4641 * nothing else in the frame. KA9Q has an option to 4642 * send data with the syn, BSD accepts data with the 4643 * syn up to the [to be] advertised window and 4644 * Solaris 2.1 gives you a protocol error. For now 4645 * we just ignore it, that fits the spec precisely 4646 * and avoids incompatibilities. It would be nice in 4647 * future to drop through and process the data. 4648 * 4649 * Now that TTCP is starting to be used we ought to 4650 * queue this data. 4651 * But, this leaves one open to an easy denial of 4652 * service attack, and SYN cookies can't defend 4653 * against this problem. So, we drop the data 4654 * in the interest of security over speed unless 4655 * it's still in use. 4656 */ 4657 kfree_skb(skb); 4658 return 0; 4659 } 4660 goto discard; 4661 4662 case TCP_SYN_SENT: 4663 queued = tcp_rcv_synsent_state_process(sk, skb, th, len); 4664 if (queued >= 0) 4665 return queued; 4666 4667 /* Do step6 onward by hand. */ 4668 tcp_urg(sk, skb, th); 4669 __kfree_skb(skb); 4670 tcp_data_snd_check(sk, tp); 4671 return 0; 4672 } 4673 4674 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && 4675 tcp_paws_discard(sk, skb)) { 4676 if (!th->rst) { 4677 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); 4678 tcp_send_dupack(sk, skb); 4679 goto discard; 4680 } 4681 /* Reset is accepted even if it did not pass PAWS. */ 4682 } 4683 4684 /* step 1: check sequence number */ 4685 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { 4686 if (!th->rst) 4687 tcp_send_dupack(sk, skb); 4688 goto discard; 4689 } 4690 4691 /* step 2: check RST bit */ 4692 if (th->rst) { 4693 tcp_reset(sk); 4694 goto discard; 4695 } 4696 4697 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 4698 4699 /* step 3: check security and precedence [ignored] */ 4700 4701 /* step 4: 4702 * 4703 * Check for a SYN in window. 4704 */ 4705 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4706 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); 4707 tcp_reset(sk); 4708 return 1; 4709 } 4710 4711 /* step 5: check the ACK field */ 4712 if (th->ack) { 4713 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH); 4714 4715 switch (sk->sk_state) { 4716 case TCP_SYN_RECV: 4717 if (acceptable) { 4718 tp->copied_seq = tp->rcv_nxt; 4719 smp_mb(); 4720 tcp_set_state(sk, TCP_ESTABLISHED); 4721 sk->sk_state_change(sk); 4722 4723 /* Note, that this wakeup is only for marginal 4724 * crossed SYN case. Passively open sockets 4725 * are not waked up, because sk->sk_sleep == 4726 * NULL and sk->sk_socket == NULL. 4727 */ 4728 if (sk->sk_socket) { 4729 sk_wake_async(sk,0,POLL_OUT); 4730 } 4731 4732 tp->snd_una = TCP_SKB_CB(skb)->ack_seq; 4733 tp->snd_wnd = ntohs(th->window) << 4734 tp->rx_opt.snd_wscale; 4735 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, 4736 TCP_SKB_CB(skb)->seq); 4737 4738 /* tcp_ack considers this ACK as duplicate 4739 * and does not calculate rtt. 4740 * Fix it at least with timestamps. 4741 */ 4742 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 4743 !tp->srtt) 4744 tcp_ack_saw_tstamp(sk, 0); 4745 4746 if (tp->rx_opt.tstamp_ok) 4747 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 4748 4749 /* Make sure socket is routed, for 4750 * correct metrics. 4751 */ 4752 icsk->icsk_af_ops->rebuild_header(sk); 4753 4754 tcp_init_metrics(sk); 4755 4756 tcp_init_congestion_control(sk); 4757 4758 /* Prevent spurious tcp_cwnd_restart() on 4759 * first data packet. 4760 */ 4761 tp->lsndtime = tcp_time_stamp; 4762 4763 tcp_mtup_init(sk); 4764 tcp_initialize_rcv_mss(sk); 4765 tcp_init_buffer_space(sk); 4766 tcp_fast_path_on(tp); 4767 } else { 4768 return 1; 4769 } 4770 break; 4771 4772 case TCP_FIN_WAIT1: 4773 if (tp->snd_una == tp->write_seq) { 4774 tcp_set_state(sk, TCP_FIN_WAIT2); 4775 sk->sk_shutdown |= SEND_SHUTDOWN; 4776 dst_confirm(sk->sk_dst_cache); 4777 4778 if (!sock_flag(sk, SOCK_DEAD)) 4779 /* Wake up lingering close() */ 4780 sk->sk_state_change(sk); 4781 else { 4782 int tmo; 4783 4784 if (tp->linger2 < 0 || 4785 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 4786 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { 4787 tcp_done(sk); 4788 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); 4789 return 1; 4790 } 4791 4792 tmo = tcp_fin_time(sk); 4793 if (tmo > TCP_TIMEWAIT_LEN) { 4794 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); 4795 } else if (th->fin || sock_owned_by_user(sk)) { 4796 /* Bad case. We could lose such FIN otherwise. 4797 * It is not a big problem, but it looks confusing 4798 * and not so rare event. We still can lose it now, 4799 * if it spins in bh_lock_sock(), but it is really 4800 * marginal case. 4801 */ 4802 inet_csk_reset_keepalive_timer(sk, tmo); 4803 } else { 4804 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 4805 goto discard; 4806 } 4807 } 4808 } 4809 break; 4810 4811 case TCP_CLOSING: 4812 if (tp->snd_una == tp->write_seq) { 4813 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 4814 goto discard; 4815 } 4816 break; 4817 4818 case TCP_LAST_ACK: 4819 if (tp->snd_una == tp->write_seq) { 4820 tcp_update_metrics(sk); 4821 tcp_done(sk); 4822 goto discard; 4823 } 4824 break; 4825 } 4826 } else 4827 goto discard; 4828 4829 /* step 6: check the URG bit */ 4830 tcp_urg(sk, skb, th); 4831 4832 /* step 7: process the segment text */ 4833 switch (sk->sk_state) { 4834 case TCP_CLOSE_WAIT: 4835 case TCP_CLOSING: 4836 case TCP_LAST_ACK: 4837 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 4838 break; 4839 case TCP_FIN_WAIT1: 4840 case TCP_FIN_WAIT2: 4841 /* RFC 793 says to queue data in these states, 4842 * RFC 1122 says we MUST send a reset. 4843 * BSD 4.4 also does reset. 4844 */ 4845 if (sk->sk_shutdown & RCV_SHUTDOWN) { 4846 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 4847 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { 4848 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); 4849 tcp_reset(sk); 4850 return 1; 4851 } 4852 } 4853 /* Fall through */ 4854 case TCP_ESTABLISHED: 4855 tcp_data_queue(sk, skb); 4856 queued = 1; 4857 break; 4858 } 4859 4860 /* tcp_data could move socket to TIME-WAIT */ 4861 if (sk->sk_state != TCP_CLOSE) { 4862 tcp_data_snd_check(sk, tp); 4863 tcp_ack_snd_check(sk); 4864 } 4865 4866 if (!queued) { 4867discard: 4868 __kfree_skb(skb); 4869 } 4870 return 0; 4871} 4872 4873EXPORT_SYMBOL(sysctl_tcp_ecn); 4874EXPORT_SYMBOL(sysctl_tcp_reordering); 4875EXPORT_SYMBOL(tcp_parse_options); 4876EXPORT_SYMBOL(tcp_rcv_established); 4877EXPORT_SYMBOL(tcp_rcv_state_process); 4878EXPORT_SYMBOL(tcp_initialize_rcv_mss); 4879