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 * Version: $Id: tcp_output.c,v 1.1.1.1 2007/08/03 18:53:51 Exp $ 9 * 10 * Authors: Ross Biro 11 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 12 * Mark Evans, <evansmp@uhura.aston.ac.uk> 13 * Corey Minyard <wf-rch!minyard@relay.EU.net> 14 * Florian La Roche, <flla@stud.uni-sb.de> 15 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> 16 * Linus Torvalds, <torvalds@cs.helsinki.fi> 17 * Alan Cox, <gw4pts@gw4pts.ampr.org> 18 * Matthew Dillon, <dillon@apollo.west.oic.com> 19 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 20 * Jorge Cwik, <jorge@laser.satlink.net> 21 */ 22 23/* 24 * Changes: Pedro Roque : Retransmit queue handled by TCP. 25 * : Fragmentation on mtu decrease 26 * : Segment collapse on retransmit 27 * : AF independence 28 * 29 * Linus Torvalds : send_delayed_ack 30 * David S. Miller : Charge memory using the right skb 31 * during syn/ack processing. 32 * David S. Miller : Output engine completely rewritten. 33 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr. 34 * Cacophonix Gaul : draft-minshall-nagle-01 35 * J Hadi Salim : ECN support 36 * 37 */ 38 39#include <net/tcp.h> 40 41#include <linux/compiler.h> 42#include <linux/module.h> 43 44/* People can turn this off for buggy TCP's found in printers etc. */ 45int sysctl_tcp_retrans_collapse __read_mostly = 1; 46 47/* People can turn this on to work with those rare, broken TCPs that 48 * interpret the window field as a signed quantity. 49 */ 50int sysctl_tcp_workaround_signed_windows __read_mostly = 0; 51 52/* This limits the percentage of the congestion window which we 53 * will allow a single TSO frame to consume. Building TSO frames 54 * which are too large can cause TCP streams to be bursty. 55 */ 56int sysctl_tcp_tso_win_divisor __read_mostly = 3; 57 58int sysctl_tcp_mtu_probing __read_mostly = 0; 59int sysctl_tcp_base_mss __read_mostly = 512; 60 61/* By default, RFC2861 behavior. */ 62int sysctl_tcp_slow_start_after_idle __read_mostly = 1; 63 64static void update_send_head(struct sock *sk, struct sk_buff *skb) 65{ 66 struct tcp_sock *tp = tcp_sk(sk); 67 68 tcp_advance_send_head(sk, skb); 69 tp->snd_nxt = TCP_SKB_CB(skb)->end_seq; 70 tcp_packets_out_inc(sk, skb); 71} 72 73/* SND.NXT, if window was not shrunk. 74 * If window has been shrunk, what should we make? It is not clear at all. 75 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-( 76 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already 77 * invalid. OK, let's make this for now: 78 */ 79static inline __u32 tcp_acceptable_seq(struct sock *sk) 80{ 81 struct tcp_sock *tp = tcp_sk(sk); 82 83 if (!before(tp->snd_una+tp->snd_wnd, tp->snd_nxt)) 84 return tp->snd_nxt; 85 else 86 return tp->snd_una+tp->snd_wnd; 87} 88 89/* Calculate mss to advertise in SYN segment. 90 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that: 91 * 92 * 1. It is independent of path mtu. 93 * 2. Ideally, it is maximal possible segment size i.e. 65535-40. 94 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of 95 * attached devices, because some buggy hosts are confused by 96 * large MSS. 97 * 4. We do not make 3, we advertise MSS, calculated from first 98 * hop device mtu, but allow to raise it to ip_rt_min_advmss. 99 * This may be overridden via information stored in routing table. 100 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible, 101 * probably even Jumbo". 102 */ 103static __u16 tcp_advertise_mss(struct sock *sk) 104{ 105 struct tcp_sock *tp = tcp_sk(sk); 106 struct dst_entry *dst = __sk_dst_get(sk); 107 int mss = tp->advmss; 108 109 if (dst && dst_metric(dst, RTAX_ADVMSS) < mss) { 110 mss = dst_metric(dst, RTAX_ADVMSS); 111 tp->advmss = mss; 112 } 113 114 return (__u16)mss; 115} 116 117/* RFC2861. Reset CWND after idle period longer RTO to "restart window". 118 * This is the first part of cwnd validation mechanism. */ 119static void tcp_cwnd_restart(struct sock *sk, struct dst_entry *dst) 120{ 121 struct tcp_sock *tp = tcp_sk(sk); 122 s32 delta = tcp_time_stamp - tp->lsndtime; 123 u32 restart_cwnd = tcp_init_cwnd(tp, dst); 124 u32 cwnd = tp->snd_cwnd; 125 126 tcp_ca_event(sk, CA_EVENT_CWND_RESTART); 127 128 tp->snd_ssthresh = tcp_current_ssthresh(sk); 129 restart_cwnd = min(restart_cwnd, cwnd); 130 131 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd) 132 cwnd >>= 1; 133 tp->snd_cwnd = max(cwnd, restart_cwnd); 134 tp->snd_cwnd_stamp = tcp_time_stamp; 135 tp->snd_cwnd_used = 0; 136} 137 138static void tcp_event_data_sent(struct tcp_sock *tp, 139 struct sk_buff *skb, struct sock *sk) 140{ 141 struct inet_connection_sock *icsk = inet_csk(sk); 142 const u32 now = tcp_time_stamp; 143 144 if (sysctl_tcp_slow_start_after_idle && 145 (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto)) 146 tcp_cwnd_restart(sk, __sk_dst_get(sk)); 147 148 tp->lsndtime = now; 149 150 /* If it is a reply for ato after last received 151 * packet, enter pingpong mode. 152 */ 153 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato) 154 icsk->icsk_ack.pingpong = 1; 155} 156 157static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts) 158{ 159 tcp_dec_quickack_mode(sk, pkts); 160 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK); 161} 162 163/* Determine a window scaling and initial window to offer. 164 * Based on the assumption that the given amount of space 165 * will be offered. Store the results in the tp structure. 166 * NOTE: for smooth operation initial space offering should 167 * be a multiple of mss if possible. We assume here that mss >= 1. 168 * This MUST be enforced by all callers. 169 */ 170void tcp_select_initial_window(int __space, __u32 mss, 171 __u32 *rcv_wnd, __u32 *window_clamp, 172 int wscale_ok, __u8 *rcv_wscale) 173{ 174 unsigned int space = (__space < 0 ? 0 : __space); 175 176 /* If no clamp set the clamp to the max possible scaled window */ 177 if (*window_clamp == 0) 178 (*window_clamp) = (65535 << 14); 179 space = min(*window_clamp, space); 180 181 /* Quantize space offering to a multiple of mss if possible. */ 182 if (space > mss) 183 space = (space / mss) * mss; 184 185 /* NOTE: offering an initial window larger than 32767 186 * will break some buggy TCP stacks. If the admin tells us 187 * it is likely we could be speaking with such a buggy stack 188 * we will truncate our initial window offering to 32K-1 189 * unless the remote has sent us a window scaling option, 190 * which we interpret as a sign the remote TCP is not 191 * misinterpreting the window field as a signed quantity. 192 */ 193 if (sysctl_tcp_workaround_signed_windows) 194 (*rcv_wnd) = min(space, MAX_TCP_WINDOW); 195 else 196 (*rcv_wnd) = space; 197 198 (*rcv_wscale) = 0; 199 if (wscale_ok) { 200 /* Set window scaling on max possible window 201 * See RFC1323 for an explanation of the limit to 14 202 */ 203 space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max); 204 space = min_t(u32, space, *window_clamp); 205 while (space > 65535 && (*rcv_wscale) < 14) { 206 space >>= 1; 207 (*rcv_wscale)++; 208 } 209 } 210 211 /* Set initial window to value enough for senders, 212 * following RFC2414. Senders, not following this RFC, 213 * will be satisfied with 2. 214 */ 215 if (mss > (1<<*rcv_wscale)) { 216 int init_cwnd = 4; 217 if (mss > 1460*3) 218 init_cwnd = 2; 219 else if (mss > 1460) 220 init_cwnd = 3; 221 if (*rcv_wnd > init_cwnd*mss) 222 *rcv_wnd = init_cwnd*mss; 223 } 224 225 /* Set the clamp no higher than max representable value */ 226 (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp); 227} 228 229/* Chose a new window to advertise, update state in tcp_sock for the 230 * socket, and return result with RFC1323 scaling applied. The return 231 * value can be stuffed directly into th->window for an outgoing 232 * frame. 233 */ 234static u16 tcp_select_window(struct sock *sk) 235{ 236 struct tcp_sock *tp = tcp_sk(sk); 237 u32 cur_win = tcp_receive_window(tp); 238 u32 new_win = __tcp_select_window(sk); 239 240 /* Never shrink the offered window */ 241 if (new_win < cur_win) { 242 /* Danger Will Robinson! 243 * Don't update rcv_wup/rcv_wnd here or else 244 * we will not be able to advertise a zero 245 * window in time. --DaveM 246 * 247 * Relax Will Robinson. 248 */ 249 new_win = cur_win; 250 } 251 tp->rcv_wnd = new_win; 252 tp->rcv_wup = tp->rcv_nxt; 253 254 /* Make sure we do not exceed the maximum possible 255 * scaled window. 256 */ 257 if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows) 258 new_win = min(new_win, MAX_TCP_WINDOW); 259 else 260 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); 261 262 /* RFC1323 scaling applied */ 263 new_win >>= tp->rx_opt.rcv_wscale; 264 265 /* If we advertise zero window, disable fast path. */ 266 if (new_win == 0) 267 tp->pred_flags = 0; 268 269 return new_win; 270} 271 272static void tcp_build_and_update_options(__be32 *ptr, struct tcp_sock *tp, 273 __u32 tstamp, __u8 **md5_hash) 274{ 275 if (tp->rx_opt.tstamp_ok) { 276 *ptr++ = htonl((TCPOPT_NOP << 24) | 277 (TCPOPT_NOP << 16) | 278 (TCPOPT_TIMESTAMP << 8) | 279 TCPOLEN_TIMESTAMP); 280 *ptr++ = htonl(tstamp); 281 *ptr++ = htonl(tp->rx_opt.ts_recent); 282 } 283 if (tp->rx_opt.eff_sacks) { 284 struct tcp_sack_block *sp = tp->rx_opt.dsack ? tp->duplicate_sack : tp->selective_acks; 285 int this_sack; 286 287 *ptr++ = htonl((TCPOPT_NOP << 24) | 288 (TCPOPT_NOP << 16) | 289 (TCPOPT_SACK << 8) | 290 (TCPOLEN_SACK_BASE + (tp->rx_opt.eff_sacks * 291 TCPOLEN_SACK_PERBLOCK))); 292 293 for (this_sack = 0; this_sack < tp->rx_opt.eff_sacks; this_sack++) { 294 *ptr++ = htonl(sp[this_sack].start_seq); 295 *ptr++ = htonl(sp[this_sack].end_seq); 296 } 297 298 if (tp->rx_opt.dsack) { 299 tp->rx_opt.dsack = 0; 300 tp->rx_opt.eff_sacks--; 301 } 302 } 303#ifdef CONFIG_TCP_MD5SIG 304 if (md5_hash) { 305 *ptr++ = htonl((TCPOPT_NOP << 24) | 306 (TCPOPT_NOP << 16) | 307 (TCPOPT_MD5SIG << 8) | 308 TCPOLEN_MD5SIG); 309 *md5_hash = (__u8 *)ptr; 310 } 311#endif 312} 313 314/* Construct a tcp options header for a SYN or SYN_ACK packet. 315 * If this is every changed make sure to change the definition of 316 * MAX_SYN_SIZE to match the new maximum number of options that you 317 * can generate. 318 * 319 * Note - that with the RFC2385 TCP option, we make room for the 320 * 16 byte MD5 hash. This will be filled in later, so the pointer for the 321 * location to be filled is passed back up. 322 */ 323static void tcp_syn_build_options(__be32 *ptr, int mss, int ts, int sack, 324 int offer_wscale, int wscale, __u32 tstamp, 325 __u32 ts_recent, __u8 **md5_hash) 326{ 327 /* We always get an MSS option. 328 * The option bytes which will be seen in normal data 329 * packets should timestamps be used, must be in the MSS 330 * advertised. But we subtract them from tp->mss_cache so 331 * that calculations in tcp_sendmsg are simpler etc. 332 * So account for this fact here if necessary. If we 333 * don't do this correctly, as a receiver we won't 334 * recognize data packets as being full sized when we 335 * should, and thus we won't abide by the delayed ACK 336 * rules correctly. 337 * SACKs don't matter, we never delay an ACK when we 338 * have any of those going out. 339 */ 340 *ptr++ = htonl((TCPOPT_MSS << 24) | (TCPOLEN_MSS << 16) | mss); 341 if (ts) { 342 if (sack) 343 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) | 344 (TCPOLEN_SACK_PERM << 16) | 345 (TCPOPT_TIMESTAMP << 8) | 346 TCPOLEN_TIMESTAMP); 347 else 348 *ptr++ = htonl((TCPOPT_NOP << 24) | 349 (TCPOPT_NOP << 16) | 350 (TCPOPT_TIMESTAMP << 8) | 351 TCPOLEN_TIMESTAMP); 352 *ptr++ = htonl(tstamp); /* TSVAL */ 353 *ptr++ = htonl(ts_recent); /* TSECR */ 354 } else if (sack) 355 *ptr++ = htonl((TCPOPT_NOP << 24) | 356 (TCPOPT_NOP << 16) | 357 (TCPOPT_SACK_PERM << 8) | 358 TCPOLEN_SACK_PERM); 359 if (offer_wscale) 360 *ptr++ = htonl((TCPOPT_NOP << 24) | 361 (TCPOPT_WINDOW << 16) | 362 (TCPOLEN_WINDOW << 8) | 363 (wscale)); 364#ifdef CONFIG_TCP_MD5SIG 365 /* 366 * If MD5 is enabled, then we set the option, and include the size 367 * (always 18). The actual MD5 hash is added just before the 368 * packet is sent. 369 */ 370 if (md5_hash) { 371 *ptr++ = htonl((TCPOPT_NOP << 24) | 372 (TCPOPT_NOP << 16) | 373 (TCPOPT_MD5SIG << 8) | 374 TCPOLEN_MD5SIG); 375 *md5_hash = (__u8 *) ptr; 376 } 377#endif 378} 379 380/* This routine actually transmits TCP packets queued in by 381 * tcp_do_sendmsg(). This is used by both the initial 382 * transmission and possible later retransmissions. 383 * All SKB's seen here are completely headerless. It is our 384 * job to build the TCP header, and pass the packet down to 385 * IP so it can do the same plus pass the packet off to the 386 * device. 387 * 388 * We are working here with either a clone of the original 389 * SKB, or a fresh unique copy made by the retransmit engine. 390 */ 391static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, gfp_t gfp_mask) 392{ 393 const struct inet_connection_sock *icsk = inet_csk(sk); 394 struct inet_sock *inet; 395 struct tcp_sock *tp; 396 struct tcp_skb_cb *tcb; 397 int tcp_header_size; 398#ifdef CONFIG_TCP_MD5SIG 399 struct tcp_md5sig_key *md5; 400 __u8 *md5_hash_location; 401#endif 402 struct tcphdr *th; 403 int sysctl_flags; 404 int err; 405 406 BUG_ON(!skb || !tcp_skb_pcount(skb)); 407 408 /* If congestion control is doing timestamping, we must 409 * take such a timestamp before we potentially clone/copy. 410 */ 411 if (icsk->icsk_ca_ops->flags & TCP_CONG_RTT_STAMP) 412 __net_timestamp(skb); 413 414 if (likely(clone_it)) { 415 if (unlikely(skb_cloned(skb))) 416 skb = pskb_copy(skb, gfp_mask); 417 else 418 skb = skb_clone(skb, gfp_mask); 419 if (unlikely(!skb)) 420 return -ENOBUFS; 421 } 422 423 inet = inet_sk(sk); 424 tp = tcp_sk(sk); 425 tcb = TCP_SKB_CB(skb); 426 tcp_header_size = tp->tcp_header_len; 427 428#define SYSCTL_FLAG_TSTAMPS 0x1 429#define SYSCTL_FLAG_WSCALE 0x2 430#define SYSCTL_FLAG_SACK 0x4 431 432 sysctl_flags = 0; 433 if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) { 434 tcp_header_size = sizeof(struct tcphdr) + TCPOLEN_MSS; 435 if (sysctl_tcp_timestamps) { 436 tcp_header_size += TCPOLEN_TSTAMP_ALIGNED; 437 sysctl_flags |= SYSCTL_FLAG_TSTAMPS; 438 } 439 if (sysctl_tcp_window_scaling) { 440 tcp_header_size += TCPOLEN_WSCALE_ALIGNED; 441 sysctl_flags |= SYSCTL_FLAG_WSCALE; 442 } 443 if (sysctl_tcp_sack) { 444 sysctl_flags |= SYSCTL_FLAG_SACK; 445 if (!(sysctl_flags & SYSCTL_FLAG_TSTAMPS)) 446 tcp_header_size += TCPOLEN_SACKPERM_ALIGNED; 447 } 448 } else if (unlikely(tp->rx_opt.eff_sacks)) { 449 /* A SACK is 2 pad bytes, a 2 byte header, plus 450 * 2 32-bit sequence numbers for each SACK block. 451 */ 452 tcp_header_size += (TCPOLEN_SACK_BASE_ALIGNED + 453 (tp->rx_opt.eff_sacks * 454 TCPOLEN_SACK_PERBLOCK)); 455 } 456 457 if (tcp_packets_in_flight(tp) == 0) 458 tcp_ca_event(sk, CA_EVENT_TX_START); 459 460#ifdef CONFIG_TCP_MD5SIG 461 /* 462 * Are we doing MD5 on this segment? If so - make 463 * room for it. 464 */ 465 md5 = tp->af_specific->md5_lookup(sk, sk); 466 if (md5) 467 tcp_header_size += TCPOLEN_MD5SIG_ALIGNED; 468#endif 469 470 skb_push(skb, tcp_header_size); 471 skb_reset_transport_header(skb); 472 skb_set_owner_w(skb, sk); 473 474 /* Build TCP header and checksum it. */ 475 th = tcp_hdr(skb); 476 th->source = inet->sport; 477 th->dest = inet->dport; 478 th->seq = htonl(tcb->seq); 479 th->ack_seq = htonl(tp->rcv_nxt); 480 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) | 481 tcb->flags); 482 483 if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) { 484 /* RFC1323: The window in SYN & SYN/ACK segments 485 * is never scaled. 486 */ 487 th->window = htons(min(tp->rcv_wnd, 65535U)); 488 } else { 489 th->window = htons(tcp_select_window(sk)); 490 } 491 th->check = 0; 492 th->urg_ptr = 0; 493 494 if (unlikely(tp->urg_mode && 495 between(tp->snd_up, tcb->seq+1, tcb->seq+0xFFFF))) { 496 th->urg_ptr = htons(tp->snd_up-tcb->seq); 497 th->urg = 1; 498 } 499 500 if (unlikely(tcb->flags & TCPCB_FLAG_SYN)) { 501 tcp_syn_build_options((__be32 *)(th + 1), 502 tcp_advertise_mss(sk), 503 (sysctl_flags & SYSCTL_FLAG_TSTAMPS), 504 (sysctl_flags & SYSCTL_FLAG_SACK), 505 (sysctl_flags & SYSCTL_FLAG_WSCALE), 506 tp->rx_opt.rcv_wscale, 507 tcb->when, 508 tp->rx_opt.ts_recent, 509 510#ifdef CONFIG_TCP_MD5SIG 511 md5 ? &md5_hash_location : 512#endif 513 NULL); 514 } else { 515 tcp_build_and_update_options((__be32 *)(th + 1), 516 tp, tcb->when, 517#ifdef CONFIG_TCP_MD5SIG 518 md5 ? &md5_hash_location : 519#endif 520 NULL); 521 TCP_ECN_send(sk, skb, tcp_header_size); 522 } 523 524#ifdef CONFIG_TCP_MD5SIG 525 /* Calculate the MD5 hash, as we have all we need now */ 526 if (md5) { 527 tp->af_specific->calc_md5_hash(md5_hash_location, 528 md5, 529 sk, NULL, NULL, 530 tcp_hdr(skb), 531 sk->sk_protocol, 532 skb->len); 533 } 534#endif 535 536 icsk->icsk_af_ops->send_check(sk, skb->len, skb); 537 538 if (likely(tcb->flags & TCPCB_FLAG_ACK)) 539 tcp_event_ack_sent(sk, tcp_skb_pcount(skb)); 540 541 if (skb->len != tcp_header_size) 542 tcp_event_data_sent(tp, skb, sk); 543 544 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq) 545 TCP_INC_STATS(TCP_MIB_OUTSEGS); 546 547 err = icsk->icsk_af_ops->queue_xmit(skb, 0); 548 if (likely(err <= 0)) 549 return err; 550 551 tcp_enter_cwr(sk, 1); 552 553 return net_xmit_eval(err); 554 555#undef SYSCTL_FLAG_TSTAMPS 556#undef SYSCTL_FLAG_WSCALE 557#undef SYSCTL_FLAG_SACK 558} 559 560 561/* This routine just queue's the buffer 562 * 563 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames, 564 * otherwise socket can stall. 565 */ 566static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) 567{ 568 struct tcp_sock *tp = tcp_sk(sk); 569 570 /* Advance write_seq and place onto the write_queue. */ 571 tp->write_seq = TCP_SKB_CB(skb)->end_seq; 572 skb_header_release(skb); 573 tcp_add_write_queue_tail(sk, skb); 574 sk_charge_skb(sk, skb); 575} 576 577static void tcp_set_skb_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now) 578{ 579 if (skb->len <= mss_now || !sk_can_gso(sk)) { 580 /* Avoid the costly divide in the normal 581 * non-TSO case. 582 */ 583 skb_shinfo(skb)->gso_segs = 1; 584 skb_shinfo(skb)->gso_size = 0; 585 skb_shinfo(skb)->gso_type = 0; 586 } else { 587 unsigned int factor; 588 589 factor = skb->len + (mss_now - 1); 590 factor /= mss_now; 591 skb_shinfo(skb)->gso_segs = factor; 592 skb_shinfo(skb)->gso_size = mss_now; 593 skb_shinfo(skb)->gso_type = sk->sk_gso_type; 594 } 595} 596 597/* Function to create two new TCP segments. Shrinks the given segment 598 * to the specified size and appends a new segment with the rest of the 599 * packet to the list. This won't be called frequently, I hope. 600 * Remember, these are still headerless SKBs at this point. 601 */ 602int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, unsigned int mss_now) 603{ 604 struct tcp_sock *tp = tcp_sk(sk); 605 struct sk_buff *buff; 606 int nsize, old_factor; 607 int nlen; 608 u16 flags; 609 610 BUG_ON(len > skb->len); 611 612 clear_all_retrans_hints(tp); 613 nsize = skb_headlen(skb) - len; 614 if (nsize < 0) 615 nsize = 0; 616 617 if (skb_cloned(skb) && 618 skb_is_nonlinear(skb) && 619 pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) 620 return -ENOMEM; 621 622 /* Get a new skb... force flag on. */ 623 buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC); 624 if (buff == NULL) 625 return -ENOMEM; /* We'll just try again later. */ 626 627 sk_charge_skb(sk, buff); 628 nlen = skb->len - len - nsize; 629 buff->truesize += nlen; 630 skb->truesize -= nlen; 631 632 /* Correct the sequence numbers. */ 633 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; 634 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; 635 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; 636 637 /* PSH and FIN should only be set in the second packet. */ 638 flags = TCP_SKB_CB(skb)->flags; 639 TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH); 640 TCP_SKB_CB(buff)->flags = flags; 641 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked; 642 TCP_SKB_CB(skb)->sacked &= ~TCPCB_AT_TAIL; 643 644 if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) { 645 /* Copy and checksum data tail into the new buffer. */ 646 buff->csum = csum_partial_copy_nocheck(skb->data + len, skb_put(buff, nsize), 647 nsize, 0); 648 649 skb_trim(skb, len); 650 651 skb->csum = csum_block_sub(skb->csum, buff->csum, len); 652 } else { 653 skb->ip_summed = CHECKSUM_PARTIAL; 654 skb_split(skb, buff, len); 655 } 656 657 buff->ip_summed = skb->ip_summed; 658 659 /* Looks stupid, but our code really uses when of 660 * skbs, which it never sent before. --ANK 661 */ 662 TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when; 663 buff->tstamp = skb->tstamp; 664 665 old_factor = tcp_skb_pcount(skb); 666 667 /* Fix up tso_factor for both original and new SKB. */ 668 tcp_set_skb_tso_segs(sk, skb, mss_now); 669 tcp_set_skb_tso_segs(sk, buff, mss_now); 670 671 /* If this packet has been sent out already, we must 672 * adjust the various packet counters. 673 */ 674 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) { 675 int diff = old_factor - tcp_skb_pcount(skb) - 676 tcp_skb_pcount(buff); 677 678 tp->packets_out -= diff; 679 680 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) 681 tp->sacked_out -= diff; 682 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) 683 tp->retrans_out -= diff; 684 685 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) { 686 tp->lost_out -= diff; 687 tp->left_out -= diff; 688 } 689 690 if (diff > 0) { 691 /* Adjust Reno SACK estimate. */ 692 if (!tp->rx_opt.sack_ok) { 693 tp->sacked_out -= diff; 694 if ((int)tp->sacked_out < 0) 695 tp->sacked_out = 0; 696 tcp_sync_left_out(tp); 697 } 698 699 tp->fackets_out -= diff; 700 if ((int)tp->fackets_out < 0) 701 tp->fackets_out = 0; 702 } 703 } 704 705 /* Link BUFF into the send queue. */ 706 skb_header_release(buff); 707 tcp_insert_write_queue_after(skb, buff, sk); 708 709 return 0; 710} 711 712/* This is similar to __pskb_pull_head() (it will go to core/skbuff.c 713 * eventually). The difference is that pulled data not copied, but 714 * immediately discarded. 715 */ 716static void __pskb_trim_head(struct sk_buff *skb, int len) 717{ 718 int i, k, eat; 719 720 eat = len; 721 k = 0; 722 for (i=0; i<skb_shinfo(skb)->nr_frags; i++) { 723 if (skb_shinfo(skb)->frags[i].size <= eat) { 724 put_page(skb_shinfo(skb)->frags[i].page); 725 eat -= skb_shinfo(skb)->frags[i].size; 726 } else { 727 skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i]; 728 if (eat) { 729 skb_shinfo(skb)->frags[k].page_offset += eat; 730 skb_shinfo(skb)->frags[k].size -= eat; 731 eat = 0; 732 } 733 k++; 734 } 735 } 736 skb_shinfo(skb)->nr_frags = k; 737 738 skb_reset_tail_pointer(skb); 739 skb->data_len -= len; 740 skb->len = skb->data_len; 741} 742 743int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) 744{ 745 if (skb_cloned(skb) && 746 pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) 747 return -ENOMEM; 748 749 /* If len == headlen, we avoid __skb_pull to preserve alignment. */ 750 if (unlikely(len < skb_headlen(skb))) 751 __skb_pull(skb, len); 752 else 753 __pskb_trim_head(skb, len - skb_headlen(skb)); 754 755 TCP_SKB_CB(skb)->seq += len; 756 skb->ip_summed = CHECKSUM_PARTIAL; 757 758 skb->truesize -= len; 759 sk->sk_wmem_queued -= len; 760 sk->sk_forward_alloc += len; 761 sock_set_flag(sk, SOCK_QUEUE_SHRUNK); 762 763 /* Any change of skb->len requires recalculation of tso 764 * factor and mss. 765 */ 766 if (tcp_skb_pcount(skb) > 1) 767 tcp_set_skb_tso_segs(sk, skb, tcp_current_mss(sk, 1)); 768 769 return 0; 770} 771 772/* Not accounting for SACKs here. */ 773int tcp_mtu_to_mss(struct sock *sk, int pmtu) 774{ 775 struct tcp_sock *tp = tcp_sk(sk); 776 struct inet_connection_sock *icsk = inet_csk(sk); 777 int mss_now; 778 779 /* Calculate base mss without TCP options: 780 It is MMS_S - sizeof(tcphdr) of rfc1122 781 */ 782 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr); 783 784 /* Clamp it (mss_clamp does not include tcp options) */ 785 if (mss_now > tp->rx_opt.mss_clamp) 786 mss_now = tp->rx_opt.mss_clamp; 787 788 /* Now subtract optional transport overhead */ 789 mss_now -= icsk->icsk_ext_hdr_len; 790 791 /* Then reserve room for full set of TCP options and 8 bytes of data */ 792 if (mss_now < 48) 793 mss_now = 48; 794 795 /* Now subtract TCP options size, not including SACKs */ 796 mss_now -= tp->tcp_header_len - sizeof(struct tcphdr); 797 798 return mss_now; 799} 800 801/* Inverse of above */ 802int tcp_mss_to_mtu(struct sock *sk, int mss) 803{ 804 struct tcp_sock *tp = tcp_sk(sk); 805 struct inet_connection_sock *icsk = inet_csk(sk); 806 int mtu; 807 808 mtu = mss + 809 tp->tcp_header_len + 810 icsk->icsk_ext_hdr_len + 811 icsk->icsk_af_ops->net_header_len; 812 813 return mtu; 814} 815 816void tcp_mtup_init(struct sock *sk) 817{ 818 struct tcp_sock *tp = tcp_sk(sk); 819 struct inet_connection_sock *icsk = inet_csk(sk); 820 821 icsk->icsk_mtup.enabled = sysctl_tcp_mtu_probing > 1; 822 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) + 823 icsk->icsk_af_ops->net_header_len; 824 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss); 825 icsk->icsk_mtup.probe_size = 0; 826} 827 828/* This function synchronize snd mss to current pmtu/exthdr set. 829 830 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts 831 for TCP options, but includes only bare TCP header. 832 833 tp->rx_opt.mss_clamp is mss negotiated at connection setup. 834 It is minimum of user_mss and mss received with SYN. 835 It also does not include TCP options. 836 837 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function. 838 839 tp->mss_cache is current effective sending mss, including 840 all tcp options except for SACKs. It is evaluated, 841 taking into account current pmtu, but never exceeds 842 tp->rx_opt.mss_clamp. 843 844 NOTE1. rfc1122 clearly states that advertised MSS 845 DOES NOT include either tcp or ip options. 846 847 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache 848 are READ ONLY outside this function. --ANK (980731) 849 */ 850 851unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu) 852{ 853 struct tcp_sock *tp = tcp_sk(sk); 854 struct inet_connection_sock *icsk = inet_csk(sk); 855 int mss_now; 856 857 if (icsk->icsk_mtup.search_high > pmtu) 858 icsk->icsk_mtup.search_high = pmtu; 859 860 mss_now = tcp_mtu_to_mss(sk, pmtu); 861 862 /* Bound mss with half of window */ 863 if (tp->max_window && mss_now > (tp->max_window>>1)) 864 mss_now = max((tp->max_window>>1), 68U - tp->tcp_header_len); 865 866 /* And store cached results */ 867 icsk->icsk_pmtu_cookie = pmtu; 868 if (icsk->icsk_mtup.enabled) 869 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)); 870 tp->mss_cache = mss_now; 871 872 return mss_now; 873} 874 875/* Compute the current effective MSS, taking SACKs and IP options, 876 * and even PMTU discovery events into account. 877 * 878 * LARGESEND note: !urg_mode is overkill, only frames up to snd_up 879 * cannot be large. However, taking into account rare use of URG, this 880 * is not a big flaw. 881 */ 882unsigned int tcp_current_mss(struct sock *sk, int large_allowed) 883{ 884 struct tcp_sock *tp = tcp_sk(sk); 885 struct dst_entry *dst = __sk_dst_get(sk); 886 u32 mss_now; 887 u16 xmit_size_goal; 888 int doing_tso = 0; 889 890 mss_now = tp->mss_cache; 891 892 if (large_allowed && sk_can_gso(sk) && !tp->urg_mode) 893 doing_tso = 1; 894 895 if (dst) { 896 u32 mtu = dst_mtu(dst); 897 if (mtu != inet_csk(sk)->icsk_pmtu_cookie) 898 mss_now = tcp_sync_mss(sk, mtu); 899 } 900 901 if (tp->rx_opt.eff_sacks) 902 mss_now -= (TCPOLEN_SACK_BASE_ALIGNED + 903 (tp->rx_opt.eff_sacks * TCPOLEN_SACK_PERBLOCK)); 904 905#ifdef CONFIG_TCP_MD5SIG 906 if (tp->af_specific->md5_lookup(sk, sk)) 907 mss_now -= TCPOLEN_MD5SIG_ALIGNED; 908#endif 909 910 xmit_size_goal = mss_now; 911 912 if (doing_tso) { 913 xmit_size_goal = (65535 - 914 inet_csk(sk)->icsk_af_ops->net_header_len - 915 inet_csk(sk)->icsk_ext_hdr_len - 916 tp->tcp_header_len); 917 918 if (tp->max_window && 919 (xmit_size_goal > (tp->max_window >> 1))) 920 xmit_size_goal = max((tp->max_window >> 1), 921 68U - tp->tcp_header_len); 922 923 xmit_size_goal -= (xmit_size_goal % mss_now); 924 } 925 tp->xmit_size_goal = xmit_size_goal; 926 927 return mss_now; 928} 929 930/* Congestion window validation. (RFC2861) */ 931 932static void tcp_cwnd_validate(struct sock *sk) 933{ 934 struct tcp_sock *tp = tcp_sk(sk); 935 __u32 packets_out = tp->packets_out; 936 937 if (packets_out >= tp->snd_cwnd) { 938 /* Network is feed fully. */ 939 tp->snd_cwnd_used = 0; 940 tp->snd_cwnd_stamp = tcp_time_stamp; 941 } else { 942 /* Network starves. */ 943 if (tp->packets_out > tp->snd_cwnd_used) 944 tp->snd_cwnd_used = tp->packets_out; 945 946 if (sysctl_tcp_slow_start_after_idle && 947 (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto) 948 tcp_cwnd_application_limited(sk); 949 } 950} 951 952static unsigned int tcp_window_allows(struct tcp_sock *tp, struct sk_buff *skb, unsigned int mss_now, unsigned int cwnd) 953{ 954 u32 window, cwnd_len; 955 956 window = (tp->snd_una + tp->snd_wnd - TCP_SKB_CB(skb)->seq); 957 cwnd_len = mss_now * cwnd; 958 return min(window, cwnd_len); 959} 960 961/* Can at least one segment of SKB be sent right now, according to the 962 * congestion window rules? If so, return how many segments are allowed. 963 */ 964static inline unsigned int tcp_cwnd_test(struct tcp_sock *tp, struct sk_buff *skb) 965{ 966 u32 in_flight, cwnd; 967 968 /* Don't be strict about the congestion window for the final FIN. */ 969 if ((TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) && 970 tcp_skb_pcount(skb) == 1) 971 return 1; 972 973 in_flight = tcp_packets_in_flight(tp); 974 cwnd = tp->snd_cwnd; 975 if (in_flight < cwnd) 976 return (cwnd - in_flight); 977 978 return 0; 979} 980 981/* This must be invoked the first time we consider transmitting 982 * SKB onto the wire. 983 */ 984static int tcp_init_tso_segs(struct sock *sk, struct sk_buff *skb, unsigned int mss_now) 985{ 986 int tso_segs = tcp_skb_pcount(skb); 987 988 if (!tso_segs || 989 (tso_segs > 1 && 990 tcp_skb_mss(skb) != mss_now)) { 991 tcp_set_skb_tso_segs(sk, skb, mss_now); 992 tso_segs = tcp_skb_pcount(skb); 993 } 994 return tso_segs; 995} 996 997static inline int tcp_minshall_check(const struct tcp_sock *tp) 998{ 999 return after(tp->snd_sml,tp->snd_una) && 1000 !after(tp->snd_sml, tp->snd_nxt); 1001} 1002 1003/* Return 0, if packet can be sent now without violation Nagle's rules: 1004 * 1. It is full sized. 1005 * 2. Or it contains FIN. (already checked by caller) 1006 * 3. Or TCP_NODELAY was set. 1007 * 4. Or TCP_CORK is not set, and all sent packets are ACKed. 1008 * With Minshall's modification: all sent small packets are ACKed. 1009 */ 1010 1011static inline int tcp_nagle_check(const struct tcp_sock *tp, 1012 const struct sk_buff *skb, 1013 unsigned mss_now, int nonagle) 1014{ 1015 return (skb->len < mss_now && 1016 ((nonagle&TCP_NAGLE_CORK) || 1017 (!nonagle && 1018 tp->packets_out && 1019 tcp_minshall_check(tp)))); 1020} 1021 1022/* Return non-zero if the Nagle test allows this packet to be 1023 * sent now. 1024 */ 1025static inline int tcp_nagle_test(struct tcp_sock *tp, struct sk_buff *skb, 1026 unsigned int cur_mss, int nonagle) 1027{ 1028 /* Nagle rule does not apply to frames, which sit in the middle of the 1029 * write_queue (they have no chances to get new data). 1030 * 1031 * This is implemented in the callers, where they modify the 'nonagle' 1032 * argument based upon the location of SKB in the send queue. 1033 */ 1034 if (nonagle & TCP_NAGLE_PUSH) 1035 return 1; 1036 1037 /* Don't use the nagle rule for urgent data (or for the final FIN). 1038 * Nagle can be ignored during F-RTO too (see RFC4138). 1039 */ 1040 if (tp->urg_mode || (tp->frto_counter == 2) || 1041 (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN)) 1042 return 1; 1043 1044 if (!tcp_nagle_check(tp, skb, cur_mss, nonagle)) 1045 return 1; 1046 1047 return 0; 1048} 1049 1050/* Does at least the first segment of SKB fit into the send window? */ 1051static inline int tcp_snd_wnd_test(struct tcp_sock *tp, struct sk_buff *skb, unsigned int cur_mss) 1052{ 1053 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 1054 1055 if (skb->len > cur_mss) 1056 end_seq = TCP_SKB_CB(skb)->seq + cur_mss; 1057 1058 return !after(end_seq, tp->snd_una + tp->snd_wnd); 1059} 1060 1061/* This checks if the data bearing packet SKB (usually tcp_send_head(sk)) 1062 * should be put on the wire right now. If so, it returns the number of 1063 * packets allowed by the congestion window. 1064 */ 1065static unsigned int tcp_snd_test(struct sock *sk, struct sk_buff *skb, 1066 unsigned int cur_mss, int nonagle) 1067{ 1068 struct tcp_sock *tp = tcp_sk(sk); 1069 unsigned int cwnd_quota; 1070 1071 tcp_init_tso_segs(sk, skb, cur_mss); 1072 1073 if (!tcp_nagle_test(tp, skb, cur_mss, nonagle)) 1074 return 0; 1075 1076 cwnd_quota = tcp_cwnd_test(tp, skb); 1077 if (cwnd_quota && 1078 !tcp_snd_wnd_test(tp, skb, cur_mss)) 1079 cwnd_quota = 0; 1080 1081 return cwnd_quota; 1082} 1083 1084int tcp_may_send_now(struct sock *sk) 1085{ 1086 struct tcp_sock *tp = tcp_sk(sk); 1087 struct sk_buff *skb = tcp_send_head(sk); 1088 1089 return (skb && 1090 tcp_snd_test(sk, skb, tcp_current_mss(sk, 1), 1091 (tcp_skb_is_last(sk, skb) ? 1092 TCP_NAGLE_PUSH : 1093 tp->nonagle))); 1094} 1095 1096/* Trim TSO SKB to LEN bytes, put the remaining data into a new packet 1097 * which is put after SKB on the list. It is very much like 1098 * tcp_fragment() except that it may make several kinds of assumptions 1099 * in order to speed up the splitting operation. In particular, we 1100 * know that all the data is in scatter-gather pages, and that the 1101 * packet has never been sent out before (and thus is not cloned). 1102 */ 1103static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, unsigned int mss_now) 1104{ 1105 struct sk_buff *buff; 1106 int nlen = skb->len - len; 1107 u16 flags; 1108 1109 /* All of a TSO frame must be composed of paged data. */ 1110 if (skb->len != skb->data_len) 1111 return tcp_fragment(sk, skb, len, mss_now); 1112 1113 buff = sk_stream_alloc_pskb(sk, 0, 0, GFP_ATOMIC); 1114 if (unlikely(buff == NULL)) 1115 return -ENOMEM; 1116 1117 sk_charge_skb(sk, buff); 1118 buff->truesize += nlen; 1119 skb->truesize -= nlen; 1120 1121 /* Correct the sequence numbers. */ 1122 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; 1123 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; 1124 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; 1125 1126 /* PSH and FIN should only be set in the second packet. */ 1127 flags = TCP_SKB_CB(skb)->flags; 1128 TCP_SKB_CB(skb)->flags = flags & ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH); 1129 TCP_SKB_CB(buff)->flags = flags; 1130 1131 /* This packet was never sent out yet, so no SACK bits. */ 1132 TCP_SKB_CB(buff)->sacked = 0; 1133 1134 buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL; 1135 skb_split(skb, buff, len); 1136 1137 /* Fix up tso_factor for both original and new SKB. */ 1138 tcp_set_skb_tso_segs(sk, skb, mss_now); 1139 tcp_set_skb_tso_segs(sk, buff, mss_now); 1140 1141 /* Link BUFF into the send queue. */ 1142 skb_header_release(buff); 1143 tcp_insert_write_queue_after(skb, buff, sk); 1144 1145 return 0; 1146} 1147 1148/* Try to defer sending, if possible, in order to minimize the amount 1149 * of TSO splitting we do. View it as a kind of TSO Nagle test. 1150 * 1151 * This algorithm is from John Heffner. 1152 */ 1153static int tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb) 1154{ 1155 struct tcp_sock *tp = tcp_sk(sk); 1156 const struct inet_connection_sock *icsk = inet_csk(sk); 1157 u32 send_win, cong_win, limit, in_flight; 1158 1159 if (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) 1160 goto send_now; 1161 1162 if (icsk->icsk_ca_state != TCP_CA_Open) 1163 goto send_now; 1164 1165 /* Defer for less than two clock ticks. */ 1166 if (!tp->tso_deferred && ((jiffies<<1)>>1) - (tp->tso_deferred>>1) > 1) 1167 goto send_now; 1168 1169 in_flight = tcp_packets_in_flight(tp); 1170 1171 BUG_ON(tcp_skb_pcount(skb) <= 1 || 1172 (tp->snd_cwnd <= in_flight)); 1173 1174 send_win = (tp->snd_una + tp->snd_wnd) - TCP_SKB_CB(skb)->seq; 1175 1176 /* From in_flight test above, we know that cwnd > in_flight. */ 1177 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache; 1178 1179 limit = min(send_win, cong_win); 1180 1181 /* If a full-sized TSO skb can be sent, do it. */ 1182 if (limit >= 65536) 1183 goto send_now; 1184 1185 if (sysctl_tcp_tso_win_divisor) { 1186 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache); 1187 1188 /* If at least some fraction of a window is available, 1189 * just use it. 1190 */ 1191 chunk /= sysctl_tcp_tso_win_divisor; 1192 if (limit >= chunk) 1193 goto send_now; 1194 } else { 1195 /* Different approach, try not to defer past a single 1196 * ACK. Receiver should ACK every other full sized 1197 * frame, so if we have space for more than 3 frames 1198 * then send now. 1199 */ 1200 if (limit > tcp_max_burst(tp) * tp->mss_cache) 1201 goto send_now; 1202 } 1203 1204 /* Ok, it looks like it is advisable to defer. */ 1205 tp->tso_deferred = 1 | (jiffies<<1); 1206 1207 return 1; 1208 1209send_now: 1210 tp->tso_deferred = 0; 1211 return 0; 1212} 1213 1214/* Create a new MTU probe if we are ready. 1215 * Returns 0 if we should wait to probe (no cwnd available), 1216 * 1 if a probe was sent, 1217 * -1 otherwise */ 1218static int tcp_mtu_probe(struct sock *sk) 1219{ 1220 struct tcp_sock *tp = tcp_sk(sk); 1221 struct inet_connection_sock *icsk = inet_csk(sk); 1222 struct sk_buff *skb, *nskb, *next; 1223 int len; 1224 int probe_size; 1225 unsigned int pif; 1226 int copy; 1227 int mss_now; 1228 1229 /* Not currently probing/verifying, 1230 * not in recovery, 1231 * have enough cwnd, and 1232 * not SACKing (the variable headers throw things off) */ 1233 if (!icsk->icsk_mtup.enabled || 1234 icsk->icsk_mtup.probe_size || 1235 inet_csk(sk)->icsk_ca_state != TCP_CA_Open || 1236 tp->snd_cwnd < 11 || 1237 tp->rx_opt.eff_sacks) 1238 return -1; 1239 1240 /* Very simple search strategy: just double the MSS. */ 1241 mss_now = tcp_current_mss(sk, 0); 1242 probe_size = 2*tp->mss_cache; 1243 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) { 1244 /* TODO: set timer for probe_converge_event */ 1245 return -1; 1246 } 1247 1248 /* Have enough data in the send queue to probe? */ 1249 len = 0; 1250 if ((skb = tcp_send_head(sk)) == NULL) 1251 return -1; 1252 while ((len += skb->len) < probe_size && !tcp_skb_is_last(sk, skb)) 1253 skb = tcp_write_queue_next(sk, skb); 1254 if (len < probe_size) 1255 return -1; 1256 1257 /* Receive window check. */ 1258 if (after(TCP_SKB_CB(skb)->seq + probe_size, tp->snd_una + tp->snd_wnd)) { 1259 if (tp->snd_wnd < probe_size) 1260 return -1; 1261 else 1262 return 0; 1263 } 1264 1265 /* Do we need to wait to drain cwnd? */ 1266 pif = tcp_packets_in_flight(tp); 1267 if (pif + 2 > tp->snd_cwnd) { 1268 /* With no packets in flight, don't stall. */ 1269 if (pif == 0) 1270 return -1; 1271 else 1272 return 0; 1273 } 1274 1275 /* We're allowed to probe. Build it now. */ 1276 if ((nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC)) == NULL) 1277 return -1; 1278 sk_charge_skb(sk, nskb); 1279 1280 skb = tcp_send_head(sk); 1281 tcp_insert_write_queue_before(nskb, skb, sk); 1282 tcp_advance_send_head(sk, skb); 1283 1284 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq; 1285 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size; 1286 TCP_SKB_CB(nskb)->flags = TCPCB_FLAG_ACK; 1287 TCP_SKB_CB(nskb)->sacked = 0; 1288 nskb->csum = 0; 1289 nskb->ip_summed = skb->ip_summed; 1290 1291 len = 0; 1292 while (len < probe_size) { 1293 next = tcp_write_queue_next(sk, skb); 1294 1295 copy = min_t(int, skb->len, probe_size - len); 1296 if (nskb->ip_summed) 1297 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy); 1298 else 1299 nskb->csum = skb_copy_and_csum_bits(skb, 0, 1300 skb_put(nskb, copy), copy, nskb->csum); 1301 1302 if (skb->len <= copy) { 1303 /* We've eaten all the data from this skb. 1304 * Throw it away. */ 1305 TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags; 1306 tcp_unlink_write_queue(skb, sk); 1307 sk_stream_free_skb(sk, skb); 1308 } else { 1309 TCP_SKB_CB(nskb)->flags |= TCP_SKB_CB(skb)->flags & 1310 ~(TCPCB_FLAG_FIN|TCPCB_FLAG_PSH); 1311 if (!skb_shinfo(skb)->nr_frags) { 1312 skb_pull(skb, copy); 1313 if (skb->ip_summed != CHECKSUM_PARTIAL) 1314 skb->csum = csum_partial(skb->data, skb->len, 0); 1315 } else { 1316 __pskb_trim_head(skb, copy); 1317 tcp_set_skb_tso_segs(sk, skb, mss_now); 1318 } 1319 TCP_SKB_CB(skb)->seq += copy; 1320 } 1321 1322 len += copy; 1323 skb = next; 1324 } 1325 tcp_init_tso_segs(sk, nskb, nskb->len); 1326 1327 /* We're ready to send. If this fails, the probe will 1328 * be resegmented into mss-sized pieces by tcp_write_xmit(). */ 1329 TCP_SKB_CB(nskb)->when = tcp_time_stamp; 1330 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) { 1331 /* Decrement cwnd here because we are sending 1332 * effectively two packets. */ 1333 tp->snd_cwnd--; 1334 update_send_head(sk, nskb); 1335 1336 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len); 1337 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq; 1338 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq; 1339 1340 return 1; 1341 } 1342 1343 return -1; 1344} 1345 1346 1347/* This routine writes packets to the network. It advances the 1348 * send_head. This happens as incoming acks open up the remote 1349 * window for us. 1350 * 1351 * Returns 1, if no segments are in flight and we have queued segments, but 1352 * cannot send anything now because of SWS or another problem. 1353 */ 1354static int tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle) 1355{ 1356 struct tcp_sock *tp = tcp_sk(sk); 1357 struct sk_buff *skb; 1358 unsigned int tso_segs, sent_pkts; 1359 int cwnd_quota; 1360 int result; 1361 1362 /* If we are closed, the bytes will have to remain here. 1363 * In time closedown will finish, we empty the write queue and all 1364 * will be happy. 1365 */ 1366 if (unlikely(sk->sk_state == TCP_CLOSE)) 1367 return 0; 1368 1369 sent_pkts = 0; 1370 1371 /* Do MTU probing. */ 1372 if ((result = tcp_mtu_probe(sk)) == 0) { 1373 return 0; 1374 } else if (result > 0) { 1375 sent_pkts = 1; 1376 } 1377 1378 while ((skb = tcp_send_head(sk))) { 1379 unsigned int limit; 1380 1381 tso_segs = tcp_init_tso_segs(sk, skb, mss_now); 1382 BUG_ON(!tso_segs); 1383 1384 cwnd_quota = tcp_cwnd_test(tp, skb); 1385 if (!cwnd_quota) 1386 break; 1387 1388 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) 1389 break; 1390 1391 if (tso_segs == 1) { 1392 if (unlikely(!tcp_nagle_test(tp, skb, mss_now, 1393 (tcp_skb_is_last(sk, skb) ? 1394 nonagle : TCP_NAGLE_PUSH)))) 1395 break; 1396 } else { 1397 if (tcp_tso_should_defer(sk, skb)) 1398 break; 1399 } 1400 1401 limit = mss_now; 1402 if (tso_segs > 1) { 1403 limit = tcp_window_allows(tp, skb, 1404 mss_now, cwnd_quota); 1405 1406 if (skb->len < limit) { 1407 unsigned int trim = skb->len % mss_now; 1408 1409 if (trim) 1410 limit = skb->len - trim; 1411 } 1412 } 1413 1414 if (skb->len > limit && 1415 unlikely(tso_fragment(sk, skb, limit, mss_now))) 1416 break; 1417 1418 TCP_SKB_CB(skb)->when = tcp_time_stamp; 1419 1420 if (unlikely(tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC))) 1421 break; 1422 1423 /* Advance the send_head. This one is sent out. 1424 * This call will increment packets_out. 1425 */ 1426 update_send_head(sk, skb); 1427 1428 tcp_minshall_update(tp, mss_now, skb); 1429 sent_pkts++; 1430 } 1431 1432 if (likely(sent_pkts)) { 1433 tcp_cwnd_validate(sk); 1434 return 0; 1435 } 1436 return !tp->packets_out && tcp_send_head(sk); 1437} 1438 1439/* Push out any pending frames which were held back due to 1440 * TCP_CORK or attempt at coalescing tiny packets. 1441 * The socket must be locked by the caller. 1442 */ 1443void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss, 1444 int nonagle) 1445{ 1446 struct sk_buff *skb = tcp_send_head(sk); 1447 1448 if (skb) { 1449 if (tcp_write_xmit(sk, cur_mss, nonagle)) 1450 tcp_check_probe_timer(sk); 1451 } 1452} 1453 1454/* Send _single_ skb sitting at the send head. This function requires 1455 * true push pending frames to setup probe timer etc. 1456 */ 1457void tcp_push_one(struct sock *sk, unsigned int mss_now) 1458{ 1459 struct tcp_sock *tp = tcp_sk(sk); 1460 struct sk_buff *skb = tcp_send_head(sk); 1461 unsigned int tso_segs, cwnd_quota; 1462 1463 BUG_ON(!skb || skb->len < mss_now); 1464 1465 tso_segs = tcp_init_tso_segs(sk, skb, mss_now); 1466 cwnd_quota = tcp_snd_test(sk, skb, mss_now, TCP_NAGLE_PUSH); 1467 1468 if (likely(cwnd_quota)) { 1469 unsigned int limit; 1470 1471 BUG_ON(!tso_segs); 1472 1473 limit = mss_now; 1474 if (tso_segs > 1) { 1475 limit = tcp_window_allows(tp, skb, 1476 mss_now, cwnd_quota); 1477 1478 if (skb->len < limit) { 1479 unsigned int trim = skb->len % mss_now; 1480 1481 if (trim) 1482 limit = skb->len - trim; 1483 } 1484 } 1485 1486 if (skb->len > limit && 1487 unlikely(tso_fragment(sk, skb, limit, mss_now))) 1488 return; 1489 1490 /* Send it out now. */ 1491 TCP_SKB_CB(skb)->when = tcp_time_stamp; 1492 1493 if (likely(!tcp_transmit_skb(sk, skb, 1, sk->sk_allocation))) { 1494 update_send_head(sk, skb); 1495 tcp_cwnd_validate(sk); 1496 return; 1497 } 1498 } 1499} 1500 1501/* This function returns the amount that we can raise the 1502 * usable window based on the following constraints 1503 * 1504 * 1. The window can never be shrunk once it is offered (RFC 793) 1505 * 2. We limit memory per socket 1506 * 1507 * RFC 1122: 1508 * "the suggested [SWS] avoidance algorithm for the receiver is to keep 1509 * RECV.NEXT + RCV.WIN fixed until: 1510 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)" 1511 * 1512 * i.e. don't raise the right edge of the window until you can raise 1513 * it at least MSS bytes. 1514 * 1515 * Unfortunately, the recommended algorithm breaks header prediction, 1516 * since header prediction assumes th->window stays fixed. 1517 * 1518 * Strictly speaking, keeping th->window fixed violates the receiver 1519 * side SWS prevention criteria. The problem is that under this rule 1520 * a stream of single byte packets will cause the right side of the 1521 * window to always advance by a single byte. 1522 * 1523 * Of course, if the sender implements sender side SWS prevention 1524 * then this will not be a problem. 1525 * 1526 * BSD seems to make the following compromise: 1527 * 1528 * If the free space is less than the 1/4 of the maximum 1529 * space available and the free space is less than 1/2 mss, 1530 * then set the window to 0. 1531 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ] 1532 * Otherwise, just prevent the window from shrinking 1533 * and from being larger than the largest representable value. 1534 * 1535 * This prevents incremental opening of the window in the regime 1536 * where TCP is limited by the speed of the reader side taking 1537 * data out of the TCP receive queue. It does nothing about 1538 * those cases where the window is constrained on the sender side 1539 * because the pipeline is full. 1540 * 1541 * BSD also seems to "accidentally" limit itself to windows that are a 1542 * multiple of MSS, at least until the free space gets quite small. 1543 * This would appear to be a side effect of the mbuf implementation. 1544 * Combining these two algorithms results in the observed behavior 1545 * of having a fixed window size at almost all times. 1546 * 1547 * Below we obtain similar behavior by forcing the offered window to 1548 * a multiple of the mss when it is feasible to do so. 1549 * 1550 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes. 1551 * Regular options like TIMESTAMP are taken into account. 1552 */ 1553u32 __tcp_select_window(struct sock *sk) 1554{ 1555 struct inet_connection_sock *icsk = inet_csk(sk); 1556 struct tcp_sock *tp = tcp_sk(sk); 1557 /* MSS for the peer's data. Previous versions used mss_clamp 1558 * here. I don't know if the value based on our guesses 1559 * of peer's MSS is better for the performance. It's more correct 1560 * but may be worse for the performance because of rcv_mss 1561 * fluctuations. --SAW 1998/11/1 1562 */ 1563 int mss = icsk->icsk_ack.rcv_mss; 1564 int free_space = tcp_space(sk); 1565 int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk)); 1566 int window; 1567 1568 if (mss > full_space) 1569 mss = full_space; 1570 1571 if (free_space < full_space/2) { 1572 icsk->icsk_ack.quick = 0; 1573 1574 if (tcp_memory_pressure) 1575 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 4U*tp->advmss); 1576 1577 if (free_space < mss) 1578 return 0; 1579 } 1580 1581 if (free_space > tp->rcv_ssthresh) 1582 free_space = tp->rcv_ssthresh; 1583 1584 /* Don't do rounding if we are using window scaling, since the 1585 * scaled window will not line up with the MSS boundary anyway. 1586 */ 1587 window = tp->rcv_wnd; 1588 if (tp->rx_opt.rcv_wscale) { 1589 window = free_space; 1590 1591 /* Advertise enough space so that it won't get scaled away. 1592 * Import case: prevent zero window announcement if 1593 * 1<<rcv_wscale > mss. 1594 */ 1595 if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window) 1596 window = (((window >> tp->rx_opt.rcv_wscale) + 1) 1597 << tp->rx_opt.rcv_wscale); 1598 } else { 1599 /* Get the largest window that is a nice multiple of mss. 1600 * Window clamp already applied above. 1601 * If our current window offering is within 1 mss of the 1602 * free space we just keep it. This prevents the divide 1603 * and multiply from happening most of the time. 1604 * We also don't do any window rounding when the free space 1605 * is too small. 1606 */ 1607 if (window <= free_space - mss || window > free_space) 1608 window = (free_space/mss)*mss; 1609 else if (mss == full_space && 1610 free_space > window + full_space/2) 1611 window = free_space; 1612 } 1613 1614 return window; 1615} 1616 1617/* Attempt to collapse two adjacent SKB's during retransmission. */ 1618static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *skb, int mss_now) 1619{ 1620 struct tcp_sock *tp = tcp_sk(sk); 1621 struct sk_buff *next_skb = tcp_write_queue_next(sk, skb); 1622 1623 /* The first test we must make is that neither of these two 1624 * SKB's are still referenced by someone else. 1625 */ 1626 if (!skb_cloned(skb) && !skb_cloned(next_skb)) { 1627 int skb_size = skb->len, next_skb_size = next_skb->len; 1628 u16 flags = TCP_SKB_CB(skb)->flags; 1629 1630 /* Also punt if next skb has been SACK'd. */ 1631 if (TCP_SKB_CB(next_skb)->sacked & TCPCB_SACKED_ACKED) 1632 return; 1633 1634 /* Next skb is out of window. */ 1635 if (after(TCP_SKB_CB(next_skb)->end_seq, tp->snd_una+tp->snd_wnd)) 1636 return; 1637 1638 /* Punt if not enough space exists in the first SKB for 1639 * the data in the second, or the total combined payload 1640 * would exceed the MSS. 1641 */ 1642 if ((next_skb_size > skb_tailroom(skb)) || 1643 ((skb_size + next_skb_size) > mss_now)) 1644 return; 1645 1646 BUG_ON(tcp_skb_pcount(skb) != 1 || 1647 tcp_skb_pcount(next_skb) != 1); 1648 1649 /* changing transmit queue under us so clear hints */ 1650 clear_all_retrans_hints(tp); 1651 1652 /* Ok. We will be able to collapse the packet. */ 1653 tcp_unlink_write_queue(next_skb, sk); 1654 1655 skb_copy_from_linear_data(next_skb, 1656 skb_put(skb, next_skb_size), 1657 next_skb_size); 1658 1659 if (next_skb->ip_summed == CHECKSUM_PARTIAL) 1660 skb->ip_summed = CHECKSUM_PARTIAL; 1661 1662 if (skb->ip_summed != CHECKSUM_PARTIAL) 1663 skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size); 1664 1665 /* Update sequence range on original skb. */ 1666 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq; 1667 1668 /* Merge over control information. */ 1669 flags |= TCP_SKB_CB(next_skb)->flags; /* This moves PSH/FIN etc. over */ 1670 TCP_SKB_CB(skb)->flags = flags; 1671 1672 /* All done, get rid of second SKB and account for it so 1673 * packet counting does not break. 1674 */ 1675 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked&(TCPCB_EVER_RETRANS|TCPCB_AT_TAIL); 1676 if (TCP_SKB_CB(next_skb)->sacked&TCPCB_SACKED_RETRANS) 1677 tp->retrans_out -= tcp_skb_pcount(next_skb); 1678 if (TCP_SKB_CB(next_skb)->sacked&TCPCB_LOST) { 1679 tp->lost_out -= tcp_skb_pcount(next_skb); 1680 tp->left_out -= tcp_skb_pcount(next_skb); 1681 } 1682 /* Reno case is special. Sigh... */ 1683 if (!tp->rx_opt.sack_ok && tp->sacked_out) { 1684 tcp_dec_pcount_approx(&tp->sacked_out, next_skb); 1685 tp->left_out -= tcp_skb_pcount(next_skb); 1686 } 1687 1688 /* Not quite right: it can be > snd.fack, but 1689 * it is better to underestimate fackets. 1690 */ 1691 tcp_dec_pcount_approx(&tp->fackets_out, next_skb); 1692 tcp_packets_out_dec(tp, next_skb); 1693 sk_stream_free_skb(sk, next_skb); 1694 } 1695} 1696 1697/* Do a simple retransmit without using the backoff mechanisms in 1698 * tcp_timer. This is used for path mtu discovery. 1699 * The socket is already locked here. 1700 */ 1701void tcp_simple_retransmit(struct sock *sk) 1702{ 1703 const struct inet_connection_sock *icsk = inet_csk(sk); 1704 struct tcp_sock *tp = tcp_sk(sk); 1705 struct sk_buff *skb; 1706 unsigned int mss = tcp_current_mss(sk, 0); 1707 int lost = 0; 1708 1709 tcp_for_write_queue(skb, sk) { 1710 if (skb == tcp_send_head(sk)) 1711 break; 1712 if (skb->len > mss && 1713 !(TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_ACKED)) { 1714 if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) { 1715 TCP_SKB_CB(skb)->sacked &= ~TCPCB_SACKED_RETRANS; 1716 tp->retrans_out -= tcp_skb_pcount(skb); 1717 } 1718 if (!(TCP_SKB_CB(skb)->sacked&TCPCB_LOST)) { 1719 TCP_SKB_CB(skb)->sacked |= TCPCB_LOST; 1720 tp->lost_out += tcp_skb_pcount(skb); 1721 lost = 1; 1722 } 1723 } 1724 } 1725 1726 clear_all_retrans_hints(tp); 1727 1728 if (!lost) 1729 return; 1730 1731 tcp_sync_left_out(tp); 1732 1733 /* Don't muck with the congestion window here. 1734 * Reason is that we do not increase amount of _data_ 1735 * in network, but units changed and effective 1736 * cwnd/ssthresh really reduced now. 1737 */ 1738 if (icsk->icsk_ca_state != TCP_CA_Loss) { 1739 tp->high_seq = tp->snd_nxt; 1740 tp->snd_ssthresh = tcp_current_ssthresh(sk); 1741 tp->prior_ssthresh = 0; 1742 tp->undo_marker = 0; 1743 tcp_set_ca_state(sk, TCP_CA_Loss); 1744 } 1745 tcp_xmit_retransmit_queue(sk); 1746} 1747 1748/* This retransmits one SKB. Policy decisions and retransmit queue 1749 * state updates are done by the caller. Returns non-zero if an 1750 * error occurred which prevented the send. 1751 */ 1752int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) 1753{ 1754 struct tcp_sock *tp = tcp_sk(sk); 1755 struct inet_connection_sock *icsk = inet_csk(sk); 1756 unsigned int cur_mss = tcp_current_mss(sk, 0); 1757 int err; 1758 1759 /* Inconslusive MTU probe */ 1760 if (icsk->icsk_mtup.probe_size) { 1761 icsk->icsk_mtup.probe_size = 0; 1762 } 1763 1764 /* Do not sent more than we queued. 1/4 is reserved for possible 1765 * copying overhead: fragmentation, tunneling, mangling etc. 1766 */ 1767 if (atomic_read(&sk->sk_wmem_alloc) > 1768 min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf)) 1769 return -EAGAIN; 1770 1771 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) { 1772 if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 1773 BUG(); 1774 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) 1775 return -ENOMEM; 1776 } 1777 1778 /* If receiver has shrunk his window, and skb is out of 1779 * new window, do not retransmit it. The exception is the 1780 * case, when window is shrunk to zero. In this case 1781 * our retransmit serves as a zero window probe. 1782 */ 1783 if (!before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd) 1784 && TCP_SKB_CB(skb)->seq != tp->snd_una) 1785 return -EAGAIN; 1786 1787 if (skb->len > cur_mss) { 1788 if (tcp_fragment(sk, skb, cur_mss, cur_mss)) 1789 return -ENOMEM; /* We'll try again later. */ 1790 } 1791 1792 /* Collapse two adjacent packets if worthwhile and we can. */ 1793 if (!(TCP_SKB_CB(skb)->flags & TCPCB_FLAG_SYN) && 1794 (skb->len < (cur_mss >> 1)) && 1795 (tcp_write_queue_next(sk, skb) != tcp_send_head(sk)) && 1796 (!tcp_skb_is_last(sk, skb)) && 1797 (skb_shinfo(skb)->nr_frags == 0 && skb_shinfo(tcp_write_queue_next(sk, skb))->nr_frags == 0) && 1798 (tcp_skb_pcount(skb) == 1 && tcp_skb_pcount(tcp_write_queue_next(sk, skb)) == 1) && 1799 (sysctl_tcp_retrans_collapse != 0)) 1800 tcp_retrans_try_collapse(sk, skb, cur_mss); 1801 1802 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk)) 1803 return -EHOSTUNREACH; /* Routing failure or similar. */ 1804 1805 /* Some Solaris stacks overoptimize and ignore the FIN on a 1806 * retransmit when old data is attached. So strip it off 1807 * since it is cheap to do so and saves bytes on the network. 1808 */ 1809 if (skb->len > 0 && 1810 (TCP_SKB_CB(skb)->flags & TCPCB_FLAG_FIN) && 1811 tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) { 1812 if (!pskb_trim(skb, 0)) { 1813 TCP_SKB_CB(skb)->seq = TCP_SKB_CB(skb)->end_seq - 1; 1814 skb_shinfo(skb)->gso_segs = 1; 1815 skb_shinfo(skb)->gso_size = 0; 1816 skb_shinfo(skb)->gso_type = 0; 1817 skb->ip_summed = CHECKSUM_NONE; 1818 skb->csum = 0; 1819 } 1820 } 1821 1822 /* Make a copy, if the first transmission SKB clone we made 1823 * is still in somebody's hands, else make a clone. 1824 */ 1825 TCP_SKB_CB(skb)->when = tcp_time_stamp; 1826 1827 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 1828 1829 if (err == 0) { 1830 /* Update global TCP statistics. */ 1831 TCP_INC_STATS(TCP_MIB_RETRANSSEGS); 1832 1833 tp->total_retrans++; 1834 1835#if FASTRETRANS_DEBUG > 0 1836 if (TCP_SKB_CB(skb)->sacked&TCPCB_SACKED_RETRANS) { 1837 if (net_ratelimit()) 1838 printk(KERN_DEBUG "retrans_out leaked.\n"); 1839 } 1840#endif 1841 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS; 1842 tp->retrans_out += tcp_skb_pcount(skb); 1843 1844 /* Save stamp of the first retransmit. */ 1845 if (!tp->retrans_stamp) 1846 tp->retrans_stamp = TCP_SKB_CB(skb)->when; 1847 1848 tp->undo_retrans++; 1849 1850 /* snd_nxt is stored to detect loss of retransmitted segment, 1851 * see tcp_input.c tcp_sacktag_write_queue(). 1852 */ 1853 TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt; 1854 } 1855 return err; 1856} 1857 1858/* This gets called after a retransmit timeout, and the initially 1859 * retransmitted data is acknowledged. It tries to continue 1860 * resending the rest of the retransmit queue, until either 1861 * we've sent it all or the congestion window limit is reached. 1862 * If doing SACK, the first ACK which comes back for a timeout 1863 * based retransmit packet might feed us FACK information again. 1864 * If so, we use it to avoid unnecessarily retransmissions. 1865 */ 1866void tcp_xmit_retransmit_queue(struct sock *sk) 1867{ 1868 const struct inet_connection_sock *icsk = inet_csk(sk); 1869 struct tcp_sock *tp = tcp_sk(sk); 1870 struct sk_buff *skb; 1871 int packet_cnt; 1872 1873 if (tp->retransmit_skb_hint) { 1874 skb = tp->retransmit_skb_hint; 1875 packet_cnt = tp->retransmit_cnt_hint; 1876 }else{ 1877 skb = tcp_write_queue_head(sk); 1878 packet_cnt = 0; 1879 } 1880 1881 /* First pass: retransmit lost packets. */ 1882 if (tp->lost_out) { 1883 tcp_for_write_queue_from(skb, sk) { 1884 __u8 sacked = TCP_SKB_CB(skb)->sacked; 1885 1886 if (skb == tcp_send_head(sk)) 1887 break; 1888 /* we could do better than to assign each time */ 1889 tp->retransmit_skb_hint = skb; 1890 tp->retransmit_cnt_hint = packet_cnt; 1891 1892 /* Assume this retransmit will generate 1893 * only one packet for congestion window 1894 * calculation purposes. This works because 1895 * tcp_retransmit_skb() will chop up the 1896 * packet to be MSS sized and all the 1897 * packet counting works out. 1898 */ 1899 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) 1900 return; 1901 1902 if (sacked & TCPCB_LOST) { 1903 if (!(sacked&(TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS))) { 1904 if (tcp_retransmit_skb(sk, skb)) { 1905 tp->retransmit_skb_hint = NULL; 1906 return; 1907 } 1908 if (icsk->icsk_ca_state != TCP_CA_Loss) 1909 NET_INC_STATS_BH(LINUX_MIB_TCPFASTRETRANS); 1910 else 1911 NET_INC_STATS_BH(LINUX_MIB_TCPSLOWSTARTRETRANS); 1912 1913 if (skb == tcp_write_queue_head(sk)) 1914 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 1915 inet_csk(sk)->icsk_rto, 1916 TCP_RTO_MAX); 1917 } 1918 1919 packet_cnt += tcp_skb_pcount(skb); 1920 if (packet_cnt >= tp->lost_out) 1921 break; 1922 } 1923 } 1924 } 1925 1926 /* OK, demanded retransmission is finished. */ 1927 1928 /* Forward retransmissions are possible only during Recovery. */ 1929 if (icsk->icsk_ca_state != TCP_CA_Recovery) 1930 return; 1931 1932 /* No forward retransmissions in Reno are possible. */ 1933 if (!tp->rx_opt.sack_ok) 1934 return; 1935 1936 /* Yeah, we have to make difficult choice between forward transmission 1937 * and retransmission... Both ways have their merits... 1938 * 1939 * For now we do not retransmit anything, while we have some new 1940 * segments to send. 1941 */ 1942 1943 if (tcp_may_send_now(sk)) 1944 return; 1945 1946 if (tp->forward_skb_hint) { 1947 skb = tp->forward_skb_hint; 1948 packet_cnt = tp->forward_cnt_hint; 1949 } else{ 1950 skb = tcp_write_queue_head(sk); 1951 packet_cnt = 0; 1952 } 1953 1954 tcp_for_write_queue_from(skb, sk) { 1955 if (skb == tcp_send_head(sk)) 1956 break; 1957 tp->forward_cnt_hint = packet_cnt; 1958 tp->forward_skb_hint = skb; 1959 1960 /* Similar to the retransmit loop above we 1961 * can pretend that the retransmitted SKB 1962 * we send out here will be composed of one 1963 * real MSS sized packet because tcp_retransmit_skb() 1964 * will fragment it if necessary. 1965 */ 1966 if (++packet_cnt > tp->fackets_out) 1967 break; 1968 1969 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) 1970 break; 1971 1972 if (TCP_SKB_CB(skb)->sacked & TCPCB_TAGBITS) 1973 continue; 1974 1975 /* Ok, retransmit it. */ 1976 if (tcp_retransmit_skb(sk, skb)) { 1977 tp->forward_skb_hint = NULL; 1978 break; 1979 } 1980 1981 if (skb == tcp_write_queue_head(sk)) 1982 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 1983 inet_csk(sk)->icsk_rto, 1984 TCP_RTO_MAX); 1985 1986 NET_INC_STATS_BH(LINUX_MIB_TCPFORWARDRETRANS); 1987 } 1988} 1989 1990 1991/* Send a fin. The caller locks the socket for us. This cannot be 1992 * allowed to fail queueing a FIN frame under any circumstances. 1993 */ 1994void tcp_send_fin(struct sock *sk) 1995{ 1996 struct tcp_sock *tp = tcp_sk(sk); 1997 struct sk_buff *skb = tcp_write_queue_tail(sk); 1998 int mss_now; 1999 2000 /* Optimization, tack on the FIN if we have a queue of 2001 * unsent frames. But be careful about outgoing SACKS 2002 * and IP options. 2003 */ 2004 mss_now = tcp_current_mss(sk, 1); 2005 2006 if (tcp_send_head(sk) != NULL) { 2007 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_FIN; 2008 TCP_SKB_CB(skb)->end_seq++; 2009 tp->write_seq++; 2010 } else { 2011 /* Socket is locked, keep trying until memory is available. */ 2012 for (;;) { 2013 skb = alloc_skb_fclone(MAX_TCP_HEADER, GFP_KERNEL); 2014 if (skb) 2015 break; 2016 yield(); 2017 } 2018 2019 /* Reserve space for headers and prepare control bits. */ 2020 skb_reserve(skb, MAX_TCP_HEADER); 2021 skb->csum = 0; 2022 TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_FIN); 2023 TCP_SKB_CB(skb)->sacked = 0; 2024 skb_shinfo(skb)->gso_segs = 1; 2025 skb_shinfo(skb)->gso_size = 0; 2026 skb_shinfo(skb)->gso_type = 0; 2027 2028 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */ 2029 TCP_SKB_CB(skb)->seq = tp->write_seq; 2030 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1; 2031 tcp_queue_skb(sk, skb); 2032 } 2033 __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF); 2034} 2035 2036/* We get here when a process closes a file descriptor (either due to 2037 * an explicit close() or as a byproduct of exit()'ing) and there 2038 * was unread data in the receive queue. This behavior is recommended 2039 * by RFC 2525, section 2.17. -DaveM 2040 */ 2041void tcp_send_active_reset(struct sock *sk, gfp_t priority) 2042{ 2043 struct sk_buff *skb; 2044 2045 /* NOTE: No TCP options attached and we never retransmit this. */ 2046 skb = alloc_skb(MAX_TCP_HEADER, priority); 2047 if (!skb) { 2048 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED); 2049 return; 2050 } 2051 2052 /* Reserve space for headers and prepare control bits. */ 2053 skb_reserve(skb, MAX_TCP_HEADER); 2054 skb->csum = 0; 2055 TCP_SKB_CB(skb)->flags = (TCPCB_FLAG_ACK | TCPCB_FLAG_RST); 2056 TCP_SKB_CB(skb)->sacked = 0; 2057 skb_shinfo(skb)->gso_segs = 1; 2058 skb_shinfo(skb)->gso_size = 0; 2059 skb_shinfo(skb)->gso_type = 0; 2060 2061 /* Send it off. */ 2062 TCP_SKB_CB(skb)->seq = tcp_acceptable_seq(sk); 2063 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq; 2064 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2065 if (tcp_transmit_skb(sk, skb, 0, priority)) 2066 NET_INC_STATS(LINUX_MIB_TCPABORTFAILED); 2067} 2068 2069/* WARNING: This routine must only be called when we have already sent 2070 * a SYN packet that crossed the incoming SYN that caused this routine 2071 * to get called. If this assumption fails then the initial rcv_wnd 2072 * and rcv_wscale values will not be correct. 2073 */ 2074int tcp_send_synack(struct sock *sk) 2075{ 2076 struct sk_buff* skb; 2077 2078 skb = tcp_write_queue_head(sk); 2079 if (skb == NULL || !(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_SYN)) { 2080 printk(KERN_DEBUG "tcp_send_synack: wrong queue state\n"); 2081 return -EFAULT; 2082 } 2083 if (!(TCP_SKB_CB(skb)->flags&TCPCB_FLAG_ACK)) { 2084 if (skb_cloned(skb)) { 2085 struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC); 2086 if (nskb == NULL) 2087 return -ENOMEM; 2088 tcp_unlink_write_queue(skb, sk); 2089 skb_header_release(nskb); 2090 __tcp_add_write_queue_head(sk, nskb); 2091 sk_stream_free_skb(sk, skb); 2092 sk_charge_skb(sk, nskb); 2093 skb = nskb; 2094 } 2095 2096 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_ACK; 2097 TCP_ECN_send_synack(tcp_sk(sk), skb); 2098 } 2099 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2100 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 2101} 2102 2103/* 2104 * Prepare a SYN-ACK. 2105 */ 2106struct sk_buff * tcp_make_synack(struct sock *sk, struct dst_entry *dst, 2107 struct request_sock *req) 2108{ 2109 struct inet_request_sock *ireq = inet_rsk(req); 2110 struct tcp_sock *tp = tcp_sk(sk); 2111 struct tcphdr *th; 2112 int tcp_header_size; 2113 struct sk_buff *skb; 2114#ifdef CONFIG_TCP_MD5SIG 2115 struct tcp_md5sig_key *md5; 2116 __u8 *md5_hash_location; 2117#endif 2118 2119 skb = sock_wmalloc(sk, MAX_TCP_HEADER + 15, 1, GFP_ATOMIC); 2120 if (skb == NULL) 2121 return NULL; 2122 2123 /* Reserve space for headers. */ 2124 skb_reserve(skb, MAX_TCP_HEADER); 2125 2126 skb->dst = dst_clone(dst); 2127 2128 tcp_header_size = (sizeof(struct tcphdr) + TCPOLEN_MSS + 2129 (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0) + 2130 (ireq->wscale_ok ? TCPOLEN_WSCALE_ALIGNED : 0) + 2131 /* SACK_PERM is in the place of NOP NOP of TS */ 2132 ((ireq->sack_ok && !ireq->tstamp_ok) ? TCPOLEN_SACKPERM_ALIGNED : 0)); 2133 2134#ifdef CONFIG_TCP_MD5SIG 2135 /* Are we doing MD5 on this segment? If so - make room for it */ 2136 md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req); 2137 if (md5) 2138 tcp_header_size += TCPOLEN_MD5SIG_ALIGNED; 2139#endif 2140 skb_push(skb, tcp_header_size); 2141 skb_reset_transport_header(skb); 2142 2143 th = tcp_hdr(skb); 2144 memset(th, 0, sizeof(struct tcphdr)); 2145 th->syn = 1; 2146 th->ack = 1; 2147 TCP_ECN_make_synack(req, th); 2148 th->source = inet_sk(sk)->sport; 2149 th->dest = ireq->rmt_port; 2150 TCP_SKB_CB(skb)->seq = tcp_rsk(req)->snt_isn; 2151 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq + 1; 2152 TCP_SKB_CB(skb)->sacked = 0; 2153 skb_shinfo(skb)->gso_segs = 1; 2154 skb_shinfo(skb)->gso_size = 0; 2155 skb_shinfo(skb)->gso_type = 0; 2156 th->seq = htonl(TCP_SKB_CB(skb)->seq); 2157 th->ack_seq = htonl(tcp_rsk(req)->rcv_isn + 1); 2158 if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */ 2159 __u8 rcv_wscale; 2160 /* Set this up on the first call only */ 2161 req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW); 2162 /* tcp_full_space because it is guaranteed to be the first packet */ 2163 tcp_select_initial_window(tcp_full_space(sk), 2164 dst_metric(dst, RTAX_ADVMSS) - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0), 2165 &req->rcv_wnd, 2166 &req->window_clamp, 2167 ireq->wscale_ok, 2168 &rcv_wscale); 2169 ireq->rcv_wscale = rcv_wscale; 2170 } 2171 2172 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */ 2173 th->window = htons(min(req->rcv_wnd, 65535U)); 2174 2175 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2176 tcp_syn_build_options((__be32 *)(th + 1), dst_metric(dst, RTAX_ADVMSS), ireq->tstamp_ok, 2177 ireq->sack_ok, ireq->wscale_ok, ireq->rcv_wscale, 2178 TCP_SKB_CB(skb)->when, 2179 req->ts_recent, 2180 ( 2181#ifdef CONFIG_TCP_MD5SIG 2182 md5 ? &md5_hash_location : 2183#endif 2184 NULL) 2185 ); 2186 2187 skb->csum = 0; 2188 th->doff = (tcp_header_size >> 2); 2189 TCP_INC_STATS(TCP_MIB_OUTSEGS); 2190 2191#ifdef CONFIG_TCP_MD5SIG 2192 /* Okay, we have all we need - do the md5 hash if needed */ 2193 if (md5) { 2194 tp->af_specific->calc_md5_hash(md5_hash_location, 2195 md5, 2196 NULL, dst, req, 2197 tcp_hdr(skb), sk->sk_protocol, 2198 skb->len); 2199 } 2200#endif 2201 2202 return skb; 2203} 2204 2205/* 2206 * Do all connect socket setups that can be done AF independent. 2207 */ 2208static void tcp_connect_init(struct sock *sk) 2209{ 2210 struct dst_entry *dst = __sk_dst_get(sk); 2211 struct tcp_sock *tp = tcp_sk(sk); 2212 __u8 rcv_wscale; 2213 2214 /* We'll fix this up when we get a response from the other end. 2215 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. 2216 */ 2217 tp->tcp_header_len = sizeof(struct tcphdr) + 2218 (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0); 2219 2220#ifdef CONFIG_TCP_MD5SIG 2221 if (tp->af_specific->md5_lookup(sk, sk) != NULL) 2222 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; 2223#endif 2224 2225 /* If user gave his TCP_MAXSEG, record it to clamp */ 2226 if (tp->rx_opt.user_mss) 2227 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss; 2228 tp->max_window = 0; 2229 tcp_mtup_init(sk); 2230 tcp_sync_mss(sk, dst_mtu(dst)); 2231 2232 if (!tp->window_clamp) 2233 tp->window_clamp = dst_metric(dst, RTAX_WINDOW); 2234 tp->advmss = dst_metric(dst, RTAX_ADVMSS); 2235 tcp_initialize_rcv_mss(sk); 2236 2237 tcp_select_initial_window(tcp_full_space(sk), 2238 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0), 2239 &tp->rcv_wnd, 2240 &tp->window_clamp, 2241 sysctl_tcp_window_scaling, 2242 &rcv_wscale); 2243 2244 tp->rx_opt.rcv_wscale = rcv_wscale; 2245 tp->rcv_ssthresh = tp->rcv_wnd; 2246 2247 sk->sk_err = 0; 2248 sock_reset_flag(sk, SOCK_DONE); 2249 tp->snd_wnd = 0; 2250 tcp_init_wl(tp, tp->write_seq, 0); 2251 tp->snd_una = tp->write_seq; 2252 tp->snd_sml = tp->write_seq; 2253 tp->rcv_nxt = 0; 2254 tp->rcv_wup = 0; 2255 tp->copied_seq = 0; 2256 2257 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; 2258 inet_csk(sk)->icsk_retransmits = 0; 2259 tcp_clear_retrans(tp); 2260} 2261 2262/* 2263 * Build a SYN and send it off. 2264 */ 2265int tcp_connect(struct sock *sk) 2266{ 2267 struct tcp_sock *tp = tcp_sk(sk); 2268 struct sk_buff *buff; 2269 2270 tcp_connect_init(sk); 2271 2272 buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation); 2273 if (unlikely(buff == NULL)) 2274 return -ENOBUFS; 2275 2276 /* Reserve space for headers. */ 2277 skb_reserve(buff, MAX_TCP_HEADER); 2278 2279 TCP_SKB_CB(buff)->flags = TCPCB_FLAG_SYN; 2280 TCP_ECN_send_syn(sk, buff); 2281 TCP_SKB_CB(buff)->sacked = 0; 2282 skb_shinfo(buff)->gso_segs = 1; 2283 skb_shinfo(buff)->gso_size = 0; 2284 skb_shinfo(buff)->gso_type = 0; 2285 buff->csum = 0; 2286 tp->snd_nxt = tp->write_seq; 2287 TCP_SKB_CB(buff)->seq = tp->write_seq++; 2288 TCP_SKB_CB(buff)->end_seq = tp->write_seq; 2289 2290 /* Send it off. */ 2291 TCP_SKB_CB(buff)->when = tcp_time_stamp; 2292 tp->retrans_stamp = TCP_SKB_CB(buff)->when; 2293 skb_header_release(buff); 2294 __tcp_add_write_queue_tail(sk, buff); 2295 sk_charge_skb(sk, buff); 2296 tp->packets_out += tcp_skb_pcount(buff); 2297 tcp_transmit_skb(sk, buff, 1, GFP_KERNEL); 2298 2299 /* We change tp->snd_nxt after the tcp_transmit_skb() call 2300 * in order to make this packet get counted in tcpOutSegs. 2301 */ 2302 tp->snd_nxt = tp->write_seq; 2303 tp->pushed_seq = tp->write_seq; 2304 TCP_INC_STATS(TCP_MIB_ACTIVEOPENS); 2305 2306 /* Timer for repeating the SYN until an answer. */ 2307 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 2308 inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 2309 return 0; 2310} 2311 2312/* Send out a delayed ack, the caller does the policy checking 2313 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check() 2314 * for details. 2315 */ 2316void tcp_send_delayed_ack(struct sock *sk) 2317{ 2318 struct inet_connection_sock *icsk = inet_csk(sk); 2319 int ato = icsk->icsk_ack.ato; 2320 unsigned long timeout; 2321 2322 if (ato > TCP_DELACK_MIN) { 2323 const struct tcp_sock *tp = tcp_sk(sk); 2324 int max_ato = HZ/2; 2325 2326 if (icsk->icsk_ack.pingpong || (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)) 2327 max_ato = TCP_DELACK_MAX; 2328 2329 /* Slow path, intersegment interval is "high". */ 2330 2331 /* If some rtt estimate is known, use it to bound delayed ack. 2332 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements 2333 * directly. 2334 */ 2335 if (tp->srtt) { 2336 int rtt = max(tp->srtt>>3, TCP_DELACK_MIN); 2337 2338 if (rtt < max_ato) 2339 max_ato = rtt; 2340 } 2341 2342 ato = min(ato, max_ato); 2343 } 2344 2345 /* Stay within the limit we were given */ 2346 timeout = jiffies + ato; 2347 2348 /* Use new timeout only if there wasn't a older one earlier. */ 2349 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) { 2350 /* If delack timer was blocked or is about to expire, 2351 * send ACK now. 2352 */ 2353 if (icsk->icsk_ack.blocked || 2354 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) { 2355 tcp_send_ack(sk); 2356 return; 2357 } 2358 2359 if (!time_before(timeout, icsk->icsk_ack.timeout)) 2360 timeout = icsk->icsk_ack.timeout; 2361 } 2362 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER; 2363 icsk->icsk_ack.timeout = timeout; 2364 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout); 2365} 2366 2367/* This routine sends an ack and also updates the window. */ 2368void tcp_send_ack(struct sock *sk) 2369{ 2370 /* If we have been reset, we may not send again. */ 2371 if (sk->sk_state != TCP_CLOSE) { 2372 struct sk_buff *buff; 2373 2374 /* We are not putting this on the write queue, so 2375 * tcp_transmit_skb() will set the ownership to this 2376 * sock. 2377 */ 2378 buff = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); 2379 if (buff == NULL) { 2380 inet_csk_schedule_ack(sk); 2381 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN; 2382 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 2383 TCP_DELACK_MAX, TCP_RTO_MAX); 2384 return; 2385 } 2386 2387 /* Reserve space for headers and prepare control bits. */ 2388 skb_reserve(buff, MAX_TCP_HEADER); 2389 buff->csum = 0; 2390 TCP_SKB_CB(buff)->flags = TCPCB_FLAG_ACK; 2391 TCP_SKB_CB(buff)->sacked = 0; 2392 skb_shinfo(buff)->gso_segs = 1; 2393 skb_shinfo(buff)->gso_size = 0; 2394 skb_shinfo(buff)->gso_type = 0; 2395 2396 /* Send it off, this clears delayed acks for us. */ 2397 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(buff)->end_seq = tcp_acceptable_seq(sk); 2398 TCP_SKB_CB(buff)->when = tcp_time_stamp; 2399 tcp_transmit_skb(sk, buff, 0, GFP_ATOMIC); 2400 } 2401} 2402 2403/* This routine sends a packet with an out of date sequence 2404 * number. It assumes the other end will try to ack it. 2405 * 2406 * Question: what should we make while urgent mode? 2407 * 4.4BSD forces sending single byte of data. We cannot send 2408 * out of window data, because we have SND.NXT==SND.MAX... 2409 * 2410 * Current solution: to send TWO zero-length segments in urgent mode: 2411 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is 2412 * out-of-date with SND.UNA-1 to probe window. 2413 */ 2414static int tcp_xmit_probe_skb(struct sock *sk, int urgent) 2415{ 2416 struct tcp_sock *tp = tcp_sk(sk); 2417 struct sk_buff *skb; 2418 2419 /* We don't queue it, tcp_transmit_skb() sets ownership. */ 2420 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); 2421 if (skb == NULL) 2422 return -1; 2423 2424 /* Reserve space for headers and set control bits. */ 2425 skb_reserve(skb, MAX_TCP_HEADER); 2426 skb->csum = 0; 2427 TCP_SKB_CB(skb)->flags = TCPCB_FLAG_ACK; 2428 TCP_SKB_CB(skb)->sacked = urgent; 2429 skb_shinfo(skb)->gso_segs = 1; 2430 skb_shinfo(skb)->gso_size = 0; 2431 skb_shinfo(skb)->gso_type = 0; 2432 2433 /* Use a previous sequence. This should cause the other 2434 * end to send an ack. Don't queue or clone SKB, just 2435 * send it. 2436 */ 2437 TCP_SKB_CB(skb)->seq = urgent ? tp->snd_una : tp->snd_una - 1; 2438 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(skb)->seq; 2439 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2440 return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC); 2441} 2442 2443int tcp_write_wakeup(struct sock *sk) 2444{ 2445 if (sk->sk_state != TCP_CLOSE) { 2446 struct tcp_sock *tp = tcp_sk(sk); 2447 struct sk_buff *skb; 2448 2449 if ((skb = tcp_send_head(sk)) != NULL && 2450 before(TCP_SKB_CB(skb)->seq, tp->snd_una+tp->snd_wnd)) { 2451 int err; 2452 unsigned int mss = tcp_current_mss(sk, 0); 2453 unsigned int seg_size = tp->snd_una+tp->snd_wnd-TCP_SKB_CB(skb)->seq; 2454 2455 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq)) 2456 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq; 2457 2458 /* We are probing the opening of a window 2459 * but the window size is != 0 2460 * must have been a result SWS avoidance ( sender ) 2461 */ 2462 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq || 2463 skb->len > mss) { 2464 seg_size = min(seg_size, mss); 2465 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; 2466 if (tcp_fragment(sk, skb, seg_size, mss)) 2467 return -1; 2468 } else if (!tcp_skb_pcount(skb)) 2469 tcp_set_skb_tso_segs(sk, skb, mss); 2470 2471 TCP_SKB_CB(skb)->flags |= TCPCB_FLAG_PSH; 2472 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2473 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 2474 if (!err) { 2475 update_send_head(sk, skb); 2476 } 2477 return err; 2478 } else { 2479 if (tp->urg_mode && 2480 between(tp->snd_up, tp->snd_una+1, tp->snd_una+0xFFFF)) 2481 tcp_xmit_probe_skb(sk, TCPCB_URG); 2482 return tcp_xmit_probe_skb(sk, 0); 2483 } 2484 } 2485 return -1; 2486} 2487 2488/* A window probe timeout has occurred. If window is not closed send 2489 * a partial packet else a zero probe. 2490 */ 2491void tcp_send_probe0(struct sock *sk) 2492{ 2493 struct inet_connection_sock *icsk = inet_csk(sk); 2494 struct tcp_sock *tp = tcp_sk(sk); 2495 int err; 2496 2497 err = tcp_write_wakeup(sk); 2498 2499 if (tp->packets_out || !tcp_send_head(sk)) { 2500 /* Cancel probe timer, if it is not required. */ 2501 icsk->icsk_probes_out = 0; 2502 icsk->icsk_backoff = 0; 2503 return; 2504 } 2505 2506 if (err <= 0) { 2507 if (icsk->icsk_backoff < sysctl_tcp_retries2) 2508 icsk->icsk_backoff++; 2509 icsk->icsk_probes_out++; 2510 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 2511 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), 2512 TCP_RTO_MAX); 2513 } else { 2514 /* If packet was not sent due to local congestion, 2515 * do not backoff and do not remember icsk_probes_out. 2516 * Let local senders to fight for local resources. 2517 * 2518 * Use accumulated backoff yet. 2519 */ 2520 if (!icsk->icsk_probes_out) 2521 icsk->icsk_probes_out = 1; 2522 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 2523 min(icsk->icsk_rto << icsk->icsk_backoff, 2524 TCP_RESOURCE_PROBE_INTERVAL), 2525 TCP_RTO_MAX); 2526 } 2527} 2528 2529EXPORT_SYMBOL(tcp_connect); 2530EXPORT_SYMBOL(tcp_make_synack); 2531EXPORT_SYMBOL(tcp_simple_retransmit); 2532EXPORT_SYMBOL(tcp_sync_mss); 2533EXPORT_SYMBOL(sysctl_tcp_tso_win_divisor); 2534EXPORT_SYMBOL(tcp_mtup_init); 2535