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 #include <linux/module.h> 23 #include <linux/gfp.h> 24 #include <net/tcp.h> 25 #include <net/rstreason.h> 26 tcp_clamp_rto_to_user_timeout(const struct sock * sk)27 static u32 tcp_clamp_rto_to_user_timeout(const struct sock *sk) 28 { 29 const struct inet_connection_sock *icsk = inet_csk(sk); 30 const struct tcp_sock *tp = tcp_sk(sk); 31 u32 elapsed, user_timeout; 32 s32 remaining; 33 34 user_timeout = READ_ONCE(icsk->icsk_user_timeout); 35 if (!user_timeout) 36 return icsk->icsk_rto; 37 38 elapsed = tcp_time_stamp_ts(tp) - tp->retrans_stamp; 39 if (tp->tcp_usec_ts) 40 elapsed /= USEC_PER_MSEC; 41 42 remaining = user_timeout - elapsed; 43 if (remaining <= 0) 44 return 1; /* user timeout has passed; fire ASAP */ 45 46 return min_t(u32, icsk->icsk_rto, msecs_to_jiffies(remaining)); 47 } 48 tcp_clamp_probe0_to_user_timeout(const struct sock * sk,u32 when)49 u32 tcp_clamp_probe0_to_user_timeout(const struct sock *sk, u32 when) 50 { 51 const struct inet_connection_sock *icsk = inet_csk(sk); 52 u32 remaining, user_timeout; 53 s32 elapsed; 54 55 user_timeout = READ_ONCE(icsk->icsk_user_timeout); 56 if (!user_timeout || !icsk->icsk_probes_tstamp) 57 return when; 58 59 elapsed = tcp_jiffies32 - icsk->icsk_probes_tstamp; 60 if (unlikely(elapsed < 0)) 61 elapsed = 0; 62 remaining = msecs_to_jiffies(user_timeout) - elapsed; 63 remaining = max_t(u32, remaining, TCP_TIMEOUT_MIN); 64 65 return min_t(u32, remaining, when); 66 } 67 68 /** 69 * tcp_write_err() - close socket and save error info 70 * @sk: The socket the error has appeared on. 71 * 72 * Returns: Nothing (void) 73 */ 74 tcp_write_err(struct sock * sk)75 static void tcp_write_err(struct sock *sk) 76 { 77 tcp_done_with_error(sk, READ_ONCE(sk->sk_err_soft) ? : ETIMEDOUT); 78 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONTIMEOUT); 79 } 80 81 /** 82 * tcp_out_of_resources() - Close socket if out of resources 83 * @sk: pointer to current socket 84 * @do_reset: send a last packet with reset flag 85 * 86 * Do not allow orphaned sockets to eat all our resources. 87 * This is direct violation of TCP specs, but it is required 88 * to prevent DoS attacks. It is called when a retransmission timeout 89 * or zero probe timeout occurs on orphaned socket. 90 * 91 * Also close if our net namespace is exiting; in that case there is no 92 * hope of ever communicating again since all netns interfaces are already 93 * down (or about to be down), and we need to release our dst references, 94 * which have been moved to the netns loopback interface, so the namespace 95 * can finish exiting. This condition is only possible if we are a kernel 96 * socket, as those do not hold references to the namespace. 97 * 98 * Criteria is still not confirmed experimentally and may change. 99 * We kill the socket, if: 100 * 1. If number of orphaned sockets exceeds an administratively configured 101 * limit. 102 * 2. If we have strong memory pressure. 103 * 3. If our net namespace is exiting. 104 */ tcp_out_of_resources(struct sock * sk,bool do_reset)105 static int tcp_out_of_resources(struct sock *sk, bool do_reset) 106 { 107 struct tcp_sock *tp = tcp_sk(sk); 108 int shift = 0; 109 110 /* If peer does not open window for long time, or did not transmit 111 * anything for long time, penalize it. */ 112 if ((s32)(tcp_jiffies32 - tp->lsndtime) > 2*TCP_RTO_MAX || !do_reset) 113 shift++; 114 115 /* If some dubious ICMP arrived, penalize even more. */ 116 if (READ_ONCE(sk->sk_err_soft)) 117 shift++; 118 119 if (tcp_check_oom(sk, shift)) { 120 /* Catch exceptional cases, when connection requires reset. 121 * 1. Last segment was sent recently. */ 122 if ((s32)(tcp_jiffies32 - tp->lsndtime) <= TCP_TIMEWAIT_LEN || 123 /* 2. Window is closed. */ 124 (!tp->snd_wnd && !tp->packets_out)) 125 do_reset = true; 126 if (do_reset) 127 tcp_send_active_reset(sk, GFP_ATOMIC, 128 SK_RST_REASON_TCP_ABORT_ON_MEMORY); 129 tcp_done(sk); 130 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPABORTONMEMORY); 131 return 1; 132 } 133 134 if (!check_net(sock_net(sk))) { 135 /* Not possible to send reset; just close */ 136 tcp_done(sk); 137 return 1; 138 } 139 140 return 0; 141 } 142 143 /** 144 * tcp_orphan_retries() - Returns maximal number of retries on an orphaned socket 145 * @sk: Pointer to the current socket. 146 * @alive: bool, socket alive state 147 */ tcp_orphan_retries(struct sock * sk,bool alive)148 static int tcp_orphan_retries(struct sock *sk, bool alive) 149 { 150 int retries = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_orphan_retries); /* May be zero. */ 151 152 /* We know from an ICMP that something is wrong. */ 153 if (READ_ONCE(sk->sk_err_soft) && !alive) 154 retries = 0; 155 156 /* However, if socket sent something recently, select some safe 157 * number of retries. 8 corresponds to >100 seconds with minimal 158 * RTO of 200msec. */ 159 if (retries == 0 && alive) 160 retries = 8; 161 return retries; 162 } 163 tcp_mtu_probing(struct inet_connection_sock * icsk,struct sock * sk)164 static void tcp_mtu_probing(struct inet_connection_sock *icsk, struct sock *sk) 165 { 166 const struct net *net = sock_net(sk); 167 int mss; 168 169 /* Black hole detection */ 170 if (!READ_ONCE(net->ipv4.sysctl_tcp_mtu_probing)) 171 return; 172 173 if (!icsk->icsk_mtup.enabled) { 174 icsk->icsk_mtup.enabled = 1; 175 icsk->icsk_mtup.probe_timestamp = tcp_jiffies32; 176 } else { 177 mss = tcp_mtu_to_mss(sk, icsk->icsk_mtup.search_low) >> 1; 178 mss = min(READ_ONCE(net->ipv4.sysctl_tcp_base_mss), mss); 179 mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_mtu_probe_floor)); 180 mss = max(mss, READ_ONCE(net->ipv4.sysctl_tcp_min_snd_mss)); 181 icsk->icsk_mtup.search_low = tcp_mss_to_mtu(sk, mss); 182 } 183 tcp_sync_mss(sk, icsk->icsk_pmtu_cookie); 184 } 185 tcp_model_timeout(struct sock * sk,unsigned int boundary,unsigned int rto_base)186 static unsigned int tcp_model_timeout(struct sock *sk, 187 unsigned int boundary, 188 unsigned int rto_base) 189 { 190 unsigned int linear_backoff_thresh, timeout; 191 192 linear_backoff_thresh = ilog2(TCP_RTO_MAX / rto_base); 193 if (boundary <= linear_backoff_thresh) 194 timeout = ((2 << boundary) - 1) * rto_base; 195 else 196 timeout = ((2 << linear_backoff_thresh) - 1) * rto_base + 197 (boundary - linear_backoff_thresh) * TCP_RTO_MAX; 198 return jiffies_to_msecs(timeout); 199 } 200 /** 201 * retransmits_timed_out() - returns true if this connection has timed out 202 * @sk: The current socket 203 * @boundary: max number of retransmissions 204 * @timeout: A custom timeout value. 205 * If set to 0 the default timeout is calculated and used. 206 * Using TCP_RTO_MIN and the number of unsuccessful retransmits. 207 * 208 * The default "timeout" value this function can calculate and use 209 * is equivalent to the timeout of a TCP Connection 210 * after "boundary" unsuccessful, exponentially backed-off 211 * retransmissions with an initial RTO of TCP_RTO_MIN. 212 */ retransmits_timed_out(struct sock * sk,unsigned int boundary,unsigned int timeout)213 static bool retransmits_timed_out(struct sock *sk, 214 unsigned int boundary, 215 unsigned int timeout) 216 { 217 struct tcp_sock *tp = tcp_sk(sk); 218 unsigned int start_ts, delta; 219 220 if (!inet_csk(sk)->icsk_retransmits) 221 return false; 222 223 start_ts = tp->retrans_stamp; 224 if (likely(timeout == 0)) { 225 unsigned int rto_base = TCP_RTO_MIN; 226 227 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) 228 rto_base = tcp_timeout_init(sk); 229 timeout = tcp_model_timeout(sk, boundary, rto_base); 230 } 231 232 if (tp->tcp_usec_ts) { 233 /* delta maybe off up to a jiffy due to timer granularity. */ 234 delta = tp->tcp_mstamp - start_ts + jiffies_to_usecs(1); 235 return (s32)(delta - timeout * USEC_PER_MSEC) >= 0; 236 } 237 return (s32)(tcp_time_stamp_ts(tp) - start_ts - timeout) >= 0; 238 } 239 240 /* A write timeout has occurred. Process the after effects. */ tcp_write_timeout(struct sock * sk)241 static int tcp_write_timeout(struct sock *sk) 242 { 243 struct inet_connection_sock *icsk = inet_csk(sk); 244 struct tcp_sock *tp = tcp_sk(sk); 245 struct net *net = sock_net(sk); 246 bool expired = false, do_reset; 247 int retry_until, max_retransmits; 248 249 if ((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV)) { 250 if (icsk->icsk_retransmits) 251 __dst_negative_advice(sk); 252 /* Paired with WRITE_ONCE() in tcp_sock_set_syncnt() */ 253 retry_until = READ_ONCE(icsk->icsk_syn_retries) ? : 254 READ_ONCE(net->ipv4.sysctl_tcp_syn_retries); 255 256 max_retransmits = retry_until; 257 if (sk->sk_state == TCP_SYN_SENT) 258 max_retransmits += READ_ONCE(net->ipv4.sysctl_tcp_syn_linear_timeouts); 259 260 expired = icsk->icsk_retransmits >= max_retransmits; 261 } else { 262 if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1), 0)) { 263 /* Black hole detection */ 264 tcp_mtu_probing(icsk, sk); 265 266 __dst_negative_advice(sk); 267 } 268 269 retry_until = READ_ONCE(net->ipv4.sysctl_tcp_retries2); 270 if (sock_flag(sk, SOCK_DEAD)) { 271 const bool alive = icsk->icsk_rto < TCP_RTO_MAX; 272 273 retry_until = tcp_orphan_retries(sk, alive); 274 do_reset = alive || 275 !retransmits_timed_out(sk, retry_until, 0); 276 277 if (tcp_out_of_resources(sk, do_reset)) 278 return 1; 279 } 280 } 281 if (!expired) 282 expired = retransmits_timed_out(sk, retry_until, 283 READ_ONCE(icsk->icsk_user_timeout)); 284 tcp_fastopen_active_detect_blackhole(sk, expired); 285 mptcp_active_detect_blackhole(sk, expired); 286 287 if (BPF_SOCK_OPS_TEST_FLAG(tp, BPF_SOCK_OPS_RTO_CB_FLAG)) 288 tcp_call_bpf_3arg(sk, BPF_SOCK_OPS_RTO_CB, 289 icsk->icsk_retransmits, 290 icsk->icsk_rto, (int)expired); 291 292 if (expired) { 293 /* Has it gone just too far? */ 294 tcp_write_err(sk); 295 return 1; 296 } 297 298 if (sk_rethink_txhash(sk)) { 299 tp->timeout_rehash++; 300 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTREHASH); 301 } 302 303 return 0; 304 } 305 306 /* Called with BH disabled */ tcp_delack_timer_handler(struct sock * sk)307 void tcp_delack_timer_handler(struct sock *sk) 308 { 309 struct inet_connection_sock *icsk = inet_csk(sk); 310 struct tcp_sock *tp = tcp_sk(sk); 311 312 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) 313 return; 314 315 /* Handling the sack compression case */ 316 if (tp->compressed_ack) { 317 tcp_mstamp_refresh(tp); 318 tcp_sack_compress_send_ack(sk); 319 return; 320 } 321 322 if (!(icsk->icsk_ack.pending & ICSK_ACK_TIMER)) 323 return; 324 325 if (time_after(icsk->icsk_ack.timeout, jiffies)) { 326 sk_reset_timer(sk, &icsk->icsk_delack_timer, icsk->icsk_ack.timeout); 327 return; 328 } 329 icsk->icsk_ack.pending &= ~ICSK_ACK_TIMER; 330 331 if (inet_csk_ack_scheduled(sk)) { 332 if (!inet_csk_in_pingpong_mode(sk)) { 333 /* Delayed ACK missed: inflate ATO. */ 334 icsk->icsk_ack.ato = min_t(u32, icsk->icsk_ack.ato << 1, icsk->icsk_rto); 335 } else { 336 /* Delayed ACK missed: leave pingpong mode and 337 * deflate ATO. 338 */ 339 inet_csk_exit_pingpong_mode(sk); 340 icsk->icsk_ack.ato = TCP_ATO_MIN; 341 } 342 tcp_mstamp_refresh(tp); 343 tcp_send_ack(sk); 344 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKS); 345 } 346 } 347 348 349 /** 350 * tcp_delack_timer() - The TCP delayed ACK timeout handler 351 * @t: Pointer to the timer. (gets casted to struct sock *) 352 * 353 * This function gets (indirectly) called when the kernel timer for a TCP packet 354 * of this socket expires. Calls tcp_delack_timer_handler() to do the actual work. 355 * 356 * Returns: Nothing (void) 357 */ tcp_delack_timer(struct timer_list * t)358 static void tcp_delack_timer(struct timer_list *t) 359 { 360 struct inet_connection_sock *icsk = 361 from_timer(icsk, t, icsk_delack_timer); 362 struct sock *sk = &icsk->icsk_inet.sk; 363 364 bh_lock_sock(sk); 365 if (!sock_owned_by_user(sk)) { 366 tcp_delack_timer_handler(sk); 367 } else { 368 __NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOCKED); 369 /* deleguate our work to tcp_release_cb() */ 370 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, &sk->sk_tsq_flags)) 371 sock_hold(sk); 372 } 373 bh_unlock_sock(sk); 374 sock_put(sk); 375 } 376 tcp_probe_timer(struct sock * sk)377 static void tcp_probe_timer(struct sock *sk) 378 { 379 struct inet_connection_sock *icsk = inet_csk(sk); 380 struct sk_buff *skb = tcp_send_head(sk); 381 struct tcp_sock *tp = tcp_sk(sk); 382 int max_probes; 383 384 if (tp->packets_out || !skb) { 385 icsk->icsk_probes_out = 0; 386 icsk->icsk_probes_tstamp = 0; 387 return; 388 } 389 390 /* RFC 1122 4.2.2.17 requires the sender to stay open indefinitely as 391 * long as the receiver continues to respond probes. We support this by 392 * default and reset icsk_probes_out with incoming ACKs. But if the 393 * socket is orphaned or the user specifies TCP_USER_TIMEOUT, we 394 * kill the socket when the retry count and the time exceeds the 395 * corresponding system limit. We also implement similar policy when 396 * we use RTO to probe window in tcp_retransmit_timer(). 397 */ 398 if (!icsk->icsk_probes_tstamp) { 399 icsk->icsk_probes_tstamp = tcp_jiffies32; 400 } else { 401 u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout); 402 403 if (user_timeout && 404 (s32)(tcp_jiffies32 - icsk->icsk_probes_tstamp) >= 405 msecs_to_jiffies(user_timeout)) 406 goto abort; 407 } 408 max_probes = READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_retries2); 409 if (sock_flag(sk, SOCK_DEAD)) { 410 const bool alive = inet_csk_rto_backoff(icsk, TCP_RTO_MAX) < TCP_RTO_MAX; 411 412 max_probes = tcp_orphan_retries(sk, alive); 413 if (!alive && icsk->icsk_backoff >= max_probes) 414 goto abort; 415 if (tcp_out_of_resources(sk, true)) 416 return; 417 } 418 419 if (icsk->icsk_probes_out >= max_probes) { 420 abort: tcp_write_err(sk); 421 } else { 422 /* Only send another probe if we didn't close things up. */ 423 tcp_send_probe0(sk); 424 } 425 } 426 tcp_update_rto_stats(struct sock * sk)427 static void tcp_update_rto_stats(struct sock *sk) 428 { 429 struct inet_connection_sock *icsk = inet_csk(sk); 430 struct tcp_sock *tp = tcp_sk(sk); 431 432 if (!icsk->icsk_retransmits) { 433 tp->total_rto_recoveries++; 434 tp->rto_stamp = tcp_time_stamp_ms(tp); 435 } 436 icsk->icsk_retransmits++; 437 tp->total_rto++; 438 } 439 440 /* 441 * Timer for Fast Open socket to retransmit SYNACK. Note that the 442 * sk here is the child socket, not the parent (listener) socket. 443 */ tcp_fastopen_synack_timer(struct sock * sk,struct request_sock * req)444 static void tcp_fastopen_synack_timer(struct sock *sk, struct request_sock *req) 445 { 446 struct inet_connection_sock *icsk = inet_csk(sk); 447 struct tcp_sock *tp = tcp_sk(sk); 448 int max_retries; 449 450 req->rsk_ops->syn_ack_timeout(req); 451 452 /* Add one more retry for fastopen. 453 * Paired with WRITE_ONCE() in tcp_sock_set_syncnt() 454 */ 455 max_retries = READ_ONCE(icsk->icsk_syn_retries) ? : 456 READ_ONCE(sock_net(sk)->ipv4.sysctl_tcp_synack_retries) + 1; 457 458 if (req->num_timeout >= max_retries) { 459 tcp_write_err(sk); 460 return; 461 } 462 /* Lower cwnd after certain SYNACK timeout like tcp_init_transfer() */ 463 if (icsk->icsk_retransmits == 1) 464 tcp_enter_loss(sk); 465 /* XXX (TFO) - Unlike regular SYN-ACK retransmit, we ignore error 466 * returned from rtx_syn_ack() to make it more persistent like 467 * regular retransmit because if the child socket has been accepted 468 * it's not good to give up too easily. 469 */ 470 inet_rtx_syn_ack(sk, req); 471 req->num_timeout++; 472 tcp_update_rto_stats(sk); 473 if (!tp->retrans_stamp) 474 tp->retrans_stamp = tcp_time_stamp_ts(tp); 475 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 476 req->timeout << req->num_timeout, TCP_RTO_MAX); 477 } 478 tcp_rtx_probe0_timed_out(const struct sock * sk,const struct sk_buff * skb,u32 rtx_delta)479 static bool tcp_rtx_probe0_timed_out(const struct sock *sk, 480 const struct sk_buff *skb, 481 u32 rtx_delta) 482 { 483 const struct inet_connection_sock *icsk = inet_csk(sk); 484 u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout); 485 const struct tcp_sock *tp = tcp_sk(sk); 486 int timeout = TCP_RTO_MAX * 2; 487 s32 rcv_delta; 488 489 if (user_timeout) { 490 /* If user application specified a TCP_USER_TIMEOUT, 491 * it does not want win 0 packets to 'reset the timer' 492 * while retransmits are not making progress. 493 */ 494 if (rtx_delta > user_timeout) 495 return true; 496 timeout = min_t(u32, timeout, msecs_to_jiffies(user_timeout)); 497 } 498 /* Note: timer interrupt might have been delayed by at least one jiffy, 499 * and tp->rcv_tstamp might very well have been written recently. 500 * rcv_delta can thus be negative. 501 */ 502 rcv_delta = icsk->icsk_timeout - tp->rcv_tstamp; 503 if (rcv_delta <= timeout) 504 return false; 505 506 return msecs_to_jiffies(rtx_delta) > timeout; 507 } 508 509 /** 510 * tcp_retransmit_timer() - The TCP retransmit timeout handler 511 * @sk: Pointer to the current socket. 512 * 513 * This function gets called when the kernel timer for a TCP packet 514 * of this socket expires. 515 * 516 * It handles retransmission, timer adjustment and other necessary measures. 517 * 518 * Returns: Nothing (void) 519 */ tcp_retransmit_timer(struct sock * sk)520 void tcp_retransmit_timer(struct sock *sk) 521 { 522 struct tcp_sock *tp = tcp_sk(sk); 523 struct net *net = sock_net(sk); 524 struct inet_connection_sock *icsk = inet_csk(sk); 525 struct request_sock *req; 526 struct sk_buff *skb; 527 528 req = rcu_dereference_protected(tp->fastopen_rsk, 529 lockdep_sock_is_held(sk)); 530 if (req) { 531 WARN_ON_ONCE(sk->sk_state != TCP_SYN_RECV && 532 sk->sk_state != TCP_FIN_WAIT1); 533 tcp_fastopen_synack_timer(sk, req); 534 /* Before we receive ACK to our SYN-ACK don't retransmit 535 * anything else (e.g., data or FIN segments). 536 */ 537 return; 538 } 539 540 if (!tp->packets_out) 541 return; 542 543 skb = tcp_rtx_queue_head(sk); 544 if (WARN_ON_ONCE(!skb)) 545 return; 546 547 if (!tp->snd_wnd && !sock_flag(sk, SOCK_DEAD) && 548 !((1 << sk->sk_state) & (TCPF_SYN_SENT | TCPF_SYN_RECV))) { 549 /* Receiver dastardly shrinks window. Our retransmits 550 * become zero probes, but we should not timeout this 551 * connection. If the socket is an orphan, time it out, 552 * we cannot allow such beasts to hang infinitely. 553 */ 554 struct inet_sock *inet = inet_sk(sk); 555 u32 rtx_delta; 556 557 rtx_delta = tcp_time_stamp_ts(tp) - (tp->retrans_stamp ?: 558 tcp_skb_timestamp_ts(tp->tcp_usec_ts, skb)); 559 if (tp->tcp_usec_ts) 560 rtx_delta /= USEC_PER_MSEC; 561 562 if (sk->sk_family == AF_INET) { 563 net_dbg_ratelimited("Probing zero-window on %pI4:%u/%u, seq=%u:%u, recv %ums ago, lasting %ums\n", 564 &inet->inet_daddr, ntohs(inet->inet_dport), 565 inet->inet_num, tp->snd_una, tp->snd_nxt, 566 jiffies_to_msecs(jiffies - tp->rcv_tstamp), 567 rtx_delta); 568 } 569 #if IS_ENABLED(CONFIG_IPV6) 570 else if (sk->sk_family == AF_INET6) { 571 net_dbg_ratelimited("Probing zero-window on %pI6:%u/%u, seq=%u:%u, recv %ums ago, lasting %ums\n", 572 &sk->sk_v6_daddr, ntohs(inet->inet_dport), 573 inet->inet_num, tp->snd_una, tp->snd_nxt, 574 jiffies_to_msecs(jiffies - tp->rcv_tstamp), 575 rtx_delta); 576 } 577 #endif 578 if (tcp_rtx_probe0_timed_out(sk, skb, rtx_delta)) { 579 tcp_write_err(sk); 580 goto out; 581 } 582 tcp_enter_loss(sk); 583 tcp_retransmit_skb(sk, skb, 1); 584 __sk_dst_reset(sk); 585 goto out_reset_timer; 586 } 587 588 __NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPTIMEOUTS); 589 if (tcp_write_timeout(sk)) 590 goto out; 591 592 if (icsk->icsk_retransmits == 0) { 593 int mib_idx = 0; 594 595 if (icsk->icsk_ca_state == TCP_CA_Recovery) { 596 if (tcp_is_sack(tp)) 597 mib_idx = LINUX_MIB_TCPSACKRECOVERYFAIL; 598 else 599 mib_idx = LINUX_MIB_TCPRENORECOVERYFAIL; 600 } else if (icsk->icsk_ca_state == TCP_CA_Loss) { 601 mib_idx = LINUX_MIB_TCPLOSSFAILURES; 602 } else if ((icsk->icsk_ca_state == TCP_CA_Disorder) || 603 tp->sacked_out) { 604 if (tcp_is_sack(tp)) 605 mib_idx = LINUX_MIB_TCPSACKFAILURES; 606 else 607 mib_idx = LINUX_MIB_TCPRENOFAILURES; 608 } 609 if (mib_idx) 610 __NET_INC_STATS(sock_net(sk), mib_idx); 611 } 612 613 tcp_enter_loss(sk); 614 615 tcp_update_rto_stats(sk); 616 if (tcp_retransmit_skb(sk, tcp_rtx_queue_head(sk), 1) > 0) { 617 /* Retransmission failed because of local congestion, 618 * Let senders fight for local resources conservatively. 619 */ 620 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 621 TCP_RESOURCE_PROBE_INTERVAL, 622 TCP_RTO_MAX); 623 goto out; 624 } 625 626 /* Increase the timeout each time we retransmit. Note that 627 * we do not increase the rtt estimate. rto is initialized 628 * from rtt, but increases here. Jacobson (SIGCOMM 88) suggests 629 * that doubling rto each time is the least we can get away with. 630 * In KA9Q, Karn uses this for the first few times, and then 631 * goes to quadratic. netBSD doubles, but only goes up to *64, 632 * and clamps at 1 to 64 sec afterwards. Note that 120 sec is 633 * defined in the protocol as the maximum possible RTT. I guess 634 * we'll have to use something other than TCP to talk to the 635 * University of Mars. 636 * 637 * PAWS allows us longer timeouts and large windows, so once 638 * implemented ftp to mars will work nicely. We will have to fix 639 * the 120 second clamps though! 640 */ 641 642 out_reset_timer: 643 /* If stream is thin, use linear timeouts. Since 'icsk_backoff' is 644 * used to reset timer, set to 0. Recalculate 'icsk_rto' as this 645 * might be increased if the stream oscillates between thin and thick, 646 * thus the old value might already be too high compared to the value 647 * set by 'tcp_set_rto' in tcp_input.c which resets the rto without 648 * backoff. Limit to TCP_THIN_LINEAR_RETRIES before initiating 649 * exponential backoff behaviour to avoid continue hammering 650 * linear-timeout retransmissions into a black hole 651 */ 652 if (sk->sk_state == TCP_ESTABLISHED && 653 (tp->thin_lto || READ_ONCE(net->ipv4.sysctl_tcp_thin_linear_timeouts)) && 654 tcp_stream_is_thin(tp) && 655 icsk->icsk_retransmits <= TCP_THIN_LINEAR_RETRIES) { 656 icsk->icsk_backoff = 0; 657 icsk->icsk_rto = clamp(__tcp_set_rto(tp), 658 tcp_rto_min(sk), 659 TCP_RTO_MAX); 660 } else if (sk->sk_state != TCP_SYN_SENT || 661 tp->total_rto > 662 READ_ONCE(net->ipv4.sysctl_tcp_syn_linear_timeouts)) { 663 /* Use normal (exponential) backoff unless linear timeouts are 664 * activated. 665 */ 666 icsk->icsk_backoff++; 667 icsk->icsk_rto = min(icsk->icsk_rto << 1, TCP_RTO_MAX); 668 } 669 inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, 670 tcp_clamp_rto_to_user_timeout(sk), TCP_RTO_MAX); 671 if (retransmits_timed_out(sk, READ_ONCE(net->ipv4.sysctl_tcp_retries1) + 1, 0)) 672 __sk_dst_reset(sk); 673 674 out:; 675 } 676 677 /* Called with bottom-half processing disabled. 678 Called by tcp_write_timer() */ tcp_write_timer_handler(struct sock * sk)679 void tcp_write_timer_handler(struct sock *sk) 680 { 681 struct inet_connection_sock *icsk = inet_csk(sk); 682 int event; 683 684 if (((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) || 685 !icsk->icsk_pending) 686 return; 687 688 if (time_after(icsk->icsk_timeout, jiffies)) { 689 sk_reset_timer(sk, &icsk->icsk_retransmit_timer, icsk->icsk_timeout); 690 return; 691 } 692 693 tcp_mstamp_refresh(tcp_sk(sk)); 694 event = icsk->icsk_pending; 695 696 switch (event) { 697 case ICSK_TIME_REO_TIMEOUT: 698 tcp_rack_reo_timeout(sk); 699 break; 700 case ICSK_TIME_LOSS_PROBE: 701 tcp_send_loss_probe(sk); 702 break; 703 case ICSK_TIME_RETRANS: 704 icsk->icsk_pending = 0; 705 tcp_retransmit_timer(sk); 706 break; 707 case ICSK_TIME_PROBE0: 708 icsk->icsk_pending = 0; 709 tcp_probe_timer(sk); 710 break; 711 } 712 } 713 tcp_write_timer(struct timer_list * t)714 static void tcp_write_timer(struct timer_list *t) 715 { 716 struct inet_connection_sock *icsk = 717 from_timer(icsk, t, icsk_retransmit_timer); 718 struct sock *sk = &icsk->icsk_inet.sk; 719 720 bh_lock_sock(sk); 721 if (!sock_owned_by_user(sk)) { 722 tcp_write_timer_handler(sk); 723 } else { 724 /* delegate our work to tcp_release_cb() */ 725 if (!test_and_set_bit(TCP_WRITE_TIMER_DEFERRED, &sk->sk_tsq_flags)) 726 sock_hold(sk); 727 } 728 bh_unlock_sock(sk); 729 sock_put(sk); 730 } 731 tcp_syn_ack_timeout(const struct request_sock * req)732 void tcp_syn_ack_timeout(const struct request_sock *req) 733 { 734 struct net *net = read_pnet(&inet_rsk(req)->ireq_net); 735 736 __NET_INC_STATS(net, LINUX_MIB_TCPTIMEOUTS); 737 } 738 EXPORT_SYMBOL(tcp_syn_ack_timeout); 739 tcp_set_keepalive(struct sock * sk,int val)740 void tcp_set_keepalive(struct sock *sk, int val) 741 { 742 if ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_LISTEN)) 743 return; 744 745 if (val && !sock_flag(sk, SOCK_KEEPOPEN)) 746 inet_csk_reset_keepalive_timer(sk, keepalive_time_when(tcp_sk(sk))); 747 else if (!val) 748 inet_csk_delete_keepalive_timer(sk); 749 } 750 EXPORT_SYMBOL_GPL(tcp_set_keepalive); 751 752 tcp_keepalive_timer(struct timer_list * t)753 static void tcp_keepalive_timer (struct timer_list *t) 754 { 755 struct sock *sk = from_timer(sk, t, sk_timer); 756 struct inet_connection_sock *icsk = inet_csk(sk); 757 struct tcp_sock *tp = tcp_sk(sk); 758 u32 elapsed; 759 760 /* Only process if socket is not in use. */ 761 bh_lock_sock(sk); 762 if (sock_owned_by_user(sk)) { 763 /* Try again later. */ 764 inet_csk_reset_keepalive_timer (sk, HZ/20); 765 goto out; 766 } 767 768 if (sk->sk_state == TCP_LISTEN) { 769 pr_err("Hmm... keepalive on a LISTEN ???\n"); 770 goto out; 771 } 772 773 tcp_mstamp_refresh(tp); 774 if (sk->sk_state == TCP_FIN_WAIT2 && sock_flag(sk, SOCK_DEAD)) { 775 if (READ_ONCE(tp->linger2) >= 0) { 776 const int tmo = tcp_fin_time(sk) - TCP_TIMEWAIT_LEN; 777 778 if (tmo > 0) { 779 tcp_time_wait(sk, TCP_FIN_WAIT2, tmo); 780 goto out; 781 } 782 } 783 tcp_send_active_reset(sk, GFP_ATOMIC, SK_RST_REASON_TCP_STATE); 784 goto death; 785 } 786 787 if (!sock_flag(sk, SOCK_KEEPOPEN) || 788 ((1 << sk->sk_state) & (TCPF_CLOSE | TCPF_SYN_SENT))) 789 goto out; 790 791 elapsed = keepalive_time_when(tp); 792 793 /* It is alive without keepalive 8) */ 794 if (tp->packets_out || !tcp_write_queue_empty(sk)) 795 goto resched; 796 797 elapsed = keepalive_time_elapsed(tp); 798 799 if (elapsed >= keepalive_time_when(tp)) { 800 u32 user_timeout = READ_ONCE(icsk->icsk_user_timeout); 801 802 /* If the TCP_USER_TIMEOUT option is enabled, use that 803 * to determine when to timeout instead. 804 */ 805 if ((user_timeout != 0 && 806 elapsed >= msecs_to_jiffies(user_timeout) && 807 icsk->icsk_probes_out > 0) || 808 (user_timeout == 0 && 809 icsk->icsk_probes_out >= keepalive_probes(tp))) { 810 tcp_send_active_reset(sk, GFP_ATOMIC, 811 SK_RST_REASON_TCP_KEEPALIVE_TIMEOUT); 812 tcp_write_err(sk); 813 goto out; 814 } 815 if (tcp_write_wakeup(sk, LINUX_MIB_TCPKEEPALIVE) <= 0) { 816 icsk->icsk_probes_out++; 817 elapsed = keepalive_intvl_when(tp); 818 } else { 819 /* If keepalive was lost due to local congestion, 820 * try harder. 821 */ 822 elapsed = TCP_RESOURCE_PROBE_INTERVAL; 823 } 824 } else { 825 /* It is tp->rcv_tstamp + keepalive_time_when(tp) */ 826 elapsed = keepalive_time_when(tp) - elapsed; 827 } 828 829 resched: 830 inet_csk_reset_keepalive_timer (sk, elapsed); 831 goto out; 832 833 death: 834 tcp_done(sk); 835 836 out: 837 bh_unlock_sock(sk); 838 sock_put(sk); 839 } 840 tcp_compressed_ack_kick(struct hrtimer * timer)841 static enum hrtimer_restart tcp_compressed_ack_kick(struct hrtimer *timer) 842 { 843 struct tcp_sock *tp = container_of(timer, struct tcp_sock, compressed_ack_timer); 844 struct sock *sk = (struct sock *)tp; 845 846 bh_lock_sock(sk); 847 if (!sock_owned_by_user(sk)) { 848 if (tp->compressed_ack) { 849 /* Since we have to send one ack finally, 850 * subtract one from tp->compressed_ack to keep 851 * LINUX_MIB_TCPACKCOMPRESSED accurate. 852 */ 853 tp->compressed_ack--; 854 tcp_send_ack(sk); 855 } 856 } else { 857 if (!test_and_set_bit(TCP_DELACK_TIMER_DEFERRED, 858 &sk->sk_tsq_flags)) 859 sock_hold(sk); 860 } 861 bh_unlock_sock(sk); 862 863 sock_put(sk); 864 865 return HRTIMER_NORESTART; 866 } 867 tcp_init_xmit_timers(struct sock * sk)868 void tcp_init_xmit_timers(struct sock *sk) 869 { 870 inet_csk_init_xmit_timers(sk, &tcp_write_timer, &tcp_delack_timer, 871 &tcp_keepalive_timer); 872 hrtimer_init(&tcp_sk(sk)->pacing_timer, CLOCK_MONOTONIC, 873 HRTIMER_MODE_ABS_PINNED_SOFT); 874 tcp_sk(sk)->pacing_timer.function = tcp_pace_kick; 875 876 hrtimer_init(&tcp_sk(sk)->compressed_ack_timer, CLOCK_MONOTONIC, 877 HRTIMER_MODE_REL_PINNED_SOFT); 878 tcp_sk(sk)->compressed_ack_timer.function = tcp_compressed_ack_kick; 879 } 880