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: Pedro Roque : Retransmit queue handled by TCP. 23 * : Fragmentation on mtu decrease 24 * : Segment collapse on retransmit 25 * : AF independence 26 * 27 * Linus Torvalds : send_delayed_ack 28 * David S. Miller : Charge memory using the right skb 29 * during syn/ack processing. 30 * David S. Miller : Output engine completely rewritten. 31 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr. 32 * Cacophonix Gaul : draft-minshall-nagle-01 33 * J Hadi Salim : ECN support 34 * 35 */ 36 37 #include <net/tcp.h> 38 39 #include <linux/compiler.h> 40 #include <linux/module.h> 41 42 /* People can turn this off for buggy TCP's found in printers etc. */ 43 int sysctl_tcp_retrans_collapse __read_mostly = 1; 44 45 /* People can turn this on to work with those rare, broken TCPs that 46 * interpret the window field as a signed quantity. 47 */ 48 int sysctl_tcp_workaround_signed_windows __read_mostly = 0; 49 50 /* This limits the percentage of the congestion window which we 51 * will allow a single TSO frame to consume. Building TSO frames 52 * which are too large can cause TCP streams to be bursty. 53 */ 54 int sysctl_tcp_tso_win_divisor __read_mostly = 3; 55 56 int sysctl_tcp_mtu_probing __read_mostly = 0; 57 int sysctl_tcp_base_mss __read_mostly = 512; 58 59 /* By default, RFC2861 behavior. */ 60 int sysctl_tcp_slow_start_after_idle __read_mostly = 1; 61 62 static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb) 63 { 64 struct tcp_sock *tp = tcp_sk(sk); 65 unsigned int prior_packets = tp->packets_out; 66 67 tcp_advance_send_head(sk, skb); 68 tp->snd_nxt = TCP_SKB_CB(skb)->end_seq; 69 70 /* Don't override Nagle indefinately with F-RTO */ 71 if (tp->frto_counter == 2) 72 tp->frto_counter = 3; 73 74 tp->packets_out += tcp_skb_pcount(skb); 75 if (!prior_packets) 76 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 77 inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 78 } 79 80 /* SND.NXT, if window was not shrunk. 81 * If window has been shrunk, what should we make? It is not clear at all. 82 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-( 83 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already 84 * invalid. OK, let's make this for now: 85 */ 86 static inline __u32 tcp_acceptable_seq(struct sock *sk) 87 { 88 struct tcp_sock *tp = tcp_sk(sk); 89 90 if (!before(tcp_wnd_end(tp), tp->snd_nxt)) 91 return tp->snd_nxt; 92 else 93 return tcp_wnd_end(tp); 94 } 95 96 /* Calculate mss to advertise in SYN segment. 97 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that: 98 * 99 * 1. It is independent of path mtu. 100 * 2. Ideally, it is maximal possible segment size i.e. 65535-40. 101 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of 102 * attached devices, because some buggy hosts are confused by 103 * large MSS. 104 * 4. We do not make 3, we advertise MSS, calculated from first 105 * hop device mtu, but allow to raise it to ip_rt_min_advmss. 106 * This may be overridden via information stored in routing table. 107 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible, 108 * probably even Jumbo". 109 */ 110 static __u16 tcp_advertise_mss(struct sock *sk) 111 { 112 struct tcp_sock *tp = tcp_sk(sk); 113 struct dst_entry *dst = __sk_dst_get(sk); 114 int mss = tp->advmss; 115 116 if (dst && dst_metric(dst, RTAX_ADVMSS) < mss) { 117 mss = dst_metric(dst, RTAX_ADVMSS); 118 tp->advmss = mss; 119 } 120 121 return (__u16)mss; 122 } 123 124 /* RFC2861. Reset CWND after idle period longer RTO to "restart window". 125 * This is the first part of cwnd validation mechanism. */ 126 static void tcp_cwnd_restart(struct sock *sk, struct dst_entry *dst) 127 { 128 struct tcp_sock *tp = tcp_sk(sk); 129 s32 delta = tcp_time_stamp - tp->lsndtime; 130 u32 restart_cwnd = tcp_init_cwnd(tp, dst); 131 u32 cwnd = tp->snd_cwnd; 132 133 tcp_ca_event(sk, CA_EVENT_CWND_RESTART); 134 135 tp->snd_ssthresh = tcp_current_ssthresh(sk); 136 restart_cwnd = min(restart_cwnd, cwnd); 137 138 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd) 139 cwnd >>= 1; 140 tp->snd_cwnd = max(cwnd, restart_cwnd); 141 tp->snd_cwnd_stamp = tcp_time_stamp; 142 tp->snd_cwnd_used = 0; 143 } 144 145 static void tcp_event_data_sent(struct tcp_sock *tp, 146 struct sk_buff *skb, struct sock *sk) 147 { 148 struct inet_connection_sock *icsk = inet_csk(sk); 149 const u32 now = tcp_time_stamp; 150 151 if (sysctl_tcp_slow_start_after_idle && 152 (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto)) 153 tcp_cwnd_restart(sk, __sk_dst_get(sk)); 154 155 tp->lsndtime = now; 156 157 /* If it is a reply for ato after last received 158 * packet, enter pingpong mode. 159 */ 160 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato) 161 icsk->icsk_ack.pingpong = 1; 162 } 163 164 static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts) 165 { 166 tcp_dec_quickack_mode(sk, pkts); 167 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK); 168 } 169 170 /* Determine a window scaling and initial window to offer. 171 * Based on the assumption that the given amount of space 172 * will be offered. Store the results in the tp structure. 173 * NOTE: for smooth operation initial space offering should 174 * be a multiple of mss if possible. We assume here that mss >= 1. 175 * This MUST be enforced by all callers. 176 */ 177 void tcp_select_initial_window(int __space, __u32 mss, 178 __u32 *rcv_wnd, __u32 *window_clamp, 179 int wscale_ok, __u8 *rcv_wscale) 180 { 181 unsigned int space = (__space < 0 ? 0 : __space); 182 183 /* If no clamp set the clamp to the max possible scaled window */ 184 if (*window_clamp == 0) 185 (*window_clamp) = (65535 << 14); 186 space = min(*window_clamp, space); 187 188 /* Quantize space offering to a multiple of mss if possible. */ 189 if (space > mss) 190 space = (space / mss) * mss; 191 192 /* NOTE: offering an initial window larger than 32767 193 * will break some buggy TCP stacks. If the admin tells us 194 * it is likely we could be speaking with such a buggy stack 195 * we will truncate our initial window offering to 32K-1 196 * unless the remote has sent us a window scaling option, 197 * which we interpret as a sign the remote TCP is not 198 * misinterpreting the window field as a signed quantity. 199 */ 200 if (sysctl_tcp_workaround_signed_windows) 201 (*rcv_wnd) = min(space, MAX_TCP_WINDOW); 202 else 203 (*rcv_wnd) = space; 204 205 (*rcv_wscale) = 0; 206 if (wscale_ok) { 207 /* Set window scaling on max possible window 208 * See RFC1323 for an explanation of the limit to 14 209 */ 210 space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max); 211 space = min_t(u32, space, *window_clamp); 212 while (space > 65535 && (*rcv_wscale) < 14) { 213 space >>= 1; 214 (*rcv_wscale)++; 215 } 216 } 217 218 /* Set initial window to value enough for senders, 219 * following RFC2414. Senders, not following this RFC, 220 * will be satisfied with 2. 221 */ 222 if (mss > (1 << *rcv_wscale)) { 223 int init_cwnd = 4; 224 if (mss > 1460 * 3) 225 init_cwnd = 2; 226 else if (mss > 1460) 227 init_cwnd = 3; 228 if (*rcv_wnd > init_cwnd * mss) 229 *rcv_wnd = init_cwnd * mss; 230 } 231 232 /* Set the clamp no higher than max representable value */ 233 (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp); 234 } 235 236 /* Chose a new window to advertise, update state in tcp_sock for the 237 * socket, and return result with RFC1323 scaling applied. The return 238 * value can be stuffed directly into th->window for an outgoing 239 * frame. 240 */ 241 static u16 tcp_select_window(struct sock *sk) 242 { 243 struct tcp_sock *tp = tcp_sk(sk); 244 u32 cur_win = tcp_receive_window(tp); 245 u32 new_win = __tcp_select_window(sk); 246 247 /* Never shrink the offered window */ 248 if (new_win < cur_win) { 249 /* Danger Will Robinson! 250 * Don't update rcv_wup/rcv_wnd here or else 251 * we will not be able to advertise a zero 252 * window in time. --DaveM 253 * 254 * Relax Will Robinson. 255 */ 256 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale); 257 } 258 tp->rcv_wnd = new_win; 259 tp->rcv_wup = tp->rcv_nxt; 260 261 /* Make sure we do not exceed the maximum possible 262 * scaled window. 263 */ 264 if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows) 265 new_win = min(new_win, MAX_TCP_WINDOW); 266 else 267 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); 268 269 /* RFC1323 scaling applied */ 270 new_win >>= tp->rx_opt.rcv_wscale; 271 272 /* If we advertise zero window, disable fast path. */ 273 if (new_win == 0) 274 tp->pred_flags = 0; 275 276 return new_win; 277 } 278 279 static inline void TCP_ECN_send_synack(struct tcp_sock *tp, struct sk_buff *skb) 280 { 281 TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_CWR; 282 if (!(tp->ecn_flags & TCP_ECN_OK)) 283 TCP_SKB_CB(skb)->flags &= ~TCPCB_FLAG_ECE; 284 } 285 286 static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb) 287 { 288 struct tcp_sock *tp = tcp_sk(sk); 289 290 tp->ecn_flags = 0; 291 if (sysctl_tcp_ecn) { 292 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ECE | TCPCB_FLAG_CWR; 293 tp->ecn_flags = TCP_ECN_OK; 294 } 295 } 296 297 static __inline__ void 298 TCP_ECN_make_synack(struct request_sock *req, struct tcphdr *th) 299 { 300 if (inet_rsk(req)->ecn_ok) 301 th->ece = 1; 302 } 303 304 static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb, 305 int tcp_header_len) 306 { 307 struct tcp_sock *tp = tcp_sk(sk); 308 309 if (tp->ecn_flags & TCP_ECN_OK) { 310 /* Not-retransmitted data segment: set ECT and inject CWR. */ 311 if (skb->len != tcp_header_len && 312 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) { 313 INET_ECN_xmit(sk); 314 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) { 315 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR; 316 tcp_hdr(skb)->cwr = 1; 317 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; 318 } 319 } else { 320 /* ACK or retransmitted segment: clear ECT|CE */ 321 INET_ECN_dontxmit(sk); 322 } 323 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR) 324 tcp_hdr(skb)->ece = 1; 325 } 326 } 327 328 /* Constructs common control bits of non-data skb. If SYN/FIN is present, 329 * auto increment end seqno. 330 */ 331 static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags) 332 { 333 skb->csum = 0; 334 335 TCP_SKB_CB(skb)->flags = flags; 336 TCP_SKB_CB(skb)->sacked = 0; 337 338 skb_shinfo(skb)->gso_segs = 1; 339 skb_shinfo(skb)->gso_size = 0; 340 skb_shinfo(skb)->gso_type = 0; 341 342 TCP_SKB_CB(skb)->seq = seq; 343 if (flags & (TCPCB_FLAG_SYN | TCPCB_FLAG_FIN)) 344 seq++; 345 TCP_SKB_CB(skb)->end_seq = seq; 346 } 347 348 #define OPTION_SACK_ADVERTISE (1 << 0) 349 #define OPTION_TS (1 << 1) 350 #define OPTION_MD5 (1 << 2) 351 352 struct tcp_out_options { 353 u8 options; /* bit field of OPTION_* */ 354 u8 ws; /* window scale, 0 to disable */ 355 u8 num_sack_blocks; /* number of SACK blocks to include */ 356 u16 mss; /* 0 to disable */ 357 __u32 tsval, tsecr; /* need to include OPTION_TS */ 358 }; 359 360 static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, 361 const struct tcp_out_options *opts, 362 __u8 **md5_hash) { 363 if (unlikely(OPTION_MD5 & opts->options)) { 364 *ptr++ = htonl((TCPOPT_NOP << 24) | 365 (TCPOPT_NOP << 16) | 366 (TCPOPT_MD5SIG << 8) | 367 TCPOLEN_MD5SIG); 368 *md5_hash = (__u8 *)ptr; 369 ptr += 4; 370 } else { 371 *md5_hash = NULL; 372 } 373 374 if (likely(OPTION_TS & opts->options)) { 375 if (unlikely(OPTION_SACK_ADVERTISE & opts->options)) { 376 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) | 377 (TCPOLEN_SACK_PERM << 16) | 378 (TCPOPT_TIMESTAMP << 8) | 379 TCPOLEN_TIMESTAMP); 380 } else { 381 *ptr++ = htonl((TCPOPT_NOP << 24) | 382 (TCPOPT_NOP << 16) | 383 (TCPOPT_TIMESTAMP << 8) | 384 TCPOLEN_TIMESTAMP); 385 } 386 *ptr++ = htonl(opts->tsval); 387 *ptr++ = htonl(opts->tsecr); 388 } 389 390 if (unlikely(opts->mss)) { 391 *ptr++ = htonl((TCPOPT_MSS << 24) | 392 (TCPOLEN_MSS << 16) | 393 opts->mss); 394 } 395 396 if (unlikely(OPTION_SACK_ADVERTISE & opts->options && 397 !(OPTION_TS & opts->options))) { 398 *ptr++ = htonl((TCPOPT_NOP << 24) | 399 (TCPOPT_NOP << 16) | 400 (TCPOPT_SACK_PERM << 8) | 401 TCPOLEN_SACK_PERM); 402 } 403 404 if (unlikely(opts->ws)) { 405 *ptr++ = htonl((TCPOPT_NOP << 24) | 406 (TCPOPT_WINDOW << 16) | 407 (TCPOLEN_WINDOW << 8) | 408 opts->ws); 409 } 410 411 if (unlikely(opts->num_sack_blocks)) { 412 struct tcp_sack_block *sp = tp->rx_opt.dsack ? 413 tp->duplicate_sack : tp->selective_acks; 414 int this_sack; 415 416 *ptr++ = htonl((TCPOPT_NOP << 24) | 417 (TCPOPT_NOP << 16) | 418 (TCPOPT_SACK << 8) | 419 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks * 420 TCPOLEN_SACK_PERBLOCK))); 421 422 for (this_sack = 0; this_sack < opts->num_sack_blocks; 423 ++this_sack) { 424 *ptr++ = htonl(sp[this_sack].start_seq); 425 *ptr++ = htonl(sp[this_sack].end_seq); 426 } 427 428 if (tp->rx_opt.dsack) { 429 tp->rx_opt.dsack = 0; 430 tp->rx_opt.eff_sacks--; 431 } 432 } 433 } 434 435 static unsigned tcp_syn_options(struct sock *sk, struct sk_buff *skb, 436 struct tcp_out_options *opts, 437 struct tcp_md5sig_key **md5) { 438 struct tcp_sock *tp = tcp_sk(sk); 439 unsigned size = 0; 440 441 #ifdef CONFIG_TCP_MD5SIG 442 *md5 = tp->af_specific->md5_lookup(sk, sk); 443 if (*md5) { 444 opts->options |= OPTION_MD5; 445 size += TCPOLEN_MD5SIG_ALIGNED; 446 } 447 #else 448 *md5 = NULL; 449 #endif 450 451 /* We always get an MSS option. The option bytes which will be seen in 452 * normal data packets should timestamps be used, must be in the MSS 453 * advertised. But we subtract them from tp->mss_cache so that 454 * calculations in tcp_sendmsg are simpler etc. So account for this 455 * fact here if necessary. If we don't do this correctly, as a 456 * receiver we won't recognize data packets as being full sized when we 457 * should, and thus we won't abide by the delayed ACK rules correctly. 458 * SACKs don't matter, we never delay an ACK when we have any of those 459 * going out. */ 460 opts->mss = tcp_advertise_mss(sk); 461 size += TCPOLEN_MSS_ALIGNED; 462 463 if (likely(sysctl_tcp_timestamps && *md5 == NULL)) { 464 opts->options |= OPTION_TS; 465 opts->tsval = TCP_SKB_CB(skb)->when; 466 opts->tsecr = tp->rx_opt.ts_recent; 467 size += TCPOLEN_TSTAMP_ALIGNED; 468 } 469 if (likely(sysctl_tcp_window_scaling)) { 470 opts->ws = tp->rx_opt.rcv_wscale; 471 if(likely(opts->ws)) 472 size += TCPOLEN_WSCALE_ALIGNED; 473 } 474 if (likely(sysctl_tcp_sack)) { 475 opts->options |= OPTION_SACK_ADVERTISE; 476 if (unlikely(!(OPTION_TS & opts->options))) 477 size += TCPOLEN_SACKPERM_ALIGNED; 478 } 479 480 return size; 481 } 482 483 static unsigned tcp_synack_options(struct sock *sk, 484 struct request_sock *req, 485 unsigned mss, struct sk_buff *skb, 486 struct tcp_out_options *opts, 487 struct tcp_md5sig_key **md5) { 488 unsigned size = 0; 489 struct inet_request_sock *ireq = inet_rsk(req); 490 char doing_ts; 491 492 #ifdef CONFIG_TCP_MD5SIG 493 *md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req); 494 if (*md5) { 495 opts->options |= OPTION_MD5; 496 size += TCPOLEN_MD5SIG_ALIGNED; 497 } 498 #else 499 *md5 = NULL; 500 #endif 501 502 /* we can't fit any SACK blocks in a packet with MD5 + TS 503 options. There was discussion about disabling SACK rather than TS in 504 order to fit in better with old, buggy kernels, but that was deemed 505 to be unnecessary. */ 506 doing_ts = ireq->tstamp_ok && !(*md5 && ireq->sack_ok); 507 508 opts->mss = mss; 509 size += TCPOLEN_MSS_ALIGNED; 510 511 if (likely(ireq->wscale_ok)) { 512 opts->ws = ireq->rcv_wscale; 513 if(likely(opts->ws)) 514 size += TCPOLEN_WSCALE_ALIGNED; 515 } 516 if (likely(doing_ts)) { 517 opts->options |= OPTION_TS; 518 opts->tsval = TCP_SKB_CB(skb)->when; 519 opts->tsecr = req->ts_recent; 520 size += TCPOLEN_TSTAMP_ALIGNED; 521 } 522 if (likely(ireq->sack_ok)) { 523 opts->options |= OPTION_SACK_ADVERTISE; 524 if (unlikely(!doing_ts)) 525 size += TCPOLEN_SACKPERM_ALIGNED; 526 } 527 528 return size; 529 } 530 531 static unsigned tcp_established_options(struct sock *sk, struct sk_buff *skb, 532 struct tcp_out_options *opts, 533 struct tcp_md5sig_key **md5) { 534 struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL; 535 struct tcp_sock *tp = tcp_sk(sk); 536 unsigned size = 0; 537 538 #ifdef CONFIG_TCP_MD5SIG 539 *md5 = tp->af_specific->md5_lookup(sk, sk); 540 if (unlikely(*md5)) { 541 opts->options |= OPTION_MD5; 542 size += TCPOLEN_MD5SIG_ALIGNED; 543 } 544 #else 545 *md5 = NULL; 546 #endif 547 548 if (likely(tp->rx_opt.tstamp_ok)) { 549 opts->options |= OPTION_TS; 550 opts->tsval = tcb ? tcb->when : 0; 551 opts->tsecr = tp->rx_opt.ts_recent; 552 size += TCPOLEN_TSTAMP_ALIGNED; 553 } 554 555 if (unlikely(tp->rx_opt.eff_sacks)) { 556 const unsigned remaining = MAX_TCP_OPTION_SPACE - size; 557 opts->num_sack_blocks = 558 min_t(unsigned, tp->rx_opt.eff_sacks, 559 (remaining - TCPOLEN_SACK_BASE_ALIGNED) / 560 TCPOLEN_SACK_PERBLOCK); 561 size += TCPOLEN_SACK_BASE_ALIGNED + 562 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK; 563 } 564 565 return size; 566 } 567 568 /* This routine actually transmits TCP packets queued in by 569 * tcp_do_sendmsg(). This is used by both the initial 570 * transmission and possible later retransmissions. 571 * All SKB's seen here are completely headerless. It is our 572 * job to build the TCP header, and pass the packet down to 573 * IP so it can do the same plus pass the packet off to the 574 * device. 575 * 576 * We are working here with either a clone of the original 577 * SKB, or a fresh unique copy made by the retransmit engine. 578 */ 579 static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, 580 gfp_t gfp_mask) 581 { 582 const struct inet_connection_sock *icsk = inet_csk(sk); 583 struct inet_sock *inet; 584 struct tcp_sock *tp; 585 struct tcp_skb_cb *tcb; 586 struct tcp_out_options opts; 587 unsigned tcp_options_size, tcp_header_size; 588 struct tcp_md5sig_key *md5; 589 __u8 *md5_hash_location; 590 struct tcphdr *th; 591 int err; 592 593 BUG_ON(!skb || !tcp_skb_pcount(skb)); 594 595 /* If congestion control is doing timestamping, we must 596 * take such a timestamp before we potentially clone/copy. 597 */ 598 if (icsk->icsk_ca_ops->flags & TCP_CONG_RTT_STAMP) 599 __net_timestamp(skb); 600 601 if (likely(clone_it)) { 602 if (unlikely(skb_cloned(skb))) 603 skb = pskb_copy(skb, gfp_mask); 604 else 605 skb = skb_clone(skb, gfp_mask); 606 if (unlikely(!skb)) 607 return -ENOBUFS; 608 } 609 610 inet = inet_sk(sk); 611 tp = tcp_sk(sk); 612 tcb = TCP_SKB_CB(skb); 613 memset(&opts, 0, sizeof(opts)); 614 615 if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) 616 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5); 617 else 618 tcp_options_size = tcp_established_options(sk, skb, &opts, 619 &md5); 620 tcp_header_size = tcp_options_size + sizeof(struct tcphdr); 621 622 if (tcp_packets_in_flight(tp) == 0) 623 tcp_ca_event(sk, CA_EVENT_TX_START); 624 625 skb_push(skb, tcp_header_size); 626 skb_reset_transport_header(skb); 627 skb_set_owner_w(skb, sk); 628 629 /* Build TCP header and checksum it. */ 630 th = tcp_hdr(skb); 631 th->source = inet->sport; 632 th->dest = inet->dport; 633 th->seq = htonl(tcb->seq); 634 th->ack_seq = htonl(tp->rcv_nxt); 635 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) | 636 tcb->flags); 637 638 if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) { 639 /* RFC1323: The window in SYN & SYN/ACK segments 640 * is never scaled. 641 */ 642 th->window = htons(min(tp->rcv_wnd, 65535U)); 643 } else { 644 th->window = htons(tcp_select_window(sk)); 645 } 646 th->check = 0; 647 th->urg_ptr = 0; 648 649 if (unlikely(tp->urg_mode && 650 between(tp->snd_up, tcb->seq + 1, tcb->seq + 0xFFFF))) { 651 th->urg_ptr = htons(tp->snd_up - tcb->seq); 652 th->urg = 1; 653 } 654 655 tcp_options_write((__be32 *)(th + 1), tp, &opts, &md5_hash_location); 656 if (likely((tcb->flags & TCPCB_FLAG_SYN) == 0)) 657 TCP_ECN_send(sk, skb, tcp_header_size); 658 659 #ifdef CONFIG_TCP_MD5SIG 660 /* Calculate the MD5 hash, as we have all we need now */ 661 if (md5) { 662 sk->sk_route_caps &= ~NETIF_F_GSO_MASK; 663 tp->af_specific->calc_md5_hash(md5_hash_location, 664 md5, sk, NULL, skb); 665 } 666 #endif 667 668 icsk->icsk_af_ops->send_check(sk, skb->len, skb); 669 670 if (likely(tcb->flags & TCPCB_FLAG_ACK)) 671 tcp_event_ack_sent(sk, tcp_skb_pcount(skb)); 672 673 if (skb->len != tcp_header_size) 674 tcp_event_data_sent(tp, skb, sk); 675 676 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq) 677 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS); 678 679 err = icsk->icsk_af_ops->queue_xmit(skb, 0); 680 if (likely(err <= 0)) 681 return err; 682 683 tcp_enter_cwr(sk, 1); 684 685 return net_xmit_eval(err); 686 } 687 688 /* This routine just queue's the buffer 689 * 690 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames, 691 * otherwise socket can stall. 692 */ 693 static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) 694 { 695 struct tcp_sock *tp = tcp_sk(sk); 696 697 /* Advance write_seq and place onto the write_queue. */ 698 tp->write_seq = TCP_SKB_CB(skb)->end_seq; 699 skb_header_release(skb); 700 tcp_add_write_queue_tail(sk, skb); 701 sk->sk_wmem_queued += skb->truesize; 702 sk_mem_charge(sk, skb->truesize); 703 } 704 705 static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, 706 unsigned int mss_now) 707 { 708 if (skb->len <= mss_now || !sk_can_gso(sk)) { 709 /* Avoid the costly divide in the normal 710 * non-TSO case. 711 */ 712 skb_shinfo(skb)->gso_segs = 1; 713 skb_shinfo(skb)->gso_size = 0; 714 skb_shinfo(skb)->gso_type = 0; 715 } else { 716 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now); 717 skb_shinfo(skb)->gso_size = mss_now; 718 skb_shinfo(skb)->gso_type = sk->sk_gso_type; 719 } 720 } 721 722 /* When a modification to fackets out becomes necessary, we need to check 723 * skb is counted to fackets_out or not. 724 */ 725 static void tcp_adjust_fackets_out(struct sock *sk, struct sk_buff *skb, 726 int decr) 727 { 728 struct tcp_sock *tp = tcp_sk(sk); 729 730 if (!tp->sacked_out || tcp_is_reno(tp)) 731 return; 732 733 if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq)) 734 tp->fackets_out -= decr; 735 } 736 737 /* Function to create two new TCP segments. Shrinks the given segment 738 * to the specified size and appends a new segment with the rest of the 739 * packet to the list. This won't be called frequently, I hope. 740 * Remember, these are still headerless SKBs at this point. 741 */ 742 int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, 743 unsigned int mss_now) 744 { 745 struct tcp_sock *tp = tcp_sk(sk); 746 struct sk_buff *buff; 747 int nsize, old_factor; 748 int nlen; 749 u16 flags; 750 751 BUG_ON(len > skb->len); 752 753 tcp_clear_retrans_hints_partial(tp); 754 nsize = skb_headlen(skb) - len; 755 if (nsize < 0) 756 nsize = 0; 757 758 if (skb_cloned(skb) && 759 skb_is_nonlinear(skb) && 760 pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) 761 return -ENOMEM; 762 763 /* Get a new skb... force flag on. */ 764 buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC); 765 if (buff == NULL) 766 return -ENOMEM; /* We'll just try again later. */ 767 768 sk->sk_wmem_queued += buff->truesize; 769 sk_mem_charge(sk, buff->truesize); 770 nlen = skb->len - len - nsize; 771 buff->truesize += nlen; 772 skb->truesize -= nlen; 773 774 /* Correct the sequence numbers. */ 775 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; 776 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; 777 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; 778 779 /* PSH and FIN should only be set in the second packet. */ 780 flags = TCP_SKB_CB(skb)->flags; 781 TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN | TCPCB_FLAG_PSH); 782 TCP_SKB_CB(buff)->flags = flags; 783 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked; 784 785 if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) { 786 /* Copy and checksum data tail into the new buffer. */ 787 buff->csum = csum_partial_copy_nocheck(skb->data + len, 788 skb_put(buff, nsize), 789 nsize, 0); 790 791 skb_trim(skb, len); 792 793 skb->csum = csum_block_sub(skb->csum, buff->csum, len); 794 } else { 795 skb->ip_summed = CHECKSUM_PARTIAL; 796 skb_split(skb, buff, len); 797 } 798 799 buff->ip_summed = skb->ip_summed; 800 801 /* Looks stupid, but our code really uses when of 802 * skbs, which it never sent before. --ANK 803 */ 804 TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when; 805 buff->tstamp = skb->tstamp; 806 807 old_factor = tcp_skb_pcount(skb); 808 809 /* Fix up tso_factor for both original and new SKB. */ 810 tcp_set_skb_tso_segs(sk, skb, mss_now); 811 tcp_set_skb_tso_segs(sk, buff, mss_now); 812 813 /* If this packet has been sent out already, we must 814 * adjust the various packet counters. 815 */ 816 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) { 817 int diff = old_factor - tcp_skb_pcount(skb) - 818 tcp_skb_pcount(buff); 819 820 tp->packets_out -= diff; 821 822 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) 823 tp->sacked_out -= diff; 824 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) 825 tp->retrans_out -= diff; 826 827 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) 828 tp->lost_out -= diff; 829 830 /* Adjust Reno SACK estimate. */ 831 if (tcp_is_reno(tp) && diff > 0) { 832 tcp_dec_pcount_approx_int(&tp->sacked_out, diff); 833 tcp_verify_left_out(tp); 834 } 835 tcp_adjust_fackets_out(sk, skb, diff); 836 } 837 838 /* Link BUFF into the send queue. */ 839 skb_header_release(buff); 840 tcp_insert_write_queue_after(skb, buff, sk); 841 842 return 0; 843 } 844 845 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c 846 * eventually). The difference is that pulled data not copied, but 847 * immediately discarded. 848 */ 849 static void __pskb_trim_head(struct sk_buff *skb, int len) 850 { 851 int i, k, eat; 852 853 eat = len; 854 k = 0; 855 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { 856 if (skb_shinfo(skb)->frags[i].size <= eat) { 857 put_page(skb_shinfo(skb)->frags[i].page); 858 eat -= skb_shinfo(skb)->frags[i].size; 859 } else { 860 skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i]; 861 if (eat) { 862 skb_shinfo(skb)->frags[k].page_offset += eat; 863 skb_shinfo(skb)->frags[k].size -= eat; 864 eat = 0; 865 } 866 k++; 867 } 868 } 869 skb_shinfo(skb)->nr_frags = k; 870 871 skb_reset_tail_pointer(skb); 872 skb->data_len -= len; 873 skb->len = skb->data_len; 874 } 875 876 int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) 877 { 878 if (skb_cloned(skb) && pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) 879 return -ENOMEM; 880 881 /* If len == headlen, we avoid __skb_pull to preserve alignment. */ 882 if (unlikely(len < skb_headlen(skb))) 883 __skb_pull(skb, len); 884 else 885 __pskb_trim_head(skb, len - skb_headlen(skb)); 886 887 TCP_SKB_CB(skb)->seq += len; 888 skb->ip_summed = CHECKSUM_PARTIAL; 889 890 skb->truesize -= len; 891 sk->sk_wmem_queued -= len; 892 sk_mem_uncharge(sk, len); 893 sock_set_flag(sk, SOCK_QUEUE_SHRUNK); 894 895 /* Any change of skb->len requires recalculation of tso 896 * factor and mss. 897 */ 898 if (tcp_skb_pcount(skb) > 1) 899 tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk, 1)); 900 901 return 0; 902 } 903 904 /* Not accounting for SACKs here. */ 905 int tcp_mtu_to_mss(struct sock *sk, int pmtu) 906 { 907 struct tcp_sock *tp = tcp_sk(sk); 908 struct inet_connection_sock *icsk = inet_csk(sk); 909 int mss_now; 910 911 /* Calculate base mss without TCP options: 912 It is MMS_S - sizeof(tcphdr) of rfc1122 913 */ 914 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr); 915 916 /* Clamp it (mss_clamp does not include tcp options) */ 917 if (mss_now > tp->rx_opt.mss_clamp) 918 mss_now = tp->rx_opt.mss_clamp; 919 920 /* Now subtract optional transport overhead */ 921 mss_now -= icsk->icsk_ext_hdr_len; 922 923 /* Then reserve room for full set of TCP options and 8 bytes of data */ 924 if (mss_now < 48) 925 mss_now = 48; 926 927 /* Now subtract TCP options size, not including SACKs */ 928 mss_now -= tp->tcp_header_len - sizeof(struct tcphdr); 929 930 return mss_now; 931 } 932 933 /* Inverse of above */ 934 int tcp_mss_to_mtu(struct sock *sk, int mss) 935 { 936 struct tcp_sock *tp = tcp_sk(sk); 937 struct inet_connection_sock *icsk = inet_csk(sk); 938 int mtu; 939 940 mtu = mss + 941 tp->tcp_header_len + 942 icsk->icsk_ext_hdr_len + 943 icsk->icsk_af_ops->net_header_len; 944 945 return mtu; 946 } 947 948 void tcp_mtup_init(struct sock *sk) 949 { 950 struct tcp_sock *tp = tcp_sk(sk); 951 struct inet_connection_sock *icsk = inet_csk(sk); 952 953 icsk->icsk_mtup.enabled = sysctl_tcp_mtu_probing > 1; 954 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) + 955 icsk->icsk_af_ops->net_header_len; 956 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss); 957 icsk->icsk_mtup.probe_size = 0; 958 } 959 960 /* Bound MSS / TSO packet size with the half of the window */ 961 static int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize) 962 { 963 if (tp->max_window && pktsize > (tp->max_window >> 1)) 964 return max(tp->max_window >> 1, 68U - tp->tcp_header_len); 965 else 966 return pktsize; 967 } 968 969 /* This function synchronize snd mss to current pmtu/exthdr set. 970 971 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts 972 for TCP options, but includes only bare TCP header. 973 974 tp->rx_opt.mss_clamp is mss negotiated at connection setup. 975 It is minimum of user_mss and mss received with SYN. 976 It also does not include TCP options. 977 978 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function. 979 980 tp->mss_cache is current effective sending mss, including 981 all tcp options except for SACKs. It is evaluated, 982 taking into account current pmtu, but never exceeds 983 tp->rx_opt.mss_clamp. 984 985 NOTE1. rfc1122 clearly states that advertised MSS 986 DOES NOT include either tcp or ip options. 987 988 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache 989 are READ ONLY outside this function. --ANK (980731) 990 */ 991 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu) 992 { 993 struct tcp_sock *tp = tcp_sk(sk); 994 struct inet_connection_sock *icsk = inet_csk(sk); 995 int mss_now; 996 997 if (icsk->icsk_mtup.search_high > pmtu) 998 icsk->icsk_mtup.search_high = pmtu; 999 1000 mss_now = tcp_mtu_to_mss(sk, pmtu); 1001 mss_now = tcp_bound_to_half_wnd(tp, mss_now); 1002 1003 /* And store cached results */ 1004 icsk->icsk_pmtu_cookie = pmtu; 1005 if (icsk->icsk_mtup.enabled) 1006 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)); 1007 tp->mss_cache = mss_now; 1008 1009 return mss_now; 1010 } 1011 1012 /* Compute the current effective MSS, taking SACKs and IP options, 1013 * and even PMTU discovery events into account. 1014 * 1015 * LARGESEND note: !urg_mode is overkill, only frames up to snd_up 1016 * cannot be large. However, taking into account rare use of URG, this 1017 * is not a big flaw. 1018 */ 1019 unsigned int tcp_current_mss(struct sock *sk, int large_allowed) 1020 { 1021 struct tcp_sock *tp = tcp_sk(sk); 1022 struct dst_entry *dst = __sk_dst_get(sk); 1023 u32 mss_now; 1024 u16 xmit_size_goal; 1025 int doing_tso = 0; 1026 unsigned header_len; 1027 struct tcp_out_options opts; 1028 struct tcp_md5sig_key *md5; 1029 1030 mss_now = tp->mss_cache; 1031 1032 if (large_allowed && sk_can_gso(sk) && !tp->urg_mode) 1033 doing_tso = 1; 1034 1035 if (dst) { 1036 u32 mtu = dst_mtu(dst); 1037 if (mtu != inet_csk(sk)->icsk_pmtu_cookie) 1038 mss_now = tcp_sync_mss(sk, mtu); 1039 } 1040 1041 header_len = tcp_established_options(sk, NULL, &opts, &md5) + 1042 sizeof(struct tcphdr); 1043 /* The mss_cache is sized based on tp->tcp_header_len, which assumes 1044 * some common options. If this is an odd packet (because we have SACK 1045 * blocks etc) then our calculated header_len will be different, and 1046 * we have to adjust mss_now correspondingly */ 1047 if (header_len != tp->tcp_header_len) { 1048 int delta = (int) header_len - tp->tcp_header_len; 1049 mss_now -= delta; 1050 } 1051 1052 xmit_size_goal = mss_now; 1053 1054 if (doing_tso) { 1055 xmit_size_goal = ((sk->sk_gso_max_size - 1) - 1056 inet_csk(sk)->icsk_af_ops->net_header_len - 1057 inet_csk(sk)->icsk_ext_hdr_len - 1058 tp->tcp_header_len); 1059 1060 xmit_size_goal = tcp_bound_to_half_wnd(tp, xmit_size_goal); 1061 xmit_size_goal -= (xmit_size_goal % mss_now); 1062 } 1063 tp->xmit_size_goal = xmit_size_goal; 1064 1065 return mss_now; 1066 } 1067 1068 /* Congestion window validation. (RFC2861) */ 1069 static void tcp_cwnd_validate(struct sock *sk) 1070 { 1071 struct tcp_sock *tp = tcp_sk(sk); 1072 1073 if (tp->packets_out >= tp->snd_cwnd) { 1074 /* Network is feed fully. */ 1075 tp->snd_cwnd_used = 0; 1076 tp->snd_cwnd_stamp = tcp_time_stamp; 1077 } else { 1078 /* Network starves. */ 1079 if (tp->packets_out > tp->snd_cwnd_used) 1080 tp->snd_cwnd_used = tp->packets_out; 1081 1082 if (sysctl_tcp_slow_start_after_idle && 1083 (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto) 1084 tcp_cwnd_application_limited(sk); 1085 } 1086 } 1087 1088 /* Returns the portion of skb which can be sent right away without 1089 * introducing MSS oddities to segment boundaries. In rare cases where 1090 * mss_now != mss_cache, we will request caller to create a small skb 1091 * per input skb which could be mostly avoided here (if desired). 1092 * 1093 * We explicitly want to create a request for splitting write queue tail 1094 * to a small skb for Nagle purposes while avoiding unnecessary modulos, 1095 * thus all the complexity (cwnd_len is always MSS multiple which we 1096 * return whenever allowed by the other factors). Basically we need the 1097 * modulo only when the receiver window alone is the limiting factor or 1098 * when we would be allowed to send the split-due-to-Nagle skb fully. 1099 */ 1100 static unsigned int tcp_mss_split_point(struct sock *sk, struct sk_buff *skb, 1101 unsigned int mss_now, unsigned int cwnd) 1102 { 1103 struct tcp_sock *tp = tcp_sk(sk); 1104 u32 needed, window, cwnd_len; 1105 1106 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; 1107 cwnd_len = mss_now * cwnd; 1108 1109 if (likely(cwnd_len <= window && skb != tcp_write_queue_tail(sk))) 1110 return cwnd_len; 1111 1112 needed = min(skb->len, window); 1113 1114 if (cwnd_len <= needed) 1115 return cwnd_len; 1116 1117 return needed - needed % mss_now; 1118 } 1119 1120 /* Can at least one segment of SKB be sent right now, according to the 1121 * congestion window rules? If so, return how many segments are allowed. 1122 */ 1123 static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp, 1124 struct sk_buff *skb) 1125 { 1126 u32 in_flight, cwnd; 1127 1128 /* Don't be strict about the congestion window for the final FIN. */ 1129 if ((TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) && 1130 tcp_skb_pcount(skb) == 1) 1131 return 1; 1132 1133 in_flight = tcp_packets_in_flight(tp); 1134 cwnd = tp->snd_cwnd; 1135 if (in_flight < cwnd) 1136 return (cwnd - in_flight); 1137 1138 return 0; 1139 } 1140 1141 /* This must be invoked the first time we consider transmitting 1142 * SKB onto the wire. 1143 */ 1144 static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, 1145 unsigned int mss_now) 1146 { 1147 int tso_segs = tcp_skb_pcount(skb); 1148 1149 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) { 1150 tcp_set_skb_tso_segs(sk, skb, mss_now); 1151 tso_segs = tcp_skb_pcount(skb); 1152 } 1153 return tso_segs; 1154 } 1155 1156 static inline int tcp_minshall_check(const struct tcp_sock *tp) 1157 { 1158 return after(tp->snd_sml,tp->snd_una) && 1159 !after(tp->snd_sml, tp->snd_nxt); 1160 } 1161 1162 /* Return 0, if packet can be sent now without violation Nagle's rules: 1163 * 1. It is full sized. 1164 * 2. Or it contains FIN. (already checked by caller) 1165 * 3. Or TCP_NODELAY was set. 1166 * 4. Or TCP_CORK is not set, and all sent packets are ACKed. 1167 * With Minshall's modification: all sent small packets are ACKed. 1168 */ 1169 static inline int tcp_nagle_check(const struct tcp_sock *tp, 1170 const struct sk_buff *skb, 1171 unsigned mss_now, int nonagle) 1172 { 1173 return (skb->len < mss_now && 1174 ((nonagle & TCP_NAGLE_CORK) || 1175 (!nonagle && tp->packets_out && tcp_minshall_check(tp)))); 1176 } 1177 1178 /* Return non-zero if the Nagle test allows this packet to be 1179 * sent now. 1180 */ 1181 static inline int tcp_nagle_test(struct tcp_sock *tp, struct sk_buff *skb, 1182 unsigned int cur_mss, int nonagle) 1183 { 1184 /* Nagle rule does not apply to frames, which sit in the middle of the 1185 * write_queue (they have no chances to get new data). 1186 * 1187 * This is implemented in the callers, where they modify the 'nonagle' 1188 * argument based upon the location of SKB in the send queue. 1189 */ 1190 if (nonagle & TCP_NAGLE_PUSH) 1191 return 1; 1192 1193 /* Don't use the nagle rule for urgent data (or for the final FIN). 1194 * Nagle can be ignored during F-RTO too (see RFC4138). 1195 */ 1196 if (tp->urg_mode || (tp->frto_counter == 2) || 1197 (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)) 1198 return 1; 1199 1200 if (!tcp_nagle_check(tp, skb, cur_mss, nonagle)) 1201 return 1; 1202 1203 return 0; 1204 } 1205 1206 /* Does at least the first segment of SKB fit into the send window? */ 1207 static inline int tcp_snd_wnd_test(struct tcp_sock *tp, struct sk_buff *skb, 1208 unsigned int cur_mss) 1209 { 1210 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 1211 1212 if (skb->len > cur_mss) 1213 end_seq = TCP_SKB_CB(skb)->seq + cur_mss; 1214 1215 return !after(end_seq, tcp_wnd_end(tp)); 1216 } 1217 1218 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk)) 1219 * should be put on the wire right now. If so, it returns the number of 1220 * packets allowed by the congestion window. 1221 */ 1222 static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb, 1223 unsigned int cur_mss, int nonagle) 1224 { 1225 struct tcp_sock *tp = tcp_sk(sk); 1226 unsigned int cwnd_quota; 1227 1228 tcp_init_tso_segs(sk, skb, cur_mss); 1229 1230 if (!tcp_nagle_test(tp, skb, cur_mss, nonagle)) 1231 return 0; 1232 1233 cwnd_quota = tcp_cwnd_test(tp, skb); 1234 if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss)) 1235 cwnd_quota = 0; 1236 1237 return cwnd_quota; 1238 } 1239 1240 int tcp_may_send_now(struct sock *sk) 1241 { 1242 struct tcp_sock *tp = tcp_sk(sk); 1243 struct sk_buff *skb = tcp_send_head(sk); 1244 1245 return (skb && 1246 tcp_snd_test(sk, skb, tcp_current_mss(sk, 1), 1247 (tcp_skb_is_last(sk, skb) ? 1248 tp->nonagle : TCP_NAGLE_PUSH))); 1249 } 1250 1251 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet 1252 * which is put after SKB on the list. It is very much like 1253 * tcp_fragment() except that it may make several kinds of assumptions 1254 * in order to speed up the splitting operation. In particular, we 1255 * know that all the data is in scatter-gather pages, and that the 1256 * packet has never been sent out before (and thus is not cloned). 1257 */ 1258 static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, 1259 unsigned int mss_now) 1260 { 1261 struct sk_buff *buff; 1262 int nlen = skb->len - len; 1263 u16 flags; 1264 1265 /* All of a TSO frame must be composed of paged data. */ 1266 if (skb->len != skb->data_len) 1267 return tcp_fragment(sk, skb, len, mss_now); 1268 1269 buff = sk_stream_alloc_skb(sk, 0, GFP_ATOMIC); 1270 if (unlikely(buff == NULL)) 1271 return -ENOMEM; 1272 1273 sk->sk_wmem_queued += buff->truesize; 1274 sk_mem_charge(sk, buff->truesize); 1275 buff->truesize += nlen; 1276 skb->truesize -= nlen; 1277 1278 /* Correct the sequence numbers. */ 1279 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; 1280 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; 1281 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; 1282 1283 /* PSH and FIN should only be set in the second packet. */ 1284 flags = TCP_SKB_CB(skb)->flags; 1285 TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN | TCPCB_FLAG_PSH); 1286 TCP_SKB_CB(buff)->flags = flags; 1287 1288 /* This packet was never sent out yet, so no SACK bits. */ 1289 TCP_SKB_CB(buff)->sacked = 0; 1290 1291 buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL; 1292 skb_split(skb, buff, len); 1293 1294 /* Fix up tso_factor for both original and new SKB. */ 1295 tcp_set_skb_tso_segs(sk, skb, mss_now); 1296 tcp_set_skb_tso_segs(sk, buff, mss_now); 1297 1298 /* Link BUFF into the send queue. */ 1299 skb_header_release(buff); 1300 tcp_insert_write_queue_after(skb, buff, sk); 1301 1302 return 0; 1303 } 1304 1305 /* Try to defer sending, if possible, in order to minimize the amount 1306 * of TSO splitting we do. View it as a kind of TSO Nagle test. 1307 * 1308 * This algorithm is from John Heffner. 1309 */ 1310 static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb) 1311 { 1312 struct tcp_sock *tp = tcp_sk(sk); 1313 const struct inet_connection_sock *icsk = inet_csk(sk); 1314 u32 send_win, cong_win, limit, in_flight; 1315 1316 if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) 1317 goto send_now; 1318 1319 if (icsk->icsk_ca_state != TCP_CA_Open) 1320 goto send_now; 1321 1322 /* Defer for less than two clock ticks. */ 1323 if (tp->tso_deferred && 1324 ((jiffies << 1) >> 1) - (tp->tso_deferred >> 1) > 1) 1325 goto send_now; 1326 1327 in_flight = tcp_packets_in_flight(tp); 1328 1329 BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight)); 1330 1331 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; 1332 1333 /* From in_flight test above, we know that cwnd > in_flight. */ 1334 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache; 1335 1336 limit = min(send_win, cong_win); 1337 1338 /* If a full-sized TSO skb can be sent, do it. */ 1339 if (limit >= sk->sk_gso_max_size) 1340 goto send_now; 1341 1342 if (sysctl_tcp_tso_win_divisor) { 1343 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache); 1344 1345 /* If at least some fraction of a window is available, 1346 * just use it. 1347 */ 1348 chunk /= sysctl_tcp_tso_win_divisor; 1349 if (limit >= chunk) 1350 goto send_now; 1351 } else { 1352 /* Different approach, try not to defer past a single 1353 * ACK. Receiver should ACK every other full sized 1354 * frame, so if we have space for more than 3 frames 1355 * then send now. 1356 */ 1357 if (limit > tcp_max_burst(tp) * tp->mss_cache) 1358 goto send_now; 1359 } 1360 1361 /* Ok, it looks like it is advisable to defer. */ 1362 tp->tso_deferred = 1 | (jiffies << 1); 1363 1364 return 1; 1365 1366 send_now: 1367 tp->tso_deferred = 0; 1368 return 0; 1369 } 1370 1371 /* Create a new MTU probe if we are ready. 1372 * Returns 0 if we should wait to probe (no cwnd available), 1373 * 1 if a probe was sent, 1374 * -1 otherwise 1375 */ 1376 static int tcp_mtu_probe(struct sock *sk) 1377 { 1378 struct tcp_sock *tp = tcp_sk(sk); 1379 struct inet_connection_sock *icsk = inet_csk(sk); 1380 struct sk_buff *skb, *nskb, *next; 1381 int len; 1382 int probe_size; 1383 int size_needed; 1384 int copy; 1385 int mss_now; 1386 1387 /* Not currently probing/verifying, 1388 * not in recovery, 1389 * have enough cwnd, and 1390 * not SACKing (the variable headers throw things off) */ 1391 if (!icsk->icsk_mtup.enabled || 1392 icsk->icsk_mtup.probe_size || 1393 inet_csk(sk)->icsk_ca_state != TCP_CA_Open || 1394 tp->snd_cwnd < 11 || 1395 tp->rx_opt.eff_sacks) 1396 return -1; 1397 1398 /* Very simple search strategy: just double the MSS. */ 1399 mss_now = tcp_current_mss(sk, 0); 1400 probe_size = 2 * tp->mss_cache; 1401 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache; 1402 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) { 1403 /* TODO: set timer for probe_converge_event */ 1404 return -1; 1405 } 1406 1407 /* Have enough data in the send queue to probe? */ 1408 if (tp->write_seq - tp->snd_nxt < size_needed) 1409 return -1; 1410 1411 if (tp->snd_wnd < size_needed) 1412 return -1; 1413 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp))) 1414 return 0; 1415 1416 /* Do we need to wait to drain cwnd? With none in flight, don't stall */ 1417 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) { 1418 if (!tcp_packets_in_flight(tp)) 1419 return -1; 1420 else 1421 return 0; 1422 } 1423 1424 /* We're allowed to probe. Build it now. */ 1425 if ((nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC)) == NULL) 1426 return -1; 1427 sk->sk_wmem_queued += nskb->truesize; 1428 sk_mem_charge(sk, nskb->truesize); 1429 1430 skb = tcp_send_head(sk); 1431 1432 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq; 1433 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size; 1434 TCP_SKB_CB(nskb)->flags = TCPCB_FLAG_ACK; 1435 TCP_SKB_CB(nskb)->sacked = 0; 1436 nskb->csum = 0; 1437 nskb->ip_summed = skb->ip_summed; 1438 1439 tcp_insert_write_queue_before(nskb, skb, sk); 1440 1441 len = 0; 1442 tcp_for_write_queue_from_safe(skb, next, sk) { 1443 copy = min_t(int, skb->len, probe_size - len); 1444 if (nskb->ip_summed) 1445 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy); 1446 else 1447 nskb->csum = skb_copy_and_csum_bits(skb, 0, 1448 skb_put(nskb, copy), 1449 copy, nskb->csum); 1450 1451 if (skb->len <= copy) { 1452 /* We've eaten all the data from this skb. 1453 * Throw it away. */ 1454 TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags; 1455 tcp_unlink_write_queue(skb, sk); 1456 sk_wmem_free_skb(sk, skb); 1457 } else { 1458 TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags & 1459 ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH); 1460 if (!skb_shinfo(skb)->nr_frags) { 1461 skb_pull(skb, copy); 1462 if (skb->ip_summed != CHECKSUM_PARTIAL) 1463 skb->csum = csum_partial(skb->data, 1464 skb->len, 0); 1465 } else { 1466 __pskb_trim_head(skb, copy); 1467 tcp_set_skb_tso_segs(sk, skb, mss_now); 1468 } 1469 TCP_SKB_CB(skb)->seq += copy; 1470 } 1471 1472 len += copy; 1473 1474 if (len >= probe_size) 1475 break; 1476 } 1477 tcp_init_tso_segs(sk, nskb, nskb->len); 1478 1479 /* We're ready to send. If this fails, the probe will 1480 * be resegmented into mss-sized pieces by tcp_write_xmit(). */ 1481 TCP_SKB_CB(nskb)->when = tcp_time_stamp; 1482 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) { 1483 /* Decrement cwnd here because we are sending 1484 * effectively two packets. */ 1485 tp->snd_cwnd--; 1486 tcp_event_new_data_sent(sk, nskb); 1487 1488 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len); 1489 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq; 1490 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq; 1491 1492 return 1; 1493 } 1494 1495 return -1; 1496 } 1497 1498 /* This routine writes packets to the network. It advances the 1499 * send_head. This happens as incoming acks open up the remote 1500 * window for us. 1501 * 1502 * Returns 1, if no segments are in flight and we have queued segments, but 1503 * cannot send anything now because of SWS or another problem. 1504 */ 1505 static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle) 1506 { 1507 struct tcp_sock *tp = tcp_sk(sk); 1508 struct sk_buff *skb; 1509 unsigned int tso_segs, sent_pkts; 1510 int cwnd_quota; 1511 int result; 1512 1513 /* If we are closed, the bytes will have to remain here. 1514 * In time closedown will finish, we empty the write queue and all 1515 * will be happy. 1516 */ 1517 if (unlikely(sk->sk_state == TCP_CLOSE)) 1518 return 0; 1519 1520 sent_pkts = 0; 1521 1522 /* Do MTU probing. */ 1523 if ((result = tcp_mtu_probe(sk)) == 0) { 1524 return 0; 1525 } else if (result > 0) { 1526 sent_pkts = 1; 1527 } 1528 1529 while ((skb = tcp_send_head(sk))) { 1530 unsigned int limit; 1531 1532 tso_segs = tcp_init_tso_segs(sk, skb, mss_now); 1533 BUG_ON(!tso_segs); 1534 1535 cwnd_quota = tcp_cwnd_test(tp, skb); 1536 if (!cwnd_quota) 1537 break; 1538 1539 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) 1540 break; 1541 1542 if (tso_segs == 1) { 1543 if (unlikely(!tcp_nagle_test(tp, skb, mss_now, 1544 (tcp_skb_is_last(sk, skb) ? 1545 nonagle : TCP_NAGLE_PUSH)))) 1546 break; 1547 } else { 1548 if (tcp_tso_should_defer(sk, skb)) 1549 break; 1550 } 1551 1552 limit = mss_now; 1553 if (tso_segs > 1) 1554 limit = tcp_mss_split_point(sk, skb, mss_now, 1555 cwnd_quota); 1556 1557 if (skb->len > limit && 1558 unlikely(tso_fragment(sk, skb, limit, mss_now))) 1559 break; 1560 1561 TCP_SKB_CB(skb)->when = tcp_time_stamp; 1562 1563 if (unlikely(tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC))) 1564 break; 1565 1566 /* Advance the send_head. This one is sent out. 1567 * This call will increment packets_out. 1568 */ 1569 tcp_event_new_data_sent(sk, skb); 1570 1571 tcp_minshall_update(tp, mss_now, skb); 1572 sent_pkts++; 1573 } 1574 1575 if (likely(sent_pkts)) { 1576 tcp_cwnd_validate(sk); 1577 return 0; 1578 } 1579 return !tp->packets_out && tcp_send_head(sk); 1580 } 1581 1582 /* Push out any pending frames which were held back due to 1583 * TCP_CORK or attempt at coalescing tiny packets. 1584 * The socket must be locked by the caller. 1585 */ 1586 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss, 1587 int nonagle) 1588 { 1589 struct sk_buff *skb = tcp_send_head(sk); 1590 1591 if (skb) { 1592 if (tcp_write_xmit(sk, cur_mss, nonagle)) 1593 tcp_check_probe_timer(sk); 1594 } 1595 } 1596 1597 /* Send _single_ skb sitting at the send head. This function requires 1598 * true push pending frames to setup probe timer etc. 1599 */ 1600 void tcp_push_one(struct sock *sk, unsigned int mss_now) 1601 { 1602 struct sk_buff *skb = tcp_send_head(sk); 1603 unsigned int tso_segs, cwnd_quota; 1604 1605 BUG_ON(!skb || skb->len < mss_now); 1606 1607 tso_segs = tcp_init_tso_segs(sk, skb, mss_now); 1608 cwnd_quota = tcp_snd_test(sk, skb, mss_now, TCP_NAGLE_PUSH); 1609 1610 if (likely(cwnd_quota)) { 1611 unsigned int limit; 1612 1613 BUG_ON(!tso_segs); 1614 1615 limit = mss_now; 1616 if (tso_segs > 1) 1617 limit = tcp_mss_split_point(sk, skb, mss_now, 1618 cwnd_quota); 1619 1620 if (skb->len > limit && 1621 unlikely(tso_fragment(sk, skb, limit, mss_now))) 1622 return; 1623 1624 /* Send it out now. */ 1625 TCP_SKB_CB(skb)->when = tcp_time_stamp; 1626 1627 if (likely(!tcp_transmit_skb(sk, skb, 1, sk->sk_allocation))) { 1628 tcp_event_new_data_sent(sk, skb); 1629 tcp_cwnd_validate(sk); 1630 return; 1631 } 1632 } 1633 } 1634 1635 /* This function returns the amount that we can raise the 1636 * usable window based on the following constraints 1637 * 1638 * 1. The window can never be shrunk once it is offered (RFC 793) 1639 * 2. We limit memory per socket 1640 * 1641 * RFC 1122: 1642 * "the suggested [SWS] avoidance algorithm for the receiver is to keep 1643 * RECV.NEXT + RCV.WIN fixed until: 1644 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)" 1645 * 1646 * i.e. don't raise the right edge of the window until you can raise 1647 * it at least MSS bytes. 1648 * 1649 * Unfortunately, the recommended algorithm breaks header prediction, 1650 * since header prediction assumes th->window stays fixed. 1651 * 1652 * Strictly speaking, keeping th->window fixed violates the receiver 1653 * side SWS prevention criteria. The problem is that under this rule 1654 * a stream of single byte packets will cause the right side of the 1655 * window to always advance by a single byte. 1656 * 1657 * Of course, if the sender implements sender side SWS prevention 1658 * then this will not be a problem. 1659 * 1660 * BSD seems to make the following compromise: 1661 * 1662 * If the free space is less than the 1/4 of the maximum 1663 * space available and the free space is less than 1/2 mss, 1664 * then set the window to 0. 1665 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ] 1666 * Otherwise, just prevent the window from shrinking 1667 * and from being larger than the largest representable value. 1668 * 1669 * This prevents incremental opening of the window in the regime 1670 * where TCP is limited by the speed of the reader side taking 1671 * data out of the TCP receive queue. It does nothing about 1672 * those cases where the window is constrained on the sender side 1673 * because the pipeline is full. 1674 * 1675 * BSD also seems to "accidentally" limit itself to windows that are a 1676 * multiple of MSS, at least until the free space gets quite small. 1677 * This would appear to be a side effect of the mbuf implementation. 1678 * Combining these two algorithms results in the observed behavior 1679 * of having a fixed window size at almost all times. 1680 * 1681 * Below we obtain similar behavior by forcing the offered window to 1682 * a multiple of the mss when it is feasible to do so. 1683 * 1684 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes. 1685 * Regular options like TIMESTAMP are taken into account. 1686 */ 1687 u32 __tcp_select_window(struct sock *sk) 1688 { 1689 struct inet_connection_sock *icsk = inet_csk(sk); 1690 struct tcp_sock *tp = tcp_sk(sk); 1691 /* MSS for the peer's data. Previous versions used mss_clamp 1692 * here. I don't know if the value based on our guesses 1693 * of peer's MSS is better for the performance. It's more correct 1694 * but may be worse for the performance because of rcv_mss 1695 * fluctuations. --SAW 1998/11/1 1696 */ 1697 int mss = icsk->icsk_ack.rcv_mss; 1698 int free_space = tcp_space(sk); 1699 int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk)); 1700 int window; 1701 1702 if (mss > full_space) 1703 mss = full_space; 1704 1705 if (free_space < (full_space >> 1)) { 1706 icsk->icsk_ack.quick = 0; 1707 1708 if (tcp_memory_pressure) 1709 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 1710 4U * tp->advmss); 1711 1712 if (free_space < mss) 1713 return 0; 1714 } 1715 1716 if (free_space > tp->rcv_ssthresh) 1717 free_space = tp->rcv_ssthresh; 1718 1719 /* Don't do rounding if we are using window scaling, since the 1720 * scaled window will not line up with the MSS boundary anyway. 1721 */ 1722 window = tp->rcv_wnd; 1723 if (tp->rx_opt.rcv_wscale) { 1724 window = free_space; 1725 1726 /* Advertise enough space so that it won't get scaled away. 1727 * Import case: prevent zero window announcement if 1728 * 1<<rcv_wscale > mss. 1729 */ 1730 if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window) 1731 window = (((window >> tp->rx_opt.rcv_wscale) + 1) 1732 << tp->rx_opt.rcv_wscale); 1733 } else { 1734 /* Get the largest window that is a nice multiple of mss. 1735 * Window clamp already applied above. 1736 * If our current window offering is within 1 mss of the 1737 * free space we just keep it. This prevents the divide 1738 * and multiply from happening most of the time. 1739 * We also don't do any window rounding when the free space 1740 * is too small. 1741 */ 1742 if (window <= free_space - mss || window > free_space) 1743 window = (free_space / mss) * mss; 1744 else if (mss == full_space && 1745 free_space > window + (full_space >> 1)) 1746 window = free_space; 1747 } 1748 1749 return window; 1750 } 1751 1752 /* Attempt to collapse two adjacent SKB's during retransmission. */ 1753 static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, 1754 int mss_now) 1755 { 1756 struct tcp_sock *tp = tcp_sk(sk); 1757 struct sk_buff *next_skb = tcp_write_queue_next(sk, skb); 1758 int skb_size, next_skb_size; 1759 u16 flags; 1760 1761 /* The first test we must make is that neither of these two 1762 * SKB's are still referenced by someone else. 1763 */ 1764 if (skb_cloned(skb) || skb_cloned(next_skb)) 1765 return; 1766 1767 skb_size = skb->len; 1768 next_skb_size = next_skb->len; 1769 flags = TCP_SKB_CB(skb)->flags; 1770 1771 /* Also punt if next skb has been SACK'd. */ 1772 if (TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_ACKED) 1773 return; 1774 1775 /* Next skb is out of window. */ 1776 if (after(TCP_SKB_CB(next_skb)->end_seq, tcp_wnd_end(tp))) 1777 return; 1778 1779 /* Punt if not enough space exists in the first SKB for 1780 * the data in the second, or the total combined payload 1781 * would exceed the MSS. 1782 */ 1783 if ((next_skb_size > skb_tailroom(skb)) || 1784 ((skb_size + next_skb_size) > mss_now)) 1785 return; 1786 1787 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1); 1788 1789 tcp_highest_sack_combine(sk, next_skb, skb); 1790 1791 /* Ok. We will be able to collapse the packet. */ 1792 tcp_unlink_write_queue(next_skb, sk); 1793 1794 skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size), 1795 next_skb_size); 1796 1797 if (next_skb->ip_summed == CHECKSUM_PARTIAL) 1798 skb->ip_summed = CHECKSUM_PARTIAL; 1799 1800 if (skb->ip_summed != CHECKSUM_PARTIAL) 1801 skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size); 1802 1803 /* Update sequence range on original skb. */ 1804 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq; 1805 1806 /* Merge over control information. */ 1807 flags |= TCP_SKB_CB(next_skb)->flags; /* This moves PSH/FIN etc. over */ 1808 TCP_SKB_CB(skb)->flags = flags; 1809 1810 /* All done, get rid of second SKB and account for it so 1811 * packet counting does not break. 1812 */ 1813 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS; 1814 if (TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_RETRANS) 1815 tp->retrans_out -= tcp_skb_pcount(next_skb); 1816 if (TCP_SKB_CB(next_skb)->sacked & TCPCB_LOST) 1817 tp->lost_out -= tcp_skb_pcount(next_skb); 1818 /* Reno case is special. Sigh... */ 1819 if (tcp_is_reno(tp) && tp->sacked_out) 1820 tcp_dec_pcount_approx(&tp->sacked_out, next_skb); 1821 1822 tcp_adjust_fackets_out(sk, next_skb, tcp_skb_pcount(next_skb)); 1823 tp->packets_out -= tcp_skb_pcount(next_skb); 1824 1825 /* changed transmit queue under us so clear hints */ 1826 tcp_clear_retrans_hints_partial(tp); 1827 1828 sk_wmem_free_skb(sk, next_skb); 1829 } 1830 1831 /* Do a simple retransmit without using the backoff mechanisms in 1832 * tcp_timer. This is used for path mtu discovery. 1833 * The socket is already locked here. 1834 */ 1835 void tcp_simple_retransmit(struct sock *sk) 1836 { 1837 const struct inet_connection_sock *icsk = inet_csk(sk); 1838 struct tcp_sock *tp = tcp_sk(sk); 1839 struct sk_buff *skb; 1840 unsigned int mss = tcp_current_mss(sk, 0); 1841 int lost = 0; 1842 1843 tcp_for_write_queue(skb, sk) { 1844 if (skb == tcp_send_head(sk)) 1845 break; 1846 if (skb->len > mss && 1847 !(TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) { 1848 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 1849 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1850 tp->retrans_out -= tcp_skb_pcount(skb); 1851 } 1852 if (!(TCP_SKB_CB(skb)->sacked & TCPCB_LOST)) { 1853 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1854 tp->lost_out += tcp_skb_pcount(skb); 1855 lost = 1; 1856 } 1857 } 1858 } 1859 1860 tcp_clear_all_retrans_hints(tp); 1861 1862 if (!lost) 1863 return; 1864 1865 if (tcp_is_reno(tp)) 1866 tcp_limit_reno_sacked(tp); 1867 1868 tcp_verify_left_out(tp); 1869 1870 /* Don't muck with the congestion window here. 1871 * Reason is that we do not increase amount of _data_ 1872 * in network, but units changed and effective 1873 * cwnd/ssthresh really reduced now. 1874 */ 1875 if (icsk->icsk_ca_state != TCP_CA_Loss) { 1876 tp->high_seq = tp->snd_nxt; 1877 tp->snd_ssthresh = tcp_current_ssthresh(sk); 1878 tp->prior_ssthresh = 0; 1879 tp->undo_marker = 0; 1880 tcp_set_ca_state(sk, TCP_CA_Loss); 1881 } 1882 tcp_xmit_retransmit_queue(sk); 1883 } 1884 1885 /* This retransmits one SKB. Policy decisions and retransmit queue 1886 * state updates are done by the caller. Returns non-zero if an 1887 * error occurred which prevented the send. 1888 */ 1889 int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) 1890 { 1891 struct tcp_sock *tp = tcp_sk(sk); 1892 struct inet_connection_sock *icsk = inet_csk(sk); 1893 unsigned int cur_mss; 1894 int err; 1895 1896 /* Inconslusive MTU probe */ 1897 if (icsk->icsk_mtup.probe_size) { 1898 icsk->icsk_mtup.probe_size = 0; 1899 } 1900 1901 /* Do not sent more than we queued. 1/4 is reserved for possible 1902 * copying overhead: fragmentation, tunneling, mangling etc. 1903 */ 1904 if (atomic_read(&sk->sk_wmem_alloc) > 1905 min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf)) 1906 return -EAGAIN; 1907 1908 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) { 1909 if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1910 BUG(); 1911 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) 1912 return -ENOMEM; 1913 } 1914 1915 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk)) 1916 return -EHOSTUNREACH; /* Routing failure or similar. */ 1917 1918 cur_mss = tcp_current_mss(sk, 0); 1919 1920 /* If receiver has shrunk his window, and skb is out of 1921 * new window, do not retransmit it. The exception is the 1922 * case, when window is shrunk to zero. In this case 1923 * our retransmit serves as a zero window probe. 1924 */ 1925 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) 1926 && TCP_SKB_CB(skb)->seq != tp->snd_una) 1927 return -EAGAIN; 1928 1929 if (skb->len > cur_mss) { 1930 if (tcp_fragment(sk, skb, cur_mss, cur_mss)) 1931 return -ENOMEM; /* We'll try again later. */ 1932 } 1933 1934 /* Collapse two adjacent packets if worthwhile and we can. */ 1935 if (!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN) && 1936 (skb->len < (cur_mss >> 1)) && 1937 (tcp_write_queue_next(sk, skb) != tcp_send_head(sk)) && 1938 (!tcp_skb_is_last(sk, skb)) && 1939 (skb_shinfo(skb)->nr_frags == 0 && 1940 skb_shinfo(tcp_write_queue_next(sk, skb))->nr_frags == 0) && 1941 (tcp_skb_pcount(skb) == 1 && 1942 tcp_skb_pcount(tcp_write_queue_next(sk, skb)) == 1) && 1943 (sysctl_tcp_retrans_collapse != 0)) 1944 tcp_retrans_try_collapse(sk, skb, cur_mss); 1945 1946 /* Some Solaris stacks overoptimize and ignore the FIN on a 1947 * retransmit when old data is attached. So strip it off 1948 * since it is cheap to do so and saves bytes on the network. 1949 */ 1950 if (skb->len > 0 && 1951 (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) && 1952 tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) { 1953 if (!pskb_trim(skb, 0)) { 1954 /* Reuse, even though it does some unnecessary work */ 1955 tcp_init_nondata_skb(skb, TCP_SKB_CB(skb)->end_seq - 1, 1956 TCP_SKB_CB(skb)->flags); 1957 skb->ip_summed = CHECKSUM_NONE; 1958 } 1959 } 1960 1961 /* Make a copy, if the first transmission SKB clone we made 1962 * is still in somebody's hands, else make a clone. 1963 */ 1964 TCP_SKB_CB(skb)->when = tcp_time_stamp; 1965 1966 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 1967 1968 if (err == 0) { 1969 /* Update global TCP statistics. */ 1970 TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS); 1971 1972 tp->total_retrans++; 1973 1974 #if FASTRETRANS_DEBUG > 0 1975 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 1976 if (net_ratelimit()) 1977 printk(KERN_DEBUG "retrans_out leaked.\n"); 1978 } 1979 #endif 1980 if (!tp->retrans_out) 1981 tp->lost_retrans_low = tp->snd_nxt; 1982 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS; 1983 tp->retrans_out += tcp_skb_pcount(skb); 1984 1985 /* Save stamp of the first retransmit. */ 1986 if (!tp->retrans_stamp) 1987 tp->retrans_stamp = TCP_SKB_CB(skb)->when; 1988 1989 tp->undo_retrans++; 1990 1991 /* snd_nxt is stored to detect loss of retransmitted segment, 1992 * see tcp_input.c tcp_sacktag_write_queue(). 1993 */ 1994 TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt; 1995 } 1996 return err; 1997 } 1998 1999 /* This gets called after a retransmit timeout, and the initially 2000 * retransmitted data is acknowledged. It tries to continue 2001 * resending the rest of the retransmit queue, until either 2002 * we've sent it all or the congestion window limit is reached. 2003 * If doing SACK, the first ACK which comes back for a timeout 2004 * based retransmit packet might feed us FACK information again. 2005 * If so, we use it to avoid unnecessarily retransmissions. 2006 */ 2007 void tcp_xmit_retransmit_queue(struct sock *sk) 2008 { 2009 const struct inet_connection_sock *icsk = inet_csk(sk); 2010 struct tcp_sock *tp = tcp_sk(sk); 2011 struct sk_buff *skb; 2012 int packet_cnt; 2013 2014 if (tp->retransmit_skb_hint) { 2015 skb = tp->retransmit_skb_hint; 2016 packet_cnt = tp->retransmit_cnt_hint; 2017 } else { 2018 skb = tcp_write_queue_head(sk); 2019 packet_cnt = 0; 2020 } 2021 2022 /* First pass: retransmit lost packets. */ 2023 if (tp->lost_out) { 2024 tcp_for_write_queue_from(skb, sk) { 2025 __u8 sacked = TCP_SKB_CB(skb)->sacked; 2026 2027 if (skb == tcp_send_head(sk)) 2028 break; 2029 /* we could do better than to assign each time */ 2030 tp->retransmit_skb_hint = skb; 2031 tp->retransmit_cnt_hint = packet_cnt; 2032 2033 /* Assume this retransmit will generate 2034 * only one packet for congestion window 2035 * calculation purposes. This works because 2036 * tcp_retransmit_skb() will chop up the 2037 * packet to be MSS sized and all the 2038 * packet counting works out. 2039 */ 2040 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) 2041 return; 2042 2043 if (sacked & TCPCB_LOST) { 2044 if (!(sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) { 2045 int mib_idx; 2046 2047 if (tcp_retransmit_skb(sk, skb)) { 2048 tp->retransmit_skb_hint = NULL; 2049 return; 2050 } 2051 if (icsk->icsk_ca_state != TCP_CA_Loss) 2052 mib_idx = LINUX_MIB_TCPFASTRETRANS; 2053 else 2054 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS; 2055 NET_INC_STATS_BH(sock_net(sk), mib_idx); 2056 2057 if (skb == tcp_write_queue_head(sk)) 2058 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 2059 inet_csk(sk)->icsk_rto, 2060 TCP_RTO_MAX); 2061 } 2062 2063 packet_cnt += tcp_skb_pcount(skb); 2064 if (packet_cnt >= tp->lost_out) 2065 break; 2066 } 2067 } 2068 } 2069 2070 /* OK, demanded retransmission is finished. */ 2071 2072 /* Forward retransmissions are possible only during Recovery. */ 2073 if (icsk->icsk_ca_state != TCP_CA_Recovery) 2074 return; 2075 2076 /* No forward retransmissions in Reno are possible. */ 2077 if (tcp_is_reno(tp)) 2078 return; 2079 2080 /* Yeah, we have to make difficult choice between forward transmission 2081 * and retransmission... Both ways have their merits... 2082 * 2083 * For now we do not retransmit anything, while we have some new 2084 * segments to send. In the other cases, follow rule 3 for 2085 * NextSeg() specified in RFC3517. 2086 */ 2087 2088 if (tcp_may_send_now(sk)) 2089 return; 2090 2091 /* If nothing is SACKed, highest_sack in the loop won't be valid */ 2092 if (!tp->sacked_out) 2093 return; 2094 2095 if (tp->forward_skb_hint) 2096 skb = tp->forward_skb_hint; 2097 else 2098 skb = tcp_write_queue_head(sk); 2099 2100 tcp_for_write_queue_from(skb, sk) { 2101 if (skb == tcp_send_head(sk)) 2102 break; 2103 tp->forward_skb_hint = skb; 2104 2105 if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp))) 2106 break; 2107 2108 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) 2109 break; 2110 2111 if (TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) 2112 continue; 2113 2114 /* Ok, retransmit it. */ 2115 if (tcp_retransmit_skb(sk, skb)) { 2116 tp->forward_skb_hint = NULL; 2117 break; 2118 } 2119 2120 if (skb == tcp_write_queue_head(sk)) 2121 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 2122 inet_csk(sk)->icsk_rto, 2123 TCP_RTO_MAX); 2124 2125 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPFORWARDRETRANS); 2126 } 2127 } 2128 2129 /* Send a fin. The caller locks the socket for us. This cannot be 2130 * allowed to fail queueing a FIN frame under any circumstances. 2131 */ 2132 void tcp_send_fin(struct sock *sk) 2133 { 2134 struct tcp_sock *tp = tcp_sk(sk); 2135 struct sk_buff *skb = tcp_write_queue_tail(sk); 2136 int mss_now; 2137 2138 /* Optimization, tack on the FIN if we have a queue of 2139 * unsent frames. But be careful about outgoing SACKS 2140 * and IP options. 2141 */ 2142 mss_now = tcp_current_mss(sk, 1); 2143 2144 if (tcp_send_head(sk) != NULL) { 2145 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN; 2146 TCP_SKB_CB(skb)->end_seq++; 2147 tp->write_seq++; 2148 } else { 2149 /* Socket is locked, keep trying until memory is available. */ 2150 for (;;) { 2151 skb = alloc_skb_fclone(MAX_TCP_HEADER, GFP_KERNEL); 2152 if (skb) 2153 break; 2154 yield(); 2155 } 2156 2157 /* Reserve space for headers and prepare control bits. */ 2158 skb_reserve(skb, MAX_TCP_HEADER); 2159 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */ 2160 tcp_init_nondata_skb(skb, tp->write_seq, 2161 TCPCB_FLAG_ACK | TCPCB_FLAG_FIN); 2162 tcp_queue_skb(sk, skb); 2163 } 2164 __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF); 2165 } 2166 2167 /* We get here when a process closes a file descriptor (either due to 2168 * an explicit close() or as a byproduct of exit()'ing) and there 2169 * was unread data in the receive queue. This behavior is recommended 2170 * by RFC 2525, section 2.17. -DaveM 2171 */ 2172 void tcp_send_active_reset(struct sock *sk, gfp_t priority) 2173 { 2174 struct sk_buff *skb; 2175 2176 /* NOTE: No TCP options attached and we never retransmit this. */ 2177 skb = alloc_skb(MAX_TCP_HEADER, priority); 2178 if (!skb) { 2179 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); 2180 return; 2181 } 2182 2183 /* Reserve space for headers and prepare control bits. */ 2184 skb_reserve(skb, MAX_TCP_HEADER); 2185 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk), 2186 TCPCB_FLAG_ACK | TCPCB_FLAG_RST); 2187 /* Send it off. */ 2188 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2189 if (tcp_transmit_skb(sk, skb, 0, priority)) 2190 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); 2191 2192 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS); 2193 } 2194 2195 /* WARNING: This routine must only be called when we have already sent 2196 * a SYN packet that crossed the incoming SYN that caused this routine 2197 * to get called. If this assumption fails then the initial rcv_wnd 2198 * and rcv_wscale values will not be correct. 2199 */ 2200 int tcp_send_synack(struct sock *sk) 2201 { 2202 struct sk_buff *skb; 2203 2204 skb = tcp_write_queue_head(sk); 2205 if (skb == NULL || !(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN)) { 2206 printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n"); 2207 return -EFAULT; 2208 } 2209 if (!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_ACK)) { 2210 if (skb_cloned(skb)) { 2211 struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC); 2212 if (nskb == NULL) 2213 return -ENOMEM; 2214 tcp_unlink_write_queue(skb, sk); 2215 skb_header_release(nskb); 2216 __tcp_add_write_queue_head(sk, nskb); 2217 sk_wmem_free_skb(sk, skb); 2218 sk->sk_wmem_queued += nskb->truesize; 2219 sk_mem_charge(sk, nskb->truesize); 2220 skb = nskb; 2221 } 2222 2223 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ACK; 2224 TCP_ECN_send_synack(tcp_sk(sk), skb); 2225 } 2226 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2227 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 2228 } 2229 2230 /* 2231 * Prepare a SYN-ACK. 2232 */ 2233 struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, 2234 struct request_sock *req) 2235 { 2236 struct inet_request_sock *ireq = inet_rsk(req); 2237 struct tcp_sock *tp = tcp_sk(sk); 2238 struct tcphdr *th; 2239 int tcp_header_size; 2240 struct tcp_out_options opts; 2241 struct sk_buff *skb; 2242 struct tcp_md5sig_key *md5; 2243 __u8 *md5_hash_location; 2244 2245 skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC); 2246 if (skb == NULL) 2247 return NULL; 2248 2249 /* Reserve space for headers. */ 2250 skb_reserve(skb, MAX_TCP_HEADER); 2251 2252 skb->dst = dst_clone(dst); 2253 2254 if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */ 2255 __u8 rcv_wscale; 2256 /* Set this up on the first call only */ 2257 req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW); 2258 /* tcp_full_space because it is guaranteed to be the first packet */ 2259 tcp_select_initial_window(tcp_full_space(sk), 2260 dst_metric(dst, RTAX_ADVMSS) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0), 2261 &req->rcv_wnd, 2262 &req->window_clamp, 2263 ireq->wscale_ok, 2264 &rcv_wscale); 2265 ireq->rcv_wscale = rcv_wscale; 2266 } 2267 2268 memset(&opts, 0, sizeof(opts)); 2269 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2270 tcp_header_size = tcp_synack_options(sk, req, 2271 dst_metric(dst, RTAX_ADVMSS), 2272 skb, &opts, &md5) + 2273 sizeof(struct tcphdr); 2274 2275 skb_push(skb, tcp_header_size); 2276 skb_reset_transport_header(skb); 2277 2278 th = tcp_hdr(skb); 2279 memset(th, 0, sizeof(struct tcphdr)); 2280 th->syn = 1; 2281 th->ack = 1; 2282 TCP_ECN_make_synack(req, th); 2283 th->source = inet_sk(sk)->sport; 2284 th->dest = ireq->rmt_port; 2285 /* Setting of flags are superfluous here for callers (and ECE is 2286 * not even correctly set) 2287 */ 2288 tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn, 2289 TCPCB_FLAG_SYN | TCPCB_FLAG_ACK); 2290 th->seq = htonl(TCP_SKB_CB(skb)->seq); 2291 th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1); 2292 2293 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */ 2294 th->window = htons(min(req->rcv_wnd, 65535U)); 2295 #ifdef CONFIG_SYN_COOKIES 2296 if (unlikely(req->cookie_ts)) 2297 TCP_SKB_CB(skb)->when = cookie_init_timestamp(req); 2298 else 2299 #endif 2300 tcp_options_write((__be32 *)(th + 1), tp, &opts, &md5_hash_location); 2301 th->doff = (tcp_header_size >> 2); 2302 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS); 2303 2304 #ifdef CONFIG_TCP_MD5SIG 2305 /* Okay, we have all we need - do the md5 hash if needed */ 2306 if (md5) { 2307 tp->af_specific->calc_md5_hash(md5_hash_location, 2308 md5, NULL, req, skb); 2309 } 2310 #endif 2311 2312 return skb; 2313 } 2314 2315 /* 2316 * Do all connect socket setups that can be done AF independent. 2317 */ 2318 static void tcp_connect_init(struct sock *sk) 2319 { 2320 struct dst_entry *dst = __sk_dst_get(sk); 2321 struct tcp_sock *tp = tcp_sk(sk); 2322 __u8 rcv_wscale; 2323 2324 /* We'll fix this up when we get a response from the other end. 2325 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. 2326 */ 2327 tp->tcp_header_len = sizeof(struct tcphdr) + 2328 (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0); 2329 2330 #ifdef CONFIG_TCP_MD5SIG 2331 if (tp->af_specific->md5_lookup(sk, sk) != NULL) 2332 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; 2333 #endif 2334 2335 /* If user gave his TCP_MAXSEG, record it to clamp */ 2336 if (tp->rx_opt.user_mss) 2337 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss; 2338 tp->max_window = 0; 2339 tcp_mtup_init(sk); 2340 tcp_sync_mss(sk, dst_mtu(dst)); 2341 2342 if (!tp->window_clamp) 2343 tp->window_clamp = dst_metric(dst, RTAX_WINDOW); 2344 tp->advmss = dst_metric(dst, RTAX_ADVMSS); 2345 tcp_initialize_rcv_mss(sk); 2346 2347 tcp_select_initial_window(tcp_full_space(sk), 2348 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0), 2349 &tp->rcv_wnd, 2350 &tp->window_clamp, 2351 sysctl_tcp_window_scaling, 2352 &rcv_wscale); 2353 2354 tp->rx_opt.rcv_wscale = rcv_wscale; 2355 tp->rcv_ssthresh = tp->rcv_wnd; 2356 2357 sk->sk_err = 0; 2358 sock_reset_flag(sk, SOCK_DONE); 2359 tp->snd_wnd = 0; 2360 tcp_init_wl(tp, tp->write_seq, 0); 2361 tp->snd_una = tp->write_seq; 2362 tp->snd_sml = tp->write_seq; 2363 tp->rcv_nxt = 0; 2364 tp->rcv_wup = 0; 2365 tp->copied_seq = 0; 2366 2367 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; 2368 inet_csk(sk)->icsk_retransmits = 0; 2369 tcp_clear_retrans(tp); 2370 } 2371 2372 /* 2373 * Build a SYN and send it off. 2374 */ 2375 int tcp_connect(struct sock *sk) 2376 { 2377 struct tcp_sock *tp = tcp_sk(sk); 2378 struct sk_buff *buff; 2379 2380 tcp_connect_init(sk); 2381 2382 buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation); 2383 if (unlikely(buff == NULL)) 2384 return -ENOBUFS; 2385 2386 /* Reserve space for headers. */ 2387 skb_reserve(buff, MAX_TCP_HEADER); 2388 2389 tp->snd_nxt = tp->write_seq; 2390 tcp_init_nondata_skb(buff, tp->write_seq++, TCPCB_FLAG_SYN); 2391 TCP_ECN_send_syn(sk, buff); 2392 2393 /* Send it off. */ 2394 TCP_SKB_CB(buff)->when = tcp_time_stamp; 2395 tp->retrans_stamp = TCP_SKB_CB(buff)->when; 2396 skb_header_release(buff); 2397 __tcp_add_write_queue_tail(sk, buff); 2398 sk->sk_wmem_queued += buff->truesize; 2399 sk_mem_charge(sk, buff->truesize); 2400 tp->packets_out += tcp_skb_pcount(buff); 2401 tcp_transmit_skb(sk, buff, 1, GFP_KERNEL); 2402 2403 /* We change tp->snd_nxt after the tcp_transmit_skb() call 2404 * in order to make this packet get counted in tcpOutSegs. 2405 */ 2406 tp->snd_nxt = tp->write_seq; 2407 tp->pushed_seq = tp->write_seq; 2408 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS); 2409 2410 /* Timer for repeating the SYN until an answer. */ 2411 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 2412 inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 2413 return 0; 2414 } 2415 2416 /* Send out a delayed ack, the caller does the policy checking 2417 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check() 2418 * for details. 2419 */ 2420 void tcp_send_delayed_ack(struct sock *sk) 2421 { 2422 struct inet_connection_sock *icsk = inet_csk(sk); 2423 int ato = icsk->icsk_ack.ato; 2424 unsigned long timeout; 2425 2426 if (ato > TCP_DELACK_MIN) { 2427 const struct tcp_sock *tp = tcp_sk(sk); 2428 int max_ato = HZ / 2; 2429 2430 if (icsk->icsk_ack.pingpong || 2431 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)) 2432 max_ato = TCP_DELACK_MAX; 2433 2434 /* Slow path, intersegment interval is "high". */ 2435 2436 /* If some rtt estimate is known, use it to bound delayed ack. 2437 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements 2438 * directly. 2439 */ 2440 if (tp->srtt) { 2441 int rtt = max(tp->srtt >> 3, TCP_DELACK_MIN); 2442 2443 if (rtt < max_ato) 2444 max_ato = rtt; 2445 } 2446 2447 ato = min(ato, max_ato); 2448 } 2449 2450 /* Stay within the limit we were given */ 2451 timeout = jiffies + ato; 2452 2453 /* Use new timeout only if there wasn't a older one earlier. */ 2454 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) { 2455 /* If delack timer was blocked or is about to expire, 2456 * send ACK now. 2457 */ 2458 if (icsk->icsk_ack.blocked || 2459 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) { 2460 tcp_send_ack(sk); 2461 return; 2462 } 2463 2464 if (!time_before(timeout, icsk->icsk_ack.timeout)) 2465 timeout = icsk->icsk_ack.timeout; 2466 } 2467 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER; 2468 icsk->icsk_ack.timeout = timeout; 2469 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout); 2470 } 2471 2472 /* This routine sends an ack and also updates the window. */ 2473 void tcp_send_ack(struct sock *sk) 2474 { 2475 struct sk_buff *buff; 2476 2477 /* If we have been reset, we may not send again. */ 2478 if (sk->sk_state == TCP_CLOSE) 2479 return; 2480 2481 /* We are not putting this on the write queue, so 2482 * tcp_transmit_skb() will set the ownership to this 2483 * sock. 2484 */ 2485 buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); 2486 if (buff == NULL) { 2487 inet_csk_schedule_ack(sk); 2488 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN; 2489 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 2490 TCP_DELACK_MAX, TCP_RTO_MAX); 2491 return; 2492 } 2493 2494 /* Reserve space for headers and prepare control bits. */ 2495 skb_reserve(buff, MAX_TCP_HEADER); 2496 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPCB_FLAG_ACK); 2497 2498 /* Send it off, this clears delayed acks for us. */ 2499 TCP_SKB_CB(buff)->when = tcp_time_stamp; 2500 tcp_transmit_skb(sk, buff, 0, GFP_ATOMIC); 2501 } 2502 2503 /* This routine sends a packet with an out of date sequence 2504 * number. It assumes the other end will try to ack it. 2505 * 2506 * Question: what should we make while urgent mode? 2507 * 4.4BSD forces sending single byte of data. We cannot send 2508 * out of window data, because we have SND.NXT==SND.MAX... 2509 * 2510 * Current solution: to send TWO zero-length segments in urgent mode: 2511 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is 2512 * out-of-date with SND.UNA-1 to probe window. 2513 */ 2514 static int tcp_xmit_probe_skb(struct sock *sk, int urgent) 2515 { 2516 struct tcp_sock *tp = tcp_sk(sk); 2517 struct sk_buff *skb; 2518 2519 /* We don't queue it, tcp_transmit_skb() sets ownership. */ 2520 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); 2521 if (skb == NULL) 2522 return -1; 2523 2524 /* Reserve space for headers and set control bits. */ 2525 skb_reserve(skb, MAX_TCP_HEADER); 2526 /* Use a previous sequence. This should cause the other 2527 * end to send an ack. Don't queue or clone SKB, just 2528 * send it. 2529 */ 2530 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPCB_FLAG_ACK); 2531 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2532 return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC); 2533 } 2534 2535 int tcp_write_wakeup(struct sock *sk) 2536 { 2537 struct tcp_sock *tp = tcp_sk(sk); 2538 struct sk_buff *skb; 2539 2540 if (sk->sk_state == TCP_CLOSE) 2541 return -1; 2542 2543 if ((skb = tcp_send_head(sk)) != NULL && 2544 before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) { 2545 int err; 2546 unsigned int mss = tcp_current_mss(sk, 0); 2547 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; 2548 2549 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq)) 2550 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq; 2551 2552 /* We are probing the opening of a window 2553 * but the window size is != 0 2554 * must have been a result SWS avoidance ( sender ) 2555 */ 2556 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq || 2557 skb->len > mss) { 2558 seg_size = min(seg_size, mss); 2559 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; 2560 if (tcp_fragment(sk, skb, seg_size, mss)) 2561 return -1; 2562 } else if (!tcp_skb_pcount(skb)) 2563 tcp_set_skb_tso_segs(sk, skb, mss); 2564 2565 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; 2566 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2567 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 2568 if (!err) 2569 tcp_event_new_data_sent(sk, skb); 2570 return err; 2571 } else { 2572 if (tp->urg_mode && 2573 between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF)) 2574 tcp_xmit_probe_skb(sk, 1); 2575 return tcp_xmit_probe_skb(sk, 0); 2576 } 2577 } 2578 2579 /* A window probe timeout has occurred. If window is not closed send 2580 * a partial packet else a zero probe. 2581 */ 2582 void tcp_send_probe0(struct sock *sk) 2583 { 2584 struct inet_connection_sock *icsk = inet_csk(sk); 2585 struct tcp_sock *tp = tcp_sk(sk); 2586 int err; 2587 2588 err = tcp_write_wakeup(sk); 2589 2590 if (tp->packets_out || !tcp_send_head(sk)) { 2591 /* Cancel probe timer, if it is not required. */ 2592 icsk->icsk_probes_out = 0; 2593 icsk->icsk_backoff = 0; 2594 return; 2595 } 2596 2597 if (err <= 0) { 2598 if (icsk->icsk_backoff < sysctl_tcp_retries2) 2599 icsk->icsk_backoff++; 2600 icsk->icsk_probes_out++; 2601 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 2602 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), 2603 TCP_RTO_MAX); 2604 } else { 2605 /* If packet was not sent due to local congestion, 2606 * do not backoff and do not remember icsk_probes_out. 2607 * Let local senders to fight for local resources. 2608 * 2609 * Use accumulated backoff yet. 2610 */ 2611 if (!icsk->icsk_probes_out) 2612 icsk->icsk_probes_out = 1; 2613 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 2614 min(icsk->icsk_rto << icsk->icsk_backoff, 2615 TCP_RESOURCE_PROBE_INTERVAL), 2616 TCP_RTO_MAX); 2617 } 2618 } 2619 2620 EXPORT_SYMBOL(tcp_select_initial_window); 2621 EXPORT_SYMBOL(tcp_connect); 2622 EXPORT_SYMBOL(tcp_make_synack); 2623 EXPORT_SYMBOL(tcp_simple_retransmit); 2624 EXPORT_SYMBOL(tcp_sync_mss); 2625 EXPORT_SYMBOL(tcp_mtup_init); 2626