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 76 int tcp_persmin; 77 SYSCTL_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 82 int tcp_persmax; 83 SYSCTL_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 88 int tcp_keepinit; 89 SYSCTL_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 94 int tcp_keepidle; 95 SYSCTL_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"); 99 100 int tcp_keepintvl; 101 SYSCTL_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"); 105 106 int tcp_delacktime; 107 SYSCTL_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"); 111 112 VNET_DEFINE(int, tcp_msl); 113 SYSCTL_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"); 117 118 int tcp_rexmit_initial; 119 SYSCTL_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"); 123 124 int tcp_rexmit_min; 125 SYSCTL_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"); 129 130 int tcp_rexmit_slop; 131 SYSCTL_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"); 135 136 VNET_DEFINE(int, tcp_always_keepalive) = 1; 137 SYSCTL_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"); 140 141 int tcp_fast_finwait2_recycle = 0; 142 SYSCTL_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"); 145 146 int tcp_finwait2_timeout; 147 SYSCTL_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"); 151 152 int tcp_keepcnt = TCPTV_KEEPCNT; 153 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0, 154 "Number of keepalive probes to send"); 155 156 /* max idle probes */ 157 int tcp_maxpersistidle; 158 159 int tcp_rexmit_drop_options = 0; 160 SYSCTL_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"); 163 164 int tcp_maxunacktime = TCPTV_MAXUNACKTIME; 165 SYSCTL_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"); 169 170 VNET_DEFINE(int, tcp_pmtud_blackhole_detect); 171 SYSCTL_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 177 VNET_DEFINE(int, tcp_pmtud_blackhole_mss) = 1200; 178 SYSCTL_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 185 VNET_DEFINE(int, tcp_v6pmtud_blackhole_mss) = 1220; 186 SYSCTL_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 193 static int per_cpu_timers = 1; 194 #else 195 static int per_cpu_timers = 0; 196 #endif 197 SYSCTL_INT(_net_inet_tcp, OID_AUTO, per_cpu_timers, CTLFLAG_RW, 198 &per_cpu_timers , 0, "run tcp timers on all cpus"); 199 200 static int 201 sysctl_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 } 215 216 VNET_DEFINE(int, tcp_retries) = TCP_MAXRXTSHIFT; 217 SYSCTL_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 */ 228 inline int 229 inp_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 } 254 255 int tcp_backoff[TCP_MAXRXTSHIFT + 1] = 256 { 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 512, 512, 512 }; 257 258 int 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 */ 269 270 typedef bool tcp_timer_t(struct tcpcb *); 271 static tcp_timer_t tcp_timer_delack; 272 static tcp_timer_t tcp_timer_2msl; 273 static tcp_timer_t tcp_timer_keep; 274 static tcp_timer_t tcp_timer_persist; 275 static tcp_timer_t tcp_timer_rexmt; 276 277 static 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 */ 291 static inline bool 292 tcp_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 } 307 308 static bool 309 tcp_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 } 329 330 static bool 331 tcp_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 } 378 379 static bool 380 tcp_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); 448 449 dropit: 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 */ 464 static bool 465 tcp_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 } 484 485 static bool 486 tcp_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); 540 541 dropit: 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 } 549 550 static bool 551 tcp_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 tcp_free_sackholes(tp); 563 if (tp->t_fb->tfb_tcp_rexmit_tmr) { 564 /* The stack has a timer action too. */ 565 (*tp->t_fb->tfb_tcp_rexmit_tmr)(tp); 566 } 567 /* 568 * Retransmission timer went off. Message has not 569 * been acked within retransmit interval. Back off 570 * to a longer retransmit interval and retransmit one segment. 571 * 572 * If we've either exceeded the maximum number of retransmissions, 573 * or we've gone long enough without making progress, then drop 574 * the session. 575 */ 576 if (++tp->t_rxtshift > V_tcp_retries || tcp_maxunacktime_check(tp)) { 577 if (tp->t_rxtshift > V_tcp_retries) 578 TCPSTAT_INC(tcps_timeoutdrop); 579 tp->t_rxtshift = V_tcp_retries; 580 tcp_log_end_status(tp, TCP_EI_STATUS_RETRAN); 581 NET_EPOCH_ENTER(et); 582 tp = tcp_drop(tp, ETIMEDOUT); 583 NET_EPOCH_EXIT(et); 584 CURVNET_RESTORE(); 585 586 return (tp != NULL); 587 } 588 if (tp->t_state == TCPS_SYN_SENT) { 589 /* 590 * If the SYN was retransmitted, indicate CWND to be 591 * limited to 1 segment in cc_conn_init(). 592 */ 593 tp->snd_cwnd = 1; 594 } else if (tp->t_rxtshift == 1) { 595 /* 596 * first retransmit; record ssthresh and cwnd so they can 597 * be recovered if this turns out to be a "bad" retransmit. 598 * A retransmit is considered "bad" if an ACK for this 599 * segment is received within RTT/2 interval; the assumption 600 * here is that the ACK was already in flight. See 601 * "On Estimating End-to-End Network Path Properties" by 602 * Allman and Paxson for more details. 603 */ 604 tp->snd_cwnd_prev = tp->snd_cwnd; 605 tp->snd_ssthresh_prev = tp->snd_ssthresh; 606 tp->snd_recover_prev = tp->snd_recover; 607 if (IN_FASTRECOVERY(tp->t_flags)) 608 tp->t_flags |= TF_WASFRECOVERY; 609 else 610 tp->t_flags &= ~TF_WASFRECOVERY; 611 if (IN_CONGRECOVERY(tp->t_flags)) 612 tp->t_flags |= TF_WASCRECOVERY; 613 else 614 tp->t_flags &= ~TF_WASCRECOVERY; 615 if ((tp->t_flags & TF_RCVD_TSTMP) == 0) 616 tp->t_badrxtwin = ticks + (tp->t_srtt >> (TCP_RTT_SHIFT + 1)); 617 /* In the event that we've negotiated timestamps 618 * badrxtwin will be set to the value that we set 619 * the retransmitted packet's to_tsval to by tcp_output 620 */ 621 tp->t_flags |= TF_PREVVALID; 622 } else 623 tp->t_flags &= ~TF_PREVVALID; 624 TCPSTAT_INC(tcps_rexmttimeo); 625 if ((tp->t_state == TCPS_SYN_SENT) || 626 (tp->t_state == TCPS_SYN_RECEIVED)) 627 rexmt = tcp_rexmit_initial * tcp_backoff[tp->t_rxtshift]; 628 else 629 rexmt = TCP_REXMTVAL(tp) * tcp_backoff[tp->t_rxtshift]; 630 TCPT_RANGESET(tp->t_rxtcur, rexmt, 631 tp->t_rttmin, TCPTV_REXMTMAX); 632 633 /* 634 * We enter the path for PLMTUD if connection is established or, if 635 * connection is FIN_WAIT_1 status, reason for the last is that if 636 * amount of data we send is very small, we could send it in couple of 637 * packets and process straight to FIN. In that case we won't catch 638 * ESTABLISHED state. 639 */ 640 #ifdef INET6 641 isipv6 = (inp->inp_vflag & INP_IPV6) ? true : false; 642 #else 643 isipv6 = false; 644 #endif 645 if (((V_tcp_pmtud_blackhole_detect == 1) || 646 (V_tcp_pmtud_blackhole_detect == 2 && !isipv6) || 647 (V_tcp_pmtud_blackhole_detect == 3 && isipv6)) && 648 ((tp->t_state == TCPS_ESTABLISHED) || 649 (tp->t_state == TCPS_FIN_WAIT_1))) { 650 if (tp->t_rxtshift == 1) { 651 /* 652 * We enter blackhole detection after the first 653 * unsuccessful timer based retransmission. 654 * Then we reduce up to two times the MSS, each 655 * candidate giving two tries of retransmissions. 656 * But we give a candidate only two tries, if it 657 * actually reduces the MSS. 658 */ 659 tp->t_blackhole_enter = 2; 660 tp->t_blackhole_exit = tp->t_blackhole_enter; 661 if (isipv6) { 662 #ifdef INET6 663 if (tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss) 664 tp->t_blackhole_exit += 2; 665 if (tp->t_maxseg > V_tcp_v6mssdflt && 666 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) 667 tp->t_blackhole_exit += 2; 668 #endif 669 } else { 670 #ifdef INET 671 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss) 672 tp->t_blackhole_exit += 2; 673 if (tp->t_maxseg > V_tcp_mssdflt && 674 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) 675 tp->t_blackhole_exit += 2; 676 #endif 677 } 678 } 679 if (((tp->t_flags2 & (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) == 680 (TF2_PLPMTU_PMTUD|TF2_PLPMTU_MAXSEGSNT)) && 681 (tp->t_rxtshift >= tp->t_blackhole_enter && 682 tp->t_rxtshift < tp->t_blackhole_exit && 683 (tp->t_rxtshift - tp->t_blackhole_enter) % 2 == 0)) { 684 /* 685 * Enter Path MTU Black-hole Detection mechanism: 686 * - Disable Path MTU Discovery (IP "DF" bit). 687 * - Reduce MTU to lower value than what we 688 * negotiated with peer. 689 */ 690 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) == 0) { 691 /* Record that we may have found a black hole. */ 692 tp->t_flags2 |= TF2_PLPMTU_BLACKHOLE; 693 /* Keep track of previous MSS. */ 694 tp->t_pmtud_saved_maxseg = tp->t_maxseg; 695 } 696 697 /* 698 * Reduce the MSS to blackhole value or to the default 699 * in an attempt to retransmit. 700 */ 701 #ifdef INET6 702 if (isipv6 && 703 tp->t_maxseg > V_tcp_v6pmtud_blackhole_mss && 704 V_tcp_v6pmtud_blackhole_mss > V_tcp_v6mssdflt) { 705 /* Use the sysctl tuneable blackhole MSS. */ 706 tp->t_maxseg = V_tcp_v6pmtud_blackhole_mss; 707 TCPSTAT_INC(tcps_pmtud_blackhole_activated); 708 } else if (isipv6) { 709 /* Use the default MSS. */ 710 tp->t_maxseg = V_tcp_v6mssdflt; 711 /* 712 * Disable Path MTU Discovery when we switch to 713 * minmss. 714 */ 715 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 716 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss); 717 } 718 #endif 719 #if defined(INET6) && defined(INET) 720 else 721 #endif 722 #ifdef INET 723 if (tp->t_maxseg > V_tcp_pmtud_blackhole_mss && 724 V_tcp_pmtud_blackhole_mss > V_tcp_mssdflt) { 725 /* Use the sysctl tuneable blackhole MSS. */ 726 tp->t_maxseg = V_tcp_pmtud_blackhole_mss; 727 TCPSTAT_INC(tcps_pmtud_blackhole_activated); 728 } else { 729 /* Use the default MSS. */ 730 tp->t_maxseg = V_tcp_mssdflt; 731 /* 732 * Disable Path MTU Discovery when we switch to 733 * minmss. 734 */ 735 tp->t_flags2 &= ~TF2_PLPMTU_PMTUD; 736 TCPSTAT_INC(tcps_pmtud_blackhole_activated_min_mss); 737 } 738 #endif 739 /* 740 * Reset the slow-start flight size 741 * as it may depend on the new MSS. 742 */ 743 if (CC_ALGO(tp)->conn_init != NULL) 744 CC_ALGO(tp)->conn_init(&tp->t_ccv); 745 } else { 746 /* 747 * If further retransmissions are still unsuccessful 748 * with a lowered MTU, maybe this isn't a blackhole and 749 * we restore the previous MSS and blackhole detection 750 * flags. 751 */ 752 if ((tp->t_flags2 & TF2_PLPMTU_BLACKHOLE) && 753 (tp->t_rxtshift >= tp->t_blackhole_exit)) { 754 tp->t_flags2 |= TF2_PLPMTU_PMTUD; 755 tp->t_flags2 &= ~TF2_PLPMTU_BLACKHOLE; 756 tp->t_maxseg = tp->t_pmtud_saved_maxseg; 757 TCPSTAT_INC(tcps_pmtud_blackhole_failed); 758 /* 759 * Reset the slow-start flight size as it 760 * may depend on the new MSS. 761 */ 762 if (CC_ALGO(tp)->conn_init != NULL) 763 CC_ALGO(tp)->conn_init(&tp->t_ccv); 764 } 765 } 766 } 767 768 /* 769 * Disable RFC1323 and SACK if we haven't got any response to 770 * our third SYN to work-around some broken terminal servers 771 * (most of which have hopefully been retired) that have bad VJ 772 * header compression code which trashes TCP segments containing 773 * unknown-to-them TCP options. 774 */ 775 if (tcp_rexmit_drop_options && (tp->t_state == TCPS_SYN_SENT) && 776 (tp->t_rxtshift == 3)) 777 tp->t_flags &= ~(TF_REQ_SCALE|TF_REQ_TSTMP|TF_SACK_PERMIT); 778 /* 779 * If we backed off this far, notify the L3 protocol that we're having 780 * connection problems. 781 */ 782 if (tp->t_rxtshift > TCP_RTT_INVALIDATE) { 783 #ifdef INET6 784 if ((inp->inp_vflag & INP_IPV6) != 0) 785 in6_losing(inp); 786 else 787 #endif 788 in_losing(inp); 789 } 790 tp->snd_nxt = tp->snd_una; 791 tp->snd_recover = tp->snd_max; 792 /* 793 * Force a segment to be sent. 794 */ 795 tp->t_flags |= TF_ACKNOW; 796 /* 797 * If timing a segment in this window, stop the timer. 798 */ 799 tp->t_rtttime = 0; 800 801 cc_cong_signal(tp, NULL, CC_RTO); 802 NET_EPOCH_ENTER(et); 803 rv = tcp_output_locked(tp); 804 NET_EPOCH_EXIT(et); 805 CURVNET_RESTORE(); 806 807 return (rv); 808 } 809 810 static void 811 tcp_bblog_timer(struct tcpcb *tp, tt_which which, tt_what what, uint32_t ticks) 812 { 813 struct tcp_log_buffer *lgb; 814 uint64_t ms; 815 816 INP_WLOCK_ASSERT(tptoinpcb(tp)); 817 if (tcp_bblogging_on(tp)) 818 lgb = tcp_log_event(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0, 819 NULL, false, NULL, NULL, 0, NULL); 820 else 821 lgb = NULL; 822 if (lgb != NULL) { 823 lgb->tlb_flex1 = (what << 8) | which; 824 if (what == TT_STARTING) { 825 /* Convert ticks to ms and store it in tlb_flex2. */ 826 if (hz == 1000) 827 lgb->tlb_flex2 = ticks; 828 else { 829 ms = (((uint64_t)ticks * 1000) + (hz - 1)) / hz; 830 if (ms > UINT32_MAX) 831 lgb->tlb_flex2 = UINT32_MAX; 832 else 833 lgb->tlb_flex2 = (uint32_t)ms; 834 } 835 } 836 } 837 } 838 839 static inline tt_which 840 tcp_timer_next(struct tcpcb *tp, sbintime_t *precision) 841 { 842 tt_which i, rv; 843 sbintime_t after, before; 844 845 for (i = 0, rv = TT_N, after = before = SBT_MAX; i < TT_N; i++) { 846 if (tp->t_timers[i] < after) { 847 after = tp->t_timers[i]; 848 rv = i; 849 } 850 before = MIN(before, tp->t_timers[i] + tp->t_precisions[i]); 851 } 852 if (precision != NULL) 853 *precision = before - after; 854 855 return (rv); 856 } 857 858 static void 859 tcp_timer_enter(void *xtp) 860 { 861 struct tcpcb *tp = xtp; 862 struct inpcb *inp = tptoinpcb(tp); 863 sbintime_t precision; 864 tt_which which; 865 bool tp_valid; 866 867 INP_WLOCK_ASSERT(inp); 868 MPASS((curthread->td_pflags & TDP_INTCPCALLOUT) == 0); 869 870 curthread->td_pflags |= TDP_INTCPCALLOUT; 871 872 which = tcp_timer_next(tp, NULL); 873 MPASS(which < TT_N); 874 tp->t_timers[which] = SBT_MAX; 875 tp->t_precisions[which] = 0; 876 877 tcp_bblog_timer(tp, which, TT_PROCESSING, 0); 878 tp_valid = tcp_timersw[which](tp); 879 if (tp_valid) { 880 tcp_bblog_timer(tp, which, TT_PROCESSED, 0); 881 if ((which = tcp_timer_next(tp, &precision)) != TT_N) { 882 callout_reset_sbt_on(&tp->t_callout, 883 tp->t_timers[which], precision, tcp_timer_enter, 884 tp, inp_to_cpuid(inp), C_ABSOLUTE); 885 } 886 INP_WUNLOCK(inp); 887 } 888 889 curthread->td_pflags &= ~TDP_INTCPCALLOUT; 890 } 891 892 /* 893 * Activate or stop (delta == 0) a TCP timer. 894 */ 895 void 896 tcp_timer_activate(struct tcpcb *tp, tt_which which, u_int delta) 897 { 898 struct inpcb *inp = tptoinpcb(tp); 899 sbintime_t precision; 900 tt_what what; 901 902 #ifdef TCP_OFFLOAD 903 if (tp->t_flags & TF_TOE) 904 return; 905 #endif 906 907 INP_WLOCK_ASSERT(inp); 908 909 if (delta > 0) { 910 what = TT_STARTING; 911 callout_when(tick_sbt * delta, 0, C_HARDCLOCK, 912 &tp->t_timers[which], &tp->t_precisions[which]); 913 } else { 914 what = TT_STOPPING; 915 tp->t_timers[which] = SBT_MAX; 916 } 917 tcp_bblog_timer(tp, which, what, delta); 918 919 if ((which = tcp_timer_next(tp, &precision)) != TT_N) 920 callout_reset_sbt_on(&tp->t_callout, tp->t_timers[which], 921 precision, tcp_timer_enter, tp, inp_to_cpuid(inp), 922 C_ABSOLUTE); 923 else 924 callout_stop(&tp->t_callout); 925 } 926 927 bool 928 tcp_timer_active(struct tcpcb *tp, tt_which which) 929 { 930 931 INP_WLOCK_ASSERT(tptoinpcb(tp)); 932 933 return (tp->t_timers[which] != SBT_MAX); 934 } 935 936 /* 937 * Stop all timers associated with tcpcb. 938 * 939 * Called only on tcpcb destruction. The tcpcb shall already be dropped from 940 * the pcb lookup database and socket is not losing the last reference. 941 * 942 * XXXGL: unfortunately our callout(9) is not able to fully stop a locked 943 * callout even when only two threads are involved: the callout itself and the 944 * thread that does callout_stop(). See where softclock_call_cc() swaps the 945 * callwheel lock to callout lock and then checks cc_exec_cancel(). This is 946 * the race window. If it happens, the tcp_timer_enter() won't be executed, 947 * however pcb lock will be locked and released, hence we can't free memory. 948 * Until callout(9) is improved, just keep retrying. In my profiling I've seen 949 * such event happening less than 1 time per hour with 20-30 Gbit/s of traffic. 950 */ 951 void 952 tcp_timer_stop(struct tcpcb *tp) 953 { 954 struct inpcb *inp = tptoinpcb(tp); 955 956 INP_WLOCK_ASSERT(inp); 957 958 if (curthread->td_pflags & TDP_INTCPCALLOUT) { 959 int stopped __diagused; 960 961 stopped = callout_stop(&tp->t_callout); 962 MPASS(stopped == 0); 963 } else while(__predict_false(callout_stop(&tp->t_callout) == 0)) { 964 INP_WUNLOCK(inp); 965 kern_yield(PRI_UNCHANGED); 966 INP_WLOCK(inp); 967 } 968 } 969