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 EXPORT_SYMBOL(sysctl_tcp_reordering); 82 int sysctl_tcp_ecn __read_mostly = 2; 83 EXPORT_SYMBOL(sysctl_tcp_ecn); 84 int sysctl_tcp_dsack __read_mostly = 1; 85 int sysctl_tcp_app_win __read_mostly = 31; 86 int sysctl_tcp_adv_win_scale __read_mostly = 2; 87 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); 88 89 int sysctl_tcp_stdurg __read_mostly; 90 int sysctl_tcp_rfc1337 __read_mostly; 91 int sysctl_tcp_max_orphans __read_mostly = NR_FILE; 92 int sysctl_tcp_frto __read_mostly = 2; 93 int sysctl_tcp_frto_response __read_mostly; 94 int sysctl_tcp_nometrics_save __read_mostly; 95 96 int sysctl_tcp_thin_dupack __read_mostly; 97 98 int sysctl_tcp_moderate_rcvbuf __read_mostly = 1; 99 int sysctl_tcp_abc __read_mostly; 100 101 #define FLAG_DATA 0x01 /* Incoming frame contained data. */ 102 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ 103 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ 104 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ 105 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ 106 #define FLAG_DATA_SACKED 0x20 /* New SACK. */ 107 #define FLAG_ECE 0x40 /* ECE in this ACK */ 108 #define FLAG_DATA_LOST 0x80 /* SACK detected data lossage. */ 109 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ 110 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */ 111 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */ 112 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */ 113 #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */ 114 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */ 115 116 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) 117 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) 118 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) 119 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) 120 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED) 121 122 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) 123 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH)) 124 125 /* Adapt the MSS value used to make delayed ack decision to the 126 * real world. 127 */ 128 static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) 129 { 130 struct inet_connection_sock *icsk = inet_csk(sk); 131 const unsigned int lss = icsk->icsk_ack.last_seg_size; 132 unsigned int len; 133 134 icsk->icsk_ack.last_seg_size = 0; 135 136 /* skb->len may jitter because of SACKs, even if peer 137 * sends good full-sized frames. 138 */ 139 len = skb_shinfo(skb)->gso_size ? : skb->len; 140 if (len >= icsk->icsk_ack.rcv_mss) { 141 icsk->icsk_ack.rcv_mss = len; 142 } else { 143 /* Otherwise, we make more careful check taking into account, 144 * that SACKs block is variable. 145 * 146 * "len" is invariant segment length, including TCP header. 147 */ 148 len += skb->data - skb_transport_header(skb); 149 if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) || 150 /* If PSH is not set, packet should be 151 * full sized, provided peer TCP is not badly broken. 152 * This observation (if it is correct 8)) allows 153 * to handle super-low mtu links fairly. 154 */ 155 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && 156 !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) { 157 /* Subtract also invariant (if peer is RFC compliant), 158 * tcp header plus fixed timestamp option length. 159 * Resulting "len" is MSS free of SACK jitter. 160 */ 161 len -= tcp_sk(sk)->tcp_header_len; 162 icsk->icsk_ack.last_seg_size = len; 163 if (len == lss) { 164 icsk->icsk_ack.rcv_mss = len; 165 return; 166 } 167 } 168 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) 169 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; 170 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; 171 } 172 } 173 174 static void tcp_incr_quickack(struct sock *sk) 175 { 176 struct inet_connection_sock *icsk = inet_csk(sk); 177 unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); 178 179 if (quickacks == 0) 180 quickacks = 2; 181 if (quickacks > icsk->icsk_ack.quick) 182 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS); 183 } 184 185 static void tcp_enter_quickack_mode(struct sock *sk) 186 { 187 struct inet_connection_sock *icsk = inet_csk(sk); 188 tcp_incr_quickack(sk); 189 icsk->icsk_ack.pingpong = 0; 190 icsk->icsk_ack.ato = TCP_ATO_MIN; 191 } 192 193 /* Send ACKs quickly, if "quick" count is not exhausted 194 * and the session is not interactive. 195 */ 196 197 static inline int tcp_in_quickack_mode(const struct sock *sk) 198 { 199 const struct inet_connection_sock *icsk = inet_csk(sk); 200 return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong; 201 } 202 203 static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp) 204 { 205 if (tp->ecn_flags & TCP_ECN_OK) 206 tp->ecn_flags |= TCP_ECN_QUEUE_CWR; 207 } 208 209 static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb) 210 { 211 if (tcp_hdr(skb)->cwr) 212 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; 213 } 214 215 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp) 216 { 217 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; 218 } 219 220 static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) 221 { 222 if (!(tp->ecn_flags & TCP_ECN_OK)) 223 return; 224 225 switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) { 226 case INET_ECN_NOT_ECT: 227 /* Funny extension: if ECT is not set on a segment, 228 * and we already seen ECT on a previous segment, 229 * it is probably a retransmit. 230 */ 231 if (tp->ecn_flags & TCP_ECN_SEEN) 232 tcp_enter_quickack_mode((struct sock *)tp); 233 break; 234 case INET_ECN_CE: 235 tp->ecn_flags |= TCP_ECN_DEMAND_CWR; 236 /* fallinto */ 237 default: 238 tp->ecn_flags |= TCP_ECN_SEEN; 239 } 240 } 241 242 static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th) 243 { 244 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr)) 245 tp->ecn_flags &= ~TCP_ECN_OK; 246 } 247 248 static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th) 249 { 250 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr)) 251 tp->ecn_flags &= ~TCP_ECN_OK; 252 } 253 254 static inline int TCP_ECN_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th) 255 { 256 if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK)) 257 return 1; 258 return 0; 259 } 260 261 /* Buffer size and advertised window tuning. 262 * 263 * 1. Tuning sk->sk_sndbuf, when connection enters established state. 264 */ 265 266 static void tcp_fixup_sndbuf(struct sock *sk) 267 { 268 int sndmem = SKB_TRUESIZE(tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER); 269 270 sndmem *= TCP_INIT_CWND; 271 if (sk->sk_sndbuf < sndmem) 272 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); 273 } 274 275 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh) 276 * 277 * All tcp_full_space() is split to two parts: "network" buffer, allocated 278 * forward and advertised in receiver window (tp->rcv_wnd) and 279 * "application buffer", required to isolate scheduling/application 280 * latencies from network. 281 * window_clamp is maximal advertised window. It can be less than 282 * tcp_full_space(), in this case tcp_full_space() - window_clamp 283 * is reserved for "application" buffer. The less window_clamp is 284 * the smoother our behaviour from viewpoint of network, but the lower 285 * throughput and the higher sensitivity of the connection to losses. 8) 286 * 287 * rcv_ssthresh is more strict window_clamp used at "slow start" 288 * phase to predict further behaviour of this connection. 289 * It is used for two goals: 290 * - to enforce header prediction at sender, even when application 291 * requires some significant "application buffer". It is check #1. 292 * - to prevent pruning of receive queue because of misprediction 293 * of receiver window. Check #2. 294 * 295 * The scheme does not work when sender sends good segments opening 296 * window and then starts to feed us spaghetti. But it should work 297 * in common situations. Otherwise, we have to rely on queue collapsing. 298 */ 299 300 /* Slow part of check#2. */ 301 static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb) 302 { 303 struct tcp_sock *tp = tcp_sk(sk); 304 /* Optimize this! */ 305 int truesize = tcp_win_from_space(skb->truesize) >> 1; 306 int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1; 307 308 while (tp->rcv_ssthresh <= window) { 309 if (truesize <= skb->len) 310 return 2 * inet_csk(sk)->icsk_ack.rcv_mss; 311 312 truesize >>= 1; 313 window >>= 1; 314 } 315 return 0; 316 } 317 318 static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb) 319 { 320 struct tcp_sock *tp = tcp_sk(sk); 321 322 /* Check #1 */ 323 if (tp->rcv_ssthresh < tp->window_clamp && 324 (int)tp->rcv_ssthresh < tcp_space(sk) && 325 !sk_under_memory_pressure(sk)) { 326 int incr; 327 328 /* Check #2. Increase window, if skb with such overhead 329 * will fit to rcvbuf in future. 330 */ 331 if (tcp_win_from_space(skb->truesize) <= skb->len) 332 incr = 2 * tp->advmss; 333 else 334 incr = __tcp_grow_window(sk, skb); 335 336 if (incr) { 337 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, 338 tp->window_clamp); 339 inet_csk(sk)->icsk_ack.quick |= 1; 340 } 341 } 342 } 343 344 /* 3. Tuning rcvbuf, when connection enters established state. */ 345 346 static void tcp_fixup_rcvbuf(struct sock *sk) 347 { 348 u32 mss = tcp_sk(sk)->advmss; 349 u32 icwnd = TCP_DEFAULT_INIT_RCVWND; 350 int rcvmem; 351 352 /* Limit to 10 segments if mss <= 1460, 353 * or 14600/mss segments, with a minimum of two segments. 354 */ 355 if (mss > 1460) 356 icwnd = max_t(u32, (1460 * TCP_DEFAULT_INIT_RCVWND) / mss, 2); 357 358 rcvmem = SKB_TRUESIZE(mss + MAX_TCP_HEADER); 359 while (tcp_win_from_space(rcvmem) < mss) 360 rcvmem += 128; 361 362 rcvmem *= icwnd; 363 364 if (sk->sk_rcvbuf < rcvmem) 365 sk->sk_rcvbuf = min(rcvmem, sysctl_tcp_rmem[2]); 366 } 367 368 /* 4. Try to fixup all. It is made immediately after connection enters 369 * established state. 370 */ 371 static void tcp_init_buffer_space(struct sock *sk) 372 { 373 struct tcp_sock *tp = tcp_sk(sk); 374 int maxwin; 375 376 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) 377 tcp_fixup_rcvbuf(sk); 378 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) 379 tcp_fixup_sndbuf(sk); 380 381 tp->rcvq_space.space = tp->rcv_wnd; 382 383 maxwin = tcp_full_space(sk); 384 385 if (tp->window_clamp >= maxwin) { 386 tp->window_clamp = maxwin; 387 388 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) 389 tp->window_clamp = max(maxwin - 390 (maxwin >> sysctl_tcp_app_win), 391 4 * tp->advmss); 392 } 393 394 /* Force reservation of one segment. */ 395 if (sysctl_tcp_app_win && 396 tp->window_clamp > 2 * tp->advmss && 397 tp->window_clamp + tp->advmss > maxwin) 398 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); 399 400 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); 401 tp->snd_cwnd_stamp = tcp_time_stamp; 402 } 403 404 /* 5. Recalculate window clamp after socket hit its memory bounds. */ 405 static void tcp_clamp_window(struct sock *sk) 406 { 407 struct tcp_sock *tp = tcp_sk(sk); 408 struct inet_connection_sock *icsk = inet_csk(sk); 409 410 icsk->icsk_ack.quick = 0; 411 412 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && 413 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && 414 !sk_under_memory_pressure(sk) && 415 sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) { 416 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), 417 sysctl_tcp_rmem[2]); 418 } 419 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) 420 tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss); 421 } 422 423 /* Initialize RCV_MSS value. 424 * RCV_MSS is an our guess about MSS used by the peer. 425 * We haven't any direct information about the MSS. 426 * It's better to underestimate the RCV_MSS rather than overestimate. 427 * Overestimations make us ACKing less frequently than needed. 428 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). 429 */ 430 void tcp_initialize_rcv_mss(struct sock *sk) 431 { 432 const struct tcp_sock *tp = tcp_sk(sk); 433 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); 434 435 hint = min(hint, tp->rcv_wnd / 2); 436 hint = min(hint, TCP_MSS_DEFAULT); 437 hint = max(hint, TCP_MIN_MSS); 438 439 inet_csk(sk)->icsk_ack.rcv_mss = hint; 440 } 441 EXPORT_SYMBOL(tcp_initialize_rcv_mss); 442 443 /* Receiver "autotuning" code. 444 * 445 * The algorithm for RTT estimation w/o timestamps is based on 446 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. 447 * <http://public.lanl.gov/radiant/pubs.html#DRS> 448 * 449 * More detail on this code can be found at 450 * <http://staff.psc.edu/jheffner/>, 451 * though this reference is out of date. A new paper 452 * is pending. 453 */ 454 static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) 455 { 456 u32 new_sample = tp->rcv_rtt_est.rtt; 457 long m = sample; 458 459 if (m == 0) 460 m = 1; 461 462 if (new_sample != 0) { 463 /* If we sample in larger samples in the non-timestamp 464 * case, we could grossly overestimate the RTT especially 465 * with chatty applications or bulk transfer apps which 466 * are stalled on filesystem I/O. 467 * 468 * Also, since we are only going for a minimum in the 469 * non-timestamp case, we do not smooth things out 470 * else with timestamps disabled convergence takes too 471 * long. 472 */ 473 if (!win_dep) { 474 m -= (new_sample >> 3); 475 new_sample += m; 476 } else if (m < new_sample) 477 new_sample = m << 3; 478 } else { 479 /* No previous measure. */ 480 new_sample = m << 3; 481 } 482 483 if (tp->rcv_rtt_est.rtt != new_sample) 484 tp->rcv_rtt_est.rtt = new_sample; 485 } 486 487 static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) 488 { 489 if (tp->rcv_rtt_est.time == 0) 490 goto new_measure; 491 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) 492 return; 493 tcp_rcv_rtt_update(tp, jiffies - tp->rcv_rtt_est.time, 1); 494 495 new_measure: 496 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; 497 tp->rcv_rtt_est.time = tcp_time_stamp; 498 } 499 500 static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, 501 const struct sk_buff *skb) 502 { 503 struct tcp_sock *tp = tcp_sk(sk); 504 if (tp->rx_opt.rcv_tsecr && 505 (TCP_SKB_CB(skb)->end_seq - 506 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) 507 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); 508 } 509 510 /* 511 * This function should be called every time data is copied to user space. 512 * It calculates the appropriate TCP receive buffer space. 513 */ 514 void tcp_rcv_space_adjust(struct sock *sk) 515 { 516 struct tcp_sock *tp = tcp_sk(sk); 517 int time; 518 int space; 519 520 if (tp->rcvq_space.time == 0) 521 goto new_measure; 522 523 time = tcp_time_stamp - tp->rcvq_space.time; 524 if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0) 525 return; 526 527 space = 2 * (tp->copied_seq - tp->rcvq_space.seq); 528 529 space = max(tp->rcvq_space.space, space); 530 531 if (tp->rcvq_space.space != space) { 532 int rcvmem; 533 534 tp->rcvq_space.space = space; 535 536 if (sysctl_tcp_moderate_rcvbuf && 537 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { 538 int new_clamp = space; 539 540 /* Receive space grows, normalize in order to 541 * take into account packet headers and sk_buff 542 * structure overhead. 543 */ 544 space /= tp->advmss; 545 if (!space) 546 space = 1; 547 rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER); 548 while (tcp_win_from_space(rcvmem) < tp->advmss) 549 rcvmem += 128; 550 space *= rcvmem; 551 space = min(space, sysctl_tcp_rmem[2]); 552 if (space > sk->sk_rcvbuf) { 553 sk->sk_rcvbuf = space; 554 555 /* Make the window clamp follow along. */ 556 tp->window_clamp = new_clamp; 557 } 558 } 559 } 560 561 new_measure: 562 tp->rcvq_space.seq = tp->copied_seq; 563 tp->rcvq_space.time = tcp_time_stamp; 564 } 565 566 /* There is something which you must keep in mind when you analyze the 567 * behavior of the tp->ato delayed ack timeout interval. When a 568 * connection starts up, we want to ack as quickly as possible. The 569 * problem is that "good" TCP's do slow start at the beginning of data 570 * transmission. The means that until we send the first few ACK's the 571 * sender will sit on his end and only queue most of his data, because 572 * he can only send snd_cwnd unacked packets at any given time. For 573 * each ACK we send, he increments snd_cwnd and transmits more of his 574 * queue. -DaveM 575 */ 576 static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) 577 { 578 struct tcp_sock *tp = tcp_sk(sk); 579 struct inet_connection_sock *icsk = inet_csk(sk); 580 u32 now; 581 582 inet_csk_schedule_ack(sk); 583 584 tcp_measure_rcv_mss(sk, skb); 585 586 tcp_rcv_rtt_measure(tp); 587 588 now = tcp_time_stamp; 589 590 if (!icsk->icsk_ack.ato) { 591 /* The _first_ data packet received, initialize 592 * delayed ACK engine. 593 */ 594 tcp_incr_quickack(sk); 595 icsk->icsk_ack.ato = TCP_ATO_MIN; 596 } else { 597 int m = now - icsk->icsk_ack.lrcvtime; 598 599 if (m <= TCP_ATO_MIN / 2) { 600 /* The fastest case is the first. */ 601 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; 602 } else if (m < icsk->icsk_ack.ato) { 603 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; 604 if (icsk->icsk_ack.ato > icsk->icsk_rto) 605 icsk->icsk_ack.ato = icsk->icsk_rto; 606 } else if (m > icsk->icsk_rto) { 607 /* Too long gap. Apparently sender failed to 608 * restart window, so that we send ACKs quickly. 609 */ 610 tcp_incr_quickack(sk); 611 sk_mem_reclaim(sk); 612 } 613 } 614 icsk->icsk_ack.lrcvtime = now; 615 616 TCP_ECN_check_ce(tp, skb); 617 618 if (skb->len >= 128) 619 tcp_grow_window(sk, skb); 620 } 621 622 /* Called to compute a smoothed rtt estimate. The data fed to this 623 * routine either comes from timestamps, or from segments that were 624 * known _not_ to have been retransmitted [see Karn/Partridge 625 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 626 * piece by Van Jacobson. 627 * NOTE: the next three routines used to be one big routine. 628 * To save cycles in the RFC 1323 implementation it was better to break 629 * it up into three procedures. -- erics 630 */ 631 static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) 632 { 633 struct tcp_sock *tp = tcp_sk(sk); 634 long m = mrtt; /* RTT */ 635 636 /* The following amusing code comes from Jacobson's 637 * article in SIGCOMM '88. Note that rtt and mdev 638 * are scaled versions of rtt and mean deviation. 639 * This is designed to be as fast as possible 640 * m stands for "measurement". 641 * 642 * On a 1990 paper the rto value is changed to: 643 * RTO = rtt + 4 * mdev 644 * 645 * Funny. This algorithm seems to be very broken. 646 * These formulae increase RTO, when it should be decreased, increase 647 * too slowly, when it should be increased quickly, decrease too quickly 648 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely 649 * does not matter how to _calculate_ it. Seems, it was trap 650 * that VJ failed to avoid. 8) 651 */ 652 if (m == 0) 653 m = 1; 654 if (tp->srtt != 0) { 655 m -= (tp->srtt >> 3); /* m is now error in rtt est */ 656 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ 657 if (m < 0) { 658 m = -m; /* m is now abs(error) */ 659 m -= (tp->mdev >> 2); /* similar update on mdev */ 660 /* This is similar to one of Eifel findings. 661 * Eifel blocks mdev updates when rtt decreases. 662 * This solution is a bit different: we use finer gain 663 * for mdev in this case (alpha*beta). 664 * Like Eifel it also prevents growth of rto, 665 * but also it limits too fast rto decreases, 666 * happening in pure Eifel. 667 */ 668 if (m > 0) 669 m >>= 3; 670 } else { 671 m -= (tp->mdev >> 2); /* similar update on mdev */ 672 } 673 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ 674 if (tp->mdev > tp->mdev_max) { 675 tp->mdev_max = tp->mdev; 676 if (tp->mdev_max > tp->rttvar) 677 tp->rttvar = tp->mdev_max; 678 } 679 if (after(tp->snd_una, tp->rtt_seq)) { 680 if (tp->mdev_max < tp->rttvar) 681 tp->rttvar -= (tp->rttvar - tp->mdev_max) >> 2; 682 tp->rtt_seq = tp->snd_nxt; 683 tp->mdev_max = tcp_rto_min(sk); 684 } 685 } else { 686 /* no previous measure. */ 687 tp->srtt = m << 3; /* take the measured time to be rtt */ 688 tp->mdev = m << 1; /* make sure rto = 3*rtt */ 689 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); 690 tp->rtt_seq = tp->snd_nxt; 691 } 692 } 693 694 /* Calculate rto without backoff. This is the second half of Van Jacobson's 695 * routine referred to above. 696 */ 697 static inline void tcp_set_rto(struct sock *sk) 698 { 699 const struct tcp_sock *tp = tcp_sk(sk); 700 /* Old crap is replaced with new one. 8) 701 * 702 * More seriously: 703 * 1. If rtt variance happened to be less 50msec, it is hallucination. 704 * It cannot be less due to utterly erratic ACK generation made 705 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ 706 * to do with delayed acks, because at cwnd>2 true delack timeout 707 * is invisible. Actually, Linux-2.4 also generates erratic 708 * ACKs in some circumstances. 709 */ 710 inet_csk(sk)->icsk_rto = __tcp_set_rto(tp); 711 712 /* 2. Fixups made earlier cannot be right. 713 * If we do not estimate RTO correctly without them, 714 * all the algo is pure shit and should be replaced 715 * with correct one. It is exactly, which we pretend to do. 716 */ 717 718 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo 719 * guarantees that rto is higher. 720 */ 721 tcp_bound_rto(sk); 722 } 723 724 /* Save metrics learned by this TCP session. 725 This function is called only, when TCP finishes successfully 726 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. 727 */ 728 void tcp_update_metrics(struct sock *sk) 729 { 730 struct tcp_sock *tp = tcp_sk(sk); 731 struct dst_entry *dst = __sk_dst_get(sk); 732 733 if (sysctl_tcp_nometrics_save) 734 return; 735 736 dst_confirm(dst); 737 738 if (dst && (dst->flags & DST_HOST)) { 739 const struct inet_connection_sock *icsk = inet_csk(sk); 740 int m; 741 unsigned long rtt; 742 743 if (icsk->icsk_backoff || !tp->srtt) { 744 /* This session failed to estimate rtt. Why? 745 * Probably, no packets returned in time. 746 * Reset our results. 747 */ 748 if (!(dst_metric_locked(dst, RTAX_RTT))) 749 dst_metric_set(dst, RTAX_RTT, 0); 750 return; 751 } 752 753 rtt = dst_metric_rtt(dst, RTAX_RTT); 754 m = rtt - tp->srtt; 755 756 /* If newly calculated rtt larger than stored one, 757 * store new one. Otherwise, use EWMA. Remember, 758 * rtt overestimation is always better than underestimation. 759 */ 760 if (!(dst_metric_locked(dst, RTAX_RTT))) { 761 if (m <= 0) 762 set_dst_metric_rtt(dst, RTAX_RTT, tp->srtt); 763 else 764 set_dst_metric_rtt(dst, RTAX_RTT, rtt - (m >> 3)); 765 } 766 767 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { 768 unsigned long var; 769 if (m < 0) 770 m = -m; 771 772 /* Scale deviation to rttvar fixed point */ 773 m >>= 1; 774 if (m < tp->mdev) 775 m = tp->mdev; 776 777 var = dst_metric_rtt(dst, RTAX_RTTVAR); 778 if (m >= var) 779 var = m; 780 else 781 var -= (var - m) >> 2; 782 783 set_dst_metric_rtt(dst, RTAX_RTTVAR, var); 784 } 785 786 if (tcp_in_initial_slowstart(tp)) { 787 /* Slow start still did not finish. */ 788 if (dst_metric(dst, RTAX_SSTHRESH) && 789 !dst_metric_locked(dst, RTAX_SSTHRESH) && 790 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) 791 dst_metric_set(dst, RTAX_SSTHRESH, tp->snd_cwnd >> 1); 792 if (!dst_metric_locked(dst, RTAX_CWND) && 793 tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) 794 dst_metric_set(dst, RTAX_CWND, tp->snd_cwnd); 795 } else if (tp->snd_cwnd > tp->snd_ssthresh && 796 icsk->icsk_ca_state == TCP_CA_Open) { 797 /* Cong. avoidance phase, cwnd is reliable. */ 798 if (!dst_metric_locked(dst, RTAX_SSTHRESH)) 799 dst_metric_set(dst, RTAX_SSTHRESH, 800 max(tp->snd_cwnd >> 1, tp->snd_ssthresh)); 801 if (!dst_metric_locked(dst, RTAX_CWND)) 802 dst_metric_set(dst, RTAX_CWND, 803 (dst_metric(dst, RTAX_CWND) + 804 tp->snd_cwnd) >> 1); 805 } else { 806 /* Else slow start did not finish, cwnd is non-sense, 807 ssthresh may be also invalid. 808 */ 809 if (!dst_metric_locked(dst, RTAX_CWND)) 810 dst_metric_set(dst, RTAX_CWND, 811 (dst_metric(dst, RTAX_CWND) + 812 tp->snd_ssthresh) >> 1); 813 if (dst_metric(dst, RTAX_SSTHRESH) && 814 !dst_metric_locked(dst, RTAX_SSTHRESH) && 815 tp->snd_ssthresh > dst_metric(dst, RTAX_SSTHRESH)) 816 dst_metric_set(dst, RTAX_SSTHRESH, tp->snd_ssthresh); 817 } 818 819 if (!dst_metric_locked(dst, RTAX_REORDERING)) { 820 if (dst_metric(dst, RTAX_REORDERING) < tp->reordering && 821 tp->reordering != sysctl_tcp_reordering) 822 dst_metric_set(dst, RTAX_REORDERING, tp->reordering); 823 } 824 } 825 } 826 827 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst) 828 { 829 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); 830 831 if (!cwnd) 832 cwnd = TCP_INIT_CWND; 833 return min_t(__u32, cwnd, tp->snd_cwnd_clamp); 834 } 835 836 /* Set slow start threshold and cwnd not falling to slow start */ 837 void tcp_enter_cwr(struct sock *sk, const int set_ssthresh) 838 { 839 struct tcp_sock *tp = tcp_sk(sk); 840 const struct inet_connection_sock *icsk = inet_csk(sk); 841 842 tp->prior_ssthresh = 0; 843 tp->bytes_acked = 0; 844 if (icsk->icsk_ca_state < TCP_CA_CWR) { 845 tp->undo_marker = 0; 846 if (set_ssthresh) 847 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 848 tp->snd_cwnd = min(tp->snd_cwnd, 849 tcp_packets_in_flight(tp) + 1U); 850 tp->snd_cwnd_cnt = 0; 851 tp->high_seq = tp->snd_nxt; 852 tp->snd_cwnd_stamp = tcp_time_stamp; 853 TCP_ECN_queue_cwr(tp); 854 855 tcp_set_ca_state(sk, TCP_CA_CWR); 856 } 857 } 858 859 /* 860 * Packet counting of FACK is based on in-order assumptions, therefore TCP 861 * disables it when reordering is detected 862 */ 863 static void tcp_disable_fack(struct tcp_sock *tp) 864 { 865 /* RFC3517 uses different metric in lost marker => reset on change */ 866 if (tcp_is_fack(tp)) 867 tp->lost_skb_hint = NULL; 868 tp->rx_opt.sack_ok &= ~TCP_FACK_ENABLED; 869 } 870 871 /* Take a notice that peer is sending D-SACKs */ 872 static void tcp_dsack_seen(struct tcp_sock *tp) 873 { 874 tp->rx_opt.sack_ok |= TCP_DSACK_SEEN; 875 } 876 877 /* Initialize metrics on socket. */ 878 879 static void tcp_init_metrics(struct sock *sk) 880 { 881 struct tcp_sock *tp = tcp_sk(sk); 882 struct dst_entry *dst = __sk_dst_get(sk); 883 884 if (dst == NULL) 885 goto reset; 886 887 dst_confirm(dst); 888 889 if (dst_metric_locked(dst, RTAX_CWND)) 890 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); 891 if (dst_metric(dst, RTAX_SSTHRESH)) { 892 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); 893 if (tp->snd_ssthresh > tp->snd_cwnd_clamp) 894 tp->snd_ssthresh = tp->snd_cwnd_clamp; 895 } else { 896 /* ssthresh may have been reduced unnecessarily during. 897 * 3WHS. Restore it back to its initial default. 898 */ 899 tp->snd_ssthresh = TCP_INFINITE_SSTHRESH; 900 } 901 if (dst_metric(dst, RTAX_REORDERING) && 902 tp->reordering != dst_metric(dst, RTAX_REORDERING)) { 903 tcp_disable_fack(tp); 904 tp->reordering = dst_metric(dst, RTAX_REORDERING); 905 } 906 907 if (dst_metric(dst, RTAX_RTT) == 0 || tp->srtt == 0) 908 goto reset; 909 910 /* Initial rtt is determined from SYN,SYN-ACK. 911 * The segment is small and rtt may appear much 912 * less than real one. Use per-dst memory 913 * to make it more realistic. 914 * 915 * A bit of theory. RTT is time passed after "normal" sized packet 916 * is sent until it is ACKed. In normal circumstances sending small 917 * packets force peer to delay ACKs and calculation is correct too. 918 * The algorithm is adaptive and, provided we follow specs, it 919 * NEVER underestimate RTT. BUT! If peer tries to make some clever 920 * tricks sort of "quick acks" for time long enough to decrease RTT 921 * to low value, and then abruptly stops to do it and starts to delay 922 * ACKs, wait for troubles. 923 */ 924 if (dst_metric_rtt(dst, RTAX_RTT) > tp->srtt) { 925 tp->srtt = dst_metric_rtt(dst, RTAX_RTT); 926 tp->rtt_seq = tp->snd_nxt; 927 } 928 if (dst_metric_rtt(dst, RTAX_RTTVAR) > tp->mdev) { 929 tp->mdev = dst_metric_rtt(dst, RTAX_RTTVAR); 930 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); 931 } 932 tcp_set_rto(sk); 933 reset: 934 if (tp->srtt == 0) { 935 /* RFC2988bis: We've failed to get a valid RTT sample from 936 * 3WHS. This is most likely due to retransmission, 937 * including spurious one. Reset the RTO back to 3secs 938 * from the more aggressive 1sec to avoid more spurious 939 * retransmission. 940 */ 941 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_FALLBACK; 942 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_FALLBACK; 943 } 944 /* Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been 945 * retransmitted. In light of RFC2988bis' more aggressive 1sec 946 * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK 947 * retransmission has occurred. 948 */ 949 if (tp->total_retrans > 1) 950 tp->snd_cwnd = 1; 951 else 952 tp->snd_cwnd = tcp_init_cwnd(tp, dst); 953 tp->snd_cwnd_stamp = tcp_time_stamp; 954 } 955 956 static void tcp_update_reordering(struct sock *sk, const int metric, 957 const int ts) 958 { 959 struct tcp_sock *tp = tcp_sk(sk); 960 if (metric > tp->reordering) { 961 int mib_idx; 962 963 tp->reordering = min(TCP_MAX_REORDERING, metric); 964 965 /* This exciting event is worth to be remembered. 8) */ 966 if (ts) 967 mib_idx = LINUX_MIB_TCPTSREORDER; 968 else if (tcp_is_reno(tp)) 969 mib_idx = LINUX_MIB_TCPRENOREORDER; 970 else if (tcp_is_fack(tp)) 971 mib_idx = LINUX_MIB_TCPFACKREORDER; 972 else 973 mib_idx = LINUX_MIB_TCPSACKREORDER; 974 975 NET_INC_STATS_BH(sock_net(sk), mib_idx); 976 #if FASTRETRANS_DEBUG > 1 977 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", 978 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, 979 tp->reordering, 980 tp->fackets_out, 981 tp->sacked_out, 982 tp->undo_marker ? tp->undo_retrans : 0); 983 #endif 984 tcp_disable_fack(tp); 985 } 986 } 987 988 /* This must be called before lost_out is incremented */ 989 static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) 990 { 991 if ((tp->retransmit_skb_hint == NULL) || 992 before(TCP_SKB_CB(skb)->seq, 993 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) 994 tp->retransmit_skb_hint = skb; 995 996 if (!tp->lost_out || 997 after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high)) 998 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; 999 } 1000 1001 static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb) 1002 { 1003 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { 1004 tcp_verify_retransmit_hint(tp, skb); 1005 1006 tp->lost_out += tcp_skb_pcount(skb); 1007 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1008 } 1009 } 1010 1011 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, 1012 struct sk_buff *skb) 1013 { 1014 tcp_verify_retransmit_hint(tp, skb); 1015 1016 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { 1017 tp->lost_out += tcp_skb_pcount(skb); 1018 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1019 } 1020 } 1021 1022 /* This procedure tags the retransmission queue when SACKs arrive. 1023 * 1024 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). 1025 * Packets in queue with these bits set are counted in variables 1026 * sacked_out, retrans_out and lost_out, correspondingly. 1027 * 1028 * Valid combinations are: 1029 * Tag InFlight Description 1030 * 0 1 - orig segment is in flight. 1031 * S 0 - nothing flies, orig reached receiver. 1032 * L 0 - nothing flies, orig lost by net. 1033 * R 2 - both orig and retransmit are in flight. 1034 * L|R 1 - orig is lost, retransmit is in flight. 1035 * S|R 1 - orig reached receiver, retrans is still in flight. 1036 * (L|S|R is logically valid, it could occur when L|R is sacked, 1037 * but it is equivalent to plain S and code short-curcuits it to S. 1038 * L|S is logically invalid, it would mean -1 packet in flight 8)) 1039 * 1040 * These 6 states form finite state machine, controlled by the following events: 1041 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) 1042 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) 1043 * 3. Loss detection event of one of three flavors: 1044 * A. Scoreboard estimator decided the packet is lost. 1045 * A'. Reno "three dupacks" marks head of queue lost. 1046 * A''. Its FACK modfication, head until snd.fack is lost. 1047 * B. SACK arrives sacking data transmitted after never retransmitted 1048 * hole was sent out. 1049 * C. SACK arrives sacking SND.NXT at the moment, when the 1050 * segment was retransmitted. 1051 * 4. D-SACK added new rule: D-SACK changes any tag to S. 1052 * 1053 * It is pleasant to note, that state diagram turns out to be commutative, 1054 * so that we are allowed not to be bothered by order of our actions, 1055 * when multiple events arrive simultaneously. (see the function below). 1056 * 1057 * Reordering detection. 1058 * -------------------- 1059 * Reordering metric is maximal distance, which a packet can be displaced 1060 * in packet stream. With SACKs we can estimate it: 1061 * 1062 * 1. SACK fills old hole and the corresponding segment was not 1063 * ever retransmitted -> reordering. Alas, we cannot use it 1064 * when segment was retransmitted. 1065 * 2. The last flaw is solved with D-SACK. D-SACK arrives 1066 * for retransmitted and already SACKed segment -> reordering.. 1067 * Both of these heuristics are not used in Loss state, when we cannot 1068 * account for retransmits accurately. 1069 * 1070 * SACK block validation. 1071 * ---------------------- 1072 * 1073 * SACK block range validation checks that the received SACK block fits to 1074 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT. 1075 * Note that SND.UNA is not included to the range though being valid because 1076 * it means that the receiver is rather inconsistent with itself reporting 1077 * SACK reneging when it should advance SND.UNA. Such SACK block this is 1078 * perfectly valid, however, in light of RFC2018 which explicitly states 1079 * that "SACK block MUST reflect the newest segment. Even if the newest 1080 * segment is going to be discarded ...", not that it looks very clever 1081 * in case of head skb. Due to potentional receiver driven attacks, we 1082 * choose to avoid immediate execution of a walk in write queue due to 1083 * reneging and defer head skb's loss recovery to standard loss recovery 1084 * procedure that will eventually trigger (nothing forbids us doing this). 1085 * 1086 * Implements also blockage to start_seq wrap-around. Problem lies in the 1087 * fact that though start_seq (s) is before end_seq (i.e., not reversed), 1088 * there's no guarantee that it will be before snd_nxt (n). The problem 1089 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt 1090 * wrap (s_w): 1091 * 1092 * <- outs wnd -> <- wrapzone -> 1093 * u e n u_w e_w s n_w 1094 * | | | | | | | 1095 * |<------------+------+----- TCP seqno space --------------+---------->| 1096 * ...-- <2^31 ->| |<--------... 1097 * ...---- >2^31 ------>| |<--------... 1098 * 1099 * Current code wouldn't be vulnerable but it's better still to discard such 1100 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat 1101 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in 1102 * snd_nxt wrap -> snd_una region will then become "well defined", i.e., 1103 * equal to the ideal case (infinite seqno space without wrap caused issues). 1104 * 1105 * With D-SACK the lower bound is extended to cover sequence space below 1106 * SND.UNA down to undo_marker, which is the last point of interest. Yet 1107 * again, D-SACK block must not to go across snd_una (for the same reason as 1108 * for the normal SACK blocks, explained above). But there all simplicity 1109 * ends, TCP might receive valid D-SACKs below that. As long as they reside 1110 * fully below undo_marker they do not affect behavior in anyway and can 1111 * therefore be safely ignored. In rare cases (which are more or less 1112 * theoretical ones), the D-SACK will nicely cross that boundary due to skb 1113 * fragmentation and packet reordering past skb's retransmission. To consider 1114 * them correctly, the acceptable range must be extended even more though 1115 * the exact amount is rather hard to quantify. However, tp->max_window can 1116 * be used as an exaggerated estimate. 1117 */ 1118 static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack, 1119 u32 start_seq, u32 end_seq) 1120 { 1121 /* Too far in future, or reversed (interpretation is ambiguous) */ 1122 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq)) 1123 return 0; 1124 1125 /* Nasty start_seq wrap-around check (see comments above) */ 1126 if (!before(start_seq, tp->snd_nxt)) 1127 return 0; 1128 1129 /* In outstanding window? ...This is valid exit for D-SACKs too. 1130 * start_seq == snd_una is non-sensical (see comments above) 1131 */ 1132 if (after(start_seq, tp->snd_una)) 1133 return 1; 1134 1135 if (!is_dsack || !tp->undo_marker) 1136 return 0; 1137 1138 /* ...Then it's D-SACK, and must reside below snd_una completely */ 1139 if (after(end_seq, tp->snd_una)) 1140 return 0; 1141 1142 if (!before(start_seq, tp->undo_marker)) 1143 return 1; 1144 1145 /* Too old */ 1146 if (!after(end_seq, tp->undo_marker)) 1147 return 0; 1148 1149 /* Undo_marker boundary crossing (overestimates a lot). Known already: 1150 * start_seq < undo_marker and end_seq >= undo_marker. 1151 */ 1152 return !before(start_seq, end_seq - tp->max_window); 1153 } 1154 1155 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving". 1156 * Event "C". Later note: FACK people cheated me again 8), we have to account 1157 * for reordering! Ugly, but should help. 1158 * 1159 * Search retransmitted skbs from write_queue that were sent when snd_nxt was 1160 * less than what is now known to be received by the other end (derived from 1161 * highest SACK block). Also calculate the lowest snd_nxt among the remaining 1162 * retransmitted skbs to avoid some costly processing per ACKs. 1163 */ 1164 static void tcp_mark_lost_retrans(struct sock *sk) 1165 { 1166 const struct inet_connection_sock *icsk = inet_csk(sk); 1167 struct tcp_sock *tp = tcp_sk(sk); 1168 struct sk_buff *skb; 1169 int cnt = 0; 1170 u32 new_low_seq = tp->snd_nxt; 1171 u32 received_upto = tcp_highest_sack_seq(tp); 1172 1173 if (!tcp_is_fack(tp) || !tp->retrans_out || 1174 !after(received_upto, tp->lost_retrans_low) || 1175 icsk->icsk_ca_state != TCP_CA_Recovery) 1176 return; 1177 1178 tcp_for_write_queue(skb, sk) { 1179 u32 ack_seq = TCP_SKB_CB(skb)->ack_seq; 1180 1181 if (skb == tcp_send_head(sk)) 1182 break; 1183 if (cnt == tp->retrans_out) 1184 break; 1185 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1186 continue; 1187 1188 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) 1189 continue; 1190 1191 /* TODO: We would like to get rid of tcp_is_fack(tp) only 1192 * constraint here (see above) but figuring out that at 1193 * least tp->reordering SACK blocks reside between ack_seq 1194 * and received_upto is not easy task to do cheaply with 1195 * the available datastructures. 1196 * 1197 * Whether FACK should check here for tp->reordering segs 1198 * in-between one could argue for either way (it would be 1199 * rather simple to implement as we could count fack_count 1200 * during the walk and do tp->fackets_out - fack_count). 1201 */ 1202 if (after(received_upto, ack_seq)) { 1203 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1204 tp->retrans_out -= tcp_skb_pcount(skb); 1205 1206 tcp_skb_mark_lost_uncond_verify(tp, skb); 1207 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT); 1208 } else { 1209 if (before(ack_seq, new_low_seq)) 1210 new_low_seq = ack_seq; 1211 cnt += tcp_skb_pcount(skb); 1212 } 1213 } 1214 1215 if (tp->retrans_out) 1216 tp->lost_retrans_low = new_low_seq; 1217 } 1218 1219 static int tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb, 1220 struct tcp_sack_block_wire *sp, int num_sacks, 1221 u32 prior_snd_una) 1222 { 1223 struct tcp_sock *tp = tcp_sk(sk); 1224 u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq); 1225 u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq); 1226 int dup_sack = 0; 1227 1228 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) { 1229 dup_sack = 1; 1230 tcp_dsack_seen(tp); 1231 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV); 1232 } else if (num_sacks > 1) { 1233 u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq); 1234 u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq); 1235 1236 if (!after(end_seq_0, end_seq_1) && 1237 !before(start_seq_0, start_seq_1)) { 1238 dup_sack = 1; 1239 tcp_dsack_seen(tp); 1240 NET_INC_STATS_BH(sock_net(sk), 1241 LINUX_MIB_TCPDSACKOFORECV); 1242 } 1243 } 1244 1245 /* D-SACK for already forgotten data... Do dumb counting. */ 1246 if (dup_sack && tp->undo_marker && tp->undo_retrans && 1247 !after(end_seq_0, prior_snd_una) && 1248 after(end_seq_0, tp->undo_marker)) 1249 tp->undo_retrans--; 1250 1251 return dup_sack; 1252 } 1253 1254 struct tcp_sacktag_state { 1255 int reord; 1256 int fack_count; 1257 int flag; 1258 }; 1259 1260 /* Check if skb is fully within the SACK block. In presence of GSO skbs, 1261 * the incoming SACK may not exactly match but we can find smaller MSS 1262 * aligned portion of it that matches. Therefore we might need to fragment 1263 * which may fail and creates some hassle (caller must handle error case 1264 * returns). 1265 * 1266 * FIXME: this could be merged to shift decision code 1267 */ 1268 static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, 1269 u32 start_seq, u32 end_seq) 1270 { 1271 int in_sack, err; 1272 unsigned int pkt_len; 1273 unsigned int mss; 1274 1275 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && 1276 !before(end_seq, TCP_SKB_CB(skb)->end_seq); 1277 1278 if (tcp_skb_pcount(skb) > 1 && !in_sack && 1279 after(TCP_SKB_CB(skb)->end_seq, start_seq)) { 1280 mss = tcp_skb_mss(skb); 1281 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); 1282 1283 if (!in_sack) { 1284 pkt_len = start_seq - TCP_SKB_CB(skb)->seq; 1285 if (pkt_len < mss) 1286 pkt_len = mss; 1287 } else { 1288 pkt_len = end_seq - TCP_SKB_CB(skb)->seq; 1289 if (pkt_len < mss) 1290 return -EINVAL; 1291 } 1292 1293 /* Round if necessary so that SACKs cover only full MSSes 1294 * and/or the remaining small portion (if present) 1295 */ 1296 if (pkt_len > mss) { 1297 unsigned int new_len = (pkt_len / mss) * mss; 1298 if (!in_sack && new_len < pkt_len) { 1299 new_len += mss; 1300 if (new_len > skb->len) 1301 return 0; 1302 } 1303 pkt_len = new_len; 1304 } 1305 err = tcp_fragment(sk, skb, pkt_len, mss); 1306 if (err < 0) 1307 return err; 1308 } 1309 1310 return in_sack; 1311 } 1312 1313 static u8 tcp_sacktag_one(const struct sk_buff *skb, struct sock *sk, 1314 struct tcp_sacktag_state *state, 1315 int dup_sack, int pcount) 1316 { 1317 struct tcp_sock *tp = tcp_sk(sk); 1318 u8 sacked = TCP_SKB_CB(skb)->sacked; 1319 int fack_count = state->fack_count; 1320 1321 /* Account D-SACK for retransmitted packet. */ 1322 if (dup_sack && (sacked & TCPCB_RETRANS)) { 1323 if (tp->undo_marker && tp->undo_retrans && 1324 after(TCP_SKB_CB(skb)->end_seq, tp->undo_marker)) 1325 tp->undo_retrans--; 1326 if (sacked & TCPCB_SACKED_ACKED) 1327 state->reord = min(fack_count, state->reord); 1328 } 1329 1330 /* Nothing to do; acked frame is about to be dropped (was ACKed). */ 1331 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1332 return sacked; 1333 1334 if (!(sacked & TCPCB_SACKED_ACKED)) { 1335 if (sacked & TCPCB_SACKED_RETRANS) { 1336 /* If the segment is not tagged as lost, 1337 * we do not clear RETRANS, believing 1338 * that retransmission is still in flight. 1339 */ 1340 if (sacked & TCPCB_LOST) { 1341 sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); 1342 tp->lost_out -= pcount; 1343 tp->retrans_out -= pcount; 1344 } 1345 } else { 1346 if (!(sacked & TCPCB_RETRANS)) { 1347 /* New sack for not retransmitted frame, 1348 * which was in hole. It is reordering. 1349 */ 1350 if (before(TCP_SKB_CB(skb)->seq, 1351 tcp_highest_sack_seq(tp))) 1352 state->reord = min(fack_count, 1353 state->reord); 1354 1355 /* SACK enhanced F-RTO (RFC4138; Appendix B) */ 1356 if (!after(TCP_SKB_CB(skb)->end_seq, tp->frto_highmark)) 1357 state->flag |= FLAG_ONLY_ORIG_SACKED; 1358 } 1359 1360 if (sacked & TCPCB_LOST) { 1361 sacked &= ~TCPCB_LOST; 1362 tp->lost_out -= pcount; 1363 } 1364 } 1365 1366 sacked |= TCPCB_SACKED_ACKED; 1367 state->flag |= FLAG_DATA_SACKED; 1368 tp->sacked_out += pcount; 1369 1370 fack_count += pcount; 1371 1372 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */ 1373 if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) && 1374 before(TCP_SKB_CB(skb)->seq, 1375 TCP_SKB_CB(tp->lost_skb_hint)->seq)) 1376 tp->lost_cnt_hint += pcount; 1377 1378 if (fack_count > tp->fackets_out) 1379 tp->fackets_out = fack_count; 1380 } 1381 1382 /* D-SACK. We can detect redundant retransmission in S|R and plain R 1383 * frames and clear it. undo_retrans is decreased above, L|R frames 1384 * are accounted above as well. 1385 */ 1386 if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) { 1387 sacked &= ~TCPCB_SACKED_RETRANS; 1388 tp->retrans_out -= pcount; 1389 } 1390 1391 return sacked; 1392 } 1393 1394 static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb, 1395 struct tcp_sacktag_state *state, 1396 unsigned int pcount, int shifted, int mss, 1397 int dup_sack) 1398 { 1399 struct tcp_sock *tp = tcp_sk(sk); 1400 struct sk_buff *prev = tcp_write_queue_prev(sk, skb); 1401 1402 BUG_ON(!pcount); 1403 1404 if (skb == tp->lost_skb_hint) 1405 tp->lost_cnt_hint += pcount; 1406 1407 TCP_SKB_CB(prev)->end_seq += shifted; 1408 TCP_SKB_CB(skb)->seq += shifted; 1409 1410 skb_shinfo(prev)->gso_segs += pcount; 1411 BUG_ON(skb_shinfo(skb)->gso_segs < pcount); 1412 skb_shinfo(skb)->gso_segs -= pcount; 1413 1414 /* When we're adding to gso_segs == 1, gso_size will be zero, 1415 * in theory this shouldn't be necessary but as long as DSACK 1416 * code can come after this skb later on it's better to keep 1417 * setting gso_size to something. 1418 */ 1419 if (!skb_shinfo(prev)->gso_size) { 1420 skb_shinfo(prev)->gso_size = mss; 1421 skb_shinfo(prev)->gso_type = sk->sk_gso_type; 1422 } 1423 1424 /* CHECKME: To clear or not to clear? Mimics normal skb currently */ 1425 if (skb_shinfo(skb)->gso_segs <= 1) { 1426 skb_shinfo(skb)->gso_size = 0; 1427 skb_shinfo(skb)->gso_type = 0; 1428 } 1429 1430 /* We discard results */ 1431 tcp_sacktag_one(skb, sk, state, dup_sack, pcount); 1432 1433 /* Difference in this won't matter, both ACKed by the same cumul. ACK */ 1434 TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS); 1435 1436 if (skb->len > 0) { 1437 BUG_ON(!tcp_skb_pcount(skb)); 1438 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED); 1439 return 0; 1440 } 1441 1442 /* Whole SKB was eaten :-) */ 1443 1444 if (skb == tp->retransmit_skb_hint) 1445 tp->retransmit_skb_hint = prev; 1446 if (skb == tp->scoreboard_skb_hint) 1447 tp->scoreboard_skb_hint = prev; 1448 if (skb == tp->lost_skb_hint) { 1449 tp->lost_skb_hint = prev; 1450 tp->lost_cnt_hint -= tcp_skb_pcount(prev); 1451 } 1452 1453 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(prev)->tcp_flags; 1454 if (skb == tcp_highest_sack(sk)) 1455 tcp_advance_highest_sack(sk, skb); 1456 1457 tcp_unlink_write_queue(skb, sk); 1458 sk_wmem_free_skb(sk, skb); 1459 1460 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED); 1461 1462 return 1; 1463 } 1464 1465 /* I wish gso_size would have a bit more sane initialization than 1466 * something-or-zero which complicates things 1467 */ 1468 static int tcp_skb_seglen(const struct sk_buff *skb) 1469 { 1470 return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb); 1471 } 1472 1473 /* Shifting pages past head area doesn't work */ 1474 static int skb_can_shift(const struct sk_buff *skb) 1475 { 1476 return !skb_headlen(skb) && skb_is_nonlinear(skb); 1477 } 1478 1479 /* Try collapsing SACK blocks spanning across multiple skbs to a single 1480 * skb. 1481 */ 1482 static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb, 1483 struct tcp_sacktag_state *state, 1484 u32 start_seq, u32 end_seq, 1485 int dup_sack) 1486 { 1487 struct tcp_sock *tp = tcp_sk(sk); 1488 struct sk_buff *prev; 1489 int mss; 1490 int pcount = 0; 1491 int len; 1492 int in_sack; 1493 1494 if (!sk_can_gso(sk)) 1495 goto fallback; 1496 1497 /* Normally R but no L won't result in plain S */ 1498 if (!dup_sack && 1499 (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS) 1500 goto fallback; 1501 if (!skb_can_shift(skb)) 1502 goto fallback; 1503 /* This frame is about to be dropped (was ACKed). */ 1504 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1505 goto fallback; 1506 1507 /* Can only happen with delayed DSACK + discard craziness */ 1508 if (unlikely(skb == tcp_write_queue_head(sk))) 1509 goto fallback; 1510 prev = tcp_write_queue_prev(sk, skb); 1511 1512 if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) 1513 goto fallback; 1514 1515 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && 1516 !before(end_seq, TCP_SKB_CB(skb)->end_seq); 1517 1518 if (in_sack) { 1519 len = skb->len; 1520 pcount = tcp_skb_pcount(skb); 1521 mss = tcp_skb_seglen(skb); 1522 1523 /* TODO: Fix DSACKs to not fragment already SACKed and we can 1524 * drop this restriction as unnecessary 1525 */ 1526 if (mss != tcp_skb_seglen(prev)) 1527 goto fallback; 1528 } else { 1529 if (!after(TCP_SKB_CB(skb)->end_seq, start_seq)) 1530 goto noop; 1531 /* CHECKME: This is non-MSS split case only?, this will 1532 * cause skipped skbs due to advancing loop btw, original 1533 * has that feature too 1534 */ 1535 if (tcp_skb_pcount(skb) <= 1) 1536 goto noop; 1537 1538 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); 1539 if (!in_sack) { 1540 /* TODO: head merge to next could be attempted here 1541 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)), 1542 * though it might not be worth of the additional hassle 1543 * 1544 * ...we can probably just fallback to what was done 1545 * previously. We could try merging non-SACKed ones 1546 * as well but it probably isn't going to buy off 1547 * because later SACKs might again split them, and 1548 * it would make skb timestamp tracking considerably 1549 * harder problem. 1550 */ 1551 goto fallback; 1552 } 1553 1554 len = end_seq - TCP_SKB_CB(skb)->seq; 1555 BUG_ON(len < 0); 1556 BUG_ON(len > skb->len); 1557 1558 /* MSS boundaries should be honoured or else pcount will 1559 * severely break even though it makes things bit trickier. 1560 * Optimize common case to avoid most of the divides 1561 */ 1562 mss = tcp_skb_mss(skb); 1563 1564 /* TODO: Fix DSACKs to not fragment already SACKed and we can 1565 * drop this restriction as unnecessary 1566 */ 1567 if (mss != tcp_skb_seglen(prev)) 1568 goto fallback; 1569 1570 if (len == mss) { 1571 pcount = 1; 1572 } else if (len < mss) { 1573 goto noop; 1574 } else { 1575 pcount = len / mss; 1576 len = pcount * mss; 1577 } 1578 } 1579 1580 if (!skb_shift(prev, skb, len)) 1581 goto fallback; 1582 if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack)) 1583 goto out; 1584 1585 /* Hole filled allows collapsing with the next as well, this is very 1586 * useful when hole on every nth skb pattern happens 1587 */ 1588 if (prev == tcp_write_queue_tail(sk)) 1589 goto out; 1590 skb = tcp_write_queue_next(sk, prev); 1591 1592 if (!skb_can_shift(skb) || 1593 (skb == tcp_send_head(sk)) || 1594 ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) || 1595 (mss != tcp_skb_seglen(skb))) 1596 goto out; 1597 1598 len = skb->len; 1599 if (skb_shift(prev, skb, len)) { 1600 pcount += tcp_skb_pcount(skb); 1601 tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0); 1602 } 1603 1604 out: 1605 state->fack_count += pcount; 1606 return prev; 1607 1608 noop: 1609 return skb; 1610 1611 fallback: 1612 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK); 1613 return NULL; 1614 } 1615 1616 static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, 1617 struct tcp_sack_block *next_dup, 1618 struct tcp_sacktag_state *state, 1619 u32 start_seq, u32 end_seq, 1620 int dup_sack_in) 1621 { 1622 struct tcp_sock *tp = tcp_sk(sk); 1623 struct sk_buff *tmp; 1624 1625 tcp_for_write_queue_from(skb, sk) { 1626 int in_sack = 0; 1627 int dup_sack = dup_sack_in; 1628 1629 if (skb == tcp_send_head(sk)) 1630 break; 1631 1632 /* queue is in-order => we can short-circuit the walk early */ 1633 if (!before(TCP_SKB_CB(skb)->seq, end_seq)) 1634 break; 1635 1636 if ((next_dup != NULL) && 1637 before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) { 1638 in_sack = tcp_match_skb_to_sack(sk, skb, 1639 next_dup->start_seq, 1640 next_dup->end_seq); 1641 if (in_sack > 0) 1642 dup_sack = 1; 1643 } 1644 1645 /* skb reference here is a bit tricky to get right, since 1646 * shifting can eat and free both this skb and the next, 1647 * so not even _safe variant of the loop is enough. 1648 */ 1649 if (in_sack <= 0) { 1650 tmp = tcp_shift_skb_data(sk, skb, state, 1651 start_seq, end_seq, dup_sack); 1652 if (tmp != NULL) { 1653 if (tmp != skb) { 1654 skb = tmp; 1655 continue; 1656 } 1657 1658 in_sack = 0; 1659 } else { 1660 in_sack = tcp_match_skb_to_sack(sk, skb, 1661 start_seq, 1662 end_seq); 1663 } 1664 } 1665 1666 if (unlikely(in_sack < 0)) 1667 break; 1668 1669 if (in_sack) { 1670 TCP_SKB_CB(skb)->sacked = tcp_sacktag_one(skb, sk, 1671 state, 1672 dup_sack, 1673 tcp_skb_pcount(skb)); 1674 1675 if (!before(TCP_SKB_CB(skb)->seq, 1676 tcp_highest_sack_seq(tp))) 1677 tcp_advance_highest_sack(sk, skb); 1678 } 1679 1680 state->fack_count += tcp_skb_pcount(skb); 1681 } 1682 return skb; 1683 } 1684 1685 /* Avoid all extra work that is being done by sacktag while walking in 1686 * a normal way 1687 */ 1688 static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, 1689 struct tcp_sacktag_state *state, 1690 u32 skip_to_seq) 1691 { 1692 tcp_for_write_queue_from(skb, sk) { 1693 if (skb == tcp_send_head(sk)) 1694 break; 1695 1696 if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq)) 1697 break; 1698 1699 state->fack_count += tcp_skb_pcount(skb); 1700 } 1701 return skb; 1702 } 1703 1704 static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb, 1705 struct sock *sk, 1706 struct tcp_sack_block *next_dup, 1707 struct tcp_sacktag_state *state, 1708 u32 skip_to_seq) 1709 { 1710 if (next_dup == NULL) 1711 return skb; 1712 1713 if (before(next_dup->start_seq, skip_to_seq)) { 1714 skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq); 1715 skb = tcp_sacktag_walk(skb, sk, NULL, state, 1716 next_dup->start_seq, next_dup->end_seq, 1717 1); 1718 } 1719 1720 return skb; 1721 } 1722 1723 static int tcp_sack_cache_ok(const struct tcp_sock *tp, const struct tcp_sack_block *cache) 1724 { 1725 return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); 1726 } 1727 1728 static int 1729 tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb, 1730 u32 prior_snd_una) 1731 { 1732 const struct inet_connection_sock *icsk = inet_csk(sk); 1733 struct tcp_sock *tp = tcp_sk(sk); 1734 const unsigned char *ptr = (skb_transport_header(ack_skb) + 1735 TCP_SKB_CB(ack_skb)->sacked); 1736 struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2); 1737 struct tcp_sack_block sp[TCP_NUM_SACKS]; 1738 struct tcp_sack_block *cache; 1739 struct tcp_sacktag_state state; 1740 struct sk_buff *skb; 1741 int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3); 1742 int used_sacks; 1743 int found_dup_sack = 0; 1744 int i, j; 1745 int first_sack_index; 1746 1747 state.flag = 0; 1748 state.reord = tp->packets_out; 1749 1750 if (!tp->sacked_out) { 1751 if (WARN_ON(tp->fackets_out)) 1752 tp->fackets_out = 0; 1753 tcp_highest_sack_reset(sk); 1754 } 1755 1756 found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire, 1757 num_sacks, prior_snd_una); 1758 if (found_dup_sack) 1759 state.flag |= FLAG_DSACKING_ACK; 1760 1761 /* Eliminate too old ACKs, but take into 1762 * account more or less fresh ones, they can 1763 * contain valid SACK info. 1764 */ 1765 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) 1766 return 0; 1767 1768 if (!tp->packets_out) 1769 goto out; 1770 1771 used_sacks = 0; 1772 first_sack_index = 0; 1773 for (i = 0; i < num_sacks; i++) { 1774 int dup_sack = !i && found_dup_sack; 1775 1776 sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq); 1777 sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq); 1778 1779 if (!tcp_is_sackblock_valid(tp, dup_sack, 1780 sp[used_sacks].start_seq, 1781 sp[used_sacks].end_seq)) { 1782 int mib_idx; 1783 1784 if (dup_sack) { 1785 if (!tp->undo_marker) 1786 mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO; 1787 else 1788 mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD; 1789 } else { 1790 /* Don't count olds caused by ACK reordering */ 1791 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) && 1792 !after(sp[used_sacks].end_seq, tp->snd_una)) 1793 continue; 1794 mib_idx = LINUX_MIB_TCPSACKDISCARD; 1795 } 1796 1797 NET_INC_STATS_BH(sock_net(sk), mib_idx); 1798 if (i == 0) 1799 first_sack_index = -1; 1800 continue; 1801 } 1802 1803 /* Ignore very old stuff early */ 1804 if (!after(sp[used_sacks].end_seq, prior_snd_una)) 1805 continue; 1806 1807 used_sacks++; 1808 } 1809 1810 /* order SACK blocks to allow in order walk of the retrans queue */ 1811 for (i = used_sacks - 1; i > 0; i--) { 1812 for (j = 0; j < i; j++) { 1813 if (after(sp[j].start_seq, sp[j + 1].start_seq)) { 1814 swap(sp[j], sp[j + 1]); 1815 1816 /* Track where the first SACK block goes to */ 1817 if (j == first_sack_index) 1818 first_sack_index = j + 1; 1819 } 1820 } 1821 } 1822 1823 skb = tcp_write_queue_head(sk); 1824 state.fack_count = 0; 1825 i = 0; 1826 1827 if (!tp->sacked_out) { 1828 /* It's already past, so skip checking against it */ 1829 cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); 1830 } else { 1831 cache = tp->recv_sack_cache; 1832 /* Skip empty blocks in at head of the cache */ 1833 while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq && 1834 !cache->end_seq) 1835 cache++; 1836 } 1837 1838 while (i < used_sacks) { 1839 u32 start_seq = sp[i].start_seq; 1840 u32 end_seq = sp[i].end_seq; 1841 int dup_sack = (found_dup_sack && (i == first_sack_index)); 1842 struct tcp_sack_block *next_dup = NULL; 1843 1844 if (found_dup_sack && ((i + 1) == first_sack_index)) 1845 next_dup = &sp[i + 1]; 1846 1847 /* Event "B" in the comment above. */ 1848 if (after(end_seq, tp->high_seq)) 1849 state.flag |= FLAG_DATA_LOST; 1850 1851 /* Skip too early cached blocks */ 1852 while (tcp_sack_cache_ok(tp, cache) && 1853 !before(start_seq, cache->end_seq)) 1854 cache++; 1855 1856 /* Can skip some work by looking recv_sack_cache? */ 1857 if (tcp_sack_cache_ok(tp, cache) && !dup_sack && 1858 after(end_seq, cache->start_seq)) { 1859 1860 /* Head todo? */ 1861 if (before(start_seq, cache->start_seq)) { 1862 skb = tcp_sacktag_skip(skb, sk, &state, 1863 start_seq); 1864 skb = tcp_sacktag_walk(skb, sk, next_dup, 1865 &state, 1866 start_seq, 1867 cache->start_seq, 1868 dup_sack); 1869 } 1870 1871 /* Rest of the block already fully processed? */ 1872 if (!after(end_seq, cache->end_seq)) 1873 goto advance_sp; 1874 1875 skb = tcp_maybe_skipping_dsack(skb, sk, next_dup, 1876 &state, 1877 cache->end_seq); 1878 1879 /* ...tail remains todo... */ 1880 if (tcp_highest_sack_seq(tp) == cache->end_seq) { 1881 /* ...but better entrypoint exists! */ 1882 skb = tcp_highest_sack(sk); 1883 if (skb == NULL) 1884 break; 1885 state.fack_count = tp->fackets_out; 1886 cache++; 1887 goto walk; 1888 } 1889 1890 skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq); 1891 /* Check overlap against next cached too (past this one already) */ 1892 cache++; 1893 continue; 1894 } 1895 1896 if (!before(start_seq, tcp_highest_sack_seq(tp))) { 1897 skb = tcp_highest_sack(sk); 1898 if (skb == NULL) 1899 break; 1900 state.fack_count = tp->fackets_out; 1901 } 1902 skb = tcp_sacktag_skip(skb, sk, &state, start_seq); 1903 1904 walk: 1905 skb = tcp_sacktag_walk(skb, sk, next_dup, &state, 1906 start_seq, end_seq, dup_sack); 1907 1908 advance_sp: 1909 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct 1910 * due to in-order walk 1911 */ 1912 if (after(end_seq, tp->frto_highmark)) 1913 state.flag &= ~FLAG_ONLY_ORIG_SACKED; 1914 1915 i++; 1916 } 1917 1918 /* Clear the head of the cache sack blocks so we can skip it next time */ 1919 for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) { 1920 tp->recv_sack_cache[i].start_seq = 0; 1921 tp->recv_sack_cache[i].end_seq = 0; 1922 } 1923 for (j = 0; j < used_sacks; j++) 1924 tp->recv_sack_cache[i++] = sp[j]; 1925 1926 tcp_mark_lost_retrans(sk); 1927 1928 tcp_verify_left_out(tp); 1929 1930 if ((state.reord < tp->fackets_out) && 1931 ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) && 1932 (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark))) 1933 tcp_update_reordering(sk, tp->fackets_out - state.reord, 0); 1934 1935 out: 1936 1937 #if FASTRETRANS_DEBUG > 0 1938 WARN_ON((int)tp->sacked_out < 0); 1939 WARN_ON((int)tp->lost_out < 0); 1940 WARN_ON((int)tp->retrans_out < 0); 1941 WARN_ON((int)tcp_packets_in_flight(tp) < 0); 1942 #endif 1943 return state.flag; 1944 } 1945 1946 /* Limits sacked_out so that sum with lost_out isn't ever larger than 1947 * packets_out. Returns zero if sacked_out adjustement wasn't necessary. 1948 */ 1949 static int tcp_limit_reno_sacked(struct tcp_sock *tp) 1950 { 1951 u32 holes; 1952 1953 holes = max(tp->lost_out, 1U); 1954 holes = min(holes, tp->packets_out); 1955 1956 if ((tp->sacked_out + holes) > tp->packets_out) { 1957 tp->sacked_out = tp->packets_out - holes; 1958 return 1; 1959 } 1960 return 0; 1961 } 1962 1963 /* If we receive more dupacks than we expected counting segments 1964 * in assumption of absent reordering, interpret this as reordering. 1965 * The only another reason could be bug in receiver TCP. 1966 */ 1967 static void tcp_check_reno_reordering(struct sock *sk, const int addend) 1968 { 1969 struct tcp_sock *tp = tcp_sk(sk); 1970 if (tcp_limit_reno_sacked(tp)) 1971 tcp_update_reordering(sk, tp->packets_out + addend, 0); 1972 } 1973 1974 /* Emulate SACKs for SACKless connection: account for a new dupack. */ 1975 1976 static void tcp_add_reno_sack(struct sock *sk) 1977 { 1978 struct tcp_sock *tp = tcp_sk(sk); 1979 tp->sacked_out++; 1980 tcp_check_reno_reordering(sk, 0); 1981 tcp_verify_left_out(tp); 1982 } 1983 1984 /* Account for ACK, ACKing some data in Reno Recovery phase. */ 1985 1986 static void tcp_remove_reno_sacks(struct sock *sk, int acked) 1987 { 1988 struct tcp_sock *tp = tcp_sk(sk); 1989 1990 if (acked > 0) { 1991 /* One ACK acked hole. The rest eat duplicate ACKs. */ 1992 if (acked - 1 >= tp->sacked_out) 1993 tp->sacked_out = 0; 1994 else 1995 tp->sacked_out -= acked - 1; 1996 } 1997 tcp_check_reno_reordering(sk, acked); 1998 tcp_verify_left_out(tp); 1999 } 2000 2001 static inline void tcp_reset_reno_sack(struct tcp_sock *tp) 2002 { 2003 tp->sacked_out = 0; 2004 } 2005 2006 static int tcp_is_sackfrto(const struct tcp_sock *tp) 2007 { 2008 return (sysctl_tcp_frto == 0x2) && !tcp_is_reno(tp); 2009 } 2010 2011 /* F-RTO can only be used if TCP has never retransmitted anything other than 2012 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here) 2013 */ 2014 int tcp_use_frto(struct sock *sk) 2015 { 2016 const struct tcp_sock *tp = tcp_sk(sk); 2017 const struct inet_connection_sock *icsk = inet_csk(sk); 2018 struct sk_buff *skb; 2019 2020 if (!sysctl_tcp_frto) 2021 return 0; 2022 2023 /* MTU probe and F-RTO won't really play nicely along currently */ 2024 if (icsk->icsk_mtup.probe_size) 2025 return 0; 2026 2027 if (tcp_is_sackfrto(tp)) 2028 return 1; 2029 2030 /* Avoid expensive walking of rexmit queue if possible */ 2031 if (tp->retrans_out > 1) 2032 return 0; 2033 2034 skb = tcp_write_queue_head(sk); 2035 if (tcp_skb_is_last(sk, skb)) 2036 return 1; 2037 skb = tcp_write_queue_next(sk, skb); /* Skips head */ 2038 tcp_for_write_queue_from(skb, sk) { 2039 if (skb == tcp_send_head(sk)) 2040 break; 2041 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2042 return 0; 2043 /* Short-circuit when first non-SACKed skb has been checked */ 2044 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 2045 break; 2046 } 2047 return 1; 2048 } 2049 2050 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO 2051 * recovery a bit and use heuristics in tcp_process_frto() to detect if 2052 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to 2053 * keep retrans_out counting accurate (with SACK F-RTO, other than head 2054 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS 2055 * bits are handled if the Loss state is really to be entered (in 2056 * tcp_enter_frto_loss). 2057 * 2058 * Do like tcp_enter_loss() would; when RTO expires the second time it 2059 * does: 2060 * "Reduce ssthresh if it has not yet been made inside this window." 2061 */ 2062 void tcp_enter_frto(struct sock *sk) 2063 { 2064 const struct inet_connection_sock *icsk = inet_csk(sk); 2065 struct tcp_sock *tp = tcp_sk(sk); 2066 struct sk_buff *skb; 2067 2068 if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) || 2069 tp->snd_una == tp->high_seq || 2070 ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) && 2071 !icsk->icsk_retransmits)) { 2072 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2073 /* Our state is too optimistic in ssthresh() call because cwnd 2074 * is not reduced until tcp_enter_frto_loss() when previous F-RTO 2075 * recovery has not yet completed. Pattern would be this: RTO, 2076 * Cumulative ACK, RTO (2xRTO for the same segment does not end 2077 * up here twice). 2078 * RFC4138 should be more specific on what to do, even though 2079 * RTO is quite unlikely to occur after the first Cumulative ACK 2080 * due to back-off and complexity of triggering events ... 2081 */ 2082 if (tp->frto_counter) { 2083 u32 stored_cwnd; 2084 stored_cwnd = tp->snd_cwnd; 2085 tp->snd_cwnd = 2; 2086 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2087 tp->snd_cwnd = stored_cwnd; 2088 } else { 2089 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2090 } 2091 /* ... in theory, cong.control module could do "any tricks" in 2092 * ssthresh(), which means that ca_state, lost bits and lost_out 2093 * counter would have to be faked before the call occurs. We 2094 * consider that too expensive, unlikely and hacky, so modules 2095 * using these in ssthresh() must deal these incompatibility 2096 * issues if they receives CA_EVENT_FRTO and frto_counter != 0 2097 */ 2098 tcp_ca_event(sk, CA_EVENT_FRTO); 2099 } 2100 2101 tp->undo_marker = tp->snd_una; 2102 tp->undo_retrans = 0; 2103 2104 skb = tcp_write_queue_head(sk); 2105 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2106 tp->undo_marker = 0; 2107 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 2108 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 2109 tp->retrans_out -= tcp_skb_pcount(skb); 2110 } 2111 tcp_verify_left_out(tp); 2112 2113 /* Too bad if TCP was application limited */ 2114 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1); 2115 2116 /* Earlier loss recovery underway (see RFC4138; Appendix B). 2117 * The last condition is necessary at least in tp->frto_counter case. 2118 */ 2119 if (tcp_is_sackfrto(tp) && (tp->frto_counter || 2120 ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) && 2121 after(tp->high_seq, tp->snd_una)) { 2122 tp->frto_highmark = tp->high_seq; 2123 } else { 2124 tp->frto_highmark = tp->snd_nxt; 2125 } 2126 tcp_set_ca_state(sk, TCP_CA_Disorder); 2127 tp->high_seq = tp->snd_nxt; 2128 tp->frto_counter = 1; 2129 } 2130 2131 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO, 2132 * which indicates that we should follow the traditional RTO recovery, 2133 * i.e. mark everything lost and do go-back-N retransmission. 2134 */ 2135 static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag) 2136 { 2137 struct tcp_sock *tp = tcp_sk(sk); 2138 struct sk_buff *skb; 2139 2140 tp->lost_out = 0; 2141 tp->retrans_out = 0; 2142 if (tcp_is_reno(tp)) 2143 tcp_reset_reno_sack(tp); 2144 2145 tcp_for_write_queue(skb, sk) { 2146 if (skb == tcp_send_head(sk)) 2147 break; 2148 2149 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 2150 /* 2151 * Count the retransmission made on RTO correctly (only when 2152 * waiting for the first ACK and did not get it)... 2153 */ 2154 if ((tp->frto_counter == 1) && !(flag & FLAG_DATA_ACKED)) { 2155 /* For some reason this R-bit might get cleared? */ 2156 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) 2157 tp->retrans_out += tcp_skb_pcount(skb); 2158 /* ...enter this if branch just for the first segment */ 2159 flag |= FLAG_DATA_ACKED; 2160 } else { 2161 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2162 tp->undo_marker = 0; 2163 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 2164 } 2165 2166 /* Marking forward transmissions that were made after RTO lost 2167 * can cause unnecessary retransmissions in some scenarios, 2168 * SACK blocks will mitigate that in some but not in all cases. 2169 * We used to not mark them but it was causing break-ups with 2170 * receivers that do only in-order receival. 2171 * 2172 * TODO: we could detect presence of such receiver and select 2173 * different behavior per flow. 2174 */ 2175 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 2176 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 2177 tp->lost_out += tcp_skb_pcount(skb); 2178 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; 2179 } 2180 } 2181 tcp_verify_left_out(tp); 2182 2183 tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments; 2184 tp->snd_cwnd_cnt = 0; 2185 tp->snd_cwnd_stamp = tcp_time_stamp; 2186 tp->frto_counter = 0; 2187 tp->bytes_acked = 0; 2188 2189 tp->reordering = min_t(unsigned int, tp->reordering, 2190 sysctl_tcp_reordering); 2191 tcp_set_ca_state(sk, TCP_CA_Loss); 2192 tp->high_seq = tp->snd_nxt; 2193 TCP_ECN_queue_cwr(tp); 2194 2195 tcp_clear_all_retrans_hints(tp); 2196 } 2197 2198 static void tcp_clear_retrans_partial(struct tcp_sock *tp) 2199 { 2200 tp->retrans_out = 0; 2201 tp->lost_out = 0; 2202 2203 tp->undo_marker = 0; 2204 tp->undo_retrans = 0; 2205 } 2206 2207 void tcp_clear_retrans(struct tcp_sock *tp) 2208 { 2209 tcp_clear_retrans_partial(tp); 2210 2211 tp->fackets_out = 0; 2212 tp->sacked_out = 0; 2213 } 2214 2215 /* Enter Loss state. If "how" is not zero, forget all SACK information 2216 * and reset tags completely, otherwise preserve SACKs. If receiver 2217 * dropped its ofo queue, we will know this due to reneging detection. 2218 */ 2219 void tcp_enter_loss(struct sock *sk, int how) 2220 { 2221 const struct inet_connection_sock *icsk = inet_csk(sk); 2222 struct tcp_sock *tp = tcp_sk(sk); 2223 struct sk_buff *skb; 2224 2225 /* Reduce ssthresh if it has not yet been made inside this window. */ 2226 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq || 2227 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { 2228 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2229 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2230 tcp_ca_event(sk, CA_EVENT_LOSS); 2231 } 2232 tp->snd_cwnd = 1; 2233 tp->snd_cwnd_cnt = 0; 2234 tp->snd_cwnd_stamp = tcp_time_stamp; 2235 2236 tp->bytes_acked = 0; 2237 tcp_clear_retrans_partial(tp); 2238 2239 if (tcp_is_reno(tp)) 2240 tcp_reset_reno_sack(tp); 2241 2242 if (!how) { 2243 /* Push undo marker, if it was plain RTO and nothing 2244 * was retransmitted. */ 2245 tp->undo_marker = tp->snd_una; 2246 } else { 2247 tp->sacked_out = 0; 2248 tp->fackets_out = 0; 2249 } 2250 tcp_clear_all_retrans_hints(tp); 2251 2252 tcp_for_write_queue(skb, sk) { 2253 if (skb == tcp_send_head(sk)) 2254 break; 2255 2256 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2257 tp->undo_marker = 0; 2258 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; 2259 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { 2260 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; 2261 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 2262 tp->lost_out += tcp_skb_pcount(skb); 2263 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; 2264 } 2265 } 2266 tcp_verify_left_out(tp); 2267 2268 tp->reordering = min_t(unsigned int, tp->reordering, 2269 sysctl_tcp_reordering); 2270 tcp_set_ca_state(sk, TCP_CA_Loss); 2271 tp->high_seq = tp->snd_nxt; 2272 TCP_ECN_queue_cwr(tp); 2273 /* Abort F-RTO algorithm if one is in progress */ 2274 tp->frto_counter = 0; 2275 } 2276 2277 /* If ACK arrived pointing to a remembered SACK, it means that our 2278 * remembered SACKs do not reflect real state of receiver i.e. 2279 * receiver _host_ is heavily congested (or buggy). 2280 * 2281 * Do processing similar to RTO timeout. 2282 */ 2283 static int tcp_check_sack_reneging(struct sock *sk, int flag) 2284 { 2285 if (flag & FLAG_SACK_RENEGING) { 2286 struct inet_connection_sock *icsk = inet_csk(sk); 2287 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSACKRENEGING); 2288 2289 tcp_enter_loss(sk, 1); 2290 icsk->icsk_retransmits++; 2291 tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); 2292 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 2293 icsk->icsk_rto, TCP_RTO_MAX); 2294 return 1; 2295 } 2296 return 0; 2297 } 2298 2299 static inline int tcp_fackets_out(const struct tcp_sock *tp) 2300 { 2301 return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out; 2302 } 2303 2304 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs 2305 * counter when SACK is enabled (without SACK, sacked_out is used for 2306 * that purpose). 2307 * 2308 * Instead, with FACK TCP uses fackets_out that includes both SACKed 2309 * segments up to the highest received SACK block so far and holes in 2310 * between them. 2311 * 2312 * With reordering, holes may still be in flight, so RFC3517 recovery 2313 * uses pure sacked_out (total number of SACKed segments) even though 2314 * it violates the RFC that uses duplicate ACKs, often these are equal 2315 * but when e.g. out-of-window ACKs or packet duplication occurs, 2316 * they differ. Since neither occurs due to loss, TCP should really 2317 * ignore them. 2318 */ 2319 static inline int tcp_dupack_heuristics(const struct tcp_sock *tp) 2320 { 2321 return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1; 2322 } 2323 2324 static inline int tcp_skb_timedout(const struct sock *sk, 2325 const struct sk_buff *skb) 2326 { 2327 return tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto; 2328 } 2329 2330 static inline int tcp_head_timedout(const struct sock *sk) 2331 { 2332 const struct tcp_sock *tp = tcp_sk(sk); 2333 2334 return tp->packets_out && 2335 tcp_skb_timedout(sk, tcp_write_queue_head(sk)); 2336 } 2337 2338 /* Linux NewReno/SACK/FACK/ECN state machine. 2339 * -------------------------------------- 2340 * 2341 * "Open" Normal state, no dubious events, fast path. 2342 * "Disorder" In all the respects it is "Open", 2343 * but requires a bit more attention. It is entered when 2344 * we see some SACKs or dupacks. It is split of "Open" 2345 * mainly to move some processing from fast path to slow one. 2346 * "CWR" CWND was reduced due to some Congestion Notification event. 2347 * It can be ECN, ICMP source quench, local device congestion. 2348 * "Recovery" CWND was reduced, we are fast-retransmitting. 2349 * "Loss" CWND was reduced due to RTO timeout or SACK reneging. 2350 * 2351 * tcp_fastretrans_alert() is entered: 2352 * - each incoming ACK, if state is not "Open" 2353 * - when arrived ACK is unusual, namely: 2354 * * SACK 2355 * * Duplicate ACK. 2356 * * ECN ECE. 2357 * 2358 * Counting packets in flight is pretty simple. 2359 * 2360 * in_flight = packets_out - left_out + retrans_out 2361 * 2362 * packets_out is SND.NXT-SND.UNA counted in packets. 2363 * 2364 * retrans_out is number of retransmitted segments. 2365 * 2366 * left_out is number of segments left network, but not ACKed yet. 2367 * 2368 * left_out = sacked_out + lost_out 2369 * 2370 * sacked_out: Packets, which arrived to receiver out of order 2371 * and hence not ACKed. With SACKs this number is simply 2372 * amount of SACKed data. Even without SACKs 2373 * it is easy to give pretty reliable estimate of this number, 2374 * counting duplicate ACKs. 2375 * 2376 * lost_out: Packets lost by network. TCP has no explicit 2377 * "loss notification" feedback from network (for now). 2378 * It means that this number can be only _guessed_. 2379 * Actually, it is the heuristics to predict lossage that 2380 * distinguishes different algorithms. 2381 * 2382 * F.e. after RTO, when all the queue is considered as lost, 2383 * lost_out = packets_out and in_flight = retrans_out. 2384 * 2385 * Essentially, we have now two algorithms counting 2386 * lost packets. 2387 * 2388 * FACK: It is the simplest heuristics. As soon as we decided 2389 * that something is lost, we decide that _all_ not SACKed 2390 * packets until the most forward SACK are lost. I.e. 2391 * lost_out = fackets_out - sacked_out and left_out = fackets_out. 2392 * It is absolutely correct estimate, if network does not reorder 2393 * packets. And it loses any connection to reality when reordering 2394 * takes place. We use FACK by default until reordering 2395 * is suspected on the path to this destination. 2396 * 2397 * NewReno: when Recovery is entered, we assume that one segment 2398 * is lost (classic Reno). While we are in Recovery and 2399 * a partial ACK arrives, we assume that one more packet 2400 * is lost (NewReno). This heuristics are the same in NewReno 2401 * and SACK. 2402 * 2403 * Imagine, that's all! Forget about all this shamanism about CWND inflation 2404 * deflation etc. CWND is real congestion window, never inflated, changes 2405 * only according to classic VJ rules. 2406 * 2407 * Really tricky (and requiring careful tuning) part of algorithm 2408 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). 2409 * The first determines the moment _when_ we should reduce CWND and, 2410 * hence, slow down forward transmission. In fact, it determines the moment 2411 * when we decide that hole is caused by loss, rather than by a reorder. 2412 * 2413 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill 2414 * holes, caused by lost packets. 2415 * 2416 * And the most logically complicated part of algorithm is undo 2417 * heuristics. We detect false retransmits due to both too early 2418 * fast retransmit (reordering) and underestimated RTO, analyzing 2419 * timestamps and D-SACKs. When we detect that some segments were 2420 * retransmitted by mistake and CWND reduction was wrong, we undo 2421 * window reduction and abort recovery phase. This logic is hidden 2422 * inside several functions named tcp_try_undo_<something>. 2423 */ 2424 2425 /* This function decides, when we should leave Disordered state 2426 * and enter Recovery phase, reducing congestion window. 2427 * 2428 * Main question: may we further continue forward transmission 2429 * with the same cwnd? 2430 */ 2431 static int tcp_time_to_recover(struct sock *sk) 2432 { 2433 struct tcp_sock *tp = tcp_sk(sk); 2434 __u32 packets_out; 2435 2436 /* Do not perform any recovery during F-RTO algorithm */ 2437 if (tp->frto_counter) 2438 return 0; 2439 2440 /* Trick#1: The loss is proven. */ 2441 if (tp->lost_out) 2442 return 1; 2443 2444 /* Not-A-Trick#2 : Classic rule... */ 2445 if (tcp_dupack_heuristics(tp) > tp->reordering) 2446 return 1; 2447 2448 /* Trick#3 : when we use RFC2988 timer restart, fast 2449 * retransmit can be triggered by timeout of queue head. 2450 */ 2451 if (tcp_is_fack(tp) && tcp_head_timedout(sk)) 2452 return 1; 2453 2454 /* Trick#4: It is still not OK... But will it be useful to delay 2455 * recovery more? 2456 */ 2457 packets_out = tp->packets_out; 2458 if (packets_out <= tp->reordering && 2459 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && 2460 !tcp_may_send_now(sk)) { 2461 /* We have nothing to send. This connection is limited 2462 * either by receiver window or by application. 2463 */ 2464 return 1; 2465 } 2466 2467 /* If a thin stream is detected, retransmit after first 2468 * received dupack. Employ only if SACK is supported in order 2469 * to avoid possible corner-case series of spurious retransmissions 2470 * Use only if there are no unsent data. 2471 */ 2472 if ((tp->thin_dupack || sysctl_tcp_thin_dupack) && 2473 tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 && 2474 tcp_is_sack(tp) && !tcp_send_head(sk)) 2475 return 1; 2476 2477 return 0; 2478 } 2479 2480 /* New heuristics: it is possible only after we switched to restart timer 2481 * each time when something is ACKed. Hence, we can detect timed out packets 2482 * during fast retransmit without falling to slow start. 2483 * 2484 * Usefulness of this as is very questionable, since we should know which of 2485 * the segments is the next to timeout which is relatively expensive to find 2486 * in general case unless we add some data structure just for that. The 2487 * current approach certainly won't find the right one too often and when it 2488 * finally does find _something_ it usually marks large part of the window 2489 * right away (because a retransmission with a larger timestamp blocks the 2490 * loop from advancing). -ij 2491 */ 2492 static void tcp_timeout_skbs(struct sock *sk) 2493 { 2494 struct tcp_sock *tp = tcp_sk(sk); 2495 struct sk_buff *skb; 2496 2497 if (!tcp_is_fack(tp) || !tcp_head_timedout(sk)) 2498 return; 2499 2500 skb = tp->scoreboard_skb_hint; 2501 if (tp->scoreboard_skb_hint == NULL) 2502 skb = tcp_write_queue_head(sk); 2503 2504 tcp_for_write_queue_from(skb, sk) { 2505 if (skb == tcp_send_head(sk)) 2506 break; 2507 if (!tcp_skb_timedout(sk, skb)) 2508 break; 2509 2510 tcp_skb_mark_lost(tp, skb); 2511 } 2512 2513 tp->scoreboard_skb_hint = skb; 2514 2515 tcp_verify_left_out(tp); 2516 } 2517 2518 /* Mark head of queue up as lost. With RFC3517 SACK, the packets is 2519 * is against sacked "cnt", otherwise it's against facked "cnt" 2520 */ 2521 static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head) 2522 { 2523 struct tcp_sock *tp = tcp_sk(sk); 2524 struct sk_buff *skb; 2525 int cnt, oldcnt; 2526 int err; 2527 unsigned int mss; 2528 2529 WARN_ON(packets > tp->packets_out); 2530 if (tp->lost_skb_hint) { 2531 skb = tp->lost_skb_hint; 2532 cnt = tp->lost_cnt_hint; 2533 /* Head already handled? */ 2534 if (mark_head && skb != tcp_write_queue_head(sk)) 2535 return; 2536 } else { 2537 skb = tcp_write_queue_head(sk); 2538 cnt = 0; 2539 } 2540 2541 tcp_for_write_queue_from(skb, sk) { 2542 if (skb == tcp_send_head(sk)) 2543 break; 2544 /* TODO: do this better */ 2545 /* this is not the most efficient way to do this... */ 2546 tp->lost_skb_hint = skb; 2547 tp->lost_cnt_hint = cnt; 2548 2549 if (after(TCP_SKB_CB(skb)->end_seq, tp->high_seq)) 2550 break; 2551 2552 oldcnt = cnt; 2553 if (tcp_is_fack(tp) || tcp_is_reno(tp) || 2554 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 2555 cnt += tcp_skb_pcount(skb); 2556 2557 if (cnt > packets) { 2558 if ((tcp_is_sack(tp) && !tcp_is_fack(tp)) || 2559 (oldcnt >= packets)) 2560 break; 2561 2562 mss = skb_shinfo(skb)->gso_size; 2563 err = tcp_fragment(sk, skb, (packets - oldcnt) * mss, mss); 2564 if (err < 0) 2565 break; 2566 cnt = packets; 2567 } 2568 2569 tcp_skb_mark_lost(tp, skb); 2570 2571 if (mark_head) 2572 break; 2573 } 2574 tcp_verify_left_out(tp); 2575 } 2576 2577 /* Account newly detected lost packet(s) */ 2578 2579 static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit) 2580 { 2581 struct tcp_sock *tp = tcp_sk(sk); 2582 2583 if (tcp_is_reno(tp)) { 2584 tcp_mark_head_lost(sk, 1, 1); 2585 } else if (tcp_is_fack(tp)) { 2586 int lost = tp->fackets_out - tp->reordering; 2587 if (lost <= 0) 2588 lost = 1; 2589 tcp_mark_head_lost(sk, lost, 0); 2590 } else { 2591 int sacked_upto = tp->sacked_out - tp->reordering; 2592 if (sacked_upto >= 0) 2593 tcp_mark_head_lost(sk, sacked_upto, 0); 2594 else if (fast_rexmit) 2595 tcp_mark_head_lost(sk, 1, 1); 2596 } 2597 2598 tcp_timeout_skbs(sk); 2599 } 2600 2601 /* CWND moderation, preventing bursts due to too big ACKs 2602 * in dubious situations. 2603 */ 2604 static inline void tcp_moderate_cwnd(struct tcp_sock *tp) 2605 { 2606 tp->snd_cwnd = min(tp->snd_cwnd, 2607 tcp_packets_in_flight(tp) + tcp_max_burst(tp)); 2608 tp->snd_cwnd_stamp = tcp_time_stamp; 2609 } 2610 2611 /* Lower bound on congestion window is slow start threshold 2612 * unless congestion avoidance choice decides to overide it. 2613 */ 2614 static inline u32 tcp_cwnd_min(const struct sock *sk) 2615 { 2616 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; 2617 2618 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh; 2619 } 2620 2621 /* Decrease cwnd each second ack. */ 2622 static void tcp_cwnd_down(struct sock *sk, int flag) 2623 { 2624 struct tcp_sock *tp = tcp_sk(sk); 2625 int decr = tp->snd_cwnd_cnt + 1; 2626 2627 if ((flag & (FLAG_ANY_PROGRESS | FLAG_DSACKING_ACK)) || 2628 (tcp_is_reno(tp) && !(flag & FLAG_NOT_DUP))) { 2629 tp->snd_cwnd_cnt = decr & 1; 2630 decr >>= 1; 2631 2632 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk)) 2633 tp->snd_cwnd -= decr; 2634 2635 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1); 2636 tp->snd_cwnd_stamp = tcp_time_stamp; 2637 } 2638 } 2639 2640 /* Nothing was retransmitted or returned timestamp is less 2641 * than timestamp of the first retransmission. 2642 */ 2643 static inline int tcp_packet_delayed(const struct tcp_sock *tp) 2644 { 2645 return !tp->retrans_stamp || 2646 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 2647 before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp)); 2648 } 2649 2650 /* Undo procedures. */ 2651 2652 #if FASTRETRANS_DEBUG > 1 2653 static void DBGUNDO(struct sock *sk, const char *msg) 2654 { 2655 struct tcp_sock *tp = tcp_sk(sk); 2656 struct inet_sock *inet = inet_sk(sk); 2657 2658 if (sk->sk_family == AF_INET) { 2659 printk(KERN_DEBUG "Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n", 2660 msg, 2661 &inet->inet_daddr, ntohs(inet->inet_dport), 2662 tp->snd_cwnd, tcp_left_out(tp), 2663 tp->snd_ssthresh, tp->prior_ssthresh, 2664 tp->packets_out); 2665 } 2666 #if IS_ENABLED(CONFIG_IPV6) 2667 else if (sk->sk_family == AF_INET6) { 2668 struct ipv6_pinfo *np = inet6_sk(sk); 2669 printk(KERN_DEBUG "Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n", 2670 msg, 2671 &np->daddr, ntohs(inet->inet_dport), 2672 tp->snd_cwnd, tcp_left_out(tp), 2673 tp->snd_ssthresh, tp->prior_ssthresh, 2674 tp->packets_out); 2675 } 2676 #endif 2677 } 2678 #else 2679 #define DBGUNDO(x...) do { } while (0) 2680 #endif 2681 2682 static void tcp_undo_cwr(struct sock *sk, const bool undo_ssthresh) 2683 { 2684 struct tcp_sock *tp = tcp_sk(sk); 2685 2686 if (tp->prior_ssthresh) { 2687 const struct inet_connection_sock *icsk = inet_csk(sk); 2688 2689 if (icsk->icsk_ca_ops->undo_cwnd) 2690 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); 2691 else 2692 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1); 2693 2694 if (undo_ssthresh && tp->prior_ssthresh > tp->snd_ssthresh) { 2695 tp->snd_ssthresh = tp->prior_ssthresh; 2696 TCP_ECN_withdraw_cwr(tp); 2697 } 2698 } else { 2699 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); 2700 } 2701 tp->snd_cwnd_stamp = tcp_time_stamp; 2702 } 2703 2704 static inline int tcp_may_undo(const struct tcp_sock *tp) 2705 { 2706 return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp)); 2707 } 2708 2709 /* People celebrate: "We love our President!" */ 2710 static int tcp_try_undo_recovery(struct sock *sk) 2711 { 2712 struct tcp_sock *tp = tcp_sk(sk); 2713 2714 if (tcp_may_undo(tp)) { 2715 int mib_idx; 2716 2717 /* Happy end! We did not retransmit anything 2718 * or our original transmission succeeded. 2719 */ 2720 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); 2721 tcp_undo_cwr(sk, true); 2722 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) 2723 mib_idx = LINUX_MIB_TCPLOSSUNDO; 2724 else 2725 mib_idx = LINUX_MIB_TCPFULLUNDO; 2726 2727 NET_INC_STATS_BH(sock_net(sk), mib_idx); 2728 tp->undo_marker = 0; 2729 } 2730 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) { 2731 /* Hold old state until something *above* high_seq 2732 * is ACKed. For Reno it is MUST to prevent false 2733 * fast retransmits (RFC2582). SACK TCP is safe. */ 2734 tcp_moderate_cwnd(tp); 2735 return 1; 2736 } 2737 tcp_set_ca_state(sk, TCP_CA_Open); 2738 return 0; 2739 } 2740 2741 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ 2742 static void tcp_try_undo_dsack(struct sock *sk) 2743 { 2744 struct tcp_sock *tp = tcp_sk(sk); 2745 2746 if (tp->undo_marker && !tp->undo_retrans) { 2747 DBGUNDO(sk, "D-SACK"); 2748 tcp_undo_cwr(sk, true); 2749 tp->undo_marker = 0; 2750 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO); 2751 } 2752 } 2753 2754 /* We can clear retrans_stamp when there are no retransmissions in the 2755 * window. It would seem that it is trivially available for us in 2756 * tp->retrans_out, however, that kind of assumptions doesn't consider 2757 * what will happen if errors occur when sending retransmission for the 2758 * second time. ...It could the that such segment has only 2759 * TCPCB_EVER_RETRANS set at the present time. It seems that checking 2760 * the head skb is enough except for some reneging corner cases that 2761 * are not worth the effort. 2762 * 2763 * Main reason for all this complexity is the fact that connection dying 2764 * time now depends on the validity of the retrans_stamp, in particular, 2765 * that successive retransmissions of a segment must not advance 2766 * retrans_stamp under any conditions. 2767 */ 2768 static int tcp_any_retrans_done(const struct sock *sk) 2769 { 2770 const struct tcp_sock *tp = tcp_sk(sk); 2771 struct sk_buff *skb; 2772 2773 if (tp->retrans_out) 2774 return 1; 2775 2776 skb = tcp_write_queue_head(sk); 2777 if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS)) 2778 return 1; 2779 2780 return 0; 2781 } 2782 2783 /* Undo during fast recovery after partial ACK. */ 2784 2785 static int tcp_try_undo_partial(struct sock *sk, int acked) 2786 { 2787 struct tcp_sock *tp = tcp_sk(sk); 2788 /* Partial ACK arrived. Force Hoe's retransmit. */ 2789 int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering); 2790 2791 if (tcp_may_undo(tp)) { 2792 /* Plain luck! Hole if filled with delayed 2793 * packet, rather than with a retransmit. 2794 */ 2795 if (!tcp_any_retrans_done(sk)) 2796 tp->retrans_stamp = 0; 2797 2798 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1); 2799 2800 DBGUNDO(sk, "Hoe"); 2801 tcp_undo_cwr(sk, false); 2802 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO); 2803 2804 /* So... Do not make Hoe's retransmit yet. 2805 * If the first packet was delayed, the rest 2806 * ones are most probably delayed as well. 2807 */ 2808 failed = 0; 2809 } 2810 return failed; 2811 } 2812 2813 /* Undo during loss recovery after partial ACK. */ 2814 static int tcp_try_undo_loss(struct sock *sk) 2815 { 2816 struct tcp_sock *tp = tcp_sk(sk); 2817 2818 if (tcp_may_undo(tp)) { 2819 struct sk_buff *skb; 2820 tcp_for_write_queue(skb, sk) { 2821 if (skb == tcp_send_head(sk)) 2822 break; 2823 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 2824 } 2825 2826 tcp_clear_all_retrans_hints(tp); 2827 2828 DBGUNDO(sk, "partial loss"); 2829 tp->lost_out = 0; 2830 tcp_undo_cwr(sk, true); 2831 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO); 2832 inet_csk(sk)->icsk_retransmits = 0; 2833 tp->undo_marker = 0; 2834 if (tcp_is_sack(tp)) 2835 tcp_set_ca_state(sk, TCP_CA_Open); 2836 return 1; 2837 } 2838 return 0; 2839 } 2840 2841 static inline void tcp_complete_cwr(struct sock *sk) 2842 { 2843 struct tcp_sock *tp = tcp_sk(sk); 2844 2845 /* Do not moderate cwnd if it's already undone in cwr or recovery. */ 2846 if (tp->undo_marker) { 2847 if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR) 2848 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 2849 else /* PRR */ 2850 tp->snd_cwnd = tp->snd_ssthresh; 2851 tp->snd_cwnd_stamp = tcp_time_stamp; 2852 } 2853 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); 2854 } 2855 2856 static void tcp_try_keep_open(struct sock *sk) 2857 { 2858 struct tcp_sock *tp = tcp_sk(sk); 2859 int state = TCP_CA_Open; 2860 2861 if (tcp_left_out(tp) || tcp_any_retrans_done(sk)) 2862 state = TCP_CA_Disorder; 2863 2864 if (inet_csk(sk)->icsk_ca_state != state) { 2865 tcp_set_ca_state(sk, state); 2866 tp->high_seq = tp->snd_nxt; 2867 } 2868 } 2869 2870 static void tcp_try_to_open(struct sock *sk, int flag) 2871 { 2872 struct tcp_sock *tp = tcp_sk(sk); 2873 2874 tcp_verify_left_out(tp); 2875 2876 if (!tp->frto_counter && !tcp_any_retrans_done(sk)) 2877 tp->retrans_stamp = 0; 2878 2879 if (flag & FLAG_ECE) 2880 tcp_enter_cwr(sk, 1); 2881 2882 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { 2883 tcp_try_keep_open(sk); 2884 if (inet_csk(sk)->icsk_ca_state != TCP_CA_Open) 2885 tcp_moderate_cwnd(tp); 2886 } else { 2887 tcp_cwnd_down(sk, flag); 2888 } 2889 } 2890 2891 static void tcp_mtup_probe_failed(struct sock *sk) 2892 { 2893 struct inet_connection_sock *icsk = inet_csk(sk); 2894 2895 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; 2896 icsk->icsk_mtup.probe_size = 0; 2897 } 2898 2899 static void tcp_mtup_probe_success(struct sock *sk) 2900 { 2901 struct tcp_sock *tp = tcp_sk(sk); 2902 struct inet_connection_sock *icsk = inet_csk(sk); 2903 2904 /* FIXME: breaks with very large cwnd */ 2905 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2906 tp->snd_cwnd = tp->snd_cwnd * 2907 tcp_mss_to_mtu(sk, tp->mss_cache) / 2908 icsk->icsk_mtup.probe_size; 2909 tp->snd_cwnd_cnt = 0; 2910 tp->snd_cwnd_stamp = tcp_time_stamp; 2911 tp->snd_ssthresh = tcp_current_ssthresh(sk); 2912 2913 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; 2914 icsk->icsk_mtup.probe_size = 0; 2915 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 2916 } 2917 2918 /* Do a simple retransmit without using the backoff mechanisms in 2919 * tcp_timer. This is used for path mtu discovery. 2920 * The socket is already locked here. 2921 */ 2922 void tcp_simple_retransmit(struct sock *sk) 2923 { 2924 const struct inet_connection_sock *icsk = inet_csk(sk); 2925 struct tcp_sock *tp = tcp_sk(sk); 2926 struct sk_buff *skb; 2927 unsigned int mss = tcp_current_mss(sk); 2928 u32 prior_lost = tp->lost_out; 2929 2930 tcp_for_write_queue(skb, sk) { 2931 if (skb == tcp_send_head(sk)) 2932 break; 2933 if (tcp_skb_seglen(skb) > mss && 2934 !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 2935 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 2936 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 2937 tp->retrans_out -= tcp_skb_pcount(skb); 2938 } 2939 tcp_skb_mark_lost_uncond_verify(tp, skb); 2940 } 2941 } 2942 2943 tcp_clear_retrans_hints_partial(tp); 2944 2945 if (prior_lost == tp->lost_out) 2946 return; 2947 2948 if (tcp_is_reno(tp)) 2949 tcp_limit_reno_sacked(tp); 2950 2951 tcp_verify_left_out(tp); 2952 2953 /* Don't muck with the congestion window here. 2954 * Reason is that we do not increase amount of _data_ 2955 * in network, but units changed and effective 2956 * cwnd/ssthresh really reduced now. 2957 */ 2958 if (icsk->icsk_ca_state != TCP_CA_Loss) { 2959 tp->high_seq = tp->snd_nxt; 2960 tp->snd_ssthresh = tcp_current_ssthresh(sk); 2961 tp->prior_ssthresh = 0; 2962 tp->undo_marker = 0; 2963 tcp_set_ca_state(sk, TCP_CA_Loss); 2964 } 2965 tcp_xmit_retransmit_queue(sk); 2966 } 2967 EXPORT_SYMBOL(tcp_simple_retransmit); 2968 2969 /* This function implements the PRR algorithm, specifcally the PRR-SSRB 2970 * (proportional rate reduction with slow start reduction bound) as described in 2971 * http://www.ietf.org/id/draft-mathis-tcpm-proportional-rate-reduction-01.txt. 2972 * It computes the number of packets to send (sndcnt) based on packets newly 2973 * delivered: 2974 * 1) If the packets in flight is larger than ssthresh, PRR spreads the 2975 * cwnd reductions across a full RTT. 2976 * 2) If packets in flight is lower than ssthresh (such as due to excess 2977 * losses and/or application stalls), do not perform any further cwnd 2978 * reductions, but instead slow start up to ssthresh. 2979 */ 2980 static void tcp_update_cwnd_in_recovery(struct sock *sk, int newly_acked_sacked, 2981 int fast_rexmit, int flag) 2982 { 2983 struct tcp_sock *tp = tcp_sk(sk); 2984 int sndcnt = 0; 2985 int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp); 2986 2987 if (tcp_packets_in_flight(tp) > tp->snd_ssthresh) { 2988 u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered + 2989 tp->prior_cwnd - 1; 2990 sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out; 2991 } else { 2992 sndcnt = min_t(int, delta, 2993 max_t(int, tp->prr_delivered - tp->prr_out, 2994 newly_acked_sacked) + 1); 2995 } 2996 2997 sndcnt = max(sndcnt, (fast_rexmit ? 1 : 0)); 2998 tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt; 2999 } 3000 3001 /* Process an event, which can update packets-in-flight not trivially. 3002 * Main goal of this function is to calculate new estimate for left_out, 3003 * taking into account both packets sitting in receiver's buffer and 3004 * packets lost by network. 3005 * 3006 * Besides that it does CWND reduction, when packet loss is detected 3007 * and changes state of machine. 3008 * 3009 * It does _not_ decide what to send, it is made in function 3010 * tcp_xmit_retransmit_queue(). 3011 */ 3012 static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, 3013 int newly_acked_sacked, bool is_dupack, 3014 int flag) 3015 { 3016 struct inet_connection_sock *icsk = inet_csk(sk); 3017 struct tcp_sock *tp = tcp_sk(sk); 3018 int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) && 3019 (tcp_fackets_out(tp) > tp->reordering)); 3020 int fast_rexmit = 0, mib_idx; 3021 3022 if (WARN_ON(!tp->packets_out && tp->sacked_out)) 3023 tp->sacked_out = 0; 3024 if (WARN_ON(!tp->sacked_out && tp->fackets_out)) 3025 tp->fackets_out = 0; 3026 3027 /* Now state machine starts. 3028 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ 3029 if (flag & FLAG_ECE) 3030 tp->prior_ssthresh = 0; 3031 3032 /* B. In all the states check for reneging SACKs. */ 3033 if (tcp_check_sack_reneging(sk, flag)) 3034 return; 3035 3036 /* C. Process data loss notification, provided it is valid. */ 3037 if (tcp_is_fack(tp) && (flag & FLAG_DATA_LOST) && 3038 before(tp->snd_una, tp->high_seq) && 3039 icsk->icsk_ca_state != TCP_CA_Open && 3040 tp->fackets_out > tp->reordering) { 3041 tcp_mark_head_lost(sk, tp->fackets_out - tp->reordering, 0); 3042 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSS); 3043 } 3044 3045 /* D. Check consistency of the current state. */ 3046 tcp_verify_left_out(tp); 3047 3048 /* E. Check state exit conditions. State can be terminated 3049 * when high_seq is ACKed. */ 3050 if (icsk->icsk_ca_state == TCP_CA_Open) { 3051 WARN_ON(tp->retrans_out != 0); 3052 tp->retrans_stamp = 0; 3053 } else if (!before(tp->snd_una, tp->high_seq)) { 3054 switch (icsk->icsk_ca_state) { 3055 case TCP_CA_Loss: 3056 icsk->icsk_retransmits = 0; 3057 if (tcp_try_undo_recovery(sk)) 3058 return; 3059 break; 3060 3061 case TCP_CA_CWR: 3062 /* CWR is to be held something *above* high_seq 3063 * is ACKed for CWR bit to reach receiver. */ 3064 if (tp->snd_una != tp->high_seq) { 3065 tcp_complete_cwr(sk); 3066 tcp_set_ca_state(sk, TCP_CA_Open); 3067 } 3068 break; 3069 3070 case TCP_CA_Recovery: 3071 if (tcp_is_reno(tp)) 3072 tcp_reset_reno_sack(tp); 3073 if (tcp_try_undo_recovery(sk)) 3074 return; 3075 tcp_complete_cwr(sk); 3076 break; 3077 } 3078 } 3079 3080 /* F. Process state. */ 3081 switch (icsk->icsk_ca_state) { 3082 case TCP_CA_Recovery: 3083 if (!(flag & FLAG_SND_UNA_ADVANCED)) { 3084 if (tcp_is_reno(tp) && is_dupack) 3085 tcp_add_reno_sack(sk); 3086 } else 3087 do_lost = tcp_try_undo_partial(sk, pkts_acked); 3088 break; 3089 case TCP_CA_Loss: 3090 if (flag & FLAG_DATA_ACKED) 3091 icsk->icsk_retransmits = 0; 3092 if (tcp_is_reno(tp) && flag & FLAG_SND_UNA_ADVANCED) 3093 tcp_reset_reno_sack(tp); 3094 if (!tcp_try_undo_loss(sk)) { 3095 tcp_moderate_cwnd(tp); 3096 tcp_xmit_retransmit_queue(sk); 3097 return; 3098 } 3099 if (icsk->icsk_ca_state != TCP_CA_Open) 3100 return; 3101 /* Loss is undone; fall through to processing in Open state. */ 3102 default: 3103 if (tcp_is_reno(tp)) { 3104 if (flag & FLAG_SND_UNA_ADVANCED) 3105 tcp_reset_reno_sack(tp); 3106 if (is_dupack) 3107 tcp_add_reno_sack(sk); 3108 } 3109 3110 if (icsk->icsk_ca_state <= TCP_CA_Disorder) 3111 tcp_try_undo_dsack(sk); 3112 3113 if (!tcp_time_to_recover(sk)) { 3114 tcp_try_to_open(sk, flag); 3115 return; 3116 } 3117 3118 /* MTU probe failure: don't reduce cwnd */ 3119 if (icsk->icsk_ca_state < TCP_CA_CWR && 3120 icsk->icsk_mtup.probe_size && 3121 tp->snd_una == tp->mtu_probe.probe_seq_start) { 3122 tcp_mtup_probe_failed(sk); 3123 /* Restores the reduction we did in tcp_mtup_probe() */ 3124 tp->snd_cwnd++; 3125 tcp_simple_retransmit(sk); 3126 return; 3127 } 3128 3129 /* Otherwise enter Recovery state */ 3130 3131 if (tcp_is_reno(tp)) 3132 mib_idx = LINUX_MIB_TCPRENORECOVERY; 3133 else 3134 mib_idx = LINUX_MIB_TCPSACKRECOVERY; 3135 3136 NET_INC_STATS_BH(sock_net(sk), mib_idx); 3137 3138 tp->high_seq = tp->snd_nxt; 3139 tp->prior_ssthresh = 0; 3140 tp->undo_marker = tp->snd_una; 3141 tp->undo_retrans = tp->retrans_out; 3142 3143 if (icsk->icsk_ca_state < TCP_CA_CWR) { 3144 if (!(flag & FLAG_ECE)) 3145 tp->prior_ssthresh = tcp_current_ssthresh(sk); 3146 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 3147 TCP_ECN_queue_cwr(tp); 3148 } 3149 3150 tp->bytes_acked = 0; 3151 tp->snd_cwnd_cnt = 0; 3152 tp->prior_cwnd = tp->snd_cwnd; 3153 tp->prr_delivered = 0; 3154 tp->prr_out = 0; 3155 tcp_set_ca_state(sk, TCP_CA_Recovery); 3156 fast_rexmit = 1; 3157 } 3158 3159 if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk))) 3160 tcp_update_scoreboard(sk, fast_rexmit); 3161 tp->prr_delivered += newly_acked_sacked; 3162 tcp_update_cwnd_in_recovery(sk, newly_acked_sacked, fast_rexmit, flag); 3163 tcp_xmit_retransmit_queue(sk); 3164 } 3165 3166 void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt) 3167 { 3168 tcp_rtt_estimator(sk, seq_rtt); 3169 tcp_set_rto(sk); 3170 inet_csk(sk)->icsk_backoff = 0; 3171 } 3172 EXPORT_SYMBOL(tcp_valid_rtt_meas); 3173 3174 /* Read draft-ietf-tcplw-high-performance before mucking 3175 * with this code. (Supersedes RFC1323) 3176 */ 3177 static void tcp_ack_saw_tstamp(struct sock *sk, int flag) 3178 { 3179 /* RTTM Rule: A TSecr value received in a segment is used to 3180 * update the averaged RTT measurement only if the segment 3181 * acknowledges some new data, i.e., only if it advances the 3182 * left edge of the send window. 3183 * 3184 * See draft-ietf-tcplw-high-performance-00, section 3.3. 3185 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> 3186 * 3187 * Changed: reset backoff as soon as we see the first valid sample. 3188 * If we do not, we get strongly overestimated rto. With timestamps 3189 * samples are accepted even from very old segments: f.e., when rtt=1 3190 * increases to 8, we retransmit 5 times and after 8 seconds delayed 3191 * answer arrives rto becomes 120 seconds! If at least one of segments 3192 * in window is lost... Voila. --ANK (010210) 3193 */ 3194 struct tcp_sock *tp = tcp_sk(sk); 3195 3196 tcp_valid_rtt_meas(sk, tcp_time_stamp - tp->rx_opt.rcv_tsecr); 3197 } 3198 3199 static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag) 3200 { 3201 /* We don't have a timestamp. Can only use 3202 * packets that are not retransmitted to determine 3203 * rtt estimates. Also, we must not reset the 3204 * backoff for rto until we get a non-retransmitted 3205 * packet. This allows us to deal with a situation 3206 * where the network delay has increased suddenly. 3207 * I.e. Karn's algorithm. (SIGCOMM '87, p5.) 3208 */ 3209 3210 if (flag & FLAG_RETRANS_DATA_ACKED) 3211 return; 3212 3213 tcp_valid_rtt_meas(sk, seq_rtt); 3214 } 3215 3216 static inline void tcp_ack_update_rtt(struct sock *sk, const int flag, 3217 const s32 seq_rtt) 3218 { 3219 const struct tcp_sock *tp = tcp_sk(sk); 3220 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ 3221 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) 3222 tcp_ack_saw_tstamp(sk, flag); 3223 else if (seq_rtt >= 0) 3224 tcp_ack_no_tstamp(sk, seq_rtt, flag); 3225 } 3226 3227 static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) 3228 { 3229 const struct inet_connection_sock *icsk = inet_csk(sk); 3230 icsk->icsk_ca_ops->cong_avoid(sk, ack, in_flight); 3231 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp; 3232 } 3233 3234 /* Restart timer after forward progress on connection. 3235 * RFC2988 recommends to restart timer to now+rto. 3236 */ 3237 static void tcp_rearm_rto(struct sock *sk) 3238 { 3239 const struct tcp_sock *tp = tcp_sk(sk); 3240 3241 if (!tp->packets_out) { 3242 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); 3243 } else { 3244 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 3245 inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 3246 } 3247 } 3248 3249 /* If we get here, the whole TSO packet has not been acked. */ 3250 static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb) 3251 { 3252 struct tcp_sock *tp = tcp_sk(sk); 3253 u32 packets_acked; 3254 3255 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)); 3256 3257 packets_acked = tcp_skb_pcount(skb); 3258 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) 3259 return 0; 3260 packets_acked -= tcp_skb_pcount(skb); 3261 3262 if (packets_acked) { 3263 BUG_ON(tcp_skb_pcount(skb) == 0); 3264 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)); 3265 } 3266 3267 return packets_acked; 3268 } 3269 3270 /* Remove acknowledged frames from the retransmission queue. If our packet 3271 * is before the ack sequence we can discard it as it's confirmed to have 3272 * arrived at the other end. 3273 */ 3274 static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets, 3275 u32 prior_snd_una) 3276 { 3277 struct tcp_sock *tp = tcp_sk(sk); 3278 const struct inet_connection_sock *icsk = inet_csk(sk); 3279 struct sk_buff *skb; 3280 u32 now = tcp_time_stamp; 3281 int fully_acked = 1; 3282 int flag = 0; 3283 u32 pkts_acked = 0; 3284 u32 reord = tp->packets_out; 3285 u32 prior_sacked = tp->sacked_out; 3286 s32 seq_rtt = -1; 3287 s32 ca_seq_rtt = -1; 3288 ktime_t last_ackt = net_invalid_timestamp(); 3289 3290 while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) { 3291 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 3292 u32 acked_pcount; 3293 u8 sacked = scb->sacked; 3294 3295 /* Determine how many packets and what bytes were acked, tso and else */ 3296 if (after(scb->end_seq, tp->snd_una)) { 3297 if (tcp_skb_pcount(skb) == 1 || 3298 !after(tp->snd_una, scb->seq)) 3299 break; 3300 3301 acked_pcount = tcp_tso_acked(sk, skb); 3302 if (!acked_pcount) 3303 break; 3304 3305 fully_acked = 0; 3306 } else { 3307 acked_pcount = tcp_skb_pcount(skb); 3308 } 3309 3310 if (sacked & TCPCB_RETRANS) { 3311 if (sacked & TCPCB_SACKED_RETRANS) 3312 tp->retrans_out -= acked_pcount; 3313 flag |= FLAG_RETRANS_DATA_ACKED; 3314 ca_seq_rtt = -1; 3315 seq_rtt = -1; 3316 if ((flag & FLAG_DATA_ACKED) || (acked_pcount > 1)) 3317 flag |= FLAG_NONHEAD_RETRANS_ACKED; 3318 } else { 3319 ca_seq_rtt = now - scb->when; 3320 last_ackt = skb->tstamp; 3321 if (seq_rtt < 0) { 3322 seq_rtt = ca_seq_rtt; 3323 } 3324 if (!(sacked & TCPCB_SACKED_ACKED)) 3325 reord = min(pkts_acked, reord); 3326 } 3327 3328 if (sacked & TCPCB_SACKED_ACKED) 3329 tp->sacked_out -= acked_pcount; 3330 if (sacked & TCPCB_LOST) 3331 tp->lost_out -= acked_pcount; 3332 3333 tp->packets_out -= acked_pcount; 3334 pkts_acked += acked_pcount; 3335 3336 /* Initial outgoing SYN's get put onto the write_queue 3337 * just like anything else we transmit. It is not 3338 * true data, and if we misinform our callers that 3339 * this ACK acks real data, we will erroneously exit 3340 * connection startup slow start one packet too 3341 * quickly. This is severely frowned upon behavior. 3342 */ 3343 if (!(scb->tcp_flags & TCPHDR_SYN)) { 3344 flag |= FLAG_DATA_ACKED; 3345 } else { 3346 flag |= FLAG_SYN_ACKED; 3347 tp->retrans_stamp = 0; 3348 } 3349 3350 if (!fully_acked) 3351 break; 3352 3353 tcp_unlink_write_queue(skb, sk); 3354 sk_wmem_free_skb(sk, skb); 3355 tp->scoreboard_skb_hint = NULL; 3356 if (skb == tp->retransmit_skb_hint) 3357 tp->retransmit_skb_hint = NULL; 3358 if (skb == tp->lost_skb_hint) 3359 tp->lost_skb_hint = NULL; 3360 } 3361 3362 if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una))) 3363 tp->snd_up = tp->snd_una; 3364 3365 if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 3366 flag |= FLAG_SACK_RENEGING; 3367 3368 if (flag & FLAG_ACKED) { 3369 const struct tcp_congestion_ops *ca_ops 3370 = inet_csk(sk)->icsk_ca_ops; 3371 3372 if (unlikely(icsk->icsk_mtup.probe_size && 3373 !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) { 3374 tcp_mtup_probe_success(sk); 3375 } 3376 3377 tcp_ack_update_rtt(sk, flag, seq_rtt); 3378 tcp_rearm_rto(sk); 3379 3380 if (tcp_is_reno(tp)) { 3381 tcp_remove_reno_sacks(sk, pkts_acked); 3382 } else { 3383 int delta; 3384 3385 /* Non-retransmitted hole got filled? That's reordering */ 3386 if (reord < prior_fackets) 3387 tcp_update_reordering(sk, tp->fackets_out - reord, 0); 3388 3389 delta = tcp_is_fack(tp) ? pkts_acked : 3390 prior_sacked - tp->sacked_out; 3391 tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta); 3392 } 3393 3394 tp->fackets_out -= min(pkts_acked, tp->fackets_out); 3395 3396 if (ca_ops->pkts_acked) { 3397 s32 rtt_us = -1; 3398 3399 /* Is the ACK triggering packet unambiguous? */ 3400 if (!(flag & FLAG_RETRANS_DATA_ACKED)) { 3401 /* High resolution needed and available? */ 3402 if (ca_ops->flags & TCP_CONG_RTT_STAMP && 3403 !ktime_equal(last_ackt, 3404 net_invalid_timestamp())) 3405 rtt_us = ktime_us_delta(ktime_get_real(), 3406 last_ackt); 3407 else if (ca_seq_rtt >= 0) 3408 rtt_us = jiffies_to_usecs(ca_seq_rtt); 3409 } 3410 3411 ca_ops->pkts_acked(sk, pkts_acked, rtt_us); 3412 } 3413 } 3414 3415 #if FASTRETRANS_DEBUG > 0 3416 WARN_ON((int)tp->sacked_out < 0); 3417 WARN_ON((int)tp->lost_out < 0); 3418 WARN_ON((int)tp->retrans_out < 0); 3419 if (!tp->packets_out && tcp_is_sack(tp)) { 3420 icsk = inet_csk(sk); 3421 if (tp->lost_out) { 3422 printk(KERN_DEBUG "Leak l=%u %d\n", 3423 tp->lost_out, icsk->icsk_ca_state); 3424 tp->lost_out = 0; 3425 } 3426 if (tp->sacked_out) { 3427 printk(KERN_DEBUG "Leak s=%u %d\n", 3428 tp->sacked_out, icsk->icsk_ca_state); 3429 tp->sacked_out = 0; 3430 } 3431 if (tp->retrans_out) { 3432 printk(KERN_DEBUG "Leak r=%u %d\n", 3433 tp->retrans_out, icsk->icsk_ca_state); 3434 tp->retrans_out = 0; 3435 } 3436 } 3437 #endif 3438 return flag; 3439 } 3440 3441 static void tcp_ack_probe(struct sock *sk) 3442 { 3443 const struct tcp_sock *tp = tcp_sk(sk); 3444 struct inet_connection_sock *icsk = inet_csk(sk); 3445 3446 /* Was it a usable window open? */ 3447 3448 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) { 3449 icsk->icsk_backoff = 0; 3450 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0); 3451 /* Socket must be waked up by subsequent tcp_data_snd_check(). 3452 * This function is not for random using! 3453 */ 3454 } else { 3455 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 3456 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), 3457 TCP_RTO_MAX); 3458 } 3459 } 3460 3461 static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag) 3462 { 3463 return !(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || 3464 inet_csk(sk)->icsk_ca_state != TCP_CA_Open; 3465 } 3466 3467 static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag) 3468 { 3469 const struct tcp_sock *tp = tcp_sk(sk); 3470 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) && 3471 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR)); 3472 } 3473 3474 /* Check that window update is acceptable. 3475 * The function assumes that snd_una<=ack<=snd_next. 3476 */ 3477 static inline int tcp_may_update_window(const struct tcp_sock *tp, 3478 const u32 ack, const u32 ack_seq, 3479 const u32 nwin) 3480 { 3481 return after(ack, tp->snd_una) || 3482 after(ack_seq, tp->snd_wl1) || 3483 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd); 3484 } 3485 3486 /* Update our send window. 3487 * 3488 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 3489 * and in FreeBSD. NetBSD's one is even worse.) is wrong. 3490 */ 3491 static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32 ack, 3492 u32 ack_seq) 3493 { 3494 struct tcp_sock *tp = tcp_sk(sk); 3495 int flag = 0; 3496 u32 nwin = ntohs(tcp_hdr(skb)->window); 3497 3498 if (likely(!tcp_hdr(skb)->syn)) 3499 nwin <<= tp->rx_opt.snd_wscale; 3500 3501 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { 3502 flag |= FLAG_WIN_UPDATE; 3503 tcp_update_wl(tp, ack_seq); 3504 3505 if (tp->snd_wnd != nwin) { 3506 tp->snd_wnd = nwin; 3507 3508 /* Note, it is the only place, where 3509 * fast path is recovered for sending TCP. 3510 */ 3511 tp->pred_flags = 0; 3512 tcp_fast_path_check(sk); 3513 3514 if (nwin > tp->max_window) { 3515 tp->max_window = nwin; 3516 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie); 3517 } 3518 } 3519 } 3520 3521 tp->snd_una = ack; 3522 3523 return flag; 3524 } 3525 3526 /* A very conservative spurious RTO response algorithm: reduce cwnd and 3527 * continue in congestion avoidance. 3528 */ 3529 static void tcp_conservative_spur_to_response(struct tcp_sock *tp) 3530 { 3531 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 3532 tp->snd_cwnd_cnt = 0; 3533 tp->bytes_acked = 0; 3534 TCP_ECN_queue_cwr(tp); 3535 tcp_moderate_cwnd(tp); 3536 } 3537 3538 /* A conservative spurious RTO response algorithm: reduce cwnd using 3539 * rate halving and continue in congestion avoidance. 3540 */ 3541 static void tcp_ratehalving_spur_to_response(struct sock *sk) 3542 { 3543 tcp_enter_cwr(sk, 0); 3544 } 3545 3546 static void tcp_undo_spur_to_response(struct sock *sk, int flag) 3547 { 3548 if (flag & FLAG_ECE) 3549 tcp_ratehalving_spur_to_response(sk); 3550 else 3551 tcp_undo_cwr(sk, true); 3552 } 3553 3554 /* F-RTO spurious RTO detection algorithm (RFC4138) 3555 * 3556 * F-RTO affects during two new ACKs following RTO (well, almost, see inline 3557 * comments). State (ACK number) is kept in frto_counter. When ACK advances 3558 * window (but not to or beyond highest sequence sent before RTO): 3559 * On First ACK, send two new segments out. 3560 * On Second ACK, RTO was likely spurious. Do spurious response (response 3561 * algorithm is not part of the F-RTO detection algorithm 3562 * given in RFC4138 but can be selected separately). 3563 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss 3564 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding 3565 * of Nagle, this is done using frto_counter states 2 and 3, when a new data 3566 * segment of any size sent during F-RTO, state 2 is upgraded to 3. 3567 * 3568 * Rationale: if the RTO was spurious, new ACKs should arrive from the 3569 * original window even after we transmit two new data segments. 3570 * 3571 * SACK version: 3572 * on first step, wait until first cumulative ACK arrives, then move to 3573 * the second step. In second step, the next ACK decides. 3574 * 3575 * F-RTO is implemented (mainly) in four functions: 3576 * - tcp_use_frto() is used to determine if TCP is can use F-RTO 3577 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is 3578 * called when tcp_use_frto() showed green light 3579 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm 3580 * - tcp_enter_frto_loss() is called if there is not enough evidence 3581 * to prove that the RTO is indeed spurious. It transfers the control 3582 * from F-RTO to the conventional RTO recovery 3583 */ 3584 static int tcp_process_frto(struct sock *sk, int flag) 3585 { 3586 struct tcp_sock *tp = tcp_sk(sk); 3587 3588 tcp_verify_left_out(tp); 3589 3590 /* Duplicate the behavior from Loss state (fastretrans_alert) */ 3591 if (flag & FLAG_DATA_ACKED) 3592 inet_csk(sk)->icsk_retransmits = 0; 3593 3594 if ((flag & FLAG_NONHEAD_RETRANS_ACKED) || 3595 ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED))) 3596 tp->undo_marker = 0; 3597 3598 if (!before(tp->snd_una, tp->frto_highmark)) { 3599 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag); 3600 return 1; 3601 } 3602 3603 if (!tcp_is_sackfrto(tp)) { 3604 /* RFC4138 shortcoming in step 2; should also have case c): 3605 * ACK isn't duplicate nor advances window, e.g., opposite dir 3606 * data, winupdate 3607 */ 3608 if (!(flag & FLAG_ANY_PROGRESS) && (flag & FLAG_NOT_DUP)) 3609 return 1; 3610 3611 if (!(flag & FLAG_DATA_ACKED)) { 3612 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3), 3613 flag); 3614 return 1; 3615 } 3616 } else { 3617 if (!(flag & FLAG_DATA_ACKED) && (tp->frto_counter == 1)) { 3618 /* Prevent sending of new data. */ 3619 tp->snd_cwnd = min(tp->snd_cwnd, 3620 tcp_packets_in_flight(tp)); 3621 return 1; 3622 } 3623 3624 if ((tp->frto_counter >= 2) && 3625 (!(flag & FLAG_FORWARD_PROGRESS) || 3626 ((flag & FLAG_DATA_SACKED) && 3627 !(flag & FLAG_ONLY_ORIG_SACKED)))) { 3628 /* RFC4138 shortcoming (see comment above) */ 3629 if (!(flag & FLAG_FORWARD_PROGRESS) && 3630 (flag & FLAG_NOT_DUP)) 3631 return 1; 3632 3633 tcp_enter_frto_loss(sk, 3, flag); 3634 return 1; 3635 } 3636 } 3637 3638 if (tp->frto_counter == 1) { 3639 /* tcp_may_send_now needs to see updated state */ 3640 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; 3641 tp->frto_counter = 2; 3642 3643 if (!tcp_may_send_now(sk)) 3644 tcp_enter_frto_loss(sk, 2, flag); 3645 3646 return 1; 3647 } else { 3648 switch (sysctl_tcp_frto_response) { 3649 case 2: 3650 tcp_undo_spur_to_response(sk, flag); 3651 break; 3652 case 1: 3653 tcp_conservative_spur_to_response(tp); 3654 break; 3655 default: 3656 tcp_ratehalving_spur_to_response(sk); 3657 break; 3658 } 3659 tp->frto_counter = 0; 3660 tp->undo_marker = 0; 3661 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSPURIOUSRTOS); 3662 } 3663 return 0; 3664 } 3665 3666 /* This routine deals with incoming acks, but not outgoing ones. */ 3667 static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) 3668 { 3669 struct inet_connection_sock *icsk = inet_csk(sk); 3670 struct tcp_sock *tp = tcp_sk(sk); 3671 u32 prior_snd_una = tp->snd_una; 3672 u32 ack_seq = TCP_SKB_CB(skb)->seq; 3673 u32 ack = TCP_SKB_CB(skb)->ack_seq; 3674 bool is_dupack = false; 3675 u32 prior_in_flight; 3676 u32 prior_fackets; 3677 int prior_packets; 3678 int prior_sacked = tp->sacked_out; 3679 int pkts_acked = 0; 3680 int newly_acked_sacked = 0; 3681 int frto_cwnd = 0; 3682 3683 /* If the ack is older than previous acks 3684 * then we can probably ignore it. 3685 */ 3686 if (before(ack, prior_snd_una)) 3687 goto old_ack; 3688 3689 /* If the ack includes data we haven't sent yet, discard 3690 * this segment (RFC793 Section 3.9). 3691 */ 3692 if (after(ack, tp->snd_nxt)) 3693 goto invalid_ack; 3694 3695 if (after(ack, prior_snd_una)) 3696 flag |= FLAG_SND_UNA_ADVANCED; 3697 3698 if (sysctl_tcp_abc) { 3699 if (icsk->icsk_ca_state < TCP_CA_CWR) 3700 tp->bytes_acked += ack - prior_snd_una; 3701 else if (icsk->icsk_ca_state == TCP_CA_Loss) 3702 /* we assume just one segment left network */ 3703 tp->bytes_acked += min(ack - prior_snd_una, 3704 tp->mss_cache); 3705 } 3706 3707 prior_fackets = tp->fackets_out; 3708 prior_in_flight = tcp_packets_in_flight(tp); 3709 3710 if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) { 3711 /* Window is constant, pure forward advance. 3712 * No more checks are required. 3713 * Note, we use the fact that SND.UNA>=SND.WL2. 3714 */ 3715 tcp_update_wl(tp, ack_seq); 3716 tp->snd_una = ack; 3717 flag |= FLAG_WIN_UPDATE; 3718 3719 tcp_ca_event(sk, CA_EVENT_FAST_ACK); 3720 3721 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS); 3722 } else { 3723 if (ack_seq != TCP_SKB_CB(skb)->end_seq) 3724 flag |= FLAG_DATA; 3725 else 3726 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPUREACKS); 3727 3728 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq); 3729 3730 if (TCP_SKB_CB(skb)->sacked) 3731 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); 3732 3733 if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) 3734 flag |= FLAG_ECE; 3735 3736 tcp_ca_event(sk, CA_EVENT_SLOW_ACK); 3737 } 3738 3739 /* We passed data and got it acked, remove any soft error 3740 * log. Something worked... 3741 */ 3742 sk->sk_err_soft = 0; 3743 icsk->icsk_probes_out = 0; 3744 tp->rcv_tstamp = tcp_time_stamp; 3745 prior_packets = tp->packets_out; 3746 if (!prior_packets) 3747 goto no_queue; 3748 3749 /* See if we can take anything off of the retransmit queue. */ 3750 flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una); 3751 3752 pkts_acked = prior_packets - tp->packets_out; 3753 newly_acked_sacked = (prior_packets - prior_sacked) - 3754 (tp->packets_out - tp->sacked_out); 3755 3756 if (tp->frto_counter) 3757 frto_cwnd = tcp_process_frto(sk, flag); 3758 /* Guarantee sacktag reordering detection against wrap-arounds */ 3759 if (before(tp->frto_highmark, tp->snd_una)) 3760 tp->frto_highmark = 0; 3761 3762 if (tcp_ack_is_dubious(sk, flag)) { 3763 /* Advance CWND, if state allows this. */ 3764 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd && 3765 tcp_may_raise_cwnd(sk, flag)) 3766 tcp_cong_avoid(sk, ack, prior_in_flight); 3767 is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP)); 3768 tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked, 3769 is_dupack, flag); 3770 } else { 3771 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd) 3772 tcp_cong_avoid(sk, ack, prior_in_flight); 3773 } 3774 3775 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) 3776 dst_confirm(__sk_dst_get(sk)); 3777 3778 return 1; 3779 3780 no_queue: 3781 /* If data was DSACKed, see if we can undo a cwnd reduction. */ 3782 if (flag & FLAG_DSACKING_ACK) 3783 tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked, 3784 is_dupack, flag); 3785 /* If this ack opens up a zero window, clear backoff. It was 3786 * being used to time the probes, and is probably far higher than 3787 * it needs to be for normal retransmission. 3788 */ 3789 if (tcp_send_head(sk)) 3790 tcp_ack_probe(sk); 3791 return 1; 3792 3793 invalid_ack: 3794 SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt); 3795 return -1; 3796 3797 old_ack: 3798 /* If data was SACKed, tag it and see if we should send more data. 3799 * If data was DSACKed, see if we can undo a cwnd reduction. 3800 */ 3801 if (TCP_SKB_CB(skb)->sacked) { 3802 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); 3803 newly_acked_sacked = tp->sacked_out - prior_sacked; 3804 tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked, 3805 is_dupack, flag); 3806 } 3807 3808 SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt); 3809 return 0; 3810 } 3811 3812 /* Look for tcp options. Normally only called on SYN and SYNACK packets. 3813 * But, this can also be called on packets in the established flow when 3814 * the fast version below fails. 3815 */ 3816 void tcp_parse_options(const struct sk_buff *skb, struct tcp_options_received *opt_rx, 3817 const u8 **hvpp, int estab) 3818 { 3819 const unsigned char *ptr; 3820 const struct tcphdr *th = tcp_hdr(skb); 3821 int length = (th->doff * 4) - sizeof(struct tcphdr); 3822 3823 ptr = (const unsigned char *)(th + 1); 3824 opt_rx->saw_tstamp = 0; 3825 3826 while (length > 0) { 3827 int opcode = *ptr++; 3828 int opsize; 3829 3830 switch (opcode) { 3831 case TCPOPT_EOL: 3832 return; 3833 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ 3834 length--; 3835 continue; 3836 default: 3837 opsize = *ptr++; 3838 if (opsize < 2) /* "silly options" */ 3839 return; 3840 if (opsize > length) 3841 return; /* don't parse partial options */ 3842 switch (opcode) { 3843 case TCPOPT_MSS: 3844 if (opsize == TCPOLEN_MSS && th->syn && !estab) { 3845 u16 in_mss = get_unaligned_be16(ptr); 3846 if (in_mss) { 3847 if (opt_rx->user_mss && 3848 opt_rx->user_mss < in_mss) 3849 in_mss = opt_rx->user_mss; 3850 opt_rx->mss_clamp = in_mss; 3851 } 3852 } 3853 break; 3854 case TCPOPT_WINDOW: 3855 if (opsize == TCPOLEN_WINDOW && th->syn && 3856 !estab && sysctl_tcp_window_scaling) { 3857 __u8 snd_wscale = *(__u8 *)ptr; 3858 opt_rx->wscale_ok = 1; 3859 if (snd_wscale > 14) { 3860 if (net_ratelimit()) 3861 printk(KERN_INFO "tcp_parse_options: Illegal window " 3862 "scaling value %d >14 received.\n", 3863 snd_wscale); 3864 snd_wscale = 14; 3865 } 3866 opt_rx->snd_wscale = snd_wscale; 3867 } 3868 break; 3869 case TCPOPT_TIMESTAMP: 3870 if ((opsize == TCPOLEN_TIMESTAMP) && 3871 ((estab && opt_rx->tstamp_ok) || 3872 (!estab && sysctl_tcp_timestamps))) { 3873 opt_rx->saw_tstamp = 1; 3874 opt_rx->rcv_tsval = get_unaligned_be32(ptr); 3875 opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4); 3876 } 3877 break; 3878 case TCPOPT_SACK_PERM: 3879 if (opsize == TCPOLEN_SACK_PERM && th->syn && 3880 !estab && sysctl_tcp_sack) { 3881 opt_rx->sack_ok = TCP_SACK_SEEN; 3882 tcp_sack_reset(opt_rx); 3883 } 3884 break; 3885 3886 case TCPOPT_SACK: 3887 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && 3888 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && 3889 opt_rx->sack_ok) { 3890 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; 3891 } 3892 break; 3893 #ifdef CONFIG_TCP_MD5SIG 3894 case TCPOPT_MD5SIG: 3895 /* 3896 * The MD5 Hash has already been 3897 * checked (see tcp_v{4,6}_do_rcv()). 3898 */ 3899 break; 3900 #endif 3901 case TCPOPT_COOKIE: 3902 /* This option is variable length. 3903 */ 3904 switch (opsize) { 3905 case TCPOLEN_COOKIE_BASE: 3906 /* not yet implemented */ 3907 break; 3908 case TCPOLEN_COOKIE_PAIR: 3909 /* not yet implemented */ 3910 break; 3911 case TCPOLEN_COOKIE_MIN+0: 3912 case TCPOLEN_COOKIE_MIN+2: 3913 case TCPOLEN_COOKIE_MIN+4: 3914 case TCPOLEN_COOKIE_MIN+6: 3915 case TCPOLEN_COOKIE_MAX: 3916 /* 16-bit multiple */ 3917 opt_rx->cookie_plus = opsize; 3918 *hvpp = ptr; 3919 break; 3920 default: 3921 /* ignore option */ 3922 break; 3923 } 3924 break; 3925 } 3926 3927 ptr += opsize-2; 3928 length -= opsize; 3929 } 3930 } 3931 } 3932 EXPORT_SYMBOL(tcp_parse_options); 3933 3934 static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, const struct tcphdr *th) 3935 { 3936 const __be32 *ptr = (const __be32 *)(th + 1); 3937 3938 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) 3939 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { 3940 tp->rx_opt.saw_tstamp = 1; 3941 ++ptr; 3942 tp->rx_opt.rcv_tsval = ntohl(*ptr); 3943 ++ptr; 3944 tp->rx_opt.rcv_tsecr = ntohl(*ptr); 3945 return 1; 3946 } 3947 return 0; 3948 } 3949 3950 /* Fast parse options. This hopes to only see timestamps. 3951 * If it is wrong it falls back on tcp_parse_options(). 3952 */ 3953 static int tcp_fast_parse_options(const struct sk_buff *skb, 3954 const struct tcphdr *th, 3955 struct tcp_sock *tp, const u8 **hvpp) 3956 { 3957 /* In the spirit of fast parsing, compare doff directly to constant 3958 * values. Because equality is used, short doff can be ignored here. 3959 */ 3960 if (th->doff == (sizeof(*th) / 4)) { 3961 tp->rx_opt.saw_tstamp = 0; 3962 return 0; 3963 } else if (tp->rx_opt.tstamp_ok && 3964 th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) { 3965 if (tcp_parse_aligned_timestamp(tp, th)) 3966 return 1; 3967 } 3968 tcp_parse_options(skb, &tp->rx_opt, hvpp, 1); 3969 return 1; 3970 } 3971 3972 #ifdef CONFIG_TCP_MD5SIG 3973 /* 3974 * Parse MD5 Signature option 3975 */ 3976 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th) 3977 { 3978 int length = (th->doff << 2) - sizeof(*th); 3979 const u8 *ptr = (const u8 *)(th + 1); 3980 3981 /* If the TCP option is too short, we can short cut */ 3982 if (length < TCPOLEN_MD5SIG) 3983 return NULL; 3984 3985 while (length > 0) { 3986 int opcode = *ptr++; 3987 int opsize; 3988 3989 switch(opcode) { 3990 case TCPOPT_EOL: 3991 return NULL; 3992 case TCPOPT_NOP: 3993 length--; 3994 continue; 3995 default: 3996 opsize = *ptr++; 3997 if (opsize < 2 || opsize > length) 3998 return NULL; 3999 if (opcode == TCPOPT_MD5SIG) 4000 return opsize == TCPOLEN_MD5SIG ? ptr : NULL; 4001 } 4002 ptr += opsize - 2; 4003 length -= opsize; 4004 } 4005 return NULL; 4006 } 4007 EXPORT_SYMBOL(tcp_parse_md5sig_option); 4008 #endif 4009 4010 static inline void tcp_store_ts_recent(struct tcp_sock *tp) 4011 { 4012 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; 4013 tp->rx_opt.ts_recent_stamp = get_seconds(); 4014 } 4015 4016 static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) 4017 { 4018 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { 4019 /* PAWS bug workaround wrt. ACK frames, the PAWS discard 4020 * extra check below makes sure this can only happen 4021 * for pure ACK frames. -DaveM 4022 * 4023 * Not only, also it occurs for expired timestamps. 4024 */ 4025 4026 if (tcp_paws_check(&tp->rx_opt, 0)) 4027 tcp_store_ts_recent(tp); 4028 } 4029 } 4030 4031 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM 4032 * 4033 * It is not fatal. If this ACK does _not_ change critical state (seqs, window) 4034 * it can pass through stack. So, the following predicate verifies that 4035 * this segment is not used for anything but congestion avoidance or 4036 * fast retransmit. Moreover, we even are able to eliminate most of such 4037 * second order effects, if we apply some small "replay" window (~RTO) 4038 * to timestamp space. 4039 * 4040 * All these measures still do not guarantee that we reject wrapped ACKs 4041 * on networks with high bandwidth, when sequence space is recycled fastly, 4042 * but it guarantees that such events will be very rare and do not affect 4043 * connection seriously. This doesn't look nice, but alas, PAWS is really 4044 * buggy extension. 4045 * 4046 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC 4047 * states that events when retransmit arrives after original data are rare. 4048 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is 4049 * the biggest problem on large power networks even with minor reordering. 4050 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe 4051 * up to bandwidth of 18Gigabit/sec. 8) ] 4052 */ 4053 4054 static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb) 4055 { 4056 const struct tcp_sock *tp = tcp_sk(sk); 4057 const struct tcphdr *th = tcp_hdr(skb); 4058 u32 seq = TCP_SKB_CB(skb)->seq; 4059 u32 ack = TCP_SKB_CB(skb)->ack_seq; 4060 4061 return (/* 1. Pure ACK with correct sequence number. */ 4062 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && 4063 4064 /* 2. ... and duplicate ACK. */ 4065 ack == tp->snd_una && 4066 4067 /* 3. ... and does not update window. */ 4068 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && 4069 4070 /* 4. ... and sits in replay window. */ 4071 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ); 4072 } 4073 4074 static inline int tcp_paws_discard(const struct sock *sk, 4075 const struct sk_buff *skb) 4076 { 4077 const struct tcp_sock *tp = tcp_sk(sk); 4078 4079 return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) && 4080 !tcp_disordered_ack(sk, skb); 4081 } 4082 4083 /* Check segment sequence number for validity. 4084 * 4085 * Segment controls are considered valid, if the segment 4086 * fits to the window after truncation to the window. Acceptability 4087 * of data (and SYN, FIN, of course) is checked separately. 4088 * See tcp_data_queue(), for example. 4089 * 4090 * Also, controls (RST is main one) are accepted using RCV.WUP instead 4091 * of RCV.NXT. Peer still did not advance his SND.UNA when we 4092 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. 4093 * (borrowed from freebsd) 4094 */ 4095 4096 static inline int tcp_sequence(const struct tcp_sock *tp, u32 seq, u32 end_seq) 4097 { 4098 return !before(end_seq, tp->rcv_wup) && 4099 !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); 4100 } 4101 4102 /* When we get a reset we do this. */ 4103 static void tcp_reset(struct sock *sk) 4104 { 4105 /* We want the right error as BSD sees it (and indeed as we do). */ 4106 switch (sk->sk_state) { 4107 case TCP_SYN_SENT: 4108 sk->sk_err = ECONNREFUSED; 4109 break; 4110 case TCP_CLOSE_WAIT: 4111 sk->sk_err = EPIPE; 4112 break; 4113 case TCP_CLOSE: 4114 return; 4115 default: 4116 sk->sk_err = ECONNRESET; 4117 } 4118 /* This barrier is coupled with smp_rmb() in tcp_poll() */ 4119 smp_wmb(); 4120 4121 if (!sock_flag(sk, SOCK_DEAD)) 4122 sk->sk_error_report(sk); 4123 4124 tcp_done(sk); 4125 } 4126 4127 /* 4128 * Process the FIN bit. This now behaves as it is supposed to work 4129 * and the FIN takes effect when it is validly part of sequence 4130 * space. Not before when we get holes. 4131 * 4132 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT 4133 * (and thence onto LAST-ACK and finally, CLOSE, we never enter 4134 * TIME-WAIT) 4135 * 4136 * If we are in FINWAIT-1, a received FIN indicates simultaneous 4137 * close and we go into CLOSING (and later onto TIME-WAIT) 4138 * 4139 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. 4140 */ 4141 static void tcp_fin(struct sock *sk) 4142 { 4143 struct tcp_sock *tp = tcp_sk(sk); 4144 4145 inet_csk_schedule_ack(sk); 4146 4147 sk->sk_shutdown |= RCV_SHUTDOWN; 4148 sock_set_flag(sk, SOCK_DONE); 4149 4150 switch (sk->sk_state) { 4151 case TCP_SYN_RECV: 4152 case TCP_ESTABLISHED: 4153 /* Move to CLOSE_WAIT */ 4154 tcp_set_state(sk, TCP_CLOSE_WAIT); 4155 inet_csk(sk)->icsk_ack.pingpong = 1; 4156 break; 4157 4158 case TCP_CLOSE_WAIT: 4159 case TCP_CLOSING: 4160 /* Received a retransmission of the FIN, do 4161 * nothing. 4162 */ 4163 break; 4164 case TCP_LAST_ACK: 4165 /* RFC793: Remain in the LAST-ACK state. */ 4166 break; 4167 4168 case TCP_FIN_WAIT1: 4169 /* This case occurs when a simultaneous close 4170 * happens, we must ack the received FIN and 4171 * enter the CLOSING state. 4172 */ 4173 tcp_send_ack(sk); 4174 tcp_set_state(sk, TCP_CLOSING); 4175 break; 4176 case TCP_FIN_WAIT2: 4177 /* Received a FIN -- send ACK and enter TIME_WAIT. */ 4178 tcp_send_ack(sk); 4179 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 4180 break; 4181 default: 4182 /* Only TCP_LISTEN and TCP_CLOSE are left, in these 4183 * cases we should never reach this piece of code. 4184 */ 4185 printk(KERN_ERR "%s: Impossible, sk->sk_state=%d\n", 4186 __func__, sk->sk_state); 4187 break; 4188 } 4189 4190 /* It _is_ possible, that we have something out-of-order _after_ FIN. 4191 * Probably, we should reset in this case. For now drop them. 4192 */ 4193 __skb_queue_purge(&tp->out_of_order_queue); 4194 if (tcp_is_sack(tp)) 4195 tcp_sack_reset(&tp->rx_opt); 4196 sk_mem_reclaim(sk); 4197 4198 if (!sock_flag(sk, SOCK_DEAD)) { 4199 sk->sk_state_change(sk); 4200 4201 /* Do not send POLL_HUP for half duplex close. */ 4202 if (sk->sk_shutdown == SHUTDOWN_MASK || 4203 sk->sk_state == TCP_CLOSE) 4204 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP); 4205 else 4206 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); 4207 } 4208 } 4209 4210 static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, 4211 u32 end_seq) 4212 { 4213 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { 4214 if (before(seq, sp->start_seq)) 4215 sp->start_seq = seq; 4216 if (after(end_seq, sp->end_seq)) 4217 sp->end_seq = end_seq; 4218 return 1; 4219 } 4220 return 0; 4221 } 4222 4223 static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq) 4224 { 4225 struct tcp_sock *tp = tcp_sk(sk); 4226 4227 if (tcp_is_sack(tp) && sysctl_tcp_dsack) { 4228 int mib_idx; 4229 4230 if (before(seq, tp->rcv_nxt)) 4231 mib_idx = LINUX_MIB_TCPDSACKOLDSENT; 4232 else 4233 mib_idx = LINUX_MIB_TCPDSACKOFOSENT; 4234 4235 NET_INC_STATS_BH(sock_net(sk), mib_idx); 4236 4237 tp->rx_opt.dsack = 1; 4238 tp->duplicate_sack[0].start_seq = seq; 4239 tp->duplicate_sack[0].end_seq = end_seq; 4240 } 4241 } 4242 4243 static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq) 4244 { 4245 struct tcp_sock *tp = tcp_sk(sk); 4246 4247 if (!tp->rx_opt.dsack) 4248 tcp_dsack_set(sk, seq, end_seq); 4249 else 4250 tcp_sack_extend(tp->duplicate_sack, seq, end_seq); 4251 } 4252 4253 static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb) 4254 { 4255 struct tcp_sock *tp = tcp_sk(sk); 4256 4257 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 4258 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4259 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); 4260 tcp_enter_quickack_mode(sk); 4261 4262 if (tcp_is_sack(tp) && sysctl_tcp_dsack) { 4263 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 4264 4265 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) 4266 end_seq = tp->rcv_nxt; 4267 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq); 4268 } 4269 } 4270 4271 tcp_send_ack(sk); 4272 } 4273 4274 /* These routines update the SACK block as out-of-order packets arrive or 4275 * in-order packets close up the sequence space. 4276 */ 4277 static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) 4278 { 4279 int this_sack; 4280 struct tcp_sack_block *sp = &tp->selective_acks[0]; 4281 struct tcp_sack_block *swalk = sp + 1; 4282 4283 /* See if the recent change to the first SACK eats into 4284 * or hits the sequence space of other SACK blocks, if so coalesce. 4285 */ 4286 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) { 4287 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { 4288 int i; 4289 4290 /* Zap SWALK, by moving every further SACK up by one slot. 4291 * Decrease num_sacks. 4292 */ 4293 tp->rx_opt.num_sacks--; 4294 for (i = this_sack; i < tp->rx_opt.num_sacks; i++) 4295 sp[i] = sp[i + 1]; 4296 continue; 4297 } 4298 this_sack++, swalk++; 4299 } 4300 } 4301 4302 static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) 4303 { 4304 struct tcp_sock *tp = tcp_sk(sk); 4305 struct tcp_sack_block *sp = &tp->selective_acks[0]; 4306 int cur_sacks = tp->rx_opt.num_sacks; 4307 int this_sack; 4308 4309 if (!cur_sacks) 4310 goto new_sack; 4311 4312 for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) { 4313 if (tcp_sack_extend(sp, seq, end_seq)) { 4314 /* Rotate this_sack to the first one. */ 4315 for (; this_sack > 0; this_sack--, sp--) 4316 swap(*sp, *(sp - 1)); 4317 if (cur_sacks > 1) 4318 tcp_sack_maybe_coalesce(tp); 4319 return; 4320 } 4321 } 4322 4323 /* Could not find an adjacent existing SACK, build a new one, 4324 * put it at the front, and shift everyone else down. We 4325 * always know there is at least one SACK present already here. 4326 * 4327 * If the sack array is full, forget about the last one. 4328 */ 4329 if (this_sack >= TCP_NUM_SACKS) { 4330 this_sack--; 4331 tp->rx_opt.num_sacks--; 4332 sp--; 4333 } 4334 for (; this_sack > 0; this_sack--, sp--) 4335 *sp = *(sp - 1); 4336 4337 new_sack: 4338 /* Build the new head SACK, and we're done. */ 4339 sp->start_seq = seq; 4340 sp->end_seq = end_seq; 4341 tp->rx_opt.num_sacks++; 4342 } 4343 4344 /* RCV.NXT advances, some SACKs should be eaten. */ 4345 4346 static void tcp_sack_remove(struct tcp_sock *tp) 4347 { 4348 struct tcp_sack_block *sp = &tp->selective_acks[0]; 4349 int num_sacks = tp->rx_opt.num_sacks; 4350 int this_sack; 4351 4352 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ 4353 if (skb_queue_empty(&tp->out_of_order_queue)) { 4354 tp->rx_opt.num_sacks = 0; 4355 return; 4356 } 4357 4358 for (this_sack = 0; this_sack < num_sacks;) { 4359 /* Check if the start of the sack is covered by RCV.NXT. */ 4360 if (!before(tp->rcv_nxt, sp->start_seq)) { 4361 int i; 4362 4363 /* RCV.NXT must cover all the block! */ 4364 WARN_ON(before(tp->rcv_nxt, sp->end_seq)); 4365 4366 /* Zap this SACK, by moving forward any other SACKS. */ 4367 for (i=this_sack+1; i < num_sacks; i++) 4368 tp->selective_acks[i-1] = tp->selective_acks[i]; 4369 num_sacks--; 4370 continue; 4371 } 4372 this_sack++; 4373 sp++; 4374 } 4375 tp->rx_opt.num_sacks = num_sacks; 4376 } 4377 4378 /* This one checks to see if we can put data from the 4379 * out_of_order queue into the receive_queue. 4380 */ 4381 static void tcp_ofo_queue(struct sock *sk) 4382 { 4383 struct tcp_sock *tp = tcp_sk(sk); 4384 __u32 dsack_high = tp->rcv_nxt; 4385 struct sk_buff *skb; 4386 4387 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { 4388 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 4389 break; 4390 4391 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { 4392 __u32 dsack = dsack_high; 4393 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) 4394 dsack_high = TCP_SKB_CB(skb)->end_seq; 4395 tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack); 4396 } 4397 4398 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 4399 SOCK_DEBUG(sk, "ofo packet was already received\n"); 4400 __skb_unlink(skb, &tp->out_of_order_queue); 4401 __kfree_skb(skb); 4402 continue; 4403 } 4404 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", 4405 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 4406 TCP_SKB_CB(skb)->end_seq); 4407 4408 __skb_unlink(skb, &tp->out_of_order_queue); 4409 __skb_queue_tail(&sk->sk_receive_queue, skb); 4410 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4411 if (tcp_hdr(skb)->fin) 4412 tcp_fin(sk); 4413 } 4414 } 4415 4416 static int tcp_prune_ofo_queue(struct sock *sk); 4417 static int tcp_prune_queue(struct sock *sk); 4418 4419 static inline int tcp_try_rmem_schedule(struct sock *sk, unsigned int size) 4420 { 4421 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || 4422 !sk_rmem_schedule(sk, size)) { 4423 4424 if (tcp_prune_queue(sk) < 0) 4425 return -1; 4426 4427 if (!sk_rmem_schedule(sk, size)) { 4428 if (!tcp_prune_ofo_queue(sk)) 4429 return -1; 4430 4431 if (!sk_rmem_schedule(sk, size)) 4432 return -1; 4433 } 4434 } 4435 return 0; 4436 } 4437 4438 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) 4439 { 4440 const struct tcphdr *th = tcp_hdr(skb); 4441 struct tcp_sock *tp = tcp_sk(sk); 4442 int eaten = -1; 4443 4444 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) 4445 goto drop; 4446 4447 skb_dst_drop(skb); 4448 __skb_pull(skb, th->doff * 4); 4449 4450 TCP_ECN_accept_cwr(tp, skb); 4451 4452 tp->rx_opt.dsack = 0; 4453 4454 /* Queue data for delivery to the user. 4455 * Packets in sequence go to the receive queue. 4456 * Out of sequence packets to the out_of_order_queue. 4457 */ 4458 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { 4459 if (tcp_receive_window(tp) == 0) 4460 goto out_of_window; 4461 4462 /* Ok. In sequence. In window. */ 4463 if (tp->ucopy.task == current && 4464 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && 4465 sock_owned_by_user(sk) && !tp->urg_data) { 4466 int chunk = min_t(unsigned int, skb->len, 4467 tp->ucopy.len); 4468 4469 __set_current_state(TASK_RUNNING); 4470 4471 local_bh_enable(); 4472 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { 4473 tp->ucopy.len -= chunk; 4474 tp->copied_seq += chunk; 4475 eaten = (chunk == skb->len); 4476 tcp_rcv_space_adjust(sk); 4477 } 4478 local_bh_disable(); 4479 } 4480 4481 if (eaten <= 0) { 4482 queue_and_out: 4483 if (eaten < 0 && 4484 tcp_try_rmem_schedule(sk, skb->truesize)) 4485 goto drop; 4486 4487 skb_set_owner_r(skb, sk); 4488 __skb_queue_tail(&sk->sk_receive_queue, skb); 4489 } 4490 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4491 if (skb->len) 4492 tcp_event_data_recv(sk, skb); 4493 if (th->fin) 4494 tcp_fin(sk); 4495 4496 if (!skb_queue_empty(&tp->out_of_order_queue)) { 4497 tcp_ofo_queue(sk); 4498 4499 /* RFC2581. 4.2. SHOULD send immediate ACK, when 4500 * gap in queue is filled. 4501 */ 4502 if (skb_queue_empty(&tp->out_of_order_queue)) 4503 inet_csk(sk)->icsk_ack.pingpong = 0; 4504 } 4505 4506 if (tp->rx_opt.num_sacks) 4507 tcp_sack_remove(tp); 4508 4509 tcp_fast_path_check(sk); 4510 4511 if (eaten > 0) 4512 __kfree_skb(skb); 4513 else if (!sock_flag(sk, SOCK_DEAD)) 4514 sk->sk_data_ready(sk, 0); 4515 return; 4516 } 4517 4518 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 4519 /* A retransmit, 2nd most common case. Force an immediate ack. */ 4520 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); 4521 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 4522 4523 out_of_window: 4524 tcp_enter_quickack_mode(sk); 4525 inet_csk_schedule_ack(sk); 4526 drop: 4527 __kfree_skb(skb); 4528 return; 4529 } 4530 4531 /* Out of window. F.e. zero window probe. */ 4532 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) 4533 goto out_of_window; 4534 4535 tcp_enter_quickack_mode(sk); 4536 4537 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4538 /* Partial packet, seq < rcv_next < end_seq */ 4539 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", 4540 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 4541 TCP_SKB_CB(skb)->end_seq); 4542 4543 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); 4544 4545 /* If window is closed, drop tail of packet. But after 4546 * remembering D-SACK for its head made in previous line. 4547 */ 4548 if (!tcp_receive_window(tp)) 4549 goto out_of_window; 4550 goto queue_and_out; 4551 } 4552 4553 TCP_ECN_check_ce(tp, skb); 4554 4555 if (tcp_try_rmem_schedule(sk, skb->truesize)) 4556 goto drop; 4557 4558 /* Disable header prediction. */ 4559 tp->pred_flags = 0; 4560 inet_csk_schedule_ack(sk); 4561 4562 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", 4563 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 4564 4565 skb_set_owner_r(skb, sk); 4566 4567 if (!skb_peek(&tp->out_of_order_queue)) { 4568 /* Initial out of order segment, build 1 SACK. */ 4569 if (tcp_is_sack(tp)) { 4570 tp->rx_opt.num_sacks = 1; 4571 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; 4572 tp->selective_acks[0].end_seq = 4573 TCP_SKB_CB(skb)->end_seq; 4574 } 4575 __skb_queue_head(&tp->out_of_order_queue, skb); 4576 } else { 4577 struct sk_buff *skb1 = skb_peek_tail(&tp->out_of_order_queue); 4578 u32 seq = TCP_SKB_CB(skb)->seq; 4579 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 4580 4581 if (seq == TCP_SKB_CB(skb1)->end_seq) { 4582 __skb_queue_after(&tp->out_of_order_queue, skb1, skb); 4583 4584 if (!tp->rx_opt.num_sacks || 4585 tp->selective_acks[0].end_seq != seq) 4586 goto add_sack; 4587 4588 /* Common case: data arrive in order after hole. */ 4589 tp->selective_acks[0].end_seq = end_seq; 4590 return; 4591 } 4592 4593 /* Find place to insert this segment. */ 4594 while (1) { 4595 if (!after(TCP_SKB_CB(skb1)->seq, seq)) 4596 break; 4597 if (skb_queue_is_first(&tp->out_of_order_queue, skb1)) { 4598 skb1 = NULL; 4599 break; 4600 } 4601 skb1 = skb_queue_prev(&tp->out_of_order_queue, skb1); 4602 } 4603 4604 /* Do skb overlap to previous one? */ 4605 if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) { 4606 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 4607 /* All the bits are present. Drop. */ 4608 __kfree_skb(skb); 4609 tcp_dsack_set(sk, seq, end_seq); 4610 goto add_sack; 4611 } 4612 if (after(seq, TCP_SKB_CB(skb1)->seq)) { 4613 /* Partial overlap. */ 4614 tcp_dsack_set(sk, seq, 4615 TCP_SKB_CB(skb1)->end_seq); 4616 } else { 4617 if (skb_queue_is_first(&tp->out_of_order_queue, 4618 skb1)) 4619 skb1 = NULL; 4620 else 4621 skb1 = skb_queue_prev( 4622 &tp->out_of_order_queue, 4623 skb1); 4624 } 4625 } 4626 if (!skb1) 4627 __skb_queue_head(&tp->out_of_order_queue, skb); 4628 else 4629 __skb_queue_after(&tp->out_of_order_queue, skb1, skb); 4630 4631 /* And clean segments covered by new one as whole. */ 4632 while (!skb_queue_is_last(&tp->out_of_order_queue, skb)) { 4633 skb1 = skb_queue_next(&tp->out_of_order_queue, skb); 4634 4635 if (!after(end_seq, TCP_SKB_CB(skb1)->seq)) 4636 break; 4637 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 4638 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, 4639 end_seq); 4640 break; 4641 } 4642 __skb_unlink(skb1, &tp->out_of_order_queue); 4643 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, 4644 TCP_SKB_CB(skb1)->end_seq); 4645 __kfree_skb(skb1); 4646 } 4647 4648 add_sack: 4649 if (tcp_is_sack(tp)) 4650 tcp_sack_new_ofo_skb(sk, seq, end_seq); 4651 } 4652 } 4653 4654 static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb, 4655 struct sk_buff_head *list) 4656 { 4657 struct sk_buff *next = NULL; 4658 4659 if (!skb_queue_is_last(list, skb)) 4660 next = skb_queue_next(list, skb); 4661 4662 __skb_unlink(skb, list); 4663 __kfree_skb(skb); 4664 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED); 4665 4666 return next; 4667 } 4668 4669 /* Collapse contiguous sequence of skbs head..tail with 4670 * sequence numbers start..end. 4671 * 4672 * If tail is NULL, this means until the end of the list. 4673 * 4674 * Segments with FIN/SYN are not collapsed (only because this 4675 * simplifies code) 4676 */ 4677 static void 4678 tcp_collapse(struct sock *sk, struct sk_buff_head *list, 4679 struct sk_buff *head, struct sk_buff *tail, 4680 u32 start, u32 end) 4681 { 4682 struct sk_buff *skb, *n; 4683 bool end_of_skbs; 4684 4685 /* First, check that queue is collapsible and find 4686 * the point where collapsing can be useful. */ 4687 skb = head; 4688 restart: 4689 end_of_skbs = true; 4690 skb_queue_walk_from_safe(list, skb, n) { 4691 if (skb == tail) 4692 break; 4693 /* No new bits? It is possible on ofo queue. */ 4694 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 4695 skb = tcp_collapse_one(sk, skb, list); 4696 if (!skb) 4697 break; 4698 goto restart; 4699 } 4700 4701 /* The first skb to collapse is: 4702 * - not SYN/FIN and 4703 * - bloated or contains data before "start" or 4704 * overlaps to the next one. 4705 */ 4706 if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin && 4707 (tcp_win_from_space(skb->truesize) > skb->len || 4708 before(TCP_SKB_CB(skb)->seq, start))) { 4709 end_of_skbs = false; 4710 break; 4711 } 4712 4713 if (!skb_queue_is_last(list, skb)) { 4714 struct sk_buff *next = skb_queue_next(list, skb); 4715 if (next != tail && 4716 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(next)->seq) { 4717 end_of_skbs = false; 4718 break; 4719 } 4720 } 4721 4722 /* Decided to skip this, advance start seq. */ 4723 start = TCP_SKB_CB(skb)->end_seq; 4724 } 4725 if (end_of_skbs || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin) 4726 return; 4727 4728 while (before(start, end)) { 4729 struct sk_buff *nskb; 4730 unsigned int header = skb_headroom(skb); 4731 int copy = SKB_MAX_ORDER(header, 0); 4732 4733 /* Too big header? This can happen with IPv6. */ 4734 if (copy < 0) 4735 return; 4736 if (end - start < copy) 4737 copy = end - start; 4738 nskb = alloc_skb(copy + header, GFP_ATOMIC); 4739 if (!nskb) 4740 return; 4741 4742 skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head); 4743 skb_set_network_header(nskb, (skb_network_header(skb) - 4744 skb->head)); 4745 skb_set_transport_header(nskb, (skb_transport_header(skb) - 4746 skb->head)); 4747 skb_reserve(nskb, header); 4748 memcpy(nskb->head, skb->head, header); 4749 memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); 4750 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; 4751 __skb_queue_before(list, skb, nskb); 4752 skb_set_owner_r(nskb, sk); 4753 4754 /* Copy data, releasing collapsed skbs. */ 4755 while (copy > 0) { 4756 int offset = start - TCP_SKB_CB(skb)->seq; 4757 int size = TCP_SKB_CB(skb)->end_seq - start; 4758 4759 BUG_ON(offset < 0); 4760 if (size > 0) { 4761 size = min(copy, size); 4762 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) 4763 BUG(); 4764 TCP_SKB_CB(nskb)->end_seq += size; 4765 copy -= size; 4766 start += size; 4767 } 4768 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 4769 skb = tcp_collapse_one(sk, skb, list); 4770 if (!skb || 4771 skb == tail || 4772 tcp_hdr(skb)->syn || 4773 tcp_hdr(skb)->fin) 4774 return; 4775 } 4776 } 4777 } 4778 } 4779 4780 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs 4781 * and tcp_collapse() them until all the queue is collapsed. 4782 */ 4783 static void tcp_collapse_ofo_queue(struct sock *sk) 4784 { 4785 struct tcp_sock *tp = tcp_sk(sk); 4786 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); 4787 struct sk_buff *head; 4788 u32 start, end; 4789 4790 if (skb == NULL) 4791 return; 4792 4793 start = TCP_SKB_CB(skb)->seq; 4794 end = TCP_SKB_CB(skb)->end_seq; 4795 head = skb; 4796 4797 for (;;) { 4798 struct sk_buff *next = NULL; 4799 4800 if (!skb_queue_is_last(&tp->out_of_order_queue, skb)) 4801 next = skb_queue_next(&tp->out_of_order_queue, skb); 4802 skb = next; 4803 4804 /* Segment is terminated when we see gap or when 4805 * we are at the end of all the queue. */ 4806 if (!skb || 4807 after(TCP_SKB_CB(skb)->seq, end) || 4808 before(TCP_SKB_CB(skb)->end_seq, start)) { 4809 tcp_collapse(sk, &tp->out_of_order_queue, 4810 head, skb, start, end); 4811 head = skb; 4812 if (!skb) 4813 break; 4814 /* Start new segment */ 4815 start = TCP_SKB_CB(skb)->seq; 4816 end = TCP_SKB_CB(skb)->end_seq; 4817 } else { 4818 if (before(TCP_SKB_CB(skb)->seq, start)) 4819 start = TCP_SKB_CB(skb)->seq; 4820 if (after(TCP_SKB_CB(skb)->end_seq, end)) 4821 end = TCP_SKB_CB(skb)->end_seq; 4822 } 4823 } 4824 } 4825 4826 /* 4827 * Purge the out-of-order queue. 4828 * Return true if queue was pruned. 4829 */ 4830 static int tcp_prune_ofo_queue(struct sock *sk) 4831 { 4832 struct tcp_sock *tp = tcp_sk(sk); 4833 int res = 0; 4834 4835 if (!skb_queue_empty(&tp->out_of_order_queue)) { 4836 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_OFOPRUNED); 4837 __skb_queue_purge(&tp->out_of_order_queue); 4838 4839 /* Reset SACK state. A conforming SACK implementation will 4840 * do the same at a timeout based retransmit. When a connection 4841 * is in a sad state like this, we care only about integrity 4842 * of the connection not performance. 4843 */ 4844 if (tp->rx_opt.sack_ok) 4845 tcp_sack_reset(&tp->rx_opt); 4846 sk_mem_reclaim(sk); 4847 res = 1; 4848 } 4849 return res; 4850 } 4851 4852 /* Reduce allocated memory if we can, trying to get 4853 * the socket within its memory limits again. 4854 * 4855 * Return less than zero if we should start dropping frames 4856 * until the socket owning process reads some of the data 4857 * to stabilize the situation. 4858 */ 4859 static int tcp_prune_queue(struct sock *sk) 4860 { 4861 struct tcp_sock *tp = tcp_sk(sk); 4862 4863 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); 4864 4865 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PRUNECALLED); 4866 4867 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) 4868 tcp_clamp_window(sk); 4869 else if (sk_under_memory_pressure(sk)) 4870 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); 4871 4872 tcp_collapse_ofo_queue(sk); 4873 if (!skb_queue_empty(&sk->sk_receive_queue)) 4874 tcp_collapse(sk, &sk->sk_receive_queue, 4875 skb_peek(&sk->sk_receive_queue), 4876 NULL, 4877 tp->copied_seq, tp->rcv_nxt); 4878 sk_mem_reclaim(sk); 4879 4880 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 4881 return 0; 4882 4883 /* Collapsing did not help, destructive actions follow. 4884 * This must not ever occur. */ 4885 4886 tcp_prune_ofo_queue(sk); 4887 4888 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 4889 return 0; 4890 4891 /* If we are really being abused, tell the caller to silently 4892 * drop receive data on the floor. It will get retransmitted 4893 * and hopefully then we'll have sufficient space. 4894 */ 4895 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_RCVPRUNED); 4896 4897 /* Massive buffer overcommit. */ 4898 tp->pred_flags = 0; 4899 return -1; 4900 } 4901 4902 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. 4903 * As additional protections, we do not touch cwnd in retransmission phases, 4904 * and if application hit its sndbuf limit recently. 4905 */ 4906 void tcp_cwnd_application_limited(struct sock *sk) 4907 { 4908 struct tcp_sock *tp = tcp_sk(sk); 4909 4910 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && 4911 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { 4912 /* Limited by application or receiver window. */ 4913 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); 4914 u32 win_used = max(tp->snd_cwnd_used, init_win); 4915 if (win_used < tp->snd_cwnd) { 4916 tp->snd_ssthresh = tcp_current_ssthresh(sk); 4917 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; 4918 } 4919 tp->snd_cwnd_used = 0; 4920 } 4921 tp->snd_cwnd_stamp = tcp_time_stamp; 4922 } 4923 4924 static int tcp_should_expand_sndbuf(const struct sock *sk) 4925 { 4926 const struct tcp_sock *tp = tcp_sk(sk); 4927 4928 /* If the user specified a specific send buffer setting, do 4929 * not modify it. 4930 */ 4931 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) 4932 return 0; 4933 4934 /* If we are under global TCP memory pressure, do not expand. */ 4935 if (sk_under_memory_pressure(sk)) 4936 return 0; 4937 4938 /* If we are under soft global TCP memory pressure, do not expand. */ 4939 if (sk_memory_allocated(sk) >= sk_prot_mem_limits(sk, 0)) 4940 return 0; 4941 4942 /* If we filled the congestion window, do not expand. */ 4943 if (tp->packets_out >= tp->snd_cwnd) 4944 return 0; 4945 4946 return 1; 4947 } 4948 4949 /* When incoming ACK allowed to free some skb from write_queue, 4950 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket 4951 * on the exit from tcp input handler. 4952 * 4953 * PROBLEM: sndbuf expansion does not work well with largesend. 4954 */ 4955 static void tcp_new_space(struct sock *sk) 4956 { 4957 struct tcp_sock *tp = tcp_sk(sk); 4958 4959 if (tcp_should_expand_sndbuf(sk)) { 4960 int sndmem = SKB_TRUESIZE(max_t(u32, 4961 tp->rx_opt.mss_clamp, 4962 tp->mss_cache) + 4963 MAX_TCP_HEADER); 4964 int demanded = max_t(unsigned int, tp->snd_cwnd, 4965 tp->reordering + 1); 4966 sndmem *= 2 * demanded; 4967 if (sndmem > sk->sk_sndbuf) 4968 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); 4969 tp->snd_cwnd_stamp = tcp_time_stamp; 4970 } 4971 4972 sk->sk_write_space(sk); 4973 } 4974 4975 static void tcp_check_space(struct sock *sk) 4976 { 4977 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { 4978 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); 4979 if (sk->sk_socket && 4980 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) 4981 tcp_new_space(sk); 4982 } 4983 } 4984 4985 static inline void tcp_data_snd_check(struct sock *sk) 4986 { 4987 tcp_push_pending_frames(sk); 4988 tcp_check_space(sk); 4989 } 4990 4991 /* 4992 * Check if sending an ack is needed. 4993 */ 4994 static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) 4995 { 4996 struct tcp_sock *tp = tcp_sk(sk); 4997 4998 /* More than one full frame received... */ 4999 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss && 5000 /* ... and right edge of window advances far enough. 5001 * (tcp_recvmsg() will send ACK otherwise). Or... 5002 */ 5003 __tcp_select_window(sk) >= tp->rcv_wnd) || 5004 /* We ACK each frame or... */ 5005 tcp_in_quickack_mode(sk) || 5006 /* We have out of order data. */ 5007 (ofo_possible && skb_peek(&tp->out_of_order_queue))) { 5008 /* Then ack it now */ 5009 tcp_send_ack(sk); 5010 } else { 5011 /* Else, send delayed ack. */ 5012 tcp_send_delayed_ack(sk); 5013 } 5014 } 5015 5016 static inline void tcp_ack_snd_check(struct sock *sk) 5017 { 5018 if (!inet_csk_ack_scheduled(sk)) { 5019 /* We sent a data segment already. */ 5020 return; 5021 } 5022 __tcp_ack_snd_check(sk, 1); 5023 } 5024 5025 /* 5026 * This routine is only called when we have urgent data 5027 * signaled. Its the 'slow' part of tcp_urg. It could be 5028 * moved inline now as tcp_urg is only called from one 5029 * place. We handle URGent data wrong. We have to - as 5030 * BSD still doesn't use the correction from RFC961. 5031 * For 1003.1g we should support a new option TCP_STDURG to permit 5032 * either form (or just set the sysctl tcp_stdurg). 5033 */ 5034 5035 static void tcp_check_urg(struct sock *sk, const struct tcphdr *th) 5036 { 5037 struct tcp_sock *tp = tcp_sk(sk); 5038 u32 ptr = ntohs(th->urg_ptr); 5039 5040 if (ptr && !sysctl_tcp_stdurg) 5041 ptr--; 5042 ptr += ntohl(th->seq); 5043 5044 /* Ignore urgent data that we've already seen and read. */ 5045 if (after(tp->copied_seq, ptr)) 5046 return; 5047 5048 /* Do not replay urg ptr. 5049 * 5050 * NOTE: interesting situation not covered by specs. 5051 * Misbehaving sender may send urg ptr, pointing to segment, 5052 * which we already have in ofo queue. We are not able to fetch 5053 * such data and will stay in TCP_URG_NOTYET until will be eaten 5054 * by recvmsg(). Seems, we are not obliged to handle such wicked 5055 * situations. But it is worth to think about possibility of some 5056 * DoSes using some hypothetical application level deadlock. 5057 */ 5058 if (before(ptr, tp->rcv_nxt)) 5059 return; 5060 5061 /* Do we already have a newer (or duplicate) urgent pointer? */ 5062 if (tp->urg_data && !after(ptr, tp->urg_seq)) 5063 return; 5064 5065 /* Tell the world about our new urgent pointer. */ 5066 sk_send_sigurg(sk); 5067 5068 /* We may be adding urgent data when the last byte read was 5069 * urgent. To do this requires some care. We cannot just ignore 5070 * tp->copied_seq since we would read the last urgent byte again 5071 * as data, nor can we alter copied_seq until this data arrives 5072 * or we break the semantics of SIOCATMARK (and thus sockatmark()) 5073 * 5074 * NOTE. Double Dutch. Rendering to plain English: author of comment 5075 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); 5076 * and expect that both A and B disappear from stream. This is _wrong_. 5077 * Though this happens in BSD with high probability, this is occasional. 5078 * Any application relying on this is buggy. Note also, that fix "works" 5079 * only in this artificial test. Insert some normal data between A and B and we will 5080 * decline of BSD again. Verdict: it is better to remove to trap 5081 * buggy users. 5082 */ 5083 if (tp->urg_seq == tp->copied_seq && tp->urg_data && 5084 !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) { 5085 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); 5086 tp->copied_seq++; 5087 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { 5088 __skb_unlink(skb, &sk->sk_receive_queue); 5089 __kfree_skb(skb); 5090 } 5091 } 5092 5093 tp->urg_data = TCP_URG_NOTYET; 5094 tp->urg_seq = ptr; 5095 5096 /* Disable header prediction. */ 5097 tp->pred_flags = 0; 5098 } 5099 5100 /* This is the 'fast' part of urgent handling. */ 5101 static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *th) 5102 { 5103 struct tcp_sock *tp = tcp_sk(sk); 5104 5105 /* Check if we get a new urgent pointer - normally not. */ 5106 if (th->urg) 5107 tcp_check_urg(sk, th); 5108 5109 /* Do we wait for any urgent data? - normally not... */ 5110 if (tp->urg_data == TCP_URG_NOTYET) { 5111 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - 5112 th->syn; 5113 5114 /* Is the urgent pointer pointing into this packet? */ 5115 if (ptr < skb->len) { 5116 u8 tmp; 5117 if (skb_copy_bits(skb, ptr, &tmp, 1)) 5118 BUG(); 5119 tp->urg_data = TCP_URG_VALID | tmp; 5120 if (!sock_flag(sk, SOCK_DEAD)) 5121 sk->sk_data_ready(sk, 0); 5122 } 5123 } 5124 } 5125 5126 static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) 5127 { 5128 struct tcp_sock *tp = tcp_sk(sk); 5129 int chunk = skb->len - hlen; 5130 int err; 5131 5132 local_bh_enable(); 5133 if (skb_csum_unnecessary(skb)) 5134 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); 5135 else 5136 err = skb_copy_and_csum_datagram_iovec(skb, hlen, 5137 tp->ucopy.iov); 5138 5139 if (!err) { 5140 tp->ucopy.len -= chunk; 5141 tp->copied_seq += chunk; 5142 tcp_rcv_space_adjust(sk); 5143 } 5144 5145 local_bh_disable(); 5146 return err; 5147 } 5148 5149 static __sum16 __tcp_checksum_complete_user(struct sock *sk, 5150 struct sk_buff *skb) 5151 { 5152 __sum16 result; 5153 5154 if (sock_owned_by_user(sk)) { 5155 local_bh_enable(); 5156 result = __tcp_checksum_complete(skb); 5157 local_bh_disable(); 5158 } else { 5159 result = __tcp_checksum_complete(skb); 5160 } 5161 return result; 5162 } 5163 5164 static inline int tcp_checksum_complete_user(struct sock *sk, 5165 struct sk_buff *skb) 5166 { 5167 return !skb_csum_unnecessary(skb) && 5168 __tcp_checksum_complete_user(sk, skb); 5169 } 5170 5171 #ifdef CONFIG_NET_DMA 5172 static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, 5173 int hlen) 5174 { 5175 struct tcp_sock *tp = tcp_sk(sk); 5176 int chunk = skb->len - hlen; 5177 int dma_cookie; 5178 int copied_early = 0; 5179 5180 if (tp->ucopy.wakeup) 5181 return 0; 5182 5183 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list) 5184 tp->ucopy.dma_chan = dma_find_channel(DMA_MEMCPY); 5185 5186 if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) { 5187 5188 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan, 5189 skb, hlen, 5190 tp->ucopy.iov, chunk, 5191 tp->ucopy.pinned_list); 5192 5193 if (dma_cookie < 0) 5194 goto out; 5195 5196 tp->ucopy.dma_cookie = dma_cookie; 5197 copied_early = 1; 5198 5199 tp->ucopy.len -= chunk; 5200 tp->copied_seq += chunk; 5201 tcp_rcv_space_adjust(sk); 5202 5203 if ((tp->ucopy.len == 0) || 5204 (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) || 5205 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) { 5206 tp->ucopy.wakeup = 1; 5207 sk->sk_data_ready(sk, 0); 5208 } 5209 } else if (chunk > 0) { 5210 tp->ucopy.wakeup = 1; 5211 sk->sk_data_ready(sk, 0); 5212 } 5213 out: 5214 return copied_early; 5215 } 5216 #endif /* CONFIG_NET_DMA */ 5217 5218 /* Does PAWS and seqno based validation of an incoming segment, flags will 5219 * play significant role here. 5220 */ 5221 static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, 5222 const struct tcphdr *th, int syn_inerr) 5223 { 5224 const u8 *hash_location; 5225 struct tcp_sock *tp = tcp_sk(sk); 5226 5227 /* RFC1323: H1. Apply PAWS check first. */ 5228 if (tcp_fast_parse_options(skb, th, tp, &hash_location) && 5229 tp->rx_opt.saw_tstamp && 5230 tcp_paws_discard(sk, skb)) { 5231 if (!th->rst) { 5232 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED); 5233 tcp_send_dupack(sk, skb); 5234 goto discard; 5235 } 5236 /* Reset is accepted even if it did not pass PAWS. */ 5237 } 5238 5239 /* Step 1: check sequence number */ 5240 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { 5241 /* RFC793, page 37: "In all states except SYN-SENT, all reset 5242 * (RST) segments are validated by checking their SEQ-fields." 5243 * And page 69: "If an incoming segment is not acceptable, 5244 * an acknowledgment should be sent in reply (unless the RST 5245 * bit is set, if so drop the segment and return)". 5246 */ 5247 if (!th->rst) 5248 tcp_send_dupack(sk, skb); 5249 goto discard; 5250 } 5251 5252 /* Step 2: check RST bit */ 5253 if (th->rst) { 5254 tcp_reset(sk); 5255 goto discard; 5256 } 5257 5258 /* ts_recent update must be made after we are sure that the packet 5259 * is in window. 5260 */ 5261 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 5262 5263 /* step 3: check security and precedence [ignored] */ 5264 5265 /* step 4: Check for a SYN in window. */ 5266 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 5267 if (syn_inerr) 5268 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); 5269 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN); 5270 tcp_reset(sk); 5271 return -1; 5272 } 5273 5274 return 1; 5275 5276 discard: 5277 __kfree_skb(skb); 5278 return 0; 5279 } 5280 5281 /* 5282 * TCP receive function for the ESTABLISHED state. 5283 * 5284 * It is split into a fast path and a slow path. The fast path is 5285 * disabled when: 5286 * - A zero window was announced from us - zero window probing 5287 * is only handled properly in the slow path. 5288 * - Out of order segments arrived. 5289 * - Urgent data is expected. 5290 * - There is no buffer space left 5291 * - Unexpected TCP flags/window values/header lengths are received 5292 * (detected by checking the TCP header against pred_flags) 5293 * - Data is sent in both directions. Fast path only supports pure senders 5294 * or pure receivers (this means either the sequence number or the ack 5295 * value must stay constant) 5296 * - Unexpected TCP option. 5297 * 5298 * When these conditions are not satisfied it drops into a standard 5299 * receive procedure patterned after RFC793 to handle all cases. 5300 * The first three cases are guaranteed by proper pred_flags setting, 5301 * the rest is checked inline. Fast processing is turned on in 5302 * tcp_data_queue when everything is OK. 5303 */ 5304 int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, 5305 const struct tcphdr *th, unsigned int len) 5306 { 5307 struct tcp_sock *tp = tcp_sk(sk); 5308 int res; 5309 5310 /* 5311 * Header prediction. 5312 * The code loosely follows the one in the famous 5313 * "30 instruction TCP receive" Van Jacobson mail. 5314 * 5315 * Van's trick is to deposit buffers into socket queue 5316 * on a device interrupt, to call tcp_recv function 5317 * on the receive process context and checksum and copy 5318 * the buffer to user space. smart... 5319 * 5320 * Our current scheme is not silly either but we take the 5321 * extra cost of the net_bh soft interrupt processing... 5322 * We do checksum and copy also but from device to kernel. 5323 */ 5324 5325 tp->rx_opt.saw_tstamp = 0; 5326 5327 /* pred_flags is 0xS?10 << 16 + snd_wnd 5328 * if header_prediction is to be made 5329 * 'S' will always be tp->tcp_header_len >> 2 5330 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to 5331 * turn it off (when there are holes in the receive 5332 * space for instance) 5333 * PSH flag is ignored. 5334 */ 5335 5336 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && 5337 TCP_SKB_CB(skb)->seq == tp->rcv_nxt && 5338 !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) { 5339 int tcp_header_len = tp->tcp_header_len; 5340 5341 /* Timestamp header prediction: tcp_header_len 5342 * is automatically equal to th->doff*4 due to pred_flags 5343 * match. 5344 */ 5345 5346 /* Check timestamp */ 5347 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { 5348 /* No? Slow path! */ 5349 if (!tcp_parse_aligned_timestamp(tp, th)) 5350 goto slow_path; 5351 5352 /* If PAWS failed, check it more carefully in slow path */ 5353 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) 5354 goto slow_path; 5355 5356 /* DO NOT update ts_recent here, if checksum fails 5357 * and timestamp was corrupted part, it will result 5358 * in a hung connection since we will drop all 5359 * future packets due to the PAWS test. 5360 */ 5361 } 5362 5363 if (len <= tcp_header_len) { 5364 /* Bulk data transfer: sender */ 5365 if (len == tcp_header_len) { 5366 /* Predicted packet is in window by definition. 5367 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 5368 * Hence, check seq<=rcv_wup reduces to: 5369 */ 5370 if (tcp_header_len == 5371 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 5372 tp->rcv_nxt == tp->rcv_wup) 5373 tcp_store_ts_recent(tp); 5374 5375 /* We know that such packets are checksummed 5376 * on entry. 5377 */ 5378 tcp_ack(sk, skb, 0); 5379 __kfree_skb(skb); 5380 tcp_data_snd_check(sk); 5381 return 0; 5382 } else { /* Header too small */ 5383 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); 5384 goto discard; 5385 } 5386 } else { 5387 int eaten = 0; 5388 int copied_early = 0; 5389 5390 if (tp->copied_seq == tp->rcv_nxt && 5391 len - tcp_header_len <= tp->ucopy.len) { 5392 #ifdef CONFIG_NET_DMA 5393 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) { 5394 copied_early = 1; 5395 eaten = 1; 5396 } 5397 #endif 5398 if (tp->ucopy.task == current && 5399 sock_owned_by_user(sk) && !copied_early) { 5400 __set_current_state(TASK_RUNNING); 5401 5402 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) 5403 eaten = 1; 5404 } 5405 if (eaten) { 5406 /* Predicted packet is in window by definition. 5407 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 5408 * Hence, check seq<=rcv_wup reduces to: 5409 */ 5410 if (tcp_header_len == 5411 (sizeof(struct tcphdr) + 5412 TCPOLEN_TSTAMP_ALIGNED) && 5413 tp->rcv_nxt == tp->rcv_wup) 5414 tcp_store_ts_recent(tp); 5415 5416 tcp_rcv_rtt_measure_ts(sk, skb); 5417 5418 __skb_pull(skb, tcp_header_len); 5419 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 5420 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITSTOUSER); 5421 } 5422 if (copied_early) 5423 tcp_cleanup_rbuf(sk, skb->len); 5424 } 5425 if (!eaten) { 5426 if (tcp_checksum_complete_user(sk, skb)) 5427 goto csum_error; 5428 5429 /* Predicted packet is in window by definition. 5430 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 5431 * Hence, check seq<=rcv_wup reduces to: 5432 */ 5433 if (tcp_header_len == 5434 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 5435 tp->rcv_nxt == tp->rcv_wup) 5436 tcp_store_ts_recent(tp); 5437 5438 tcp_rcv_rtt_measure_ts(sk, skb); 5439 5440 if ((int)skb->truesize > sk->sk_forward_alloc) 5441 goto step5; 5442 5443 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS); 5444 5445 /* Bulk data transfer: receiver */ 5446 __skb_pull(skb, tcp_header_len); 5447 __skb_queue_tail(&sk->sk_receive_queue, skb); 5448 skb_set_owner_r(skb, sk); 5449 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 5450 } 5451 5452 tcp_event_data_recv(sk, skb); 5453 5454 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { 5455 /* Well, only one small jumplet in fast path... */ 5456 tcp_ack(sk, skb, FLAG_DATA); 5457 tcp_data_snd_check(sk); 5458 if (!inet_csk_ack_scheduled(sk)) 5459 goto no_ack; 5460 } 5461 5462 if (!copied_early || tp->rcv_nxt != tp->rcv_wup) 5463 __tcp_ack_snd_check(sk, 0); 5464 no_ack: 5465 #ifdef CONFIG_NET_DMA 5466 if (copied_early) 5467 __skb_queue_tail(&sk->sk_async_wait_queue, skb); 5468 else 5469 #endif 5470 if (eaten) 5471 __kfree_skb(skb); 5472 else 5473 sk->sk_data_ready(sk, 0); 5474 return 0; 5475 } 5476 } 5477 5478 slow_path: 5479 if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb)) 5480 goto csum_error; 5481 5482 /* 5483 * Standard slow path. 5484 */ 5485 5486 res = tcp_validate_incoming(sk, skb, th, 1); 5487 if (res <= 0) 5488 return -res; 5489 5490 step5: 5491 if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0) 5492 goto discard; 5493 5494 tcp_rcv_rtt_measure_ts(sk, skb); 5495 5496 /* Process urgent data. */ 5497 tcp_urg(sk, skb, th); 5498 5499 /* step 7: process the segment text */ 5500 tcp_data_queue(sk, skb); 5501 5502 tcp_data_snd_check(sk); 5503 tcp_ack_snd_check(sk); 5504 return 0; 5505 5506 csum_error: 5507 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); 5508 5509 discard: 5510 __kfree_skb(skb); 5511 return 0; 5512 } 5513 EXPORT_SYMBOL(tcp_rcv_established); 5514 5515 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 5516 const struct tcphdr *th, unsigned int len) 5517 { 5518 const u8 *hash_location; 5519 struct inet_connection_sock *icsk = inet_csk(sk); 5520 struct tcp_sock *tp = tcp_sk(sk); 5521 struct tcp_cookie_values *cvp = tp->cookie_values; 5522 int saved_clamp = tp->rx_opt.mss_clamp; 5523 5524 tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0); 5525 5526 if (th->ack) { 5527 /* rfc793: 5528 * "If the state is SYN-SENT then 5529 * first check the ACK bit 5530 * If the ACK bit is set 5531 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send 5532 * a reset (unless the RST bit is set, if so drop 5533 * the segment and return)" 5534 * 5535 * We do not send data with SYN, so that RFC-correct 5536 * test reduces to: 5537 */ 5538 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt) 5539 goto reset_and_undo; 5540 5541 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 5542 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, 5543 tcp_time_stamp)) { 5544 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSACTIVEREJECTED); 5545 goto reset_and_undo; 5546 } 5547 5548 /* Now ACK is acceptable. 5549 * 5550 * "If the RST bit is set 5551 * If the ACK was acceptable then signal the user "error: 5552 * connection reset", drop the segment, enter CLOSED state, 5553 * delete TCB, and return." 5554 */ 5555 5556 if (th->rst) { 5557 tcp_reset(sk); 5558 goto discard; 5559 } 5560 5561 /* rfc793: 5562 * "fifth, if neither of the SYN or RST bits is set then 5563 * drop the segment and return." 5564 * 5565 * See note below! 5566 * --ANK(990513) 5567 */ 5568 if (!th->syn) 5569 goto discard_and_undo; 5570 5571 /* rfc793: 5572 * "If the SYN bit is on ... 5573 * are acceptable then ... 5574 * (our SYN has been ACKed), change the connection 5575 * state to ESTABLISHED..." 5576 */ 5577 5578 TCP_ECN_rcv_synack(tp, th); 5579 5580 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 5581 tcp_ack(sk, skb, FLAG_SLOWPATH); 5582 5583 /* Ok.. it's good. Set up sequence numbers and 5584 * move to established. 5585 */ 5586 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 5587 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 5588 5589 /* RFC1323: The window in SYN & SYN/ACK segments is 5590 * never scaled. 5591 */ 5592 tp->snd_wnd = ntohs(th->window); 5593 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); 5594 5595 if (!tp->rx_opt.wscale_ok) { 5596 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; 5597 tp->window_clamp = min(tp->window_clamp, 65535U); 5598 } 5599 5600 if (tp->rx_opt.saw_tstamp) { 5601 tp->rx_opt.tstamp_ok = 1; 5602 tp->tcp_header_len = 5603 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 5604 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 5605 tcp_store_ts_recent(tp); 5606 } else { 5607 tp->tcp_header_len = sizeof(struct tcphdr); 5608 } 5609 5610 if (tcp_is_sack(tp) && sysctl_tcp_fack) 5611 tcp_enable_fack(tp); 5612 5613 tcp_mtup_init(sk); 5614 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 5615 tcp_initialize_rcv_mss(sk); 5616 5617 /* Remember, tcp_poll() does not lock socket! 5618 * Change state from SYN-SENT only after copied_seq 5619 * is initialized. */ 5620 tp->copied_seq = tp->rcv_nxt; 5621 5622 if (cvp != NULL && 5623 cvp->cookie_pair_size > 0 && 5624 tp->rx_opt.cookie_plus > 0) { 5625 int cookie_size = tp->rx_opt.cookie_plus 5626 - TCPOLEN_COOKIE_BASE; 5627 int cookie_pair_size = cookie_size 5628 + cvp->cookie_desired; 5629 5630 /* A cookie extension option was sent and returned. 5631 * Note that each incoming SYNACK replaces the 5632 * Responder cookie. The initial exchange is most 5633 * fragile, as protection against spoofing relies 5634 * entirely upon the sequence and timestamp (above). 5635 * This replacement strategy allows the correct pair to 5636 * pass through, while any others will be filtered via 5637 * Responder verification later. 5638 */ 5639 if (sizeof(cvp->cookie_pair) >= cookie_pair_size) { 5640 memcpy(&cvp->cookie_pair[cvp->cookie_desired], 5641 hash_location, cookie_size); 5642 cvp->cookie_pair_size = cookie_pair_size; 5643 } 5644 } 5645 5646 smp_mb(); 5647 tcp_set_state(sk, TCP_ESTABLISHED); 5648 5649 security_inet_conn_established(sk, skb); 5650 5651 /* Make sure socket is routed, for correct metrics. */ 5652 icsk->icsk_af_ops->rebuild_header(sk); 5653 5654 tcp_init_metrics(sk); 5655 5656 tcp_init_congestion_control(sk); 5657 5658 /* Prevent spurious tcp_cwnd_restart() on first data 5659 * packet. 5660 */ 5661 tp->lsndtime = tcp_time_stamp; 5662 5663 tcp_init_buffer_space(sk); 5664 5665 if (sock_flag(sk, SOCK_KEEPOPEN)) 5666 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); 5667 5668 if (!tp->rx_opt.snd_wscale) 5669 __tcp_fast_path_on(tp, tp->snd_wnd); 5670 else 5671 tp->pred_flags = 0; 5672 5673 if (!sock_flag(sk, SOCK_DEAD)) { 5674 sk->sk_state_change(sk); 5675 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT); 5676 } 5677 5678 if (sk->sk_write_pending || 5679 icsk->icsk_accept_queue.rskq_defer_accept || 5680 icsk->icsk_ack.pingpong) { 5681 /* Save one ACK. Data will be ready after 5682 * several ticks, if write_pending is set. 5683 * 5684 * It may be deleted, but with this feature tcpdumps 5685 * look so _wonderfully_ clever, that I was not able 5686 * to stand against the temptation 8) --ANK 5687 */ 5688 inet_csk_schedule_ack(sk); 5689 icsk->icsk_ack.lrcvtime = tcp_time_stamp; 5690 icsk->icsk_ack.ato = TCP_ATO_MIN; 5691 tcp_incr_quickack(sk); 5692 tcp_enter_quickack_mode(sk); 5693 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 5694 TCP_DELACK_MAX, TCP_RTO_MAX); 5695 5696 discard: 5697 __kfree_skb(skb); 5698 return 0; 5699 } else { 5700 tcp_send_ack(sk); 5701 } 5702 return -1; 5703 } 5704 5705 /* No ACK in the segment */ 5706 5707 if (th->rst) { 5708 /* rfc793: 5709 * "If the RST bit is set 5710 * 5711 * Otherwise (no ACK) drop the segment and return." 5712 */ 5713 5714 goto discard_and_undo; 5715 } 5716 5717 /* PAWS check. */ 5718 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && 5719 tcp_paws_reject(&tp->rx_opt, 0)) 5720 goto discard_and_undo; 5721 5722 if (th->syn) { 5723 /* We see SYN without ACK. It is attempt of 5724 * simultaneous connect with crossed SYNs. 5725 * Particularly, it can be connect to self. 5726 */ 5727 tcp_set_state(sk, TCP_SYN_RECV); 5728 5729 if (tp->rx_opt.saw_tstamp) { 5730 tp->rx_opt.tstamp_ok = 1; 5731 tcp_store_ts_recent(tp); 5732 tp->tcp_header_len = 5733 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 5734 } else { 5735 tp->tcp_header_len = sizeof(struct tcphdr); 5736 } 5737 5738 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 5739 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 5740 5741 /* RFC1323: The window in SYN & SYN/ACK segments is 5742 * never scaled. 5743 */ 5744 tp->snd_wnd = ntohs(th->window); 5745 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 5746 tp->max_window = tp->snd_wnd; 5747 5748 TCP_ECN_rcv_syn(tp, th); 5749 5750 tcp_mtup_init(sk); 5751 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 5752 tcp_initialize_rcv_mss(sk); 5753 5754 tcp_send_synack(sk); 5755 #if 0 5756 /* Note, we could accept data and URG from this segment. 5757 * There are no obstacles to make this. 5758 * 5759 * However, if we ignore data in ACKless segments sometimes, 5760 * we have no reasons to accept it sometimes. 5761 * Also, seems the code doing it in step6 of tcp_rcv_state_process 5762 * is not flawless. So, discard packet for sanity. 5763 * Uncomment this return to process the data. 5764 */ 5765 return -1; 5766 #else 5767 goto discard; 5768 #endif 5769 } 5770 /* "fifth, if neither of the SYN or RST bits is set then 5771 * drop the segment and return." 5772 */ 5773 5774 discard_and_undo: 5775 tcp_clear_options(&tp->rx_opt); 5776 tp->rx_opt.mss_clamp = saved_clamp; 5777 goto discard; 5778 5779 reset_and_undo: 5780 tcp_clear_options(&tp->rx_opt); 5781 tp->rx_opt.mss_clamp = saved_clamp; 5782 return 1; 5783 } 5784 5785 /* 5786 * This function implements the receiving procedure of RFC 793 for 5787 * all states except ESTABLISHED and TIME_WAIT. 5788 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be 5789 * address independent. 5790 */ 5791 5792 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, 5793 const struct tcphdr *th, unsigned int len) 5794 { 5795 struct tcp_sock *tp = tcp_sk(sk); 5796 struct inet_connection_sock *icsk = inet_csk(sk); 5797 int queued = 0; 5798 int res; 5799 5800 tp->rx_opt.saw_tstamp = 0; 5801 5802 switch (sk->sk_state) { 5803 case TCP_CLOSE: 5804 goto discard; 5805 5806 case TCP_LISTEN: 5807 if (th->ack) 5808 return 1; 5809 5810 if (th->rst) 5811 goto discard; 5812 5813 if (th->syn) { 5814 if (th->fin) 5815 goto discard; 5816 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0) 5817 return 1; 5818 5819 /* Now we have several options: In theory there is 5820 * nothing else in the frame. KA9Q has an option to 5821 * send data with the syn, BSD accepts data with the 5822 * syn up to the [to be] advertised window and 5823 * Solaris 2.1 gives you a protocol error. For now 5824 * we just ignore it, that fits the spec precisely 5825 * and avoids incompatibilities. It would be nice in 5826 * future to drop through and process the data. 5827 * 5828 * Now that TTCP is starting to be used we ought to 5829 * queue this data. 5830 * But, this leaves one open to an easy denial of 5831 * service attack, and SYN cookies can't defend 5832 * against this problem. So, we drop the data 5833 * in the interest of security over speed unless 5834 * it's still in use. 5835 */ 5836 kfree_skb(skb); 5837 return 0; 5838 } 5839 goto discard; 5840 5841 case TCP_SYN_SENT: 5842 queued = tcp_rcv_synsent_state_process(sk, skb, th, len); 5843 if (queued >= 0) 5844 return queued; 5845 5846 /* Do step6 onward by hand. */ 5847 tcp_urg(sk, skb, th); 5848 __kfree_skb(skb); 5849 tcp_data_snd_check(sk); 5850 return 0; 5851 } 5852 5853 res = tcp_validate_incoming(sk, skb, th, 0); 5854 if (res <= 0) 5855 return -res; 5856 5857 /* step 5: check the ACK field */ 5858 if (th->ack) { 5859 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH) > 0; 5860 5861 switch (sk->sk_state) { 5862 case TCP_SYN_RECV: 5863 if (acceptable) { 5864 tp->copied_seq = tp->rcv_nxt; 5865 smp_mb(); 5866 tcp_set_state(sk, TCP_ESTABLISHED); 5867 sk->sk_state_change(sk); 5868 5869 /* Note, that this wakeup is only for marginal 5870 * crossed SYN case. Passively open sockets 5871 * are not waked up, because sk->sk_sleep == 5872 * NULL and sk->sk_socket == NULL. 5873 */ 5874 if (sk->sk_socket) 5875 sk_wake_async(sk, 5876 SOCK_WAKE_IO, POLL_OUT); 5877 5878 tp->snd_una = TCP_SKB_CB(skb)->ack_seq; 5879 tp->snd_wnd = ntohs(th->window) << 5880 tp->rx_opt.snd_wscale; 5881 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); 5882 5883 if (tp->rx_opt.tstamp_ok) 5884 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 5885 5886 /* Make sure socket is routed, for 5887 * correct metrics. 5888 */ 5889 icsk->icsk_af_ops->rebuild_header(sk); 5890 5891 tcp_init_metrics(sk); 5892 5893 tcp_init_congestion_control(sk); 5894 5895 /* Prevent spurious tcp_cwnd_restart() on 5896 * first data packet. 5897 */ 5898 tp->lsndtime = tcp_time_stamp; 5899 5900 tcp_mtup_init(sk); 5901 tcp_initialize_rcv_mss(sk); 5902 tcp_init_buffer_space(sk); 5903 tcp_fast_path_on(tp); 5904 } else { 5905 return 1; 5906 } 5907 break; 5908 5909 case TCP_FIN_WAIT1: 5910 if (tp->snd_una == tp->write_seq) { 5911 tcp_set_state(sk, TCP_FIN_WAIT2); 5912 sk->sk_shutdown |= SEND_SHUTDOWN; 5913 dst_confirm(__sk_dst_get(sk)); 5914 5915 if (!sock_flag(sk, SOCK_DEAD)) 5916 /* Wake up lingering close() */ 5917 sk->sk_state_change(sk); 5918 else { 5919 int tmo; 5920 5921 if (tp->linger2 < 0 || 5922 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 5923 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { 5924 tcp_done(sk); 5925 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA); 5926 return 1; 5927 } 5928 5929 tmo = tcp_fin_time(sk); 5930 if (tmo > TCP_TIMEWAIT_LEN) { 5931 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); 5932 } else if (th->fin || sock_owned_by_user(sk)) { 5933 /* Bad case. We could lose such FIN otherwise. 5934 * It is not a big problem, but it looks confusing 5935 * and not so rare event. We still can lose it now, 5936 * if it spins in bh_lock_sock(), but it is really 5937 * marginal case. 5938 */ 5939 inet_csk_reset_keepalive_timer(sk, tmo); 5940 } else { 5941 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 5942 goto discard; 5943 } 5944 } 5945 } 5946 break; 5947 5948 case TCP_CLOSING: 5949 if (tp->snd_una == tp->write_seq) { 5950 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 5951 goto discard; 5952 } 5953 break; 5954 5955 case TCP_LAST_ACK: 5956 if (tp->snd_una == tp->write_seq) { 5957 tcp_update_metrics(sk); 5958 tcp_done(sk); 5959 goto discard; 5960 } 5961 break; 5962 } 5963 } else 5964 goto discard; 5965 5966 /* step 6: check the URG bit */ 5967 tcp_urg(sk, skb, th); 5968 5969 /* step 7: process the segment text */ 5970 switch (sk->sk_state) { 5971 case TCP_CLOSE_WAIT: 5972 case TCP_CLOSING: 5973 case TCP_LAST_ACK: 5974 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 5975 break; 5976 case TCP_FIN_WAIT1: 5977 case TCP_FIN_WAIT2: 5978 /* RFC 793 says to queue data in these states, 5979 * RFC 1122 says we MUST send a reset. 5980 * BSD 4.4 also does reset. 5981 */ 5982 if (sk->sk_shutdown & RCV_SHUTDOWN) { 5983 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 5984 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { 5985 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA); 5986 tcp_reset(sk); 5987 return 1; 5988 } 5989 } 5990 /* Fall through */ 5991 case TCP_ESTABLISHED: 5992 tcp_data_queue(sk, skb); 5993 queued = 1; 5994 break; 5995 } 5996 5997 /* tcp_data could move socket to TIME-WAIT */ 5998 if (sk->sk_state != TCP_CLOSE) { 5999 tcp_data_snd_check(sk); 6000 tcp_ack_snd_check(sk); 6001 } 6002 6003 if (!queued) { 6004 discard: 6005 __kfree_skb(skb); 6006 } 6007 return 0; 6008 } 6009 EXPORT_SYMBOL(tcp_rcv_state_process); 6010