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 #define pr_fmt(fmt) "TCP: " fmt 38 39 #include <net/tcp.h> 40 41 #include <linux/compiler.h> 42 #include <linux/gfp.h> 43 #include <linux/module.h> 44 45 /* People can turn this off for buggy TCP's found in printers etc. */ 46 int sysctl_tcp_retrans_collapse __read_mostly = 1; 47 48 /* People can turn this on to work with those rare, broken TCPs that 49 * interpret the window field as a signed quantity. 50 */ 51 int sysctl_tcp_workaround_signed_windows __read_mostly = 0; 52 53 /* Default TSQ limit of two TSO segments */ 54 int sysctl_tcp_limit_output_bytes __read_mostly = 131072; 55 56 /* This limits the percentage of the congestion window which we 57 * will allow a single TSO frame to consume. Building TSO frames 58 * which are too large can cause TCP streams to be bursty. 59 */ 60 int sysctl_tcp_tso_win_divisor __read_mostly = 3; 61 62 int sysctl_tcp_mtu_probing __read_mostly = 0; 63 int sysctl_tcp_base_mss __read_mostly = TCP_BASE_MSS; 64 65 /* By default, RFC2861 behavior. */ 66 int sysctl_tcp_slow_start_after_idle __read_mostly = 1; 67 68 int sysctl_tcp_cookie_size __read_mostly = 0; /* TCP_COOKIE_MAX */ 69 EXPORT_SYMBOL_GPL(sysctl_tcp_cookie_size); 70 71 static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, 72 int push_one, gfp_t gfp); 73 74 /* Account for new data that has been sent to the network. */ 75 static void tcp_event_new_data_sent(struct sock *sk, const struct sk_buff *skb) 76 { 77 struct tcp_sock *tp = tcp_sk(sk); 78 unsigned int prior_packets = tp->packets_out; 79 80 tcp_advance_send_head(sk, skb); 81 tp->snd_nxt = TCP_SKB_CB(skb)->end_seq; 82 83 /* Don't override Nagle indefinitely with F-RTO */ 84 if (tp->frto_counter == 2) 85 tp->frto_counter = 3; 86 87 tp->packets_out += tcp_skb_pcount(skb); 88 if (!prior_packets || tp->early_retrans_delayed) 89 tcp_rearm_rto(sk); 90 } 91 92 /* SND.NXT, if window was not shrunk. 93 * If window has been shrunk, what should we make? It is not clear at all. 94 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-( 95 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already 96 * invalid. OK, let's make this for now: 97 */ 98 static inline __u32 tcp_acceptable_seq(const struct sock *sk) 99 { 100 const struct tcp_sock *tp = tcp_sk(sk); 101 102 if (!before(tcp_wnd_end(tp), tp->snd_nxt)) 103 return tp->snd_nxt; 104 else 105 return tcp_wnd_end(tp); 106 } 107 108 /* Calculate mss to advertise in SYN segment. 109 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that: 110 * 111 * 1. It is independent of path mtu. 112 * 2. Ideally, it is maximal possible segment size i.e. 65535-40. 113 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of 114 * attached devices, because some buggy hosts are confused by 115 * large MSS. 116 * 4. We do not make 3, we advertise MSS, calculated from first 117 * hop device mtu, but allow to raise it to ip_rt_min_advmss. 118 * This may be overridden via information stored in routing table. 119 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible, 120 * probably even Jumbo". 121 */ 122 static __u16 tcp_advertise_mss(struct sock *sk) 123 { 124 struct tcp_sock *tp = tcp_sk(sk); 125 const struct dst_entry *dst = __sk_dst_get(sk); 126 int mss = tp->advmss; 127 128 if (dst) { 129 unsigned int metric = dst_metric_advmss(dst); 130 131 if (metric < mss) { 132 mss = metric; 133 tp->advmss = mss; 134 } 135 } 136 137 return (__u16)mss; 138 } 139 140 /* RFC2861. Reset CWND after idle period longer RTO to "restart window". 141 * This is the first part of cwnd validation mechanism. */ 142 static void tcp_cwnd_restart(struct sock *sk, const struct dst_entry *dst) 143 { 144 struct tcp_sock *tp = tcp_sk(sk); 145 s32 delta = tcp_time_stamp - tp->lsndtime; 146 u32 restart_cwnd = tcp_init_cwnd(tp, dst); 147 u32 cwnd = tp->snd_cwnd; 148 149 tcp_ca_event(sk, CA_EVENT_CWND_RESTART); 150 151 tp->snd_ssthresh = tcp_current_ssthresh(sk); 152 restart_cwnd = min(restart_cwnd, cwnd); 153 154 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd) 155 cwnd >>= 1; 156 tp->snd_cwnd = max(cwnd, restart_cwnd); 157 tp->snd_cwnd_stamp = tcp_time_stamp; 158 tp->snd_cwnd_used = 0; 159 } 160 161 /* Congestion state accounting after a packet has been sent. */ 162 static void tcp_event_data_sent(struct tcp_sock *tp, 163 struct sock *sk) 164 { 165 struct inet_connection_sock *icsk = inet_csk(sk); 166 const u32 now = tcp_time_stamp; 167 168 if (sysctl_tcp_slow_start_after_idle && 169 (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto)) 170 tcp_cwnd_restart(sk, __sk_dst_get(sk)); 171 172 tp->lsndtime = now; 173 174 /* If it is a reply for ato after last received 175 * packet, enter pingpong mode. 176 */ 177 if ((u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato) 178 icsk->icsk_ack.pingpong = 1; 179 } 180 181 /* Account for an ACK we sent. */ 182 static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts) 183 { 184 tcp_dec_quickack_mode(sk, pkts); 185 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK); 186 } 187 188 /* Determine a window scaling and initial window to offer. 189 * Based on the assumption that the given amount of space 190 * will be offered. Store the results in the tp structure. 191 * NOTE: for smooth operation initial space offering should 192 * be a multiple of mss if possible. We assume here that mss >= 1. 193 * This MUST be enforced by all callers. 194 */ 195 void tcp_select_initial_window(int __space, __u32 mss, 196 __u32 *rcv_wnd, __u32 *window_clamp, 197 int wscale_ok, __u8 *rcv_wscale, 198 __u32 init_rcv_wnd) 199 { 200 unsigned int space = (__space < 0 ? 0 : __space); 201 202 /* If no clamp set the clamp to the max possible scaled window */ 203 if (*window_clamp == 0) 204 (*window_clamp) = (65535 << 14); 205 space = min(*window_clamp, space); 206 207 /* Quantize space offering to a multiple of mss if possible. */ 208 if (space > mss) 209 space = (space / mss) * mss; 210 211 /* NOTE: offering an initial window larger than 32767 212 * will break some buggy TCP stacks. If the admin tells us 213 * it is likely we could be speaking with such a buggy stack 214 * we will truncate our initial window offering to 32K-1 215 * unless the remote has sent us a window scaling option, 216 * which we interpret as a sign the remote TCP is not 217 * misinterpreting the window field as a signed quantity. 218 */ 219 if (sysctl_tcp_workaround_signed_windows) 220 (*rcv_wnd) = min(space, MAX_TCP_WINDOW); 221 else 222 (*rcv_wnd) = space; 223 224 (*rcv_wscale) = 0; 225 if (wscale_ok) { 226 /* Set window scaling on max possible window 227 * See RFC1323 for an explanation of the limit to 14 228 */ 229 space = max_t(u32, sysctl_tcp_rmem[2], sysctl_rmem_max); 230 space = min_t(u32, space, *window_clamp); 231 while (space > 65535 && (*rcv_wscale) < 14) { 232 space >>= 1; 233 (*rcv_wscale)++; 234 } 235 } 236 237 /* Set initial window to a value enough for senders starting with 238 * initial congestion window of TCP_DEFAULT_INIT_RCVWND. Place 239 * a limit on the initial window when mss is larger than 1460. 240 */ 241 if (mss > (1 << *rcv_wscale)) { 242 int init_cwnd = TCP_DEFAULT_INIT_RCVWND; 243 if (mss > 1460) 244 init_cwnd = 245 max_t(u32, (1460 * TCP_DEFAULT_INIT_RCVWND) / mss, 2); 246 /* when initializing use the value from init_rcv_wnd 247 * rather than the default from above 248 */ 249 if (init_rcv_wnd) 250 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss); 251 else 252 *rcv_wnd = min(*rcv_wnd, init_cwnd * mss); 253 } 254 255 /* Set the clamp no higher than max representable value */ 256 (*window_clamp) = min(65535U << (*rcv_wscale), *window_clamp); 257 } 258 EXPORT_SYMBOL(tcp_select_initial_window); 259 260 /* Chose a new window to advertise, update state in tcp_sock for the 261 * socket, and return result with RFC1323 scaling applied. The return 262 * value can be stuffed directly into th->window for an outgoing 263 * frame. 264 */ 265 static u16 tcp_select_window(struct sock *sk) 266 { 267 struct tcp_sock *tp = tcp_sk(sk); 268 u32 cur_win = tcp_receive_window(tp); 269 u32 new_win = __tcp_select_window(sk); 270 271 /* Never shrink the offered window */ 272 if (new_win < cur_win) { 273 /* Danger Will Robinson! 274 * Don't update rcv_wup/rcv_wnd here or else 275 * we will not be able to advertise a zero 276 * window in time. --DaveM 277 * 278 * Relax Will Robinson. 279 */ 280 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale); 281 } 282 tp->rcv_wnd = new_win; 283 tp->rcv_wup = tp->rcv_nxt; 284 285 /* Make sure we do not exceed the maximum possible 286 * scaled window. 287 */ 288 if (!tp->rx_opt.rcv_wscale && sysctl_tcp_workaround_signed_windows) 289 new_win = min(new_win, MAX_TCP_WINDOW); 290 else 291 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); 292 293 /* RFC1323 scaling applied */ 294 new_win >>= tp->rx_opt.rcv_wscale; 295 296 /* If we advertise zero window, disable fast path. */ 297 if (new_win == 0) 298 tp->pred_flags = 0; 299 300 return new_win; 301 } 302 303 /* Packet ECN state for a SYN-ACK */ 304 static inline void TCP_ECN_send_synack(const struct tcp_sock *tp, struct sk_buff *skb) 305 { 306 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR; 307 if (!(tp->ecn_flags & TCP_ECN_OK)) 308 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE; 309 } 310 311 /* Packet ECN state for a SYN. */ 312 static inline void TCP_ECN_send_syn(struct sock *sk, struct sk_buff *skb) 313 { 314 struct tcp_sock *tp = tcp_sk(sk); 315 316 tp->ecn_flags = 0; 317 if (sock_net(sk)->ipv4.sysctl_tcp_ecn == 1) { 318 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR; 319 tp->ecn_flags = TCP_ECN_OK; 320 } 321 } 322 323 static __inline__ void 324 TCP_ECN_make_synack(const struct request_sock *req, struct tcphdr *th) 325 { 326 if (inet_rsk(req)->ecn_ok) 327 th->ece = 1; 328 } 329 330 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to 331 * be sent. 332 */ 333 static inline void TCP_ECN_send(struct sock *sk, struct sk_buff *skb, 334 int tcp_header_len) 335 { 336 struct tcp_sock *tp = tcp_sk(sk); 337 338 if (tp->ecn_flags & TCP_ECN_OK) { 339 /* Not-retransmitted data segment: set ECT and inject CWR. */ 340 if (skb->len != tcp_header_len && 341 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) { 342 INET_ECN_xmit(sk); 343 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) { 344 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR; 345 tcp_hdr(skb)->cwr = 1; 346 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; 347 } 348 } else { 349 /* ACK or retransmitted segment: clear ECT|CE */ 350 INET_ECN_dontxmit(sk); 351 } 352 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR) 353 tcp_hdr(skb)->ece = 1; 354 } 355 } 356 357 /* Constructs common control bits of non-data skb. If SYN/FIN is present, 358 * auto increment end seqno. 359 */ 360 static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags) 361 { 362 skb->ip_summed = CHECKSUM_PARTIAL; 363 skb->csum = 0; 364 365 TCP_SKB_CB(skb)->tcp_flags = flags; 366 TCP_SKB_CB(skb)->sacked = 0; 367 368 skb_shinfo(skb)->gso_segs = 1; 369 skb_shinfo(skb)->gso_size = 0; 370 skb_shinfo(skb)->gso_type = 0; 371 372 TCP_SKB_CB(skb)->seq = seq; 373 if (flags & (TCPHDR_SYN | TCPHDR_FIN)) 374 seq++; 375 TCP_SKB_CB(skb)->end_seq = seq; 376 } 377 378 static inline bool tcp_urg_mode(const struct tcp_sock *tp) 379 { 380 return tp->snd_una != tp->snd_up; 381 } 382 383 #define OPTION_SACK_ADVERTISE (1 << 0) 384 #define OPTION_TS (1 << 1) 385 #define OPTION_MD5 (1 << 2) 386 #define OPTION_WSCALE (1 << 3) 387 #define OPTION_COOKIE_EXTENSION (1 << 4) 388 #define OPTION_FAST_OPEN_COOKIE (1 << 8) 389 390 struct tcp_out_options { 391 u16 options; /* bit field of OPTION_* */ 392 u16 mss; /* 0 to disable */ 393 u8 ws; /* window scale, 0 to disable */ 394 u8 num_sack_blocks; /* number of SACK blocks to include */ 395 u8 hash_size; /* bytes in hash_location */ 396 __u8 *hash_location; /* temporary pointer, overloaded */ 397 __u32 tsval, tsecr; /* need to include OPTION_TS */ 398 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */ 399 }; 400 401 /* The sysctl int routines are generic, so check consistency here. 402 */ 403 static u8 tcp_cookie_size_check(u8 desired) 404 { 405 int cookie_size; 406 407 if (desired > 0) 408 /* previously specified */ 409 return desired; 410 411 cookie_size = ACCESS_ONCE(sysctl_tcp_cookie_size); 412 if (cookie_size <= 0) 413 /* no default specified */ 414 return 0; 415 416 if (cookie_size <= TCP_COOKIE_MIN) 417 /* value too small, specify minimum */ 418 return TCP_COOKIE_MIN; 419 420 if (cookie_size >= TCP_COOKIE_MAX) 421 /* value too large, specify maximum */ 422 return TCP_COOKIE_MAX; 423 424 if (cookie_size & 1) 425 /* 8-bit multiple, illegal, fix it */ 426 cookie_size++; 427 428 return (u8)cookie_size; 429 } 430 431 /* Write previously computed TCP options to the packet. 432 * 433 * Beware: Something in the Internet is very sensitive to the ordering of 434 * TCP options, we learned this through the hard way, so be careful here. 435 * Luckily we can at least blame others for their non-compliance but from 436 * inter-operatibility perspective it seems that we're somewhat stuck with 437 * the ordering which we have been using if we want to keep working with 438 * those broken things (not that it currently hurts anybody as there isn't 439 * particular reason why the ordering would need to be changed). 440 * 441 * At least SACK_PERM as the first option is known to lead to a disaster 442 * (but it may well be that other scenarios fail similarly). 443 */ 444 static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, 445 struct tcp_out_options *opts) 446 { 447 u16 options = opts->options; /* mungable copy */ 448 449 /* Having both authentication and cookies for security is redundant, 450 * and there's certainly not enough room. Instead, the cookie-less 451 * extension variant is proposed. 452 * 453 * Consider the pessimal case with authentication. The options 454 * could look like: 455 * COOKIE|MD5(20) + MSS(4) + SACK|TS(12) + WSCALE(4) == 40 456 */ 457 if (unlikely(OPTION_MD5 & options)) { 458 if (unlikely(OPTION_COOKIE_EXTENSION & options)) { 459 *ptr++ = htonl((TCPOPT_COOKIE << 24) | 460 (TCPOLEN_COOKIE_BASE << 16) | 461 (TCPOPT_MD5SIG << 8) | 462 TCPOLEN_MD5SIG); 463 } else { 464 *ptr++ = htonl((TCPOPT_NOP << 24) | 465 (TCPOPT_NOP << 16) | 466 (TCPOPT_MD5SIG << 8) | 467 TCPOLEN_MD5SIG); 468 } 469 options &= ~OPTION_COOKIE_EXTENSION; 470 /* overload cookie hash location */ 471 opts->hash_location = (__u8 *)ptr; 472 ptr += 4; 473 } 474 475 if (unlikely(opts->mss)) { 476 *ptr++ = htonl((TCPOPT_MSS << 24) | 477 (TCPOLEN_MSS << 16) | 478 opts->mss); 479 } 480 481 if (likely(OPTION_TS & options)) { 482 if (unlikely(OPTION_SACK_ADVERTISE & options)) { 483 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) | 484 (TCPOLEN_SACK_PERM << 16) | 485 (TCPOPT_TIMESTAMP << 8) | 486 TCPOLEN_TIMESTAMP); 487 options &= ~OPTION_SACK_ADVERTISE; 488 } else { 489 *ptr++ = htonl((TCPOPT_NOP << 24) | 490 (TCPOPT_NOP << 16) | 491 (TCPOPT_TIMESTAMP << 8) | 492 TCPOLEN_TIMESTAMP); 493 } 494 *ptr++ = htonl(opts->tsval); 495 *ptr++ = htonl(opts->tsecr); 496 } 497 498 /* Specification requires after timestamp, so do it now. 499 * 500 * Consider the pessimal case without authentication. The options 501 * could look like: 502 * MSS(4) + SACK|TS(12) + COOKIE(20) + WSCALE(4) == 40 503 */ 504 if (unlikely(OPTION_COOKIE_EXTENSION & options)) { 505 __u8 *cookie_copy = opts->hash_location; 506 u8 cookie_size = opts->hash_size; 507 508 /* 8-bit multiple handled in tcp_cookie_size_check() above, 509 * and elsewhere. 510 */ 511 if (0x2 & cookie_size) { 512 __u8 *p = (__u8 *)ptr; 513 514 /* 16-bit multiple */ 515 *p++ = TCPOPT_COOKIE; 516 *p++ = TCPOLEN_COOKIE_BASE + cookie_size; 517 *p++ = *cookie_copy++; 518 *p++ = *cookie_copy++; 519 ptr++; 520 cookie_size -= 2; 521 } else { 522 /* 32-bit multiple */ 523 *ptr++ = htonl(((TCPOPT_NOP << 24) | 524 (TCPOPT_NOP << 16) | 525 (TCPOPT_COOKIE << 8) | 526 TCPOLEN_COOKIE_BASE) + 527 cookie_size); 528 } 529 530 if (cookie_size > 0) { 531 memcpy(ptr, cookie_copy, cookie_size); 532 ptr += (cookie_size / 4); 533 } 534 } 535 536 if (unlikely(OPTION_SACK_ADVERTISE & options)) { 537 *ptr++ = htonl((TCPOPT_NOP << 24) | 538 (TCPOPT_NOP << 16) | 539 (TCPOPT_SACK_PERM << 8) | 540 TCPOLEN_SACK_PERM); 541 } 542 543 if (unlikely(OPTION_WSCALE & options)) { 544 *ptr++ = htonl((TCPOPT_NOP << 24) | 545 (TCPOPT_WINDOW << 16) | 546 (TCPOLEN_WINDOW << 8) | 547 opts->ws); 548 } 549 550 if (unlikely(opts->num_sack_blocks)) { 551 struct tcp_sack_block *sp = tp->rx_opt.dsack ? 552 tp->duplicate_sack : tp->selective_acks; 553 int this_sack; 554 555 *ptr++ = htonl((TCPOPT_NOP << 24) | 556 (TCPOPT_NOP << 16) | 557 (TCPOPT_SACK << 8) | 558 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks * 559 TCPOLEN_SACK_PERBLOCK))); 560 561 for (this_sack = 0; this_sack < opts->num_sack_blocks; 562 ++this_sack) { 563 *ptr++ = htonl(sp[this_sack].start_seq); 564 *ptr++ = htonl(sp[this_sack].end_seq); 565 } 566 567 tp->rx_opt.dsack = 0; 568 } 569 570 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) { 571 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie; 572 573 *ptr++ = htonl((TCPOPT_EXP << 24) | 574 ((TCPOLEN_EXP_FASTOPEN_BASE + foc->len) << 16) | 575 TCPOPT_FASTOPEN_MAGIC); 576 577 memcpy(ptr, foc->val, foc->len); 578 if ((foc->len & 3) == 2) { 579 u8 *align = ((u8 *)ptr) + foc->len; 580 align[0] = align[1] = TCPOPT_NOP; 581 } 582 ptr += (foc->len + 3) >> 2; 583 } 584 } 585 586 /* Compute TCP options for SYN packets. This is not the final 587 * network wire format yet. 588 */ 589 static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, 590 struct tcp_out_options *opts, 591 struct tcp_md5sig_key **md5) 592 { 593 struct tcp_sock *tp = tcp_sk(sk); 594 struct tcp_cookie_values *cvp = tp->cookie_values; 595 unsigned int remaining = MAX_TCP_OPTION_SPACE; 596 u8 cookie_size = (!tp->rx_opt.cookie_out_never && cvp != NULL) ? 597 tcp_cookie_size_check(cvp->cookie_desired) : 598 0; 599 struct tcp_fastopen_request *fastopen = tp->fastopen_req; 600 601 #ifdef CONFIG_TCP_MD5SIG 602 *md5 = tp->af_specific->md5_lookup(sk, sk); 603 if (*md5) { 604 opts->options |= OPTION_MD5; 605 remaining -= TCPOLEN_MD5SIG_ALIGNED; 606 } 607 #else 608 *md5 = NULL; 609 #endif 610 611 /* We always get an MSS option. The option bytes which will be seen in 612 * normal data packets should timestamps be used, must be in the MSS 613 * advertised. But we subtract them from tp->mss_cache so that 614 * calculations in tcp_sendmsg are simpler etc. So account for this 615 * fact here if necessary. If we don't do this correctly, as a 616 * receiver we won't recognize data packets as being full sized when we 617 * should, and thus we won't abide by the delayed ACK rules correctly. 618 * SACKs don't matter, we never delay an ACK when we have any of those 619 * going out. */ 620 opts->mss = tcp_advertise_mss(sk); 621 remaining -= TCPOLEN_MSS_ALIGNED; 622 623 if (likely(sysctl_tcp_timestamps && *md5 == NULL)) { 624 opts->options |= OPTION_TS; 625 opts->tsval = TCP_SKB_CB(skb)->when + tp->tsoffset; 626 opts->tsecr = tp->rx_opt.ts_recent; 627 remaining -= TCPOLEN_TSTAMP_ALIGNED; 628 } 629 if (likely(sysctl_tcp_window_scaling)) { 630 opts->ws = tp->rx_opt.rcv_wscale; 631 opts->options |= OPTION_WSCALE; 632 remaining -= TCPOLEN_WSCALE_ALIGNED; 633 } 634 if (likely(sysctl_tcp_sack)) { 635 opts->options |= OPTION_SACK_ADVERTISE; 636 if (unlikely(!(OPTION_TS & opts->options))) 637 remaining -= TCPOLEN_SACKPERM_ALIGNED; 638 } 639 640 if (fastopen && fastopen->cookie.len >= 0) { 641 u32 need = TCPOLEN_EXP_FASTOPEN_BASE + fastopen->cookie.len; 642 need = (need + 3) & ~3U; /* Align to 32 bits */ 643 if (remaining >= need) { 644 opts->options |= OPTION_FAST_OPEN_COOKIE; 645 opts->fastopen_cookie = &fastopen->cookie; 646 remaining -= need; 647 tp->syn_fastopen = 1; 648 } 649 } 650 /* Note that timestamps are required by the specification. 651 * 652 * Odd numbers of bytes are prohibited by the specification, ensuring 653 * that the cookie is 16-bit aligned, and the resulting cookie pair is 654 * 32-bit aligned. 655 */ 656 if (*md5 == NULL && 657 (OPTION_TS & opts->options) && 658 cookie_size > 0) { 659 int need = TCPOLEN_COOKIE_BASE + cookie_size; 660 661 if (0x2 & need) { 662 /* 32-bit multiple */ 663 need += 2; /* NOPs */ 664 665 if (need > remaining) { 666 /* try shrinking cookie to fit */ 667 cookie_size -= 2; 668 need -= 4; 669 } 670 } 671 while (need > remaining && TCP_COOKIE_MIN <= cookie_size) { 672 cookie_size -= 4; 673 need -= 4; 674 } 675 if (TCP_COOKIE_MIN <= cookie_size) { 676 opts->options |= OPTION_COOKIE_EXTENSION; 677 opts->hash_location = (__u8 *)&cvp->cookie_pair[0]; 678 opts->hash_size = cookie_size; 679 680 /* Remember for future incarnations. */ 681 cvp->cookie_desired = cookie_size; 682 683 if (cvp->cookie_desired != cvp->cookie_pair_size) { 684 /* Currently use random bytes as a nonce, 685 * assuming these are completely unpredictable 686 * by hostile users of the same system. 687 */ 688 get_random_bytes(&cvp->cookie_pair[0], 689 cookie_size); 690 cvp->cookie_pair_size = cookie_size; 691 } 692 693 remaining -= need; 694 } 695 } 696 return MAX_TCP_OPTION_SPACE - remaining; 697 } 698 699 /* Set up TCP options for SYN-ACKs. */ 700 static unsigned int tcp_synack_options(struct sock *sk, 701 struct request_sock *req, 702 unsigned int mss, struct sk_buff *skb, 703 struct tcp_out_options *opts, 704 struct tcp_md5sig_key **md5, 705 struct tcp_extend_values *xvp, 706 struct tcp_fastopen_cookie *foc) 707 { 708 struct inet_request_sock *ireq = inet_rsk(req); 709 unsigned int remaining = MAX_TCP_OPTION_SPACE; 710 u8 cookie_plus = (xvp != NULL && !xvp->cookie_out_never) ? 711 xvp->cookie_plus : 712 0; 713 714 #ifdef CONFIG_TCP_MD5SIG 715 *md5 = tcp_rsk(req)->af_specific->md5_lookup(sk, req); 716 if (*md5) { 717 opts->options |= OPTION_MD5; 718 remaining -= TCPOLEN_MD5SIG_ALIGNED; 719 720 /* We can't fit any SACK blocks in a packet with MD5 + TS 721 * options. There was discussion about disabling SACK 722 * rather than TS in order to fit in better with old, 723 * buggy kernels, but that was deemed to be unnecessary. 724 */ 725 ireq->tstamp_ok &= !ireq->sack_ok; 726 } 727 #else 728 *md5 = NULL; 729 #endif 730 731 /* We always send an MSS option. */ 732 opts->mss = mss; 733 remaining -= TCPOLEN_MSS_ALIGNED; 734 735 if (likely(ireq->wscale_ok)) { 736 opts->ws = ireq->rcv_wscale; 737 opts->options |= OPTION_WSCALE; 738 remaining -= TCPOLEN_WSCALE_ALIGNED; 739 } 740 if (likely(ireq->tstamp_ok)) { 741 opts->options |= OPTION_TS; 742 opts->tsval = TCP_SKB_CB(skb)->when; 743 opts->tsecr = req->ts_recent; 744 remaining -= TCPOLEN_TSTAMP_ALIGNED; 745 } 746 if (likely(ireq->sack_ok)) { 747 opts->options |= OPTION_SACK_ADVERTISE; 748 if (unlikely(!ireq->tstamp_ok)) 749 remaining -= TCPOLEN_SACKPERM_ALIGNED; 750 } 751 if (foc != NULL) { 752 u32 need = TCPOLEN_EXP_FASTOPEN_BASE + foc->len; 753 need = (need + 3) & ~3U; /* Align to 32 bits */ 754 if (remaining >= need) { 755 opts->options |= OPTION_FAST_OPEN_COOKIE; 756 opts->fastopen_cookie = foc; 757 remaining -= need; 758 } 759 } 760 /* Similar rationale to tcp_syn_options() applies here, too. 761 * If the <SYN> options fit, the same options should fit now! 762 */ 763 if (*md5 == NULL && 764 ireq->tstamp_ok && 765 cookie_plus > TCPOLEN_COOKIE_BASE) { 766 int need = cookie_plus; /* has TCPOLEN_COOKIE_BASE */ 767 768 if (0x2 & need) { 769 /* 32-bit multiple */ 770 need += 2; /* NOPs */ 771 } 772 if (need <= remaining) { 773 opts->options |= OPTION_COOKIE_EXTENSION; 774 opts->hash_size = cookie_plus - TCPOLEN_COOKIE_BASE; 775 remaining -= need; 776 } else { 777 /* There's no error return, so flag it. */ 778 xvp->cookie_out_never = 1; /* true */ 779 opts->hash_size = 0; 780 } 781 } 782 return MAX_TCP_OPTION_SPACE - remaining; 783 } 784 785 /* Compute TCP options for ESTABLISHED sockets. This is not the 786 * final wire format yet. 787 */ 788 static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb, 789 struct tcp_out_options *opts, 790 struct tcp_md5sig_key **md5) 791 { 792 struct tcp_skb_cb *tcb = skb ? TCP_SKB_CB(skb) : NULL; 793 struct tcp_sock *tp = tcp_sk(sk); 794 unsigned int size = 0; 795 unsigned int eff_sacks; 796 797 #ifdef CONFIG_TCP_MD5SIG 798 *md5 = tp->af_specific->md5_lookup(sk, sk); 799 if (unlikely(*md5)) { 800 opts->options |= OPTION_MD5; 801 size += TCPOLEN_MD5SIG_ALIGNED; 802 } 803 #else 804 *md5 = NULL; 805 #endif 806 807 if (likely(tp->rx_opt.tstamp_ok)) { 808 opts->options |= OPTION_TS; 809 opts->tsval = tcb ? tcb->when + tp->tsoffset : 0; 810 opts->tsecr = tp->rx_opt.ts_recent; 811 size += TCPOLEN_TSTAMP_ALIGNED; 812 } 813 814 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack; 815 if (unlikely(eff_sacks)) { 816 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size; 817 opts->num_sack_blocks = 818 min_t(unsigned int, eff_sacks, 819 (remaining - TCPOLEN_SACK_BASE_ALIGNED) / 820 TCPOLEN_SACK_PERBLOCK); 821 size += TCPOLEN_SACK_BASE_ALIGNED + 822 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK; 823 } 824 825 return size; 826 } 827 828 829 /* TCP SMALL QUEUES (TSQ) 830 * 831 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev) 832 * to reduce RTT and bufferbloat. 833 * We do this using a special skb destructor (tcp_wfree). 834 * 835 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb 836 * needs to be reallocated in a driver. 837 * The invariant being skb->truesize substracted from sk->sk_wmem_alloc 838 * 839 * Since transmit from skb destructor is forbidden, we use a tasklet 840 * to process all sockets that eventually need to send more skbs. 841 * We use one tasklet per cpu, with its own queue of sockets. 842 */ 843 struct tsq_tasklet { 844 struct tasklet_struct tasklet; 845 struct list_head head; /* queue of tcp sockets */ 846 }; 847 static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet); 848 849 static void tcp_tsq_handler(struct sock *sk) 850 { 851 if ((1 << sk->sk_state) & 852 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING | 853 TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) 854 tcp_write_xmit(sk, tcp_current_mss(sk), 0, 0, GFP_ATOMIC); 855 } 856 /* 857 * One tasklest per cpu tries to send more skbs. 858 * We run in tasklet context but need to disable irqs when 859 * transfering tsq->head because tcp_wfree() might 860 * interrupt us (non NAPI drivers) 861 */ 862 static void tcp_tasklet_func(unsigned long data) 863 { 864 struct tsq_tasklet *tsq = (struct tsq_tasklet *)data; 865 LIST_HEAD(list); 866 unsigned long flags; 867 struct list_head *q, *n; 868 struct tcp_sock *tp; 869 struct sock *sk; 870 871 local_irq_save(flags); 872 list_splice_init(&tsq->head, &list); 873 local_irq_restore(flags); 874 875 list_for_each_safe(q, n, &list) { 876 tp = list_entry(q, struct tcp_sock, tsq_node); 877 list_del(&tp->tsq_node); 878 879 sk = (struct sock *)tp; 880 bh_lock_sock(sk); 881 882 if (!sock_owned_by_user(sk)) { 883 tcp_tsq_handler(sk); 884 } else { 885 /* defer the work to tcp_release_cb() */ 886 set_bit(TCP_TSQ_DEFERRED, &tp->tsq_flags); 887 } 888 bh_unlock_sock(sk); 889 890 clear_bit(TSQ_QUEUED, &tp->tsq_flags); 891 sk_free(sk); 892 } 893 } 894 895 #define TCP_DEFERRED_ALL ((1UL << TCP_TSQ_DEFERRED) | \ 896 (1UL << TCP_WRITE_TIMER_DEFERRED) | \ 897 (1UL << TCP_DELACK_TIMER_DEFERRED) | \ 898 (1UL << TCP_MTU_REDUCED_DEFERRED)) 899 /** 900 * tcp_release_cb - tcp release_sock() callback 901 * @sk: socket 902 * 903 * called from release_sock() to perform protocol dependent 904 * actions before socket release. 905 */ 906 void tcp_release_cb(struct sock *sk) 907 { 908 struct tcp_sock *tp = tcp_sk(sk); 909 unsigned long flags, nflags; 910 911 /* perform an atomic operation only if at least one flag is set */ 912 do { 913 flags = tp->tsq_flags; 914 if (!(flags & TCP_DEFERRED_ALL)) 915 return; 916 nflags = flags & ~TCP_DEFERRED_ALL; 917 } while (cmpxchg(&tp->tsq_flags, flags, nflags) != flags); 918 919 if (flags & (1UL << TCP_TSQ_DEFERRED)) 920 tcp_tsq_handler(sk); 921 922 if (flags & (1UL << TCP_WRITE_TIMER_DEFERRED)) { 923 tcp_write_timer_handler(sk); 924 __sock_put(sk); 925 } 926 if (flags & (1UL << TCP_DELACK_TIMER_DEFERRED)) { 927 tcp_delack_timer_handler(sk); 928 __sock_put(sk); 929 } 930 if (flags & (1UL << TCP_MTU_REDUCED_DEFERRED)) { 931 sk->sk_prot->mtu_reduced(sk); 932 __sock_put(sk); 933 } 934 } 935 EXPORT_SYMBOL(tcp_release_cb); 936 937 void __init tcp_tasklet_init(void) 938 { 939 int i; 940 941 for_each_possible_cpu(i) { 942 struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i); 943 944 INIT_LIST_HEAD(&tsq->head); 945 tasklet_init(&tsq->tasklet, 946 tcp_tasklet_func, 947 (unsigned long)tsq); 948 } 949 } 950 951 /* 952 * Write buffer destructor automatically called from kfree_skb. 953 * We cant xmit new skbs from this context, as we might already 954 * hold qdisc lock. 955 */ 956 static void tcp_wfree(struct sk_buff *skb) 957 { 958 struct sock *sk = skb->sk; 959 struct tcp_sock *tp = tcp_sk(sk); 960 961 if (test_and_clear_bit(TSQ_THROTTLED, &tp->tsq_flags) && 962 !test_and_set_bit(TSQ_QUEUED, &tp->tsq_flags)) { 963 unsigned long flags; 964 struct tsq_tasklet *tsq; 965 966 /* Keep a ref on socket. 967 * This last ref will be released in tcp_tasklet_func() 968 */ 969 atomic_sub(skb->truesize - 1, &sk->sk_wmem_alloc); 970 971 /* queue this socket to tasklet queue */ 972 local_irq_save(flags); 973 tsq = &__get_cpu_var(tsq_tasklet); 974 list_add(&tp->tsq_node, &tsq->head); 975 tasklet_schedule(&tsq->tasklet); 976 local_irq_restore(flags); 977 } else { 978 sock_wfree(skb); 979 } 980 } 981 982 /* This routine actually transmits TCP packets queued in by 983 * tcp_do_sendmsg(). This is used by both the initial 984 * transmission and possible later retransmissions. 985 * All SKB's seen here are completely headerless. It is our 986 * job to build the TCP header, and pass the packet down to 987 * IP so it can do the same plus pass the packet off to the 988 * device. 989 * 990 * We are working here with either a clone of the original 991 * SKB, or a fresh unique copy made by the retransmit engine. 992 */ 993 static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, 994 gfp_t gfp_mask) 995 { 996 const struct inet_connection_sock *icsk = inet_csk(sk); 997 struct inet_sock *inet; 998 struct tcp_sock *tp; 999 struct tcp_skb_cb *tcb; 1000 struct tcp_out_options opts; 1001 unsigned int tcp_options_size, tcp_header_size; 1002 struct tcp_md5sig_key *md5; 1003 struct tcphdr *th; 1004 int err; 1005 1006 BUG_ON(!skb || !tcp_skb_pcount(skb)); 1007 1008 /* If congestion control is doing timestamping, we must 1009 * take such a timestamp before we potentially clone/copy. 1010 */ 1011 if (icsk->icsk_ca_ops->flags & TCP_CONG_RTT_STAMP) 1012 __net_timestamp(skb); 1013 1014 if (likely(clone_it)) { 1015 if (unlikely(skb_cloned(skb))) 1016 skb = pskb_copy(skb, gfp_mask); 1017 else 1018 skb = skb_clone(skb, gfp_mask); 1019 if (unlikely(!skb)) 1020 return -ENOBUFS; 1021 } 1022 1023 inet = inet_sk(sk); 1024 tp = tcp_sk(sk); 1025 tcb = TCP_SKB_CB(skb); 1026 memset(&opts, 0, sizeof(opts)); 1027 1028 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) 1029 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5); 1030 else 1031 tcp_options_size = tcp_established_options(sk, skb, &opts, 1032 &md5); 1033 tcp_header_size = tcp_options_size + sizeof(struct tcphdr); 1034 1035 if (tcp_packets_in_flight(tp) == 0) { 1036 tcp_ca_event(sk, CA_EVENT_TX_START); 1037 skb->ooo_okay = 1; 1038 } else 1039 skb->ooo_okay = 0; 1040 1041 skb_push(skb, tcp_header_size); 1042 skb_reset_transport_header(skb); 1043 1044 skb_orphan(skb); 1045 skb->sk = sk; 1046 skb->destructor = (sysctl_tcp_limit_output_bytes > 0) ? 1047 tcp_wfree : sock_wfree; 1048 atomic_add(skb->truesize, &sk->sk_wmem_alloc); 1049 1050 /* Build TCP header and checksum it. */ 1051 th = tcp_hdr(skb); 1052 th->source = inet->inet_sport; 1053 th->dest = inet->inet_dport; 1054 th->seq = htonl(tcb->seq); 1055 th->ack_seq = htonl(tp->rcv_nxt); 1056 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) | 1057 tcb->tcp_flags); 1058 1059 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) { 1060 /* RFC1323: The window in SYN & SYN/ACK segments 1061 * is never scaled. 1062 */ 1063 th->window = htons(min(tp->rcv_wnd, 65535U)); 1064 } else { 1065 th->window = htons(tcp_select_window(sk)); 1066 } 1067 th->check = 0; 1068 th->urg_ptr = 0; 1069 1070 /* The urg_mode check is necessary during a below snd_una win probe */ 1071 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) { 1072 if (before(tp->snd_up, tcb->seq + 0x10000)) { 1073 th->urg_ptr = htons(tp->snd_up - tcb->seq); 1074 th->urg = 1; 1075 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) { 1076 th->urg_ptr = htons(0xFFFF); 1077 th->urg = 1; 1078 } 1079 } 1080 1081 tcp_options_write((__be32 *)(th + 1), tp, &opts); 1082 if (likely((tcb->tcp_flags & TCPHDR_SYN) == 0)) 1083 TCP_ECN_send(sk, skb, tcp_header_size); 1084 1085 #ifdef CONFIG_TCP_MD5SIG 1086 /* Calculate the MD5 hash, as we have all we need now */ 1087 if (md5) { 1088 sk_nocaps_add(sk, NETIF_F_GSO_MASK); 1089 tp->af_specific->calc_md5_hash(opts.hash_location, 1090 md5, sk, NULL, skb); 1091 } 1092 #endif 1093 1094 icsk->icsk_af_ops->send_check(sk, skb); 1095 1096 if (likely(tcb->tcp_flags & TCPHDR_ACK)) 1097 tcp_event_ack_sent(sk, tcp_skb_pcount(skb)); 1098 1099 if (skb->len != tcp_header_size) 1100 tcp_event_data_sent(tp, sk); 1101 1102 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq) 1103 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS, 1104 tcp_skb_pcount(skb)); 1105 1106 err = icsk->icsk_af_ops->queue_xmit(skb, &inet->cork.fl); 1107 if (likely(err <= 0)) 1108 return err; 1109 1110 tcp_enter_cwr(sk, 1); 1111 1112 return net_xmit_eval(err); 1113 } 1114 1115 /* This routine just queues the buffer for sending. 1116 * 1117 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames, 1118 * otherwise socket can stall. 1119 */ 1120 static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) 1121 { 1122 struct tcp_sock *tp = tcp_sk(sk); 1123 1124 /* Advance write_seq and place onto the write_queue. */ 1125 tp->write_seq = TCP_SKB_CB(skb)->end_seq; 1126 skb_header_release(skb); 1127 tcp_add_write_queue_tail(sk, skb); 1128 sk->sk_wmem_queued += skb->truesize; 1129 sk_mem_charge(sk, skb->truesize); 1130 } 1131 1132 /* Initialize TSO segments for a packet. */ 1133 static void tcp_set_skb_tso_segs(const struct sock *sk, struct sk_buff *skb, 1134 unsigned int mss_now) 1135 { 1136 if (skb->len <= mss_now || !sk_can_gso(sk) || 1137 skb->ip_summed == CHECKSUM_NONE) { 1138 /* Avoid the costly divide in the normal 1139 * non-TSO case. 1140 */ 1141 skb_shinfo(skb)->gso_segs = 1; 1142 skb_shinfo(skb)->gso_size = 0; 1143 skb_shinfo(skb)->gso_type = 0; 1144 } else { 1145 skb_shinfo(skb)->gso_segs = DIV_ROUND_UP(skb->len, mss_now); 1146 skb_shinfo(skb)->gso_size = mss_now; 1147 skb_shinfo(skb)->gso_type = sk->sk_gso_type; 1148 } 1149 } 1150 1151 /* When a modification to fackets out becomes necessary, we need to check 1152 * skb is counted to fackets_out or not. 1153 */ 1154 static void tcp_adjust_fackets_out(struct sock *sk, const struct sk_buff *skb, 1155 int decr) 1156 { 1157 struct tcp_sock *tp = tcp_sk(sk); 1158 1159 if (!tp->sacked_out || tcp_is_reno(tp)) 1160 return; 1161 1162 if (after(tcp_highest_sack_seq(tp), TCP_SKB_CB(skb)->seq)) 1163 tp->fackets_out -= decr; 1164 } 1165 1166 /* Pcount in the middle of the write queue got changed, we need to do various 1167 * tweaks to fix counters 1168 */ 1169 static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr) 1170 { 1171 struct tcp_sock *tp = tcp_sk(sk); 1172 1173 tp->packets_out -= decr; 1174 1175 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) 1176 tp->sacked_out -= decr; 1177 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) 1178 tp->retrans_out -= decr; 1179 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) 1180 tp->lost_out -= decr; 1181 1182 /* Reno case is special. Sigh... */ 1183 if (tcp_is_reno(tp) && decr > 0) 1184 tp->sacked_out -= min_t(u32, tp->sacked_out, decr); 1185 1186 tcp_adjust_fackets_out(sk, skb, decr); 1187 1188 if (tp->lost_skb_hint && 1189 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) && 1190 (tcp_is_fack(tp) || (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED))) 1191 tp->lost_cnt_hint -= decr; 1192 1193 tcp_verify_left_out(tp); 1194 } 1195 1196 /* Function to create two new TCP segments. Shrinks the given segment 1197 * to the specified size and appends a new segment with the rest of the 1198 * packet to the list. This won't be called frequently, I hope. 1199 * Remember, these are still headerless SKBs at this point. 1200 */ 1201 int tcp_fragment(struct sock *sk, struct sk_buff *skb, u32 len, 1202 unsigned int mss_now) 1203 { 1204 struct tcp_sock *tp = tcp_sk(sk); 1205 struct sk_buff *buff; 1206 int nsize, old_factor; 1207 int nlen; 1208 u8 flags; 1209 1210 if (WARN_ON(len > skb->len)) 1211 return -EINVAL; 1212 1213 nsize = skb_headlen(skb) - len; 1214 if (nsize < 0) 1215 nsize = 0; 1216 1217 if (skb_cloned(skb) && 1218 skb_is_nonlinear(skb) && 1219 pskb_expand_head(skb, 0, 0, GFP_ATOMIC)) 1220 return -ENOMEM; 1221 1222 /* Get a new skb... force flag on. */ 1223 buff = sk_stream_alloc_skb(sk, nsize, GFP_ATOMIC); 1224 if (buff == NULL) 1225 return -ENOMEM; /* We'll just try again later. */ 1226 1227 sk->sk_wmem_queued += buff->truesize; 1228 sk_mem_charge(sk, buff->truesize); 1229 nlen = skb->len - len - nsize; 1230 buff->truesize += nlen; 1231 skb->truesize -= nlen; 1232 1233 /* Correct the sequence numbers. */ 1234 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; 1235 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; 1236 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; 1237 1238 /* PSH and FIN should only be set in the second packet. */ 1239 flags = TCP_SKB_CB(skb)->tcp_flags; 1240 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH); 1241 TCP_SKB_CB(buff)->tcp_flags = flags; 1242 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked; 1243 1244 if (!skb_shinfo(skb)->nr_frags && skb->ip_summed != CHECKSUM_PARTIAL) { 1245 /* Copy and checksum data tail into the new buffer. */ 1246 buff->csum = csum_partial_copy_nocheck(skb->data + len, 1247 skb_put(buff, nsize), 1248 nsize, 0); 1249 1250 skb_trim(skb, len); 1251 1252 skb->csum = csum_block_sub(skb->csum, buff->csum, len); 1253 } else { 1254 skb->ip_summed = CHECKSUM_PARTIAL; 1255 skb_split(skb, buff, len); 1256 } 1257 1258 buff->ip_summed = skb->ip_summed; 1259 1260 /* Looks stupid, but our code really uses when of 1261 * skbs, which it never sent before. --ANK 1262 */ 1263 TCP_SKB_CB(buff)->when = TCP_SKB_CB(skb)->when; 1264 buff->tstamp = skb->tstamp; 1265 1266 old_factor = tcp_skb_pcount(skb); 1267 1268 /* Fix up tso_factor for both original and new SKB. */ 1269 tcp_set_skb_tso_segs(sk, skb, mss_now); 1270 tcp_set_skb_tso_segs(sk, buff, mss_now); 1271 1272 /* If this packet has been sent out already, we must 1273 * adjust the various packet counters. 1274 */ 1275 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) { 1276 int diff = old_factor - tcp_skb_pcount(skb) - 1277 tcp_skb_pcount(buff); 1278 1279 if (diff) 1280 tcp_adjust_pcount(sk, skb, diff); 1281 } 1282 1283 /* Link BUFF into the send queue. */ 1284 skb_header_release(buff); 1285 tcp_insert_write_queue_after(skb, buff, sk); 1286 1287 return 0; 1288 } 1289 1290 /* This is similar to __pskb_pull_head() (it will go to core/skbuff.c 1291 * eventually). The difference is that pulled data not copied, but 1292 * immediately discarded. 1293 */ 1294 static void __pskb_trim_head(struct sk_buff *skb, int len) 1295 { 1296 int i, k, eat; 1297 1298 eat = min_t(int, len, skb_headlen(skb)); 1299 if (eat) { 1300 __skb_pull(skb, eat); 1301 len -= eat; 1302 if (!len) 1303 return; 1304 } 1305 eat = len; 1306 k = 0; 1307 for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) { 1308 int size = skb_frag_size(&skb_shinfo(skb)->frags[i]); 1309 1310 if (size <= eat) { 1311 skb_frag_unref(skb, i); 1312 eat -= size; 1313 } else { 1314 skb_shinfo(skb)->frags[k] = skb_shinfo(skb)->frags[i]; 1315 if (eat) { 1316 skb_shinfo(skb)->frags[k].page_offset += eat; 1317 skb_frag_size_sub(&skb_shinfo(skb)->frags[k], eat); 1318 eat = 0; 1319 } 1320 k++; 1321 } 1322 } 1323 skb_shinfo(skb)->nr_frags = k; 1324 1325 skb_reset_tail_pointer(skb); 1326 skb->data_len -= len; 1327 skb->len = skb->data_len; 1328 } 1329 1330 /* Remove acked data from a packet in the transmit queue. */ 1331 int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) 1332 { 1333 if (skb_unclone(skb, GFP_ATOMIC)) 1334 return -ENOMEM; 1335 1336 __pskb_trim_head(skb, len); 1337 1338 TCP_SKB_CB(skb)->seq += len; 1339 skb->ip_summed = CHECKSUM_PARTIAL; 1340 1341 skb->truesize -= len; 1342 sk->sk_wmem_queued -= len; 1343 sk_mem_uncharge(sk, len); 1344 sock_set_flag(sk, SOCK_QUEUE_SHRUNK); 1345 1346 /* Any change of skb->len requires recalculation of tso factor. */ 1347 if (tcp_skb_pcount(skb) > 1) 1348 tcp_set_skb_tso_segs(sk, skb, tcp_skb_mss(skb)); 1349 1350 return 0; 1351 } 1352 1353 /* Calculate MSS not accounting any TCP options. */ 1354 static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu) 1355 { 1356 const struct tcp_sock *tp = tcp_sk(sk); 1357 const struct inet_connection_sock *icsk = inet_csk(sk); 1358 int mss_now; 1359 1360 /* Calculate base mss without TCP options: 1361 It is MMS_S - sizeof(tcphdr) of rfc1122 1362 */ 1363 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr); 1364 1365 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */ 1366 if (icsk->icsk_af_ops->net_frag_header_len) { 1367 const struct dst_entry *dst = __sk_dst_get(sk); 1368 1369 if (dst && dst_allfrag(dst)) 1370 mss_now -= icsk->icsk_af_ops->net_frag_header_len; 1371 } 1372 1373 /* Clamp it (mss_clamp does not include tcp options) */ 1374 if (mss_now > tp->rx_opt.mss_clamp) 1375 mss_now = tp->rx_opt.mss_clamp; 1376 1377 /* Now subtract optional transport overhead */ 1378 mss_now -= icsk->icsk_ext_hdr_len; 1379 1380 /* Then reserve room for full set of TCP options and 8 bytes of data */ 1381 if (mss_now < 48) 1382 mss_now = 48; 1383 return mss_now; 1384 } 1385 1386 /* Calculate MSS. Not accounting for SACKs here. */ 1387 int tcp_mtu_to_mss(struct sock *sk, int pmtu) 1388 { 1389 /* Subtract TCP options size, not including SACKs */ 1390 return __tcp_mtu_to_mss(sk, pmtu) - 1391 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr)); 1392 } 1393 1394 /* Inverse of above */ 1395 int tcp_mss_to_mtu(struct sock *sk, int mss) 1396 { 1397 const struct tcp_sock *tp = tcp_sk(sk); 1398 const struct inet_connection_sock *icsk = inet_csk(sk); 1399 int mtu; 1400 1401 mtu = mss + 1402 tp->tcp_header_len + 1403 icsk->icsk_ext_hdr_len + 1404 icsk->icsk_af_ops->net_header_len; 1405 1406 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */ 1407 if (icsk->icsk_af_ops->net_frag_header_len) { 1408 const struct dst_entry *dst = __sk_dst_get(sk); 1409 1410 if (dst && dst_allfrag(dst)) 1411 mtu += icsk->icsk_af_ops->net_frag_header_len; 1412 } 1413 return mtu; 1414 } 1415 1416 /* MTU probing init per socket */ 1417 void tcp_mtup_init(struct sock *sk) 1418 { 1419 struct tcp_sock *tp = tcp_sk(sk); 1420 struct inet_connection_sock *icsk = inet_csk(sk); 1421 1422 icsk->icsk_mtup.enabled = sysctl_tcp_mtu_probing > 1; 1423 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) + 1424 icsk->icsk_af_ops->net_header_len; 1425 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, sysctl_tcp_base_mss); 1426 icsk->icsk_mtup.probe_size = 0; 1427 } 1428 EXPORT_SYMBOL(tcp_mtup_init); 1429 1430 /* This function synchronize snd mss to current pmtu/exthdr set. 1431 1432 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts 1433 for TCP options, but includes only bare TCP header. 1434 1435 tp->rx_opt.mss_clamp is mss negotiated at connection setup. 1436 It is minimum of user_mss and mss received with SYN. 1437 It also does not include TCP options. 1438 1439 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function. 1440 1441 tp->mss_cache is current effective sending mss, including 1442 all tcp options except for SACKs. It is evaluated, 1443 taking into account current pmtu, but never exceeds 1444 tp->rx_opt.mss_clamp. 1445 1446 NOTE1. rfc1122 clearly states that advertised MSS 1447 DOES NOT include either tcp or ip options. 1448 1449 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache 1450 are READ ONLY outside this function. --ANK (980731) 1451 */ 1452 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu) 1453 { 1454 struct tcp_sock *tp = tcp_sk(sk); 1455 struct inet_connection_sock *icsk = inet_csk(sk); 1456 int mss_now; 1457 1458 if (icsk->icsk_mtup.search_high > pmtu) 1459 icsk->icsk_mtup.search_high = pmtu; 1460 1461 mss_now = tcp_mtu_to_mss(sk, pmtu); 1462 mss_now = tcp_bound_to_half_wnd(tp, mss_now); 1463 1464 /* And store cached results */ 1465 icsk->icsk_pmtu_cookie = pmtu; 1466 if (icsk->icsk_mtup.enabled) 1467 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)); 1468 tp->mss_cache = mss_now; 1469 1470 return mss_now; 1471 } 1472 EXPORT_SYMBOL(tcp_sync_mss); 1473 1474 /* Compute the current effective MSS, taking SACKs and IP options, 1475 * and even PMTU discovery events into account. 1476 */ 1477 unsigned int tcp_current_mss(struct sock *sk) 1478 { 1479 const struct tcp_sock *tp = tcp_sk(sk); 1480 const struct dst_entry *dst = __sk_dst_get(sk); 1481 u32 mss_now; 1482 unsigned int header_len; 1483 struct tcp_out_options opts; 1484 struct tcp_md5sig_key *md5; 1485 1486 mss_now = tp->mss_cache; 1487 1488 if (dst) { 1489 u32 mtu = dst_mtu(dst); 1490 if (mtu != inet_csk(sk)->icsk_pmtu_cookie) 1491 mss_now = tcp_sync_mss(sk, mtu); 1492 } 1493 1494 header_len = tcp_established_options(sk, NULL, &opts, &md5) + 1495 sizeof(struct tcphdr); 1496 /* The mss_cache is sized based on tp->tcp_header_len, which assumes 1497 * some common options. If this is an odd packet (because we have SACK 1498 * blocks etc) then our calculated header_len will be different, and 1499 * we have to adjust mss_now correspondingly */ 1500 if (header_len != tp->tcp_header_len) { 1501 int delta = (int) header_len - tp->tcp_header_len; 1502 mss_now -= delta; 1503 } 1504 1505 return mss_now; 1506 } 1507 1508 /* Congestion window validation. (RFC2861) */ 1509 static void tcp_cwnd_validate(struct sock *sk) 1510 { 1511 struct tcp_sock *tp = tcp_sk(sk); 1512 1513 if (tp->packets_out >= tp->snd_cwnd) { 1514 /* Network is feed fully. */ 1515 tp->snd_cwnd_used = 0; 1516 tp->snd_cwnd_stamp = tcp_time_stamp; 1517 } else { 1518 /* Network starves. */ 1519 if (tp->packets_out > tp->snd_cwnd_used) 1520 tp->snd_cwnd_used = tp->packets_out; 1521 1522 if (sysctl_tcp_slow_start_after_idle && 1523 (s32)(tcp_time_stamp - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto) 1524 tcp_cwnd_application_limited(sk); 1525 } 1526 } 1527 1528 /* Returns the portion of skb which can be sent right away without 1529 * introducing MSS oddities to segment boundaries. In rare cases where 1530 * mss_now != mss_cache, we will request caller to create a small skb 1531 * per input skb which could be mostly avoided here (if desired). 1532 * 1533 * We explicitly want to create a request for splitting write queue tail 1534 * to a small skb for Nagle purposes while avoiding unnecessary modulos, 1535 * thus all the complexity (cwnd_len is always MSS multiple which we 1536 * return whenever allowed by the other factors). Basically we need the 1537 * modulo only when the receiver window alone is the limiting factor or 1538 * when we would be allowed to send the split-due-to-Nagle skb fully. 1539 */ 1540 static unsigned int tcp_mss_split_point(const struct sock *sk, const struct sk_buff *skb, 1541 unsigned int mss_now, unsigned int max_segs) 1542 { 1543 const struct tcp_sock *tp = tcp_sk(sk); 1544 u32 needed, window, max_len; 1545 1546 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; 1547 max_len = mss_now * max_segs; 1548 1549 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk))) 1550 return max_len; 1551 1552 needed = min(skb->len, window); 1553 1554 if (max_len <= needed) 1555 return max_len; 1556 1557 return needed - needed % mss_now; 1558 } 1559 1560 /* Can at least one segment of SKB be sent right now, according to the 1561 * congestion window rules? If so, return how many segments are allowed. 1562 */ 1563 static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp, 1564 const struct sk_buff *skb) 1565 { 1566 u32 in_flight, cwnd; 1567 1568 /* Don't be strict about the congestion window for the final FIN. */ 1569 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) && 1570 tcp_skb_pcount(skb) == 1) 1571 return 1; 1572 1573 in_flight = tcp_packets_in_flight(tp); 1574 cwnd = tp->snd_cwnd; 1575 if (in_flight < cwnd) 1576 return (cwnd - in_flight); 1577 1578 return 0; 1579 } 1580 1581 /* Initialize TSO state of a skb. 1582 * This must be invoked the first time we consider transmitting 1583 * SKB onto the wire. 1584 */ 1585 static int tcp_init_tso_segs(const struct sock *sk, struct sk_buff *skb, 1586 unsigned int mss_now) 1587 { 1588 int tso_segs = tcp_skb_pcount(skb); 1589 1590 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) { 1591 tcp_set_skb_tso_segs(sk, skb, mss_now); 1592 tso_segs = tcp_skb_pcount(skb); 1593 } 1594 return tso_segs; 1595 } 1596 1597 /* Minshall's variant of the Nagle send check. */ 1598 static inline bool tcp_minshall_check(const struct tcp_sock *tp) 1599 { 1600 return after(tp->snd_sml, tp->snd_una) && 1601 !after(tp->snd_sml, tp->snd_nxt); 1602 } 1603 1604 /* Return false, if packet can be sent now without violation Nagle's rules: 1605 * 1. It is full sized. 1606 * 2. Or it contains FIN. (already checked by caller) 1607 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set. 1608 * 4. Or TCP_CORK is not set, and all sent packets are ACKed. 1609 * With Minshall's modification: all sent small packets are ACKed. 1610 */ 1611 static inline bool tcp_nagle_check(const struct tcp_sock *tp, 1612 const struct sk_buff *skb, 1613 unsigned int mss_now, int nonagle) 1614 { 1615 return skb->len < mss_now && 1616 ((nonagle & TCP_NAGLE_CORK) || 1617 (!nonagle && tp->packets_out && tcp_minshall_check(tp))); 1618 } 1619 1620 /* Return true if the Nagle test allows this packet to be 1621 * sent now. 1622 */ 1623 static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb, 1624 unsigned int cur_mss, int nonagle) 1625 { 1626 /* Nagle rule does not apply to frames, which sit in the middle of the 1627 * write_queue (they have no chances to get new data). 1628 * 1629 * This is implemented in the callers, where they modify the 'nonagle' 1630 * argument based upon the location of SKB in the send queue. 1631 */ 1632 if (nonagle & TCP_NAGLE_PUSH) 1633 return true; 1634 1635 /* Don't use the nagle rule for urgent data (or for the final FIN). 1636 * Nagle can be ignored during F-RTO too (see RFC4138). 1637 */ 1638 if (tcp_urg_mode(tp) || (tp->frto_counter == 2) || 1639 (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)) 1640 return true; 1641 1642 if (!tcp_nagle_check(tp, skb, cur_mss, nonagle)) 1643 return true; 1644 1645 return false; 1646 } 1647 1648 /* Does at least the first segment of SKB fit into the send window? */ 1649 static bool tcp_snd_wnd_test(const struct tcp_sock *tp, 1650 const struct sk_buff *skb, 1651 unsigned int cur_mss) 1652 { 1653 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 1654 1655 if (skb->len > cur_mss) 1656 end_seq = TCP_SKB_CB(skb)->seq + cur_mss; 1657 1658 return !after(end_seq, tcp_wnd_end(tp)); 1659 } 1660 1661 /* This checks if the data bearing packet SKB (usually tcp_send_head(sk)) 1662 * should be put on the wire right now. If so, it returns the number of 1663 * packets allowed by the congestion window. 1664 */ 1665 static unsigned int tcp_snd_test(const struct sock *sk, struct sk_buff *skb, 1666 unsigned int cur_mss, int nonagle) 1667 { 1668 const struct tcp_sock *tp = tcp_sk(sk); 1669 unsigned int cwnd_quota; 1670 1671 tcp_init_tso_segs(sk, skb, cur_mss); 1672 1673 if (!tcp_nagle_test(tp, skb, cur_mss, nonagle)) 1674 return 0; 1675 1676 cwnd_quota = tcp_cwnd_test(tp, skb); 1677 if (cwnd_quota && !tcp_snd_wnd_test(tp, skb, cur_mss)) 1678 cwnd_quota = 0; 1679 1680 return cwnd_quota; 1681 } 1682 1683 /* Test if sending is allowed right now. */ 1684 bool tcp_may_send_now(struct sock *sk) 1685 { 1686 const struct tcp_sock *tp = tcp_sk(sk); 1687 struct sk_buff *skb = tcp_send_head(sk); 1688 1689 return skb && 1690 tcp_snd_test(sk, skb, tcp_current_mss(sk), 1691 (tcp_skb_is_last(sk, skb) ? 1692 tp->nonagle : TCP_NAGLE_PUSH)); 1693 } 1694 1695 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet 1696 * which is put after SKB on the list. It is very much like 1697 * tcp_fragment() except that it may make several kinds of assumptions 1698 * in order to speed up the splitting operation. In particular, we 1699 * know that all the data is in scatter-gather pages, and that the 1700 * packet has never been sent out before (and thus is not cloned). 1701 */ 1702 static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, 1703 unsigned int mss_now, gfp_t gfp) 1704 { 1705 struct sk_buff *buff; 1706 int nlen = skb->len - len; 1707 u8 flags; 1708 1709 /* All of a TSO frame must be composed of paged data. */ 1710 if (skb->len != skb->data_len) 1711 return tcp_fragment(sk, skb, len, mss_now); 1712 1713 buff = sk_stream_alloc_skb(sk, 0, gfp); 1714 if (unlikely(buff == NULL)) 1715 return -ENOMEM; 1716 1717 sk->sk_wmem_queued += buff->truesize; 1718 sk_mem_charge(sk, buff->truesize); 1719 buff->truesize += nlen; 1720 skb->truesize -= nlen; 1721 1722 /* Correct the sequence numbers. */ 1723 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; 1724 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; 1725 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; 1726 1727 /* PSH and FIN should only be set in the second packet. */ 1728 flags = TCP_SKB_CB(skb)->tcp_flags; 1729 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH); 1730 TCP_SKB_CB(buff)->tcp_flags = flags; 1731 1732 /* This packet was never sent out yet, so no SACK bits. */ 1733 TCP_SKB_CB(buff)->sacked = 0; 1734 1735 buff->ip_summed = skb->ip_summed = CHECKSUM_PARTIAL; 1736 skb_split(skb, buff, len); 1737 1738 /* Fix up tso_factor for both original and new SKB. */ 1739 tcp_set_skb_tso_segs(sk, skb, mss_now); 1740 tcp_set_skb_tso_segs(sk, buff, mss_now); 1741 1742 /* Link BUFF into the send queue. */ 1743 skb_header_release(buff); 1744 tcp_insert_write_queue_after(skb, buff, sk); 1745 1746 return 0; 1747 } 1748 1749 /* Try to defer sending, if possible, in order to minimize the amount 1750 * of TSO splitting we do. View it as a kind of TSO Nagle test. 1751 * 1752 * This algorithm is from John Heffner. 1753 */ 1754 static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb) 1755 { 1756 struct tcp_sock *tp = tcp_sk(sk); 1757 const struct inet_connection_sock *icsk = inet_csk(sk); 1758 u32 send_win, cong_win, limit, in_flight; 1759 int win_divisor; 1760 1761 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) 1762 goto send_now; 1763 1764 if (icsk->icsk_ca_state != TCP_CA_Open) 1765 goto send_now; 1766 1767 /* Defer for less than two clock ticks. */ 1768 if (tp->tso_deferred && 1769 (((u32)jiffies << 1) >> 1) - (tp->tso_deferred >> 1) > 1) 1770 goto send_now; 1771 1772 in_flight = tcp_packets_in_flight(tp); 1773 1774 BUG_ON(tcp_skb_pcount(skb) <= 1 || (tp->snd_cwnd <= in_flight)); 1775 1776 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; 1777 1778 /* From in_flight test above, we know that cwnd > in_flight. */ 1779 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache; 1780 1781 limit = min(send_win, cong_win); 1782 1783 /* If a full-sized TSO skb can be sent, do it. */ 1784 if (limit >= min_t(unsigned int, sk->sk_gso_max_size, 1785 sk->sk_gso_max_segs * tp->mss_cache)) 1786 goto send_now; 1787 1788 /* Middle in queue won't get any more data, full sendable already? */ 1789 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len)) 1790 goto send_now; 1791 1792 win_divisor = ACCESS_ONCE(sysctl_tcp_tso_win_divisor); 1793 if (win_divisor) { 1794 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache); 1795 1796 /* If at least some fraction of a window is available, 1797 * just use it. 1798 */ 1799 chunk /= win_divisor; 1800 if (limit >= chunk) 1801 goto send_now; 1802 } else { 1803 /* Different approach, try not to defer past a single 1804 * ACK. Receiver should ACK every other full sized 1805 * frame, so if we have space for more than 3 frames 1806 * then send now. 1807 */ 1808 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache) 1809 goto send_now; 1810 } 1811 1812 /* Ok, it looks like it is advisable to defer. 1813 * Do not rearm the timer if already set to not break TCP ACK clocking. 1814 */ 1815 if (!tp->tso_deferred) 1816 tp->tso_deferred = 1 | (jiffies << 1); 1817 1818 return true; 1819 1820 send_now: 1821 tp->tso_deferred = 0; 1822 return false; 1823 } 1824 1825 /* Create a new MTU probe if we are ready. 1826 * MTU probe is regularly attempting to increase the path MTU by 1827 * deliberately sending larger packets. This discovers routing 1828 * changes resulting in larger path MTUs. 1829 * 1830 * Returns 0 if we should wait to probe (no cwnd available), 1831 * 1 if a probe was sent, 1832 * -1 otherwise 1833 */ 1834 static int tcp_mtu_probe(struct sock *sk) 1835 { 1836 struct tcp_sock *tp = tcp_sk(sk); 1837 struct inet_connection_sock *icsk = inet_csk(sk); 1838 struct sk_buff *skb, *nskb, *next; 1839 int len; 1840 int probe_size; 1841 int size_needed; 1842 int copy; 1843 int mss_now; 1844 1845 /* Not currently probing/verifying, 1846 * not in recovery, 1847 * have enough cwnd, and 1848 * not SACKing (the variable headers throw things off) */ 1849 if (!icsk->icsk_mtup.enabled || 1850 icsk->icsk_mtup.probe_size || 1851 inet_csk(sk)->icsk_ca_state != TCP_CA_Open || 1852 tp->snd_cwnd < 11 || 1853 tp->rx_opt.num_sacks || tp->rx_opt.dsack) 1854 return -1; 1855 1856 /* Very simple search strategy: just double the MSS. */ 1857 mss_now = tcp_current_mss(sk); 1858 probe_size = 2 * tp->mss_cache; 1859 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache; 1860 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high)) { 1861 /* TODO: set timer for probe_converge_event */ 1862 return -1; 1863 } 1864 1865 /* Have enough data in the send queue to probe? */ 1866 if (tp->write_seq - tp->snd_nxt < size_needed) 1867 return -1; 1868 1869 if (tp->snd_wnd < size_needed) 1870 return -1; 1871 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp))) 1872 return 0; 1873 1874 /* Do we need to wait to drain cwnd? With none in flight, don't stall */ 1875 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) { 1876 if (!tcp_packets_in_flight(tp)) 1877 return -1; 1878 else 1879 return 0; 1880 } 1881 1882 /* We're allowed to probe. Build it now. */ 1883 if ((nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC)) == NULL) 1884 return -1; 1885 sk->sk_wmem_queued += nskb->truesize; 1886 sk_mem_charge(sk, nskb->truesize); 1887 1888 skb = tcp_send_head(sk); 1889 1890 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq; 1891 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size; 1892 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK; 1893 TCP_SKB_CB(nskb)->sacked = 0; 1894 nskb->csum = 0; 1895 nskb->ip_summed = skb->ip_summed; 1896 1897 tcp_insert_write_queue_before(nskb, skb, sk); 1898 1899 len = 0; 1900 tcp_for_write_queue_from_safe(skb, next, sk) { 1901 copy = min_t(int, skb->len, probe_size - len); 1902 if (nskb->ip_summed) 1903 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy); 1904 else 1905 nskb->csum = skb_copy_and_csum_bits(skb, 0, 1906 skb_put(nskb, copy), 1907 copy, nskb->csum); 1908 1909 if (skb->len <= copy) { 1910 /* We've eaten all the data from this skb. 1911 * Throw it away. */ 1912 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags; 1913 tcp_unlink_write_queue(skb, sk); 1914 sk_wmem_free_skb(sk, skb); 1915 } else { 1916 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags & 1917 ~(TCPHDR_FIN|TCPHDR_PSH); 1918 if (!skb_shinfo(skb)->nr_frags) { 1919 skb_pull(skb, copy); 1920 if (skb->ip_summed != CHECKSUM_PARTIAL) 1921 skb->csum = csum_partial(skb->data, 1922 skb->len, 0); 1923 } else { 1924 __pskb_trim_head(skb, copy); 1925 tcp_set_skb_tso_segs(sk, skb, mss_now); 1926 } 1927 TCP_SKB_CB(skb)->seq += copy; 1928 } 1929 1930 len += copy; 1931 1932 if (len >= probe_size) 1933 break; 1934 } 1935 tcp_init_tso_segs(sk, nskb, nskb->len); 1936 1937 /* We're ready to send. If this fails, the probe will 1938 * be resegmented into mss-sized pieces by tcp_write_xmit(). */ 1939 TCP_SKB_CB(nskb)->when = tcp_time_stamp; 1940 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) { 1941 /* Decrement cwnd here because we are sending 1942 * effectively two packets. */ 1943 tp->snd_cwnd--; 1944 tcp_event_new_data_sent(sk, nskb); 1945 1946 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len); 1947 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq; 1948 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq; 1949 1950 return 1; 1951 } 1952 1953 return -1; 1954 } 1955 1956 /* This routine writes packets to the network. It advances the 1957 * send_head. This happens as incoming acks open up the remote 1958 * window for us. 1959 * 1960 * LARGESEND note: !tcp_urg_mode is overkill, only frames between 1961 * snd_up-64k-mss .. snd_up cannot be large. However, taking into 1962 * account rare use of URG, this is not a big flaw. 1963 * 1964 * Returns true, if no segments are in flight and we have queued segments, 1965 * but cannot send anything now because of SWS or another problem. 1966 */ 1967 static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, 1968 int push_one, gfp_t gfp) 1969 { 1970 struct tcp_sock *tp = tcp_sk(sk); 1971 struct sk_buff *skb; 1972 unsigned int tso_segs, sent_pkts; 1973 int cwnd_quota; 1974 int result; 1975 1976 sent_pkts = 0; 1977 1978 if (!push_one) { 1979 /* Do MTU probing. */ 1980 result = tcp_mtu_probe(sk); 1981 if (!result) { 1982 return false; 1983 } else if (result > 0) { 1984 sent_pkts = 1; 1985 } 1986 } 1987 1988 while ((skb = tcp_send_head(sk))) { 1989 unsigned int limit; 1990 1991 1992 tso_segs = tcp_init_tso_segs(sk, skb, mss_now); 1993 BUG_ON(!tso_segs); 1994 1995 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) 1996 goto repair; /* Skip network transmission */ 1997 1998 cwnd_quota = tcp_cwnd_test(tp, skb); 1999 if (!cwnd_quota) 2000 break; 2001 2002 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) 2003 break; 2004 2005 if (tso_segs == 1) { 2006 if (unlikely(!tcp_nagle_test(tp, skb, mss_now, 2007 (tcp_skb_is_last(sk, skb) ? 2008 nonagle : TCP_NAGLE_PUSH)))) 2009 break; 2010 } else { 2011 if (!push_one && tcp_tso_should_defer(sk, skb)) 2012 break; 2013 } 2014 2015 /* TSQ : sk_wmem_alloc accounts skb truesize, 2016 * including skb overhead. But thats OK. 2017 */ 2018 if (atomic_read(&sk->sk_wmem_alloc) >= sysctl_tcp_limit_output_bytes) { 2019 set_bit(TSQ_THROTTLED, &tp->tsq_flags); 2020 break; 2021 } 2022 limit = mss_now; 2023 if (tso_segs > 1 && !tcp_urg_mode(tp)) 2024 limit = tcp_mss_split_point(sk, skb, mss_now, 2025 min_t(unsigned int, 2026 cwnd_quota, 2027 sk->sk_gso_max_segs)); 2028 2029 if (skb->len > limit && 2030 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp))) 2031 break; 2032 2033 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2034 2035 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp))) 2036 break; 2037 2038 repair: 2039 /* Advance the send_head. This one is sent out. 2040 * This call will increment packets_out. 2041 */ 2042 tcp_event_new_data_sent(sk, skb); 2043 2044 tcp_minshall_update(tp, mss_now, skb); 2045 sent_pkts += tcp_skb_pcount(skb); 2046 2047 if (push_one) 2048 break; 2049 } 2050 2051 if (likely(sent_pkts)) { 2052 if (tcp_in_cwnd_reduction(sk)) 2053 tp->prr_out += sent_pkts; 2054 tcp_cwnd_validate(sk); 2055 return false; 2056 } 2057 return !tp->packets_out && tcp_send_head(sk); 2058 } 2059 2060 /* Push out any pending frames which were held back due to 2061 * TCP_CORK or attempt at coalescing tiny packets. 2062 * The socket must be locked by the caller. 2063 */ 2064 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss, 2065 int nonagle) 2066 { 2067 /* If we are closed, the bytes will have to remain here. 2068 * In time closedown will finish, we empty the write queue and 2069 * all will be happy. 2070 */ 2071 if (unlikely(sk->sk_state == TCP_CLOSE)) 2072 return; 2073 2074 if (tcp_write_xmit(sk, cur_mss, nonagle, 0, 2075 sk_gfp_atomic(sk, GFP_ATOMIC))) 2076 tcp_check_probe_timer(sk); 2077 } 2078 2079 /* Send _single_ skb sitting at the send head. This function requires 2080 * true push pending frames to setup probe timer etc. 2081 */ 2082 void tcp_push_one(struct sock *sk, unsigned int mss_now) 2083 { 2084 struct sk_buff *skb = tcp_send_head(sk); 2085 2086 BUG_ON(!skb || skb->len < mss_now); 2087 2088 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation); 2089 } 2090 2091 /* This function returns the amount that we can raise the 2092 * usable window based on the following constraints 2093 * 2094 * 1. The window can never be shrunk once it is offered (RFC 793) 2095 * 2. We limit memory per socket 2096 * 2097 * RFC 1122: 2098 * "the suggested [SWS] avoidance algorithm for the receiver is to keep 2099 * RECV.NEXT + RCV.WIN fixed until: 2100 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)" 2101 * 2102 * i.e. don't raise the right edge of the window until you can raise 2103 * it at least MSS bytes. 2104 * 2105 * Unfortunately, the recommended algorithm breaks header prediction, 2106 * since header prediction assumes th->window stays fixed. 2107 * 2108 * Strictly speaking, keeping th->window fixed violates the receiver 2109 * side SWS prevention criteria. The problem is that under this rule 2110 * a stream of single byte packets will cause the right side of the 2111 * window to always advance by a single byte. 2112 * 2113 * Of course, if the sender implements sender side SWS prevention 2114 * then this will not be a problem. 2115 * 2116 * BSD seems to make the following compromise: 2117 * 2118 * If the free space is less than the 1/4 of the maximum 2119 * space available and the free space is less than 1/2 mss, 2120 * then set the window to 0. 2121 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ] 2122 * Otherwise, just prevent the window from shrinking 2123 * and from being larger than the largest representable value. 2124 * 2125 * This prevents incremental opening of the window in the regime 2126 * where TCP is limited by the speed of the reader side taking 2127 * data out of the TCP receive queue. It does nothing about 2128 * those cases where the window is constrained on the sender side 2129 * because the pipeline is full. 2130 * 2131 * BSD also seems to "accidentally" limit itself to windows that are a 2132 * multiple of MSS, at least until the free space gets quite small. 2133 * This would appear to be a side effect of the mbuf implementation. 2134 * Combining these two algorithms results in the observed behavior 2135 * of having a fixed window size at almost all times. 2136 * 2137 * Below we obtain similar behavior by forcing the offered window to 2138 * a multiple of the mss when it is feasible to do so. 2139 * 2140 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes. 2141 * Regular options like TIMESTAMP are taken into account. 2142 */ 2143 u32 __tcp_select_window(struct sock *sk) 2144 { 2145 struct inet_connection_sock *icsk = inet_csk(sk); 2146 struct tcp_sock *tp = tcp_sk(sk); 2147 /* MSS for the peer's data. Previous versions used mss_clamp 2148 * here. I don't know if the value based on our guesses 2149 * of peer's MSS is better for the performance. It's more correct 2150 * but may be worse for the performance because of rcv_mss 2151 * fluctuations. --SAW 1998/11/1 2152 */ 2153 int mss = icsk->icsk_ack.rcv_mss; 2154 int free_space = tcp_space(sk); 2155 int full_space = min_t(int, tp->window_clamp, tcp_full_space(sk)); 2156 int window; 2157 2158 if (mss > full_space) 2159 mss = full_space; 2160 2161 if (free_space < (full_space >> 1)) { 2162 icsk->icsk_ack.quick = 0; 2163 2164 if (sk_under_memory_pressure(sk)) 2165 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 2166 4U * tp->advmss); 2167 2168 if (free_space < mss) 2169 return 0; 2170 } 2171 2172 if (free_space > tp->rcv_ssthresh) 2173 free_space = tp->rcv_ssthresh; 2174 2175 /* Don't do rounding if we are using window scaling, since the 2176 * scaled window will not line up with the MSS boundary anyway. 2177 */ 2178 window = tp->rcv_wnd; 2179 if (tp->rx_opt.rcv_wscale) { 2180 window = free_space; 2181 2182 /* Advertise enough space so that it won't get scaled away. 2183 * Import case: prevent zero window announcement if 2184 * 1<<rcv_wscale > mss. 2185 */ 2186 if (((window >> tp->rx_opt.rcv_wscale) << tp->rx_opt.rcv_wscale) != window) 2187 window = (((window >> tp->rx_opt.rcv_wscale) + 1) 2188 << tp->rx_opt.rcv_wscale); 2189 } else { 2190 /* Get the largest window that is a nice multiple of mss. 2191 * Window clamp already applied above. 2192 * If our current window offering is within 1 mss of the 2193 * free space we just keep it. This prevents the divide 2194 * and multiply from happening most of the time. 2195 * We also don't do any window rounding when the free space 2196 * is too small. 2197 */ 2198 if (window <= free_space - mss || window > free_space) 2199 window = (free_space / mss) * mss; 2200 else if (mss == full_space && 2201 free_space > window + (full_space >> 1)) 2202 window = free_space; 2203 } 2204 2205 return window; 2206 } 2207 2208 /* Collapses two adjacent SKB's during retransmission. */ 2209 static void tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb) 2210 { 2211 struct tcp_sock *tp = tcp_sk(sk); 2212 struct sk_buff *next_skb = tcp_write_queue_next(sk, skb); 2213 int skb_size, next_skb_size; 2214 2215 skb_size = skb->len; 2216 next_skb_size = next_skb->len; 2217 2218 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1); 2219 2220 tcp_highest_sack_combine(sk, next_skb, skb); 2221 2222 tcp_unlink_write_queue(next_skb, sk); 2223 2224 skb_copy_from_linear_data(next_skb, skb_put(skb, next_skb_size), 2225 next_skb_size); 2226 2227 if (next_skb->ip_summed == CHECKSUM_PARTIAL) 2228 skb->ip_summed = CHECKSUM_PARTIAL; 2229 2230 if (skb->ip_summed != CHECKSUM_PARTIAL) 2231 skb->csum = csum_block_add(skb->csum, next_skb->csum, skb_size); 2232 2233 /* Update sequence range on original skb. */ 2234 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq; 2235 2236 /* Merge over control information. This moves PSH/FIN etc. over */ 2237 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags; 2238 2239 /* All done, get rid of second SKB and account for it so 2240 * packet counting does not break. 2241 */ 2242 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS; 2243 2244 /* changed transmit queue under us so clear hints */ 2245 tcp_clear_retrans_hints_partial(tp); 2246 if (next_skb == tp->retransmit_skb_hint) 2247 tp->retransmit_skb_hint = skb; 2248 2249 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb)); 2250 2251 sk_wmem_free_skb(sk, next_skb); 2252 } 2253 2254 /* Check if coalescing SKBs is legal. */ 2255 static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb) 2256 { 2257 if (tcp_skb_pcount(skb) > 1) 2258 return false; 2259 /* TODO: SACK collapsing could be used to remove this condition */ 2260 if (skb_shinfo(skb)->nr_frags != 0) 2261 return false; 2262 if (skb_cloned(skb)) 2263 return false; 2264 if (skb == tcp_send_head(sk)) 2265 return false; 2266 /* Some heurestics for collapsing over SACK'd could be invented */ 2267 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) 2268 return false; 2269 2270 return true; 2271 } 2272 2273 /* Collapse packets in the retransmit queue to make to create 2274 * less packets on the wire. This is only done on retransmission. 2275 */ 2276 static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to, 2277 int space) 2278 { 2279 struct tcp_sock *tp = tcp_sk(sk); 2280 struct sk_buff *skb = to, *tmp; 2281 bool first = true; 2282 2283 if (!sysctl_tcp_retrans_collapse) 2284 return; 2285 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN) 2286 return; 2287 2288 tcp_for_write_queue_from_safe(skb, tmp, sk) { 2289 if (!tcp_can_collapse(sk, skb)) 2290 break; 2291 2292 space -= skb->len; 2293 2294 if (first) { 2295 first = false; 2296 continue; 2297 } 2298 2299 if (space < 0) 2300 break; 2301 /* Punt if not enough space exists in the first SKB for 2302 * the data in the second 2303 */ 2304 if (skb->len > skb_availroom(to)) 2305 break; 2306 2307 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp))) 2308 break; 2309 2310 tcp_collapse_retrans(sk, to); 2311 } 2312 } 2313 2314 /* This retransmits one SKB. Policy decisions and retransmit queue 2315 * state updates are done by the caller. Returns non-zero if an 2316 * error occurred which prevented the send. 2317 */ 2318 int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) 2319 { 2320 struct tcp_sock *tp = tcp_sk(sk); 2321 struct inet_connection_sock *icsk = inet_csk(sk); 2322 unsigned int cur_mss; 2323 2324 /* Inconslusive MTU probe */ 2325 if (icsk->icsk_mtup.probe_size) { 2326 icsk->icsk_mtup.probe_size = 0; 2327 } 2328 2329 /* Do not sent more than we queued. 1/4 is reserved for possible 2330 * copying overhead: fragmentation, tunneling, mangling etc. 2331 */ 2332 if (atomic_read(&sk->sk_wmem_alloc) > 2333 min(sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), sk->sk_sndbuf)) 2334 return -EAGAIN; 2335 2336 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) { 2337 if (before(TCP_SKB_CB(skb)->end_seq, tp->snd_una)) 2338 BUG(); 2339 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) 2340 return -ENOMEM; 2341 } 2342 2343 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk)) 2344 return -EHOSTUNREACH; /* Routing failure or similar. */ 2345 2346 cur_mss = tcp_current_mss(sk); 2347 2348 /* If receiver has shrunk his window, and skb is out of 2349 * new window, do not retransmit it. The exception is the 2350 * case, when window is shrunk to zero. In this case 2351 * our retransmit serves as a zero window probe. 2352 */ 2353 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) && 2354 TCP_SKB_CB(skb)->seq != tp->snd_una) 2355 return -EAGAIN; 2356 2357 if (skb->len > cur_mss) { 2358 if (tcp_fragment(sk, skb, cur_mss, cur_mss)) 2359 return -ENOMEM; /* We'll try again later. */ 2360 } else { 2361 int oldpcount = tcp_skb_pcount(skb); 2362 2363 if (unlikely(oldpcount > 1)) { 2364 tcp_init_tso_segs(sk, skb, cur_mss); 2365 tcp_adjust_pcount(sk, skb, oldpcount - tcp_skb_pcount(skb)); 2366 } 2367 } 2368 2369 tcp_retrans_try_collapse(sk, skb, cur_mss); 2370 2371 /* Some Solaris stacks overoptimize and ignore the FIN on a 2372 * retransmit when old data is attached. So strip it off 2373 * since it is cheap to do so and saves bytes on the network. 2374 */ 2375 if (skb->len > 0 && 2376 (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) && 2377 tp->snd_una == (TCP_SKB_CB(skb)->end_seq - 1)) { 2378 if (!pskb_trim(skb, 0)) { 2379 /* Reuse, even though it does some unnecessary work */ 2380 tcp_init_nondata_skb(skb, TCP_SKB_CB(skb)->end_seq - 1, 2381 TCP_SKB_CB(skb)->tcp_flags); 2382 skb->ip_summed = CHECKSUM_NONE; 2383 } 2384 } 2385 2386 /* Make a copy, if the first transmission SKB clone we made 2387 * is still in somebody's hands, else make a clone. 2388 */ 2389 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2390 2391 /* make sure skb->data is aligned on arches that require it 2392 * and check if ack-trimming & collapsing extended the headroom 2393 * beyond what csum_start can cover. 2394 */ 2395 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) || 2396 skb_headroom(skb) >= 0xFFFF)) { 2397 struct sk_buff *nskb = __pskb_copy(skb, MAX_TCP_HEADER, 2398 GFP_ATOMIC); 2399 return nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) : 2400 -ENOBUFS; 2401 } else { 2402 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 2403 } 2404 } 2405 2406 int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb) 2407 { 2408 struct tcp_sock *tp = tcp_sk(sk); 2409 int err = __tcp_retransmit_skb(sk, skb); 2410 2411 if (err == 0) { 2412 /* Update global TCP statistics. */ 2413 TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS); 2414 2415 tp->total_retrans++; 2416 2417 #if FASTRETRANS_DEBUG > 0 2418 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 2419 net_dbg_ratelimited("retrans_out leaked\n"); 2420 } 2421 #endif 2422 if (!tp->retrans_out) 2423 tp->lost_retrans_low = tp->snd_nxt; 2424 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS; 2425 tp->retrans_out += tcp_skb_pcount(skb); 2426 2427 /* Save stamp of the first retransmit. */ 2428 if (!tp->retrans_stamp) 2429 tp->retrans_stamp = TCP_SKB_CB(skb)->when; 2430 2431 tp->undo_retrans += tcp_skb_pcount(skb); 2432 2433 /* snd_nxt is stored to detect loss of retransmitted segment, 2434 * see tcp_input.c tcp_sacktag_write_queue(). 2435 */ 2436 TCP_SKB_CB(skb)->ack_seq = tp->snd_nxt; 2437 } 2438 return err; 2439 } 2440 2441 /* Check if we forward retransmits are possible in the current 2442 * window/congestion state. 2443 */ 2444 static bool tcp_can_forward_retransmit(struct sock *sk) 2445 { 2446 const struct inet_connection_sock *icsk = inet_csk(sk); 2447 const struct tcp_sock *tp = tcp_sk(sk); 2448 2449 /* Forward retransmissions are possible only during Recovery. */ 2450 if (icsk->icsk_ca_state != TCP_CA_Recovery) 2451 return false; 2452 2453 /* No forward retransmissions in Reno are possible. */ 2454 if (tcp_is_reno(tp)) 2455 return false; 2456 2457 /* Yeah, we have to make difficult choice between forward transmission 2458 * and retransmission... Both ways have their merits... 2459 * 2460 * For now we do not retransmit anything, while we have some new 2461 * segments to send. In the other cases, follow rule 3 for 2462 * NextSeg() specified in RFC3517. 2463 */ 2464 2465 if (tcp_may_send_now(sk)) 2466 return false; 2467 2468 return true; 2469 } 2470 2471 /* This gets called after a retransmit timeout, and the initially 2472 * retransmitted data is acknowledged. It tries to continue 2473 * resending the rest of the retransmit queue, until either 2474 * we've sent it all or the congestion window limit is reached. 2475 * If doing SACK, the first ACK which comes back for a timeout 2476 * based retransmit packet might feed us FACK information again. 2477 * If so, we use it to avoid unnecessarily retransmissions. 2478 */ 2479 void tcp_xmit_retransmit_queue(struct sock *sk) 2480 { 2481 const struct inet_connection_sock *icsk = inet_csk(sk); 2482 struct tcp_sock *tp = tcp_sk(sk); 2483 struct sk_buff *skb; 2484 struct sk_buff *hole = NULL; 2485 u32 last_lost; 2486 int mib_idx; 2487 int fwd_rexmitting = 0; 2488 2489 if (!tp->packets_out) 2490 return; 2491 2492 if (!tp->lost_out) 2493 tp->retransmit_high = tp->snd_una; 2494 2495 if (tp->retransmit_skb_hint) { 2496 skb = tp->retransmit_skb_hint; 2497 last_lost = TCP_SKB_CB(skb)->end_seq; 2498 if (after(last_lost, tp->retransmit_high)) 2499 last_lost = tp->retransmit_high; 2500 } else { 2501 skb = tcp_write_queue_head(sk); 2502 last_lost = tp->snd_una; 2503 } 2504 2505 tcp_for_write_queue_from(skb, sk) { 2506 __u8 sacked = TCP_SKB_CB(skb)->sacked; 2507 2508 if (skb == tcp_send_head(sk)) 2509 break; 2510 /* we could do better than to assign each time */ 2511 if (hole == NULL) 2512 tp->retransmit_skb_hint = skb; 2513 2514 /* Assume this retransmit will generate 2515 * only one packet for congestion window 2516 * calculation purposes. This works because 2517 * tcp_retransmit_skb() will chop up the 2518 * packet to be MSS sized and all the 2519 * packet counting works out. 2520 */ 2521 if (tcp_packets_in_flight(tp) >= tp->snd_cwnd) 2522 return; 2523 2524 if (fwd_rexmitting) { 2525 begin_fwd: 2526 if (!before(TCP_SKB_CB(skb)->seq, tcp_highest_sack_seq(tp))) 2527 break; 2528 mib_idx = LINUX_MIB_TCPFORWARDRETRANS; 2529 2530 } else if (!before(TCP_SKB_CB(skb)->seq, tp->retransmit_high)) { 2531 tp->retransmit_high = last_lost; 2532 if (!tcp_can_forward_retransmit(sk)) 2533 break; 2534 /* Backtrack if necessary to non-L'ed skb */ 2535 if (hole != NULL) { 2536 skb = hole; 2537 hole = NULL; 2538 } 2539 fwd_rexmitting = 1; 2540 goto begin_fwd; 2541 2542 } else if (!(sacked & TCPCB_LOST)) { 2543 if (hole == NULL && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED))) 2544 hole = skb; 2545 continue; 2546 2547 } else { 2548 last_lost = TCP_SKB_CB(skb)->end_seq; 2549 if (icsk->icsk_ca_state != TCP_CA_Loss) 2550 mib_idx = LINUX_MIB_TCPFASTRETRANS; 2551 else 2552 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS; 2553 } 2554 2555 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS)) 2556 continue; 2557 2558 if (tcp_retransmit_skb(sk, skb)) { 2559 NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL); 2560 return; 2561 } 2562 NET_INC_STATS_BH(sock_net(sk), mib_idx); 2563 2564 if (tcp_in_cwnd_reduction(sk)) 2565 tp->prr_out += tcp_skb_pcount(skb); 2566 2567 if (skb == tcp_write_queue_head(sk)) 2568 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 2569 inet_csk(sk)->icsk_rto, 2570 TCP_RTO_MAX); 2571 } 2572 } 2573 2574 /* Send a fin. The caller locks the socket for us. This cannot be 2575 * allowed to fail queueing a FIN frame under any circumstances. 2576 */ 2577 void tcp_send_fin(struct sock *sk) 2578 { 2579 struct tcp_sock *tp = tcp_sk(sk); 2580 struct sk_buff *skb = tcp_write_queue_tail(sk); 2581 int mss_now; 2582 2583 /* Optimization, tack on the FIN if we have a queue of 2584 * unsent frames. But be careful about outgoing SACKS 2585 * and IP options. 2586 */ 2587 mss_now = tcp_current_mss(sk); 2588 2589 if (tcp_send_head(sk) != NULL) { 2590 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_FIN; 2591 TCP_SKB_CB(skb)->end_seq++; 2592 tp->write_seq++; 2593 } else { 2594 /* Socket is locked, keep trying until memory is available. */ 2595 for (;;) { 2596 skb = alloc_skb_fclone(MAX_TCP_HEADER, 2597 sk->sk_allocation); 2598 if (skb) 2599 break; 2600 yield(); 2601 } 2602 2603 /* Reserve space for headers and prepare control bits. */ 2604 skb_reserve(skb, MAX_TCP_HEADER); 2605 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */ 2606 tcp_init_nondata_skb(skb, tp->write_seq, 2607 TCPHDR_ACK | TCPHDR_FIN); 2608 tcp_queue_skb(sk, skb); 2609 } 2610 __tcp_push_pending_frames(sk, mss_now, TCP_NAGLE_OFF); 2611 } 2612 2613 /* We get here when a process closes a file descriptor (either due to 2614 * an explicit close() or as a byproduct of exit()'ing) and there 2615 * was unread data in the receive queue. This behavior is recommended 2616 * by RFC 2525, section 2.17. -DaveM 2617 */ 2618 void tcp_send_active_reset(struct sock *sk, gfp_t priority) 2619 { 2620 struct sk_buff *skb; 2621 2622 /* NOTE: No TCP options attached and we never retransmit this. */ 2623 skb = alloc_skb(MAX_TCP_HEADER, priority); 2624 if (!skb) { 2625 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); 2626 return; 2627 } 2628 2629 /* Reserve space for headers and prepare control bits. */ 2630 skb_reserve(skb, MAX_TCP_HEADER); 2631 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk), 2632 TCPHDR_ACK | TCPHDR_RST); 2633 /* Send it off. */ 2634 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2635 if (tcp_transmit_skb(sk, skb, 0, priority)) 2636 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); 2637 2638 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS); 2639 } 2640 2641 /* Send a crossed SYN-ACK during socket establishment. 2642 * WARNING: This routine must only be called when we have already sent 2643 * a SYN packet that crossed the incoming SYN that caused this routine 2644 * to get called. If this assumption fails then the initial rcv_wnd 2645 * and rcv_wscale values will not be correct. 2646 */ 2647 int tcp_send_synack(struct sock *sk) 2648 { 2649 struct sk_buff *skb; 2650 2651 skb = tcp_write_queue_head(sk); 2652 if (skb == NULL || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) { 2653 pr_debug("%s: wrong queue state\n", __func__); 2654 return -EFAULT; 2655 } 2656 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) { 2657 if (skb_cloned(skb)) { 2658 struct sk_buff *nskb = skb_copy(skb, GFP_ATOMIC); 2659 if (nskb == NULL) 2660 return -ENOMEM; 2661 tcp_unlink_write_queue(skb, sk); 2662 skb_header_release(nskb); 2663 __tcp_add_write_queue_head(sk, nskb); 2664 sk_wmem_free_skb(sk, skb); 2665 sk->sk_wmem_queued += nskb->truesize; 2666 sk_mem_charge(sk, nskb->truesize); 2667 skb = nskb; 2668 } 2669 2670 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK; 2671 TCP_ECN_send_synack(tcp_sk(sk), skb); 2672 } 2673 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2674 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 2675 } 2676 2677 /** 2678 * tcp_make_synack - Prepare a SYN-ACK. 2679 * sk: listener socket 2680 * dst: dst entry attached to the SYNACK 2681 * req: request_sock pointer 2682 * rvp: request_values pointer 2683 * 2684 * Allocate one skb and build a SYNACK packet. 2685 * @dst is consumed : Caller should not use it again. 2686 */ 2687 struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst, 2688 struct request_sock *req, 2689 struct request_values *rvp, 2690 struct tcp_fastopen_cookie *foc) 2691 { 2692 struct tcp_out_options opts; 2693 struct tcp_extend_values *xvp = tcp_xv(rvp); 2694 struct inet_request_sock *ireq = inet_rsk(req); 2695 struct tcp_sock *tp = tcp_sk(sk); 2696 const struct tcp_cookie_values *cvp = tp->cookie_values; 2697 struct tcphdr *th; 2698 struct sk_buff *skb; 2699 struct tcp_md5sig_key *md5; 2700 int tcp_header_size; 2701 int mss; 2702 int s_data_desired = 0; 2703 2704 if (cvp != NULL && cvp->s_data_constant && cvp->s_data_desired) 2705 s_data_desired = cvp->s_data_desired; 2706 skb = alloc_skb(MAX_TCP_HEADER + 15 + s_data_desired, 2707 sk_gfp_atomic(sk, GFP_ATOMIC)); 2708 if (unlikely(!skb)) { 2709 dst_release(dst); 2710 return NULL; 2711 } 2712 /* Reserve space for headers. */ 2713 skb_reserve(skb, MAX_TCP_HEADER); 2714 2715 skb_dst_set(skb, dst); 2716 security_skb_owned_by(skb, sk); 2717 2718 mss = dst_metric_advmss(dst); 2719 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < mss) 2720 mss = tp->rx_opt.user_mss; 2721 2722 if (req->rcv_wnd == 0) { /* ignored for retransmitted syns */ 2723 __u8 rcv_wscale; 2724 /* Set this up on the first call only */ 2725 req->window_clamp = tp->window_clamp ? : dst_metric(dst, RTAX_WINDOW); 2726 2727 /* limit the window selection if the user enforce a smaller rx buffer */ 2728 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK && 2729 (req->window_clamp > tcp_full_space(sk) || req->window_clamp == 0)) 2730 req->window_clamp = tcp_full_space(sk); 2731 2732 /* tcp_full_space because it is guaranteed to be the first packet */ 2733 tcp_select_initial_window(tcp_full_space(sk), 2734 mss - (ireq->tstamp_ok ? TCPOLEN_TSTAMP_ALIGNED : 0), 2735 &req->rcv_wnd, 2736 &req->window_clamp, 2737 ireq->wscale_ok, 2738 &rcv_wscale, 2739 dst_metric(dst, RTAX_INITRWND)); 2740 ireq->rcv_wscale = rcv_wscale; 2741 } 2742 2743 memset(&opts, 0, sizeof(opts)); 2744 #ifdef CONFIG_SYN_COOKIES 2745 if (unlikely(req->cookie_ts)) 2746 TCP_SKB_CB(skb)->when = cookie_init_timestamp(req); 2747 else 2748 #endif 2749 TCP_SKB_CB(skb)->when = tcp_time_stamp; 2750 tcp_header_size = tcp_synack_options(sk, req, mss, 2751 skb, &opts, &md5, xvp, foc) 2752 + sizeof(*th); 2753 2754 skb_push(skb, tcp_header_size); 2755 skb_reset_transport_header(skb); 2756 2757 th = tcp_hdr(skb); 2758 memset(th, 0, sizeof(struct tcphdr)); 2759 th->syn = 1; 2760 th->ack = 1; 2761 TCP_ECN_make_synack(req, th); 2762 th->source = ireq->loc_port; 2763 th->dest = ireq->rmt_port; 2764 /* Setting of flags are superfluous here for callers (and ECE is 2765 * not even correctly set) 2766 */ 2767 tcp_init_nondata_skb(skb, tcp_rsk(req)->snt_isn, 2768 TCPHDR_SYN | TCPHDR_ACK); 2769 2770 if (OPTION_COOKIE_EXTENSION & opts.options) { 2771 if (s_data_desired) { 2772 u8 *buf = skb_put(skb, s_data_desired); 2773 2774 /* copy data directly from the listening socket. */ 2775 memcpy(buf, cvp->s_data_payload, s_data_desired); 2776 TCP_SKB_CB(skb)->end_seq += s_data_desired; 2777 } 2778 2779 if (opts.hash_size > 0) { 2780 __u32 workspace[SHA_WORKSPACE_WORDS]; 2781 u32 *mess = &xvp->cookie_bakery[COOKIE_DIGEST_WORDS]; 2782 u32 *tail = &mess[COOKIE_MESSAGE_WORDS-1]; 2783 2784 /* Secret recipe depends on the Timestamp, (future) 2785 * Sequence and Acknowledgment Numbers, Initiator 2786 * Cookie, and others handled by IP variant caller. 2787 */ 2788 *tail-- ^= opts.tsval; 2789 *tail-- ^= tcp_rsk(req)->rcv_isn + 1; 2790 *tail-- ^= TCP_SKB_CB(skb)->seq + 1; 2791 2792 /* recommended */ 2793 *tail-- ^= (((__force u32)th->dest << 16) | (__force u32)th->source); 2794 *tail-- ^= (u32)(unsigned long)cvp; /* per sockopt */ 2795 2796 sha_transform((__u32 *)&xvp->cookie_bakery[0], 2797 (char *)mess, 2798 &workspace[0]); 2799 opts.hash_location = 2800 (__u8 *)&xvp->cookie_bakery[0]; 2801 } 2802 } 2803 2804 th->seq = htonl(TCP_SKB_CB(skb)->seq); 2805 /* XXX data is queued and acked as is. No buffer/window check */ 2806 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt); 2807 2808 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */ 2809 th->window = htons(min(req->rcv_wnd, 65535U)); 2810 tcp_options_write((__be32 *)(th + 1), tp, &opts); 2811 th->doff = (tcp_header_size >> 2); 2812 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS, tcp_skb_pcount(skb)); 2813 2814 #ifdef CONFIG_TCP_MD5SIG 2815 /* Okay, we have all we need - do the md5 hash if needed */ 2816 if (md5) { 2817 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location, 2818 md5, NULL, req, skb); 2819 } 2820 #endif 2821 2822 return skb; 2823 } 2824 EXPORT_SYMBOL(tcp_make_synack); 2825 2826 /* Do all connect socket setups that can be done AF independent. */ 2827 void tcp_connect_init(struct sock *sk) 2828 { 2829 const struct dst_entry *dst = __sk_dst_get(sk); 2830 struct tcp_sock *tp = tcp_sk(sk); 2831 __u8 rcv_wscale; 2832 2833 /* We'll fix this up when we get a response from the other end. 2834 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. 2835 */ 2836 tp->tcp_header_len = sizeof(struct tcphdr) + 2837 (sysctl_tcp_timestamps ? TCPOLEN_TSTAMP_ALIGNED : 0); 2838 2839 #ifdef CONFIG_TCP_MD5SIG 2840 if (tp->af_specific->md5_lookup(sk, sk) != NULL) 2841 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; 2842 #endif 2843 2844 /* If user gave his TCP_MAXSEG, record it to clamp */ 2845 if (tp->rx_opt.user_mss) 2846 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss; 2847 tp->max_window = 0; 2848 tcp_mtup_init(sk); 2849 tcp_sync_mss(sk, dst_mtu(dst)); 2850 2851 if (!tp->window_clamp) 2852 tp->window_clamp = dst_metric(dst, RTAX_WINDOW); 2853 tp->advmss = dst_metric_advmss(dst); 2854 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->advmss) 2855 tp->advmss = tp->rx_opt.user_mss; 2856 2857 tcp_initialize_rcv_mss(sk); 2858 2859 /* limit the window selection if the user enforce a smaller rx buffer */ 2860 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK && 2861 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0)) 2862 tp->window_clamp = tcp_full_space(sk); 2863 2864 tcp_select_initial_window(tcp_full_space(sk), 2865 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0), 2866 &tp->rcv_wnd, 2867 &tp->window_clamp, 2868 sysctl_tcp_window_scaling, 2869 &rcv_wscale, 2870 dst_metric(dst, RTAX_INITRWND)); 2871 2872 tp->rx_opt.rcv_wscale = rcv_wscale; 2873 tp->rcv_ssthresh = tp->rcv_wnd; 2874 2875 sk->sk_err = 0; 2876 sock_reset_flag(sk, SOCK_DONE); 2877 tp->snd_wnd = 0; 2878 tcp_init_wl(tp, 0); 2879 tp->snd_una = tp->write_seq; 2880 tp->snd_sml = tp->write_seq; 2881 tp->snd_up = tp->write_seq; 2882 tp->snd_nxt = tp->write_seq; 2883 2884 if (likely(!tp->repair)) 2885 tp->rcv_nxt = 0; 2886 tp->rcv_wup = tp->rcv_nxt; 2887 tp->copied_seq = tp->rcv_nxt; 2888 2889 inet_csk(sk)->icsk_rto = TCP_TIMEOUT_INIT; 2890 inet_csk(sk)->icsk_retransmits = 0; 2891 tcp_clear_retrans(tp); 2892 } 2893 2894 static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb) 2895 { 2896 struct tcp_sock *tp = tcp_sk(sk); 2897 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); 2898 2899 tcb->end_seq += skb->len; 2900 skb_header_release(skb); 2901 __tcp_add_write_queue_tail(sk, skb); 2902 sk->sk_wmem_queued += skb->truesize; 2903 sk_mem_charge(sk, skb->truesize); 2904 tp->write_seq = tcb->end_seq; 2905 tp->packets_out += tcp_skb_pcount(skb); 2906 } 2907 2908 /* Build and send a SYN with data and (cached) Fast Open cookie. However, 2909 * queue a data-only packet after the regular SYN, such that regular SYNs 2910 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges 2911 * only the SYN sequence, the data are retransmitted in the first ACK. 2912 * If cookie is not cached or other error occurs, falls back to send a 2913 * regular SYN with Fast Open cookie request option. 2914 */ 2915 static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn) 2916 { 2917 struct tcp_sock *tp = tcp_sk(sk); 2918 struct tcp_fastopen_request *fo = tp->fastopen_req; 2919 int syn_loss = 0, space, i, err = 0, iovlen = fo->data->msg_iovlen; 2920 struct sk_buff *syn_data = NULL, *data; 2921 unsigned long last_syn_loss = 0; 2922 2923 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */ 2924 tcp_fastopen_cache_get(sk, &tp->rx_opt.mss_clamp, &fo->cookie, 2925 &syn_loss, &last_syn_loss); 2926 /* Recurring FO SYN losses: revert to regular handshake temporarily */ 2927 if (syn_loss > 1 && 2928 time_before(jiffies, last_syn_loss + (60*HZ << syn_loss))) { 2929 fo->cookie.len = -1; 2930 goto fallback; 2931 } 2932 2933 if (sysctl_tcp_fastopen & TFO_CLIENT_NO_COOKIE) 2934 fo->cookie.len = -1; 2935 else if (fo->cookie.len <= 0) 2936 goto fallback; 2937 2938 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and 2939 * user-MSS. Reserve maximum option space for middleboxes that add 2940 * private TCP options. The cost is reduced data space in SYN :( 2941 */ 2942 if (tp->rx_opt.user_mss && tp->rx_opt.user_mss < tp->rx_opt.mss_clamp) 2943 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss; 2944 space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) - 2945 MAX_TCP_OPTION_SPACE; 2946 2947 syn_data = skb_copy_expand(syn, skb_headroom(syn), space, 2948 sk->sk_allocation); 2949 if (syn_data == NULL) 2950 goto fallback; 2951 2952 for (i = 0; i < iovlen && syn_data->len < space; ++i) { 2953 struct iovec *iov = &fo->data->msg_iov[i]; 2954 unsigned char __user *from = iov->iov_base; 2955 int len = iov->iov_len; 2956 2957 if (syn_data->len + len > space) 2958 len = space - syn_data->len; 2959 else if (i + 1 == iovlen) 2960 /* No more data pending in inet_wait_for_connect() */ 2961 fo->data = NULL; 2962 2963 if (skb_add_data(syn_data, from, len)) 2964 goto fallback; 2965 } 2966 2967 /* Queue a data-only packet after the regular SYN for retransmission */ 2968 data = pskb_copy(syn_data, sk->sk_allocation); 2969 if (data == NULL) 2970 goto fallback; 2971 TCP_SKB_CB(data)->seq++; 2972 TCP_SKB_CB(data)->tcp_flags &= ~TCPHDR_SYN; 2973 TCP_SKB_CB(data)->tcp_flags = (TCPHDR_ACK|TCPHDR_PSH); 2974 tcp_connect_queue_skb(sk, data); 2975 fo->copied = data->len; 2976 2977 if (tcp_transmit_skb(sk, syn_data, 0, sk->sk_allocation) == 0) { 2978 tp->syn_data = (fo->copied > 0); 2979 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFASTOPENACTIVE); 2980 goto done; 2981 } 2982 syn_data = NULL; 2983 2984 fallback: 2985 /* Send a regular SYN with Fast Open cookie request option */ 2986 if (fo->cookie.len > 0) 2987 fo->cookie.len = 0; 2988 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation); 2989 if (err) 2990 tp->syn_fastopen = 0; 2991 kfree_skb(syn_data); 2992 done: 2993 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */ 2994 return err; 2995 } 2996 2997 /* Build a SYN and send it off. */ 2998 int tcp_connect(struct sock *sk) 2999 { 3000 struct tcp_sock *tp = tcp_sk(sk); 3001 struct sk_buff *buff; 3002 int err; 3003 3004 tcp_connect_init(sk); 3005 3006 if (unlikely(tp->repair)) { 3007 tcp_finish_connect(sk, NULL); 3008 return 0; 3009 } 3010 3011 buff = alloc_skb_fclone(MAX_TCP_HEADER + 15, sk->sk_allocation); 3012 if (unlikely(buff == NULL)) 3013 return -ENOBUFS; 3014 3015 /* Reserve space for headers. */ 3016 skb_reserve(buff, MAX_TCP_HEADER); 3017 3018 tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN); 3019 tp->retrans_stamp = TCP_SKB_CB(buff)->when = tcp_time_stamp; 3020 tcp_connect_queue_skb(sk, buff); 3021 TCP_ECN_send_syn(sk, buff); 3022 3023 /* Send off SYN; include data in Fast Open. */ 3024 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) : 3025 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation); 3026 if (err == -ECONNREFUSED) 3027 return err; 3028 3029 /* We change tp->snd_nxt after the tcp_transmit_skb() call 3030 * in order to make this packet get counted in tcpOutSegs. 3031 */ 3032 tp->snd_nxt = tp->write_seq; 3033 tp->pushed_seq = tp->write_seq; 3034 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS); 3035 3036 /* Timer for repeating the SYN until an answer. */ 3037 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 3038 inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 3039 return 0; 3040 } 3041 EXPORT_SYMBOL(tcp_connect); 3042 3043 /* Send out a delayed ack, the caller does the policy checking 3044 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check() 3045 * for details. 3046 */ 3047 void tcp_send_delayed_ack(struct sock *sk) 3048 { 3049 struct inet_connection_sock *icsk = inet_csk(sk); 3050 int ato = icsk->icsk_ack.ato; 3051 unsigned long timeout; 3052 3053 if (ato > TCP_DELACK_MIN) { 3054 const struct tcp_sock *tp = tcp_sk(sk); 3055 int max_ato = HZ / 2; 3056 3057 if (icsk->icsk_ack.pingpong || 3058 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)) 3059 max_ato = TCP_DELACK_MAX; 3060 3061 /* Slow path, intersegment interval is "high". */ 3062 3063 /* If some rtt estimate is known, use it to bound delayed ack. 3064 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements 3065 * directly. 3066 */ 3067 if (tp->srtt) { 3068 int rtt = max(tp->srtt >> 3, TCP_DELACK_MIN); 3069 3070 if (rtt < max_ato) 3071 max_ato = rtt; 3072 } 3073 3074 ato = min(ato, max_ato); 3075 } 3076 3077 /* Stay within the limit we were given */ 3078 timeout = jiffies + ato; 3079 3080 /* Use new timeout only if there wasn't a older one earlier. */ 3081 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) { 3082 /* If delack timer was blocked or is about to expire, 3083 * send ACK now. 3084 */ 3085 if (icsk->icsk_ack.blocked || 3086 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) { 3087 tcp_send_ack(sk); 3088 return; 3089 } 3090 3091 if (!time_before(timeout, icsk->icsk_ack.timeout)) 3092 timeout = icsk->icsk_ack.timeout; 3093 } 3094 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER; 3095 icsk->icsk_ack.timeout = timeout; 3096 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout); 3097 } 3098 3099 /* This routine sends an ack and also updates the window. */ 3100 void tcp_send_ack(struct sock *sk) 3101 { 3102 struct sk_buff *buff; 3103 3104 /* If we have been reset, we may not send again. */ 3105 if (sk->sk_state == TCP_CLOSE) 3106 return; 3107 3108 /* We are not putting this on the write queue, so 3109 * tcp_transmit_skb() will set the ownership to this 3110 * sock. 3111 */ 3112 buff = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC)); 3113 if (buff == NULL) { 3114 inet_csk_schedule_ack(sk); 3115 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN; 3116 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 3117 TCP_DELACK_MAX, TCP_RTO_MAX); 3118 return; 3119 } 3120 3121 /* Reserve space for headers and prepare control bits. */ 3122 skb_reserve(buff, MAX_TCP_HEADER); 3123 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK); 3124 3125 /* Send it off, this clears delayed acks for us. */ 3126 TCP_SKB_CB(buff)->when = tcp_time_stamp; 3127 tcp_transmit_skb(sk, buff, 0, sk_gfp_atomic(sk, GFP_ATOMIC)); 3128 } 3129 3130 /* This routine sends a packet with an out of date sequence 3131 * number. It assumes the other end will try to ack it. 3132 * 3133 * Question: what should we make while urgent mode? 3134 * 4.4BSD forces sending single byte of data. We cannot send 3135 * out of window data, because we have SND.NXT==SND.MAX... 3136 * 3137 * Current solution: to send TWO zero-length segments in urgent mode: 3138 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is 3139 * out-of-date with SND.UNA-1 to probe window. 3140 */ 3141 static int tcp_xmit_probe_skb(struct sock *sk, int urgent) 3142 { 3143 struct tcp_sock *tp = tcp_sk(sk); 3144 struct sk_buff *skb; 3145 3146 /* We don't queue it, tcp_transmit_skb() sets ownership. */ 3147 skb = alloc_skb(MAX_TCP_HEADER, sk_gfp_atomic(sk, GFP_ATOMIC)); 3148 if (skb == NULL) 3149 return -1; 3150 3151 /* Reserve space for headers and set control bits. */ 3152 skb_reserve(skb, MAX_TCP_HEADER); 3153 /* Use a previous sequence. This should cause the other 3154 * end to send an ack. Don't queue or clone SKB, just 3155 * send it. 3156 */ 3157 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK); 3158 TCP_SKB_CB(skb)->when = tcp_time_stamp; 3159 return tcp_transmit_skb(sk, skb, 0, GFP_ATOMIC); 3160 } 3161 3162 void tcp_send_window_probe(struct sock *sk) 3163 { 3164 if (sk->sk_state == TCP_ESTABLISHED) { 3165 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1; 3166 tcp_sk(sk)->snd_nxt = tcp_sk(sk)->write_seq; 3167 tcp_xmit_probe_skb(sk, 0); 3168 } 3169 } 3170 3171 /* Initiate keepalive or window probe from timer. */ 3172 int tcp_write_wakeup(struct sock *sk) 3173 { 3174 struct tcp_sock *tp = tcp_sk(sk); 3175 struct sk_buff *skb; 3176 3177 if (sk->sk_state == TCP_CLOSE) 3178 return -1; 3179 3180 if ((skb = tcp_send_head(sk)) != NULL && 3181 before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) { 3182 int err; 3183 unsigned int mss = tcp_current_mss(sk); 3184 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; 3185 3186 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq)) 3187 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq; 3188 3189 /* We are probing the opening of a window 3190 * but the window size is != 0 3191 * must have been a result SWS avoidance ( sender ) 3192 */ 3193 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq || 3194 skb->len > mss) { 3195 seg_size = min(seg_size, mss); 3196 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH; 3197 if (tcp_fragment(sk, skb, seg_size, mss)) 3198 return -1; 3199 } else if (!tcp_skb_pcount(skb)) 3200 tcp_set_skb_tso_segs(sk, skb, mss); 3201 3202 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH; 3203 TCP_SKB_CB(skb)->when = tcp_time_stamp; 3204 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 3205 if (!err) 3206 tcp_event_new_data_sent(sk, skb); 3207 return err; 3208 } else { 3209 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF)) 3210 tcp_xmit_probe_skb(sk, 1); 3211 return tcp_xmit_probe_skb(sk, 0); 3212 } 3213 } 3214 3215 /* A window probe timeout has occurred. If window is not closed send 3216 * a partial packet else a zero probe. 3217 */ 3218 void tcp_send_probe0(struct sock *sk) 3219 { 3220 struct inet_connection_sock *icsk = inet_csk(sk); 3221 struct tcp_sock *tp = tcp_sk(sk); 3222 int err; 3223 3224 err = tcp_write_wakeup(sk); 3225 3226 if (tp->packets_out || !tcp_send_head(sk)) { 3227 /* Cancel probe timer, if it is not required. */ 3228 icsk->icsk_probes_out = 0; 3229 icsk->icsk_backoff = 0; 3230 return; 3231 } 3232 3233 if (err <= 0) { 3234 if (icsk->icsk_backoff < sysctl_tcp_retries2) 3235 icsk->icsk_backoff++; 3236 icsk->icsk_probes_out++; 3237 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 3238 min(icsk->icsk_rto << icsk->icsk_backoff, TCP_RTO_MAX), 3239 TCP_RTO_MAX); 3240 } else { 3241 /* If packet was not sent due to local congestion, 3242 * do not backoff and do not remember icsk_probes_out. 3243 * Let local senders to fight for local resources. 3244 * 3245 * Use accumulated backoff yet. 3246 */ 3247 if (!icsk->icsk_probes_out) 3248 icsk->icsk_probes_out = 1; 3249 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0, 3250 min(icsk->icsk_rto << icsk->icsk_backoff, 3251 TCP_RESOURCE_PROBE_INTERVAL), 3252 TCP_RTO_MAX); 3253 } 3254 } 3255