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 #define pr_fmt(fmt) "TCP: " fmt 65 66 #include <linux/mm.h> 67 #include <linux/slab.h> 68 #include <linux/module.h> 69 #include <linux/sysctl.h> 70 #include <linux/kernel.h> 71 #include <net/dst.h> 72 #include <net/tcp.h> 73 #include <net/inet_common.h> 74 #include <linux/ipsec.h> 75 #include <asm/unaligned.h> 76 #include <net/netdma.h> 77 78 int sysctl_tcp_timestamps __read_mostly = 1; 79 int sysctl_tcp_window_scaling __read_mostly = 1; 80 int sysctl_tcp_sack __read_mostly = 1; 81 int sysctl_tcp_fack __read_mostly = 1; 82 int sysctl_tcp_reordering __read_mostly = TCP_FASTRETRANS_THRESH; 83 EXPORT_SYMBOL(sysctl_tcp_reordering); 84 int sysctl_tcp_ecn __read_mostly = 2; 85 EXPORT_SYMBOL(sysctl_tcp_ecn); 86 int sysctl_tcp_dsack __read_mostly = 1; 87 int sysctl_tcp_app_win __read_mostly = 31; 88 int sysctl_tcp_adv_win_scale __read_mostly = 2; 89 EXPORT_SYMBOL(sysctl_tcp_adv_win_scale); 90 91 int sysctl_tcp_stdurg __read_mostly; 92 int sysctl_tcp_rfc1337 __read_mostly; 93 int sysctl_tcp_max_orphans __read_mostly = NR_FILE; 94 int sysctl_tcp_frto __read_mostly = 2; 95 int sysctl_tcp_frto_response __read_mostly; 96 int sysctl_tcp_nometrics_save __read_mostly; 97 98 int sysctl_tcp_thin_dupack __read_mostly; 99 100 int sysctl_tcp_moderate_rcvbuf __read_mostly = 1; 101 int sysctl_tcp_abc __read_mostly; 102 103 #define FLAG_DATA 0x01 /* Incoming frame contained data. */ 104 #define FLAG_WIN_UPDATE 0x02 /* Incoming ACK was a window update. */ 105 #define FLAG_DATA_ACKED 0x04 /* This ACK acknowledged new data. */ 106 #define FLAG_RETRANS_DATA_ACKED 0x08 /* "" "" some of which was retransmitted. */ 107 #define FLAG_SYN_ACKED 0x10 /* This ACK acknowledged SYN. */ 108 #define FLAG_DATA_SACKED 0x20 /* New SACK. */ 109 #define FLAG_ECE 0x40 /* ECE in this ACK */ 110 #define FLAG_SLOWPATH 0x100 /* Do not skip RFC checks for window update.*/ 111 #define FLAG_ONLY_ORIG_SACKED 0x200 /* SACKs only non-rexmit sent before RTO */ 112 #define FLAG_SND_UNA_ADVANCED 0x400 /* Snd_una was changed (!= FLAG_DATA_ACKED) */ 113 #define FLAG_DSACKING_ACK 0x800 /* SACK blocks contained D-SACK info */ 114 #define FLAG_NONHEAD_RETRANS_ACKED 0x1000 /* Non-head rexmitted data was ACKed */ 115 #define FLAG_SACK_RENEGING 0x2000 /* snd_una advanced to a sacked seq */ 116 117 #define FLAG_ACKED (FLAG_DATA_ACKED|FLAG_SYN_ACKED) 118 #define FLAG_NOT_DUP (FLAG_DATA|FLAG_WIN_UPDATE|FLAG_ACKED) 119 #define FLAG_CA_ALERT (FLAG_DATA_SACKED|FLAG_ECE) 120 #define FLAG_FORWARD_PROGRESS (FLAG_ACKED|FLAG_DATA_SACKED) 121 #define FLAG_ANY_PROGRESS (FLAG_FORWARD_PROGRESS|FLAG_SND_UNA_ADVANCED) 122 123 #define TCP_REMNANT (TCP_FLAG_FIN|TCP_FLAG_URG|TCP_FLAG_SYN|TCP_FLAG_PSH) 124 #define TCP_HP_BITS (~(TCP_RESERVED_BITS|TCP_FLAG_PSH)) 125 126 /* Adapt the MSS value used to make delayed ack decision to the 127 * real world. 128 */ 129 static void tcp_measure_rcv_mss(struct sock *sk, const struct sk_buff *skb) 130 { 131 struct inet_connection_sock *icsk = inet_csk(sk); 132 const unsigned int lss = icsk->icsk_ack.last_seg_size; 133 unsigned int len; 134 135 icsk->icsk_ack.last_seg_size = 0; 136 137 /* skb->len may jitter because of SACKs, even if peer 138 * sends good full-sized frames. 139 */ 140 len = skb_shinfo(skb)->gso_size ? : skb->len; 141 if (len >= icsk->icsk_ack.rcv_mss) { 142 icsk->icsk_ack.rcv_mss = len; 143 } else { 144 /* Otherwise, we make more careful check taking into account, 145 * that SACKs block is variable. 146 * 147 * "len" is invariant segment length, including TCP header. 148 */ 149 len += skb->data - skb_transport_header(skb); 150 if (len >= TCP_MSS_DEFAULT + sizeof(struct tcphdr) || 151 /* If PSH is not set, packet should be 152 * full sized, provided peer TCP is not badly broken. 153 * This observation (if it is correct 8)) allows 154 * to handle super-low mtu links fairly. 155 */ 156 (len >= TCP_MIN_MSS + sizeof(struct tcphdr) && 157 !(tcp_flag_word(tcp_hdr(skb)) & TCP_REMNANT))) { 158 /* Subtract also invariant (if peer is RFC compliant), 159 * tcp header plus fixed timestamp option length. 160 * Resulting "len" is MSS free of SACK jitter. 161 */ 162 len -= tcp_sk(sk)->tcp_header_len; 163 icsk->icsk_ack.last_seg_size = len; 164 if (len == lss) { 165 icsk->icsk_ack.rcv_mss = len; 166 return; 167 } 168 } 169 if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) 170 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; 171 icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; 172 } 173 } 174 175 static void tcp_incr_quickack(struct sock *sk) 176 { 177 struct inet_connection_sock *icsk = inet_csk(sk); 178 unsigned quickacks = tcp_sk(sk)->rcv_wnd / (2 * icsk->icsk_ack.rcv_mss); 179 180 if (quickacks == 0) 181 quickacks = 2; 182 if (quickacks > icsk->icsk_ack.quick) 183 icsk->icsk_ack.quick = min(quickacks, TCP_MAX_QUICKACKS); 184 } 185 186 static void tcp_enter_quickack_mode(struct sock *sk) 187 { 188 struct inet_connection_sock *icsk = inet_csk(sk); 189 tcp_incr_quickack(sk); 190 icsk->icsk_ack.pingpong = 0; 191 icsk->icsk_ack.ato = TCP_ATO_MIN; 192 } 193 194 /* Send ACKs quickly, if "quick" count is not exhausted 195 * and the session is not interactive. 196 */ 197 198 static inline int tcp_in_quickack_mode(const struct sock *sk) 199 { 200 const struct inet_connection_sock *icsk = inet_csk(sk); 201 return icsk->icsk_ack.quick && !icsk->icsk_ack.pingpong; 202 } 203 204 static inline void TCP_ECN_queue_cwr(struct tcp_sock *tp) 205 { 206 if (tp->ecn_flags & TCP_ECN_OK) 207 tp->ecn_flags |= TCP_ECN_QUEUE_CWR; 208 } 209 210 static inline void TCP_ECN_accept_cwr(struct tcp_sock *tp, const struct sk_buff *skb) 211 { 212 if (tcp_hdr(skb)->cwr) 213 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; 214 } 215 216 static inline void TCP_ECN_withdraw_cwr(struct tcp_sock *tp) 217 { 218 tp->ecn_flags &= ~TCP_ECN_DEMAND_CWR; 219 } 220 221 static inline void TCP_ECN_check_ce(struct tcp_sock *tp, const struct sk_buff *skb) 222 { 223 if (!(tp->ecn_flags & TCP_ECN_OK)) 224 return; 225 226 switch (TCP_SKB_CB(skb)->ip_dsfield & INET_ECN_MASK) { 227 case INET_ECN_NOT_ECT: 228 /* Funny extension: if ECT is not set on a segment, 229 * and we already seen ECT on a previous segment, 230 * it is probably a retransmit. 231 */ 232 if (tp->ecn_flags & TCP_ECN_SEEN) 233 tcp_enter_quickack_mode((struct sock *)tp); 234 break; 235 case INET_ECN_CE: 236 tp->ecn_flags |= TCP_ECN_DEMAND_CWR; 237 /* fallinto */ 238 default: 239 tp->ecn_flags |= TCP_ECN_SEEN; 240 } 241 } 242 243 static inline void TCP_ECN_rcv_synack(struct tcp_sock *tp, const struct tcphdr *th) 244 { 245 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || th->cwr)) 246 tp->ecn_flags &= ~TCP_ECN_OK; 247 } 248 249 static inline void TCP_ECN_rcv_syn(struct tcp_sock *tp, const struct tcphdr *th) 250 { 251 if ((tp->ecn_flags & TCP_ECN_OK) && (!th->ece || !th->cwr)) 252 tp->ecn_flags &= ~TCP_ECN_OK; 253 } 254 255 static inline int TCP_ECN_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr *th) 256 { 257 if (th->ece && !th->syn && (tp->ecn_flags & TCP_ECN_OK)) 258 return 1; 259 return 0; 260 } 261 262 /* Buffer size and advertised window tuning. 263 * 264 * 1. Tuning sk->sk_sndbuf, when connection enters established state. 265 */ 266 267 static void tcp_fixup_sndbuf(struct sock *sk) 268 { 269 int sndmem = SKB_TRUESIZE(tcp_sk(sk)->rx_opt.mss_clamp + MAX_TCP_HEADER); 270 271 sndmem *= TCP_INIT_CWND; 272 if (sk->sk_sndbuf < sndmem) 273 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); 274 } 275 276 /* 2. Tuning advertised window (window_clamp, rcv_ssthresh) 277 * 278 * All tcp_full_space() is split to two parts: "network" buffer, allocated 279 * forward and advertised in receiver window (tp->rcv_wnd) and 280 * "application buffer", required to isolate scheduling/application 281 * latencies from network. 282 * window_clamp is maximal advertised window. It can be less than 283 * tcp_full_space(), in this case tcp_full_space() - window_clamp 284 * is reserved for "application" buffer. The less window_clamp is 285 * the smoother our behaviour from viewpoint of network, but the lower 286 * throughput and the higher sensitivity of the connection to losses. 8) 287 * 288 * rcv_ssthresh is more strict window_clamp used at "slow start" 289 * phase to predict further behaviour of this connection. 290 * It is used for two goals: 291 * - to enforce header prediction at sender, even when application 292 * requires some significant "application buffer". It is check #1. 293 * - to prevent pruning of receive queue because of misprediction 294 * of receiver window. Check #2. 295 * 296 * The scheme does not work when sender sends good segments opening 297 * window and then starts to feed us spaghetti. But it should work 298 * in common situations. Otherwise, we have to rely on queue collapsing. 299 */ 300 301 /* Slow part of check#2. */ 302 static int __tcp_grow_window(const struct sock *sk, const struct sk_buff *skb) 303 { 304 struct tcp_sock *tp = tcp_sk(sk); 305 /* Optimize this! */ 306 int truesize = tcp_win_from_space(skb->truesize) >> 1; 307 int window = tcp_win_from_space(sysctl_tcp_rmem[2]) >> 1; 308 309 while (tp->rcv_ssthresh <= window) { 310 if (truesize <= skb->len) 311 return 2 * inet_csk(sk)->icsk_ack.rcv_mss; 312 313 truesize >>= 1; 314 window >>= 1; 315 } 316 return 0; 317 } 318 319 static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb) 320 { 321 struct tcp_sock *tp = tcp_sk(sk); 322 323 /* Check #1 */ 324 if (tp->rcv_ssthresh < tp->window_clamp && 325 (int)tp->rcv_ssthresh < tcp_space(sk) && 326 !sk_under_memory_pressure(sk)) { 327 int incr; 328 329 /* Check #2. Increase window, if skb with such overhead 330 * will fit to rcvbuf in future. 331 */ 332 if (tcp_win_from_space(skb->truesize) <= skb->len) 333 incr = 2 * tp->advmss; 334 else 335 incr = __tcp_grow_window(sk, skb); 336 337 if (incr) { 338 tp->rcv_ssthresh = min(tp->rcv_ssthresh + incr, 339 tp->window_clamp); 340 inet_csk(sk)->icsk_ack.quick |= 1; 341 } 342 } 343 } 344 345 /* 3. Tuning rcvbuf, when connection enters established state. */ 346 347 static void tcp_fixup_rcvbuf(struct sock *sk) 348 { 349 u32 mss = tcp_sk(sk)->advmss; 350 u32 icwnd = TCP_DEFAULT_INIT_RCVWND; 351 int rcvmem; 352 353 /* Limit to 10 segments if mss <= 1460, 354 * or 14600/mss segments, with a minimum of two segments. 355 */ 356 if (mss > 1460) 357 icwnd = max_t(u32, (1460 * TCP_DEFAULT_INIT_RCVWND) / mss, 2); 358 359 rcvmem = SKB_TRUESIZE(mss + MAX_TCP_HEADER); 360 while (tcp_win_from_space(rcvmem) < mss) 361 rcvmem += 128; 362 363 rcvmem *= icwnd; 364 365 if (sk->sk_rcvbuf < rcvmem) 366 sk->sk_rcvbuf = min(rcvmem, sysctl_tcp_rmem[2]); 367 } 368 369 /* 4. Try to fixup all. It is made immediately after connection enters 370 * established state. 371 */ 372 static void tcp_init_buffer_space(struct sock *sk) 373 { 374 struct tcp_sock *tp = tcp_sk(sk); 375 int maxwin; 376 377 if (!(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) 378 tcp_fixup_rcvbuf(sk); 379 if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) 380 tcp_fixup_sndbuf(sk); 381 382 tp->rcvq_space.space = tp->rcv_wnd; 383 384 maxwin = tcp_full_space(sk); 385 386 if (tp->window_clamp >= maxwin) { 387 tp->window_clamp = maxwin; 388 389 if (sysctl_tcp_app_win && maxwin > 4 * tp->advmss) 390 tp->window_clamp = max(maxwin - 391 (maxwin >> sysctl_tcp_app_win), 392 4 * tp->advmss); 393 } 394 395 /* Force reservation of one segment. */ 396 if (sysctl_tcp_app_win && 397 tp->window_clamp > 2 * tp->advmss && 398 tp->window_clamp + tp->advmss > maxwin) 399 tp->window_clamp = max(2 * tp->advmss, maxwin - tp->advmss); 400 401 tp->rcv_ssthresh = min(tp->rcv_ssthresh, tp->window_clamp); 402 tp->snd_cwnd_stamp = tcp_time_stamp; 403 } 404 405 /* 5. Recalculate window clamp after socket hit its memory bounds. */ 406 static void tcp_clamp_window(struct sock *sk) 407 { 408 struct tcp_sock *tp = tcp_sk(sk); 409 struct inet_connection_sock *icsk = inet_csk(sk); 410 411 icsk->icsk_ack.quick = 0; 412 413 if (sk->sk_rcvbuf < sysctl_tcp_rmem[2] && 414 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK) && 415 !sk_under_memory_pressure(sk) && 416 sk_memory_allocated(sk) < sk_prot_mem_limits(sk, 0)) { 417 sk->sk_rcvbuf = min(atomic_read(&sk->sk_rmem_alloc), 418 sysctl_tcp_rmem[2]); 419 } 420 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf) 421 tp->rcv_ssthresh = min(tp->window_clamp, 2U * tp->advmss); 422 } 423 424 /* Initialize RCV_MSS value. 425 * RCV_MSS is an our guess about MSS used by the peer. 426 * We haven't any direct information about the MSS. 427 * It's better to underestimate the RCV_MSS rather than overestimate. 428 * Overestimations make us ACKing less frequently than needed. 429 * Underestimations are more easy to detect and fix by tcp_measure_rcv_mss(). 430 */ 431 void tcp_initialize_rcv_mss(struct sock *sk) 432 { 433 const struct tcp_sock *tp = tcp_sk(sk); 434 unsigned int hint = min_t(unsigned int, tp->advmss, tp->mss_cache); 435 436 hint = min(hint, tp->rcv_wnd / 2); 437 hint = min(hint, TCP_MSS_DEFAULT); 438 hint = max(hint, TCP_MIN_MSS); 439 440 inet_csk(sk)->icsk_ack.rcv_mss = hint; 441 } 442 EXPORT_SYMBOL(tcp_initialize_rcv_mss); 443 444 /* Receiver "autotuning" code. 445 * 446 * The algorithm for RTT estimation w/o timestamps is based on 447 * Dynamic Right-Sizing (DRS) by Wu Feng and Mike Fisk of LANL. 448 * <http://public.lanl.gov/radiant/pubs.html#DRS> 449 * 450 * More detail on this code can be found at 451 * <http://staff.psc.edu/jheffner/>, 452 * though this reference is out of date. A new paper 453 * is pending. 454 */ 455 static void tcp_rcv_rtt_update(struct tcp_sock *tp, u32 sample, int win_dep) 456 { 457 u32 new_sample = tp->rcv_rtt_est.rtt; 458 long m = sample; 459 460 if (m == 0) 461 m = 1; 462 463 if (new_sample != 0) { 464 /* If we sample in larger samples in the non-timestamp 465 * case, we could grossly overestimate the RTT especially 466 * with chatty applications or bulk transfer apps which 467 * are stalled on filesystem I/O. 468 * 469 * Also, since we are only going for a minimum in the 470 * non-timestamp case, we do not smooth things out 471 * else with timestamps disabled convergence takes too 472 * long. 473 */ 474 if (!win_dep) { 475 m -= (new_sample >> 3); 476 new_sample += m; 477 } else if (m < new_sample) 478 new_sample = m << 3; 479 } else { 480 /* No previous measure. */ 481 new_sample = m << 3; 482 } 483 484 if (tp->rcv_rtt_est.rtt != new_sample) 485 tp->rcv_rtt_est.rtt = new_sample; 486 } 487 488 static inline void tcp_rcv_rtt_measure(struct tcp_sock *tp) 489 { 490 if (tp->rcv_rtt_est.time == 0) 491 goto new_measure; 492 if (before(tp->rcv_nxt, tp->rcv_rtt_est.seq)) 493 return; 494 tcp_rcv_rtt_update(tp, jiffies - tp->rcv_rtt_est.time, 1); 495 496 new_measure: 497 tp->rcv_rtt_est.seq = tp->rcv_nxt + tp->rcv_wnd; 498 tp->rcv_rtt_est.time = tcp_time_stamp; 499 } 500 501 static inline void tcp_rcv_rtt_measure_ts(struct sock *sk, 502 const struct sk_buff *skb) 503 { 504 struct tcp_sock *tp = tcp_sk(sk); 505 if (tp->rx_opt.rcv_tsecr && 506 (TCP_SKB_CB(skb)->end_seq - 507 TCP_SKB_CB(skb)->seq >= inet_csk(sk)->icsk_ack.rcv_mss)) 508 tcp_rcv_rtt_update(tp, tcp_time_stamp - tp->rx_opt.rcv_tsecr, 0); 509 } 510 511 /* 512 * This function should be called every time data is copied to user space. 513 * It calculates the appropriate TCP receive buffer space. 514 */ 515 void tcp_rcv_space_adjust(struct sock *sk) 516 { 517 struct tcp_sock *tp = tcp_sk(sk); 518 int time; 519 int space; 520 521 if (tp->rcvq_space.time == 0) 522 goto new_measure; 523 524 time = tcp_time_stamp - tp->rcvq_space.time; 525 if (time < (tp->rcv_rtt_est.rtt >> 3) || tp->rcv_rtt_est.rtt == 0) 526 return; 527 528 space = 2 * (tp->copied_seq - tp->rcvq_space.seq); 529 530 space = max(tp->rcvq_space.space, space); 531 532 if (tp->rcvq_space.space != space) { 533 int rcvmem; 534 535 tp->rcvq_space.space = space; 536 537 if (sysctl_tcp_moderate_rcvbuf && 538 !(sk->sk_userlocks & SOCK_RCVBUF_LOCK)) { 539 int new_clamp = space; 540 541 /* Receive space grows, normalize in order to 542 * take into account packet headers and sk_buff 543 * structure overhead. 544 */ 545 space /= tp->advmss; 546 if (!space) 547 space = 1; 548 rcvmem = SKB_TRUESIZE(tp->advmss + MAX_TCP_HEADER); 549 while (tcp_win_from_space(rcvmem) < tp->advmss) 550 rcvmem += 128; 551 space *= rcvmem; 552 space = min(space, sysctl_tcp_rmem[2]); 553 if (space > sk->sk_rcvbuf) { 554 sk->sk_rcvbuf = space; 555 556 /* Make the window clamp follow along. */ 557 tp->window_clamp = new_clamp; 558 } 559 } 560 } 561 562 new_measure: 563 tp->rcvq_space.seq = tp->copied_seq; 564 tp->rcvq_space.time = tcp_time_stamp; 565 } 566 567 /* There is something which you must keep in mind when you analyze the 568 * behavior of the tp->ato delayed ack timeout interval. When a 569 * connection starts up, we want to ack as quickly as possible. The 570 * problem is that "good" TCP's do slow start at the beginning of data 571 * transmission. The means that until we send the first few ACK's the 572 * sender will sit on his end and only queue most of his data, because 573 * he can only send snd_cwnd unacked packets at any given time. For 574 * each ACK we send, he increments snd_cwnd and transmits more of his 575 * queue. -DaveM 576 */ 577 static void tcp_event_data_recv(struct sock *sk, struct sk_buff *skb) 578 { 579 struct tcp_sock *tp = tcp_sk(sk); 580 struct inet_connection_sock *icsk = inet_csk(sk); 581 u32 now; 582 583 inet_csk_schedule_ack(sk); 584 585 tcp_measure_rcv_mss(sk, skb); 586 587 tcp_rcv_rtt_measure(tp); 588 589 now = tcp_time_stamp; 590 591 if (!icsk->icsk_ack.ato) { 592 /* The _first_ data packet received, initialize 593 * delayed ACK engine. 594 */ 595 tcp_incr_quickack(sk); 596 icsk->icsk_ack.ato = TCP_ATO_MIN; 597 } else { 598 int m = now - icsk->icsk_ack.lrcvtime; 599 600 if (m <= TCP_ATO_MIN / 2) { 601 /* The fastest case is the first. */ 602 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + TCP_ATO_MIN / 2; 603 } else if (m < icsk->icsk_ack.ato) { 604 icsk->icsk_ack.ato = (icsk->icsk_ack.ato >> 1) + m; 605 if (icsk->icsk_ack.ato > icsk->icsk_rto) 606 icsk->icsk_ack.ato = icsk->icsk_rto; 607 } else if (m > icsk->icsk_rto) { 608 /* Too long gap. Apparently sender failed to 609 * restart window, so that we send ACKs quickly. 610 */ 611 tcp_incr_quickack(sk); 612 sk_mem_reclaim(sk); 613 } 614 } 615 icsk->icsk_ack.lrcvtime = now; 616 617 TCP_ECN_check_ce(tp, skb); 618 619 if (skb->len >= 128) 620 tcp_grow_window(sk, skb); 621 } 622 623 /* Called to compute a smoothed rtt estimate. The data fed to this 624 * routine either comes from timestamps, or from segments that were 625 * known _not_ to have been retransmitted [see Karn/Partridge 626 * Proceedings SIGCOMM 87]. The algorithm is from the SIGCOMM 88 627 * piece by Van Jacobson. 628 * NOTE: the next three routines used to be one big routine. 629 * To save cycles in the RFC 1323 implementation it was better to break 630 * it up into three procedures. -- erics 631 */ 632 static void tcp_rtt_estimator(struct sock *sk, const __u32 mrtt) 633 { 634 struct tcp_sock *tp = tcp_sk(sk); 635 long m = mrtt; /* RTT */ 636 637 /* The following amusing code comes from Jacobson's 638 * article in SIGCOMM '88. Note that rtt and mdev 639 * are scaled versions of rtt and mean deviation. 640 * This is designed to be as fast as possible 641 * m stands for "measurement". 642 * 643 * On a 1990 paper the rto value is changed to: 644 * RTO = rtt + 4 * mdev 645 * 646 * Funny. This algorithm seems to be very broken. 647 * These formulae increase RTO, when it should be decreased, increase 648 * too slowly, when it should be increased quickly, decrease too quickly 649 * etc. I guess in BSD RTO takes ONE value, so that it is absolutely 650 * does not matter how to _calculate_ it. Seems, it was trap 651 * that VJ failed to avoid. 8) 652 */ 653 if (m == 0) 654 m = 1; 655 if (tp->srtt != 0) { 656 m -= (tp->srtt >> 3); /* m is now error in rtt est */ 657 tp->srtt += m; /* rtt = 7/8 rtt + 1/8 new */ 658 if (m < 0) { 659 m = -m; /* m is now abs(error) */ 660 m -= (tp->mdev >> 2); /* similar update on mdev */ 661 /* This is similar to one of Eifel findings. 662 * Eifel blocks mdev updates when rtt decreases. 663 * This solution is a bit different: we use finer gain 664 * for mdev in this case (alpha*beta). 665 * Like Eifel it also prevents growth of rto, 666 * but also it limits too fast rto decreases, 667 * happening in pure Eifel. 668 */ 669 if (m > 0) 670 m >>= 3; 671 } else { 672 m -= (tp->mdev >> 2); /* similar update on mdev */ 673 } 674 tp->mdev += m; /* mdev = 3/4 mdev + 1/4 new */ 675 if (tp->mdev > tp->mdev_max) { 676 tp->mdev_max = tp->mdev; 677 if (tp->mdev_max > tp->rttvar) 678 tp->rttvar = tp->mdev_max; 679 } 680 if (after(tp->snd_una, tp->rtt_seq)) { 681 if (tp->mdev_max < tp->rttvar) 682 tp->rttvar -= (tp->rttvar - tp->mdev_max) >> 2; 683 tp->rtt_seq = tp->snd_nxt; 684 tp->mdev_max = tcp_rto_min(sk); 685 } 686 } else { 687 /* no previous measure. */ 688 tp->srtt = m << 3; /* take the measured time to be rtt */ 689 tp->mdev = m << 1; /* make sure rto = 3*rtt */ 690 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); 691 tp->rtt_seq = tp->snd_nxt; 692 } 693 } 694 695 /* Calculate rto without backoff. This is the second half of Van Jacobson's 696 * routine referred to above. 697 */ 698 static inline void tcp_set_rto(struct sock *sk) 699 { 700 const struct tcp_sock *tp = tcp_sk(sk); 701 /* Old crap is replaced with new one. 8) 702 * 703 * More seriously: 704 * 1. If rtt variance happened to be less 50msec, it is hallucination. 705 * It cannot be less due to utterly erratic ACK generation made 706 * at least by solaris and freebsd. "Erratic ACKs" has _nothing_ 707 * to do with delayed acks, because at cwnd>2 true delack timeout 708 * is invisible. Actually, Linux-2.4 also generates erratic 709 * ACKs in some circumstances. 710 */ 711 inet_csk(sk)->icsk_rto = __tcp_set_rto(tp); 712 713 /* 2. Fixups made earlier cannot be right. 714 * If we do not estimate RTO correctly without them, 715 * all the algo is pure shit and should be replaced 716 * with correct one. It is exactly, which we pretend to do. 717 */ 718 719 /* NOTE: clamping at TCP_RTO_MIN is not required, current algo 720 * guarantees that rto is higher. 721 */ 722 tcp_bound_rto(sk); 723 } 724 725 /* Save metrics learned by this TCP session. 726 This function is called only, when TCP finishes successfully 727 i.e. when it enters TIME-WAIT or goes from LAST-ACK to CLOSE. 728 */ 729 void tcp_update_metrics(struct sock *sk) 730 { 731 struct tcp_sock *tp = tcp_sk(sk); 732 struct dst_entry *dst = __sk_dst_get(sk); 733 734 if (sysctl_tcp_nometrics_save) 735 return; 736 737 dst_confirm(dst); 738 739 if (dst && (dst->flags & DST_HOST)) { 740 const struct inet_connection_sock *icsk = inet_csk(sk); 741 int m; 742 unsigned long rtt; 743 744 if (icsk->icsk_backoff || !tp->srtt) { 745 /* This session failed to estimate rtt. Why? 746 * Probably, no packets returned in time. 747 * Reset our results. 748 */ 749 if (!(dst_metric_locked(dst, RTAX_RTT))) 750 dst_metric_set(dst, RTAX_RTT, 0); 751 return; 752 } 753 754 rtt = dst_metric_rtt(dst, RTAX_RTT); 755 m = rtt - tp->srtt; 756 757 /* If newly calculated rtt larger than stored one, 758 * store new one. Otherwise, use EWMA. Remember, 759 * rtt overestimation is always better than underestimation. 760 */ 761 if (!(dst_metric_locked(dst, RTAX_RTT))) { 762 if (m <= 0) 763 set_dst_metric_rtt(dst, RTAX_RTT, tp->srtt); 764 else 765 set_dst_metric_rtt(dst, RTAX_RTT, rtt - (m >> 3)); 766 } 767 768 if (!(dst_metric_locked(dst, RTAX_RTTVAR))) { 769 unsigned long var; 770 if (m < 0) 771 m = -m; 772 773 /* Scale deviation to rttvar fixed point */ 774 m >>= 1; 775 if (m < tp->mdev) 776 m = tp->mdev; 777 778 var = dst_metric_rtt(dst, RTAX_RTTVAR); 779 if (m >= var) 780 var = m; 781 else 782 var -= (var - m) >> 2; 783 784 set_dst_metric_rtt(dst, RTAX_RTTVAR, var); 785 } 786 787 if (tcp_in_initial_slowstart(tp)) { 788 /* Slow start still did not finish. */ 789 if (dst_metric(dst, RTAX_SSTHRESH) && 790 !dst_metric_locked(dst, RTAX_SSTHRESH) && 791 (tp->snd_cwnd >> 1) > dst_metric(dst, RTAX_SSTHRESH)) 792 dst_metric_set(dst, RTAX_SSTHRESH, tp->snd_cwnd >> 1); 793 if (!dst_metric_locked(dst, RTAX_CWND) && 794 tp->snd_cwnd > dst_metric(dst, RTAX_CWND)) 795 dst_metric_set(dst, RTAX_CWND, tp->snd_cwnd); 796 } else if (tp->snd_cwnd > tp->snd_ssthresh && 797 icsk->icsk_ca_state == TCP_CA_Open) { 798 /* Cong. avoidance phase, cwnd is reliable. */ 799 if (!dst_metric_locked(dst, RTAX_SSTHRESH)) 800 dst_metric_set(dst, RTAX_SSTHRESH, 801 max(tp->snd_cwnd >> 1, tp->snd_ssthresh)); 802 if (!dst_metric_locked(dst, RTAX_CWND)) 803 dst_metric_set(dst, RTAX_CWND, 804 (dst_metric(dst, RTAX_CWND) + 805 tp->snd_cwnd) >> 1); 806 } else { 807 /* Else slow start did not finish, cwnd is non-sense, 808 ssthresh may be also invalid. 809 */ 810 if (!dst_metric_locked(dst, RTAX_CWND)) 811 dst_metric_set(dst, RTAX_CWND, 812 (dst_metric(dst, RTAX_CWND) + 813 tp->snd_ssthresh) >> 1); 814 if (dst_metric(dst, RTAX_SSTHRESH) && 815 !dst_metric_locked(dst, RTAX_SSTHRESH) && 816 tp->snd_ssthresh > dst_metric(dst, RTAX_SSTHRESH)) 817 dst_metric_set(dst, RTAX_SSTHRESH, tp->snd_ssthresh); 818 } 819 820 if (!dst_metric_locked(dst, RTAX_REORDERING)) { 821 if (dst_metric(dst, RTAX_REORDERING) < tp->reordering && 822 tp->reordering != sysctl_tcp_reordering) 823 dst_metric_set(dst, RTAX_REORDERING, tp->reordering); 824 } 825 } 826 } 827 828 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst) 829 { 830 __u32 cwnd = (dst ? dst_metric(dst, RTAX_INITCWND) : 0); 831 832 if (!cwnd) 833 cwnd = TCP_INIT_CWND; 834 return min_t(__u32, cwnd, tp->snd_cwnd_clamp); 835 } 836 837 /* Set slow start threshold and cwnd not falling to slow start */ 838 void tcp_enter_cwr(struct sock *sk, const int set_ssthresh) 839 { 840 struct tcp_sock *tp = tcp_sk(sk); 841 const struct inet_connection_sock *icsk = inet_csk(sk); 842 843 tp->prior_ssthresh = 0; 844 tp->bytes_acked = 0; 845 if (icsk->icsk_ca_state < TCP_CA_CWR) { 846 tp->undo_marker = 0; 847 if (set_ssthresh) 848 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 849 tp->snd_cwnd = min(tp->snd_cwnd, 850 tcp_packets_in_flight(tp) + 1U); 851 tp->snd_cwnd_cnt = 0; 852 tp->high_seq = tp->snd_nxt; 853 tp->snd_cwnd_stamp = tcp_time_stamp; 854 TCP_ECN_queue_cwr(tp); 855 856 tcp_set_ca_state(sk, TCP_CA_CWR); 857 } 858 } 859 860 /* 861 * Packet counting of FACK is based on in-order assumptions, therefore TCP 862 * disables it when reordering is detected 863 */ 864 static void tcp_disable_fack(struct tcp_sock *tp) 865 { 866 /* RFC3517 uses different metric in lost marker => reset on change */ 867 if (tcp_is_fack(tp)) 868 tp->lost_skb_hint = NULL; 869 tp->rx_opt.sack_ok &= ~TCP_FACK_ENABLED; 870 } 871 872 /* Take a notice that peer is sending D-SACKs */ 873 static void tcp_dsack_seen(struct tcp_sock *tp) 874 { 875 tp->rx_opt.sack_ok |= TCP_DSACK_SEEN; 876 } 877 878 /* Initialize metrics on socket. */ 879 880 static void tcp_init_metrics(struct sock *sk) 881 { 882 struct tcp_sock *tp = tcp_sk(sk); 883 struct dst_entry *dst = __sk_dst_get(sk); 884 885 if (dst == NULL) 886 goto reset; 887 888 dst_confirm(dst); 889 890 if (dst_metric_locked(dst, RTAX_CWND)) 891 tp->snd_cwnd_clamp = dst_metric(dst, RTAX_CWND); 892 if (dst_metric(dst, RTAX_SSTHRESH)) { 893 tp->snd_ssthresh = dst_metric(dst, RTAX_SSTHRESH); 894 if (tp->snd_ssthresh > tp->snd_cwnd_clamp) 895 tp->snd_ssthresh = tp->snd_cwnd_clamp; 896 } else { 897 /* ssthresh may have been reduced unnecessarily during. 898 * 3WHS. Restore it back to its initial default. 899 */ 900 tp->snd_ssthresh = TCP_INFINITE_SSTHRESH; 901 } 902 if (dst_metric(dst, RTAX_REORDERING) && 903 tp->reordering != dst_metric(dst, RTAX_REORDERING)) { 904 tcp_disable_fack(tp); 905 tp->reordering = dst_metric(dst, RTAX_REORDERING); 906 } 907 908 if (dst_metric(dst, RTAX_RTT) == 0 || tp->srtt == 0) 909 goto reset; 910 911 /* Initial rtt is determined from SYN,SYN-ACK. 912 * The segment is small and rtt may appear much 913 * less than real one. Use per-dst memory 914 * to make it more realistic. 915 * 916 * A bit of theory. RTT is time passed after "normal" sized packet 917 * is sent until it is ACKed. In normal circumstances sending small 918 * packets force peer to delay ACKs and calculation is correct too. 919 * The algorithm is adaptive and, provided we follow specs, it 920 * NEVER underestimate RTT. BUT! If peer tries to make some clever 921 * tricks sort of "quick acks" for time long enough to decrease RTT 922 * to low value, and then abruptly stops to do it and starts to delay 923 * ACKs, wait for troubles. 924 */ 925 if (dst_metric_rtt(dst, RTAX_RTT) > tp->srtt) { 926 tp->srtt = dst_metric_rtt(dst, RTAX_RTT); 927 tp->rtt_seq = tp->snd_nxt; 928 } 929 if (dst_metric_rtt(dst, RTAX_RTTVAR) > tp->mdev) { 930 tp->mdev = dst_metric_rtt(dst, RTAX_RTTVAR); 931 tp->mdev_max = tp->rttvar = max(tp->mdev, tcp_rto_min(sk)); 932 } 933 tcp_set_rto(sk); 934 reset: 935 if (tp->srtt == 0) { 936 /* RFC2988bis: We've failed to get a valid RTT sample from 937 * 3WHS. This is most likely due to retransmission, 938 * including spurious one. Reset the RTO back to 3secs 939 * from the more aggressive 1sec to avoid more spurious 940 * retransmission. 941 */ 942 tp->mdev = tp->mdev_max = tp->rttvar = TCP_TIMEOUT_FALLBACK; 943 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_FALLBACK; 944 } 945 /* Cut cwnd down to 1 per RFC5681 if SYN or SYN-ACK has been 946 * retransmitted. In light of RFC2988bis' more aggressive 1sec 947 * initRTO, we only reset cwnd when more than 1 SYN/SYN-ACK 948 * retransmission has occurred. 949 */ 950 if (tp->total_retrans > 1) 951 tp->snd_cwnd = 1; 952 else 953 tp->snd_cwnd = tcp_init_cwnd(tp, dst); 954 tp->snd_cwnd_stamp = tcp_time_stamp; 955 } 956 957 static void tcp_update_reordering(struct sock *sk, const int metric, 958 const int ts) 959 { 960 struct tcp_sock *tp = tcp_sk(sk); 961 if (metric > tp->reordering) { 962 int mib_idx; 963 964 tp->reordering = min(TCP_MAX_REORDERING, metric); 965 966 /* This exciting event is worth to be remembered. 8) */ 967 if (ts) 968 mib_idx = LINUX_MIB_TCPTSREORDER; 969 else if (tcp_is_reno(tp)) 970 mib_idx = LINUX_MIB_TCPRENOREORDER; 971 else if (tcp_is_fack(tp)) 972 mib_idx = LINUX_MIB_TCPFACKREORDER; 973 else 974 mib_idx = LINUX_MIB_TCPSACKREORDER; 975 976 NET_INC_STATS_BH(sock_net(sk), mib_idx); 977 #if FASTRETRANS_DEBUG > 1 978 printk(KERN_DEBUG "Disorder%d %d %u f%u s%u rr%d\n", 979 tp->rx_opt.sack_ok, inet_csk(sk)->icsk_ca_state, 980 tp->reordering, 981 tp->fackets_out, 982 tp->sacked_out, 983 tp->undo_marker ? tp->undo_retrans : 0); 984 #endif 985 tcp_disable_fack(tp); 986 } 987 } 988 989 /* This must be called before lost_out is incremented */ 990 static void tcp_verify_retransmit_hint(struct tcp_sock *tp, struct sk_buff *skb) 991 { 992 if ((tp->retransmit_skb_hint == NULL) || 993 before(TCP_SKB_CB(skb)->seq, 994 TCP_SKB_CB(tp->retransmit_skb_hint)->seq)) 995 tp->retransmit_skb_hint = skb; 996 997 if (!tp->lost_out || 998 after(TCP_SKB_CB(skb)->end_seq, tp->retransmit_high)) 999 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; 1000 } 1001 1002 static void tcp_skb_mark_lost(struct tcp_sock *tp, struct sk_buff *skb) 1003 { 1004 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { 1005 tcp_verify_retransmit_hint(tp, skb); 1006 1007 tp->lost_out += tcp_skb_pcount(skb); 1008 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1009 } 1010 } 1011 1012 static void tcp_skb_mark_lost_uncond_verify(struct tcp_sock *tp, 1013 struct sk_buff *skb) 1014 { 1015 tcp_verify_retransmit_hint(tp, skb); 1016 1017 if (!(TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_ACKED))) { 1018 tp->lost_out += tcp_skb_pcount(skb); 1019 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1020 } 1021 } 1022 1023 /* This procedure tags the retransmission queue when SACKs arrive. 1024 * 1025 * We have three tag bits: SACKED(S), RETRANS(R) and LOST(L). 1026 * Packets in queue with these bits set are counted in variables 1027 * sacked_out, retrans_out and lost_out, correspondingly. 1028 * 1029 * Valid combinations are: 1030 * Tag InFlight Description 1031 * 0 1 - orig segment is in flight. 1032 * S 0 - nothing flies, orig reached receiver. 1033 * L 0 - nothing flies, orig lost by net. 1034 * R 2 - both orig and retransmit are in flight. 1035 * L|R 1 - orig is lost, retransmit is in flight. 1036 * S|R 1 - orig reached receiver, retrans is still in flight. 1037 * (L|S|R is logically valid, it could occur when L|R is sacked, 1038 * but it is equivalent to plain S and code short-curcuits it to S. 1039 * L|S is logically invalid, it would mean -1 packet in flight 8)) 1040 * 1041 * These 6 states form finite state machine, controlled by the following events: 1042 * 1. New ACK (+SACK) arrives. (tcp_sacktag_write_queue()) 1043 * 2. Retransmission. (tcp_retransmit_skb(), tcp_xmit_retransmit_queue()) 1044 * 3. Loss detection event of two flavors: 1045 * A. Scoreboard estimator decided the packet is lost. 1046 * A'. Reno "three dupacks" marks head of queue lost. 1047 * A''. Its FACK modification, head until snd.fack is lost. 1048 * B. SACK arrives sacking SND.NXT at the moment, when the 1049 * segment was retransmitted. 1050 * 4. D-SACK added new rule: D-SACK changes any tag to S. 1051 * 1052 * It is pleasant to note, that state diagram turns out to be commutative, 1053 * so that we are allowed not to be bothered by order of our actions, 1054 * when multiple events arrive simultaneously. (see the function below). 1055 * 1056 * Reordering detection. 1057 * -------------------- 1058 * Reordering metric is maximal distance, which a packet can be displaced 1059 * in packet stream. With SACKs we can estimate it: 1060 * 1061 * 1. SACK fills old hole and the corresponding segment was not 1062 * ever retransmitted -> reordering. Alas, we cannot use it 1063 * when segment was retransmitted. 1064 * 2. The last flaw is solved with D-SACK. D-SACK arrives 1065 * for retransmitted and already SACKed segment -> reordering.. 1066 * Both of these heuristics are not used in Loss state, when we cannot 1067 * account for retransmits accurately. 1068 * 1069 * SACK block validation. 1070 * ---------------------- 1071 * 1072 * SACK block range validation checks that the received SACK block fits to 1073 * the expected sequence limits, i.e., it is between SND.UNA and SND.NXT. 1074 * Note that SND.UNA is not included to the range though being valid because 1075 * it means that the receiver is rather inconsistent with itself reporting 1076 * SACK reneging when it should advance SND.UNA. Such SACK block this is 1077 * perfectly valid, however, in light of RFC2018 which explicitly states 1078 * that "SACK block MUST reflect the newest segment. Even if the newest 1079 * segment is going to be discarded ...", not that it looks very clever 1080 * in case of head skb. Due to potentional receiver driven attacks, we 1081 * choose to avoid immediate execution of a walk in write queue due to 1082 * reneging and defer head skb's loss recovery to standard loss recovery 1083 * procedure that will eventually trigger (nothing forbids us doing this). 1084 * 1085 * Implements also blockage to start_seq wrap-around. Problem lies in the 1086 * fact that though start_seq (s) is before end_seq (i.e., not reversed), 1087 * there's no guarantee that it will be before snd_nxt (n). The problem 1088 * happens when start_seq resides between end_seq wrap (e_w) and snd_nxt 1089 * wrap (s_w): 1090 * 1091 * <- outs wnd -> <- wrapzone -> 1092 * u e n u_w e_w s n_w 1093 * | | | | | | | 1094 * |<------------+------+----- TCP seqno space --------------+---------->| 1095 * ...-- <2^31 ->| |<--------... 1096 * ...---- >2^31 ------>| |<--------... 1097 * 1098 * Current code wouldn't be vulnerable but it's better still to discard such 1099 * crazy SACK blocks. Doing this check for start_seq alone closes somewhat 1100 * similar case (end_seq after snd_nxt wrap) as earlier reversed check in 1101 * snd_nxt wrap -> snd_una region will then become "well defined", i.e., 1102 * equal to the ideal case (infinite seqno space without wrap caused issues). 1103 * 1104 * With D-SACK the lower bound is extended to cover sequence space below 1105 * SND.UNA down to undo_marker, which is the last point of interest. Yet 1106 * again, D-SACK block must not to go across snd_una (for the same reason as 1107 * for the normal SACK blocks, explained above). But there all simplicity 1108 * ends, TCP might receive valid D-SACKs below that. As long as they reside 1109 * fully below undo_marker they do not affect behavior in anyway and can 1110 * therefore be safely ignored. In rare cases (which are more or less 1111 * theoretical ones), the D-SACK will nicely cross that boundary due to skb 1112 * fragmentation and packet reordering past skb's retransmission. To consider 1113 * them correctly, the acceptable range must be extended even more though 1114 * the exact amount is rather hard to quantify. However, tp->max_window can 1115 * be used as an exaggerated estimate. 1116 */ 1117 static int tcp_is_sackblock_valid(struct tcp_sock *tp, int is_dsack, 1118 u32 start_seq, u32 end_seq) 1119 { 1120 /* Too far in future, or reversed (interpretation is ambiguous) */ 1121 if (after(end_seq, tp->snd_nxt) || !before(start_seq, end_seq)) 1122 return 0; 1123 1124 /* Nasty start_seq wrap-around check (see comments above) */ 1125 if (!before(start_seq, tp->snd_nxt)) 1126 return 0; 1127 1128 /* In outstanding window? ...This is valid exit for D-SACKs too. 1129 * start_seq == snd_una is non-sensical (see comments above) 1130 */ 1131 if (after(start_seq, tp->snd_una)) 1132 return 1; 1133 1134 if (!is_dsack || !tp->undo_marker) 1135 return 0; 1136 1137 /* ...Then it's D-SACK, and must reside below snd_una completely */ 1138 if (after(end_seq, tp->snd_una)) 1139 return 0; 1140 1141 if (!before(start_seq, tp->undo_marker)) 1142 return 1; 1143 1144 /* Too old */ 1145 if (!after(end_seq, tp->undo_marker)) 1146 return 0; 1147 1148 /* Undo_marker boundary crossing (overestimates a lot). Known already: 1149 * start_seq < undo_marker and end_seq >= undo_marker. 1150 */ 1151 return !before(start_seq, end_seq - tp->max_window); 1152 } 1153 1154 /* Check for lost retransmit. This superb idea is borrowed from "ratehalving". 1155 * Event "B". Later note: FACK people cheated me again 8), we have to account 1156 * for reordering! Ugly, but should help. 1157 * 1158 * Search retransmitted skbs from write_queue that were sent when snd_nxt was 1159 * less than what is now known to be received by the other end (derived from 1160 * highest SACK block). Also calculate the lowest snd_nxt among the remaining 1161 * retransmitted skbs to avoid some costly processing per ACKs. 1162 */ 1163 static void tcp_mark_lost_retrans(struct sock *sk) 1164 { 1165 const struct inet_connection_sock *icsk = inet_csk(sk); 1166 struct tcp_sock *tp = tcp_sk(sk); 1167 struct sk_buff *skb; 1168 int cnt = 0; 1169 u32 new_low_seq = tp->snd_nxt; 1170 u32 received_upto = tcp_highest_sack_seq(tp); 1171 1172 if (!tcp_is_fack(tp) || !tp->retrans_out || 1173 !after(received_upto, tp->lost_retrans_low) || 1174 icsk->icsk_ca_state != TCP_CA_Recovery) 1175 return; 1176 1177 tcp_for_write_queue(skb, sk) { 1178 u32 ack_seq = TCP_SKB_CB(skb)->ack_seq; 1179 1180 if (skb == tcp_send_head(sk)) 1181 break; 1182 if (cnt == tp->retrans_out) 1183 break; 1184 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1185 continue; 1186 1187 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS)) 1188 continue; 1189 1190 /* TODO: We would like to get rid of tcp_is_fack(tp) only 1191 * constraint here (see above) but figuring out that at 1192 * least tp->reordering SACK blocks reside between ack_seq 1193 * and received_upto is not easy task to do cheaply with 1194 * the available datastructures. 1195 * 1196 * Whether FACK should check here for tp->reordering segs 1197 * in-between one could argue for either way (it would be 1198 * rather simple to implement as we could count fack_count 1199 * during the walk and do tp->fackets_out - fack_count). 1200 */ 1201 if (after(received_upto, ack_seq)) { 1202 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1203 tp->retrans_out -= tcp_skb_pcount(skb); 1204 1205 tcp_skb_mark_lost_uncond_verify(tp, skb); 1206 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSTRETRANSMIT); 1207 } else { 1208 if (before(ack_seq, new_low_seq)) 1209 new_low_seq = ack_seq; 1210 cnt += tcp_skb_pcount(skb); 1211 } 1212 } 1213 1214 if (tp->retrans_out) 1215 tp->lost_retrans_low = new_low_seq; 1216 } 1217 1218 static int tcp_check_dsack(struct sock *sk, const struct sk_buff *ack_skb, 1219 struct tcp_sack_block_wire *sp, int num_sacks, 1220 u32 prior_snd_una) 1221 { 1222 struct tcp_sock *tp = tcp_sk(sk); 1223 u32 start_seq_0 = get_unaligned_be32(&sp[0].start_seq); 1224 u32 end_seq_0 = get_unaligned_be32(&sp[0].end_seq); 1225 int dup_sack = 0; 1226 1227 if (before(start_seq_0, TCP_SKB_CB(ack_skb)->ack_seq)) { 1228 dup_sack = 1; 1229 tcp_dsack_seen(tp); 1230 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKRECV); 1231 } else if (num_sacks > 1) { 1232 u32 end_seq_1 = get_unaligned_be32(&sp[1].end_seq); 1233 u32 start_seq_1 = get_unaligned_be32(&sp[1].start_seq); 1234 1235 if (!after(end_seq_0, end_seq_1) && 1236 !before(start_seq_0, start_seq_1)) { 1237 dup_sack = 1; 1238 tcp_dsack_seen(tp); 1239 NET_INC_STATS_BH(sock_net(sk), 1240 LINUX_MIB_TCPDSACKOFORECV); 1241 } 1242 } 1243 1244 /* D-SACK for already forgotten data... Do dumb counting. */ 1245 if (dup_sack && tp->undo_marker && tp->undo_retrans && 1246 !after(end_seq_0, prior_snd_una) && 1247 after(end_seq_0, tp->undo_marker)) 1248 tp->undo_retrans--; 1249 1250 return dup_sack; 1251 } 1252 1253 struct tcp_sacktag_state { 1254 int reord; 1255 int fack_count; 1256 int flag; 1257 }; 1258 1259 /* Check if skb is fully within the SACK block. In presence of GSO skbs, 1260 * the incoming SACK may not exactly match but we can find smaller MSS 1261 * aligned portion of it that matches. Therefore we might need to fragment 1262 * which may fail and creates some hassle (caller must handle error case 1263 * returns). 1264 * 1265 * FIXME: this could be merged to shift decision code 1266 */ 1267 static int tcp_match_skb_to_sack(struct sock *sk, struct sk_buff *skb, 1268 u32 start_seq, u32 end_seq) 1269 { 1270 int in_sack, err; 1271 unsigned int pkt_len; 1272 unsigned int mss; 1273 1274 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && 1275 !before(end_seq, TCP_SKB_CB(skb)->end_seq); 1276 1277 if (tcp_skb_pcount(skb) > 1 && !in_sack && 1278 after(TCP_SKB_CB(skb)->end_seq, start_seq)) { 1279 mss = tcp_skb_mss(skb); 1280 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); 1281 1282 if (!in_sack) { 1283 pkt_len = start_seq - TCP_SKB_CB(skb)->seq; 1284 if (pkt_len < mss) 1285 pkt_len = mss; 1286 } else { 1287 pkt_len = end_seq - TCP_SKB_CB(skb)->seq; 1288 if (pkt_len < mss) 1289 return -EINVAL; 1290 } 1291 1292 /* Round if necessary so that SACKs cover only full MSSes 1293 * and/or the remaining small portion (if present) 1294 */ 1295 if (pkt_len > mss) { 1296 unsigned int new_len = (pkt_len / mss) * mss; 1297 if (!in_sack && new_len < pkt_len) { 1298 new_len += mss; 1299 if (new_len > skb->len) 1300 return 0; 1301 } 1302 pkt_len = new_len; 1303 } 1304 err = tcp_fragment(sk, skb, pkt_len, mss); 1305 if (err < 0) 1306 return err; 1307 } 1308 1309 return in_sack; 1310 } 1311 1312 /* Mark the given newly-SACKed range as such, adjusting counters and hints. */ 1313 static u8 tcp_sacktag_one(struct sock *sk, 1314 struct tcp_sacktag_state *state, u8 sacked, 1315 u32 start_seq, u32 end_seq, 1316 int dup_sack, int pcount) 1317 { 1318 struct tcp_sock *tp = tcp_sk(sk); 1319 int fack_count = state->fack_count; 1320 1321 /* Account D-SACK for retransmitted packet. */ 1322 if (dup_sack && (sacked & TCPCB_RETRANS)) { 1323 if (tp->undo_marker && tp->undo_retrans && 1324 after(end_seq, tp->undo_marker)) 1325 tp->undo_retrans--; 1326 if (sacked & TCPCB_SACKED_ACKED) 1327 state->reord = min(fack_count, state->reord); 1328 } 1329 1330 /* Nothing to do; acked frame is about to be dropped (was ACKed). */ 1331 if (!after(end_seq, tp->snd_una)) 1332 return sacked; 1333 1334 if (!(sacked & TCPCB_SACKED_ACKED)) { 1335 if (sacked & TCPCB_SACKED_RETRANS) { 1336 /* If the segment is not tagged as lost, 1337 * we do not clear RETRANS, believing 1338 * that retransmission is still in flight. 1339 */ 1340 if (sacked & TCPCB_LOST) { 1341 sacked &= ~(TCPCB_LOST|TCPCB_SACKED_RETRANS); 1342 tp->lost_out -= pcount; 1343 tp->retrans_out -= pcount; 1344 } 1345 } else { 1346 if (!(sacked & TCPCB_RETRANS)) { 1347 /* New sack for not retransmitted frame, 1348 * which was in hole. It is reordering. 1349 */ 1350 if (before(start_seq, 1351 tcp_highest_sack_seq(tp))) 1352 state->reord = min(fack_count, 1353 state->reord); 1354 1355 /* SACK enhanced F-RTO (RFC4138; Appendix B) */ 1356 if (!after(end_seq, tp->frto_highmark)) 1357 state->flag |= FLAG_ONLY_ORIG_SACKED; 1358 } 1359 1360 if (sacked & TCPCB_LOST) { 1361 sacked &= ~TCPCB_LOST; 1362 tp->lost_out -= pcount; 1363 } 1364 } 1365 1366 sacked |= TCPCB_SACKED_ACKED; 1367 state->flag |= FLAG_DATA_SACKED; 1368 tp->sacked_out += pcount; 1369 1370 fack_count += pcount; 1371 1372 /* Lost marker hint past SACKed? Tweak RFC3517 cnt */ 1373 if (!tcp_is_fack(tp) && (tp->lost_skb_hint != NULL) && 1374 before(start_seq, TCP_SKB_CB(tp->lost_skb_hint)->seq)) 1375 tp->lost_cnt_hint += pcount; 1376 1377 if (fack_count > tp->fackets_out) 1378 tp->fackets_out = fack_count; 1379 } 1380 1381 /* D-SACK. We can detect redundant retransmission in S|R and plain R 1382 * frames and clear it. undo_retrans is decreased above, L|R frames 1383 * are accounted above as well. 1384 */ 1385 if (dup_sack && (sacked & TCPCB_SACKED_RETRANS)) { 1386 sacked &= ~TCPCB_SACKED_RETRANS; 1387 tp->retrans_out -= pcount; 1388 } 1389 1390 return sacked; 1391 } 1392 1393 /* Shift newly-SACKed bytes from this skb to the immediately previous 1394 * already-SACKed sk_buff. Mark the newly-SACKed bytes as such. 1395 */ 1396 static int tcp_shifted_skb(struct sock *sk, struct sk_buff *skb, 1397 struct tcp_sacktag_state *state, 1398 unsigned int pcount, int shifted, int mss, 1399 int dup_sack) 1400 { 1401 struct tcp_sock *tp = tcp_sk(sk); 1402 struct sk_buff *prev = tcp_write_queue_prev(sk, skb); 1403 u32 start_seq = TCP_SKB_CB(skb)->seq; /* start of newly-SACKed */ 1404 u32 end_seq = start_seq + shifted; /* end of newly-SACKed */ 1405 1406 BUG_ON(!pcount); 1407 1408 /* Adjust counters and hints for the newly sacked sequence 1409 * range but discard the return value since prev is already 1410 * marked. We must tag the range first because the seq 1411 * advancement below implicitly advances 1412 * tcp_highest_sack_seq() when skb is highest_sack. 1413 */ 1414 tcp_sacktag_one(sk, state, TCP_SKB_CB(skb)->sacked, 1415 start_seq, end_seq, dup_sack, pcount); 1416 1417 if (skb == tp->lost_skb_hint) 1418 tp->lost_cnt_hint += pcount; 1419 1420 TCP_SKB_CB(prev)->end_seq += shifted; 1421 TCP_SKB_CB(skb)->seq += shifted; 1422 1423 skb_shinfo(prev)->gso_segs += pcount; 1424 BUG_ON(skb_shinfo(skb)->gso_segs < pcount); 1425 skb_shinfo(skb)->gso_segs -= pcount; 1426 1427 /* When we're adding to gso_segs == 1, gso_size will be zero, 1428 * in theory this shouldn't be necessary but as long as DSACK 1429 * code can come after this skb later on it's better to keep 1430 * setting gso_size to something. 1431 */ 1432 if (!skb_shinfo(prev)->gso_size) { 1433 skb_shinfo(prev)->gso_size = mss; 1434 skb_shinfo(prev)->gso_type = sk->sk_gso_type; 1435 } 1436 1437 /* CHECKME: To clear or not to clear? Mimics normal skb currently */ 1438 if (skb_shinfo(skb)->gso_segs <= 1) { 1439 skb_shinfo(skb)->gso_size = 0; 1440 skb_shinfo(skb)->gso_type = 0; 1441 } 1442 1443 /* Difference in this won't matter, both ACKed by the same cumul. ACK */ 1444 TCP_SKB_CB(prev)->sacked |= (TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS); 1445 1446 if (skb->len > 0) { 1447 BUG_ON(!tcp_skb_pcount(skb)); 1448 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED); 1449 return 0; 1450 } 1451 1452 /* Whole SKB was eaten :-) */ 1453 1454 if (skb == tp->retransmit_skb_hint) 1455 tp->retransmit_skb_hint = prev; 1456 if (skb == tp->scoreboard_skb_hint) 1457 tp->scoreboard_skb_hint = prev; 1458 if (skb == tp->lost_skb_hint) { 1459 tp->lost_skb_hint = prev; 1460 tp->lost_cnt_hint -= tcp_skb_pcount(prev); 1461 } 1462 1463 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(prev)->tcp_flags; 1464 if (skb == tcp_highest_sack(sk)) 1465 tcp_advance_highest_sack(sk, skb); 1466 1467 tcp_unlink_write_queue(skb, sk); 1468 sk_wmem_free_skb(sk, skb); 1469 1470 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED); 1471 1472 return 1; 1473 } 1474 1475 /* I wish gso_size would have a bit more sane initialization than 1476 * something-or-zero which complicates things 1477 */ 1478 static int tcp_skb_seglen(const struct sk_buff *skb) 1479 { 1480 return tcp_skb_pcount(skb) == 1 ? skb->len : tcp_skb_mss(skb); 1481 } 1482 1483 /* Shifting pages past head area doesn't work */ 1484 static int skb_can_shift(const struct sk_buff *skb) 1485 { 1486 return !skb_headlen(skb) && skb_is_nonlinear(skb); 1487 } 1488 1489 /* Try collapsing SACK blocks spanning across multiple skbs to a single 1490 * skb. 1491 */ 1492 static struct sk_buff *tcp_shift_skb_data(struct sock *sk, struct sk_buff *skb, 1493 struct tcp_sacktag_state *state, 1494 u32 start_seq, u32 end_seq, 1495 int dup_sack) 1496 { 1497 struct tcp_sock *tp = tcp_sk(sk); 1498 struct sk_buff *prev; 1499 int mss; 1500 int pcount = 0; 1501 int len; 1502 int in_sack; 1503 1504 if (!sk_can_gso(sk)) 1505 goto fallback; 1506 1507 /* Normally R but no L won't result in plain S */ 1508 if (!dup_sack && 1509 (TCP_SKB_CB(skb)->sacked & (TCPCB_LOST|TCPCB_SACKED_RETRANS)) == TCPCB_SACKED_RETRANS) 1510 goto fallback; 1511 if (!skb_can_shift(skb)) 1512 goto fallback; 1513 /* This frame is about to be dropped (was ACKed). */ 1514 if (!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1515 goto fallback; 1516 1517 /* Can only happen with delayed DSACK + discard craziness */ 1518 if (unlikely(skb == tcp_write_queue_head(sk))) 1519 goto fallback; 1520 prev = tcp_write_queue_prev(sk, skb); 1521 1522 if ((TCP_SKB_CB(prev)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) 1523 goto fallback; 1524 1525 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq) && 1526 !before(end_seq, TCP_SKB_CB(skb)->end_seq); 1527 1528 if (in_sack) { 1529 len = skb->len; 1530 pcount = tcp_skb_pcount(skb); 1531 mss = tcp_skb_seglen(skb); 1532 1533 /* TODO: Fix DSACKs to not fragment already SACKed and we can 1534 * drop this restriction as unnecessary 1535 */ 1536 if (mss != tcp_skb_seglen(prev)) 1537 goto fallback; 1538 } else { 1539 if (!after(TCP_SKB_CB(skb)->end_seq, start_seq)) 1540 goto noop; 1541 /* CHECKME: This is non-MSS split case only?, this will 1542 * cause skipped skbs due to advancing loop btw, original 1543 * has that feature too 1544 */ 1545 if (tcp_skb_pcount(skb) <= 1) 1546 goto noop; 1547 1548 in_sack = !after(start_seq, TCP_SKB_CB(skb)->seq); 1549 if (!in_sack) { 1550 /* TODO: head merge to next could be attempted here 1551 * if (!after(TCP_SKB_CB(skb)->end_seq, end_seq)), 1552 * though it might not be worth of the additional hassle 1553 * 1554 * ...we can probably just fallback to what was done 1555 * previously. We could try merging non-SACKed ones 1556 * as well but it probably isn't going to buy off 1557 * because later SACKs might again split them, and 1558 * it would make skb timestamp tracking considerably 1559 * harder problem. 1560 */ 1561 goto fallback; 1562 } 1563 1564 len = end_seq - TCP_SKB_CB(skb)->seq; 1565 BUG_ON(len < 0); 1566 BUG_ON(len > skb->len); 1567 1568 /* MSS boundaries should be honoured or else pcount will 1569 * severely break even though it makes things bit trickier. 1570 * Optimize common case to avoid most of the divides 1571 */ 1572 mss = tcp_skb_mss(skb); 1573 1574 /* TODO: Fix DSACKs to not fragment already SACKed and we can 1575 * drop this restriction as unnecessary 1576 */ 1577 if (mss != tcp_skb_seglen(prev)) 1578 goto fallback; 1579 1580 if (len == mss) { 1581 pcount = 1; 1582 } else if (len < mss) { 1583 goto noop; 1584 } else { 1585 pcount = len / mss; 1586 len = pcount * mss; 1587 } 1588 } 1589 1590 /* tcp_sacktag_one() won't SACK-tag ranges below snd_una */ 1591 if (!after(TCP_SKB_CB(skb)->seq + len, tp->snd_una)) 1592 goto fallback; 1593 1594 if (!skb_shift(prev, skb, len)) 1595 goto fallback; 1596 if (!tcp_shifted_skb(sk, skb, state, pcount, len, mss, dup_sack)) 1597 goto out; 1598 1599 /* Hole filled allows collapsing with the next as well, this is very 1600 * useful when hole on every nth skb pattern happens 1601 */ 1602 if (prev == tcp_write_queue_tail(sk)) 1603 goto out; 1604 skb = tcp_write_queue_next(sk, prev); 1605 1606 if (!skb_can_shift(skb) || 1607 (skb == tcp_send_head(sk)) || 1608 ((TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) != TCPCB_SACKED_ACKED) || 1609 (mss != tcp_skb_seglen(skb))) 1610 goto out; 1611 1612 len = skb->len; 1613 if (skb_shift(prev, skb, len)) { 1614 pcount += tcp_skb_pcount(skb); 1615 tcp_shifted_skb(sk, skb, state, tcp_skb_pcount(skb), len, mss, 0); 1616 } 1617 1618 out: 1619 state->fack_count += pcount; 1620 return prev; 1621 1622 noop: 1623 return skb; 1624 1625 fallback: 1626 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK); 1627 return NULL; 1628 } 1629 1630 static struct sk_buff *tcp_sacktag_walk(struct sk_buff *skb, struct sock *sk, 1631 struct tcp_sack_block *next_dup, 1632 struct tcp_sacktag_state *state, 1633 u32 start_seq, u32 end_seq, 1634 int dup_sack_in) 1635 { 1636 struct tcp_sock *tp = tcp_sk(sk); 1637 struct sk_buff *tmp; 1638 1639 tcp_for_write_queue_from(skb, sk) { 1640 int in_sack = 0; 1641 int dup_sack = dup_sack_in; 1642 1643 if (skb == tcp_send_head(sk)) 1644 break; 1645 1646 /* queue is in-order => we can short-circuit the walk early */ 1647 if (!before(TCP_SKB_CB(skb)->seq, end_seq)) 1648 break; 1649 1650 if ((next_dup != NULL) && 1651 before(TCP_SKB_CB(skb)->seq, next_dup->end_seq)) { 1652 in_sack = tcp_match_skb_to_sack(sk, skb, 1653 next_dup->start_seq, 1654 next_dup->end_seq); 1655 if (in_sack > 0) 1656 dup_sack = 1; 1657 } 1658 1659 /* skb reference here is a bit tricky to get right, since 1660 * shifting can eat and free both this skb and the next, 1661 * so not even _safe variant of the loop is enough. 1662 */ 1663 if (in_sack <= 0) { 1664 tmp = tcp_shift_skb_data(sk, skb, state, 1665 start_seq, end_seq, dup_sack); 1666 if (tmp != NULL) { 1667 if (tmp != skb) { 1668 skb = tmp; 1669 continue; 1670 } 1671 1672 in_sack = 0; 1673 } else { 1674 in_sack = tcp_match_skb_to_sack(sk, skb, 1675 start_seq, 1676 end_seq); 1677 } 1678 } 1679 1680 if (unlikely(in_sack < 0)) 1681 break; 1682 1683 if (in_sack) { 1684 TCP_SKB_CB(skb)->sacked = 1685 tcp_sacktag_one(sk, 1686 state, 1687 TCP_SKB_CB(skb)->sacked, 1688 TCP_SKB_CB(skb)->seq, 1689 TCP_SKB_CB(skb)->end_seq, 1690 dup_sack, 1691 tcp_skb_pcount(skb)); 1692 1693 if (!before(TCP_SKB_CB(skb)->seq, 1694 tcp_highest_sack_seq(tp))) 1695 tcp_advance_highest_sack(sk, skb); 1696 } 1697 1698 state->fack_count += tcp_skb_pcount(skb); 1699 } 1700 return skb; 1701 } 1702 1703 /* Avoid all extra work that is being done by sacktag while walking in 1704 * a normal way 1705 */ 1706 static struct sk_buff *tcp_sacktag_skip(struct sk_buff *skb, struct sock *sk, 1707 struct tcp_sacktag_state *state, 1708 u32 skip_to_seq) 1709 { 1710 tcp_for_write_queue_from(skb, sk) { 1711 if (skb == tcp_send_head(sk)) 1712 break; 1713 1714 if (after(TCP_SKB_CB(skb)->end_seq, skip_to_seq)) 1715 break; 1716 1717 state->fack_count += tcp_skb_pcount(skb); 1718 } 1719 return skb; 1720 } 1721 1722 static struct sk_buff *tcp_maybe_skipping_dsack(struct sk_buff *skb, 1723 struct sock *sk, 1724 struct tcp_sack_block *next_dup, 1725 struct tcp_sacktag_state *state, 1726 u32 skip_to_seq) 1727 { 1728 if (next_dup == NULL) 1729 return skb; 1730 1731 if (before(next_dup->start_seq, skip_to_seq)) { 1732 skb = tcp_sacktag_skip(skb, sk, state, next_dup->start_seq); 1733 skb = tcp_sacktag_walk(skb, sk, NULL, state, 1734 next_dup->start_seq, next_dup->end_seq, 1735 1); 1736 } 1737 1738 return skb; 1739 } 1740 1741 static int tcp_sack_cache_ok(const struct tcp_sock *tp, const struct tcp_sack_block *cache) 1742 { 1743 return cache < tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); 1744 } 1745 1746 static int 1747 tcp_sacktag_write_queue(struct sock *sk, const struct sk_buff *ack_skb, 1748 u32 prior_snd_una) 1749 { 1750 const struct inet_connection_sock *icsk = inet_csk(sk); 1751 struct tcp_sock *tp = tcp_sk(sk); 1752 const unsigned char *ptr = (skb_transport_header(ack_skb) + 1753 TCP_SKB_CB(ack_skb)->sacked); 1754 struct tcp_sack_block_wire *sp_wire = (struct tcp_sack_block_wire *)(ptr+2); 1755 struct tcp_sack_block sp[TCP_NUM_SACKS]; 1756 struct tcp_sack_block *cache; 1757 struct tcp_sacktag_state state; 1758 struct sk_buff *skb; 1759 int num_sacks = min(TCP_NUM_SACKS, (ptr[1] - TCPOLEN_SACK_BASE) >> 3); 1760 int used_sacks; 1761 int found_dup_sack = 0; 1762 int i, j; 1763 int first_sack_index; 1764 1765 state.flag = 0; 1766 state.reord = tp->packets_out; 1767 1768 if (!tp->sacked_out) { 1769 if (WARN_ON(tp->fackets_out)) 1770 tp->fackets_out = 0; 1771 tcp_highest_sack_reset(sk); 1772 } 1773 1774 found_dup_sack = tcp_check_dsack(sk, ack_skb, sp_wire, 1775 num_sacks, prior_snd_una); 1776 if (found_dup_sack) 1777 state.flag |= FLAG_DSACKING_ACK; 1778 1779 /* Eliminate too old ACKs, but take into 1780 * account more or less fresh ones, they can 1781 * contain valid SACK info. 1782 */ 1783 if (before(TCP_SKB_CB(ack_skb)->ack_seq, prior_snd_una - tp->max_window)) 1784 return 0; 1785 1786 if (!tp->packets_out) 1787 goto out; 1788 1789 used_sacks = 0; 1790 first_sack_index = 0; 1791 for (i = 0; i < num_sacks; i++) { 1792 int dup_sack = !i && found_dup_sack; 1793 1794 sp[used_sacks].start_seq = get_unaligned_be32(&sp_wire[i].start_seq); 1795 sp[used_sacks].end_seq = get_unaligned_be32(&sp_wire[i].end_seq); 1796 1797 if (!tcp_is_sackblock_valid(tp, dup_sack, 1798 sp[used_sacks].start_seq, 1799 sp[used_sacks].end_seq)) { 1800 int mib_idx; 1801 1802 if (dup_sack) { 1803 if (!tp->undo_marker) 1804 mib_idx = LINUX_MIB_TCPDSACKIGNOREDNOUNDO; 1805 else 1806 mib_idx = LINUX_MIB_TCPDSACKIGNOREDOLD; 1807 } else { 1808 /* Don't count olds caused by ACK reordering */ 1809 if ((TCP_SKB_CB(ack_skb)->ack_seq != tp->snd_una) && 1810 !after(sp[used_sacks].end_seq, tp->snd_una)) 1811 continue; 1812 mib_idx = LINUX_MIB_TCPSACKDISCARD; 1813 } 1814 1815 NET_INC_STATS_BH(sock_net(sk), mib_idx); 1816 if (i == 0) 1817 first_sack_index = -1; 1818 continue; 1819 } 1820 1821 /* Ignore very old stuff early */ 1822 if (!after(sp[used_sacks].end_seq, prior_snd_una)) 1823 continue; 1824 1825 used_sacks++; 1826 } 1827 1828 /* order SACK blocks to allow in order walk of the retrans queue */ 1829 for (i = used_sacks - 1; i > 0; i--) { 1830 for (j = 0; j < i; j++) { 1831 if (after(sp[j].start_seq, sp[j + 1].start_seq)) { 1832 swap(sp[j], sp[j + 1]); 1833 1834 /* Track where the first SACK block goes to */ 1835 if (j == first_sack_index) 1836 first_sack_index = j + 1; 1837 } 1838 } 1839 } 1840 1841 skb = tcp_write_queue_head(sk); 1842 state.fack_count = 0; 1843 i = 0; 1844 1845 if (!tp->sacked_out) { 1846 /* It's already past, so skip checking against it */ 1847 cache = tp->recv_sack_cache + ARRAY_SIZE(tp->recv_sack_cache); 1848 } else { 1849 cache = tp->recv_sack_cache; 1850 /* Skip empty blocks in at head of the cache */ 1851 while (tcp_sack_cache_ok(tp, cache) && !cache->start_seq && 1852 !cache->end_seq) 1853 cache++; 1854 } 1855 1856 while (i < used_sacks) { 1857 u32 start_seq = sp[i].start_seq; 1858 u32 end_seq = sp[i].end_seq; 1859 int dup_sack = (found_dup_sack && (i == first_sack_index)); 1860 struct tcp_sack_block *next_dup = NULL; 1861 1862 if (found_dup_sack && ((i + 1) == first_sack_index)) 1863 next_dup = &sp[i + 1]; 1864 1865 /* Skip too early cached blocks */ 1866 while (tcp_sack_cache_ok(tp, cache) && 1867 !before(start_seq, cache->end_seq)) 1868 cache++; 1869 1870 /* Can skip some work by looking recv_sack_cache? */ 1871 if (tcp_sack_cache_ok(tp, cache) && !dup_sack && 1872 after(end_seq, cache->start_seq)) { 1873 1874 /* Head todo? */ 1875 if (before(start_seq, cache->start_seq)) { 1876 skb = tcp_sacktag_skip(skb, sk, &state, 1877 start_seq); 1878 skb = tcp_sacktag_walk(skb, sk, next_dup, 1879 &state, 1880 start_seq, 1881 cache->start_seq, 1882 dup_sack); 1883 } 1884 1885 /* Rest of the block already fully processed? */ 1886 if (!after(end_seq, cache->end_seq)) 1887 goto advance_sp; 1888 1889 skb = tcp_maybe_skipping_dsack(skb, sk, next_dup, 1890 &state, 1891 cache->end_seq); 1892 1893 /* ...tail remains todo... */ 1894 if (tcp_highest_sack_seq(tp) == cache->end_seq) { 1895 /* ...but better entrypoint exists! */ 1896 skb = tcp_highest_sack(sk); 1897 if (skb == NULL) 1898 break; 1899 state.fack_count = tp->fackets_out; 1900 cache++; 1901 goto walk; 1902 } 1903 1904 skb = tcp_sacktag_skip(skb, sk, &state, cache->end_seq); 1905 /* Check overlap against next cached too (past this one already) */ 1906 cache++; 1907 continue; 1908 } 1909 1910 if (!before(start_seq, tcp_highest_sack_seq(tp))) { 1911 skb = tcp_highest_sack(sk); 1912 if (skb == NULL) 1913 break; 1914 state.fack_count = tp->fackets_out; 1915 } 1916 skb = tcp_sacktag_skip(skb, sk, &state, start_seq); 1917 1918 walk: 1919 skb = tcp_sacktag_walk(skb, sk, next_dup, &state, 1920 start_seq, end_seq, dup_sack); 1921 1922 advance_sp: 1923 /* SACK enhanced FRTO (RFC4138, Appendix B): Clearing correct 1924 * due to in-order walk 1925 */ 1926 if (after(end_seq, tp->frto_highmark)) 1927 state.flag &= ~FLAG_ONLY_ORIG_SACKED; 1928 1929 i++; 1930 } 1931 1932 /* Clear the head of the cache sack blocks so we can skip it next time */ 1933 for (i = 0; i < ARRAY_SIZE(tp->recv_sack_cache) - used_sacks; i++) { 1934 tp->recv_sack_cache[i].start_seq = 0; 1935 tp->recv_sack_cache[i].end_seq = 0; 1936 } 1937 for (j = 0; j < used_sacks; j++) 1938 tp->recv_sack_cache[i++] = sp[j]; 1939 1940 tcp_mark_lost_retrans(sk); 1941 1942 tcp_verify_left_out(tp); 1943 1944 if ((state.reord < tp->fackets_out) && 1945 ((icsk->icsk_ca_state != TCP_CA_Loss) || tp->undo_marker) && 1946 (!tp->frto_highmark || after(tp->snd_una, tp->frto_highmark))) 1947 tcp_update_reordering(sk, tp->fackets_out - state.reord, 0); 1948 1949 out: 1950 1951 #if FASTRETRANS_DEBUG > 0 1952 WARN_ON((int)tp->sacked_out < 0); 1953 WARN_ON((int)tp->lost_out < 0); 1954 WARN_ON((int)tp->retrans_out < 0); 1955 WARN_ON((int)tcp_packets_in_flight(tp) < 0); 1956 #endif 1957 return state.flag; 1958 } 1959 1960 /* Limits sacked_out so that sum with lost_out isn't ever larger than 1961 * packets_out. Returns zero if sacked_out adjustement wasn't necessary. 1962 */ 1963 static int tcp_limit_reno_sacked(struct tcp_sock *tp) 1964 { 1965 u32 holes; 1966 1967 holes = max(tp->lost_out, 1U); 1968 holes = min(holes, tp->packets_out); 1969 1970 if ((tp->sacked_out + holes) > tp->packets_out) { 1971 tp->sacked_out = tp->packets_out - holes; 1972 return 1; 1973 } 1974 return 0; 1975 } 1976 1977 /* If we receive more dupacks than we expected counting segments 1978 * in assumption of absent reordering, interpret this as reordering. 1979 * The only another reason could be bug in receiver TCP. 1980 */ 1981 static void tcp_check_reno_reordering(struct sock *sk, const int addend) 1982 { 1983 struct tcp_sock *tp = tcp_sk(sk); 1984 if (tcp_limit_reno_sacked(tp)) 1985 tcp_update_reordering(sk, tp->packets_out + addend, 0); 1986 } 1987 1988 /* Emulate SACKs for SACKless connection: account for a new dupack. */ 1989 1990 static void tcp_add_reno_sack(struct sock *sk) 1991 { 1992 struct tcp_sock *tp = tcp_sk(sk); 1993 tp->sacked_out++; 1994 tcp_check_reno_reordering(sk, 0); 1995 tcp_verify_left_out(tp); 1996 } 1997 1998 /* Account for ACK, ACKing some data in Reno Recovery phase. */ 1999 2000 static void tcp_remove_reno_sacks(struct sock *sk, int acked) 2001 { 2002 struct tcp_sock *tp = tcp_sk(sk); 2003 2004 if (acked > 0) { 2005 /* One ACK acked hole. The rest eat duplicate ACKs. */ 2006 if (acked - 1 >= tp->sacked_out) 2007 tp->sacked_out = 0; 2008 else 2009 tp->sacked_out -= acked - 1; 2010 } 2011 tcp_check_reno_reordering(sk, acked); 2012 tcp_verify_left_out(tp); 2013 } 2014 2015 static inline void tcp_reset_reno_sack(struct tcp_sock *tp) 2016 { 2017 tp->sacked_out = 0; 2018 } 2019 2020 static int tcp_is_sackfrto(const struct tcp_sock *tp) 2021 { 2022 return (sysctl_tcp_frto == 0x2) && !tcp_is_reno(tp); 2023 } 2024 2025 /* F-RTO can only be used if TCP has never retransmitted anything other than 2026 * head (SACK enhanced variant from Appendix B of RFC4138 is more robust here) 2027 */ 2028 int tcp_use_frto(struct sock *sk) 2029 { 2030 const struct tcp_sock *tp = tcp_sk(sk); 2031 const struct inet_connection_sock *icsk = inet_csk(sk); 2032 struct sk_buff *skb; 2033 2034 if (!sysctl_tcp_frto) 2035 return 0; 2036 2037 /* MTU probe and F-RTO won't really play nicely along currently */ 2038 if (icsk->icsk_mtup.probe_size) 2039 return 0; 2040 2041 if (tcp_is_sackfrto(tp)) 2042 return 1; 2043 2044 /* Avoid expensive walking of rexmit queue if possible */ 2045 if (tp->retrans_out > 1) 2046 return 0; 2047 2048 skb = tcp_write_queue_head(sk); 2049 if (tcp_skb_is_last(sk, skb)) 2050 return 1; 2051 skb = tcp_write_queue_next(sk, skb); /* Skips head */ 2052 tcp_for_write_queue_from(skb, sk) { 2053 if (skb == tcp_send_head(sk)) 2054 break; 2055 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2056 return 0; 2057 /* Short-circuit when first non-SACKed skb has been checked */ 2058 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 2059 break; 2060 } 2061 return 1; 2062 } 2063 2064 /* RTO occurred, but do not yet enter Loss state. Instead, defer RTO 2065 * recovery a bit and use heuristics in tcp_process_frto() to detect if 2066 * the RTO was spurious. Only clear SACKED_RETRANS of the head here to 2067 * keep retrans_out counting accurate (with SACK F-RTO, other than head 2068 * may still have that bit set); TCPCB_LOST and remaining SACKED_RETRANS 2069 * bits are handled if the Loss state is really to be entered (in 2070 * tcp_enter_frto_loss). 2071 * 2072 * Do like tcp_enter_loss() would; when RTO expires the second time it 2073 * does: 2074 * "Reduce ssthresh if it has not yet been made inside this window." 2075 */ 2076 void tcp_enter_frto(struct sock *sk) 2077 { 2078 const struct inet_connection_sock *icsk = inet_csk(sk); 2079 struct tcp_sock *tp = tcp_sk(sk); 2080 struct sk_buff *skb; 2081 2082 if ((!tp->frto_counter && icsk->icsk_ca_state <= TCP_CA_Disorder) || 2083 tp->snd_una == tp->high_seq || 2084 ((icsk->icsk_ca_state == TCP_CA_Loss || tp->frto_counter) && 2085 !icsk->icsk_retransmits)) { 2086 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2087 /* Our state is too optimistic in ssthresh() call because cwnd 2088 * is not reduced until tcp_enter_frto_loss() when previous F-RTO 2089 * recovery has not yet completed. Pattern would be this: RTO, 2090 * Cumulative ACK, RTO (2xRTO for the same segment does not end 2091 * up here twice). 2092 * RFC4138 should be more specific on what to do, even though 2093 * RTO is quite unlikely to occur after the first Cumulative ACK 2094 * due to back-off and complexity of triggering events ... 2095 */ 2096 if (tp->frto_counter) { 2097 u32 stored_cwnd; 2098 stored_cwnd = tp->snd_cwnd; 2099 tp->snd_cwnd = 2; 2100 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2101 tp->snd_cwnd = stored_cwnd; 2102 } else { 2103 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2104 } 2105 /* ... in theory, cong.control module could do "any tricks" in 2106 * ssthresh(), which means that ca_state, lost bits and lost_out 2107 * counter would have to be faked before the call occurs. We 2108 * consider that too expensive, unlikely and hacky, so modules 2109 * using these in ssthresh() must deal these incompatibility 2110 * issues if they receives CA_EVENT_FRTO and frto_counter != 0 2111 */ 2112 tcp_ca_event(sk, CA_EVENT_FRTO); 2113 } 2114 2115 tp->undo_marker = tp->snd_una; 2116 tp->undo_retrans = 0; 2117 2118 skb = tcp_write_queue_head(sk); 2119 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2120 tp->undo_marker = 0; 2121 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 2122 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 2123 tp->retrans_out -= tcp_skb_pcount(skb); 2124 } 2125 tcp_verify_left_out(tp); 2126 2127 /* Too bad if TCP was application limited */ 2128 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1); 2129 2130 /* Earlier loss recovery underway (see RFC4138; Appendix B). 2131 * The last condition is necessary at least in tp->frto_counter case. 2132 */ 2133 if (tcp_is_sackfrto(tp) && (tp->frto_counter || 2134 ((1 << icsk->icsk_ca_state) & (TCPF_CA_Recovery|TCPF_CA_Loss))) && 2135 after(tp->high_seq, tp->snd_una)) { 2136 tp->frto_highmark = tp->high_seq; 2137 } else { 2138 tp->frto_highmark = tp->snd_nxt; 2139 } 2140 tcp_set_ca_state(sk, TCP_CA_Disorder); 2141 tp->high_seq = tp->snd_nxt; 2142 tp->frto_counter = 1; 2143 } 2144 2145 /* Enter Loss state after F-RTO was applied. Dupack arrived after RTO, 2146 * which indicates that we should follow the traditional RTO recovery, 2147 * i.e. mark everything lost and do go-back-N retransmission. 2148 */ 2149 static void tcp_enter_frto_loss(struct sock *sk, int allowed_segments, int flag) 2150 { 2151 struct tcp_sock *tp = tcp_sk(sk); 2152 struct sk_buff *skb; 2153 2154 tp->lost_out = 0; 2155 tp->retrans_out = 0; 2156 if (tcp_is_reno(tp)) 2157 tcp_reset_reno_sack(tp); 2158 2159 tcp_for_write_queue(skb, sk) { 2160 if (skb == tcp_send_head(sk)) 2161 break; 2162 2163 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 2164 /* 2165 * Count the retransmission made on RTO correctly (only when 2166 * waiting for the first ACK and did not get it)... 2167 */ 2168 if ((tp->frto_counter == 1) && !(flag & FLAG_DATA_ACKED)) { 2169 /* For some reason this R-bit might get cleared? */ 2170 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) 2171 tp->retrans_out += tcp_skb_pcount(skb); 2172 /* ...enter this if branch just for the first segment */ 2173 flag |= FLAG_DATA_ACKED; 2174 } else { 2175 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2176 tp->undo_marker = 0; 2177 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 2178 } 2179 2180 /* Marking forward transmissions that were made after RTO lost 2181 * can cause unnecessary retransmissions in some scenarios, 2182 * SACK blocks will mitigate that in some but not in all cases. 2183 * We used to not mark them but it was causing break-ups with 2184 * receivers that do only in-order receival. 2185 * 2186 * TODO: we could detect presence of such receiver and select 2187 * different behavior per flow. 2188 */ 2189 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 2190 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 2191 tp->lost_out += tcp_skb_pcount(skb); 2192 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; 2193 } 2194 } 2195 tcp_verify_left_out(tp); 2196 2197 tp->snd_cwnd = tcp_packets_in_flight(tp) + allowed_segments; 2198 tp->snd_cwnd_cnt = 0; 2199 tp->snd_cwnd_stamp = tcp_time_stamp; 2200 tp->frto_counter = 0; 2201 tp->bytes_acked = 0; 2202 2203 tp->reordering = min_t(unsigned int, tp->reordering, 2204 sysctl_tcp_reordering); 2205 tcp_set_ca_state(sk, TCP_CA_Loss); 2206 tp->high_seq = tp->snd_nxt; 2207 TCP_ECN_queue_cwr(tp); 2208 2209 tcp_clear_all_retrans_hints(tp); 2210 } 2211 2212 static void tcp_clear_retrans_partial(struct tcp_sock *tp) 2213 { 2214 tp->retrans_out = 0; 2215 tp->lost_out = 0; 2216 2217 tp->undo_marker = 0; 2218 tp->undo_retrans = 0; 2219 } 2220 2221 void tcp_clear_retrans(struct tcp_sock *tp) 2222 { 2223 tcp_clear_retrans_partial(tp); 2224 2225 tp->fackets_out = 0; 2226 tp->sacked_out = 0; 2227 } 2228 2229 /* Enter Loss state. If "how" is not zero, forget all SACK information 2230 * and reset tags completely, otherwise preserve SACKs. If receiver 2231 * dropped its ofo queue, we will know this due to reneging detection. 2232 */ 2233 void tcp_enter_loss(struct sock *sk, int how) 2234 { 2235 const struct inet_connection_sock *icsk = inet_csk(sk); 2236 struct tcp_sock *tp = tcp_sk(sk); 2237 struct sk_buff *skb; 2238 2239 /* Reduce ssthresh if it has not yet been made inside this window. */ 2240 if (icsk->icsk_ca_state <= TCP_CA_Disorder || tp->snd_una == tp->high_seq || 2241 (icsk->icsk_ca_state == TCP_CA_Loss && !icsk->icsk_retransmits)) { 2242 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2243 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 2244 tcp_ca_event(sk, CA_EVENT_LOSS); 2245 } 2246 tp->snd_cwnd = 1; 2247 tp->snd_cwnd_cnt = 0; 2248 tp->snd_cwnd_stamp = tcp_time_stamp; 2249 2250 tp->bytes_acked = 0; 2251 tcp_clear_retrans_partial(tp); 2252 2253 if (tcp_is_reno(tp)) 2254 tcp_reset_reno_sack(tp); 2255 2256 if (!how) { 2257 /* Push undo marker, if it was plain RTO and nothing 2258 * was retransmitted. */ 2259 tp->undo_marker = tp->snd_una; 2260 } else { 2261 tp->sacked_out = 0; 2262 tp->fackets_out = 0; 2263 } 2264 tcp_clear_all_retrans_hints(tp); 2265 2266 tcp_for_write_queue(skb, sk) { 2267 if (skb == tcp_send_head(sk)) 2268 break; 2269 2270 if (TCP_SKB_CB(skb)->sacked & TCPCB_RETRANS) 2271 tp->undo_marker = 0; 2272 TCP_SKB_CB(skb)->sacked &= (~TCPCB_TAGBITS)|TCPCB_SACKED_ACKED; 2273 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED) || how) { 2274 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_ACKED; 2275 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 2276 tp->lost_out += tcp_skb_pcount(skb); 2277 tp->retransmit_high = TCP_SKB_CB(skb)->end_seq; 2278 } 2279 } 2280 tcp_verify_left_out(tp); 2281 2282 tp->reordering = min_t(unsigned int, tp->reordering, 2283 sysctl_tcp_reordering); 2284 tcp_set_ca_state(sk, TCP_CA_Loss); 2285 tp->high_seq = tp->snd_nxt; 2286 TCP_ECN_queue_cwr(tp); 2287 /* Abort F-RTO algorithm if one is in progress */ 2288 tp->frto_counter = 0; 2289 } 2290 2291 /* If ACK arrived pointing to a remembered SACK, it means that our 2292 * remembered SACKs do not reflect real state of receiver i.e. 2293 * receiver _host_ is heavily congested (or buggy). 2294 * 2295 * Do processing similar to RTO timeout. 2296 */ 2297 static int tcp_check_sack_reneging(struct sock *sk, int flag) 2298 { 2299 if (flag & FLAG_SACK_RENEGING) { 2300 struct inet_connection_sock *icsk = inet_csk(sk); 2301 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSACKRENEGING); 2302 2303 tcp_enter_loss(sk, 1); 2304 icsk->icsk_retransmits++; 2305 tcp_retransmit_skb(sk, tcp_write_queue_head(sk)); 2306 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 2307 icsk->icsk_rto, TCP_RTO_MAX); 2308 return 1; 2309 } 2310 return 0; 2311 } 2312 2313 static inline int tcp_fackets_out(const struct tcp_sock *tp) 2314 { 2315 return tcp_is_reno(tp) ? tp->sacked_out + 1 : tp->fackets_out; 2316 } 2317 2318 /* Heurestics to calculate number of duplicate ACKs. There's no dupACKs 2319 * counter when SACK is enabled (without SACK, sacked_out is used for 2320 * that purpose). 2321 * 2322 * Instead, with FACK TCP uses fackets_out that includes both SACKed 2323 * segments up to the highest received SACK block so far and holes in 2324 * between them. 2325 * 2326 * With reordering, holes may still be in flight, so RFC3517 recovery 2327 * uses pure sacked_out (total number of SACKed segments) even though 2328 * it violates the RFC that uses duplicate ACKs, often these are equal 2329 * but when e.g. out-of-window ACKs or packet duplication occurs, 2330 * they differ. Since neither occurs due to loss, TCP should really 2331 * ignore them. 2332 */ 2333 static inline int tcp_dupack_heuristics(const struct tcp_sock *tp) 2334 { 2335 return tcp_is_fack(tp) ? tp->fackets_out : tp->sacked_out + 1; 2336 } 2337 2338 static inline int tcp_skb_timedout(const struct sock *sk, 2339 const struct sk_buff *skb) 2340 { 2341 return tcp_time_stamp - TCP_SKB_CB(skb)->when > inet_csk(sk)->icsk_rto; 2342 } 2343 2344 static inline int tcp_head_timedout(const struct sock *sk) 2345 { 2346 const struct tcp_sock *tp = tcp_sk(sk); 2347 2348 return tp->packets_out && 2349 tcp_skb_timedout(sk, tcp_write_queue_head(sk)); 2350 } 2351 2352 /* Linux NewReno/SACK/FACK/ECN state machine. 2353 * -------------------------------------- 2354 * 2355 * "Open" Normal state, no dubious events, fast path. 2356 * "Disorder" In all the respects it is "Open", 2357 * but requires a bit more attention. It is entered when 2358 * we see some SACKs or dupacks. It is split of "Open" 2359 * mainly to move some processing from fast path to slow one. 2360 * "CWR" CWND was reduced due to some Congestion Notification event. 2361 * It can be ECN, ICMP source quench, local device congestion. 2362 * "Recovery" CWND was reduced, we are fast-retransmitting. 2363 * "Loss" CWND was reduced due to RTO timeout or SACK reneging. 2364 * 2365 * tcp_fastretrans_alert() is entered: 2366 * - each incoming ACK, if state is not "Open" 2367 * - when arrived ACK is unusual, namely: 2368 * * SACK 2369 * * Duplicate ACK. 2370 * * ECN ECE. 2371 * 2372 * Counting packets in flight is pretty simple. 2373 * 2374 * in_flight = packets_out - left_out + retrans_out 2375 * 2376 * packets_out is SND.NXT-SND.UNA counted in packets. 2377 * 2378 * retrans_out is number of retransmitted segments. 2379 * 2380 * left_out is number of segments left network, but not ACKed yet. 2381 * 2382 * left_out = sacked_out + lost_out 2383 * 2384 * sacked_out: Packets, which arrived to receiver out of order 2385 * and hence not ACKed. With SACKs this number is simply 2386 * amount of SACKed data. Even without SACKs 2387 * it is easy to give pretty reliable estimate of this number, 2388 * counting duplicate ACKs. 2389 * 2390 * lost_out: Packets lost by network. TCP has no explicit 2391 * "loss notification" feedback from network (for now). 2392 * It means that this number can be only _guessed_. 2393 * Actually, it is the heuristics to predict lossage that 2394 * distinguishes different algorithms. 2395 * 2396 * F.e. after RTO, when all the queue is considered as lost, 2397 * lost_out = packets_out and in_flight = retrans_out. 2398 * 2399 * Essentially, we have now two algorithms counting 2400 * lost packets. 2401 * 2402 * FACK: It is the simplest heuristics. As soon as we decided 2403 * that something is lost, we decide that _all_ not SACKed 2404 * packets until the most forward SACK are lost. I.e. 2405 * lost_out = fackets_out - sacked_out and left_out = fackets_out. 2406 * It is absolutely correct estimate, if network does not reorder 2407 * packets. And it loses any connection to reality when reordering 2408 * takes place. We use FACK by default until reordering 2409 * is suspected on the path to this destination. 2410 * 2411 * NewReno: when Recovery is entered, we assume that one segment 2412 * is lost (classic Reno). While we are in Recovery and 2413 * a partial ACK arrives, we assume that one more packet 2414 * is lost (NewReno). This heuristics are the same in NewReno 2415 * and SACK. 2416 * 2417 * Imagine, that's all! Forget about all this shamanism about CWND inflation 2418 * deflation etc. CWND is real congestion window, never inflated, changes 2419 * only according to classic VJ rules. 2420 * 2421 * Really tricky (and requiring careful tuning) part of algorithm 2422 * is hidden in functions tcp_time_to_recover() and tcp_xmit_retransmit_queue(). 2423 * The first determines the moment _when_ we should reduce CWND and, 2424 * hence, slow down forward transmission. In fact, it determines the moment 2425 * when we decide that hole is caused by loss, rather than by a reorder. 2426 * 2427 * tcp_xmit_retransmit_queue() decides, _what_ we should retransmit to fill 2428 * holes, caused by lost packets. 2429 * 2430 * And the most logically complicated part of algorithm is undo 2431 * heuristics. We detect false retransmits due to both too early 2432 * fast retransmit (reordering) and underestimated RTO, analyzing 2433 * timestamps and D-SACKs. When we detect that some segments were 2434 * retransmitted by mistake and CWND reduction was wrong, we undo 2435 * window reduction and abort recovery phase. This logic is hidden 2436 * inside several functions named tcp_try_undo_<something>. 2437 */ 2438 2439 /* This function decides, when we should leave Disordered state 2440 * and enter Recovery phase, reducing congestion window. 2441 * 2442 * Main question: may we further continue forward transmission 2443 * with the same cwnd? 2444 */ 2445 static int tcp_time_to_recover(struct sock *sk) 2446 { 2447 struct tcp_sock *tp = tcp_sk(sk); 2448 __u32 packets_out; 2449 2450 /* Do not perform any recovery during F-RTO algorithm */ 2451 if (tp->frto_counter) 2452 return 0; 2453 2454 /* Trick#1: The loss is proven. */ 2455 if (tp->lost_out) 2456 return 1; 2457 2458 /* Not-A-Trick#2 : Classic rule... */ 2459 if (tcp_dupack_heuristics(tp) > tp->reordering) 2460 return 1; 2461 2462 /* Trick#3 : when we use RFC2988 timer restart, fast 2463 * retransmit can be triggered by timeout of queue head. 2464 */ 2465 if (tcp_is_fack(tp) && tcp_head_timedout(sk)) 2466 return 1; 2467 2468 /* Trick#4: It is still not OK... But will it be useful to delay 2469 * recovery more? 2470 */ 2471 packets_out = tp->packets_out; 2472 if (packets_out <= tp->reordering && 2473 tp->sacked_out >= max_t(__u32, packets_out/2, sysctl_tcp_reordering) && 2474 !tcp_may_send_now(sk)) { 2475 /* We have nothing to send. This connection is limited 2476 * either by receiver window or by application. 2477 */ 2478 return 1; 2479 } 2480 2481 /* If a thin stream is detected, retransmit after first 2482 * received dupack. Employ only if SACK is supported in order 2483 * to avoid possible corner-case series of spurious retransmissions 2484 * Use only if there are no unsent data. 2485 */ 2486 if ((tp->thin_dupack || sysctl_tcp_thin_dupack) && 2487 tcp_stream_is_thin(tp) && tcp_dupack_heuristics(tp) > 1 && 2488 tcp_is_sack(tp) && !tcp_send_head(sk)) 2489 return 1; 2490 2491 return 0; 2492 } 2493 2494 /* New heuristics: it is possible only after we switched to restart timer 2495 * each time when something is ACKed. Hence, we can detect timed out packets 2496 * during fast retransmit without falling to slow start. 2497 * 2498 * Usefulness of this as is very questionable, since we should know which of 2499 * the segments is the next to timeout which is relatively expensive to find 2500 * in general case unless we add some data structure just for that. The 2501 * current approach certainly won't find the right one too often and when it 2502 * finally does find _something_ it usually marks large part of the window 2503 * right away (because a retransmission with a larger timestamp blocks the 2504 * loop from advancing). -ij 2505 */ 2506 static void tcp_timeout_skbs(struct sock *sk) 2507 { 2508 struct tcp_sock *tp = tcp_sk(sk); 2509 struct sk_buff *skb; 2510 2511 if (!tcp_is_fack(tp) || !tcp_head_timedout(sk)) 2512 return; 2513 2514 skb = tp->scoreboard_skb_hint; 2515 if (tp->scoreboard_skb_hint == NULL) 2516 skb = tcp_write_queue_head(sk); 2517 2518 tcp_for_write_queue_from(skb, sk) { 2519 if (skb == tcp_send_head(sk)) 2520 break; 2521 if (!tcp_skb_timedout(sk, skb)) 2522 break; 2523 2524 tcp_skb_mark_lost(tp, skb); 2525 } 2526 2527 tp->scoreboard_skb_hint = skb; 2528 2529 tcp_verify_left_out(tp); 2530 } 2531 2532 /* Detect loss in event "A" above by marking head of queue up as lost. 2533 * For FACK or non-SACK(Reno) senders, the first "packets" number of segments 2534 * are considered lost. For RFC3517 SACK, a segment is considered lost if it 2535 * has at least tp->reordering SACKed seqments above it; "packets" refers to 2536 * the maximum SACKed segments to pass before reaching this limit. 2537 */ 2538 static void tcp_mark_head_lost(struct sock *sk, int packets, int mark_head) 2539 { 2540 struct tcp_sock *tp = tcp_sk(sk); 2541 struct sk_buff *skb; 2542 int cnt, oldcnt; 2543 int err; 2544 unsigned int mss; 2545 /* Use SACK to deduce losses of new sequences sent during recovery */ 2546 const u32 loss_high = tcp_is_sack(tp) ? tp->snd_nxt : tp->high_seq; 2547 2548 WARN_ON(packets > tp->packets_out); 2549 if (tp->lost_skb_hint) { 2550 skb = tp->lost_skb_hint; 2551 cnt = tp->lost_cnt_hint; 2552 /* Head already handled? */ 2553 if (mark_head && skb != tcp_write_queue_head(sk)) 2554 return; 2555 } else { 2556 skb = tcp_write_queue_head(sk); 2557 cnt = 0; 2558 } 2559 2560 tcp_for_write_queue_from(skb, sk) { 2561 if (skb == tcp_send_head(sk)) 2562 break; 2563 /* TODO: do this better */ 2564 /* this is not the most efficient way to do this... */ 2565 tp->lost_skb_hint = skb; 2566 tp->lost_cnt_hint = cnt; 2567 2568 if (after(TCP_SKB_CB(skb)->end_seq, loss_high)) 2569 break; 2570 2571 oldcnt = cnt; 2572 if (tcp_is_fack(tp) || tcp_is_reno(tp) || 2573 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 2574 cnt += tcp_skb_pcount(skb); 2575 2576 if (cnt > packets) { 2577 if ((tcp_is_sack(tp) && !tcp_is_fack(tp)) || 2578 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) || 2579 (oldcnt >= packets)) 2580 break; 2581 2582 mss = skb_shinfo(skb)->gso_size; 2583 err = tcp_fragment(sk, skb, (packets - oldcnt) * mss, mss); 2584 if (err < 0) 2585 break; 2586 cnt = packets; 2587 } 2588 2589 tcp_skb_mark_lost(tp, skb); 2590 2591 if (mark_head) 2592 break; 2593 } 2594 tcp_verify_left_out(tp); 2595 } 2596 2597 /* Account newly detected lost packet(s) */ 2598 2599 static void tcp_update_scoreboard(struct sock *sk, int fast_rexmit) 2600 { 2601 struct tcp_sock *tp = tcp_sk(sk); 2602 2603 if (tcp_is_reno(tp)) { 2604 tcp_mark_head_lost(sk, 1, 1); 2605 } else if (tcp_is_fack(tp)) { 2606 int lost = tp->fackets_out - tp->reordering; 2607 if (lost <= 0) 2608 lost = 1; 2609 tcp_mark_head_lost(sk, lost, 0); 2610 } else { 2611 int sacked_upto = tp->sacked_out - tp->reordering; 2612 if (sacked_upto >= 0) 2613 tcp_mark_head_lost(sk, sacked_upto, 0); 2614 else if (fast_rexmit) 2615 tcp_mark_head_lost(sk, 1, 1); 2616 } 2617 2618 tcp_timeout_skbs(sk); 2619 } 2620 2621 /* CWND moderation, preventing bursts due to too big ACKs 2622 * in dubious situations. 2623 */ 2624 static inline void tcp_moderate_cwnd(struct tcp_sock *tp) 2625 { 2626 tp->snd_cwnd = min(tp->snd_cwnd, 2627 tcp_packets_in_flight(tp) + tcp_max_burst(tp)); 2628 tp->snd_cwnd_stamp = tcp_time_stamp; 2629 } 2630 2631 /* Lower bound on congestion window is slow start threshold 2632 * unless congestion avoidance choice decides to overide it. 2633 */ 2634 static inline u32 tcp_cwnd_min(const struct sock *sk) 2635 { 2636 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; 2637 2638 return ca_ops->min_cwnd ? ca_ops->min_cwnd(sk) : tcp_sk(sk)->snd_ssthresh; 2639 } 2640 2641 /* Decrease cwnd each second ack. */ 2642 static void tcp_cwnd_down(struct sock *sk, int flag) 2643 { 2644 struct tcp_sock *tp = tcp_sk(sk); 2645 int decr = tp->snd_cwnd_cnt + 1; 2646 2647 if ((flag & (FLAG_ANY_PROGRESS | FLAG_DSACKING_ACK)) || 2648 (tcp_is_reno(tp) && !(flag & FLAG_NOT_DUP))) { 2649 tp->snd_cwnd_cnt = decr & 1; 2650 decr >>= 1; 2651 2652 if (decr && tp->snd_cwnd > tcp_cwnd_min(sk)) 2653 tp->snd_cwnd -= decr; 2654 2655 tp->snd_cwnd = min(tp->snd_cwnd, tcp_packets_in_flight(tp) + 1); 2656 tp->snd_cwnd_stamp = tcp_time_stamp; 2657 } 2658 } 2659 2660 /* Nothing was retransmitted or returned timestamp is less 2661 * than timestamp of the first retransmission. 2662 */ 2663 static inline int tcp_packet_delayed(const struct tcp_sock *tp) 2664 { 2665 return !tp->retrans_stamp || 2666 (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 2667 before(tp->rx_opt.rcv_tsecr, tp->retrans_stamp)); 2668 } 2669 2670 /* Undo procedures. */ 2671 2672 #if FASTRETRANS_DEBUG > 1 2673 static void DBGUNDO(struct sock *sk, const char *msg) 2674 { 2675 struct tcp_sock *tp = tcp_sk(sk); 2676 struct inet_sock *inet = inet_sk(sk); 2677 2678 if (sk->sk_family == AF_INET) { 2679 printk(KERN_DEBUG "Undo %s %pI4/%u c%u l%u ss%u/%u p%u\n", 2680 msg, 2681 &inet->inet_daddr, ntohs(inet->inet_dport), 2682 tp->snd_cwnd, tcp_left_out(tp), 2683 tp->snd_ssthresh, tp->prior_ssthresh, 2684 tp->packets_out); 2685 } 2686 #if IS_ENABLED(CONFIG_IPV6) 2687 else if (sk->sk_family == AF_INET6) { 2688 struct ipv6_pinfo *np = inet6_sk(sk); 2689 printk(KERN_DEBUG "Undo %s %pI6/%u c%u l%u ss%u/%u p%u\n", 2690 msg, 2691 &np->daddr, ntohs(inet->inet_dport), 2692 tp->snd_cwnd, tcp_left_out(tp), 2693 tp->snd_ssthresh, tp->prior_ssthresh, 2694 tp->packets_out); 2695 } 2696 #endif 2697 } 2698 #else 2699 #define DBGUNDO(x...) do { } while (0) 2700 #endif 2701 2702 static void tcp_undo_cwr(struct sock *sk, const bool undo_ssthresh) 2703 { 2704 struct tcp_sock *tp = tcp_sk(sk); 2705 2706 if (tp->prior_ssthresh) { 2707 const struct inet_connection_sock *icsk = inet_csk(sk); 2708 2709 if (icsk->icsk_ca_ops->undo_cwnd) 2710 tp->snd_cwnd = icsk->icsk_ca_ops->undo_cwnd(sk); 2711 else 2712 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh << 1); 2713 2714 if (undo_ssthresh && tp->prior_ssthresh > tp->snd_ssthresh) { 2715 tp->snd_ssthresh = tp->prior_ssthresh; 2716 TCP_ECN_withdraw_cwr(tp); 2717 } 2718 } else { 2719 tp->snd_cwnd = max(tp->snd_cwnd, tp->snd_ssthresh); 2720 } 2721 tp->snd_cwnd_stamp = tcp_time_stamp; 2722 } 2723 2724 static inline int tcp_may_undo(const struct tcp_sock *tp) 2725 { 2726 return tp->undo_marker && (!tp->undo_retrans || tcp_packet_delayed(tp)); 2727 } 2728 2729 /* People celebrate: "We love our President!" */ 2730 static int tcp_try_undo_recovery(struct sock *sk) 2731 { 2732 struct tcp_sock *tp = tcp_sk(sk); 2733 2734 if (tcp_may_undo(tp)) { 2735 int mib_idx; 2736 2737 /* Happy end! We did not retransmit anything 2738 * or our original transmission succeeded. 2739 */ 2740 DBGUNDO(sk, inet_csk(sk)->icsk_ca_state == TCP_CA_Loss ? "loss" : "retrans"); 2741 tcp_undo_cwr(sk, true); 2742 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Loss) 2743 mib_idx = LINUX_MIB_TCPLOSSUNDO; 2744 else 2745 mib_idx = LINUX_MIB_TCPFULLUNDO; 2746 2747 NET_INC_STATS_BH(sock_net(sk), mib_idx); 2748 tp->undo_marker = 0; 2749 } 2750 if (tp->snd_una == tp->high_seq && tcp_is_reno(tp)) { 2751 /* Hold old state until something *above* high_seq 2752 * is ACKed. For Reno it is MUST to prevent false 2753 * fast retransmits (RFC2582). SACK TCP is safe. */ 2754 tcp_moderate_cwnd(tp); 2755 return 1; 2756 } 2757 tcp_set_ca_state(sk, TCP_CA_Open); 2758 return 0; 2759 } 2760 2761 /* Try to undo cwnd reduction, because D-SACKs acked all retransmitted data */ 2762 static void tcp_try_undo_dsack(struct sock *sk) 2763 { 2764 struct tcp_sock *tp = tcp_sk(sk); 2765 2766 if (tp->undo_marker && !tp->undo_retrans) { 2767 DBGUNDO(sk, "D-SACK"); 2768 tcp_undo_cwr(sk, true); 2769 tp->undo_marker = 0; 2770 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPDSACKUNDO); 2771 } 2772 } 2773 2774 /* We can clear retrans_stamp when there are no retransmissions in the 2775 * window. It would seem that it is trivially available for us in 2776 * tp->retrans_out, however, that kind of assumptions doesn't consider 2777 * what will happen if errors occur when sending retransmission for the 2778 * second time. ...It could the that such segment has only 2779 * TCPCB_EVER_RETRANS set at the present time. It seems that checking 2780 * the head skb is enough except for some reneging corner cases that 2781 * are not worth the effort. 2782 * 2783 * Main reason for all this complexity is the fact that connection dying 2784 * time now depends on the validity of the retrans_stamp, in particular, 2785 * that successive retransmissions of a segment must not advance 2786 * retrans_stamp under any conditions. 2787 */ 2788 static int tcp_any_retrans_done(const struct sock *sk) 2789 { 2790 const struct tcp_sock *tp = tcp_sk(sk); 2791 struct sk_buff *skb; 2792 2793 if (tp->retrans_out) 2794 return 1; 2795 2796 skb = tcp_write_queue_head(sk); 2797 if (unlikely(skb && TCP_SKB_CB(skb)->sacked & TCPCB_EVER_RETRANS)) 2798 return 1; 2799 2800 return 0; 2801 } 2802 2803 /* Undo during fast recovery after partial ACK. */ 2804 2805 static int tcp_try_undo_partial(struct sock *sk, int acked) 2806 { 2807 struct tcp_sock *tp = tcp_sk(sk); 2808 /* Partial ACK arrived. Force Hoe's retransmit. */ 2809 int failed = tcp_is_reno(tp) || (tcp_fackets_out(tp) > tp->reordering); 2810 2811 if (tcp_may_undo(tp)) { 2812 /* Plain luck! Hole if filled with delayed 2813 * packet, rather than with a retransmit. 2814 */ 2815 if (!tcp_any_retrans_done(sk)) 2816 tp->retrans_stamp = 0; 2817 2818 tcp_update_reordering(sk, tcp_fackets_out(tp) + acked, 1); 2819 2820 DBGUNDO(sk, "Hoe"); 2821 tcp_undo_cwr(sk, false); 2822 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPARTIALUNDO); 2823 2824 /* So... Do not make Hoe's retransmit yet. 2825 * If the first packet was delayed, the rest 2826 * ones are most probably delayed as well. 2827 */ 2828 failed = 0; 2829 } 2830 return failed; 2831 } 2832 2833 /* Undo during loss recovery after partial ACK. */ 2834 static int tcp_try_undo_loss(struct sock *sk) 2835 { 2836 struct tcp_sock *tp = tcp_sk(sk); 2837 2838 if (tcp_may_undo(tp)) { 2839 struct sk_buff *skb; 2840 tcp_for_write_queue(skb, sk) { 2841 if (skb == tcp_send_head(sk)) 2842 break; 2843 TCP_SKB_CB(skb)->sacked &= ~TCPCB_LOST; 2844 } 2845 2846 tcp_clear_all_retrans_hints(tp); 2847 2848 DBGUNDO(sk, "partial loss"); 2849 tp->lost_out = 0; 2850 tcp_undo_cwr(sk, true); 2851 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPLOSSUNDO); 2852 inet_csk(sk)->icsk_retransmits = 0; 2853 tp->undo_marker = 0; 2854 if (tcp_is_sack(tp)) 2855 tcp_set_ca_state(sk, TCP_CA_Open); 2856 return 1; 2857 } 2858 return 0; 2859 } 2860 2861 static inline void tcp_complete_cwr(struct sock *sk) 2862 { 2863 struct tcp_sock *tp = tcp_sk(sk); 2864 2865 /* Do not moderate cwnd if it's already undone in cwr or recovery. */ 2866 if (tp->undo_marker) { 2867 if (inet_csk(sk)->icsk_ca_state == TCP_CA_CWR) 2868 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 2869 else /* PRR */ 2870 tp->snd_cwnd = tp->snd_ssthresh; 2871 tp->snd_cwnd_stamp = tcp_time_stamp; 2872 } 2873 tcp_ca_event(sk, CA_EVENT_COMPLETE_CWR); 2874 } 2875 2876 static void tcp_try_keep_open(struct sock *sk) 2877 { 2878 struct tcp_sock *tp = tcp_sk(sk); 2879 int state = TCP_CA_Open; 2880 2881 if (tcp_left_out(tp) || tcp_any_retrans_done(sk)) 2882 state = TCP_CA_Disorder; 2883 2884 if (inet_csk(sk)->icsk_ca_state != state) { 2885 tcp_set_ca_state(sk, state); 2886 tp->high_seq = tp->snd_nxt; 2887 } 2888 } 2889 2890 static void tcp_try_to_open(struct sock *sk, int flag) 2891 { 2892 struct tcp_sock *tp = tcp_sk(sk); 2893 2894 tcp_verify_left_out(tp); 2895 2896 if (!tp->frto_counter && !tcp_any_retrans_done(sk)) 2897 tp->retrans_stamp = 0; 2898 2899 if (flag & FLAG_ECE) 2900 tcp_enter_cwr(sk, 1); 2901 2902 if (inet_csk(sk)->icsk_ca_state != TCP_CA_CWR) { 2903 tcp_try_keep_open(sk); 2904 if (inet_csk(sk)->icsk_ca_state != TCP_CA_Open) 2905 tcp_moderate_cwnd(tp); 2906 } else { 2907 tcp_cwnd_down(sk, flag); 2908 } 2909 } 2910 2911 static void tcp_mtup_probe_failed(struct sock *sk) 2912 { 2913 struct inet_connection_sock *icsk = inet_csk(sk); 2914 2915 icsk->icsk_mtup.search_high = icsk->icsk_mtup.probe_size - 1; 2916 icsk->icsk_mtup.probe_size = 0; 2917 } 2918 2919 static void tcp_mtup_probe_success(struct sock *sk) 2920 { 2921 struct tcp_sock *tp = tcp_sk(sk); 2922 struct inet_connection_sock *icsk = inet_csk(sk); 2923 2924 /* FIXME: breaks with very large cwnd */ 2925 tp->prior_ssthresh = tcp_current_ssthresh(sk); 2926 tp->snd_cwnd = tp->snd_cwnd * 2927 tcp_mss_to_mtu(sk, tp->mss_cache) / 2928 icsk->icsk_mtup.probe_size; 2929 tp->snd_cwnd_cnt = 0; 2930 tp->snd_cwnd_stamp = tcp_time_stamp; 2931 tp->snd_ssthresh = tcp_current_ssthresh(sk); 2932 2933 icsk->icsk_mtup.search_low = icsk->icsk_mtup.probe_size; 2934 icsk->icsk_mtup.probe_size = 0; 2935 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 2936 } 2937 2938 /* Do a simple retransmit without using the backoff mechanisms in 2939 * tcp_timer. This is used for path mtu discovery. 2940 * The socket is already locked here. 2941 */ 2942 void tcp_simple_retransmit(struct sock *sk) 2943 { 2944 const struct inet_connection_sock *icsk = inet_csk(sk); 2945 struct tcp_sock *tp = tcp_sk(sk); 2946 struct sk_buff *skb; 2947 unsigned int mss = tcp_current_mss(sk); 2948 u32 prior_lost = tp->lost_out; 2949 2950 tcp_for_write_queue(skb, sk) { 2951 if (skb == tcp_send_head(sk)) 2952 break; 2953 if (tcp_skb_seglen(skb) > mss && 2954 !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 2955 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 2956 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 2957 tp->retrans_out -= tcp_skb_pcount(skb); 2958 } 2959 tcp_skb_mark_lost_uncond_verify(tp, skb); 2960 } 2961 } 2962 2963 tcp_clear_retrans_hints_partial(tp); 2964 2965 if (prior_lost == tp->lost_out) 2966 return; 2967 2968 if (tcp_is_reno(tp)) 2969 tcp_limit_reno_sacked(tp); 2970 2971 tcp_verify_left_out(tp); 2972 2973 /* Don't muck with the congestion window here. 2974 * Reason is that we do not increase amount of _data_ 2975 * in network, but units changed and effective 2976 * cwnd/ssthresh really reduced now. 2977 */ 2978 if (icsk->icsk_ca_state != TCP_CA_Loss) { 2979 tp->high_seq = tp->snd_nxt; 2980 tp->snd_ssthresh = tcp_current_ssthresh(sk); 2981 tp->prior_ssthresh = 0; 2982 tp->undo_marker = 0; 2983 tcp_set_ca_state(sk, TCP_CA_Loss); 2984 } 2985 tcp_xmit_retransmit_queue(sk); 2986 } 2987 EXPORT_SYMBOL(tcp_simple_retransmit); 2988 2989 /* This function implements the PRR algorithm, specifcally the PRR-SSRB 2990 * (proportional rate reduction with slow start reduction bound) as described in 2991 * http://www.ietf.org/id/draft-mathis-tcpm-proportional-rate-reduction-01.txt. 2992 * It computes the number of packets to send (sndcnt) based on packets newly 2993 * delivered: 2994 * 1) If the packets in flight is larger than ssthresh, PRR spreads the 2995 * cwnd reductions across a full RTT. 2996 * 2) If packets in flight is lower than ssthresh (such as due to excess 2997 * losses and/or application stalls), do not perform any further cwnd 2998 * reductions, but instead slow start up to ssthresh. 2999 */ 3000 static void tcp_update_cwnd_in_recovery(struct sock *sk, int newly_acked_sacked, 3001 int fast_rexmit, int flag) 3002 { 3003 struct tcp_sock *tp = tcp_sk(sk); 3004 int sndcnt = 0; 3005 int delta = tp->snd_ssthresh - tcp_packets_in_flight(tp); 3006 3007 if (tcp_packets_in_flight(tp) > tp->snd_ssthresh) { 3008 u64 dividend = (u64)tp->snd_ssthresh * tp->prr_delivered + 3009 tp->prior_cwnd - 1; 3010 sndcnt = div_u64(dividend, tp->prior_cwnd) - tp->prr_out; 3011 } else { 3012 sndcnt = min_t(int, delta, 3013 max_t(int, tp->prr_delivered - tp->prr_out, 3014 newly_acked_sacked) + 1); 3015 } 3016 3017 sndcnt = max(sndcnt, (fast_rexmit ? 1 : 0)); 3018 tp->snd_cwnd = tcp_packets_in_flight(tp) + sndcnt; 3019 } 3020 3021 /* Process an event, which can update packets-in-flight not trivially. 3022 * Main goal of this function is to calculate new estimate for left_out, 3023 * taking into account both packets sitting in receiver's buffer and 3024 * packets lost by network. 3025 * 3026 * Besides that it does CWND reduction, when packet loss is detected 3027 * and changes state of machine. 3028 * 3029 * It does _not_ decide what to send, it is made in function 3030 * tcp_xmit_retransmit_queue(). 3031 */ 3032 static void tcp_fastretrans_alert(struct sock *sk, int pkts_acked, 3033 int newly_acked_sacked, bool is_dupack, 3034 int flag) 3035 { 3036 struct inet_connection_sock *icsk = inet_csk(sk); 3037 struct tcp_sock *tp = tcp_sk(sk); 3038 int do_lost = is_dupack || ((flag & FLAG_DATA_SACKED) && 3039 (tcp_fackets_out(tp) > tp->reordering)); 3040 int fast_rexmit = 0, mib_idx; 3041 3042 if (WARN_ON(!tp->packets_out && tp->sacked_out)) 3043 tp->sacked_out = 0; 3044 if (WARN_ON(!tp->sacked_out && tp->fackets_out)) 3045 tp->fackets_out = 0; 3046 3047 /* Now state machine starts. 3048 * A. ECE, hence prohibit cwnd undoing, the reduction is required. */ 3049 if (flag & FLAG_ECE) 3050 tp->prior_ssthresh = 0; 3051 3052 /* B. In all the states check for reneging SACKs. */ 3053 if (tcp_check_sack_reneging(sk, flag)) 3054 return; 3055 3056 /* C. Check consistency of the current state. */ 3057 tcp_verify_left_out(tp); 3058 3059 /* D. Check state exit conditions. State can be terminated 3060 * when high_seq is ACKed. */ 3061 if (icsk->icsk_ca_state == TCP_CA_Open) { 3062 WARN_ON(tp->retrans_out != 0); 3063 tp->retrans_stamp = 0; 3064 } else if (!before(tp->snd_una, tp->high_seq)) { 3065 switch (icsk->icsk_ca_state) { 3066 case TCP_CA_Loss: 3067 icsk->icsk_retransmits = 0; 3068 if (tcp_try_undo_recovery(sk)) 3069 return; 3070 break; 3071 3072 case TCP_CA_CWR: 3073 /* CWR is to be held something *above* high_seq 3074 * is ACKed for CWR bit to reach receiver. */ 3075 if (tp->snd_una != tp->high_seq) { 3076 tcp_complete_cwr(sk); 3077 tcp_set_ca_state(sk, TCP_CA_Open); 3078 } 3079 break; 3080 3081 case TCP_CA_Recovery: 3082 if (tcp_is_reno(tp)) 3083 tcp_reset_reno_sack(tp); 3084 if (tcp_try_undo_recovery(sk)) 3085 return; 3086 tcp_complete_cwr(sk); 3087 break; 3088 } 3089 } 3090 3091 /* E. Process state. */ 3092 switch (icsk->icsk_ca_state) { 3093 case TCP_CA_Recovery: 3094 if (!(flag & FLAG_SND_UNA_ADVANCED)) { 3095 if (tcp_is_reno(tp) && is_dupack) 3096 tcp_add_reno_sack(sk); 3097 } else 3098 do_lost = tcp_try_undo_partial(sk, pkts_acked); 3099 break; 3100 case TCP_CA_Loss: 3101 if (flag & FLAG_DATA_ACKED) 3102 icsk->icsk_retransmits = 0; 3103 if (tcp_is_reno(tp) && flag & FLAG_SND_UNA_ADVANCED) 3104 tcp_reset_reno_sack(tp); 3105 if (!tcp_try_undo_loss(sk)) { 3106 tcp_moderate_cwnd(tp); 3107 tcp_xmit_retransmit_queue(sk); 3108 return; 3109 } 3110 if (icsk->icsk_ca_state != TCP_CA_Open) 3111 return; 3112 /* Loss is undone; fall through to processing in Open state. */ 3113 default: 3114 if (tcp_is_reno(tp)) { 3115 if (flag & FLAG_SND_UNA_ADVANCED) 3116 tcp_reset_reno_sack(tp); 3117 if (is_dupack) 3118 tcp_add_reno_sack(sk); 3119 } 3120 3121 if (icsk->icsk_ca_state <= TCP_CA_Disorder) 3122 tcp_try_undo_dsack(sk); 3123 3124 if (!tcp_time_to_recover(sk)) { 3125 tcp_try_to_open(sk, flag); 3126 return; 3127 } 3128 3129 /* MTU probe failure: don't reduce cwnd */ 3130 if (icsk->icsk_ca_state < TCP_CA_CWR && 3131 icsk->icsk_mtup.probe_size && 3132 tp->snd_una == tp->mtu_probe.probe_seq_start) { 3133 tcp_mtup_probe_failed(sk); 3134 /* Restores the reduction we did in tcp_mtup_probe() */ 3135 tp->snd_cwnd++; 3136 tcp_simple_retransmit(sk); 3137 return; 3138 } 3139 3140 /* Otherwise enter Recovery state */ 3141 3142 if (tcp_is_reno(tp)) 3143 mib_idx = LINUX_MIB_TCPRENORECOVERY; 3144 else 3145 mib_idx = LINUX_MIB_TCPSACKRECOVERY; 3146 3147 NET_INC_STATS_BH(sock_net(sk), mib_idx); 3148 3149 tp->high_seq = tp->snd_nxt; 3150 tp->prior_ssthresh = 0; 3151 tp->undo_marker = tp->snd_una; 3152 tp->undo_retrans = tp->retrans_out; 3153 3154 if (icsk->icsk_ca_state < TCP_CA_CWR) { 3155 if (!(flag & FLAG_ECE)) 3156 tp->prior_ssthresh = tcp_current_ssthresh(sk); 3157 tp->snd_ssthresh = icsk->icsk_ca_ops->ssthresh(sk); 3158 TCP_ECN_queue_cwr(tp); 3159 } 3160 3161 tp->bytes_acked = 0; 3162 tp->snd_cwnd_cnt = 0; 3163 tp->prior_cwnd = tp->snd_cwnd; 3164 tp->prr_delivered = 0; 3165 tp->prr_out = 0; 3166 tcp_set_ca_state(sk, TCP_CA_Recovery); 3167 fast_rexmit = 1; 3168 } 3169 3170 if (do_lost || (tcp_is_fack(tp) && tcp_head_timedout(sk))) 3171 tcp_update_scoreboard(sk, fast_rexmit); 3172 tp->prr_delivered += newly_acked_sacked; 3173 tcp_update_cwnd_in_recovery(sk, newly_acked_sacked, fast_rexmit, flag); 3174 tcp_xmit_retransmit_queue(sk); 3175 } 3176 3177 void tcp_valid_rtt_meas(struct sock *sk, u32 seq_rtt) 3178 { 3179 tcp_rtt_estimator(sk, seq_rtt); 3180 tcp_set_rto(sk); 3181 inet_csk(sk)->icsk_backoff = 0; 3182 } 3183 EXPORT_SYMBOL(tcp_valid_rtt_meas); 3184 3185 /* Read draft-ietf-tcplw-high-performance before mucking 3186 * with this code. (Supersedes RFC1323) 3187 */ 3188 static void tcp_ack_saw_tstamp(struct sock *sk, int flag) 3189 { 3190 /* RTTM Rule: A TSecr value received in a segment is used to 3191 * update the averaged RTT measurement only if the segment 3192 * acknowledges some new data, i.e., only if it advances the 3193 * left edge of the send window. 3194 * 3195 * See draft-ietf-tcplw-high-performance-00, section 3.3. 3196 * 1998/04/10 Andrey V. Savochkin <saw@msu.ru> 3197 * 3198 * Changed: reset backoff as soon as we see the first valid sample. 3199 * If we do not, we get strongly overestimated rto. With timestamps 3200 * samples are accepted even from very old segments: f.e., when rtt=1 3201 * increases to 8, we retransmit 5 times and after 8 seconds delayed 3202 * answer arrives rto becomes 120 seconds! If at least one of segments 3203 * in window is lost... Voila. --ANK (010210) 3204 */ 3205 struct tcp_sock *tp = tcp_sk(sk); 3206 3207 tcp_valid_rtt_meas(sk, tcp_time_stamp - tp->rx_opt.rcv_tsecr); 3208 } 3209 3210 static void tcp_ack_no_tstamp(struct sock *sk, u32 seq_rtt, int flag) 3211 { 3212 /* We don't have a timestamp. Can only use 3213 * packets that are not retransmitted to determine 3214 * rtt estimates. Also, we must not reset the 3215 * backoff for rto until we get a non-retransmitted 3216 * packet. This allows us to deal with a situation 3217 * where the network delay has increased suddenly. 3218 * I.e. Karn's algorithm. (SIGCOMM '87, p5.) 3219 */ 3220 3221 if (flag & FLAG_RETRANS_DATA_ACKED) 3222 return; 3223 3224 tcp_valid_rtt_meas(sk, seq_rtt); 3225 } 3226 3227 static inline void tcp_ack_update_rtt(struct sock *sk, const int flag, 3228 const s32 seq_rtt) 3229 { 3230 const struct tcp_sock *tp = tcp_sk(sk); 3231 /* Note that peer MAY send zero echo. In this case it is ignored. (rfc1323) */ 3232 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr) 3233 tcp_ack_saw_tstamp(sk, flag); 3234 else if (seq_rtt >= 0) 3235 tcp_ack_no_tstamp(sk, seq_rtt, flag); 3236 } 3237 3238 static void tcp_cong_avoid(struct sock *sk, u32 ack, u32 in_flight) 3239 { 3240 const struct inet_connection_sock *icsk = inet_csk(sk); 3241 icsk->icsk_ca_ops->cong_avoid(sk, ack, in_flight); 3242 tcp_sk(sk)->snd_cwnd_stamp = tcp_time_stamp; 3243 } 3244 3245 /* Restart timer after forward progress on connection. 3246 * RFC2988 recommends to restart timer to now+rto. 3247 */ 3248 static void tcp_rearm_rto(struct sock *sk) 3249 { 3250 const struct tcp_sock *tp = tcp_sk(sk); 3251 3252 if (!tp->packets_out) { 3253 inet_csk_clear_xmit_timer(sk, ICSK_TIME_RETRANS); 3254 } else { 3255 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 3256 inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 3257 } 3258 } 3259 3260 /* If we get here, the whole TSO packet has not been acked. */ 3261 static u32 tcp_tso_acked(struct sock *sk, struct sk_buff *skb) 3262 { 3263 struct tcp_sock *tp = tcp_sk(sk); 3264 u32 packets_acked; 3265 3266 BUG_ON(!after(TCP_SKB_CB(skb)->end_seq, tp->snd_una)); 3267 3268 packets_acked = tcp_skb_pcount(skb); 3269 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) 3270 return 0; 3271 packets_acked -= tcp_skb_pcount(skb); 3272 3273 if (packets_acked) { 3274 BUG_ON(tcp_skb_pcount(skb) == 0); 3275 BUG_ON(!before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)); 3276 } 3277 3278 return packets_acked; 3279 } 3280 3281 /* Remove acknowledged frames from the retransmission queue. If our packet 3282 * is before the ack sequence we can discard it as it's confirmed to have 3283 * arrived at the other end. 3284 */ 3285 static int tcp_clean_rtx_queue(struct sock *sk, int prior_fackets, 3286 u32 prior_snd_una) 3287 { 3288 struct tcp_sock *tp = tcp_sk(sk); 3289 const struct inet_connection_sock *icsk = inet_csk(sk); 3290 struct sk_buff *skb; 3291 u32 now = tcp_time_stamp; 3292 int fully_acked = 1; 3293 int flag = 0; 3294 u32 pkts_acked = 0; 3295 u32 reord = tp->packets_out; 3296 u32 prior_sacked = tp->sacked_out; 3297 s32 seq_rtt = -1; 3298 s32 ca_seq_rtt = -1; 3299 ktime_t last_ackt = net_invalid_timestamp(); 3300 3301 while ((skb = tcp_write_queue_head(sk)) && skb != tcp_send_head(sk)) { 3302 struct tcp_skb_cb *scb = TCP_SKB_CB(skb); 3303 u32 acked_pcount; 3304 u8 sacked = scb->sacked; 3305 3306 /* Determine how many packets and what bytes were acked, tso and else */ 3307 if (after(scb->end_seq, tp->snd_una)) { 3308 if (tcp_skb_pcount(skb) == 1 || 3309 !after(tp->snd_una, scb->seq)) 3310 break; 3311 3312 acked_pcount = tcp_tso_acked(sk, skb); 3313 if (!acked_pcount) 3314 break; 3315 3316 fully_acked = 0; 3317 } else { 3318 acked_pcount = tcp_skb_pcount(skb); 3319 } 3320 3321 if (sacked & TCPCB_RETRANS) { 3322 if (sacked & TCPCB_SACKED_RETRANS) 3323 tp->retrans_out -= acked_pcount; 3324 flag |= FLAG_RETRANS_DATA_ACKED; 3325 ca_seq_rtt = -1; 3326 seq_rtt = -1; 3327 if ((flag & FLAG_DATA_ACKED) || (acked_pcount > 1)) 3328 flag |= FLAG_NONHEAD_RETRANS_ACKED; 3329 } else { 3330 ca_seq_rtt = now - scb->when; 3331 last_ackt = skb->tstamp; 3332 if (seq_rtt < 0) { 3333 seq_rtt = ca_seq_rtt; 3334 } 3335 if (!(sacked & TCPCB_SACKED_ACKED)) 3336 reord = min(pkts_acked, reord); 3337 } 3338 3339 if (sacked & TCPCB_SACKED_ACKED) 3340 tp->sacked_out -= acked_pcount; 3341 if (sacked & TCPCB_LOST) 3342 tp->lost_out -= acked_pcount; 3343 3344 tp->packets_out -= acked_pcount; 3345 pkts_acked += acked_pcount; 3346 3347 /* Initial outgoing SYN's get put onto the write_queue 3348 * just like anything else we transmit. It is not 3349 * true data, and if we misinform our callers that 3350 * this ACK acks real data, we will erroneously exit 3351 * connection startup slow start one packet too 3352 * quickly. This is severely frowned upon behavior. 3353 */ 3354 if (!(scb->tcp_flags & TCPHDR_SYN)) { 3355 flag |= FLAG_DATA_ACKED; 3356 } else { 3357 flag |= FLAG_SYN_ACKED; 3358 tp->retrans_stamp = 0; 3359 } 3360 3361 if (!fully_acked) 3362 break; 3363 3364 tcp_unlink_write_queue(skb, sk); 3365 sk_wmem_free_skb(sk, skb); 3366 tp->scoreboard_skb_hint = NULL; 3367 if (skb == tp->retransmit_skb_hint) 3368 tp->retransmit_skb_hint = NULL; 3369 if (skb == tp->lost_skb_hint) 3370 tp->lost_skb_hint = NULL; 3371 } 3372 3373 if (likely(between(tp->snd_up, prior_snd_una, tp->snd_una))) 3374 tp->snd_up = tp->snd_una; 3375 3376 if (skb && (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 3377 flag |= FLAG_SACK_RENEGING; 3378 3379 if (flag & FLAG_ACKED) { 3380 const struct tcp_congestion_ops *ca_ops 3381 = inet_csk(sk)->icsk_ca_ops; 3382 3383 if (unlikely(icsk->icsk_mtup.probe_size && 3384 !after(tp->mtu_probe.probe_seq_end, tp->snd_una))) { 3385 tcp_mtup_probe_success(sk); 3386 } 3387 3388 tcp_ack_update_rtt(sk, flag, seq_rtt); 3389 tcp_rearm_rto(sk); 3390 3391 if (tcp_is_reno(tp)) { 3392 tcp_remove_reno_sacks(sk, pkts_acked); 3393 } else { 3394 int delta; 3395 3396 /* Non-retransmitted hole got filled? That's reordering */ 3397 if (reord < prior_fackets) 3398 tcp_update_reordering(sk, tp->fackets_out - reord, 0); 3399 3400 delta = tcp_is_fack(tp) ? pkts_acked : 3401 prior_sacked - tp->sacked_out; 3402 tp->lost_cnt_hint -= min(tp->lost_cnt_hint, delta); 3403 } 3404 3405 tp->fackets_out -= min(pkts_acked, tp->fackets_out); 3406 3407 if (ca_ops->pkts_acked) { 3408 s32 rtt_us = -1; 3409 3410 /* Is the ACK triggering packet unambiguous? */ 3411 if (!(flag & FLAG_RETRANS_DATA_ACKED)) { 3412 /* High resolution needed and available? */ 3413 if (ca_ops->flags & TCP_CONG_RTT_STAMP && 3414 !ktime_equal(last_ackt, 3415 net_invalid_timestamp())) 3416 rtt_us = ktime_us_delta(ktime_get_real(), 3417 last_ackt); 3418 else if (ca_seq_rtt >= 0) 3419 rtt_us = jiffies_to_usecs(ca_seq_rtt); 3420 } 3421 3422 ca_ops->pkts_acked(sk, pkts_acked, rtt_us); 3423 } 3424 } 3425 3426 #if FASTRETRANS_DEBUG > 0 3427 WARN_ON((int)tp->sacked_out < 0); 3428 WARN_ON((int)tp->lost_out < 0); 3429 WARN_ON((int)tp->retrans_out < 0); 3430 if (!tp->packets_out && tcp_is_sack(tp)) { 3431 icsk = inet_csk(sk); 3432 if (tp->lost_out) { 3433 printk(KERN_DEBUG "Leak l=%u %d\n", 3434 tp->lost_out, icsk->icsk_ca_state); 3435 tp->lost_out = 0; 3436 } 3437 if (tp->sacked_out) { 3438 printk(KERN_DEBUG "Leak s=%u %d\n", 3439 tp->sacked_out, icsk->icsk_ca_state); 3440 tp->sacked_out = 0; 3441 } 3442 if (tp->retrans_out) { 3443 printk(KERN_DEBUG "Leak r=%u %d\n", 3444 tp->retrans_out, icsk->icsk_ca_state); 3445 tp->retrans_out = 0; 3446 } 3447 } 3448 #endif 3449 return flag; 3450 } 3451 3452 static void tcp_ack_probe(struct sock *sk) 3453 { 3454 const struct tcp_sock *tp = tcp_sk(sk); 3455 struct inet_connection_sock *icsk = inet_csk(sk); 3456 3457 /* Was it a usable window open? */ 3458 3459 if (!after(TCP_SKB_CB(tcp_send_head(sk))->end_seq, tcp_wnd_end(tp))) { 3460 icsk->icsk_backoff = 0; 3461 inet_csk_clear_xmit_timer(sk, ICSK_TIME_PROBE0); 3462 /* Socket must be waked up by subsequent tcp_data_snd_check(). 3463 * This function is not for random using! 3464 */ 3465 } else { 3466 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 3467 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), 3468 TCP_RTO_MAX); 3469 } 3470 } 3471 3472 static inline int tcp_ack_is_dubious(const struct sock *sk, const int flag) 3473 { 3474 return !(flag & FLAG_NOT_DUP) || (flag & FLAG_CA_ALERT) || 3475 inet_csk(sk)->icsk_ca_state != TCP_CA_Open; 3476 } 3477 3478 static inline int tcp_may_raise_cwnd(const struct sock *sk, const int flag) 3479 { 3480 const struct tcp_sock *tp = tcp_sk(sk); 3481 return (!(flag & FLAG_ECE) || tp->snd_cwnd < tp->snd_ssthresh) && 3482 !((1 << inet_csk(sk)->icsk_ca_state) & (TCPF_CA_Recovery | TCPF_CA_CWR)); 3483 } 3484 3485 /* Check that window update is acceptable. 3486 * The function assumes that snd_una<=ack<=snd_next. 3487 */ 3488 static inline int tcp_may_update_window(const struct tcp_sock *tp, 3489 const u32 ack, const u32 ack_seq, 3490 const u32 nwin) 3491 { 3492 return after(ack, tp->snd_una) || 3493 after(ack_seq, tp->snd_wl1) || 3494 (ack_seq == tp->snd_wl1 && nwin > tp->snd_wnd); 3495 } 3496 3497 /* Update our send window. 3498 * 3499 * Window update algorithm, described in RFC793/RFC1122 (used in linux-2.2 3500 * and in FreeBSD. NetBSD's one is even worse.) is wrong. 3501 */ 3502 static int tcp_ack_update_window(struct sock *sk, const struct sk_buff *skb, u32 ack, 3503 u32 ack_seq) 3504 { 3505 struct tcp_sock *tp = tcp_sk(sk); 3506 int flag = 0; 3507 u32 nwin = ntohs(tcp_hdr(skb)->window); 3508 3509 if (likely(!tcp_hdr(skb)->syn)) 3510 nwin <<= tp->rx_opt.snd_wscale; 3511 3512 if (tcp_may_update_window(tp, ack, ack_seq, nwin)) { 3513 flag |= FLAG_WIN_UPDATE; 3514 tcp_update_wl(tp, ack_seq); 3515 3516 if (tp->snd_wnd != nwin) { 3517 tp->snd_wnd = nwin; 3518 3519 /* Note, it is the only place, where 3520 * fast path is recovered for sending TCP. 3521 */ 3522 tp->pred_flags = 0; 3523 tcp_fast_path_check(sk); 3524 3525 if (nwin > tp->max_window) { 3526 tp->max_window = nwin; 3527 tcp_sync_mss(sk, inet_csk(sk)->icsk_pmtu_cookie); 3528 } 3529 } 3530 } 3531 3532 tp->snd_una = ack; 3533 3534 return flag; 3535 } 3536 3537 /* A very conservative spurious RTO response algorithm: reduce cwnd and 3538 * continue in congestion avoidance. 3539 */ 3540 static void tcp_conservative_spur_to_response(struct tcp_sock *tp) 3541 { 3542 tp->snd_cwnd = min(tp->snd_cwnd, tp->snd_ssthresh); 3543 tp->snd_cwnd_cnt = 0; 3544 tp->bytes_acked = 0; 3545 TCP_ECN_queue_cwr(tp); 3546 tcp_moderate_cwnd(tp); 3547 } 3548 3549 /* A conservative spurious RTO response algorithm: reduce cwnd using 3550 * rate halving and continue in congestion avoidance. 3551 */ 3552 static void tcp_ratehalving_spur_to_response(struct sock *sk) 3553 { 3554 tcp_enter_cwr(sk, 0); 3555 } 3556 3557 static void tcp_undo_spur_to_response(struct sock *sk, int flag) 3558 { 3559 if (flag & FLAG_ECE) 3560 tcp_ratehalving_spur_to_response(sk); 3561 else 3562 tcp_undo_cwr(sk, true); 3563 } 3564 3565 /* F-RTO spurious RTO detection algorithm (RFC4138) 3566 * 3567 * F-RTO affects during two new ACKs following RTO (well, almost, see inline 3568 * comments). State (ACK number) is kept in frto_counter. When ACK advances 3569 * window (but not to or beyond highest sequence sent before RTO): 3570 * On First ACK, send two new segments out. 3571 * On Second ACK, RTO was likely spurious. Do spurious response (response 3572 * algorithm is not part of the F-RTO detection algorithm 3573 * given in RFC4138 but can be selected separately). 3574 * Otherwise (basically on duplicate ACK), RTO was (likely) caused by a loss 3575 * and TCP falls back to conventional RTO recovery. F-RTO allows overriding 3576 * of Nagle, this is done using frto_counter states 2 and 3, when a new data 3577 * segment of any size sent during F-RTO, state 2 is upgraded to 3. 3578 * 3579 * Rationale: if the RTO was spurious, new ACKs should arrive from the 3580 * original window even after we transmit two new data segments. 3581 * 3582 * SACK version: 3583 * on first step, wait until first cumulative ACK arrives, then move to 3584 * the second step. In second step, the next ACK decides. 3585 * 3586 * F-RTO is implemented (mainly) in four functions: 3587 * - tcp_use_frto() is used to determine if TCP is can use F-RTO 3588 * - tcp_enter_frto() prepares TCP state on RTO if F-RTO is used, it is 3589 * called when tcp_use_frto() showed green light 3590 * - tcp_process_frto() handles incoming ACKs during F-RTO algorithm 3591 * - tcp_enter_frto_loss() is called if there is not enough evidence 3592 * to prove that the RTO is indeed spurious. It transfers the control 3593 * from F-RTO to the conventional RTO recovery 3594 */ 3595 static int tcp_process_frto(struct sock *sk, int flag) 3596 { 3597 struct tcp_sock *tp = tcp_sk(sk); 3598 3599 tcp_verify_left_out(tp); 3600 3601 /* Duplicate the behavior from Loss state (fastretrans_alert) */ 3602 if (flag & FLAG_DATA_ACKED) 3603 inet_csk(sk)->icsk_retransmits = 0; 3604 3605 if ((flag & FLAG_NONHEAD_RETRANS_ACKED) || 3606 ((tp->frto_counter >= 2) && (flag & FLAG_RETRANS_DATA_ACKED))) 3607 tp->undo_marker = 0; 3608 3609 if (!before(tp->snd_una, tp->frto_highmark)) { 3610 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 2 : 3), flag); 3611 return 1; 3612 } 3613 3614 if (!tcp_is_sackfrto(tp)) { 3615 /* RFC4138 shortcoming in step 2; should also have case c): 3616 * ACK isn't duplicate nor advances window, e.g., opposite dir 3617 * data, winupdate 3618 */ 3619 if (!(flag & FLAG_ANY_PROGRESS) && (flag & FLAG_NOT_DUP)) 3620 return 1; 3621 3622 if (!(flag & FLAG_DATA_ACKED)) { 3623 tcp_enter_frto_loss(sk, (tp->frto_counter == 1 ? 0 : 3), 3624 flag); 3625 return 1; 3626 } 3627 } else { 3628 if (!(flag & FLAG_DATA_ACKED) && (tp->frto_counter == 1)) { 3629 /* Prevent sending of new data. */ 3630 tp->snd_cwnd = min(tp->snd_cwnd, 3631 tcp_packets_in_flight(tp)); 3632 return 1; 3633 } 3634 3635 if ((tp->frto_counter >= 2) && 3636 (!(flag & FLAG_FORWARD_PROGRESS) || 3637 ((flag & FLAG_DATA_SACKED) && 3638 !(flag & FLAG_ONLY_ORIG_SACKED)))) { 3639 /* RFC4138 shortcoming (see comment above) */ 3640 if (!(flag & FLAG_FORWARD_PROGRESS) && 3641 (flag & FLAG_NOT_DUP)) 3642 return 1; 3643 3644 tcp_enter_frto_loss(sk, 3, flag); 3645 return 1; 3646 } 3647 } 3648 3649 if (tp->frto_counter == 1) { 3650 /* tcp_may_send_now needs to see updated state */ 3651 tp->snd_cwnd = tcp_packets_in_flight(tp) + 2; 3652 tp->frto_counter = 2; 3653 3654 if (!tcp_may_send_now(sk)) 3655 tcp_enter_frto_loss(sk, 2, flag); 3656 3657 return 1; 3658 } else { 3659 switch (sysctl_tcp_frto_response) { 3660 case 2: 3661 tcp_undo_spur_to_response(sk, flag); 3662 break; 3663 case 1: 3664 tcp_conservative_spur_to_response(tp); 3665 break; 3666 default: 3667 tcp_ratehalving_spur_to_response(sk); 3668 break; 3669 } 3670 tp->frto_counter = 0; 3671 tp->undo_marker = 0; 3672 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSPURIOUSRTOS); 3673 } 3674 return 0; 3675 } 3676 3677 /* This routine deals with incoming acks, but not outgoing ones. */ 3678 static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) 3679 { 3680 struct inet_connection_sock *icsk = inet_csk(sk); 3681 struct tcp_sock *tp = tcp_sk(sk); 3682 u32 prior_snd_una = tp->snd_una; 3683 u32 ack_seq = TCP_SKB_CB(skb)->seq; 3684 u32 ack = TCP_SKB_CB(skb)->ack_seq; 3685 bool is_dupack = false; 3686 u32 prior_in_flight; 3687 u32 prior_fackets; 3688 int prior_packets; 3689 int prior_sacked = tp->sacked_out; 3690 int pkts_acked = 0; 3691 int newly_acked_sacked = 0; 3692 int frto_cwnd = 0; 3693 3694 /* If the ack is older than previous acks 3695 * then we can probably ignore it. 3696 */ 3697 if (before(ack, prior_snd_una)) 3698 goto old_ack; 3699 3700 /* If the ack includes data we haven't sent yet, discard 3701 * this segment (RFC793 Section 3.9). 3702 */ 3703 if (after(ack, tp->snd_nxt)) 3704 goto invalid_ack; 3705 3706 if (after(ack, prior_snd_una)) 3707 flag |= FLAG_SND_UNA_ADVANCED; 3708 3709 if (sysctl_tcp_abc) { 3710 if (icsk->icsk_ca_state < TCP_CA_CWR) 3711 tp->bytes_acked += ack - prior_snd_una; 3712 else if (icsk->icsk_ca_state == TCP_CA_Loss) 3713 /* we assume just one segment left network */ 3714 tp->bytes_acked += min(ack - prior_snd_una, 3715 tp->mss_cache); 3716 } 3717 3718 prior_fackets = tp->fackets_out; 3719 prior_in_flight = tcp_packets_in_flight(tp); 3720 3721 if (!(flag & FLAG_SLOWPATH) && after(ack, prior_snd_una)) { 3722 /* Window is constant, pure forward advance. 3723 * No more checks are required. 3724 * Note, we use the fact that SND.UNA>=SND.WL2. 3725 */ 3726 tcp_update_wl(tp, ack_seq); 3727 tp->snd_una = ack; 3728 flag |= FLAG_WIN_UPDATE; 3729 3730 tcp_ca_event(sk, CA_EVENT_FAST_ACK); 3731 3732 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS); 3733 } else { 3734 if (ack_seq != TCP_SKB_CB(skb)->end_seq) 3735 flag |= FLAG_DATA; 3736 else 3737 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPPUREACKS); 3738 3739 flag |= tcp_ack_update_window(sk, skb, ack, ack_seq); 3740 3741 if (TCP_SKB_CB(skb)->sacked) 3742 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); 3743 3744 if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) 3745 flag |= FLAG_ECE; 3746 3747 tcp_ca_event(sk, CA_EVENT_SLOW_ACK); 3748 } 3749 3750 /* We passed data and got it acked, remove any soft error 3751 * log. Something worked... 3752 */ 3753 sk->sk_err_soft = 0; 3754 icsk->icsk_probes_out = 0; 3755 tp->rcv_tstamp = tcp_time_stamp; 3756 prior_packets = tp->packets_out; 3757 if (!prior_packets) 3758 goto no_queue; 3759 3760 /* See if we can take anything off of the retransmit queue. */ 3761 flag |= tcp_clean_rtx_queue(sk, prior_fackets, prior_snd_una); 3762 3763 pkts_acked = prior_packets - tp->packets_out; 3764 newly_acked_sacked = (prior_packets - prior_sacked) - 3765 (tp->packets_out - tp->sacked_out); 3766 3767 if (tp->frto_counter) 3768 frto_cwnd = tcp_process_frto(sk, flag); 3769 /* Guarantee sacktag reordering detection against wrap-arounds */ 3770 if (before(tp->frto_highmark, tp->snd_una)) 3771 tp->frto_highmark = 0; 3772 3773 if (tcp_ack_is_dubious(sk, flag)) { 3774 /* Advance CWND, if state allows this. */ 3775 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd && 3776 tcp_may_raise_cwnd(sk, flag)) 3777 tcp_cong_avoid(sk, ack, prior_in_flight); 3778 is_dupack = !(flag & (FLAG_SND_UNA_ADVANCED | FLAG_NOT_DUP)); 3779 tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked, 3780 is_dupack, flag); 3781 } else { 3782 if ((flag & FLAG_DATA_ACKED) && !frto_cwnd) 3783 tcp_cong_avoid(sk, ack, prior_in_flight); 3784 } 3785 3786 if ((flag & FLAG_FORWARD_PROGRESS) || !(flag & FLAG_NOT_DUP)) 3787 dst_confirm(__sk_dst_get(sk)); 3788 3789 return 1; 3790 3791 no_queue: 3792 /* If data was DSACKed, see if we can undo a cwnd reduction. */ 3793 if (flag & FLAG_DSACKING_ACK) 3794 tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked, 3795 is_dupack, flag); 3796 /* If this ack opens up a zero window, clear backoff. It was 3797 * being used to time the probes, and is probably far higher than 3798 * it needs to be for normal retransmission. 3799 */ 3800 if (tcp_send_head(sk)) 3801 tcp_ack_probe(sk); 3802 return 1; 3803 3804 invalid_ack: 3805 SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt); 3806 return -1; 3807 3808 old_ack: 3809 /* If data was SACKed, tag it and see if we should send more data. 3810 * If data was DSACKed, see if we can undo a cwnd reduction. 3811 */ 3812 if (TCP_SKB_CB(skb)->sacked) { 3813 flag |= tcp_sacktag_write_queue(sk, skb, prior_snd_una); 3814 newly_acked_sacked = tp->sacked_out - prior_sacked; 3815 tcp_fastretrans_alert(sk, pkts_acked, newly_acked_sacked, 3816 is_dupack, flag); 3817 } 3818 3819 SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt); 3820 return 0; 3821 } 3822 3823 /* Look for tcp options. Normally only called on SYN and SYNACK packets. 3824 * But, this can also be called on packets in the established flow when 3825 * the fast version below fails. 3826 */ 3827 void tcp_parse_options(const struct sk_buff *skb, struct tcp_options_received *opt_rx, 3828 const u8 **hvpp, int estab) 3829 { 3830 const unsigned char *ptr; 3831 const struct tcphdr *th = tcp_hdr(skb); 3832 int length = (th->doff * 4) - sizeof(struct tcphdr); 3833 3834 ptr = (const unsigned char *)(th + 1); 3835 opt_rx->saw_tstamp = 0; 3836 3837 while (length > 0) { 3838 int opcode = *ptr++; 3839 int opsize; 3840 3841 switch (opcode) { 3842 case TCPOPT_EOL: 3843 return; 3844 case TCPOPT_NOP: /* Ref: RFC 793 section 3.1 */ 3845 length--; 3846 continue; 3847 default: 3848 opsize = *ptr++; 3849 if (opsize < 2) /* "silly options" */ 3850 return; 3851 if (opsize > length) 3852 return; /* don't parse partial options */ 3853 switch (opcode) { 3854 case TCPOPT_MSS: 3855 if (opsize == TCPOLEN_MSS && th->syn && !estab) { 3856 u16 in_mss = get_unaligned_be16(ptr); 3857 if (in_mss) { 3858 if (opt_rx->user_mss && 3859 opt_rx->user_mss < in_mss) 3860 in_mss = opt_rx->user_mss; 3861 opt_rx->mss_clamp = in_mss; 3862 } 3863 } 3864 break; 3865 case TCPOPT_WINDOW: 3866 if (opsize == TCPOLEN_WINDOW && th->syn && 3867 !estab && sysctl_tcp_window_scaling) { 3868 __u8 snd_wscale = *(__u8 *)ptr; 3869 opt_rx->wscale_ok = 1; 3870 if (snd_wscale > 14) { 3871 if (net_ratelimit()) 3872 pr_info("%s: Illegal window scaling value %d >14 received\n", 3873 __func__, 3874 snd_wscale); 3875 snd_wscale = 14; 3876 } 3877 opt_rx->snd_wscale = snd_wscale; 3878 } 3879 break; 3880 case TCPOPT_TIMESTAMP: 3881 if ((opsize == TCPOLEN_TIMESTAMP) && 3882 ((estab && opt_rx->tstamp_ok) || 3883 (!estab && sysctl_tcp_timestamps))) { 3884 opt_rx->saw_tstamp = 1; 3885 opt_rx->rcv_tsval = get_unaligned_be32(ptr); 3886 opt_rx->rcv_tsecr = get_unaligned_be32(ptr + 4); 3887 } 3888 break; 3889 case TCPOPT_SACK_PERM: 3890 if (opsize == TCPOLEN_SACK_PERM && th->syn && 3891 !estab && sysctl_tcp_sack) { 3892 opt_rx->sack_ok = TCP_SACK_SEEN; 3893 tcp_sack_reset(opt_rx); 3894 } 3895 break; 3896 3897 case TCPOPT_SACK: 3898 if ((opsize >= (TCPOLEN_SACK_BASE + TCPOLEN_SACK_PERBLOCK)) && 3899 !((opsize - TCPOLEN_SACK_BASE) % TCPOLEN_SACK_PERBLOCK) && 3900 opt_rx->sack_ok) { 3901 TCP_SKB_CB(skb)->sacked = (ptr - 2) - (unsigned char *)th; 3902 } 3903 break; 3904 #ifdef CONFIG_TCP_MD5SIG 3905 case TCPOPT_MD5SIG: 3906 /* 3907 * The MD5 Hash has already been 3908 * checked (see tcp_v{4,6}_do_rcv()). 3909 */ 3910 break; 3911 #endif 3912 case TCPOPT_COOKIE: 3913 /* This option is variable length. 3914 */ 3915 switch (opsize) { 3916 case TCPOLEN_COOKIE_BASE: 3917 /* not yet implemented */ 3918 break; 3919 case TCPOLEN_COOKIE_PAIR: 3920 /* not yet implemented */ 3921 break; 3922 case TCPOLEN_COOKIE_MIN+0: 3923 case TCPOLEN_COOKIE_MIN+2: 3924 case TCPOLEN_COOKIE_MIN+4: 3925 case TCPOLEN_COOKIE_MIN+6: 3926 case TCPOLEN_COOKIE_MAX: 3927 /* 16-bit multiple */ 3928 opt_rx->cookie_plus = opsize; 3929 *hvpp = ptr; 3930 break; 3931 default: 3932 /* ignore option */ 3933 break; 3934 } 3935 break; 3936 } 3937 3938 ptr += opsize-2; 3939 length -= opsize; 3940 } 3941 } 3942 } 3943 EXPORT_SYMBOL(tcp_parse_options); 3944 3945 static int tcp_parse_aligned_timestamp(struct tcp_sock *tp, const struct tcphdr *th) 3946 { 3947 const __be32 *ptr = (const __be32 *)(th + 1); 3948 3949 if (*ptr == htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) 3950 | (TCPOPT_TIMESTAMP << 8) | TCPOLEN_TIMESTAMP)) { 3951 tp->rx_opt.saw_tstamp = 1; 3952 ++ptr; 3953 tp->rx_opt.rcv_tsval = ntohl(*ptr); 3954 ++ptr; 3955 tp->rx_opt.rcv_tsecr = ntohl(*ptr); 3956 return 1; 3957 } 3958 return 0; 3959 } 3960 3961 /* Fast parse options. This hopes to only see timestamps. 3962 * If it is wrong it falls back on tcp_parse_options(). 3963 */ 3964 static int tcp_fast_parse_options(const struct sk_buff *skb, 3965 const struct tcphdr *th, 3966 struct tcp_sock *tp, const u8 **hvpp) 3967 { 3968 /* In the spirit of fast parsing, compare doff directly to constant 3969 * values. Because equality is used, short doff can be ignored here. 3970 */ 3971 if (th->doff == (sizeof(*th) / 4)) { 3972 tp->rx_opt.saw_tstamp = 0; 3973 return 0; 3974 } else if (tp->rx_opt.tstamp_ok && 3975 th->doff == ((sizeof(*th) + TCPOLEN_TSTAMP_ALIGNED) / 4)) { 3976 if (tcp_parse_aligned_timestamp(tp, th)) 3977 return 1; 3978 } 3979 tcp_parse_options(skb, &tp->rx_opt, hvpp, 1); 3980 return 1; 3981 } 3982 3983 #ifdef CONFIG_TCP_MD5SIG 3984 /* 3985 * Parse MD5 Signature option 3986 */ 3987 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th) 3988 { 3989 int length = (th->doff << 2) - sizeof(*th); 3990 const u8 *ptr = (const u8 *)(th + 1); 3991 3992 /* If the TCP option is too short, we can short cut */ 3993 if (length < TCPOLEN_MD5SIG) 3994 return NULL; 3995 3996 while (length > 0) { 3997 int opcode = *ptr++; 3998 int opsize; 3999 4000 switch(opcode) { 4001 case TCPOPT_EOL: 4002 return NULL; 4003 case TCPOPT_NOP: 4004 length--; 4005 continue; 4006 default: 4007 opsize = *ptr++; 4008 if (opsize < 2 || opsize > length) 4009 return NULL; 4010 if (opcode == TCPOPT_MD5SIG) 4011 return opsize == TCPOLEN_MD5SIG ? ptr : NULL; 4012 } 4013 ptr += opsize - 2; 4014 length -= opsize; 4015 } 4016 return NULL; 4017 } 4018 EXPORT_SYMBOL(tcp_parse_md5sig_option); 4019 #endif 4020 4021 static inline void tcp_store_ts_recent(struct tcp_sock *tp) 4022 { 4023 tp->rx_opt.ts_recent = tp->rx_opt.rcv_tsval; 4024 tp->rx_opt.ts_recent_stamp = get_seconds(); 4025 } 4026 4027 static inline void tcp_replace_ts_recent(struct tcp_sock *tp, u32 seq) 4028 { 4029 if (tp->rx_opt.saw_tstamp && !after(seq, tp->rcv_wup)) { 4030 /* PAWS bug workaround wrt. ACK frames, the PAWS discard 4031 * extra check below makes sure this can only happen 4032 * for pure ACK frames. -DaveM 4033 * 4034 * Not only, also it occurs for expired timestamps. 4035 */ 4036 4037 if (tcp_paws_check(&tp->rx_opt, 0)) 4038 tcp_store_ts_recent(tp); 4039 } 4040 } 4041 4042 /* Sorry, PAWS as specified is broken wrt. pure-ACKs -DaveM 4043 * 4044 * It is not fatal. If this ACK does _not_ change critical state (seqs, window) 4045 * it can pass through stack. So, the following predicate verifies that 4046 * this segment is not used for anything but congestion avoidance or 4047 * fast retransmit. Moreover, we even are able to eliminate most of such 4048 * second order effects, if we apply some small "replay" window (~RTO) 4049 * to timestamp space. 4050 * 4051 * All these measures still do not guarantee that we reject wrapped ACKs 4052 * on networks with high bandwidth, when sequence space is recycled fastly, 4053 * but it guarantees that such events will be very rare and do not affect 4054 * connection seriously. This doesn't look nice, but alas, PAWS is really 4055 * buggy extension. 4056 * 4057 * [ Later note. Even worse! It is buggy for segments _with_ data. RFC 4058 * states that events when retransmit arrives after original data are rare. 4059 * It is a blatant lie. VJ forgot about fast retransmit! 8)8) It is 4060 * the biggest problem on large power networks even with minor reordering. 4061 * OK, let's give it small replay window. If peer clock is even 1hz, it is safe 4062 * up to bandwidth of 18Gigabit/sec. 8) ] 4063 */ 4064 4065 static int tcp_disordered_ack(const struct sock *sk, const struct sk_buff *skb) 4066 { 4067 const struct tcp_sock *tp = tcp_sk(sk); 4068 const struct tcphdr *th = tcp_hdr(skb); 4069 u32 seq = TCP_SKB_CB(skb)->seq; 4070 u32 ack = TCP_SKB_CB(skb)->ack_seq; 4071 4072 return (/* 1. Pure ACK with correct sequence number. */ 4073 (th->ack && seq == TCP_SKB_CB(skb)->end_seq && seq == tp->rcv_nxt) && 4074 4075 /* 2. ... and duplicate ACK. */ 4076 ack == tp->snd_una && 4077 4078 /* 3. ... and does not update window. */ 4079 !tcp_may_update_window(tp, ack, seq, ntohs(th->window) << tp->rx_opt.snd_wscale) && 4080 4081 /* 4. ... and sits in replay window. */ 4082 (s32)(tp->rx_opt.ts_recent - tp->rx_opt.rcv_tsval) <= (inet_csk(sk)->icsk_rto * 1024) / HZ); 4083 } 4084 4085 static inline int tcp_paws_discard(const struct sock *sk, 4086 const struct sk_buff *skb) 4087 { 4088 const struct tcp_sock *tp = tcp_sk(sk); 4089 4090 return !tcp_paws_check(&tp->rx_opt, TCP_PAWS_WINDOW) && 4091 !tcp_disordered_ack(sk, skb); 4092 } 4093 4094 /* Check segment sequence number for validity. 4095 * 4096 * Segment controls are considered valid, if the segment 4097 * fits to the window after truncation to the window. Acceptability 4098 * of data (and SYN, FIN, of course) is checked separately. 4099 * See tcp_data_queue(), for example. 4100 * 4101 * Also, controls (RST is main one) are accepted using RCV.WUP instead 4102 * of RCV.NXT. Peer still did not advance his SND.UNA when we 4103 * delayed ACK, so that hisSND.UNA<=ourRCV.WUP. 4104 * (borrowed from freebsd) 4105 */ 4106 4107 static inline int tcp_sequence(const struct tcp_sock *tp, u32 seq, u32 end_seq) 4108 { 4109 return !before(end_seq, tp->rcv_wup) && 4110 !after(seq, tp->rcv_nxt + tcp_receive_window(tp)); 4111 } 4112 4113 /* When we get a reset we do this. */ 4114 static void tcp_reset(struct sock *sk) 4115 { 4116 /* We want the right error as BSD sees it (and indeed as we do). */ 4117 switch (sk->sk_state) { 4118 case TCP_SYN_SENT: 4119 sk->sk_err = ECONNREFUSED; 4120 break; 4121 case TCP_CLOSE_WAIT: 4122 sk->sk_err = EPIPE; 4123 break; 4124 case TCP_CLOSE: 4125 return; 4126 default: 4127 sk->sk_err = ECONNRESET; 4128 } 4129 /* This barrier is coupled with smp_rmb() in tcp_poll() */ 4130 smp_wmb(); 4131 4132 if (!sock_flag(sk, SOCK_DEAD)) 4133 sk->sk_error_report(sk); 4134 4135 tcp_done(sk); 4136 } 4137 4138 /* 4139 * Process the FIN bit. This now behaves as it is supposed to work 4140 * and the FIN takes effect when it is validly part of sequence 4141 * space. Not before when we get holes. 4142 * 4143 * If we are ESTABLISHED, a received fin moves us to CLOSE-WAIT 4144 * (and thence onto LAST-ACK and finally, CLOSE, we never enter 4145 * TIME-WAIT) 4146 * 4147 * If we are in FINWAIT-1, a received FIN indicates simultaneous 4148 * close and we go into CLOSING (and later onto TIME-WAIT) 4149 * 4150 * If we are in FINWAIT-2, a received FIN moves us to TIME-WAIT. 4151 */ 4152 static void tcp_fin(struct sock *sk) 4153 { 4154 struct tcp_sock *tp = tcp_sk(sk); 4155 4156 inet_csk_schedule_ack(sk); 4157 4158 sk->sk_shutdown |= RCV_SHUTDOWN; 4159 sock_set_flag(sk, SOCK_DONE); 4160 4161 switch (sk->sk_state) { 4162 case TCP_SYN_RECV: 4163 case TCP_ESTABLISHED: 4164 /* Move to CLOSE_WAIT */ 4165 tcp_set_state(sk, TCP_CLOSE_WAIT); 4166 inet_csk(sk)->icsk_ack.pingpong = 1; 4167 break; 4168 4169 case TCP_CLOSE_WAIT: 4170 case TCP_CLOSING: 4171 /* Received a retransmission of the FIN, do 4172 * nothing. 4173 */ 4174 break; 4175 case TCP_LAST_ACK: 4176 /* RFC793: Remain in the LAST-ACK state. */ 4177 break; 4178 4179 case TCP_FIN_WAIT1: 4180 /* This case occurs when a simultaneous close 4181 * happens, we must ack the received FIN and 4182 * enter the CLOSING state. 4183 */ 4184 tcp_send_ack(sk); 4185 tcp_set_state(sk, TCP_CLOSING); 4186 break; 4187 case TCP_FIN_WAIT2: 4188 /* Received a FIN -- send ACK and enter TIME_WAIT. */ 4189 tcp_send_ack(sk); 4190 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 4191 break; 4192 default: 4193 /* Only TCP_LISTEN and TCP_CLOSE are left, in these 4194 * cases we should never reach this piece of code. 4195 */ 4196 pr_err("%s: Impossible, sk->sk_state=%d\n", 4197 __func__, sk->sk_state); 4198 break; 4199 } 4200 4201 /* It _is_ possible, that we have something out-of-order _after_ FIN. 4202 * Probably, we should reset in this case. For now drop them. 4203 */ 4204 __skb_queue_purge(&tp->out_of_order_queue); 4205 if (tcp_is_sack(tp)) 4206 tcp_sack_reset(&tp->rx_opt); 4207 sk_mem_reclaim(sk); 4208 4209 if (!sock_flag(sk, SOCK_DEAD)) { 4210 sk->sk_state_change(sk); 4211 4212 /* Do not send POLL_HUP for half duplex close. */ 4213 if (sk->sk_shutdown == SHUTDOWN_MASK || 4214 sk->sk_state == TCP_CLOSE) 4215 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_HUP); 4216 else 4217 sk_wake_async(sk, SOCK_WAKE_WAITD, POLL_IN); 4218 } 4219 } 4220 4221 static inline int tcp_sack_extend(struct tcp_sack_block *sp, u32 seq, 4222 u32 end_seq) 4223 { 4224 if (!after(seq, sp->end_seq) && !after(sp->start_seq, end_seq)) { 4225 if (before(seq, sp->start_seq)) 4226 sp->start_seq = seq; 4227 if (after(end_seq, sp->end_seq)) 4228 sp->end_seq = end_seq; 4229 return 1; 4230 } 4231 return 0; 4232 } 4233 4234 static void tcp_dsack_set(struct sock *sk, u32 seq, u32 end_seq) 4235 { 4236 struct tcp_sock *tp = tcp_sk(sk); 4237 4238 if (tcp_is_sack(tp) && sysctl_tcp_dsack) { 4239 int mib_idx; 4240 4241 if (before(seq, tp->rcv_nxt)) 4242 mib_idx = LINUX_MIB_TCPDSACKOLDSENT; 4243 else 4244 mib_idx = LINUX_MIB_TCPDSACKOFOSENT; 4245 4246 NET_INC_STATS_BH(sock_net(sk), mib_idx); 4247 4248 tp->rx_opt.dsack = 1; 4249 tp->duplicate_sack[0].start_seq = seq; 4250 tp->duplicate_sack[0].end_seq = end_seq; 4251 } 4252 } 4253 4254 static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq) 4255 { 4256 struct tcp_sock *tp = tcp_sk(sk); 4257 4258 if (!tp->rx_opt.dsack) 4259 tcp_dsack_set(sk, seq, end_seq); 4260 else 4261 tcp_sack_extend(tp->duplicate_sack, seq, end_seq); 4262 } 4263 4264 static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb) 4265 { 4266 struct tcp_sock *tp = tcp_sk(sk); 4267 4268 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 4269 before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4270 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); 4271 tcp_enter_quickack_mode(sk); 4272 4273 if (tcp_is_sack(tp) && sysctl_tcp_dsack) { 4274 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 4275 4276 if (after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) 4277 end_seq = tp->rcv_nxt; 4278 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, end_seq); 4279 } 4280 } 4281 4282 tcp_send_ack(sk); 4283 } 4284 4285 /* These routines update the SACK block as out-of-order packets arrive or 4286 * in-order packets close up the sequence space. 4287 */ 4288 static void tcp_sack_maybe_coalesce(struct tcp_sock *tp) 4289 { 4290 int this_sack; 4291 struct tcp_sack_block *sp = &tp->selective_acks[0]; 4292 struct tcp_sack_block *swalk = sp + 1; 4293 4294 /* See if the recent change to the first SACK eats into 4295 * or hits the sequence space of other SACK blocks, if so coalesce. 4296 */ 4297 for (this_sack = 1; this_sack < tp->rx_opt.num_sacks;) { 4298 if (tcp_sack_extend(sp, swalk->start_seq, swalk->end_seq)) { 4299 int i; 4300 4301 /* Zap SWALK, by moving every further SACK up by one slot. 4302 * Decrease num_sacks. 4303 */ 4304 tp->rx_opt.num_sacks--; 4305 for (i = this_sack; i < tp->rx_opt.num_sacks; i++) 4306 sp[i] = sp[i + 1]; 4307 continue; 4308 } 4309 this_sack++, swalk++; 4310 } 4311 } 4312 4313 static void tcp_sack_new_ofo_skb(struct sock *sk, u32 seq, u32 end_seq) 4314 { 4315 struct tcp_sock *tp = tcp_sk(sk); 4316 struct tcp_sack_block *sp = &tp->selective_acks[0]; 4317 int cur_sacks = tp->rx_opt.num_sacks; 4318 int this_sack; 4319 4320 if (!cur_sacks) 4321 goto new_sack; 4322 4323 for (this_sack = 0; this_sack < cur_sacks; this_sack++, sp++) { 4324 if (tcp_sack_extend(sp, seq, end_seq)) { 4325 /* Rotate this_sack to the first one. */ 4326 for (; this_sack > 0; this_sack--, sp--) 4327 swap(*sp, *(sp - 1)); 4328 if (cur_sacks > 1) 4329 tcp_sack_maybe_coalesce(tp); 4330 return; 4331 } 4332 } 4333 4334 /* Could not find an adjacent existing SACK, build a new one, 4335 * put it at the front, and shift everyone else down. We 4336 * always know there is at least one SACK present already here. 4337 * 4338 * If the sack array is full, forget about the last one. 4339 */ 4340 if (this_sack >= TCP_NUM_SACKS) { 4341 this_sack--; 4342 tp->rx_opt.num_sacks--; 4343 sp--; 4344 } 4345 for (; this_sack > 0; this_sack--, sp--) 4346 *sp = *(sp - 1); 4347 4348 new_sack: 4349 /* Build the new head SACK, and we're done. */ 4350 sp->start_seq = seq; 4351 sp->end_seq = end_seq; 4352 tp->rx_opt.num_sacks++; 4353 } 4354 4355 /* RCV.NXT advances, some SACKs should be eaten. */ 4356 4357 static void tcp_sack_remove(struct tcp_sock *tp) 4358 { 4359 struct tcp_sack_block *sp = &tp->selective_acks[0]; 4360 int num_sacks = tp->rx_opt.num_sacks; 4361 int this_sack; 4362 4363 /* Empty ofo queue, hence, all the SACKs are eaten. Clear. */ 4364 if (skb_queue_empty(&tp->out_of_order_queue)) { 4365 tp->rx_opt.num_sacks = 0; 4366 return; 4367 } 4368 4369 for (this_sack = 0; this_sack < num_sacks;) { 4370 /* Check if the start of the sack is covered by RCV.NXT. */ 4371 if (!before(tp->rcv_nxt, sp->start_seq)) { 4372 int i; 4373 4374 /* RCV.NXT must cover all the block! */ 4375 WARN_ON(before(tp->rcv_nxt, sp->end_seq)); 4376 4377 /* Zap this SACK, by moving forward any other SACKS. */ 4378 for (i=this_sack+1; i < num_sacks; i++) 4379 tp->selective_acks[i-1] = tp->selective_acks[i]; 4380 num_sacks--; 4381 continue; 4382 } 4383 this_sack++; 4384 sp++; 4385 } 4386 tp->rx_opt.num_sacks = num_sacks; 4387 } 4388 4389 /* This one checks to see if we can put data from the 4390 * out_of_order queue into the receive_queue. 4391 */ 4392 static void tcp_ofo_queue(struct sock *sk) 4393 { 4394 struct tcp_sock *tp = tcp_sk(sk); 4395 __u32 dsack_high = tp->rcv_nxt; 4396 struct sk_buff *skb; 4397 4398 while ((skb = skb_peek(&tp->out_of_order_queue)) != NULL) { 4399 if (after(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 4400 break; 4401 4402 if (before(TCP_SKB_CB(skb)->seq, dsack_high)) { 4403 __u32 dsack = dsack_high; 4404 if (before(TCP_SKB_CB(skb)->end_seq, dsack_high)) 4405 dsack_high = TCP_SKB_CB(skb)->end_seq; 4406 tcp_dsack_extend(sk, TCP_SKB_CB(skb)->seq, dsack); 4407 } 4408 4409 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 4410 SOCK_DEBUG(sk, "ofo packet was already received\n"); 4411 __skb_unlink(skb, &tp->out_of_order_queue); 4412 __kfree_skb(skb); 4413 continue; 4414 } 4415 SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n", 4416 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 4417 TCP_SKB_CB(skb)->end_seq); 4418 4419 __skb_unlink(skb, &tp->out_of_order_queue); 4420 __skb_queue_tail(&sk->sk_receive_queue, skb); 4421 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4422 if (tcp_hdr(skb)->fin) 4423 tcp_fin(sk); 4424 } 4425 } 4426 4427 static int tcp_prune_ofo_queue(struct sock *sk); 4428 static int tcp_prune_queue(struct sock *sk); 4429 4430 static inline int tcp_try_rmem_schedule(struct sock *sk, unsigned int size) 4431 { 4432 if (atomic_read(&sk->sk_rmem_alloc) > sk->sk_rcvbuf || 4433 !sk_rmem_schedule(sk, size)) { 4434 4435 if (tcp_prune_queue(sk) < 0) 4436 return -1; 4437 4438 if (!sk_rmem_schedule(sk, size)) { 4439 if (!tcp_prune_ofo_queue(sk)) 4440 return -1; 4441 4442 if (!sk_rmem_schedule(sk, size)) 4443 return -1; 4444 } 4445 } 4446 return 0; 4447 } 4448 4449 static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb) 4450 { 4451 struct tcp_sock *tp = tcp_sk(sk); 4452 struct sk_buff *skb1; 4453 u32 seq, end_seq; 4454 4455 TCP_ECN_check_ce(tp, skb); 4456 4457 if (tcp_try_rmem_schedule(sk, skb->truesize)) { 4458 /* TODO: should increment a counter */ 4459 __kfree_skb(skb); 4460 return; 4461 } 4462 4463 /* Disable header prediction. */ 4464 tp->pred_flags = 0; 4465 inet_csk_schedule_ack(sk); 4466 4467 SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n", 4468 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 4469 4470 skb1 = skb_peek_tail(&tp->out_of_order_queue); 4471 if (!skb1) { 4472 /* Initial out of order segment, build 1 SACK. */ 4473 if (tcp_is_sack(tp)) { 4474 tp->rx_opt.num_sacks = 1; 4475 tp->selective_acks[0].start_seq = TCP_SKB_CB(skb)->seq; 4476 tp->selective_acks[0].end_seq = 4477 TCP_SKB_CB(skb)->end_seq; 4478 } 4479 __skb_queue_head(&tp->out_of_order_queue, skb); 4480 goto end; 4481 } 4482 4483 seq = TCP_SKB_CB(skb)->seq; 4484 end_seq = TCP_SKB_CB(skb)->end_seq; 4485 4486 if (seq == TCP_SKB_CB(skb1)->end_seq) { 4487 /* Packets in ofo can stay in queue a long time. 4488 * Better try to coalesce them right now 4489 * to avoid future tcp_collapse_ofo_queue(), 4490 * probably the most expensive function in tcp stack. 4491 */ 4492 if (skb->len <= skb_tailroom(skb1) && !tcp_hdr(skb)->fin) { 4493 NET_INC_STATS_BH(sock_net(sk), 4494 LINUX_MIB_TCPRCVCOALESCE); 4495 BUG_ON(skb_copy_bits(skb, 0, 4496 skb_put(skb1, skb->len), 4497 skb->len)); 4498 TCP_SKB_CB(skb1)->end_seq = end_seq; 4499 TCP_SKB_CB(skb1)->ack_seq = TCP_SKB_CB(skb)->ack_seq; 4500 __kfree_skb(skb); 4501 skb = NULL; 4502 } else { 4503 __skb_queue_after(&tp->out_of_order_queue, skb1, skb); 4504 } 4505 4506 if (!tp->rx_opt.num_sacks || 4507 tp->selective_acks[0].end_seq != seq) 4508 goto add_sack; 4509 4510 /* Common case: data arrive in order after hole. */ 4511 tp->selective_acks[0].end_seq = end_seq; 4512 goto end; 4513 } 4514 4515 /* Find place to insert this segment. */ 4516 while (1) { 4517 if (!after(TCP_SKB_CB(skb1)->seq, seq)) 4518 break; 4519 if (skb_queue_is_first(&tp->out_of_order_queue, skb1)) { 4520 skb1 = NULL; 4521 break; 4522 } 4523 skb1 = skb_queue_prev(&tp->out_of_order_queue, skb1); 4524 } 4525 4526 /* Do skb overlap to previous one? */ 4527 if (skb1 && before(seq, TCP_SKB_CB(skb1)->end_seq)) { 4528 if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 4529 /* All the bits are present. Drop. */ 4530 __kfree_skb(skb); 4531 skb = NULL; 4532 tcp_dsack_set(sk, seq, end_seq); 4533 goto add_sack; 4534 } 4535 if (after(seq, TCP_SKB_CB(skb1)->seq)) { 4536 /* Partial overlap. */ 4537 tcp_dsack_set(sk, seq, 4538 TCP_SKB_CB(skb1)->end_seq); 4539 } else { 4540 if (skb_queue_is_first(&tp->out_of_order_queue, 4541 skb1)) 4542 skb1 = NULL; 4543 else 4544 skb1 = skb_queue_prev( 4545 &tp->out_of_order_queue, 4546 skb1); 4547 } 4548 } 4549 if (!skb1) 4550 __skb_queue_head(&tp->out_of_order_queue, skb); 4551 else 4552 __skb_queue_after(&tp->out_of_order_queue, skb1, skb); 4553 4554 /* And clean segments covered by new one as whole. */ 4555 while (!skb_queue_is_last(&tp->out_of_order_queue, skb)) { 4556 skb1 = skb_queue_next(&tp->out_of_order_queue, skb); 4557 4558 if (!after(end_seq, TCP_SKB_CB(skb1)->seq)) 4559 break; 4560 if (before(end_seq, TCP_SKB_CB(skb1)->end_seq)) { 4561 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, 4562 end_seq); 4563 break; 4564 } 4565 __skb_unlink(skb1, &tp->out_of_order_queue); 4566 tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq, 4567 TCP_SKB_CB(skb1)->end_seq); 4568 __kfree_skb(skb1); 4569 } 4570 4571 add_sack: 4572 if (tcp_is_sack(tp)) 4573 tcp_sack_new_ofo_skb(sk, seq, end_seq); 4574 end: 4575 if (skb) 4576 skb_set_owner_r(skb, sk); 4577 } 4578 4579 4580 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb) 4581 { 4582 const struct tcphdr *th = tcp_hdr(skb); 4583 struct tcp_sock *tp = tcp_sk(sk); 4584 int eaten = -1; 4585 4586 if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) 4587 goto drop; 4588 4589 skb_dst_drop(skb); 4590 __skb_pull(skb, th->doff * 4); 4591 4592 TCP_ECN_accept_cwr(tp, skb); 4593 4594 tp->rx_opt.dsack = 0; 4595 4596 /* Queue data for delivery to the user. 4597 * Packets in sequence go to the receive queue. 4598 * Out of sequence packets to the out_of_order_queue. 4599 */ 4600 if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) { 4601 if (tcp_receive_window(tp) == 0) 4602 goto out_of_window; 4603 4604 /* Ok. In sequence. In window. */ 4605 if (tp->ucopy.task == current && 4606 tp->copied_seq == tp->rcv_nxt && tp->ucopy.len && 4607 sock_owned_by_user(sk) && !tp->urg_data) { 4608 int chunk = min_t(unsigned int, skb->len, 4609 tp->ucopy.len); 4610 4611 __set_current_state(TASK_RUNNING); 4612 4613 local_bh_enable(); 4614 if (!skb_copy_datagram_iovec(skb, 0, tp->ucopy.iov, chunk)) { 4615 tp->ucopy.len -= chunk; 4616 tp->copied_seq += chunk; 4617 eaten = (chunk == skb->len); 4618 tcp_rcv_space_adjust(sk); 4619 } 4620 local_bh_disable(); 4621 } 4622 4623 if (eaten <= 0) { 4624 queue_and_out: 4625 if (eaten < 0 && 4626 tcp_try_rmem_schedule(sk, skb->truesize)) 4627 goto drop; 4628 4629 skb_set_owner_r(skb, sk); 4630 __skb_queue_tail(&sk->sk_receive_queue, skb); 4631 } 4632 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 4633 if (skb->len) 4634 tcp_event_data_recv(sk, skb); 4635 if (th->fin) 4636 tcp_fin(sk); 4637 4638 if (!skb_queue_empty(&tp->out_of_order_queue)) { 4639 tcp_ofo_queue(sk); 4640 4641 /* RFC2581. 4.2. SHOULD send immediate ACK, when 4642 * gap in queue is filled. 4643 */ 4644 if (skb_queue_empty(&tp->out_of_order_queue)) 4645 inet_csk(sk)->icsk_ack.pingpong = 0; 4646 } 4647 4648 if (tp->rx_opt.num_sacks) 4649 tcp_sack_remove(tp); 4650 4651 tcp_fast_path_check(sk); 4652 4653 if (eaten > 0) 4654 __kfree_skb(skb); 4655 else if (!sock_flag(sk, SOCK_DEAD)) 4656 sk->sk_data_ready(sk, 0); 4657 return; 4658 } 4659 4660 if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) { 4661 /* A retransmit, 2nd most common case. Force an immediate ack. */ 4662 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_DELAYEDACKLOST); 4663 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq); 4664 4665 out_of_window: 4666 tcp_enter_quickack_mode(sk); 4667 inet_csk_schedule_ack(sk); 4668 drop: 4669 __kfree_skb(skb); 4670 return; 4671 } 4672 4673 /* Out of window. F.e. zero window probe. */ 4674 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp))) 4675 goto out_of_window; 4676 4677 tcp_enter_quickack_mode(sk); 4678 4679 if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 4680 /* Partial packet, seq < rcv_next < end_seq */ 4681 SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n", 4682 tp->rcv_nxt, TCP_SKB_CB(skb)->seq, 4683 TCP_SKB_CB(skb)->end_seq); 4684 4685 tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt); 4686 4687 /* If window is closed, drop tail of packet. But after 4688 * remembering D-SACK for its head made in previous line. 4689 */ 4690 if (!tcp_receive_window(tp)) 4691 goto out_of_window; 4692 goto queue_and_out; 4693 } 4694 4695 tcp_data_queue_ofo(sk, skb); 4696 } 4697 4698 static struct sk_buff *tcp_collapse_one(struct sock *sk, struct sk_buff *skb, 4699 struct sk_buff_head *list) 4700 { 4701 struct sk_buff *next = NULL; 4702 4703 if (!skb_queue_is_last(list, skb)) 4704 next = skb_queue_next(list, skb); 4705 4706 __skb_unlink(skb, list); 4707 __kfree_skb(skb); 4708 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRCVCOLLAPSED); 4709 4710 return next; 4711 } 4712 4713 /* Collapse contiguous sequence of skbs head..tail with 4714 * sequence numbers start..end. 4715 * 4716 * If tail is NULL, this means until the end of the list. 4717 * 4718 * Segments with FIN/SYN are not collapsed (only because this 4719 * simplifies code) 4720 */ 4721 static void 4722 tcp_collapse(struct sock *sk, struct sk_buff_head *list, 4723 struct sk_buff *head, struct sk_buff *tail, 4724 u32 start, u32 end) 4725 { 4726 struct sk_buff *skb, *n; 4727 bool end_of_skbs; 4728 4729 /* First, check that queue is collapsible and find 4730 * the point where collapsing can be useful. */ 4731 skb = head; 4732 restart: 4733 end_of_skbs = true; 4734 skb_queue_walk_from_safe(list, skb, n) { 4735 if (skb == tail) 4736 break; 4737 /* No new bits? It is possible on ofo queue. */ 4738 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 4739 skb = tcp_collapse_one(sk, skb, list); 4740 if (!skb) 4741 break; 4742 goto restart; 4743 } 4744 4745 /* The first skb to collapse is: 4746 * - not SYN/FIN and 4747 * - bloated or contains data before "start" or 4748 * overlaps to the next one. 4749 */ 4750 if (!tcp_hdr(skb)->syn && !tcp_hdr(skb)->fin && 4751 (tcp_win_from_space(skb->truesize) > skb->len || 4752 before(TCP_SKB_CB(skb)->seq, start))) { 4753 end_of_skbs = false; 4754 break; 4755 } 4756 4757 if (!skb_queue_is_last(list, skb)) { 4758 struct sk_buff *next = skb_queue_next(list, skb); 4759 if (next != tail && 4760 TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(next)->seq) { 4761 end_of_skbs = false; 4762 break; 4763 } 4764 } 4765 4766 /* Decided to skip this, advance start seq. */ 4767 start = TCP_SKB_CB(skb)->end_seq; 4768 } 4769 if (end_of_skbs || tcp_hdr(skb)->syn || tcp_hdr(skb)->fin) 4770 return; 4771 4772 while (before(start, end)) { 4773 struct sk_buff *nskb; 4774 unsigned int header = skb_headroom(skb); 4775 int copy = SKB_MAX_ORDER(header, 0); 4776 4777 /* Too big header? This can happen with IPv6. */ 4778 if (copy < 0) 4779 return; 4780 if (end - start < copy) 4781 copy = end - start; 4782 nskb = alloc_skb(copy + header, GFP_ATOMIC); 4783 if (!nskb) 4784 return; 4785 4786 skb_set_mac_header(nskb, skb_mac_header(skb) - skb->head); 4787 skb_set_network_header(nskb, (skb_network_header(skb) - 4788 skb->head)); 4789 skb_set_transport_header(nskb, (skb_transport_header(skb) - 4790 skb->head)); 4791 skb_reserve(nskb, header); 4792 memcpy(nskb->head, skb->head, header); 4793 memcpy(nskb->cb, skb->cb, sizeof(skb->cb)); 4794 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(nskb)->end_seq = start; 4795 __skb_queue_before(list, skb, nskb); 4796 skb_set_owner_r(nskb, sk); 4797 4798 /* Copy data, releasing collapsed skbs. */ 4799 while (copy > 0) { 4800 int offset = start - TCP_SKB_CB(skb)->seq; 4801 int size = TCP_SKB_CB(skb)->end_seq - start; 4802 4803 BUG_ON(offset < 0); 4804 if (size > 0) { 4805 size = min(copy, size); 4806 if (skb_copy_bits(skb, offset, skb_put(nskb, size), size)) 4807 BUG(); 4808 TCP_SKB_CB(nskb)->end_seq += size; 4809 copy -= size; 4810 start += size; 4811 } 4812 if (!before(start, TCP_SKB_CB(skb)->end_seq)) { 4813 skb = tcp_collapse_one(sk, skb, list); 4814 if (!skb || 4815 skb == tail || 4816 tcp_hdr(skb)->syn || 4817 tcp_hdr(skb)->fin) 4818 return; 4819 } 4820 } 4821 } 4822 } 4823 4824 /* Collapse ofo queue. Algorithm: select contiguous sequence of skbs 4825 * and tcp_collapse() them until all the queue is collapsed. 4826 */ 4827 static void tcp_collapse_ofo_queue(struct sock *sk) 4828 { 4829 struct tcp_sock *tp = tcp_sk(sk); 4830 struct sk_buff *skb = skb_peek(&tp->out_of_order_queue); 4831 struct sk_buff *head; 4832 u32 start, end; 4833 4834 if (skb == NULL) 4835 return; 4836 4837 start = TCP_SKB_CB(skb)->seq; 4838 end = TCP_SKB_CB(skb)->end_seq; 4839 head = skb; 4840 4841 for (;;) { 4842 struct sk_buff *next = NULL; 4843 4844 if (!skb_queue_is_last(&tp->out_of_order_queue, skb)) 4845 next = skb_queue_next(&tp->out_of_order_queue, skb); 4846 skb = next; 4847 4848 /* Segment is terminated when we see gap or when 4849 * we are at the end of all the queue. */ 4850 if (!skb || 4851 after(TCP_SKB_CB(skb)->seq, end) || 4852 before(TCP_SKB_CB(skb)->end_seq, start)) { 4853 tcp_collapse(sk, &tp->out_of_order_queue, 4854 head, skb, start, end); 4855 head = skb; 4856 if (!skb) 4857 break; 4858 /* Start new segment */ 4859 start = TCP_SKB_CB(skb)->seq; 4860 end = TCP_SKB_CB(skb)->end_seq; 4861 } else { 4862 if (before(TCP_SKB_CB(skb)->seq, start)) 4863 start = TCP_SKB_CB(skb)->seq; 4864 if (after(TCP_SKB_CB(skb)->end_seq, end)) 4865 end = TCP_SKB_CB(skb)->end_seq; 4866 } 4867 } 4868 } 4869 4870 /* 4871 * Purge the out-of-order queue. 4872 * Return true if queue was pruned. 4873 */ 4874 static int tcp_prune_ofo_queue(struct sock *sk) 4875 { 4876 struct tcp_sock *tp = tcp_sk(sk); 4877 int res = 0; 4878 4879 if (!skb_queue_empty(&tp->out_of_order_queue)) { 4880 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_OFOPRUNED); 4881 __skb_queue_purge(&tp->out_of_order_queue); 4882 4883 /* Reset SACK state. A conforming SACK implementation will 4884 * do the same at a timeout based retransmit. When a connection 4885 * is in a sad state like this, we care only about integrity 4886 * of the connection not performance. 4887 */ 4888 if (tp->rx_opt.sack_ok) 4889 tcp_sack_reset(&tp->rx_opt); 4890 sk_mem_reclaim(sk); 4891 res = 1; 4892 } 4893 return res; 4894 } 4895 4896 /* Reduce allocated memory if we can, trying to get 4897 * the socket within its memory limits again. 4898 * 4899 * Return less than zero if we should start dropping frames 4900 * until the socket owning process reads some of the data 4901 * to stabilize the situation. 4902 */ 4903 static int tcp_prune_queue(struct sock *sk) 4904 { 4905 struct tcp_sock *tp = tcp_sk(sk); 4906 4907 SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq); 4908 4909 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PRUNECALLED); 4910 4911 if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf) 4912 tcp_clamp_window(sk); 4913 else if (sk_under_memory_pressure(sk)) 4914 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U * tp->advmss); 4915 4916 tcp_collapse_ofo_queue(sk); 4917 if (!skb_queue_empty(&sk->sk_receive_queue)) 4918 tcp_collapse(sk, &sk->sk_receive_queue, 4919 skb_peek(&sk->sk_receive_queue), 4920 NULL, 4921 tp->copied_seq, tp->rcv_nxt); 4922 sk_mem_reclaim(sk); 4923 4924 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 4925 return 0; 4926 4927 /* Collapsing did not help, destructive actions follow. 4928 * This must not ever occur. */ 4929 4930 tcp_prune_ofo_queue(sk); 4931 4932 if (atomic_read(&sk->sk_rmem_alloc) <= sk->sk_rcvbuf) 4933 return 0; 4934 4935 /* If we are really being abused, tell the caller to silently 4936 * drop receive data on the floor. It will get retransmitted 4937 * and hopefully then we'll have sufficient space. 4938 */ 4939 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_RCVPRUNED); 4940 4941 /* Massive buffer overcommit. */ 4942 tp->pred_flags = 0; 4943 return -1; 4944 } 4945 4946 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. 4947 * As additional protections, we do not touch cwnd in retransmission phases, 4948 * and if application hit its sndbuf limit recently. 4949 */ 4950 void tcp_cwnd_application_limited(struct sock *sk) 4951 { 4952 struct tcp_sock *tp = tcp_sk(sk); 4953 4954 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && 4955 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { 4956 /* Limited by application or receiver window. */ 4957 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); 4958 u32 win_used = max(tp->snd_cwnd_used, init_win); 4959 if (win_used < tp->snd_cwnd) { 4960 tp->snd_ssthresh = tcp_current_ssthresh(sk); 4961 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; 4962 } 4963 tp->snd_cwnd_used = 0; 4964 } 4965 tp->snd_cwnd_stamp = tcp_time_stamp; 4966 } 4967 4968 static int tcp_should_expand_sndbuf(const struct sock *sk) 4969 { 4970 const struct tcp_sock *tp = tcp_sk(sk); 4971 4972 /* If the user specified a specific send buffer setting, do 4973 * not modify it. 4974 */ 4975 if (sk->sk_userlocks & SOCK_SNDBUF_LOCK) 4976 return 0; 4977 4978 /* If we are under global TCP memory pressure, do not expand. */ 4979 if (sk_under_memory_pressure(sk)) 4980 return 0; 4981 4982 /* If we are under soft global TCP memory pressure, do not expand. */ 4983 if (sk_memory_allocated(sk) >= sk_prot_mem_limits(sk, 0)) 4984 return 0; 4985 4986 /* If we filled the congestion window, do not expand. */ 4987 if (tp->packets_out >= tp->snd_cwnd) 4988 return 0; 4989 4990 return 1; 4991 } 4992 4993 /* When incoming ACK allowed to free some skb from write_queue, 4994 * we remember this event in flag SOCK_QUEUE_SHRUNK and wake up socket 4995 * on the exit from tcp input handler. 4996 * 4997 * PROBLEM: sndbuf expansion does not work well with largesend. 4998 */ 4999 static void tcp_new_space(struct sock *sk) 5000 { 5001 struct tcp_sock *tp = tcp_sk(sk); 5002 5003 if (tcp_should_expand_sndbuf(sk)) { 5004 int sndmem = SKB_TRUESIZE(max_t(u32, 5005 tp->rx_opt.mss_clamp, 5006 tp->mss_cache) + 5007 MAX_TCP_HEADER); 5008 int demanded = max_t(unsigned int, tp->snd_cwnd, 5009 tp->reordering + 1); 5010 sndmem *= 2 * demanded; 5011 if (sndmem > sk->sk_sndbuf) 5012 sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); 5013 tp->snd_cwnd_stamp = tcp_time_stamp; 5014 } 5015 5016 sk->sk_write_space(sk); 5017 } 5018 5019 static void tcp_check_space(struct sock *sk) 5020 { 5021 if (sock_flag(sk, SOCK_QUEUE_SHRUNK)) { 5022 sock_reset_flag(sk, SOCK_QUEUE_SHRUNK); 5023 if (sk->sk_socket && 5024 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) 5025 tcp_new_space(sk); 5026 } 5027 } 5028 5029 static inline void tcp_data_snd_check(struct sock *sk) 5030 { 5031 tcp_push_pending_frames(sk); 5032 tcp_check_space(sk); 5033 } 5034 5035 /* 5036 * Check if sending an ack is needed. 5037 */ 5038 static void __tcp_ack_snd_check(struct sock *sk, int ofo_possible) 5039 { 5040 struct tcp_sock *tp = tcp_sk(sk); 5041 5042 /* More than one full frame received... */ 5043 if (((tp->rcv_nxt - tp->rcv_wup) > inet_csk(sk)->icsk_ack.rcv_mss && 5044 /* ... and right edge of window advances far enough. 5045 * (tcp_recvmsg() will send ACK otherwise). Or... 5046 */ 5047 __tcp_select_window(sk) >= tp->rcv_wnd) || 5048 /* We ACK each frame or... */ 5049 tcp_in_quickack_mode(sk) || 5050 /* We have out of order data. */ 5051 (ofo_possible && skb_peek(&tp->out_of_order_queue))) { 5052 /* Then ack it now */ 5053 tcp_send_ack(sk); 5054 } else { 5055 /* Else, send delayed ack. */ 5056 tcp_send_delayed_ack(sk); 5057 } 5058 } 5059 5060 static inline void tcp_ack_snd_check(struct sock *sk) 5061 { 5062 if (!inet_csk_ack_scheduled(sk)) { 5063 /* We sent a data segment already. */ 5064 return; 5065 } 5066 __tcp_ack_snd_check(sk, 1); 5067 } 5068 5069 /* 5070 * This routine is only called when we have urgent data 5071 * signaled. Its the 'slow' part of tcp_urg. It could be 5072 * moved inline now as tcp_urg is only called from one 5073 * place. We handle URGent data wrong. We have to - as 5074 * BSD still doesn't use the correction from RFC961. 5075 * For 1003.1g we should support a new option TCP_STDURG to permit 5076 * either form (or just set the sysctl tcp_stdurg). 5077 */ 5078 5079 static void tcp_check_urg(struct sock *sk, const struct tcphdr *th) 5080 { 5081 struct tcp_sock *tp = tcp_sk(sk); 5082 u32 ptr = ntohs(th->urg_ptr); 5083 5084 if (ptr && !sysctl_tcp_stdurg) 5085 ptr--; 5086 ptr += ntohl(th->seq); 5087 5088 /* Ignore urgent data that we've already seen and read. */ 5089 if (after(tp->copied_seq, ptr)) 5090 return; 5091 5092 /* Do not replay urg ptr. 5093 * 5094 * NOTE: interesting situation not covered by specs. 5095 * Misbehaving sender may send urg ptr, pointing to segment, 5096 * which we already have in ofo queue. We are not able to fetch 5097 * such data and will stay in TCP_URG_NOTYET until will be eaten 5098 * by recvmsg(). Seems, we are not obliged to handle such wicked 5099 * situations. But it is worth to think about possibility of some 5100 * DoSes using some hypothetical application level deadlock. 5101 */ 5102 if (before(ptr, tp->rcv_nxt)) 5103 return; 5104 5105 /* Do we already have a newer (or duplicate) urgent pointer? */ 5106 if (tp->urg_data && !after(ptr, tp->urg_seq)) 5107 return; 5108 5109 /* Tell the world about our new urgent pointer. */ 5110 sk_send_sigurg(sk); 5111 5112 /* We may be adding urgent data when the last byte read was 5113 * urgent. To do this requires some care. We cannot just ignore 5114 * tp->copied_seq since we would read the last urgent byte again 5115 * as data, nor can we alter copied_seq until this data arrives 5116 * or we break the semantics of SIOCATMARK (and thus sockatmark()) 5117 * 5118 * NOTE. Double Dutch. Rendering to plain English: author of comment 5119 * above did something sort of send("A", MSG_OOB); send("B", MSG_OOB); 5120 * and expect that both A and B disappear from stream. This is _wrong_. 5121 * Though this happens in BSD with high probability, this is occasional. 5122 * Any application relying on this is buggy. Note also, that fix "works" 5123 * only in this artificial test. Insert some normal data between A and B and we will 5124 * decline of BSD again. Verdict: it is better to remove to trap 5125 * buggy users. 5126 */ 5127 if (tp->urg_seq == tp->copied_seq && tp->urg_data && 5128 !sock_flag(sk, SOCK_URGINLINE) && tp->copied_seq != tp->rcv_nxt) { 5129 struct sk_buff *skb = skb_peek(&sk->sk_receive_queue); 5130 tp->copied_seq++; 5131 if (skb && !before(tp->copied_seq, TCP_SKB_CB(skb)->end_seq)) { 5132 __skb_unlink(skb, &sk->sk_receive_queue); 5133 __kfree_skb(skb); 5134 } 5135 } 5136 5137 tp->urg_data = TCP_URG_NOTYET; 5138 tp->urg_seq = ptr; 5139 5140 /* Disable header prediction. */ 5141 tp->pred_flags = 0; 5142 } 5143 5144 /* This is the 'fast' part of urgent handling. */ 5145 static void tcp_urg(struct sock *sk, struct sk_buff *skb, const struct tcphdr *th) 5146 { 5147 struct tcp_sock *tp = tcp_sk(sk); 5148 5149 /* Check if we get a new urgent pointer - normally not. */ 5150 if (th->urg) 5151 tcp_check_urg(sk, th); 5152 5153 /* Do we wait for any urgent data? - normally not... */ 5154 if (tp->urg_data == TCP_URG_NOTYET) { 5155 u32 ptr = tp->urg_seq - ntohl(th->seq) + (th->doff * 4) - 5156 th->syn; 5157 5158 /* Is the urgent pointer pointing into this packet? */ 5159 if (ptr < skb->len) { 5160 u8 tmp; 5161 if (skb_copy_bits(skb, ptr, &tmp, 1)) 5162 BUG(); 5163 tp->urg_data = TCP_URG_VALID | tmp; 5164 if (!sock_flag(sk, SOCK_DEAD)) 5165 sk->sk_data_ready(sk, 0); 5166 } 5167 } 5168 } 5169 5170 static int tcp_copy_to_iovec(struct sock *sk, struct sk_buff *skb, int hlen) 5171 { 5172 struct tcp_sock *tp = tcp_sk(sk); 5173 int chunk = skb->len - hlen; 5174 int err; 5175 5176 local_bh_enable(); 5177 if (skb_csum_unnecessary(skb)) 5178 err = skb_copy_datagram_iovec(skb, hlen, tp->ucopy.iov, chunk); 5179 else 5180 err = skb_copy_and_csum_datagram_iovec(skb, hlen, 5181 tp->ucopy.iov); 5182 5183 if (!err) { 5184 tp->ucopy.len -= chunk; 5185 tp->copied_seq += chunk; 5186 tcp_rcv_space_adjust(sk); 5187 } 5188 5189 local_bh_disable(); 5190 return err; 5191 } 5192 5193 static __sum16 __tcp_checksum_complete_user(struct sock *sk, 5194 struct sk_buff *skb) 5195 { 5196 __sum16 result; 5197 5198 if (sock_owned_by_user(sk)) { 5199 local_bh_enable(); 5200 result = __tcp_checksum_complete(skb); 5201 local_bh_disable(); 5202 } else { 5203 result = __tcp_checksum_complete(skb); 5204 } 5205 return result; 5206 } 5207 5208 static inline int tcp_checksum_complete_user(struct sock *sk, 5209 struct sk_buff *skb) 5210 { 5211 return !skb_csum_unnecessary(skb) && 5212 __tcp_checksum_complete_user(sk, skb); 5213 } 5214 5215 #ifdef CONFIG_NET_DMA 5216 static int tcp_dma_try_early_copy(struct sock *sk, struct sk_buff *skb, 5217 int hlen) 5218 { 5219 struct tcp_sock *tp = tcp_sk(sk); 5220 int chunk = skb->len - hlen; 5221 int dma_cookie; 5222 int copied_early = 0; 5223 5224 if (tp->ucopy.wakeup) 5225 return 0; 5226 5227 if (!tp->ucopy.dma_chan && tp->ucopy.pinned_list) 5228 tp->ucopy.dma_chan = dma_find_channel(DMA_MEMCPY); 5229 5230 if (tp->ucopy.dma_chan && skb_csum_unnecessary(skb)) { 5231 5232 dma_cookie = dma_skb_copy_datagram_iovec(tp->ucopy.dma_chan, 5233 skb, hlen, 5234 tp->ucopy.iov, chunk, 5235 tp->ucopy.pinned_list); 5236 5237 if (dma_cookie < 0) 5238 goto out; 5239 5240 tp->ucopy.dma_cookie = dma_cookie; 5241 copied_early = 1; 5242 5243 tp->ucopy.len -= chunk; 5244 tp->copied_seq += chunk; 5245 tcp_rcv_space_adjust(sk); 5246 5247 if ((tp->ucopy.len == 0) || 5248 (tcp_flag_word(tcp_hdr(skb)) & TCP_FLAG_PSH) || 5249 (atomic_read(&sk->sk_rmem_alloc) > (sk->sk_rcvbuf >> 1))) { 5250 tp->ucopy.wakeup = 1; 5251 sk->sk_data_ready(sk, 0); 5252 } 5253 } else if (chunk > 0) { 5254 tp->ucopy.wakeup = 1; 5255 sk->sk_data_ready(sk, 0); 5256 } 5257 out: 5258 return copied_early; 5259 } 5260 #endif /* CONFIG_NET_DMA */ 5261 5262 /* Does PAWS and seqno based validation of an incoming segment, flags will 5263 * play significant role here. 5264 */ 5265 static int tcp_validate_incoming(struct sock *sk, struct sk_buff *skb, 5266 const struct tcphdr *th, int syn_inerr) 5267 { 5268 const u8 *hash_location; 5269 struct tcp_sock *tp = tcp_sk(sk); 5270 5271 /* RFC1323: H1. Apply PAWS check first. */ 5272 if (tcp_fast_parse_options(skb, th, tp, &hash_location) && 5273 tp->rx_opt.saw_tstamp && 5274 tcp_paws_discard(sk, skb)) { 5275 if (!th->rst) { 5276 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSESTABREJECTED); 5277 tcp_send_dupack(sk, skb); 5278 goto discard; 5279 } 5280 /* Reset is accepted even if it did not pass PAWS. */ 5281 } 5282 5283 /* Step 1: check sequence number */ 5284 if (!tcp_sequence(tp, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq)) { 5285 /* RFC793, page 37: "In all states except SYN-SENT, all reset 5286 * (RST) segments are validated by checking their SEQ-fields." 5287 * And page 69: "If an incoming segment is not acceptable, 5288 * an acknowledgment should be sent in reply (unless the RST 5289 * bit is set, if so drop the segment and return)". 5290 */ 5291 if (!th->rst) 5292 tcp_send_dupack(sk, skb); 5293 goto discard; 5294 } 5295 5296 /* Step 2: check RST bit */ 5297 if (th->rst) { 5298 tcp_reset(sk); 5299 goto discard; 5300 } 5301 5302 /* ts_recent update must be made after we are sure that the packet 5303 * is in window. 5304 */ 5305 tcp_replace_ts_recent(tp, TCP_SKB_CB(skb)->seq); 5306 5307 /* step 3: check security and precedence [ignored] */ 5308 5309 /* step 4: Check for a SYN in window. */ 5310 if (th->syn && !before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) { 5311 if (syn_inerr) 5312 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); 5313 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONSYN); 5314 tcp_reset(sk); 5315 return -1; 5316 } 5317 5318 return 1; 5319 5320 discard: 5321 __kfree_skb(skb); 5322 return 0; 5323 } 5324 5325 /* 5326 * TCP receive function for the ESTABLISHED state. 5327 * 5328 * It is split into a fast path and a slow path. The fast path is 5329 * disabled when: 5330 * - A zero window was announced from us - zero window probing 5331 * is only handled properly in the slow path. 5332 * - Out of order segments arrived. 5333 * - Urgent data is expected. 5334 * - There is no buffer space left 5335 * - Unexpected TCP flags/window values/header lengths are received 5336 * (detected by checking the TCP header against pred_flags) 5337 * - Data is sent in both directions. Fast path only supports pure senders 5338 * or pure receivers (this means either the sequence number or the ack 5339 * value must stay constant) 5340 * - Unexpected TCP option. 5341 * 5342 * When these conditions are not satisfied it drops into a standard 5343 * receive procedure patterned after RFC793 to handle all cases. 5344 * The first three cases are guaranteed by proper pred_flags setting, 5345 * the rest is checked inline. Fast processing is turned on in 5346 * tcp_data_queue when everything is OK. 5347 */ 5348 int tcp_rcv_established(struct sock *sk, struct sk_buff *skb, 5349 const struct tcphdr *th, unsigned int len) 5350 { 5351 struct tcp_sock *tp = tcp_sk(sk); 5352 int res; 5353 5354 /* 5355 * Header prediction. 5356 * The code loosely follows the one in the famous 5357 * "30 instruction TCP receive" Van Jacobson mail. 5358 * 5359 * Van's trick is to deposit buffers into socket queue 5360 * on a device interrupt, to call tcp_recv function 5361 * on the receive process context and checksum and copy 5362 * the buffer to user space. smart... 5363 * 5364 * Our current scheme is not silly either but we take the 5365 * extra cost of the net_bh soft interrupt processing... 5366 * We do checksum and copy also but from device to kernel. 5367 */ 5368 5369 tp->rx_opt.saw_tstamp = 0; 5370 5371 /* pred_flags is 0xS?10 << 16 + snd_wnd 5372 * if header_prediction is to be made 5373 * 'S' will always be tp->tcp_header_len >> 2 5374 * '?' will be 0 for the fast path, otherwise pred_flags is 0 to 5375 * turn it off (when there are holes in the receive 5376 * space for instance) 5377 * PSH flag is ignored. 5378 */ 5379 5380 if ((tcp_flag_word(th) & TCP_HP_BITS) == tp->pred_flags && 5381 TCP_SKB_CB(skb)->seq == tp->rcv_nxt && 5382 !after(TCP_SKB_CB(skb)->ack_seq, tp->snd_nxt)) { 5383 int tcp_header_len = tp->tcp_header_len; 5384 5385 /* Timestamp header prediction: tcp_header_len 5386 * is automatically equal to th->doff*4 due to pred_flags 5387 * match. 5388 */ 5389 5390 /* Check timestamp */ 5391 if (tcp_header_len == sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) { 5392 /* No? Slow path! */ 5393 if (!tcp_parse_aligned_timestamp(tp, th)) 5394 goto slow_path; 5395 5396 /* If PAWS failed, check it more carefully in slow path */ 5397 if ((s32)(tp->rx_opt.rcv_tsval - tp->rx_opt.ts_recent) < 0) 5398 goto slow_path; 5399 5400 /* DO NOT update ts_recent here, if checksum fails 5401 * and timestamp was corrupted part, it will result 5402 * in a hung connection since we will drop all 5403 * future packets due to the PAWS test. 5404 */ 5405 } 5406 5407 if (len <= tcp_header_len) { 5408 /* Bulk data transfer: sender */ 5409 if (len == tcp_header_len) { 5410 /* Predicted packet is in window by definition. 5411 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 5412 * Hence, check seq<=rcv_wup reduces to: 5413 */ 5414 if (tcp_header_len == 5415 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 5416 tp->rcv_nxt == tp->rcv_wup) 5417 tcp_store_ts_recent(tp); 5418 5419 /* We know that such packets are checksummed 5420 * on entry. 5421 */ 5422 tcp_ack(sk, skb, 0); 5423 __kfree_skb(skb); 5424 tcp_data_snd_check(sk); 5425 return 0; 5426 } else { /* Header too small */ 5427 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); 5428 goto discard; 5429 } 5430 } else { 5431 int eaten = 0; 5432 int copied_early = 0; 5433 5434 if (tp->copied_seq == tp->rcv_nxt && 5435 len - tcp_header_len <= tp->ucopy.len) { 5436 #ifdef CONFIG_NET_DMA 5437 if (tcp_dma_try_early_copy(sk, skb, tcp_header_len)) { 5438 copied_early = 1; 5439 eaten = 1; 5440 } 5441 #endif 5442 if (tp->ucopy.task == current && 5443 sock_owned_by_user(sk) && !copied_early) { 5444 __set_current_state(TASK_RUNNING); 5445 5446 if (!tcp_copy_to_iovec(sk, skb, tcp_header_len)) 5447 eaten = 1; 5448 } 5449 if (eaten) { 5450 /* Predicted packet is in window by definition. 5451 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 5452 * Hence, check seq<=rcv_wup reduces to: 5453 */ 5454 if (tcp_header_len == 5455 (sizeof(struct tcphdr) + 5456 TCPOLEN_TSTAMP_ALIGNED) && 5457 tp->rcv_nxt == tp->rcv_wup) 5458 tcp_store_ts_recent(tp); 5459 5460 tcp_rcv_rtt_measure_ts(sk, skb); 5461 5462 __skb_pull(skb, tcp_header_len); 5463 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 5464 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITSTOUSER); 5465 } 5466 if (copied_early) 5467 tcp_cleanup_rbuf(sk, skb->len); 5468 } 5469 if (!eaten) { 5470 if (tcp_checksum_complete_user(sk, skb)) 5471 goto csum_error; 5472 5473 /* Predicted packet is in window by definition. 5474 * seq == rcv_nxt and rcv_wup <= rcv_nxt. 5475 * Hence, check seq<=rcv_wup reduces to: 5476 */ 5477 if (tcp_header_len == 5478 (sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED) && 5479 tp->rcv_nxt == tp->rcv_wup) 5480 tcp_store_ts_recent(tp); 5481 5482 tcp_rcv_rtt_measure_ts(sk, skb); 5483 5484 if ((int)skb->truesize > sk->sk_forward_alloc) 5485 goto step5; 5486 5487 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPHITS); 5488 5489 /* Bulk data transfer: receiver */ 5490 __skb_pull(skb, tcp_header_len); 5491 __skb_queue_tail(&sk->sk_receive_queue, skb); 5492 skb_set_owner_r(skb, sk); 5493 tp->rcv_nxt = TCP_SKB_CB(skb)->end_seq; 5494 } 5495 5496 tcp_event_data_recv(sk, skb); 5497 5498 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_una) { 5499 /* Well, only one small jumplet in fast path... */ 5500 tcp_ack(sk, skb, FLAG_DATA); 5501 tcp_data_snd_check(sk); 5502 if (!inet_csk_ack_scheduled(sk)) 5503 goto no_ack; 5504 } 5505 5506 if (!copied_early || tp->rcv_nxt != tp->rcv_wup) 5507 __tcp_ack_snd_check(sk, 0); 5508 no_ack: 5509 #ifdef CONFIG_NET_DMA 5510 if (copied_early) 5511 __skb_queue_tail(&sk->sk_async_wait_queue, skb); 5512 else 5513 #endif 5514 if (eaten) 5515 __kfree_skb(skb); 5516 else 5517 sk->sk_data_ready(sk, 0); 5518 return 0; 5519 } 5520 } 5521 5522 slow_path: 5523 if (len < (th->doff << 2) || tcp_checksum_complete_user(sk, skb)) 5524 goto csum_error; 5525 5526 /* 5527 * Standard slow path. 5528 */ 5529 5530 res = tcp_validate_incoming(sk, skb, th, 1); 5531 if (res <= 0) 5532 return -res; 5533 5534 step5: 5535 if (th->ack && tcp_ack(sk, skb, FLAG_SLOWPATH) < 0) 5536 goto discard; 5537 5538 tcp_rcv_rtt_measure_ts(sk, skb); 5539 5540 /* Process urgent data. */ 5541 tcp_urg(sk, skb, th); 5542 5543 /* step 7: process the segment text */ 5544 tcp_data_queue(sk, skb); 5545 5546 tcp_data_snd_check(sk); 5547 tcp_ack_snd_check(sk); 5548 return 0; 5549 5550 csum_error: 5551 TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS); 5552 5553 discard: 5554 __kfree_skb(skb); 5555 return 0; 5556 } 5557 EXPORT_SYMBOL(tcp_rcv_established); 5558 5559 static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb, 5560 const struct tcphdr *th, unsigned int len) 5561 { 5562 const u8 *hash_location; 5563 struct inet_connection_sock *icsk = inet_csk(sk); 5564 struct tcp_sock *tp = tcp_sk(sk); 5565 struct tcp_cookie_values *cvp = tp->cookie_values; 5566 int saved_clamp = tp->rx_opt.mss_clamp; 5567 5568 tcp_parse_options(skb, &tp->rx_opt, &hash_location, 0); 5569 5570 if (th->ack) { 5571 /* rfc793: 5572 * "If the state is SYN-SENT then 5573 * first check the ACK bit 5574 * If the ACK bit is set 5575 * If SEG.ACK =< ISS, or SEG.ACK > SND.NXT, send 5576 * a reset (unless the RST bit is set, if so drop 5577 * the segment and return)" 5578 * 5579 * We do not send data with SYN, so that RFC-correct 5580 * test reduces to: 5581 */ 5582 if (TCP_SKB_CB(skb)->ack_seq != tp->snd_nxt) 5583 goto reset_and_undo; 5584 5585 if (tp->rx_opt.saw_tstamp && tp->rx_opt.rcv_tsecr && 5586 !between(tp->rx_opt.rcv_tsecr, tp->retrans_stamp, 5587 tcp_time_stamp)) { 5588 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_PAWSACTIVEREJECTED); 5589 goto reset_and_undo; 5590 } 5591 5592 /* Now ACK is acceptable. 5593 * 5594 * "If the RST bit is set 5595 * If the ACK was acceptable then signal the user "error: 5596 * connection reset", drop the segment, enter CLOSED state, 5597 * delete TCB, and return." 5598 */ 5599 5600 if (th->rst) { 5601 tcp_reset(sk); 5602 goto discard; 5603 } 5604 5605 /* rfc793: 5606 * "fifth, if neither of the SYN or RST bits is set then 5607 * drop the segment and return." 5608 * 5609 * See note below! 5610 * --ANK(990513) 5611 */ 5612 if (!th->syn) 5613 goto discard_and_undo; 5614 5615 /* rfc793: 5616 * "If the SYN bit is on ... 5617 * are acceptable then ... 5618 * (our SYN has been ACKed), change the connection 5619 * state to ESTABLISHED..." 5620 */ 5621 5622 TCP_ECN_rcv_synack(tp, th); 5623 5624 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 5625 tcp_ack(sk, skb, FLAG_SLOWPATH); 5626 5627 /* Ok.. it's good. Set up sequence numbers and 5628 * move to established. 5629 */ 5630 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 5631 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 5632 5633 /* RFC1323: The window in SYN & SYN/ACK segments is 5634 * never scaled. 5635 */ 5636 tp->snd_wnd = ntohs(th->window); 5637 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); 5638 5639 if (!tp->rx_opt.wscale_ok) { 5640 tp->rx_opt.snd_wscale = tp->rx_opt.rcv_wscale = 0; 5641 tp->window_clamp = min(tp->window_clamp, 65535U); 5642 } 5643 5644 if (tp->rx_opt.saw_tstamp) { 5645 tp->rx_opt.tstamp_ok = 1; 5646 tp->tcp_header_len = 5647 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 5648 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 5649 tcp_store_ts_recent(tp); 5650 } else { 5651 tp->tcp_header_len = sizeof(struct tcphdr); 5652 } 5653 5654 if (tcp_is_sack(tp) && sysctl_tcp_fack) 5655 tcp_enable_fack(tp); 5656 5657 tcp_mtup_init(sk); 5658 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 5659 tcp_initialize_rcv_mss(sk); 5660 5661 /* Remember, tcp_poll() does not lock socket! 5662 * Change state from SYN-SENT only after copied_seq 5663 * is initialized. */ 5664 tp->copied_seq = tp->rcv_nxt; 5665 5666 if (cvp != NULL && 5667 cvp->cookie_pair_size > 0 && 5668 tp->rx_opt.cookie_plus > 0) { 5669 int cookie_size = tp->rx_opt.cookie_plus 5670 - TCPOLEN_COOKIE_BASE; 5671 int cookie_pair_size = cookie_size 5672 + cvp->cookie_desired; 5673 5674 /* A cookie extension option was sent and returned. 5675 * Note that each incoming SYNACK replaces the 5676 * Responder cookie. The initial exchange is most 5677 * fragile, as protection against spoofing relies 5678 * entirely upon the sequence and timestamp (above). 5679 * This replacement strategy allows the correct pair to 5680 * pass through, while any others will be filtered via 5681 * Responder verification later. 5682 */ 5683 if (sizeof(cvp->cookie_pair) >= cookie_pair_size) { 5684 memcpy(&cvp->cookie_pair[cvp->cookie_desired], 5685 hash_location, cookie_size); 5686 cvp->cookie_pair_size = cookie_pair_size; 5687 } 5688 } 5689 5690 smp_mb(); 5691 tcp_set_state(sk, TCP_ESTABLISHED); 5692 5693 security_inet_conn_established(sk, skb); 5694 5695 /* Make sure socket is routed, for correct metrics. */ 5696 icsk->icsk_af_ops->rebuild_header(sk); 5697 5698 tcp_init_metrics(sk); 5699 5700 tcp_init_congestion_control(sk); 5701 5702 /* Prevent spurious tcp_cwnd_restart() on first data 5703 * packet. 5704 */ 5705 tp->lsndtime = tcp_time_stamp; 5706 5707 tcp_init_buffer_space(sk); 5708 5709 if (sock_flag(sk, SOCK_KEEPOPEN)) 5710 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tp)); 5711 5712 if (!tp->rx_opt.snd_wscale) 5713 __tcp_fast_path_on(tp, tp->snd_wnd); 5714 else 5715 tp->pred_flags = 0; 5716 5717 if (!sock_flag(sk, SOCK_DEAD)) { 5718 sk->sk_state_change(sk); 5719 sk_wake_async(sk, SOCK_WAKE_IO, POLL_OUT); 5720 } 5721 5722 if (sk->sk_write_pending || 5723 icsk->icsk_accept_queue.rskq_defer_accept || 5724 icsk->icsk_ack.pingpong) { 5725 /* Save one ACK. Data will be ready after 5726 * several ticks, if write_pending is set. 5727 * 5728 * It may be deleted, but with this feature tcpdumps 5729 * look so _wonderfully_ clever, that I was not able 5730 * to stand against the temptation 8) --ANK 5731 */ 5732 inet_csk_schedule_ack(sk); 5733 icsk->icsk_ack.lrcvtime = tcp_time_stamp; 5734 icsk->icsk_ack.ato = TCP_ATO_MIN; 5735 tcp_incr_quickack(sk); 5736 tcp_enter_quickack_mode(sk); 5737 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 5738 TCP_DELACK_MAX, TCP_RTO_MAX); 5739 5740 discard: 5741 __kfree_skb(skb); 5742 return 0; 5743 } else { 5744 tcp_send_ack(sk); 5745 } 5746 return -1; 5747 } 5748 5749 /* No ACK in the segment */ 5750 5751 if (th->rst) { 5752 /* rfc793: 5753 * "If the RST bit is set 5754 * 5755 * Otherwise (no ACK) drop the segment and return." 5756 */ 5757 5758 goto discard_and_undo; 5759 } 5760 5761 /* PAWS check. */ 5762 if (tp->rx_opt.ts_recent_stamp && tp->rx_opt.saw_tstamp && 5763 tcp_paws_reject(&tp->rx_opt, 0)) 5764 goto discard_and_undo; 5765 5766 if (th->syn) { 5767 /* We see SYN without ACK. It is attempt of 5768 * simultaneous connect with crossed SYNs. 5769 * Particularly, it can be connect to self. 5770 */ 5771 tcp_set_state(sk, TCP_SYN_RECV); 5772 5773 if (tp->rx_opt.saw_tstamp) { 5774 tp->rx_opt.tstamp_ok = 1; 5775 tcp_store_ts_recent(tp); 5776 tp->tcp_header_len = 5777 sizeof(struct tcphdr) + TCPOLEN_TSTAMP_ALIGNED; 5778 } else { 5779 tp->tcp_header_len = sizeof(struct tcphdr); 5780 } 5781 5782 tp->rcv_nxt = TCP_SKB_CB(skb)->seq + 1; 5783 tp->rcv_wup = TCP_SKB_CB(skb)->seq + 1; 5784 5785 /* RFC1323: The window in SYN & SYN/ACK segments is 5786 * never scaled. 5787 */ 5788 tp->snd_wnd = ntohs(th->window); 5789 tp->snd_wl1 = TCP_SKB_CB(skb)->seq; 5790 tp->max_window = tp->snd_wnd; 5791 5792 TCP_ECN_rcv_syn(tp, th); 5793 5794 tcp_mtup_init(sk); 5795 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 5796 tcp_initialize_rcv_mss(sk); 5797 5798 tcp_send_synack(sk); 5799 #if 0 5800 /* Note, we could accept data and URG from this segment. 5801 * There are no obstacles to make this. 5802 * 5803 * However, if we ignore data in ACKless segments sometimes, 5804 * we have no reasons to accept it sometimes. 5805 * Also, seems the code doing it in step6 of tcp_rcv_state_process 5806 * is not flawless. So, discard packet for sanity. 5807 * Uncomment this return to process the data. 5808 */ 5809 return -1; 5810 #else 5811 goto discard; 5812 #endif 5813 } 5814 /* "fifth, if neither of the SYN or RST bits is set then 5815 * drop the segment and return." 5816 */ 5817 5818 discard_and_undo: 5819 tcp_clear_options(&tp->rx_opt); 5820 tp->rx_opt.mss_clamp = saved_clamp; 5821 goto discard; 5822 5823 reset_and_undo: 5824 tcp_clear_options(&tp->rx_opt); 5825 tp->rx_opt.mss_clamp = saved_clamp; 5826 return 1; 5827 } 5828 5829 /* 5830 * This function implements the receiving procedure of RFC 793 for 5831 * all states except ESTABLISHED and TIME_WAIT. 5832 * It's called from both tcp_v4_rcv and tcp_v6_rcv and should be 5833 * address independent. 5834 */ 5835 5836 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb, 5837 const struct tcphdr *th, unsigned int len) 5838 { 5839 struct tcp_sock *tp = tcp_sk(sk); 5840 struct inet_connection_sock *icsk = inet_csk(sk); 5841 int queued = 0; 5842 int res; 5843 5844 tp->rx_opt.saw_tstamp = 0; 5845 5846 switch (sk->sk_state) { 5847 case TCP_CLOSE: 5848 goto discard; 5849 5850 case TCP_LISTEN: 5851 if (th->ack) 5852 return 1; 5853 5854 if (th->rst) 5855 goto discard; 5856 5857 if (th->syn) { 5858 if (th->fin) 5859 goto discard; 5860 if (icsk->icsk_af_ops->conn_request(sk, skb) < 0) 5861 return 1; 5862 5863 /* Now we have several options: In theory there is 5864 * nothing else in the frame. KA9Q has an option to 5865 * send data with the syn, BSD accepts data with the 5866 * syn up to the [to be] advertised window and 5867 * Solaris 2.1 gives you a protocol error. For now 5868 * we just ignore it, that fits the spec precisely 5869 * and avoids incompatibilities. It would be nice in 5870 * future to drop through and process the data. 5871 * 5872 * Now that TTCP is starting to be used we ought to 5873 * queue this data. 5874 * But, this leaves one open to an easy denial of 5875 * service attack, and SYN cookies can't defend 5876 * against this problem. So, we drop the data 5877 * in the interest of security over speed unless 5878 * it's still in use. 5879 */ 5880 kfree_skb(skb); 5881 return 0; 5882 } 5883 goto discard; 5884 5885 case TCP_SYN_SENT: 5886 queued = tcp_rcv_synsent_state_process(sk, skb, th, len); 5887 if (queued >= 0) 5888 return queued; 5889 5890 /* Do step6 onward by hand. */ 5891 tcp_urg(sk, skb, th); 5892 __kfree_skb(skb); 5893 tcp_data_snd_check(sk); 5894 return 0; 5895 } 5896 5897 res = tcp_validate_incoming(sk, skb, th, 0); 5898 if (res <= 0) 5899 return -res; 5900 5901 /* step 5: check the ACK field */ 5902 if (th->ack) { 5903 int acceptable = tcp_ack(sk, skb, FLAG_SLOWPATH) > 0; 5904 5905 switch (sk->sk_state) { 5906 case TCP_SYN_RECV: 5907 if (acceptable) { 5908 tp->copied_seq = tp->rcv_nxt; 5909 smp_mb(); 5910 tcp_set_state(sk, TCP_ESTABLISHED); 5911 sk->sk_state_change(sk); 5912 5913 /* Note, that this wakeup is only for marginal 5914 * crossed SYN case. Passively open sockets 5915 * are not waked up, because sk->sk_sleep == 5916 * NULL and sk->sk_socket == NULL. 5917 */ 5918 if (sk->sk_socket) 5919 sk_wake_async(sk, 5920 SOCK_WAKE_IO, POLL_OUT); 5921 5922 tp->snd_una = TCP_SKB_CB(skb)->ack_seq; 5923 tp->snd_wnd = ntohs(th->window) << 5924 tp->rx_opt.snd_wscale; 5925 tcp_init_wl(tp, TCP_SKB_CB(skb)->seq); 5926 5927 if (tp->rx_opt.tstamp_ok) 5928 tp->advmss -= TCPOLEN_TSTAMP_ALIGNED; 5929 5930 /* Make sure socket is routed, for 5931 * correct metrics. 5932 */ 5933 icsk->icsk_af_ops->rebuild_header(sk); 5934 5935 tcp_init_metrics(sk); 5936 5937 tcp_init_congestion_control(sk); 5938 5939 /* Prevent spurious tcp_cwnd_restart() on 5940 * first data packet. 5941 */ 5942 tp->lsndtime = tcp_time_stamp; 5943 5944 tcp_mtup_init(sk); 5945 tcp_initialize_rcv_mss(sk); 5946 tcp_init_buffer_space(sk); 5947 tcp_fast_path_on(tp); 5948 } else { 5949 return 1; 5950 } 5951 break; 5952 5953 case TCP_FIN_WAIT1: 5954 if (tp->snd_una == tp->write_seq) { 5955 tcp_set_state(sk, TCP_FIN_WAIT2); 5956 sk->sk_shutdown |= SEND_SHUTDOWN; 5957 dst_confirm(__sk_dst_get(sk)); 5958 5959 if (!sock_flag(sk, SOCK_DEAD)) 5960 /* Wake up lingering close() */ 5961 sk->sk_state_change(sk); 5962 else { 5963 int tmo; 5964 5965 if (tp->linger2 < 0 || 5966 (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 5967 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt))) { 5968 tcp_done(sk); 5969 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA); 5970 return 1; 5971 } 5972 5973 tmo = tcp_fin_time(sk); 5974 if (tmo > TCP_TIMEWAIT_LEN) { 5975 inet_csk_reset_keepalive_timer(sk, tmo - TCP_TIMEWAIT_LEN); 5976 } else if (th->fin || sock_owned_by_user(sk)) { 5977 /* Bad case. We could lose such FIN otherwise. 5978 * It is not a big problem, but it looks confusing 5979 * and not so rare event. We still can lose it now, 5980 * if it spins in bh_lock_sock(), but it is really 5981 * marginal case. 5982 */ 5983 inet_csk_reset_keepalive_timer(sk, tmo); 5984 } else { 5985 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 5986 goto discard; 5987 } 5988 } 5989 } 5990 break; 5991 5992 case TCP_CLOSING: 5993 if (tp->snd_una == tp->write_seq) { 5994 tcp_time_wait(sk, TCP_TIME_WAIT, 0); 5995 goto discard; 5996 } 5997 break; 5998 5999 case TCP_LAST_ACK: 6000 if (tp->snd_una == tp->write_seq) { 6001 tcp_update_metrics(sk); 6002 tcp_done(sk); 6003 goto discard; 6004 } 6005 break; 6006 } 6007 } else 6008 goto discard; 6009 6010 /* step 6: check the URG bit */ 6011 tcp_urg(sk, skb, th); 6012 6013 /* step 7: process the segment text */ 6014 switch (sk->sk_state) { 6015 case TCP_CLOSE_WAIT: 6016 case TCP_CLOSING: 6017 case TCP_LAST_ACK: 6018 if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) 6019 break; 6020 case TCP_FIN_WAIT1: 6021 case TCP_FIN_WAIT2: 6022 /* RFC 793 says to queue data in these states, 6023 * RFC 1122 says we MUST send a reset. 6024 * BSD 4.4 also does reset. 6025 */ 6026 if (sk->sk_shutdown & RCV_SHUTDOWN) { 6027 if (TCP_SKB_CB(skb)->end_seq != TCP_SKB_CB(skb)->seq && 6028 after(TCP_SKB_CB(skb)->end_seq - th->fin, tp->rcv_nxt)) { 6029 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPABORTONDATA); 6030 tcp_reset(sk); 6031 return 1; 6032 } 6033 } 6034 /* Fall through */ 6035 case TCP_ESTABLISHED: 6036 tcp_data_queue(sk, skb); 6037 queued = 1; 6038 break; 6039 } 6040 6041 /* tcp_data could move socket to TIME-WAIT */ 6042 if (sk->sk_state != TCP_CLOSE) { 6043 tcp_data_snd_check(sk); 6044 tcp_ack_snd_check(sk); 6045 } 6046 6047 if (!queued) { 6048 discard: 6049 __kfree_skb(skb); 6050 } 6051 return 0; 6052 } 6053 EXPORT_SYMBOL(tcp_rcv_state_process); 6054