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