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sys/netinet/tcp_timer.c
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1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)tcp_timer.c 8.2 (Berkeley) 5/24/95 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_inet.h" 38 #include "opt_inet6.h" 39 #include "opt_rss.h" 40 41 #include <sys/param.h> 42 #include <sys/kernel.h> 43 #include <sys/lock.h> 44 #include <sys/mbuf.h> 45 #include <sys/mutex.h> 46 #include <sys/protosw.h> 47 #include <sys/smp.h> 48 #include <sys/socket.h> 49 #include <sys/socketvar.h> 50 #include <sys/sysctl.h> 51 #include <sys/systm.h> 52 53 #include <net/if.h> 54 #include <net/route.h> 55 #include <net/rss_config.h> 56 #include <net/vnet.h> 57 #include <net/netisr.h> 58 59 #include <netinet/in.h> 60 #include <netinet/in_kdtrace.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/in_rss.h> 63 #include <netinet/in_systm.h> 64 #ifdef INET6 65 #include <netinet6/in6_pcb.h> 66 #endif 67 #include <netinet/ip_var.h> 68 #include <netinet/tcp.h> 69 #include <netinet/tcp_fsm.h> 70 #include <netinet/tcp_log_buf.h> 71 #include <netinet/tcp_timer.h> 72 #include <netinet/tcp_var.h> 73 #include <netinet/tcp_seq.h> 74 #include <netinet/cc/cc.h> 75 #ifdef INET6 76 #include <netinet6/tcp6_var.h> 77 #endif 78 #include <netinet/tcpip.h> 79 80 int tcp_persmin; 81 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin, 82 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 83 &tcp_persmin, 0, sysctl_msec_to_ticks, "I", 84 "minimum persistence interval"); 85 86 int tcp_persmax; 87 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax, 88 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 89 &tcp_persmax, 0, sysctl_msec_to_ticks, "I", 90 "maximum persistence interval"); 91 92 int tcp_keepinit; 93 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, 94 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 95 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", 96 "time to establish connection"); 97 98 int tcp_keepidle; 99 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, 100 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 101 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", 102 "time before keepalive probes begin"); 103 104 int tcp_keepintvl; 105 SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, 106 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 107 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", 108 "time between keepalive probes"); 109 110 int tcp_delacktime; 111 SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, 112 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 113 &tcp_delacktime, 0, sysctl_msec_to_ticks, "I", 114 "Time before a delayed ACK is sent"); 115 116 VNET_DEFINE(int, tcp_msl); 117 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, 118 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_VNET, 119 &VNET_NAME(tcp_msl), 0, sysctl_msec_to_ticks, "I", 120 "Maximum segment lifetime"); 121 122 int tcp_rexmit_initial; 123 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_initial, 124 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 125 &tcp_rexmit_initial, 0, sysctl_msec_to_ticks, "I", 126 "Initial Retransmission Timeout"); 127 128 int tcp_rexmit_min; 129 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, 130 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 131 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", 132 "Minimum Retransmission Timeout"); 133 134 int tcp_rexmit_slop; 135 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, 136 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 137 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I", 138 "Retransmission Timer Slop"); 139 140 VNET_DEFINE(int, tcp_always_keepalive) = 1; 141 SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_VNET|CTLFLAG_RW, 142 &VNET_NAME(tcp_always_keepalive) , 0, 143 "Assume SO_KEEPALIVE on all TCP connections"); 144 145 int tcp_fast_finwait2_recycle = 0; 146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW, 147 &tcp_fast_finwait2_recycle, 0, 148 "Recycle closed FIN_WAIT_2 connections faster"); 149 150 int tcp_finwait2_timeout; 151 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, 152 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 153 &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", 154 "FIN-WAIT2 timeout"); 155 156 int tcp_keepcnt = TCPTV_KEEPCNT; 157 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0, 158 "Number of keepalive probes to send"); 159 160 /* max idle probes */ 161 int tcp_maxpersistidle; 162 163 int tcp_rexmit_drop_options = 0; 164 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW, 165 &tcp_rexmit_drop_options, 0, 166 "Drop TCP options from 3rd and later retransmitted SYN"); 167 168 int tcp_maxunacktime = TCPTV_MAXUNACKTIME; 169 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxunacktime, 170 CTLTYPE_INT|CTLFLAG_RW | CTLFLAG_NEEDGIANT, 171 &tcp_maxunacktime, 0, sysctl_msec_to_ticks, "I", 172 "Maximum time (in ms) that a session can linger without making progress"); 173 174 VNET_DEFINE(int, tcp_pmtud_blackhole_detect); 175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection, 176 CTLFLAG_RW|CTLFLAG_VNET, 177 &VNET_NAME(tcp_pmtud_blackhole_detect), 0, 178 "Path MTU Discovery Black Hole Detection Enabled"); 179 180 #ifdef INET 181 VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200; 182 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss, 183 CTLFLAG_RW|CTLFLAG_VNET, 184 &VNET_NAME(tcp_pmtud_blackhole_mss), 0, 185 "Path MTU Discovery Black Hole Detection lowered MSS"); 186 #endif 187 188 #ifdef INET6 189 VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220; 190 SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss, 191 CTLFLAG_RW|CTLFLAG_VNET, 192 &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0, 193 "Path MTU Discovery IPv6 Black Hole Detection lowered MSS"); 194 #endif 195 196 #ifdef RSS 197 static int per_cpu_timers = 1; 198 #else 199 static int per_cpu_timers = 0; 200 #endif 201 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW, 202 &per_cpu_timers , 0, "run tcp timers on all cpus"); 203 204 /* 205 * Map the given inp to a CPU id. 206 * 207 * This queries RSS if it's compiled in, else it defaults to the current 208 * CPU ID. 209 */ 210 inline int 211 inp_to_cpuid(struct inpcb *inp) 212 { 213 u_int cpuid; 214 215 if (per_cpu_timers) { 216 #ifdef RSS 217 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype); 218 if (cpuid == NETISR_CPUID_NONE) 219 return (curcpu); /* XXX */ 220 else 221 return (cpuid); 222 #endif 223 /* 224 * We don't have a flowid -> cpuid mapping, so cheat and 225 * just map unknown cpuids to curcpu. Not the best, but 226 * apparently better than defaulting to swi 0. 227 */ 228 cpuid = inp->inp_flowid % (mp_maxid + 1); 229 if (! CPU_ABSENT(cpuid)) 230 return (cpuid); 231 return (curcpu); 232 } else { 233 return (0); 234 } 235 } 236 237 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 238 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 }; 239 240 int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */ 241 242 /* 243 * TCP timer processing. 244 * 245 * Each connection has 5 timers associated with it, which can be scheduled 246 * simultaneously. They all are serviced by one callout tcp_timer_enter(). 247 * This function executes the next timer via tcp_timersw[] vector. Each 248 * timer is supposed to return 'true' unless the connection was destroyed. 249 * In the former case tcp_timer_enter() will schedule callout for next timer. 250 */ 251 252 typedef bool tcp_timer_t(struct tcpcb *); 253 static tcp_timer_t tcp_timer_delack; 254 static tcp_timer_t tcp_timer_2msl; 255 static tcp_timer_t tcp_timer_keep; 256 static tcp_timer_t tcp_timer_persist; 257 static tcp_timer_t tcp_timer_rexmt; 258 259 static tcp_timer_t * const tcp_timersw[TT_N] = { 260 [TT_DELACK] = tcp_timer_delack, 261 [TT_REXMT] = tcp_timer_rexmt, 262 [TT_PERSIST] = tcp_timer_persist, 263 [TT_KEEP] = tcp_timer_keep, 264 [TT_2MSL] = tcp_timer_2msl, 265 }; 266 267 /* 268 * tcp_output_locked() s a timer specific variation of call to tcp_output(), 269 * see tcp_var.h for the rest. It handles drop request from advanced stacks, 270 * but keeps tcpcb locked unless tcp_drop() destroyed it. 271 * Returns true if tcpcb is valid and locked. 272 */ 273 static inline bool 274 tcp_output_locked(struct tcpcb *tp) 275 { 276 int rv; 277 278 INP_WLOCK_ASSERT(tptoinpcb(tp)); 279 280 if ((rv = tp->t_fb->tfb_tcp_output(tp)) < 0) { 281 KASSERT(tp->t_fb->tfb_flags & TCP_FUNC_OUTPUT_CANDROP, 282 ("TCP stack %s requested tcp_drop(%p)", 283 tp->t_fb->tfb_tcp_block_name, tp)); 284 tp = tcp_drop(tp, rv); 285 } 286 287 return (tp != NULL); 288 } 289 290 static bool 291 tcp_timer_delack(struct tcpcb *tp) 292 { 293 struct epoch_tracker et; 294 #if defined(INVARIANTS) || defined(VIMAGE) 295 struct inpcb *inp = tptoinpcb(tp); 296 #endif 297 bool rv; 298 299 INP_WLOCK_ASSERT(inp); 300 301 CURVNET_SET(inp->inp_vnet); 302 tp->t_flags |= TF_ACKNOW; 303 TCPSTAT_INC(tcps_delack); 304 NET_EPOCH_ENTER(et); 305 rv = tcp_output_locked(tp); 306 NET_EPOCH_EXIT(et); 307 CURVNET_RESTORE(); 308 309 return (rv); 310 } 311 312 static bool 313 tcp_timer_2msl(struct tcpcb *tp) 314 { 315 struct inpcb *inp = tptoinpcb(tp); 316 bool close = false; 317 318 INP_WLOCK_ASSERT(inp); 319 320 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO); 321 CURVNET_SET(inp->inp_vnet); 322 tcp_log_end_status(tp, TCP_EI_STATUS_2MSL); 323 tcp_free_sackholes(tp); 324 /* 325 * 2 MSL timeout in shutdown went off. If we're closed but 326 * still waiting for peer to close and connection has been idle 327 * too long delete connection control block. Otherwise, check 328 * again in a bit. 329 * 330 * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed, 331 * there's no point in hanging onto FIN_WAIT_2 socket. Just close it. 332 * Ignore fact that there were recent incoming segments. 333 * 334 * XXXGL: check if inp_socket shall always be !NULL here? 335 */ 336 if (tp->t_state == TCPS_TIME_WAIT) { 337 close = true; 338 } else if (tp->t_state == TCPS_FIN_WAIT_2 && 339 tcp_fast_finwait2_recycle && inp->inp_socket && 340 (inp->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) { 341 TCPSTAT_INC(tcps_finwait2_drops); 342 close = true; 343 } else { 344 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) 345 tcp_timer_activate(tp, TT_2MSL, TP_KEEPINTVL(tp)); 346 else 347 close = true; 348 } 349 if (close) { 350 struct epoch_tracker et; 351 352 NET_EPOCH_ENTER(et); 353 tp = tcp_close(tp); 354 NET_EPOCH_EXIT(et); 355 } 356 CURVNET_RESTORE(); 357 358 return (tp != NULL); 359 } 360 361 static bool 362 tcp_timer_keep(struct tcpcb *tp) 363 { 364 struct epoch_tracker et; 365 struct inpcb *inp = tptoinpcb(tp); 366 struct tcptemp *t_template; 367 368 INP_WLOCK_ASSERT(inp); 369 370 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO); 371 CURVNET_SET(inp->inp_vnet); 372 /* 373 * Because we don't regularly reset the keepalive callout in 374 * the ESTABLISHED state, it may be that we don't actually need 375 * to send a keepalive yet. If that occurs, schedule another 376 * call for the next time the keepalive timer might expire. 377 */ 378 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 379 u_int idletime; 380 381 idletime = ticks - tp->t_rcvtime; 382 if (idletime < TP_KEEPIDLE(tp)) { 383 tcp_timer_activate(tp, TT_KEEP, 384 TP_KEEPIDLE(tp) - idletime); 385 CURVNET_RESTORE(); 386 return (true); 387 } 388 } 389 390 /* 391 * Keep-alive timer went off; send something 392 * or drop connection if idle for too long. 393 */ 394 TCPSTAT_INC(tcps_keeptimeo); 395 if (tp->t_state < TCPS_ESTABLISHED) 396 goto dropit; 397 if ((V_tcp_always_keepalive || 398 inp->inp_socket->so_options & SO_KEEPALIVE) && 399 tp->t_state <= TCPS_CLOSING) { 400 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp)) 401 goto dropit; 402 /* 403 * Send a packet designed to force a response 404 * if the peer is up and reachable: 405 * either an ACK if the connection is still alive, 406 * or an RST if the peer has closed the connection 407 * due to timeout or reboot. 408 * Using sequence number tp->snd_una-1 409 * causes the transmitted zero-length segment 410 * to lie outside the receive window; 411 * by the protocol spec, this requires the 412 * correspondent TCP to respond. 413 */ 414 TCPSTAT_INC(tcps_keepprobe); 415 t_template = tcpip_maketemplate(inp); 416 if (t_template) { 417 NET_EPOCH_ENTER(et); 418 tcp_respond(tp, t_template->tt_ipgen, 419 &t_template->tt_t, (struct mbuf *)NULL, 420 tp->rcv_nxt, tp->snd_una - 1, 0); 421 NET_EPOCH_EXIT(et); 422 free(t_template, M_TEMP); 423 } 424 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINTVL(tp)); 425 } else 426 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 427 428 CURVNET_RESTORE(); 429 return (true); 430 431 dropit: 432 TCPSTAT_INC(tcps_keepdrops); 433 NET_EPOCH_ENTER(et); 434 tcp_log_end_status(tp, TCP_EI_STATUS_KEEP_MAX); 435 tp = tcp_drop(tp, ETIMEDOUT); 436 NET_EPOCH_EXIT(et); 437 CURVNET_RESTORE(); 438 439 return (tp != NULL); 440 } 441 442 /* 443 * Has this session exceeded the maximum time without seeing a substantive 444 * acknowledgement? If so, return true; otherwise false. 445 */ 446 static bool 447 tcp_maxunacktime_check(struct tcpcb *tp) 448 { 449 450 /* Are we tracking this timer for this session? */ 451 if (TP_MAXUNACKTIME(tp) == 0) 452 return false; 453 454 /* Do we have a current measurement. */ 455 if (tp->t_acktime == 0) 456 return false; 457 458 /* Are we within the acceptable range? */ 459 if (TSTMP_GT(TP_MAXUNACKTIME(tp) + tp->t_acktime, (u_int)ticks)) 460 return false; 461 462 /* We exceeded the timer. */ 463 TCPSTAT_INC(tcps_progdrops); 464 return true; 465 } 466 467 static bool 468 tcp_timer_persist(struct tcpcb *tp) 469 { 470 struct epoch_tracker et; 471 #if defined(INVARIANTS) || defined(VIMAGE) 472 struct inpcb *inp = tptoinpcb(tp); 473 #endif 474 bool progdrop, rv; 475 476 INP_WLOCK_ASSERT(inp); 477 478 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO); 479 CURVNET_SET(inp->inp_vnet); 480 /* 481 * Persistence timer into zero window. 482 * Force a byte to be output, if possible. 483 */ 484 TCPSTAT_INC(tcps_persisttimeo); 485 /* 486 * Hack: if the peer is dead/unreachable, we do not 487 * time out if the window is closed. After a full 488 * backoff, drop the connection if the idle time 489 * (no responses to probes) reaches the maximum 490 * backoff that we would use if retransmitting. 491 * Also, drop the connection if we haven't been making 492 * progress. 493 */ 494 progdrop = tcp_maxunacktime_check(tp); 495 if (progdrop || (tp->t_rxtshift == TCP_MAXRXTSHIFT && 496 (ticks - tp->t_rcvtime >= tcp_maxpersistidle || 497 ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff))) { 498 if (!progdrop) 499 TCPSTAT_INC(tcps_persistdrop); 500 tcp_log_end_status(tp, TCP_EI_STATUS_PERSIST_MAX); 501 goto dropit; 502 } 503 /* 504 * If the user has closed the socket then drop a persisting 505 * connection after a much reduced timeout. 506 */ 507 if (tp->t_state > TCPS_CLOSE_WAIT && 508 (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) { 509 TCPSTAT_INC(tcps_persistdrop); 510 tcp_log_end_status(tp, TCP_EI_STATUS_PERSIST_MAX); 511 goto dropit; 512 } 513 tcp_setpersist(tp); 514 tp->t_flags |= TF_FORCEDATA; 515 NET_EPOCH_ENTER(et); 516 if ((rv = tcp_output_locked(tp))) 517 tp->t_flags &= ~TF_FORCEDATA; 518 NET_EPOCH_EXIT(et); 519 CURVNET_RESTORE(); 520 521 return (rv); 522 523 dropit: 524 NET_EPOCH_ENTER(et); 525 tp = tcp_drop(tp, ETIMEDOUT); 526 NET_EPOCH_EXIT(et); 527 CURVNET_RESTORE(); 528 529 return (tp != NULL); 530 } 531 532 static bool 533 tcp_timer_rexmt(struct tcpcb *tp) 534 { 535 struct epoch_tracker et; 536 struct inpcb *inp = tptoinpcb(tp); 537 int rexmt; 538 bool isipv6, rv; 539 540 INP_WLOCK_ASSERT(inp); 541 542 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO); 543 CURVNET_SET(inp->inp_vnet); 544 tcp_free_sackholes(tp); 545 TCP_LOG_EVENT(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0, NULL, false); 546 if (tp->t_fb->tfb_tcp_rexmit_tmr) { 547 /* The stack has a timer action too. */ 548 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp); 549 } 550 /* 551 * Retransmission timer went off. Message has not 552 * been acked within retransmit interval. Back off 553 * to a longer retransmit interval and retransmit one segment. 554 * 555 * If we've either exceeded the maximum number of retransmissions, 556 * or we've gone long enough without making progress, then drop 557 * the session. 558 */ 559 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT || tcp_maxunacktime_check(tp)) { 560 if (tp->t_rxtshift > TCP_MAXRXTSHIFT) 561 TCPSTAT_INC(tcps_timeoutdrop); 562 tp->t_rxtshift = TCP_MAXRXTSHIFT; 563 tcp_log_end_status(tp, TCP_EI_STATUS_RETRAN); 564 NET_EPOCH_ENTER(et); 565 tp = tcp_drop(tp, ETIMEDOUT); 566 NET_EPOCH_EXIT(et); 567 CURVNET_RESTORE(); 568 569 return (tp != NULL); 570 } 571 if (tp->t_state == TCPS_SYN_SENT) { 572 /* 573 * If the SYN was retransmitted, indicate CWND to be 574 * limited to 1 segment in cc_conn_init(). 575 */ 576 tp->snd_cwnd = 1; 577 } else if (tp->t_rxtshift == 1) { 578 /* 579 * first retransmit; record ssthresh and cwnd so they can 580 * be recovered if this turns out to be a "bad" retransmit. 581 * A retransmit is considered "bad" if an ACK for this 582 * segment is received within RTT/2 interval; the assumption 583 * here is that the ACK was already in flight. See 584 * "On Estimating End-to-End Network Path Properties" by 585 * Allman and Paxson for more details. 586 */ 587 tp->snd_cwnd_prev = tp->snd_cwnd; 588 tp->snd_ssthresh_prev = tp->snd_ssthresh; 589 tp->snd_recover_prev = tp->snd_recover; 590 if (IN_FASTRECOVERY(tp->t_flags)) 591 tp->t_flags |= TF_WASFRECOVERY; 592 else 593 tp->t_flags &= ~TF_WASFRECOVERY; 594 if (IN_CONGRECOVERY(tp->t_flags)) 595 tp->t_flags |= TF_WASCRECOVERY; 596 else 597 tp->t_flags &= ~TF_WASCRECOVERY; 598 if ((tp->t_flags & TF_RCVD_TSTMP) == 0) 599 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 600 /* In the event that we've negotiated timestamps 601 * badrxtwin will be set to the value that we set 602 * the retransmitted packet's to_tsval to by tcp_output 603 */ 604 tp->t_flags |= TF_PREVVALID; 605 } else 606 tp->t_flags &= ~TF_PREVVALID; 607 TCPSTAT_INC(tcps_rexmttimeo); 608 if ((tp->t_state == TCPS_SYN_SENT) || 609 (tp->t_state == TCPS_SYN_RECEIVED)) 610 rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift]; 611 else 612 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 613 TCPT_RANGESET(tp->t_rxtcur, rexmt, 614 tp->t_rttmin, TCPTV_REXMTMAX); 615 616 /* 617 * We enter the path for PLMTUD if connection is established or, if 618 * connection is FIN_WAIT_1 status, reason for the last is that if 619 * amount of data we send is very small, we could send it in couple of 620 * packets and process straight to FIN. In that case we won't catch 621 * ESTABLISHED state. 622 */ 623 #ifdef INET6 624 isipv6 = (inp->inp_vflag & INP_IPV6) ? true : false; 625 #else 626 isipv6 = false; 627 #endif 628 if (((V_tcp_pmtud_blackhole_detect == 1) || 629 (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) || 630 (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) && 631 ((tp->t_state == TCPS_ESTABLISHED) || 632 (tp->t_state == TCPS_FIN_WAIT_1))) { 633 if (tp->t_rxtshift == 1) { 634 /* 635 * We enter blackhole detection after the first 636 * unsuccessful timer based retransmission. 637 * Then we reduce up to two times the MSS, each 638 * candidate giving two tries of retransmissions. 639 * But we give a candidate only two tries, if it 640 * actually reduces the MSS. 641 */ 642 tp->t_blackhole_enter = 2; 643 tp->t_blackhole_exit = tp->t_blackhole_enter; 644 if (isipv6) { 645 #ifdef INET6 646 if (tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) 647 tp->t_blackhole_exit += 2; 648 if (tp->t_maxseg > V_tcp_v6mssdflt && 649 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) 650 tp->t_blackhole_exit += 2; 651 #endif 652 } else { 653 #ifdef INET 654 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss) 655 tp->t_blackhole_exit += 2; 656 if (tp->t_maxseg > V_tcp_mssdflt && 657 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) 658 tp->t_blackhole_exit += 2; 659 #endif 660 } 661 } 662 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) == 663 (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) && 664 (tp->t_rxtshift >= tp->t_blackhole_enter && 665 tp->t_rxtshift < tp->t_blackhole_exit && 666 (tp->t_rxtshift - tp->t_blackhole_enter) % 2 == 0)) { 667 /* 668 * Enter Path MTU Black-hole Detection mechanism: 669 * - Disable Path MTU Discovery (IP "DF" bit). 670 * - Reduce MTU to lower value than what we 671 * negotiated with peer. 672 */ 673 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) { 674 /* Record that we may have found a black hole. */ 675 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE; 676 /* Keep track of previous MSS. */ 677 tp->t_pmtud_saved_maxseg = tp->t_maxseg; 678 } 679 680 /* 681 * Reduce the MSS to blackhole value or to the default 682 * in an attempt to retransmit. 683 */ 684 #ifdef INET6 685 if (isipv6 && 686 tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss && 687 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) { 688 /* Use the sysctl tuneable blackhole MSS. */ 689 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss; 690 TCPSTAT_INC(tcps_pmtud_blackhole_activated); 691 } else if (isipv6) { 692 /* Use the default MSS. */ 693 tp->t_maxseg = V_tcp_v6mssdflt; 694 /* 695 * Disable Path MTU Discovery when we switch to 696 * minmss. 697 */ 698 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 699 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss); 700 } 701 #endif 702 #if defined(INET6) && defined(INET) 703 else 704 #endif 705 #ifdef INET 706 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss && 707 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) { 708 /* Use the sysctl tuneable blackhole MSS. */ 709 tp->t_maxseg = V_tcp_pmtud_blackhole_mss; 710 TCPSTAT_INC(tcps_pmtud_blackhole_activated); 711 } else { 712 /* Use the default MSS. */ 713 tp->t_maxseg = V_tcp_mssdflt; 714 /* 715 * Disable Path MTU Discovery when we switch to 716 * minmss. 717 */ 718 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 719 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss); 720 } 721 #endif 722 /* 723 * Reset the slow-start flight size 724 * as it may depend on the new MSS. 725 */ 726 if (CC_ALGO(tp)->conn_init != NULL) 727 CC_ALGO(tp)->conn_init(&tp->t_ccv); 728 } else { 729 /* 730 * If further retransmissions are still unsuccessful 731 * with a lowered MTU, maybe this isn't a blackhole and 732 * we restore the previous MSS and blackhole detection 733 * flags. 734 */ 735 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) && 736 (tp->t_rxtshift >= tp->t_blackhole_exit)) { 737 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 738 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE; 739 tp->t_maxseg = tp->t_pmtud_saved_maxseg; 740 TCPSTAT_INC(tcps_pmtud_blackhole_failed); 741 /* 742 * Reset the slow-start flight size as it 743 * may depend on the new MSS. 744 */ 745 if (CC_ALGO(tp)->conn_init != NULL) 746 CC_ALGO(tp)->conn_init(&tp->t_ccv); 747 } 748 } 749 } 750 751 /* 752 * Disable RFC1323 and SACK if we haven't got any response to 753 * our third SYN to work-around some broken terminal servers 754 * (most of which have hopefully been retired) that have bad VJ 755 * header compression code which trashes TCP segments containing 756 * unknown-to-them TCP options. 757 */ 758 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) && 759 (tp->t_rxtshift == 3)) 760 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT); 761 /* 762 * If we backed off this far, notify the L3 protocol that we're having 763 * connection problems. 764 */ 765 if (tp->t_rxtshift > TCP_RTT_INVALIDATE) { 766 #ifdef INET6 767 if ((inp->inp_vflag & INP_IPV6) != 0) 768 in6_losing(inp); 769 else 770 #endif 771 in_losing(inp); 772 } 773 tp->snd_nxt = tp->snd_una; 774 tp->snd_recover = tp->snd_max; 775 /* 776 * Force a segment to be sent. 777 */ 778 tp->t_flags |= TF_ACKNOW; 779 /* 780 * If timing a segment in this window, stop the timer. 781 */ 782 tp->t_rtttime = 0; 783 784 cc_cong_signal(tp, NULL, CC_RTO); 785 NET_EPOCH_ENTER(et); 786 rv = tcp_output_locked(tp); 787 NET_EPOCH_EXIT(et); 788 CURVNET_RESTORE(); 789 790 return (rv); 791 } 792 793 static inline tt_which 794 tcp_timer_next(struct tcpcb *tp, sbintime_t *precision) 795 { 796 tt_which i, rv; 797 sbintime_t after, before; 798 799 for (i = 0, rv = TT_N, after = before = SBT_MAX; i < TT_N; i++) { 800 if (tp->t_timers[i] < after) { 801 after = tp->t_timers[i]; 802 rv = i; 803 } 804 before = MIN(before, tp->t_timers[i] + tp->t_precisions[i]); 805 } 806 if (precision != NULL) 807 *precision = before - after; 808 809 return (rv); 810 } 811 812 static void 813 tcp_timer_enter(void *xtp) 814 { 815 struct tcpcb *tp = xtp; 816 struct inpcb *inp = tptoinpcb(tp); 817 sbintime_t precision; 818 tt_which which; 819 820 INP_WLOCK_ASSERT(inp); 821 MPASS((curthread->td_pflags & TDP_INTCPCALLOUT) == 0); 822 823 curthread->td_pflags |= TDP_INTCPCALLOUT; 824 825 which = tcp_timer_next(tp, NULL); 826 MPASS(which < TT_N); 827 tp->t_timers[which] = SBT_MAX; 828 tp->t_precisions[which] = 0; 829 830 if (tcp_timersw[which](tp)) { 831 if ((which = tcp_timer_next(tp, &precision)) != TT_N) { 832 callout_reset_sbt_on(&tp->t_callout, 833 tp->t_timers[which], precision, tcp_timer_enter, 834 tp, inp_to_cpuid(inp), C_ABSOLUTE); 835 } 836 INP_WUNLOCK(inp); 837 } 838 839 curthread->td_pflags &= ~TDP_INTCPCALLOUT; 840 } 841 842 /* 843 * Activate or stop (delta == 0) a TCP timer. 844 */ 845 void 846 tcp_timer_activate(struct tcpcb *tp, tt_which which, u_int delta) 847 { 848 struct inpcb *inp = tptoinpcb(tp); 849 sbintime_t precision; 850 851 #ifdef TCP_OFFLOAD 852 if (tp->t_flags & TF_TOE) 853 return; 854 #endif 855 856 INP_WLOCK_ASSERT(inp); 857 858 if (delta > 0) 859 callout_when(tick_sbt * delta, 0, C_HARDCLOCK, 860 &tp->t_timers[which], &tp->t_precisions[which]); 861 else 862 tp->t_timers[which] = SBT_MAX; 863 864 if ((which = tcp_timer_next(tp, &precision)) != TT_N) 865 callout_reset_sbt_on(&tp->t_callout, tp->t_timers[which], 866 precision, tcp_timer_enter, tp, inp_to_cpuid(inp), 867 C_ABSOLUTE); 868 else 869 callout_stop(&tp->t_callout); 870 } 871 872 bool 873 tcp_timer_active(struct tcpcb *tp, tt_which which) 874 { 875 876 INP_WLOCK_ASSERT(tptoinpcb(tp)); 877 878 return (tp->t_timers[which] != SBT_MAX); 879 } 880 881 /* 882 * Stop all timers associated with tcpcb. 883 * 884 * Called only on tcpcb destruction. The tcpcb shall already be dropped from 885 * the pcb lookup database and socket is not losing the last reference. 886 * 887 * XXXGL: unfortunately our callout(9) is not able to fully stop a locked 888 * callout even when only two threads are involved: the callout itself and the 889 * thread that does callout_stop(). See where softclock_call_cc() swaps the 890 * callwheel lock to callout lock and then checks cc_exec_cancel(). This is 891 * the race window. If it happens, the tcp_timer_enter() won't be executed, 892 * however pcb lock will be locked and released, hence we can't free memory. 893 * Until callout(9) is improved, just keep retrying. In my profiling I've seen 894 * such event happening less than 1 time per hour with 20-30 Gbit/s of traffic. 895 */ 896 void 897 tcp_timer_stop(struct tcpcb *tp) 898 { 899 struct inpcb *inp = tptoinpcb(tp); 900 901 INP_WLOCK_ASSERT(inp); 902 903 if (curthread->td_pflags & TDP_INTCPCALLOUT) { 904 int stopped __diagused; 905 906 stopped = callout_stop(&tp->t_callout); 907 MPASS(stopped == 0); 908 } else while(__predict_false(callout_stop(&tp->t_callout) == 0)) { 909 INP_WUNLOCK(inp); 910 kern_yield(PRI_UNCHANGED); 911 INP_WLOCK(inp); 912 } 913 }
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