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 32#include <sys/cdefs.h> 33#include "opt_inet.h" 34#include "opt_inet6.h" 35#include "opt_rss.h" 36 37#include <sys/param.h> 38#include <sys/kernel.h> 39#include <sys/lock.h> 40#include <sys/mbuf.h> 41#include <sys/mutex.h> 42#include <sys/protosw.h> 43#include <sys/smp.h> 44#include <sys/socket.h> 45#include <sys/socketvar.h> 46#include <sys/sysctl.h> 47#include <sys/systm.h> 48 49#include <net/if.h> 50#include <net/route.h> 51#include <net/rss_config.h> 52#include <net/vnet.h> 53#include <net/netisr.h> 54 55#include <netinet/in.h> 56#include <netinet/in_kdtrace.h> 57#include <netinet/in_pcb.h> 58#include <netinet/in_rss.h> 59#include <netinet/in_systm.h> 60#ifdef INET6 61#include <netinet6/in6_pcb.h> 62#endif 63#include <netinet/ip_var.h> 64#include <netinet/tcp.h> 65#include <netinet/tcp_fsm.h> 66#include <netinet/tcp_timer.h> 67#include <netinet/tcp_var.h> 68#include <netinet/tcp_log_buf.h> 69#include <netinet/tcp_seq.h> 70#include <netinet/cc/cc.h> 71#ifdef INET6 72#include <netinet6/tcp6_var.h> 73#endif 74#include <netinet/tcpip.h> 75 76int tcp_persmin; 77SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin, 78 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 79 &tcp_persmin, 0, sysctl_msec_to_ticks, "I", 80 "minimum persistence interval"); 81 82int tcp_persmax; 83SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax, 84 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 85 &tcp_persmax, 0, sysctl_msec_to_ticks, "I", 86 "maximum persistence interval"); 87 88int tcp_keepinit; 89SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINIT, keepinit, 90 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 91 &tcp_keepinit, 0, sysctl_msec_to_ticks, "I", 92 "time to establish connection"); 93 94int tcp_keepidle; 95SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPIDLE, keepidle, 96 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 97 &tcp_keepidle, 0, sysctl_msec_to_ticks, "I", 98 "time before keepalive probes begin"); 99 100int tcp_keepintvl; 101SYSCTL_PROC(_net_inet_tcp, TCPCTL_KEEPINTVL, keepintvl, 102 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 103 &tcp_keepintvl, 0, sysctl_msec_to_ticks, "I", 104 "time between keepalive probes"); 105 106int tcp_delacktime; 107SYSCTL_PROC(_net_inet_tcp, TCPCTL_DELACKTIME, delacktime, 108 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 109 &tcp_delacktime, 0, sysctl_msec_to_ticks, "I", 110 "Time before a delayed ACK is sent"); 111 112VNET_DEFINE(int, tcp_msl); 113SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, 114 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_VNET, 115 &VNET_NAME(tcp_msl), 0, sysctl_msec_to_ticks, "I", 116 "Maximum segment lifetime"); 117 118int tcp_rexmit_initial; 119SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_initial, 120 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 121 &tcp_rexmit_initial, 0, sysctl_msec_to_ticks, "I", 122 "Initial Retransmission Timeout"); 123 124int tcp_rexmit_min; 125SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, 126 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 127 &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", 128 "Minimum Retransmission Timeout"); 129 130int tcp_rexmit_slop; 131SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, 132 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 133 &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I", 134 "Retransmission Timer Slop"); 135 136VNET_DEFINE(int, tcp_always_keepalive) = 1; 137SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_VNET|CTLFLAG_RW, 138 &VNET_NAME(tcp_always_keepalive) , 0, 139 "Assume SO_KEEPALIVE on all TCP connections"); 140 141int tcp_fast_finwait2_recycle = 0; 142SYSCTL_INT(_net_inet_tcp, OID_AUTO, fast_finwait2_recycle, CTLFLAG_RW, 143 &tcp_fast_finwait2_recycle, 0, 144 "Recycle closed FIN_WAIT_2 connections faster"); 145 146int tcp_finwait2_timeout; 147SYSCTL_PROC(_net_inet_tcp, OID_AUTO, finwait2_timeout, 148 CTLTYPE_INT | CTLFLAG_RW | CTLFLAG_NEEDGIANT, 149 &tcp_finwait2_timeout, 0, sysctl_msec_to_ticks, "I", 150 "FIN-WAIT2 timeout"); 151 152int tcp_keepcnt = TCPTV_KEEPCNT; 153SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0, 154 "Number of keepalive probes to send"); 155 156 /* max idle probes */ 157int tcp_maxpersistidle; 158 159int tcp_rexmit_drop_options = 0; 160SYSCTL_INT(_net_inet_tcp, OID_AUTO, rexmit_drop_options, CTLFLAG_RW, 161 &tcp_rexmit_drop_options, 0, 162 "Drop TCP options from 3rd and later retransmitted SYN"); 163 164int tcp_maxunacktime = TCPTV_MAXUNACKTIME; 165SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxunacktime, 166 CTLTYPE_INT|CTLFLAG_RW | CTLFLAG_NEEDGIANT, 167 &tcp_maxunacktime, 0, sysctl_msec_to_ticks, "I", 168 "Maximum time (in ms) that a session can linger without making progress"); 169 170VNET_DEFINE(int, tcp_pmtud_blackhole_detect); 171SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_detection, 172 CTLFLAG_RW|CTLFLAG_VNET, 173 &VNET_NAME(tcp_pmtud_blackhole_detect), 0, 174 "Path MTU Discovery Black Hole Detection Enabled"); 175 176#ifdef INET 177VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200; 178SYSCTL_INT(_net_inet_tcp, OID_AUTO, pmtud_blackhole_mss, 179 CTLFLAG_RW|CTLFLAG_VNET, 180 &VNET_NAME(tcp_pmtud_blackhole_mss), 0, 181 "Path MTU Discovery Black Hole Detection lowered MSS"); 182#endif 183 184#ifdef INET6 185VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220; 186SYSCTL_INT(_net_inet_tcp, OID_AUTO, v6pmtud_blackhole_mss, 187 CTLFLAG_RW|CTLFLAG_VNET, 188 &VNET_NAME(tcp_v6pmtud_blackhole_mss), 0, 189 "Path MTU Discovery IPv6 Black Hole Detection lowered MSS"); 190#endif 191 192#ifdef RSS 193static int per_cpu_timers = 1; 194#else 195static int per_cpu_timers = 0; 196#endif 197SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW, 198 &per_cpu_timers , 0, "run tcp timers on all cpus"); 199 200static int 201sysctl_net_inet_tcp_retries(SYSCTL_HANDLER_ARGS) 202{ 203 int error, new; 204 205 new = V_tcp_retries; 206 error = sysctl_handle_int(oidp, &new, 0, req); 207 if (error == 0 && req->newptr) { 208 if ((new < 1) || (new > TCP_MAXRXTSHIFT)) 209 error = EINVAL; 210 else 211 V_tcp_retries = new; 212 } 213 return (error); 214} 215 216VNET_DEFINE(int, tcp_retries) = TCP_MAXRXTSHIFT; 217SYSCTL_PROC(_net_inet_tcp, OID_AUTO, retries, 218 CTLTYPE_INT | CTLFLAG_VNET | CTLFLAG_RW, 219 &VNET_NAME(tcp_retries), 0, sysctl_net_inet_tcp_retries, "I", 220 "maximum number of consecutive timer based retransmissions"); 221 222/* 223 * Map the given inp to a CPU id. 224 * 225 * This queries RSS if it's compiled in, else it defaults to the current 226 * CPU ID. 227 */ 228inline int 229inp_to_cpuid(struct inpcb *inp) 230{ 231 u_int cpuid; 232 233 if (per_cpu_timers) { 234#ifdef RSS 235 cpuid = rss_hash2cpuid(inp->inp_flowid, inp->inp_flowtype); 236 if (cpuid == NETISR_CPUID_NONE) 237 return (curcpu); /* XXX */ 238 else 239 return (cpuid); 240#endif 241 /* 242 * We don't have a flowid -> cpuid mapping, so cheat and 243 * just map unknown cpuids to curcpu. Not the best, but 244 * apparently better than defaulting to swi 0. 245 */ 246 cpuid = inp->inp_flowid % (mp_maxid + 1); 247 if (! CPU_ABSENT(cpuid)) 248 return (cpuid); 249 return (curcpu); 250 } else { 251 return (0); 252 } 253} 254 255int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 256 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 }; 257 258int tcp_totbackoff = 2559; /* sum of tcp_backoff[] */ 259 260/* 261 * TCP timer processing. 262 * 263 * Each connection has 5 timers associated with it, which can be scheduled 264 * simultaneously. They all are serviced by one callout tcp_timer_enter(). 265 * This function executes the next timer via tcp_timersw[] vector. Each 266 * timer is supposed to return 'true' unless the connection was destroyed. 267 * In the former case tcp_timer_enter() will schedule callout for next timer. 268 */ 269 270typedef bool tcp_timer_t(struct tcpcb *); 271static tcp_timer_t tcp_timer_delack; 272static tcp_timer_t tcp_timer_2msl; 273static tcp_timer_t tcp_timer_keep; 274static tcp_timer_t tcp_timer_persist; 275static tcp_timer_t tcp_timer_rexmt; 276 277static tcp_timer_t * const tcp_timersw[TT_N] = { 278 [TT_DELACK] = tcp_timer_delack, 279 [TT_REXMT] = tcp_timer_rexmt, 280 [TT_PERSIST] = tcp_timer_persist, 281 [TT_KEEP] = tcp_timer_keep, 282 [TT_2MSL] = tcp_timer_2msl, 283}; 284 285/* 286 * tcp_output_locked() s a timer specific variation of call to tcp_output(), 287 * see tcp_var.h for the rest. It handles drop request from advanced stacks, 288 * but keeps tcpcb locked unless tcp_drop() destroyed it. 289 * Returns true if tcpcb is valid and locked. 290 */ 291static inline bool 292tcp_output_locked(struct tcpcb *tp) 293{ 294 int rv; 295 296 INP_WLOCK_ASSERT(tptoinpcb(tp)); 297 298 if ((rv = tp->t_fb->tfb_tcp_output(tp)) < 0) { 299 KASSERT(tp->t_fb->tfb_flags & TCP_FUNC_OUTPUT_CANDROP, 300 ("TCP stack %s requested tcp_drop(%p)", 301 tp->t_fb->tfb_tcp_block_name, tp)); 302 tp = tcp_drop(tp, -rv); 303 } 304 305 return (tp != NULL); 306} 307 308static bool 309tcp_timer_delack(struct tcpcb *tp) 310{ 311 struct epoch_tracker et; 312#if defined(INVARIANTS) || defined(VIMAGE) 313 struct inpcb *inp = tptoinpcb(tp); 314#endif 315 bool rv; 316 317 INP_WLOCK_ASSERT(inp); 318 319 CURVNET_SET(inp->inp_vnet); 320 tp->t_flags |= TF_ACKNOW; 321 TCPSTAT_INC(tcps_delack); 322 NET_EPOCH_ENTER(et); 323 rv = tcp_output_locked(tp); 324 NET_EPOCH_EXIT(et); 325 CURVNET_RESTORE(); 326 327 return (rv); 328} 329 330static bool 331tcp_timer_2msl(struct tcpcb *tp) 332{ 333 struct inpcb *inp = tptoinpcb(tp); 334 bool close = false; 335 336 INP_WLOCK_ASSERT(inp); 337 338 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO); 339 CURVNET_SET(inp->inp_vnet); 340 tcp_log_end_status(tp, TCP_EI_STATUS_2MSL); 341 tcp_free_sackholes(tp); 342 /* 343 * 2 MSL timeout in shutdown went off. If we're closed but 344 * still waiting for peer to close and connection has been idle 345 * too long delete connection control block. Otherwise, check 346 * again in a bit. 347 * 348 * If fastrecycle of FIN_WAIT_2, in FIN_WAIT_2 and receiver has closed, 349 * there's no point in hanging onto FIN_WAIT_2 socket. Just close it. 350 * Ignore fact that there were recent incoming segments. 351 * 352 * XXXGL: check if inp_socket shall always be !NULL here? 353 */ 354 if (tp->t_state == TCPS_TIME_WAIT) { 355 close = true; 356 } else if (tp->t_state == TCPS_FIN_WAIT_2 && 357 tcp_fast_finwait2_recycle && inp->inp_socket && 358 (inp->inp_socket->so_rcv.sb_state & SBS_CANTRCVMORE)) { 359 TCPSTAT_INC(tcps_finwait2_drops); 360 close = true; 361 } else { 362 if (ticks - tp->t_rcvtime <= TP_MAXIDLE(tp)) 363 tcp_timer_activate(tp, TT_2MSL, TP_KEEPINTVL(tp)); 364 else 365 close = true; 366 } 367 if (close) { 368 struct epoch_tracker et; 369 370 NET_EPOCH_ENTER(et); 371 tp = tcp_close(tp); 372 NET_EPOCH_EXIT(et); 373 } 374 CURVNET_RESTORE(); 375 376 return (tp != NULL); 377} 378 379static bool 380tcp_timer_keep(struct tcpcb *tp) 381{ 382 struct epoch_tracker et; 383 struct inpcb *inp = tptoinpcb(tp); 384 struct tcptemp *t_template; 385 386 INP_WLOCK_ASSERT(inp); 387 388 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO); 389 CURVNET_SET(inp->inp_vnet); 390 /* 391 * Because we don't regularly reset the keepalive callout in 392 * the ESTABLISHED state, it may be that we don't actually need 393 * to send a keepalive yet. If that occurs, schedule another 394 * call for the next time the keepalive timer might expire. 395 */ 396 if (TCPS_HAVEESTABLISHED(tp->t_state)) { 397 u_int idletime; 398 399 idletime = ticks - tp->t_rcvtime; 400 if (idletime < TP_KEEPIDLE(tp)) { 401 tcp_timer_activate(tp, TT_KEEP, 402 TP_KEEPIDLE(tp) - idletime); 403 CURVNET_RESTORE(); 404 return (true); 405 } 406 } 407 408 /* 409 * Keep-alive timer went off; send something 410 * or drop connection if idle for too long. 411 */ 412 TCPSTAT_INC(tcps_keeptimeo); 413 if (tp->t_state < TCPS_ESTABLISHED) 414 goto dropit; 415 if ((V_tcp_always_keepalive || 416 inp->inp_socket->so_options & SO_KEEPALIVE) && 417 tp->t_state <= TCPS_CLOSING) { 418 if (ticks - tp->t_rcvtime >= TP_KEEPIDLE(tp) + TP_MAXIDLE(tp)) 419 goto dropit; 420 /* 421 * Send a packet designed to force a response 422 * if the peer is up and reachable: 423 * either an ACK if the connection is still alive, 424 * or an RST if the peer has closed the connection 425 * due to timeout or reboot. 426 * Using sequence number tp->snd_una-1 427 * causes the transmitted zero-length segment 428 * to lie outside the receive window; 429 * by the protocol spec, this requires the 430 * correspondent TCP to respond. 431 */ 432 TCPSTAT_INC(tcps_keepprobe); 433 t_template = tcpip_maketemplate(inp); 434 if (t_template) { 435 NET_EPOCH_ENTER(et); 436 tcp_respond(tp, t_template->tt_ipgen, 437 &t_template->tt_t, (struct mbuf *)NULL, 438 tp->rcv_nxt, tp->snd_una - 1, 0); 439 NET_EPOCH_EXIT(et); 440 free(t_template, M_TEMP); 441 } 442 tcp_timer_activate(tp, TT_KEEP, TP_KEEPINTVL(tp)); 443 } else 444 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 445 446 CURVNET_RESTORE(); 447 return (true); 448 449dropit: 450 TCPSTAT_INC(tcps_keepdrops); 451 NET_EPOCH_ENTER(et); 452 tcp_log_end_status(tp, TCP_EI_STATUS_KEEP_MAX); 453 tp = tcp_drop(tp, ETIMEDOUT); 454 NET_EPOCH_EXIT(et); 455 CURVNET_RESTORE(); 456 457 return (tp != NULL); 458} 459 460/* 461 * Has this session exceeded the maximum time without seeing a substantive 462 * acknowledgement? If so, return true; otherwise false. 463 */ 464static bool 465tcp_maxunacktime_check(struct tcpcb *tp) 466{ 467 468 /* Are we tracking this timer for this session? */ 469 if (TP_MAXUNACKTIME(tp) == 0) 470 return false; 471 472 /* Do we have a current measurement. */ 473 if (tp->t_acktime == 0) 474 return false; 475 476 /* Are we within the acceptable range? */ 477 if (TSTMP_GT(TP_MAXUNACKTIME(tp) + tp->t_acktime, (u_int)ticks)) 478 return false; 479 480 /* We exceeded the timer. */ 481 TCPSTAT_INC(tcps_progdrops); 482 return true; 483} 484 485static bool 486tcp_timer_persist(struct tcpcb *tp) 487{ 488 struct epoch_tracker et; 489#if defined(INVARIANTS) || defined(VIMAGE) 490 struct inpcb *inp = tptoinpcb(tp); 491#endif 492 bool progdrop, rv; 493 494 INP_WLOCK_ASSERT(inp); 495 496 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO); 497 CURVNET_SET(inp->inp_vnet); 498 /* 499 * Persistence timer into zero window. 500 * Force a byte to be output, if possible. 501 */ 502 TCPSTAT_INC(tcps_persisttimeo); 503 /* 504 * Hack: if the peer is dead/unreachable, we do not 505 * time out if the window is closed. After a full 506 * backoff, drop the connection if the idle time 507 * (no responses to probes) reaches the maximum 508 * backoff that we would use if retransmitting. 509 * Also, drop the connection if we haven't been making 510 * progress. 511 */ 512 progdrop = tcp_maxunacktime_check(tp); 513 if (progdrop || (tp->t_rxtshift >= V_tcp_retries && 514 (ticks - tp->t_rcvtime >= tcp_maxpersistidle || 515 ticks - tp->t_rcvtime >= TCP_REXMTVAL(tp) * tcp_totbackoff))) { 516 if (!progdrop) 517 TCPSTAT_INC(tcps_persistdrop); 518 tcp_log_end_status(tp, TCP_EI_STATUS_PERSIST_MAX); 519 goto dropit; 520 } 521 /* 522 * If the user has closed the socket then drop a persisting 523 * connection after a much reduced timeout. 524 */ 525 if (tp->t_state > TCPS_CLOSE_WAIT && 526 (ticks - tp->t_rcvtime) >= TCPTV_PERSMAX) { 527 TCPSTAT_INC(tcps_persistdrop); 528 tcp_log_end_status(tp, TCP_EI_STATUS_PERSIST_MAX); 529 goto dropit; 530 } 531 tcp_setpersist(tp); 532 tp->t_flags |= TF_FORCEDATA; 533 NET_EPOCH_ENTER(et); 534 if ((rv = tcp_output_locked(tp))) 535 tp->t_flags &= ~TF_FORCEDATA; 536 NET_EPOCH_EXIT(et); 537 CURVNET_RESTORE(); 538 539 return (rv); 540 541dropit: 542 NET_EPOCH_ENTER(et); 543 tp = tcp_drop(tp, ETIMEDOUT); 544 NET_EPOCH_EXIT(et); 545 CURVNET_RESTORE(); 546 547 return (tp != NULL); 548} 549 550static bool 551tcp_timer_rexmt(struct tcpcb *tp) 552{ 553 struct epoch_tracker et; 554 struct inpcb *inp = tptoinpcb(tp); 555 int rexmt; 556 bool isipv6, rv; 557 558 INP_WLOCK_ASSERT(inp); 559 560 TCP_PROBE2(debug__user, tp, PRU_SLOWTIMO); 561 CURVNET_SET(inp->inp_vnet); 562 if (tp->t_fb->tfb_tcp_rexmit_tmr) { 563 /* The stack has a timer action too. */ 564 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp); 565 } 566 /* 567 * Retransmission timer went off. Message has not 568 * been acked within retransmit interval. Back off 569 * to a longer retransmit interval and retransmit one segment. 570 * 571 * If we've either exceeded the maximum number of retransmissions, 572 * or we've gone long enough without making progress, then drop 573 * the session. 574 */ 575 if (++tp->t_rxtshift > V_tcp_retries || tcp_maxunacktime_check(tp)) { 576 if (tp->t_rxtshift > V_tcp_retries) 577 TCPSTAT_INC(tcps_timeoutdrop); 578 tp->t_rxtshift = V_tcp_retries; 579 tcp_log_end_status(tp, TCP_EI_STATUS_RETRAN); 580 NET_EPOCH_ENTER(et); 581 tp = tcp_drop(tp, ETIMEDOUT); 582 NET_EPOCH_EXIT(et); 583 CURVNET_RESTORE(); 584 585 return (tp != NULL); 586 } 587 if (tp->t_state == TCPS_SYN_SENT) { 588 /* 589 * If the SYN was retransmitted, indicate CWND to be 590 * limited to 1 segment in cc_conn_init(). 591 */ 592 tp->snd_cwnd = 1; 593 } else if (tp->t_rxtshift == 1) { 594 /* 595 * first retransmit; record ssthresh and cwnd so they can 596 * be recovered if this turns out to be a "bad" retransmit. 597 * A retransmit is considered "bad" if an ACK for this 598 * segment is received within RTT/2 interval; the assumption 599 * here is that the ACK was already in flight. See 600 * "On Estimating End-to-End Network Path Properties" by 601 * Allman and Paxson for more details. 602 */ 603 tp->snd_cwnd_prev = tp->snd_cwnd; 604 tp->snd_ssthresh_prev = tp->snd_ssthresh; 605 tp->snd_recover_prev = tp->snd_recover; 606 if (IN_FASTRECOVERY(tp->t_flags)) 607 tp->t_flags |= TF_WASFRECOVERY; 608 else 609 tp->t_flags &= ~TF_WASFRECOVERY; 610 if (IN_CONGRECOVERY(tp->t_flags)) 611 tp->t_flags |= TF_WASCRECOVERY; 612 else 613 tp->t_flags &= ~TF_WASCRECOVERY; 614 if ((tp->t_flags & TF_RCVD_TSTMP) == 0) 615 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 616 /* In the event that we've negotiated timestamps 617 * badrxtwin will be set to the value that we set 618 * the retransmitted packet's to_tsval to by tcp_output 619 */ 620 tp->t_flags |= TF_PREVVALID; 621 tcp_resend_sackholes(tp); 622 } else { 623 tp->t_flags &= ~TF_PREVVALID; 624 tcp_free_sackholes(tp); 625 } 626 TCPSTAT_INC(tcps_rexmttimeo); 627 if ((tp->t_state == TCPS_SYN_SENT) || 628 (tp->t_state == TCPS_SYN_RECEIVED)) 629 rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift]; 630 else 631 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 632 TCPT_RANGESET(tp->t_rxtcur, rexmt, 633 tp->t_rttmin, TCPTV_REXMTMAX); 634 635 /* 636 * We enter the path for PLMTUD if connection is established or, if 637 * connection is FIN_WAIT_1 status, reason for the last is that if 638 * amount of data we send is very small, we could send it in couple of 639 * packets and process straight to FIN. In that case we won't catch 640 * ESTABLISHED state. 641 */ 642#ifdef INET6 643 isipv6 = (inp->inp_vflag & INP_IPV6) ? true : false; 644#else 645 isipv6 = false; 646#endif 647 if (((V_tcp_pmtud_blackhole_detect == 1) || 648 (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) || 649 (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) && 650 ((tp->t_state == TCPS_ESTABLISHED) || 651 (tp->t_state == TCPS_FIN_WAIT_1))) { 652 if (tp->t_rxtshift == 1) { 653 /* 654 * We enter blackhole detection after the first 655 * unsuccessful timer based retransmission. 656 * Then we reduce up to two times the MSS, each 657 * candidate giving two tries of retransmissions. 658 * But we give a candidate only two tries, if it 659 * actually reduces the MSS. 660 */ 661 tp->t_blackhole_enter = 2; 662 tp->t_blackhole_exit = tp->t_blackhole_enter; 663 if (isipv6) { 664#ifdef INET6 665 if (tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) 666 tp->t_blackhole_exit += 2; 667 if (tp->t_maxseg > V_tcp_v6mssdflt && 668 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) 669 tp->t_blackhole_exit += 2; 670#endif 671 } else { 672#ifdef INET 673 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss) 674 tp->t_blackhole_exit += 2; 675 if (tp->t_maxseg > V_tcp_mssdflt && 676 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) 677 tp->t_blackhole_exit += 2; 678#endif 679 } 680 } 681 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) == 682 (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) && 683 (tp->t_rxtshift >= tp->t_blackhole_enter && 684 tp->t_rxtshift < tp->t_blackhole_exit && 685 (tp->t_rxtshift - tp->t_blackhole_enter) % 2 == 0)) { 686 /* 687 * Enter Path MTU Black-hole Detection mechanism: 688 * - Disable Path MTU Discovery (IP "DF" bit). 689 * - Reduce MTU to lower value than what we 690 * negotiated with peer. 691 */ 692 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) { 693 /* Record that we may have found a black hole. */ 694 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE; 695 /* Keep track of previous MSS. */ 696 tp->t_pmtud_saved_maxseg = tp->t_maxseg; 697 } 698 699 /* 700 * Reduce the MSS to blackhole value or to the default 701 * in an attempt to retransmit. 702 */ 703#ifdef INET6 704 if (isipv6 && 705 tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss && 706 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) { 707 /* Use the sysctl tuneable blackhole MSS. */ 708 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss; 709 TCPSTAT_INC(tcps_pmtud_blackhole_activated); 710 } else if (isipv6) { 711 /* Use the default MSS. */ 712 tp->t_maxseg = V_tcp_v6mssdflt; 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#if defined(INET6) && defined(INET) 722 else 723#endif 724#ifdef INET 725 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss && 726 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) { 727 /* Use the sysctl tuneable blackhole MSS. */ 728 tp->t_maxseg = V_tcp_pmtud_blackhole_mss; 729 TCPSTAT_INC(tcps_pmtud_blackhole_activated); 730 } else { 731 /* Use the default MSS. */ 732 tp->t_maxseg = V_tcp_mssdflt; 733 /* 734 * Disable Path MTU Discovery when we switch to 735 * minmss. 736 */ 737 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 738 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss); 739 } 740#endif 741 /* 742 * Reset the slow-start flight size 743 * as it 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 } else { 748 /* 749 * If further retransmissions are still unsuccessful 750 * with a lowered MTU, maybe this isn't a blackhole and 751 * we restore the previous MSS and blackhole detection 752 * flags. 753 */ 754 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) && 755 (tp->t_rxtshift >= tp->t_blackhole_exit)) { 756 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 757 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE; 758 tp->t_maxseg = tp->t_pmtud_saved_maxseg; 759 if (tp->t_maxseg < V_tcp_mssdflt) { 760 /* 761 * The MSS is so small we should not 762 * process incoming SACK's since we are 763 * subject to attack in such a case. 764 */ 765 tp->t_flags2 |= TF2_PROC_SACK_PROHIBIT; 766 } else { 767 tp->t_flags2 &= ~TF2_PROC_SACK_PROHIBIT; 768 } 769 TCPSTAT_INC(tcps_pmtud_blackhole_failed); 770 /* 771 * Reset the slow-start flight size as it 772 * may depend on the new MSS. 773 */ 774 if (CC_ALGO(tp)->conn_init != NULL) 775 CC_ALGO(tp)->conn_init(&tp->t_ccv); 776 } 777 } 778 } 779 780 /* 781 * Disable RFC1323 and SACK if we haven't got any response to 782 * our third SYN to work-around some broken terminal servers 783 * (most of which have hopefully been retired) that have bad VJ 784 * header compression code which trashes TCP segments containing 785 * unknown-to-them TCP options. 786 */ 787 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) && 788 (tp->t_rxtshift == 3)) 789 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT); 790 /* 791 * If we backed off this far, notify the L3 protocol that we're having 792 * connection problems. 793 */ 794 if (tp->t_rxtshift > TCP_RTT_INVALIDATE) { 795#ifdef INET6 796 if ((inp->inp_vflag & INP_IPV6) != 0) 797 in6_losing(inp); 798 else 799#endif 800 in_losing(inp); 801 } 802 tp->snd_nxt = tp->snd_una; 803 tp->snd_recover = tp->snd_max; 804 /* 805 * Force a segment to be sent. 806 */ 807 tp->t_flags |= TF_ACKNOW; 808 /* 809 * If timing a segment in this window, stop the timer. 810 */ 811 tp->t_rtttime = 0; 812 813 cc_cong_signal(tp, NULL, CC_RTO); 814 NET_EPOCH_ENTER(et); 815 rv = tcp_output_locked(tp); 816 NET_EPOCH_EXIT(et); 817 CURVNET_RESTORE(); 818 819 return (rv); 820} 821 822static void 823tcp_bblog_timer(struct tcpcb *tp, tt_which which, tt_what what, uint32_t ticks) 824{ 825 struct tcp_log_buffer *lgb; 826 uint64_t ms; 827 828 INP_WLOCK_ASSERT(tptoinpcb(tp)); 829 if (tcp_bblogging_on(tp)) 830 lgb = tcp_log_event(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0, 831 NULL, false, NULL, NULL, 0, NULL); 832 else 833 lgb = NULL; 834 if (lgb != NULL) { 835 lgb->tlb_flex1 = (what << 8) | which; 836 if (what == TT_STARTING) { 837 /* Convert ticks to ms and store it in tlb_flex2. */ 838 if (hz == 1000) 839 lgb->tlb_flex2 = ticks; 840 else { 841 ms = (((uint64_t)ticks * 1000) + (hz - 1)) / hz; 842 if (ms > UINT32_MAX) 843 lgb->tlb_flex2 = UINT32_MAX; 844 else 845 lgb->tlb_flex2 = (uint32_t)ms; 846 } 847 } 848 } 849} 850 851static inline tt_which 852tcp_timer_next(struct tcpcb *tp, sbintime_t *precision) 853{ 854 tt_which i, rv; 855 sbintime_t after, before; 856 857 for (i = 0, rv = TT_N, after = before = SBT_MAX; i < TT_N; i++) { 858 if (tp->t_timers[i] < after) { 859 after = tp->t_timers[i]; 860 rv = i; 861 } 862 before = MIN(before, tp->t_timers[i] + tp->t_precisions[i]); 863 } 864 if (precision != NULL) 865 *precision = before - after; 866 867 return (rv); 868} 869 870static void 871tcp_timer_enter(void *xtp) 872{ 873 struct tcpcb *tp = xtp; 874 struct inpcb *inp = tptoinpcb(tp); 875 sbintime_t precision; 876 tt_which which; 877 bool tp_valid; 878 879 INP_WLOCK_ASSERT(inp); 880 MPASS((curthread->td_pflags & TDP_INTCPCALLOUT) == 0); 881 882 curthread->td_pflags |= TDP_INTCPCALLOUT; 883 884 which = tcp_timer_next(tp, NULL); 885 MPASS(which < TT_N); 886 tp->t_timers[which] = SBT_MAX; 887 tp->t_precisions[which] = 0; 888 889 tcp_bblog_timer(tp, which, TT_PROCESSING, 0); 890 tp_valid = tcp_timersw[which](tp); 891 if (tp_valid) { 892 tcp_bblog_timer(tp, which, TT_PROCESSED, 0); 893 if ((which = tcp_timer_next(tp, &precision)) != TT_N) { 894 MPASS(tp->t_state > TCPS_CLOSED); 895 callout_reset_sbt_on(&tp->t_callout, 896 tp->t_timers[which], precision, tcp_timer_enter, 897 tp, inp_to_cpuid(inp), C_ABSOLUTE); 898 } 899 INP_WUNLOCK(inp); 900 } 901 902 curthread->td_pflags &= ~TDP_INTCPCALLOUT; 903} 904 905/* 906 * Activate or stop (delta == 0) a TCP timer. 907 */ 908void 909tcp_timer_activate(struct tcpcb *tp, tt_which which, u_int delta) 910{ 911 struct inpcb *inp = tptoinpcb(tp); 912 sbintime_t precision; 913 tt_what what; 914 915#ifdef TCP_OFFLOAD 916 if (tp->t_flags & TF_TOE) 917 return; 918#endif 919 920 INP_WLOCK_ASSERT(inp); 921 MPASS(tp->t_state > TCPS_CLOSED); 922 923 if (delta > 0) { 924 what = TT_STARTING; 925 callout_when(tick_sbt * delta, 0, C_HARDCLOCK, 926 &tp->t_timers[which], &tp->t_precisions[which]); 927 } else { 928 what = TT_STOPPING; 929 tp->t_timers[which] = SBT_MAX; 930 } 931 tcp_bblog_timer(tp, which, what, delta); 932 933 if ((which = tcp_timer_next(tp, &precision)) != TT_N) 934 callout_reset_sbt_on(&tp->t_callout, tp->t_timers[which], 935 precision, tcp_timer_enter, tp, inp_to_cpuid(inp), 936 C_ABSOLUTE); 937 else 938 callout_stop(&tp->t_callout); 939} 940 941bool 942tcp_timer_active(struct tcpcb *tp, tt_which which) 943{ 944 945 INP_WLOCK_ASSERT(tptoinpcb(tp)); 946 947 return (tp->t_timers[which] != SBT_MAX); 948} 949 950/* 951 * Stop all timers associated with tcpcb. 952 * 953 * Called when tcpcb moves to TCPS_CLOSED. 954 * 955 * XXXGL: unfortunately our callout(9) is not able to fully stop a locked 956 * callout even when only two threads are involved: the callout itself and the 957 * thread that does callout_stop(). See where softclock_call_cc() swaps the 958 * callwheel lock to callout lock and then checks cc_exec_cancel(). This is 959 * the race window. If it happens, the tcp_timer_enter() won't be executed, 960 * however pcb lock will be locked and released, hence we can't free memory. 961 * Until callout(9) is improved, just keep retrying. In my profiling I've seen 962 * such event happening less than 1 time per hour with 20-30 Gbit/s of traffic. 963 */ 964void 965tcp_timer_stop(struct tcpcb *tp) 966{ 967 struct inpcb *inp = tptoinpcb(tp); 968 969 INP_WLOCK_ASSERT(inp); 970 971 if (curthread->td_pflags & TDP_INTCPCALLOUT) { 972 int stopped __diagused; 973 974 stopped = callout_stop(&tp->t_callout); 975 MPASS(stopped == 0); 976 for (tt_which i = 0; i < TT_N; i++) 977 tp->t_timers[i] = SBT_MAX; 978 } else while(__predict_false(callout_stop(&tp->t_callout) == 0)) { 979 INP_WUNLOCK(inp); 980 kern_yield(PRI_UNCHANGED); 981 INP_WLOCK(inp); 982 } 983} 984