1 /* 2 * INET An implementation of the TCP/IP protocol suite for the LINUX 3 * operating system. INET is implemented using the BSD Socket 4 * interface as the means of communication with the user level. 5 * 6 * Implementation of the Transmission Control Protocol(TCP). 7 * 8 * Authors: Ross Biro 9 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 10 * Mark Evans, <evansmp@uhura.aston.ac.uk> 11 * Corey Minyard <wf-rch!minyard@relay.EU.net> 12 * Florian La Roche, <flla@stud.uni-sb.de> 13 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> 14 * Linus Torvalds, <torvalds@cs.helsinki.fi> 15 * Alan Cox, <gw4pts@gw4pts.ampr.org> 16 * Matthew Dillon, <dillon@apollo.west.oic.com> 17 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 18 * Jorge Cwik, <jorge@laser.satlink.net> 19 */ 20 21 /* 22 * Changes: 23 * Pedro Roque : Fast Retransmit/Recovery. 24 * Two receive queues. 25 * Retransmit queue handled by TCP. 26 * Better retransmit timer handling. 27 * New congestion avoidance. 28 * Header prediction. 29 * Variable renaming. 30 * 31 * Eric : Fast Retransmit. 32 * Randy Scott : MSS option defines. 33 * Eric Schenk : Fixes to slow start algorithm. 34 * Eric Schenk : Yet another double ACK bug. 35 * Eric Schenk : Delayed ACK bug fixes. 36 * Eric Schenk : Floyd style fast retrans war avoidance. 37 * David S. Miller : Don't allow zero congestion window. 38 * Eric Schenk : Fix retransmitter so that it sends 39 * next packet on ack of previous packet. 40 * Andi Kleen : Moved open_request checking here 41 * and process RSTs for open_requests. 42 * Andi Kleen : Better prune_queue, and other fixes. 43 * Andrey Savochkin: Fix RTT measurements in the presence of 44 * timestamps. 45 * Andrey Savochkin: Check sequence numbers correctly when 46 * removing SACKs due to in sequence incoming 47 * data segments. 48 * Andi Kleen: Make sure we never ack data there is not 49 * enough room for. Also make this condition 50 * a fatal error if it might still happen. 51 * Andi Kleen: Add tcp_measure_rcv_mss to make 52 * connections with MSS<min(MTU,ann. MSS) 53 * work without delayed acks. 54 * Andi Kleen: Process packets with PSH set in the 55 * fast path. 56 * J Hadi Salim: ECN support 57 * Andrei Gurtov, 58 * Pasi Sarolahti, 59 * Panu Kuhlberg: Experimental audit of TCP (re)transmission 60 * engine. Lots of bugs are found. 61 * Pasi Sarolahti: F-RTO for dealing with spurious RTOs 62 */ 63 64 #include <linux/mm.h> 65 #include <linux/slab.h> 66 #include <linux/module.h> 67 #include <linux/sysctl.h> 68 #include <linux/kernel.h> 69 #include <net/dst.h> 70 #include <net/tcp.h> 71 #include <net/inet_common.h> 72 #include <linux/ipsec.h> 73 #include <asm/unaligned.h> 74 #include <net/netdma.h> 75 76 int sysctl_tcp_timestamps __read_mostly = 1; 77 int sysctl_tcp_window_scaling __read_mostly = 1; 78 int sysctl_tcp_sack __read_mostly = 1; 79 int sysctl_tcp_fack __read_mostly = 1; 80 int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH; 81 int sysctl_tcp_ecn __read_mostly = 2; 82 int sysctl_tcp_dsack __read_mostly = 1; 83 int sysctl_tcp_app_win __read_mostly = 31; 84 int sysctl_tcp_adv_win_scale __read_mostly = 2; 85 86 int sysctl_tcp_stdurg __read_mostly; 87 int sysctl_tcp_rfc1337 __read_mostly; 88 int sysctl_tcp_max_orphans __read_mostly = NR_FILE; 89 int sysctl_tcp_frto __read_mostly = 2; 90 int sysctl_tcp_frto_response __read_mostly; 91 int sysctl_tcp_nometrics_save __read_mostly; 92 93 int sysctl_tcp_thin_dupack __read_mostly; 94 95 int sysctl_tcp_moderate_rcvbuf __read_mostly = 1; 96 int sysctl_tcp_abc __read_mostly; 97 98 #define FLAG_DATA 0x01 /* Incoming frame contained data. */ 99 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ 100 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ 101 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ 102 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ 103 #define FLAG_DATA_SACKED 0x20 /* New SACK. */ 104 #define FLAG_ECE 0x40 /* ECE in this ACK */ 105 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */ 106 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ 107 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */ 108 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */ 109 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */ 110 #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */ 111 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */ 112 113 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) 114 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) 115 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) 116 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) 117 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED) 118 119 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) 120 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH)) 121 122 /* Adapt the MSS value used to make delayed ack decision to the 123 * real world. 124 */ 125 static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) 126 { 127 struct inet_connection_sock *icsk = inet_csk(sk); 128 const unsigned int lss = icsk->icsk_ack.last_seg_size; 129 unsigned int len; 130 131 icsk->icsk_ack.last_seg_size = 0; 132 133 /* skb->len may jitter because of SACKs, even if peer 134 * sends good full-sized frames. 135 */ 136 len = skb_shinfo(skb)->gso_size ? : skb->len; 137 if (len >= icsk->icsk_ack.rcv_mss) { 138 icsk->icsk_ack.rcv_mss = len; 139 } else { 140 /* Otherwise, we make more careful check taking into account, 141 * that SACKs block is variable. 142 * 143 * "len" is invariant segment length, including TCP header. 144 */ 145 len += skb->data - skb_transport_header(skb); 146 if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) || 147 /* If PSH is not set, packet should be 148 * full sized, provided peer TCP is not badly broken. 149 * This observation (if it is correct 8)) allows 150 * to handle super-low mtu links fairly. 151 */ 152 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && 153 !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) { 154 /* Subtract also invariant (if peer is RFC compliant), 155 * tcp header plus fixed timestamp option length. 156 * Resulting "len" is MSS free of SACK jitter. 157 */ 158 len -= tcp_sk(sk)->tcp_header_len; 159 icsk->icsk_ack.last_seg_size = len; 160 if (len == lss) { 161 icsk->icsk_ack.rcv_mss = len; 162 return; 163 } 164 } 165 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) 166 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; 167 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; 168 } 169 } 170 171 static void tcp_incr_quickack(struct sock *sk) 172 { 173 struct inet_connection_sock *icsk = inet_csk(sk); 174 unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); 175 176 if (quickacks == 0) 177 quickacks = 2; 178 if (quickacks > icsk->icsk_ack.quick) 179 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS); 180 } 181 182 void tcp_enter_quickack_mode(struct sock *sk) 183 { 184 struct inet_connection_sock *icsk = inet_csk(sk); 185 tcp_incr_quickack(sk); 186 icsk->icsk_ack.pingpong = 0; 187 icsk->icsk_ack.ato = TCP_ATO_MIN; 188 } 189 190 /* Send ACKs quickly, if "quick" count is not exhausted 191 * and the session is not interactive. 192 */ 193 194 static inline int tcp_in_quickack_mode(const struct sock *sk) 195 { 196 const struct inet_connection_sock *icsk = inet_csk(sk); 197 return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong; 198 } 199 200 static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp) 201 { 202 if (tp->ecn_flags & TCP_ECN_OK) 203 tp->ecn_flags |= TCP_ECN_QUEUE_CWR; 204 } 205 206 static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, struct sk_buff *skb) 207 { 208 if (tcp_hdr(skb)->cwr) 209 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; 210 } 211 212 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp) 213 { 214 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; 215 } 216 217 static inline void TCP_ECN_check_ce(struct tcp_sock *tp, struct sk_buff *skb) 218 { 219 if (tp->ecn_flags & TCP_ECN_OK) { 220 if (INET_ECN_is_ce(TCP_SKB_CB(skb)->flags)) 221 tp->ecn_flags |= TCP_ECN_DEMAND_CWR; 222 /* Funny extension: if ECT is not set on a segment, 223 * it is surely retransmit. It is not in ECN RFC, 224 * but Linux follows this rule. */ 225 else if (INET_ECN_is_not_ect((TCP_SKB_CB(skb)->flags))) 226 tcp_enter_quickack_mode((struct sock *)tp); 227 } 228 } 229 230 static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, struct tcphdr *th) 231 { 232 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr)) 233 tp->ecn_flags &= ~TCP_ECN_OK; 234 } 235 236 static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, struct tcphdr *th) 237 { 238 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr)) 239 tp->ecn_flags &= ~TCP_ECN_OK; 240 } 241 242 static inline int TCP_ECN_rcv_ecn_echo(struct tcp_sock *tp, struct tcphdr *th) 243 { 244 if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK)) 245 return 1; 246 return 0; 247 } 248 249 /* Buffer size and advertised window tuning. 250 * 251 * 1. Tuning sk->sk_sndbuf, when connection enters established state. 252 */ 253 254 static void tcp_fixup_sndbuf(struct sock *sk) 255 { 256 int sndmem = tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER + 16 + 257 sizeof(struct sk_buff); 258 259 if (sk->sk_sndbuf < 3 * sndmem) 260 sk->sk_sndbuf = min(3 * sndmem, sysctl_tcp_wmem[2]); 261 } 262 263 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh) 264 * 265 * All tcp_full_space() is split to two parts: "network" buffer, allocated 266 * forward and advertised in receiver window (tp->rcv_wnd) and 267 * "application buffer", required to isolate scheduling/application 268 * latencies from network. 269 * window_clamp is maximal advertised window. It can be less than 270 * tcp_full_space(), in this case tcp_full_space() - window_clamp 271 * is reserved for "application" buffer. The less window_clamp is 272 * the smoother our behaviour from viewpoint of network, but the lower 273 * throughput and the higher sensitivity of the connection to losses. 8) 274 * 275 * rcv_ssthresh is more strict window_clamp used at "slow start" 276 * phase to predict further behaviour of this connection. 277 * It is used for two goals: 278 * - to enforce header prediction at sender, even when application 279 * requires some significant "application buffer". It is check #1. 280 * - to prevent pruning of receive queue because of misprediction 281 * of receiver window. Check #2. 282 * 283 * The scheme does not work when sender sends good segments opening 284 * window and then starts to feed us spaghetti. But it should work 285 * in common situations. Otherwise, we have to rely on queue collapsing. 286 */ 287 288 /* Slow part of check#2. */ 289 static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb) 290 { 291 struct tcp_sock *tp = tcp_sk(sk); 292 /* Optimize this! */ 293 int truesize = tcp_win_from_space(skb->truesize) >> 1; 294 int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1; 295 296 while (tp->rcv_ssthresh <= window) { 297 if (truesize <= skb->len) 298 return 2 * inet_csk(sk)->icsk_ack.rcv_mss; 299 300 truesize >>= 1; 301 window >>= 1; 302 } 303 return 0; 304 } 305 306 static void tcp_grow_window(struct sock *sk, struct sk_buff *skb) 307 { 308 struct tcp_sock *tp = tcp_sk(sk); 309 310 /* Check #1 */ 311 if (tp->rcv_ssthresh < tp->window_clamp && 312 (int)tp->rcv_ssthresh < tcp_space(sk) && 313 !tcp_memory_pressure) { 314 int incr; 315 316 /* Check #2. Increase window, if skb with such overhead 317 * will fit to rcvbuf in future. 318 */ 319 if (tcp_win_from_space(skb->truesize) <= skb->len) 320 incr = 2 * tp->advmss; 321 else 322 incr = __tcp_grow_window(sk, skb); 323 324 if (incr) { 325 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, 326 tp->window_clamp); 327 inet_csk(sk)->icsk_ack.quick |= 1; 328 } 329 } 330 } 331 332 /* 3. Tuning rcvbuf, when connection enters established state. */ 333 334 static void tcp_fixup_rcvbuf(struct sock *sk) 335 { 336 struct tcp_sock *tp = tcp_sk(sk); 337 int rcvmem = tp->advmss + MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); 338 339 /* Try to select rcvbuf so that 4 mss-sized segments 340 * will fit to window and corresponding skbs will fit to our rcvbuf. 341 * (was 3; 4 is minimum to allow fast retransmit to work.) 342 */ 343 while (tcp_win_from_space(rcvmem) < tp->advmss) 344 rcvmem += 128; 345 if (sk->sk_rcvbuf < 4 * rcvmem) 346 sk->sk_rcvbuf = min(4 * rcvmem, sysctl_tcp_rmem[2]); 347 } 348 349 /* 4. Try to fixup all. It is made immediately after connection enters 350 * established state. 351 */ 352 static void tcp_init_buffer_space(struct sock *sk) 353 { 354 struct tcp_sock *tp = tcp_sk(sk); 355 int maxwin; 356 357 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) 358 tcp_fixup_rcvbuf(sk); 359 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) 360 tcp_fixup_sndbuf(sk); 361 362 tp->rcvq_space.space = tp->rcv_wnd; 363 364 maxwin = tcp_full_space(sk); 365 366 if (tp->window_clamp >= maxwin) { 367 tp->window_clamp = maxwin; 368 369 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) 370 tp->window_clamp = max(maxwin - 371 (maxwin >> sysctl_tcp_app_win), 372 4 * tp->advmss); 373 } 374 375 /* Force reservation of one segment. */ 376 if (sysctl_tcp_app_win && 377 tp->window_clamp > 2 * tp->advmss && 378 tp->window_clamp + tp->advmss > maxwin) 379 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); 380 381 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); 382 tp->snd_cwnd_stamp = tcp_time_stamp; 383 } 384 385 /* 5. Recalculate window clamp after socket hit its memory bounds. */ 386 static void tcp_clamp_window(struct sock *sk) 387 { 388 struct tcp_sock *tp = tcp_sk(sk); 389 struct inet_connection_sock *icsk = inet_csk(sk); 390 391 icsk->icsk_ack.quick = 0; 392 393 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && 394 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && 395 !tcp_memory_pressure && 396 atomic_read(&tcp_memory_allocated) < sysctl_tcp_mem[0]) { 397 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), 398 sysctl_tcp_rmem[2]); 399 } 400 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) 401 tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss); 402 } 403 404 /* Initialize RCV_MSS value. 405 * RCV_MSS is an our guess about MSS used by the peer. 406 * We haven't any direct information about the MSS. 407 * It's better to underestimate the RCV_MSS rather than overestimate. 408 * Overestimations make us ACKing less frequently than needed. 409 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). 410 */ 411 void tcp_initialize_rcv_mss(struct sock *sk) 412 { 413 struct tcp_sock *tp = tcp_sk(sk); 414 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); 415 416 hint = min(hint, tp->rcv_wnd / 2); 417 hint = min(hint, TCP_MSS_DEFAULT); 418 hint = max(hint, TCP_MIN_MSS); 419 420 inet_csk(sk)->icsk_ack.rcv_mss = hint; 421 } 422 423 /* Receiver "autotuning" code. 424 * 425 * The algorithm for RTT estimation w/o timestamps is based on 426 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. 427 * <http://www.lanl.gov/radiant/website/pubs/drs/lacsi2001.ps> 428 * 429 * More detail on this code can be found at 430 * <http://www.psc.edu/~jheffner/senior_thesis.ps>, 431 * though this reference is out of date. A new paper 432 * is pending. 433 */ 434 static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) 435 { 436 u32 new_sample = tp->rcv_rtt_est.rtt; 437 long m = sample; 438 439 if (m == 0) 440 m = 1; 441 442 if (new_sample != 0) { 443 /* If we sample in larger samples in the non-timestamp 444 * case, we could grossly overestimate the RTT especially 445 * with chatty applications or bulk transfer apps which 446 * are stalled on filesystem I/O. 447 * 448 * Also, since we are only going for a minimum in the 449 * non-timestamp case, we do not smooth things out 450 * else with timestamps disabled convergence takes too 451 * long. 452 */ 453 if (!win_dep) { 454 m -= (new_sample >> 3); 455 new_sample += m; 456 } else if (m < new_sample) 457 new_sample = m << 3; 458 } else { 459 /* No previous measure. */ 460 new_sample = m << 3; 461 } 462 463 if (tp->rcv_rtt_est.rtt != new_sample) 464 tp->rcv_rtt_est.rtt = new_sample; 465 } 466 467 static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) 468 { 469 if (tp->rcv_rtt_est.time == 0) 470 goto new_measure; 471 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) 472 return; 473 tcp_rcv_rtt_update(tp, jiffies - tp->rcv_rtt_est.time, 1); 474 475 new_measure: 476 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; 477 tp->rcv_rtt_est.time = tcp_time_stamp; 478 } 479 480 static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, 481 const struct sk_buff *skb) 482 { 483 struct tcp_sock *tp = tcp_sk(sk); 484 if (tp->rx_opt.rcv_tsecr && 485 (TCP_SKB_CB(skb)->end_seq - 486 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) 487 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); 488 } 489 490 /* 491 * This function should be called every time data is copied to user space. 492 * It calculates the appropriate TCP receive buffer space. 493 */ 494 void tcp_rcv_space_adjust(struct sock *sk) 495 { 496 struct tcp_sock *tp = tcp_sk(sk); 497 int time; 498 int space; 499 500 if (tp->rcvq_space.time == 0) 501 goto new_measure; 502 503 time = tcp_time_stamp - tp->rcvq_space.time; 504 if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0) 505 return; 506 507 space = 2 * (tp->copied_seq - tp->rcvq_space.seq); 508 509 space = max(tp->rcvq_space.space, space); 510 511 if (tp->rcvq_space.space != space) { 512 int rcvmem; 513 514 tp->rcvq_space.space = space; 515 516 if (sysctl_tcp_moderate_rcvbuf && 517 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { 518 int new_clamp = space; 519 520 /* Receive space grows, normalize in order to 521 * take into account packet headers and sk_buff 522 * structure overhead. 523 */ 524 space /= tp->advmss; 525 if (!space) 526 space = 1; 527 rcvmem = (tp->advmss + MAX_TCP_HEADER + 528 16 + sizeof(struct sk_buff)); 529 while (tcp_win_from_space(rcvmem) < tp->advmss) 530 rcvmem += 128; 531 space *= rcvmem; 532 space = min(space, sysctl_tcp_rmem[2]); 533 if (space > sk->sk_rcvbuf) { 534 sk->sk_rcvbuf = space; 535 536 /* Make the window clamp follow along. */ 537 tp->window_clamp = new_clamp; 538 } 539 } 540 } 541 542 new_measure: 543 tp->rcvq_space.seq = tp->copied_seq; 544 tp->rcvq_space.time = tcp_time_stamp; 545 } 546 547 /* There is something which you must keep in mind when you analyze the 548 * behavior of the tp->ato delayed ack timeout interval. When a 549 * connection starts up, we want to ack as quickly as possible. The 550 * problem is that "good" TCP's do slow start at the beginning of data 551 * transmission. The means that until we send the first few ACK's the 552 * sender will sit on his end and only queue most of his data, because 553 * he can only send snd_cwnd unacked packets at any given time. For 554 * each ACK we send, he increments snd_cwnd and transmits more of his 555 * queue. -DaveM 556 */ 557 static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) 558 { 559 struct tcp_sock *tp = tcp_sk(sk); 560 struct inet_connection_sock *icsk = inet_csk(sk); 561 u32 now; 562 563 inet_csk_schedule_ack(sk); 564 565 tcp_measure_rcv_mss(sk, skb); 566 567 tcp_rcv_rtt_measure(tp); 568 569 now = tcp_time_stamp; 570 571 if (!icsk->icsk_ack.ato) { 572 /* The _first_ data packet received, initialize 573 * delayed ACK engine. 574 */ 575 tcp_incr_quickack(sk); 576 icsk->icsk_ack.ato = TCP_ATO_MIN; 577 } else { 578 int m = now - icsk->icsk_ack.lrcvtime; 579 580 if (m <= TCP_ATO_MIN / 2) { 581 /* The fastest case is the first. */ 582 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; 583 } else if (m < icsk->icsk_ack.ato) { 584 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; 585 if (icsk->icsk_ack.ato > icsk->icsk_rto) 586 icsk->icsk_ack.ato = icsk->icsk_rto; 587 } else if (m > icsk->icsk_rto) { 588 /* Too long gap. Apparently sender failed to 589 * restart window, so that we send ACKs quickly. 590 */ 591 tcp_incr_quickack(sk); 592 sk_mem_reclaim(sk); 593 } 594 } 595 icsk->icsk_ack.lrcvtime = now; 596 597 TCP_ECN_check_ce(tp, skb); 598 599 if (skb->len >= 128) 600 tcp_grow_window(sk, skb); 601 } 602 603 /* Called to compute a smoothed rtt estimate. The data fed to this 604 * routine either comes from timestamps, or from segments that were 605 * known _not_ to have been retransmitted [see Karn/Partridge 606 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 607 * piece by Van Jacobson. 608 * NOTE: the next three routines used to be one big routine. 609 * To save cycles in the RFC 1323 implementation it was better to break 610 * it up into three procedures. -- erics 611 */ 612 static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) 613 { 614 struct tcp_sock *tp = tcp_sk(sk); 615 long m = mrtt; /* RTT */ 616 617 /* The following amusing code comes from Jacobson's 618 * article in SIGCOMM '88. Note that rtt and mdev 619 * are scaled versions of rtt and mean deviation. 620 * This is designed to be as fast as possible 621 * m stands for "measurement". 622 * 623 * On a 1990 paper the rto value is changed to: 624 * RTO = rtt + 4 * mdev 625 * 626 * Funny. This algorithm seems to be very broken. 627 * These formulae increase RTO, when it should be decreased, increase 628 * too slowly, when it should be increased quickly, decrease too quickly 629 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely 630 * does not matter how to _calculate_ it. Seems, it was trap 631 * that VJ failed to avoid. 8) 632 */ 633 if (m == 0) 634 m = 1; 635 if (tp->srtt != 0) { 636 m -= (tp->srtt >> 3); /* m is now error in rtt est */ 637 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ 638 if (m < 0) { 639 m = -m; /* m is now abs(error) */ 640 m -= (tp->mdev >> 2); /* similar update on mdev */ 641 /* This is similar to one of Eifel findings. 642 * Eifel blocks mdev updates when rtt decreases. 643 * This solution is a bit different: we use finer gain 644 * for mdev in this case (alpha*beta). 645 * Like Eifel it also prevents growth of rto, 646 * but also it limits too fast rto decreases, 647 * happening in pure Eifel. 648 */ 649 if (m > 0) 650 m >>= 3; 651 } else { 652 m -= (tp->mdev >> 2); /* similar update on mdev */ 653 } 654 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ 655 if (tp->mdev > tp->mdev_max) { 656 tp->mdev_max = tp->mdev; 657 if (tp->mdev_max > tp->rttvar) 658 tp->rttvar = tp->mdev_max; 659 } 660 if (after(tp->snd_una, tp->rtt_seq)) { 661 if (tp->mdev_max < tp->rttvar) 662 tp->rttvar -= (tp->rttvar - tp->mdev_max) >> 2; 663 tp->rtt_seq = tp->snd_nxt; 664 tp->mdev_max = tcp_rto_min(sk); 665 } 666 } else { 667 /* no previous measure. */ 668 tp->srtt = m << 3; /* take the measured time to be rtt */ 669 tp->mdev = m << 1; /* make sure rto = 3*rtt */ 670 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); 671 tp->rtt_seq = tp->snd_nxt; 672 } 673 } 674 675 /* Calculate rto without backoff. This is the second half of Van Jacobson's 676 * routine referred to above. 677 */ 678 static inline void tcp_set_rto(struct sock *sk) 679 { 680 const struct tcp_sock *tp = tcp_sk(sk); 681 /* Old crap is replaced with new one. 8) 682 * 683 * More seriously: 684 * 1. If rtt variance happened to be less 50msec, it is hallucination. 685 * It cannot be less due to utterly erratic ACK generation made 686 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ 687 * to do with delayed acks, because at cwnd>2 true delack timeout 688 * is invisible. Actually, Linux-2.4 also generates erratic 689 * ACKs in some circumstances. 690 */ 691 inet_csk(sk)->icsk_rto = __tcp_set_rto(tp); 692 693 /* 2. Fixups made earlier cannot be right. 694 * If we do not estimate RTO correctly without them, 695 * all the algo is pure shit and should be replaced 696 * with correct one. It is exactly, which we pretend to do. 697 */ 698 699 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo 700 * guarantees that rto is higher. 701 */ 702 tcp_bound_rto(sk); 703 } 704 705 /* Save metrics learned by this TCP session. 706 This function is called only, when TCP finishes successfully 707 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. 708 */ 709 void tcp_update_metrics(struct sock *sk) 710 { 711 struct tcp_sock *tp = tcp_sk(sk); 712 struct dst_entry *dst = __sk_dst_get(sk); 713 714 if (sysctl_tcp_nometrics_save) 715 return; 716 717 dst_confirm(dst); 718 719 if (dst && (dst->flags & DST_HOST)) { 720 const struct inet_connection_sock *icsk = inet_csk(sk); 721 int m; 722 unsigned long rtt; 723 724 if (icsk->icsk_backoff || !tp->srtt) { 725 /* This session failed to estimate rtt. Why? 726 * Probably, no packets returned in time. 727 * Reset our results. 728 */ 729 if (!(dst_metric_locked(dst, RTAX_RTT))) 730 dst->metrics[RTAX_RTT - 1] = 0; 731 return; 732 } 733 734 rtt = dst_metric_rtt(dst, RTAX_RTT); 735 m = rtt - tp->srtt; 736 737 /* If newly calculated rtt larger than stored one, 738 * store new one. Otherwise, use EWMA. Remember, 739 * rtt overestimation is always better than underestimation. 740 */ 741 if (!(dst_metric_locked(dst, RTAX_RTT))) { 742 if (m <= 0) 743 set_dst_metric_rtt(dst, RTAX_RTT, tp->srtt); 744 else 745 set_dst_metric_rtt(dst, RTAX_RTT, rtt - (m >> 3)); 746 } 747 748 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { 749 unsigned long var; 750 if (m < 0) 751 m = -m; 752 753 /* Scale deviation to rttvar fixed point */ 754 m >>= 1; 755 if (m < tp->mdev) 756 m = tp->mdev; 757 758 var = dst_metric_rtt(dst, RTAX_RTTVAR); 759 if (m >= var) 760 var = m; 761 else 762 var -= (var - m) >> 2; 763 764 set_dst_metric_rtt(dst, RTAX_RTTVAR, var); 765 } 766 767 if (tcp_in_initial_slowstart(tp)) { 768 /* Slow start still did not finish. */ 769 if (dst_metric(dst, RTAX_SSTHRESH) && 770 !dst_metric_locked(dst, RTAX_SSTHRESH) && 771 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) 772 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_cwnd >> 1; 773 if (!dst_metric_locked(dst, RTAX_CWND) && 774 tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) 775 dst->metrics[RTAX_CWND - 1] = tp->snd_cwnd; 776 } else if (tp->snd_cwnd > tp->snd_ssthresh && 777 icsk->icsk_ca_state == TCP_CA_Open) { 778 /* Cong. avoidance phase, cwnd is reliable. */ 779 if (!dst_metric_locked(dst, RTAX_SSTHRESH)) 780 dst->metrics[RTAX_SSTHRESH-1] = 781 max(tp->snd_cwnd >> 1, tp->snd_ssthresh); 782 if (!dst_metric_locked(dst, RTAX_CWND)) 783 dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_cwnd) >> 1; 784 } else { 785 /* Else slow start did not finish, cwnd is non-sense, 786 ssthresh may be also invalid. 787 */ 788 if (!dst_metric_locked(dst, RTAX_CWND)) 789 dst->metrics[RTAX_CWND-1] = (dst_metric(dst, RTAX_CWND) + tp->snd_ssthresh) >> 1; 790 if (dst_metric(dst, RTAX_SSTHRESH) && 791 !dst_metric_locked(dst, RTAX_SSTHRESH) && 792 tp->snd_ssthresh > dst_metric(dst, RTAX_SSTHRESH)) 793 dst->metrics[RTAX_SSTHRESH-1] = tp->snd_ssthresh; 794 } 795 796 if (!dst_metric_locked(dst, RTAX_REORDERING)) { 797 if (dst_metric(dst, RTAX_REORDERING) < tp->reordering && 798 tp->reordering != sysctl_tcp_reordering) 799 dst->metrics[RTAX_REORDERING-1] = tp->reordering; 800 } 801 } 802 } 803 804 /* Numbers are taken from RFC3390. 805 * 806 * John Heffner states: 807 * 808 * The RFC specifies a window of no more than 4380 bytes 809 * unless 2*MSS > 4380. Reading the pseudocode in the RFC 810 * is a bit misleading because they use a clamp at 4380 bytes 811 * rather than use a multiplier in the relevant range. 812 */ 813 __u32 tcp_init_cwnd(struct tcp_sock *tp, struct dst_entry *dst) 814 { 815 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); 816 817 if (!cwnd) { 818 if (tp->mss_cache > 1460) 819 cwnd = 2; 820 else 821 cwnd = (tp->mss_cache > 1095) ? 3 : 4; 822 } 823 return min_t(__u32, cwnd, tp->snd_cwnd_clamp); 824 } 825 826 /* Set slow start threshold and cwnd not falling to slow start */ 827 void tcp_enter_cwr(struct sock *sk, const int set_ssthresh) 828 { 829 struct tcp_sock *tp = tcp_sk(sk); 830 const struct inet_connection_sock *icsk = inet_csk(sk); 831 832 tp->prior_ssthresh = 0; 833 tp->bytes_acked = 0; 834 if (icsk->icsk_ca_state < TCP_CA_CWR) { 835 tp->undo_marker = 0; 836 if (set_ssthresh) 837 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 838 tp->snd_cwnd = min(tp->snd_cwnd, 839 tcp_packets_in_flight(tp) + 1U); 840 tp->snd_cwnd_cnt = 0; 841 tp->high_seq = tp->snd_nxt; 842 tp->snd_cwnd_stamp = tcp_time_stamp; 843 TCP_ECN_queue_cwr(tp); 844 845 tcp_set_ca_state(sk, TCP_CA_CWR); 846 } 847 } 848 849 /* 850 * Packet counting of FACK is based on in-order assumptions, therefore TCP 851 * disables it when reordering is detected 852 */ 853 static void tcp_disable_fack(struct tcp_sock *tp) 854 { 855 /* RFC3517 uses different metric in lost marker => reset on change */ 856 if (tcp_is_fack(tp)) 857 tp->lost_skb_hint = NULL; 858 tp->rx_opt.sack_ok &= ~2; 859 } 860 861 /* Take a notice that peer is sending D-SACKs */ 862 static void tcp_dsack_seen(struct tcp_sock *tp) 863 { 864 tp->rx_opt.sack_ok |= 4; 865 } 866 867 /* Initialize metrics on socket. */ 868 869 static void tcp_init_metrics(struct sock *sk) 870 { 871 struct tcp_sock *tp = tcp_sk(sk); 872 struct dst_entry *dst = __sk_dst_get(sk); 873 874 if (dst == NULL) 875 goto reset; 876 877 dst_confirm(dst); 878 879 if (dst_metric_locked(dst, RTAX_CWND)) 880 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); 881 if (dst_metric(dst, RTAX_SSTHRESH)) { 882 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); 883 if (tp->snd_ssthresh > tp->snd_cwnd_clamp) 884 tp->snd_ssthresh = tp->snd_cwnd_clamp; 885 } 886 if (dst_metric(dst, RTAX_REORDERING) && 887 tp->reordering != dst_metric(dst, RTAX_REORDERING)) { 888 tcp_disable_fack(tp); 889 tp->reordering = dst_metric(dst, RTAX_REORDERING); 890 } 891 892 if (dst_metric(dst, RTAX_RTT) == 0) 893 goto reset; 894 895 if (!tp->srtt && dst_metric_rtt(dst, RTAX_RTT) < (TCP_TIMEOUT_INIT << 3)) 896 goto reset; 897 898 /* Initial rtt is determined from SYN,SYN-ACK. 899 * The segment is small and rtt may appear much 900 * less than real one. Use per-dst memory 901 * to make it more realistic. 902 * 903 * A bit of theory. RTT is time passed after "normal" sized packet 904 * is sent until it is ACKed. In normal circumstances sending small 905 * packets force peer to delay ACKs and calculation is correct too. 906 * The algorithm is adaptive and, provided we follow specs, it 907 * NEVER underestimate RTT. BUT! If peer tries to make some clever 908 * tricks sort of "quick acks" for time long enough to decrease RTT 909 * to low value, and then abruptly stops to do it and starts to delay 910 * ACKs, wait for troubles. 911 */ 912 if (dst_metric_rtt(dst, RTAX_RTT) > tp->srtt) { 913 tp->srtt = dst_metric_rtt(dst, RTAX_RTT); 914 tp->rtt_seq = tp->snd_nxt; 915 } 916 if (dst_metric_rtt(dst, RTAX_RTTVAR) > tp->mdev) { 917 tp->mdev = dst_metric_rtt(dst, RTAX_RTTVAR); 918 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); 919 } 920 tcp_set_rto(sk); 921 if (inet_csk(sk)->icsk_rto < TCP_TIMEOUT_INIT && !tp->rx_opt.saw_tstamp) 922 goto reset; 923 924 cwnd: 925 tp->snd_cwnd = tcp_init_cwnd(tp, dst); 926 tp->snd_cwnd_stamp = tcp_time_stamp; 927 return; 928 929 reset: 930 /* Play conservative. If timestamps are not 931 * supported, TCP will fail to recalculate correct 932 * rtt, if initial rto is too small. FORGET ALL AND RESET! 933 */ 934 if (!tp->rx_opt.saw_tstamp && tp->srtt) { 935 tp->srtt = 0; 936 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_INIT; 937 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; 938 } 939 goto cwnd; 940 } 941 942 static void tcp_update_reordering(struct sock *sk, const int metric, 943 const int ts) 944 { 945 struct tcp_sock *tp = tcp_sk(sk); 946 if (metric > tp->reordering) { 947 int mib_idx; 948 949 tp->reordering = min(TCP_MAX_REORDERING, metric); 950 951 /* This exciting event is worth to be remembered. 8) */ 952 if (ts) 953 mib_idx = LINUX_MIB_TCPTSREORDER; 954 else if (tcp_is_reno(tp)) 955 mib_idx = LINUX_MIB_TCPRENOREORDER; 956 else if (tcp_is_fack(tp)) 957 mib_idx = LINUX_MIB_TCPFACKREORDER; 958 else 959 mib_idx = LINUX_MIB_TCPSACKREORDER; 960 961 NET_INC_STATS_BH(sock_net(sk), mib_idx); 962 #if FASTRETRANS_DEBUG > 1 963 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", 964 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, 965 tp->reordering, 966 tp->fackets_out, 967 tp->sacked_out, 968 tp->undo_marker ? tp->undo_retrans : 0); 969 #endif 970 tcp_disable_fack(tp); 971 } 972 } 973 974 /* This must be called before lost_out is incremented */ 975 static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) 976 { 977 if ((tp->retransmit_skb_hint == NULL) || 978 before(TCP_SKB_CB(skb)->seq, 979 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) 980 tp->retransmit_skb_hint = skb; 981 982 if (!tp->lost_out || 983 after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high)) 984 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; 985 } 986 987 static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb) 988 { 989 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { 990 tcp_verify_retransmit_hint(tp, skb); 991 992 tp->lost_out += tcp_skb_pcount(skb); 993 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 994 } 995 } 996 997 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, 998 struct sk_buff *skb) 999 { 1000 tcp_verify_retransmit_hint(tp, skb); 1001 1002 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { 1003 tp->lost_out += tcp_skb_pcount(skb); 1004 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1005 } 1006 } 1007 1008 /* This procedure tags the retransmission queue when SACKs arrive. 1009 * 1010 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). 1011 * Packets in queue with these bits set are counted in variables 1012 * sacked_out, retrans_out and lost_out, correspondingly. 1013 * 1014 * Valid combinations are: 1015 * Tag InFlight Description 1016 * 0 1 - orig segment is in flight. 1017 * S 0 - nothing flies, orig reached receiver. 1018 * L 0 - nothing flies, orig lost by net. 1019 * R 2 - both orig and retransmit are in flight. 1020 * L|R 1 - orig is lost, retransmit is in flight. 1021 * S|R 1 - orig reached receiver, retrans is still in flight. 1022 * (L|S|R is logically valid, it could occur when L|R is sacked, 1023 * but it is equivalent to plain S and code short-curcuits it to S. 1024 * L|S is logically invalid, it would mean -1 packet in flight 8)) 1025 * 1026 * These 6 states form finite state machine, controlled by the following events: 1027 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) 1028 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) 1029 * 3. Loss detection event of one of three flavors: 1030 * A. Scoreboard estimator decided the packet is lost. 1031 * A'. Reno "three dupacks" marks head of queue lost. 1032 * A''. Its FACK modfication, head until snd.fack is lost. 1033 * B. SACK arrives sacking data transmitted after never retransmitted 1034 * hole was sent out. 1035 * C. SACK arrives sacking SND.NXT at the moment, when the 1036 * segment was retransmitted. 1037 * 4. D-SACK added new rule: D-SACK changes any tag to S. 1038 * 1039 * It is pleasant to note, that state diagram turns out to be commutative, 1040 * so that we are allowed not to be bothered by order of our actions, 1041 * when multiple events arrive simultaneously. (see the function below). 1042 * 1043 * Reordering detection. 1044 * -------------------- 1045 * Reordering metric is maximal distance, which a packet can be displaced 1046 * in packet stream. With SACKs we can estimate it: 1047 * 1048 * 1. SACK fills old hole and the corresponding segment was not 1049 * ever retransmitted -> reordering. Alas, we cannot use it 1050 * when segment was retransmitted. 1051 * 2. The last flaw is solved with D-SACK. D-SACK arrives 1052 * for retransmitted and already SACKed segment -> reordering.. 1053 * Both of these heuristics are not used in Loss state, when we cannot 1054 * account for retransmits accurately. 1055 * 1056 * SACK block validation. 1057 * ---------------------- 1058 * 1059 * SACK block range validation checks that the received SACK block fits to 1060 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT. 1061 * Note that SND.UNA is not included to the range though being valid because 1062 * it means that the receiver is rather inconsistent with itself reporting 1063 * SACK reneging when it should advance SND.UNA. Such SACK block this is 1064 * perfectly valid, however, in light of RFC2018 which explicitly states 1065 * that "SACK block MUST reflect the newest segment. Even if the newest 1066 * segment is going to be discarded ...", not that it looks very clever 1067 * in case of head skb. Due to potentional receiver driven attacks, we 1068 * choose to avoid immediate execution of a walk in write queue due to 1069 * reneging and defer head skb's loss recovery to standard loss recovery 1070 * procedure that will eventually trigger (nothing forbids us doing this). 1071 * 1072 * Implements also blockage to start_seq wrap-around. Problem lies in the 1073 * fact that though start_seq (s) is before end_seq (i.e., not reversed), 1074 * there's no guarantee that it will be before snd_nxt (n). The problem 1075 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt 1076 * wrap (s_w): 1077 * 1078 * <- outs wnd -> <- wrapzone -> 1079 * u e n u_w e_w s n_w 1080 * | | | | | | | 1081 * |<------------+------+----- TCP seqno space --------------+---------->| 1082 * ...-- <2^31 ->| |<--------... 1083 * ...---- >2^31 ------>| |<--------... 1084 * 1085 * Current code wouldn't be vulnerable but it's better still to discard such 1086 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat 1087 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in 1088 * snd_nxt wrap -> snd_una region will then become "well defined", i.e., 1089 * equal to the ideal case (infinite seqno space without wrap caused issues). 1090 * 1091 * With D-SACK the lower bound is extended to cover sequence space below 1092 * SND.UNA down to undo_marker, which is the last point of interest. Yet 1093 * again, D-SACK block must not to go across snd_una (for the same reason as 1094 * for the normal SACK blocks, explained above). But there all simplicity 1095 * ends, TCP might receive valid D-SACKs below that. As long as they reside 1096 * fully below undo_marker they do not affect behavior in anyway and can 1097 * therefore be safely ignored. In rare cases (which are more or less 1098 * theoretical ones), the D-SACK will nicely cross that boundary due to skb 1099 * fragmentation and packet reordering past skb's retransmission. To consider 1100 * them correctly, the acceptable range must be extended even more though 1101 * the exact amount is rather hard to quantify. However, tp->max_window can 1102 * be used as an exaggerated estimate. 1103 */ 1104 static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack, 1105 u32 start_seq, u32 end_seq) 1106 { 1107 /* Too far in future, or reversed (interpretation is ambiguous) */ 1108 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq)) 1109 return 0; 1110 1111 /* Nasty start_seq wrap-around check (see comments above) */ 1112 if (!before(start_seq, tp->snd_nxt)) 1113 return 0; 1114 1115 /* In outstanding window? ...This is valid exit for D-SACKs too. 1116 * start_seq == snd_una is non-sensical (see comments above) 1117 */ 1118 if (after(start_seq, tp->snd_una)) 1119 return 1; 1120 1121 if (!is_dsack || !tp->undo_marker) 1122 return 0; 1123 1124 /* ...Then it's D-SACK, and must reside below snd_una completely */ 1125 if (!after(end_seq, tp->snd_una)) 1126 return 0; 1127 1128 if (!before(start_seq, tp->undo_marker)) 1129 return 1; 1130 1131 /* Too old */ 1132 if (!after(end_seq, tp->undo_marker)) 1133 return 0; 1134 1135 /* Undo_marker boundary crossing (overestimates a lot). Known already: 1136 * start_seq < undo_marker and end_seq >= undo_marker. 1137 */ 1138 return !before(start_seq, end_seq - tp->max_window); 1139 } 1140 1141 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving". 1142 * Event "C". Later note: FACK people cheated me again 8), we have to account 1143 * for reordering! Ugly, but should help. 1144 * 1145 * Search retransmitted skbs from write_queue that were sent when snd_nxt was 1146 * less than what is now known to be received by the other end (derived from 1147 * highest SACK block). Also calculate the lowest snd_nxt among the remaining 1148 * retransmitted skbs to avoid some costly processing per ACKs. 1149 */ 1150 static void tcp_mark_lost_retrans(struct sock *sk) 1151 { 1152 const struct inet_connection_sock *icsk = inet_csk(sk); 1153 struct tcp_sock *tp = tcp_sk(sk); 1154 struct sk_buff *skb; 1155 int cnt = 0; 1156 u32 new_low_seq = tp->snd_nxt; 1157 u32 received_upto = tcp_highest_sack_seq(tp); 1158 1159 if (!tcp_is_fack(tp) || !tp->retrans_out || 1160 !after(received_upto, tp->lost_retrans_low) || 1161 icsk->icsk_ca_state != TCP_CA_Recovery) 1162 return; 1163 1164 tcp_for_write_queue(skb, sk) { 1165 u32 ack_seq = TCP_SKB_CB(skb)->ack_seq; 1166 1167 if (skb == tcp_send_head(sk)) 1168 break; 1169 if (cnt == tp->retrans_out) 1170 break; 1171 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1172 continue; 1173 1174 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) 1175 continue; 1176 1177 /* TODO: We would like to get rid of tcp_is_fack(tp) only 1178 * constraint here (see above) but figuring out that at 1179 * least tp->reordering SACK blocks reside between ack_seq 1180 * and received_upto is not easy task to do cheaply with 1181 * the available datastructures. 1182 * 1183 * Whether FACK should check here for tp->reordering segs 1184 * in-between one could argue for either way (it would be 1185 * rather simple to implement as we could count fack_count 1186 * during the walk and do tp->fackets_out - fack_count). 1187 */ 1188 if (after(received_upto, ack_seq)) { 1189 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1190 tp->retrans_out -= tcp_skb_pcount(skb); 1191 1192 tcp_skb_mark_lost_uncond_verify(tp, skb); 1193 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT); 1194 } else { 1195 if (before(ack_seq, new_low_seq)) 1196 new_low_seq = ack_seq; 1197 cnt += tcp_skb_pcount(skb); 1198 } 1199 } 1200 1201 if (tp->retrans_out) 1202 tp->lost_retrans_low = new_low_seq; 1203 } 1204 1205 static int tcp_check_dsack(struct sock *sk, struct sk_buff *ack_skb, 1206 struct tcp_sack_block_wire *sp, int num_sacks, 1207 u32 prior_snd_una) 1208 { 1209 struct tcp_sock *tp = tcp_sk(sk); 1210 u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq); 1211 u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq); 1212 int dup_sack = 0; 1213 1214 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) { 1215 dup_sack = 1; 1216 tcp_dsack_seen(tp); 1217 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV); 1218 } else if (num_sacks > 1) { 1219 u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq); 1220 u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq); 1221 1222 if (!after(end_seq_0, end_seq_1) && 1223 !before(start_seq_0, start_seq_1)) { 1224 dup_sack = 1; 1225 tcp_dsack_seen(tp); 1226 NET_INC_STATS_BH(sock_net(sk), 1227 LINUX_MIB_TCPDSACKOFORECV); 1228 } 1229 } 1230 1231 /* D-SACK for already forgotten data... Do dumb counting. */ 1232 if (dup_sack && 1233 !after(end_seq_0, prior_snd_una) && 1234 after(end_seq_0, tp->undo_marker)) 1235 tp->undo_retrans--; 1236 1237 return dup_sack; 1238 } 1239 1240 struct tcp_sacktag_state { 1241 int reord; 1242 int fack_count; 1243 int flag; 1244 }; 1245 1246 /* Check if skb is fully within the SACK block. In presence of GSO skbs, 1247 * the incoming SACK may not exactly match but we can find smaller MSS 1248 * aligned portion of it that matches. Therefore we might need to fragment 1249 * which may fail and creates some hassle (caller must handle error case 1250 * returns). 1251 * 1252 * FIXME: this could be merged to shift decision code 1253 */ 1254 static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, 1255 u32 start_seq, u32 end_seq) 1256 { 1257 int in_sack, err; 1258 unsigned int pkt_len; 1259 unsigned int mss; 1260 1261 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && 1262 !before(end_seq, TCP_SKB_CB(skb)->end_seq); 1263 1264 if (tcp_skb_pcount(skb) > 1 && !in_sack && 1265 after(TCP_SKB_CB(skb)->end_seq, start_seq)) { 1266 mss = tcp_skb_mss(skb); 1267 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); 1268 1269 if (!in_sack) { 1270 pkt_len = start_seq - TCP_SKB_CB(skb)->seq; 1271 if (pkt_len < mss) 1272 pkt_len = mss; 1273 } else { 1274 pkt_len = end_seq - TCP_SKB_CB(skb)->seq; 1275 if (pkt_len < mss) 1276 return -EINVAL; 1277 } 1278 1279 /* Round if necessary so that SACKs cover only full MSSes 1280 * and/or the remaining small portion (if present) 1281 */ 1282 if (pkt_len > mss) { 1283 unsigned int new_len = (pkt_len / mss) * mss; 1284 if (!in_sack && new_len < pkt_len) { 1285 new_len += mss; 1286 if (new_len > skb->len) 1287 return 0; 1288 } 1289 pkt_len = new_len; 1290 } 1291 err = tcp_fragment(sk, skb, pkt_len, mss); 1292 if (err < 0) 1293 return err; 1294 } 1295 1296 return in_sack; 1297 } 1298 1299 static u8 tcp_sacktag_one(struct sk_buff *skb, struct sock *sk, 1300 struct tcp_sacktag_state *state, 1301 int dup_sack, int pcount) 1302 { 1303 struct tcp_sock *tp = tcp_sk(sk); 1304 u8 sacked = TCP_SKB_CB(skb)->sacked; 1305 int fack_count = state->fack_count; 1306 1307 /* Account D-SACK for retransmitted packet. */ 1308 if (dup_sack && (sacked & TCPCB_RETRANS)) { 1309 if (after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) 1310 tp->undo_retrans--; 1311 if (sacked & TCPCB_SACKED_ACKED) 1312 state->reord = min(fack_count, state->reord); 1313 } 1314 1315 /* Nothing to do; acked frame is about to be dropped (was ACKed). */ 1316 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1317 return sacked; 1318 1319 if (!(sacked & TCPCB_SACKED_ACKED)) { 1320 if (sacked & TCPCB_SACKED_RETRANS) { 1321 /* If the segment is not tagged as lost, 1322 * we do not clear RETRANS, believing 1323 * that retransmission is still in flight. 1324 */ 1325 if (sacked & TCPCB_LOST) { 1326 sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); 1327 tp->lost_out -= pcount; 1328 tp->retrans_out -= pcount; 1329 } 1330 } else { 1331 if (!(sacked & TCPCB_RETRANS)) { 1332 /* New sack for not retransmitted frame, 1333 * which was in hole. It is reordering. 1334 */ 1335 if (before(TCP_SKB_CB(skb)->seq, 1336 tcp_highest_sack_seq(tp))) 1337 state->reord = min(fack_count, 1338 state->reord); 1339 1340 /* SACK enhanced F-RTO (RFC4138; Appendix B) */ 1341 if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark)) 1342 state->flag |= FLAG_ONLY_ORIG_SACKED; 1343 } 1344 1345 if (sacked & TCPCB_LOST) { 1346 sacked &= ~TCPCB_LOST; 1347 tp->lost_out -= pcount; 1348 } 1349 } 1350 1351 sacked |= TCPCB_SACKED_ACKED; 1352 state->flag |= FLAG_DATA_SACKED; 1353 tp->sacked_out += pcount; 1354 1355 fack_count += pcount; 1356 1357 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */ 1358 if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) && 1359 before(TCP_SKB_CB(skb)->seq, 1360 TCP_SKB_CB(tp->lost_skb_hint)->seq)) 1361 tp->lost_cnt_hint += pcount; 1362 1363 if (fack_count > tp->fackets_out) 1364 tp->fackets_out = fack_count; 1365 } 1366 1367 /* D-SACK. We can detect redundant retransmission in S|R and plain R 1368 * frames and clear it. undo_retrans is decreased above, L|R frames 1369 * are accounted above as well. 1370 */ 1371 if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) { 1372 sacked &= ~TCPCB_SACKED_RETRANS; 1373 tp->retrans_out -= pcount; 1374 } 1375 1376 return sacked; 1377 } 1378 1379 static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb, 1380 struct tcp_sacktag_state *state, 1381 unsigned int pcount, int shifted, int mss, 1382 int dup_sack) 1383 { 1384 struct tcp_sock *tp = tcp_sk(sk); 1385 struct sk_buff *prev = tcp_write_queue_prev(sk, skb); 1386 1387 BUG_ON(!pcount); 1388 1389 /* Tweak before seqno plays */ 1390 if (!tcp_is_fack(tp) && tcp_is_sack(tp) && tp->lost_skb_hint && 1391 !before(TCP_SKB_CB(tp->lost_skb_hint)->seq, TCP_SKB_CB(skb)->seq)) 1392 tp->lost_cnt_hint += pcount; 1393 1394 TCP_SKB_CB(prev)->end_seq += shifted; 1395 TCP_SKB_CB(skb)->seq += shifted; 1396 1397 skb_shinfo(prev)->gso_segs += pcount; 1398 BUG_ON(skb_shinfo(skb)->gso_segs < pcount); 1399 skb_shinfo(skb)->gso_segs -= pcount; 1400 1401 /* When we're adding to gso_segs == 1, gso_size will be zero, 1402 * in theory this shouldn't be necessary but as long as DSACK 1403 * code can come after this skb later on it's better to keep 1404 * setting gso_size to something. 1405 */ 1406 if (!skb_shinfo(prev)->gso_size) { 1407 skb_shinfo(prev)->gso_size = mss; 1408 skb_shinfo(prev)->gso_type = sk->sk_gso_type; 1409 } 1410 1411 /* CHECKME: To clear or not to clear? Mimics normal skb currently */ 1412 if (skb_shinfo(skb)->gso_segs <= 1) { 1413 skb_shinfo(skb)->gso_size = 0; 1414 skb_shinfo(skb)->gso_type = 0; 1415 } 1416 1417 /* We discard results */ 1418 tcp_sacktag_one(skb, sk, state, dup_sack, pcount); 1419 1420 /* Difference in this won't matter, both ACKed by the same cumul. ACK */ 1421 TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS); 1422 1423 if (skb->len > 0) { 1424 BUG_ON(!tcp_skb_pcount(skb)); 1425 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED); 1426 return 0; 1427 } 1428 1429 /* Whole SKB was eaten :-) */ 1430 1431 if (skb == tp->retransmit_skb_hint) 1432 tp->retransmit_skb_hint = prev; 1433 if (skb == tp->scoreboard_skb_hint) 1434 tp->scoreboard_skb_hint = prev; 1435 if (skb == tp->lost_skb_hint) { 1436 tp->lost_skb_hint = prev; 1437 tp->lost_cnt_hint -= tcp_skb_pcount(prev); 1438 } 1439 1440 TCP_SKB_CB(skb)->flags |= TCP_SKB_CB(prev)->flags; 1441 if (skb == tcp_highest_sack(sk)) 1442 tcp_advance_highest_sack(sk, skb); 1443 1444 tcp_unlink_write_queue(skb, sk); 1445 sk_wmem_free_skb(sk, skb); 1446 1447 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED); 1448 1449 return 1; 1450 } 1451 1452 /* I wish gso_size would have a bit more sane initialization than 1453 * something-or-zero which complicates things 1454 */ 1455 static int tcp_skb_seglen(struct sk_buff *skb) 1456 { 1457 return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb); 1458 } 1459 1460 /* Shifting pages past head area doesn't work */ 1461 static int skb_can_shift(struct sk_buff *skb) 1462 { 1463 return !skb_headlen(skb) && skb_is_nonlinear(skb); 1464 } 1465 1466 /* Try collapsing SACK blocks spanning across multiple skbs to a single 1467 * skb. 1468 */ 1469 static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb, 1470 struct tcp_sacktag_state *state, 1471 u32 start_seq, u32 end_seq, 1472 int dup_sack) 1473 { 1474 struct tcp_sock *tp = tcp_sk(sk); 1475 struct sk_buff *prev; 1476 int mss; 1477 int pcount = 0; 1478 int len; 1479 int in_sack; 1480 1481 if (!sk_can_gso(sk)) 1482 goto fallback; 1483 1484 /* Normally R but no L won't result in plain S */ 1485 if (!dup_sack && 1486 (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS) 1487 goto fallback; 1488 if (!skb_can_shift(skb)) 1489 goto fallback; 1490 /* This frame is about to be dropped (was ACKed). */ 1491 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1492 goto fallback; 1493 1494 /* Can only happen with delayed DSACK + discard craziness */ 1495 if (unlikely(skb == tcp_write_queue_head(sk))) 1496 goto fallback; 1497 prev = tcp_write_queue_prev(sk, skb); 1498 1499 if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) 1500 goto fallback; 1501 1502 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && 1503 !before(end_seq, TCP_SKB_CB(skb)->end_seq); 1504 1505 if (in_sack) { 1506 len = skb->len; 1507 pcount = tcp_skb_pcount(skb); 1508 mss = tcp_skb_seglen(skb); 1509 1510 /* TODO: Fix DSACKs to not fragment already SACKed and we can 1511 * drop this restriction as unnecessary 1512 */ 1513 if (mss != tcp_skb_seglen(prev)) 1514 goto fallback; 1515 } else { 1516 if (!after(TCP_SKB_CB(skb)->end_seq, start_seq)) 1517 goto noop; 1518 /* CHECKME: This is non-MSS split case only?, this will 1519 * cause skipped skbs due to advancing loop btw, original 1520 * has that feature too 1521 */ 1522 if (tcp_skb_pcount(skb) <= 1) 1523 goto noop; 1524 1525 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); 1526 if (!in_sack) { 1527 /* TODO: head merge to next could be attempted here 1528 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)), 1529 * though it might not be worth of the additional hassle 1530 * 1531 * ...we can probably just fallback to what was done 1532 * previously. We could try merging non-SACKed ones 1533 * as well but it probably isn't going to buy off 1534 * because later SACKs might again split them, and 1535 * it would make skb timestamp tracking considerably 1536 * harder problem. 1537 */ 1538 goto fallback; 1539 } 1540 1541 len = end_seq - TCP_SKB_CB(skb)->seq; 1542 BUG_ON(len < 0); 1543 BUG_ON(len > skb->len); 1544 1545 /* MSS boundaries should be honoured or else pcount will 1546 * severely break even though it makes things bit trickier. 1547 * Optimize common case to avoid most of the divides 1548 */ 1549 mss = tcp_skb_mss(skb); 1550 1551 /* TODO: Fix DSACKs to not fragment already SACKed and we can 1552 * drop this restriction as unnecessary 1553 */ 1554 if (mss != tcp_skb_seglen(prev)) 1555 goto fallback; 1556 1557 if (len == mss) { 1558 pcount = 1; 1559 } else if (len < mss) { 1560 goto noop; 1561 } else { 1562 pcount = len / mss; 1563 len = pcount * mss; 1564 } 1565 } 1566 1567 if (!skb_shift(prev, skb, len)) 1568 goto fallback; 1569 if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack)) 1570 goto out; 1571 1572 /* Hole filled allows collapsing with the next as well, this is very 1573 * useful when hole on every nth skb pattern happens 1574 */ 1575 if (prev == tcp_write_queue_tail(sk)) 1576 goto out; 1577 skb = tcp_write_queue_next(sk, prev); 1578 1579 if (!skb_can_shift(skb) || 1580 (skb == tcp_send_head(sk)) || 1581 ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) || 1582 (mss != tcp_skb_seglen(skb))) 1583 goto out; 1584 1585 len = skb->len; 1586 if (skb_shift(prev, skb, len)) { 1587 pcount += tcp_skb_pcount(skb); 1588 tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0); 1589 } 1590 1591 out: 1592 state->fack_count += pcount; 1593 return prev; 1594 1595 noop: 1596 return skb; 1597 1598 fallback: 1599 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK); 1600 return NULL; 1601 } 1602 1603 static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, 1604 struct tcp_sack_block *next_dup, 1605 struct tcp_sacktag_state *state, 1606 u32 start_seq, u32 end_seq, 1607 int dup_sack_in) 1608 { 1609 struct tcp_sock *tp = tcp_sk(sk); 1610 struct sk_buff *tmp; 1611 1612 tcp_for_write_queue_from(skb, sk) { 1613 int in_sack = 0; 1614 int dup_sack = dup_sack_in; 1615 1616 if (skb == tcp_send_head(sk)) 1617 break; 1618 1619 /* queue is in-order => we can short-circuit the walk early */ 1620 if (!before(TCP_SKB_CB(skb)->seq, end_seq)) 1621 break; 1622 1623 if ((next_dup != NULL) && 1624 before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) { 1625 in_sack = tcp_match_skb_to_sack(sk, skb, 1626 next_dup->start_seq, 1627 next_dup->end_seq); 1628 if (in_sack > 0) 1629 dup_sack = 1; 1630 } 1631 1632 /* skb reference here is a bit tricky to get right, since 1633 * shifting can eat and free both this skb and the next, 1634 * so not even _safe variant of the loop is enough. 1635 */ 1636 if (in_sack <= 0) { 1637 tmp = tcp_shift_skb_data(sk, skb, state, 1638 start_seq, end_seq, dup_sack); 1639 if (tmp != NULL) { 1640 if (tmp != skb) { 1641 skb = tmp; 1642 continue; 1643 } 1644 1645 in_sack = 0; 1646 } else { 1647 in_sack = tcp_match_skb_to_sack(sk, skb, 1648 start_seq, 1649 end_seq); 1650 } 1651 } 1652 1653 if (unlikely(in_sack < 0)) 1654 break; 1655 1656 if (in_sack) { 1657 TCP_SKB_CB(skb)->sacked = tcp_sacktag_one(skb, sk, 1658 state, 1659 dup_sack, 1660 tcp_skb_pcount(skb)); 1661 1662 if (!before(TCP_SKB_CB(skb)->seq, 1663 tcp_highest_sack_seq(tp))) 1664 tcp_advance_highest_sack(sk, skb); 1665 } 1666 1667 state->fack_count += tcp_skb_pcount(skb); 1668 } 1669 return skb; 1670 } 1671 1672 /* Avoid all extra work that is being done by sacktag while walking in 1673 * a normal way 1674 */ 1675 static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, 1676 struct tcp_sacktag_state *state, 1677 u32 skip_to_seq) 1678 { 1679 tcp_for_write_queue_from(skb, sk) { 1680 if (skb == tcp_send_head(sk)) 1681 break; 1682 1683 if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq)) 1684 break; 1685 1686 state->fack_count += tcp_skb_pcount(skb); 1687 } 1688 return skb; 1689 } 1690 1691 static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb, 1692 struct sock *sk, 1693 struct tcp_sack_block *next_dup, 1694 struct tcp_sacktag_state *state, 1695 u32 skip_to_seq) 1696 { 1697 if (next_dup == NULL) 1698 return skb; 1699 1700 if (before(next_dup->start_seq, skip_to_seq)) { 1701 skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq); 1702 skb = tcp_sacktag_walk(skb, sk, NULL, state, 1703 next_dup->start_seq, next_dup->end_seq, 1704 1); 1705 } 1706 1707 return skb; 1708 } 1709 1710 static int tcp_sack_cache_ok(struct tcp_sock *tp, struct tcp_sack_block *cache) 1711 { 1712 return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); 1713 } 1714 1715 static int 1716 tcp_sacktag_write_queue(struct sock *sk, struct sk_buff *ack_skb, 1717 u32 prior_snd_una) 1718 { 1719 const struct inet_connection_sock *icsk = inet_csk(sk); 1720 struct tcp_sock *tp = tcp_sk(sk); 1721 unsigned char *ptr = (skb_transport_header(ack_skb) + 1722 TCP_SKB_CB(ack_skb)->sacked); 1723 struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2); 1724 struct tcp_sack_block sp[TCP_NUM_SACKS]; 1725 struct tcp_sack_block *cache; 1726 struct tcp_sacktag_state state; 1727 struct sk_buff *skb; 1728 int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3); 1729 int used_sacks; 1730 int found_dup_sack = 0; 1731 int i, j; 1732 int first_sack_index; 1733 1734 state.flag = 0; 1735 state.reord = tp->packets_out; 1736 1737 if (!tp->sacked_out) { 1738 if (WARN_ON(tp->fackets_out)) 1739 tp->fackets_out = 0; 1740 tcp_highest_sack_reset(sk); 1741 } 1742 1743 found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire, 1744 num_sacks, prior_snd_una); 1745 if (found_dup_sack) 1746 state.flag |= FLAG_DSACKING_ACK; 1747 1748 /* Eliminate too old ACKs, but take into 1749 * account more or less fresh ones, they can 1750 * contain valid SACK info. 1751 */ 1752 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) 1753 return 0; 1754 1755 if (!tp->packets_out) 1756 goto out; 1757 1758 used_sacks = 0; 1759 first_sack_index = 0; 1760 for (i = 0; i < num_sacks; i++) { 1761 int dup_sack = !i && found_dup_sack; 1762 1763 sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq); 1764 sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq); 1765 1766 if (!tcp_is_sackblock_valid(tp, dup_sack, 1767 sp[used_sacks].start_seq, 1768 sp[used_sacks].end_seq)) { 1769 int mib_idx; 1770 1771 if (dup_sack) { 1772 if (!tp->undo_marker) 1773 mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO; 1774 else 1775 mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD; 1776 } else { 1777 /* Don't count olds caused by ACK reordering */ 1778 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) && 1779 !after(sp[used_sacks].end_seq, tp->snd_una)) 1780 continue; 1781 mib_idx = LINUX_MIB_TCPSACKDISCARD; 1782 } 1783 1784 NET_INC_STATS_BH(sock_net(sk), mib_idx); 1785 if (i == 0) 1786 first_sack_index = -1; 1787 continue; 1788 } 1789 1790 /* Ignore very old stuff early */ 1791 if (!after(sp[used_sacks].end_seq, prior_snd_una)) 1792 continue; 1793 1794 used_sacks++; 1795 } 1796 1797 /* order SACK blocks to allow in order walk of the retrans queue */ 1798 for (i = used_sacks - 1; i > 0; i--) { 1799 for (j = 0; j < i; j++) { 1800 if (after(sp[j].start_seq, sp[j + 1].start_seq)) { 1801 swap(sp[j], sp[j + 1]); 1802 1803 /* Track where the first SACK block goes to */ 1804 if (j == first_sack_index) 1805 first_sack_index = j + 1; 1806 } 1807 } 1808 } 1809 1810 skb = tcp_write_queue_head(sk); 1811 state.fack_count = 0; 1812 i = 0; 1813 1814 if (!tp->sacked_out) { 1815 /* It's already past, so skip checking against it */ 1816 cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); 1817 } else { 1818 cache = tp->recv_sack_cache; 1819 /* Skip empty blocks in at head of the cache */ 1820 while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq && 1821 !cache->end_seq) 1822 cache++; 1823 } 1824 1825 while (i < used_sacks) { 1826 u32 start_seq = sp[i].start_seq; 1827 u32 end_seq = sp[i].end_seq; 1828 int dup_sack = (found_dup_sack && (i == first_sack_index)); 1829 struct tcp_sack_block *next_dup = NULL; 1830 1831 if (found_dup_sack && ((i + 1) == first_sack_index)) 1832 next_dup = &sp[i + 1]; 1833 1834 /* Event "B" in the comment above. */ 1835 if (after(end_seq, tp->high_seq)) 1836 state.flag |= FLAG_DATA_LOST; 1837 1838 /* Skip too early cached blocks */ 1839 while (tcp_sack_cache_ok(tp, cache) && 1840 !before(start_seq, cache->end_seq)) 1841 cache++; 1842 1843 /* Can skip some work by looking recv_sack_cache? */ 1844 if (tcp_sack_cache_ok(tp, cache) && !dup_sack && 1845 after(end_seq, cache->start_seq)) { 1846 1847 /* Head todo? */ 1848 if (before(start_seq, cache->start_seq)) { 1849 skb = tcp_sacktag_skip(skb, sk, &state, 1850 start_seq); 1851 skb = tcp_sacktag_walk(skb, sk, next_dup, 1852 &state, 1853 start_seq, 1854 cache->start_seq, 1855 dup_sack); 1856 } 1857 1858 /* Rest of the block already fully processed? */ 1859 if (!after(end_seq, cache->end_seq)) 1860 goto advance_sp; 1861 1862 skb = tcp_maybe_skipping_dsack(skb, sk, next_dup, 1863 &state, 1864 cache->end_seq); 1865 1866 /* ...tail remains todo... */ 1867 if (tcp_highest_sack_seq(tp) == cache->end_seq) { 1868 /* ...but better entrypoint exists! */ 1869 skb = tcp_highest_sack(sk); 1870 if (skb == NULL) 1871 break; 1872 state.fack_count = tp->fackets_out; 1873 cache++; 1874 goto walk; 1875 } 1876 1877 skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq); 1878 /* Check overlap against next cached too (past this one already) */ 1879 cache++; 1880 continue; 1881 } 1882 1883 if (!before(start_seq, tcp_highest_sack_seq(tp))) { 1884 skb = tcp_highest_sack(sk); 1885 if (skb == NULL) 1886 break; 1887 state.fack_count = tp->fackets_out; 1888 } 1889 skb = tcp_sacktag_skip(skb, sk, &state, start_seq); 1890 1891 walk: 1892 skb = tcp_sacktag_walk(skb, sk, next_dup, &state, 1893 start_seq, end_seq, dup_sack); 1894 1895 advance_sp: 1896 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct 1897 * due to in-order walk 1898 */ 1899 if (after(end_seq, tp->frto_highmark)) 1900 state.flag &= ~FLAG_ONLY_ORIG_SACKED; 1901 1902 i++; 1903 } 1904 1905 /* Clear the head of the cache sack blocks so we can skip it next time */ 1906 for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) { 1907 tp->recv_sack_cache[i].start_seq = 0; 1908 tp->recv_sack_cache[i].end_seq = 0; 1909 } 1910 for (j = 0; j < used_sacks; j++) 1911 tp->recv_sack_cache[i++] = sp[j]; 1912 1913 tcp_mark_lost_retrans(sk); 1914 1915 tcp_verify_left_out(tp); 1916 1917 if ((state.reord < tp->fackets_out) && 1918 ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) && 1919 (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark))) 1920 tcp_update_reordering(sk, tp->fackets_out - state.reord, 0); 1921 1922 out: 1923 1924 #if FASTRETRANS_DEBUG > 0 1925 WARN_ON((int)tp->sacked_out < 0); 1926 WARN_ON((int)tp->lost_out < 0); 1927 WARN_ON((int)tp->retrans_out < 0); 1928 WARN_ON((int)tcp_packets_in_flight(tp) < 0); 1929 #endif 1930 return state.flag; 1931 } 1932 1933 /* Limits sacked_out so that sum with lost_out isn't ever larger than 1934 * packets_out. Returns zero if sacked_out adjustement wasn't necessary. 1935 */ 1936 static int tcp_limit_reno_sacked(struct tcp_sock *tp) 1937 { 1938 u32 holes; 1939 1940 holes = max(tp->lost_out, 1U); 1941 holes = min(holes, tp->packets_out); 1942 1943 if ((tp->sacked_out + holes) > tp->packets_out) { 1944 tp->sacked_out = tp->packets_out - holes; 1945 return 1; 1946 } 1947 return 0; 1948 } 1949 1950 /* If we receive more dupacks than we expected counting segments 1951 * in assumption of absent reordering, interpret this as reordering. 1952 * The only another reason could be bug in receiver TCP. 1953 */ 1954 static void tcp_check_reno_reordering(struct sock *sk, const int addend) 1955 { 1956 struct tcp_sock *tp = tcp_sk(sk); 1957 if (tcp_limit_reno_sacked(tp)) 1958 tcp_update_reordering(sk, tp->packets_out + addend, 0); 1959 } 1960 1961 /* Emulate SACKs for SACKless connection: account for a new dupack. */ 1962 1963 static void tcp_add_reno_sack(struct sock *sk) 1964 { 1965 struct tcp_sock *tp = tcp_sk(sk); 1966 tp->sacked_out++; 1967 tcp_check_reno_reordering(sk, 0); 1968 tcp_verify_left_out(tp); 1969 } 1970 1971 /* Account for ACK, ACKing some data in Reno Recovery phase. */ 1972 1973 static void tcp_remove_reno_sacks(struct sock *sk, int acked) 1974 { 1975 struct tcp_sock *tp = tcp_sk(sk); 1976 1977 if (acked > 0) { 1978 /* One ACK acked hole. The rest eat duplicate ACKs. */ 1979 if (acked - 1 >= tp->sacked_out) 1980 tp->sacked_out = 0; 1981 else 1982 tp->sacked_out -= acked - 1; 1983 } 1984 tcp_check_reno_reordering(sk, acked); 1985 tcp_verify_left_out(tp); 1986 } 1987 1988 static inline void tcp_reset_reno_sack(struct tcp_sock *tp) 1989 { 1990 tp->sacked_out = 0; 1991 } 1992 1993 static int tcp_is_sackfrto(const struct tcp_sock *tp) 1994 { 1995 return (sysctl_tcp_frto == 0x2) && !tcp_is_reno(tp); 1996 } 1997 1998 /* F-RTO can only be used if TCP has never retransmitted anything other than 1999 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here) 2000 */ 2001 int tcp_use_frto(struct sock *sk) 2002 { 2003 const struct tcp_sock *tp = tcp_sk(sk); 2004 const struct inet_connection_sock *icsk = inet_csk(sk); 2005 struct sk_buff *skb; 2006 2007 if (!sysctl_tcp_frto) 2008 return 0; 2009 2010 /* MTU probe and F-RTO won't really play nicely along currently */ 2011 if (icsk->icsk_mtup.probe_size) 2012 return 0; 2013 2014 if (tcp_is_sackfrto(tp)) 2015 return 1; 2016 2017 /* Avoid expensive walking of rexmit queue if possible */ 2018 if (tp->retrans_out > 1) 2019 return 0; 2020 2021 skb = tcp_write_queue_head(sk); 2022 if (tcp_skb_is_last(sk, skb)) 2023 return 1; 2024 skb = tcp_write_queue_next(sk, skb); /* Skips head */ 2025 tcp_for_write_queue_from(skb, sk) { 2026 if (skb == tcp_send_head(sk)) 2027 break; 2028 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2029 return 0; 2030 /* Short-circuit when first non-SACKed skb has been checked */ 2031 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 2032 break; 2033 } 2034 return 1; 2035 } 2036 2037 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO 2038 * recovery a bit and use heuristics in tcp_process_frto() to detect if 2039 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to 2040 * keep retrans_out counting accurate (with SACK F-RTO, other than head 2041 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS 2042 * bits are handled if the Loss state is really to be entered (in 2043 * tcp_enter_frto_loss). 2044 * 2045 * Do like tcp_enter_loss() would; when RTO expires the second time it 2046 * does: 2047 * "Reduce ssthresh if it has not yet been made inside this window." 2048 */ 2049 void tcp_enter_frto(struct sock *sk) 2050 { 2051 const struct inet_connection_sock *icsk = inet_csk(sk); 2052 struct tcp_sock *tp = tcp_sk(sk); 2053 struct sk_buff *skb; 2054 2055 if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) || 2056 tp->snd_una == tp->high_seq || 2057 ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) && 2058 !icsk->icsk_retransmits)) { 2059 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2060 /* Our state is too optimistic in ssthresh() call because cwnd 2061 * is not reduced until tcp_enter_frto_loss() when previous F-RTO 2062 * recovery has not yet completed. Pattern would be this: RTO, 2063 * Cumulative ACK, RTO (2xRTO for the same segment does not end 2064 * up here twice). 2065 * RFC4138 should be more specific on what to do, even though 2066 * RTO is quite unlikely to occur after the first Cumulative ACK 2067 * due to back-off and complexity of triggering events ... 2068 */ 2069 if (tp->frto_counter) { 2070 u32 stored_cwnd; 2071 stored_cwnd = tp->snd_cwnd; 2072 tp->snd_cwnd = 2; 2073 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2074 tp->snd_cwnd = stored_cwnd; 2075 } else { 2076 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2077 } 2078 /* ... in theory, cong.control module could do "any tricks" in 2079 * ssthresh(), which means that ca_state, lost bits and lost_out 2080 * counter would have to be faked before the call occurs. We 2081 * consider that too expensive, unlikely and hacky, so modules 2082 * using these in ssthresh() must deal these incompatibility 2083 * issues if they receives CA_EVENT_FRTO and frto_counter != 0 2084 */ 2085 tcp_ca_event(sk, CA_EVENT_FRTO); 2086 } 2087 2088 tp->undo_marker = tp->snd_una; 2089 tp->undo_retrans = 0; 2090 2091 skb = tcp_write_queue_head(sk); 2092 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2093 tp->undo_marker = 0; 2094 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 2095 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 2096 tp->retrans_out -= tcp_skb_pcount(skb); 2097 } 2098 tcp_verify_left_out(tp); 2099 2100 /* Too bad if TCP was application limited */ 2101 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1); 2102 2103 /* Earlier loss recovery underway (see RFC4138; Appendix B). 2104 * The last condition is necessary at least in tp->frto_counter case. 2105 */ 2106 if (tcp_is_sackfrto(tp) && (tp->frto_counter || 2107 ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) && 2108 after(tp->high_seq, tp->snd_una)) { 2109 tp->frto_highmark = tp->high_seq; 2110 } else { 2111 tp->frto_highmark = tp->snd_nxt; 2112 } 2113 tcp_set_ca_state(sk, TCP_CA_Disorder); 2114 tp->high_seq = tp->snd_nxt; 2115 tp->frto_counter = 1; 2116 } 2117 2118 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO, 2119 * which indicates that we should follow the traditional RTO recovery, 2120 * i.e. mark everything lost and do go-back-N retransmission. 2121 */ 2122 static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag) 2123 { 2124 struct tcp_sock *tp = tcp_sk(sk); 2125 struct sk_buff *skb; 2126 2127 tp->lost_out = 0; 2128 tp->retrans_out = 0; 2129 if (tcp_is_reno(tp)) 2130 tcp_reset_reno_sack(tp); 2131 2132 tcp_for_write_queue(skb, sk) { 2133 if (skb == tcp_send_head(sk)) 2134 break; 2135 2136 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 2137 /* 2138 * Count the retransmission made on RTO correctly (only when 2139 * waiting for the first ACK and did not get it)... 2140 */ 2141 if ((tp->frto_counter == 1) && !(flag & FLAG_DATA_ACKED)) { 2142 /* For some reason this R-bit might get cleared? */ 2143 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) 2144 tp->retrans_out += tcp_skb_pcount(skb); 2145 /* ...enter this if branch just for the first segment */ 2146 flag |= FLAG_DATA_ACKED; 2147 } else { 2148 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2149 tp->undo_marker = 0; 2150 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 2151 } 2152 2153 /* Marking forward transmissions that were made after RTO lost 2154 * can cause unnecessary retransmissions in some scenarios, 2155 * SACK blocks will mitigate that in some but not in all cases. 2156 * We used to not mark them but it was causing break-ups with 2157 * receivers that do only in-order receival. 2158 * 2159 * TODO: we could detect presence of such receiver and select 2160 * different behavior per flow. 2161 */ 2162 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 2163 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 2164 tp->lost_out += tcp_skb_pcount(skb); 2165 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; 2166 } 2167 } 2168 tcp_verify_left_out(tp); 2169 2170 tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments; 2171 tp->snd_cwnd_cnt = 0; 2172 tp->snd_cwnd_stamp = tcp_time_stamp; 2173 tp->frto_counter = 0; 2174 tp->bytes_acked = 0; 2175 2176 tp->reordering = min_t(unsigned int, tp->reordering, 2177 sysctl_tcp_reordering); 2178 tcp_set_ca_state(sk, TCP_CA_Loss); 2179 tp->high_seq = tp->snd_nxt; 2180 TCP_ECN_queue_cwr(tp); 2181 2182 tcp_clear_all_retrans_hints(tp); 2183 } 2184 2185 static void tcp_clear_retrans_partial(struct tcp_sock *tp) 2186 { 2187 tp->retrans_out = 0; 2188 tp->lost_out = 0; 2189 2190 tp->undo_marker = 0; 2191 tp->undo_retrans = 0; 2192 } 2193 2194 void tcp_clear_retrans(struct tcp_sock *tp) 2195 { 2196 tcp_clear_retrans_partial(tp); 2197 2198 tp->fackets_out = 0; 2199 tp->sacked_out = 0; 2200 } 2201 2202 /* Enter Loss state. If "how" is not zero, forget all SACK information 2203 * and reset tags completely, otherwise preserve SACKs. If receiver 2204 * dropped its ofo queue, we will know this due to reneging detection. 2205 */ 2206 void tcp_enter_loss(struct sock *sk, int how) 2207 { 2208 const struct inet_connection_sock *icsk = inet_csk(sk); 2209 struct tcp_sock *tp = tcp_sk(sk); 2210 struct sk_buff *skb; 2211 2212 /* Reduce ssthresh if it has not yet been made inside this window. */ 2213 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq || 2214 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { 2215 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2216 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2217 tcp_ca_event(sk, CA_EVENT_LOSS); 2218 } 2219 tp->snd_cwnd = 1; 2220 tp->snd_cwnd_cnt = 0; 2221 tp->snd_cwnd_stamp = tcp_time_stamp; 2222 2223 tp->bytes_acked = 0; 2224 tcp_clear_retrans_partial(tp); 2225 2226 if (tcp_is_reno(tp)) 2227 tcp_reset_reno_sack(tp); 2228 2229 if (!how) { 2230 /* Push undo marker, if it was plain RTO and nothing 2231 * was retransmitted. */ 2232 tp->undo_marker = tp->snd_una; 2233 } else { 2234 tp->sacked_out = 0; 2235 tp->fackets_out = 0; 2236 } 2237 tcp_clear_all_retrans_hints(tp); 2238 2239 tcp_for_write_queue(skb, sk) { 2240 if (skb == tcp_send_head(sk)) 2241 break; 2242 2243 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2244 tp->undo_marker = 0; 2245 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; 2246 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { 2247 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; 2248 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 2249 tp->lost_out += tcp_skb_pcount(skb); 2250 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; 2251 } 2252 } 2253 tcp_verify_left_out(tp); 2254 2255 tp->reordering = min_t(unsigned int, tp->reordering, 2256 sysctl_tcp_reordering); 2257 tcp_set_ca_state(sk, TCP_CA_Loss); 2258 tp->high_seq = tp->snd_nxt; 2259 TCP_ECN_queue_cwr(tp); 2260 /* Abort F-RTO algorithm if one is in progress */ 2261 tp->frto_counter = 0; 2262 } 2263 2264 /* If ACK arrived pointing to a remembered SACK, it means that our 2265 * remembered SACKs do not reflect real state of receiver i.e. 2266 * receiver _host_ is heavily congested (or buggy). 2267 * 2268 * Do processing similar to RTO timeout. 2269 */ 2270 static int tcp_check_sack_reneging(struct sock *sk, int flag) 2271 { 2272 if (flag & FLAG_SACK_RENEGING) { 2273 struct inet_connection_sock *icsk = inet_csk(sk); 2274 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSACKRENEGING); 2275 2276 tcp_enter_loss(sk, 1); 2277 icsk->icsk_retransmits++; 2278 tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); 2279 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 2280 icsk->icsk_rto, TCP_RTO_MAX); 2281 return 1; 2282 } 2283 return 0; 2284 } 2285 2286 static inline int tcp_fackets_out(struct tcp_sock *tp) 2287 { 2288 return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out; 2289 } 2290 2291 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs 2292 * counter when SACK is enabled (without SACK, sacked_out is used for 2293 * that purpose). 2294 * 2295 * Instead, with FACK TCP uses fackets_out that includes both SACKed 2296 * segments up to the highest received SACK block so far and holes in 2297 * between them. 2298 * 2299 * With reordering, holes may still be in flight, so RFC3517 recovery 2300 * uses pure sacked_out (total number of SACKed segments) even though 2301 * it violates the RFC that uses duplicate ACKs, often these are equal 2302 * but when e.g. out-of-window ACKs or packet duplication occurs, 2303 * they differ. Since neither occurs due to loss, TCP should really 2304 * ignore them. 2305 */ 2306 static inline int tcp_dupack_heuristics(struct tcp_sock *tp) 2307 { 2308 return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1; 2309 } 2310 2311 static inline int tcp_skb_timedout(struct sock *sk, struct sk_buff *skb) 2312 { 2313 return (tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto); 2314 } 2315 2316 static inline int tcp_head_timedout(struct sock *sk) 2317 { 2318 struct tcp_sock *tp = tcp_sk(sk); 2319 2320 return tp->packets_out && 2321 tcp_skb_timedout(sk, tcp_write_queue_head(sk)); 2322 } 2323 2324 /* Linux NewReno/SACK/FACK/ECN state machine. 2325 * -------------------------------------- 2326 * 2327 * "Open" Normal state, no dubious events, fast path. 2328 * "Disorder" In all the respects it is "Open", 2329 * but requires a bit more attention. It is entered when 2330 * we see some SACKs or dupacks. It is split of "Open" 2331 * mainly to move some processing from fast path to slow one. 2332 * "CWR" CWND was reduced due to some Congestion Notification event. 2333 * It can be ECN, ICMP source quench, local device congestion. 2334 * "Recovery" CWND was reduced, we are fast-retransmitting. 2335 * "Loss" CWND was reduced due to RTO timeout or SACK reneging. 2336 * 2337 * tcp_fastretrans_alert() is entered: 2338 * - each incoming ACK, if state is not "Open" 2339 * - when arrived ACK is unusual, namely: 2340 * * SACK 2341 * * Duplicate ACK. 2342 * * ECN ECE. 2343 * 2344 * Counting packets in flight is pretty simple. 2345 * 2346 * in_flight = packets_out - left_out + retrans_out 2347 * 2348 * packets_out is SND.NXT-SND.UNA counted in packets. 2349 * 2350 * retrans_out is number of retransmitted segments. 2351 * 2352 * left_out is number of segments left network, but not ACKed yet. 2353 * 2354 * left_out = sacked_out + lost_out 2355 * 2356 * sacked_out: Packets, which arrived to receiver out of order 2357 * and hence not ACKed. With SACKs this number is simply 2358 * amount of SACKed data. Even without SACKs 2359 * it is easy to give pretty reliable estimate of this number, 2360 * counting duplicate ACKs. 2361 * 2362 * lost_out: Packets lost by network. TCP has no explicit 2363 * "loss notification" feedback from network (for now). 2364 * It means that this number can be only _guessed_. 2365 * Actually, it is the heuristics to predict lossage that 2366 * distinguishes different algorithms. 2367 * 2368 * F.e. after RTO, when all the queue is considered as lost, 2369 * lost_out = packets_out and in_flight = retrans_out. 2370 * 2371 * Essentially, we have now two algorithms counting 2372 * lost packets. 2373 * 2374 * FACK: It is the simplest heuristics. As soon as we decided 2375 * that something is lost, we decide that _all_ not SACKed 2376 * packets until the most forward SACK are lost. I.e. 2377 * lost_out = fackets_out - sacked_out and left_out = fackets_out. 2378 * It is absolutely correct estimate, if network does not reorder 2379 * packets. And it loses any connection to reality when reordering 2380 * takes place. We use FACK by default until reordering 2381 * is suspected on the path to this destination. 2382 * 2383 * NewReno: when Recovery is entered, we assume that one segment 2384 * is lost (classic Reno). While we are in Recovery and 2385 * a partial ACK arrives, we assume that one more packet 2386 * is lost (NewReno). This heuristics are the same in NewReno 2387 * and SACK. 2388 * 2389 * Imagine, that's all! Forget about all this shamanism about CWND inflation 2390 * deflation etc. CWND is real congestion window, never inflated, changes 2391 * only according to classic VJ rules. 2392 * 2393 * Really tricky (and requiring careful tuning) part of algorithm 2394 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). 2395 * The first determines the moment _when_ we should reduce CWND and, 2396 * hence, slow down forward transmission. In fact, it determines the moment 2397 * when we decide that hole is caused by loss, rather than by a reorder. 2398 * 2399 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill 2400 * holes, caused by lost packets. 2401 * 2402 * And the most logically complicated part of algorithm is undo 2403 * heuristics. We detect false retransmits due to both too early 2404 * fast retransmit (reordering) and underestimated RTO, analyzing 2405 * timestamps and D-SACKs. When we detect that some segments were 2406 * retransmitted by mistake and CWND reduction was wrong, we undo 2407 * window reduction and abort recovery phase. This logic is hidden 2408 * inside several functions named tcp_try_undo_<something>. 2409 */ 2410 2411 /* This function decides, when we should leave Disordered state 2412 * and enter Recovery phase, reducing congestion window. 2413 * 2414 * Main question: may we further continue forward transmission 2415 * with the same cwnd? 2416 */ 2417 static int tcp_time_to_recover(struct sock *sk) 2418 { 2419 struct tcp_sock *tp = tcp_sk(sk); 2420 __u32 packets_out; 2421 2422 /* Do not perform any recovery during F-RTO algorithm */ 2423 if (tp->frto_counter) 2424 return 0; 2425 2426 /* Trick#1: The loss is proven. */ 2427 if (tp->lost_out) 2428 return 1; 2429 2430 /* Not-A-Trick#2 : Classic rule... */ 2431 if (tcp_dupack_heuristics(tp) > tp->reordering) 2432 return 1; 2433 2434 /* Trick#3 : when we use RFC2988 timer restart, fast 2435 * retransmit can be triggered by timeout of queue head. 2436 */ 2437 if (tcp_is_fack(tp) && tcp_head_timedout(sk)) 2438 return 1; 2439 2440 /* Trick#4: It is still not OK... But will it be useful to delay 2441 * recovery more? 2442 */ 2443 packets_out = tp->packets_out; 2444 if (packets_out <= tp->reordering && 2445 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && 2446 !tcp_may_send_now(sk)) { 2447 /* We have nothing to send. This connection is limited 2448 * either by receiver window or by application. 2449 */ 2450 return 1; 2451 } 2452 2453 /* If a thin stream is detected, retransmit after first 2454 * received dupack. Employ only if SACK is supported in order 2455 * to avoid possible corner-case series of spurious retransmissions 2456 * Use only if there are no unsent data. 2457 */ 2458 if ((tp->thin_dupack || sysctl_tcp_thin_dupack) && 2459 tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 && 2460 tcp_is_sack(tp) && !tcp_send_head(sk)) 2461 return 1; 2462 2463 return 0; 2464 } 2465 2466 /* New heuristics: it is possible only after we switched to restart timer 2467 * each time when something is ACKed. Hence, we can detect timed out packets 2468 * during fast retransmit without falling to slow start. 2469 * 2470 * Usefulness of this as is very questionable, since we should know which of 2471 * the segments is the next to timeout which is relatively expensive to find 2472 * in general case unless we add some data structure just for that. The 2473 * current approach certainly won't find the right one too often and when it 2474 * finally does find _something_ it usually marks large part of the window 2475 * right away (because a retransmission with a larger timestamp blocks the 2476 * loop from advancing). -ij 2477 */ 2478 static void tcp_timeout_skbs(struct sock *sk) 2479 { 2480 struct tcp_sock *tp = tcp_sk(sk); 2481 struct sk_buff *skb; 2482 2483 if (!tcp_is_fack(tp) || !tcp_head_timedout(sk)) 2484 return; 2485 2486 skb = tp->scoreboard_skb_hint; 2487 if (tp->scoreboard_skb_hint == NULL) 2488 skb = tcp_write_queue_head(sk); 2489 2490 tcp_for_write_queue_from(skb, sk) { 2491 if (skb == tcp_send_head(sk)) 2492 break; 2493 if (!tcp_skb_timedout(sk, skb)) 2494 break; 2495 2496 tcp_skb_mark_lost(tp, skb); 2497 } 2498 2499 tp->scoreboard_skb_hint = skb; 2500 2501 tcp_verify_left_out(tp); 2502 } 2503 2504 /* Mark head of queue up as lost. With RFC3517 SACK, the packets is 2505 * is against sacked "cnt", otherwise it's against facked "cnt" 2506 */ 2507 static void tcp_mark_head_lost(struct sock *sk, int packets) 2508 { 2509 struct tcp_sock *tp = tcp_sk(sk); 2510 struct sk_buff *skb; 2511 int cnt, oldcnt; 2512 int err; 2513 unsigned int mss; 2514 2515 if (packets == 0) 2516 return; 2517 2518 WARN_ON(packets > tp->packets_out); 2519 if (tp->lost_skb_hint) { 2520 skb = tp->lost_skb_hint; 2521 cnt = tp->lost_cnt_hint; 2522 } else { 2523 skb = tcp_write_queue_head(sk); 2524 cnt = 0; 2525 } 2526 2527 tcp_for_write_queue_from(skb, sk) { 2528 if (skb == tcp_send_head(sk)) 2529 break; 2530 /* TODO: do this better */ 2531 /* this is not the most efficient way to do this... */ 2532 tp->lost_skb_hint = skb; 2533 tp->lost_cnt_hint = cnt; 2534 2535 if (after(TCP_SKB_CB(skb)->end_seq, tp->high_seq)) 2536 break; 2537 2538 oldcnt = cnt; 2539 if (tcp_is_fack(tp) || tcp_is_reno(tp) || 2540 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 2541 cnt += tcp_skb_pcount(skb); 2542 2543 if (cnt > packets) { 2544 if (tcp_is_sack(tp) || (oldcnt >= packets)) 2545 break; 2546 2547 mss = skb_shinfo(skb)->gso_size; 2548 err = tcp_fragment(sk, skb, (packets - oldcnt) * mss, mss); 2549 if (err < 0) 2550 break; 2551 cnt = packets; 2552 } 2553 2554 tcp_skb_mark_lost(tp, skb); 2555 } 2556 tcp_verify_left_out(tp); 2557 } 2558 2559 /* Account newly detected lost packet(s) */ 2560 2561 static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit) 2562 { 2563 struct tcp_sock *tp = tcp_sk(sk); 2564 2565 if (tcp_is_reno(tp)) { 2566 tcp_mark_head_lost(sk, 1); 2567 } else if (tcp_is_fack(tp)) { 2568 int lost = tp->fackets_out - tp->reordering; 2569 if (lost <= 0) 2570 lost = 1; 2571 tcp_mark_head_lost(sk, lost); 2572 } else { 2573 int sacked_upto = tp->sacked_out - tp->reordering; 2574 if (sacked_upto < fast_rexmit) 2575 sacked_upto = fast_rexmit; 2576 tcp_mark_head_lost(sk, sacked_upto); 2577 } 2578 2579 tcp_timeout_skbs(sk); 2580 } 2581 2582 /* CWND moderation, preventing bursts due to too big ACKs 2583 * in dubious situations. 2584 */ 2585 static inline void tcp_moderate_cwnd(struct tcp_sock *tp) 2586 { 2587 tp->snd_cwnd = min(tp->snd_cwnd, 2588 tcp_packets_in_flight(tp) + tcp_max_burst(tp)); 2589 tp->snd_cwnd_stamp = tcp_time_stamp; 2590 } 2591 2592 /* Lower bound on congestion window is slow start threshold 2593 * unless congestion avoidance choice decides to overide it. 2594 */ 2595 static inline u32 tcp_cwnd_min(const struct sock *sk) 2596 { 2597 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; 2598 2599 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh; 2600 } 2601 2602 /* Decrease cwnd each second ack. */ 2603 static void tcp_cwnd_down(struct sock *sk, int flag) 2604 { 2605 struct tcp_sock *tp = tcp_sk(sk); 2606 int decr = tp->snd_cwnd_cnt + 1; 2607 2608 if ((flag & (FLAG_ANY_PROGRESS | FLAG_DSACKING_ACK)) || 2609 (tcp_is_reno(tp) && !(flag & FLAG_NOT_DUP))) { 2610 tp->snd_cwnd_cnt = decr & 1; 2611 decr >>= 1; 2612 2613 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk)) 2614 tp->snd_cwnd -= decr; 2615 2616 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1); 2617 tp->snd_cwnd_stamp = tcp_time_stamp; 2618 } 2619 } 2620 2621 /* Nothing was retransmitted or returned timestamp is less 2622 * than timestamp of the first retransmission. 2623 */ 2624 static inline int tcp_packet_delayed(struct tcp_sock *tp) 2625 { 2626 return !tp->retrans_stamp || 2627 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 2628 before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp)); 2629 } 2630 2631 /* Undo procedures. */ 2632 2633 #if FASTRETRANS_DEBUG > 1 2634 static void DBGUNDO(struct sock *sk, const char *msg) 2635 { 2636 struct tcp_sock *tp = tcp_sk(sk); 2637 struct inet_sock *inet = inet_sk(sk); 2638 2639 if (sk->sk_family == AF_INET) { 2640 printk(KERN_DEBUG "Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n", 2641 msg, 2642 &inet->inet_daddr, ntohs(inet->inet_dport), 2643 tp->snd_cwnd, tcp_left_out(tp), 2644 tp->snd_ssthresh, tp->prior_ssthresh, 2645 tp->packets_out); 2646 } 2647 #if defined(CONFIG_IPV6) || defined(CONFIG_IPV6_MODULE) 2648 else if (sk->sk_family == AF_INET6) { 2649 struct ipv6_pinfo *np = inet6_sk(sk); 2650 printk(KERN_DEBUG "Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n", 2651 msg, 2652 &np->daddr, ntohs(inet->inet_dport), 2653 tp->snd_cwnd, tcp_left_out(tp), 2654 tp->snd_ssthresh, tp->prior_ssthresh, 2655 tp->packets_out); 2656 } 2657 #endif 2658 } 2659 #else 2660 #define DBGUNDO(x...) do { } while (0) 2661 #endif 2662 2663 static void tcp_undo_cwr(struct sock *sk, const int undo) 2664 { 2665 struct tcp_sock *tp = tcp_sk(sk); 2666 2667 if (tp->prior_ssthresh) { 2668 const struct inet_connection_sock *icsk = inet_csk(sk); 2669 2670 if (icsk->icsk_ca_ops->undo_cwnd) 2671 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); 2672 else 2673 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1); 2674 2675 if (undo && tp->prior_ssthresh > tp->snd_ssthresh) { 2676 tp->snd_ssthresh = tp->prior_ssthresh; 2677 TCP_ECN_withdraw_cwr(tp); 2678 } 2679 } else { 2680 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); 2681 } 2682 tcp_moderate_cwnd(tp); 2683 tp->snd_cwnd_stamp = tcp_time_stamp; 2684 } 2685 2686 static inline int tcp_may_undo(struct tcp_sock *tp) 2687 { 2688 return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp)); 2689 } 2690 2691 /* People celebrate: "We love our President!" */ 2692 static int tcp_try_undo_recovery(struct sock *sk) 2693 { 2694 struct tcp_sock *tp = tcp_sk(sk); 2695 2696 if (tcp_may_undo(tp)) { 2697 int mib_idx; 2698 2699 /* Happy end! We did not retransmit anything 2700 * or our original transmission succeeded. 2701 */ 2702 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); 2703 tcp_undo_cwr(sk, 1); 2704 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) 2705 mib_idx = LINUX_MIB_TCPLOSSUNDO; 2706 else 2707 mib_idx = LINUX_MIB_TCPFULLUNDO; 2708 2709 NET_INC_STATS_BH(sock_net(sk), mib_idx); 2710 tp->undo_marker = 0; 2711 } 2712 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) { 2713 /* Hold old state until something *above* high_seq 2714 * is ACKed. For Reno it is MUST to prevent false 2715 * fast retransmits (RFC2582). SACK TCP is safe. */ 2716 tcp_moderate_cwnd(tp); 2717 return 1; 2718 } 2719 tcp_set_ca_state(sk, TCP_CA_Open); 2720 return 0; 2721 } 2722 2723 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ 2724 static void tcp_try_undo_dsack(struct sock *sk) 2725 { 2726 struct tcp_sock *tp = tcp_sk(sk); 2727 2728 if (tp->undo_marker && !tp->undo_retrans) { 2729 DBGUNDO(sk, "D-SACK"); 2730 tcp_undo_cwr(sk, 1); 2731 tp->undo_marker = 0; 2732 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO); 2733 } 2734 } 2735 2736 /* We can clear retrans_stamp when there are no retransmissions in the 2737 * window. It would seem that it is trivially available for us in 2738 * tp->retrans_out, however, that kind of assumptions doesn't consider 2739 * what will happen if errors occur when sending retransmission for the 2740 * second time. ...It could the that such segment has only 2741 * TCPCB_EVER_RETRANS set at the present time. It seems that checking 2742 * the head skb is enough except for some reneging corner cases that 2743 * are not worth the effort. 2744 * 2745 * Main reason for all this complexity is the fact that connection dying 2746 * time now depends on the validity of the retrans_stamp, in particular, 2747 * that successive retransmissions of a segment must not advance 2748 * retrans_stamp under any conditions. 2749 */ 2750 static int tcp_any_retrans_done(struct sock *sk) 2751 { 2752 struct tcp_sock *tp = tcp_sk(sk); 2753 struct sk_buff *skb; 2754 2755 if (tp->retrans_out) 2756 return 1; 2757 2758 skb = tcp_write_queue_head(sk); 2759 if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS)) 2760 return 1; 2761 2762 return 0; 2763 } 2764 2765 /* Undo during fast recovery after partial ACK. */ 2766 2767 static int tcp_try_undo_partial(struct sock *sk, int acked) 2768 { 2769 struct tcp_sock *tp = tcp_sk(sk); 2770 /* Partial ACK arrived. Force Hoe's retransmit. */ 2771 int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering); 2772 2773 if (tcp_may_undo(tp)) { 2774 /* Plain luck! Hole if filled with delayed 2775 * packet, rather than with a retransmit. 2776 */ 2777 if (!tcp_any_retrans_done(sk)) 2778 tp->retrans_stamp = 0; 2779 2780 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1); 2781 2782 DBGUNDO(sk, "Hoe"); 2783 tcp_undo_cwr(sk, 0); 2784 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO); 2785 2786 /* So... Do not make Hoe's retransmit yet. 2787 * If the first packet was delayed, the rest 2788 * ones are most probably delayed as well. 2789 */ 2790 failed = 0; 2791 } 2792 return failed; 2793 } 2794 2795 /* Undo during loss recovery after partial ACK. */ 2796 static int tcp_try_undo_loss(struct sock *sk) 2797 { 2798 struct tcp_sock *tp = tcp_sk(sk); 2799 2800 if (tcp_may_undo(tp)) { 2801 struct sk_buff *skb; 2802 tcp_for_write_queue(skb, sk) { 2803 if (skb == tcp_send_head(sk)) 2804 break; 2805 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 2806 } 2807 2808 tcp_clear_all_retrans_hints(tp); 2809 2810 DBGUNDO(sk, "partial loss"); 2811 tp->lost_out = 0; 2812 tcp_undo_cwr(sk, 1); 2813 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO); 2814 inet_csk(sk)->icsk_retransmits = 0; 2815 tp->undo_marker = 0; 2816 if (tcp_is_sack(tp)) 2817 tcp_set_ca_state(sk, TCP_CA_Open); 2818 return 1; 2819 } 2820 return 0; 2821 } 2822 2823 static inline void tcp_complete_cwr(struct sock *sk) 2824 { 2825 struct tcp_sock *tp = tcp_sk(sk); 2826 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 2827 tp->snd_cwnd_stamp = tcp_time_stamp; 2828 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); 2829 } 2830 2831 static void tcp_try_keep_open(struct sock *sk) 2832 { 2833 struct tcp_sock *tp = tcp_sk(sk); 2834 int state = TCP_CA_Open; 2835 2836 if (tcp_left_out(tp) || tcp_any_retrans_done(sk) || tp->undo_marker) 2837 state = TCP_CA_Disorder; 2838 2839 if (inet_csk(sk)->icsk_ca_state != state) { 2840 tcp_set_ca_state(sk, state); 2841 tp->high_seq = tp->snd_nxt; 2842 } 2843 } 2844 2845 static void tcp_try_to_open(struct sock *sk, int flag) 2846 { 2847 struct tcp_sock *tp = tcp_sk(sk); 2848 2849 tcp_verify_left_out(tp); 2850 2851 if (!tp->frto_counter && !tcp_any_retrans_done(sk)) 2852 tp->retrans_stamp = 0; 2853 2854 if (flag & FLAG_ECE) 2855 tcp_enter_cwr(sk, 1); 2856 2857 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { 2858 tcp_try_keep_open(sk); 2859 tcp_moderate_cwnd(tp); 2860 } else { 2861 tcp_cwnd_down(sk, flag); 2862 } 2863 } 2864 2865 static void tcp_mtup_probe_failed(struct sock *sk) 2866 { 2867 struct inet_connection_sock *icsk = inet_csk(sk); 2868 2869 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; 2870 icsk->icsk_mtup.probe_size = 0; 2871 } 2872 2873 static void tcp_mtup_probe_success(struct sock *sk) 2874 { 2875 struct tcp_sock *tp = tcp_sk(sk); 2876 struct inet_connection_sock *icsk = inet_csk(sk); 2877 2878 /* FIXME: breaks with very large cwnd */ 2879 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2880 tp->snd_cwnd = tp->snd_cwnd * 2881 tcp_mss_to_mtu(sk, tp->mss_cache) / 2882 icsk->icsk_mtup.probe_size; 2883 tp->snd_cwnd_cnt = 0; 2884 tp->snd_cwnd_stamp = tcp_time_stamp; 2885 tp->rcv_ssthresh = tcp_current_ssthresh(sk); 2886 2887 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; 2888 icsk->icsk_mtup.probe_size = 0; 2889 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 2890 } 2891 2892 /* Do a simple retransmit without using the backoff mechanisms in 2893 * tcp_timer. This is used for path mtu discovery. 2894 * The socket is already locked here. 2895 */ 2896 void tcp_simple_retransmit(struct sock *sk) 2897 { 2898 const struct inet_connection_sock *icsk = inet_csk(sk); 2899 struct tcp_sock *tp = tcp_sk(sk); 2900 struct sk_buff *skb; 2901 unsigned int mss = tcp_current_mss(sk); 2902 u32 prior_lost = tp->lost_out; 2903 2904 tcp_for_write_queue(skb, sk) { 2905 if (skb == tcp_send_head(sk)) 2906 break; 2907 if (tcp_skb_seglen(skb) > mss && 2908 !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 2909 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 2910 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 2911 tp->retrans_out -= tcp_skb_pcount(skb); 2912 } 2913 tcp_skb_mark_lost_uncond_verify(tp, skb); 2914 } 2915 } 2916 2917 tcp_clear_retrans_hints_partial(tp); 2918 2919 if (prior_lost == tp->lost_out) 2920 return; 2921 2922 if (tcp_is_reno(tp)) 2923 tcp_limit_reno_sacked(tp); 2924 2925 tcp_verify_left_out(tp); 2926 2927 /* Don't muck with the congestion window here. 2928 * Reason is that we do not increase amount of _data_ 2929 * in network, but units changed and effective 2930 * cwnd/ssthresh really reduced now. 2931 */ 2932 if (icsk->icsk_ca_state != TCP_CA_Loss) { 2933 tp->high_seq = tp->snd_nxt; 2934 tp->snd_ssthresh = tcp_current_ssthresh(sk); 2935 tp->prior_ssthresh = 0; 2936 tp->undo_marker = 0; 2937 tcp_set_ca_state(sk, TCP_CA_Loss); 2938 } 2939 tcp_xmit_retransmit_queue(sk); 2940 } 2941 2942 /* Process an event, which can update packets-in-flight not trivially. 2943 * Main goal of this function is to calculate new estimate for left_out, 2944 * taking into account both packets sitting in receiver's buffer and 2945 * packets lost by network. 2946 * 2947 * Besides that it does CWND reduction, when packet loss is detected 2948 * and changes state of machine. 2949 * 2950 * It does _not_ decide what to send, it is made in function 2951 * tcp_xmit_retransmit_queue(). 2952 */ 2953 static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, int flag) 2954 { 2955 struct inet_connection_sock *icsk = inet_csk(sk); 2956 struct tcp_sock *tp = tcp_sk(sk); 2957 int is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP)); 2958 int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) && 2959 (tcp_fackets_out(tp) > tp->reordering)); 2960 int fast_rexmit = 0, mib_idx; 2961 2962 if (WARN_ON(!tp->packets_out && tp->sacked_out)) 2963 tp->sacked_out = 0; 2964 if (WARN_ON(!tp->sacked_out && tp->fackets_out)) 2965 tp->fackets_out = 0; 2966 2967 /* Now state machine starts. 2968 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ 2969 if (flag & FLAG_ECE) 2970 tp->prior_ssthresh = 0; 2971 2972 /* B. In all the states check for reneging SACKs. */ 2973 if (tcp_check_sack_reneging(sk, flag)) 2974 return; 2975 2976 /* C. Process data loss notification, provided it is valid. */ 2977 if (tcp_is_fack(tp) && (flag & FLAG_DATA_LOST) && 2978 before(tp->snd_una, tp->high_seq) && 2979 icsk->icsk_ca_state != TCP_CA_Open && 2980 tp->fackets_out > tp->reordering) { 2981 tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering); 2982 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSS); 2983 } 2984 2985 /* D. Check consistency of the current state. */ 2986 tcp_verify_left_out(tp); 2987 2988 /* E. Check state exit conditions. State can be terminated 2989 * when high_seq is ACKed. */ 2990 if (icsk->icsk_ca_state == TCP_CA_Open) { 2991 WARN_ON(tp->retrans_out != 0); 2992 tp->retrans_stamp = 0; 2993 } else if (!before(tp->snd_una, tp->high_seq)) { 2994 switch (icsk->icsk_ca_state) { 2995 case TCP_CA_Loss: 2996 icsk->icsk_retransmits = 0; 2997 if (tcp_try_undo_recovery(sk)) 2998 return; 2999 break; 3000 3001 case TCP_CA_CWR: 3002 /* CWR is to be held something *above* high_seq 3003 * is ACKed for CWR bit to reach receiver. */ 3004 if (tp->snd_una != tp->high_seq) { 3005 tcp_complete_cwr(sk); 3006 tcp_set_ca_state(sk, TCP_CA_Open); 3007 } 3008 break; 3009 3010 case TCP_CA_Disorder: 3011 tcp_try_undo_dsack(sk); 3012 if (!tp->undo_marker || 3013 /* For SACK case do not Open to allow to undo 3014 * catching for all duplicate ACKs. */ 3015 tcp_is_reno(tp) || tp->snd_una != tp->high_seq) { 3016 tp->undo_marker = 0; 3017 tcp_set_ca_state(sk, TCP_CA_Open); 3018 } 3019 break; 3020 3021 case TCP_CA_Recovery: 3022 if (tcp_is_reno(tp)) 3023 tcp_reset_reno_sack(tp); 3024 if (tcp_try_undo_recovery(sk)) 3025 return; 3026 tcp_complete_cwr(sk); 3027 break; 3028 } 3029 } 3030 3031 /* F. Process state. */ 3032 switch (icsk->icsk_ca_state) { 3033 case TCP_CA_Recovery: 3034 if (!(flag & FLAG_SND_UNA_ADVANCED)) { 3035 if (tcp_is_reno(tp) && is_dupack) 3036 tcp_add_reno_sack(sk); 3037 } else 3038 do_lost = tcp_try_undo_partial(sk, pkts_acked); 3039 break; 3040 case TCP_CA_Loss: 3041 if (flag & FLAG_DATA_ACKED) 3042 icsk->icsk_retransmits = 0; 3043 if (tcp_is_reno(tp) && flag & FLAG_SND_UNA_ADVANCED) 3044 tcp_reset_reno_sack(tp); 3045 if (!tcp_try_undo_loss(sk)) { 3046 tcp_moderate_cwnd(tp); 3047 tcp_xmit_retransmit_queue(sk); 3048 return; 3049 } 3050 if (icsk->icsk_ca_state != TCP_CA_Open) 3051 return; 3052 /* Loss is undone; fall through to processing in Open state. */ 3053 default: 3054 if (tcp_is_reno(tp)) { 3055 if (flag & FLAG_SND_UNA_ADVANCED) 3056 tcp_reset_reno_sack(tp); 3057 if (is_dupack) 3058 tcp_add_reno_sack(sk); 3059 } 3060 3061 if (icsk->icsk_ca_state == TCP_CA_Disorder) 3062 tcp_try_undo_dsack(sk); 3063 3064 if (!tcp_time_to_recover(sk)) { 3065 tcp_try_to_open(sk, flag); 3066 return; 3067 } 3068 3069 /* MTU probe failure: don't reduce cwnd */ 3070 if (icsk->icsk_ca_state < TCP_CA_CWR && 3071 icsk->icsk_mtup.probe_size && 3072 tp->snd_una == tp->mtu_probe.probe_seq_start) { 3073 tcp_mtup_probe_failed(sk); 3074 /* Restores the reduction we did in tcp_mtup_probe() */ 3075 tp->snd_cwnd++; 3076 tcp_simple_retransmit(sk); 3077 return; 3078 } 3079 3080 /* Otherwise enter Recovery state */ 3081 3082 if (tcp_is_reno(tp)) 3083 mib_idx = LINUX_MIB_TCPRENORECOVERY; 3084 else 3085 mib_idx = LINUX_MIB_TCPSACKRECOVERY; 3086 3087 NET_INC_STATS_BH(sock_net(sk), mib_idx); 3088 3089 tp->high_seq = tp->snd_nxt; 3090 tp->prior_ssthresh = 0; 3091 tp->undo_marker = tp->snd_una; 3092 tp->undo_retrans = tp->retrans_out; 3093 3094 if (icsk->icsk_ca_state < TCP_CA_CWR) { 3095 if (!(flag & FLAG_ECE)) 3096 tp->prior_ssthresh = tcp_current_ssthresh(sk); 3097 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 3098 TCP_ECN_queue_cwr(tp); 3099 } 3100 3101 tp->bytes_acked = 0; 3102 tp->snd_cwnd_cnt = 0; 3103 tcp_set_ca_state(sk, TCP_CA_Recovery); 3104 fast_rexmit = 1; 3105 } 3106 3107 if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk))) 3108 tcp_update_scoreboard(sk, fast_rexmit); 3109 tcp_cwnd_down(sk, flag); 3110 tcp_xmit_retransmit_queue(sk); 3111 } 3112 3113 static void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt) 3114 { 3115 tcp_rtt_estimator(sk, seq_rtt); 3116 tcp_set_rto(sk); 3117 inet_csk(sk)->icsk_backoff = 0; 3118 } 3119 3120 /* Read draft-ietf-tcplw-high-performance before mucking 3121 * with this code. (Supersedes RFC1323) 3122 */ 3123 static void tcp_ack_saw_tstamp(struct sock *sk, int flag) 3124 { 3125 /* RTTM Rule: A TSecr value received in a segment is used to 3126 * update the averaged RTT measurement only if the segment 3127 * acknowledges some new data, i.e., only if it advances the 3128 * left edge of the send window. 3129 * 3130 * See draft-ietf-tcplw-high-performance-00, section 3.3. 3131 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> 3132 * 3133 * Changed: reset backoff as soon as we see the first valid sample. 3134 * If we do not, we get strongly overestimated rto. With timestamps 3135 * samples are accepted even from very old segments: f.e., when rtt=1 3136 * increases to 8, we retransmit 5 times and after 8 seconds delayed 3137 * answer arrives rto becomes 120 seconds! If at least one of segments 3138 * in window is lost... Voila. --ANK (010210) 3139 */ 3140 struct tcp_sock *tp = tcp_sk(sk); 3141 3142 tcp_valid_rtt_meas(sk, tcp_time_stamp - tp->rx_opt.rcv_tsecr); 3143 } 3144 3145 static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag) 3146 { 3147 /* We don't have a timestamp. Can only use 3148 * packets that are not retransmitted to determine 3149 * rtt estimates. Also, we must not reset the 3150 * backoff for rto until we get a non-retransmitted 3151 * packet. This allows us to deal with a situation 3152 * where the network delay has increased suddenly. 3153 * I.e. Karn's algorithm. (SIGCOMM '87, p5.) 3154 */ 3155 3156 if (flag & FLAG_RETRANS_DATA_ACKED) 3157 return; 3158 3159 tcp_valid_rtt_meas(sk, seq_rtt); 3160 } 3161 3162 static inline void tcp_ack_update_rtt(struct sock *sk, const int flag, 3163 const s32 seq_rtt) 3164 { 3165 const struct tcp_sock *tp = tcp_sk(sk); 3166 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ 3167 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) 3168 tcp_ack_saw_tstamp(sk, flag); 3169 else if (seq_rtt >= 0) 3170 tcp_ack_no_tstamp(sk, seq_rtt, flag); 3171 } 3172 3173 static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) 3174 { 3175 const struct inet_connection_sock *icsk = inet_csk(sk); 3176 icsk->icsk_ca_ops->cong_avoid(sk, ack, in_flight); 3177 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp; 3178 } 3179 3180 /* Restart timer after forward progress on connection. 3181 * RFC2988 recommends to restart timer to now+rto. 3182 */ 3183 static void tcp_rearm_rto(struct sock *sk) 3184 { 3185 struct tcp_sock *tp = tcp_sk(sk); 3186 3187 if (!tp->packets_out) { 3188 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); 3189 } else { 3190 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 3191 inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 3192 } 3193 } 3194 3195 /* If we get here, the whole TSO packet has not been acked. */ 3196 static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb) 3197 { 3198 struct tcp_sock *tp = tcp_sk(sk); 3199 u32 packets_acked; 3200 3201 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)); 3202 3203 packets_acked = tcp_skb_pcount(skb); 3204 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) 3205 return 0; 3206 packets_acked -= tcp_skb_pcount(skb); 3207 3208 if (packets_acked) { 3209 BUG_ON(tcp_skb_pcount(skb) == 0); 3210 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)); 3211 } 3212 3213 return packets_acked; 3214 } 3215 3216 /* Remove acknowledged frames from the retransmission queue. If our packet 3217 * is before the ack sequence we can discard it as it's confirmed to have 3218 * arrived at the other end. 3219 */ 3220 static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets, 3221 u32 prior_snd_una) 3222 { 3223 struct tcp_sock *tp = tcp_sk(sk); 3224 const struct inet_connection_sock *icsk = inet_csk(sk); 3225 struct sk_buff *skb; 3226 u32 now = tcp_time_stamp; 3227 int fully_acked = 1; 3228 int flag = 0; 3229 u32 pkts_acked = 0; 3230 u32 reord = tp->packets_out; 3231 u32 prior_sacked = tp->sacked_out; 3232 s32 seq_rtt = -1; 3233 s32 ca_seq_rtt = -1; 3234 ktime_t last_ackt = net_invalid_timestamp(); 3235 3236 while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) { 3237 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 3238 u32 acked_pcount; 3239 u8 sacked = scb->sacked; 3240 3241 /* Determine how many packets and what bytes were acked, tso and else */ 3242 if (after(scb->end_seq, tp->snd_una)) { 3243 if (tcp_skb_pcount(skb) == 1 || 3244 !after(tp->snd_una, scb->seq)) 3245 break; 3246 3247 acked_pcount = tcp_tso_acked(sk, skb); 3248 if (!acked_pcount) 3249 break; 3250 3251 fully_acked = 0; 3252 } else { 3253 acked_pcount = tcp_skb_pcount(skb); 3254 } 3255 3256 if (sacked & TCPCB_RETRANS) { 3257 if (sacked & TCPCB_SACKED_RETRANS) 3258 tp->retrans_out -= acked_pcount; 3259 flag |= FLAG_RETRANS_DATA_ACKED; 3260 ca_seq_rtt = -1; 3261 seq_rtt = -1; 3262 if ((flag & FLAG_DATA_ACKED) || (acked_pcount > 1)) 3263 flag |= FLAG_NONHEAD_RETRANS_ACKED; 3264 } else { 3265 ca_seq_rtt = now - scb->when; 3266 last_ackt = skb->tstamp; 3267 if (seq_rtt < 0) { 3268 seq_rtt = ca_seq_rtt; 3269 } 3270 if (!(sacked & TCPCB_SACKED_ACKED)) 3271 reord = min(pkts_acked, reord); 3272 } 3273 3274 if (sacked & TCPCB_SACKED_ACKED) 3275 tp->sacked_out -= acked_pcount; 3276 if (sacked & TCPCB_LOST) 3277 tp->lost_out -= acked_pcount; 3278 3279 tp->packets_out -= acked_pcount; 3280 pkts_acked += acked_pcount; 3281 3282 /* Initial outgoing SYN's get put onto the write_queue 3283 * just like anything else we transmit. It is not 3284 * true data, and if we misinform our callers that 3285 * this ACK acks real data, we will erroneously exit 3286 * connection startup slow start one packet too 3287 * quickly. This is severely frowned upon behavior. 3288 */ 3289 if (!(scb->flags & TCPCB_FLAG_SYN)) { 3290 flag |= FLAG_DATA_ACKED; 3291 } else { 3292 flag |= FLAG_SYN_ACKED; 3293 tp->retrans_stamp = 0; 3294 } 3295 3296 if (!fully_acked) 3297 break; 3298 3299 tcp_unlink_write_queue(skb, sk); 3300 sk_wmem_free_skb(sk, skb); 3301 tp->scoreboard_skb_hint = NULL; 3302 if (skb == tp->retransmit_skb_hint) 3303 tp->retransmit_skb_hint = NULL; 3304 if (skb == tp->lost_skb_hint) 3305 tp->lost_skb_hint = NULL; 3306 } 3307 3308 if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una))) 3309 tp->snd_up = tp->snd_una; 3310 3311 if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 3312 flag |= FLAG_SACK_RENEGING; 3313 3314 if (flag & FLAG_ACKED) { 3315 const struct tcp_congestion_ops *ca_ops 3316 = inet_csk(sk)->icsk_ca_ops; 3317 3318 if (unlikely(icsk->icsk_mtup.probe_size && 3319 !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) { 3320 tcp_mtup_probe_success(sk); 3321 } 3322 3323 tcp_ack_update_rtt(sk, flag, seq_rtt); 3324 tcp_rearm_rto(sk); 3325 3326 if (tcp_is_reno(tp)) { 3327 tcp_remove_reno_sacks(sk, pkts_acked); 3328 } else { 3329 int delta; 3330 3331 /* Non-retransmitted hole got filled? That's reordering */ 3332 if (reord < prior_fackets) 3333 tcp_update_reordering(sk, tp->fackets_out - reord, 0); 3334 3335 delta = tcp_is_fack(tp) ? pkts_acked : 3336 prior_sacked - tp->sacked_out; 3337 tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta); 3338 } 3339 3340 tp->fackets_out -= min(pkts_acked, tp->fackets_out); 3341 3342 if (ca_ops->pkts_acked) { 3343 s32 rtt_us = -1; 3344 3345 /* Is the ACK triggering packet unambiguous? */ 3346 if (!(flag & FLAG_RETRANS_DATA_ACKED)) { 3347 /* High resolution needed and available? */ 3348 if (ca_ops->flags & TCP_CONG_RTT_STAMP && 3349 !ktime_equal(last_ackt, 3350 net_invalid_timestamp())) 3351 rtt_us = ktime_us_delta(ktime_get_real(), 3352 last_ackt); 3353 else if (ca_seq_rtt > 0) 3354 rtt_us = jiffies_to_usecs(ca_seq_rtt); 3355 } 3356 3357 ca_ops->pkts_acked(sk, pkts_acked, rtt_us); 3358 } 3359 } 3360 3361 #if FASTRETRANS_DEBUG > 0 3362 WARN_ON((int)tp->sacked_out < 0); 3363 WARN_ON((int)tp->lost_out < 0); 3364 WARN_ON((int)tp->retrans_out < 0); 3365 if (!tp->packets_out && tcp_is_sack(tp)) { 3366 icsk = inet_csk(sk); 3367 if (tp->lost_out) { 3368 printk(KERN_DEBUG "Leak l=%u %d\n", 3369 tp->lost_out, icsk->icsk_ca_state); 3370 tp->lost_out = 0; 3371 } 3372 if (tp->sacked_out) { 3373 printk(KERN_DEBUG "Leak s=%u %d\n", 3374 tp->sacked_out, icsk->icsk_ca_state); 3375 tp->sacked_out = 0; 3376 } 3377 if (tp->retrans_out) { 3378 printk(KERN_DEBUG "Leak r=%u %d\n", 3379 tp->retrans_out, icsk->icsk_ca_state); 3380 tp->retrans_out = 0; 3381 } 3382 } 3383 #endif 3384 return flag; 3385 } 3386 3387 static void tcp_ack_probe(struct sock *sk) 3388 { 3389 const struct tcp_sock *tp = tcp_sk(sk); 3390 struct inet_connection_sock *icsk = inet_csk(sk); 3391 3392 /* Was it a usable window open? */ 3393 3394 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) { 3395 icsk->icsk_backoff = 0; 3396 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0); 3397 /* Socket must be waked up by subsequent tcp_data_snd_check(). 3398 * This function is not for random using! 3399 */ 3400 } else { 3401 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 3402 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), 3403 TCP_RTO_MAX); 3404 } 3405 } 3406 3407 static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag) 3408 { 3409 return (!(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || 3410 inet_csk(sk)->icsk_ca_state != TCP_CA_Open); 3411 } 3412 3413 static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag) 3414 { 3415 const struct tcp_sock *tp = tcp_sk(sk); 3416 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) && 3417 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR)); 3418 } 3419 3420 /* Check that window update is acceptable. 3421 * The function assumes that snd_una<=ack<=snd_next. 3422 */ 3423 static inline int tcp_may_update_window(const struct tcp_sock *tp, 3424 const u32 ack, const u32 ack_seq, 3425 const u32 nwin) 3426 { 3427 return (after(ack, tp->snd_una) || 3428 after(ack_seq, tp->snd_wl1) || 3429 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd)); 3430 } 3431 3432 /* Update our send window. 3433 * 3434 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 3435 * and in FreeBSD. NetBSD's one is even worse.) is wrong. 3436 */ 3437 static int tcp_ack_update_window(struct sock *sk, struct sk_buff *skb, u32 ack, 3438 u32 ack_seq) 3439 { 3440 struct tcp_sock *tp = tcp_sk(sk); 3441 int flag = 0; 3442 u32 nwin = ntohs(tcp_hdr(skb)->window); 3443 3444 if (likely(!tcp_hdr(skb)->syn)) 3445 nwin <<= tp->rx_opt.snd_wscale; 3446 3447 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { 3448 flag |= FLAG_WIN_UPDATE; 3449 tcp_update_wl(tp, ack_seq); 3450 3451 if (tp->snd_wnd != nwin) { 3452 tp->snd_wnd = nwin; 3453 3454 /* Note, it is the only place, where 3455 * fast path is recovered for sending TCP. 3456 */ 3457 tp->pred_flags = 0; 3458 tcp_fast_path_check(sk); 3459 3460 if (nwin > tp->max_window) { 3461 tp->max_window = nwin; 3462 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie); 3463 } 3464 } 3465 } 3466 3467 tp->snd_una = ack; 3468 3469 return flag; 3470 } 3471 3472 /* A very conservative spurious RTO response algorithm: reduce cwnd and 3473 * continue in congestion avoidance. 3474 */ 3475 static void tcp_conservative_spur_to_response(struct tcp_sock *tp) 3476 { 3477 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 3478 tp->snd_cwnd_cnt = 0; 3479 tp->bytes_acked = 0; 3480 TCP_ECN_queue_cwr(tp); 3481 tcp_moderate_cwnd(tp); 3482 } 3483 3484 /* A conservative spurious RTO response algorithm: reduce cwnd using 3485 * rate halving and continue in congestion avoidance. 3486 */ 3487 static void tcp_ratehalving_spur_to_response(struct sock *sk) 3488 { 3489 tcp_enter_cwr(sk, 0); 3490 } 3491 3492 static void tcp_undo_spur_to_response(struct sock *sk, int flag) 3493 { 3494 if (flag & FLAG_ECE) 3495 tcp_ratehalving_spur_to_response(sk); 3496 else 3497 tcp_undo_cwr(sk, 1); 3498 } 3499 3500 /* F-RTO spurious RTO detection algorithm (RFC4138) 3501 * 3502 * F-RTO affects during two new ACKs following RTO (well, almost, see inline 3503 * comments). State (ACK number) is kept in frto_counter. When ACK advances 3504 * window (but not to or beyond highest sequence sent before RTO): 3505 * On First ACK, send two new segments out. 3506 * On Second ACK, RTO was likely spurious. Do spurious response (response 3507 * algorithm is not part of the F-RTO detection algorithm 3508 * given in RFC4138 but can be selected separately). 3509 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss 3510 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding 3511 * of Nagle, this is done using frto_counter states 2 and 3, when a new data 3512 * segment of any size sent during F-RTO, state 2 is upgraded to 3. 3513 * 3514 * Rationale: if the RTO was spurious, new ACKs should arrive from the 3515 * original window even after we transmit two new data segments. 3516 * 3517 * SACK version: 3518 * on first step, wait until first cumulative ACK arrives, then move to 3519 * the second step. In second step, the next ACK decides. 3520 * 3521 * F-RTO is implemented (mainly) in four functions: 3522 * - tcp_use_frto() is used to determine if TCP is can use F-RTO 3523 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is 3524 * called when tcp_use_frto() showed green light 3525 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm 3526 * - tcp_enter_frto_loss() is called if there is not enough evidence 3527 * to prove that the RTO is indeed spurious. It transfers the control 3528 * from F-RTO to the conventional RTO recovery 3529 */ 3530 static int tcp_process_frto(struct sock *sk, int flag) 3531 { 3532 struct tcp_sock *tp = tcp_sk(sk); 3533 3534 tcp_verify_left_out(tp); 3535 3536 /* Duplicate the behavior from Loss state (fastretrans_alert) */ 3537 if (flag & FLAG_DATA_ACKED) 3538 inet_csk(sk)->icsk_retransmits = 0; 3539 3540 if ((flag & FLAG_NONHEAD_RETRANS_ACKED) || 3541 ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED))) 3542 tp->undo_marker = 0; 3543 3544 if (!before(tp->snd_una, tp->frto_highmark)) { 3545 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag); 3546 return 1; 3547 } 3548 3549 if (!tcp_is_sackfrto(tp)) { 3550 /* RFC4138 shortcoming in step 2; should also have case c): 3551 * ACK isn't duplicate nor advances window, e.g., opposite dir 3552 * data, winupdate 3553 */ 3554 if (!(flag & FLAG_ANY_PROGRESS) && (flag & FLAG_NOT_DUP)) 3555 return 1; 3556 3557 if (!(flag & FLAG_DATA_ACKED)) { 3558 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3), 3559 flag); 3560 return 1; 3561 } 3562 } else { 3563 if (!(flag & FLAG_DATA_ACKED) && (tp->frto_counter == 1)) { 3564 /* Prevent sending of new data. */ 3565 tp->snd_cwnd = min(tp->snd_cwnd, 3566 tcp_packets_in_flight(tp)); 3567 return 1; 3568 } 3569 3570 if ((tp->frto_counter >= 2) && 3571 (!(flag & FLAG_FORWARD_PROGRESS) || 3572 ((flag & FLAG_DATA_SACKED) && 3573 !(flag & FLAG_ONLY_ORIG_SACKED)))) { 3574 /* RFC4138 shortcoming (see comment above) */ 3575 if (!(flag & FLAG_FORWARD_PROGRESS) && 3576 (flag & FLAG_NOT_DUP)) 3577 return 1; 3578 3579 tcp_enter_frto_loss(sk, 3, flag); 3580 return 1; 3581 } 3582 } 3583 3584 if (tp->frto_counter == 1) { 3585 /* tcp_may_send_now needs to see updated state */ 3586 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; 3587 tp->frto_counter = 2; 3588 3589 if (!tcp_may_send_now(sk)) 3590 tcp_enter_frto_loss(sk, 2, flag); 3591 3592 return 1; 3593 } else { 3594 switch (sysctl_tcp_frto_response) { 3595 case 2: 3596 tcp_undo_spur_to_response(sk, flag); 3597 break; 3598 case 1: 3599 tcp_conservative_spur_to_response(tp); 3600 break; 3601 default: 3602 tcp_ratehalving_spur_to_response(sk); 3603 break; 3604 } 3605 tp->frto_counter = 0; 3606 tp->undo_marker = 0; 3607 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSPURIOUSRTOS); 3608 } 3609 return 0; 3610 } 3611 3612 /* This routine deals with incoming acks, but not outgoing ones. */ 3613 static int tcp_ack(struct sock *sk, struct sk_buff *skb, int flag) 3614 { 3615 struct inet_connection_sock *icsk = inet_csk(sk); 3616 struct tcp_sock *tp = tcp_sk(sk); 3617 u32 prior_snd_una = tp->snd_una; 3618 u32 ack_seq = TCP_SKB_CB(skb)->seq; 3619 u32 ack = TCP_SKB_CB(skb)->ack_seq; 3620 u32 prior_in_flight; 3621 u32 prior_fackets; 3622 int prior_packets; 3623 int frto_cwnd = 0; 3624 3625 /* If the ack is older than previous acks 3626 * then we can probably ignore it. 3627 */ 3628 if (before(ack, prior_snd_una)) 3629 goto old_ack; 3630 3631 /* If the ack includes data we haven't sent yet, discard 3632 * this segment (RFC793 Section 3.9). 3633 */ 3634 if (after(ack, tp->snd_nxt)) 3635 goto invalid_ack; 3636 3637 if (after(ack, prior_snd_una)) 3638 flag |= FLAG_SND_UNA_ADVANCED; 3639 3640 if (sysctl_tcp_abc) { 3641 if (icsk->icsk_ca_state < TCP_CA_CWR) 3642 tp->bytes_acked += ack - prior_snd_una; 3643 else if (icsk->icsk_ca_state == TCP_CA_Loss) 3644 /* we assume just one segment left network */ 3645 tp->bytes_acked += min(ack - prior_snd_una, 3646 tp->mss_cache); 3647 } 3648 3649 prior_fackets = tp->fackets_out; 3650 prior_in_flight = tcp_packets_in_flight(tp); 3651 3652 if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) { 3653 /* Window is constant, pure forward advance. 3654 * No more checks are required. 3655 * Note, we use the fact that SND.UNA>=SND.WL2. 3656 */ 3657 tcp_update_wl(tp, ack_seq); 3658 tp->snd_una = ack; 3659 flag |= FLAG_WIN_UPDATE; 3660 3661 tcp_ca_event(sk, CA_EVENT_FAST_ACK); 3662 3663 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS); 3664 } else { 3665 if (ack_seq != TCP_SKB_CB(skb)->end_seq) 3666 flag |= FLAG_DATA; 3667 else 3668 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPUREACKS); 3669 3670 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq); 3671 3672 if (TCP_SKB_CB(skb)->sacked) 3673 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); 3674 3675 if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) 3676 flag |= FLAG_ECE; 3677 3678 tcp_ca_event(sk, CA_EVENT_SLOW_ACK); 3679 } 3680 3681 /* We passed data and got it acked, remove any soft error 3682 * log. Something worked... 3683 */ 3684 sk->sk_err_soft = 0; 3685 icsk->icsk_probes_out = 0; 3686 tp->rcv_tstamp = tcp_time_stamp; 3687 prior_packets = tp->packets_out; 3688 if (!prior_packets) 3689 goto no_queue; 3690 3691 /* See if we can take anything off of the retransmit queue. */ 3692 flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una); 3693 3694 if (tp->frto_counter) 3695 frto_cwnd = tcp_process_frto(sk, flag); 3696 /* Guarantee sacktag reordering detection against wrap-arounds */ 3697 if (before(tp->frto_highmark, tp->snd_una)) 3698 tp->frto_highmark = 0; 3699 3700 if (tcp_ack_is_dubious(sk, flag)) { 3701 /* Advance CWND, if state allows this. */ 3702 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd && 3703 tcp_may_raise_cwnd(sk, flag)) 3704 tcp_cong_avoid(sk, ack, prior_in_flight); 3705 tcp_fastretrans_alert(sk, prior_packets - tp->packets_out, 3706 flag); 3707 } else { 3708 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd) 3709 tcp_cong_avoid(sk, ack, prior_in_flight); 3710 } 3711 3712 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) 3713 dst_confirm(__sk_dst_get(sk)); 3714 3715 return 1; 3716 3717 no_queue: 3718 /* If this ack opens up a zero window, clear backoff. It was 3719 * being used to time the probes, and is probably far higher than 3720 * it needs to be for normal retransmission. 3721 */ 3722 if (tcp_send_head(sk)) 3723 tcp_ack_probe(sk); 3724 return 1; 3725 3726 invalid_ack: 3727 SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt); 3728 return -1; 3729 3730 old_ack: 3731 if (TCP_SKB_CB(skb)->sacked) { 3732 tcp_sacktag_write_queue(sk, skb, prior_snd_una); 3733 if (icsk->icsk_ca_state == TCP_CA_Open) 3734 tcp_try_keep_open(sk); 3735 } 3736 3737 SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt); 3738 return 0; 3739 } 3740 3741 /* Look for tcp options. Normally only called on SYN and SYNACK packets. 3742 * But, this can also be called on packets in the established flow when 3743 * the fast version below fails. 3744 */ 3745 void tcp_parse_options(struct sk_buff *skb, struct tcp_options_received *opt_rx, 3746 u8 **hvpp, int estab) 3747 { 3748 unsigned char *ptr; 3749 struct tcphdr *th = tcp_hdr(skb); 3750 int length = (th->doff * 4) - sizeof(struct tcphdr); 3751 3752 ptr = (unsigned char *)(th + 1); 3753 opt_rx->saw_tstamp = 0; 3754 3755 while (length > 0) { 3756 int opcode = *ptr++; 3757 int opsize; 3758 3759 switch (opcode) { 3760 case TCPOPT_EOL: 3761 return; 3762 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ 3763 length--; 3764 continue; 3765 default: 3766 opsize = *ptr++; 3767 if (opsize < 2) /* "silly options" */ 3768 return; 3769 if (opsize > length) 3770 return; /* don't parse partial options */ 3771 switch (opcode) { 3772 case TCPOPT_MSS: 3773 if (opsize == TCPOLEN_MSS && th->syn && !estab) { 3774 u16 in_mss = get_unaligned_be16(ptr); 3775 if (in_mss) { 3776 if (opt_rx->user_mss && 3777 opt_rx->user_mss < in_mss) 3778 in_mss = opt_rx->user_mss; 3779 opt_rx->mss_clamp = in_mss; 3780 } 3781 } 3782 break; 3783 case TCPOPT_WINDOW: 3784 if (opsize == TCPOLEN_WINDOW && th->syn && 3785 !estab && sysctl_tcp_window_scaling) { 3786 __u8 snd_wscale = *(__u8 *)ptr; 3787 opt_rx->wscale_ok = 1; 3788 if (snd_wscale > 14) { 3789 if (net_ratelimit()) 3790 printk(KERN_INFO "tcp_parse_options: Illegal window " 3791 "scaling value %d >14 received.\n", 3792 snd_wscale); 3793 snd_wscale = 14; 3794 } 3795 opt_rx->snd_wscale = snd_wscale; 3796 } 3797 break; 3798 case TCPOPT_TIMESTAMP: 3799 if ((opsize == TCPOLEN_TIMESTAMP) && 3800 ((estab && opt_rx->tstamp_ok) || 3801 (!estab && sysctl_tcp_timestamps))) { 3802 opt_rx->saw_tstamp = 1; 3803 opt_rx->rcv_tsval = get_unaligned_be32(ptr); 3804 opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4); 3805 } 3806 break; 3807 case TCPOPT_SACK_PERM: 3808 if (opsize == TCPOLEN_SACK_PERM && th->syn && 3809 !estab && sysctl_tcp_sack) { 3810 opt_rx->sack_ok = 1; 3811 tcp_sack_reset(opt_rx); 3812 } 3813 break; 3814 3815 case TCPOPT_SACK: 3816 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && 3817 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && 3818 opt_rx->sack_ok) { 3819 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; 3820 } 3821 break; 3822 #ifdef CONFIG_TCP_MD5SIG 3823 case TCPOPT_MD5SIG: 3824 /* 3825 * The MD5 Hash has already been 3826 * checked (see tcp_v{4,6}_do_rcv()). 3827 */ 3828 break; 3829 #endif 3830 case TCPOPT_COOKIE: 3831 /* This option is variable length. 3832 */ 3833 switch (opsize) { 3834 case TCPOLEN_COOKIE_BASE: 3835 /* not yet implemented */ 3836 break; 3837 case TCPOLEN_COOKIE_PAIR: 3838 /* not yet implemented */ 3839 break; 3840 case TCPOLEN_COOKIE_MIN+0: 3841 case TCPOLEN_COOKIE_MIN+2: 3842 case TCPOLEN_COOKIE_MIN+4: 3843 case TCPOLEN_COOKIE_MIN+6: 3844 case TCPOLEN_COOKIE_MAX: 3845 /* 16-bit multiple */ 3846 opt_rx->cookie_plus = opsize; 3847 *hvpp = ptr; 3848 break; 3849 default: 3850 /* ignore option */ 3851 break; 3852 } 3853 break; 3854 } 3855 3856 ptr += opsize-2; 3857 length -= opsize; 3858 } 3859 } 3860 } 3861 3862 static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, struct tcphdr *th) 3863 { 3864 __be32 *ptr = (__be32 *)(th + 1); 3865 3866 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) 3867 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { 3868 tp->rx_opt.saw_tstamp = 1; 3869 ++ptr; 3870 tp->rx_opt.rcv_tsval = ntohl(*ptr); 3871 ++ptr; 3872 tp->rx_opt.rcv_tsecr = ntohl(*ptr); 3873 return 1; 3874 } 3875 return 0; 3876 } 3877 3878 /* Fast parse options. This hopes to only see timestamps. 3879 * If it is wrong it falls back on tcp_parse_options(). 3880 */ 3881 static int tcp_fast_parse_options(struct sk_buff *skb, struct tcphdr *th, 3882 struct tcp_sock *tp, u8 **hvpp) 3883 { 3884 /* In the spirit of fast parsing, compare doff directly to constant 3885 * values. Because equality is used, short doff can be ignored here. 3886 */ 3887 if (th->doff == (sizeof(*th) / 4)) { 3888 tp->rx_opt.saw_tstamp = 0; 3889 return 0; 3890 } else if (tp->rx_opt.tstamp_ok && 3891 th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) { 3892 if (tcp_parse_aligned_timestamp(tp, th)) 3893 return 1; 3894 } 3895 tcp_parse_options(skb, &tp->rx_opt, hvpp, 1); 3896 return 1; 3897 } 3898 3899 #ifdef CONFIG_TCP_MD5SIG 3900 /* 3901 * Parse MD5 Signature option 3902 */ 3903 u8 *tcp_parse_md5sig_option(struct tcphdr *th) 3904 { 3905 int length = (th->doff << 2) - sizeof (*th); 3906 u8 *ptr = (u8*)(th + 1); 3907 3908 /* If the TCP option is too short, we can short cut */ 3909 if (length < TCPOLEN_MD5SIG) 3910 return NULL; 3911 3912 while (length > 0) { 3913 int opcode = *ptr++; 3914 int opsize; 3915 3916 switch(opcode) { 3917 case TCPOPT_EOL: 3918 return NULL; 3919 case TCPOPT_NOP: 3920 length--; 3921 continue; 3922 default: 3923 opsize = *ptr++; 3924 if (opsize < 2 || opsize > length) 3925 return NULL; 3926 if (opcode == TCPOPT_MD5SIG) 3927 return ptr; 3928 } 3929 ptr += opsize - 2; 3930 length -= opsize; 3931 } 3932 return NULL; 3933 } 3934 #endif 3935 3936 static inline void tcp_store_ts_recent(struct tcp_sock *tp) 3937 { 3938 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; 3939 tp->rx_opt.ts_recent_stamp = get_seconds(); 3940 } 3941 3942 static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) 3943 { 3944 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { 3945 /* PAWS bug workaround wrt. ACK frames, the PAWS discard 3946 * extra check below makes sure this can only happen 3947 * for pure ACK frames. -DaveM 3948 * 3949 * Not only, also it occurs for expired timestamps. 3950 */ 3951 3952 if (tcp_paws_check(&tp->rx_opt, 0)) 3953 tcp_store_ts_recent(tp); 3954 } 3955 } 3956 3957 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM 3958 * 3959 * It is not fatal. If this ACK does _not_ change critical state (seqs, window) 3960 * it can pass through stack. So, the following predicate verifies that 3961 * this segment is not used for anything but congestion avoidance or 3962 * fast retransmit. Moreover, we even are able to eliminate most of such 3963 * second order effects, if we apply some small "replay" window (~RTO) 3964 * to timestamp space. 3965 * 3966 * All these measures still do not guarantee that we reject wrapped ACKs 3967 * on networks with high bandwidth, when sequence space is recycled fastly, 3968 * but it guarantees that such events will be very rare and do not affect 3969 * connection seriously. This doesn't look nice, but alas, PAWS is really 3970 * buggy extension. 3971 * 3972 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC 3973 * states that events when retransmit arrives after original data are rare. 3974 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is 3975 * the biggest problem on large power networks even with minor reordering. 3976 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe 3977 * up to bandwidth of 18Gigabit/sec. 8) ] 3978 */ 3979 3980 static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb) 3981 { 3982 struct tcp_sock *tp = tcp_sk(sk); 3983 struct tcphdr *th = tcp_hdr(skb); 3984 u32 seq = TCP_SKB_CB(skb)->seq; 3985 u32 ack = TCP_SKB_CB(skb)->ack_seq; 3986 3987 return (/* 1. Pure ACK with correct sequence number. */ 3988 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && 3989 3990 /* 2. ... and duplicate ACK. */ 3991 ack == tp->snd_una && 3992 3993 /* 3. ... and does not update window. */ 3994 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && 3995 3996 /* 4. ... and sits in replay window. */ 3997 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ); 3998 } 3999 4000 static inline int tcp_paws_discard(const struct sock *sk, 4001 const struct sk_buff *skb) 4002 { 4003 const struct tcp_sock *tp = tcp_sk(sk); 4004 4005 return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) && 4006 !tcp_disordered_ack(sk, skb); 4007 } 4008 4009 /* Check segment sequence number for validity. 4010 * 4011 * Segment controls are considered valid, if the segment 4012 * fits to the window after truncation to the window. Acceptability 4013 * of data (and SYN, FIN, of course) is checked separately. 4014 * See tcp_data_queue(), for example. 4015 * 4016 * Also, controls (RST is main one) are accepted using RCV.WUP instead 4017 * of RCV.NXT. Peer still did not advance his SND.UNA when we 4018 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. 4019 * (borrowed from freebsd) 4020 */ 4021 4022 static inline int tcp_sequence(struct tcp_sock *tp, u32 seq, u32 end_seq) 4023 { 4024 return !before(end_seq, tp->rcv_wup) && 4025 !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); 4026 } 4027 4028 /* When we get a reset we do this. */ 4029 static void tcp_reset(struct sock *sk) 4030 { 4031 /* We want the right error as BSD sees it (and indeed as we do). */ 4032 switch (sk->sk_state) { 4033 case TCP_SYN_SENT: 4034 sk->sk_err = ECONNREFUSED; 4035 break; 4036 case TCP_CLOSE_WAIT: 4037 sk->sk_err = EPIPE; 4038 break; 4039 case TCP_CLOSE: 4040 return; 4041 default: 4042 sk->sk_err = ECONNRESET; 4043 } 4044 4045 if (!sock_flag(sk, SOCK_DEAD)) 4046 sk->sk_error_report(sk); 4047 4048 tcp_done(sk); 4049 } 4050 4051 /* 4052 * Process the FIN bit. This now behaves as it is supposed to work 4053 * and the FIN takes effect when it is validly part of sequence 4054 * space. Not before when we get holes. 4055 * 4056 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT 4057 * (and thence onto LAST-ACK and finally, CLOSE, we never enter 4058 * TIME-WAIT) 4059 * 4060 * If we are in FINWAIT-1, a received FIN indicates simultaneous 4061 * close and we go into CLOSING (and later onto TIME-WAIT) 4062 * 4063 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. 4064 */ 4065 static void tcp_fin(struct sk_buff *skb, struct sock *sk, struct tcphdr *th) 4066 { 4067 struct tcp_sock *tp = tcp_sk(sk); 4068 4069 inet_csk_schedule_ack(sk); 4070 4071 sk->sk_shutdown |= RCV_SHUTDOWN; 4072 sock_set_flag(sk, SOCK_DONE); 4073 4074 switch (sk->sk_state) { 4075 case TCP_SYN_RECV: 4076 case TCP_ESTABLISHED: 4077 /* Move to CLOSE_WAIT */ 4078 tcp_set_state(sk, TCP_CLOSE_WAIT); 4079 inet_csk(sk)->icsk_ack.pingpong = 1; 4080 break; 4081 4082 case TCP_CLOSE_WAIT: 4083 case TCP_CLOSING: 4084 /* Received a retransmission of the FIN, do 4085 * nothing. 4086 */ 4087 break; 4088 case TCP_LAST_ACK: 4089 /* RFC793: Remain in the LAST-ACK state. */ 4090 break; 4091 4092 case TCP_FIN_WAIT1: 4093 /* This case occurs when a simultaneous close 4094 * happens, we must ack the received FIN and 4095 * enter the CLOSING state. 4096 */ 4097 tcp_send_ack(sk); 4098 tcp_set_state(sk, TCP_CLOSING); 4099 break; 4100 case TCP_FIN_WAIT2: 4101 /* Received a FIN -- send ACK and enter TIME_WAIT. */ 4102 tcp_send_ack(sk); 4103 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 4104 break; 4105 default: 4106 /* Only TCP_LISTEN and TCP_CLOSE are left, in these 4107 * cases we should never reach this piece of code. 4108 */ 4109 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n", 4110 __func__, sk->sk_state); 4111 break; 4112 } 4113 4114 /* It _is_ possible, that we have something out-of-order _after_ FIN. 4115 * Probably, we should reset in this case. For now drop them. 4116 */ 4117 __skb_queue_purge(&tp->out_of_order_queue); 4118 if (tcp_is_sack(tp)) 4119 tcp_sack_reset(&tp->rx_opt); 4120 sk_mem_reclaim(sk); 4121 4122 if (!sock_flag(sk, SOCK_DEAD)) { 4123 sk->sk_state_change(sk); 4124 4125 /* Do not send POLL_HUP for half duplex close. */ 4126 if (sk->sk_shutdown == SHUTDOWN_MASK || 4127 sk->sk_state == TCP_CLOSE) 4128 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP); 4129 else 4130 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); 4131 } 4132 } 4133 4134 static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, 4135 u32 end_seq) 4136 { 4137 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { 4138 if (before(seq, sp->start_seq)) 4139 sp->start_seq = seq; 4140 if (after(end_seq, sp->end_seq)) 4141 sp->end_seq = end_seq; 4142 return 1; 4143 } 4144 return 0; 4145 } 4146 4147 static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq) 4148 { 4149 struct tcp_sock *tp = tcp_sk(sk); 4150 4151 if (tcp_is_sack(tp) && sysctl_tcp_dsack) { 4152 int mib_idx; 4153 4154 if (before(seq, tp->rcv_nxt)) 4155 mib_idx = LINUX_MIB_TCPDSACKOLDSENT; 4156 else 4157 mib_idx = LINUX_MIB_TCPDSACKOFOSENT; 4158 4159 NET_INC_STATS_BH(sock_net(sk), mib_idx); 4160 4161 tp->rx_opt.dsack = 1; 4162 tp->duplicate_sack[0].start_seq = seq; 4163 tp->duplicate_sack[0].end_seq = end_seq; 4164 } 4165 } 4166 4167 static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq) 4168 { 4169 struct tcp_sock *tp = tcp_sk(sk); 4170 4171 if (!tp->rx_opt.dsack) 4172 tcp_dsack_set(sk, seq, end_seq); 4173 else 4174 tcp_sack_extend(tp->duplicate_sack, seq, end_seq); 4175 } 4176 4177 static void tcp_send_dupack(struct sock *sk, struct sk_buff *skb) 4178 { 4179 struct tcp_sock *tp = tcp_sk(sk); 4180 4181 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 4182 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4183 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); 4184 tcp_enter_quickack_mode(sk); 4185 4186 if (tcp_is_sack(tp) && sysctl_tcp_dsack) { 4187 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 4188 4189 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) 4190 end_seq = tp->rcv_nxt; 4191 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq); 4192 } 4193 } 4194 4195 tcp_send_ack(sk); 4196 } 4197 4198 /* These routines update the SACK block as out-of-order packets arrive or 4199 * in-order packets close up the sequence space. 4200 */ 4201 static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) 4202 { 4203 int this_sack; 4204 struct tcp_sack_block *sp = &tp->selective_acks[0]; 4205 struct tcp_sack_block *swalk = sp + 1; 4206 4207 /* See if the recent change to the first SACK eats into 4208 * or hits the sequence space of other SACK blocks, if so coalesce. 4209 */ 4210 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) { 4211 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { 4212 int i; 4213 4214 /* Zap SWALK, by moving every further SACK up by one slot. 4215 * Decrease num_sacks. 4216 */ 4217 tp->rx_opt.num_sacks--; 4218 for (i = this_sack; i < tp->rx_opt.num_sacks; i++) 4219 sp[i] = sp[i + 1]; 4220 continue; 4221 } 4222 this_sack++, swalk++; 4223 } 4224 } 4225 4226 static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) 4227 { 4228 struct tcp_sock *tp = tcp_sk(sk); 4229 struct tcp_sack_block *sp = &tp->selective_acks[0]; 4230 int cur_sacks = tp->rx_opt.num_sacks; 4231 int this_sack; 4232 4233 if (!cur_sacks) 4234 goto new_sack; 4235 4236 for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) { 4237 if (tcp_sack_extend(sp, seq, end_seq)) { 4238 /* Rotate this_sack to the first one. */ 4239 for (; this_sack > 0; this_sack--, sp--) 4240 swap(*sp, *(sp - 1)); 4241 if (cur_sacks > 1) 4242 tcp_sack_maybe_coalesce(tp); 4243 return; 4244 } 4245 } 4246 4247 /* Could not find an adjacent existing SACK, build a new one, 4248 * put it at the front, and shift everyone else down. We 4249 * always know there is at least one SACK present already here. 4250 * 4251 * If the sack array is full, forget about the last one. 4252 */ 4253 if (this_sack >= TCP_NUM_SACKS) { 4254 this_sack--; 4255 tp->rx_opt.num_sacks--; 4256 sp--; 4257 } 4258 for (; this_sack > 0; this_sack--, sp--) 4259 *sp = *(sp - 1); 4260 4261 new_sack: 4262 /* Build the new head SACK, and we're done. */ 4263 sp->start_seq = seq; 4264 sp->end_seq = end_seq; 4265 tp->rx_opt.num_sacks++; 4266 } 4267 4268 /* RCV.NXT advances, some SACKs should be eaten. */ 4269 4270 static void tcp_sack_remove(struct tcp_sock *tp) 4271 { 4272 struct tcp_sack_block *sp = &tp->selective_acks[0]; 4273 int num_sacks = tp->rx_opt.num_sacks; 4274 int this_sack; 4275 4276 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ 4277 if (skb_queue_empty(&tp->out_of_order_queue)) { 4278 tp->rx_opt.num_sacks = 0; 4279 return; 4280 } 4281 4282 for (this_sack = 0; this_sack < num_sacks;) { 4283 /* Check if the start of the sack is covered by RCV.NXT. */ 4284 if (!before(tp->rcv_nxt, sp->start_seq)) { 4285 int i; 4286 4287 /* RCV.NXT must cover all the block! */ 4288 WARN_ON(before(tp->rcv_nxt, sp->end_seq)); 4289 4290 /* Zap this SACK, by moving forward any other SACKS. */ 4291 for (i=this_sack+1; i < num_sacks; i++) 4292 tp->selective_acks[i-1] = tp->selective_acks[i]; 4293 num_sacks--; 4294 continue; 4295 } 4296 this_sack++; 4297 sp++; 4298 } 4299 tp->rx_opt.num_sacks = num_sacks; 4300 } 4301 4302 /* This one checks to see if we can put data from the 4303 * out_of_order queue into the receive_queue. 4304 */ 4305 static void tcp_ofo_queue(struct sock *sk) 4306 { 4307 struct tcp_sock *tp = tcp_sk(sk); 4308 __u32 dsack_high = tp->rcv_nxt; 4309 struct sk_buff *skb; 4310 4311 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { 4312 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 4313 break; 4314 4315 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { 4316 __u32 dsack = dsack_high; 4317 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) 4318 dsack_high = TCP_SKB_CB(skb)->end_seq; 4319 tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack); 4320 } 4321 4322 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 4323 SOCK_DEBUG(sk, "ofo packet was already received\n"); 4324 __skb_unlink(skb, &tp->out_of_order_queue); 4325 __kfree_skb(skb); 4326 continue; 4327 } 4328 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", 4329 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 4330 TCP_SKB_CB(skb)->end_seq); 4331 4332 __skb_unlink(skb, &tp->out_of_order_queue); 4333 __skb_queue_tail(&sk->sk_receive_queue, skb); 4334 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4335 if (tcp_hdr(skb)->fin) 4336 tcp_fin(skb, sk, tcp_hdr(skb)); 4337 } 4338 } 4339 4340 static int tcp_prune_ofo_queue(struct sock *sk); 4341 static int tcp_prune_queue(struct sock *sk); 4342 4343 static inline int tcp_try_rmem_schedule(struct sock *sk, unsigned int size) 4344 { 4345 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || 4346 !sk_rmem_schedule(sk, size)) { 4347 4348 if (tcp_prune_queue(sk) < 0) 4349 return -1; 4350 4351 if (!sk_rmem_schedule(sk, size)) { 4352 if (!tcp_prune_ofo_queue(sk)) 4353 return -1; 4354 4355 if (!sk_rmem_schedule(sk, size)) 4356 return -1; 4357 } 4358 } 4359 return 0; 4360 } 4361 4362 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) 4363 { 4364 struct tcphdr *th = tcp_hdr(skb); 4365 struct tcp_sock *tp = tcp_sk(sk); 4366 int eaten = -1; 4367 4368 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) 4369 goto drop; 4370 4371 skb_dst_drop(skb); 4372 __skb_pull(skb, th->doff * 4); 4373 4374 TCP_ECN_accept_cwr(tp, skb); 4375 4376 tp->rx_opt.dsack = 0; 4377 4378 /* Queue data for delivery to the user. 4379 * Packets in sequence go to the receive queue. 4380 * Out of sequence packets to the out_of_order_queue. 4381 */ 4382 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { 4383 if (tcp_receive_window(tp) == 0) 4384 goto out_of_window; 4385 4386 /* Ok. In sequence. In window. */ 4387 if (tp->ucopy.task == current && 4388 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && 4389 sock_owned_by_user(sk) && !tp->urg_data) { 4390 int chunk = min_t(unsigned int, skb->len, 4391 tp->ucopy.len); 4392 4393 __set_current_state(TASK_RUNNING); 4394 4395 local_bh_enable(); 4396 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { 4397 tp->ucopy.len -= chunk; 4398 tp->copied_seq += chunk; 4399 eaten = (chunk == skb->len && !th->fin); 4400 tcp_rcv_space_adjust(sk); 4401 } 4402 local_bh_disable(); 4403 } 4404 4405 if (eaten <= 0) { 4406 queue_and_out: 4407 if (eaten < 0 && 4408 tcp_try_rmem_schedule(sk, skb->truesize)) 4409 goto drop; 4410 4411 skb_set_owner_r(skb, sk); 4412 __skb_queue_tail(&sk->sk_receive_queue, skb); 4413 } 4414 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4415 if (skb->len) 4416 tcp_event_data_recv(sk, skb); 4417 if (th->fin) 4418 tcp_fin(skb, sk, th); 4419 4420 if (!skb_queue_empty(&tp->out_of_order_queue)) { 4421 tcp_ofo_queue(sk); 4422 4423 /* RFC2581. 4.2. SHOULD send immediate ACK, when 4424 * gap in queue is filled. 4425 */ 4426 if (skb_queue_empty(&tp->out_of_order_queue)) 4427 inet_csk(sk)->icsk_ack.pingpong = 0; 4428 } 4429 4430 if (tp->rx_opt.num_sacks) 4431 tcp_sack_remove(tp); 4432 4433 tcp_fast_path_check(sk); 4434 4435 if (eaten > 0) 4436 __kfree_skb(skb); 4437 else if (!sock_flag(sk, SOCK_DEAD)) 4438 sk->sk_data_ready(sk, 0); 4439 return; 4440 } 4441 4442 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 4443 /* A retransmit, 2nd most common case. Force an immediate ack. */ 4444 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); 4445 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 4446 4447 out_of_window: 4448 tcp_enter_quickack_mode(sk); 4449 inet_csk_schedule_ack(sk); 4450 drop: 4451 __kfree_skb(skb); 4452 return; 4453 } 4454 4455 /* Out of window. F.e. zero window probe. */ 4456 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) 4457 goto out_of_window; 4458 4459 tcp_enter_quickack_mode(sk); 4460 4461 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4462 /* Partial packet, seq < rcv_next < end_seq */ 4463 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", 4464 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 4465 TCP_SKB_CB(skb)->end_seq); 4466 4467 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); 4468 4469 /* If window is closed, drop tail of packet. But after 4470 * remembering D-SACK for its head made in previous line. 4471 */ 4472 if (!tcp_receive_window(tp)) 4473 goto out_of_window; 4474 goto queue_and_out; 4475 } 4476 4477 TCP_ECN_check_ce(tp, skb); 4478 4479 if (tcp_try_rmem_schedule(sk, skb->truesize)) 4480 goto drop; 4481 4482 /* Disable header prediction. */ 4483 tp->pred_flags = 0; 4484 inet_csk_schedule_ack(sk); 4485 4486 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", 4487 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 4488 4489 skb_set_owner_r(skb, sk); 4490 4491 if (!skb_peek(&tp->out_of_order_queue)) { 4492 /* Initial out of order segment, build 1 SACK. */ 4493 if (tcp_is_sack(tp)) { 4494 tp->rx_opt.num_sacks = 1; 4495 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; 4496 tp->selective_acks[0].end_seq = 4497 TCP_SKB_CB(skb)->end_seq; 4498 } 4499 __skb_queue_head(&tp->out_of_order_queue, skb); 4500 } else { 4501 struct sk_buff *skb1 = skb_peek_tail(&tp->out_of_order_queue); 4502 u32 seq = TCP_SKB_CB(skb)->seq; 4503 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 4504 4505 if (seq == TCP_SKB_CB(skb1)->end_seq) { 4506 __skb_queue_after(&tp->out_of_order_queue, skb1, skb); 4507 4508 if (!tp->rx_opt.num_sacks || 4509 tp->selective_acks[0].end_seq != seq) 4510 goto add_sack; 4511 4512 /* Common case: data arrive in order after hole. */ 4513 tp->selective_acks[0].end_seq = end_seq; 4514 return; 4515 } 4516 4517 /* Find place to insert this segment. */ 4518 while (1) { 4519 if (!after(TCP_SKB_CB(skb1)->seq, seq)) 4520 break; 4521 if (skb_queue_is_first(&tp->out_of_order_queue, skb1)) { 4522 skb1 = NULL; 4523 break; 4524 } 4525 skb1 = skb_queue_prev(&tp->out_of_order_queue, skb1); 4526 } 4527 4528 /* Do skb overlap to previous one? */ 4529 if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) { 4530 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 4531 /* All the bits are present. Drop. */ 4532 __kfree_skb(skb); 4533 tcp_dsack_set(sk, seq, end_seq); 4534 goto add_sack; 4535 } 4536 if (after(seq, TCP_SKB_CB(skb1)->seq)) { 4537 /* Partial overlap. */ 4538 tcp_dsack_set(sk, seq, 4539 TCP_SKB_CB(skb1)->end_seq); 4540 } else { 4541 if (skb_queue_is_first(&tp->out_of_order_queue, 4542 skb1)) 4543 skb1 = NULL; 4544 else 4545 skb1 = skb_queue_prev( 4546 &tp->out_of_order_queue, 4547 skb1); 4548 } 4549 } 4550 if (!skb1) 4551 __skb_queue_head(&tp->out_of_order_queue, skb); 4552 else 4553 __skb_queue_after(&tp->out_of_order_queue, skb1, skb); 4554 4555 /* And clean segments covered by new one as whole. */ 4556 while (!skb_queue_is_last(&tp->out_of_order_queue, skb)) { 4557 skb1 = skb_queue_next(&tp->out_of_order_queue, skb); 4558 4559 if (!after(end_seq, TCP_SKB_CB(skb1)->seq)) 4560 break; 4561 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 4562 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, 4563 end_seq); 4564 break; 4565 } 4566 __skb_unlink(skb1, &tp->out_of_order_queue); 4567 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, 4568 TCP_SKB_CB(skb1)->end_seq); 4569 __kfree_skb(skb1); 4570 } 4571 4572 add_sack: 4573 if (tcp_is_sack(tp)) 4574 tcp_sack_new_ofo_skb(sk, seq, end_seq); 4575 } 4576 } 4577 4578 static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb, 4579 struct sk_buff_head *list) 4580 { 4581 struct sk_buff *next = NULL; 4582 4583 if (!skb_queue_is_last(list, skb)) 4584 next = skb_queue_next(list, skb); 4585 4586 __skb_unlink(skb, list); 4587 __kfree_skb(skb); 4588 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED); 4589 4590 return next; 4591 } 4592 4593 /* Collapse contiguous sequence of skbs head..tail with 4594 * sequence numbers start..end. 4595 * 4596 * If tail is NULL, this means until the end of the list. 4597 * 4598 * Segments with FIN/SYN are not collapsed (only because this 4599 * simplifies code) 4600 */ 4601 static void 4602 tcp_collapse(struct sock *sk, struct sk_buff_head *list, 4603 struct sk_buff *head, struct sk_buff *tail, 4604 u32 start, u32 end) 4605 { 4606 struct sk_buff *skb, *n; 4607 bool end_of_skbs; 4608 4609 /* First, check that queue is collapsible and find 4610 * the point where collapsing can be useful. */ 4611 skb = head; 4612 restart: 4613 end_of_skbs = true; 4614 skb_queue_walk_from_safe(list, skb, n) { 4615 if (skb == tail) 4616 break; 4617 /* No new bits? It is possible on ofo queue. */ 4618 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 4619 skb = tcp_collapse_one(sk, skb, list); 4620 if (!skb) 4621 break; 4622 goto restart; 4623 } 4624 4625 /* The first skb to collapse is: 4626 * - not SYN/FIN and 4627 * - bloated or contains data before "start" or 4628 * overlaps to the next one. 4629 */ 4630 if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin && 4631 (tcp_win_from_space(skb->truesize) > skb->len || 4632 before(TCP_SKB_CB(skb)->seq, start))) { 4633 end_of_skbs = false; 4634 break; 4635 } 4636 4637 if (!skb_queue_is_last(list, skb)) { 4638 struct sk_buff *next = skb_queue_next(list, skb); 4639 if (next != tail && 4640 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(next)->seq) { 4641 end_of_skbs = false; 4642 break; 4643 } 4644 } 4645 4646 /* Decided to skip this, advance start seq. */ 4647 start = TCP_SKB_CB(skb)->end_seq; 4648 } 4649 if (end_of_skbs || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin) 4650 return; 4651 4652 while (before(start, end)) { 4653 struct sk_buff *nskb; 4654 unsigned int header = skb_headroom(skb); 4655 int copy = SKB_MAX_ORDER(header, 0); 4656 4657 /* Too big header? This can happen with IPv6. */ 4658 if (copy < 0) 4659 return; 4660 if (end - start < copy) 4661 copy = end - start; 4662 nskb = alloc_skb(copy + header, GFP_ATOMIC); 4663 if (!nskb) 4664 return; 4665 4666 skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head); 4667 skb_set_network_header(nskb, (skb_network_header(skb) - 4668 skb->head)); 4669 skb_set_transport_header(nskb, (skb_transport_header(skb) - 4670 skb->head)); 4671 skb_reserve(nskb, header); 4672 memcpy(nskb->head, skb->head, header); 4673 memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); 4674 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; 4675 __skb_queue_before(list, skb, nskb); 4676 skb_set_owner_r(nskb, sk); 4677 4678 /* Copy data, releasing collapsed skbs. */ 4679 while (copy > 0) { 4680 int offset = start - TCP_SKB_CB(skb)->seq; 4681 int size = TCP_SKB_CB(skb)->end_seq - start; 4682 4683 BUG_ON(offset < 0); 4684 if (size > 0) { 4685 size = min(copy, size); 4686 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) 4687 BUG(); 4688 TCP_SKB_CB(nskb)->end_seq += size; 4689 copy -= size; 4690 start += size; 4691 } 4692 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 4693 skb = tcp_collapse_one(sk, skb, list); 4694 if (!skb || 4695 skb == tail || 4696 tcp_hdr(skb)->syn || 4697 tcp_hdr(skb)->fin) 4698 return; 4699 } 4700 } 4701 } 4702 } 4703 4704 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs 4705 * and tcp_collapse() them until all the queue is collapsed. 4706 */ 4707 static void tcp_collapse_ofo_queue(struct sock *sk) 4708 { 4709 struct tcp_sock *tp = tcp_sk(sk); 4710 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); 4711 struct sk_buff *head; 4712 u32 start, end; 4713 4714 if (skb == NULL) 4715 return; 4716 4717 start = TCP_SKB_CB(skb)->seq; 4718 end = TCP_SKB_CB(skb)->end_seq; 4719 head = skb; 4720 4721 for (;;) { 4722 struct sk_buff *next = NULL; 4723 4724 if (!skb_queue_is_last(&tp->out_of_order_queue, skb)) 4725 next = skb_queue_next(&tp->out_of_order_queue, skb); 4726 skb = next; 4727 4728 /* Segment is terminated when we see gap or when 4729 * we are at the end of all the queue. */ 4730 if (!skb || 4731 after(TCP_SKB_CB(skb)->seq, end) || 4732 before(TCP_SKB_CB(skb)->end_seq, start)) { 4733 tcp_collapse(sk, &tp->out_of_order_queue, 4734 head, skb, start, end); 4735 head = skb; 4736 if (!skb) 4737 break; 4738 /* Start new segment */ 4739 start = TCP_SKB_CB(skb)->seq; 4740 end = TCP_SKB_CB(skb)->end_seq; 4741 } else { 4742 if (before(TCP_SKB_CB(skb)->seq, start)) 4743 start = TCP_SKB_CB(skb)->seq; 4744 if (after(TCP_SKB_CB(skb)->end_seq, end)) 4745 end = TCP_SKB_CB(skb)->end_seq; 4746 } 4747 } 4748 } 4749 4750 /* 4751 * Purge the out-of-order queue. 4752 * Return true if queue was pruned. 4753 */ 4754 static int tcp_prune_ofo_queue(struct sock *sk) 4755 { 4756 struct tcp_sock *tp = tcp_sk(sk); 4757 int res = 0; 4758 4759 if (!skb_queue_empty(&tp->out_of_order_queue)) { 4760 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_OFOPRUNED); 4761 __skb_queue_purge(&tp->out_of_order_queue); 4762 4763 /* Reset SACK state. A conforming SACK implementation will 4764 * do the same at a timeout based retransmit. When a connection 4765 * is in a sad state like this, we care only about integrity 4766 * of the connection not performance. 4767 */ 4768 if (tp->rx_opt.sack_ok) 4769 tcp_sack_reset(&tp->rx_opt); 4770 sk_mem_reclaim(sk); 4771 res = 1; 4772 } 4773 return res; 4774 } 4775 4776 /* Reduce allocated memory if we can, trying to get 4777 * the socket within its memory limits again. 4778 * 4779 * Return less than zero if we should start dropping frames 4780 * until the socket owning process reads some of the data 4781 * to stabilize the situation. 4782 */ 4783 static int tcp_prune_queue(struct sock *sk) 4784 { 4785 struct tcp_sock *tp = tcp_sk(sk); 4786 4787 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); 4788 4789 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PRUNECALLED); 4790 4791 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) 4792 tcp_clamp_window(sk); 4793 else if (tcp_memory_pressure) 4794 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); 4795 4796 tcp_collapse_ofo_queue(sk); 4797 if (!skb_queue_empty(&sk->sk_receive_queue)) 4798 tcp_collapse(sk, &sk->sk_receive_queue, 4799 skb_peek(&sk->sk_receive_queue), 4800 NULL, 4801 tp->copied_seq, tp->rcv_nxt); 4802 sk_mem_reclaim(sk); 4803 4804 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 4805 return 0; 4806 4807 /* Collapsing did not help, destructive actions follow. 4808 * This must not ever occur. */ 4809 4810 tcp_prune_ofo_queue(sk); 4811 4812 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 4813 return 0; 4814 4815 /* If we are really being abused, tell the caller to silently 4816 * drop receive data on the floor. It will get retransmitted 4817 * and hopefully then we'll have sufficient space. 4818 */ 4819 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_RCVPRUNED); 4820 4821 /* Massive buffer overcommit. */ 4822 tp->pred_flags = 0; 4823 return -1; 4824 } 4825 4826 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. 4827 * As additional protections, we do not touch cwnd in retransmission phases, 4828 * and if application hit its sndbuf limit recently. 4829 */ 4830 void tcp_cwnd_application_limited(struct sock *sk) 4831 { 4832 struct tcp_sock *tp = tcp_sk(sk); 4833 4834 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && 4835 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { 4836 /* Limited by application or receiver window. */ 4837 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); 4838 u32 win_used = max(tp->snd_cwnd_used, init_win); 4839 if (win_used < tp->snd_cwnd) { 4840 tp->snd_ssthresh = tcp_current_ssthresh(sk); 4841 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; 4842 } 4843 tp->snd_cwnd_used = 0; 4844 } 4845 tp->snd_cwnd_stamp = tcp_time_stamp; 4846 } 4847 4848 static int tcp_should_expand_sndbuf(struct sock *sk) 4849 { 4850 struct tcp_sock *tp = tcp_sk(sk); 4851 4852 /* If the user specified a specific send buffer setting, do 4853 * not modify it. 4854 */ 4855 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) 4856 return 0; 4857 4858 /* If we are under global TCP memory pressure, do not expand. */ 4859 if (tcp_memory_pressure) 4860 return 0; 4861 4862 /* If we are under soft global TCP memory pressure, do not expand. */ 4863 if (atomic_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0]) 4864 return 0; 4865 4866 /* If we filled the congestion window, do not expand. */ 4867 if (tp->packets_out >= tp->snd_cwnd) 4868 return 0; 4869 4870 return 1; 4871 } 4872 4873 /* When incoming ACK allowed to free some skb from write_queue, 4874 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket 4875 * on the exit from tcp input handler. 4876 * 4877 * PROBLEM: sndbuf expansion does not work well with largesend. 4878 */ 4879 static void tcp_new_space(struct sock *sk) 4880 { 4881 struct tcp_sock *tp = tcp_sk(sk); 4882 4883 if (tcp_should_expand_sndbuf(sk)) { 4884 int sndmem = max_t(u32, tp->rx_opt.mss_clamp, tp->mss_cache) + 4885 MAX_TCP_HEADER + 16 + sizeof(struct sk_buff); 4886 int demanded = max_t(unsigned int, tp->snd_cwnd, 4887 tp->reordering + 1); 4888 sndmem *= 2 * demanded; 4889 if (sndmem > sk->sk_sndbuf) 4890 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); 4891 tp->snd_cwnd_stamp = tcp_time_stamp; 4892 } 4893 4894 sk->sk_write_space(sk); 4895 } 4896 4897 static void tcp_check_space(struct sock *sk) 4898 { 4899 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { 4900 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); 4901 if (sk->sk_socket && 4902 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) 4903 tcp_new_space(sk); 4904 } 4905 } 4906 4907 static inline void tcp_data_snd_check(struct sock *sk) 4908 { 4909 tcp_push_pending_frames(sk); 4910 tcp_check_space(sk); 4911 } 4912 4913 /* 4914 * Check if sending an ack is needed. 4915 */ 4916 static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) 4917 { 4918 struct tcp_sock *tp = tcp_sk(sk); 4919 4920 /* More than one full frame received... */ 4921 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss && 4922 /* ... and right edge of window advances far enough. 4923 * (tcp_recvmsg() will send ACK otherwise). Or... 4924 */ 4925 __tcp_select_window(sk) >= tp->rcv_wnd) || 4926 /* We ACK each frame or... */ 4927 tcp_in_quickack_mode(sk) || 4928 /* We have out of order data. */ 4929 (ofo_possible && skb_peek(&tp->out_of_order_queue))) { 4930 /* Then ack it now */ 4931 tcp_send_ack(sk); 4932 } else { 4933 /* Else, send delayed ack. */ 4934 tcp_send_delayed_ack(sk); 4935 } 4936 } 4937 4938 static inline void tcp_ack_snd_check(struct sock *sk) 4939 { 4940 if (!inet_csk_ack_scheduled(sk)) { 4941 /* We sent a data segment already. */ 4942 return; 4943 } 4944 __tcp_ack_snd_check(sk, 1); 4945 } 4946 4947 /* 4948 * This routine is only called when we have urgent data 4949 * signaled. Its the 'slow' part of tcp_urg. It could be 4950 * moved inline now as tcp_urg is only called from one 4951 * place. We handle URGent data wrong. We have to - as 4952 * BSD still doesn't use the correction from RFC961. 4953 * For 1003.1g we should support a new option TCP_STDURG to permit 4954 * either form (or just set the sysctl tcp_stdurg). 4955 */ 4956 4957 static void tcp_check_urg(struct sock *sk, struct tcphdr *th) 4958 { 4959 struct tcp_sock *tp = tcp_sk(sk); 4960 u32 ptr = ntohs(th->urg_ptr); 4961 4962 if (ptr && !sysctl_tcp_stdurg) 4963 ptr--; 4964 ptr += ntohl(th->seq); 4965 4966 /* Ignore urgent data that we've already seen and read. */ 4967 if (after(tp->copied_seq, ptr)) 4968 return; 4969 4970 /* Do not replay urg ptr. 4971 * 4972 * NOTE: interesting situation not covered by specs. 4973 * Misbehaving sender may send urg ptr, pointing to segment, 4974 * which we already have in ofo queue. We are not able to fetch 4975 * such data and will stay in TCP_URG_NOTYET until will be eaten 4976 * by recvmsg(). Seems, we are not obliged to handle such wicked 4977 * situations. But it is worth to think about possibility of some 4978 * DoSes using some hypothetical application level deadlock. 4979 */ 4980 if (before(ptr, tp->rcv_nxt)) 4981 return; 4982 4983 /* Do we already have a newer (or duplicate) urgent pointer? */ 4984 if (tp->urg_data && !after(ptr, tp->urg_seq)) 4985 return; 4986 4987 /* Tell the world about our new urgent pointer. */ 4988 sk_send_sigurg(sk); 4989 4990 /* We may be adding urgent data when the last byte read was 4991 * urgent. To do this requires some care. We cannot just ignore 4992 * tp->copied_seq since we would read the last urgent byte again 4993 * as data, nor can we alter copied_seq until this data arrives 4994 * or we break the semantics of SIOCATMARK (and thus sockatmark()) 4995 * 4996 * NOTE. Double Dutch. Rendering to plain English: author of comment 4997 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); 4998 * and expect that both A and B disappear from stream. This is _wrong_. 4999 * Though this happens in BSD with high probability, this is occasional. 5000 * Any application relying on this is buggy. Note also, that fix "works" 5001 * only in this artificial test. Insert some normal data between A and B and we will 5002 * decline of BSD again. Verdict: it is better to remove to trap 5003 * buggy users. 5004 */ 5005 if (tp->urg_seq == tp->copied_seq && tp->urg_data && 5006 !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) { 5007 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); 5008 tp->copied_seq++; 5009 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { 5010 __skb_unlink(skb, &sk->sk_receive_queue); 5011 __kfree_skb(skb); 5012 } 5013 } 5014 5015 tp->urg_data = TCP_URG_NOTYET; 5016 tp->urg_seq = ptr; 5017 5018 /* Disable header prediction. */ 5019 tp->pred_flags = 0; 5020 } 5021 5022 /* This is the 'fast' part of urgent handling. */ 5023 static void tcp_urg(struct sock *sk, struct sk_buff *skb, struct tcphdr *th) 5024 { 5025 struct tcp_sock *tp = tcp_sk(sk); 5026 5027 /* Check if we get a new urgent pointer - normally not. */ 5028 if (th->urg) 5029 tcp_check_urg(sk, th); 5030 5031 /* Do we wait for any urgent data? - normally not... */ 5032 if (tp->urg_data == TCP_URG_NOTYET) { 5033 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - 5034 th->syn; 5035 5036 /* Is the urgent pointer pointing into this packet? */ 5037 if (ptr < skb->len) { 5038 u8 tmp; 5039 if (skb_copy_bits(skb, ptr, &tmp, 1)) 5040 BUG(); 5041 tp->urg_data = TCP_URG_VALID | tmp; 5042 if (!sock_flag(sk, SOCK_DEAD)) 5043 sk->sk_data_ready(sk, 0); 5044 } 5045 } 5046 } 5047 5048 static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) 5049 { 5050 struct tcp_sock *tp = tcp_sk(sk); 5051 int chunk = skb->len - hlen; 5052 int err; 5053 5054 local_bh_enable(); 5055 if (skb_csum_unnecessary(skb)) 5056 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); 5057 else 5058 err = skb_copy_and_csum_datagram_iovec(skb, hlen, 5059 tp->ucopy.iov); 5060 5061 if (!err) { 5062 tp->ucopy.len -= chunk; 5063 tp->copied_seq += chunk; 5064 tcp_rcv_space_adjust(sk); 5065 } 5066 5067 local_bh_disable(); 5068 return err; 5069 } 5070 5071 static __sum16 __tcp_checksum_complete_user(struct sock *sk, 5072 struct sk_buff *skb) 5073 { 5074 __sum16 result; 5075 5076 if (sock_owned_by_user(sk)) { 5077 local_bh_enable(); 5078 result = __tcp_checksum_complete(skb); 5079 local_bh_disable(); 5080 } else { 5081 result = __tcp_checksum_complete(skb); 5082 } 5083 return result; 5084 } 5085 5086 static inline int tcp_checksum_complete_user(struct sock *sk, 5087 struct sk_buff *skb) 5088 { 5089 return !skb_csum_unnecessary(skb) && 5090 __tcp_checksum_complete_user(sk, skb); 5091 } 5092 5093 #ifdef CONFIG_NET_DMA 5094 static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, 5095 int hlen) 5096 { 5097 struct tcp_sock *tp = tcp_sk(sk); 5098 int chunk = skb->len - hlen; 5099 int dma_cookie; 5100 int copied_early = 0; 5101 5102 if (tp->ucopy.wakeup) 5103 return 0; 5104 5105 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list) 5106 tp->ucopy.dma_chan = dma_find_channel(DMA_MEMCPY); 5107 5108 if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) { 5109 5110 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan, 5111 skb, hlen, 5112 tp->ucopy.iov, chunk, 5113 tp->ucopy.pinned_list); 5114 5115 if (dma_cookie < 0) 5116 goto out; 5117 5118 tp->ucopy.dma_cookie = dma_cookie; 5119 copied_early = 1; 5120 5121 tp->ucopy.len -= chunk; 5122 tp->copied_seq += chunk; 5123 tcp_rcv_space_adjust(sk); 5124 5125 if ((tp->ucopy.len == 0) || 5126 (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) || 5127 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) { 5128 tp->ucopy.wakeup = 1; 5129 sk->sk_data_ready(sk, 0); 5130 } 5131 } else if (chunk > 0) { 5132 tp->ucopy.wakeup = 1; 5133 sk->sk_data_ready(sk, 0); 5134 } 5135 out: 5136 return copied_early; 5137 } 5138 #endif /* CONFIG_NET_DMA */ 5139 5140 /* Does PAWS and seqno based validation of an incoming segment, flags will 5141 * play significant role here. 5142 */ 5143 static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, 5144 struct tcphdr *th, int syn_inerr) 5145 { 5146 u8 *hash_location; 5147 struct tcp_sock *tp = tcp_sk(sk); 5148 5149 /* RFC1323: H1. Apply PAWS check first. */ 5150 if (tcp_fast_parse_options(skb, th, tp, &hash_location) && 5151 tp->rx_opt.saw_tstamp && 5152 tcp_paws_discard(sk, skb)) { 5153 if (!th->rst) { 5154 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED); 5155 tcp_send_dupack(sk, skb); 5156 goto discard; 5157 } 5158 /* Reset is accepted even if it did not pass PAWS. */ 5159 } 5160 5161 /* Step 1: check sequence number */ 5162 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { 5163 /* RFC793, page 37: "In all states except SYN-SENT, all reset 5164 * (RST) segments are validated by checking their SEQ-fields." 5165 * And page 69: "If an incoming segment is not acceptable, 5166 * an acknowledgment should be sent in reply (unless the RST 5167 * bit is set, if so drop the segment and return)". 5168 */ 5169 if (!th->rst) 5170 tcp_send_dupack(sk, skb); 5171 goto discard; 5172 } 5173 5174 /* Step 2: check RST bit */ 5175 if (th->rst) { 5176 tcp_reset(sk); 5177 goto discard; 5178 } 5179 5180 /* ts_recent update must be made after we are sure that the packet 5181 * is in window. 5182 */ 5183 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 5184 5185 /* step 3: check security and precedence [ignored] */ 5186 5187 /* step 4: Check for a SYN in window. */ 5188 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 5189 if (syn_inerr) 5190 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); 5191 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN); 5192 tcp_reset(sk); 5193 return -1; 5194 } 5195 5196 return 1; 5197 5198 discard: 5199 __kfree_skb(skb); 5200 return 0; 5201 } 5202 5203 /* 5204 * TCP receive function for the ESTABLISHED state. 5205 * 5206 * It is split into a fast path and a slow path. The fast path is 5207 * disabled when: 5208 * - A zero window was announced from us - zero window probing 5209 * is only handled properly in the slow path. 5210 * - Out of order segments arrived. 5211 * - Urgent data is expected. 5212 * - There is no buffer space left 5213 * - Unexpected TCP flags/window values/header lengths are received 5214 * (detected by checking the TCP header against pred_flags) 5215 * - Data is sent in both directions. Fast path only supports pure senders 5216 * or pure receivers (this means either the sequence number or the ack 5217 * value must stay constant) 5218 * - Unexpected TCP option. 5219 * 5220 * When these conditions are not satisfied it drops into a standard 5221 * receive procedure patterned after RFC793 to handle all cases. 5222 * The first three cases are guaranteed by proper pred_flags setting, 5223 * the rest is checked inline. Fast processing is turned on in 5224 * tcp_data_queue when everything is OK. 5225 */ 5226 int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, 5227 struct tcphdr *th, unsigned len) 5228 { 5229 struct tcp_sock *tp = tcp_sk(sk); 5230 int res; 5231 5232 /* 5233 * Header prediction. 5234 * The code loosely follows the one in the famous 5235 * "30 instruction TCP receive" Van Jacobson mail. 5236 * 5237 * Van's trick is to deposit buffers into socket queue 5238 * on a device interrupt, to call tcp_recv function 5239 * on the receive process context and checksum and copy 5240 * the buffer to user space. smart... 5241 * 5242 * Our current scheme is not silly either but we take the 5243 * extra cost of the net_bh soft interrupt processing... 5244 * We do checksum and copy also but from device to kernel. 5245 */ 5246 5247 tp->rx_opt.saw_tstamp = 0; 5248 5249 /* pred_flags is 0xS?10 << 16 + snd_wnd 5250 * if header_prediction is to be made 5251 * 'S' will always be tp->tcp_header_len >> 2 5252 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to 5253 * turn it off (when there are holes in the receive 5254 * space for instance) 5255 * PSH flag is ignored. 5256 */ 5257 5258 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && 5259 TCP_SKB_CB(skb)->seq == tp->rcv_nxt && 5260 !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) { 5261 int tcp_header_len = tp->tcp_header_len; 5262 5263 /* Timestamp header prediction: tcp_header_len 5264 * is automatically equal to th->doff*4 due to pred_flags 5265 * match. 5266 */ 5267 5268 /* Check timestamp */ 5269 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { 5270 /* No? Slow path! */ 5271 if (!tcp_parse_aligned_timestamp(tp, th)) 5272 goto slow_path; 5273 5274 /* If PAWS failed, check it more carefully in slow path */ 5275 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) 5276 goto slow_path; 5277 5278 /* DO NOT update ts_recent here, if checksum fails 5279 * and timestamp was corrupted part, it will result 5280 * in a hung connection since we will drop all 5281 * future packets due to the PAWS test. 5282 */ 5283 } 5284 5285 if (len <= tcp_header_len) { 5286 /* Bulk data transfer: sender */ 5287 if (len == tcp_header_len) { 5288 /* Predicted packet is in window by definition. 5289 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 5290 * Hence, check seq<=rcv_wup reduces to: 5291 */ 5292 if (tcp_header_len == 5293 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 5294 tp->rcv_nxt == tp->rcv_wup) 5295 tcp_store_ts_recent(tp); 5296 5297 /* We know that such packets are checksummed 5298 * on entry. 5299 */ 5300 tcp_ack(sk, skb, 0); 5301 __kfree_skb(skb); 5302 tcp_data_snd_check(sk); 5303 return 0; 5304 } else { /* Header too small */ 5305 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); 5306 goto discard; 5307 } 5308 } else { 5309 int eaten = 0; 5310 int copied_early = 0; 5311 5312 if (tp->copied_seq == tp->rcv_nxt && 5313 len - tcp_header_len <= tp->ucopy.len) { 5314 #ifdef CONFIG_NET_DMA 5315 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) { 5316 copied_early = 1; 5317 eaten = 1; 5318 } 5319 #endif 5320 if (tp->ucopy.task == current && 5321 sock_owned_by_user(sk) && !copied_early) { 5322 __set_current_state(TASK_RUNNING); 5323 5324 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) 5325 eaten = 1; 5326 } 5327 if (eaten) { 5328 /* Predicted packet is in window by definition. 5329 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 5330 * Hence, check seq<=rcv_wup reduces to: 5331 */ 5332 if (tcp_header_len == 5333 (sizeof(struct tcphdr) + 5334 TCPOLEN_TSTAMP_ALIGNED) && 5335 tp->rcv_nxt == tp->rcv_wup) 5336 tcp_store_ts_recent(tp); 5337 5338 tcp_rcv_rtt_measure_ts(sk, skb); 5339 5340 __skb_pull(skb, tcp_header_len); 5341 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 5342 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITSTOUSER); 5343 } 5344 if (copied_early) 5345 tcp_cleanup_rbuf(sk, skb->len); 5346 } 5347 if (!eaten) { 5348 if (tcp_checksum_complete_user(sk, skb)) 5349 goto csum_error; 5350 5351 /* Predicted packet is in window by definition. 5352 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 5353 * Hence, check seq<=rcv_wup reduces to: 5354 */ 5355 if (tcp_header_len == 5356 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 5357 tp->rcv_nxt == tp->rcv_wup) 5358 tcp_store_ts_recent(tp); 5359 5360 tcp_rcv_rtt_measure_ts(sk, skb); 5361 5362 if ((int)skb->truesize > sk->sk_forward_alloc) 5363 goto step5; 5364 5365 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS); 5366 5367 /* Bulk data transfer: receiver */ 5368 __skb_pull(skb, tcp_header_len); 5369 __skb_queue_tail(&sk->sk_receive_queue, skb); 5370 skb_set_owner_r(skb, sk); 5371 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 5372 } 5373 5374 tcp_event_data_recv(sk, skb); 5375 5376 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { 5377 /* Well, only one small jumplet in fast path... */ 5378 tcp_ack(sk, skb, FLAG_DATA); 5379 tcp_data_snd_check(sk); 5380 if (!inet_csk_ack_scheduled(sk)) 5381 goto no_ack; 5382 } 5383 5384 if (!copied_early || tp->rcv_nxt != tp->rcv_wup) 5385 __tcp_ack_snd_check(sk, 0); 5386 no_ack: 5387 #ifdef CONFIG_NET_DMA 5388 if (copied_early) 5389 __skb_queue_tail(&sk->sk_async_wait_queue, skb); 5390 else 5391 #endif 5392 if (eaten) 5393 __kfree_skb(skb); 5394 else 5395 sk->sk_data_ready(sk, 0); 5396 return 0; 5397 } 5398 } 5399 5400 slow_path: 5401 if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb)) 5402 goto csum_error; 5403 5404 /* 5405 * Standard slow path. 5406 */ 5407 5408 res = tcp_validate_incoming(sk, skb, th, 1); 5409 if (res <= 0) 5410 return -res; 5411 5412 step5: 5413 if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0) 5414 goto discard; 5415 5416 tcp_rcv_rtt_measure_ts(sk, skb); 5417 5418 /* Process urgent data. */ 5419 tcp_urg(sk, skb, th); 5420 5421 /* step 7: process the segment text */ 5422 tcp_data_queue(sk, skb); 5423 5424 tcp_data_snd_check(sk); 5425 tcp_ack_snd_check(sk); 5426 return 0; 5427 5428 csum_error: 5429 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); 5430 5431 discard: 5432 __kfree_skb(skb); 5433 return 0; 5434 } 5435 5436 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 5437 struct tcphdr *th, unsigned len) 5438 { 5439 u8 *hash_location; 5440 struct inet_connection_sock *icsk = inet_csk(sk); 5441 struct tcp_sock *tp = tcp_sk(sk); 5442 struct tcp_cookie_values *cvp = tp->cookie_values; 5443 int saved_clamp = tp->rx_opt.mss_clamp; 5444 5445 tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0); 5446 5447 if (th->ack) { 5448 /* rfc793: 5449 * "If the state is SYN-SENT then 5450 * first check the ACK bit 5451 * If the ACK bit is set 5452 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send 5453 * a reset (unless the RST bit is set, if so drop 5454 * the segment and return)" 5455 * 5456 * We do not send data with SYN, so that RFC-correct 5457 * test reduces to: 5458 */ 5459 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt) 5460 goto reset_and_undo; 5461 5462 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 5463 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, 5464 tcp_time_stamp)) { 5465 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSACTIVEREJECTED); 5466 goto reset_and_undo; 5467 } 5468 5469 /* Now ACK is acceptable. 5470 * 5471 * "If the RST bit is set 5472 * If the ACK was acceptable then signal the user "error: 5473 * connection reset", drop the segment, enter CLOSED state, 5474 * delete TCB, and return." 5475 */ 5476 5477 if (th->rst) { 5478 tcp_reset(sk); 5479 goto discard; 5480 } 5481 5482 /* rfc793: 5483 * "fifth, if neither of the SYN or RST bits is set then 5484 * drop the segment and return." 5485 * 5486 * See note below! 5487 * --ANK(990513) 5488 */ 5489 if (!th->syn) 5490 goto discard_and_undo; 5491 5492 /* rfc793: 5493 * "If the SYN bit is on ... 5494 * are acceptable then ... 5495 * (our SYN has been ACKed), change the connection 5496 * state to ESTABLISHED..." 5497 */ 5498 5499 TCP_ECN_rcv_synack(tp, th); 5500 5501 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 5502 tcp_ack(sk, skb, FLAG_SLOWPATH); 5503 5504 /* Ok.. it's good. Set up sequence numbers and 5505 * move to established. 5506 */ 5507 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 5508 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 5509 5510 /* RFC1323: The window in SYN & SYN/ACK segments is 5511 * never scaled. 5512 */ 5513 tp->snd_wnd = ntohs(th->window); 5514 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); 5515 5516 if (!tp->rx_opt.wscale_ok) { 5517 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; 5518 tp->window_clamp = min(tp->window_clamp, 65535U); 5519 } 5520 5521 if (tp->rx_opt.saw_tstamp) { 5522 tp->rx_opt.tstamp_ok = 1; 5523 tp->tcp_header_len = 5524 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 5525 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 5526 tcp_store_ts_recent(tp); 5527 } else { 5528 tp->tcp_header_len = sizeof(struct tcphdr); 5529 } 5530 5531 if (tcp_is_sack(tp) && sysctl_tcp_fack) 5532 tcp_enable_fack(tp); 5533 5534 tcp_mtup_init(sk); 5535 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 5536 tcp_initialize_rcv_mss(sk); 5537 5538 /* Remember, tcp_poll() does not lock socket! 5539 * Change state from SYN-SENT only after copied_seq 5540 * is initialized. */ 5541 tp->copied_seq = tp->rcv_nxt; 5542 5543 if (cvp != NULL && 5544 cvp->cookie_pair_size > 0 && 5545 tp->rx_opt.cookie_plus > 0) { 5546 int cookie_size = tp->rx_opt.cookie_plus 5547 - TCPOLEN_COOKIE_BASE; 5548 int cookie_pair_size = cookie_size 5549 + cvp->cookie_desired; 5550 5551 /* A cookie extension option was sent and returned. 5552 * Note that each incoming SYNACK replaces the 5553 * Responder cookie. The initial exchange is most 5554 * fragile, as protection against spoofing relies 5555 * entirely upon the sequence and timestamp (above). 5556 * This replacement strategy allows the correct pair to 5557 * pass through, while any others will be filtered via 5558 * Responder verification later. 5559 */ 5560 if (sizeof(cvp->cookie_pair) >= cookie_pair_size) { 5561 memcpy(&cvp->cookie_pair[cvp->cookie_desired], 5562 hash_location, cookie_size); 5563 cvp->cookie_pair_size = cookie_pair_size; 5564 } 5565 } 5566 5567 smp_mb(); 5568 tcp_set_state(sk, TCP_ESTABLISHED); 5569 5570 security_inet_conn_established(sk, skb); 5571 5572 /* Make sure socket is routed, for correct metrics. */ 5573 icsk->icsk_af_ops->rebuild_header(sk); 5574 5575 tcp_init_metrics(sk); 5576 5577 tcp_init_congestion_control(sk); 5578 5579 /* Prevent spurious tcp_cwnd_restart() on first data 5580 * packet. 5581 */ 5582 tp->lsndtime = tcp_time_stamp; 5583 5584 tcp_init_buffer_space(sk); 5585 5586 if (sock_flag(sk, SOCK_KEEPOPEN)) 5587 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); 5588 5589 if (!tp->rx_opt.snd_wscale) 5590 __tcp_fast_path_on(tp, tp->snd_wnd); 5591 else 5592 tp->pred_flags = 0; 5593 5594 if (!sock_flag(sk, SOCK_DEAD)) { 5595 sk->sk_state_change(sk); 5596 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT); 5597 } 5598 5599 if (sk->sk_write_pending || 5600 icsk->icsk_accept_queue.rskq_defer_accept || 5601 icsk->icsk_ack.pingpong) { 5602 /* Save one ACK. Data will be ready after 5603 * several ticks, if write_pending is set. 5604 * 5605 * It may be deleted, but with this feature tcpdumps 5606 * look so _wonderfully_ clever, that I was not able 5607 * to stand against the temptation 8) --ANK 5608 */ 5609 inet_csk_schedule_ack(sk); 5610 icsk->icsk_ack.lrcvtime = tcp_time_stamp; 5611 icsk->icsk_ack.ato = TCP_ATO_MIN; 5612 tcp_incr_quickack(sk); 5613 tcp_enter_quickack_mode(sk); 5614 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 5615 TCP_DELACK_MAX, TCP_RTO_MAX); 5616 5617 discard: 5618 __kfree_skb(skb); 5619 return 0; 5620 } else { 5621 tcp_send_ack(sk); 5622 } 5623 return -1; 5624 } 5625 5626 /* No ACK in the segment */ 5627 5628 if (th->rst) { 5629 /* rfc793: 5630 * "If the RST bit is set 5631 * 5632 * Otherwise (no ACK) drop the segment and return." 5633 */ 5634 5635 goto discard_and_undo; 5636 } 5637 5638 /* PAWS check. */ 5639 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && 5640 tcp_paws_reject(&tp->rx_opt, 0)) 5641 goto discard_and_undo; 5642 5643 if (th->syn) { 5644 /* We see SYN without ACK. It is attempt of 5645 * simultaneous connect with crossed SYNs. 5646 * Particularly, it can be connect to self. 5647 */ 5648 tcp_set_state(sk, TCP_SYN_RECV); 5649 5650 if (tp->rx_opt.saw_tstamp) { 5651 tp->rx_opt.tstamp_ok = 1; 5652 tcp_store_ts_recent(tp); 5653 tp->tcp_header_len = 5654 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 5655 } else { 5656 tp->tcp_header_len = sizeof(struct tcphdr); 5657 } 5658 5659 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 5660 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 5661 5662 /* RFC1323: The window in SYN & SYN/ACK segments is 5663 * never scaled. 5664 */ 5665 tp->snd_wnd = ntohs(th->window); 5666 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 5667 tp->max_window = tp->snd_wnd; 5668 5669 TCP_ECN_rcv_syn(tp, th); 5670 5671 tcp_mtup_init(sk); 5672 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 5673 tcp_initialize_rcv_mss(sk); 5674 5675 tcp_send_synack(sk); 5676 #if 0 5677 /* Note, we could accept data and URG from this segment. 5678 * There are no obstacles to make this. 5679 * 5680 * However, if we ignore data in ACKless segments sometimes, 5681 * we have no reasons to accept it sometimes. 5682 * Also, seems the code doing it in step6 of tcp_rcv_state_process 5683 * is not flawless. So, discard packet for sanity. 5684 * Uncomment this return to process the data. 5685 */ 5686 return -1; 5687 #else 5688 goto discard; 5689 #endif 5690 } 5691 /* "fifth, if neither of the SYN or RST bits is set then 5692 * drop the segment and return." 5693 */ 5694 5695 discard_and_undo: 5696 tcp_clear_options(&tp->rx_opt); 5697 tp->rx_opt.mss_clamp = saved_clamp; 5698 goto discard; 5699 5700 reset_and_undo: 5701 tcp_clear_options(&tp->rx_opt); 5702 tp->rx_opt.mss_clamp = saved_clamp; 5703 return 1; 5704 } 5705 5706 /* 5707 * This function implements the receiving procedure of RFC 793 for 5708 * all states except ESTABLISHED and TIME_WAIT. 5709 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be 5710 * address independent. 5711 */ 5712 5713 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, 5714 struct tcphdr *th, unsigned len) 5715 { 5716 struct tcp_sock *tp = tcp_sk(sk); 5717 struct inet_connection_sock *icsk = inet_csk(sk); 5718 int queued = 0; 5719 int res; 5720 5721 tp->rx_opt.saw_tstamp = 0; 5722 5723 switch (sk->sk_state) { 5724 case TCP_CLOSE: 5725 goto discard; 5726 5727 case TCP_LISTEN: 5728 if (th->ack) 5729 return 1; 5730 5731 if (th->rst) 5732 goto discard; 5733 5734 if (th->syn) { 5735 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0) 5736 return 1; 5737 5738 /* Now we have several options: In theory there is 5739 * nothing else in the frame. KA9Q has an option to 5740 * send data with the syn, BSD accepts data with the 5741 * syn up to the [to be] advertised window and 5742 * Solaris 2.1 gives you a protocol error. For now 5743 * we just ignore it, that fits the spec precisely 5744 * and avoids incompatibilities. It would be nice in 5745 * future to drop through and process the data. 5746 * 5747 * Now that TTCP is starting to be used we ought to 5748 * queue this data. 5749 * But, this leaves one open to an easy denial of 5750 * service attack, and SYN cookies can't defend 5751 * against this problem. So, we drop the data 5752 * in the interest of security over speed unless 5753 * it's still in use. 5754 */ 5755 kfree_skb(skb); 5756 return 0; 5757 } 5758 goto discard; 5759 5760 case TCP_SYN_SENT: 5761 queued = tcp_rcv_synsent_state_process(sk, skb, th, len); 5762 if (queued >= 0) 5763 return queued; 5764 5765 /* Do step6 onward by hand. */ 5766 tcp_urg(sk, skb, th); 5767 __kfree_skb(skb); 5768 tcp_data_snd_check(sk); 5769 return 0; 5770 } 5771 5772 res = tcp_validate_incoming(sk, skb, th, 0); 5773 if (res <= 0) 5774 return -res; 5775 5776 /* step 5: check the ACK field */ 5777 if (th->ack) { 5778 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH) > 0; 5779 5780 switch (sk->sk_state) { 5781 case TCP_SYN_RECV: 5782 if (acceptable) { 5783 tp->copied_seq = tp->rcv_nxt; 5784 smp_mb(); 5785 tcp_set_state(sk, TCP_ESTABLISHED); 5786 sk->sk_state_change(sk); 5787 5788 /* Note, that this wakeup is only for marginal 5789 * crossed SYN case. Passively open sockets 5790 * are not waked up, because sk->sk_sleep == 5791 * NULL and sk->sk_socket == NULL. 5792 */ 5793 if (sk->sk_socket) 5794 sk_wake_async(sk, 5795 SOCK_WAKE_IO, POLL_OUT); 5796 5797 tp->snd_una = TCP_SKB_CB(skb)->ack_seq; 5798 tp->snd_wnd = ntohs(th->window) << 5799 tp->rx_opt.snd_wscale; 5800 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); 5801 5802 /* tcp_ack considers this ACK as duplicate 5803 * and does not calculate rtt. 5804 * Force it here. 5805 */ 5806 tcp_ack_update_rtt(sk, 0, 0); 5807 5808 if (tp->rx_opt.tstamp_ok) 5809 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 5810 5811 /* Make sure socket is routed, for 5812 * correct metrics. 5813 */ 5814 icsk->icsk_af_ops->rebuild_header(sk); 5815 5816 tcp_init_metrics(sk); 5817 5818 tcp_init_congestion_control(sk); 5819 5820 /* Prevent spurious tcp_cwnd_restart() on 5821 * first data packet. 5822 */ 5823 tp->lsndtime = tcp_time_stamp; 5824 5825 tcp_mtup_init(sk); 5826 tcp_initialize_rcv_mss(sk); 5827 tcp_init_buffer_space(sk); 5828 tcp_fast_path_on(tp); 5829 } else { 5830 return 1; 5831 } 5832 break; 5833 5834 case TCP_FIN_WAIT1: 5835 if (tp->snd_una == tp->write_seq) { 5836 tcp_set_state(sk, TCP_FIN_WAIT2); 5837 sk->sk_shutdown |= SEND_SHUTDOWN; 5838 dst_confirm(__sk_dst_get(sk)); 5839 5840 if (!sock_flag(sk, SOCK_DEAD)) 5841 /* Wake up lingering close() */ 5842 sk->sk_state_change(sk); 5843 else { 5844 int tmo; 5845 5846 if (tp->linger2 < 0 || 5847 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 5848 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { 5849 tcp_done(sk); 5850 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA); 5851 return 1; 5852 } 5853 5854 tmo = tcp_fin_time(sk); 5855 if (tmo > TCP_TIMEWAIT_LEN) { 5856 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); 5857 } else if (th->fin || sock_owned_by_user(sk)) { 5858 /* Bad case. We could lose such FIN otherwise. 5859 * It is not a big problem, but it looks confusing 5860 * and not so rare event. We still can lose it now, 5861 * if it spins in bh_lock_sock(), but it is really 5862 * marginal case. 5863 */ 5864 inet_csk_reset_keepalive_timer(sk, tmo); 5865 } else { 5866 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 5867 goto discard; 5868 } 5869 } 5870 } 5871 break; 5872 5873 case TCP_CLOSING: 5874 if (tp->snd_una == tp->write_seq) { 5875 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 5876 goto discard; 5877 } 5878 break; 5879 5880 case TCP_LAST_ACK: 5881 if (tp->snd_una == tp->write_seq) { 5882 tcp_update_metrics(sk); 5883 tcp_done(sk); 5884 goto discard; 5885 } 5886 break; 5887 } 5888 } else 5889 goto discard; 5890 5891 /* step 6: check the URG bit */ 5892 tcp_urg(sk, skb, th); 5893 5894 /* step 7: process the segment text */ 5895 switch (sk->sk_state) { 5896 case TCP_CLOSE_WAIT: 5897 case TCP_CLOSING: 5898 case TCP_LAST_ACK: 5899 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 5900 break; 5901 case TCP_FIN_WAIT1: 5902 case TCP_FIN_WAIT2: 5903 /* RFC 793 says to queue data in these states, 5904 * RFC 1122 says we MUST send a reset. 5905 * BSD 4.4 also does reset. 5906 */ 5907 if (sk->sk_shutdown & RCV_SHUTDOWN) { 5908 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 5909 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { 5910 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA); 5911 tcp_reset(sk); 5912 return 1; 5913 } 5914 } 5915 /* Fall through */ 5916 case TCP_ESTABLISHED: 5917 tcp_data_queue(sk, skb); 5918 queued = 1; 5919 break; 5920 } 5921 5922 /* tcp_data could move socket to TIME-WAIT */ 5923 if (sk->sk_state != TCP_CLOSE) { 5924 tcp_data_snd_check(sk); 5925 tcp_ack_snd_check(sk); 5926 } 5927 5928 if (!queued) { 5929 discard: 5930 __kfree_skb(skb); 5931 } 5932 return 0; 5933 } 5934 5935 EXPORT_SYMBOL(sysctl_tcp_ecn); 5936 EXPORT_SYMBOL(sysctl_tcp_reordering); 5937 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); 5938 EXPORT_SYMBOL(tcp_parse_options); 5939 #ifdef CONFIG_TCP_MD5SIG 5940 EXPORT_SYMBOL(tcp_parse_md5sig_option); 5941 #endif 5942 EXPORT_SYMBOL(tcp_rcv_established); 5943 EXPORT_SYMBOL(tcp_rcv_state_process); 5944 EXPORT_SYMBOL(tcp_initialize_rcv_mss); 5945