1 /* 2 * INET An implementation of the TCP/IP protocol suite for the LINUX 3 * operating system. INET is implemented using the BSD Socket 4 * interface as the means of communication with the user level. 5 * 6 * Implementation of the Transmission Control Protocol(TCP). 7 * 8 * Version: $Id: tcp_input.c,v 1.243 2002/02/01 22:01:04 davem Exp $ 9 * 10 * Authors: Ross Biro 11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 12 * Mark Evans, <evansmp@uhura.aston.ac.uk> 13 * Corey Minyard <wf-rch!minyard@relay.EU.net> 14 * Florian La Roche, <flla@stud.uni-sb.de> 15 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> 16 * Linus Torvalds, <torvalds@cs.helsinki.fi> 17 * Alan Cox, <gw4pts@gw4pts.ampr.org> 18 * Matthew Dillon, <dillon@apollo.west.oic.com> 19 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 20 * Jorge Cwik, <jorge@laser.satlink.net> 21 */ 22 23 /* 24 * Changes: 25 * Pedro Roque : Fast Retransmit/Recovery. 26 * Two receive queues. 27 * Retransmit queue handled by TCP. 28 * Better retransmit timer handling. 29 * New congestion avoidance. 30 * Header prediction. 31 * Variable renaming. 32 * 33 * Eric : Fast Retransmit. 34 * Randy Scott : MSS option defines. 35 * Eric Schenk : Fixes to slow start algorithm. 36 * Eric Schenk : Yet another double ACK bug. 37 * Eric Schenk : Delayed ACK bug fixes. 38 * Eric Schenk : Floyd style fast retrans war avoidance. 39 * David S. Miller : Don't allow zero congestion window. 40 * Eric Schenk : Fix retransmitter so that it sends 41 * next packet on ack of previous packet. 42 * Andi Kleen : Moved open_request checking here 43 * and process RSTs for open_requests. 44 * Andi Kleen : Better prune_queue, and other fixes. 45 * Andrey Savochkin: Fix RTT measurements in the presence of 46 * timestamps. 47 * Andrey Savochkin: Check sequence numbers correctly when 48 * removing SACKs due to in sequence incoming 49 * data segments. 50 * Andi Kleen: Make sure we never ack data there is not 51 * enough room for. Also make this condition 52 * a fatal error if it might still happen. 53 * Andi Kleen: Add tcp_measure_rcv_mss to make 54 * connections with MSS<min(MTU,ann. MSS) 55 * work without delayed acks. 56 * Andi Kleen: Process packets with PSH set in the 57 * fast path. 58 * J Hadi Salim: ECN support 59 * Andrei Gurtov, 60 * Pasi Sarolahti, 61 * Panu Kuhlberg: Experimental audit of TCP (re)transmission 62 * engine. Lots of bugs are found. 63 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs 64 */ 65 66 #include <linux/mm.h> 67 #include <linux/module.h> 68 #include <linux/sysctl.h> 69 #include <net/tcp.h> 70 #include <net/inet_common.h> 71 #include <linux/ipsec.h> 72 #include <asm/unaligned.h> 73 #include <net/netdma.h> 74 75 int sysctl_tcp_timestamps __read_mostly = 1; 76 int sysctl_tcp_window_scaling __read_mostly = 1; 77 int sysctl_tcp_sack __read_mostly = 1; 78 int sysctl_tcp_fack __read_mostly = 1; 79 int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH; 80 int sysctl_tcp_ecn __read_mostly; 81 int sysctl_tcp_dsack __read_mostly = 1; 82 int sysctl_tcp_app_win __read_mostly = 31; 83 int sysctl_tcp_adv_win_scale __read_mostly = 2; 84 85 int sysctl_tcp_stdurg __read_mostly; 86 int sysctl_tcp_rfc1337 __read_mostly; 87 int sysctl_tcp_max_orphans __read_mostly = NR_FILE; 88 int sysctl_tcp_frto __read_mostly; 89 int sysctl_tcp_nometrics_save __read_mostly; 90 91 int sysctl_tcp_moderate_rcvbuf __read_mostly = 1; 92 int sysctl_tcp_abc __read_mostly; 93 94 #define FLAG_DATA 0x01 /* Incoming frame contained data. */ 95 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ 96 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ 97 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ 98 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ 99 #define FLAG_DATA_SACKED 0x20 /* New SACK. */ 100 #define FLAG_ECE 0x40 /* ECE in this ACK */ 101 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */ 102 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ 103 104 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) 105 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) 106 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) 107 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) 108 109 #define IsReno(tp) ((tp)->rx_opt.sack_ok == 0) 110 #define IsFack(tp) ((tp)->rx_opt.sack_ok & 2) 111 #define IsDSack(tp) ((tp)->rx_opt.sack_ok & 4) 112 113 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) 114 115 /* Adapt the MSS value used to make delayed ack decision to the 116 * real world. 117 */ 118 static void tcp_measure_rcv_mss(struct sock *sk, 119 const struct sk_buff *skb) 120 { 121 struct inet_connection_sock *icsk = inet_csk(sk); 122 const unsigned int lss = icsk->icsk_ack.last_seg_size; 123 unsigned int len; 124 125 icsk->icsk_ack.last_seg_size = 0; 126 127 /* skb->len may jitter because of SACKs, even if peer 128 * sends good full-sized frames. 129 */ 130 len = skb_shinfo(skb)->gso_size ?: skb->len; 131 if (len >= icsk->icsk_ack.rcv_mss) { 132 icsk->icsk_ack.rcv_mss = len; 133 } else { 134 /* Otherwise, we make more careful check taking into account, 135 * that SACKs block is variable. 136 * 137 * "len" is invariant segment length, including TCP header. 138 */ 139 len += skb->data - skb->h.raw; 140 if (len >= TCP_MIN_RCVMSS + sizeof(struct tcphdr) || 141 /* If PSH is not set, packet should be 142 * full sized, provided peer TCP is not badly broken. 143 * This observation (if it is correct 8)) allows 144 * to handle super-low mtu links fairly. 145 */ 146 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && 147 !(tcp_flag_word(skb->h.th)&TCP_REMNANT))) { 148 /* Subtract also invariant (if peer is RFC compliant), 149 * tcp header plus fixed timestamp option length. 150 * Resulting "len" is MSS free of SACK jitter. 151 */ 152 len -= tcp_sk(sk)->tcp_header_len; 153 icsk->icsk_ack.last_seg_size = len; 154 if (len == lss) { 155 icsk->icsk_ack.rcv_mss = len; 156 return; 157 } 158 } 159 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) 160 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; 161 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; 162 } 163 } 164 165 static void tcp_incr_quickack(struct sock *sk) 166 { 167 struct inet_connection_sock *icsk = inet_csk(sk); 168 unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); 169 170 if (quickacks==0) 171 quickacks=2; 172 if (quickacks > icsk->icsk_ack.quick) 173 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS); 174 } 175 176 void tcp_enter_quickack_mode(struct sock *sk) 177 { 178 struct inet_connection_sock *icsk = inet_csk(sk); 179 tcp_incr_quickack(sk); 180 icsk->icsk_ack.pingpong = 0; 181 icsk->icsk_ack.ato = TCP_ATO_MIN; 182 } 183 184 /* Send ACKs quickly, if "quick" count is not exhausted 185 * and the session is not interactive. 186 */ 187 188 static inline int tcp_in_quickack_mode(const struct sock *sk) 189 { 190 const struct inet_connection_sock *icsk = inet_csk(sk); 191 return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong; 192 } 193 194 /* Buffer size and advertised window tuning. 195 * 196 * 1. Tuning sk->sk_sndbuf, when connection enters established state. 197 */ 198 199 static void tcp_fixup_sndbuf(struct sock *sk) 200 { 201 int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 + 202 sizeof(struct sk_buff); 203 204 if (sk->sk_sndbuf < 3 * sndmem) 205 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]); 206 } 207 208 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh) 209 * 210 * All tcp_full_space() is split to two parts: "network" buffer, allocated 211 * forward and advertised in receiver window (tp->rcv_wnd) and 212 * "application buffer", required to isolate scheduling/application 213 * latencies from network. 214 * window_clamp is maximal advertised window. It can be less than 215 * tcp_full_space(), in this case tcp_full_space() - window_clamp 216 * is reserved for "application" buffer. The less window_clamp is 217 * the smoother our behaviour from viewpoint of network, but the lower 218 * throughput and the higher sensitivity of the connection to losses. 8) 219 * 220 * rcv_ssthresh is more strict window_clamp used at "slow start" 221 * phase to predict further behaviour of this connection. 222 * It is used for two goals: 223 * - to enforce header prediction at sender, even when application 224 * requires some significant "application buffer". It is check #1. 225 * - to prevent pruning of receive queue because of misprediction 226 * of receiver window. Check #2. 227 * 228 * The scheme does not work when sender sends good segments opening 229 * window and then starts to feed us spaghetti. But it should work 230 * in common situations. Otherwise, we have to rely on queue collapsing. 231 */ 232 233 /* Slow part of check#2. */ 234 static int __tcp_grow_window(const struct sock *sk, struct tcp_sock *tp, 235 const struct sk_buff *skb) 236 { 237 /* Optimize this! */ 238 int truesize = tcp_win_from_space(skb->truesize)/2; 239 int window = tcp_win_from_space(sysctl_tcp_rmem[2])/2; 240 241 while (tp->rcv_ssthresh <= window) { 242 if (truesize <= skb->len) 243 return 2 * inet_csk(sk)->icsk_ack.rcv_mss; 244 245 truesize >>= 1; 246 window >>= 1; 247 } 248 return 0; 249 } 250 251 static void tcp_grow_window(struct sock *sk, struct tcp_sock *tp, 252 struct sk_buff *skb) 253 { 254 /* Check #1 */ 255 if (tp->rcv_ssthresh < tp->window_clamp && 256 (int)tp->rcv_ssthresh < tcp_space(sk) && 257 !tcp_memory_pressure) { 258 int incr; 259 260 /* Check #2. Increase window, if skb with such overhead 261 * will fit to rcvbuf in future. 262 */ 263 if (tcp_win_from_space(skb->truesize) <= skb->len) 264 incr = 2*tp->advmss; 265 else 266 incr = __tcp_grow_window(sk, tp, skb); 267 268 if (incr) { 269 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, tp->window_clamp); 270 inet_csk(sk)->icsk_ack.quick |= 1; 271 } 272 } 273 } 274 275 /* 3. Tuning rcvbuf, when connection enters established state. */ 276 277 static void tcp_fixup_rcvbuf(struct sock *sk) 278 { 279 struct tcp_sock *tp = tcp_sk(sk); 280 int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); 281 282 /* Try to select rcvbuf so that 4 mss-sized segments 283 * will fit to window and corresponding skbs will fit to our rcvbuf. 284 * (was 3; 4 is minimum to allow fast retransmit to work.) 285 */ 286 while (tcp_win_from_space(rcvmem) < tp->advmss) 287 rcvmem += 128; 288 if (sk->sk_rcvbuf < 4 * rcvmem) 289 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]); 290 } 291 292 /* 4. Try to fixup all. It is made immediately after connection enters 293 * established state. 294 */ 295 static void tcp_init_buffer_space(struct sock *sk) 296 { 297 struct tcp_sock *tp = tcp_sk(sk); 298 int maxwin; 299 300 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) 301 tcp_fixup_rcvbuf(sk); 302 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) 303 tcp_fixup_sndbuf(sk); 304 305 tp->rcvq_space.space = tp->rcv_wnd; 306 307 maxwin = tcp_full_space(sk); 308 309 if (tp->window_clamp >= maxwin) { 310 tp->window_clamp = maxwin; 311 312 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) 313 tp->window_clamp = max(maxwin - 314 (maxwin >> sysctl_tcp_app_win), 315 4 * tp->advmss); 316 } 317 318 /* Force reservation of one segment. */ 319 if (sysctl_tcp_app_win && 320 tp->window_clamp > 2 * tp->advmss && 321 tp->window_clamp + tp->advmss > maxwin) 322 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); 323 324 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); 325 tp->snd_cwnd_stamp = tcp_time_stamp; 326 } 327 328 /* 5. Recalculate window clamp after socket hit its memory bounds. */ 329 static void tcp_clamp_window(struct sock *sk, struct tcp_sock *tp) 330 { 331 struct inet_connection_sock *icsk = inet_csk(sk); 332 333 icsk->icsk_ack.quick = 0; 334 335 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && 336 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && 337 !tcp_memory_pressure && 338 atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) { 339 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), 340 sysctl_tcp_rmem[2]); 341 } 342 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) 343 tp->rcv_ssthresh = min(tp->window_clamp, 2U*tp->advmss); 344 } 345 346 347 /* Initialize RCV_MSS value. 348 * RCV_MSS is an our guess about MSS used by the peer. 349 * We haven't any direct information about the MSS. 350 * It's better to underestimate the RCV_MSS rather than overestimate. 351 * Overestimations make us ACKing less frequently than needed. 352 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). 353 */ 354 void tcp_initialize_rcv_mss(struct sock *sk) 355 { 356 struct tcp_sock *tp = tcp_sk(sk); 357 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); 358 359 hint = min(hint, tp->rcv_wnd/2); 360 hint = min(hint, TCP_MIN_RCVMSS); 361 hint = max(hint, TCP_MIN_MSS); 362 363 inet_csk(sk)->icsk_ack.rcv_mss = hint; 364 } 365 366 /* Receiver "autotuning" code. 367 * 368 * The algorithm for RTT estimation w/o timestamps is based on 369 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. 370 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps> 371 * 372 * More detail on this code can be found at 373 * <http://www.psc.edu/~jheffner/senior_thesis.ps>, 374 * though this reference is out of date. A new paper 375 * is pending. 376 */ 377 static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) 378 { 379 u32 new_sample = tp->rcv_rtt_est.rtt; 380 long m = sample; 381 382 if (m == 0) 383 m = 1; 384 385 if (new_sample != 0) { 386 /* If we sample in larger samples in the non-timestamp 387 * case, we could grossly overestimate the RTT especially 388 * with chatty applications or bulk transfer apps which 389 * are stalled on filesystem I/O. 390 * 391 * Also, since we are only going for a minimum in the 392 * non-timestamp case, we do not smooth things out 393 * else with timestamps disabled convergence takes too 394 * long. 395 */ 396 if (!win_dep) { 397 m -= (new_sample >> 3); 398 new_sample += m; 399 } else if (m < new_sample) 400 new_sample = m << 3; 401 } else { 402 /* No previous measure. */ 403 new_sample = m << 3; 404 } 405 406 if (tp->rcv_rtt_est.rtt != new_sample) 407 tp->rcv_rtt_est.rtt = new_sample; 408 } 409 410 static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) 411 { 412 if (tp->rcv_rtt_est.time == 0) 413 goto new_measure; 414 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) 415 return; 416 tcp_rcv_rtt_update(tp, 417 jiffies - tp->rcv_rtt_est.time, 418 1); 419 420 new_measure: 421 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; 422 tp->rcv_rtt_est.time = tcp_time_stamp; 423 } 424 425 static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, const struct sk_buff *skb) 426 { 427 struct tcp_sock *tp = tcp_sk(sk); 428 if (tp->rx_opt.rcv_tsecr && 429 (TCP_SKB_CB(skb)->end_seq - 430 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) 431 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); 432 } 433 434 /* 435 * This function should be called every time data is copied to user space. 436 * It calculates the appropriate TCP receive buffer space. 437 */ 438 void tcp_rcv_space_adjust(struct sock *sk) 439 { 440 struct tcp_sock *tp = tcp_sk(sk); 441 int time; 442 int space; 443 444 if (tp->rcvq_space.time == 0) 445 goto new_measure; 446 447 time = tcp_time_stamp - tp->rcvq_space.time; 448 if (time < (tp->rcv_rtt_est.rtt >> 3) || 449 tp->rcv_rtt_est.rtt == 0) 450 return; 451 452 space = 2 * (tp->copied_seq - tp->rcvq_space.seq); 453 454 space = max(tp->rcvq_space.space, space); 455 456 if (tp->rcvq_space.space != space) { 457 int rcvmem; 458 459 tp->rcvq_space.space = space; 460 461 if (sysctl_tcp_moderate_rcvbuf && 462 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { 463 int new_clamp = space; 464 465 /* Receive space grows, normalize in order to 466 * take into account packet headers and sk_buff 467 * structure overhead. 468 */ 469 space /= tp->advmss; 470 if (!space) 471 space = 1; 472 rcvmem = (tp->advmss + MAX_TCP_HEADER + 473 16 + sizeof(struct sk_buff)); 474 while (tcp_win_from_space(rcvmem) < tp->advmss) 475 rcvmem += 128; 476 space *= rcvmem; 477 space = min(space, sysctl_tcp_rmem[2]); 478 if (space > sk->sk_rcvbuf) { 479 sk->sk_rcvbuf = space; 480 481 /* Make the window clamp follow along. */ 482 tp->window_clamp = new_clamp; 483 } 484 } 485 } 486 487 new_measure: 488 tp->rcvq_space.seq = tp->copied_seq; 489 tp->rcvq_space.time = tcp_time_stamp; 490 } 491 492 /* There is something which you must keep in mind when you analyze the 493 * behavior of the tp->ato delayed ack timeout interval. When a 494 * connection starts up, we want to ack as quickly as possible. The 495 * problem is that "good" TCP's do slow start at the beginning of data 496 * transmission. The means that until we send the first few ACK's the 497 * sender will sit on his end and only queue most of his data, because 498 * he can only send snd_cwnd unacked packets at any given time. For 499 * each ACK we send, he increments snd_cwnd and transmits more of his 500 * queue. -DaveM 501 */ 502 static void tcp_event_data_recv(struct sock *sk, struct tcp_sock *tp, struct sk_buff *skb) 503 { 504 struct inet_connection_sock *icsk = inet_csk(sk); 505 u32 now; 506 507 inet_csk_schedule_ack(sk); 508 509 tcp_measure_rcv_mss(sk, skb); 510 511 tcp_rcv_rtt_measure(tp); 512 513 now = tcp_time_stamp; 514 515 if (!icsk->icsk_ack.ato) { 516 /* The _first_ data packet received, initialize 517 * delayed ACK engine. 518 */ 519 tcp_incr_quickack(sk); 520 icsk->icsk_ack.ato = TCP_ATO_MIN; 521 } else { 522 int m = now - icsk->icsk_ack.lrcvtime; 523 524 if (m <= TCP_ATO_MIN/2) { 525 /* The fastest case is the first. */ 526 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; 527 } else if (m < icsk->icsk_ack.ato) { 528 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; 529 if (icsk->icsk_ack.ato > icsk->icsk_rto) 530 icsk->icsk_ack.ato = icsk->icsk_rto; 531 } else if (m > icsk->icsk_rto) { 532 /* Too long gap. Apparently sender failed to 533 * restart window, so that we send ACKs quickly. 534 */ 535 tcp_incr_quickack(sk); 536 sk_stream_mem_reclaim(sk); 537 } 538 } 539 icsk->icsk_ack.lrcvtime = now; 540 541 TCP_ECN_check_ce(tp, skb); 542 543 if (skb->len >= 128) 544 tcp_grow_window(sk, tp, skb); 545 } 546 547 /* Called to compute a smoothed rtt estimate. The data fed to this 548 * routine either comes from timestamps, or from segments that were 549 * known _not_ to have been retransmitted [see Karn/Partridge 550 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 551 * piece by Van Jacobson. 552 * NOTE: the next three routines used to be one big routine. 553 * To save cycles in the RFC 1323 implementation it was better to break 554 * it up into three procedures. -- erics 555 */ 556 static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) 557 { 558 struct tcp_sock *tp = tcp_sk(sk); 559 long m = mrtt; /* RTT */ 560 561 /* The following amusing code comes from Jacobson's 562 * article in SIGCOMM '88. Note that rtt and mdev 563 * are scaled versions of rtt and mean deviation. 564 * This is designed to be as fast as possible 565 * m stands for "measurement". 566 * 567 * On a 1990 paper the rto value is changed to: 568 * RTO = rtt + 4 * mdev 569 * 570 * Funny. This algorithm seems to be very broken. 571 * These formulae increase RTO, when it should be decreased, increase 572 * too slowly, when it should be increased quickly, decrease too quickly 573 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely 574 * does not matter how to _calculate_ it. Seems, it was trap 575 * that VJ failed to avoid. 8) 576 */ 577 if(m == 0) 578 m = 1; 579 if (tp->srtt != 0) { 580 m -= (tp->srtt >> 3); /* m is now error in rtt est */ 581 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ 582 if (m < 0) { 583 m = -m; /* m is now abs(error) */ 584 m -= (tp->mdev >> 2); /* similar update on mdev */ 585 /* This is similar to one of Eifel findings. 586 * Eifel blocks mdev updates when rtt decreases. 587 * This solution is a bit different: we use finer gain 588 * for mdev in this case (alpha*beta). 589 * Like Eifel it also prevents growth of rto, 590 * but also it limits too fast rto decreases, 591 * happening in pure Eifel. 592 */ 593 if (m > 0) 594 m >>= 3; 595 } else { 596 m -= (tp->mdev >> 2); /* similar update on mdev */ 597 } 598 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ 599 if (tp->mdev > tp->mdev_max) { 600 tp->mdev_max = tp->mdev; 601 if (tp->mdev_max > tp->rttvar) 602 tp->rttvar = tp->mdev_max; 603 } 604 if (after(tp->snd_una, tp->rtt_seq)) { 605 if (tp->mdev_max < tp->rttvar) 606 tp->rttvar -= (tp->rttvar-tp->mdev_max)>>2; 607 tp->rtt_seq = tp->snd_nxt; 608 tp->mdev_max = TCP_RTO_MIN; 609 } 610 } else { 611 /* no previous measure. */ 612 tp->srtt = m<<3; /* take the measured time to be rtt */ 613 tp->mdev = m<<1; /* make sure rto = 3*rtt */ 614 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); 615 tp->rtt_seq = tp->snd_nxt; 616 } 617 } 618 619 /* Calculate rto without backoff. This is the second half of Van Jacobson's 620 * routine referred to above. 621 */ 622 static inline void tcp_set_rto(struct sock *sk) 623 { 624 const struct tcp_sock *tp = tcp_sk(sk); 625 /* Old crap is replaced with new one. 8) 626 * 627 * More seriously: 628 * 1. If rtt variance happened to be less 50msec, it is hallucination. 629 * It cannot be less due to utterly erratic ACK generation made 630 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ 631 * to do with delayed acks, because at cwnd>2 true delack timeout 632 * is invisible. Actually, Linux-2.4 also generates erratic 633 * ACKs in some circumstances. 634 */ 635 inet_csk(sk)->icsk_rto = (tp->srtt >> 3) + tp->rttvar; 636 637 /* 2. Fixups made earlier cannot be right. 638 * If we do not estimate RTO correctly without them, 639 * all the algo is pure shit and should be replaced 640 * with correct one. It is exactly, which we pretend to do. 641 */ 642 } 643 644 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo 645 * guarantees that rto is higher. 646 */ 647 static inline void tcp_bound_rto(struct sock *sk) 648 { 649 if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX) 650 inet_csk(sk)->icsk_rto = TCP_RTO_MAX; 651 } 652 653 /* Save metrics learned by this TCP session. 654 This function is called only, when TCP finishes successfully 655 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. 656 */ 657 void tcp_update_metrics(struct sock *sk) 658 { 659 struct tcp_sock *tp = tcp_sk(sk); 660 struct dst_entry *dst = __sk_dst_get(sk); 661 662 if (sysctl_tcp_nometrics_save) 663 return; 664 665 dst_confirm(dst); 666 667 if (dst && (dst->flags&DST_HOST)) { 668 const struct inet_connection_sock *icsk = inet_csk(sk); 669 int m; 670 671 if (icsk->icsk_backoff || !tp->srtt) { 672 /* This session failed to estimate rtt. Why? 673 * Probably, no packets returned in time. 674 * Reset our results. 675 */ 676 if (!(dst_metric_locked(dst, RTAX_RTT))) 677 dst->metrics[RTAX_RTT-1] = 0; 678 return; 679 } 680 681 m = dst_metric(dst, RTAX_RTT) - tp->srtt; 682 683 /* If newly calculated rtt larger than stored one, 684 * store new one. Otherwise, use EWMA. Remember, 685 * rtt overestimation is always better than underestimation. 686 */ 687 if (!(dst_metric_locked(dst, RTAX_RTT))) { 688 if (m <= 0) 689 dst->metrics[RTAX_RTT-1] = tp->srtt; 690 else 691 dst->metrics[RTAX_RTT-1] -= (m>>3); 692 } 693 694 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { 695 if (m < 0) 696 m = -m; 697 698 /* Scale deviation to rttvar fixed point */ 699 m >>= 1; 700 if (m < tp->mdev) 701 m = tp->mdev; 702 703 if (m >= dst_metric(dst, RTAX_RTTVAR)) 704 dst->metrics[RTAX_RTTVAR-1] = m; 705 else 706 dst->metrics[RTAX_RTTVAR-1] -= 707 (dst->metrics[RTAX_RTTVAR-1] - m)>>2; 708 } 709 710 if (tp->snd_ssthresh >= 0xFFFF) { 711 /* Slow start still did not finish. */ 712 if (dst_metric(dst, RTAX_SSTHRESH) && 713 !dst_metric_locked(dst, RTAX_SSTHRESH) && 714 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) 715 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1; 716 if (!dst_metric_locked(dst, RTAX_CWND) && 717 tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) 718 dst->metrics[RTAX_CWND-1] = tp->snd_cwnd; 719 } else if (tp->snd_cwnd > tp->snd_ssthresh && 720 icsk->icsk_ca_state == TCP_CA_Open) { 721 /* Cong. avoidance phase, cwnd is reliable. */ 722 if (!dst_metric_locked(dst, RTAX_SSTHRESH)) 723 dst->metrics[RTAX_SSTHRESH-1] = 724 max(tp->snd_cwnd >> 1, tp->snd_ssthresh); 725 if (!dst_metric_locked(dst, RTAX_CWND)) 726 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_cwnd) >> 1; 727 } else { 728 /* Else slow start did not finish, cwnd is non-sense, 729 ssthresh may be also invalid. 730 */ 731 if (!dst_metric_locked(dst, RTAX_CWND)) 732 dst->metrics[RTAX_CWND-1] = (dst->metrics[RTAX_CWND-1] + tp->snd_ssthresh) >> 1; 733 if (dst->metrics[RTAX_SSTHRESH-1] && 734 !dst_metric_locked(dst, RTAX_SSTHRESH) && 735 tp->snd_ssthresh > dst->metrics[RTAX_SSTHRESH-1]) 736 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh; 737 } 738 739 if (!dst_metric_locked(dst, RTAX_REORDERING)) { 740 if (dst->metrics[RTAX_REORDERING-1] < tp->reordering && 741 tp->reordering != sysctl_tcp_reordering) 742 dst->metrics[RTAX_REORDERING-1] = tp->reordering; 743 } 744 } 745 } 746 747 /* Numbers are taken from RFC2414. */ 748 __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst) 749 { 750 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); 751 752 if (!cwnd) { 753 if (tp->mss_cache > 1460) 754 cwnd = 2; 755 else 756 cwnd = (tp->mss_cache > 1095) ? 3 : 4; 757 } 758 return min_t(__u32, cwnd, tp->snd_cwnd_clamp); 759 } 760 761 /* Set slow start threshold and cwnd not falling to slow start */ 762 void tcp_enter_cwr(struct sock *sk) 763 { 764 struct tcp_sock *tp = tcp_sk(sk); 765 766 tp->prior_ssthresh = 0; 767 tp->bytes_acked = 0; 768 if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) { 769 tp->undo_marker = 0; 770 tp->snd_ssthresh = inet_csk(sk)->icsk_ca_ops->ssthresh(sk); 771 tp->snd_cwnd = min(tp->snd_cwnd, 772 tcp_packets_in_flight(tp) + 1U); 773 tp->snd_cwnd_cnt = 0; 774 tp->high_seq = tp->snd_nxt; 775 tp->snd_cwnd_stamp = tcp_time_stamp; 776 TCP_ECN_queue_cwr(tp); 777 778 tcp_set_ca_state(sk, TCP_CA_CWR); 779 } 780 } 781 782 /* Initialize metrics on socket. */ 783 784 static void tcp_init_metrics(struct sock *sk) 785 { 786 struct tcp_sock *tp = tcp_sk(sk); 787 struct dst_entry *dst = __sk_dst_get(sk); 788 789 if (dst == NULL) 790 goto reset; 791 792 dst_confirm(dst); 793 794 if (dst_metric_locked(dst, RTAX_CWND)) 795 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); 796 if (dst_metric(dst, RTAX_SSTHRESH)) { 797 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); 798 if (tp->snd_ssthresh > tp->snd_cwnd_clamp) 799 tp->snd_ssthresh = tp->snd_cwnd_clamp; 800 } 801 if (dst_metric(dst, RTAX_REORDERING) && 802 tp->reordering != dst_metric(dst, RTAX_REORDERING)) { 803 tp->rx_opt.sack_ok &= ~2; 804 tp->reordering = dst_metric(dst, RTAX_REORDERING); 805 } 806 807 if (dst_metric(dst, RTAX_RTT) == 0) 808 goto reset; 809 810 if (!tp->srtt && dst_metric(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3)) 811 goto reset; 812 813 /* Initial rtt is determined from SYN,SYN-ACK. 814 * The segment is small and rtt may appear much 815 * less than real one. Use per-dst memory 816 * to make it more realistic. 817 * 818 * A bit of theory. RTT is time passed after "normal" sized packet 819 * is sent until it is ACKed. In normal circumstances sending small 820 * packets force peer to delay ACKs and calculation is correct too. 821 * The algorithm is adaptive and, provided we follow specs, it 822 * NEVER underestimate RTT. BUT! If peer tries to make some clever 823 * tricks sort of "quick acks" for time long enough to decrease RTT 824 * to low value, and then abruptly stops to do it and starts to delay 825 * ACKs, wait for troubles. 826 */ 827 if (dst_metric(dst, RTAX_RTT) > tp->srtt) { 828 tp->srtt = dst_metric(dst, RTAX_RTT); 829 tp->rtt_seq = tp->snd_nxt; 830 } 831 if (dst_metric(dst, RTAX_RTTVAR) > tp->mdev) { 832 tp->mdev = dst_metric(dst, RTAX_RTTVAR); 833 tp->mdev_max = tp->rttvar = max(tp->mdev, TCP_RTO_MIN); 834 } 835 tcp_set_rto(sk); 836 tcp_bound_rto(sk); 837 if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp) 838 goto reset; 839 tp->snd_cwnd = tcp_init_cwnd(tp, dst); 840 tp->snd_cwnd_stamp = tcp_time_stamp; 841 return; 842 843 reset: 844 /* Play conservative. If timestamps are not 845 * supported, TCP will fail to recalculate correct 846 * rtt, if initial rto is too small. FORGET ALL AND RESET! 847 */ 848 if (!tp->rx_opt.saw_tstamp && tp->srtt) { 849 tp->srtt = 0; 850 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT; 851 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; 852 } 853 } 854 855 static void tcp_update_reordering(struct sock *sk, const int metric, 856 const int ts) 857 { 858 struct tcp_sock *tp = tcp_sk(sk); 859 if (metric > tp->reordering) { 860 tp->reordering = min(TCP_MAX_REORDERING, metric); 861 862 /* This exciting event is worth to be remembered. 8) */ 863 if (ts) 864 NET_INC_STATS_BH(LINUX_MIB_TCPTSREORDER); 865 else if (IsReno(tp)) 866 NET_INC_STATS_BH(LINUX_MIB_TCPRENOREORDER); 867 else if (IsFack(tp)) 868 NET_INC_STATS_BH(LINUX_MIB_TCPFACKREORDER); 869 else 870 NET_INC_STATS_BH(LINUX_MIB_TCPSACKREORDER); 871 #if FASTRETRANS_DEBUG > 1 872 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", 873 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, 874 tp->reordering, 875 tp->fackets_out, 876 tp->sacked_out, 877 tp->undo_marker ? tp->undo_retrans : 0); 878 #endif 879 /* Disable FACK yet. */ 880 tp->rx_opt.sack_ok &= ~2; 881 } 882 } 883 884 /* This procedure tags the retransmission queue when SACKs arrive. 885 * 886 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). 887 * Packets in queue with these bits set are counted in variables 888 * sacked_out, retrans_out and lost_out, correspondingly. 889 * 890 * Valid combinations are: 891 * Tag InFlight Description 892 * 0 1 - orig segment is in flight. 893 * S 0 - nothing flies, orig reached receiver. 894 * L 0 - nothing flies, orig lost by net. 895 * R 2 - both orig and retransmit are in flight. 896 * L|R 1 - orig is lost, retransmit is in flight. 897 * S|R 1 - orig reached receiver, retrans is still in flight. 898 * (L|S|R is logically valid, it could occur when L|R is sacked, 899 * but it is equivalent to plain S and code short-curcuits it to S. 900 * L|S is logically invalid, it would mean -1 packet in flight 8)) 901 * 902 * These 6 states form finite state machine, controlled by the following events: 903 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) 904 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) 905 * 3. Loss detection event of one of three flavors: 906 * A. Scoreboard estimator decided the packet is lost. 907 * A'. Reno "three dupacks" marks head of queue lost. 908 * A''. Its FACK modfication, head until snd.fack is lost. 909 * B. SACK arrives sacking data transmitted after never retransmitted 910 * hole was sent out. 911 * C. SACK arrives sacking SND.NXT at the moment, when the 912 * segment was retransmitted. 913 * 4. D-SACK added new rule: D-SACK changes any tag to S. 914 * 915 * It is pleasant to note, that state diagram turns out to be commutative, 916 * so that we are allowed not to be bothered by order of our actions, 917 * when multiple events arrive simultaneously. (see the function below). 918 * 919 * Reordering detection. 920 * -------------------- 921 * Reordering metric is maximal distance, which a packet can be displaced 922 * in packet stream. With SACKs we can estimate it: 923 * 924 * 1. SACK fills old hole and the corresponding segment was not 925 * ever retransmitted -> reordering. Alas, we cannot use it 926 * when segment was retransmitted. 927 * 2. The last flaw is solved with D-SACK. D-SACK arrives 928 * for retransmitted and already SACKed segment -> reordering.. 929 * Both of these heuristics are not used in Loss state, when we cannot 930 * account for retransmits accurately. 931 */ 932 static int 933 tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, u32 prior_snd_una) 934 { 935 const struct inet_connection_sock *icsk = inet_csk(sk); 936 struct tcp_sock *tp = tcp_sk(sk); 937 unsigned char *ptr = ack_skb->h.raw + TCP_SKB_CB(ack_skb)->sacked; 938 struct tcp_sack_block_wire *sp = (struct tcp_sack_block_wire *)(ptr+2); 939 struct sk_buff *cached_skb; 940 int num_sacks = (ptr[1] - TCPOLEN_SACK_BASE)>>3; 941 int reord = tp->packets_out; 942 int prior_fackets; 943 u32 lost_retrans = 0; 944 int flag = 0; 945 int dup_sack = 0; 946 int cached_fack_count; 947 int i; 948 int first_sack_index; 949 950 if (!tp->sacked_out) 951 tp->fackets_out = 0; 952 prior_fackets = tp->fackets_out; 953 954 /* Check for D-SACK. */ 955 if (before(ntohl(sp[0].start_seq), TCP_SKB_CB(ack_skb)->ack_seq)) { 956 dup_sack = 1; 957 tp->rx_opt.sack_ok |= 4; 958 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKRECV); 959 } else if (num_sacks > 1 && 960 !after(ntohl(sp[0].end_seq), ntohl(sp[1].end_seq)) && 961 !before(ntohl(sp[0].start_seq), ntohl(sp[1].start_seq))) { 962 dup_sack = 1; 963 tp->rx_opt.sack_ok |= 4; 964 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFORECV); 965 } 966 967 /* D-SACK for already forgotten data... 968 * Do dumb counting. */ 969 if (dup_sack && 970 !after(ntohl(sp[0].end_seq), prior_snd_una) && 971 after(ntohl(sp[0].end_seq), tp->undo_marker)) 972 tp->undo_retrans--; 973 974 /* Eliminate too old ACKs, but take into 975 * account more or less fresh ones, they can 976 * contain valid SACK info. 977 */ 978 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) 979 return 0; 980 981 /* SACK fastpath: 982 * if the only SACK change is the increase of the end_seq of 983 * the first block then only apply that SACK block 984 * and use retrans queue hinting otherwise slowpath */ 985 flag = 1; 986 for (i = 0; i < num_sacks; i++) { 987 __be32 start_seq = sp[i].start_seq; 988 __be32 end_seq = sp[i].end_seq; 989 990 if (i == 0) { 991 if (tp->recv_sack_cache[i].start_seq != start_seq) 992 flag = 0; 993 } else { 994 if ((tp->recv_sack_cache[i].start_seq != start_seq) || 995 (tp->recv_sack_cache[i].end_seq != end_seq)) 996 flag = 0; 997 } 998 tp->recv_sack_cache[i].start_seq = start_seq; 999 tp->recv_sack_cache[i].end_seq = end_seq; 1000 } 1001 /* Clear the rest of the cache sack blocks so they won't match mistakenly. */ 1002 for (; i < ARRAY_SIZE(tp->recv_sack_cache); i++) { 1003 tp->recv_sack_cache[i].start_seq = 0; 1004 tp->recv_sack_cache[i].end_seq = 0; 1005 } 1006 1007 first_sack_index = 0; 1008 if (flag) 1009 num_sacks = 1; 1010 else { 1011 int j; 1012 tp->fastpath_skb_hint = NULL; 1013 1014 /* order SACK blocks to allow in order walk of the retrans queue */ 1015 for (i = num_sacks-1; i > 0; i--) { 1016 for (j = 0; j < i; j++){ 1017 if (after(ntohl(sp[j].start_seq), 1018 ntohl(sp[j+1].start_seq))){ 1019 struct tcp_sack_block_wire tmp; 1020 1021 tmp = sp[j]; 1022 sp[j] = sp[j+1]; 1023 sp[j+1] = tmp; 1024 1025 /* Track where the first SACK block goes to */ 1026 if (j == first_sack_index) 1027 first_sack_index = j+1; 1028 } 1029 1030 } 1031 } 1032 } 1033 1034 /* clear flag as used for different purpose in following code */ 1035 flag = 0; 1036 1037 /* Use SACK fastpath hint if valid */ 1038 cached_skb = tp->fastpath_skb_hint; 1039 cached_fack_count = tp->fastpath_cnt_hint; 1040 if (!cached_skb) { 1041 cached_skb = sk->sk_write_queue.next; 1042 cached_fack_count = 0; 1043 } 1044 1045 for (i=0; i<num_sacks; i++, sp++) { 1046 struct sk_buff *skb; 1047 __u32 start_seq = ntohl(sp->start_seq); 1048 __u32 end_seq = ntohl(sp->end_seq); 1049 int fack_count; 1050 1051 skb = cached_skb; 1052 fack_count = cached_fack_count; 1053 1054 /* Event "B" in the comment above. */ 1055 if (after(end_seq, tp->high_seq)) 1056 flag |= FLAG_DATA_LOST; 1057 1058 sk_stream_for_retrans_queue_from(skb, sk) { 1059 int in_sack, pcount; 1060 u8 sacked; 1061 1062 cached_skb = skb; 1063 cached_fack_count = fack_count; 1064 if (i == first_sack_index) { 1065 tp->fastpath_skb_hint = skb; 1066 tp->fastpath_cnt_hint = fack_count; 1067 } 1068 1069 /* The retransmission queue is always in order, so 1070 * we can short-circuit the walk early. 1071 */ 1072 if (!before(TCP_SKB_CB(skb)->seq, end_seq)) 1073 break; 1074 1075 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && 1076 !before(end_seq, TCP_SKB_CB(skb)->end_seq); 1077 1078 pcount = tcp_skb_pcount(skb); 1079 1080 if (pcount > 1 && !in_sack && 1081 after(TCP_SKB_CB(skb)->end_seq, start_seq)) { 1082 unsigned int pkt_len; 1083 1084 in_sack = !after(start_seq, 1085 TCP_SKB_CB(skb)->seq); 1086 1087 if (!in_sack) 1088 pkt_len = (start_seq - 1089 TCP_SKB_CB(skb)->seq); 1090 else 1091 pkt_len = (end_seq - 1092 TCP_SKB_CB(skb)->seq); 1093 if (tcp_fragment(sk, skb, pkt_len, skb_shinfo(skb)->gso_size)) 1094 break; 1095 pcount = tcp_skb_pcount(skb); 1096 } 1097 1098 fack_count += pcount; 1099 1100 sacked = TCP_SKB_CB(skb)->sacked; 1101 1102 /* Account D-SACK for retransmitted packet. */ 1103 if ((dup_sack && in_sack) && 1104 (sacked & TCPCB_RETRANS) && 1105 after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) 1106 tp->undo_retrans--; 1107 1108 /* The frame is ACKed. */ 1109 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) { 1110 if (sacked&TCPCB_RETRANS) { 1111 if ((dup_sack && in_sack) && 1112 (sacked&TCPCB_SACKED_ACKED)) 1113 reord = min(fack_count, reord); 1114 } else { 1115 /* If it was in a hole, we detected reordering. */ 1116 if (fack_count < prior_fackets && 1117 !(sacked&TCPCB_SACKED_ACKED)) 1118 reord = min(fack_count, reord); 1119 } 1120 1121 /* Nothing to do; acked frame is about to be dropped. */ 1122 continue; 1123 } 1124 1125 if ((sacked&TCPCB_SACKED_RETRANS) && 1126 after(end_seq, TCP_SKB_CB(skb)->ack_seq) && 1127 (!lost_retrans || after(end_seq, lost_retrans))) 1128 lost_retrans = end_seq; 1129 1130 if (!in_sack) 1131 continue; 1132 1133 if (!(sacked&TCPCB_SACKED_ACKED)) { 1134 if (sacked & TCPCB_SACKED_RETRANS) { 1135 /* If the segment is not tagged as lost, 1136 * we do not clear RETRANS, believing 1137 * that retransmission is still in flight. 1138 */ 1139 if (sacked & TCPCB_LOST) { 1140 TCP_SKB_CB(skb)->sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); 1141 tp->lost_out -= tcp_skb_pcount(skb); 1142 tp->retrans_out -= tcp_skb_pcount(skb); 1143 1144 /* clear lost hint */ 1145 tp->retransmit_skb_hint = NULL; 1146 } 1147 } else { 1148 /* New sack for not retransmitted frame, 1149 * which was in hole. It is reordering. 1150 */ 1151 if (!(sacked & TCPCB_RETRANS) && 1152 fack_count < prior_fackets) 1153 reord = min(fack_count, reord); 1154 1155 if (sacked & TCPCB_LOST) { 1156 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 1157 tp->lost_out -= tcp_skb_pcount(skb); 1158 1159 /* clear lost hint */ 1160 tp->retransmit_skb_hint = NULL; 1161 } 1162 } 1163 1164 TCP_SKB_CB(skb)->sacked |= TCPCB_SACKED_ACKED; 1165 flag |= FLAG_DATA_SACKED; 1166 tp->sacked_out += tcp_skb_pcount(skb); 1167 1168 if (fack_count > tp->fackets_out) 1169 tp->fackets_out = fack_count; 1170 } else { 1171 if (dup_sack && (sacked&TCPCB_RETRANS)) 1172 reord = min(fack_count, reord); 1173 } 1174 1175 /* D-SACK. We can detect redundant retransmission 1176 * in S|R and plain R frames and clear it. 1177 * undo_retrans is decreased above, L|R frames 1178 * are accounted above as well. 1179 */ 1180 if (dup_sack && 1181 (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS)) { 1182 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1183 tp->retrans_out -= tcp_skb_pcount(skb); 1184 tp->retransmit_skb_hint = NULL; 1185 } 1186 } 1187 } 1188 1189 /* Check for lost retransmit. This superb idea is 1190 * borrowed from "ratehalving". Event "C". 1191 * Later note: FACK people cheated me again 8), 1192 * we have to account for reordering! Ugly, 1193 * but should help. 1194 */ 1195 if (lost_retrans && icsk->icsk_ca_state == TCP_CA_Recovery) { 1196 struct sk_buff *skb; 1197 1198 sk_stream_for_retrans_queue(skb, sk) { 1199 if (after(TCP_SKB_CB(skb)->seq, lost_retrans)) 1200 break; 1201 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1202 continue; 1203 if ((TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) && 1204 after(lost_retrans, TCP_SKB_CB(skb)->ack_seq) && 1205 (IsFack(tp) || 1206 !before(lost_retrans, 1207 TCP_SKB_CB(skb)->ack_seq + tp->reordering * 1208 tp->mss_cache))) { 1209 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1210 tp->retrans_out -= tcp_skb_pcount(skb); 1211 1212 /* clear lost hint */ 1213 tp->retransmit_skb_hint = NULL; 1214 1215 if (!(TCP_SKB_CB(skb)->sacked&(TCPCB_LOST|TCPCB_SACKED_ACKED))) { 1216 tp->lost_out += tcp_skb_pcount(skb); 1217 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1218 flag |= FLAG_DATA_SACKED; 1219 NET_INC_STATS_BH(LINUX_MIB_TCPLOSTRETRANSMIT); 1220 } 1221 } 1222 } 1223 } 1224 1225 tp->left_out = tp->sacked_out + tp->lost_out; 1226 1227 if ((reord < tp->fackets_out) && icsk->icsk_ca_state != TCP_CA_Loss) 1228 tcp_update_reordering(sk, ((tp->fackets_out + 1) - reord), 0); 1229 1230 #if FASTRETRANS_DEBUG > 0 1231 BUG_TRAP((int)tp->sacked_out >= 0); 1232 BUG_TRAP((int)tp->lost_out >= 0); 1233 BUG_TRAP((int)tp->retrans_out >= 0); 1234 BUG_TRAP((int)tcp_packets_in_flight(tp) >= 0); 1235 #endif 1236 return flag; 1237 } 1238 1239 /* RTO occurred, but do not yet enter loss state. Instead, transmit two new 1240 * segments to see from the next ACKs whether any data was really missing. 1241 * If the RTO was spurious, new ACKs should arrive. 1242 */ 1243 void tcp_enter_frto(struct sock *sk) 1244 { 1245 const struct inet_connection_sock *icsk = inet_csk(sk); 1246 struct tcp_sock *tp = tcp_sk(sk); 1247 struct sk_buff *skb; 1248 1249 tp->frto_counter = 1; 1250 1251 if (icsk->icsk_ca_state <= TCP_CA_Disorder || 1252 tp->snd_una == tp->high_seq || 1253 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { 1254 tp->prior_ssthresh = tcp_current_ssthresh(sk); 1255 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 1256 tcp_ca_event(sk, CA_EVENT_FRTO); 1257 } 1258 1259 /* Have to clear retransmission markers here to keep the bookkeeping 1260 * in shape, even though we are not yet in Loss state. 1261 * If something was really lost, it is eventually caught up 1262 * in tcp_enter_frto_loss. 1263 */ 1264 tp->retrans_out = 0; 1265 tp->undo_marker = tp->snd_una; 1266 tp->undo_retrans = 0; 1267 1268 sk_stream_for_retrans_queue(skb, sk) { 1269 TCP_SKB_CB(skb)->sacked &= ~TCPCB_RETRANS; 1270 } 1271 tcp_sync_left_out(tp); 1272 1273 tcp_set_ca_state(sk, TCP_CA_Open); 1274 tp->frto_highmark = tp->snd_nxt; 1275 } 1276 1277 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO, 1278 * which indicates that we should follow the traditional RTO recovery, 1279 * i.e. mark everything lost and do go-back-N retransmission. 1280 */ 1281 static void tcp_enter_frto_loss(struct sock *sk) 1282 { 1283 struct tcp_sock *tp = tcp_sk(sk); 1284 struct sk_buff *skb; 1285 int cnt = 0; 1286 1287 tp->sacked_out = 0; 1288 tp->lost_out = 0; 1289 tp->fackets_out = 0; 1290 1291 sk_stream_for_retrans_queue(skb, sk) { 1292 cnt += tcp_skb_pcount(skb); 1293 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 1294 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) { 1295 1296 /* Do not mark those segments lost that were 1297 * forward transmitted after RTO 1298 */ 1299 if (!after(TCP_SKB_CB(skb)->end_seq, 1300 tp->frto_highmark)) { 1301 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1302 tp->lost_out += tcp_skb_pcount(skb); 1303 } 1304 } else { 1305 tp->sacked_out += tcp_skb_pcount(skb); 1306 tp->fackets_out = cnt; 1307 } 1308 } 1309 tcp_sync_left_out(tp); 1310 1311 tp->snd_cwnd = tp->frto_counter + tcp_packets_in_flight(tp)+1; 1312 tp->snd_cwnd_cnt = 0; 1313 tp->snd_cwnd_stamp = tcp_time_stamp; 1314 tp->undo_marker = 0; 1315 tp->frto_counter = 0; 1316 1317 tp->reordering = min_t(unsigned int, tp->reordering, 1318 sysctl_tcp_reordering); 1319 tcp_set_ca_state(sk, TCP_CA_Loss); 1320 tp->high_seq = tp->frto_highmark; 1321 TCP_ECN_queue_cwr(tp); 1322 1323 clear_all_retrans_hints(tp); 1324 } 1325 1326 void tcp_clear_retrans(struct tcp_sock *tp) 1327 { 1328 tp->left_out = 0; 1329 tp->retrans_out = 0; 1330 1331 tp->fackets_out = 0; 1332 tp->sacked_out = 0; 1333 tp->lost_out = 0; 1334 1335 tp->undo_marker = 0; 1336 tp->undo_retrans = 0; 1337 } 1338 1339 /* Enter Loss state. If "how" is not zero, forget all SACK information 1340 * and reset tags completely, otherwise preserve SACKs. If receiver 1341 * dropped its ofo queue, we will know this due to reneging detection. 1342 */ 1343 void tcp_enter_loss(struct sock *sk, int how) 1344 { 1345 const struct inet_connection_sock *icsk = inet_csk(sk); 1346 struct tcp_sock *tp = tcp_sk(sk); 1347 struct sk_buff *skb; 1348 int cnt = 0; 1349 1350 /* Reduce ssthresh if it has not yet been made inside this window. */ 1351 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq || 1352 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { 1353 tp->prior_ssthresh = tcp_current_ssthresh(sk); 1354 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 1355 tcp_ca_event(sk, CA_EVENT_LOSS); 1356 } 1357 tp->snd_cwnd = 1; 1358 tp->snd_cwnd_cnt = 0; 1359 tp->snd_cwnd_stamp = tcp_time_stamp; 1360 1361 tp->bytes_acked = 0; 1362 tcp_clear_retrans(tp); 1363 1364 /* Push undo marker, if it was plain RTO and nothing 1365 * was retransmitted. */ 1366 if (!how) 1367 tp->undo_marker = tp->snd_una; 1368 1369 sk_stream_for_retrans_queue(skb, sk) { 1370 cnt += tcp_skb_pcount(skb); 1371 if (TCP_SKB_CB(skb)->sacked&TCPCB_RETRANS) 1372 tp->undo_marker = 0; 1373 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; 1374 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { 1375 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; 1376 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1377 tp->lost_out += tcp_skb_pcount(skb); 1378 } else { 1379 tp->sacked_out += tcp_skb_pcount(skb); 1380 tp->fackets_out = cnt; 1381 } 1382 } 1383 tcp_sync_left_out(tp); 1384 1385 tp->reordering = min_t(unsigned int, tp->reordering, 1386 sysctl_tcp_reordering); 1387 tcp_set_ca_state(sk, TCP_CA_Loss); 1388 tp->high_seq = tp->snd_nxt; 1389 TCP_ECN_queue_cwr(tp); 1390 1391 clear_all_retrans_hints(tp); 1392 } 1393 1394 static int tcp_check_sack_reneging(struct sock *sk) 1395 { 1396 struct sk_buff *skb; 1397 1398 /* If ACK arrived pointing to a remembered SACK, 1399 * it means that our remembered SACKs do not reflect 1400 * real state of receiver i.e. 1401 * receiver _host_ is heavily congested (or buggy). 1402 * Do processing similar to RTO timeout. 1403 */ 1404 if ((skb = skb_peek(&sk->sk_write_queue)) != NULL && 1405 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 1406 struct inet_connection_sock *icsk = inet_csk(sk); 1407 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRENEGING); 1408 1409 tcp_enter_loss(sk, 1); 1410 icsk->icsk_retransmits++; 1411 tcp_retransmit_skb(sk, skb_peek(&sk->sk_write_queue)); 1412 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 1413 icsk->icsk_rto, TCP_RTO_MAX); 1414 return 1; 1415 } 1416 return 0; 1417 } 1418 1419 static inline int tcp_fackets_out(struct tcp_sock *tp) 1420 { 1421 return IsReno(tp) ? tp->sacked_out+1 : tp->fackets_out; 1422 } 1423 1424 static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb) 1425 { 1426 return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto); 1427 } 1428 1429 static inline int tcp_head_timedout(struct sock *sk, struct tcp_sock *tp) 1430 { 1431 return tp->packets_out && 1432 tcp_skb_timedout(sk, skb_peek(&sk->sk_write_queue)); 1433 } 1434 1435 /* Linux NewReno/SACK/FACK/ECN state machine. 1436 * -------------------------------------- 1437 * 1438 * "Open" Normal state, no dubious events, fast path. 1439 * "Disorder" In all the respects it is "Open", 1440 * but requires a bit more attention. It is entered when 1441 * we see some SACKs or dupacks. It is split of "Open" 1442 * mainly to move some processing from fast path to slow one. 1443 * "CWR" CWND was reduced due to some Congestion Notification event. 1444 * It can be ECN, ICMP source quench, local device congestion. 1445 * "Recovery" CWND was reduced, we are fast-retransmitting. 1446 * "Loss" CWND was reduced due to RTO timeout or SACK reneging. 1447 * 1448 * tcp_fastretrans_alert() is entered: 1449 * - each incoming ACK, if state is not "Open" 1450 * - when arrived ACK is unusual, namely: 1451 * * SACK 1452 * * Duplicate ACK. 1453 * * ECN ECE. 1454 * 1455 * Counting packets in flight is pretty simple. 1456 * 1457 * in_flight = packets_out - left_out + retrans_out 1458 * 1459 * packets_out is SND.NXT-SND.UNA counted in packets. 1460 * 1461 * retrans_out is number of retransmitted segments. 1462 * 1463 * left_out is number of segments left network, but not ACKed yet. 1464 * 1465 * left_out = sacked_out + lost_out 1466 * 1467 * sacked_out: Packets, which arrived to receiver out of order 1468 * and hence not ACKed. With SACKs this number is simply 1469 * amount of SACKed data. Even without SACKs 1470 * it is easy to give pretty reliable estimate of this number, 1471 * counting duplicate ACKs. 1472 * 1473 * lost_out: Packets lost by network. TCP has no explicit 1474 * "loss notification" feedback from network (for now). 1475 * It means that this number can be only _guessed_. 1476 * Actually, it is the heuristics to predict lossage that 1477 * distinguishes different algorithms. 1478 * 1479 * F.e. after RTO, when all the queue is considered as lost, 1480 * lost_out = packets_out and in_flight = retrans_out. 1481 * 1482 * Essentially, we have now two algorithms counting 1483 * lost packets. 1484 * 1485 * FACK: It is the simplest heuristics. As soon as we decided 1486 * that something is lost, we decide that _all_ not SACKed 1487 * packets until the most forward SACK are lost. I.e. 1488 * lost_out = fackets_out - sacked_out and left_out = fackets_out. 1489 * It is absolutely correct estimate, if network does not reorder 1490 * packets. And it loses any connection to reality when reordering 1491 * takes place. We use FACK by default until reordering 1492 * is suspected on the path to this destination. 1493 * 1494 * NewReno: when Recovery is entered, we assume that one segment 1495 * is lost (classic Reno). While we are in Recovery and 1496 * a partial ACK arrives, we assume that one more packet 1497 * is lost (NewReno). This heuristics are the same in NewReno 1498 * and SACK. 1499 * 1500 * Imagine, that's all! Forget about all this shamanism about CWND inflation 1501 * deflation etc. CWND is real congestion window, never inflated, changes 1502 * only according to classic VJ rules. 1503 * 1504 * Really tricky (and requiring careful tuning) part of algorithm 1505 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). 1506 * The first determines the moment _when_ we should reduce CWND and, 1507 * hence, slow down forward transmission. In fact, it determines the moment 1508 * when we decide that hole is caused by loss, rather than by a reorder. 1509 * 1510 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill 1511 * holes, caused by lost packets. 1512 * 1513 * And the most logically complicated part of algorithm is undo 1514 * heuristics. We detect false retransmits due to both too early 1515 * fast retransmit (reordering) and underestimated RTO, analyzing 1516 * timestamps and D-SACKs. When we detect that some segments were 1517 * retransmitted by mistake and CWND reduction was wrong, we undo 1518 * window reduction and abort recovery phase. This logic is hidden 1519 * inside several functions named tcp_try_undo_<something>. 1520 */ 1521 1522 /* This function decides, when we should leave Disordered state 1523 * and enter Recovery phase, reducing congestion window. 1524 * 1525 * Main question: may we further continue forward transmission 1526 * with the same cwnd? 1527 */ 1528 static int tcp_time_to_recover(struct sock *sk, struct tcp_sock *tp) 1529 { 1530 __u32 packets_out; 1531 1532 /* Trick#1: The loss is proven. */ 1533 if (tp->lost_out) 1534 return 1; 1535 1536 /* Not-A-Trick#2 : Classic rule... */ 1537 if (tcp_fackets_out(tp) > tp->reordering) 1538 return 1; 1539 1540 /* Trick#3 : when we use RFC2988 timer restart, fast 1541 * retransmit can be triggered by timeout of queue head. 1542 */ 1543 if (tcp_head_timedout(sk, tp)) 1544 return 1; 1545 1546 /* Trick#4: It is still not OK... But will it be useful to delay 1547 * recovery more? 1548 */ 1549 packets_out = tp->packets_out; 1550 if (packets_out <= tp->reordering && 1551 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && 1552 !tcp_may_send_now(sk, tp)) { 1553 /* We have nothing to send. This connection is limited 1554 * either by receiver window or by application. 1555 */ 1556 return 1; 1557 } 1558 1559 return 0; 1560 } 1561 1562 /* If we receive more dupacks than we expected counting segments 1563 * in assumption of absent reordering, interpret this as reordering. 1564 * The only another reason could be bug in receiver TCP. 1565 */ 1566 static void tcp_check_reno_reordering(struct sock *sk, const int addend) 1567 { 1568 struct tcp_sock *tp = tcp_sk(sk); 1569 u32 holes; 1570 1571 holes = max(tp->lost_out, 1U); 1572 holes = min(holes, tp->packets_out); 1573 1574 if ((tp->sacked_out + holes) > tp->packets_out) { 1575 tp->sacked_out = tp->packets_out - holes; 1576 tcp_update_reordering(sk, tp->packets_out + addend, 0); 1577 } 1578 } 1579 1580 /* Emulate SACKs for SACKless connection: account for a new dupack. */ 1581 1582 static void tcp_add_reno_sack(struct sock *sk) 1583 { 1584 struct tcp_sock *tp = tcp_sk(sk); 1585 tp->sacked_out++; 1586 tcp_check_reno_reordering(sk, 0); 1587 tcp_sync_left_out(tp); 1588 } 1589 1590 /* Account for ACK, ACKing some data in Reno Recovery phase. */ 1591 1592 static void tcp_remove_reno_sacks(struct sock *sk, struct tcp_sock *tp, int acked) 1593 { 1594 if (acked > 0) { 1595 /* One ACK acked hole. The rest eat duplicate ACKs. */ 1596 if (acked-1 >= tp->sacked_out) 1597 tp->sacked_out = 0; 1598 else 1599 tp->sacked_out -= acked-1; 1600 } 1601 tcp_check_reno_reordering(sk, acked); 1602 tcp_sync_left_out(tp); 1603 } 1604 1605 static inline void tcp_reset_reno_sack(struct tcp_sock *tp) 1606 { 1607 tp->sacked_out = 0; 1608 tp->left_out = tp->lost_out; 1609 } 1610 1611 /* Mark head of queue up as lost. */ 1612 static void tcp_mark_head_lost(struct sock *sk, struct tcp_sock *tp, 1613 int packets, u32 high_seq) 1614 { 1615 struct sk_buff *skb; 1616 int cnt; 1617 1618 BUG_TRAP(packets <= tp->packets_out); 1619 if (tp->lost_skb_hint) { 1620 skb = tp->lost_skb_hint; 1621 cnt = tp->lost_cnt_hint; 1622 } else { 1623 skb = sk->sk_write_queue.next; 1624 cnt = 0; 1625 } 1626 1627 sk_stream_for_retrans_queue_from(skb, sk) { 1628 /* TODO: do this better */ 1629 /* this is not the most efficient way to do this... */ 1630 tp->lost_skb_hint = skb; 1631 tp->lost_cnt_hint = cnt; 1632 cnt += tcp_skb_pcount(skb); 1633 if (cnt > packets || after(TCP_SKB_CB(skb)->end_seq, high_seq)) 1634 break; 1635 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) { 1636 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1637 tp->lost_out += tcp_skb_pcount(skb); 1638 1639 /* clear xmit_retransmit_queue hints 1640 * if this is beyond hint */ 1641 if(tp->retransmit_skb_hint != NULL && 1642 before(TCP_SKB_CB(skb)->seq, 1643 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) { 1644 1645 tp->retransmit_skb_hint = NULL; 1646 } 1647 } 1648 } 1649 tcp_sync_left_out(tp); 1650 } 1651 1652 /* Account newly detected lost packet(s) */ 1653 1654 static void tcp_update_scoreboard(struct sock *sk, struct tcp_sock *tp) 1655 { 1656 if (IsFack(tp)) { 1657 int lost = tp->fackets_out - tp->reordering; 1658 if (lost <= 0) 1659 lost = 1; 1660 tcp_mark_head_lost(sk, tp, lost, tp->high_seq); 1661 } else { 1662 tcp_mark_head_lost(sk, tp, 1, tp->high_seq); 1663 } 1664 1665 /* New heuristics: it is possible only after we switched 1666 * to restart timer each time when something is ACKed. 1667 * Hence, we can detect timed out packets during fast 1668 * retransmit without falling to slow start. 1669 */ 1670 if (!IsReno(tp) && tcp_head_timedout(sk, tp)) { 1671 struct sk_buff *skb; 1672 1673 skb = tp->scoreboard_skb_hint ? tp->scoreboard_skb_hint 1674 : sk->sk_write_queue.next; 1675 1676 sk_stream_for_retrans_queue_from(skb, sk) { 1677 if (!tcp_skb_timedout(sk, skb)) 1678 break; 1679 1680 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_TAGBITS)) { 1681 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1682 tp->lost_out += tcp_skb_pcount(skb); 1683 1684 /* clear xmit_retrans hint */ 1685 if (tp->retransmit_skb_hint && 1686 before(TCP_SKB_CB(skb)->seq, 1687 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) 1688 1689 tp->retransmit_skb_hint = NULL; 1690 } 1691 } 1692 1693 tp->scoreboard_skb_hint = skb; 1694 1695 tcp_sync_left_out(tp); 1696 } 1697 } 1698 1699 /* CWND moderation, preventing bursts due to too big ACKs 1700 * in dubious situations. 1701 */ 1702 static inline void tcp_moderate_cwnd(struct tcp_sock *tp) 1703 { 1704 tp->snd_cwnd = min(tp->snd_cwnd, 1705 tcp_packets_in_flight(tp)+tcp_max_burst(tp)); 1706 tp->snd_cwnd_stamp = tcp_time_stamp; 1707 } 1708 1709 /* Lower bound on congestion window is slow start threshold 1710 * unless congestion avoidance choice decides to overide it. 1711 */ 1712 static inline u32 tcp_cwnd_min(const struct sock *sk) 1713 { 1714 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; 1715 1716 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh; 1717 } 1718 1719 /* Decrease cwnd each second ack. */ 1720 static void tcp_cwnd_down(struct sock *sk) 1721 { 1722 struct tcp_sock *tp = tcp_sk(sk); 1723 int decr = tp->snd_cwnd_cnt + 1; 1724 1725 tp->snd_cwnd_cnt = decr&1; 1726 decr >>= 1; 1727 1728 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk)) 1729 tp->snd_cwnd -= decr; 1730 1731 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp)+1); 1732 tp->snd_cwnd_stamp = tcp_time_stamp; 1733 } 1734 1735 /* Nothing was retransmitted or returned timestamp is less 1736 * than timestamp of the first retransmission. 1737 */ 1738 static inline int tcp_packet_delayed(struct tcp_sock *tp) 1739 { 1740 return !tp->retrans_stamp || 1741 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 1742 (__s32)(tp->rx_opt.rcv_tsecr - tp->retrans_stamp) < 0); 1743 } 1744 1745 /* Undo procedures. */ 1746 1747 #if FASTRETRANS_DEBUG > 1 1748 static void DBGUNDO(struct sock *sk, struct tcp_sock *tp, const char *msg) 1749 { 1750 struct inet_sock *inet = inet_sk(sk); 1751 printk(KERN_DEBUG "Undo %s %u.%u.%u.%u/%u c%u l%u ss%u/%u p%u\n", 1752 msg, 1753 NIPQUAD(inet->daddr), ntohs(inet->dport), 1754 tp->snd_cwnd, tp->left_out, 1755 tp->snd_ssthresh, tp->prior_ssthresh, 1756 tp->packets_out); 1757 } 1758 #else 1759 #define DBGUNDO(x...) do { } while (0) 1760 #endif 1761 1762 static void tcp_undo_cwr(struct sock *sk, const int undo) 1763 { 1764 struct tcp_sock *tp = tcp_sk(sk); 1765 1766 if (tp->prior_ssthresh) { 1767 const struct inet_connection_sock *icsk = inet_csk(sk); 1768 1769 if (icsk->icsk_ca_ops->undo_cwnd) 1770 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); 1771 else 1772 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh<<1); 1773 1774 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) { 1775 tp->snd_ssthresh = tp->prior_ssthresh; 1776 TCP_ECN_withdraw_cwr(tp); 1777 } 1778 } else { 1779 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); 1780 } 1781 tcp_moderate_cwnd(tp); 1782 tp->snd_cwnd_stamp = tcp_time_stamp; 1783 1784 /* There is something screwy going on with the retrans hints after 1785 an undo */ 1786 clear_all_retrans_hints(tp); 1787 } 1788 1789 static inline int tcp_may_undo(struct tcp_sock *tp) 1790 { 1791 return tp->undo_marker && 1792 (!tp->undo_retrans || tcp_packet_delayed(tp)); 1793 } 1794 1795 /* People celebrate: "We love our President!" */ 1796 static int tcp_try_undo_recovery(struct sock *sk, struct tcp_sock *tp) 1797 { 1798 if (tcp_may_undo(tp)) { 1799 /* Happy end! We did not retransmit anything 1800 * or our original transmission succeeded. 1801 */ 1802 DBGUNDO(sk, tp, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); 1803 tcp_undo_cwr(sk, 1); 1804 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) 1805 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); 1806 else 1807 NET_INC_STATS_BH(LINUX_MIB_TCPFULLUNDO); 1808 tp->undo_marker = 0; 1809 } 1810 if (tp->snd_una == tp->high_seq && IsReno(tp)) { 1811 /* Hold old state until something *above* high_seq 1812 * is ACKed. For Reno it is MUST to prevent false 1813 * fast retransmits (RFC2582). SACK TCP is safe. */ 1814 tcp_moderate_cwnd(tp); 1815 return 1; 1816 } 1817 tcp_set_ca_state(sk, TCP_CA_Open); 1818 return 0; 1819 } 1820 1821 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ 1822 static void tcp_try_undo_dsack(struct sock *sk, struct tcp_sock *tp) 1823 { 1824 if (tp->undo_marker && !tp->undo_retrans) { 1825 DBGUNDO(sk, tp, "D-SACK"); 1826 tcp_undo_cwr(sk, 1); 1827 tp->undo_marker = 0; 1828 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKUNDO); 1829 } 1830 } 1831 1832 /* Undo during fast recovery after partial ACK. */ 1833 1834 static int tcp_try_undo_partial(struct sock *sk, struct tcp_sock *tp, 1835 int acked) 1836 { 1837 /* Partial ACK arrived. Force Hoe's retransmit. */ 1838 int failed = IsReno(tp) || tp->fackets_out>tp->reordering; 1839 1840 if (tcp_may_undo(tp)) { 1841 /* Plain luck! Hole if filled with delayed 1842 * packet, rather than with a retransmit. 1843 */ 1844 if (tp->retrans_out == 0) 1845 tp->retrans_stamp = 0; 1846 1847 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1); 1848 1849 DBGUNDO(sk, tp, "Hoe"); 1850 tcp_undo_cwr(sk, 0); 1851 NET_INC_STATS_BH(LINUX_MIB_TCPPARTIALUNDO); 1852 1853 /* So... Do not make Hoe's retransmit yet. 1854 * If the first packet was delayed, the rest 1855 * ones are most probably delayed as well. 1856 */ 1857 failed = 0; 1858 } 1859 return failed; 1860 } 1861 1862 /* Undo during loss recovery after partial ACK. */ 1863 static int tcp_try_undo_loss(struct sock *sk, struct tcp_sock *tp) 1864 { 1865 if (tcp_may_undo(tp)) { 1866 struct sk_buff *skb; 1867 sk_stream_for_retrans_queue(skb, sk) { 1868 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 1869 } 1870 1871 clear_all_retrans_hints(tp); 1872 1873 DBGUNDO(sk, tp, "partial loss"); 1874 tp->lost_out = 0; 1875 tp->left_out = tp->sacked_out; 1876 tcp_undo_cwr(sk, 1); 1877 NET_INC_STATS_BH(LINUX_MIB_TCPLOSSUNDO); 1878 inet_csk(sk)->icsk_retransmits = 0; 1879 tp->undo_marker = 0; 1880 if (!IsReno(tp)) 1881 tcp_set_ca_state(sk, TCP_CA_Open); 1882 return 1; 1883 } 1884 return 0; 1885 } 1886 1887 static inline void tcp_complete_cwr(struct sock *sk) 1888 { 1889 struct tcp_sock *tp = tcp_sk(sk); 1890 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 1891 tp->snd_cwnd_stamp = tcp_time_stamp; 1892 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); 1893 } 1894 1895 static void tcp_try_to_open(struct sock *sk, struct tcp_sock *tp, int flag) 1896 { 1897 tp->left_out = tp->sacked_out; 1898 1899 if (tp->retrans_out == 0) 1900 tp->retrans_stamp = 0; 1901 1902 if (flag&FLAG_ECE) 1903 tcp_enter_cwr(sk); 1904 1905 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { 1906 int state = TCP_CA_Open; 1907 1908 if (tp->left_out || tp->retrans_out || tp->undo_marker) 1909 state = TCP_CA_Disorder; 1910 1911 if (inet_csk(sk)->icsk_ca_state != state) { 1912 tcp_set_ca_state(sk, state); 1913 tp->high_seq = tp->snd_nxt; 1914 } 1915 tcp_moderate_cwnd(tp); 1916 } else { 1917 tcp_cwnd_down(sk); 1918 } 1919 } 1920 1921 static void tcp_mtup_probe_failed(struct sock *sk) 1922 { 1923 struct inet_connection_sock *icsk = inet_csk(sk); 1924 1925 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; 1926 icsk->icsk_mtup.probe_size = 0; 1927 } 1928 1929 static void tcp_mtup_probe_success(struct sock *sk, struct sk_buff *skb) 1930 { 1931 struct tcp_sock *tp = tcp_sk(sk); 1932 struct inet_connection_sock *icsk = inet_csk(sk); 1933 1934 /* FIXME: breaks with very large cwnd */ 1935 tp->prior_ssthresh = tcp_current_ssthresh(sk); 1936 tp->snd_cwnd = tp->snd_cwnd * 1937 tcp_mss_to_mtu(sk, tp->mss_cache) / 1938 icsk->icsk_mtup.probe_size; 1939 tp->snd_cwnd_cnt = 0; 1940 tp->snd_cwnd_stamp = tcp_time_stamp; 1941 tp->rcv_ssthresh = tcp_current_ssthresh(sk); 1942 1943 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; 1944 icsk->icsk_mtup.probe_size = 0; 1945 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 1946 } 1947 1948 1949 /* Process an event, which can update packets-in-flight not trivially. 1950 * Main goal of this function is to calculate new estimate for left_out, 1951 * taking into account both packets sitting in receiver's buffer and 1952 * packets lost by network. 1953 * 1954 * Besides that it does CWND reduction, when packet loss is detected 1955 * and changes state of machine. 1956 * 1957 * It does _not_ decide what to send, it is made in function 1958 * tcp_xmit_retransmit_queue(). 1959 */ 1960 static void 1961 tcp_fastretrans_alert(struct sock *sk, u32 prior_snd_una, 1962 int prior_packets, int flag) 1963 { 1964 struct inet_connection_sock *icsk = inet_csk(sk); 1965 struct tcp_sock *tp = tcp_sk(sk); 1966 int is_dupack = (tp->snd_una == prior_snd_una && !(flag&FLAG_NOT_DUP)); 1967 1968 /* Some technical things: 1969 * 1. Reno does not count dupacks (sacked_out) automatically. */ 1970 if (!tp->packets_out) 1971 tp->sacked_out = 0; 1972 /* 2. SACK counts snd_fack in packets inaccurately. */ 1973 if (tp->sacked_out == 0) 1974 tp->fackets_out = 0; 1975 1976 /* Now state machine starts. 1977 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ 1978 if (flag&FLAG_ECE) 1979 tp->prior_ssthresh = 0; 1980 1981 /* B. In all the states check for reneging SACKs. */ 1982 if (tp->sacked_out && tcp_check_sack_reneging(sk)) 1983 return; 1984 1985 /* C. Process data loss notification, provided it is valid. */ 1986 if ((flag&FLAG_DATA_LOST) && 1987 before(tp->snd_una, tp->high_seq) && 1988 icsk->icsk_ca_state != TCP_CA_Open && 1989 tp->fackets_out > tp->reordering) { 1990 tcp_mark_head_lost(sk, tp, tp->fackets_out-tp->reordering, tp->high_seq); 1991 NET_INC_STATS_BH(LINUX_MIB_TCPLOSS); 1992 } 1993 1994 /* D. Synchronize left_out to current state. */ 1995 tcp_sync_left_out(tp); 1996 1997 /* E. Check state exit conditions. State can be terminated 1998 * when high_seq is ACKed. */ 1999 if (icsk->icsk_ca_state == TCP_CA_Open) { 2000 if (!sysctl_tcp_frto) 2001 BUG_TRAP(tp->retrans_out == 0); 2002 tp->retrans_stamp = 0; 2003 } else if (!before(tp->snd_una, tp->high_seq)) { 2004 switch (icsk->icsk_ca_state) { 2005 case TCP_CA_Loss: 2006 icsk->icsk_retransmits = 0; 2007 if (tcp_try_undo_recovery(sk, tp)) 2008 return; 2009 break; 2010 2011 case TCP_CA_CWR: 2012 /* CWR is to be held something *above* high_seq 2013 * is ACKed for CWR bit to reach receiver. */ 2014 if (tp->snd_una != tp->high_seq) { 2015 tcp_complete_cwr(sk); 2016 tcp_set_ca_state(sk, TCP_CA_Open); 2017 } 2018 break; 2019 2020 case TCP_CA_Disorder: 2021 tcp_try_undo_dsack(sk, tp); 2022 if (!tp->undo_marker || 2023 /* For SACK case do not Open to allow to undo 2024 * catching for all duplicate ACKs. */ 2025 IsReno(tp) || tp->snd_una != tp->high_seq) { 2026 tp->undo_marker = 0; 2027 tcp_set_ca_state(sk, TCP_CA_Open); 2028 } 2029 break; 2030 2031 case TCP_CA_Recovery: 2032 if (IsReno(tp)) 2033 tcp_reset_reno_sack(tp); 2034 if (tcp_try_undo_recovery(sk, tp)) 2035 return; 2036 tcp_complete_cwr(sk); 2037 break; 2038 } 2039 } 2040 2041 /* F. Process state. */ 2042 switch (icsk->icsk_ca_state) { 2043 case TCP_CA_Recovery: 2044 if (prior_snd_una == tp->snd_una) { 2045 if (IsReno(tp) && is_dupack) 2046 tcp_add_reno_sack(sk); 2047 } else { 2048 int acked = prior_packets - tp->packets_out; 2049 if (IsReno(tp)) 2050 tcp_remove_reno_sacks(sk, tp, acked); 2051 is_dupack = tcp_try_undo_partial(sk, tp, acked); 2052 } 2053 break; 2054 case TCP_CA_Loss: 2055 if (flag&FLAG_DATA_ACKED) 2056 icsk->icsk_retransmits = 0; 2057 if (!tcp_try_undo_loss(sk, tp)) { 2058 tcp_moderate_cwnd(tp); 2059 tcp_xmit_retransmit_queue(sk); 2060 return; 2061 } 2062 if (icsk->icsk_ca_state != TCP_CA_Open) 2063 return; 2064 /* Loss is undone; fall through to processing in Open state. */ 2065 default: 2066 if (IsReno(tp)) { 2067 if (tp->snd_una != prior_snd_una) 2068 tcp_reset_reno_sack(tp); 2069 if (is_dupack) 2070 tcp_add_reno_sack(sk); 2071 } 2072 2073 if (icsk->icsk_ca_state == TCP_CA_Disorder) 2074 tcp_try_undo_dsack(sk, tp); 2075 2076 if (!tcp_time_to_recover(sk, tp)) { 2077 tcp_try_to_open(sk, tp, flag); 2078 return; 2079 } 2080 2081 /* MTU probe failure: don't reduce cwnd */ 2082 if (icsk->icsk_ca_state < TCP_CA_CWR && 2083 icsk->icsk_mtup.probe_size && 2084 tp->snd_una == tp->mtu_probe.probe_seq_start) { 2085 tcp_mtup_probe_failed(sk); 2086 /* Restores the reduction we did in tcp_mtup_probe() */ 2087 tp->snd_cwnd++; 2088 tcp_simple_retransmit(sk); 2089 return; 2090 } 2091 2092 /* Otherwise enter Recovery state */ 2093 2094 if (IsReno(tp)) 2095 NET_INC_STATS_BH(LINUX_MIB_TCPRENORECOVERY); 2096 else 2097 NET_INC_STATS_BH(LINUX_MIB_TCPSACKRECOVERY); 2098 2099 tp->high_seq = tp->snd_nxt; 2100 tp->prior_ssthresh = 0; 2101 tp->undo_marker = tp->snd_una; 2102 tp->undo_retrans = tp->retrans_out; 2103 2104 if (icsk->icsk_ca_state < TCP_CA_CWR) { 2105 if (!(flag&FLAG_ECE)) 2106 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2107 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2108 TCP_ECN_queue_cwr(tp); 2109 } 2110 2111 tp->bytes_acked = 0; 2112 tp->snd_cwnd_cnt = 0; 2113 tcp_set_ca_state(sk, TCP_CA_Recovery); 2114 } 2115 2116 if (is_dupack || tcp_head_timedout(sk, tp)) 2117 tcp_update_scoreboard(sk, tp); 2118 tcp_cwnd_down(sk); 2119 tcp_xmit_retransmit_queue(sk); 2120 } 2121 2122 /* Read draft-ietf-tcplw-high-performance before mucking 2123 * with this code. (Supersedes RFC1323) 2124 */ 2125 static void tcp_ack_saw_tstamp(struct sock *sk, int flag) 2126 { 2127 /* RTTM Rule: A TSecr value received in a segment is used to 2128 * update the averaged RTT measurement only if the segment 2129 * acknowledges some new data, i.e., only if it advances the 2130 * left edge of the send window. 2131 * 2132 * See draft-ietf-tcplw-high-performance-00, section 3.3. 2133 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> 2134 * 2135 * Changed: reset backoff as soon as we see the first valid sample. 2136 * If we do not, we get strongly overestimated rto. With timestamps 2137 * samples are accepted even from very old segments: f.e., when rtt=1 2138 * increases to 8, we retransmit 5 times and after 8 seconds delayed 2139 * answer arrives rto becomes 120 seconds! If at least one of segments 2140 * in window is lost... Voila. --ANK (010210) 2141 */ 2142 struct tcp_sock *tp = tcp_sk(sk); 2143 const __u32 seq_rtt = tcp_time_stamp - tp->rx_opt.rcv_tsecr; 2144 tcp_rtt_estimator(sk, seq_rtt); 2145 tcp_set_rto(sk); 2146 inet_csk(sk)->icsk_backoff = 0; 2147 tcp_bound_rto(sk); 2148 } 2149 2150 static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag) 2151 { 2152 /* We don't have a timestamp. Can only use 2153 * packets that are not retransmitted to determine 2154 * rtt estimates. Also, we must not reset the 2155 * backoff for rto until we get a non-retransmitted 2156 * packet. This allows us to deal with a situation 2157 * where the network delay has increased suddenly. 2158 * I.e. Karn's algorithm. (SIGCOMM '87, p5.) 2159 */ 2160 2161 if (flag & FLAG_RETRANS_DATA_ACKED) 2162 return; 2163 2164 tcp_rtt_estimator(sk, seq_rtt); 2165 tcp_set_rto(sk); 2166 inet_csk(sk)->icsk_backoff = 0; 2167 tcp_bound_rto(sk); 2168 } 2169 2170 static inline void tcp_ack_update_rtt(struct sock *sk, const int flag, 2171 const s32 seq_rtt) 2172 { 2173 const struct tcp_sock *tp = tcp_sk(sk); 2174 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ 2175 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) 2176 tcp_ack_saw_tstamp(sk, flag); 2177 else if (seq_rtt >= 0) 2178 tcp_ack_no_tstamp(sk, seq_rtt, flag); 2179 } 2180 2181 static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 rtt, 2182 u32 in_flight, int good) 2183 { 2184 const struct inet_connection_sock *icsk = inet_csk(sk); 2185 icsk->icsk_ca_ops->cong_avoid(sk, ack, rtt, in_flight, good); 2186 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp; 2187 } 2188 2189 /* Restart timer after forward progress on connection. 2190 * RFC2988 recommends to restart timer to now+rto. 2191 */ 2192 2193 static void tcp_ack_packets_out(struct sock *sk, struct tcp_sock *tp) 2194 { 2195 if (!tp->packets_out) { 2196 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); 2197 } else { 2198 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 2199 } 2200 } 2201 2202 static int tcp_tso_acked(struct sock *sk, struct sk_buff *skb, 2203 __u32 now, __s32 *seq_rtt) 2204 { 2205 struct tcp_sock *tp = tcp_sk(sk); 2206 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 2207 __u32 seq = tp->snd_una; 2208 __u32 packets_acked; 2209 int acked = 0; 2210 2211 /* If we get here, the whole TSO packet has not been 2212 * acked. 2213 */ 2214 BUG_ON(!after(scb->end_seq, seq)); 2215 2216 packets_acked = tcp_skb_pcount(skb); 2217 if (tcp_trim_head(sk, skb, seq - scb->seq)) 2218 return 0; 2219 packets_acked -= tcp_skb_pcount(skb); 2220 2221 if (packets_acked) { 2222 __u8 sacked = scb->sacked; 2223 2224 acked |= FLAG_DATA_ACKED; 2225 if (sacked) { 2226 if (sacked & TCPCB_RETRANS) { 2227 if (sacked & TCPCB_SACKED_RETRANS) 2228 tp->retrans_out -= packets_acked; 2229 acked |= FLAG_RETRANS_DATA_ACKED; 2230 *seq_rtt = -1; 2231 } else if (*seq_rtt < 0) 2232 *seq_rtt = now - scb->when; 2233 if (sacked & TCPCB_SACKED_ACKED) 2234 tp->sacked_out -= packets_acked; 2235 if (sacked & TCPCB_LOST) 2236 tp->lost_out -= packets_acked; 2237 if (sacked & TCPCB_URG) { 2238 if (tp->urg_mode && 2239 !before(seq, tp->snd_up)) 2240 tp->urg_mode = 0; 2241 } 2242 } else if (*seq_rtt < 0) 2243 *seq_rtt = now - scb->when; 2244 2245 if (tp->fackets_out) { 2246 __u32 dval = min(tp->fackets_out, packets_acked); 2247 tp->fackets_out -= dval; 2248 } 2249 tp->packets_out -= packets_acked; 2250 2251 BUG_ON(tcp_skb_pcount(skb) == 0); 2252 BUG_ON(!before(scb->seq, scb->end_seq)); 2253 } 2254 2255 return acked; 2256 } 2257 2258 static u32 tcp_usrtt(struct timeval *tv) 2259 { 2260 struct timeval now; 2261 2262 do_gettimeofday(&now); 2263 return (now.tv_sec - tv->tv_sec) * 1000000 + (now.tv_usec - tv->tv_usec); 2264 } 2265 2266 /* Remove acknowledged frames from the retransmission queue. */ 2267 static int tcp_clean_rtx_queue(struct sock *sk, __s32 *seq_rtt_p) 2268 { 2269 struct tcp_sock *tp = tcp_sk(sk); 2270 const struct inet_connection_sock *icsk = inet_csk(sk); 2271 struct sk_buff *skb; 2272 __u32 now = tcp_time_stamp; 2273 int acked = 0; 2274 __s32 seq_rtt = -1; 2275 u32 pkts_acked = 0; 2276 void (*rtt_sample)(struct sock *sk, u32 usrtt) 2277 = icsk->icsk_ca_ops->rtt_sample; 2278 struct timeval tv = { .tv_sec = 0, .tv_usec = 0 }; 2279 2280 while ((skb = skb_peek(&sk->sk_write_queue)) && 2281 skb != sk->sk_send_head) { 2282 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 2283 __u8 sacked = scb->sacked; 2284 2285 /* If our packet is before the ack sequence we can 2286 * discard it as it's confirmed to have arrived at 2287 * the other end. 2288 */ 2289 if (after(scb->end_seq, tp->snd_una)) { 2290 if (tcp_skb_pcount(skb) > 1 && 2291 after(tp->snd_una, scb->seq)) 2292 acked |= tcp_tso_acked(sk, skb, 2293 now, &seq_rtt); 2294 break; 2295 } 2296 2297 /* Initial outgoing SYN's get put onto the write_queue 2298 * just like anything else we transmit. It is not 2299 * true data, and if we misinform our callers that 2300 * this ACK acks real data, we will erroneously exit 2301 * connection startup slow start one packet too 2302 * quickly. This is severely frowned upon behavior. 2303 */ 2304 if (!(scb->flags & TCPCB_FLAG_SYN)) { 2305 acked |= FLAG_DATA_ACKED; 2306 ++pkts_acked; 2307 } else { 2308 acked |= FLAG_SYN_ACKED; 2309 tp->retrans_stamp = 0; 2310 } 2311 2312 /* MTU probing checks */ 2313 if (icsk->icsk_mtup.probe_size) { 2314 if (!after(tp->mtu_probe.probe_seq_end, TCP_SKB_CB(skb)->end_seq)) { 2315 tcp_mtup_probe_success(sk, skb); 2316 } 2317 } 2318 2319 if (sacked) { 2320 if (sacked & TCPCB_RETRANS) { 2321 if(sacked & TCPCB_SACKED_RETRANS) 2322 tp->retrans_out -= tcp_skb_pcount(skb); 2323 acked |= FLAG_RETRANS_DATA_ACKED; 2324 seq_rtt = -1; 2325 } else if (seq_rtt < 0) { 2326 seq_rtt = now - scb->when; 2327 skb_get_timestamp(skb, &tv); 2328 } 2329 if (sacked & TCPCB_SACKED_ACKED) 2330 tp->sacked_out -= tcp_skb_pcount(skb); 2331 if (sacked & TCPCB_LOST) 2332 tp->lost_out -= tcp_skb_pcount(skb); 2333 if (sacked & TCPCB_URG) { 2334 if (tp->urg_mode && 2335 !before(scb->end_seq, tp->snd_up)) 2336 tp->urg_mode = 0; 2337 } 2338 } else if (seq_rtt < 0) { 2339 seq_rtt = now - scb->when; 2340 skb_get_timestamp(skb, &tv); 2341 } 2342 tcp_dec_pcount_approx(&tp->fackets_out, skb); 2343 tcp_packets_out_dec(tp, skb); 2344 __skb_unlink(skb, &sk->sk_write_queue); 2345 sk_stream_free_skb(sk, skb); 2346 clear_all_retrans_hints(tp); 2347 } 2348 2349 if (acked&FLAG_ACKED) { 2350 tcp_ack_update_rtt(sk, acked, seq_rtt); 2351 tcp_ack_packets_out(sk, tp); 2352 if (rtt_sample && !(acked & FLAG_RETRANS_DATA_ACKED)) 2353 (*rtt_sample)(sk, tcp_usrtt(&tv)); 2354 2355 if (icsk->icsk_ca_ops->pkts_acked) 2356 icsk->icsk_ca_ops->pkts_acked(sk, pkts_acked); 2357 } 2358 2359 #if FASTRETRANS_DEBUG > 0 2360 BUG_TRAP((int)tp->sacked_out >= 0); 2361 BUG_TRAP((int)tp->lost_out >= 0); 2362 BUG_TRAP((int)tp->retrans_out >= 0); 2363 if (!tp->packets_out && tp->rx_opt.sack_ok) { 2364 const struct inet_connection_sock *icsk = inet_csk(sk); 2365 if (tp->lost_out) { 2366 printk(KERN_DEBUG "Leak l=%u %d\n", 2367 tp->lost_out, icsk->icsk_ca_state); 2368 tp->lost_out = 0; 2369 } 2370 if (tp->sacked_out) { 2371 printk(KERN_DEBUG "Leak s=%u %d\n", 2372 tp->sacked_out, icsk->icsk_ca_state); 2373 tp->sacked_out = 0; 2374 } 2375 if (tp->retrans_out) { 2376 printk(KERN_DEBUG "Leak r=%u %d\n", 2377 tp->retrans_out, icsk->icsk_ca_state); 2378 tp->retrans_out = 0; 2379 } 2380 } 2381 #endif 2382 *seq_rtt_p = seq_rtt; 2383 return acked; 2384 } 2385 2386 static void tcp_ack_probe(struct sock *sk) 2387 { 2388 const struct tcp_sock *tp = tcp_sk(sk); 2389 struct inet_connection_sock *icsk = inet_csk(sk); 2390 2391 /* Was it a usable window open? */ 2392 2393 if (!after(TCP_SKB_CB(sk->sk_send_head)->end_seq, 2394 tp->snd_una + tp->snd_wnd)) { 2395 icsk->icsk_backoff = 0; 2396 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0); 2397 /* Socket must be waked up by subsequent tcp_data_snd_check(). 2398 * This function is not for random using! 2399 */ 2400 } else { 2401 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 2402 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), 2403 TCP_RTO_MAX); 2404 } 2405 } 2406 2407 static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag) 2408 { 2409 return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || 2410 inet_csk(sk)->icsk_ca_state != TCP_CA_Open); 2411 } 2412 2413 static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag) 2414 { 2415 const struct tcp_sock *tp = tcp_sk(sk); 2416 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) && 2417 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR)); 2418 } 2419 2420 /* Check that window update is acceptable. 2421 * The function assumes that snd_una<=ack<=snd_next. 2422 */ 2423 static inline int tcp_may_update_window(const struct tcp_sock *tp, const u32 ack, 2424 const u32 ack_seq, const u32 nwin) 2425 { 2426 return (after(ack, tp->snd_una) || 2427 after(ack_seq, tp->snd_wl1) || 2428 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd)); 2429 } 2430 2431 /* Update our send window. 2432 * 2433 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 2434 * and in FreeBSD. NetBSD's one is even worse.) is wrong. 2435 */ 2436 static int tcp_ack_update_window(struct sock *sk, struct tcp_sock *tp, 2437 struct sk_buff *skb, u32 ack, u32 ack_seq) 2438 { 2439 int flag = 0; 2440 u32 nwin = ntohs(skb->h.th->window); 2441 2442 if (likely(!skb->h.th->syn)) 2443 nwin <<= tp->rx_opt.snd_wscale; 2444 2445 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { 2446 flag |= FLAG_WIN_UPDATE; 2447 tcp_update_wl(tp, ack, ack_seq); 2448 2449 if (tp->snd_wnd != nwin) { 2450 tp->snd_wnd = nwin; 2451 2452 /* Note, it is the only place, where 2453 * fast path is recovered for sending TCP. 2454 */ 2455 tp->pred_flags = 0; 2456 tcp_fast_path_check(sk, tp); 2457 2458 if (nwin > tp->max_window) { 2459 tp->max_window = nwin; 2460 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie); 2461 } 2462 } 2463 } 2464 2465 tp->snd_una = ack; 2466 2467 return flag; 2468 } 2469 2470 static void tcp_process_frto(struct sock *sk, u32 prior_snd_una) 2471 { 2472 struct tcp_sock *tp = tcp_sk(sk); 2473 2474 tcp_sync_left_out(tp); 2475 2476 if (tp->snd_una == prior_snd_una || 2477 !before(tp->snd_una, tp->frto_highmark)) { 2478 /* RTO was caused by loss, start retransmitting in 2479 * go-back-N slow start 2480 */ 2481 tcp_enter_frto_loss(sk); 2482 return; 2483 } 2484 2485 if (tp->frto_counter == 1) { 2486 /* First ACK after RTO advances the window: allow two new 2487 * segments out. 2488 */ 2489 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; 2490 } else { 2491 /* Also the second ACK after RTO advances the window. 2492 * The RTO was likely spurious. Reduce cwnd and continue 2493 * in congestion avoidance 2494 */ 2495 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 2496 tcp_moderate_cwnd(tp); 2497 } 2498 2499 /* F-RTO affects on two new ACKs following RTO. 2500 * At latest on third ACK the TCP behavior is back to normal. 2501 */ 2502 tp->frto_counter = (tp->frto_counter + 1) % 3; 2503 } 2504 2505 /* This routine deals with incoming acks, but not outgoing ones. */ 2506 static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) 2507 { 2508 struct inet_connection_sock *icsk = inet_csk(sk); 2509 struct tcp_sock *tp = tcp_sk(sk); 2510 u32 prior_snd_una = tp->snd_una; 2511 u32 ack_seq = TCP_SKB_CB(skb)->seq; 2512 u32 ack = TCP_SKB_CB(skb)->ack_seq; 2513 u32 prior_in_flight; 2514 s32 seq_rtt; 2515 int prior_packets; 2516 2517 /* If the ack is newer than sent or older than previous acks 2518 * then we can probably ignore it. 2519 */ 2520 if (after(ack, tp->snd_nxt)) 2521 goto uninteresting_ack; 2522 2523 if (before(ack, prior_snd_una)) 2524 goto old_ack; 2525 2526 if (sysctl_tcp_abc) { 2527 if (icsk->icsk_ca_state < TCP_CA_CWR) 2528 tp->bytes_acked += ack - prior_snd_una; 2529 else if (icsk->icsk_ca_state == TCP_CA_Loss) 2530 /* we assume just one segment left network */ 2531 tp->bytes_acked += min(ack - prior_snd_una, tp->mss_cache); 2532 } 2533 2534 if (!(flag&FLAG_SLOWPATH) && after(ack, prior_snd_una)) { 2535 /* Window is constant, pure forward advance. 2536 * No more checks are required. 2537 * Note, we use the fact that SND.UNA>=SND.WL2. 2538 */ 2539 tcp_update_wl(tp, ack, ack_seq); 2540 tp->snd_una = ack; 2541 flag |= FLAG_WIN_UPDATE; 2542 2543 tcp_ca_event(sk, CA_EVENT_FAST_ACK); 2544 2545 NET_INC_STATS_BH(LINUX_MIB_TCPHPACKS); 2546 } else { 2547 if (ack_seq != TCP_SKB_CB(skb)->end_seq) 2548 flag |= FLAG_DATA; 2549 else 2550 NET_INC_STATS_BH(LINUX_MIB_TCPPUREACKS); 2551 2552 flag |= tcp_ack_update_window(sk, tp, skb, ack, ack_seq); 2553 2554 if (TCP_SKB_CB(skb)->sacked) 2555 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); 2556 2557 if (TCP_ECN_rcv_ecn_echo(tp, skb->h.th)) 2558 flag |= FLAG_ECE; 2559 2560 tcp_ca_event(sk, CA_EVENT_SLOW_ACK); 2561 } 2562 2563 /* We passed data and got it acked, remove any soft error 2564 * log. Something worked... 2565 */ 2566 sk->sk_err_soft = 0; 2567 tp->rcv_tstamp = tcp_time_stamp; 2568 prior_packets = tp->packets_out; 2569 if (!prior_packets) 2570 goto no_queue; 2571 2572 prior_in_flight = tcp_packets_in_flight(tp); 2573 2574 /* See if we can take anything off of the retransmit queue. */ 2575 flag |= tcp_clean_rtx_queue(sk, &seq_rtt); 2576 2577 if (tp->frto_counter) 2578 tcp_process_frto(sk, prior_snd_una); 2579 2580 if (tcp_ack_is_dubious(sk, flag)) { 2581 /* Advance CWND, if state allows this. */ 2582 if ((flag & FLAG_DATA_ACKED) && tcp_may_raise_cwnd(sk, flag)) 2583 tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 0); 2584 tcp_fastretrans_alert(sk, prior_snd_una, prior_packets, flag); 2585 } else { 2586 if ((flag & FLAG_DATA_ACKED)) 2587 tcp_cong_avoid(sk, ack, seq_rtt, prior_in_flight, 1); 2588 } 2589 2590 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag&FLAG_NOT_DUP)) 2591 dst_confirm(sk->sk_dst_cache); 2592 2593 return 1; 2594 2595 no_queue: 2596 icsk->icsk_probes_out = 0; 2597 2598 /* If this ack opens up a zero window, clear backoff. It was 2599 * being used to time the probes, and is probably far higher than 2600 * it needs to be for normal retransmission. 2601 */ 2602 if (sk->sk_send_head) 2603 tcp_ack_probe(sk); 2604 return 1; 2605 2606 old_ack: 2607 if (TCP_SKB_CB(skb)->sacked) 2608 tcp_sacktag_write_queue(sk, skb, prior_snd_una); 2609 2610 uninteresting_ack: 2611 SOCK_DEBUG(sk, "Ack %u out of %u:%u\n", ack, tp->snd_una, tp->snd_nxt); 2612 return 0; 2613 } 2614 2615 2616 /* Look for tcp options. Normally only called on SYN and SYNACK packets. 2617 * But, this can also be called on packets in the established flow when 2618 * the fast version below fails. 2619 */ 2620 void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, int estab) 2621 { 2622 unsigned char *ptr; 2623 struct tcphdr *th = skb->h.th; 2624 int length=(th->doff*4)-sizeof(struct tcphdr); 2625 2626 ptr = (unsigned char *)(th + 1); 2627 opt_rx->saw_tstamp = 0; 2628 2629 while(length>0) { 2630 int opcode=*ptr++; 2631 int opsize; 2632 2633 switch (opcode) { 2634 case TCPOPT_EOL: 2635 return; 2636 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ 2637 length--; 2638 continue; 2639 default: 2640 opsize=*ptr++; 2641 if (opsize < 2) /* "silly options" */ 2642 return; 2643 if (opsize > length) 2644 return; /* don't parse partial options */ 2645 switch(opcode) { 2646 case TCPOPT_MSS: 2647 if(opsize==TCPOLEN_MSS && th->syn && !estab) { 2648 u16 in_mss = ntohs(get_unaligned((__be16 *)ptr)); 2649 if (in_mss) { 2650 if (opt_rx->user_mss && opt_rx->user_mss < in_mss) 2651 in_mss = opt_rx->user_mss; 2652 opt_rx->mss_clamp = in_mss; 2653 } 2654 } 2655 break; 2656 case TCPOPT_WINDOW: 2657 if(opsize==TCPOLEN_WINDOW && th->syn && !estab) 2658 if (sysctl_tcp_window_scaling) { 2659 __u8 snd_wscale = *(__u8 *) ptr; 2660 opt_rx->wscale_ok = 1; 2661 if (snd_wscale > 14) { 2662 if(net_ratelimit()) 2663 printk(KERN_INFO "tcp_parse_options: Illegal window " 2664 "scaling value %d >14 received.\n", 2665 snd_wscale); 2666 snd_wscale = 14; 2667 } 2668 opt_rx->snd_wscale = snd_wscale; 2669 } 2670 break; 2671 case TCPOPT_TIMESTAMP: 2672 if(opsize==TCPOLEN_TIMESTAMP) { 2673 if ((estab && opt_rx->tstamp_ok) || 2674 (!estab && sysctl_tcp_timestamps)) { 2675 opt_rx->saw_tstamp = 1; 2676 opt_rx->rcv_tsval = ntohl(get_unaligned((__be32 *)ptr)); 2677 opt_rx->rcv_tsecr = ntohl(get_unaligned((__be32 *)(ptr+4))); 2678 } 2679 } 2680 break; 2681 case TCPOPT_SACK_PERM: 2682 if(opsize==TCPOLEN_SACK_PERM && th->syn && !estab) { 2683 if (sysctl_tcp_sack) { 2684 opt_rx->sack_ok = 1; 2685 tcp_sack_reset(opt_rx); 2686 } 2687 } 2688 break; 2689 2690 case TCPOPT_SACK: 2691 if((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && 2692 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && 2693 opt_rx->sack_ok) { 2694 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; 2695 } 2696 #ifdef CONFIG_TCP_MD5SIG 2697 case TCPOPT_MD5SIG: 2698 /* 2699 * The MD5 Hash has already been 2700 * checked (see tcp_v{4,6}_do_rcv()). 2701 */ 2702 break; 2703 #endif 2704 }; 2705 ptr+=opsize-2; 2706 length-=opsize; 2707 }; 2708 } 2709 } 2710 2711 /* Fast parse options. This hopes to only see timestamps. 2712 * If it is wrong it falls back on tcp_parse_options(). 2713 */ 2714 static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th, 2715 struct tcp_sock *tp) 2716 { 2717 if (th->doff == sizeof(struct tcphdr)>>2) { 2718 tp->rx_opt.saw_tstamp = 0; 2719 return 0; 2720 } else if (tp->rx_opt.tstamp_ok && 2721 th->doff == (sizeof(struct tcphdr)>>2)+(TCPOLEN_TSTAMP_ALIGNED>>2)) { 2722 __be32 *ptr = (__be32 *)(th + 1); 2723 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) 2724 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { 2725 tp->rx_opt.saw_tstamp = 1; 2726 ++ptr; 2727 tp->rx_opt.rcv_tsval = ntohl(*ptr); 2728 ++ptr; 2729 tp->rx_opt.rcv_tsecr = ntohl(*ptr); 2730 return 1; 2731 } 2732 } 2733 tcp_parse_options(skb, &tp->rx_opt, 1); 2734 return 1; 2735 } 2736 2737 static inline void tcp_store_ts_recent(struct tcp_sock *tp) 2738 { 2739 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; 2740 tp->rx_opt.ts_recent_stamp = xtime.tv_sec; 2741 } 2742 2743 static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) 2744 { 2745 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { 2746 /* PAWS bug workaround wrt. ACK frames, the PAWS discard 2747 * extra check below makes sure this can only happen 2748 * for pure ACK frames. -DaveM 2749 * 2750 * Not only, also it occurs for expired timestamps. 2751 */ 2752 2753 if((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) >= 0 || 2754 xtime.tv_sec >= tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS) 2755 tcp_store_ts_recent(tp); 2756 } 2757 } 2758 2759 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM 2760 * 2761 * It is not fatal. If this ACK does _not_ change critical state (seqs, window) 2762 * it can pass through stack. So, the following predicate verifies that 2763 * this segment is not used for anything but congestion avoidance or 2764 * fast retransmit. Moreover, we even are able to eliminate most of such 2765 * second order effects, if we apply some small "replay" window (~RTO) 2766 * to timestamp space. 2767 * 2768 * All these measures still do not guarantee that we reject wrapped ACKs 2769 * on networks with high bandwidth, when sequence space is recycled fastly, 2770 * but it guarantees that such events will be very rare and do not affect 2771 * connection seriously. This doesn't look nice, but alas, PAWS is really 2772 * buggy extension. 2773 * 2774 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC 2775 * states that events when retransmit arrives after original data are rare. 2776 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is 2777 * the biggest problem on large power networks even with minor reordering. 2778 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe 2779 * up to bandwidth of 18Gigabit/sec. 8) ] 2780 */ 2781 2782 static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb) 2783 { 2784 struct tcp_sock *tp = tcp_sk(sk); 2785 struct tcphdr *th = skb->h.th; 2786 u32 seq = TCP_SKB_CB(skb)->seq; 2787 u32 ack = TCP_SKB_CB(skb)->ack_seq; 2788 2789 return (/* 1. Pure ACK with correct sequence number. */ 2790 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && 2791 2792 /* 2. ... and duplicate ACK. */ 2793 ack == tp->snd_una && 2794 2795 /* 3. ... and does not update window. */ 2796 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && 2797 2798 /* 4. ... and sits in replay window. */ 2799 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ); 2800 } 2801 2802 static inline int tcp_paws_discard(const struct sock *sk, const struct sk_buff *skb) 2803 { 2804 const struct tcp_sock *tp = tcp_sk(sk); 2805 return ((s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) > TCP_PAWS_WINDOW && 2806 xtime.tv_sec < tp->rx_opt.ts_recent_stamp + TCP_PAWS_24DAYS && 2807 !tcp_disordered_ack(sk, skb)); 2808 } 2809 2810 /* Check segment sequence number for validity. 2811 * 2812 * Segment controls are considered valid, if the segment 2813 * fits to the window after truncation to the window. Acceptability 2814 * of data (and SYN, FIN, of course) is checked separately. 2815 * See tcp_data_queue(), for example. 2816 * 2817 * Also, controls (RST is main one) are accepted using RCV.WUP instead 2818 * of RCV.NXT. Peer still did not advance his SND.UNA when we 2819 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. 2820 * (borrowed from freebsd) 2821 */ 2822 2823 static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq) 2824 { 2825 return !before(end_seq, tp->rcv_wup) && 2826 !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); 2827 } 2828 2829 /* When we get a reset we do this. */ 2830 static void tcp_reset(struct sock *sk) 2831 { 2832 /* We want the right error as BSD sees it (and indeed as we do). */ 2833 switch (sk->sk_state) { 2834 case TCP_SYN_SENT: 2835 sk->sk_err = ECONNREFUSED; 2836 break; 2837 case TCP_CLOSE_WAIT: 2838 sk->sk_err = EPIPE; 2839 break; 2840 case TCP_CLOSE: 2841 return; 2842 default: 2843 sk->sk_err = ECONNRESET; 2844 } 2845 2846 if (!sock_flag(sk, SOCK_DEAD)) 2847 sk->sk_error_report(sk); 2848 2849 tcp_done(sk); 2850 } 2851 2852 /* 2853 * Process the FIN bit. This now behaves as it is supposed to work 2854 * and the FIN takes effect when it is validly part of sequence 2855 * space. Not before when we get holes. 2856 * 2857 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT 2858 * (and thence onto LAST-ACK and finally, CLOSE, we never enter 2859 * TIME-WAIT) 2860 * 2861 * If we are in FINWAIT-1, a received FIN indicates simultaneous 2862 * close and we go into CLOSING (and later onto TIME-WAIT) 2863 * 2864 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. 2865 */ 2866 static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th) 2867 { 2868 struct tcp_sock *tp = tcp_sk(sk); 2869 2870 inet_csk_schedule_ack(sk); 2871 2872 sk->sk_shutdown |= RCV_SHUTDOWN; 2873 sock_set_flag(sk, SOCK_DONE); 2874 2875 switch (sk->sk_state) { 2876 case TCP_SYN_RECV: 2877 case TCP_ESTABLISHED: 2878 /* Move to CLOSE_WAIT */ 2879 tcp_set_state(sk, TCP_CLOSE_WAIT); 2880 inet_csk(sk)->icsk_ack.pingpong = 1; 2881 break; 2882 2883 case TCP_CLOSE_WAIT: 2884 case TCP_CLOSING: 2885 /* Received a retransmission of the FIN, do 2886 * nothing. 2887 */ 2888 break; 2889 case TCP_LAST_ACK: 2890 /* RFC793: Remain in the LAST-ACK state. */ 2891 break; 2892 2893 case TCP_FIN_WAIT1: 2894 /* This case occurs when a simultaneous close 2895 * happens, we must ack the received FIN and 2896 * enter the CLOSING state. 2897 */ 2898 tcp_send_ack(sk); 2899 tcp_set_state(sk, TCP_CLOSING); 2900 break; 2901 case TCP_FIN_WAIT2: 2902 /* Received a FIN -- send ACK and enter TIME_WAIT. */ 2903 tcp_send_ack(sk); 2904 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 2905 break; 2906 default: 2907 /* Only TCP_LISTEN and TCP_CLOSE are left, in these 2908 * cases we should never reach this piece of code. 2909 */ 2910 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n", 2911 __FUNCTION__, sk->sk_state); 2912 break; 2913 }; 2914 2915 /* It _is_ possible, that we have something out-of-order _after_ FIN. 2916 * Probably, we should reset in this case. For now drop them. 2917 */ 2918 __skb_queue_purge(&tp->out_of_order_queue); 2919 if (tp->rx_opt.sack_ok) 2920 tcp_sack_reset(&tp->rx_opt); 2921 sk_stream_mem_reclaim(sk); 2922 2923 if (!sock_flag(sk, SOCK_DEAD)) { 2924 sk->sk_state_change(sk); 2925 2926 /* Do not send POLL_HUP for half duplex close. */ 2927 if (sk->sk_shutdown == SHUTDOWN_MASK || 2928 sk->sk_state == TCP_CLOSE) 2929 sk_wake_async(sk, 1, POLL_HUP); 2930 else 2931 sk_wake_async(sk, 1, POLL_IN); 2932 } 2933 } 2934 2935 static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, u32 end_seq) 2936 { 2937 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { 2938 if (before(seq, sp->start_seq)) 2939 sp->start_seq = seq; 2940 if (after(end_seq, sp->end_seq)) 2941 sp->end_seq = end_seq; 2942 return 1; 2943 } 2944 return 0; 2945 } 2946 2947 static void tcp_dsack_set(struct tcp_sock *tp, u32 seq, u32 end_seq) 2948 { 2949 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) { 2950 if (before(seq, tp->rcv_nxt)) 2951 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOLDSENT); 2952 else 2953 NET_INC_STATS_BH(LINUX_MIB_TCPDSACKOFOSENT); 2954 2955 tp->rx_opt.dsack = 1; 2956 tp->duplicate_sack[0].start_seq = seq; 2957 tp->duplicate_sack[0].end_seq = end_seq; 2958 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + 1, 4 - tp->rx_opt.tstamp_ok); 2959 } 2960 } 2961 2962 static void tcp_dsack_extend(struct tcp_sock *tp, u32 seq, u32 end_seq) 2963 { 2964 if (!tp->rx_opt.dsack) 2965 tcp_dsack_set(tp, seq, end_seq); 2966 else 2967 tcp_sack_extend(tp->duplicate_sack, seq, end_seq); 2968 } 2969 2970 static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb) 2971 { 2972 struct tcp_sock *tp = tcp_sk(sk); 2973 2974 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 2975 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 2976 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); 2977 tcp_enter_quickack_mode(sk); 2978 2979 if (tp->rx_opt.sack_ok && sysctl_tcp_dsack) { 2980 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 2981 2982 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) 2983 end_seq = tp->rcv_nxt; 2984 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, end_seq); 2985 } 2986 } 2987 2988 tcp_send_ack(sk); 2989 } 2990 2991 /* These routines update the SACK block as out-of-order packets arrive or 2992 * in-order packets close up the sequence space. 2993 */ 2994 static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) 2995 { 2996 int this_sack; 2997 struct tcp_sack_block *sp = &tp->selective_acks[0]; 2998 struct tcp_sack_block *swalk = sp+1; 2999 3000 /* See if the recent change to the first SACK eats into 3001 * or hits the sequence space of other SACK blocks, if so coalesce. 3002 */ 3003 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks; ) { 3004 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { 3005 int i; 3006 3007 /* Zap SWALK, by moving every further SACK up by one slot. 3008 * Decrease num_sacks. 3009 */ 3010 tp->rx_opt.num_sacks--; 3011 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); 3012 for(i=this_sack; i < tp->rx_opt.num_sacks; i++) 3013 sp[i] = sp[i+1]; 3014 continue; 3015 } 3016 this_sack++, swalk++; 3017 } 3018 } 3019 3020 static inline void tcp_sack_swap(struct tcp_sack_block *sack1, struct tcp_sack_block *sack2) 3021 { 3022 __u32 tmp; 3023 3024 tmp = sack1->start_seq; 3025 sack1->start_seq = sack2->start_seq; 3026 sack2->start_seq = tmp; 3027 3028 tmp = sack1->end_seq; 3029 sack1->end_seq = sack2->end_seq; 3030 sack2->end_seq = tmp; 3031 } 3032 3033 static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) 3034 { 3035 struct tcp_sock *tp = tcp_sk(sk); 3036 struct tcp_sack_block *sp = &tp->selective_acks[0]; 3037 int cur_sacks = tp->rx_opt.num_sacks; 3038 int this_sack; 3039 3040 if (!cur_sacks) 3041 goto new_sack; 3042 3043 for (this_sack=0; this_sack<cur_sacks; this_sack++, sp++) { 3044 if (tcp_sack_extend(sp, seq, end_seq)) { 3045 /* Rotate this_sack to the first one. */ 3046 for (; this_sack>0; this_sack--, sp--) 3047 tcp_sack_swap(sp, sp-1); 3048 if (cur_sacks > 1) 3049 tcp_sack_maybe_coalesce(tp); 3050 return; 3051 } 3052 } 3053 3054 /* Could not find an adjacent existing SACK, build a new one, 3055 * put it at the front, and shift everyone else down. We 3056 * always know there is at least one SACK present already here. 3057 * 3058 * If the sack array is full, forget about the last one. 3059 */ 3060 if (this_sack >= 4) { 3061 this_sack--; 3062 tp->rx_opt.num_sacks--; 3063 sp--; 3064 } 3065 for(; this_sack > 0; this_sack--, sp--) 3066 *sp = *(sp-1); 3067 3068 new_sack: 3069 /* Build the new head SACK, and we're done. */ 3070 sp->start_seq = seq; 3071 sp->end_seq = end_seq; 3072 tp->rx_opt.num_sacks++; 3073 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); 3074 } 3075 3076 /* RCV.NXT advances, some SACKs should be eaten. */ 3077 3078 static void tcp_sack_remove(struct tcp_sock *tp) 3079 { 3080 struct tcp_sack_block *sp = &tp->selective_acks[0]; 3081 int num_sacks = tp->rx_opt.num_sacks; 3082 int this_sack; 3083 3084 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ 3085 if (skb_queue_empty(&tp->out_of_order_queue)) { 3086 tp->rx_opt.num_sacks = 0; 3087 tp->rx_opt.eff_sacks = tp->rx_opt.dsack; 3088 return; 3089 } 3090 3091 for(this_sack = 0; this_sack < num_sacks; ) { 3092 /* Check if the start of the sack is covered by RCV.NXT. */ 3093 if (!before(tp->rcv_nxt, sp->start_seq)) { 3094 int i; 3095 3096 /* RCV.NXT must cover all the block! */ 3097 BUG_TRAP(!before(tp->rcv_nxt, sp->end_seq)); 3098 3099 /* Zap this SACK, by moving forward any other SACKS. */ 3100 for (i=this_sack+1; i < num_sacks; i++) 3101 tp->selective_acks[i-1] = tp->selective_acks[i]; 3102 num_sacks--; 3103 continue; 3104 } 3105 this_sack++; 3106 sp++; 3107 } 3108 if (num_sacks != tp->rx_opt.num_sacks) { 3109 tp->rx_opt.num_sacks = num_sacks; 3110 tp->rx_opt.eff_sacks = min(tp->rx_opt.num_sacks + tp->rx_opt.dsack, 4 - tp->rx_opt.tstamp_ok); 3111 } 3112 } 3113 3114 /* This one checks to see if we can put data from the 3115 * out_of_order queue into the receive_queue. 3116 */ 3117 static void tcp_ofo_queue(struct sock *sk) 3118 { 3119 struct tcp_sock *tp = tcp_sk(sk); 3120 __u32 dsack_high = tp->rcv_nxt; 3121 struct sk_buff *skb; 3122 3123 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { 3124 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 3125 break; 3126 3127 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { 3128 __u32 dsack = dsack_high; 3129 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) 3130 dsack_high = TCP_SKB_CB(skb)->end_seq; 3131 tcp_dsack_extend(tp, TCP_SKB_CB(skb)->seq, dsack); 3132 } 3133 3134 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 3135 SOCK_DEBUG(sk, "ofo packet was already received \n"); 3136 __skb_unlink(skb, &tp->out_of_order_queue); 3137 __kfree_skb(skb); 3138 continue; 3139 } 3140 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", 3141 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 3142 TCP_SKB_CB(skb)->end_seq); 3143 3144 __skb_unlink(skb, &tp->out_of_order_queue); 3145 __skb_queue_tail(&sk->sk_receive_queue, skb); 3146 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 3147 if(skb->h.th->fin) 3148 tcp_fin(skb, sk, skb->h.th); 3149 } 3150 } 3151 3152 static int tcp_prune_queue(struct sock *sk); 3153 3154 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) 3155 { 3156 struct tcphdr *th = skb->h.th; 3157 struct tcp_sock *tp = tcp_sk(sk); 3158 int eaten = -1; 3159 3160 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) 3161 goto drop; 3162 3163 __skb_pull(skb, th->doff*4); 3164 3165 TCP_ECN_accept_cwr(tp, skb); 3166 3167 if (tp->rx_opt.dsack) { 3168 tp->rx_opt.dsack = 0; 3169 tp->rx_opt.eff_sacks = min_t(unsigned int, tp->rx_opt.num_sacks, 3170 4 - tp->rx_opt.tstamp_ok); 3171 } 3172 3173 /* Queue data for delivery to the user. 3174 * Packets in sequence go to the receive queue. 3175 * Out of sequence packets to the out_of_order_queue. 3176 */ 3177 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { 3178 if (tcp_receive_window(tp) == 0) 3179 goto out_of_window; 3180 3181 /* Ok. In sequence. In window. */ 3182 if (tp->ucopy.task == current && 3183 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && 3184 sock_owned_by_user(sk) && !tp->urg_data) { 3185 int chunk = min_t(unsigned int, skb->len, 3186 tp->ucopy.len); 3187 3188 __set_current_state(TASK_RUNNING); 3189 3190 local_bh_enable(); 3191 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { 3192 tp->ucopy.len -= chunk; 3193 tp->copied_seq += chunk; 3194 eaten = (chunk == skb->len && !th->fin); 3195 tcp_rcv_space_adjust(sk); 3196 } 3197 local_bh_disable(); 3198 } 3199 3200 if (eaten <= 0) { 3201 queue_and_out: 3202 if (eaten < 0 && 3203 (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || 3204 !sk_stream_rmem_schedule(sk, skb))) { 3205 if (tcp_prune_queue(sk) < 0 || 3206 !sk_stream_rmem_schedule(sk, skb)) 3207 goto drop; 3208 } 3209 sk_stream_set_owner_r(skb, sk); 3210 __skb_queue_tail(&sk->sk_receive_queue, skb); 3211 } 3212 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 3213 if(skb->len) 3214 tcp_event_data_recv(sk, tp, skb); 3215 if(th->fin) 3216 tcp_fin(skb, sk, th); 3217 3218 if (!skb_queue_empty(&tp->out_of_order_queue)) { 3219 tcp_ofo_queue(sk); 3220 3221 /* RFC2581. 4.2. SHOULD send immediate ACK, when 3222 * gap in queue is filled. 3223 */ 3224 if (skb_queue_empty(&tp->out_of_order_queue)) 3225 inet_csk(sk)->icsk_ack.pingpong = 0; 3226 } 3227 3228 if (tp->rx_opt.num_sacks) 3229 tcp_sack_remove(tp); 3230 3231 tcp_fast_path_check(sk, tp); 3232 3233 if (eaten > 0) 3234 __kfree_skb(skb); 3235 else if (!sock_flag(sk, SOCK_DEAD)) 3236 sk->sk_data_ready(sk, 0); 3237 return; 3238 } 3239 3240 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 3241 /* A retransmit, 2nd most common case. Force an immediate ack. */ 3242 NET_INC_STATS_BH(LINUX_MIB_DELAYEDACKLOST); 3243 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 3244 3245 out_of_window: 3246 tcp_enter_quickack_mode(sk); 3247 inet_csk_schedule_ack(sk); 3248 drop: 3249 __kfree_skb(skb); 3250 return; 3251 } 3252 3253 /* Out of window. F.e. zero window probe. */ 3254 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) 3255 goto out_of_window; 3256 3257 tcp_enter_quickack_mode(sk); 3258 3259 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 3260 /* Partial packet, seq < rcv_next < end_seq */ 3261 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", 3262 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 3263 TCP_SKB_CB(skb)->end_seq); 3264 3265 tcp_dsack_set(tp, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); 3266 3267 /* If window is closed, drop tail of packet. But after 3268 * remembering D-SACK for its head made in previous line. 3269 */ 3270 if (!tcp_receive_window(tp)) 3271 goto out_of_window; 3272 goto queue_and_out; 3273 } 3274 3275 TCP_ECN_check_ce(tp, skb); 3276 3277 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || 3278 !sk_stream_rmem_schedule(sk, skb)) { 3279 if (tcp_prune_queue(sk) < 0 || 3280 !sk_stream_rmem_schedule(sk, skb)) 3281 goto drop; 3282 } 3283 3284 /* Disable header prediction. */ 3285 tp->pred_flags = 0; 3286 inet_csk_schedule_ack(sk); 3287 3288 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", 3289 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 3290 3291 sk_stream_set_owner_r(skb, sk); 3292 3293 if (!skb_peek(&tp->out_of_order_queue)) { 3294 /* Initial out of order segment, build 1 SACK. */ 3295 if (tp->rx_opt.sack_ok) { 3296 tp->rx_opt.num_sacks = 1; 3297 tp->rx_opt.dsack = 0; 3298 tp->rx_opt.eff_sacks = 1; 3299 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; 3300 tp->selective_acks[0].end_seq = 3301 TCP_SKB_CB(skb)->end_seq; 3302 } 3303 __skb_queue_head(&tp->out_of_order_queue,skb); 3304 } else { 3305 struct sk_buff *skb1 = tp->out_of_order_queue.prev; 3306 u32 seq = TCP_SKB_CB(skb)->seq; 3307 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 3308 3309 if (seq == TCP_SKB_CB(skb1)->end_seq) { 3310 __skb_append(skb1, skb, &tp->out_of_order_queue); 3311 3312 if (!tp->rx_opt.num_sacks || 3313 tp->selective_acks[0].end_seq != seq) 3314 goto add_sack; 3315 3316 /* Common case: data arrive in order after hole. */ 3317 tp->selective_acks[0].end_seq = end_seq; 3318 return; 3319 } 3320 3321 /* Find place to insert this segment. */ 3322 do { 3323 if (!after(TCP_SKB_CB(skb1)->seq, seq)) 3324 break; 3325 } while ((skb1 = skb1->prev) != 3326 (struct sk_buff*)&tp->out_of_order_queue); 3327 3328 /* Do skb overlap to previous one? */ 3329 if (skb1 != (struct sk_buff*)&tp->out_of_order_queue && 3330 before(seq, TCP_SKB_CB(skb1)->end_seq)) { 3331 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 3332 /* All the bits are present. Drop. */ 3333 __kfree_skb(skb); 3334 tcp_dsack_set(tp, seq, end_seq); 3335 goto add_sack; 3336 } 3337 if (after(seq, TCP_SKB_CB(skb1)->seq)) { 3338 /* Partial overlap. */ 3339 tcp_dsack_set(tp, seq, TCP_SKB_CB(skb1)->end_seq); 3340 } else { 3341 skb1 = skb1->prev; 3342 } 3343 } 3344 __skb_insert(skb, skb1, skb1->next, &tp->out_of_order_queue); 3345 3346 /* And clean segments covered by new one as whole. */ 3347 while ((skb1 = skb->next) != 3348 (struct sk_buff*)&tp->out_of_order_queue && 3349 after(end_seq, TCP_SKB_CB(skb1)->seq)) { 3350 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 3351 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, end_seq); 3352 break; 3353 } 3354 __skb_unlink(skb1, &tp->out_of_order_queue); 3355 tcp_dsack_extend(tp, TCP_SKB_CB(skb1)->seq, TCP_SKB_CB(skb1)->end_seq); 3356 __kfree_skb(skb1); 3357 } 3358 3359 add_sack: 3360 if (tp->rx_opt.sack_ok) 3361 tcp_sack_new_ofo_skb(sk, seq, end_seq); 3362 } 3363 } 3364 3365 /* Collapse contiguous sequence of skbs head..tail with 3366 * sequence numbers start..end. 3367 * Segments with FIN/SYN are not collapsed (only because this 3368 * simplifies code) 3369 */ 3370 static void 3371 tcp_collapse(struct sock *sk, struct sk_buff_head *list, 3372 struct sk_buff *head, struct sk_buff *tail, 3373 u32 start, u32 end) 3374 { 3375 struct sk_buff *skb; 3376 3377 /* First, check that queue is collapsible and find 3378 * the point where collapsing can be useful. */ 3379 for (skb = head; skb != tail; ) { 3380 /* No new bits? It is possible on ofo queue. */ 3381 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 3382 struct sk_buff *next = skb->next; 3383 __skb_unlink(skb, list); 3384 __kfree_skb(skb); 3385 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); 3386 skb = next; 3387 continue; 3388 } 3389 3390 /* The first skb to collapse is: 3391 * - not SYN/FIN and 3392 * - bloated or contains data before "start" or 3393 * overlaps to the next one. 3394 */ 3395 if (!skb->h.th->syn && !skb->h.th->fin && 3396 (tcp_win_from_space(skb->truesize) > skb->len || 3397 before(TCP_SKB_CB(skb)->seq, start) || 3398 (skb->next != tail && 3399 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb->next)->seq))) 3400 break; 3401 3402 /* Decided to skip this, advance start seq. */ 3403 start = TCP_SKB_CB(skb)->end_seq; 3404 skb = skb->next; 3405 } 3406 if (skb == tail || skb->h.th->syn || skb->h.th->fin) 3407 return; 3408 3409 while (before(start, end)) { 3410 struct sk_buff *nskb; 3411 int header = skb_headroom(skb); 3412 int copy = SKB_MAX_ORDER(header, 0); 3413 3414 /* Too big header? This can happen with IPv6. */ 3415 if (copy < 0) 3416 return; 3417 if (end-start < copy) 3418 copy = end-start; 3419 nskb = alloc_skb(copy+header, GFP_ATOMIC); 3420 if (!nskb) 3421 return; 3422 skb_reserve(nskb, header); 3423 memcpy(nskb->head, skb->head, header); 3424 nskb->nh.raw = nskb->head + (skb->nh.raw-skb->head); 3425 nskb->h.raw = nskb->head + (skb->h.raw-skb->head); 3426 nskb->mac.raw = nskb->head + (skb->mac.raw-skb->head); 3427 memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); 3428 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; 3429 __skb_insert(nskb, skb->prev, skb, list); 3430 sk_stream_set_owner_r(nskb, sk); 3431 3432 /* Copy data, releasing collapsed skbs. */ 3433 while (copy > 0) { 3434 int offset = start - TCP_SKB_CB(skb)->seq; 3435 int size = TCP_SKB_CB(skb)->end_seq - start; 3436 3437 BUG_ON(offset < 0); 3438 if (size > 0) { 3439 size = min(copy, size); 3440 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) 3441 BUG(); 3442 TCP_SKB_CB(nskb)->end_seq += size; 3443 copy -= size; 3444 start += size; 3445 } 3446 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 3447 struct sk_buff *next = skb->next; 3448 __skb_unlink(skb, list); 3449 __kfree_skb(skb); 3450 NET_INC_STATS_BH(LINUX_MIB_TCPRCVCOLLAPSED); 3451 skb = next; 3452 if (skb == tail || skb->h.th->syn || skb->h.th->fin) 3453 return; 3454 } 3455 } 3456 } 3457 } 3458 3459 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs 3460 * and tcp_collapse() them until all the queue is collapsed. 3461 */ 3462 static void tcp_collapse_ofo_queue(struct sock *sk) 3463 { 3464 struct tcp_sock *tp = tcp_sk(sk); 3465 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); 3466 struct sk_buff *head; 3467 u32 start, end; 3468 3469 if (skb == NULL) 3470 return; 3471 3472 start = TCP_SKB_CB(skb)->seq; 3473 end = TCP_SKB_CB(skb)->end_seq; 3474 head = skb; 3475 3476 for (;;) { 3477 skb = skb->next; 3478 3479 /* Segment is terminated when we see gap or when 3480 * we are at the end of all the queue. */ 3481 if (skb == (struct sk_buff *)&tp->out_of_order_queue || 3482 after(TCP_SKB_CB(skb)->seq, end) || 3483 before(TCP_SKB_CB(skb)->end_seq, start)) { 3484 tcp_collapse(sk, &tp->out_of_order_queue, 3485 head, skb, start, end); 3486 head = skb; 3487 if (skb == (struct sk_buff *)&tp->out_of_order_queue) 3488 break; 3489 /* Start new segment */ 3490 start = TCP_SKB_CB(skb)->seq; 3491 end = TCP_SKB_CB(skb)->end_seq; 3492 } else { 3493 if (before(TCP_SKB_CB(skb)->seq, start)) 3494 start = TCP_SKB_CB(skb)->seq; 3495 if (after(TCP_SKB_CB(skb)->end_seq, end)) 3496 end = TCP_SKB_CB(skb)->end_seq; 3497 } 3498 } 3499 } 3500 3501 /* Reduce allocated memory if we can, trying to get 3502 * the socket within its memory limits again. 3503 * 3504 * Return less than zero if we should start dropping frames 3505 * until the socket owning process reads some of the data 3506 * to stabilize the situation. 3507 */ 3508 static int tcp_prune_queue(struct sock *sk) 3509 { 3510 struct tcp_sock *tp = tcp_sk(sk); 3511 3512 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); 3513 3514 NET_INC_STATS_BH(LINUX_MIB_PRUNECALLED); 3515 3516 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) 3517 tcp_clamp_window(sk, tp); 3518 else if (tcp_memory_pressure) 3519 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); 3520 3521 tcp_collapse_ofo_queue(sk); 3522 tcp_collapse(sk, &sk->sk_receive_queue, 3523 sk->sk_receive_queue.next, 3524 (struct sk_buff*)&sk->sk_receive_queue, 3525 tp->copied_seq, tp->rcv_nxt); 3526 sk_stream_mem_reclaim(sk); 3527 3528 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 3529 return 0; 3530 3531 /* Collapsing did not help, destructive actions follow. 3532 * This must not ever occur. */ 3533 3534 /* First, purge the out_of_order queue. */ 3535 if (!skb_queue_empty(&tp->out_of_order_queue)) { 3536 NET_INC_STATS_BH(LINUX_MIB_OFOPRUNED); 3537 __skb_queue_purge(&tp->out_of_order_queue); 3538 3539 /* Reset SACK state. A conforming SACK implementation will 3540 * do the same at a timeout based retransmit. When a connection 3541 * is in a sad state like this, we care only about integrity 3542 * of the connection not performance. 3543 */ 3544 if (tp->rx_opt.sack_ok) 3545 tcp_sack_reset(&tp->rx_opt); 3546 sk_stream_mem_reclaim(sk); 3547 } 3548 3549 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 3550 return 0; 3551 3552 /* If we are really being abused, tell the caller to silently 3553 * drop receive data on the floor. It will get retransmitted 3554 * and hopefully then we'll have sufficient space. 3555 */ 3556 NET_INC_STATS_BH(LINUX_MIB_RCVPRUNED); 3557 3558 /* Massive buffer overcommit. */ 3559 tp->pred_flags = 0; 3560 return -1; 3561 } 3562 3563 3564 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. 3565 * As additional protections, we do not touch cwnd in retransmission phases, 3566 * and if application hit its sndbuf limit recently. 3567 */ 3568 void tcp_cwnd_application_limited(struct sock *sk) 3569 { 3570 struct tcp_sock *tp = tcp_sk(sk); 3571 3572 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && 3573 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { 3574 /* Limited by application or receiver window. */ 3575 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); 3576 u32 win_used = max(tp->snd_cwnd_used, init_win); 3577 if (win_used < tp->snd_cwnd) { 3578 tp->snd_ssthresh = tcp_current_ssthresh(sk); 3579 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; 3580 } 3581 tp->snd_cwnd_used = 0; 3582 } 3583 tp->snd_cwnd_stamp = tcp_time_stamp; 3584 } 3585 3586 static int tcp_should_expand_sndbuf(struct sock *sk, struct tcp_sock *tp) 3587 { 3588 /* If the user specified a specific send buffer setting, do 3589 * not modify it. 3590 */ 3591 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) 3592 return 0; 3593 3594 /* If we are under global TCP memory pressure, do not expand. */ 3595 if (tcp_memory_pressure) 3596 return 0; 3597 3598 /* If we are under soft global TCP memory pressure, do not expand. */ 3599 if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0]) 3600 return 0; 3601 3602 /* If we filled the congestion window, do not expand. */ 3603 if (tp->packets_out >= tp->snd_cwnd) 3604 return 0; 3605 3606 return 1; 3607 } 3608 3609 /* When incoming ACK allowed to free some skb from write_queue, 3610 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket 3611 * on the exit from tcp input handler. 3612 * 3613 * PROBLEM: sndbuf expansion does not work well with largesend. 3614 */ 3615 static void tcp_new_space(struct sock *sk) 3616 { 3617 struct tcp_sock *tp = tcp_sk(sk); 3618 3619 if (tcp_should_expand_sndbuf(sk, tp)) { 3620 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + 3621 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff), 3622 demanded = max_t(unsigned int, tp->snd_cwnd, 3623 tp->reordering + 1); 3624 sndmem *= 2*demanded; 3625 if (sndmem > sk->sk_sndbuf) 3626 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); 3627 tp->snd_cwnd_stamp = tcp_time_stamp; 3628 } 3629 3630 sk->sk_write_space(sk); 3631 } 3632 3633 static void tcp_check_space(struct sock *sk) 3634 { 3635 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { 3636 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); 3637 if (sk->sk_socket && 3638 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) 3639 tcp_new_space(sk); 3640 } 3641 } 3642 3643 static inline void tcp_data_snd_check(struct sock *sk, struct tcp_sock *tp) 3644 { 3645 tcp_push_pending_frames(sk, tp); 3646 tcp_check_space(sk); 3647 } 3648 3649 /* 3650 * Check if sending an ack is needed. 3651 */ 3652 static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) 3653 { 3654 struct tcp_sock *tp = tcp_sk(sk); 3655 3656 /* More than one full frame received... */ 3657 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss 3658 /* ... and right edge of window advances far enough. 3659 * (tcp_recvmsg() will send ACK otherwise). Or... 3660 */ 3661 && __tcp_select_window(sk) >= tp->rcv_wnd) || 3662 /* We ACK each frame or... */ 3663 tcp_in_quickack_mode(sk) || 3664 /* We have out of order data. */ 3665 (ofo_possible && 3666 skb_peek(&tp->out_of_order_queue))) { 3667 /* Then ack it now */ 3668 tcp_send_ack(sk); 3669 } else { 3670 /* Else, send delayed ack. */ 3671 tcp_send_delayed_ack(sk); 3672 } 3673 } 3674 3675 static inline void tcp_ack_snd_check(struct sock *sk) 3676 { 3677 if (!inet_csk_ack_scheduled(sk)) { 3678 /* We sent a data segment already. */ 3679 return; 3680 } 3681 __tcp_ack_snd_check(sk, 1); 3682 } 3683 3684 /* 3685 * This routine is only called when we have urgent data 3686 * signaled. Its the 'slow' part of tcp_urg. It could be 3687 * moved inline now as tcp_urg is only called from one 3688 * place. We handle URGent data wrong. We have to - as 3689 * BSD still doesn't use the correction from RFC961. 3690 * For 1003.1g we should support a new option TCP_STDURG to permit 3691 * either form (or just set the sysctl tcp_stdurg). 3692 */ 3693 3694 static void tcp_check_urg(struct sock * sk, struct tcphdr * th) 3695 { 3696 struct tcp_sock *tp = tcp_sk(sk); 3697 u32 ptr = ntohs(th->urg_ptr); 3698 3699 if (ptr && !sysctl_tcp_stdurg) 3700 ptr--; 3701 ptr += ntohl(th->seq); 3702 3703 /* Ignore urgent data that we've already seen and read. */ 3704 if (after(tp->copied_seq, ptr)) 3705 return; 3706 3707 /* Do not replay urg ptr. 3708 * 3709 * NOTE: interesting situation not covered by specs. 3710 * Misbehaving sender may send urg ptr, pointing to segment, 3711 * which we already have in ofo queue. We are not able to fetch 3712 * such data and will stay in TCP_URG_NOTYET until will be eaten 3713 * by recvmsg(). Seems, we are not obliged to handle such wicked 3714 * situations. But it is worth to think about possibility of some 3715 * DoSes using some hypothetical application level deadlock. 3716 */ 3717 if (before(ptr, tp->rcv_nxt)) 3718 return; 3719 3720 /* Do we already have a newer (or duplicate) urgent pointer? */ 3721 if (tp->urg_data && !after(ptr, tp->urg_seq)) 3722 return; 3723 3724 /* Tell the world about our new urgent pointer. */ 3725 sk_send_sigurg(sk); 3726 3727 /* We may be adding urgent data when the last byte read was 3728 * urgent. To do this requires some care. We cannot just ignore 3729 * tp->copied_seq since we would read the last urgent byte again 3730 * as data, nor can we alter copied_seq until this data arrives 3731 * or we break the semantics of SIOCATMARK (and thus sockatmark()) 3732 * 3733 * NOTE. Double Dutch. Rendering to plain English: author of comment 3734 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); 3735 * and expect that both A and B disappear from stream. This is _wrong_. 3736 * Though this happens in BSD with high probability, this is occasional. 3737 * Any application relying on this is buggy. Note also, that fix "works" 3738 * only in this artificial test. Insert some normal data between A and B and we will 3739 * decline of BSD again. Verdict: it is better to remove to trap 3740 * buggy users. 3741 */ 3742 if (tp->urg_seq == tp->copied_seq && tp->urg_data && 3743 !sock_flag(sk, SOCK_URGINLINE) && 3744 tp->copied_seq != tp->rcv_nxt) { 3745 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); 3746 tp->copied_seq++; 3747 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { 3748 __skb_unlink(skb, &sk->sk_receive_queue); 3749 __kfree_skb(skb); 3750 } 3751 } 3752 3753 tp->urg_data = TCP_URG_NOTYET; 3754 tp->urg_seq = ptr; 3755 3756 /* Disable header prediction. */ 3757 tp->pred_flags = 0; 3758 } 3759 3760 /* This is the 'fast' part of urgent handling. */ 3761 static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th) 3762 { 3763 struct tcp_sock *tp = tcp_sk(sk); 3764 3765 /* Check if we get a new urgent pointer - normally not. */ 3766 if (th->urg) 3767 tcp_check_urg(sk,th); 3768 3769 /* Do we wait for any urgent data? - normally not... */ 3770 if (tp->urg_data == TCP_URG_NOTYET) { 3771 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - 3772 th->syn; 3773 3774 /* Is the urgent pointer pointing into this packet? */ 3775 if (ptr < skb->len) { 3776 u8 tmp; 3777 if (skb_copy_bits(skb, ptr, &tmp, 1)) 3778 BUG(); 3779 tp->urg_data = TCP_URG_VALID | tmp; 3780 if (!sock_flag(sk, SOCK_DEAD)) 3781 sk->sk_data_ready(sk, 0); 3782 } 3783 } 3784 } 3785 3786 static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) 3787 { 3788 struct tcp_sock *tp = tcp_sk(sk); 3789 int chunk = skb->len - hlen; 3790 int err; 3791 3792 local_bh_enable(); 3793 if (skb->ip_summed==CHECKSUM_UNNECESSARY) 3794 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); 3795 else 3796 err = skb_copy_and_csum_datagram_iovec(skb, hlen, 3797 tp->ucopy.iov); 3798 3799 if (!err) { 3800 tp->ucopy.len -= chunk; 3801 tp->copied_seq += chunk; 3802 tcp_rcv_space_adjust(sk); 3803 } 3804 3805 local_bh_disable(); 3806 return err; 3807 } 3808 3809 static __sum16 __tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) 3810 { 3811 __sum16 result; 3812 3813 if (sock_owned_by_user(sk)) { 3814 local_bh_enable(); 3815 result = __tcp_checksum_complete(skb); 3816 local_bh_disable(); 3817 } else { 3818 result = __tcp_checksum_complete(skb); 3819 } 3820 return result; 3821 } 3822 3823 static inline int tcp_checksum_complete_user(struct sock *sk, struct sk_buff *skb) 3824 { 3825 return skb->ip_summed != CHECKSUM_UNNECESSARY && 3826 __tcp_checksum_complete_user(sk, skb); 3827 } 3828 3829 #ifdef CONFIG_NET_DMA 3830 static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, int hlen) 3831 { 3832 struct tcp_sock *tp = tcp_sk(sk); 3833 int chunk = skb->len - hlen; 3834 int dma_cookie; 3835 int copied_early = 0; 3836 3837 if (tp->ucopy.wakeup) 3838 return 0; 3839 3840 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list) 3841 tp->ucopy.dma_chan = get_softnet_dma(); 3842 3843 if (tp->ucopy.dma_chan && skb->ip_summed == CHECKSUM_UNNECESSARY) { 3844 3845 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan, 3846 skb, hlen, tp->ucopy.iov, chunk, tp->ucopy.pinned_list); 3847 3848 if (dma_cookie < 0) 3849 goto out; 3850 3851 tp->ucopy.dma_cookie = dma_cookie; 3852 copied_early = 1; 3853 3854 tp->ucopy.len -= chunk; 3855 tp->copied_seq += chunk; 3856 tcp_rcv_space_adjust(sk); 3857 3858 if ((tp->ucopy.len == 0) || 3859 (tcp_flag_word(skb->h.th) & TCP_FLAG_PSH) || 3860 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) { 3861 tp->ucopy.wakeup = 1; 3862 sk->sk_data_ready(sk, 0); 3863 } 3864 } else if (chunk > 0) { 3865 tp->ucopy.wakeup = 1; 3866 sk->sk_data_ready(sk, 0); 3867 } 3868 out: 3869 return copied_early; 3870 } 3871 #endif /* CONFIG_NET_DMA */ 3872 3873 /* 3874 * TCP receive function for the ESTABLISHED state. 3875 * 3876 * It is split into a fast path and a slow path. The fast path is 3877 * disabled when: 3878 * - A zero window was announced from us - zero window probing 3879 * is only handled properly in the slow path. 3880 * - Out of order segments arrived. 3881 * - Urgent data is expected. 3882 * - There is no buffer space left 3883 * - Unexpected TCP flags/window values/header lengths are received 3884 * (detected by checking the TCP header against pred_flags) 3885 * - Data is sent in both directions. Fast path only supports pure senders 3886 * or pure receivers (this means either the sequence number or the ack 3887 * value must stay constant) 3888 * - Unexpected TCP option. 3889 * 3890 * When these conditions are not satisfied it drops into a standard 3891 * receive procedure patterned after RFC793 to handle all cases. 3892 * The first three cases are guaranteed by proper pred_flags setting, 3893 * the rest is checked inline. Fast processing is turned on in 3894 * tcp_data_queue when everything is OK. 3895 */ 3896 int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, 3897 struct tcphdr *th, unsigned len) 3898 { 3899 struct tcp_sock *tp = tcp_sk(sk); 3900 3901 /* 3902 * Header prediction. 3903 * The code loosely follows the one in the famous 3904 * "30 instruction TCP receive" Van Jacobson mail. 3905 * 3906 * Van's trick is to deposit buffers into socket queue 3907 * on a device interrupt, to call tcp_recv function 3908 * on the receive process context and checksum and copy 3909 * the buffer to user space. smart... 3910 * 3911 * Our current scheme is not silly either but we take the 3912 * extra cost of the net_bh soft interrupt processing... 3913 * We do checksum and copy also but from device to kernel. 3914 */ 3915 3916 tp->rx_opt.saw_tstamp = 0; 3917 3918 /* pred_flags is 0xS?10 << 16 + snd_wnd 3919 * if header_prediction is to be made 3920 * 'S' will always be tp->tcp_header_len >> 2 3921 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to 3922 * turn it off (when there are holes in the receive 3923 * space for instance) 3924 * PSH flag is ignored. 3925 */ 3926 3927 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && 3928 TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { 3929 int tcp_header_len = tp->tcp_header_len; 3930 3931 /* Timestamp header prediction: tcp_header_len 3932 * is automatically equal to th->doff*4 due to pred_flags 3933 * match. 3934 */ 3935 3936 /* Check timestamp */ 3937 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { 3938 __be32 *ptr = (__be32 *)(th + 1); 3939 3940 /* No? Slow path! */ 3941 if (*ptr != htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) 3942 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) 3943 goto slow_path; 3944 3945 tp->rx_opt.saw_tstamp = 1; 3946 ++ptr; 3947 tp->rx_opt.rcv_tsval = ntohl(*ptr); 3948 ++ptr; 3949 tp->rx_opt.rcv_tsecr = ntohl(*ptr); 3950 3951 /* If PAWS failed, check it more carefully in slow path */ 3952 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) 3953 goto slow_path; 3954 3955 /* DO NOT update ts_recent here, if checksum fails 3956 * and timestamp was corrupted part, it will result 3957 * in a hung connection since we will drop all 3958 * future packets due to the PAWS test. 3959 */ 3960 } 3961 3962 if (len <= tcp_header_len) { 3963 /* Bulk data transfer: sender */ 3964 if (len == tcp_header_len) { 3965 /* Predicted packet is in window by definition. 3966 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 3967 * Hence, check seq<=rcv_wup reduces to: 3968 */ 3969 if (tcp_header_len == 3970 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 3971 tp->rcv_nxt == tp->rcv_wup) 3972 tcp_store_ts_recent(tp); 3973 3974 /* We know that such packets are checksummed 3975 * on entry. 3976 */ 3977 tcp_ack(sk, skb, 0); 3978 __kfree_skb(skb); 3979 tcp_data_snd_check(sk, tp); 3980 return 0; 3981 } else { /* Header too small */ 3982 TCP_INC_STATS_BH(TCP_MIB_INERRS); 3983 goto discard; 3984 } 3985 } else { 3986 int eaten = 0; 3987 int copied_early = 0; 3988 3989 if (tp->copied_seq == tp->rcv_nxt && 3990 len - tcp_header_len <= tp->ucopy.len) { 3991 #ifdef CONFIG_NET_DMA 3992 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) { 3993 copied_early = 1; 3994 eaten = 1; 3995 } 3996 #endif 3997 if (tp->ucopy.task == current && sock_owned_by_user(sk) && !copied_early) { 3998 __set_current_state(TASK_RUNNING); 3999 4000 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) 4001 eaten = 1; 4002 } 4003 if (eaten) { 4004 /* Predicted packet is in window by definition. 4005 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 4006 * Hence, check seq<=rcv_wup reduces to: 4007 */ 4008 if (tcp_header_len == 4009 (sizeof(struct tcphdr) + 4010 TCPOLEN_TSTAMP_ALIGNED) && 4011 tp->rcv_nxt == tp->rcv_wup) 4012 tcp_store_ts_recent(tp); 4013 4014 tcp_rcv_rtt_measure_ts(sk, skb); 4015 4016 __skb_pull(skb, tcp_header_len); 4017 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4018 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITSTOUSER); 4019 } 4020 if (copied_early) 4021 tcp_cleanup_rbuf(sk, skb->len); 4022 } 4023 if (!eaten) { 4024 if (tcp_checksum_complete_user(sk, skb)) 4025 goto csum_error; 4026 4027 /* Predicted packet is in window by definition. 4028 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 4029 * Hence, check seq<=rcv_wup reduces to: 4030 */ 4031 if (tcp_header_len == 4032 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 4033 tp->rcv_nxt == tp->rcv_wup) 4034 tcp_store_ts_recent(tp); 4035 4036 tcp_rcv_rtt_measure_ts(sk, skb); 4037 4038 if ((int)skb->truesize > sk->sk_forward_alloc) 4039 goto step5; 4040 4041 NET_INC_STATS_BH(LINUX_MIB_TCPHPHITS); 4042 4043 /* Bulk data transfer: receiver */ 4044 __skb_pull(skb,tcp_header_len); 4045 __skb_queue_tail(&sk->sk_receive_queue, skb); 4046 sk_stream_set_owner_r(skb, sk); 4047 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4048 } 4049 4050 tcp_event_data_recv(sk, tp, skb); 4051 4052 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { 4053 /* Well, only one small jumplet in fast path... */ 4054 tcp_ack(sk, skb, FLAG_DATA); 4055 tcp_data_snd_check(sk, tp); 4056 if (!inet_csk_ack_scheduled(sk)) 4057 goto no_ack; 4058 } 4059 4060 __tcp_ack_snd_check(sk, 0); 4061 no_ack: 4062 #ifdef CONFIG_NET_DMA 4063 if (copied_early) 4064 __skb_queue_tail(&sk->sk_async_wait_queue, skb); 4065 else 4066 #endif 4067 if (eaten) 4068 __kfree_skb(skb); 4069 else 4070 sk->sk_data_ready(sk, 0); 4071 return 0; 4072 } 4073 } 4074 4075 slow_path: 4076 if (len < (th->doff<<2) || tcp_checksum_complete_user(sk, skb)) 4077 goto csum_error; 4078 4079 /* 4080 * RFC1323: H1. Apply PAWS check first. 4081 */ 4082 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && 4083 tcp_paws_discard(sk, skb)) { 4084 if (!th->rst) { 4085 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); 4086 tcp_send_dupack(sk, skb); 4087 goto discard; 4088 } 4089 /* Resets are accepted even if PAWS failed. 4090 4091 ts_recent update must be made after we are sure 4092 that the packet is in window. 4093 */ 4094 } 4095 4096 /* 4097 * Standard slow path. 4098 */ 4099 4100 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { 4101 /* RFC793, page 37: "In all states except SYN-SENT, all reset 4102 * (RST) segments are validated by checking their SEQ-fields." 4103 * And page 69: "If an incoming segment is not acceptable, 4104 * an acknowledgment should be sent in reply (unless the RST bit 4105 * is set, if so drop the segment and return)". 4106 */ 4107 if (!th->rst) 4108 tcp_send_dupack(sk, skb); 4109 goto discard; 4110 } 4111 4112 if(th->rst) { 4113 tcp_reset(sk); 4114 goto discard; 4115 } 4116 4117 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 4118 4119 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4120 TCP_INC_STATS_BH(TCP_MIB_INERRS); 4121 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); 4122 tcp_reset(sk); 4123 return 1; 4124 } 4125 4126 step5: 4127 if(th->ack) 4128 tcp_ack(sk, skb, FLAG_SLOWPATH); 4129 4130 tcp_rcv_rtt_measure_ts(sk, skb); 4131 4132 /* Process urgent data. */ 4133 tcp_urg(sk, skb, th); 4134 4135 /* step 7: process the segment text */ 4136 tcp_data_queue(sk, skb); 4137 4138 tcp_data_snd_check(sk, tp); 4139 tcp_ack_snd_check(sk); 4140 return 0; 4141 4142 csum_error: 4143 TCP_INC_STATS_BH(TCP_MIB_INERRS); 4144 4145 discard: 4146 __kfree_skb(skb); 4147 return 0; 4148 } 4149 4150 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 4151 struct tcphdr *th, unsigned len) 4152 { 4153 struct tcp_sock *tp = tcp_sk(sk); 4154 struct inet_connection_sock *icsk = inet_csk(sk); 4155 int saved_clamp = tp->rx_opt.mss_clamp; 4156 4157 tcp_parse_options(skb, &tp->rx_opt, 0); 4158 4159 if (th->ack) { 4160 /* rfc793: 4161 * "If the state is SYN-SENT then 4162 * first check the ACK bit 4163 * If the ACK bit is set 4164 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send 4165 * a reset (unless the RST bit is set, if so drop 4166 * the segment and return)" 4167 * 4168 * We do not send data with SYN, so that RFC-correct 4169 * test reduces to: 4170 */ 4171 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt) 4172 goto reset_and_undo; 4173 4174 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 4175 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, 4176 tcp_time_stamp)) { 4177 NET_INC_STATS_BH(LINUX_MIB_PAWSACTIVEREJECTED); 4178 goto reset_and_undo; 4179 } 4180 4181 /* Now ACK is acceptable. 4182 * 4183 * "If the RST bit is set 4184 * If the ACK was acceptable then signal the user "error: 4185 * connection reset", drop the segment, enter CLOSED state, 4186 * delete TCB, and return." 4187 */ 4188 4189 if (th->rst) { 4190 tcp_reset(sk); 4191 goto discard; 4192 } 4193 4194 /* rfc793: 4195 * "fifth, if neither of the SYN or RST bits is set then 4196 * drop the segment and return." 4197 * 4198 * See note below! 4199 * --ANK(990513) 4200 */ 4201 if (!th->syn) 4202 goto discard_and_undo; 4203 4204 /* rfc793: 4205 * "If the SYN bit is on ... 4206 * are acceptable then ... 4207 * (our SYN has been ACKed), change the connection 4208 * state to ESTABLISHED..." 4209 */ 4210 4211 TCP_ECN_rcv_synack(tp, th); 4212 4213 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 4214 tcp_ack(sk, skb, FLAG_SLOWPATH); 4215 4216 /* Ok.. it's good. Set up sequence numbers and 4217 * move to established. 4218 */ 4219 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 4220 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 4221 4222 /* RFC1323: The window in SYN & SYN/ACK segments is 4223 * never scaled. 4224 */ 4225 tp->snd_wnd = ntohs(th->window); 4226 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, TCP_SKB_CB(skb)->seq); 4227 4228 if (!tp->rx_opt.wscale_ok) { 4229 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; 4230 tp->window_clamp = min(tp->window_clamp, 65535U); 4231 } 4232 4233 if (tp->rx_opt.saw_tstamp) { 4234 tp->rx_opt.tstamp_ok = 1; 4235 tp->tcp_header_len = 4236 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 4237 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 4238 tcp_store_ts_recent(tp); 4239 } else { 4240 tp->tcp_header_len = sizeof(struct tcphdr); 4241 } 4242 4243 if (tp->rx_opt.sack_ok && sysctl_tcp_fack) 4244 tp->rx_opt.sack_ok |= 2; 4245 4246 tcp_mtup_init(sk); 4247 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 4248 tcp_initialize_rcv_mss(sk); 4249 4250 /* Remember, tcp_poll() does not lock socket! 4251 * Change state from SYN-SENT only after copied_seq 4252 * is initialized. */ 4253 tp->copied_seq = tp->rcv_nxt; 4254 smp_mb(); 4255 tcp_set_state(sk, TCP_ESTABLISHED); 4256 4257 security_inet_conn_established(sk, skb); 4258 4259 /* Make sure socket is routed, for correct metrics. */ 4260 icsk->icsk_af_ops->rebuild_header(sk); 4261 4262 tcp_init_metrics(sk); 4263 4264 tcp_init_congestion_control(sk); 4265 4266 /* Prevent spurious tcp_cwnd_restart() on first data 4267 * packet. 4268 */ 4269 tp->lsndtime = tcp_time_stamp; 4270 4271 tcp_init_buffer_space(sk); 4272 4273 if (sock_flag(sk, SOCK_KEEPOPEN)) 4274 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); 4275 4276 if (!tp->rx_opt.snd_wscale) 4277 __tcp_fast_path_on(tp, tp->snd_wnd); 4278 else 4279 tp->pred_flags = 0; 4280 4281 if (!sock_flag(sk, SOCK_DEAD)) { 4282 sk->sk_state_change(sk); 4283 sk_wake_async(sk, 0, POLL_OUT); 4284 } 4285 4286 if (sk->sk_write_pending || 4287 icsk->icsk_accept_queue.rskq_defer_accept || 4288 icsk->icsk_ack.pingpong) { 4289 /* Save one ACK. Data will be ready after 4290 * several ticks, if write_pending is set. 4291 * 4292 * It may be deleted, but with this feature tcpdumps 4293 * look so _wonderfully_ clever, that I was not able 4294 * to stand against the temptation 8) --ANK 4295 */ 4296 inet_csk_schedule_ack(sk); 4297 icsk->icsk_ack.lrcvtime = tcp_time_stamp; 4298 icsk->icsk_ack.ato = TCP_ATO_MIN; 4299 tcp_incr_quickack(sk); 4300 tcp_enter_quickack_mode(sk); 4301 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 4302 TCP_DELACK_MAX, TCP_RTO_MAX); 4303 4304 discard: 4305 __kfree_skb(skb); 4306 return 0; 4307 } else { 4308 tcp_send_ack(sk); 4309 } 4310 return -1; 4311 } 4312 4313 /* No ACK in the segment */ 4314 4315 if (th->rst) { 4316 /* rfc793: 4317 * "If the RST bit is set 4318 * 4319 * Otherwise (no ACK) drop the segment and return." 4320 */ 4321 4322 goto discard_and_undo; 4323 } 4324 4325 /* PAWS check. */ 4326 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && tcp_paws_check(&tp->rx_opt, 0)) 4327 goto discard_and_undo; 4328 4329 if (th->syn) { 4330 /* We see SYN without ACK. It is attempt of 4331 * simultaneous connect with crossed SYNs. 4332 * Particularly, it can be connect to self. 4333 */ 4334 tcp_set_state(sk, TCP_SYN_RECV); 4335 4336 if (tp->rx_opt.saw_tstamp) { 4337 tp->rx_opt.tstamp_ok = 1; 4338 tcp_store_ts_recent(tp); 4339 tp->tcp_header_len = 4340 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 4341 } else { 4342 tp->tcp_header_len = sizeof(struct tcphdr); 4343 } 4344 4345 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 4346 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 4347 4348 /* RFC1323: The window in SYN & SYN/ACK segments is 4349 * never scaled. 4350 */ 4351 tp->snd_wnd = ntohs(th->window); 4352 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 4353 tp->max_window = tp->snd_wnd; 4354 4355 TCP_ECN_rcv_syn(tp, th); 4356 4357 tcp_mtup_init(sk); 4358 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 4359 tcp_initialize_rcv_mss(sk); 4360 4361 4362 tcp_send_synack(sk); 4363 #if 0 4364 /* Note, we could accept data and URG from this segment. 4365 * There are no obstacles to make this. 4366 * 4367 * However, if we ignore data in ACKless segments sometimes, 4368 * we have no reasons to accept it sometimes. 4369 * Also, seems the code doing it in step6 of tcp_rcv_state_process 4370 * is not flawless. So, discard packet for sanity. 4371 * Uncomment this return to process the data. 4372 */ 4373 return -1; 4374 #else 4375 goto discard; 4376 #endif 4377 } 4378 /* "fifth, if neither of the SYN or RST bits is set then 4379 * drop the segment and return." 4380 */ 4381 4382 discard_and_undo: 4383 tcp_clear_options(&tp->rx_opt); 4384 tp->rx_opt.mss_clamp = saved_clamp; 4385 goto discard; 4386 4387 reset_and_undo: 4388 tcp_clear_options(&tp->rx_opt); 4389 tp->rx_opt.mss_clamp = saved_clamp; 4390 return 1; 4391 } 4392 4393 4394 /* 4395 * This function implements the receiving procedure of RFC 793 for 4396 * all states except ESTABLISHED and TIME_WAIT. 4397 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be 4398 * address independent. 4399 */ 4400 4401 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, 4402 struct tcphdr *th, unsigned len) 4403 { 4404 struct tcp_sock *tp = tcp_sk(sk); 4405 struct inet_connection_sock *icsk = inet_csk(sk); 4406 int queued = 0; 4407 4408 tp->rx_opt.saw_tstamp = 0; 4409 4410 switch (sk->sk_state) { 4411 case TCP_CLOSE: 4412 goto discard; 4413 4414 case TCP_LISTEN: 4415 if(th->ack) 4416 return 1; 4417 4418 if(th->rst) 4419 goto discard; 4420 4421 if(th->syn) { 4422 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0) 4423 return 1; 4424 4425 /* Now we have several options: In theory there is 4426 * nothing else in the frame. KA9Q has an option to 4427 * send data with the syn, BSD accepts data with the 4428 * syn up to the [to be] advertised window and 4429 * Solaris 2.1 gives you a protocol error. For now 4430 * we just ignore it, that fits the spec precisely 4431 * and avoids incompatibilities. It would be nice in 4432 * future to drop through and process the data. 4433 * 4434 * Now that TTCP is starting to be used we ought to 4435 * queue this data. 4436 * But, this leaves one open to an easy denial of 4437 * service attack, and SYN cookies can't defend 4438 * against this problem. So, we drop the data 4439 * in the interest of security over speed unless 4440 * it's still in use. 4441 */ 4442 kfree_skb(skb); 4443 return 0; 4444 } 4445 goto discard; 4446 4447 case TCP_SYN_SENT: 4448 queued = tcp_rcv_synsent_state_process(sk, skb, th, len); 4449 if (queued >= 0) 4450 return queued; 4451 4452 /* Do step6 onward by hand. */ 4453 tcp_urg(sk, skb, th); 4454 __kfree_skb(skb); 4455 tcp_data_snd_check(sk, tp); 4456 return 0; 4457 } 4458 4459 if (tcp_fast_parse_options(skb, th, tp) && tp->rx_opt.saw_tstamp && 4460 tcp_paws_discard(sk, skb)) { 4461 if (!th->rst) { 4462 NET_INC_STATS_BH(LINUX_MIB_PAWSESTABREJECTED); 4463 tcp_send_dupack(sk, skb); 4464 goto discard; 4465 } 4466 /* Reset is accepted even if it did not pass PAWS. */ 4467 } 4468 4469 /* step 1: check sequence number */ 4470 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { 4471 if (!th->rst) 4472 tcp_send_dupack(sk, skb); 4473 goto discard; 4474 } 4475 4476 /* step 2: check RST bit */ 4477 if(th->rst) { 4478 tcp_reset(sk); 4479 goto discard; 4480 } 4481 4482 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 4483 4484 /* step 3: check security and precedence [ignored] */ 4485 4486 /* step 4: 4487 * 4488 * Check for a SYN in window. 4489 */ 4490 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4491 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONSYN); 4492 tcp_reset(sk); 4493 return 1; 4494 } 4495 4496 /* step 5: check the ACK field */ 4497 if (th->ack) { 4498 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH); 4499 4500 switch(sk->sk_state) { 4501 case TCP_SYN_RECV: 4502 if (acceptable) { 4503 tp->copied_seq = tp->rcv_nxt; 4504 smp_mb(); 4505 tcp_set_state(sk, TCP_ESTABLISHED); 4506 sk->sk_state_change(sk); 4507 4508 /* Note, that this wakeup is only for marginal 4509 * crossed SYN case. Passively open sockets 4510 * are not waked up, because sk->sk_sleep == 4511 * NULL and sk->sk_socket == NULL. 4512 */ 4513 if (sk->sk_socket) { 4514 sk_wake_async(sk,0,POLL_OUT); 4515 } 4516 4517 tp->snd_una = TCP_SKB_CB(skb)->ack_seq; 4518 tp->snd_wnd = ntohs(th->window) << 4519 tp->rx_opt.snd_wscale; 4520 tcp_init_wl(tp, TCP_SKB_CB(skb)->ack_seq, 4521 TCP_SKB_CB(skb)->seq); 4522 4523 /* tcp_ack considers this ACK as duplicate 4524 * and does not calculate rtt. 4525 * Fix it at least with timestamps. 4526 */ 4527 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 4528 !tp->srtt) 4529 tcp_ack_saw_tstamp(sk, 0); 4530 4531 if (tp->rx_opt.tstamp_ok) 4532 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 4533 4534 /* Make sure socket is routed, for 4535 * correct metrics. 4536 */ 4537 icsk->icsk_af_ops->rebuild_header(sk); 4538 4539 tcp_init_metrics(sk); 4540 4541 tcp_init_congestion_control(sk); 4542 4543 /* Prevent spurious tcp_cwnd_restart() on 4544 * first data packet. 4545 */ 4546 tp->lsndtime = tcp_time_stamp; 4547 4548 tcp_mtup_init(sk); 4549 tcp_initialize_rcv_mss(sk); 4550 tcp_init_buffer_space(sk); 4551 tcp_fast_path_on(tp); 4552 } else { 4553 return 1; 4554 } 4555 break; 4556 4557 case TCP_FIN_WAIT1: 4558 if (tp->snd_una == tp->write_seq) { 4559 tcp_set_state(sk, TCP_FIN_WAIT2); 4560 sk->sk_shutdown |= SEND_SHUTDOWN; 4561 dst_confirm(sk->sk_dst_cache); 4562 4563 if (!sock_flag(sk, SOCK_DEAD)) 4564 /* Wake up lingering close() */ 4565 sk->sk_state_change(sk); 4566 else { 4567 int tmo; 4568 4569 if (tp->linger2 < 0 || 4570 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 4571 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { 4572 tcp_done(sk); 4573 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); 4574 return 1; 4575 } 4576 4577 tmo = tcp_fin_time(sk); 4578 if (tmo > TCP_TIMEWAIT_LEN) { 4579 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); 4580 } else if (th->fin || sock_owned_by_user(sk)) { 4581 /* Bad case. We could lose such FIN otherwise. 4582 * It is not a big problem, but it looks confusing 4583 * and not so rare event. We still can lose it now, 4584 * if it spins in bh_lock_sock(), but it is really 4585 * marginal case. 4586 */ 4587 inet_csk_reset_keepalive_timer(sk, tmo); 4588 } else { 4589 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 4590 goto discard; 4591 } 4592 } 4593 } 4594 break; 4595 4596 case TCP_CLOSING: 4597 if (tp->snd_una == tp->write_seq) { 4598 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 4599 goto discard; 4600 } 4601 break; 4602 4603 case TCP_LAST_ACK: 4604 if (tp->snd_una == tp->write_seq) { 4605 tcp_update_metrics(sk); 4606 tcp_done(sk); 4607 goto discard; 4608 } 4609 break; 4610 } 4611 } else 4612 goto discard; 4613 4614 /* step 6: check the URG bit */ 4615 tcp_urg(sk, skb, th); 4616 4617 /* step 7: process the segment text */ 4618 switch (sk->sk_state) { 4619 case TCP_CLOSE_WAIT: 4620 case TCP_CLOSING: 4621 case TCP_LAST_ACK: 4622 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 4623 break; 4624 case TCP_FIN_WAIT1: 4625 case TCP_FIN_WAIT2: 4626 /* RFC 793 says to queue data in these states, 4627 * RFC 1122 says we MUST send a reset. 4628 * BSD 4.4 also does reset. 4629 */ 4630 if (sk->sk_shutdown & RCV_SHUTDOWN) { 4631 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 4632 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { 4633 NET_INC_STATS_BH(LINUX_MIB_TCPABORTONDATA); 4634 tcp_reset(sk); 4635 return 1; 4636 } 4637 } 4638 /* Fall through */ 4639 case TCP_ESTABLISHED: 4640 tcp_data_queue(sk, skb); 4641 queued = 1; 4642 break; 4643 } 4644 4645 /* tcp_data could move socket to TIME-WAIT */ 4646 if (sk->sk_state != TCP_CLOSE) { 4647 tcp_data_snd_check(sk, tp); 4648 tcp_ack_snd_check(sk); 4649 } 4650 4651 if (!queued) { 4652 discard: 4653 __kfree_skb(skb); 4654 } 4655 return 0; 4656 } 4657 4658 EXPORT_SYMBOL(sysctl_tcp_ecn); 4659 EXPORT_SYMBOL(sysctl_tcp_reordering); 4660 EXPORT_SYMBOL(tcp_parse_options); 4661 EXPORT_SYMBOL(tcp_rcv_established); 4662 EXPORT_SYMBOL(tcp_rcv_state_process); 4663 EXPORT_SYMBOL(tcp_initialize_rcv_mss); 4664