1 // SPDX-License-Identifier: GPL-2.0-only 2 /* 3 * INET An implementation of the TCP/IP protocol suite for the LINUX 4 * operating system. INET is implemented using the BSD Socket 5 * interface as the means of communication with the user level. 6 * 7 * Implementation of the Transmission Control Protocol(TCP). 8 * 9 * Authors: Ross Biro 10 * Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG> 11 * Mark Evans, <evansmp@uhura.aston.ac.uk> 12 * Corey Minyard <wf-rch!minyard@relay.EU.net> 13 * Florian La Roche, <flla@stud.uni-sb.de> 14 * Charles Hedrick, <hedrick@klinzhai.rutgers.edu> 15 * Linus Torvalds, <torvalds@cs.helsinki.fi> 16 * Alan Cox, <gw4pts@gw4pts.ampr.org> 17 * Matthew Dillon, <dillon@apollo.west.oic.com> 18 * Arnt Gulbrandsen, <agulbra@nvg.unit.no> 19 * Jorge Cwik, <jorge@laser.satlink.net> 20 */ 21 22 /* 23 * Changes: Pedro Roque : Retransmit queue handled by TCP. 24 * : Fragmentation on mtu decrease 25 * : Segment collapse on retransmit 26 * : AF independence 27 * 28 * Linus Torvalds : send_delayed_ack 29 * David S. Miller : Charge memory using the right skb 30 * during syn/ack processing. 31 * David S. Miller : Output engine completely rewritten. 32 * Andrea Arcangeli: SYNACK carry ts_recent in tsecr. 33 * Cacophonix Gaul : draft-minshall-nagle-01 34 * J Hadi Salim : ECN support 35 * 36 */ 37 38 #define pr_fmt(fmt) "TCP: " fmt 39 40 #include <net/tcp.h> 41 42 #include <linux/compiler.h> 43 #include <linux/gfp.h> 44 #include <linux/module.h> 45 #include <linux/static_key.h> 46 47 #include <trace/events/tcp.h> 48 49 /* Refresh clocks of a TCP socket, 50 * ensuring monotically increasing values. 51 */ 52 void tcp_mstamp_refresh(struct tcp_sock *tp) 53 { 54 u64 val = tcp_clock_ns(); 55 56 tp->tcp_clock_cache = val; 57 tp->tcp_mstamp = div_u64(val, NSEC_PER_USEC); 58 } 59 60 static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, 61 int push_one, gfp_t gfp); 62 63 /* Account for new data that has been sent to the network. */ 64 static void tcp_event_new_data_sent(struct sock *sk, struct sk_buff *skb) 65 { 66 struct inet_connection_sock *icsk = inet_csk(sk); 67 struct tcp_sock *tp = tcp_sk(sk); 68 unsigned int prior_packets = tp->packets_out; 69 70 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(skb)->end_seq); 71 72 __skb_unlink(skb, &sk->sk_write_queue); 73 tcp_rbtree_insert(&sk->tcp_rtx_queue, skb); 74 75 tp->packets_out += tcp_skb_pcount(skb); 76 if (!prior_packets || icsk->icsk_pending == ICSK_TIME_LOSS_PROBE) 77 tcp_rearm_rto(sk); 78 79 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT, 80 tcp_skb_pcount(skb)); 81 } 82 83 /* SND.NXT, if window was not shrunk or the amount of shrunk was less than one 84 * window scaling factor due to loss of precision. 85 * If window has been shrunk, what should we make? It is not clear at all. 86 * Using SND.UNA we will fail to open window, SND.NXT is out of window. :-( 87 * Anything in between SND.UNA...SND.UNA+SND.WND also can be already 88 * invalid. OK, let's make this for now: 89 */ 90 static inline __u32 tcp_acceptable_seq(const struct sock *sk) 91 { 92 const struct tcp_sock *tp = tcp_sk(sk); 93 94 if (!before(tcp_wnd_end(tp), tp->snd_nxt) || 95 (tp->rx_opt.wscale_ok && 96 ((tp->snd_nxt - tcp_wnd_end(tp)) < (1 << tp->rx_opt.rcv_wscale)))) 97 return tp->snd_nxt; 98 else 99 return tcp_wnd_end(tp); 100 } 101 102 /* Calculate mss to advertise in SYN segment. 103 * RFC1122, RFC1063, draft-ietf-tcpimpl-pmtud-01 state that: 104 * 105 * 1. It is independent of path mtu. 106 * 2. Ideally, it is maximal possible segment size i.e. 65535-40. 107 * 3. For IPv4 it is reasonable to calculate it from maximal MTU of 108 * attached devices, because some buggy hosts are confused by 109 * large MSS. 110 * 4. We do not make 3, we advertise MSS, calculated from first 111 * hop device mtu, but allow to raise it to ip_rt_min_advmss. 112 * This may be overridden via information stored in routing table. 113 * 5. Value 65535 for MSS is valid in IPv6 and means "as large as possible, 114 * probably even Jumbo". 115 */ 116 static __u16 tcp_advertise_mss(struct sock *sk) 117 { 118 struct tcp_sock *tp = tcp_sk(sk); 119 const struct dst_entry *dst = __sk_dst_get(sk); 120 int mss = tp->advmss; 121 122 if (dst) { 123 unsigned int metric = dst_metric_advmss(dst); 124 125 if (metric < mss) { 126 mss = metric; 127 tp->advmss = mss; 128 } 129 } 130 131 return (__u16)mss; 132 } 133 134 /* RFC2861. Reset CWND after idle period longer RTO to "restart window". 135 * This is the first part of cwnd validation mechanism. 136 */ 137 void tcp_cwnd_restart(struct sock *sk, s32 delta) 138 { 139 struct tcp_sock *tp = tcp_sk(sk); 140 u32 restart_cwnd = tcp_init_cwnd(tp, __sk_dst_get(sk)); 141 u32 cwnd = tp->snd_cwnd; 142 143 tcp_ca_event(sk, CA_EVENT_CWND_RESTART); 144 145 tp->snd_ssthresh = tcp_current_ssthresh(sk); 146 restart_cwnd = min(restart_cwnd, cwnd); 147 148 while ((delta -= inet_csk(sk)->icsk_rto) > 0 && cwnd > restart_cwnd) 149 cwnd >>= 1; 150 tp->snd_cwnd = max(cwnd, restart_cwnd); 151 tp->snd_cwnd_stamp = tcp_jiffies32; 152 tp->snd_cwnd_used = 0; 153 } 154 155 /* Congestion state accounting after a packet has been sent. */ 156 static void tcp_event_data_sent(struct tcp_sock *tp, 157 struct sock *sk) 158 { 159 struct inet_connection_sock *icsk = inet_csk(sk); 160 const u32 now = tcp_jiffies32; 161 162 if (tcp_packets_in_flight(tp) == 0) 163 tcp_ca_event(sk, CA_EVENT_TX_START); 164 165 /* If this is the first data packet sent in response to the 166 * previous received data, 167 * and it is a reply for ato after last received packet, 168 * increase pingpong count. 169 */ 170 if (before(tp->lsndtime, icsk->icsk_ack.lrcvtime) && 171 (u32)(now - icsk->icsk_ack.lrcvtime) < icsk->icsk_ack.ato) 172 inet_csk_inc_pingpong_cnt(sk); 173 174 tp->lsndtime = now; 175 } 176 177 /* Account for an ACK we sent. */ 178 static inline void tcp_event_ack_sent(struct sock *sk, unsigned int pkts, 179 u32 rcv_nxt) 180 { 181 struct tcp_sock *tp = tcp_sk(sk); 182 183 if (unlikely(tp->compressed_ack > TCP_FASTRETRANS_THRESH)) { 184 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPACKCOMPRESSED, 185 tp->compressed_ack - TCP_FASTRETRANS_THRESH); 186 tp->compressed_ack = TCP_FASTRETRANS_THRESH; 187 if (hrtimer_try_to_cancel(&tp->compressed_ack_timer) == 1) 188 __sock_put(sk); 189 } 190 191 if (unlikely(rcv_nxt != tp->rcv_nxt)) 192 return; /* Special ACK sent by DCTCP to reflect ECN */ 193 tcp_dec_quickack_mode(sk, pkts); 194 inet_csk_clear_xmit_timer(sk, ICSK_TIME_DACK); 195 } 196 197 /* Determine a window scaling and initial window to offer. 198 * Based on the assumption that the given amount of space 199 * will be offered. Store the results in the tp structure. 200 * NOTE: for smooth operation initial space offering should 201 * be a multiple of mss if possible. We assume here that mss >= 1. 202 * This MUST be enforced by all callers. 203 */ 204 void tcp_select_initial_window(const struct sock *sk, int __space, __u32 mss, 205 __u32 *rcv_wnd, __u32 *window_clamp, 206 int wscale_ok, __u8 *rcv_wscale, 207 __u32 init_rcv_wnd) 208 { 209 unsigned int space = (__space < 0 ? 0 : __space); 210 211 /* If no clamp set the clamp to the max possible scaled window */ 212 if (*window_clamp == 0) 213 (*window_clamp) = (U16_MAX << TCP_MAX_WSCALE); 214 space = min(*window_clamp, space); 215 216 /* Quantize space offering to a multiple of mss if possible. */ 217 if (space > mss) 218 space = rounddown(space, mss); 219 220 /* NOTE: offering an initial window larger than 32767 221 * will break some buggy TCP stacks. If the admin tells us 222 * it is likely we could be speaking with such a buggy stack 223 * we will truncate our initial window offering to 32K-1 224 * unless the remote has sent us a window scaling option, 225 * which we interpret as a sign the remote TCP is not 226 * misinterpreting the window field as a signed quantity. 227 */ 228 if (sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows) 229 (*rcv_wnd) = min(space, MAX_TCP_WINDOW); 230 else 231 (*rcv_wnd) = min_t(u32, space, U16_MAX); 232 233 if (init_rcv_wnd) 234 *rcv_wnd = min(*rcv_wnd, init_rcv_wnd * mss); 235 236 *rcv_wscale = 0; 237 if (wscale_ok) { 238 /* Set window scaling on max possible window */ 239 space = max_t(u32, space, sock_net(sk)->ipv4.sysctl_tcp_rmem[2]); 240 space = max_t(u32, space, sysctl_rmem_max); 241 space = min_t(u32, space, *window_clamp); 242 *rcv_wscale = clamp_t(int, ilog2(space) - 15, 243 0, TCP_MAX_WSCALE); 244 } 245 /* Set the clamp no higher than max representable value */ 246 (*window_clamp) = min_t(__u32, U16_MAX << (*rcv_wscale), *window_clamp); 247 } 248 EXPORT_SYMBOL(tcp_select_initial_window); 249 250 /* Chose a new window to advertise, update state in tcp_sock for the 251 * socket, and return result with RFC1323 scaling applied. The return 252 * value can be stuffed directly into th->window for an outgoing 253 * frame. 254 */ 255 static u16 tcp_select_window(struct sock *sk) 256 { 257 struct tcp_sock *tp = tcp_sk(sk); 258 u32 old_win = tp->rcv_wnd; 259 u32 cur_win = tcp_receive_window(tp); 260 u32 new_win = __tcp_select_window(sk); 261 262 /* Never shrink the offered window */ 263 if (new_win < cur_win) { 264 /* Danger Will Robinson! 265 * Don't update rcv_wup/rcv_wnd here or else 266 * we will not be able to advertise a zero 267 * window in time. --DaveM 268 * 269 * Relax Will Robinson. 270 */ 271 if (new_win == 0) 272 NET_INC_STATS(sock_net(sk), 273 LINUX_MIB_TCPWANTZEROWINDOWADV); 274 new_win = ALIGN(cur_win, 1 << tp->rx_opt.rcv_wscale); 275 } 276 tp->rcv_wnd = new_win; 277 tp->rcv_wup = tp->rcv_nxt; 278 279 /* Make sure we do not exceed the maximum possible 280 * scaled window. 281 */ 282 if (!tp->rx_opt.rcv_wscale && 283 sock_net(sk)->ipv4.sysctl_tcp_workaround_signed_windows) 284 new_win = min(new_win, MAX_TCP_WINDOW); 285 else 286 new_win = min(new_win, (65535U << tp->rx_opt.rcv_wscale)); 287 288 /* RFC1323 scaling applied */ 289 new_win >>= tp->rx_opt.rcv_wscale; 290 291 /* If we advertise zero window, disable fast path. */ 292 if (new_win == 0) { 293 tp->pred_flags = 0; 294 if (old_win) 295 NET_INC_STATS(sock_net(sk), 296 LINUX_MIB_TCPTOZEROWINDOWADV); 297 } else if (old_win == 0) { 298 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPFROMZEROWINDOWADV); 299 } 300 301 return new_win; 302 } 303 304 /* Packet ECN state for a SYN-ACK */ 305 static void tcp_ecn_send_synack(struct sock *sk, struct sk_buff *skb) 306 { 307 const struct tcp_sock *tp = tcp_sk(sk); 308 309 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_CWR; 310 if (!(tp->ecn_flags & TCP_ECN_OK)) 311 TCP_SKB_CB(skb)->tcp_flags &= ~TCPHDR_ECE; 312 else if (tcp_ca_needs_ecn(sk) || 313 tcp_bpf_ca_needs_ecn(sk)) 314 INET_ECN_xmit(sk); 315 } 316 317 /* Packet ECN state for a SYN. */ 318 static void tcp_ecn_send_syn(struct sock *sk, struct sk_buff *skb) 319 { 320 struct tcp_sock *tp = tcp_sk(sk); 321 bool bpf_needs_ecn = tcp_bpf_ca_needs_ecn(sk); 322 bool use_ecn = sock_net(sk)->ipv4.sysctl_tcp_ecn == 1 || 323 tcp_ca_needs_ecn(sk) || bpf_needs_ecn; 324 325 if (!use_ecn) { 326 const struct dst_entry *dst = __sk_dst_get(sk); 327 328 if (dst && dst_feature(dst, RTAX_FEATURE_ECN)) 329 use_ecn = true; 330 } 331 332 tp->ecn_flags = 0; 333 334 if (use_ecn) { 335 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ECE | TCPHDR_CWR; 336 tp->ecn_flags = TCP_ECN_OK; 337 if (tcp_ca_needs_ecn(sk) || bpf_needs_ecn) 338 INET_ECN_xmit(sk); 339 } 340 } 341 342 static void tcp_ecn_clear_syn(struct sock *sk, struct sk_buff *skb) 343 { 344 if (sock_net(sk)->ipv4.sysctl_tcp_ecn_fallback) 345 /* tp->ecn_flags are cleared at a later point in time when 346 * SYN ACK is ultimatively being received. 347 */ 348 TCP_SKB_CB(skb)->tcp_flags &= ~(TCPHDR_ECE | TCPHDR_CWR); 349 } 350 351 static void 352 tcp_ecn_make_synack(const struct request_sock *req, struct tcphdr *th) 353 { 354 if (inet_rsk(req)->ecn_ok) 355 th->ece = 1; 356 } 357 358 /* Set up ECN state for a packet on a ESTABLISHED socket that is about to 359 * be sent. 360 */ 361 static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb, 362 struct tcphdr *th, int tcp_header_len) 363 { 364 struct tcp_sock *tp = tcp_sk(sk); 365 366 if (tp->ecn_flags & TCP_ECN_OK) { 367 /* Not-retransmitted data segment: set ECT and inject CWR. */ 368 if (skb->len != tcp_header_len && 369 !before(TCP_SKB_CB(skb)->seq, tp->snd_nxt)) { 370 INET_ECN_xmit(sk); 371 if (tp->ecn_flags & TCP_ECN_QUEUE_CWR) { 372 tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR; 373 th->cwr = 1; 374 skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; 375 } 376 } else if (!tcp_ca_needs_ecn(sk)) { 377 /* ACK or retransmitted segment: clear ECT|CE */ 378 INET_ECN_dontxmit(sk); 379 } 380 if (tp->ecn_flags & TCP_ECN_DEMAND_CWR) 381 th->ece = 1; 382 } 383 } 384 385 /* Constructs common control bits of non-data skb. If SYN/FIN is present, 386 * auto increment end seqno. 387 */ 388 static void tcp_init_nondata_skb(struct sk_buff *skb, u32 seq, u8 flags) 389 { 390 skb->ip_summed = CHECKSUM_PARTIAL; 391 392 TCP_SKB_CB(skb)->tcp_flags = flags; 393 TCP_SKB_CB(skb)->sacked = 0; 394 395 tcp_skb_pcount_set(skb, 1); 396 397 TCP_SKB_CB(skb)->seq = seq; 398 if (flags & (TCPHDR_SYN | TCPHDR_FIN)) 399 seq++; 400 TCP_SKB_CB(skb)->end_seq = seq; 401 } 402 403 static inline bool tcp_urg_mode(const struct tcp_sock *tp) 404 { 405 return tp->snd_una != tp->snd_up; 406 } 407 408 #define OPTION_SACK_ADVERTISE (1 << 0) 409 #define OPTION_TS (1 << 1) 410 #define OPTION_MD5 (1 << 2) 411 #define OPTION_WSCALE (1 << 3) 412 #define OPTION_FAST_OPEN_COOKIE (1 << 8) 413 #define OPTION_SMC (1 << 9) 414 415 static void smc_options_write(__be32 *ptr, u16 *options) 416 { 417 #if IS_ENABLED(CONFIG_SMC) 418 if (static_branch_unlikely(&tcp_have_smc)) { 419 if (unlikely(OPTION_SMC & *options)) { 420 *ptr++ = htonl((TCPOPT_NOP << 24) | 421 (TCPOPT_NOP << 16) | 422 (TCPOPT_EXP << 8) | 423 (TCPOLEN_EXP_SMC_BASE)); 424 *ptr++ = htonl(TCPOPT_SMC_MAGIC); 425 } 426 } 427 #endif 428 } 429 430 struct tcp_out_options { 431 u16 options; /* bit field of OPTION_* */ 432 u16 mss; /* 0 to disable */ 433 u8 ws; /* window scale, 0 to disable */ 434 u8 num_sack_blocks; /* number of SACK blocks to include */ 435 u8 hash_size; /* bytes in hash_location */ 436 __u8 *hash_location; /* temporary pointer, overloaded */ 437 __u32 tsval, tsecr; /* need to include OPTION_TS */ 438 struct tcp_fastopen_cookie *fastopen_cookie; /* Fast open cookie */ 439 }; 440 441 /* Write previously computed TCP options to the packet. 442 * 443 * Beware: Something in the Internet is very sensitive to the ordering of 444 * TCP options, we learned this through the hard way, so be careful here. 445 * Luckily we can at least blame others for their non-compliance but from 446 * inter-operability perspective it seems that we're somewhat stuck with 447 * the ordering which we have been using if we want to keep working with 448 * those broken things (not that it currently hurts anybody as there isn't 449 * particular reason why the ordering would need to be changed). 450 * 451 * At least SACK_PERM as the first option is known to lead to a disaster 452 * (but it may well be that other scenarios fail similarly). 453 */ 454 static void tcp_options_write(__be32 *ptr, struct tcp_sock *tp, 455 struct tcp_out_options *opts) 456 { 457 u16 options = opts->options; /* mungable copy */ 458 459 if (unlikely(OPTION_MD5 & options)) { 460 *ptr++ = htonl((TCPOPT_NOP << 24) | (TCPOPT_NOP << 16) | 461 (TCPOPT_MD5SIG << 8) | TCPOLEN_MD5SIG); 462 /* overload cookie hash location */ 463 opts->hash_location = (__u8 *)ptr; 464 ptr += 4; 465 } 466 467 if (unlikely(opts->mss)) { 468 *ptr++ = htonl((TCPOPT_MSS << 24) | 469 (TCPOLEN_MSS << 16) | 470 opts->mss); 471 } 472 473 if (likely(OPTION_TS & options)) { 474 if (unlikely(OPTION_SACK_ADVERTISE & options)) { 475 *ptr++ = htonl((TCPOPT_SACK_PERM << 24) | 476 (TCPOLEN_SACK_PERM << 16) | 477 (TCPOPT_TIMESTAMP << 8) | 478 TCPOLEN_TIMESTAMP); 479 options &= ~OPTION_SACK_ADVERTISE; 480 } else { 481 *ptr++ = htonl((TCPOPT_NOP << 24) | 482 (TCPOPT_NOP << 16) | 483 (TCPOPT_TIMESTAMP << 8) | 484 TCPOLEN_TIMESTAMP); 485 } 486 *ptr++ = htonl(opts->tsval); 487 *ptr++ = htonl(opts->tsecr); 488 } 489 490 if (unlikely(OPTION_SACK_ADVERTISE & options)) { 491 *ptr++ = htonl((TCPOPT_NOP << 24) | 492 (TCPOPT_NOP << 16) | 493 (TCPOPT_SACK_PERM << 8) | 494 TCPOLEN_SACK_PERM); 495 } 496 497 if (unlikely(OPTION_WSCALE & options)) { 498 *ptr++ = htonl((TCPOPT_NOP << 24) | 499 (TCPOPT_WINDOW << 16) | 500 (TCPOLEN_WINDOW << 8) | 501 opts->ws); 502 } 503 504 if (unlikely(opts->num_sack_blocks)) { 505 struct tcp_sack_block *sp = tp->rx_opt.dsack ? 506 tp->duplicate_sack : tp->selective_acks; 507 int this_sack; 508 509 *ptr++ = htonl((TCPOPT_NOP << 24) | 510 (TCPOPT_NOP << 16) | 511 (TCPOPT_SACK << 8) | 512 (TCPOLEN_SACK_BASE + (opts->num_sack_blocks * 513 TCPOLEN_SACK_PERBLOCK))); 514 515 for (this_sack = 0; this_sack < opts->num_sack_blocks; 516 ++this_sack) { 517 *ptr++ = htonl(sp[this_sack].start_seq); 518 *ptr++ = htonl(sp[this_sack].end_seq); 519 } 520 521 tp->rx_opt.dsack = 0; 522 } 523 524 if (unlikely(OPTION_FAST_OPEN_COOKIE & options)) { 525 struct tcp_fastopen_cookie *foc = opts->fastopen_cookie; 526 u8 *p = (u8 *)ptr; 527 u32 len; /* Fast Open option length */ 528 529 if (foc->exp) { 530 len = TCPOLEN_EXP_FASTOPEN_BASE + foc->len; 531 *ptr = htonl((TCPOPT_EXP << 24) | (len << 16) | 532 TCPOPT_FASTOPEN_MAGIC); 533 p += TCPOLEN_EXP_FASTOPEN_BASE; 534 } else { 535 len = TCPOLEN_FASTOPEN_BASE + foc->len; 536 *p++ = TCPOPT_FASTOPEN; 537 *p++ = len; 538 } 539 540 memcpy(p, foc->val, foc->len); 541 if ((len & 3) == 2) { 542 p[foc->len] = TCPOPT_NOP; 543 p[foc->len + 1] = TCPOPT_NOP; 544 } 545 ptr += (len + 3) >> 2; 546 } 547 548 smc_options_write(ptr, &options); 549 } 550 551 static void smc_set_option(const struct tcp_sock *tp, 552 struct tcp_out_options *opts, 553 unsigned int *remaining) 554 { 555 #if IS_ENABLED(CONFIG_SMC) 556 if (static_branch_unlikely(&tcp_have_smc)) { 557 if (tp->syn_smc) { 558 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) { 559 opts->options |= OPTION_SMC; 560 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED; 561 } 562 } 563 } 564 #endif 565 } 566 567 static void smc_set_option_cond(const struct tcp_sock *tp, 568 const struct inet_request_sock *ireq, 569 struct tcp_out_options *opts, 570 unsigned int *remaining) 571 { 572 #if IS_ENABLED(CONFIG_SMC) 573 if (static_branch_unlikely(&tcp_have_smc)) { 574 if (tp->syn_smc && ireq->smc_ok) { 575 if (*remaining >= TCPOLEN_EXP_SMC_BASE_ALIGNED) { 576 opts->options |= OPTION_SMC; 577 *remaining -= TCPOLEN_EXP_SMC_BASE_ALIGNED; 578 } 579 } 580 } 581 #endif 582 } 583 584 /* Compute TCP options for SYN packets. This is not the final 585 * network wire format yet. 586 */ 587 static unsigned int tcp_syn_options(struct sock *sk, struct sk_buff *skb, 588 struct tcp_out_options *opts, 589 struct tcp_md5sig_key **md5) 590 { 591 struct tcp_sock *tp = tcp_sk(sk); 592 unsigned int remaining = MAX_TCP_OPTION_SPACE; 593 struct tcp_fastopen_request *fastopen = tp->fastopen_req; 594 595 *md5 = NULL; 596 #ifdef CONFIG_TCP_MD5SIG 597 if (static_branch_unlikely(&tcp_md5_needed) && 598 rcu_access_pointer(tp->md5sig_info)) { 599 *md5 = tp->af_specific->md5_lookup(sk, sk); 600 if (*md5) { 601 opts->options |= OPTION_MD5; 602 remaining -= TCPOLEN_MD5SIG_ALIGNED; 603 } 604 } 605 #endif 606 607 /* We always get an MSS option. The option bytes which will be seen in 608 * normal data packets should timestamps be used, must be in the MSS 609 * advertised. But we subtract them from tp->mss_cache so that 610 * calculations in tcp_sendmsg are simpler etc. So account for this 611 * fact here if necessary. If we don't do this correctly, as a 612 * receiver we won't recognize data packets as being full sized when we 613 * should, and thus we won't abide by the delayed ACK rules correctly. 614 * SACKs don't matter, we never delay an ACK when we have any of those 615 * going out. */ 616 opts->mss = tcp_advertise_mss(sk); 617 remaining -= TCPOLEN_MSS_ALIGNED; 618 619 if (likely(sock_net(sk)->ipv4.sysctl_tcp_timestamps && !*md5)) { 620 opts->options |= OPTION_TS; 621 opts->tsval = tcp_skb_timestamp(skb) + tp->tsoffset; 622 opts->tsecr = tp->rx_opt.ts_recent; 623 remaining -= TCPOLEN_TSTAMP_ALIGNED; 624 } 625 if (likely(sock_net(sk)->ipv4.sysctl_tcp_window_scaling)) { 626 opts->ws = tp->rx_opt.rcv_wscale; 627 opts->options |= OPTION_WSCALE; 628 remaining -= TCPOLEN_WSCALE_ALIGNED; 629 } 630 if (likely(sock_net(sk)->ipv4.sysctl_tcp_sack)) { 631 opts->options |= OPTION_SACK_ADVERTISE; 632 if (unlikely(!(OPTION_TS & opts->options))) 633 remaining -= TCPOLEN_SACKPERM_ALIGNED; 634 } 635 636 if (fastopen && fastopen->cookie.len >= 0) { 637 u32 need = fastopen->cookie.len; 638 639 need += fastopen->cookie.exp ? TCPOLEN_EXP_FASTOPEN_BASE : 640 TCPOLEN_FASTOPEN_BASE; 641 need = (need + 3) & ~3U; /* Align to 32 bits */ 642 if (remaining >= need) { 643 opts->options |= OPTION_FAST_OPEN_COOKIE; 644 opts->fastopen_cookie = &fastopen->cookie; 645 remaining -= need; 646 tp->syn_fastopen = 1; 647 tp->syn_fastopen_exp = fastopen->cookie.exp ? 1 : 0; 648 } 649 } 650 651 smc_set_option(tp, opts, &remaining); 652 653 return MAX_TCP_OPTION_SPACE - remaining; 654 } 655 656 /* Set up TCP options for SYN-ACKs. */ 657 static unsigned int tcp_synack_options(const struct sock *sk, 658 struct request_sock *req, 659 unsigned int mss, struct sk_buff *skb, 660 struct tcp_out_options *opts, 661 const struct tcp_md5sig_key *md5, 662 struct tcp_fastopen_cookie *foc) 663 { 664 struct inet_request_sock *ireq = inet_rsk(req); 665 unsigned int remaining = MAX_TCP_OPTION_SPACE; 666 667 #ifdef CONFIG_TCP_MD5SIG 668 if (md5) { 669 opts->options |= OPTION_MD5; 670 remaining -= TCPOLEN_MD5SIG_ALIGNED; 671 672 /* We can't fit any SACK blocks in a packet with MD5 + TS 673 * options. There was discussion about disabling SACK 674 * rather than TS in order to fit in better with old, 675 * buggy kernels, but that was deemed to be unnecessary. 676 */ 677 ireq->tstamp_ok &= !ireq->sack_ok; 678 } 679 #endif 680 681 /* We always send an MSS option. */ 682 opts->mss = mss; 683 remaining -= TCPOLEN_MSS_ALIGNED; 684 685 if (likely(ireq->wscale_ok)) { 686 opts->ws = ireq->rcv_wscale; 687 opts->options |= OPTION_WSCALE; 688 remaining -= TCPOLEN_WSCALE_ALIGNED; 689 } 690 if (likely(ireq->tstamp_ok)) { 691 opts->options |= OPTION_TS; 692 opts->tsval = tcp_skb_timestamp(skb) + tcp_rsk(req)->ts_off; 693 opts->tsecr = req->ts_recent; 694 remaining -= TCPOLEN_TSTAMP_ALIGNED; 695 } 696 if (likely(ireq->sack_ok)) { 697 opts->options |= OPTION_SACK_ADVERTISE; 698 if (unlikely(!ireq->tstamp_ok)) 699 remaining -= TCPOLEN_SACKPERM_ALIGNED; 700 } 701 if (foc != NULL && foc->len >= 0) { 702 u32 need = foc->len; 703 704 need += foc->exp ? TCPOLEN_EXP_FASTOPEN_BASE : 705 TCPOLEN_FASTOPEN_BASE; 706 need = (need + 3) & ~3U; /* Align to 32 bits */ 707 if (remaining >= need) { 708 opts->options |= OPTION_FAST_OPEN_COOKIE; 709 opts->fastopen_cookie = foc; 710 remaining -= need; 711 } 712 } 713 714 smc_set_option_cond(tcp_sk(sk), ireq, opts, &remaining); 715 716 return MAX_TCP_OPTION_SPACE - remaining; 717 } 718 719 /* Compute TCP options for ESTABLISHED sockets. This is not the 720 * final wire format yet. 721 */ 722 static unsigned int tcp_established_options(struct sock *sk, struct sk_buff *skb, 723 struct tcp_out_options *opts, 724 struct tcp_md5sig_key **md5) 725 { 726 struct tcp_sock *tp = tcp_sk(sk); 727 unsigned int size = 0; 728 unsigned int eff_sacks; 729 730 opts->options = 0; 731 732 *md5 = NULL; 733 #ifdef CONFIG_TCP_MD5SIG 734 if (static_branch_unlikely(&tcp_md5_needed) && 735 rcu_access_pointer(tp->md5sig_info)) { 736 *md5 = tp->af_specific->md5_lookup(sk, sk); 737 if (*md5) { 738 opts->options |= OPTION_MD5; 739 size += TCPOLEN_MD5SIG_ALIGNED; 740 } 741 } 742 #endif 743 744 if (likely(tp->rx_opt.tstamp_ok)) { 745 opts->options |= OPTION_TS; 746 opts->tsval = skb ? tcp_skb_timestamp(skb) + tp->tsoffset : 0; 747 opts->tsecr = tp->rx_opt.ts_recent; 748 size += TCPOLEN_TSTAMP_ALIGNED; 749 } 750 751 eff_sacks = tp->rx_opt.num_sacks + tp->rx_opt.dsack; 752 if (unlikely(eff_sacks)) { 753 const unsigned int remaining = MAX_TCP_OPTION_SPACE - size; 754 opts->num_sack_blocks = 755 min_t(unsigned int, eff_sacks, 756 (remaining - TCPOLEN_SACK_BASE_ALIGNED) / 757 TCPOLEN_SACK_PERBLOCK); 758 size += TCPOLEN_SACK_BASE_ALIGNED + 759 opts->num_sack_blocks * TCPOLEN_SACK_PERBLOCK; 760 } 761 762 return size; 763 } 764 765 766 /* TCP SMALL QUEUES (TSQ) 767 * 768 * TSQ goal is to keep small amount of skbs per tcp flow in tx queues (qdisc+dev) 769 * to reduce RTT and bufferbloat. 770 * We do this using a special skb destructor (tcp_wfree). 771 * 772 * Its important tcp_wfree() can be replaced by sock_wfree() in the event skb 773 * needs to be reallocated in a driver. 774 * The invariant being skb->truesize subtracted from sk->sk_wmem_alloc 775 * 776 * Since transmit from skb destructor is forbidden, we use a tasklet 777 * to process all sockets that eventually need to send more skbs. 778 * We use one tasklet per cpu, with its own queue of sockets. 779 */ 780 struct tsq_tasklet { 781 struct tasklet_struct tasklet; 782 struct list_head head; /* queue of tcp sockets */ 783 }; 784 static DEFINE_PER_CPU(struct tsq_tasklet, tsq_tasklet); 785 786 static void tcp_tsq_write(struct sock *sk) 787 { 788 if ((1 << sk->sk_state) & 789 (TCPF_ESTABLISHED | TCPF_FIN_WAIT1 | TCPF_CLOSING | 790 TCPF_CLOSE_WAIT | TCPF_LAST_ACK)) { 791 struct tcp_sock *tp = tcp_sk(sk); 792 793 if (tp->lost_out > tp->retrans_out && 794 tp->snd_cwnd > tcp_packets_in_flight(tp)) { 795 tcp_mstamp_refresh(tp); 796 tcp_xmit_retransmit_queue(sk); 797 } 798 799 tcp_write_xmit(sk, tcp_current_mss(sk), tp->nonagle, 800 0, GFP_ATOMIC); 801 } 802 } 803 804 static void tcp_tsq_handler(struct sock *sk) 805 { 806 bh_lock_sock(sk); 807 if (!sock_owned_by_user(sk)) 808 tcp_tsq_write(sk); 809 else if (!test_and_set_bit(TCP_TSQ_DEFERRED, &sk->sk_tsq_flags)) 810 sock_hold(sk); 811 bh_unlock_sock(sk); 812 } 813 /* 814 * One tasklet per cpu tries to send more skbs. 815 * We run in tasklet context but need to disable irqs when 816 * transferring tsq->head because tcp_wfree() might 817 * interrupt us (non NAPI drivers) 818 */ 819 static void tcp_tasklet_func(unsigned long data) 820 { 821 struct tsq_tasklet *tsq = (struct tsq_tasklet *)data; 822 LIST_HEAD(list); 823 unsigned long flags; 824 struct list_head *q, *n; 825 struct tcp_sock *tp; 826 struct sock *sk; 827 828 local_irq_save(flags); 829 list_splice_init(&tsq->head, &list); 830 local_irq_restore(flags); 831 832 list_for_each_safe(q, n, &list) { 833 tp = list_entry(q, struct tcp_sock, tsq_node); 834 list_del(&tp->tsq_node); 835 836 sk = (struct sock *)tp; 837 smp_mb__before_atomic(); 838 clear_bit(TSQ_QUEUED, &sk->sk_tsq_flags); 839 840 tcp_tsq_handler(sk); 841 sk_free(sk); 842 } 843 } 844 845 #define TCP_DEFERRED_ALL (TCPF_TSQ_DEFERRED | \ 846 TCPF_WRITE_TIMER_DEFERRED | \ 847 TCPF_DELACK_TIMER_DEFERRED | \ 848 TCPF_MTU_REDUCED_DEFERRED) 849 /** 850 * tcp_release_cb - tcp release_sock() callback 851 * @sk: socket 852 * 853 * called from release_sock() to perform protocol dependent 854 * actions before socket release. 855 */ 856 void tcp_release_cb(struct sock *sk) 857 { 858 unsigned long flags, nflags; 859 860 /* perform an atomic operation only if at least one flag is set */ 861 do { 862 flags = sk->sk_tsq_flags; 863 if (!(flags & TCP_DEFERRED_ALL)) 864 return; 865 nflags = flags & ~TCP_DEFERRED_ALL; 866 } while (cmpxchg(&sk->sk_tsq_flags, flags, nflags) != flags); 867 868 if (flags & TCPF_TSQ_DEFERRED) { 869 tcp_tsq_write(sk); 870 __sock_put(sk); 871 } 872 /* Here begins the tricky part : 873 * We are called from release_sock() with : 874 * 1) BH disabled 875 * 2) sk_lock.slock spinlock held 876 * 3) socket owned by us (sk->sk_lock.owned == 1) 877 * 878 * But following code is meant to be called from BH handlers, 879 * so we should keep BH disabled, but early release socket ownership 880 */ 881 sock_release_ownership(sk); 882 883 if (flags & TCPF_WRITE_TIMER_DEFERRED) { 884 tcp_write_timer_handler(sk); 885 __sock_put(sk); 886 } 887 if (flags & TCPF_DELACK_TIMER_DEFERRED) { 888 tcp_delack_timer_handler(sk); 889 __sock_put(sk); 890 } 891 if (flags & TCPF_MTU_REDUCED_DEFERRED) { 892 inet_csk(sk)->icsk_af_ops->mtu_reduced(sk); 893 __sock_put(sk); 894 } 895 } 896 EXPORT_SYMBOL(tcp_release_cb); 897 898 void __init tcp_tasklet_init(void) 899 { 900 int i; 901 902 for_each_possible_cpu(i) { 903 struct tsq_tasklet *tsq = &per_cpu(tsq_tasklet, i); 904 905 INIT_LIST_HEAD(&tsq->head); 906 tasklet_init(&tsq->tasklet, 907 tcp_tasklet_func, 908 (unsigned long)tsq); 909 } 910 } 911 912 /* 913 * Write buffer destructor automatically called from kfree_skb. 914 * We can't xmit new skbs from this context, as we might already 915 * hold qdisc lock. 916 */ 917 void tcp_wfree(struct sk_buff *skb) 918 { 919 struct sock *sk = skb->sk; 920 struct tcp_sock *tp = tcp_sk(sk); 921 unsigned long flags, nval, oval; 922 923 /* Keep one reference on sk_wmem_alloc. 924 * Will be released by sk_free() from here or tcp_tasklet_func() 925 */ 926 WARN_ON(refcount_sub_and_test(skb->truesize - 1, &sk->sk_wmem_alloc)); 927 928 /* If this softirq is serviced by ksoftirqd, we are likely under stress. 929 * Wait until our queues (qdisc + devices) are drained. 930 * This gives : 931 * - less callbacks to tcp_write_xmit(), reducing stress (batches) 932 * - chance for incoming ACK (processed by another cpu maybe) 933 * to migrate this flow (skb->ooo_okay will be eventually set) 934 */ 935 if (refcount_read(&sk->sk_wmem_alloc) >= SKB_TRUESIZE(1) && this_cpu_ksoftirqd() == current) 936 goto out; 937 938 for (oval = READ_ONCE(sk->sk_tsq_flags);; oval = nval) { 939 struct tsq_tasklet *tsq; 940 bool empty; 941 942 if (!(oval & TSQF_THROTTLED) || (oval & TSQF_QUEUED)) 943 goto out; 944 945 nval = (oval & ~TSQF_THROTTLED) | TSQF_QUEUED; 946 nval = cmpxchg(&sk->sk_tsq_flags, oval, nval); 947 if (nval != oval) 948 continue; 949 950 /* queue this socket to tasklet queue */ 951 local_irq_save(flags); 952 tsq = this_cpu_ptr(&tsq_tasklet); 953 empty = list_empty(&tsq->head); 954 list_add(&tp->tsq_node, &tsq->head); 955 if (empty) 956 tasklet_schedule(&tsq->tasklet); 957 local_irq_restore(flags); 958 return; 959 } 960 out: 961 sk_free(sk); 962 } 963 964 /* Note: Called under soft irq. 965 * We can call TCP stack right away, unless socket is owned by user. 966 */ 967 enum hrtimer_restart tcp_pace_kick(struct hrtimer *timer) 968 { 969 struct tcp_sock *tp = container_of(timer, struct tcp_sock, pacing_timer); 970 struct sock *sk = (struct sock *)tp; 971 972 tcp_tsq_handler(sk); 973 sock_put(sk); 974 975 return HRTIMER_NORESTART; 976 } 977 978 static void tcp_update_skb_after_send(struct sock *sk, struct sk_buff *skb, 979 u64 prior_wstamp) 980 { 981 struct tcp_sock *tp = tcp_sk(sk); 982 983 if (sk->sk_pacing_status != SK_PACING_NONE) { 984 unsigned long rate = sk->sk_pacing_rate; 985 986 /* Original sch_fq does not pace first 10 MSS 987 * Note that tp->data_segs_out overflows after 2^32 packets, 988 * this is a minor annoyance. 989 */ 990 if (rate != ~0UL && rate && tp->data_segs_out >= 10) { 991 u64 len_ns = div64_ul((u64)skb->len * NSEC_PER_SEC, rate); 992 u64 credit = tp->tcp_wstamp_ns - prior_wstamp; 993 994 /* take into account OS jitter */ 995 len_ns -= min_t(u64, len_ns / 2, credit); 996 tp->tcp_wstamp_ns += len_ns; 997 } 998 } 999 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue); 1000 } 1001 1002 /* This routine actually transmits TCP packets queued in by 1003 * tcp_do_sendmsg(). This is used by both the initial 1004 * transmission and possible later retransmissions. 1005 * All SKB's seen here are completely headerless. It is our 1006 * job to build the TCP header, and pass the packet down to 1007 * IP so it can do the same plus pass the packet off to the 1008 * device. 1009 * 1010 * We are working here with either a clone of the original 1011 * SKB, or a fresh unique copy made by the retransmit engine. 1012 */ 1013 static int __tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, 1014 int clone_it, gfp_t gfp_mask, u32 rcv_nxt) 1015 { 1016 const struct inet_connection_sock *icsk = inet_csk(sk); 1017 struct inet_sock *inet; 1018 struct tcp_sock *tp; 1019 struct tcp_skb_cb *tcb; 1020 struct tcp_out_options opts; 1021 unsigned int tcp_options_size, tcp_header_size; 1022 struct sk_buff *oskb = NULL; 1023 struct tcp_md5sig_key *md5; 1024 struct tcphdr *th; 1025 u64 prior_wstamp; 1026 int err; 1027 1028 BUG_ON(!skb || !tcp_skb_pcount(skb)); 1029 tp = tcp_sk(sk); 1030 prior_wstamp = tp->tcp_wstamp_ns; 1031 tp->tcp_wstamp_ns = max(tp->tcp_wstamp_ns, tp->tcp_clock_cache); 1032 skb->skb_mstamp_ns = tp->tcp_wstamp_ns; 1033 if (clone_it) { 1034 TCP_SKB_CB(skb)->tx.in_flight = TCP_SKB_CB(skb)->end_seq 1035 - tp->snd_una; 1036 oskb = skb; 1037 1038 tcp_skb_tsorted_save(oskb) { 1039 if (unlikely(skb_cloned(oskb))) 1040 skb = pskb_copy(oskb, gfp_mask); 1041 else 1042 skb = skb_clone(oskb, gfp_mask); 1043 } tcp_skb_tsorted_restore(oskb); 1044 1045 if (unlikely(!skb)) 1046 return -ENOBUFS; 1047 } 1048 1049 inet = inet_sk(sk); 1050 tcb = TCP_SKB_CB(skb); 1051 memset(&opts, 0, sizeof(opts)); 1052 1053 if (unlikely(tcb->tcp_flags & TCPHDR_SYN)) { 1054 tcp_options_size = tcp_syn_options(sk, skb, &opts, &md5); 1055 } else { 1056 tcp_options_size = tcp_established_options(sk, skb, &opts, 1057 &md5); 1058 /* Force a PSH flag on all (GSO) packets to expedite GRO flush 1059 * at receiver : This slightly improve GRO performance. 1060 * Note that we do not force the PSH flag for non GSO packets, 1061 * because they might be sent under high congestion events, 1062 * and in this case it is better to delay the delivery of 1-MSS 1063 * packets and thus the corresponding ACK packet that would 1064 * release the following packet. 1065 */ 1066 if (tcp_skb_pcount(skb) > 1) 1067 tcb->tcp_flags |= TCPHDR_PSH; 1068 } 1069 tcp_header_size = tcp_options_size + sizeof(struct tcphdr); 1070 1071 /* if no packet is in qdisc/device queue, then allow XPS to select 1072 * another queue. We can be called from tcp_tsq_handler() 1073 * which holds one reference to sk. 1074 * 1075 * TODO: Ideally, in-flight pure ACK packets should not matter here. 1076 * One way to get this would be to set skb->truesize = 2 on them. 1077 */ 1078 skb->ooo_okay = sk_wmem_alloc_get(sk) < SKB_TRUESIZE(1); 1079 1080 /* If we had to use memory reserve to allocate this skb, 1081 * this might cause drops if packet is looped back : 1082 * Other socket might not have SOCK_MEMALLOC. 1083 * Packets not looped back do not care about pfmemalloc. 1084 */ 1085 skb->pfmemalloc = 0; 1086 1087 skb_push(skb, tcp_header_size); 1088 skb_reset_transport_header(skb); 1089 1090 skb_orphan(skb); 1091 skb->sk = sk; 1092 skb->destructor = skb_is_tcp_pure_ack(skb) ? __sock_wfree : tcp_wfree; 1093 skb_set_hash_from_sk(skb, sk); 1094 refcount_add(skb->truesize, &sk->sk_wmem_alloc); 1095 1096 skb_set_dst_pending_confirm(skb, sk->sk_dst_pending_confirm); 1097 1098 /* Build TCP header and checksum it. */ 1099 th = (struct tcphdr *)skb->data; 1100 th->source = inet->inet_sport; 1101 th->dest = inet->inet_dport; 1102 th->seq = htonl(tcb->seq); 1103 th->ack_seq = htonl(rcv_nxt); 1104 *(((__be16 *)th) + 6) = htons(((tcp_header_size >> 2) << 12) | 1105 tcb->tcp_flags); 1106 1107 th->check = 0; 1108 th->urg_ptr = 0; 1109 1110 /* The urg_mode check is necessary during a below snd_una win probe */ 1111 if (unlikely(tcp_urg_mode(tp) && before(tcb->seq, tp->snd_up))) { 1112 if (before(tp->snd_up, tcb->seq + 0x10000)) { 1113 th->urg_ptr = htons(tp->snd_up - tcb->seq); 1114 th->urg = 1; 1115 } else if (after(tcb->seq + 0xFFFF, tp->snd_nxt)) { 1116 th->urg_ptr = htons(0xFFFF); 1117 th->urg = 1; 1118 } 1119 } 1120 1121 tcp_options_write((__be32 *)(th + 1), tp, &opts); 1122 skb_shinfo(skb)->gso_type = sk->sk_gso_type; 1123 if (likely(!(tcb->tcp_flags & TCPHDR_SYN))) { 1124 th->window = htons(tcp_select_window(sk)); 1125 tcp_ecn_send(sk, skb, th, tcp_header_size); 1126 } else { 1127 /* RFC1323: The window in SYN & SYN/ACK segments 1128 * is never scaled. 1129 */ 1130 th->window = htons(min(tp->rcv_wnd, 65535U)); 1131 } 1132 #ifdef CONFIG_TCP_MD5SIG 1133 /* Calculate the MD5 hash, as we have all we need now */ 1134 if (md5) { 1135 sk_nocaps_add(sk, NETIF_F_GSO_MASK); 1136 tp->af_specific->calc_md5_hash(opts.hash_location, 1137 md5, sk, skb); 1138 } 1139 #endif 1140 1141 icsk->icsk_af_ops->send_check(sk, skb); 1142 1143 if (likely(tcb->tcp_flags & TCPHDR_ACK)) 1144 tcp_event_ack_sent(sk, tcp_skb_pcount(skb), rcv_nxt); 1145 1146 if (skb->len != tcp_header_size) { 1147 tcp_event_data_sent(tp, sk); 1148 tp->data_segs_out += tcp_skb_pcount(skb); 1149 tp->bytes_sent += skb->len - tcp_header_size; 1150 } 1151 1152 if (after(tcb->end_seq, tp->snd_nxt) || tcb->seq == tcb->end_seq) 1153 TCP_ADD_STATS(sock_net(sk), TCP_MIB_OUTSEGS, 1154 tcp_skb_pcount(skb)); 1155 1156 tp->segs_out += tcp_skb_pcount(skb); 1157 /* OK, its time to fill skb_shinfo(skb)->gso_{segs|size} */ 1158 skb_shinfo(skb)->gso_segs = tcp_skb_pcount(skb); 1159 skb_shinfo(skb)->gso_size = tcp_skb_mss(skb); 1160 1161 /* Leave earliest departure time in skb->tstamp (skb->skb_mstamp_ns) */ 1162 1163 /* Cleanup our debris for IP stacks */ 1164 memset(skb->cb, 0, max(sizeof(struct inet_skb_parm), 1165 sizeof(struct inet6_skb_parm))); 1166 1167 tcp_add_tx_delay(skb, tp); 1168 1169 err = icsk->icsk_af_ops->queue_xmit(sk, skb, &inet->cork.fl); 1170 1171 if (unlikely(err > 0)) { 1172 tcp_enter_cwr(sk); 1173 err = net_xmit_eval(err); 1174 } 1175 if (!err && oskb) { 1176 tcp_update_skb_after_send(sk, oskb, prior_wstamp); 1177 tcp_rate_skb_sent(sk, oskb); 1178 } 1179 return err; 1180 } 1181 1182 static int tcp_transmit_skb(struct sock *sk, struct sk_buff *skb, int clone_it, 1183 gfp_t gfp_mask) 1184 { 1185 return __tcp_transmit_skb(sk, skb, clone_it, gfp_mask, 1186 tcp_sk(sk)->rcv_nxt); 1187 } 1188 1189 /* This routine just queues the buffer for sending. 1190 * 1191 * NOTE: probe0 timer is not checked, do not forget tcp_push_pending_frames, 1192 * otherwise socket can stall. 1193 */ 1194 static void tcp_queue_skb(struct sock *sk, struct sk_buff *skb) 1195 { 1196 struct tcp_sock *tp = tcp_sk(sk); 1197 1198 /* Advance write_seq and place onto the write_queue. */ 1199 WRITE_ONCE(tp->write_seq, TCP_SKB_CB(skb)->end_seq); 1200 __skb_header_release(skb); 1201 tcp_add_write_queue_tail(sk, skb); 1202 sk_wmem_queued_add(sk, skb->truesize); 1203 sk_mem_charge(sk, skb->truesize); 1204 } 1205 1206 /* Initialize TSO segments for a packet. */ 1207 static void tcp_set_skb_tso_segs(struct sk_buff *skb, unsigned int mss_now) 1208 { 1209 if (skb->len <= mss_now) { 1210 /* Avoid the costly divide in the normal 1211 * non-TSO case. 1212 */ 1213 tcp_skb_pcount_set(skb, 1); 1214 TCP_SKB_CB(skb)->tcp_gso_size = 0; 1215 } else { 1216 tcp_skb_pcount_set(skb, DIV_ROUND_UP(skb->len, mss_now)); 1217 TCP_SKB_CB(skb)->tcp_gso_size = mss_now; 1218 } 1219 } 1220 1221 /* Pcount in the middle of the write queue got changed, we need to do various 1222 * tweaks to fix counters 1223 */ 1224 static void tcp_adjust_pcount(struct sock *sk, const struct sk_buff *skb, int decr) 1225 { 1226 struct tcp_sock *tp = tcp_sk(sk); 1227 1228 tp->packets_out -= decr; 1229 1230 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) 1231 tp->sacked_out -= decr; 1232 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) 1233 tp->retrans_out -= decr; 1234 if (TCP_SKB_CB(skb)->sacked & TCPCB_LOST) 1235 tp->lost_out -= decr; 1236 1237 /* Reno case is special. Sigh... */ 1238 if (tcp_is_reno(tp) && decr > 0) 1239 tp->sacked_out -= min_t(u32, tp->sacked_out, decr); 1240 1241 if (tp->lost_skb_hint && 1242 before(TCP_SKB_CB(skb)->seq, TCP_SKB_CB(tp->lost_skb_hint)->seq) && 1243 (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED)) 1244 tp->lost_cnt_hint -= decr; 1245 1246 tcp_verify_left_out(tp); 1247 } 1248 1249 static bool tcp_has_tx_tstamp(const struct sk_buff *skb) 1250 { 1251 return TCP_SKB_CB(skb)->txstamp_ack || 1252 (skb_shinfo(skb)->tx_flags & SKBTX_ANY_TSTAMP); 1253 } 1254 1255 static void tcp_fragment_tstamp(struct sk_buff *skb, struct sk_buff *skb2) 1256 { 1257 struct skb_shared_info *shinfo = skb_shinfo(skb); 1258 1259 if (unlikely(tcp_has_tx_tstamp(skb)) && 1260 !before(shinfo->tskey, TCP_SKB_CB(skb2)->seq)) { 1261 struct skb_shared_info *shinfo2 = skb_shinfo(skb2); 1262 u8 tsflags = shinfo->tx_flags & SKBTX_ANY_TSTAMP; 1263 1264 shinfo->tx_flags &= ~tsflags; 1265 shinfo2->tx_flags |= tsflags; 1266 swap(shinfo->tskey, shinfo2->tskey); 1267 TCP_SKB_CB(skb2)->txstamp_ack = TCP_SKB_CB(skb)->txstamp_ack; 1268 TCP_SKB_CB(skb)->txstamp_ack = 0; 1269 } 1270 } 1271 1272 static void tcp_skb_fragment_eor(struct sk_buff *skb, struct sk_buff *skb2) 1273 { 1274 TCP_SKB_CB(skb2)->eor = TCP_SKB_CB(skb)->eor; 1275 TCP_SKB_CB(skb)->eor = 0; 1276 } 1277 1278 /* Insert buff after skb on the write or rtx queue of sk. */ 1279 static void tcp_insert_write_queue_after(struct sk_buff *skb, 1280 struct sk_buff *buff, 1281 struct sock *sk, 1282 enum tcp_queue tcp_queue) 1283 { 1284 if (tcp_queue == TCP_FRAG_IN_WRITE_QUEUE) 1285 __skb_queue_after(&sk->sk_write_queue, skb, buff); 1286 else 1287 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff); 1288 } 1289 1290 /* Function to create two new TCP segments. Shrinks the given segment 1291 * to the specified size and appends a new segment with the rest of the 1292 * packet to the list. This won't be called frequently, I hope. 1293 * Remember, these are still headerless SKBs at this point. 1294 */ 1295 int tcp_fragment(struct sock *sk, enum tcp_queue tcp_queue, 1296 struct sk_buff *skb, u32 len, 1297 unsigned int mss_now, gfp_t gfp) 1298 { 1299 struct tcp_sock *tp = tcp_sk(sk); 1300 struct sk_buff *buff; 1301 int nsize, old_factor; 1302 long limit; 1303 int nlen; 1304 u8 flags; 1305 1306 if (WARN_ON(len > skb->len)) 1307 return -EINVAL; 1308 1309 nsize = skb_headlen(skb) - len; 1310 if (nsize < 0) 1311 nsize = 0; 1312 1313 /* tcp_sendmsg() can overshoot sk_wmem_queued by one full size skb. 1314 * We need some allowance to not penalize applications setting small 1315 * SO_SNDBUF values. 1316 * Also allow first and last skb in retransmit queue to be split. 1317 */ 1318 limit = sk->sk_sndbuf + 2 * SKB_TRUESIZE(GSO_MAX_SIZE); 1319 if (unlikely((sk->sk_wmem_queued >> 1) > limit && 1320 tcp_queue != TCP_FRAG_IN_WRITE_QUEUE && 1321 skb != tcp_rtx_queue_head(sk) && 1322 skb != tcp_rtx_queue_tail(sk))) { 1323 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPWQUEUETOOBIG); 1324 return -ENOMEM; 1325 } 1326 1327 if (skb_unclone(skb, gfp)) 1328 return -ENOMEM; 1329 1330 /* Get a new skb... force flag on. */ 1331 buff = sk_stream_alloc_skb(sk, nsize, gfp, true); 1332 if (!buff) 1333 return -ENOMEM; /* We'll just try again later. */ 1334 skb_copy_decrypted(buff, skb); 1335 1336 sk_wmem_queued_add(sk, buff->truesize); 1337 sk_mem_charge(sk, buff->truesize); 1338 nlen = skb->len - len - nsize; 1339 buff->truesize += nlen; 1340 skb->truesize -= nlen; 1341 1342 /* Correct the sequence numbers. */ 1343 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; 1344 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; 1345 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; 1346 1347 /* PSH and FIN should only be set in the second packet. */ 1348 flags = TCP_SKB_CB(skb)->tcp_flags; 1349 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH); 1350 TCP_SKB_CB(buff)->tcp_flags = flags; 1351 TCP_SKB_CB(buff)->sacked = TCP_SKB_CB(skb)->sacked; 1352 tcp_skb_fragment_eor(skb, buff); 1353 1354 skb_split(skb, buff, len); 1355 1356 buff->ip_summed = CHECKSUM_PARTIAL; 1357 1358 buff->tstamp = skb->tstamp; 1359 tcp_fragment_tstamp(skb, buff); 1360 1361 old_factor = tcp_skb_pcount(skb); 1362 1363 /* Fix up tso_factor for both original and new SKB. */ 1364 tcp_set_skb_tso_segs(skb, mss_now); 1365 tcp_set_skb_tso_segs(buff, mss_now); 1366 1367 /* Update delivered info for the new segment */ 1368 TCP_SKB_CB(buff)->tx = TCP_SKB_CB(skb)->tx; 1369 1370 /* If this packet has been sent out already, we must 1371 * adjust the various packet counters. 1372 */ 1373 if (!before(tp->snd_nxt, TCP_SKB_CB(buff)->end_seq)) { 1374 int diff = old_factor - tcp_skb_pcount(skb) - 1375 tcp_skb_pcount(buff); 1376 1377 if (diff) 1378 tcp_adjust_pcount(sk, skb, diff); 1379 } 1380 1381 /* Link BUFF into the send queue. */ 1382 __skb_header_release(buff); 1383 tcp_insert_write_queue_after(skb, buff, sk, tcp_queue); 1384 if (tcp_queue == TCP_FRAG_IN_RTX_QUEUE) 1385 list_add(&buff->tcp_tsorted_anchor, &skb->tcp_tsorted_anchor); 1386 1387 return 0; 1388 } 1389 1390 /* This is similar to __pskb_pull_tail(). The difference is that pulled 1391 * data is not copied, but immediately discarded. 1392 */ 1393 static int __pskb_trim_head(struct sk_buff *skb, int len) 1394 { 1395 struct skb_shared_info *shinfo; 1396 int i, k, eat; 1397 1398 eat = min_t(int, len, skb_headlen(skb)); 1399 if (eat) { 1400 __skb_pull(skb, eat); 1401 len -= eat; 1402 if (!len) 1403 return 0; 1404 } 1405 eat = len; 1406 k = 0; 1407 shinfo = skb_shinfo(skb); 1408 for (i = 0; i < shinfo->nr_frags; i++) { 1409 int size = skb_frag_size(&shinfo->frags[i]); 1410 1411 if (size <= eat) { 1412 skb_frag_unref(skb, i); 1413 eat -= size; 1414 } else { 1415 shinfo->frags[k] = shinfo->frags[i]; 1416 if (eat) { 1417 skb_frag_off_add(&shinfo->frags[k], eat); 1418 skb_frag_size_sub(&shinfo->frags[k], eat); 1419 eat = 0; 1420 } 1421 k++; 1422 } 1423 } 1424 shinfo->nr_frags = k; 1425 1426 skb->data_len -= len; 1427 skb->len = skb->data_len; 1428 return len; 1429 } 1430 1431 /* Remove acked data from a packet in the transmit queue. */ 1432 int tcp_trim_head(struct sock *sk, struct sk_buff *skb, u32 len) 1433 { 1434 u32 delta_truesize; 1435 1436 if (skb_unclone(skb, GFP_ATOMIC)) 1437 return -ENOMEM; 1438 1439 delta_truesize = __pskb_trim_head(skb, len); 1440 1441 TCP_SKB_CB(skb)->seq += len; 1442 skb->ip_summed = CHECKSUM_PARTIAL; 1443 1444 if (delta_truesize) { 1445 skb->truesize -= delta_truesize; 1446 sk_wmem_queued_add(sk, -delta_truesize); 1447 sk_mem_uncharge(sk, delta_truesize); 1448 sock_set_flag(sk, SOCK_QUEUE_SHRUNK); 1449 } 1450 1451 /* Any change of skb->len requires recalculation of tso factor. */ 1452 if (tcp_skb_pcount(skb) > 1) 1453 tcp_set_skb_tso_segs(skb, tcp_skb_mss(skb)); 1454 1455 return 0; 1456 } 1457 1458 /* Calculate MSS not accounting any TCP options. */ 1459 static inline int __tcp_mtu_to_mss(struct sock *sk, int pmtu) 1460 { 1461 const struct tcp_sock *tp = tcp_sk(sk); 1462 const struct inet_connection_sock *icsk = inet_csk(sk); 1463 int mss_now; 1464 1465 /* Calculate base mss without TCP options: 1466 It is MMS_S - sizeof(tcphdr) of rfc1122 1467 */ 1468 mss_now = pmtu - icsk->icsk_af_ops->net_header_len - sizeof(struct tcphdr); 1469 1470 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */ 1471 if (icsk->icsk_af_ops->net_frag_header_len) { 1472 const struct dst_entry *dst = __sk_dst_get(sk); 1473 1474 if (dst && dst_allfrag(dst)) 1475 mss_now -= icsk->icsk_af_ops->net_frag_header_len; 1476 } 1477 1478 /* Clamp it (mss_clamp does not include tcp options) */ 1479 if (mss_now > tp->rx_opt.mss_clamp) 1480 mss_now = tp->rx_opt.mss_clamp; 1481 1482 /* Now subtract optional transport overhead */ 1483 mss_now -= icsk->icsk_ext_hdr_len; 1484 1485 /* Then reserve room for full set of TCP options and 8 bytes of data */ 1486 mss_now = max(mss_now, sock_net(sk)->ipv4.sysctl_tcp_min_snd_mss); 1487 return mss_now; 1488 } 1489 1490 /* Calculate MSS. Not accounting for SACKs here. */ 1491 int tcp_mtu_to_mss(struct sock *sk, int pmtu) 1492 { 1493 /* Subtract TCP options size, not including SACKs */ 1494 return __tcp_mtu_to_mss(sk, pmtu) - 1495 (tcp_sk(sk)->tcp_header_len - sizeof(struct tcphdr)); 1496 } 1497 1498 /* Inverse of above */ 1499 int tcp_mss_to_mtu(struct sock *sk, int mss) 1500 { 1501 const struct tcp_sock *tp = tcp_sk(sk); 1502 const struct inet_connection_sock *icsk = inet_csk(sk); 1503 int mtu; 1504 1505 mtu = mss + 1506 tp->tcp_header_len + 1507 icsk->icsk_ext_hdr_len + 1508 icsk->icsk_af_ops->net_header_len; 1509 1510 /* IPv6 adds a frag_hdr in case RTAX_FEATURE_ALLFRAG is set */ 1511 if (icsk->icsk_af_ops->net_frag_header_len) { 1512 const struct dst_entry *dst = __sk_dst_get(sk); 1513 1514 if (dst && dst_allfrag(dst)) 1515 mtu += icsk->icsk_af_ops->net_frag_header_len; 1516 } 1517 return mtu; 1518 } 1519 EXPORT_SYMBOL(tcp_mss_to_mtu); 1520 1521 /* MTU probing init per socket */ 1522 void tcp_mtup_init(struct sock *sk) 1523 { 1524 struct tcp_sock *tp = tcp_sk(sk); 1525 struct inet_connection_sock *icsk = inet_csk(sk); 1526 struct net *net = sock_net(sk); 1527 1528 icsk->icsk_mtup.enabled = net->ipv4.sysctl_tcp_mtu_probing > 1; 1529 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + sizeof(struct tcphdr) + 1530 icsk->icsk_af_ops->net_header_len; 1531 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, net->ipv4.sysctl_tcp_base_mss); 1532 icsk->icsk_mtup.probe_size = 0; 1533 if (icsk->icsk_mtup.enabled) 1534 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32; 1535 } 1536 EXPORT_SYMBOL(tcp_mtup_init); 1537 1538 /* This function synchronize snd mss to current pmtu/exthdr set. 1539 1540 tp->rx_opt.user_mss is mss set by user by TCP_MAXSEG. It does NOT counts 1541 for TCP options, but includes only bare TCP header. 1542 1543 tp->rx_opt.mss_clamp is mss negotiated at connection setup. 1544 It is minimum of user_mss and mss received with SYN. 1545 It also does not include TCP options. 1546 1547 inet_csk(sk)->icsk_pmtu_cookie is last pmtu, seen by this function. 1548 1549 tp->mss_cache is current effective sending mss, including 1550 all tcp options except for SACKs. It is evaluated, 1551 taking into account current pmtu, but never exceeds 1552 tp->rx_opt.mss_clamp. 1553 1554 NOTE1. rfc1122 clearly states that advertised MSS 1555 DOES NOT include either tcp or ip options. 1556 1557 NOTE2. inet_csk(sk)->icsk_pmtu_cookie and tp->mss_cache 1558 are READ ONLY outside this function. --ANK (980731) 1559 */ 1560 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu) 1561 { 1562 struct tcp_sock *tp = tcp_sk(sk); 1563 struct inet_connection_sock *icsk = inet_csk(sk); 1564 int mss_now; 1565 1566 if (icsk->icsk_mtup.search_high > pmtu) 1567 icsk->icsk_mtup.search_high = pmtu; 1568 1569 mss_now = tcp_mtu_to_mss(sk, pmtu); 1570 mss_now = tcp_bound_to_half_wnd(tp, mss_now); 1571 1572 /* And store cached results */ 1573 icsk->icsk_pmtu_cookie = pmtu; 1574 if (icsk->icsk_mtup.enabled) 1575 mss_now = min(mss_now, tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low)); 1576 tp->mss_cache = mss_now; 1577 1578 return mss_now; 1579 } 1580 EXPORT_SYMBOL(tcp_sync_mss); 1581 1582 /* Compute the current effective MSS, taking SACKs and IP options, 1583 * and even PMTU discovery events into account. 1584 */ 1585 unsigned int tcp_current_mss(struct sock *sk) 1586 { 1587 const struct tcp_sock *tp = tcp_sk(sk); 1588 const struct dst_entry *dst = __sk_dst_get(sk); 1589 u32 mss_now; 1590 unsigned int header_len; 1591 struct tcp_out_options opts; 1592 struct tcp_md5sig_key *md5; 1593 1594 mss_now = tp->mss_cache; 1595 1596 if (dst) { 1597 u32 mtu = dst_mtu(dst); 1598 if (mtu != inet_csk(sk)->icsk_pmtu_cookie) 1599 mss_now = tcp_sync_mss(sk, mtu); 1600 } 1601 1602 header_len = tcp_established_options(sk, NULL, &opts, &md5) + 1603 sizeof(struct tcphdr); 1604 /* The mss_cache is sized based on tp->tcp_header_len, which assumes 1605 * some common options. If this is an odd packet (because we have SACK 1606 * blocks etc) then our calculated header_len will be different, and 1607 * we have to adjust mss_now correspondingly */ 1608 if (header_len != tp->tcp_header_len) { 1609 int delta = (int) header_len - tp->tcp_header_len; 1610 mss_now -= delta; 1611 } 1612 1613 return mss_now; 1614 } 1615 1616 /* RFC2861, slow part. Adjust cwnd, after it was not full during one rto. 1617 * As additional protections, we do not touch cwnd in retransmission phases, 1618 * and if application hit its sndbuf limit recently. 1619 */ 1620 static void tcp_cwnd_application_limited(struct sock *sk) 1621 { 1622 struct tcp_sock *tp = tcp_sk(sk); 1623 1624 if (inet_csk(sk)->icsk_ca_state == TCP_CA_Open && 1625 sk->sk_socket && !test_bit(SOCK_NOSPACE, &sk->sk_socket->flags)) { 1626 /* Limited by application or receiver window. */ 1627 u32 init_win = tcp_init_cwnd(tp, __sk_dst_get(sk)); 1628 u32 win_used = max(tp->snd_cwnd_used, init_win); 1629 if (win_used < tp->snd_cwnd) { 1630 tp->snd_ssthresh = tcp_current_ssthresh(sk); 1631 tp->snd_cwnd = (tp->snd_cwnd + win_used) >> 1; 1632 } 1633 tp->snd_cwnd_used = 0; 1634 } 1635 tp->snd_cwnd_stamp = tcp_jiffies32; 1636 } 1637 1638 static void tcp_cwnd_validate(struct sock *sk, bool is_cwnd_limited) 1639 { 1640 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; 1641 struct tcp_sock *tp = tcp_sk(sk); 1642 1643 /* Track the maximum number of outstanding packets in each 1644 * window, and remember whether we were cwnd-limited then. 1645 */ 1646 if (!before(tp->snd_una, tp->max_packets_seq) || 1647 tp->packets_out > tp->max_packets_out) { 1648 tp->max_packets_out = tp->packets_out; 1649 tp->max_packets_seq = tp->snd_nxt; 1650 tp->is_cwnd_limited = is_cwnd_limited; 1651 } 1652 1653 if (tcp_is_cwnd_limited(sk)) { 1654 /* Network is feed fully. */ 1655 tp->snd_cwnd_used = 0; 1656 tp->snd_cwnd_stamp = tcp_jiffies32; 1657 } else { 1658 /* Network starves. */ 1659 if (tp->packets_out > tp->snd_cwnd_used) 1660 tp->snd_cwnd_used = tp->packets_out; 1661 1662 if (sock_net(sk)->ipv4.sysctl_tcp_slow_start_after_idle && 1663 (s32)(tcp_jiffies32 - tp->snd_cwnd_stamp) >= inet_csk(sk)->icsk_rto && 1664 !ca_ops->cong_control) 1665 tcp_cwnd_application_limited(sk); 1666 1667 /* The following conditions together indicate the starvation 1668 * is caused by insufficient sender buffer: 1669 * 1) just sent some data (see tcp_write_xmit) 1670 * 2) not cwnd limited (this else condition) 1671 * 3) no more data to send (tcp_write_queue_empty()) 1672 * 4) application is hitting buffer limit (SOCK_NOSPACE) 1673 */ 1674 if (tcp_write_queue_empty(sk) && sk->sk_socket && 1675 test_bit(SOCK_NOSPACE, &sk->sk_socket->flags) && 1676 (1 << sk->sk_state) & (TCPF_ESTABLISHED | TCPF_CLOSE_WAIT)) 1677 tcp_chrono_start(sk, TCP_CHRONO_SNDBUF_LIMITED); 1678 } 1679 } 1680 1681 /* Minshall's variant of the Nagle send check. */ 1682 static bool tcp_minshall_check(const struct tcp_sock *tp) 1683 { 1684 return after(tp->snd_sml, tp->snd_una) && 1685 !after(tp->snd_sml, tp->snd_nxt); 1686 } 1687 1688 /* Update snd_sml if this skb is under mss 1689 * Note that a TSO packet might end with a sub-mss segment 1690 * The test is really : 1691 * if ((skb->len % mss) != 0) 1692 * tp->snd_sml = TCP_SKB_CB(skb)->end_seq; 1693 * But we can avoid doing the divide again given we already have 1694 * skb_pcount = skb->len / mss_now 1695 */ 1696 static void tcp_minshall_update(struct tcp_sock *tp, unsigned int mss_now, 1697 const struct sk_buff *skb) 1698 { 1699 if (skb->len < tcp_skb_pcount(skb) * mss_now) 1700 tp->snd_sml = TCP_SKB_CB(skb)->end_seq; 1701 } 1702 1703 /* Return false, if packet can be sent now without violation Nagle's rules: 1704 * 1. It is full sized. (provided by caller in %partial bool) 1705 * 2. Or it contains FIN. (already checked by caller) 1706 * 3. Or TCP_CORK is not set, and TCP_NODELAY is set. 1707 * 4. Or TCP_CORK is not set, and all sent packets are ACKed. 1708 * With Minshall's modification: all sent small packets are ACKed. 1709 */ 1710 static bool tcp_nagle_check(bool partial, const struct tcp_sock *tp, 1711 int nonagle) 1712 { 1713 return partial && 1714 ((nonagle & TCP_NAGLE_CORK) || 1715 (!nonagle && tp->packets_out && tcp_minshall_check(tp))); 1716 } 1717 1718 /* Return how many segs we'd like on a TSO packet, 1719 * to send one TSO packet per ms 1720 */ 1721 static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now, 1722 int min_tso_segs) 1723 { 1724 u32 bytes, segs; 1725 1726 bytes = min_t(unsigned long, 1727 sk->sk_pacing_rate >> sk->sk_pacing_shift, 1728 sk->sk_gso_max_size - 1 - MAX_TCP_HEADER); 1729 1730 /* Goal is to send at least one packet per ms, 1731 * not one big TSO packet every 100 ms. 1732 * This preserves ACK clocking and is consistent 1733 * with tcp_tso_should_defer() heuristic. 1734 */ 1735 segs = max_t(u32, bytes / mss_now, min_tso_segs); 1736 1737 return segs; 1738 } 1739 1740 /* Return the number of segments we want in the skb we are transmitting. 1741 * See if congestion control module wants to decide; otherwise, autosize. 1742 */ 1743 static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now) 1744 { 1745 const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; 1746 u32 min_tso, tso_segs; 1747 1748 min_tso = ca_ops->min_tso_segs ? 1749 ca_ops->min_tso_segs(sk) : 1750 sock_net(sk)->ipv4.sysctl_tcp_min_tso_segs; 1751 1752 tso_segs = tcp_tso_autosize(sk, mss_now, min_tso); 1753 return min_t(u32, tso_segs, sk->sk_gso_max_segs); 1754 } 1755 1756 /* Returns the portion of skb which can be sent right away */ 1757 static unsigned int tcp_mss_split_point(const struct sock *sk, 1758 const struct sk_buff *skb, 1759 unsigned int mss_now, 1760 unsigned int max_segs, 1761 int nonagle) 1762 { 1763 const struct tcp_sock *tp = tcp_sk(sk); 1764 u32 partial, needed, window, max_len; 1765 1766 window = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; 1767 max_len = mss_now * max_segs; 1768 1769 if (likely(max_len <= window && skb != tcp_write_queue_tail(sk))) 1770 return max_len; 1771 1772 needed = min(skb->len, window); 1773 1774 if (max_len <= needed) 1775 return max_len; 1776 1777 partial = needed % mss_now; 1778 /* If last segment is not a full MSS, check if Nagle rules allow us 1779 * to include this last segment in this skb. 1780 * Otherwise, we'll split the skb at last MSS boundary 1781 */ 1782 if (tcp_nagle_check(partial != 0, tp, nonagle)) 1783 return needed - partial; 1784 1785 return needed; 1786 } 1787 1788 /* Can at least one segment of SKB be sent right now, according to the 1789 * congestion window rules? If so, return how many segments are allowed. 1790 */ 1791 static inline unsigned int tcp_cwnd_test(const struct tcp_sock *tp, 1792 const struct sk_buff *skb) 1793 { 1794 u32 in_flight, cwnd, halfcwnd; 1795 1796 /* Don't be strict about the congestion window for the final FIN. */ 1797 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) && 1798 tcp_skb_pcount(skb) == 1) 1799 return 1; 1800 1801 in_flight = tcp_packets_in_flight(tp); 1802 cwnd = tp->snd_cwnd; 1803 if (in_flight >= cwnd) 1804 return 0; 1805 1806 /* For better scheduling, ensure we have at least 1807 * 2 GSO packets in flight. 1808 */ 1809 halfcwnd = max(cwnd >> 1, 1U); 1810 return min(halfcwnd, cwnd - in_flight); 1811 } 1812 1813 /* Initialize TSO state of a skb. 1814 * This must be invoked the first time we consider transmitting 1815 * SKB onto the wire. 1816 */ 1817 static int tcp_init_tso_segs(struct sk_buff *skb, unsigned int mss_now) 1818 { 1819 int tso_segs = tcp_skb_pcount(skb); 1820 1821 if (!tso_segs || (tso_segs > 1 && tcp_skb_mss(skb) != mss_now)) { 1822 tcp_set_skb_tso_segs(skb, mss_now); 1823 tso_segs = tcp_skb_pcount(skb); 1824 } 1825 return tso_segs; 1826 } 1827 1828 1829 /* Return true if the Nagle test allows this packet to be 1830 * sent now. 1831 */ 1832 static inline bool tcp_nagle_test(const struct tcp_sock *tp, const struct sk_buff *skb, 1833 unsigned int cur_mss, int nonagle) 1834 { 1835 /* Nagle rule does not apply to frames, which sit in the middle of the 1836 * write_queue (they have no chances to get new data). 1837 * 1838 * This is implemented in the callers, where they modify the 'nonagle' 1839 * argument based upon the location of SKB in the send queue. 1840 */ 1841 if (nonagle & TCP_NAGLE_PUSH) 1842 return true; 1843 1844 /* Don't use the nagle rule for urgent data (or for the final FIN). */ 1845 if (tcp_urg_mode(tp) || (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN)) 1846 return true; 1847 1848 if (!tcp_nagle_check(skb->len < cur_mss, tp, nonagle)) 1849 return true; 1850 1851 return false; 1852 } 1853 1854 /* Does at least the first segment of SKB fit into the send window? */ 1855 static bool tcp_snd_wnd_test(const struct tcp_sock *tp, 1856 const struct sk_buff *skb, 1857 unsigned int cur_mss) 1858 { 1859 u32 end_seq = TCP_SKB_CB(skb)->end_seq; 1860 1861 if (skb->len > cur_mss) 1862 end_seq = TCP_SKB_CB(skb)->seq + cur_mss; 1863 1864 return !after(end_seq, tcp_wnd_end(tp)); 1865 } 1866 1867 /* Trim TSO SKB to LEN bytes, put the remaining data into a new packet 1868 * which is put after SKB on the list. It is very much like 1869 * tcp_fragment() except that it may make several kinds of assumptions 1870 * in order to speed up the splitting operation. In particular, we 1871 * know that all the data is in scatter-gather pages, and that the 1872 * packet has never been sent out before (and thus is not cloned). 1873 */ 1874 static int tso_fragment(struct sock *sk, struct sk_buff *skb, unsigned int len, 1875 unsigned int mss_now, gfp_t gfp) 1876 { 1877 int nlen = skb->len - len; 1878 struct sk_buff *buff; 1879 u8 flags; 1880 1881 /* All of a TSO frame must be composed of paged data. */ 1882 if (skb->len != skb->data_len) 1883 return tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE, 1884 skb, len, mss_now, gfp); 1885 1886 buff = sk_stream_alloc_skb(sk, 0, gfp, true); 1887 if (unlikely(!buff)) 1888 return -ENOMEM; 1889 skb_copy_decrypted(buff, skb); 1890 1891 sk_wmem_queued_add(sk, buff->truesize); 1892 sk_mem_charge(sk, buff->truesize); 1893 buff->truesize += nlen; 1894 skb->truesize -= nlen; 1895 1896 /* Correct the sequence numbers. */ 1897 TCP_SKB_CB(buff)->seq = TCP_SKB_CB(skb)->seq + len; 1898 TCP_SKB_CB(buff)->end_seq = TCP_SKB_CB(skb)->end_seq; 1899 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(buff)->seq; 1900 1901 /* PSH and FIN should only be set in the second packet. */ 1902 flags = TCP_SKB_CB(skb)->tcp_flags; 1903 TCP_SKB_CB(skb)->tcp_flags = flags & ~(TCPHDR_FIN | TCPHDR_PSH); 1904 TCP_SKB_CB(buff)->tcp_flags = flags; 1905 1906 /* This packet was never sent out yet, so no SACK bits. */ 1907 TCP_SKB_CB(buff)->sacked = 0; 1908 1909 tcp_skb_fragment_eor(skb, buff); 1910 1911 buff->ip_summed = CHECKSUM_PARTIAL; 1912 skb_split(skb, buff, len); 1913 tcp_fragment_tstamp(skb, buff); 1914 1915 /* Fix up tso_factor for both original and new SKB. */ 1916 tcp_set_skb_tso_segs(skb, mss_now); 1917 tcp_set_skb_tso_segs(buff, mss_now); 1918 1919 /* Link BUFF into the send queue. */ 1920 __skb_header_release(buff); 1921 tcp_insert_write_queue_after(skb, buff, sk, TCP_FRAG_IN_WRITE_QUEUE); 1922 1923 return 0; 1924 } 1925 1926 /* Try to defer sending, if possible, in order to minimize the amount 1927 * of TSO splitting we do. View it as a kind of TSO Nagle test. 1928 * 1929 * This algorithm is from John Heffner. 1930 */ 1931 static bool tcp_tso_should_defer(struct sock *sk, struct sk_buff *skb, 1932 bool *is_cwnd_limited, 1933 bool *is_rwnd_limited, 1934 u32 max_segs) 1935 { 1936 const struct inet_connection_sock *icsk = inet_csk(sk); 1937 u32 send_win, cong_win, limit, in_flight; 1938 struct tcp_sock *tp = tcp_sk(sk); 1939 struct sk_buff *head; 1940 int win_divisor; 1941 s64 delta; 1942 1943 if (icsk->icsk_ca_state >= TCP_CA_Recovery) 1944 goto send_now; 1945 1946 /* Avoid bursty behavior by allowing defer 1947 * only if the last write was recent (1 ms). 1948 * Note that tp->tcp_wstamp_ns can be in the future if we have 1949 * packets waiting in a qdisc or device for EDT delivery. 1950 */ 1951 delta = tp->tcp_clock_cache - tp->tcp_wstamp_ns - NSEC_PER_MSEC; 1952 if (delta > 0) 1953 goto send_now; 1954 1955 in_flight = tcp_packets_in_flight(tp); 1956 1957 BUG_ON(tcp_skb_pcount(skb) <= 1); 1958 BUG_ON(tp->snd_cwnd <= in_flight); 1959 1960 send_win = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; 1961 1962 /* From in_flight test above, we know that cwnd > in_flight. */ 1963 cong_win = (tp->snd_cwnd - in_flight) * tp->mss_cache; 1964 1965 limit = min(send_win, cong_win); 1966 1967 /* If a full-sized TSO skb can be sent, do it. */ 1968 if (limit >= max_segs * tp->mss_cache) 1969 goto send_now; 1970 1971 /* Middle in queue won't get any more data, full sendable already? */ 1972 if ((skb != tcp_write_queue_tail(sk)) && (limit >= skb->len)) 1973 goto send_now; 1974 1975 win_divisor = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_tso_win_divisor); 1976 if (win_divisor) { 1977 u32 chunk = min(tp->snd_wnd, tp->snd_cwnd * tp->mss_cache); 1978 1979 /* If at least some fraction of a window is available, 1980 * just use it. 1981 */ 1982 chunk /= win_divisor; 1983 if (limit >= chunk) 1984 goto send_now; 1985 } else { 1986 /* Different approach, try not to defer past a single 1987 * ACK. Receiver should ACK every other full sized 1988 * frame, so if we have space for more than 3 frames 1989 * then send now. 1990 */ 1991 if (limit > tcp_max_tso_deferred_mss(tp) * tp->mss_cache) 1992 goto send_now; 1993 } 1994 1995 /* TODO : use tsorted_sent_queue ? */ 1996 head = tcp_rtx_queue_head(sk); 1997 if (!head) 1998 goto send_now; 1999 delta = tp->tcp_clock_cache - head->tstamp; 2000 /* If next ACK is likely to come too late (half srtt), do not defer */ 2001 if ((s64)(delta - (u64)NSEC_PER_USEC * (tp->srtt_us >> 4)) < 0) 2002 goto send_now; 2003 2004 /* Ok, it looks like it is advisable to defer. 2005 * Three cases are tracked : 2006 * 1) We are cwnd-limited 2007 * 2) We are rwnd-limited 2008 * 3) We are application limited. 2009 */ 2010 if (cong_win < send_win) { 2011 if (cong_win <= skb->len) { 2012 *is_cwnd_limited = true; 2013 return true; 2014 } 2015 } else { 2016 if (send_win <= skb->len) { 2017 *is_rwnd_limited = true; 2018 return true; 2019 } 2020 } 2021 2022 /* If this packet won't get more data, do not wait. */ 2023 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_FIN) || 2024 TCP_SKB_CB(skb)->eor) 2025 goto send_now; 2026 2027 return true; 2028 2029 send_now: 2030 return false; 2031 } 2032 2033 static inline void tcp_mtu_check_reprobe(struct sock *sk) 2034 { 2035 struct inet_connection_sock *icsk = inet_csk(sk); 2036 struct tcp_sock *tp = tcp_sk(sk); 2037 struct net *net = sock_net(sk); 2038 u32 interval; 2039 s32 delta; 2040 2041 interval = net->ipv4.sysctl_tcp_probe_interval; 2042 delta = tcp_jiffies32 - icsk->icsk_mtup.probe_timestamp; 2043 if (unlikely(delta >= interval * HZ)) { 2044 int mss = tcp_current_mss(sk); 2045 2046 /* Update current search range */ 2047 icsk->icsk_mtup.probe_size = 0; 2048 icsk->icsk_mtup.search_high = tp->rx_opt.mss_clamp + 2049 sizeof(struct tcphdr) + 2050 icsk->icsk_af_ops->net_header_len; 2051 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); 2052 2053 /* Update probe time stamp */ 2054 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32; 2055 } 2056 } 2057 2058 static bool tcp_can_coalesce_send_queue_head(struct sock *sk, int len) 2059 { 2060 struct sk_buff *skb, *next; 2061 2062 skb = tcp_send_head(sk); 2063 tcp_for_write_queue_from_safe(skb, next, sk) { 2064 if (len <= skb->len) 2065 break; 2066 2067 if (unlikely(TCP_SKB_CB(skb)->eor) || tcp_has_tx_tstamp(skb)) 2068 return false; 2069 2070 len -= skb->len; 2071 } 2072 2073 return true; 2074 } 2075 2076 /* Create a new MTU probe if we are ready. 2077 * MTU probe is regularly attempting to increase the path MTU by 2078 * deliberately sending larger packets. This discovers routing 2079 * changes resulting in larger path MTUs. 2080 * 2081 * Returns 0 if we should wait to probe (no cwnd available), 2082 * 1 if a probe was sent, 2083 * -1 otherwise 2084 */ 2085 static int tcp_mtu_probe(struct sock *sk) 2086 { 2087 struct inet_connection_sock *icsk = inet_csk(sk); 2088 struct tcp_sock *tp = tcp_sk(sk); 2089 struct sk_buff *skb, *nskb, *next; 2090 struct net *net = sock_net(sk); 2091 int probe_size; 2092 int size_needed; 2093 int copy, len; 2094 int mss_now; 2095 int interval; 2096 2097 /* Not currently probing/verifying, 2098 * not in recovery, 2099 * have enough cwnd, and 2100 * not SACKing (the variable headers throw things off) 2101 */ 2102 if (likely(!icsk->icsk_mtup.enabled || 2103 icsk->icsk_mtup.probe_size || 2104 inet_csk(sk)->icsk_ca_state != TCP_CA_Open || 2105 tp->snd_cwnd < 11 || 2106 tp->rx_opt.num_sacks || tp->rx_opt.dsack)) 2107 return -1; 2108 2109 /* Use binary search for probe_size between tcp_mss_base, 2110 * and current mss_clamp. if (search_high - search_low) 2111 * smaller than a threshold, backoff from probing. 2112 */ 2113 mss_now = tcp_current_mss(sk); 2114 probe_size = tcp_mtu_to_mss(sk, (icsk->icsk_mtup.search_high + 2115 icsk->icsk_mtup.search_low) >> 1); 2116 size_needed = probe_size + (tp->reordering + 1) * tp->mss_cache; 2117 interval = icsk->icsk_mtup.search_high - icsk->icsk_mtup.search_low; 2118 /* When misfortune happens, we are reprobing actively, 2119 * and then reprobe timer has expired. We stick with current 2120 * probing process by not resetting search range to its orignal. 2121 */ 2122 if (probe_size > tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_high) || 2123 interval < net->ipv4.sysctl_tcp_probe_threshold) { 2124 /* Check whether enough time has elaplased for 2125 * another round of probing. 2126 */ 2127 tcp_mtu_check_reprobe(sk); 2128 return -1; 2129 } 2130 2131 /* Have enough data in the send queue to probe? */ 2132 if (tp->write_seq - tp->snd_nxt < size_needed) 2133 return -1; 2134 2135 if (tp->snd_wnd < size_needed) 2136 return -1; 2137 if (after(tp->snd_nxt + size_needed, tcp_wnd_end(tp))) 2138 return 0; 2139 2140 /* Do we need to wait to drain cwnd? With none in flight, don't stall */ 2141 if (tcp_packets_in_flight(tp) + 2 > tp->snd_cwnd) { 2142 if (!tcp_packets_in_flight(tp)) 2143 return -1; 2144 else 2145 return 0; 2146 } 2147 2148 if (!tcp_can_coalesce_send_queue_head(sk, probe_size)) 2149 return -1; 2150 2151 /* We're allowed to probe. Build it now. */ 2152 nskb = sk_stream_alloc_skb(sk, probe_size, GFP_ATOMIC, false); 2153 if (!nskb) 2154 return -1; 2155 sk_wmem_queued_add(sk, nskb->truesize); 2156 sk_mem_charge(sk, nskb->truesize); 2157 2158 skb = tcp_send_head(sk); 2159 skb_copy_decrypted(nskb, skb); 2160 2161 TCP_SKB_CB(nskb)->seq = TCP_SKB_CB(skb)->seq; 2162 TCP_SKB_CB(nskb)->end_seq = TCP_SKB_CB(skb)->seq + probe_size; 2163 TCP_SKB_CB(nskb)->tcp_flags = TCPHDR_ACK; 2164 TCP_SKB_CB(nskb)->sacked = 0; 2165 nskb->csum = 0; 2166 nskb->ip_summed = CHECKSUM_PARTIAL; 2167 2168 tcp_insert_write_queue_before(nskb, skb, sk); 2169 tcp_highest_sack_replace(sk, skb, nskb); 2170 2171 len = 0; 2172 tcp_for_write_queue_from_safe(skb, next, sk) { 2173 copy = min_t(int, skb->len, probe_size - len); 2174 skb_copy_bits(skb, 0, skb_put(nskb, copy), copy); 2175 2176 if (skb->len <= copy) { 2177 /* We've eaten all the data from this skb. 2178 * Throw it away. */ 2179 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags; 2180 /* If this is the last SKB we copy and eor is set 2181 * we need to propagate it to the new skb. 2182 */ 2183 TCP_SKB_CB(nskb)->eor = TCP_SKB_CB(skb)->eor; 2184 tcp_skb_collapse_tstamp(nskb, skb); 2185 tcp_unlink_write_queue(skb, sk); 2186 sk_wmem_free_skb(sk, skb); 2187 } else { 2188 TCP_SKB_CB(nskb)->tcp_flags |= TCP_SKB_CB(skb)->tcp_flags & 2189 ~(TCPHDR_FIN|TCPHDR_PSH); 2190 if (!skb_shinfo(skb)->nr_frags) { 2191 skb_pull(skb, copy); 2192 } else { 2193 __pskb_trim_head(skb, copy); 2194 tcp_set_skb_tso_segs(skb, mss_now); 2195 } 2196 TCP_SKB_CB(skb)->seq += copy; 2197 } 2198 2199 len += copy; 2200 2201 if (len >= probe_size) 2202 break; 2203 } 2204 tcp_init_tso_segs(nskb, nskb->len); 2205 2206 /* We're ready to send. If this fails, the probe will 2207 * be resegmented into mss-sized pieces by tcp_write_xmit(). 2208 */ 2209 if (!tcp_transmit_skb(sk, nskb, 1, GFP_ATOMIC)) { 2210 /* Decrement cwnd here because we are sending 2211 * effectively two packets. */ 2212 tp->snd_cwnd--; 2213 tcp_event_new_data_sent(sk, nskb); 2214 2215 icsk->icsk_mtup.probe_size = tcp_mss_to_mtu(sk, nskb->len); 2216 tp->mtu_probe.probe_seq_start = TCP_SKB_CB(nskb)->seq; 2217 tp->mtu_probe.probe_seq_end = TCP_SKB_CB(nskb)->end_seq; 2218 2219 return 1; 2220 } 2221 2222 return -1; 2223 } 2224 2225 static bool tcp_pacing_check(struct sock *sk) 2226 { 2227 struct tcp_sock *tp = tcp_sk(sk); 2228 2229 if (!tcp_needs_internal_pacing(sk)) 2230 return false; 2231 2232 if (tp->tcp_wstamp_ns <= tp->tcp_clock_cache) 2233 return false; 2234 2235 if (!hrtimer_is_queued(&tp->pacing_timer)) { 2236 hrtimer_start(&tp->pacing_timer, 2237 ns_to_ktime(tp->tcp_wstamp_ns), 2238 HRTIMER_MODE_ABS_PINNED_SOFT); 2239 sock_hold(sk); 2240 } 2241 return true; 2242 } 2243 2244 /* TCP Small Queues : 2245 * Control number of packets in qdisc/devices to two packets / or ~1 ms. 2246 * (These limits are doubled for retransmits) 2247 * This allows for : 2248 * - better RTT estimation and ACK scheduling 2249 * - faster recovery 2250 * - high rates 2251 * Alas, some drivers / subsystems require a fair amount 2252 * of queued bytes to ensure line rate. 2253 * One example is wifi aggregation (802.11 AMPDU) 2254 */ 2255 static bool tcp_small_queue_check(struct sock *sk, const struct sk_buff *skb, 2256 unsigned int factor) 2257 { 2258 unsigned long limit; 2259 2260 limit = max_t(unsigned long, 2261 2 * skb->truesize, 2262 sk->sk_pacing_rate >> sk->sk_pacing_shift); 2263 if (sk->sk_pacing_status == SK_PACING_NONE) 2264 limit = min_t(unsigned long, limit, 2265 sock_net(sk)->ipv4.sysctl_tcp_limit_output_bytes); 2266 limit <<= factor; 2267 2268 if (static_branch_unlikely(&tcp_tx_delay_enabled) && 2269 tcp_sk(sk)->tcp_tx_delay) { 2270 u64 extra_bytes = (u64)sk->sk_pacing_rate * tcp_sk(sk)->tcp_tx_delay; 2271 2272 /* TSQ is based on skb truesize sum (sk_wmem_alloc), so we 2273 * approximate our needs assuming an ~100% skb->truesize overhead. 2274 * USEC_PER_SEC is approximated by 2^20. 2275 * do_div(extra_bytes, USEC_PER_SEC/2) is replaced by a right shift. 2276 */ 2277 extra_bytes >>= (20 - 1); 2278 limit += extra_bytes; 2279 } 2280 if (refcount_read(&sk->sk_wmem_alloc) > limit) { 2281 /* Always send skb if rtx queue is empty. 2282 * No need to wait for TX completion to call us back, 2283 * after softirq/tasklet schedule. 2284 * This helps when TX completions are delayed too much. 2285 */ 2286 if (tcp_rtx_queue_empty(sk)) 2287 return false; 2288 2289 set_bit(TSQ_THROTTLED, &sk->sk_tsq_flags); 2290 /* It is possible TX completion already happened 2291 * before we set TSQ_THROTTLED, so we must 2292 * test again the condition. 2293 */ 2294 smp_mb__after_atomic(); 2295 if (refcount_read(&sk->sk_wmem_alloc) > limit) 2296 return true; 2297 } 2298 return false; 2299 } 2300 2301 static void tcp_chrono_set(struct tcp_sock *tp, const enum tcp_chrono new) 2302 { 2303 const u32 now = tcp_jiffies32; 2304 enum tcp_chrono old = tp->chrono_type; 2305 2306 if (old > TCP_CHRONO_UNSPEC) 2307 tp->chrono_stat[old - 1] += now - tp->chrono_start; 2308 tp->chrono_start = now; 2309 tp->chrono_type = new; 2310 } 2311 2312 void tcp_chrono_start(struct sock *sk, const enum tcp_chrono type) 2313 { 2314 struct tcp_sock *tp = tcp_sk(sk); 2315 2316 /* If there are multiple conditions worthy of tracking in a 2317 * chronograph then the highest priority enum takes precedence 2318 * over the other conditions. So that if something "more interesting" 2319 * starts happening, stop the previous chrono and start a new one. 2320 */ 2321 if (type > tp->chrono_type) 2322 tcp_chrono_set(tp, type); 2323 } 2324 2325 void tcp_chrono_stop(struct sock *sk, const enum tcp_chrono type) 2326 { 2327 struct tcp_sock *tp = tcp_sk(sk); 2328 2329 2330 /* There are multiple conditions worthy of tracking in a 2331 * chronograph, so that the highest priority enum takes 2332 * precedence over the other conditions (see tcp_chrono_start). 2333 * If a condition stops, we only stop chrono tracking if 2334 * it's the "most interesting" or current chrono we are 2335 * tracking and starts busy chrono if we have pending data. 2336 */ 2337 if (tcp_rtx_and_write_queues_empty(sk)) 2338 tcp_chrono_set(tp, TCP_CHRONO_UNSPEC); 2339 else if (type == tp->chrono_type) 2340 tcp_chrono_set(tp, TCP_CHRONO_BUSY); 2341 } 2342 2343 /* This routine writes packets to the network. It advances the 2344 * send_head. This happens as incoming acks open up the remote 2345 * window for us. 2346 * 2347 * LARGESEND note: !tcp_urg_mode is overkill, only frames between 2348 * snd_up-64k-mss .. snd_up cannot be large. However, taking into 2349 * account rare use of URG, this is not a big flaw. 2350 * 2351 * Send at most one packet when push_one > 0. Temporarily ignore 2352 * cwnd limit to force at most one packet out when push_one == 2. 2353 2354 * Returns true, if no segments are in flight and we have queued segments, 2355 * but cannot send anything now because of SWS or another problem. 2356 */ 2357 static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, 2358 int push_one, gfp_t gfp) 2359 { 2360 struct tcp_sock *tp = tcp_sk(sk); 2361 struct sk_buff *skb; 2362 unsigned int tso_segs, sent_pkts; 2363 int cwnd_quota; 2364 int result; 2365 bool is_cwnd_limited = false, is_rwnd_limited = false; 2366 u32 max_segs; 2367 2368 sent_pkts = 0; 2369 2370 tcp_mstamp_refresh(tp); 2371 if (!push_one) { 2372 /* Do MTU probing. */ 2373 result = tcp_mtu_probe(sk); 2374 if (!result) { 2375 return false; 2376 } else if (result > 0) { 2377 sent_pkts = 1; 2378 } 2379 } 2380 2381 max_segs = tcp_tso_segs(sk, mss_now); 2382 while ((skb = tcp_send_head(sk))) { 2383 unsigned int limit; 2384 2385 if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE) { 2386 /* "skb_mstamp_ns" is used as a start point for the retransmit timer */ 2387 skb->skb_mstamp_ns = tp->tcp_wstamp_ns = tp->tcp_clock_cache; 2388 list_move_tail(&skb->tcp_tsorted_anchor, &tp->tsorted_sent_queue); 2389 tcp_init_tso_segs(skb, mss_now); 2390 goto repair; /* Skip network transmission */ 2391 } 2392 2393 if (tcp_pacing_check(sk)) 2394 break; 2395 2396 tso_segs = tcp_init_tso_segs(skb, mss_now); 2397 BUG_ON(!tso_segs); 2398 2399 cwnd_quota = tcp_cwnd_test(tp, skb); 2400 if (!cwnd_quota) { 2401 if (push_one == 2) 2402 /* Force out a loss probe pkt. */ 2403 cwnd_quota = 1; 2404 else 2405 break; 2406 } 2407 2408 if (unlikely(!tcp_snd_wnd_test(tp, skb, mss_now))) { 2409 is_rwnd_limited = true; 2410 break; 2411 } 2412 2413 if (tso_segs == 1) { 2414 if (unlikely(!tcp_nagle_test(tp, skb, mss_now, 2415 (tcp_skb_is_last(sk, skb) ? 2416 nonagle : TCP_NAGLE_PUSH)))) 2417 break; 2418 } else { 2419 if (!push_one && 2420 tcp_tso_should_defer(sk, skb, &is_cwnd_limited, 2421 &is_rwnd_limited, max_segs)) 2422 break; 2423 } 2424 2425 limit = mss_now; 2426 if (tso_segs > 1 && !tcp_urg_mode(tp)) 2427 limit = tcp_mss_split_point(sk, skb, mss_now, 2428 min_t(unsigned int, 2429 cwnd_quota, 2430 max_segs), 2431 nonagle); 2432 2433 if (skb->len > limit && 2434 unlikely(tso_fragment(sk, skb, limit, mss_now, gfp))) 2435 break; 2436 2437 if (tcp_small_queue_check(sk, skb, 0)) 2438 break; 2439 2440 if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp))) 2441 break; 2442 2443 repair: 2444 /* Advance the send_head. This one is sent out. 2445 * This call will increment packets_out. 2446 */ 2447 tcp_event_new_data_sent(sk, skb); 2448 2449 tcp_minshall_update(tp, mss_now, skb); 2450 sent_pkts += tcp_skb_pcount(skb); 2451 2452 if (push_one) 2453 break; 2454 } 2455 2456 if (is_rwnd_limited) 2457 tcp_chrono_start(sk, TCP_CHRONO_RWND_LIMITED); 2458 else 2459 tcp_chrono_stop(sk, TCP_CHRONO_RWND_LIMITED); 2460 2461 if (likely(sent_pkts)) { 2462 if (tcp_in_cwnd_reduction(sk)) 2463 tp->prr_out += sent_pkts; 2464 2465 /* Send one loss probe per tail loss episode. */ 2466 if (push_one != 2) 2467 tcp_schedule_loss_probe(sk, false); 2468 is_cwnd_limited |= (tcp_packets_in_flight(tp) >= tp->snd_cwnd); 2469 tcp_cwnd_validate(sk, is_cwnd_limited); 2470 return false; 2471 } 2472 return !tp->packets_out && !tcp_write_queue_empty(sk); 2473 } 2474 2475 bool tcp_schedule_loss_probe(struct sock *sk, bool advancing_rto) 2476 { 2477 struct inet_connection_sock *icsk = inet_csk(sk); 2478 struct tcp_sock *tp = tcp_sk(sk); 2479 u32 timeout, rto_delta_us; 2480 int early_retrans; 2481 2482 /* Don't do any loss probe on a Fast Open connection before 3WHS 2483 * finishes. 2484 */ 2485 if (rcu_access_pointer(tp->fastopen_rsk)) 2486 return false; 2487 2488 early_retrans = sock_net(sk)->ipv4.sysctl_tcp_early_retrans; 2489 /* Schedule a loss probe in 2*RTT for SACK capable connections 2490 * not in loss recovery, that are either limited by cwnd or application. 2491 */ 2492 if ((early_retrans != 3 && early_retrans != 4) || 2493 !tp->packets_out || !tcp_is_sack(tp) || 2494 (icsk->icsk_ca_state != TCP_CA_Open && 2495 icsk->icsk_ca_state != TCP_CA_CWR)) 2496 return false; 2497 2498 /* Probe timeout is 2*rtt. Add minimum RTO to account 2499 * for delayed ack when there's one outstanding packet. If no RTT 2500 * sample is available then probe after TCP_TIMEOUT_INIT. 2501 */ 2502 if (tp->srtt_us) { 2503 timeout = usecs_to_jiffies(tp->srtt_us >> 2); 2504 if (tp->packets_out == 1) 2505 timeout += TCP_RTO_MIN; 2506 else 2507 timeout += TCP_TIMEOUT_MIN; 2508 } else { 2509 timeout = TCP_TIMEOUT_INIT; 2510 } 2511 2512 /* If the RTO formula yields an earlier time, then use that time. */ 2513 rto_delta_us = advancing_rto ? 2514 jiffies_to_usecs(inet_csk(sk)->icsk_rto) : 2515 tcp_rto_delta_us(sk); /* How far in future is RTO? */ 2516 if (rto_delta_us > 0) 2517 timeout = min_t(u32, timeout, usecs_to_jiffies(rto_delta_us)); 2518 2519 tcp_reset_xmit_timer(sk, ICSK_TIME_LOSS_PROBE, timeout, 2520 TCP_RTO_MAX, NULL); 2521 return true; 2522 } 2523 2524 /* Thanks to skb fast clones, we can detect if a prior transmit of 2525 * a packet is still in a qdisc or driver queue. 2526 * In this case, there is very little point doing a retransmit ! 2527 */ 2528 static bool skb_still_in_host_queue(const struct sock *sk, 2529 const struct sk_buff *skb) 2530 { 2531 if (unlikely(skb_fclone_busy(sk, skb))) { 2532 NET_INC_STATS(sock_net(sk), 2533 LINUX_MIB_TCPSPURIOUS_RTX_HOSTQUEUES); 2534 return true; 2535 } 2536 return false; 2537 } 2538 2539 /* When probe timeout (PTO) fires, try send a new segment if possible, else 2540 * retransmit the last segment. 2541 */ 2542 void tcp_send_loss_probe(struct sock *sk) 2543 { 2544 struct tcp_sock *tp = tcp_sk(sk); 2545 struct sk_buff *skb; 2546 int pcount; 2547 int mss = tcp_current_mss(sk); 2548 2549 skb = tcp_send_head(sk); 2550 if (skb && tcp_snd_wnd_test(tp, skb, mss)) { 2551 pcount = tp->packets_out; 2552 tcp_write_xmit(sk, mss, TCP_NAGLE_OFF, 2, GFP_ATOMIC); 2553 if (tp->packets_out > pcount) 2554 goto probe_sent; 2555 goto rearm_timer; 2556 } 2557 skb = skb_rb_last(&sk->tcp_rtx_queue); 2558 if (unlikely(!skb)) { 2559 WARN_ONCE(tp->packets_out, 2560 "invalid inflight: %u state %u cwnd %u mss %d\n", 2561 tp->packets_out, sk->sk_state, tp->snd_cwnd, mss); 2562 inet_csk(sk)->icsk_pending = 0; 2563 return; 2564 } 2565 2566 /* At most one outstanding TLP retransmission. */ 2567 if (tp->tlp_high_seq) 2568 goto rearm_timer; 2569 2570 if (skb_still_in_host_queue(sk, skb)) 2571 goto rearm_timer; 2572 2573 pcount = tcp_skb_pcount(skb); 2574 if (WARN_ON(!pcount)) 2575 goto rearm_timer; 2576 2577 if ((pcount > 1) && (skb->len > (pcount - 1) * mss)) { 2578 if (unlikely(tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, 2579 (pcount - 1) * mss, mss, 2580 GFP_ATOMIC))) 2581 goto rearm_timer; 2582 skb = skb_rb_next(skb); 2583 } 2584 2585 if (WARN_ON(!skb || !tcp_skb_pcount(skb))) 2586 goto rearm_timer; 2587 2588 if (__tcp_retransmit_skb(sk, skb, 1)) 2589 goto rearm_timer; 2590 2591 /* Record snd_nxt for loss detection. */ 2592 tp->tlp_high_seq = tp->snd_nxt; 2593 2594 probe_sent: 2595 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPLOSSPROBES); 2596 /* Reset s.t. tcp_rearm_rto will restart timer from now */ 2597 inet_csk(sk)->icsk_pending = 0; 2598 rearm_timer: 2599 tcp_rearm_rto(sk); 2600 } 2601 2602 /* Push out any pending frames which were held back due to 2603 * TCP_CORK or attempt at coalescing tiny packets. 2604 * The socket must be locked by the caller. 2605 */ 2606 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss, 2607 int nonagle) 2608 { 2609 /* If we are closed, the bytes will have to remain here. 2610 * In time closedown will finish, we empty the write queue and 2611 * all will be happy. 2612 */ 2613 if (unlikely(sk->sk_state == TCP_CLOSE)) 2614 return; 2615 2616 if (tcp_write_xmit(sk, cur_mss, nonagle, 0, 2617 sk_gfp_mask(sk, GFP_ATOMIC))) 2618 tcp_check_probe_timer(sk); 2619 } 2620 2621 /* Send _single_ skb sitting at the send head. This function requires 2622 * true push pending frames to setup probe timer etc. 2623 */ 2624 void tcp_push_one(struct sock *sk, unsigned int mss_now) 2625 { 2626 struct sk_buff *skb = tcp_send_head(sk); 2627 2628 BUG_ON(!skb || skb->len < mss_now); 2629 2630 tcp_write_xmit(sk, mss_now, TCP_NAGLE_PUSH, 1, sk->sk_allocation); 2631 } 2632 2633 /* This function returns the amount that we can raise the 2634 * usable window based on the following constraints 2635 * 2636 * 1. The window can never be shrunk once it is offered (RFC 793) 2637 * 2. We limit memory per socket 2638 * 2639 * RFC 1122: 2640 * "the suggested [SWS] avoidance algorithm for the receiver is to keep 2641 * RECV.NEXT + RCV.WIN fixed until: 2642 * RCV.BUFF - RCV.USER - RCV.WINDOW >= min(1/2 RCV.BUFF, MSS)" 2643 * 2644 * i.e. don't raise the right edge of the window until you can raise 2645 * it at least MSS bytes. 2646 * 2647 * Unfortunately, the recommended algorithm breaks header prediction, 2648 * since header prediction assumes th->window stays fixed. 2649 * 2650 * Strictly speaking, keeping th->window fixed violates the receiver 2651 * side SWS prevention criteria. The problem is that under this rule 2652 * a stream of single byte packets will cause the right side of the 2653 * window to always advance by a single byte. 2654 * 2655 * Of course, if the sender implements sender side SWS prevention 2656 * then this will not be a problem. 2657 * 2658 * BSD seems to make the following compromise: 2659 * 2660 * If the free space is less than the 1/4 of the maximum 2661 * space available and the free space is less than 1/2 mss, 2662 * then set the window to 0. 2663 * [ Actually, bsd uses MSS and 1/4 of maximal _window_ ] 2664 * Otherwise, just prevent the window from shrinking 2665 * and from being larger than the largest representable value. 2666 * 2667 * This prevents incremental opening of the window in the regime 2668 * where TCP is limited by the speed of the reader side taking 2669 * data out of the TCP receive queue. It does nothing about 2670 * those cases where the window is constrained on the sender side 2671 * because the pipeline is full. 2672 * 2673 * BSD also seems to "accidentally" limit itself to windows that are a 2674 * multiple of MSS, at least until the free space gets quite small. 2675 * This would appear to be a side effect of the mbuf implementation. 2676 * Combining these two algorithms results in the observed behavior 2677 * of having a fixed window size at almost all times. 2678 * 2679 * Below we obtain similar behavior by forcing the offered window to 2680 * a multiple of the mss when it is feasible to do so. 2681 * 2682 * Note, we don't "adjust" for TIMESTAMP or SACK option bytes. 2683 * Regular options like TIMESTAMP are taken into account. 2684 */ 2685 u32 __tcp_select_window(struct sock *sk) 2686 { 2687 struct inet_connection_sock *icsk = inet_csk(sk); 2688 struct tcp_sock *tp = tcp_sk(sk); 2689 /* MSS for the peer's data. Previous versions used mss_clamp 2690 * here. I don't know if the value based on our guesses 2691 * of peer's MSS is better for the performance. It's more correct 2692 * but may be worse for the performance because of rcv_mss 2693 * fluctuations. --SAW 1998/11/1 2694 */ 2695 int mss = icsk->icsk_ack.rcv_mss; 2696 int free_space = tcp_space(sk); 2697 int allowed_space = tcp_full_space(sk); 2698 int full_space = min_t(int, tp->window_clamp, allowed_space); 2699 int window; 2700 2701 if (unlikely(mss > full_space)) { 2702 mss = full_space; 2703 if (mss <= 0) 2704 return 0; 2705 } 2706 if (free_space < (full_space >> 1)) { 2707 icsk->icsk_ack.quick = 0; 2708 2709 if (tcp_under_memory_pressure(sk)) 2710 tp->rcv_ssthresh = min(tp->rcv_ssthresh, 2711 4U * tp->advmss); 2712 2713 /* free_space might become our new window, make sure we don't 2714 * increase it due to wscale. 2715 */ 2716 free_space = round_down(free_space, 1 << tp->rx_opt.rcv_wscale); 2717 2718 /* if free space is less than mss estimate, or is below 1/16th 2719 * of the maximum allowed, try to move to zero-window, else 2720 * tcp_clamp_window() will grow rcv buf up to tcp_rmem[2], and 2721 * new incoming data is dropped due to memory limits. 2722 * With large window, mss test triggers way too late in order 2723 * to announce zero window in time before rmem limit kicks in. 2724 */ 2725 if (free_space < (allowed_space >> 4) || free_space < mss) 2726 return 0; 2727 } 2728 2729 if (free_space > tp->rcv_ssthresh) 2730 free_space = tp->rcv_ssthresh; 2731 2732 /* Don't do rounding if we are using window scaling, since the 2733 * scaled window will not line up with the MSS boundary anyway. 2734 */ 2735 if (tp->rx_opt.rcv_wscale) { 2736 window = free_space; 2737 2738 /* Advertise enough space so that it won't get scaled away. 2739 * Import case: prevent zero window announcement if 2740 * 1<<rcv_wscale > mss. 2741 */ 2742 window = ALIGN(window, (1 << tp->rx_opt.rcv_wscale)); 2743 } else { 2744 window = tp->rcv_wnd; 2745 /* Get the largest window that is a nice multiple of mss. 2746 * Window clamp already applied above. 2747 * If our current window offering is within 1 mss of the 2748 * free space we just keep it. This prevents the divide 2749 * and multiply from happening most of the time. 2750 * We also don't do any window rounding when the free space 2751 * is too small. 2752 */ 2753 if (window <= free_space - mss || window > free_space) 2754 window = rounddown(free_space, mss); 2755 else if (mss == full_space && 2756 free_space > window + (full_space >> 1)) 2757 window = free_space; 2758 } 2759 2760 return window; 2761 } 2762 2763 void tcp_skb_collapse_tstamp(struct sk_buff *skb, 2764 const struct sk_buff *next_skb) 2765 { 2766 if (unlikely(tcp_has_tx_tstamp(next_skb))) { 2767 const struct skb_shared_info *next_shinfo = 2768 skb_shinfo(next_skb); 2769 struct skb_shared_info *shinfo = skb_shinfo(skb); 2770 2771 shinfo->tx_flags |= next_shinfo->tx_flags & SKBTX_ANY_TSTAMP; 2772 shinfo->tskey = next_shinfo->tskey; 2773 TCP_SKB_CB(skb)->txstamp_ack |= 2774 TCP_SKB_CB(next_skb)->txstamp_ack; 2775 } 2776 } 2777 2778 /* Collapses two adjacent SKB's during retransmission. */ 2779 static bool tcp_collapse_retrans(struct sock *sk, struct sk_buff *skb) 2780 { 2781 struct tcp_sock *tp = tcp_sk(sk); 2782 struct sk_buff *next_skb = skb_rb_next(skb); 2783 int next_skb_size; 2784 2785 next_skb_size = next_skb->len; 2786 2787 BUG_ON(tcp_skb_pcount(skb) != 1 || tcp_skb_pcount(next_skb) != 1); 2788 2789 if (next_skb_size) { 2790 if (next_skb_size <= skb_availroom(skb)) 2791 skb_copy_bits(next_skb, 0, skb_put(skb, next_skb_size), 2792 next_skb_size); 2793 else if (!tcp_skb_shift(skb, next_skb, 1, next_skb_size)) 2794 return false; 2795 } 2796 tcp_highest_sack_replace(sk, next_skb, skb); 2797 2798 /* Update sequence range on original skb. */ 2799 TCP_SKB_CB(skb)->end_seq = TCP_SKB_CB(next_skb)->end_seq; 2800 2801 /* Merge over control information. This moves PSH/FIN etc. over */ 2802 TCP_SKB_CB(skb)->tcp_flags |= TCP_SKB_CB(next_skb)->tcp_flags; 2803 2804 /* All done, get rid of second SKB and account for it so 2805 * packet counting does not break. 2806 */ 2807 TCP_SKB_CB(skb)->sacked |= TCP_SKB_CB(next_skb)->sacked & TCPCB_EVER_RETRANS; 2808 TCP_SKB_CB(skb)->eor = TCP_SKB_CB(next_skb)->eor; 2809 2810 /* changed transmit queue under us so clear hints */ 2811 tcp_clear_retrans_hints_partial(tp); 2812 if (next_skb == tp->retransmit_skb_hint) 2813 tp->retransmit_skb_hint = skb; 2814 2815 tcp_adjust_pcount(sk, next_skb, tcp_skb_pcount(next_skb)); 2816 2817 tcp_skb_collapse_tstamp(skb, next_skb); 2818 2819 tcp_rtx_queue_unlink_and_free(next_skb, sk); 2820 return true; 2821 } 2822 2823 /* Check if coalescing SKBs is legal. */ 2824 static bool tcp_can_collapse(const struct sock *sk, const struct sk_buff *skb) 2825 { 2826 if (tcp_skb_pcount(skb) > 1) 2827 return false; 2828 if (skb_cloned(skb)) 2829 return false; 2830 /* Some heuristics for collapsing over SACK'd could be invented */ 2831 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_ACKED) 2832 return false; 2833 2834 return true; 2835 } 2836 2837 /* Collapse packets in the retransmit queue to make to create 2838 * less packets on the wire. This is only done on retransmission. 2839 */ 2840 static void tcp_retrans_try_collapse(struct sock *sk, struct sk_buff *to, 2841 int space) 2842 { 2843 struct tcp_sock *tp = tcp_sk(sk); 2844 struct sk_buff *skb = to, *tmp; 2845 bool first = true; 2846 2847 if (!sock_net(sk)->ipv4.sysctl_tcp_retrans_collapse) 2848 return; 2849 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN) 2850 return; 2851 2852 skb_rbtree_walk_from_safe(skb, tmp) { 2853 if (!tcp_can_collapse(sk, skb)) 2854 break; 2855 2856 if (!tcp_skb_can_collapse_to(to)) 2857 break; 2858 2859 space -= skb->len; 2860 2861 if (first) { 2862 first = false; 2863 continue; 2864 } 2865 2866 if (space < 0) 2867 break; 2868 2869 if (after(TCP_SKB_CB(skb)->end_seq, tcp_wnd_end(tp))) 2870 break; 2871 2872 if (!tcp_collapse_retrans(sk, to)) 2873 break; 2874 } 2875 } 2876 2877 /* This retransmits one SKB. Policy decisions and retransmit queue 2878 * state updates are done by the caller. Returns non-zero if an 2879 * error occurred which prevented the send. 2880 */ 2881 int __tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) 2882 { 2883 struct inet_connection_sock *icsk = inet_csk(sk); 2884 struct tcp_sock *tp = tcp_sk(sk); 2885 unsigned int cur_mss; 2886 int diff, len, err; 2887 2888 2889 /* Inconclusive MTU probe */ 2890 if (icsk->icsk_mtup.probe_size) 2891 icsk->icsk_mtup.probe_size = 0; 2892 2893 /* Do not sent more than we queued. 1/4 is reserved for possible 2894 * copying overhead: fragmentation, tunneling, mangling etc. 2895 */ 2896 if (refcount_read(&sk->sk_wmem_alloc) > 2897 min_t(u32, sk->sk_wmem_queued + (sk->sk_wmem_queued >> 2), 2898 sk->sk_sndbuf)) 2899 return -EAGAIN; 2900 2901 if (skb_still_in_host_queue(sk, skb)) 2902 return -EBUSY; 2903 2904 if (before(TCP_SKB_CB(skb)->seq, tp->snd_una)) { 2905 if (unlikely(before(TCP_SKB_CB(skb)->end_seq, tp->snd_una))) { 2906 WARN_ON_ONCE(1); 2907 return -EINVAL; 2908 } 2909 if (tcp_trim_head(sk, skb, tp->snd_una - TCP_SKB_CB(skb)->seq)) 2910 return -ENOMEM; 2911 } 2912 2913 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk)) 2914 return -EHOSTUNREACH; /* Routing failure or similar. */ 2915 2916 cur_mss = tcp_current_mss(sk); 2917 2918 /* If receiver has shrunk his window, and skb is out of 2919 * new window, do not retransmit it. The exception is the 2920 * case, when window is shrunk to zero. In this case 2921 * our retransmit serves as a zero window probe. 2922 */ 2923 if (!before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp)) && 2924 TCP_SKB_CB(skb)->seq != tp->snd_una) 2925 return -EAGAIN; 2926 2927 len = cur_mss * segs; 2928 if (skb->len > len) { 2929 if (tcp_fragment(sk, TCP_FRAG_IN_RTX_QUEUE, skb, len, 2930 cur_mss, GFP_ATOMIC)) 2931 return -ENOMEM; /* We'll try again later. */ 2932 } else { 2933 if (skb_unclone(skb, GFP_ATOMIC)) 2934 return -ENOMEM; 2935 2936 diff = tcp_skb_pcount(skb); 2937 tcp_set_skb_tso_segs(skb, cur_mss); 2938 diff -= tcp_skb_pcount(skb); 2939 if (diff) 2940 tcp_adjust_pcount(sk, skb, diff); 2941 if (skb->len < cur_mss) 2942 tcp_retrans_try_collapse(sk, skb, cur_mss); 2943 } 2944 2945 /* RFC3168, section 6.1.1.1. ECN fallback */ 2946 if ((TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN_ECN) == TCPHDR_SYN_ECN) 2947 tcp_ecn_clear_syn(sk, skb); 2948 2949 /* Update global and local TCP statistics. */ 2950 segs = tcp_skb_pcount(skb); 2951 TCP_ADD_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS, segs); 2952 if (TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN) 2953 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS); 2954 tp->total_retrans += segs; 2955 tp->bytes_retrans += skb->len; 2956 2957 /* make sure skb->data is aligned on arches that require it 2958 * and check if ack-trimming & collapsing extended the headroom 2959 * beyond what csum_start can cover. 2960 */ 2961 if (unlikely((NET_IP_ALIGN && ((unsigned long)skb->data & 3)) || 2962 skb_headroom(skb) >= 0xFFFF)) { 2963 struct sk_buff *nskb; 2964 2965 tcp_skb_tsorted_save(skb) { 2966 nskb = __pskb_copy(skb, MAX_TCP_HEADER, GFP_ATOMIC); 2967 err = nskb ? tcp_transmit_skb(sk, nskb, 0, GFP_ATOMIC) : 2968 -ENOBUFS; 2969 } tcp_skb_tsorted_restore(skb); 2970 2971 if (!err) { 2972 tcp_update_skb_after_send(sk, skb, tp->tcp_wstamp_ns); 2973 tcp_rate_skb_sent(sk, skb); 2974 } 2975 } else { 2976 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 2977 } 2978 2979 /* To avoid taking spuriously low RTT samples based on a timestamp 2980 * for a transmit that never happened, always mark EVER_RETRANS 2981 */ 2982 TCP_SKB_CB(skb)->sacked |= TCPCB_EVER_RETRANS; 2983 2984 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RETRANS_CB_FLAG)) 2985 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RETRANS_CB, 2986 TCP_SKB_CB(skb)->seq, segs, err); 2987 2988 if (likely(!err)) { 2989 trace_tcp_retransmit_skb(sk, skb); 2990 } else if (err != -EBUSY) { 2991 NET_ADD_STATS(sock_net(sk), LINUX_MIB_TCPRETRANSFAIL, segs); 2992 } 2993 return err; 2994 } 2995 2996 int tcp_retransmit_skb(struct sock *sk, struct sk_buff *skb, int segs) 2997 { 2998 struct tcp_sock *tp = tcp_sk(sk); 2999 int err = __tcp_retransmit_skb(sk, skb, segs); 3000 3001 if (err == 0) { 3002 #if FASTRETRANS_DEBUG > 0 3003 if (TCP_SKB_CB(skb)->sacked & TCPCB_SACKED_RETRANS) { 3004 net_dbg_ratelimited("retrans_out leaked\n"); 3005 } 3006 #endif 3007 TCP_SKB_CB(skb)->sacked |= TCPCB_RETRANS; 3008 tp->retrans_out += tcp_skb_pcount(skb); 3009 } 3010 3011 /* Save stamp of the first (attempted) retransmit. */ 3012 if (!tp->retrans_stamp) 3013 tp->retrans_stamp = tcp_skb_timestamp(skb); 3014 3015 if (tp->undo_retrans < 0) 3016 tp->undo_retrans = 0; 3017 tp->undo_retrans += tcp_skb_pcount(skb); 3018 return err; 3019 } 3020 3021 /* This gets called after a retransmit timeout, and the initially 3022 * retransmitted data is acknowledged. It tries to continue 3023 * resending the rest of the retransmit queue, until either 3024 * we've sent it all or the congestion window limit is reached. 3025 */ 3026 void tcp_xmit_retransmit_queue(struct sock *sk) 3027 { 3028 const struct inet_connection_sock *icsk = inet_csk(sk); 3029 struct sk_buff *skb, *rtx_head, *hole = NULL; 3030 struct tcp_sock *tp = tcp_sk(sk); 3031 u32 max_segs; 3032 int mib_idx; 3033 3034 if (!tp->packets_out) 3035 return; 3036 3037 rtx_head = tcp_rtx_queue_head(sk); 3038 skb = tp->retransmit_skb_hint ?: rtx_head; 3039 max_segs = tcp_tso_segs(sk, tcp_current_mss(sk)); 3040 skb_rbtree_walk_from(skb) { 3041 __u8 sacked; 3042 int segs; 3043 3044 if (tcp_pacing_check(sk)) 3045 break; 3046 3047 /* we could do better than to assign each time */ 3048 if (!hole) 3049 tp->retransmit_skb_hint = skb; 3050 3051 segs = tp->snd_cwnd - tcp_packets_in_flight(tp); 3052 if (segs <= 0) 3053 return; 3054 sacked = TCP_SKB_CB(skb)->sacked; 3055 /* In case tcp_shift_skb_data() have aggregated large skbs, 3056 * we need to make sure not sending too bigs TSO packets 3057 */ 3058 segs = min_t(int, segs, max_segs); 3059 3060 if (tp->retrans_out >= tp->lost_out) { 3061 break; 3062 } else if (!(sacked & TCPCB_LOST)) { 3063 if (!hole && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED))) 3064 hole = skb; 3065 continue; 3066 3067 } else { 3068 if (icsk->icsk_ca_state != TCP_CA_Loss) 3069 mib_idx = LINUX_MIB_TCPFASTRETRANS; 3070 else 3071 mib_idx = LINUX_MIB_TCPSLOWSTARTRETRANS; 3072 } 3073 3074 if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS)) 3075 continue; 3076 3077 if (tcp_small_queue_check(sk, skb, 1)) 3078 return; 3079 3080 if (tcp_retransmit_skb(sk, skb, segs)) 3081 return; 3082 3083 NET_ADD_STATS(sock_net(sk), mib_idx, tcp_skb_pcount(skb)); 3084 3085 if (tcp_in_cwnd_reduction(sk)) 3086 tp->prr_out += tcp_skb_pcount(skb); 3087 3088 if (skb == rtx_head && 3089 icsk->icsk_pending != ICSK_TIME_REO_TIMEOUT) 3090 tcp_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 3091 inet_csk(sk)->icsk_rto, 3092 TCP_RTO_MAX, 3093 skb); 3094 } 3095 } 3096 3097 /* We allow to exceed memory limits for FIN packets to expedite 3098 * connection tear down and (memory) recovery. 3099 * Otherwise tcp_send_fin() could be tempted to either delay FIN 3100 * or even be forced to close flow without any FIN. 3101 * In general, we want to allow one skb per socket to avoid hangs 3102 * with edge trigger epoll() 3103 */ 3104 void sk_forced_mem_schedule(struct sock *sk, int size) 3105 { 3106 int amt; 3107 3108 if (size <= sk->sk_forward_alloc) 3109 return; 3110 amt = sk_mem_pages(size); 3111 sk->sk_forward_alloc += amt * SK_MEM_QUANTUM; 3112 sk_memory_allocated_add(sk, amt); 3113 3114 if (mem_cgroup_sockets_enabled && sk->sk_memcg) 3115 mem_cgroup_charge_skmem(sk->sk_memcg, amt); 3116 } 3117 3118 /* Send a FIN. The caller locks the socket for us. 3119 * We should try to send a FIN packet really hard, but eventually give up. 3120 */ 3121 void tcp_send_fin(struct sock *sk) 3122 { 3123 struct sk_buff *skb, *tskb = tcp_write_queue_tail(sk); 3124 struct tcp_sock *tp = tcp_sk(sk); 3125 3126 /* Optimization, tack on the FIN if we have one skb in write queue and 3127 * this skb was not yet sent, or we are under memory pressure. 3128 * Note: in the latter case, FIN packet will be sent after a timeout, 3129 * as TCP stack thinks it has already been transmitted. 3130 */ 3131 if (!tskb && tcp_under_memory_pressure(sk)) 3132 tskb = skb_rb_last(&sk->tcp_rtx_queue); 3133 3134 if (tskb) { 3135 TCP_SKB_CB(tskb)->tcp_flags |= TCPHDR_FIN; 3136 TCP_SKB_CB(tskb)->end_seq++; 3137 tp->write_seq++; 3138 if (tcp_write_queue_empty(sk)) { 3139 /* This means tskb was already sent. 3140 * Pretend we included the FIN on previous transmit. 3141 * We need to set tp->snd_nxt to the value it would have 3142 * if FIN had been sent. This is because retransmit path 3143 * does not change tp->snd_nxt. 3144 */ 3145 WRITE_ONCE(tp->snd_nxt, tp->snd_nxt + 1); 3146 return; 3147 } 3148 } else { 3149 skb = alloc_skb_fclone(MAX_TCP_HEADER, sk->sk_allocation); 3150 if (unlikely(!skb)) 3151 return; 3152 3153 INIT_LIST_HEAD(&skb->tcp_tsorted_anchor); 3154 skb_reserve(skb, MAX_TCP_HEADER); 3155 sk_forced_mem_schedule(sk, skb->truesize); 3156 /* FIN eats a sequence byte, write_seq advanced by tcp_queue_skb(). */ 3157 tcp_init_nondata_skb(skb, tp->write_seq, 3158 TCPHDR_ACK | TCPHDR_FIN); 3159 tcp_queue_skb(sk, skb); 3160 } 3161 __tcp_push_pending_frames(sk, tcp_current_mss(sk), TCP_NAGLE_OFF); 3162 } 3163 3164 /* We get here when a process closes a file descriptor (either due to 3165 * an explicit close() or as a byproduct of exit()'ing) and there 3166 * was unread data in the receive queue. This behavior is recommended 3167 * by RFC 2525, section 2.17. -DaveM 3168 */ 3169 void tcp_send_active_reset(struct sock *sk, gfp_t priority) 3170 { 3171 struct sk_buff *skb; 3172 3173 TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTRSTS); 3174 3175 /* NOTE: No TCP options attached and we never retransmit this. */ 3176 skb = alloc_skb(MAX_TCP_HEADER, priority); 3177 if (!skb) { 3178 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); 3179 return; 3180 } 3181 3182 /* Reserve space for headers and prepare control bits. */ 3183 skb_reserve(skb, MAX_TCP_HEADER); 3184 tcp_init_nondata_skb(skb, tcp_acceptable_seq(sk), 3185 TCPHDR_ACK | TCPHDR_RST); 3186 tcp_mstamp_refresh(tcp_sk(sk)); 3187 /* Send it off. */ 3188 if (tcp_transmit_skb(sk, skb, 0, priority)) 3189 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTFAILED); 3190 3191 /* skb of trace_tcp_send_reset() keeps the skb that caused RST, 3192 * skb here is different to the troublesome skb, so use NULL 3193 */ 3194 trace_tcp_send_reset(sk, NULL); 3195 } 3196 3197 /* Send a crossed SYN-ACK during socket establishment. 3198 * WARNING: This routine must only be called when we have already sent 3199 * a SYN packet that crossed the incoming SYN that caused this routine 3200 * to get called. If this assumption fails then the initial rcv_wnd 3201 * and rcv_wscale values will not be correct. 3202 */ 3203 int tcp_send_synack(struct sock *sk) 3204 { 3205 struct sk_buff *skb; 3206 3207 skb = tcp_rtx_queue_head(sk); 3208 if (!skb || !(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_SYN)) { 3209 pr_err("%s: wrong queue state\n", __func__); 3210 return -EFAULT; 3211 } 3212 if (!(TCP_SKB_CB(skb)->tcp_flags & TCPHDR_ACK)) { 3213 if (skb_cloned(skb)) { 3214 struct sk_buff *nskb; 3215 3216 tcp_skb_tsorted_save(skb) { 3217 nskb = skb_copy(skb, GFP_ATOMIC); 3218 } tcp_skb_tsorted_restore(skb); 3219 if (!nskb) 3220 return -ENOMEM; 3221 INIT_LIST_HEAD(&nskb->tcp_tsorted_anchor); 3222 tcp_rtx_queue_unlink_and_free(skb, sk); 3223 __skb_header_release(nskb); 3224 tcp_rbtree_insert(&sk->tcp_rtx_queue, nskb); 3225 sk_wmem_queued_add(sk, nskb->truesize); 3226 sk_mem_charge(sk, nskb->truesize); 3227 skb = nskb; 3228 } 3229 3230 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_ACK; 3231 tcp_ecn_send_synack(sk, skb); 3232 } 3233 return tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 3234 } 3235 3236 /** 3237 * tcp_make_synack - Prepare a SYN-ACK. 3238 * sk: listener socket 3239 * dst: dst entry attached to the SYNACK 3240 * req: request_sock pointer 3241 * 3242 * Allocate one skb and build a SYNACK packet. 3243 * @dst is consumed : Caller should not use it again. 3244 */ 3245 struct sk_buff *tcp_make_synack(const struct sock *sk, struct dst_entry *dst, 3246 struct request_sock *req, 3247 struct tcp_fastopen_cookie *foc, 3248 enum tcp_synack_type synack_type) 3249 { 3250 struct inet_request_sock *ireq = inet_rsk(req); 3251 const struct tcp_sock *tp = tcp_sk(sk); 3252 struct tcp_md5sig_key *md5 = NULL; 3253 struct tcp_out_options opts; 3254 struct sk_buff *skb; 3255 int tcp_header_size; 3256 struct tcphdr *th; 3257 int mss; 3258 u64 now; 3259 3260 skb = alloc_skb(MAX_TCP_HEADER, GFP_ATOMIC); 3261 if (unlikely(!skb)) { 3262 dst_release(dst); 3263 return NULL; 3264 } 3265 /* Reserve space for headers. */ 3266 skb_reserve(skb, MAX_TCP_HEADER); 3267 3268 switch (synack_type) { 3269 case TCP_SYNACK_NORMAL: 3270 skb_set_owner_w(skb, req_to_sk(req)); 3271 break; 3272 case TCP_SYNACK_COOKIE: 3273 /* Under synflood, we do not attach skb to a socket, 3274 * to avoid false sharing. 3275 */ 3276 break; 3277 case TCP_SYNACK_FASTOPEN: 3278 /* sk is a const pointer, because we want to express multiple 3279 * cpu might call us concurrently. 3280 * sk->sk_wmem_alloc in an atomic, we can promote to rw. 3281 */ 3282 skb_set_owner_w(skb, (struct sock *)sk); 3283 break; 3284 } 3285 skb_dst_set(skb, dst); 3286 3287 mss = tcp_mss_clamp(tp, dst_metric_advmss(dst)); 3288 3289 memset(&opts, 0, sizeof(opts)); 3290 now = tcp_clock_ns(); 3291 #ifdef CONFIG_SYN_COOKIES 3292 if (unlikely(req->cookie_ts)) 3293 skb->skb_mstamp_ns = cookie_init_timestamp(req, now); 3294 else 3295 #endif 3296 { 3297 skb->skb_mstamp_ns = now; 3298 if (!tcp_rsk(req)->snt_synack) /* Timestamp first SYNACK */ 3299 tcp_rsk(req)->snt_synack = tcp_skb_timestamp_us(skb); 3300 } 3301 3302 #ifdef CONFIG_TCP_MD5SIG 3303 rcu_read_lock(); 3304 md5 = tcp_rsk(req)->af_specific->req_md5_lookup(sk, req_to_sk(req)); 3305 #endif 3306 skb_set_hash(skb, tcp_rsk(req)->txhash, PKT_HASH_TYPE_L4); 3307 tcp_header_size = tcp_synack_options(sk, req, mss, skb, &opts, md5, 3308 foc) + sizeof(*th); 3309 3310 skb_push(skb, tcp_header_size); 3311 skb_reset_transport_header(skb); 3312 3313 th = (struct tcphdr *)skb->data; 3314 memset(th, 0, sizeof(struct tcphdr)); 3315 th->syn = 1; 3316 th->ack = 1; 3317 tcp_ecn_make_synack(req, th); 3318 th->source = htons(ireq->ir_num); 3319 th->dest = ireq->ir_rmt_port; 3320 skb->mark = ireq->ir_mark; 3321 skb->ip_summed = CHECKSUM_PARTIAL; 3322 th->seq = htonl(tcp_rsk(req)->snt_isn); 3323 /* XXX data is queued and acked as is. No buffer/window check */ 3324 th->ack_seq = htonl(tcp_rsk(req)->rcv_nxt); 3325 3326 /* RFC1323: The window in SYN & SYN/ACK segments is never scaled. */ 3327 th->window = htons(min(req->rsk_rcv_wnd, 65535U)); 3328 tcp_options_write((__be32 *)(th + 1), NULL, &opts); 3329 th->doff = (tcp_header_size >> 2); 3330 __TCP_INC_STATS(sock_net(sk), TCP_MIB_OUTSEGS); 3331 3332 #ifdef CONFIG_TCP_MD5SIG 3333 /* Okay, we have all we need - do the md5 hash if needed */ 3334 if (md5) 3335 tcp_rsk(req)->af_specific->calc_md5_hash(opts.hash_location, 3336 md5, req_to_sk(req), skb); 3337 rcu_read_unlock(); 3338 #endif 3339 3340 skb->skb_mstamp_ns = now; 3341 tcp_add_tx_delay(skb, tp); 3342 3343 return skb; 3344 } 3345 EXPORT_SYMBOL(tcp_make_synack); 3346 3347 static void tcp_ca_dst_init(struct sock *sk, const struct dst_entry *dst) 3348 { 3349 struct inet_connection_sock *icsk = inet_csk(sk); 3350 const struct tcp_congestion_ops *ca; 3351 u32 ca_key = dst_metric(dst, RTAX_CC_ALGO); 3352 3353 if (ca_key == TCP_CA_UNSPEC) 3354 return; 3355 3356 rcu_read_lock(); 3357 ca = tcp_ca_find_key(ca_key); 3358 if (likely(ca && try_module_get(ca->owner))) { 3359 module_put(icsk->icsk_ca_ops->owner); 3360 icsk->icsk_ca_dst_locked = tcp_ca_dst_locked(dst); 3361 icsk->icsk_ca_ops = ca; 3362 } 3363 rcu_read_unlock(); 3364 } 3365 3366 /* Do all connect socket setups that can be done AF independent. */ 3367 static void tcp_connect_init(struct sock *sk) 3368 { 3369 const struct dst_entry *dst = __sk_dst_get(sk); 3370 struct tcp_sock *tp = tcp_sk(sk); 3371 __u8 rcv_wscale; 3372 u32 rcv_wnd; 3373 3374 /* We'll fix this up when we get a response from the other end. 3375 * See tcp_input.c:tcp_rcv_state_process case TCP_SYN_SENT. 3376 */ 3377 tp->tcp_header_len = sizeof(struct tcphdr); 3378 if (sock_net(sk)->ipv4.sysctl_tcp_timestamps) 3379 tp->tcp_header_len += TCPOLEN_TSTAMP_ALIGNED; 3380 3381 #ifdef CONFIG_TCP_MD5SIG 3382 if (tp->af_specific->md5_lookup(sk, sk)) 3383 tp->tcp_header_len += TCPOLEN_MD5SIG_ALIGNED; 3384 #endif 3385 3386 /* If user gave his TCP_MAXSEG, record it to clamp */ 3387 if (tp->rx_opt.user_mss) 3388 tp->rx_opt.mss_clamp = tp->rx_opt.user_mss; 3389 tp->max_window = 0; 3390 tcp_mtup_init(sk); 3391 tcp_sync_mss(sk, dst_mtu(dst)); 3392 3393 tcp_ca_dst_init(sk, dst); 3394 3395 if (!tp->window_clamp) 3396 tp->window_clamp = dst_metric(dst, RTAX_WINDOW); 3397 tp->advmss = tcp_mss_clamp(tp, dst_metric_advmss(dst)); 3398 3399 tcp_initialize_rcv_mss(sk); 3400 3401 /* limit the window selection if the user enforce a smaller rx buffer */ 3402 if (sk->sk_userlocks & SOCK_RCVBUF_LOCK && 3403 (tp->window_clamp > tcp_full_space(sk) || tp->window_clamp == 0)) 3404 tp->window_clamp = tcp_full_space(sk); 3405 3406 rcv_wnd = tcp_rwnd_init_bpf(sk); 3407 if (rcv_wnd == 0) 3408 rcv_wnd = dst_metric(dst, RTAX_INITRWND); 3409 3410 tcp_select_initial_window(sk, tcp_full_space(sk), 3411 tp->advmss - (tp->rx_opt.ts_recent_stamp ? tp->tcp_header_len - sizeof(struct tcphdr) : 0), 3412 &tp->rcv_wnd, 3413 &tp->window_clamp, 3414 sock_net(sk)->ipv4.sysctl_tcp_window_scaling, 3415 &rcv_wscale, 3416 rcv_wnd); 3417 3418 tp->rx_opt.rcv_wscale = rcv_wscale; 3419 tp->rcv_ssthresh = tp->rcv_wnd; 3420 3421 sk->sk_err = 0; 3422 sock_reset_flag(sk, SOCK_DONE); 3423 tp->snd_wnd = 0; 3424 tcp_init_wl(tp, 0); 3425 tcp_write_queue_purge(sk); 3426 tp->snd_una = tp->write_seq; 3427 tp->snd_sml = tp->write_seq; 3428 tp->snd_up = tp->write_seq; 3429 WRITE_ONCE(tp->snd_nxt, tp->write_seq); 3430 3431 if (likely(!tp->repair)) 3432 tp->rcv_nxt = 0; 3433 else 3434 tp->rcv_tstamp = tcp_jiffies32; 3435 tp->rcv_wup = tp->rcv_nxt; 3436 WRITE_ONCE(tp->copied_seq, tp->rcv_nxt); 3437 3438 inet_csk(sk)->icsk_rto = tcp_timeout_init(sk); 3439 inet_csk(sk)->icsk_retransmits = 0; 3440 tcp_clear_retrans(tp); 3441 } 3442 3443 static void tcp_connect_queue_skb(struct sock *sk, struct sk_buff *skb) 3444 { 3445 struct tcp_sock *tp = tcp_sk(sk); 3446 struct tcp_skb_cb *tcb = TCP_SKB_CB(skb); 3447 3448 tcb->end_seq += skb->len; 3449 __skb_header_release(skb); 3450 sk_wmem_queued_add(sk, skb->truesize); 3451 sk_mem_charge(sk, skb->truesize); 3452 WRITE_ONCE(tp->write_seq, tcb->end_seq); 3453 tp->packets_out += tcp_skb_pcount(skb); 3454 } 3455 3456 /* Build and send a SYN with data and (cached) Fast Open cookie. However, 3457 * queue a data-only packet after the regular SYN, such that regular SYNs 3458 * are retransmitted on timeouts. Also if the remote SYN-ACK acknowledges 3459 * only the SYN sequence, the data are retransmitted in the first ACK. 3460 * If cookie is not cached or other error occurs, falls back to send a 3461 * regular SYN with Fast Open cookie request option. 3462 */ 3463 static int tcp_send_syn_data(struct sock *sk, struct sk_buff *syn) 3464 { 3465 struct tcp_sock *tp = tcp_sk(sk); 3466 struct tcp_fastopen_request *fo = tp->fastopen_req; 3467 int space, err = 0; 3468 struct sk_buff *syn_data; 3469 3470 tp->rx_opt.mss_clamp = tp->advmss; /* If MSS is not cached */ 3471 if (!tcp_fastopen_cookie_check(sk, &tp->rx_opt.mss_clamp, &fo->cookie)) 3472 goto fallback; 3473 3474 /* MSS for SYN-data is based on cached MSS and bounded by PMTU and 3475 * user-MSS. Reserve maximum option space for middleboxes that add 3476 * private TCP options. The cost is reduced data space in SYN :( 3477 */ 3478 tp->rx_opt.mss_clamp = tcp_mss_clamp(tp, tp->rx_opt.mss_clamp); 3479 3480 space = __tcp_mtu_to_mss(sk, inet_csk(sk)->icsk_pmtu_cookie) - 3481 MAX_TCP_OPTION_SPACE; 3482 3483 space = min_t(size_t, space, fo->size); 3484 3485 /* limit to order-0 allocations */ 3486 space = min_t(size_t, space, SKB_MAX_HEAD(MAX_TCP_HEADER)); 3487 3488 syn_data = sk_stream_alloc_skb(sk, space, sk->sk_allocation, false); 3489 if (!syn_data) 3490 goto fallback; 3491 syn_data->ip_summed = CHECKSUM_PARTIAL; 3492 memcpy(syn_data->cb, syn->cb, sizeof(syn->cb)); 3493 if (space) { 3494 int copied = copy_from_iter(skb_put(syn_data, space), space, 3495 &fo->data->msg_iter); 3496 if (unlikely(!copied)) { 3497 tcp_skb_tsorted_anchor_cleanup(syn_data); 3498 kfree_skb(syn_data); 3499 goto fallback; 3500 } 3501 if (copied != space) { 3502 skb_trim(syn_data, copied); 3503 space = copied; 3504 } 3505 skb_zcopy_set(syn_data, fo->uarg, NULL); 3506 } 3507 /* No more data pending in inet_wait_for_connect() */ 3508 if (space == fo->size) 3509 fo->data = NULL; 3510 fo->copied = space; 3511 3512 tcp_connect_queue_skb(sk, syn_data); 3513 if (syn_data->len) 3514 tcp_chrono_start(sk, TCP_CHRONO_BUSY); 3515 3516 err = tcp_transmit_skb(sk, syn_data, 1, sk->sk_allocation); 3517 3518 syn->skb_mstamp_ns = syn_data->skb_mstamp_ns; 3519 3520 /* Now full SYN+DATA was cloned and sent (or not), 3521 * remove the SYN from the original skb (syn_data) 3522 * we keep in write queue in case of a retransmit, as we 3523 * also have the SYN packet (with no data) in the same queue. 3524 */ 3525 TCP_SKB_CB(syn_data)->seq++; 3526 TCP_SKB_CB(syn_data)->tcp_flags = TCPHDR_ACK | TCPHDR_PSH; 3527 if (!err) { 3528 tp->syn_data = (fo->copied > 0); 3529 tcp_rbtree_insert(&sk->tcp_rtx_queue, syn_data); 3530 NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPORIGDATASENT); 3531 goto done; 3532 } 3533 3534 /* data was not sent, put it in write_queue */ 3535 __skb_queue_tail(&sk->sk_write_queue, syn_data); 3536 tp->packets_out -= tcp_skb_pcount(syn_data); 3537 3538 fallback: 3539 /* Send a regular SYN with Fast Open cookie request option */ 3540 if (fo->cookie.len > 0) 3541 fo->cookie.len = 0; 3542 err = tcp_transmit_skb(sk, syn, 1, sk->sk_allocation); 3543 if (err) 3544 tp->syn_fastopen = 0; 3545 done: 3546 fo->cookie.len = -1; /* Exclude Fast Open option for SYN retries */ 3547 return err; 3548 } 3549 3550 /* Build a SYN and send it off. */ 3551 int tcp_connect(struct sock *sk) 3552 { 3553 struct tcp_sock *tp = tcp_sk(sk); 3554 struct sk_buff *buff; 3555 int err; 3556 3557 tcp_call_bpf(sk, BPF_SOCK_OPS_TCP_CONNECT_CB, 0, NULL); 3558 3559 if (inet_csk(sk)->icsk_af_ops->rebuild_header(sk)) 3560 return -EHOSTUNREACH; /* Routing failure or similar. */ 3561 3562 tcp_connect_init(sk); 3563 3564 if (unlikely(tp->repair)) { 3565 tcp_finish_connect(sk, NULL); 3566 return 0; 3567 } 3568 3569 buff = sk_stream_alloc_skb(sk, 0, sk->sk_allocation, true); 3570 if (unlikely(!buff)) 3571 return -ENOBUFS; 3572 3573 tcp_init_nondata_skb(buff, tp->write_seq++, TCPHDR_SYN); 3574 tcp_mstamp_refresh(tp); 3575 tp->retrans_stamp = tcp_time_stamp(tp); 3576 tcp_connect_queue_skb(sk, buff); 3577 tcp_ecn_send_syn(sk, buff); 3578 tcp_rbtree_insert(&sk->tcp_rtx_queue, buff); 3579 3580 /* Send off SYN; include data in Fast Open. */ 3581 err = tp->fastopen_req ? tcp_send_syn_data(sk, buff) : 3582 tcp_transmit_skb(sk, buff, 1, sk->sk_allocation); 3583 if (err == -ECONNREFUSED) 3584 return err; 3585 3586 /* We change tp->snd_nxt after the tcp_transmit_skb() call 3587 * in order to make this packet get counted in tcpOutSegs. 3588 */ 3589 WRITE_ONCE(tp->snd_nxt, tp->write_seq); 3590 tp->pushed_seq = tp->write_seq; 3591 buff = tcp_send_head(sk); 3592 if (unlikely(buff)) { 3593 WRITE_ONCE(tp->snd_nxt, TCP_SKB_CB(buff)->seq); 3594 tp->pushed_seq = TCP_SKB_CB(buff)->seq; 3595 } 3596 TCP_INC_STATS(sock_net(sk), TCP_MIB_ACTIVEOPENS); 3597 3598 /* Timer for repeating the SYN until an answer. */ 3599 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 3600 inet_csk(sk)->icsk_rto, TCP_RTO_MAX); 3601 return 0; 3602 } 3603 EXPORT_SYMBOL(tcp_connect); 3604 3605 /* Send out a delayed ack, the caller does the policy checking 3606 * to see if we should even be here. See tcp_input.c:tcp_ack_snd_check() 3607 * for details. 3608 */ 3609 void tcp_send_delayed_ack(struct sock *sk) 3610 { 3611 struct inet_connection_sock *icsk = inet_csk(sk); 3612 int ato = icsk->icsk_ack.ato; 3613 unsigned long timeout; 3614 3615 if (ato > TCP_DELACK_MIN) { 3616 const struct tcp_sock *tp = tcp_sk(sk); 3617 int max_ato = HZ / 2; 3618 3619 if (inet_csk_in_pingpong_mode(sk) || 3620 (icsk->icsk_ack.pending & ICSK_ACK_PUSHED)) 3621 max_ato = TCP_DELACK_MAX; 3622 3623 /* Slow path, intersegment interval is "high". */ 3624 3625 /* If some rtt estimate is known, use it to bound delayed ack. 3626 * Do not use inet_csk(sk)->icsk_rto here, use results of rtt measurements 3627 * directly. 3628 */ 3629 if (tp->srtt_us) { 3630 int rtt = max_t(int, usecs_to_jiffies(tp->srtt_us >> 3), 3631 TCP_DELACK_MIN); 3632 3633 if (rtt < max_ato) 3634 max_ato = rtt; 3635 } 3636 3637 ato = min(ato, max_ato); 3638 } 3639 3640 /* Stay within the limit we were given */ 3641 timeout = jiffies + ato; 3642 3643 /* Use new timeout only if there wasn't a older one earlier. */ 3644 if (icsk->icsk_ack.pending & ICSK_ACK_TIMER) { 3645 /* If delack timer was blocked or is about to expire, 3646 * send ACK now. 3647 */ 3648 if (icsk->icsk_ack.blocked || 3649 time_before_eq(icsk->icsk_ack.timeout, jiffies + (ato >> 2))) { 3650 tcp_send_ack(sk); 3651 return; 3652 } 3653 3654 if (!time_before(timeout, icsk->icsk_ack.timeout)) 3655 timeout = icsk->icsk_ack.timeout; 3656 } 3657 icsk->icsk_ack.pending |= ICSK_ACK_SCHED | ICSK_ACK_TIMER; 3658 icsk->icsk_ack.timeout = timeout; 3659 sk_reset_timer(sk, &icsk->icsk_delack_timer, timeout); 3660 } 3661 3662 /* This routine sends an ack and also updates the window. */ 3663 void __tcp_send_ack(struct sock *sk, u32 rcv_nxt) 3664 { 3665 struct sk_buff *buff; 3666 3667 /* If we have been reset, we may not send again. */ 3668 if (sk->sk_state == TCP_CLOSE) 3669 return; 3670 3671 /* We are not putting this on the write queue, so 3672 * tcp_transmit_skb() will set the ownership to this 3673 * sock. 3674 */ 3675 buff = alloc_skb(MAX_TCP_HEADER, 3676 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN)); 3677 if (unlikely(!buff)) { 3678 inet_csk_schedule_ack(sk); 3679 inet_csk(sk)->icsk_ack.ato = TCP_ATO_MIN; 3680 inet_csk_reset_xmit_timer(sk, ICSK_TIME_DACK, 3681 TCP_DELACK_MAX, TCP_RTO_MAX); 3682 return; 3683 } 3684 3685 /* Reserve space for headers and prepare control bits. */ 3686 skb_reserve(buff, MAX_TCP_HEADER); 3687 tcp_init_nondata_skb(buff, tcp_acceptable_seq(sk), TCPHDR_ACK); 3688 3689 /* We do not want pure acks influencing TCP Small Queues or fq/pacing 3690 * too much. 3691 * SKB_TRUESIZE(max(1 .. 66, MAX_TCP_HEADER)) is unfortunately ~784 3692 */ 3693 skb_set_tcp_pure_ack(buff); 3694 3695 /* Send it off, this clears delayed acks for us. */ 3696 __tcp_transmit_skb(sk, buff, 0, (__force gfp_t)0, rcv_nxt); 3697 } 3698 EXPORT_SYMBOL_GPL(__tcp_send_ack); 3699 3700 void tcp_send_ack(struct sock *sk) 3701 { 3702 __tcp_send_ack(sk, tcp_sk(sk)->rcv_nxt); 3703 } 3704 3705 /* This routine sends a packet with an out of date sequence 3706 * number. It assumes the other end will try to ack it. 3707 * 3708 * Question: what should we make while urgent mode? 3709 * 4.4BSD forces sending single byte of data. We cannot send 3710 * out of window data, because we have SND.NXT==SND.MAX... 3711 * 3712 * Current solution: to send TWO zero-length segments in urgent mode: 3713 * one is with SEG.SEQ=SND.UNA to deliver urgent pointer, another is 3714 * out-of-date with SND.UNA-1 to probe window. 3715 */ 3716 static int tcp_xmit_probe_skb(struct sock *sk, int urgent, int mib) 3717 { 3718 struct tcp_sock *tp = tcp_sk(sk); 3719 struct sk_buff *skb; 3720 3721 /* We don't queue it, tcp_transmit_skb() sets ownership. */ 3722 skb = alloc_skb(MAX_TCP_HEADER, 3723 sk_gfp_mask(sk, GFP_ATOMIC | __GFP_NOWARN)); 3724 if (!skb) 3725 return -1; 3726 3727 /* Reserve space for headers and set control bits. */ 3728 skb_reserve(skb, MAX_TCP_HEADER); 3729 /* Use a previous sequence. This should cause the other 3730 * end to send an ack. Don't queue or clone SKB, just 3731 * send it. 3732 */ 3733 tcp_init_nondata_skb(skb, tp->snd_una - !urgent, TCPHDR_ACK); 3734 NET_INC_STATS(sock_net(sk), mib); 3735 return tcp_transmit_skb(sk, skb, 0, (__force gfp_t)0); 3736 } 3737 3738 /* Called from setsockopt( ... TCP_REPAIR ) */ 3739 void tcp_send_window_probe(struct sock *sk) 3740 { 3741 if (sk->sk_state == TCP_ESTABLISHED) { 3742 tcp_sk(sk)->snd_wl1 = tcp_sk(sk)->rcv_nxt - 1; 3743 tcp_mstamp_refresh(tcp_sk(sk)); 3744 tcp_xmit_probe_skb(sk, 0, LINUX_MIB_TCPWINPROBE); 3745 } 3746 } 3747 3748 /* Initiate keepalive or window probe from timer. */ 3749 int tcp_write_wakeup(struct sock *sk, int mib) 3750 { 3751 struct tcp_sock *tp = tcp_sk(sk); 3752 struct sk_buff *skb; 3753 3754 if (sk->sk_state == TCP_CLOSE) 3755 return -1; 3756 3757 skb = tcp_send_head(sk); 3758 if (skb && before(TCP_SKB_CB(skb)->seq, tcp_wnd_end(tp))) { 3759 int err; 3760 unsigned int mss = tcp_current_mss(sk); 3761 unsigned int seg_size = tcp_wnd_end(tp) - TCP_SKB_CB(skb)->seq; 3762 3763 if (before(tp->pushed_seq, TCP_SKB_CB(skb)->end_seq)) 3764 tp->pushed_seq = TCP_SKB_CB(skb)->end_seq; 3765 3766 /* We are probing the opening of a window 3767 * but the window size is != 0 3768 * must have been a result SWS avoidance ( sender ) 3769 */ 3770 if (seg_size < TCP_SKB_CB(skb)->end_seq - TCP_SKB_CB(skb)->seq || 3771 skb->len > mss) { 3772 seg_size = min(seg_size, mss); 3773 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH; 3774 if (tcp_fragment(sk, TCP_FRAG_IN_WRITE_QUEUE, 3775 skb, seg_size, mss, GFP_ATOMIC)) 3776 return -1; 3777 } else if (!tcp_skb_pcount(skb)) 3778 tcp_set_skb_tso_segs(skb, mss); 3779 3780 TCP_SKB_CB(skb)->tcp_flags |= TCPHDR_PSH; 3781 err = tcp_transmit_skb(sk, skb, 1, GFP_ATOMIC); 3782 if (!err) 3783 tcp_event_new_data_sent(sk, skb); 3784 return err; 3785 } else { 3786 if (between(tp->snd_up, tp->snd_una + 1, tp->snd_una + 0xFFFF)) 3787 tcp_xmit_probe_skb(sk, 1, mib); 3788 return tcp_xmit_probe_skb(sk, 0, mib); 3789 } 3790 } 3791 3792 /* A window probe timeout has occurred. If window is not closed send 3793 * a partial packet else a zero probe. 3794 */ 3795 void tcp_send_probe0(struct sock *sk) 3796 { 3797 struct inet_connection_sock *icsk = inet_csk(sk); 3798 struct tcp_sock *tp = tcp_sk(sk); 3799 struct net *net = sock_net(sk); 3800 unsigned long timeout; 3801 int err; 3802 3803 err = tcp_write_wakeup(sk, LINUX_MIB_TCPWINPROBE); 3804 3805 if (tp->packets_out || tcp_write_queue_empty(sk)) { 3806 /* Cancel probe timer, if it is not required. */ 3807 icsk->icsk_probes_out = 0; 3808 icsk->icsk_backoff = 0; 3809 return; 3810 } 3811 3812 icsk->icsk_probes_out++; 3813 if (err <= 0) { 3814 if (icsk->icsk_backoff < net->ipv4.sysctl_tcp_retries2) 3815 icsk->icsk_backoff++; 3816 timeout = tcp_probe0_when(sk, TCP_RTO_MAX); 3817 } else { 3818 /* If packet was not sent due to local congestion, 3819 * Let senders fight for local resources conservatively. 3820 */ 3821 timeout = TCP_RESOURCE_PROBE_INTERVAL; 3822 } 3823 tcp_reset_xmit_timer(sk, ICSK_TIME_PROBE0, timeout, TCP_RTO_MAX, NULL); 3824 } 3825 3826 int tcp_rtx_synack(const struct sock *sk, struct request_sock *req) 3827 { 3828 const struct tcp_request_sock_ops *af_ops = tcp_rsk(req)->af_specific; 3829 struct flowi fl; 3830 int res; 3831 3832 tcp_rsk(req)->txhash = net_tx_rndhash(); 3833 res = af_ops->send_synack(sk, NULL, &fl, req, NULL, TCP_SYNACK_NORMAL); 3834 if (!res) { 3835 __TCP_INC_STATS(sock_net(sk), TCP_MIB_RETRANSSEGS); 3836 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNRETRANS); 3837 if (unlikely(tcp_passive_fastopen(sk))) 3838 tcp_sk(sk)->total_retrans++; 3839 trace_tcp_retransmit_synack(sk, req); 3840 } 3841 return res; 3842 } 3843 EXPORT_SYMBOL(tcp_rtx_synack); 3844