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 1.1.1.1 2007/08/03 18:53:51 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_transport_header(skb); 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(tcp_hdr(skb)) & 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, const struct sk_buff *skb) 239{ 240 struct tcp_sock *tp = tcp_sk(sk); 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, 256 struct sk_buff *skb) 257{ 258 struct tcp_sock *tp = tcp_sk(sk); 259 260 /* Check #1 */ 261 if (tp->rcv_ssthresh < tp->window_clamp && 262 (int)tp->rcv_ssthresh < tcp_space(sk) && 263 !tcp_memory_pressure) { 264 int incr; 265 266 /* Check #2. Increase window, if skb with such overhead 267 * will fit to rcvbuf in future. 268 */ 269 if (tcp_win_from_space(skb->truesize) <= skb->len) 270 incr = 2*tp->advmss; 271 else 272 incr = __tcp_grow_window(sk, skb); 273 274 if (incr) { 275 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp); 276 inet_csk(sk)->icsk_ack.quick |= 1; 277 } 278 } 279} 280 281/* 3. Tuning rcvbuf, when connection enters established state. */ 282 283static void tcp_fixup_rcvbuf(struct sock *sk) 284{ 285 struct tcp_sock *tp = tcp_sk(sk); 286 int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); 287 288 /* Try to select rcvbuf so that 4 mss-sized segments 289 * will fit to window and corresponding skbs will fit to our rcvbuf. 290 * (was 3; 4 is minimum to allow fast retransmit to work.) 291 */ 292 while (tcp_win_from_space(rcvmem) < tp->advmss) 293 rcvmem += 128; 294 if (sk->sk_rcvbuf < 4 * rcvmem) 295 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]); 296} 297 298/* 4. Try to fixup all. It is made immediately after connection enters 299 * established state. 300 */ 301static void tcp_init_buffer_space(struct sock *sk) 302{ 303 struct tcp_sock *tp = tcp_sk(sk); 304 int maxwin; 305 306 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) 307 tcp_fixup_rcvbuf(sk); 308 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) 309 tcp_fixup_sndbuf(sk); 310 311 tp->rcvq_space.space = tp->rcv_wnd; 312 313 maxwin = tcp_full_space(sk); 314 315 if (tp->window_clamp >= maxwin) { 316 tp->window_clamp = maxwin; 317 318 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) 319 tp->window_clamp = max(maxwin - 320 (maxwin >> sysctl_tcp_app_win), 321 4 * tp->advmss); 322 } 323 324 /* Force reservation of one segment. */ 325 if (sysctl_tcp_app_win && 326 tp->window_clamp > 2 * tp->advmss && 327 tp->window_clamp + tp->advmss > maxwin) 328 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); 329 330 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); 331 tp->snd_cwnd_stamp = tcp_time_stamp; 332} 333 334/* 5. Recalculate window clamp after socket hit its memory bounds. */ 335static void tcp_clamp_window(struct sock *sk) 336{ 337 struct tcp_sock *tp = tcp_sk(sk); 338 struct inet_connection_sock *icsk = inet_csk(sk); 339 340 icsk->icsk_ack.quick = 0; 341 342 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && 343 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && 344 !tcp_memory_pressure && 345 atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) { 346 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), 347 sysctl_tcp_rmem[2]); 348 } 349 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) 350 tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss); 351} 352 353 354/* Initialize RCV_MSS value. 355 * RCV_MSS is an our guess about MSS used by the peer. 356 * We haven't any direct information about the MSS. 357 * It's better to underestimate the RCV_MSS rather than overestimate. 358 * Overestimations make us ACKing less frequently than needed. 359 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). 360 */ 361void tcp_initialize_rcv_mss(struct sock *sk) 362{ 363 struct tcp_sock *tp = tcp_sk(sk); 364 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); 365 366 hint = min(hint, tp->rcv_wnd/2); 367 hint = min(hint, TCP_MIN_RCVMSS); 368 hint = max(hint, TCP_MIN_MSS); 369 370 inet_csk(sk)->icsk_ack.rcv_mss = hint; 371} 372 373/* Receiver "autotuning" code. 374 * 375 * The algorithm for RTT estimation w/o timestamps is based on 376 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. 377 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps> 378 * 379 * More detail on this code can be found at 380 * <http://www.psc.edu/~jheffner/senior_thesis.ps>, 381 * though this reference is out of date. A new paper 382 * is pending. 383 */ 384static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) 385{ 386 u32 new_sample = tp->rcv_rtt_est.rtt; 387 long m = sample; 388 389 if (m == 0) 390 m = 1; 391 392 if (new_sample != 0) { 393 /* If we sample in larger samples in the non-timestamp 394 * case, we could grossly overestimate the RTT especially 395 * with chatty applications or bulk transfer apps which 396 * are stalled on filesystem I/O. 397 * 398 * Also, since we are only going for a minimum in the 399 * non-timestamp case, we do not smooth things out 400 * else with timestamps disabled convergence takes too 401 * long. 402 */ 403 if (!win_dep) { 404 m -= (new_sample >> 3); 405 new_sample += m; 406 } else if (m < new_sample) 407 new_sample = m << 3; 408 } else { 409 /* No previous measure. */ 410 new_sample = m << 3; 411 } 412 413 if (tp->rcv_rtt_est.rtt != new_sample) 414 tp->rcv_rtt_est.rtt = new_sample; 415} 416 417static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) 418{ 419 if (tp->rcv_rtt_est.time == 0) 420 goto new_measure; 421 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) 422 return; 423 tcp_rcv_rtt_update(tp, 424 jiffies - tp->rcv_rtt_est.time, 425 1); 426 427new_measure: 428 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; 429 tp->rcv_rtt_est.time = tcp_time_stamp; 430} 431 432static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb) 433{ 434 struct tcp_sock *tp = tcp_sk(sk); 435 if (tp->rx_opt.rcv_tsecr && 436 (TCP_SKB_CB(skb)->end_seq - 437 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) 438 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); 439} 440 441/* 442 * This function should be called every time data is copied to user space. 443 * It calculates the appropriate TCP receive buffer space. 444 */ 445void tcp_rcv_space_adjust(struct sock *sk) 446{ 447 struct tcp_sock *tp = tcp_sk(sk); 448 int time; 449 int space; 450 451 if (tp->rcvq_space.time == 0) 452 goto new_measure; 453 454 time = tcp_time_stamp - tp->rcvq_space.time; 455 if (time < (tp->rcv_rtt_est.rtt >> 3) || 456 tp->rcv_rtt_est.rtt == 0) 457 return; 458 459 space = 2 * (tp->copied_seq - tp->rcvq_space.seq); 460 461 space = max(tp->rcvq_space.space, space); 462 463 if (tp->rcvq_space.space != space) { 464 int rcvmem; 465 466 tp->rcvq_space.space = space; 467 468 if (sysctl_tcp_moderate_rcvbuf && 469 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { 470 int new_clamp = space; 471 472 /* Receive space grows, normalize in order to 473 * take into account packet headers and sk_buff 474 * structure overhead. 475 */ 476 space /= tp->advmss; 477 if (!space) 478 space = 1; 479 rcvmem = (tp->advmss + MAX_TCP_HEADER + 480 16 + sizeof(struct sk_buff)); 481 while (tcp_win_from_space(rcvmem) < tp->advmss) 482 rcvmem += 128; 483 space *= rcvmem; 484 space = min(space, sysctl_tcp_rmem[2]); 485 if (space > sk->sk_rcvbuf) { 486 sk->sk_rcvbuf = space; 487 488 /* Make the window clamp follow along. */ 489 tp->window_clamp = new_clamp; 490 } 491 } 492 } 493 494new_measure: 495 tp->rcvq_space.seq = tp->copied_seq; 496 tp->rcvq_space.time = tcp_time_stamp; 497} 498 499/* There is something which you must keep in mind when you analyze the 500 * behavior of the tp->ato delayed ack timeout interval. When a 501 * connection starts up, we want to ack as quickly as possible. The 502 * problem is that "good" TCP's do slow start at the beginning of data 503 * transmission. The means that until we send the first few ACK's the 504 * sender will sit on his end and only queue most of his data, because 505 * he can only send snd_cwnd unacked packets at any given time. For 506 * each ACK we send, he increments snd_cwnd and transmits more of his 507 * queue. -DaveM 508 */ 509static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) 510{ 511 struct tcp_sock *tp = tcp_sk(sk); 512 struct inet_connection_sock *icsk = inet_csk(sk); 513 u32 now; 514 515 inet_csk_schedule_ack(sk); 516 517 tcp_measure_rcv_mss(sk, skb); 518 519 tcp_rcv_rtt_measure(tp); 520 521 now = tcp_time_stamp; 522 523 if (!icsk->icsk_ack.ato) { 524 /* The _first_ data packet received, initialize 525 * delayed ACK engine. 526 */ 527 tcp_incr_quickack(sk); 528 icsk->icsk_ack.ato = TCP_ATO_MIN; 529 } else { 530 int m = now - icsk->icsk_ack.lrcvtime; 531 532 if (m <= TCP_ATO_MIN/2) { 533 /* The fastest case is the first. */ 534 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; 535 } else if (m < icsk->icsk_ack.ato) { 536 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; 537 if (icsk->icsk_ack.ato > icsk->icsk_rto) 538 icsk->icsk_ack.ato = icsk->icsk_rto; 539 } else if (m > icsk->icsk_rto) { 540 /* Too long gap. Apparently sender failed to 541 * restart window, so that we send ACKs quickly. 542 */ 543 tcp_incr_quickack(sk); 544 sk_stream_mem_reclaim(sk); 545 } 546 } 547 icsk->icsk_ack.lrcvtime = now; 548 549 TCP_ECN_check_ce(tp, skb); 550 551 if (skb->len >= 128) 552 tcp_grow_window(sk, skb); 553} 554 555/* Called to compute a smoothed rtt estimate. The data fed to this 556 * routine either comes from timestamps, or from segments that were 557 * known _not_ to have been retransmitted [see Karn/Partridge 558 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 559 * piece by Van Jacobson. 560 * NOTE: the next three routines used to be one big routine. 561 * To save cycles in the RFC 1323 implementation it was better to break 562 * it up into three procedures. -- erics 563 */ 564static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) 565{ 566 struct tcp_sock *tp = tcp_sk(sk); 567 long m = mrtt; /* RTT */ 568 569 /* The following amusing code comes from Jacobson's 570 * article in SIGCOMM '88. Note that rtt and mdev 571 * are scaled versions of rtt and mean deviation. 572 * This is designed to be as fast as possible 573 * m stands for "measurement". 574 * 575 * On a 1990 paper the rto value is changed to: 576 * RTO = rtt + 4 * mdev 577 * 578 * Funny. This algorithm seems to be very broken. 579 * These formulae increase RTO, when it should be decreased, increase 580 * too slowly, when it should be increased quickly, decrease too quickly 581 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely 582 * does not matter how to _calculate_ it. Seems, it was trap 583 * that VJ failed to avoid. 8) 584 */ 585 if (m == 0) 586 m = 1; 587 if (tp->srtt != 0) { 588 m -= (tp->srtt >> 3); /* m is now error in rtt est */ 589 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ 590 if (m < 0) { 591 m = -m; /* m is now abs(error) */ 592 m -= (tp->mdev >> 2); /* similar update on mdev */ 593 /* This is similar to one of Eifel findings. 594 * Eifel blocks mdev updates when rtt decreases. 595 * This solution is a bit different: we use finer gain 596 * for mdev in this case (alpha*beta). 597 * Like Eifel it also prevents growth of rto, 598 * but also it limits too fast rto decreases, 599 * happening in pure Eifel. 600 */ 601 if (m > 0) 602 m >>= 3; 603 } else { 604 m -= (tp->mdev >> 2); /* similar update on mdev */ 605 } 606 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ 607 if (tp->mdev > tp->mdev_max) { 608 tp->mdev_max = tp->mdev; 609 if (tp->mdev_max > tp->rttvar) 610 tp->rttvar = tp->mdev_max; 611 } 612 if (after(tp->snd_una, tp->rtt_seq)) { 613 if (tp->mdev_max < tp->rttvar) 614 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2; 615 tp->rtt_seq = tp->snd_nxt; 616 tp->mdev_max = TCP_RTO_MIN; 617 } 618 } else { 619 /* no previous measure. */ 620 tp->srtt = m<<3; /* take the measured time to be rtt */ 621 tp->mdev = m<<1; /* make sure rto = 3*rtt */ 622 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); 623 tp->rtt_seq = tp->snd_nxt; 624 } 625} 626 627/* Calculate rto without backoff. This is the second half of Van Jacobson's 628 * routine referred to above. 629 */ 630static inline void tcp_set_rto(struct sock *sk) 631{ 632 const struct tcp_sock *tp = tcp_sk(sk); 633 /* Old crap is replaced with new one. 8) 634 * 635 * More seriously: 636 * 1. If rtt variance happened to be less 50msec, it is hallucination. 637 * It cannot be less due to utterly erratic ACK generation made 638 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ 639 * to do with delayed acks, because at cwnd>2 true delack timeout 640 * is invisible. Actually, Linux-2.4 also generates erratic 641 * ACKs in some circumstances. 642 */ 643 inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar; 644 645 /* 2. Fixups made earlier cannot be right. 646 * If we do not estimate RTO correctly without them, 647 * all the algo is pure shit and should be replaced 648 * with correct one. It is exactly, which we pretend to do. 649 */ 650} 651 652/* NOTE: clamping at TCP_RTO_MIN is not required, current algo 653 * guarantees that rto is higher. 654 */ 655static inline void tcp_bound_rto(struct sock *sk) 656{ 657 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX) 658 inet_csk(sk)->icsk_rto = TCP_RTO_MAX; 659} 660 661/* Save metrics learned by this TCP session. 662 This function is called only, when TCP finishes successfully 663 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. 664 */ 665void tcp_update_metrics(struct sock *sk) 666{ 667 struct tcp_sock *tp = tcp_sk(sk); 668 struct dst_entry *dst = __sk_dst_get(sk); 669 670 if (sysctl_tcp_nometrics_save) 671 return; 672 673 dst_confirm(dst); 674 675 if (dst && (dst->flags&DST_HOST)) { 676 const struct inet_connection_sock *icsk = inet_csk(sk); 677 int m; 678 679 if (icsk->icsk_backoff || !tp->srtt) { 680 /* This session failed to estimate rtt. Why? 681 * Probably, no packets returned in time. 682 * Reset our results. 683 */ 684 if (!(dst_metric_locked(dst, RTAX_RTT))) 685 dst->metrics[RTAX_RTT-1] = 0; 686 return; 687 } 688 689 m = dst_metric(dst, RTAX_RTT) - tp->srtt; 690 691 /* If newly calculated rtt larger than stored one, 692 * store new one. Otherwise, use EWMA. Remember, 693 * rtt overestimation is always better than underestimation. 694 */ 695 if (!(dst_metric_locked(dst, RTAX_RTT))) { 696 if (m <= 0) 697 dst->metrics[RTAX_RTT-1] = tp->srtt; 698 else 699 dst->metrics[RTAX_RTT-1] -= (m>>3); 700 } 701 702 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { 703 if (m < 0) 704 m = -m; 705 706 /* Scale deviation to rttvar fixed point */ 707 m >>= 1; 708 if (m < tp->mdev) 709 m = tp->mdev; 710 711 if (m >= dst_metric(dst, RTAX_RTTVAR)) 712 dst->metrics[RTAX_RTTVAR-1] = m; 713 else 714 dst->metrics[RTAX_RTTVAR-1] -= 715 (dst->metrics[RTAX_RTTVAR-1] - m)>>2; 716 } 717 718 if (tp->snd_ssthresh >= 0xFFFF) { 719 /* Slow start still did not finish. */ 720 if (dst_metric(dst, RTAX_SSTHRESH) && 721 !dst_metric_locked(dst, RTAX_SSTHRESH) && 722 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) 723 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1; 724 if (!dst_metric_locked(dst, RTAX_CWND) && 725 tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) 726 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd; 727 } else if (tp->snd_cwnd > tp->snd_ssthresh && 728 icsk->icsk_ca_state == TCP_CA_Open) { 729 /* Cong. avoidance phase, cwnd is reliable. */ 730 if (!dst_metric_locked(dst, RTAX_SSTHRESH)) 731 dst->metrics[RTAX_SSTHRESH-1] = 732 max(tp->snd_cwnd >> 1, tp->snd_ssthresh); 733 if (!dst_metric_locked(dst, RTAX_CWND)) 734 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1; 735 } else { 736 /* Else slow start did not finish, cwnd is non-sense, 737 ssthresh may be also invalid. 738 */ 739 if (!dst_metric_locked(dst, RTAX_CWND)) 740 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1; 741 if (dst->metrics[RTAX_SSTHRESH-1] && 742 !dst_metric_locked(dst, RTAX_SSTHRESH) && 743 tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1]) 744 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh; 745 } 746 747 if (!dst_metric_locked(dst, RTAX_REORDERING)) { 748 if (dst->metrics[RTAX_REORDERING-1] < tp->reordering && 749 tp->reordering != sysctl_tcp_reordering) 750 dst->metrics[RTAX_REORDERING-1] = tp->reordering; 751 } 752 } 753} 754 755/* Numbers are taken from RFC2414. */ 756__u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst) 757{ 758 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); 759 760 if (!cwnd) { 761 if (tp->mss_cache > 1460) 762 cwnd = 2; 763 else 764 cwnd = (tp->mss_cache > 1095) ? 3 : 4; 765 } 766 return min_t(__u32, cwnd, tp->snd_cwnd_clamp); 767} 768 769/* Set slow start threshold and cwnd not falling to slow start */ 770void tcp_enter_cwr(struct sock *sk, const int set_ssthresh) 771{ 772 struct tcp_sock *tp = tcp_sk(sk); 773 const struct inet_connection_sock *icsk = inet_csk(sk); 774 775 tp->prior_ssthresh = 0; 776 tp->bytes_acked = 0; 777 if (icsk->icsk_ca_state < TCP_CA_CWR) { 778 tp->undo_marker = 0; 779 if (set_ssthresh) 780 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 781 tp->snd_cwnd = min(tp->snd_cwnd, 782 tcp_packets_in_flight(tp) + 1U); 783 tp->snd_cwnd_cnt = 0; 784 tp->high_seq = tp->snd_nxt; 785 tp->snd_cwnd_stamp = tcp_time_stamp; 786 TCP_ECN_queue_cwr(tp); 787 788 tcp_set_ca_state(sk, TCP_CA_CWR); 789 } 790} 791 792/* Initialize metrics on socket. */ 793 794static void tcp_init_metrics(struct sock *sk) 795{ 796 struct tcp_sock *tp = tcp_sk(sk); 797 struct dst_entry *dst = __sk_dst_get(sk); 798 799 if (dst == NULL) 800 goto reset; 801 802 dst_confirm(dst); 803 804 if (dst_metric_locked(dst, RTAX_CWND)) 805 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); 806 if (dst_metric(dst, RTAX_SSTHRESH)) { 807 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); 808 if (tp->snd_ssthresh > tp->snd_cwnd_clamp) 809 tp->snd_ssthresh = tp->snd_cwnd_clamp; 810 } 811 if (dst_metric(dst, RTAX_REORDERING) && 812 tp->reordering != dst_metric(dst, RTAX_REORDERING)) { 813 tp->rx_opt.sack_ok &= ~2; 814 tp->reordering = dst_metric(dst, RTAX_REORDERING); 815 } 816 817 if (dst_metric(dst, RTAX_RTT) == 0) 818 goto reset; 819 820 if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3)) 821 goto reset; 822 823 /* Initial rtt is determined from SYN,SYN-ACK. 824 * The segment is small and rtt may appear much 825 * less than real one. Use per-dst memory 826 * to make it more realistic. 827 * 828 * A bit of theory. RTT is time passed after "normal" sized packet 829 * is sent until it is ACKed. In normal circumstances sending small 830 * packets force peer to delay ACKs and calculation is correct too. 831 * The algorithm is adaptive and, provided we follow specs, it 832 * NEVER underestimate RTT. BUT! If peer tries to make some clever 833 * tricks sort of "quick acks" for time long enough to decrease RTT 834 * to low value, and then abruptly stops to do it and starts to delay 835 * ACKs, wait for troubles. 836 */ 837 if (dst_metric(dst, RTAX_RTT) > tp->srtt) { 838 tp->srtt = dst_metric(dst, RTAX_RTT); 839 tp->rtt_seq = tp->snd_nxt; 840 } 841 if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) { 842 tp->mdev = dst_metric(dst, RTAX_RTTVAR); 843 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); 844 } 845 tcp_set_rto(sk); 846 tcp_bound_rto(sk); 847 if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp) 848 goto reset; 849 tp->snd_cwnd = tcp_init_cwnd(tp, dst); 850 tp->snd_cwnd_stamp = tcp_time_stamp; 851 return; 852 853reset: 854 /* Play conservative. If timestamps are not 855 * supported, TCP will fail to recalculate correct 856 * rtt, if initial rto is too small. FORGET ALL AND RESET! 857 */ 858 if (!tp->rx_opt.saw_tstamp && tp->srtt) { 859 tp->srtt = 0; 860 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT; 861 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; 862 } 863} 864 865static void tcp_update_reordering(struct sock *sk, const int metric, 866 const int ts) 867{ 868 struct tcp_sock *tp = tcp_sk(sk); 869 if (metric > tp->reordering) { 870 tp->reordering = min(TCP_MAX_REORDERING, metric); 871 872 /* This exciting event is worth to be remembered. 8) */ 873 if (ts) 874 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER); 875 else if (IsReno(tp)) 876 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER); 877 else if (IsFack(tp)) 878 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER); 879 else 880 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER); 881#if FASTRETRANS_DEBUG > 1 882 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", 883 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, 884 tp->reordering, 885 tp->fackets_out, 886 tp->sacked_out, 887 tp->undo_marker ? tp->undo_retrans : 0); 888#endif 889 /* Disable FACK yet. */ 890 tp->rx_opt.sack_ok &= ~2; 891 } 892} 893 894/* This procedure tags the retransmission queue when SACKs arrive. 895 * 896 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). 897 * Packets in queue with these bits set are counted in variables 898 * sacked_out, retrans_out and lost_out, correspondingly. 899 * 900 * Valid combinations are: 901 * Tag InFlight Description 902 * 0 1 - orig segment is in flight. 903 * S 0 - nothing flies, orig reached receiver. 904 * L 0 - nothing flies, orig lost by net. 905 * R 2 - both orig and retransmit are in flight. 906 * L|R 1 - orig is lost, retransmit is in flight. 907 * S|R 1 - orig reached receiver, retrans is still in flight. 908 * (L|S|R is logically valid, it could occur when L|R is sacked, 909 * but it is equivalent to plain S and code short-curcuits it to S. 910 * L|S is logically invalid, it would mean -1 packet in flight 8)) 911 * 912 * These 6 states form finite state machine, controlled by the following events: 913 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) 914 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) 915 * 3. Loss detection event of one of three flavors: 916 * A. Scoreboard estimator decided the packet is lost. 917 * A'. Reno "three dupacks" marks head of queue lost. 918 * A''. Its FACK modfication, head until snd.fack is lost. 919 * B. SACK arrives sacking data transmitted after never retransmitted 920 * hole was sent out. 921 * C. SACK arrives sacking SND.NXT at the moment, when the 922 * segment was retransmitted. 923 * 4. D-SACK added new rule: D-SACK changes any tag to S. 924 * 925 * It is pleasant to note, that state diagram turns out to be commutative, 926 * so that we are allowed not to be bothered by order of our actions, 927 * when multiple events arrive simultaneously. (see the function below). 928 * 929 * Reordering detection. 930 * -------------------- 931 * Reordering metric is maximal distance, which a packet can be displaced 932 * in packet stream. With SACKs we can estimate it: 933 * 934 * 1. SACK fills old hole and the corresponding segment was not 935 * ever retransmitted -> reordering. Alas, we cannot use it 936 * when segment was retransmitted. 937 * 2. The last flaw is solved with D-SACK. D-SACK arrives 938 * for retransmitted and already SACKed segment -> reordering.. 939 * Both of these heuristics are not used in Loss state, when we cannot 940 * account for retransmits accurately. 941 */ 942static int 943tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una) 944{ 945 const struct inet_connection_sock *icsk = inet_csk(sk); 946 struct tcp_sock *tp = tcp_sk(sk); 947 unsigned char *ptr = (skb_transport_header(ack_skb) + 948 TCP_SKB_CB(ack_skb)->sacked); 949 struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2); 950 struct sk_buff *cached_skb; 951 int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3; 952 int reord = tp->packets_out; 953 int prior_fackets; 954 u32 lost_retrans = 0; 955 int flag = 0; 956 int found_dup_sack = 0; 957 int cached_fack_count; 958 int i; 959 int first_sack_index; 960 961 if (!tp->sacked_out) 962 tp->fackets_out = 0; 963 prior_fackets = tp->fackets_out; 964 965 /* Check for D-SACK. */ 966 if (before(ntohl(sp[0].start_seq), TCP_SKB_CB(ack_skb)->ack_seq)) { 967 found_dup_sack = 1; 968 tp->rx_opt.sack_ok |= 4; 969 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV); 970 } else if (num_sacks > 1 && 971 !after(ntohl(sp[0].end_seq), ntohl(sp[1].end_seq)) && 972 !before(ntohl(sp[0].start_seq), ntohl(sp[1].start_seq))) { 973 found_dup_sack = 1; 974 tp->rx_opt.sack_ok |= 4; 975 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV); 976 } 977 978 /* D-SACK for already forgotten data... 979 * Do dumb counting. */ 980 if (found_dup_sack && 981 !after(ntohl(sp[0].end_seq), prior_snd_una) && 982 after(ntohl(sp[0].end_seq), tp->undo_marker)) 983 tp->undo_retrans--; 984 985 /* Eliminate too old ACKs, but take into 986 * account more or less fresh ones, they can 987 * contain valid SACK info. 988 */ 989 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) 990 return 0; 991 992 /* SACK fastpath: 993 * if the only SACK change is the increase of the end_seq of 994 * the first block then only apply that SACK block 995 * and use retrans queue hinting otherwise slowpath */ 996 flag = 1; 997 for (i = 0; i < num_sacks; i++) { 998 __be32 start_seq = sp[i].start_seq; 999 __be32 end_seq = sp[i].end_seq; 1000 1001 if (i == 0) { 1002 if (tp->recv_sack_cache[i].start_seq != start_seq) 1003 flag = 0; 1004 } else { 1005 if ((tp->recv_sack_cache[i].start_seq != start_seq) || 1006 (tp->recv_sack_cache[i].end_seq != end_seq)) 1007 flag = 0; 1008 } 1009 tp->recv_sack_cache[i].start_seq = start_seq; 1010 tp->recv_sack_cache[i].end_seq = end_seq; 1011 } 1012 /* Clear the rest of the cache sack blocks so they won't match mistakenly. */ 1013 for (; i < ARRAY_SIZE(tp->recv_sack_cache); i++) { 1014 tp->recv_sack_cache[i].start_seq = 0; 1015 tp->recv_sack_cache[i].end_seq = 0; 1016 } 1017 1018 first_sack_index = 0; 1019 if (flag) 1020 num_sacks = 1; 1021 else { 1022 int j; 1023 tp->fastpath_skb_hint = NULL; 1024 1025 /* order SACK blocks to allow in order walk of the retrans queue */ 1026 for (i = num_sacks-1; i > 0; i--) { 1027 for (j = 0; j < i; j++){ 1028 if (after(ntohl(sp[j].start_seq), 1029 ntohl(sp[j+1].start_seq))){ 1030 struct tcp_sack_block_wire tmp; 1031 1032 tmp = sp[j]; 1033 sp[j] = sp[j+1]; 1034 sp[j+1] = tmp; 1035 1036 /* Track where the first SACK block goes to */ 1037 if (j == first_sack_index) 1038 first_sack_index = j+1; 1039 } 1040 1041 } 1042 } 1043 } 1044 1045 /* clear flag as used for different purpose in following code */ 1046 flag = 0; 1047 1048 /* Use SACK fastpath hint if valid */ 1049 cached_skb = tp->fastpath_skb_hint; 1050 cached_fack_count = tp->fastpath_cnt_hint; 1051 if (!cached_skb) { 1052 cached_skb = tcp_write_queue_head(sk); 1053 cached_fack_count = 0; 1054 } 1055 1056 for (i=0; i<num_sacks; i++, sp++) { 1057 struct sk_buff *skb; 1058 __u32 start_seq = ntohl(sp->start_seq); 1059 __u32 end_seq = ntohl(sp->end_seq); 1060 int fack_count; 1061 int dup_sack = (found_dup_sack && (i == first_sack_index)); 1062 1063 skb = cached_skb; 1064 fack_count = cached_fack_count; 1065 1066 /* Event "B" in the comment above. */ 1067 if (after(end_seq, tp->high_seq)) 1068 flag |= FLAG_DATA_LOST; 1069 1070 tcp_for_write_queue_from(skb, sk) { 1071 int in_sack, pcount; 1072 u8 sacked; 1073 1074 if (skb == tcp_send_head(sk)) 1075 break; 1076 1077 cached_skb = skb; 1078 cached_fack_count = fack_count; 1079 if (i == first_sack_index) { 1080 tp->fastpath_skb_hint = skb; 1081 tp->fastpath_cnt_hint = fack_count; 1082 } 1083 1084 /* The retransmission queue is always in order, so 1085 * we can short-circuit the walk early. 1086 */ 1087 if (!before(TCP_SKB_CB(skb)->seq, end_seq)) 1088 break; 1089 1090 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && 1091 !before(end_seq, TCP_SKB_CB(skb)->end_seq); 1092 1093 pcount = tcp_skb_pcount(skb); 1094 1095 if (pcount > 1 && !in_sack && 1096 after(TCP_SKB_CB(skb)->end_seq, start_seq)) { 1097 unsigned int pkt_len; 1098 1099 in_sack = !after(start_seq, 1100 TCP_SKB_CB(skb)->seq); 1101 1102 if (!in_sack) 1103 pkt_len = (start_seq - 1104 TCP_SKB_CB(skb)->seq); 1105 else 1106 pkt_len = (end_seq - 1107 TCP_SKB_CB(skb)->seq); 1108 if (tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size)) 1109 break; 1110 pcount = tcp_skb_pcount(skb); 1111 } 1112 1113 fack_count += pcount; 1114 1115 sacked = TCP_SKB_CB(skb)->sacked; 1116 1117 /* Account D-SACK for retransmitted packet. */ 1118 if ((dup_sack && in_sack) && 1119 (sacked & TCPCB_RETRANS) && 1120 after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) 1121 tp->undo_retrans--; 1122 1123 /* The frame is ACKed. */ 1124 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) { 1125 if (sacked&TCPCB_RETRANS) { 1126 if ((dup_sack && in_sack) && 1127 (sacked&TCPCB_SACKED_ACKED)) 1128 reord = min(fack_count, reord); 1129 } else { 1130 /* If it was in a hole, we detected reordering. */ 1131 if (fack_count < prior_fackets && 1132 !(sacked&TCPCB_SACKED_ACKED)) 1133 reord = min(fack_count, reord); 1134 } 1135 1136 /* Nothing to do; acked frame is about to be dropped. */ 1137 continue; 1138 } 1139 1140 if ((sacked&TCPCB_SACKED_RETRANS) && 1141 after(end_seq, TCP_SKB_CB(skb)->ack_seq) && 1142 (!lost_retrans || after(end_seq, lost_retrans))) 1143 lost_retrans = end_seq; 1144 1145 if (!in_sack) 1146 continue; 1147 1148 if (!(sacked&TCPCB_SACKED_ACKED)) { 1149 if (sacked & TCPCB_SACKED_RETRANS) { 1150 /* If the segment is not tagged as lost, 1151 * we do not clear RETRANS, believing 1152 * that retransmission is still in flight. 1153 */ 1154 if (sacked & TCPCB_LOST) { 1155 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); 1156 tp->lost_out -= tcp_skb_pcount(skb); 1157 tp->retrans_out -= tcp_skb_pcount(skb); 1158 1159 /* clear lost hint */ 1160 tp->retransmit_skb_hint = NULL; 1161 } 1162 } else { 1163 /* New sack for not retransmitted frame, 1164 * which was in hole. It is reordering. 1165 */ 1166 if (!(sacked & TCPCB_RETRANS) && 1167 fack_count < prior_fackets) 1168 reord = min(fack_count, reord); 1169 1170 if (sacked & TCPCB_LOST) { 1171 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 1172 tp->lost_out -= tcp_skb_pcount(skb); 1173 1174 /* clear lost hint */ 1175 tp->retransmit_skb_hint = NULL; 1176 } 1177 /* SACK enhanced F-RTO detection. 1178 * Set flag if and only if non-rexmitted 1179 * segments below frto_highmark are 1180 * SACKed (RFC4138; Appendix B). 1181 * Clearing correct due to in-order walk 1182 */ 1183 if (after(end_seq, tp->frto_highmark)) { 1184 flag &= ~FLAG_ONLY_ORIG_SACKED; 1185 } else { 1186 if (!(sacked & TCPCB_RETRANS)) 1187 flag |= FLAG_ONLY_ORIG_SACKED; 1188 } 1189 } 1190 1191 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED; 1192 flag |= FLAG_DATA_SACKED; 1193 tp->sacked_out += tcp_skb_pcount(skb); 1194 1195 if (fack_count > tp->fackets_out) 1196 tp->fackets_out = fack_count; 1197 } else { 1198 if (dup_sack && (sacked&TCPCB_RETRANS)) 1199 reord = min(fack_count, reord); 1200 } 1201 1202 /* D-SACK. We can detect redundant retransmission 1203 * in S|R and plain R frames and clear it. 1204 * undo_retrans is decreased above, L|R frames 1205 * are accounted above as well. 1206 */ 1207 if (dup_sack && 1208 (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) { 1209 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1210 tp->retrans_out -= tcp_skb_pcount(skb); 1211 tp->retransmit_skb_hint = NULL; 1212 } 1213 } 1214 } 1215 1216 /* Check for lost retransmit. This superb idea is 1217 * borrowed from "ratehalving". Event "C". 1218 * Later note: FACK people cheated me again 8), 1219 * we have to account for reordering! Ugly, 1220 * but should help. 1221 */ 1222 if (lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) { 1223 struct sk_buff *skb; 1224 1225 tcp_for_write_queue(skb, sk) { 1226 if (skb == tcp_send_head(sk)) 1227 break; 1228 if (after(TCP_SKB_CB(skb)->seq, lost_retrans)) 1229 break; 1230 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1231 continue; 1232 if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) && 1233 after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) && 1234 (IsFack(tp) || 1235 !before(lost_retrans, 1236 TCP_SKB_CB(skb)->ack_seq + tp->reordering * 1237 tp->mss_cache))) { 1238 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1239 tp->retrans_out -= tcp_skb_pcount(skb); 1240 1241 /* clear lost hint */ 1242 tp->retransmit_skb_hint = NULL; 1243 1244 if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) { 1245 tp->lost_out += tcp_skb_pcount(skb); 1246 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1247 flag |= FLAG_DATA_SACKED; 1248 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT); 1249 } 1250 } 1251 } 1252 } 1253 1254 tp->left_out = tp->sacked_out + tp->lost_out; 1255 1256 if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss && 1257 (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark))) 1258 tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0); 1259 1260#if FASTRETRANS_DEBUG > 0 1261 BUG_TRAP((int)tp->sacked_out >= 0); 1262 BUG_TRAP((int)tp->lost_out >= 0); 1263 BUG_TRAP((int)tp->retrans_out >= 0); 1264 BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0); 1265#endif 1266 return flag; 1267} 1268 1269/* F-RTO can only be used if TCP has never retransmitted anything other than 1270 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here) 1271 */ 1272int tcp_use_frto(struct sock *sk) 1273{ 1274 const struct tcp_sock *tp = tcp_sk(sk); 1275 struct sk_buff *skb; 1276 1277 if (!sysctl_tcp_frto) 1278 return 0; 1279 1280 if (IsSackFrto()) 1281 return 1; 1282 1283 /* Avoid expensive walking of rexmit queue if possible */ 1284 if (tp->retrans_out > 1) 1285 return 0; 1286 1287 skb = tcp_write_queue_head(sk); 1288 skb = tcp_write_queue_next(sk, skb); /* Skips head */ 1289 tcp_for_write_queue_from(skb, sk) { 1290 if (skb == tcp_send_head(sk)) 1291 break; 1292 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS) 1293 return 0; 1294 /* Short-circuit when first non-SACKed skb has been checked */ 1295 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) 1296 break; 1297 } 1298 return 1; 1299} 1300 1301/* RTO occurred, but do not yet enter Loss state. Instead, defer RTO 1302 * recovery a bit and use heuristics in tcp_process_frto() to detect if 1303 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to 1304 * keep retrans_out counting accurate (with SACK F-RTO, other than head 1305 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS 1306 * bits are handled if the Loss state is really to be entered (in 1307 * tcp_enter_frto_loss). 1308 * 1309 * Do like tcp_enter_loss() would; when RTO expires the second time it 1310 * does: 1311 * "Reduce ssthresh if it has not yet been made inside this window." 1312 */ 1313void tcp_enter_frto(struct sock *sk) 1314{ 1315 const struct inet_connection_sock *icsk = inet_csk(sk); 1316 struct tcp_sock *tp = tcp_sk(sk); 1317 struct sk_buff *skb; 1318 1319 if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) || 1320 tp->snd_una == tp->high_seq || 1321 ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) && 1322 !icsk->icsk_retransmits)) { 1323 tp->prior_ssthresh = tcp_current_ssthresh(sk); 1324 /* Our state is too optimistic in ssthresh() call because cwnd 1325 * is not reduced until tcp_enter_frto_loss() when previous FRTO 1326 * recovery has not yet completed. Pattern would be this: RTO, 1327 * Cumulative ACK, RTO (2xRTO for the same segment does not end 1328 * up here twice). 1329 * RFC4138 should be more specific on what to do, even though 1330 * RTO is quite unlikely to occur after the first Cumulative ACK 1331 * due to back-off and complexity of triggering events ... 1332 */ 1333 if (tp->frto_counter) { 1334 u32 stored_cwnd; 1335 stored_cwnd = tp->snd_cwnd; 1336 tp->snd_cwnd = 2; 1337 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 1338 tp->snd_cwnd = stored_cwnd; 1339 } else { 1340 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 1341 } 1342 /* ... in theory, cong.control module could do "any tricks" in 1343 * ssthresh(), which means that ca_state, lost bits and lost_out 1344 * counter would have to be faked before the call occurs. We 1345 * consider that too expensive, unlikely and hacky, so modules 1346 * using these in ssthresh() must deal these incompatibility 1347 * issues if they receives CA_EVENT_FRTO and frto_counter != 0 1348 */ 1349 tcp_ca_event(sk, CA_EVENT_FRTO); 1350 } 1351 1352 tp->undo_marker = tp->snd_una; 1353 tp->undo_retrans = 0; 1354 1355 skb = tcp_write_queue_head(sk); 1356 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 1357 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1358 tp->retrans_out -= tcp_skb_pcount(skb); 1359 } 1360 tcp_sync_left_out(tp); 1361 1362 /* Earlier loss recovery underway (see RFC4138; Appendix B). 1363 * The last condition is necessary at least in tp->frto_counter case. 1364 */ 1365 if (IsSackFrto() && (tp->frto_counter || 1366 ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) && 1367 after(tp->high_seq, tp->snd_una)) { 1368 tp->frto_highmark = tp->high_seq; 1369 } else { 1370 tp->frto_highmark = tp->snd_nxt; 1371 } 1372 tcp_set_ca_state(sk, TCP_CA_Disorder); 1373 tp->high_seq = tp->snd_nxt; 1374 tp->frto_counter = 1; 1375} 1376 1377/* Enter Loss state after F-RTO was applied. Dupack arrived after RTO, 1378 * which indicates that we should follow the traditional RTO recovery, 1379 * i.e. mark everything lost and do go-back-N retransmission. 1380 */ 1381static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag) 1382{ 1383 struct tcp_sock *tp = tcp_sk(sk); 1384 struct sk_buff *skb; 1385 int cnt = 0; 1386 1387 tp->sacked_out = 0; 1388 tp->lost_out = 0; 1389 tp->fackets_out = 0; 1390 tp->retrans_out = 0; 1391 1392 tcp_for_write_queue(skb, sk) { 1393 if (skb == tcp_send_head(sk)) 1394 break; 1395 cnt += tcp_skb_pcount(skb); 1396 /* 1397 * Count the retransmission made on RTO correctly (only when 1398 * waiting for the first ACK and did not get it)... 1399 */ 1400 if ((tp->frto_counter == 1) && !(flag&FLAG_DATA_ACKED)) { 1401 tp->retrans_out += tcp_skb_pcount(skb); 1402 /* ...enter this if branch just for the first segment */ 1403 flag |= FLAG_DATA_ACKED; 1404 } else { 1405 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); 1406 } 1407 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) { 1408 1409 /* Do not mark those segments lost that were 1410 * forward transmitted after RTO 1411 */ 1412 if (!after(TCP_SKB_CB(skb)->end_seq, 1413 tp->frto_highmark)) { 1414 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1415 tp->lost_out += tcp_skb_pcount(skb); 1416 } 1417 } else { 1418 tp->sacked_out += tcp_skb_pcount(skb); 1419 tp->fackets_out = cnt; 1420 } 1421 } 1422 tcp_sync_left_out(tp); 1423 1424 tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments; 1425 tp->snd_cwnd_cnt = 0; 1426 tp->snd_cwnd_stamp = tcp_time_stamp; 1427 tp->undo_marker = 0; 1428 tp->frto_counter = 0; 1429 1430 tp->reordering = min_t(unsigned int, tp->reordering, 1431 sysctl_tcp_reordering); 1432 tcp_set_ca_state(sk, TCP_CA_Loss); 1433 tp->high_seq = tp->frto_highmark; 1434 TCP_ECN_queue_cwr(tp); 1435 1436 clear_all_retrans_hints(tp); 1437} 1438 1439void tcp_clear_retrans(struct tcp_sock *tp) 1440{ 1441 tp->left_out = 0; 1442 tp->retrans_out = 0; 1443 1444 tp->fackets_out = 0; 1445 tp->sacked_out = 0; 1446 tp->lost_out = 0; 1447 1448 tp->undo_marker = 0; 1449 tp->undo_retrans = 0; 1450} 1451 1452/* Enter Loss state. If "how" is not zero, forget all SACK information 1453 * and reset tags completely, otherwise preserve SACKs. If receiver 1454 * dropped its ofo queue, we will know this due to reneging detection. 1455 */ 1456void tcp_enter_loss(struct sock *sk, int how) 1457{ 1458 const struct inet_connection_sock *icsk = inet_csk(sk); 1459 struct tcp_sock *tp = tcp_sk(sk); 1460 struct sk_buff *skb; 1461 int cnt = 0; 1462 1463 /* Reduce ssthresh if it has not yet been made inside this window. */ 1464 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq || 1465 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { 1466 tp->prior_ssthresh = tcp_current_ssthresh(sk); 1467 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 1468 tcp_ca_event(sk, CA_EVENT_LOSS); 1469 } 1470 tp->snd_cwnd = 1; 1471 tp->snd_cwnd_cnt = 0; 1472 tp->snd_cwnd_stamp = tcp_time_stamp; 1473 1474 tp->bytes_acked = 0; 1475 tcp_clear_retrans(tp); 1476 1477 /* Push undo marker, if it was plain RTO and nothing 1478 * was retransmitted. */ 1479 if (!how) 1480 tp->undo_marker = tp->snd_una; 1481 1482 tcp_for_write_queue(skb, sk) { 1483 if (skb == tcp_send_head(sk)) 1484 break; 1485 cnt += tcp_skb_pcount(skb); 1486 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS) 1487 tp->undo_marker = 0; 1488 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; 1489 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { 1490 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; 1491 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1492 tp->lost_out += tcp_skb_pcount(skb); 1493 } else { 1494 tp->sacked_out += tcp_skb_pcount(skb); 1495 tp->fackets_out = cnt; 1496 } 1497 } 1498 tcp_sync_left_out(tp); 1499 1500 tp->reordering = min_t(unsigned int, tp->reordering, 1501 sysctl_tcp_reordering); 1502 tcp_set_ca_state(sk, TCP_CA_Loss); 1503 tp->high_seq = tp->snd_nxt; 1504 TCP_ECN_queue_cwr(tp); 1505 /* Abort FRTO algorithm if one is in progress */ 1506 tp->frto_counter = 0; 1507 1508 clear_all_retrans_hints(tp); 1509} 1510 1511static int tcp_check_sack_reneging(struct sock *sk) 1512{ 1513 struct sk_buff *skb; 1514 1515 /* If ACK arrived pointing to a remembered SACK, 1516 * it means that our remembered SACKs do not reflect 1517 * real state of receiver i.e. 1518 * receiver _host_ is heavily congested (or buggy). 1519 * Do processing similar to RTO timeout. 1520 */ 1521 if ((skb = tcp_write_queue_head(sk)) != NULL && 1522 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 1523 struct inet_connection_sock *icsk = inet_csk(sk); 1524 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING); 1525 1526 tcp_enter_loss(sk, 1); 1527 icsk->icsk_retransmits++; 1528 tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); 1529 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 1530 icsk->icsk_rto, TCP_RTO_MAX); 1531 return 1; 1532 } 1533 return 0; 1534} 1535 1536static inline int tcp_fackets_out(struct tcp_sock *tp) 1537{ 1538 return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out; 1539} 1540 1541static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb) 1542{ 1543 return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto); 1544} 1545 1546static inline int tcp_head_timedout(struct sock *sk) 1547{ 1548 struct tcp_sock *tp = tcp_sk(sk); 1549 1550 return tp->packets_out && 1551 tcp_skb_timedout(sk, tcp_write_queue_head(sk)); 1552} 1553 1554/* Linux NewReno/SACK/FACK/ECN state machine. 1555 * -------------------------------------- 1556 * 1557 * "Open" Normal state, no dubious events, fast path. 1558 * "Disorder" In all the respects it is "Open", 1559 * but requires a bit more attention. It is entered when 1560 * we see some SACKs or dupacks. It is split of "Open" 1561 * mainly to move some processing from fast path to slow one. 1562 * "CWR" CWND was reduced due to some Congestion Notification event. 1563 * It can be ECN, ICMP source quench, local device congestion. 1564 * "Recovery" CWND was reduced, we are fast-retransmitting. 1565 * "Loss" CWND was reduced due to RTO timeout or SACK reneging. 1566 * 1567 * tcp_fastretrans_alert() is entered: 1568 * - each incoming ACK, if state is not "Open" 1569 * - when arrived ACK is unusual, namely: 1570 * * SACK 1571 * * Duplicate ACK. 1572 * * ECN ECE. 1573 * 1574 * Counting packets in flight is pretty simple. 1575 * 1576 * in_flight = packets_out - left_out + retrans_out 1577 * 1578 * packets_out is SND.NXT-SND.UNA counted in packets. 1579 * 1580 * retrans_out is number of retransmitted segments. 1581 * 1582 * left_out is number of segments left network, but not ACKed yet. 1583 * 1584 * left_out = sacked_out + lost_out 1585 * 1586 * sacked_out: Packets, which arrived to receiver out of order 1587 * and hence not ACKed. With SACKs this number is simply 1588 * amount of SACKed data. Even without SACKs 1589 * it is easy to give pretty reliable estimate of this number, 1590 * counting duplicate ACKs. 1591 * 1592 * lost_out: Packets lost by network. TCP has no explicit 1593 * "loss notification" feedback from network (for now). 1594 * It means that this number can be only _guessed_. 1595 * Actually, it is the heuristics to predict lossage that 1596 * distinguishes different algorithms. 1597 * 1598 * F.e. after RTO, when all the queue is considered as lost, 1599 * lost_out = packets_out and in_flight = retrans_out. 1600 * 1601 * Essentially, we have now two algorithms counting 1602 * lost packets. 1603 * 1604 * FACK: It is the simplest heuristics. As soon as we decided 1605 * that something is lost, we decide that _all_ not SACKed 1606 * packets until the most forward SACK are lost. I.e. 1607 * lost_out = fackets_out - sacked_out and left_out = fackets_out. 1608 * It is absolutely correct estimate, if network does not reorder 1609 * packets. And it loses any connection to reality when reordering 1610 * takes place. We use FACK by default until reordering 1611 * is suspected on the path to this destination. 1612 * 1613 * NewReno: when Recovery is entered, we assume that one segment 1614 * is lost (classic Reno). While we are in Recovery and 1615 * a partial ACK arrives, we assume that one more packet 1616 * is lost (NewReno). This heuristics are the same in NewReno 1617 * and SACK. 1618 * 1619 * Imagine, that's all! Forget about all this shamanism about CWND inflation 1620 * deflation etc. CWND is real congestion window, never inflated, changes 1621 * only according to classic VJ rules. 1622 * 1623 * Really tricky (and requiring careful tuning) part of algorithm 1624 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). 1625 * The first determines the moment _when_ we should reduce CWND and, 1626 * hence, slow down forward transmission. In fact, it determines the moment 1627 * when we decide that hole is caused by loss, rather than by a reorder. 1628 * 1629 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill 1630 * holes, caused by lost packets. 1631 * 1632 * And the most logically complicated part of algorithm is undo 1633 * heuristics. We detect false retransmits due to both too early 1634 * fast retransmit (reordering) and underestimated RTO, analyzing 1635 * timestamps and D-SACKs. When we detect that some segments were 1636 * retransmitted by mistake and CWND reduction was wrong, we undo 1637 * window reduction and abort recovery phase. This logic is hidden 1638 * inside several functions named tcp_try_undo_<something>. 1639 */ 1640 1641/* This function decides, when we should leave Disordered state 1642 * and enter Recovery phase, reducing congestion window. 1643 * 1644 * Main question: may we further continue forward transmission 1645 * with the same cwnd? 1646 */ 1647static int tcp_time_to_recover(struct sock *sk) 1648{ 1649 struct tcp_sock *tp = tcp_sk(sk); 1650 __u32 packets_out; 1651 1652 /* Do not perform any recovery during FRTO algorithm */ 1653 if (tp->frto_counter) 1654 return 0; 1655 1656 /* Trick#1: The loss is proven. */ 1657 if (tp->lost_out) 1658 return 1; 1659 1660 /* Not-A-Trick#2 : Classic rule... */ 1661 if (tcp_fackets_out(tp) > tp->reordering) 1662 return 1; 1663 1664 /* Trick#3 : when we use RFC2988 timer restart, fast 1665 * retransmit can be triggered by timeout of queue head. 1666 */ 1667 if (tcp_head_timedout(sk)) 1668 return 1; 1669 1670 /* Trick#4: It is still not OK... But will it be useful to delay 1671 * recovery more? 1672 */ 1673 packets_out = tp->packets_out; 1674 if (packets_out <= tp->reordering && 1675 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && 1676 !tcp_may_send_now(sk)) { 1677 /* We have nothing to send. This connection is limited 1678 * either by receiver window or by application. 1679 */ 1680 return 1; 1681 } 1682 1683 return 0; 1684} 1685 1686/* If we receive more dupacks than we expected counting segments 1687 * in assumption of absent reordering, interpret this as reordering. 1688 * The only another reason could be bug in receiver TCP. 1689 */ 1690static void tcp_check_reno_reordering(struct sock *sk, const int addend) 1691{ 1692 struct tcp_sock *tp = tcp_sk(sk); 1693 u32 holes; 1694 1695 holes = max(tp->lost_out, 1U); 1696 holes = min(holes, tp->packets_out); 1697 1698 if ((tp->sacked_out + holes) > tp->packets_out) { 1699 tp->sacked_out = tp->packets_out - holes; 1700 tcp_update_reordering(sk, tp->packets_out + addend, 0); 1701 } 1702} 1703 1704/* Emulate SACKs for SACKless connection: account for a new dupack. */ 1705 1706static void tcp_add_reno_sack(struct sock *sk) 1707{ 1708 struct tcp_sock *tp = tcp_sk(sk); 1709 tp->sacked_out++; 1710 tcp_check_reno_reordering(sk, 0); 1711 tcp_sync_left_out(tp); 1712} 1713 1714/* Account for ACK, ACKing some data in Reno Recovery phase. */ 1715 1716static void tcp_remove_reno_sacks(struct sock *sk, int acked) 1717{ 1718 struct tcp_sock *tp = tcp_sk(sk); 1719 1720 if (acked > 0) { 1721 /* One ACK acked hole. The rest eat duplicate ACKs. */ 1722 if (acked-1 >= tp->sacked_out) 1723 tp->sacked_out = 0; 1724 else 1725 tp->sacked_out -= acked-1; 1726 } 1727 tcp_check_reno_reordering(sk, acked); 1728 tcp_sync_left_out(tp); 1729} 1730 1731static inline void tcp_reset_reno_sack(struct tcp_sock *tp) 1732{ 1733 tp->sacked_out = 0; 1734 tp->left_out = tp->lost_out; 1735} 1736 1737/* Mark head of queue up as lost. */ 1738static void tcp_mark_head_lost(struct sock *sk, 1739 int packets, u32 high_seq) 1740{ 1741 struct tcp_sock *tp = tcp_sk(sk); 1742 struct sk_buff *skb; 1743 int cnt; 1744 1745 BUG_TRAP(packets <= tp->packets_out); 1746 if (tp->lost_skb_hint) { 1747 skb = tp->lost_skb_hint; 1748 cnt = tp->lost_cnt_hint; 1749 } else { 1750 skb = tcp_write_queue_head(sk); 1751 cnt = 0; 1752 } 1753 1754 tcp_for_write_queue_from(skb, sk) { 1755 if (skb == tcp_send_head(sk)) 1756 break; 1757 /* TODO: do this better */ 1758 /* this is not the most efficient way to do this... */ 1759 tp->lost_skb_hint = skb; 1760 tp->lost_cnt_hint = cnt; 1761 cnt += tcp_skb_pcount(skb); 1762 if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, high_seq)) 1763 break; 1764 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) { 1765 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1766 tp->lost_out += tcp_skb_pcount(skb); 1767 1768 /* clear xmit_retransmit_queue hints 1769 * if this is beyond hint */ 1770 if (tp->retransmit_skb_hint != NULL && 1771 before(TCP_SKB_CB(skb)->seq, 1772 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) 1773 tp->retransmit_skb_hint = NULL; 1774 1775 } 1776 } 1777 tcp_sync_left_out(tp); 1778} 1779 1780/* Account newly detected lost packet(s) */ 1781 1782static void tcp_update_scoreboard(struct sock *sk) 1783{ 1784 struct tcp_sock *tp = tcp_sk(sk); 1785 1786 if (IsFack(tp)) { 1787 int lost = tp->fackets_out - tp->reordering; 1788 if (lost <= 0) 1789 lost = 1; 1790 tcp_mark_head_lost(sk, lost, tp->high_seq); 1791 } else { 1792 tcp_mark_head_lost(sk, 1, tp->high_seq); 1793 } 1794 1795 /* New heuristics: it is possible only after we switched 1796 * to restart timer each time when something is ACKed. 1797 * Hence, we can detect timed out packets during fast 1798 * retransmit without falling to slow start. 1799 */ 1800 if (!IsReno(tp) && tcp_head_timedout(sk)) { 1801 struct sk_buff *skb; 1802 1803 skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint 1804 : tcp_write_queue_head(sk); 1805 1806 tcp_for_write_queue_from(skb, sk) { 1807 if (skb == tcp_send_head(sk)) 1808 break; 1809 if (!tcp_skb_timedout(sk, skb)) 1810 break; 1811 1812 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) { 1813 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1814 tp->lost_out += tcp_skb_pcount(skb); 1815 1816 /* clear xmit_retrans hint */ 1817 if (tp->retransmit_skb_hint && 1818 before(TCP_SKB_CB(skb)->seq, 1819 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) 1820 1821 tp->retransmit_skb_hint = NULL; 1822 } 1823 } 1824 1825 tp->scoreboard_skb_hint = skb; 1826 1827 tcp_sync_left_out(tp); 1828 } 1829} 1830 1831/* CWND moderation, preventing bursts due to too big ACKs 1832 * in dubious situations. 1833 */ 1834static inline void tcp_moderate_cwnd(struct tcp_sock *tp) 1835{ 1836 tp->snd_cwnd = min(tp->snd_cwnd, 1837 tcp_packets_in_flight(tp)+tcp_max_burst(tp)); 1838 tp->snd_cwnd_stamp = tcp_time_stamp; 1839} 1840 1841/* Lower bound on congestion window is slow start threshold 1842 * unless congestion avoidance choice decides to overide it. 1843 */ 1844static inline u32 tcp_cwnd_min(const struct sock *sk) 1845{ 1846 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; 1847 1848 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh; 1849} 1850 1851/* Decrease cwnd each second ack. */ 1852static void tcp_cwnd_down(struct sock *sk) 1853{ 1854 struct tcp_sock *tp = tcp_sk(sk); 1855 int decr = tp->snd_cwnd_cnt + 1; 1856 1857 tp->snd_cwnd_cnt = decr&1; 1858 decr >>= 1; 1859 1860 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk)) 1861 tp->snd_cwnd -= decr; 1862 1863 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1); 1864 tp->snd_cwnd_stamp = tcp_time_stamp; 1865} 1866 1867/* Nothing was retransmitted or returned timestamp is less 1868 * than timestamp of the first retransmission. 1869 */ 1870static inline int tcp_packet_delayed(struct tcp_sock *tp) 1871{ 1872 return !tp->retrans_stamp || 1873 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 1874 (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0); 1875} 1876 1877/* Undo procedures. */ 1878 1879#if FASTRETRANS_DEBUG > 1 1880static void DBGUNDO(struct sock *sk, const char *msg) 1881{ 1882 struct tcp_sock *tp = tcp_sk(sk); 1883 struct inet_sock *inet = inet_sk(sk); 1884 1885 printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n", 1886 msg, 1887 NIPQUAD(inet->daddr), ntohs(inet->dport), 1888 tp->snd_cwnd, tp->left_out, 1889 tp->snd_ssthresh, tp->prior_ssthresh, 1890 tp->packets_out); 1891} 1892#else 1893#define DBGUNDO(x...) do { } while (0) 1894#endif 1895 1896static void tcp_undo_cwr(struct sock *sk, const int undo) 1897{ 1898 struct tcp_sock *tp = tcp_sk(sk); 1899 1900 if (tp->prior_ssthresh) { 1901 const struct inet_connection_sock *icsk = inet_csk(sk); 1902 1903 if (icsk->icsk_ca_ops->undo_cwnd) 1904 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); 1905 else 1906 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1); 1907 1908 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) { 1909 tp->snd_ssthresh = tp->prior_ssthresh; 1910 TCP_ECN_withdraw_cwr(tp); 1911 } 1912 } else { 1913 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); 1914 } 1915 tcp_moderate_cwnd(tp); 1916 tp->snd_cwnd_stamp = tcp_time_stamp; 1917 1918 /* There is something screwy going on with the retrans hints after 1919 an undo */ 1920 clear_all_retrans_hints(tp); 1921} 1922 1923static inline int tcp_may_undo(struct tcp_sock *tp) 1924{ 1925 return tp->undo_marker && 1926 (!tp->undo_retrans || tcp_packet_delayed(tp)); 1927} 1928 1929/* People celebrate: "We love our President!" */ 1930static int tcp_try_undo_recovery(struct sock *sk) 1931{ 1932 struct tcp_sock *tp = tcp_sk(sk); 1933 1934 if (tcp_may_undo(tp)) { 1935 /* Happy end! We did not retransmit anything 1936 * or our original transmission succeeded. 1937 */ 1938 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); 1939 tcp_undo_cwr(sk, 1); 1940 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) 1941 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); 1942 else 1943 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO); 1944 tp->undo_marker = 0; 1945 } 1946 if (tp->snd_una == tp->high_seq && IsReno(tp)) { 1947 /* Hold old state until something *above* high_seq 1948 * is ACKed. For Reno it is MUST to prevent false 1949 * fast retransmits (RFC2582). SACK TCP is safe. */ 1950 tcp_moderate_cwnd(tp); 1951 return 1; 1952 } 1953 tcp_set_ca_state(sk, TCP_CA_Open); 1954 return 0; 1955} 1956 1957/* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ 1958static void tcp_try_undo_dsack(struct sock *sk) 1959{ 1960 struct tcp_sock *tp = tcp_sk(sk); 1961 1962 if (tp->undo_marker && !tp->undo_retrans) { 1963 DBGUNDO(sk, "D-SACK"); 1964 tcp_undo_cwr(sk, 1); 1965 tp->undo_marker = 0; 1966 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO); 1967 } 1968} 1969 1970/* Undo during fast recovery after partial ACK. */ 1971 1972static int tcp_try_undo_partial(struct sock *sk, int acked) 1973{ 1974 struct tcp_sock *tp = tcp_sk(sk); 1975 /* Partial ACK arrived. Force Hoe's retransmit. */ 1976 int failed = IsReno(tp) || tp->fackets_out>tp->reordering; 1977 1978 if (tcp_may_undo(tp)) { 1979 /* Plain luck! Hole if filled with delayed 1980 * packet, rather than with a retransmit. 1981 */ 1982 if (tp->retrans_out == 0) 1983 tp->retrans_stamp = 0; 1984 1985 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1); 1986 1987 DBGUNDO(sk, "Hoe"); 1988 tcp_undo_cwr(sk, 0); 1989 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO); 1990 1991 /* So... Do not make Hoe's retransmit yet. 1992 * If the first packet was delayed, the rest 1993 * ones are most probably delayed as well. 1994 */ 1995 failed = 0; 1996 } 1997 return failed; 1998} 1999 2000/* Undo during loss recovery after partial ACK. */ 2001static int tcp_try_undo_loss(struct sock *sk) 2002{ 2003 struct tcp_sock *tp = tcp_sk(sk); 2004 2005 if (tcp_may_undo(tp)) { 2006 struct sk_buff *skb; 2007 tcp_for_write_queue(skb, sk) { 2008 if (skb == tcp_send_head(sk)) 2009 break; 2010 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 2011 } 2012 2013 clear_all_retrans_hints(tp); 2014 2015 DBGUNDO(sk, "partial loss"); 2016 tp->lost_out = 0; 2017 tp->left_out = tp->sacked_out; 2018 tcp_undo_cwr(sk, 1); 2019 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); 2020 inet_csk(sk)->icsk_retransmits = 0; 2021 tp->undo_marker = 0; 2022 if (!IsReno(tp)) 2023 tcp_set_ca_state(sk, TCP_CA_Open); 2024 return 1; 2025 } 2026 return 0; 2027} 2028 2029static inline void tcp_complete_cwr(struct sock *sk) 2030{ 2031 struct tcp_sock *tp = tcp_sk(sk); 2032 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 2033 tp->snd_cwnd_stamp = tcp_time_stamp; 2034 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); 2035} 2036 2037static void tcp_try_to_open(struct sock *sk, int flag) 2038{ 2039 struct tcp_sock *tp = tcp_sk(sk); 2040 2041 tcp_sync_left_out(tp); 2042 2043 if (tp->retrans_out == 0) 2044 tp->retrans_stamp = 0; 2045 2046 if (flag&FLAG_ECE) 2047 tcp_enter_cwr(sk, 1); 2048 2049 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { 2050 int state = TCP_CA_Open; 2051 2052 if (tp->left_out || tp->retrans_out || tp->undo_marker) 2053 state = TCP_CA_Disorder; 2054 2055 if (inet_csk(sk)->icsk_ca_state != state) { 2056 tcp_set_ca_state(sk, state); 2057 tp->high_seq = tp->snd_nxt; 2058 } 2059 tcp_moderate_cwnd(tp); 2060 } else { 2061 tcp_cwnd_down(sk); 2062 } 2063} 2064 2065static void tcp_mtup_probe_failed(struct sock *sk) 2066{ 2067 struct inet_connection_sock *icsk = inet_csk(sk); 2068 2069 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; 2070 icsk->icsk_mtup.probe_size = 0; 2071} 2072 2073static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb) 2074{ 2075 struct tcp_sock *tp = tcp_sk(sk); 2076 struct inet_connection_sock *icsk = inet_csk(sk); 2077 2078 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2079 tp->snd_cwnd = tp->snd_cwnd * 2080 tcp_mss_to_mtu(sk, tp->mss_cache) / 2081 icsk->icsk_mtup.probe_size; 2082 tp->snd_cwnd_cnt = 0; 2083 tp->snd_cwnd_stamp = tcp_time_stamp; 2084 tp->rcv_ssthresh = tcp_current_ssthresh(sk); 2085 2086 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; 2087 icsk->icsk_mtup.probe_size = 0; 2088 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 2089} 2090 2091 2092/* Process an event, which can update packets-in-flight not trivially. 2093 * Main goal of this function is to calculate new estimate for left_out, 2094 * taking into account both packets sitting in receiver's buffer and 2095 * packets lost by network. 2096 * 2097 * Besides that it does CWND reduction, when packet loss is detected 2098 * and changes state of machine. 2099 * 2100 * It does _not_ decide what to send, it is made in function 2101 * tcp_xmit_retransmit_queue(). 2102 */ 2103static void 2104tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una, 2105 int prior_packets, int flag) 2106{ 2107 struct inet_connection_sock *icsk = inet_csk(sk); 2108 struct tcp_sock *tp = tcp_sk(sk); 2109 int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP)); 2110 2111 /* Some technical things: 2112 * 1. Reno does not count dupacks (sacked_out) automatically. */ 2113 if (!tp->packets_out) 2114 tp->sacked_out = 0; 2115 /* 2. SACK counts snd_fack in packets inaccurately. */ 2116 if (tp->sacked_out == 0) 2117 tp->fackets_out = 0; 2118 2119 /* Now state machine starts. 2120 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ 2121 if (flag&FLAG_ECE) 2122 tp->prior_ssthresh = 0; 2123 2124 /* B. In all the states check for reneging SACKs. */ 2125 if (tp->sacked_out && tcp_check_sack_reneging(sk)) 2126 return; 2127 2128 /* C. Process data loss notification, provided it is valid. */ 2129 if ((flag&FLAG_DATA_LOST) && 2130 before(tp->snd_una, tp->high_seq) && 2131 icsk->icsk_ca_state != TCP_CA_Open && 2132 tp->fackets_out > tp->reordering) { 2133 tcp_mark_head_lost(sk, tp->fackets_out-tp->reordering, tp->high_seq); 2134 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS); 2135 } 2136 2137 /* D. Synchronize left_out to current state. */ 2138 tcp_sync_left_out(tp); 2139 2140 /* E. Check state exit conditions. State can be terminated 2141 * when high_seq is ACKed. */ 2142 if (icsk->icsk_ca_state == TCP_CA_Open) { 2143 BUG_TRAP(tp->retrans_out == 0); 2144 tp->retrans_stamp = 0; 2145 } else if (!before(tp->snd_una, tp->high_seq)) { 2146 switch (icsk->icsk_ca_state) { 2147 case TCP_CA_Loss: 2148 icsk->icsk_retransmits = 0; 2149 if (tcp_try_undo_recovery(sk)) 2150 return; 2151 break; 2152 2153 case TCP_CA_CWR: 2154 /* CWR is to be held something *above* high_seq 2155 * is ACKed for CWR bit to reach receiver. */ 2156 if (tp->snd_una != tp->high_seq) { 2157 tcp_complete_cwr(sk); 2158 tcp_set_ca_state(sk, TCP_CA_Open); 2159 } 2160 break; 2161 2162 case TCP_CA_Disorder: 2163 tcp_try_undo_dsack(sk); 2164 if (!tp->undo_marker || 2165 /* For SACK case do not Open to allow to undo 2166 * catching for all duplicate ACKs. */ 2167 IsReno(tp) || tp->snd_una != tp->high_seq) { 2168 tp->undo_marker = 0; 2169 tcp_set_ca_state(sk, TCP_CA_Open); 2170 } 2171 break; 2172 2173 case TCP_CA_Recovery: 2174 if (IsReno(tp)) 2175 tcp_reset_reno_sack(tp); 2176 if (tcp_try_undo_recovery(sk)) 2177 return; 2178 tcp_complete_cwr(sk); 2179 break; 2180 } 2181 } 2182 2183 /* F. Process state. */ 2184 switch (icsk->icsk_ca_state) { 2185 case TCP_CA_Recovery: 2186 if (prior_snd_una == tp->snd_una) { 2187 if (IsReno(tp) && is_dupack) 2188 tcp_add_reno_sack(sk); 2189 } else { 2190 int acked = prior_packets - tp->packets_out; 2191 if (IsReno(tp)) 2192 tcp_remove_reno_sacks(sk, acked); 2193 is_dupack = tcp_try_undo_partial(sk, acked); 2194 } 2195 break; 2196 case TCP_CA_Loss: 2197 if (flag&FLAG_DATA_ACKED) 2198 icsk->icsk_retransmits = 0; 2199 if (!tcp_try_undo_loss(sk)) { 2200 tcp_moderate_cwnd(tp); 2201 tcp_xmit_retransmit_queue(sk); 2202 return; 2203 } 2204 if (icsk->icsk_ca_state != TCP_CA_Open) 2205 return; 2206 /* Loss is undone; fall through to processing in Open state. */ 2207 default: 2208 if (IsReno(tp)) { 2209 if (tp->snd_una != prior_snd_una) 2210 tcp_reset_reno_sack(tp); 2211 if (is_dupack) 2212 tcp_add_reno_sack(sk); 2213 } 2214 2215 if (icsk->icsk_ca_state == TCP_CA_Disorder) 2216 tcp_try_undo_dsack(sk); 2217 2218 if (!tcp_time_to_recover(sk)) { 2219 tcp_try_to_open(sk, flag); 2220 return; 2221 } 2222 2223 /* MTU probe failure: don't reduce cwnd */ 2224 if (icsk->icsk_ca_state < TCP_CA_CWR && 2225 icsk->icsk_mtup.probe_size && 2226 tp->snd_una == tp->mtu_probe.probe_seq_start) { 2227 tcp_mtup_probe_failed(sk); 2228 /* Restores the reduction we did in tcp_mtup_probe() */ 2229 tp->snd_cwnd++; 2230 tcp_simple_retransmit(sk); 2231 return; 2232 } 2233 2234 /* Otherwise enter Recovery state */ 2235 2236 if (IsReno(tp)) 2237 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY); 2238 else 2239 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY); 2240 2241 tp->high_seq = tp->snd_nxt; 2242 tp->prior_ssthresh = 0; 2243 tp->undo_marker = tp->snd_una; 2244 tp->undo_retrans = tp->retrans_out; 2245 2246 if (icsk->icsk_ca_state < TCP_CA_CWR) { 2247 if (!(flag&FLAG_ECE)) 2248 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2249 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2250 TCP_ECN_queue_cwr(tp); 2251 } 2252 2253 tp->bytes_acked = 0; 2254 tp->snd_cwnd_cnt = 0; 2255 tcp_set_ca_state(sk, TCP_CA_Recovery); 2256 } 2257 2258 if (is_dupack || tcp_head_timedout(sk)) 2259 tcp_update_scoreboard(sk); 2260 tcp_cwnd_down(sk); 2261 tcp_xmit_retransmit_queue(sk); 2262} 2263 2264/* Read draft-ietf-tcplw-high-performance before mucking 2265 * with this code. (Supersedes RFC1323) 2266 */ 2267static void tcp_ack_saw_tstamp(struct sock *sk, int flag) 2268{ 2269 /* RTTM Rule: A TSecr value received in a segment is used to 2270 * update the averaged RTT measurement only if the segment 2271 * acknowledges some new data, i.e., only if it advances the 2272 * left edge of the send window. 2273 * 2274 * See draft-ietf-tcplw-high-performance-00, section 3.3. 2275 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> 2276 * 2277 * Changed: reset backoff as soon as we see the first valid sample. 2278 * If we do not, we get strongly overestimated rto. With timestamps 2279 * samples are accepted even from very old segments: f.e., when rtt=1 2280 * increases to 8, we retransmit 5 times and after 8 seconds delayed 2281 * answer arrives rto becomes 120 seconds! If at least one of segments 2282 * in window is lost... Voila. --ANK (010210) 2283 */ 2284 struct tcp_sock *tp = tcp_sk(sk); 2285 const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr; 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 void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag) 2293{ 2294 /* We don't have a timestamp. Can only use 2295 * packets that are not retransmitted to determine 2296 * rtt estimates. Also, we must not reset the 2297 * backoff for rto until we get a non-retransmitted 2298 * packet. This allows us to deal with a situation 2299 * where the network delay has increased suddenly. 2300 * I.e. Karn's algorithm. (SIGCOMM '87, p5.) 2301 */ 2302 2303 if (flag & FLAG_RETRANS_DATA_ACKED) 2304 return; 2305 2306 tcp_rtt_estimator(sk, seq_rtt); 2307 tcp_set_rto(sk); 2308 inet_csk(sk)->icsk_backoff = 0; 2309 tcp_bound_rto(sk); 2310} 2311 2312static inline void tcp_ack_update_rtt(struct sock *sk, const int flag, 2313 const s32 seq_rtt) 2314{ 2315 const struct tcp_sock *tp = tcp_sk(sk); 2316 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ 2317 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) 2318 tcp_ack_saw_tstamp(sk, flag); 2319 else if (seq_rtt >= 0) 2320 tcp_ack_no_tstamp(sk, seq_rtt, flag); 2321} 2322 2323static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt, 2324 u32 in_flight, int good) 2325{ 2326 const struct inet_connection_sock *icsk = inet_csk(sk); 2327 icsk->icsk_ca_ops->cong_avoid(sk, ack, rtt, in_flight, good); 2328 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp; 2329} 2330 2331/* Restart timer after forward progress on connection. 2332 * RFC2988 recommends to restart timer to now+rto. 2333 */ 2334 2335static void tcp_ack_packets_out(struct sock *sk) 2336{ 2337 struct tcp_sock *tp = tcp_sk(sk); 2338 2339 if (!tp->packets_out) { 2340 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); 2341 } else { 2342 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 2343 } 2344} 2345 2346static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb, 2347 __u32 now, __s32 *seq_rtt) 2348{ 2349 struct tcp_sock *tp = tcp_sk(sk); 2350 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 2351 __u32 seq = tp->snd_una; 2352 __u32 packets_acked; 2353 int acked = 0; 2354 2355 /* If we get here, the whole TSO packet has not been 2356 * acked. 2357 */ 2358 BUG_ON(!after(scb->end_seq, seq)); 2359 2360 packets_acked = tcp_skb_pcount(skb); 2361 if (tcp_trim_head(sk, skb, seq - scb->seq)) 2362 return 0; 2363 packets_acked -= tcp_skb_pcount(skb); 2364 2365 if (packets_acked) { 2366 __u8 sacked = scb->sacked; 2367 2368 acked |= FLAG_DATA_ACKED; 2369 if (sacked) { 2370 if (sacked & TCPCB_RETRANS) { 2371 if (sacked & TCPCB_SACKED_RETRANS) 2372 tp->retrans_out -= packets_acked; 2373 acked |= FLAG_RETRANS_DATA_ACKED; 2374 *seq_rtt = -1; 2375 } else if (*seq_rtt < 0) 2376 *seq_rtt = now - scb->when; 2377 if (sacked & TCPCB_SACKED_ACKED) 2378 tp->sacked_out -= packets_acked; 2379 if (sacked & TCPCB_LOST) 2380 tp->lost_out -= packets_acked; 2381 if (sacked & TCPCB_URG) { 2382 if (tp->urg_mode && 2383 !before(seq, tp->snd_up)) 2384 tp->urg_mode = 0; 2385 } 2386 } else if (*seq_rtt < 0) 2387 *seq_rtt = now - scb->when; 2388 2389 if (tp->fackets_out) { 2390 __u32 dval = min(tp->fackets_out, packets_acked); 2391 tp->fackets_out -= dval; 2392 } 2393 tp->packets_out -= packets_acked; 2394 2395 BUG_ON(tcp_skb_pcount(skb) == 0); 2396 BUG_ON(!before(scb->seq, scb->end_seq)); 2397 } 2398 2399 return acked; 2400} 2401 2402/* Remove acknowledged frames from the retransmission queue. */ 2403static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p) 2404{ 2405 struct tcp_sock *tp = tcp_sk(sk); 2406 const struct inet_connection_sock *icsk = inet_csk(sk); 2407 struct sk_buff *skb; 2408 __u32 now = tcp_time_stamp; 2409 int acked = 0; 2410 int prior_packets = tp->packets_out; 2411 __s32 seq_rtt = -1; 2412 ktime_t last_ackt = net_invalid_timestamp(); 2413 2414 while ((skb = tcp_write_queue_head(sk)) && 2415 skb != tcp_send_head(sk)) { 2416 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 2417 __u8 sacked = scb->sacked; 2418 2419 /* If our packet is before the ack sequence we can 2420 * discard it as it's confirmed to have arrived at 2421 * the other end. 2422 */ 2423 if (after(scb->end_seq, tp->snd_una)) { 2424 if (tcp_skb_pcount(skb) > 1 && 2425 after(tp->snd_una, scb->seq)) 2426 acked |= tcp_tso_acked(sk, skb, 2427 now, &seq_rtt); 2428 break; 2429 } 2430 2431 /* Initial outgoing SYN's get put onto the write_queue 2432 * just like anything else we transmit. It is not 2433 * true data, and if we misinform our callers that 2434 * this ACK acks real data, we will erroneously exit 2435 * connection startup slow start one packet too 2436 * quickly. This is severely frowned upon behavior. 2437 */ 2438 if (!(scb->flags & TCPCB_FLAG_SYN)) { 2439 acked |= FLAG_DATA_ACKED; 2440 } else { 2441 acked |= FLAG_SYN_ACKED; 2442 tp->retrans_stamp = 0; 2443 } 2444 2445 /* MTU probing checks */ 2446 if (icsk->icsk_mtup.probe_size) { 2447 if (!after(tp->mtu_probe.probe_seq_end, TCP_SKB_CB(skb)->end_seq)) { 2448 tcp_mtup_probe_success(sk, skb); 2449 } 2450 } 2451 2452 if (sacked) { 2453 if (sacked & TCPCB_RETRANS) { 2454 if (sacked & TCPCB_SACKED_RETRANS) 2455 tp->retrans_out -= tcp_skb_pcount(skb); 2456 acked |= FLAG_RETRANS_DATA_ACKED; 2457 seq_rtt = -1; 2458 } else if (seq_rtt < 0) { 2459 seq_rtt = now - scb->when; 2460 last_ackt = skb->tstamp; 2461 } 2462 if (sacked & TCPCB_SACKED_ACKED) 2463 tp->sacked_out -= tcp_skb_pcount(skb); 2464 if (sacked & TCPCB_LOST) 2465 tp->lost_out -= tcp_skb_pcount(skb); 2466 if (sacked & TCPCB_URG) { 2467 if (tp->urg_mode && 2468 !before(scb->end_seq, tp->snd_up)) 2469 tp->urg_mode = 0; 2470 } 2471 } else if (seq_rtt < 0) { 2472 seq_rtt = now - scb->when; 2473 last_ackt = skb->tstamp; 2474 } 2475 tcp_dec_pcount_approx(&tp->fackets_out, skb); 2476 tcp_packets_out_dec(tp, skb); 2477 tcp_unlink_write_queue(skb, sk); 2478 sk_stream_free_skb(sk, skb); 2479 clear_all_retrans_hints(tp); 2480 } 2481 2482 if (acked&FLAG_ACKED) { 2483 u32 pkts_acked = prior_packets - tp->packets_out; 2484 const struct tcp_congestion_ops *ca_ops 2485 = inet_csk(sk)->icsk_ca_ops; 2486 2487 tcp_ack_update_rtt(sk, acked, seq_rtt); 2488 tcp_ack_packets_out(sk); 2489 2490 /* Is the ACK triggering packet unambiguous? */ 2491 if (acked & FLAG_RETRANS_DATA_ACKED) 2492 last_ackt = net_invalid_timestamp(); 2493 2494 if (ca_ops->pkts_acked) 2495 ca_ops->pkts_acked(sk, pkts_acked, last_ackt); 2496 } 2497 2498#if FASTRETRANS_DEBUG > 0 2499 BUG_TRAP((int)tp->sacked_out >= 0); 2500 BUG_TRAP((int)tp->lost_out >= 0); 2501 BUG_TRAP((int)tp->retrans_out >= 0); 2502 if (!tp->packets_out && tp->rx_opt.sack_ok) { 2503 const struct inet_connection_sock *icsk = inet_csk(sk); 2504 if (tp->lost_out) { 2505 printk(KERN_DEBUG "Leak l=%u %d\n", 2506 tp->lost_out, icsk->icsk_ca_state); 2507 tp->lost_out = 0; 2508 } 2509 if (tp->sacked_out) { 2510 printk(KERN_DEBUG "Leak s=%u %d\n", 2511 tp->sacked_out, icsk->icsk_ca_state); 2512 tp->sacked_out = 0; 2513 } 2514 if (tp->retrans_out) { 2515 printk(KERN_DEBUG "Leak r=%u %d\n", 2516 tp->retrans_out, icsk->icsk_ca_state); 2517 tp->retrans_out = 0; 2518 } 2519 } 2520#endif 2521 *seq_rtt_p = seq_rtt; 2522 return acked; 2523} 2524 2525static void tcp_ack_probe(struct sock *sk) 2526{ 2527 const struct tcp_sock *tp = tcp_sk(sk); 2528 struct inet_connection_sock *icsk = inet_csk(sk); 2529 2530 /* Was it a usable window open? */ 2531 2532 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, 2533 tp->snd_una + tp->snd_wnd)) { 2534 icsk->icsk_backoff = 0; 2535 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0); 2536 /* Socket must be waked up by subsequent tcp_data_snd_check(). 2537 * This function is not for random using! 2538 */ 2539 } else { 2540 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 2541 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), 2542 TCP_RTO_MAX); 2543 } 2544} 2545 2546static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag) 2547{ 2548 return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || 2549 inet_csk(sk)->icsk_ca_state != TCP_CA_Open); 2550} 2551 2552static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag) 2553{ 2554 const struct tcp_sock *tp = tcp_sk(sk); 2555 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) && 2556 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR)); 2557} 2558 2559/* Check that window update is acceptable. 2560 * The function assumes that snd_una<=ack<=snd_next. 2561 */ 2562static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack, 2563 const u32 ack_seq, const u32 nwin) 2564{ 2565 return (after(ack, tp->snd_una) || 2566 after(ack_seq, tp->snd_wl1) || 2567 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd)); 2568} 2569 2570/* Update our send window. 2571 * 2572 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 2573 * and in FreeBSD. NetBSD's one is even worse.) is wrong. 2574 */ 2575static int tcp_ack_update_window(struct sock *sk, struct sk_buff *skb, u32 ack, 2576 u32 ack_seq) 2577{ 2578 struct tcp_sock *tp = tcp_sk(sk); 2579 int flag = 0; 2580 u32 nwin = ntohs(tcp_hdr(skb)->window); 2581 2582 if (likely(!tcp_hdr(skb)->syn)) 2583 nwin <<= tp->rx_opt.snd_wscale; 2584 2585 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { 2586 flag |= FLAG_WIN_UPDATE; 2587 tcp_update_wl(tp, ack, ack_seq); 2588 2589 if (tp->snd_wnd != nwin) { 2590 tp->snd_wnd = nwin; 2591 2592 /* Note, it is the only place, where 2593 * fast path is recovered for sending TCP. 2594 */ 2595 tp->pred_flags = 0; 2596 tcp_fast_path_check(sk); 2597 2598 if (nwin > tp->max_window) { 2599 tp->max_window = nwin; 2600 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie); 2601 } 2602 } 2603 } 2604 2605 tp->snd_una = ack; 2606 2607 return flag; 2608} 2609 2610/* A very conservative spurious RTO response algorithm: reduce cwnd and 2611 * continue in congestion avoidance. 2612 */ 2613static void tcp_conservative_spur_to_response(struct tcp_sock *tp) 2614{ 2615 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 2616 tp->snd_cwnd_cnt = 0; 2617 TCP_ECN_queue_cwr(tp); 2618 tcp_moderate_cwnd(tp); 2619} 2620 2621/* A conservative spurious RTO response algorithm: reduce cwnd using 2622 * rate halving and continue in congestion avoidance. 2623 */ 2624static void tcp_ratehalving_spur_to_response(struct sock *sk) 2625{ 2626 tcp_enter_cwr(sk, 0); 2627} 2628 2629static void tcp_undo_spur_to_response(struct sock *sk, int flag) 2630{ 2631 if (flag&FLAG_ECE) 2632 tcp_ratehalving_spur_to_response(sk); 2633 else 2634 tcp_undo_cwr(sk, 1); 2635} 2636 2637/* F-RTO spurious RTO detection algorithm (RFC4138) 2638 * 2639 * F-RTO affects during two new ACKs following RTO (well, almost, see inline 2640 * comments). State (ACK number) is kept in frto_counter. When ACK advances 2641 * window (but not to or beyond highest sequence sent before RTO): 2642 * On First ACK, send two new segments out. 2643 * On Second ACK, RTO was likely spurious. Do spurious response (response 2644 * algorithm is not part of the F-RTO detection algorithm 2645 * given in RFC4138 but can be selected separately). 2646 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss 2647 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding 2648 * of Nagle, this is done using frto_counter states 2 and 3, when a new data 2649 * segment of any size sent during F-RTO, state 2 is upgraded to 3. 2650 * 2651 * Rationale: if the RTO was spurious, new ACKs should arrive from the 2652 * original window even after we transmit two new data segments. 2653 * 2654 * SACK version: 2655 * on first step, wait until first cumulative ACK arrives, then move to 2656 * the second step. In second step, the next ACK decides. 2657 * 2658 * F-RTO is implemented (mainly) in four functions: 2659 * - tcp_use_frto() is used to determine if TCP is can use F-RTO 2660 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is 2661 * called when tcp_use_frto() showed green light 2662 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm 2663 * - tcp_enter_frto_loss() is called if there is not enough evidence 2664 * to prove that the RTO is indeed spurious. It transfers the control 2665 * from F-RTO to the conventional RTO recovery 2666 */ 2667static int tcp_process_frto(struct sock *sk, u32 prior_snd_una, int flag) 2668{ 2669 struct tcp_sock *tp = tcp_sk(sk); 2670 2671 tcp_sync_left_out(tp); 2672 2673 /* Duplicate the behavior from Loss state (fastretrans_alert) */ 2674 if (flag&FLAG_DATA_ACKED) 2675 inet_csk(sk)->icsk_retransmits = 0; 2676 2677 if (!before(tp->snd_una, tp->frto_highmark)) { 2678 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag); 2679 return 1; 2680 } 2681 2682 if (!IsSackFrto() || IsReno(tp)) { 2683 /* RFC4138 shortcoming in step 2; should also have case c): 2684 * ACK isn't duplicate nor advances window, e.g., opposite dir 2685 * data, winupdate 2686 */ 2687 if ((tp->snd_una == prior_snd_una) && (flag&FLAG_NOT_DUP) && 2688 !(flag&FLAG_FORWARD_PROGRESS)) 2689 return 1; 2690 2691 if (!(flag&FLAG_DATA_ACKED)) { 2692 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3), 2693 flag); 2694 return 1; 2695 } 2696 } else { 2697 if (!(flag&FLAG_DATA_ACKED) && (tp->frto_counter == 1)) { 2698 /* Prevent sending of new data. */ 2699 tp->snd_cwnd = min(tp->snd_cwnd, 2700 tcp_packets_in_flight(tp)); 2701 return 1; 2702 } 2703 2704 if ((tp->frto_counter >= 2) && 2705 (!(flag&FLAG_FORWARD_PROGRESS) || 2706 ((flag&FLAG_DATA_SACKED) && !(flag&FLAG_ONLY_ORIG_SACKED)))) { 2707 /* RFC4138 shortcoming (see comment above) */ 2708 if (!(flag&FLAG_FORWARD_PROGRESS) && (flag&FLAG_NOT_DUP)) 2709 return 1; 2710 2711 tcp_enter_frto_loss(sk, 3, flag); 2712 return 1; 2713 } 2714 } 2715 2716 if (tp->frto_counter == 1) { 2717 /* Sending of the next skb must be allowed or no FRTO */ 2718 if (!tcp_send_head(sk) || 2719 after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, 2720 tp->snd_una + tp->snd_wnd)) { 2721 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), 2722 flag); 2723 return 1; 2724 } 2725 2726 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; 2727 tp->frto_counter = 2; 2728 return 1; 2729 } else { 2730 switch (sysctl_tcp_frto_response) { 2731 case 2: 2732 tcp_undo_spur_to_response(sk, flag); 2733 break; 2734 case 1: 2735 tcp_conservative_spur_to_response(tp); 2736 break; 2737 default: 2738 tcp_ratehalving_spur_to_response(sk); 2739 break; 2740 } 2741 tp->frto_counter = 0; 2742 } 2743 return 0; 2744} 2745 2746/* This routine deals with incoming acks, but not outgoing ones. */ 2747static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) 2748{ 2749 struct inet_connection_sock *icsk = inet_csk(sk); 2750 struct tcp_sock *tp = tcp_sk(sk); 2751 u32 prior_snd_una = tp->snd_una; 2752 u32 ack_seq = TCP_SKB_CB(skb)->seq; 2753 u32 ack = TCP_SKB_CB(skb)->ack_seq; 2754 u32 prior_in_flight; 2755 s32 seq_rtt; 2756 int prior_packets; 2757 int frto_cwnd = 0; 2758 2759 /* If the ack is newer than sent or older than previous acks 2760 * then we can probably ignore it. 2761 */ 2762 if (after(ack, tp->snd_nxt)) 2763 goto uninteresting_ack; 2764 2765 if (before(ack, prior_snd_una)) 2766 goto old_ack; 2767 2768 if (sysctl_tcp_abc) { 2769 if (icsk->icsk_ca_state < TCP_CA_CWR) 2770 tp->bytes_acked += ack - prior_snd_una; 2771 else if (icsk->icsk_ca_state == TCP_CA_Loss) 2772 /* we assume just one segment left network */ 2773 tp->bytes_acked += min(ack - prior_snd_una, tp->mss_cache); 2774 } 2775 2776 if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) { 2777 /* Window is constant, pure forward advance. 2778 * No more checks are required. 2779 * Note, we use the fact that SND.UNA>=SND.WL2. 2780 */ 2781 tcp_update_wl(tp, ack, ack_seq); 2782 tp->snd_una = ack; 2783 flag |= FLAG_WIN_UPDATE; 2784 2785 tcp_ca_event(sk, CA_EVENT_FAST_ACK); 2786 2787 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS); 2788 } else { 2789 if (ack_seq != TCP_SKB_CB(skb)->end_seq) 2790 flag |= FLAG_DATA; 2791 else 2792 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS); 2793 2794 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq); 2795 2796 if (TCP_SKB_CB(skb)->sacked) 2797 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); 2798 2799 if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) 2800 flag |= FLAG_ECE; 2801 2802 tcp_ca_event(sk, CA_EVENT_SLOW_ACK); 2803 } 2804 2805 /* We passed data and got it acked, remove any soft error 2806 * log. Something worked... 2807 */ 2808 sk->sk_err_soft = 0; 2809 tp->rcv_tstamp = tcp_time_stamp; 2810 prior_packets = tp->packets_out; 2811 if (!prior_packets) 2812 goto no_queue; 2813 2814 prior_in_flight = tcp_packets_in_flight(tp); 2815 2816 /* See if we can take anything off of the retransmit queue. */ 2817 flag |= tcp_clean_rtx_queue(sk, &seq_rtt); 2818 2819 if (tp->frto_counter) 2820 frto_cwnd = tcp_process_frto(sk, prior_snd_una, flag); 2821 2822 if (tcp_ack_is_dubious(sk, flag)) { 2823 /* Advance CWND, if state allows this. */ 2824 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd && 2825 tcp_may_raise_cwnd(sk, flag)) 2826 tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 0); 2827 tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag); 2828 } else { 2829 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd) 2830 tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1); 2831 } 2832 2833 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP)) 2834 dst_confirm(sk->sk_dst_cache); 2835 2836 return 1; 2837 2838no_queue: 2839 icsk->icsk_probes_out = 0; 2840 2841 /* If this ack opens up a zero window, clear backoff. It was 2842 * being used to time the probes, and is probably far higher than 2843 * it needs to be for normal retransmission. 2844 */ 2845 if (tcp_send_head(sk)) 2846 tcp_ack_probe(sk); 2847 return 1; 2848 2849old_ack: 2850 if (TCP_SKB_CB(skb)->sacked) 2851 tcp_sacktag_write_queue(sk, skb, prior_snd_una); 2852 2853uninteresting_ack: 2854 SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt); 2855 return 0; 2856} 2857 2858 2859/* Look for tcp options. Normally only called on SYN and SYNACK packets. 2860 * But, this can also be called on packets in the established flow when 2861 * the fast version below fails. 2862 */ 2863void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab) 2864{ 2865 unsigned char *ptr; 2866 struct tcphdr *th = tcp_hdr(skb); 2867 int length=(th->doff*4)-sizeof(struct tcphdr); 2868 2869 ptr = (unsigned char *)(th + 1); 2870 opt_rx->saw_tstamp = 0; 2871 2872 while (length > 0) { 2873 int opcode=*ptr++; 2874 int opsize; 2875 2876 switch (opcode) { 2877 case TCPOPT_EOL: 2878 return; 2879 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ 2880 length--; 2881 continue; 2882 default: 2883 opsize=*ptr++; 2884 if (opsize < 2) /* "silly options" */ 2885 return; 2886 if (opsize > length) 2887 return; /* don't parse partial options */ 2888 switch (opcode) { 2889 case TCPOPT_MSS: 2890 if (opsize==TCPOLEN_MSS && th->syn && !estab) { 2891 u16 in_mss = ntohs(get_unaligned((__be16 *)ptr)); 2892 if (in_mss) { 2893 if (opt_rx->user_mss && opt_rx->user_mss < in_mss) 2894 in_mss = opt_rx->user_mss; 2895 opt_rx->mss_clamp = in_mss; 2896 } 2897 } 2898 break; 2899 case TCPOPT_WINDOW: 2900 if (opsize==TCPOLEN_WINDOW && th->syn && !estab) 2901 if (sysctl_tcp_window_scaling) { 2902 __u8 snd_wscale = *(__u8 *) ptr; 2903 opt_rx->wscale_ok = 1; 2904 if (snd_wscale > 14) { 2905 if (net_ratelimit()) 2906 printk(KERN_INFO "tcp_parse_options: Illegal window " 2907 "scaling value %d >14 received.\n", 2908 snd_wscale); 2909 snd_wscale = 14; 2910 } 2911 opt_rx->snd_wscale = snd_wscale; 2912 } 2913 break; 2914 case TCPOPT_TIMESTAMP: 2915 if (opsize==TCPOLEN_TIMESTAMP) { 2916 if ((estab && opt_rx->tstamp_ok) || 2917 (!estab && sysctl_tcp_timestamps)) { 2918 opt_rx->saw_tstamp = 1; 2919 opt_rx->rcv_tsval = ntohl(get_unaligned((__be32 *)ptr)); 2920 opt_rx->rcv_tsecr = ntohl(get_unaligned((__be32 *)(ptr+4))); 2921 } 2922 } 2923 break; 2924 case TCPOPT_SACK_PERM: 2925 if (opsize==TCPOLEN_SACK_PERM && th->syn && !estab) { 2926 if (sysctl_tcp_sack) { 2927 opt_rx->sack_ok = 1; 2928 tcp_sack_reset(opt_rx); 2929 } 2930 } 2931 break; 2932 2933 case TCPOPT_SACK: 2934 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && 2935 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && 2936 opt_rx->sack_ok) { 2937 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; 2938 } 2939 break; 2940#ifdef CONFIG_TCP_MD5SIG 2941 case TCPOPT_MD5SIG: 2942 /* 2943 * The MD5 Hash has already been 2944 * checked (see tcp_v{4,6}_do_rcv()). 2945 */ 2946 break; 2947#endif 2948 } 2949 2950 ptr+=opsize-2; 2951 length-=opsize; 2952 } 2953 } 2954} 2955 2956/* Fast parse options. This hopes to only see timestamps. 2957 * If it is wrong it falls back on tcp_parse_options(). 2958 */ 2959static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th, 2960 struct tcp_sock *tp) 2961{ 2962 if (th->doff == sizeof(struct tcphdr)>>2) { 2963 tp->rx_opt.saw_tstamp = 0; 2964 return 0; 2965 } else if (tp->rx_opt.tstamp_ok && 2966 th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) { 2967 __be32 *ptr = (__be32 *)(th + 1); 2968 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) 2969 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { 2970 tp->rx_opt.saw_tstamp = 1; 2971 ++ptr; 2972 tp->rx_opt.rcv_tsval = ntohl(*ptr); 2973 ++ptr; 2974 tp->rx_opt.rcv_tsecr = ntohl(*ptr); 2975 return 1; 2976 } 2977 } 2978 tcp_parse_options(skb, &tp->rx_opt, 1); 2979 return 1; 2980} 2981 2982static inline void tcp_store_ts_recent(struct tcp_sock *tp) 2983{ 2984 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; 2985 tp->rx_opt.ts_recent_stamp = get_seconds(); 2986} 2987 2988static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) 2989{ 2990 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { 2991 2992 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 || 2993 get_seconds() >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS) 2994 tcp_store_ts_recent(tp); 2995 } 2996} 2997 2998/* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM 2999 * 3000 * It is not fatal. If this ACK does _not_ change critical state (seqs, window) 3001 * it can pass through stack. So, the following predicate verifies that 3002 * this segment is not used for anything but congestion avoidance or 3003 * fast retransmit. Moreover, we even are able to eliminate most of such 3004 * second order effects, if we apply some small "replay" window (~RTO) 3005 * to timestamp space. 3006 * 3007 * All these measures still do not guarantee that we reject wrapped ACKs 3008 * on networks with high bandwidth, when sequence space is recycled fastly, 3009 * but it guarantees that such events will be very rare and do not affect 3010 * connection seriously. This doesn't look nice, but alas, PAWS is really 3011 * buggy extension. 3012 * 3013 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC 3014 * states that events when retransmit arrives after original data are rare. 3015 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is 3016 * the biggest problem on large power networks even with minor reordering. 3017 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe 3018 * up to bandwidth of 18Gigabit/sec. 8) ] 3019 */ 3020 3021static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb) 3022{ 3023 struct tcp_sock *tp = tcp_sk(sk); 3024 struct tcphdr *th = tcp_hdr(skb); 3025 u32 seq = TCP_SKB_CB(skb)->seq; 3026 u32 ack = TCP_SKB_CB(skb)->ack_seq; 3027 3028 return (/* 1. Pure ACK with correct sequence number. */ 3029 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && 3030 3031 /* 2. ... and duplicate ACK. */ 3032 ack == tp->snd_una && 3033 3034 /* 3. ... and does not update window. */ 3035 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && 3036 3037 /* 4. ... and sits in replay window. */ 3038 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ); 3039} 3040 3041static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb) 3042{ 3043 const struct tcp_sock *tp = tcp_sk(sk); 3044 return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW && 3045 get_seconds() < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS && 3046 !tcp_disordered_ack(sk, skb)); 3047} 3048 3049/* Check segment sequence number for validity. 3050 * 3051 * Segment controls are considered valid, if the segment 3052 * fits to the window after truncation to the window. Acceptability 3053 * of data (and SYN, FIN, of course) is checked separately. 3054 * See tcp_data_queue(), for example. 3055 * 3056 * Also, controls (RST is main one) are accepted using RCV.WUP instead 3057 * of RCV.NXT. Peer still did not advance his SND.UNA when we 3058 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. 3059 * (borrowed from freebsd) 3060 */ 3061 3062static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq) 3063{ 3064 return !before(end_seq, tp->rcv_wup) && 3065 !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); 3066} 3067 3068/* When we get a reset we do this. */ 3069static void tcp_reset(struct sock *sk) 3070{ 3071 /* We want the right error as BSD sees it (and indeed as we do). */ 3072 switch (sk->sk_state) { 3073 case TCP_SYN_SENT: 3074 sk->sk_err = ECONNREFUSED; 3075 break; 3076 case TCP_CLOSE_WAIT: 3077 sk->sk_err = EPIPE; 3078 break; 3079 case TCP_CLOSE: 3080 return; 3081 default: 3082 sk->sk_err = ECONNRESET; 3083 } 3084 3085 if (!sock_flag(sk, SOCK_DEAD)) 3086 sk->sk_error_report(sk); 3087 3088 tcp_done(sk); 3089} 3090 3091/* 3092 * Process the FIN bit. This now behaves as it is supposed to work 3093 * and the FIN takes effect when it is validly part of sequence 3094 * space. Not before when we get holes. 3095 * 3096 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT 3097 * (and thence onto LAST-ACK and finally, CLOSE, we never enter 3098 * TIME-WAIT) 3099 * 3100 * If we are in FINWAIT-1, a received FIN indicates simultaneous 3101 * close and we go into CLOSING (and later onto TIME-WAIT) 3102 * 3103 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. 3104 */ 3105static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th) 3106{ 3107 struct tcp_sock *tp = tcp_sk(sk); 3108 3109 inet_csk_schedule_ack(sk); 3110 3111 sk->sk_shutdown |= RCV_SHUTDOWN; 3112 sock_set_flag(sk, SOCK_DONE); 3113 3114 switch (sk->sk_state) { 3115 case TCP_SYN_RECV: 3116 case TCP_ESTABLISHED: 3117 /* Move to CLOSE_WAIT */ 3118 tcp_set_state(sk, TCP_CLOSE_WAIT); 3119 inet_csk(sk)->icsk_ack.pingpong = 1; 3120 break; 3121 3122 case TCP_CLOSE_WAIT: 3123 case TCP_CLOSING: 3124 /* Received a retransmission of the FIN, do 3125 * nothing. 3126 */ 3127 break; 3128 case TCP_LAST_ACK: 3129 /* RFC793: Remain in the LAST-ACK state. */ 3130 break; 3131 3132 case TCP_FIN_WAIT1: 3133 /* This case occurs when a simultaneous close 3134 * happens, we must ack the received FIN and 3135 * enter the CLOSING state. 3136 */ 3137 tcp_send_ack(sk); 3138 tcp_set_state(sk, TCP_CLOSING); 3139 break; 3140 case TCP_FIN_WAIT2: 3141 /* Received a FIN -- send ACK and enter TIME_WAIT. */ 3142 tcp_send_ack(sk); 3143 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 3144 break; 3145 default: 3146 /* Only TCP_LISTEN and TCP_CLOSE are left, in these 3147 * cases we should never reach this piece of code. 3148 */ 3149 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n", 3150 __FUNCTION__, sk->sk_state); 3151 break; 3152 } 3153 3154 /* It _is_ possible, that we have something out-of-order _after_ FIN. 3155 * Probably, we should reset in this case. For now drop them. 3156 */ 3157 __skb_queue_purge(&tp->out_of_order_queue); 3158 if (tp->rx_opt.sack_ok) 3159 tcp_sack_reset(&tp->rx_opt); 3160 sk_stream_mem_reclaim(sk); 3161 3162 if (!sock_flag(sk, SOCK_DEAD)) { 3163 sk->sk_state_change(sk); 3164 3165 /* Do not send POLL_HUP for half duplex close. */ 3166 if (sk->sk_shutdown == SHUTDOWN_MASK || 3167 sk->sk_state == TCP_CLOSE) 3168 sk_wake_async(sk, 1, POLL_HUP); 3169 else 3170 sk_wake_async(sk, 1, POLL_IN); 3171 } 3172} 3173 3174static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq) 3175{ 3176 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { 3177 if (before(seq, sp->start_seq)) 3178 sp->start_seq = seq; 3179 if (after(end_seq, sp->end_seq)) 3180 sp->end_seq = end_seq; 3181 return 1; 3182 } 3183 return 0; 3184} 3185 3186static void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq) 3187{ 3188 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) { 3189 if (before(seq, tp->rcv_nxt)) 3190 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT); 3191 else 3192 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT); 3193 3194 tp->rx_opt.dsack = 1; 3195 tp->duplicate_sack[0].start_seq = seq; 3196 tp->duplicate_sack[0].end_seq = end_seq; 3197 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok); 3198 } 3199} 3200 3201static void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq) 3202{ 3203 if (!tp->rx_opt.dsack) 3204 tcp_dsack_set(tp, seq, end_seq); 3205 else 3206 tcp_sack_extend(tp->duplicate_sack, seq, end_seq); 3207} 3208 3209static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb) 3210{ 3211 struct tcp_sock *tp = tcp_sk(sk); 3212 3213 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 3214 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 3215 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); 3216 tcp_enter_quickack_mode(sk); 3217 3218 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) { 3219 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 3220 3221 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) 3222 end_seq = tp->rcv_nxt; 3223 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq); 3224 } 3225 } 3226 3227 tcp_send_ack(sk); 3228} 3229 3230/* These routines update the SACK block as out-of-order packets arrive or 3231 * in-order packets close up the sequence space. 3232 */ 3233static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) 3234{ 3235 int this_sack; 3236 struct tcp_sack_block *sp = &tp->selective_acks[0]; 3237 struct tcp_sack_block *swalk = sp+1; 3238 3239 /* See if the recent change to the first SACK eats into 3240 * or hits the sequence space of other SACK blocks, if so coalesce. 3241 */ 3242 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) { 3243 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { 3244 int i; 3245 3246 /* Zap SWALK, by moving every further SACK up by one slot. 3247 * Decrease num_sacks. 3248 */ 3249 tp->rx_opt.num_sacks--; 3250 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); 3251 for (i=this_sack; i < tp->rx_opt.num_sacks; i++) 3252 sp[i] = sp[i+1]; 3253 continue; 3254 } 3255 this_sack++, swalk++; 3256 } 3257} 3258 3259static inline void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2) 3260{ 3261 __u32 tmp; 3262 3263 tmp = sack1->start_seq; 3264 sack1->start_seq = sack2->start_seq; 3265 sack2->start_seq = tmp; 3266 3267 tmp = sack1->end_seq; 3268 sack1->end_seq = sack2->end_seq; 3269 sack2->end_seq = tmp; 3270} 3271 3272static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) 3273{ 3274 struct tcp_sock *tp = tcp_sk(sk); 3275 struct tcp_sack_block *sp = &tp->selective_acks[0]; 3276 int cur_sacks = tp->rx_opt.num_sacks; 3277 int this_sack; 3278 3279 if (!cur_sacks) 3280 goto new_sack; 3281 3282 for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) { 3283 if (tcp_sack_extend(sp, seq, end_seq)) { 3284 /* Rotate this_sack to the first one. */ 3285 for (; this_sack>0; this_sack--, sp--) 3286 tcp_sack_swap(sp, sp-1); 3287 if (cur_sacks > 1) 3288 tcp_sack_maybe_coalesce(tp); 3289 return; 3290 } 3291 } 3292 3293 /* Could not find an adjacent existing SACK, build a new one, 3294 * put it at the front, and shift everyone else down. We 3295 * always know there is at least one SACK present already here. 3296 * 3297 * If the sack array is full, forget about the last one. 3298 */ 3299 if (this_sack >= 4) { 3300 this_sack--; 3301 tp->rx_opt.num_sacks--; 3302 sp--; 3303 } 3304 for (; this_sack > 0; this_sack--, sp--) 3305 *sp = *(sp-1); 3306 3307new_sack: 3308 /* Build the new head SACK, and we're done. */ 3309 sp->start_seq = seq; 3310 sp->end_seq = end_seq; 3311 tp->rx_opt.num_sacks++; 3312 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); 3313} 3314 3315/* RCV.NXT advances, some SACKs should be eaten. */ 3316 3317static void tcp_sack_remove(struct tcp_sock *tp) 3318{ 3319 struct tcp_sack_block *sp = &tp->selective_acks[0]; 3320 int num_sacks = tp->rx_opt.num_sacks; 3321 int this_sack; 3322 3323 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ 3324 if (skb_queue_empty(&tp->out_of_order_queue)) { 3325 tp->rx_opt.num_sacks = 0; 3326 tp->rx_opt.eff_sacks = tp->rx_opt.dsack; 3327 return; 3328 } 3329 3330 for (this_sack = 0; this_sack < num_sacks; ) { 3331 /* Check if the start of the sack is covered by RCV.NXT. */ 3332 if (!before(tp->rcv_nxt, sp->start_seq)) { 3333 int i; 3334 3335 /* RCV.NXT must cover all the block! */ 3336 BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq)); 3337 3338 /* Zap this SACK, by moving forward any other SACKS. */ 3339 for (i=this_sack+1; i < num_sacks; i++) 3340 tp->selective_acks[i-1] = tp->selective_acks[i]; 3341 num_sacks--; 3342 continue; 3343 } 3344 this_sack++; 3345 sp++; 3346 } 3347 if (num_sacks != tp->rx_opt.num_sacks) { 3348 tp->rx_opt.num_sacks = num_sacks; 3349 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); 3350 } 3351} 3352 3353/* This one checks to see if we can put data from the 3354 * out_of_order queue into the receive_queue. 3355 */ 3356static void tcp_ofo_queue(struct sock *sk) 3357{ 3358 struct tcp_sock *tp = tcp_sk(sk); 3359 __u32 dsack_high = tp->rcv_nxt; 3360 struct sk_buff *skb; 3361 3362 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { 3363 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 3364 break; 3365 3366 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { 3367 __u32 dsack = dsack_high; 3368 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) 3369 dsack_high = TCP_SKB_CB(skb)->end_seq; 3370 tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack); 3371 } 3372 3373 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 3374 SOCK_DEBUG(sk, "ofo packet was already received \n"); 3375 __skb_unlink(skb, &tp->out_of_order_queue); 3376 __kfree_skb(skb); 3377 continue; 3378 } 3379 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", 3380 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 3381 TCP_SKB_CB(skb)->end_seq); 3382 3383 __skb_unlink(skb, &tp->out_of_order_queue); 3384 __skb_queue_tail(&sk->sk_receive_queue, skb); 3385 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 3386 if (tcp_hdr(skb)->fin) 3387 tcp_fin(skb, sk, tcp_hdr(skb)); 3388 } 3389} 3390 3391static int tcp_prune_queue(struct sock *sk); 3392 3393static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) 3394{ 3395 struct tcphdr *th = tcp_hdr(skb); 3396 struct tcp_sock *tp = tcp_sk(sk); 3397 int eaten = -1; 3398 3399 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) 3400 goto drop; 3401 3402 __skb_pull(skb, th->doff*4); 3403 3404 TCP_ECN_accept_cwr(tp, skb); 3405 3406 if (tp->rx_opt.dsack) { 3407 tp->rx_opt.dsack = 0; 3408 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks, 3409 4 - tp->rx_opt.tstamp_ok); 3410 } 3411 3412 /* Queue data for delivery to the user. 3413 * Packets in sequence go to the receive queue. 3414 * Out of sequence packets to the out_of_order_queue. 3415 */ 3416 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { 3417 if (tcp_receive_window(tp) == 0) 3418 goto out_of_window; 3419 3420 /* Ok. In sequence. In window. */ 3421 if (tp->ucopy.task == current && 3422 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && 3423 sock_owned_by_user(sk) && !tp->urg_data) { 3424 int chunk = min_t(unsigned int, skb->len, 3425 tp->ucopy.len); 3426 3427 __set_current_state(TASK_RUNNING); 3428 3429 local_bh_enable(); 3430 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { 3431 tp->ucopy.len -= chunk; 3432 tp->copied_seq += chunk; 3433 eaten = (chunk == skb->len && !th->fin); 3434 tcp_rcv_space_adjust(sk); 3435 } 3436 local_bh_disable(); 3437 } 3438 3439 if (eaten <= 0) { 3440queue_and_out: 3441 if (eaten < 0 && 3442 (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || 3443 !sk_stream_rmem_schedule(sk, skb))) { 3444 if (tcp_prune_queue(sk) < 0 || 3445 !sk_stream_rmem_schedule(sk, skb)) 3446 goto drop; 3447 } 3448 sk_stream_set_owner_r(skb, sk); 3449 __skb_queue_tail(&sk->sk_receive_queue, skb); 3450 } 3451 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 3452 if (skb->len) 3453 tcp_event_data_recv(sk, skb); 3454 if (th->fin) 3455 tcp_fin(skb, sk, th); 3456 3457 if (!skb_queue_empty(&tp->out_of_order_queue)) { 3458 tcp_ofo_queue(sk); 3459 3460 /* RFC2581. 4.2. SHOULD send immediate ACK, when 3461 * gap in queue is filled. 3462 */ 3463 if (skb_queue_empty(&tp->out_of_order_queue)) 3464 inet_csk(sk)->icsk_ack.pingpong = 0; 3465 } 3466 3467 if (tp->rx_opt.num_sacks) 3468 tcp_sack_remove(tp); 3469 3470 tcp_fast_path_check(sk); 3471 3472 if (eaten > 0) 3473 __kfree_skb(skb); 3474 else if (!sock_flag(sk, SOCK_DEAD)) 3475 sk->sk_data_ready(sk, 0); 3476 return; 3477 } 3478 3479 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 3480 /* A retransmit, 2nd most common case. Force an immediate ack. */ 3481 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); 3482 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 3483 3484out_of_window: 3485 tcp_enter_quickack_mode(sk); 3486 inet_csk_schedule_ack(sk); 3487drop: 3488 __kfree_skb(skb); 3489 return; 3490 } 3491 3492 /* Out of window. F.e. zero window probe. */ 3493 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) 3494 goto out_of_window; 3495 3496 tcp_enter_quickack_mode(sk); 3497 3498 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 3499 /* Partial packet, seq < rcv_next < end_seq */ 3500 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", 3501 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 3502 TCP_SKB_CB(skb)->end_seq); 3503 3504 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); 3505 3506 /* If window is closed, drop tail of packet. But after 3507 * remembering D-SACK for its head made in previous line. 3508 */ 3509 if (!tcp_receive_window(tp)) 3510 goto out_of_window; 3511 goto queue_and_out; 3512 } 3513 3514 TCP_ECN_check_ce(tp, skb); 3515 3516 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || 3517 !sk_stream_rmem_schedule(sk, skb)) { 3518 if (tcp_prune_queue(sk) < 0 || 3519 !sk_stream_rmem_schedule(sk, skb)) 3520 goto drop; 3521 } 3522 3523 /* Disable header prediction. */ 3524 tp->pred_flags = 0; 3525 inet_csk_schedule_ack(sk); 3526 3527 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", 3528 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 3529 3530 sk_stream_set_owner_r(skb, sk); 3531 3532 if (!skb_peek(&tp->out_of_order_queue)) { 3533 /* Initial out of order segment, build 1 SACK. */ 3534 if (tp->rx_opt.sack_ok) { 3535 tp->rx_opt.num_sacks = 1; 3536 tp->rx_opt.dsack = 0; 3537 tp->rx_opt.eff_sacks = 1; 3538 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; 3539 tp->selective_acks[0].end_seq = 3540 TCP_SKB_CB(skb)->end_seq; 3541 } 3542 __skb_queue_head(&tp->out_of_order_queue,skb); 3543 } else { 3544 struct sk_buff *skb1 = tp->out_of_order_queue.prev; 3545 u32 seq = TCP_SKB_CB(skb)->seq; 3546 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 3547 3548 if (seq == TCP_SKB_CB(skb1)->end_seq) { 3549 __skb_append(skb1, skb, &tp->out_of_order_queue); 3550 3551 if (!tp->rx_opt.num_sacks || 3552 tp->selective_acks[0].end_seq != seq) 3553 goto add_sack; 3554 3555 /* Common case: data arrive in order after hole. */ 3556 tp->selective_acks[0].end_seq = end_seq; 3557 return; 3558 } 3559 3560 /* Find place to insert this segment. */ 3561 do { 3562 if (!after(TCP_SKB_CB(skb1)->seq, seq)) 3563 break; 3564 } while ((skb1 = skb1->prev) != 3565 (struct sk_buff*)&tp->out_of_order_queue); 3566 3567 /* Do skb overlap to previous one? */ 3568 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue && 3569 before(seq, TCP_SKB_CB(skb1)->end_seq)) { 3570 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 3571 /* All the bits are present. Drop. */ 3572 __kfree_skb(skb); 3573 tcp_dsack_set(tp, seq, end_seq); 3574 goto add_sack; 3575 } 3576 if (after(seq, TCP_SKB_CB(skb1)->seq)) { 3577 /* Partial overlap. */ 3578 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq); 3579 } else { 3580 skb1 = skb1->prev; 3581 } 3582 } 3583 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue); 3584 3585 /* And clean segments covered by new one as whole. */ 3586 while ((skb1 = skb->next) != 3587 (struct sk_buff*)&tp->out_of_order_queue && 3588 after(end_seq, TCP_SKB_CB(skb1)->seq)) { 3589 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 3590 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq); 3591 break; 3592 } 3593 __skb_unlink(skb1, &tp->out_of_order_queue); 3594 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq); 3595 __kfree_skb(skb1); 3596 } 3597 3598add_sack: 3599 if (tp->rx_opt.sack_ok) 3600 tcp_sack_new_ofo_skb(sk, seq, end_seq); 3601 } 3602} 3603 3604/* Collapse contiguous sequence of skbs head..tail with 3605 * sequence numbers start..end. 3606 * Segments with FIN/SYN are not collapsed (only because this 3607 * simplifies code) 3608 */ 3609static void 3610tcp_collapse(struct sock *sk, struct sk_buff_head *list, 3611 struct sk_buff *head, struct sk_buff *tail, 3612 u32 start, u32 end) 3613{ 3614 struct sk_buff *skb; 3615 3616 /* First, check that queue is collapsible and find 3617 * the point where collapsing can be useful. */ 3618 for (skb = head; skb != tail; ) { 3619 /* No new bits? It is possible on ofo queue. */ 3620 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 3621 struct sk_buff *next = skb->next; 3622 __skb_unlink(skb, list); 3623 __kfree_skb(skb); 3624 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); 3625 skb = next; 3626 continue; 3627 } 3628 3629 /* The first skb to collapse is: 3630 * - not SYN/FIN and 3631 * - bloated or contains data before "start" or 3632 * overlaps to the next one. 3633 */ 3634 if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin && 3635 (tcp_win_from_space(skb->truesize) > skb->len || 3636 before(TCP_SKB_CB(skb)->seq, start) || 3637 (skb->next != tail && 3638 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq))) 3639 break; 3640 3641 /* Decided to skip this, advance start seq. */ 3642 start = TCP_SKB_CB(skb)->end_seq; 3643 skb = skb->next; 3644 } 3645 if (skb == tail || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin) 3646 return; 3647 3648 while (before(start, end)) { 3649 struct sk_buff *nskb; 3650 int header = skb_headroom(skb); 3651 int copy = SKB_MAX_ORDER(header, 0); 3652 3653 /* Too big header? This can happen with IPv6. */ 3654 if (copy < 0) 3655 return; 3656 if (end-start < copy) 3657 copy = end-start; 3658 nskb = alloc_skb(copy+header, GFP_ATOMIC); 3659 if (!nskb) 3660 return; 3661 3662 skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head); 3663 skb_set_network_header(nskb, (skb_network_header(skb) - 3664 skb->head)); 3665 skb_set_transport_header(nskb, (skb_transport_header(skb) - 3666 skb->head)); 3667 skb_reserve(nskb, header); 3668 memcpy(nskb->head, skb->head, header); 3669 memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); 3670 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; 3671 __skb_insert(nskb, skb->prev, skb, list); 3672 sk_stream_set_owner_r(nskb, sk); 3673 3674 /* Copy data, releasing collapsed skbs. */ 3675 while (copy > 0) { 3676 int offset = start - TCP_SKB_CB(skb)->seq; 3677 int size = TCP_SKB_CB(skb)->end_seq - start; 3678 3679 BUG_ON(offset < 0); 3680 if (size > 0) { 3681 size = min(copy, size); 3682 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) 3683 BUG(); 3684 TCP_SKB_CB(nskb)->end_seq += size; 3685 copy -= size; 3686 start += size; 3687 } 3688 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 3689 struct sk_buff *next = skb->next; 3690 __skb_unlink(skb, list); 3691 __kfree_skb(skb); 3692 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); 3693 skb = next; 3694 if (skb == tail || 3695 tcp_hdr(skb)->syn || 3696 tcp_hdr(skb)->fin) 3697 return; 3698 } 3699 } 3700 } 3701} 3702 3703/* Collapse ofo queue. Algorithm: select contiguous sequence of skbs 3704 * and tcp_collapse() them until all the queue is collapsed. 3705 */ 3706static void tcp_collapse_ofo_queue(struct sock *sk) 3707{ 3708 struct tcp_sock *tp = tcp_sk(sk); 3709 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); 3710 struct sk_buff *head; 3711 u32 start, end; 3712 3713 if (skb == NULL) 3714 return; 3715 3716 start = TCP_SKB_CB(skb)->seq; 3717 end = TCP_SKB_CB(skb)->end_seq; 3718 head = skb; 3719 3720 for (;;) { 3721 skb = skb->next; 3722 3723 /* Segment is terminated when we see gap or when 3724 * we are at the end of all the queue. */ 3725 if (skb == (struct sk_buff *)&tp->out_of_order_queue || 3726 after(TCP_SKB_CB(skb)->seq, end) || 3727 before(TCP_SKB_CB(skb)->end_seq, start)) { 3728 tcp_collapse(sk, &tp->out_of_order_queue, 3729 head, skb, start, end); 3730 head = skb; 3731 if (skb == (struct sk_buff *)&tp->out_of_order_queue) 3732 break; 3733 /* Start new segment */ 3734 start = TCP_SKB_CB(skb)->seq; 3735 end = TCP_SKB_CB(skb)->end_seq; 3736 } else { 3737 if (before(TCP_SKB_CB(skb)->seq, start)) 3738 start = TCP_SKB_CB(skb)->seq; 3739 if (after(TCP_SKB_CB(skb)->end_seq, end)) 3740 end = TCP_SKB_CB(skb)->end_seq; 3741 } 3742 } 3743} 3744 3745/* Reduce allocated memory if we can, trying to get 3746 * the socket within its memory limits again. 3747 * 3748 * Return less than zero if we should start dropping frames 3749 * until the socket owning process reads some of the data 3750 * to stabilize the situation. 3751 */ 3752static int tcp_prune_queue(struct sock *sk) 3753{ 3754 struct tcp_sock *tp = tcp_sk(sk); 3755 3756 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); 3757 3758 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED); 3759 3760 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) 3761 tcp_clamp_window(sk); 3762 else if (tcp_memory_pressure) 3763 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); 3764 3765 tcp_collapse_ofo_queue(sk); 3766 tcp_collapse(sk, &sk->sk_receive_queue, 3767 sk->sk_receive_queue.next, 3768 (struct sk_buff*)&sk->sk_receive_queue, 3769 tp->copied_seq, tp->rcv_nxt); 3770 sk_stream_mem_reclaim(sk); 3771 3772 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 3773 return 0; 3774 3775 /* Collapsing did not help, destructive actions follow. 3776 * This must not ever occur. */ 3777 3778 /* First, purge the out_of_order queue. */ 3779 if (!skb_queue_empty(&tp->out_of_order_queue)) { 3780 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED); 3781 __skb_queue_purge(&tp->out_of_order_queue); 3782 3783 /* Reset SACK state. A conforming SACK implementation will 3784 * do the same at a timeout based retransmit. When a connection 3785 * is in a sad state like this, we care only about integrity 3786 * of the connection not performance. 3787 */ 3788 if (tp->rx_opt.sack_ok) 3789 tcp_sack_reset(&tp->rx_opt); 3790 sk_stream_mem_reclaim(sk); 3791 } 3792 3793 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 3794 return 0; 3795 3796 /* If we are really being abused, tell the caller to silently 3797 * drop receive data on the floor. It will get retransmitted 3798 * and hopefully then we'll have sufficient space. 3799 */ 3800 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED); 3801 3802 /* Massive buffer overcommit. */ 3803 tp->pred_flags = 0; 3804 return -1; 3805} 3806 3807 3808/* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. 3809 * As additional protections, we do not touch cwnd in retransmission phases, 3810 * and if application hit its sndbuf limit recently. 3811 */ 3812void tcp_cwnd_application_limited(struct sock *sk) 3813{ 3814 struct tcp_sock *tp = tcp_sk(sk); 3815 3816 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && 3817 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { 3818 /* Limited by application or receiver window. */ 3819 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); 3820 u32 win_used = max(tp->snd_cwnd_used, init_win); 3821 if (win_used < tp->snd_cwnd) { 3822 tp->snd_ssthresh = tcp_current_ssthresh(sk); 3823 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; 3824 } 3825 tp->snd_cwnd_used = 0; 3826 } 3827 tp->snd_cwnd_stamp = tcp_time_stamp; 3828} 3829 3830static int tcp_should_expand_sndbuf(struct sock *sk) 3831{ 3832 struct tcp_sock *tp = tcp_sk(sk); 3833 3834 /* If the user specified a specific send buffer setting, do 3835 * not modify it. 3836 */ 3837 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) 3838 return 0; 3839 3840 /* If we are under global TCP memory pressure, do not expand. */ 3841 if (tcp_memory_pressure) 3842 return 0; 3843 3844 /* If we are under soft global TCP memory pressure, do not expand. */ 3845 if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0]) 3846 return 0; 3847 3848 /* If we filled the congestion window, do not expand. */ 3849 if (tp->packets_out >= tp->snd_cwnd) 3850 return 0; 3851 3852 return 1; 3853} 3854 3855/* When incoming ACK allowed to free some skb from write_queue, 3856 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket 3857 * on the exit from tcp input handler. 3858 * 3859 * PROBLEM: sndbuf expansion does not work well with largesend. 3860 */ 3861static void tcp_new_space(struct sock *sk) 3862{ 3863 struct tcp_sock *tp = tcp_sk(sk); 3864 3865 if (tcp_should_expand_sndbuf(sk)) { 3866 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + 3867 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff), 3868 demanded = max_t(unsigned int, tp->snd_cwnd, 3869 tp->reordering + 1); 3870 sndmem *= 2*demanded; 3871 if (sndmem > sk->sk_sndbuf) 3872 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); 3873 tp->snd_cwnd_stamp = tcp_time_stamp; 3874 } 3875 3876 sk->sk_write_space(sk); 3877} 3878 3879static void tcp_check_space(struct sock *sk) 3880{ 3881 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { 3882 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); 3883 if (sk->sk_socket && 3884 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) 3885 tcp_new_space(sk); 3886 } 3887} 3888 3889static inline void tcp_data_snd_check(struct sock *sk) 3890{ 3891 tcp_push_pending_frames(sk); 3892 tcp_check_space(sk); 3893} 3894 3895/* 3896 * Check if sending an ack is needed. 3897 */ 3898static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) 3899{ 3900 struct tcp_sock *tp = tcp_sk(sk); 3901 3902 /* More than one full frame received... */ 3903 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss 3904 /* ... and right edge of window advances far enough. 3905 * (tcp_recvmsg() will send ACK otherwise). Or... 3906 */ 3907 && __tcp_select_window(sk) >= tp->rcv_wnd) || 3908 /* We ACK each frame or... */ 3909 tcp_in_quickack_mode(sk) || 3910 /* We have out of order data. */ 3911 (ofo_possible && 3912 skb_peek(&tp->out_of_order_queue))) { 3913 /* Then ack it now */ 3914 tcp_send_ack(sk); 3915 } else { 3916 /* Else, send delayed ack. */ 3917 tcp_send_delayed_ack(sk); 3918 } 3919} 3920 3921static inline void tcp_ack_snd_check(struct sock *sk) 3922{ 3923 if (!inet_csk_ack_scheduled(sk)) { 3924 /* We sent a data segment already. */ 3925 return; 3926 } 3927 __tcp_ack_snd_check(sk, 1); 3928} 3929 3930/* 3931 * This routine is only called when we have urgent data 3932 * signaled. Its the 'slow' part of tcp_urg. It could be 3933 * moved inline now as tcp_urg is only called from one 3934 * place. We handle URGent data wrong. We have to - as 3935 * BSD still doesn't use the correction from RFC961. 3936 * For 1003.1g we should support a new option TCP_STDURG to permit 3937 * either form (or just set the sysctl tcp_stdurg). 3938 */ 3939 3940static void tcp_check_urg(struct sock * sk, struct tcphdr * th) 3941{ 3942 struct tcp_sock *tp = tcp_sk(sk); 3943 u32 ptr = ntohs(th->urg_ptr); 3944 3945 if (ptr && !sysctl_tcp_stdurg) 3946 ptr--; 3947 ptr += ntohl(th->seq); 3948 3949 /* Ignore urgent data that we've already seen and read. */ 3950 if (after(tp->copied_seq, ptr)) 3951 return; 3952 3953 /* Do not replay urg ptr. 3954 * 3955 * NOTE: interesting situation not covered by specs. 3956 * Misbehaving sender may send urg ptr, pointing to segment, 3957 * which we already have in ofo queue. We are not able to fetch 3958 * such data and will stay in TCP_URG_NOTYET until will be eaten 3959 * by recvmsg(). Seems, we are not obliged to handle such wicked 3960 * situations. But it is worth to think about possibility of some 3961 * DoSes using some hypothetical application level deadlock. 3962 */ 3963 if (before(ptr, tp->rcv_nxt)) 3964 return; 3965 3966 /* Do we already have a newer (or duplicate) urgent pointer? */ 3967 if (tp->urg_data && !after(ptr, tp->urg_seq)) 3968 return; 3969 3970 /* Tell the world about our new urgent pointer. */ 3971 sk_send_sigurg(sk); 3972 3973 /* We may be adding urgent data when the last byte read was 3974 * urgent. To do this requires some care. We cannot just ignore 3975 * tp->copied_seq since we would read the last urgent byte again 3976 * as data, nor can we alter copied_seq until this data arrives 3977 * or we break the semantics of SIOCATMARK (and thus sockatmark()) 3978 * 3979 * NOTE. Double Dutch. Rendering to plain English: author of comment 3980 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); 3981 * and expect that both A and B disappear from stream. This is _wrong_. 3982 * Though this happens in BSD with high probability, this is occasional. 3983 * Any application relying on this is buggy. Note also, that fix "works" 3984 * only in this artificial test. Insert some normal data between A and B and we will 3985 * decline of BSD again. Verdict: it is better to remove to trap 3986 * buggy users. 3987 */ 3988 if (tp->urg_seq == tp->copied_seq && tp->urg_data && 3989 !sock_flag(sk, SOCK_URGINLINE) && 3990 tp->copied_seq != tp->rcv_nxt) { 3991 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); 3992 tp->copied_seq++; 3993 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { 3994 __skb_unlink(skb, &sk->sk_receive_queue); 3995 __kfree_skb(skb); 3996 } 3997 } 3998 3999 tp->urg_data = TCP_URG_NOTYET; 4000 tp->urg_seq = ptr; 4001 4002 /* Disable header prediction. */ 4003 tp->pred_flags = 0; 4004} 4005 4006/* This is the 'fast' part of urgent handling. */ 4007static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th) 4008{ 4009 struct tcp_sock *tp = tcp_sk(sk); 4010 4011 /* Check if we get a new urgent pointer - normally not. */ 4012 if (th->urg) 4013 tcp_check_urg(sk,th); 4014 4015 /* Do we wait for any urgent data? - normally not... */ 4016 if (tp->urg_data == TCP_URG_NOTYET) { 4017 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - 4018 th->syn; 4019 4020 /* Is the urgent pointer pointing into this packet? */ 4021 if (ptr < skb->len) { 4022 u8 tmp; 4023 if (skb_copy_bits(skb, ptr, &tmp, 1)) 4024 BUG(); 4025 tp->urg_data = TCP_URG_VALID | tmp; 4026 if (!sock_flag(sk, SOCK_DEAD)) 4027 sk->sk_data_ready(sk, 0); 4028 } 4029 } 4030} 4031 4032static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) 4033{ 4034 struct tcp_sock *tp = tcp_sk(sk); 4035 int chunk = skb->len - hlen; 4036 int err; 4037 4038 local_bh_enable(); 4039 if (skb_csum_unnecessary(skb)) 4040 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); 4041 else 4042 err = skb_copy_and_csum_datagram_iovec(skb, hlen, 4043 tp->ucopy.iov); 4044 4045 if (!err) { 4046 tp->ucopy.len -= chunk; 4047 tp->copied_seq += chunk; 4048 tcp_rcv_space_adjust(sk); 4049 } 4050 4051 local_bh_disable(); 4052 return err; 4053} 4054 4055static __sum16 __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) 4056{ 4057 __sum16 result; 4058 4059 if (sock_owned_by_user(sk)) { 4060 local_bh_enable(); 4061 result = __tcp_checksum_complete(skb); 4062 local_bh_disable(); 4063 } else { 4064 result = __tcp_checksum_complete(skb); 4065 } 4066 return result; 4067} 4068 4069static inline int tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) 4070{ 4071 return !skb_csum_unnecessary(skb) && 4072 __tcp_checksum_complete_user(sk, skb); 4073} 4074 4075#ifdef CONFIG_NET_DMA 4076static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, int hlen) 4077{ 4078 struct tcp_sock *tp = tcp_sk(sk); 4079 int chunk = skb->len - hlen; 4080 int dma_cookie; 4081 int copied_early = 0; 4082 4083 if (tp->ucopy.wakeup) 4084 return 0; 4085 4086 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list) 4087 tp->ucopy.dma_chan = get_softnet_dma(); 4088 4089 if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) { 4090 4091 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan, 4092 skb, hlen, tp->ucopy.iov, chunk, tp->ucopy.pinned_list); 4093 4094 if (dma_cookie < 0) 4095 goto out; 4096 4097 tp->ucopy.dma_cookie = dma_cookie; 4098 copied_early = 1; 4099 4100 tp->ucopy.len -= chunk; 4101 tp->copied_seq += chunk; 4102 tcp_rcv_space_adjust(sk); 4103 4104 if ((tp->ucopy.len == 0) || 4105 (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) || 4106 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) { 4107 tp->ucopy.wakeup = 1; 4108 sk->sk_data_ready(sk, 0); 4109 } 4110 } else if (chunk > 0) { 4111 tp->ucopy.wakeup = 1; 4112 sk->sk_data_ready(sk, 0); 4113 } 4114out: 4115 return copied_early; 4116} 4117#endif /* CONFIG_NET_DMA */ 4118 4119/* 4120 * TCP receive function for the ESTABLISHED state. 4121 * 4122 * It is split into a fast path and a slow path. The fast path is 4123 * disabled when: 4124 * - A zero window was announced from us - zero window probing 4125 * is only handled properly in the slow path. 4126 * - Out of order segments arrived. 4127 * - Urgent data is expected. 4128 * - There is no buffer space left 4129 * - Unexpected TCP flags/window values/header lengths are received 4130 * (detected by checking the TCP header against pred_flags) 4131 * - Data is sent in both directions. Fast path only supports pure senders 4132 * or pure receivers (this means either the sequence number or the ack 4133 * value must stay constant) 4134 * - Unexpected TCP option. 4135 * 4136 * When these conditions are not satisfied it drops into a standard 4137 * receive procedure patterned after RFC793 to handle all cases. 4138 * The first three cases are guaranteed by proper pred_flags setting, 4139 * the rest is checked inline. Fast processing is turned on in 4140 * tcp_data_queue when everything is OK. 4141 */ 4142int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, 4143 struct tcphdr *th, unsigned len) 4144{ 4145 struct tcp_sock *tp = tcp_sk(sk); 4146 4147 /* 4148 * Header prediction. 4149 * The code loosely follows the one in the famous 4150 * "30 instruction TCP receive" Van Jacobson mail. 4151 * 4152 * Van's trick is to deposit buffers into socket queue 4153 * on a device interrupt, to call tcp_recv function 4154 * on the receive process context and checksum and copy 4155 * the buffer to user space. smart... 4156 * 4157 * Our current scheme is not silly either but we take the 4158 * extra cost of the net_bh soft interrupt processing... 4159 * We do checksum and copy also but from device to kernel. 4160 */ 4161 4162 tp->rx_opt.saw_tstamp = 0; 4163 4164 /* pred_flags is 0xS?10 << 16 + snd_wnd 4165 * if header_prediction is to be made 4166 * 'S' will always be tp->tcp_header_len >> 2 4167 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to 4168 * turn it off (when there are holes in the receive 4169 * space for instance) 4170 * PSH flag is ignored. 4171 */ 4172 4173 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && 4174 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { 4175 int tcp_header_len = tp->tcp_header_len; 4176 4177 /* Timestamp header prediction: tcp_header_len 4178 * is automatically equal to th->doff*4 due to pred_flags 4179 * match. 4180 */ 4181 4182 /* Check timestamp */ 4183 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { 4184 __be32 *ptr = (__be32 *)(th + 1); 4185 4186 /* No? Slow path! */ 4187 if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) 4188 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) 4189 goto slow_path; 4190 4191 tp->rx_opt.saw_tstamp = 1; 4192 ++ptr; 4193 tp->rx_opt.rcv_tsval = ntohl(*ptr); 4194 ++ptr; 4195 tp->rx_opt.rcv_tsecr = ntohl(*ptr); 4196 4197 /* If PAWS failed, check it more carefully in slow path */ 4198 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) 4199 goto slow_path; 4200 4201 /* DO NOT update ts_recent here, if checksum fails 4202 * and timestamp was corrupted part, it will result 4203 * in a hung connection since we will drop all 4204 * future packets due to the PAWS test. 4205 */ 4206 } 4207 4208 if (len <= tcp_header_len) { 4209 /* Bulk data transfer: sender */ 4210 if (len == tcp_header_len) { 4211 /* Predicted packet is in window by definition. 4212 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 4213 * Hence, check seq<=rcv_wup reduces to: 4214 */ 4215 if (tcp_header_len == 4216 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 4217 tp->rcv_nxt == tp->rcv_wup) 4218 tcp_store_ts_recent(tp); 4219 4220 /* We know that such packets are checksummed 4221 * on entry. 4222 */ 4223 tcp_ack(sk, skb, 0); 4224 __kfree_skb(skb); 4225 tcp_data_snd_check(sk); 4226 return 0; 4227 } else { /* Header too small */ 4228 TCP_INC_STATS_BH(TCP_MIB_INERRS); 4229 goto discard; 4230 } 4231 } else { 4232 int eaten = 0; 4233 int copied_early = 0; 4234 4235 if (tp->copied_seq == tp->rcv_nxt && 4236 len - tcp_header_len <= tp->ucopy.len) { 4237#ifdef CONFIG_NET_DMA 4238 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) { 4239 copied_early = 1; 4240 eaten = 1; 4241 } 4242#endif 4243 if (tp->ucopy.task == current && sock_owned_by_user(sk) && !copied_early) { 4244 __set_current_state(TASK_RUNNING); 4245 4246 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) 4247 eaten = 1; 4248 } 4249 if (eaten) { 4250 /* Predicted packet is in window by definition. 4251 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 4252 * Hence, check seq<=rcv_wup reduces to: 4253 */ 4254 if (tcp_header_len == 4255 (sizeof(struct tcphdr) + 4256 TCPOLEN_TSTAMP_ALIGNED) && 4257 tp->rcv_nxt == tp->rcv_wup) 4258 tcp_store_ts_recent(tp); 4259 4260 tcp_rcv_rtt_measure_ts(sk, skb); 4261 4262 __skb_pull(skb, tcp_header_len); 4263 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4264 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER); 4265 } 4266 if (copied_early) 4267 tcp_cleanup_rbuf(sk, skb->len); 4268 } 4269 if (!eaten) { 4270 if (tcp_checksum_complete_user(sk, skb)) 4271 goto csum_error; 4272 4273 /* Predicted packet is in window by definition. 4274 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 4275 * Hence, check seq<=rcv_wup reduces to: 4276 */ 4277 if (tcp_header_len == 4278 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 4279 tp->rcv_nxt == tp->rcv_wup) 4280 tcp_store_ts_recent(tp); 4281 4282 tcp_rcv_rtt_measure_ts(sk, skb); 4283 4284 if ((int)skb->truesize > sk->sk_forward_alloc) 4285 goto step5; 4286 4287 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS); 4288 4289 /* Bulk data transfer: receiver */ 4290 __skb_pull(skb,tcp_header_len); 4291 __skb_queue_tail(&sk->sk_receive_queue, skb); 4292 sk_stream_set_owner_r(skb, sk); 4293 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4294 } 4295 4296 tcp_event_data_recv(sk, skb); 4297 4298 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { 4299 /* Well, only one small jumplet in fast path... */ 4300 tcp_ack(sk, skb, FLAG_DATA); 4301 tcp_data_snd_check(sk); 4302 if (!inet_csk_ack_scheduled(sk)) 4303 goto no_ack; 4304 } 4305 4306 __tcp_ack_snd_check(sk, 0); 4307no_ack: 4308#ifdef CONFIG_NET_DMA 4309 if (copied_early) 4310 __skb_queue_tail(&sk->sk_async_wait_queue, skb); 4311 else 4312#endif 4313 if (eaten) 4314 __kfree_skb(skb); 4315 else 4316 sk->sk_data_ready(sk, 0); 4317 return 0; 4318 } 4319 } 4320 4321slow_path: 4322 if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb)) 4323 goto csum_error; 4324 4325 /* 4326 * RFC1323: H1. Apply PAWS check first. 4327 */ 4328 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && 4329 tcp_paws_discard(sk, skb)) { 4330 if (!th->rst) { 4331 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); 4332 tcp_send_dupack(sk, skb); 4333 goto discard; 4334 } 4335 /* Resets are accepted even if PAWS failed. 4336 4337 ts_recent update must be made after we are sure 4338 that the packet is in window. 4339 */ 4340 } 4341 4342 /* 4343 * Standard slow path. 4344 */ 4345 4346 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { 4347 /* RFC793, page 37: "In all states except SYN-SENT, all reset 4348 * (RST) segments are validated by checking their SEQ-fields." 4349 * And page 69: "If an incoming segment is not acceptable, 4350 * an acknowledgment should be sent in reply (unless the RST bit 4351 * is set, if so drop the segment and return)". 4352 */ 4353 if (!th->rst) 4354 tcp_send_dupack(sk, skb); 4355 goto discard; 4356 } 4357 4358 if (th->rst) { 4359 tcp_reset(sk); 4360 goto discard; 4361 } 4362 4363 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 4364 4365 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4366 TCP_INC_STATS_BH(TCP_MIB_INERRS); 4367 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); 4368 tcp_reset(sk); 4369 return 1; 4370 } 4371 4372step5: 4373 if (th->ack) 4374 tcp_ack(sk, skb, FLAG_SLOWPATH); 4375 4376 tcp_rcv_rtt_measure_ts(sk, skb); 4377 4378 /* Process urgent data. */ 4379 tcp_urg(sk, skb, th); 4380 4381 /* step 7: process the segment text */ 4382 tcp_data_queue(sk, skb); 4383 4384 tcp_data_snd_check(sk); 4385 tcp_ack_snd_check(sk); 4386 return 0; 4387 4388csum_error: 4389 TCP_INC_STATS_BH(TCP_MIB_INERRS); 4390 4391discard: 4392 __kfree_skb(skb); 4393 return 0; 4394} 4395 4396static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 4397 struct tcphdr *th, unsigned len) 4398{ 4399 struct tcp_sock *tp = tcp_sk(sk); 4400 struct inet_connection_sock *icsk = inet_csk(sk); 4401 int saved_clamp = tp->rx_opt.mss_clamp; 4402 4403 tcp_parse_options(skb, &tp->rx_opt, 0); 4404 4405 if (th->ack) { 4406 /* rfc793: 4407 * "If the state is SYN-SENT then 4408 * first check the ACK bit 4409 * If the ACK bit is set 4410 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send 4411 * a reset (unless the RST bit is set, if so drop 4412 * the segment and return)" 4413 * 4414 * We do not send data with SYN, so that RFC-correct 4415 * test reduces to: 4416 */ 4417 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt) 4418 goto reset_and_undo; 4419 4420 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 4421 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, 4422 tcp_time_stamp)) { 4423 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED); 4424 goto reset_and_undo; 4425 } 4426 4427 /* Now ACK is acceptable. 4428 * 4429 * "If the RST bit is set 4430 * If the ACK was acceptable then signal the user "error: 4431 * connection reset", drop the segment, enter CLOSED state, 4432 * delete TCB, and return." 4433 */ 4434 4435 if (th->rst) { 4436 tcp_reset(sk); 4437 goto discard; 4438 } 4439 4440 /* rfc793: 4441 * "fifth, if neither of the SYN or RST bits is set then 4442 * drop the segment and return." 4443 * 4444 * See note below! 4445 * --ANK(990513) 4446 */ 4447 if (!th->syn) 4448 goto discard_and_undo; 4449 4450 /* rfc793: 4451 * "If the SYN bit is on ... 4452 * are acceptable then ... 4453 * (our SYN has been ACKed), change the connection 4454 * state to ESTABLISHED..." 4455 */ 4456 4457 TCP_ECN_rcv_synack(tp, th); 4458 4459 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 4460 tcp_ack(sk, skb, FLAG_SLOWPATH); 4461 4462 /* Ok.. it's good. Set up sequence numbers and 4463 * move to established. 4464 */ 4465 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 4466 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 4467 4468 /* RFC1323: The window in SYN & SYN/ACK segments is 4469 * never scaled. 4470 */ 4471 tp->snd_wnd = ntohs(th->window); 4472 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq); 4473 4474 if (!tp->rx_opt.wscale_ok) { 4475 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; 4476 tp->window_clamp = min(tp->window_clamp, 65535U); 4477 } 4478 4479 if (tp->rx_opt.saw_tstamp) { 4480 tp->rx_opt.tstamp_ok = 1; 4481 tp->tcp_header_len = 4482 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 4483 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 4484 tcp_store_ts_recent(tp); 4485 } else { 4486 tp->tcp_header_len = sizeof(struct tcphdr); 4487 } 4488 4489 if (tp->rx_opt.sack_ok && sysctl_tcp_fack) 4490 tp->rx_opt.sack_ok |= 2; 4491 4492 tcp_mtup_init(sk); 4493 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 4494 tcp_initialize_rcv_mss(sk); 4495 4496 /* Remember, tcp_poll() does not lock socket! 4497 * Change state from SYN-SENT only after copied_seq 4498 * is initialized. */ 4499 tp->copied_seq = tp->rcv_nxt; 4500 smp_mb(); 4501 tcp_set_state(sk, TCP_ESTABLISHED); 4502 4503 security_inet_conn_established(sk, skb); 4504 4505 /* Make sure socket is routed, for correct metrics. */ 4506 icsk->icsk_af_ops->rebuild_header(sk); 4507 4508 tcp_init_metrics(sk); 4509 4510 tcp_init_congestion_control(sk); 4511 4512 /* Prevent spurious tcp_cwnd_restart() on first data 4513 * packet. 4514 */ 4515 tp->lsndtime = tcp_time_stamp; 4516 4517 tcp_init_buffer_space(sk); 4518 4519 if (sock_flag(sk, SOCK_KEEPOPEN)) 4520 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); 4521 4522 if (!tp->rx_opt.snd_wscale) 4523 __tcp_fast_path_on(tp, tp->snd_wnd); 4524 else 4525 tp->pred_flags = 0; 4526 4527 if (!sock_flag(sk, SOCK_DEAD)) { 4528 sk->sk_state_change(sk); 4529 sk_wake_async(sk, 0, POLL_OUT); 4530 } 4531 4532 if (sk->sk_write_pending || 4533 icsk->icsk_accept_queue.rskq_defer_accept || 4534 icsk->icsk_ack.pingpong) { 4535 /* Save one ACK. Data will be ready after 4536 * several ticks, if write_pending is set. 4537 * 4538 * It may be deleted, but with this feature tcpdumps 4539 * look so _wonderfully_ clever, that I was not able 4540 * to stand against the temptation 8) --ANK 4541 */ 4542 inet_csk_schedule_ack(sk); 4543 icsk->icsk_ack.lrcvtime = tcp_time_stamp; 4544 icsk->icsk_ack.ato = TCP_ATO_MIN; 4545 tcp_incr_quickack(sk); 4546 tcp_enter_quickack_mode(sk); 4547 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 4548 TCP_DELACK_MAX, TCP_RTO_MAX); 4549 4550discard: 4551 __kfree_skb(skb); 4552 return 0; 4553 } else { 4554 tcp_send_ack(sk); 4555 } 4556 return -1; 4557 } 4558 4559 /* No ACK in the segment */ 4560 4561 if (th->rst) { 4562 /* rfc793: 4563 * "If the RST bit is set 4564 * 4565 * Otherwise (no ACK) drop the segment and return." 4566 */ 4567 4568 goto discard_and_undo; 4569 } 4570 4571 /* PAWS check. */ 4572 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0)) 4573 goto discard_and_undo; 4574 4575 if (th->syn) { 4576 /* We see SYN without ACK. It is attempt of 4577 * simultaneous connect with crossed SYNs. 4578 * Particularly, it can be connect to self. 4579 */ 4580 tcp_set_state(sk, TCP_SYN_RECV); 4581 4582 if (tp->rx_opt.saw_tstamp) { 4583 tp->rx_opt.tstamp_ok = 1; 4584 tcp_store_ts_recent(tp); 4585 tp->tcp_header_len = 4586 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 4587 } else { 4588 tp->tcp_header_len = sizeof(struct tcphdr); 4589 } 4590 4591 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 4592 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 4593 4594 /* RFC1323: The window in SYN & SYN/ACK segments is 4595 * never scaled. 4596 */ 4597 tp->snd_wnd = ntohs(th->window); 4598 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 4599 tp->max_window = tp->snd_wnd; 4600 4601 TCP_ECN_rcv_syn(tp, th); 4602 4603 tcp_mtup_init(sk); 4604 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 4605 tcp_initialize_rcv_mss(sk); 4606 4607 4608 tcp_send_synack(sk); 4609 goto discard; 4610 } 4611 /* "fifth, if neither of the SYN or RST bits is set then 4612 * drop the segment and return." 4613 */ 4614 4615discard_and_undo: 4616 tcp_clear_options(&tp->rx_opt); 4617 tp->rx_opt.mss_clamp = saved_clamp; 4618 goto discard; 4619 4620reset_and_undo: 4621 tcp_clear_options(&tp->rx_opt); 4622 tp->rx_opt.mss_clamp = saved_clamp; 4623 return 1; 4624} 4625 4626 4627/* 4628 * This function implements the receiving procedure of RFC 793 for 4629 * all states except ESTABLISHED and TIME_WAIT. 4630 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be 4631 * address independent. 4632 */ 4633 4634int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, 4635 struct tcphdr *th, unsigned len) 4636{ 4637 struct tcp_sock *tp = tcp_sk(sk); 4638 struct inet_connection_sock *icsk = inet_csk(sk); 4639 int queued = 0; 4640 4641 tp->rx_opt.saw_tstamp = 0; 4642 4643 switch (sk->sk_state) { 4644 case TCP_CLOSE: 4645 goto discard; 4646 4647 case TCP_LISTEN: 4648 if (th->ack) 4649 return 1; 4650 4651 if (th->rst) 4652 goto discard; 4653 4654 if (th->syn) { 4655 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0) 4656 return 1; 4657 4658 /* Now we have several options: In theory there is 4659 * nothing else in the frame. KA9Q has an option to 4660 * send data with the syn, BSD accepts data with the 4661 * syn up to the [to be] advertised window and 4662 * Solaris 2.1 gives you a protocol error. For now 4663 * we just ignore it, that fits the spec precisely 4664 * and avoids incompatibilities. It would be nice in 4665 * future to drop through and process the data. 4666 * 4667 * Now that TTCP is starting to be used we ought to 4668 * queue this data. 4669 * But, this leaves one open to an easy denial of 4670 * service attack, and SYN cookies can't defend 4671 * against this problem. So, we drop the data 4672 * in the interest of security over speed unless 4673 * it's still in use. 4674 */ 4675 kfree_skb(skb); 4676 return 0; 4677 } 4678 goto discard; 4679 4680 case TCP_SYN_SENT: 4681 queued = tcp_rcv_synsent_state_process(sk, skb, th, len); 4682 if (queued >= 0) 4683 return queued; 4684 4685 /* Do step6 onward by hand. */ 4686 tcp_urg(sk, skb, th); 4687 __kfree_skb(skb); 4688 tcp_data_snd_check(sk); 4689 return 0; 4690 } 4691 4692 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && 4693 tcp_paws_discard(sk, skb)) { 4694 if (!th->rst) { 4695 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); 4696 tcp_send_dupack(sk, skb); 4697 goto discard; 4698 } 4699 /* Reset is accepted even if it did not pass PAWS. */ 4700 } 4701 4702 /* step 1: check sequence number */ 4703 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { 4704 if (!th->rst) 4705 tcp_send_dupack(sk, skb); 4706 goto discard; 4707 } 4708 4709 /* step 2: check RST bit */ 4710 if (th->rst) { 4711 tcp_reset(sk); 4712 goto discard; 4713 } 4714 4715 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 4716 4717 /* step 3: check security and precedence [ignored] */ 4718 4719 /* step 4: 4720 * 4721 * Check for a SYN in window. 4722 */ 4723 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4724 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); 4725 tcp_reset(sk); 4726 return 1; 4727 } 4728 4729 /* step 5: check the ACK field */ 4730 if (th->ack) { 4731 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH); 4732 4733 switch (sk->sk_state) { 4734 case TCP_SYN_RECV: 4735 if (acceptable) { 4736 tp->copied_seq = tp->rcv_nxt; 4737 smp_mb(); 4738 tcp_set_state(sk, TCP_ESTABLISHED); 4739 sk->sk_state_change(sk); 4740 4741 /* Note, that this wakeup is only for marginal 4742 * crossed SYN case. Passively open sockets 4743 * are not waked up, because sk->sk_sleep == 4744 * NULL and sk->sk_socket == NULL. 4745 */ 4746 if (sk->sk_socket) { 4747 sk_wake_async(sk,0,POLL_OUT); 4748 } 4749 4750 tp->snd_una = TCP_SKB_CB(skb)->ack_seq; 4751 tp->snd_wnd = ntohs(th->window) << 4752 tp->rx_opt.snd_wscale; 4753 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, 4754 TCP_SKB_CB(skb)->seq); 4755 4756 /* tcp_ack considers this ACK as duplicate 4757 * and does not calculate rtt. 4758 * Fix it at least with timestamps. 4759 */ 4760 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 4761 !tp->srtt) 4762 tcp_ack_saw_tstamp(sk, 0); 4763 4764 if (tp->rx_opt.tstamp_ok) 4765 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 4766 4767 /* Make sure socket is routed, for 4768 * correct metrics. 4769 */ 4770 icsk->icsk_af_ops->rebuild_header(sk); 4771 4772 tcp_init_metrics(sk); 4773 4774 tcp_init_congestion_control(sk); 4775 4776 /* Prevent spurious tcp_cwnd_restart() on 4777 * first data packet. 4778 */ 4779 tp->lsndtime = tcp_time_stamp; 4780 4781 tcp_mtup_init(sk); 4782 tcp_initialize_rcv_mss(sk); 4783 tcp_init_buffer_space(sk); 4784 tcp_fast_path_on(tp); 4785 } else { 4786 return 1; 4787 } 4788 break; 4789 4790 case TCP_FIN_WAIT1: 4791 if (tp->snd_una == tp->write_seq) { 4792 tcp_set_state(sk, TCP_FIN_WAIT2); 4793 sk->sk_shutdown |= SEND_SHUTDOWN; 4794 dst_confirm(sk->sk_dst_cache); 4795 4796 if (!sock_flag(sk, SOCK_DEAD)) 4797 /* Wake up lingering close() */ 4798 sk->sk_state_change(sk); 4799 else { 4800 int tmo; 4801 4802 if (tp->linger2 < 0 || 4803 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 4804 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { 4805 tcp_done(sk); 4806 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); 4807 return 1; 4808 } 4809 4810 tmo = tcp_fin_time(sk); 4811 if (tmo > TCP_TIMEWAIT_LEN) { 4812 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); 4813 } else if (th->fin || sock_owned_by_user(sk)) { 4814 /* Bad case. We could lose such FIN otherwise. 4815 * It is not a big problem, but it looks confusing 4816 * and not so rare event. We still can lose it now, 4817 * if it spins in bh_lock_sock(), but it is really 4818 * marginal case. 4819 */ 4820 inet_csk_reset_keepalive_timer(sk, tmo); 4821 } else { 4822 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 4823 goto discard; 4824 } 4825 } 4826 } 4827 break; 4828 4829 case TCP_CLOSING: 4830 if (tp->snd_una == tp->write_seq) { 4831 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 4832 goto discard; 4833 } 4834 break; 4835 4836 case TCP_LAST_ACK: 4837 if (tp->snd_una == tp->write_seq) { 4838 tcp_update_metrics(sk); 4839 tcp_done(sk); 4840 goto discard; 4841 } 4842 break; 4843 } 4844 } else 4845 goto discard; 4846 4847 /* step 6: check the URG bit */ 4848 tcp_urg(sk, skb, th); 4849 4850 /* step 7: process the segment text */ 4851 switch (sk->sk_state) { 4852 case TCP_CLOSE_WAIT: 4853 case TCP_CLOSING: 4854 case TCP_LAST_ACK: 4855 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 4856 break; 4857 case TCP_FIN_WAIT1: 4858 case TCP_FIN_WAIT2: 4859 /* RFC 793 says to queue data in these states, 4860 * RFC 1122 says we MUST send a reset. 4861 * BSD 4.4 also does reset. 4862 */ 4863 if (sk->sk_shutdown & RCV_SHUTDOWN) { 4864 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 4865 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { 4866 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); 4867 tcp_reset(sk); 4868 return 1; 4869 } 4870 } 4871 /* Fall through */ 4872 case TCP_ESTABLISHED: 4873 tcp_data_queue(sk, skb); 4874 queued = 1; 4875 break; 4876 } 4877 4878 /* tcp_data could move socket to TIME-WAIT */ 4879 if (sk->sk_state != TCP_CLOSE) { 4880 tcp_data_snd_check(sk); 4881 tcp_ack_snd_check(sk); 4882 } 4883 4884 if (!queued) { 4885discard: 4886 __kfree_skb(skb); 4887 } 4888 return 0; 4889} 4890 4891EXPORT_SYMBOL(sysctl_tcp_ecn); 4892EXPORT_SYMBOL(sysctl_tcp_reordering); 4893EXPORT_SYMBOL(tcp_parse_options); 4894EXPORT_SYMBOL(tcp_rcv_established); 4895EXPORT_SYMBOL(tcp_rcv_state_process); 4896EXPORT_SYMBOL(tcp_initialize_rcv_mss); 4897