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_timer.h> 71 #include <netinet/tcp_var.h> 72 #include <netinet/tcp_log_buf.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 if (tp->t_fb->tfb_tcp_rexmit_tmr) { 546 /* The stack has a timer action too. */ 547 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp); 548 } 549 /* 550 * Retransmission timer went off. Message has not 551 * been acked within retransmit interval. Back off 552 * to a longer retransmit interval and retransmit one segment. 553 * 554 * If we've either exceeded the maximum number of retransmissions, 555 * or we've gone long enough without making progress, then drop 556 * the session. 557 */ 558 if (++tp->t_rxtshift > TCP_MAXRXTSHIFT || tcp_maxunacktime_check(tp)) { 559 if (tp->t_rxtshift > TCP_MAXRXTSHIFT) 560 TCPSTAT_INC(tcps_timeoutdrop); 561 tp->t_rxtshift = TCP_MAXRXTSHIFT; 562 tcp_log_end_status(tp, TCP_EI_STATUS_RETRAN); 563 NET_EPOCH_ENTER(et); 564 tp = tcp_drop(tp, ETIMEDOUT); 565 NET_EPOCH_EXIT(et); 566 CURVNET_RESTORE(); 567 568 return (tp != NULL); 569 } 570 if (tp->t_state == TCPS_SYN_SENT) { 571 /* 572 * If the SYN was retransmitted, indicate CWND to be 573 * limited to 1 segment in cc_conn_init(). 574 */ 575 tp->snd_cwnd = 1; 576 } else if (tp->t_rxtshift == 1) { 577 /* 578 * first retransmit; record ssthresh and cwnd so they can 579 * be recovered if this turns out to be a "bad" retransmit. 580 * A retransmit is considered "bad" if an ACK for this 581 * segment is received within RTT/2 interval; the assumption 582 * here is that the ACK was already in flight. See 583 * "On Estimating End-to-End Network Path Properties" by 584 * Allman and Paxson for more details. 585 */ 586 tp->snd_cwnd_prev = tp->snd_cwnd; 587 tp->snd_ssthresh_prev = tp->snd_ssthresh; 588 tp->snd_recover_prev = tp->snd_recover; 589 if (IN_FASTRECOVERY(tp->t_flags)) 590 tp->t_flags |= TF_WASFRECOVERY; 591 else 592 tp->t_flags &= ~TF_WASFRECOVERY; 593 if (IN_CONGRECOVERY(tp->t_flags)) 594 tp->t_flags |= TF_WASCRECOVERY; 595 else 596 tp->t_flags &= ~TF_WASCRECOVERY; 597 if ((tp->t_flags & TF_RCVD_TSTMP) == 0) 598 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 599 /* In the event that we've negotiated timestamps 600 * badrxtwin will be set to the value that we set 601 * the retransmitted packet's to_tsval to by tcp_output 602 */ 603 tp->t_flags |= TF_PREVVALID; 604 } else 605 tp->t_flags &= ~TF_PREVVALID; 606 TCPSTAT_INC(tcps_rexmttimeo); 607 if ((tp->t_state == TCPS_SYN_SENT) || 608 (tp->t_state == TCPS_SYN_RECEIVED)) 609 rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift]; 610 else 611 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 612 TCPT_RANGESET(tp->t_rxtcur, rexmt, 613 tp->t_rttmin, TCPTV_REXMTMAX); 614 615 /* 616 * We enter the path for PLMTUD if connection is established or, if 617 * connection is FIN_WAIT_1 status, reason for the last is that if 618 * amount of data we send is very small, we could send it in couple of 619 * packets and process straight to FIN. In that case we won't catch 620 * ESTABLISHED state. 621 */ 622 #ifdef INET6 623 isipv6 = (inp->inp_vflag & INP_IPV6) ? true : false; 624 #else 625 isipv6 = false; 626 #endif 627 if (((V_tcp_pmtud_blackhole_detect == 1) || 628 (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) || 629 (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) && 630 ((tp->t_state == TCPS_ESTABLISHED) || 631 (tp->t_state == TCPS_FIN_WAIT_1))) { 632 if (tp->t_rxtshift == 1) { 633 /* 634 * We enter blackhole detection after the first 635 * unsuccessful timer based retransmission. 636 * Then we reduce up to two times the MSS, each 637 * candidate giving two tries of retransmissions. 638 * But we give a candidate only two tries, if it 639 * actually reduces the MSS. 640 */ 641 tp->t_blackhole_enter = 2; 642 tp->t_blackhole_exit = tp->t_blackhole_enter; 643 if (isipv6) { 644 #ifdef INET6 645 if (tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) 646 tp->t_blackhole_exit += 2; 647 if (tp->t_maxseg > V_tcp_v6mssdflt && 648 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) 649 tp->t_blackhole_exit += 2; 650 #endif 651 } else { 652 #ifdef INET 653 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss) 654 tp->t_blackhole_exit += 2; 655 if (tp->t_maxseg > V_tcp_mssdflt && 656 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) 657 tp->t_blackhole_exit += 2; 658 #endif 659 } 660 } 661 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) == 662 (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) && 663 (tp->t_rxtshift >= tp->t_blackhole_enter && 664 tp->t_rxtshift < tp->t_blackhole_exit && 665 (tp->t_rxtshift - tp->t_blackhole_enter) % 2 == 0)) { 666 /* 667 * Enter Path MTU Black-hole Detection mechanism: 668 * - Disable Path MTU Discovery (IP "DF" bit). 669 * - Reduce MTU to lower value than what we 670 * negotiated with peer. 671 */ 672 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) { 673 /* Record that we may have found a black hole. */ 674 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE; 675 /* Keep track of previous MSS. */ 676 tp->t_pmtud_saved_maxseg = tp->t_maxseg; 677 } 678 679 /* 680 * Reduce the MSS to blackhole value or to the default 681 * in an attempt to retransmit. 682 */ 683 #ifdef INET6 684 if (isipv6 && 685 tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss && 686 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) { 687 /* Use the sysctl tuneable blackhole MSS. */ 688 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss; 689 TCPSTAT_INC(tcps_pmtud_blackhole_activated); 690 } else if (isipv6) { 691 /* Use the default MSS. */ 692 tp->t_maxseg = V_tcp_v6mssdflt; 693 /* 694 * Disable Path MTU Discovery when we switch to 695 * minmss. 696 */ 697 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 698 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss); 699 } 700 #endif 701 #if defined(INET6) && defined(INET) 702 else 703 #endif 704 #ifdef INET 705 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss && 706 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) { 707 /* Use the sysctl tuneable blackhole MSS. */ 708 tp->t_maxseg = V_tcp_pmtud_blackhole_mss; 709 TCPSTAT_INC(tcps_pmtud_blackhole_activated); 710 } else { 711 /* Use the default MSS. */ 712 tp->t_maxseg = V_tcp_mssdflt; 713 /* 714 * Disable Path MTU Discovery when we switch to 715 * minmss. 716 */ 717 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 718 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss); 719 } 720 #endif 721 /* 722 * Reset the slow-start flight size 723 * as it may depend on the new MSS. 724 */ 725 if (CC_ALGO(tp)->conn_init != NULL) 726 CC_ALGO(tp)->conn_init(&tp->t_ccv); 727 } else { 728 /* 729 * If further retransmissions are still unsuccessful 730 * with a lowered MTU, maybe this isn't a blackhole and 731 * we restore the previous MSS and blackhole detection 732 * flags. 733 */ 734 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) && 735 (tp->t_rxtshift >= tp->t_blackhole_exit)) { 736 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 737 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE; 738 tp->t_maxseg = tp->t_pmtud_saved_maxseg; 739 TCPSTAT_INC(tcps_pmtud_blackhole_failed); 740 /* 741 * Reset the slow-start flight size as it 742 * may depend on the new MSS. 743 */ 744 if (CC_ALGO(tp)->conn_init != NULL) 745 CC_ALGO(tp)->conn_init(&tp->t_ccv); 746 } 747 } 748 } 749 750 /* 751 * Disable RFC1323 and SACK if we haven't got any response to 752 * our third SYN to work-around some broken terminal servers 753 * (most of which have hopefully been retired) that have bad VJ 754 * header compression code which trashes TCP segments containing 755 * unknown-to-them TCP options. 756 */ 757 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) && 758 (tp->t_rxtshift == 3)) 759 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT); 760 /* 761 * If we backed off this far, notify the L3 protocol that we're having 762 * connection problems. 763 */ 764 if (tp->t_rxtshift > TCP_RTT_INVALIDATE) { 765 #ifdef INET6 766 if ((inp->inp_vflag & INP_IPV6) != 0) 767 in6_losing(inp); 768 else 769 #endif 770 in_losing(inp); 771 } 772 tp->snd_nxt = tp->snd_una; 773 tp->snd_recover = tp->snd_max; 774 /* 775 * Force a segment to be sent. 776 */ 777 tp->t_flags |= TF_ACKNOW; 778 /* 779 * If timing a segment in this window, stop the timer. 780 */ 781 tp->t_rtttime = 0; 782 783 cc_cong_signal(tp, NULL, CC_RTO); 784 NET_EPOCH_ENTER(et); 785 rv = tcp_output_locked(tp); 786 NET_EPOCH_EXIT(et); 787 CURVNET_RESTORE(); 788 789 return (rv); 790 } 791 792 static void 793 tcp_bblog_timer(struct tcpcb *tp, tt_which which, tt_what what, uint32_t ticks) 794 { 795 struct tcp_log_buffer *lgb; 796 uint64_t ms; 797 798 INP_WLOCK_ASSERT(tptoinpcb(tp)); 799 if (tcp_bblogging_on(tp)) 800 lgb = tcp_log_event(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0, 801 NULL, false, NULL, NULL, 0, NULL); 802 else 803 lgb = NULL; 804 if (lgb != NULL) { 805 lgb->tlb_flex1 = (what << 8) | which; 806 if (what == TT_STARTING) { 807 /* Convert ticks to ms and store it in tlb_flex2. */ 808 if (hz == 1000) 809 lgb->tlb_flex2 = ticks; 810 else { 811 ms = (((uint64_t)ticks * 1000) + (hz - 1)) / hz; 812 if (ms > UINT32_MAX) 813 lgb->tlb_flex2 = UINT32_MAX; 814 else 815 lgb->tlb_flex2 = (uint32_t)ms; 816 } 817 } 818 } 819 } 820 821 static inline tt_which 822 tcp_timer_next(struct tcpcb *tp, sbintime_t *precision) 823 { 824 tt_which i, rv; 825 sbintime_t after, before; 826 827 for (i = 0, rv = TT_N, after = before = SBT_MAX; i < TT_N; i++) { 828 if (tp->t_timers[i] < after) { 829 after = tp->t_timers[i]; 830 rv = i; 831 } 832 before = MIN(before, tp->t_timers[i] + tp->t_precisions[i]); 833 } 834 if (precision != NULL) 835 *precision = before - after; 836 837 return (rv); 838 } 839 840 static void 841 tcp_timer_enter(void *xtp) 842 { 843 struct tcpcb *tp = xtp; 844 struct inpcb *inp = tptoinpcb(tp); 845 sbintime_t precision; 846 tt_which which; 847 bool tp_valid; 848 849 INP_WLOCK_ASSERT(inp); 850 MPASS((curthread->td_pflags & TDP_INTCPCALLOUT) == 0); 851 852 curthread->td_pflags |= TDP_INTCPCALLOUT; 853 854 which = tcp_timer_next(tp, NULL); 855 MPASS(which < TT_N); 856 tp->t_timers[which] = SBT_MAX; 857 tp->t_precisions[which] = 0; 858 859 tcp_bblog_timer(tp, which, TT_PROCESSING, 0); 860 tp_valid = tcp_timersw[which](tp); 861 if (tp_valid) { 862 tcp_bblog_timer(tp, which, TT_PROCESSED, 0); 863 if ((which = tcp_timer_next(tp, &precision)) != TT_N) { 864 callout_reset_sbt_on(&tp->t_callout, 865 tp->t_timers[which], precision, tcp_timer_enter, 866 tp, inp_to_cpuid(inp), C_ABSOLUTE); 867 } 868 INP_WUNLOCK(inp); 869 } 870 871 curthread->td_pflags &= ~TDP_INTCPCALLOUT; 872 } 873 874 /* 875 * Activate or stop (delta == 0) a TCP timer. 876 */ 877 void 878 tcp_timer_activate(struct tcpcb *tp, tt_which which, u_int delta) 879 { 880 struct inpcb *inp = tptoinpcb(tp); 881 sbintime_t precision; 882 tt_what what; 883 884 #ifdef TCP_OFFLOAD 885 if (tp->t_flags & TF_TOE) 886 return; 887 #endif 888 889 INP_WLOCK_ASSERT(inp); 890 891 if (delta > 0) { 892 what = TT_STARTING; 893 callout_when(tick_sbt * delta, 0, C_HARDCLOCK, 894 &tp->t_timers[which], &tp->t_precisions[which]); 895 } else { 896 what = TT_STOPPING; 897 tp->t_timers[which] = SBT_MAX; 898 } 899 tcp_bblog_timer(tp, which, what, delta); 900 901 if ((which = tcp_timer_next(tp, &precision)) != TT_N) 902 callout_reset_sbt_on(&tp->t_callout, tp->t_timers[which], 903 precision, tcp_timer_enter, tp, inp_to_cpuid(inp), 904 C_ABSOLUTE); 905 else 906 callout_stop(&tp->t_callout); 907 } 908 909 bool 910 tcp_timer_active(struct tcpcb *tp, tt_which which) 911 { 912 913 INP_WLOCK_ASSERT(tptoinpcb(tp)); 914 915 return (tp->t_timers[which] != SBT_MAX); 916 } 917 918 /* 919 * Stop all timers associated with tcpcb. 920 * 921 * Called only on tcpcb destruction. The tcpcb shall already be dropped from 922 * the pcb lookup database and socket is not losing the last reference. 923 * 924 * XXXGL: unfortunately our callout(9) is not able to fully stop a locked 925 * callout even when only two threads are involved: the callout itself and the 926 * thread that does callout_stop(). See where softclock_call_cc() swaps the 927 * callwheel lock to callout lock and then checks cc_exec_cancel(). This is 928 * the race window. If it happens, the tcp_timer_enter() won't be executed, 929 * however pcb lock will be locked and released, hence we can't free memory. 930 * Until callout(9) is improved, just keep retrying. In my profiling I've seen 931 * such event happening less than 1 time per hour with 20-30 Gbit/s of traffic. 932 */ 933 void 934 tcp_timer_stop(struct tcpcb *tp) 935 { 936 struct inpcb *inp = tptoinpcb(tp); 937 938 INP_WLOCK_ASSERT(inp); 939 940 if (curthread->td_pflags & TDP_INTCPCALLOUT) { 941 int stopped __diagused; 942 943 stopped = callout_stop(&tp->t_callout); 944 MPASS(stopped == 0); 945 } else while(__predict_false(callout_stop(&tp->t_callout) == 0)) { 946 INP_WUNLOCK(inp); 947 kern_yield(PRI_UNCHANGED); 948 INP_WLOCK(inp); 949 } 950 } 951