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
sysctl_net_inet_tcp_retries(SYSCTL_HANDLER_ARGS)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
inp_to_cpuid(struct inpcb * inp)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
tcp_output_locked(struct tcpcb * tp)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
tcp_timer_delack(struct tcpcb * tp)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
tcp_timer_2msl(struct tcpcb * tp)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
tcp_timer_keep(struct tcpcb * tp)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
tcp_maxunacktime_check(struct tcpcb * tp)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
tcp_timer_persist(struct tcpcb * tp)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
tcp_timer_rexmt(struct tcpcb * tp)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 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 /* Do not overwrite the snd_cwnd on SYN retransmissions. */
814 if (tp->t_state != TCPS_SYN_SENT)
815 cc_cong_signal(tp, NULL, CC_RTO);
816 NET_EPOCH_ENTER(et);
817 rv = tcp_output_locked(tp);
818 NET_EPOCH_EXIT(et);
819 CURVNET_RESTORE();
820
821 return (rv);
822 }
823
824 static void
tcp_bblog_timer(struct tcpcb * tp,tt_which which,tt_what what,uint32_t ticks)825 tcp_bblog_timer(struct tcpcb *tp, tt_which which, tt_what what, uint32_t ticks)
826 {
827 struct tcp_log_buffer *lgb;
828 uint64_t ms;
829
830 INP_WLOCK_ASSERT(tptoinpcb(tp));
831 if (tcp_bblogging_on(tp))
832 lgb = tcp_log_event(tp, NULL, NULL, NULL, TCP_LOG_RTO, 0, 0,
833 NULL, false, NULL, NULL, 0, NULL);
834 else
835 lgb = NULL;
836 if (lgb != NULL) {
837 lgb->tlb_flex1 = (what << 8) | which;
838 if (what == TT_STARTING) {
839 /* Convert ticks to ms and store it in tlb_flex2. */
840 if (hz == 1000)
841 lgb->tlb_flex2 = ticks;
842 else {
843 ms = (((uint64_t)ticks * 1000) + (hz - 1)) / hz;
844 if (ms > UINT32_MAX)
845 lgb->tlb_flex2 = UINT32_MAX;
846 else
847 lgb->tlb_flex2 = (uint32_t)ms;
848 }
849 }
850 }
851 }
852
853 static inline tt_which
tcp_timer_next(struct tcpcb * tp,sbintime_t * precision)854 tcp_timer_next(struct tcpcb *tp, sbintime_t *precision)
855 {
856 tt_which i, rv;
857 sbintime_t after, before;
858
859 for (i = 0, rv = TT_N, after = before = SBT_MAX; i < TT_N; i++) {
860 if (tp->t_timers[i] < after) {
861 after = tp->t_timers[i];
862 rv = i;
863 }
864 before = MIN(before, tp->t_timers[i] + tp->t_precisions[i]);
865 }
866 if (precision != NULL)
867 *precision = before - after;
868
869 return (rv);
870 }
871
872 static void
tcp_timer_enter(void * xtp)873 tcp_timer_enter(void *xtp)
874 {
875 struct tcpcb *tp = xtp;
876 struct inpcb *inp = tptoinpcb(tp);
877 sbintime_t precision;
878 tt_which which;
879
880 INP_WLOCK_ASSERT(inp);
881
882 which = tcp_timer_next(tp, NULL);
883 MPASS(which < TT_N);
884 tp->t_timers[which] = SBT_MAX;
885 tp->t_precisions[which] = 0;
886
887 tcp_bblog_timer(tp, which, TT_PROCESSING, 0);
888 if (tcp_timersw[which](tp)) {
889 tcp_bblog_timer(tp, which, TT_PROCESSED, 0);
890 if ((which = tcp_timer_next(tp, &precision)) != TT_N) {
891 MPASS(tp->t_state > TCPS_CLOSED);
892 callout_reset_sbt_on(&tp->t_callout,
893 tp->t_timers[which], precision, tcp_timer_enter,
894 tp, inp_to_cpuid(inp), C_ABSOLUTE);
895 }
896 INP_WUNLOCK(inp);
897 }
898 }
899
900 /*
901 * Activate or stop (delta == 0) a TCP timer.
902 */
903 void
tcp_timer_activate(struct tcpcb * tp,tt_which which,u_int delta)904 tcp_timer_activate(struct tcpcb *tp, tt_which which, u_int delta)
905 {
906 struct inpcb *inp = tptoinpcb(tp);
907 sbintime_t precision;
908 tt_what what;
909
910 #ifdef TCP_OFFLOAD
911 if (tp->t_flags & TF_TOE)
912 return;
913 #endif
914
915 INP_WLOCK_ASSERT(inp);
916 MPASS(tp->t_state > TCPS_CLOSED);
917
918 if (delta > 0) {
919 what = TT_STARTING;
920 callout_when(tick_sbt * delta, 0, C_HARDCLOCK,
921 &tp->t_timers[which], &tp->t_precisions[which]);
922 } else {
923 what = TT_STOPPING;
924 tp->t_timers[which] = SBT_MAX;
925 }
926 tcp_bblog_timer(tp, which, what, delta);
927
928 if ((which = tcp_timer_next(tp, &precision)) != TT_N)
929 callout_reset_sbt_on(&tp->t_callout, tp->t_timers[which],
930 precision, tcp_timer_enter, tp, inp_to_cpuid(inp),
931 C_ABSOLUTE);
932 else
933 callout_stop(&tp->t_callout);
934 }
935
936 bool
tcp_timer_active(struct tcpcb * tp,tt_which which)937 tcp_timer_active(struct tcpcb *tp, tt_which which)
938 {
939
940 INP_WLOCK_ASSERT(tptoinpcb(tp));
941
942 return (tp->t_timers[which] != SBT_MAX);
943 }
944
945 /*
946 * Stop all timers associated with tcpcb.
947 * Called when tcpcb moves to TCPS_CLOSED.
948 */
949 void
tcp_timer_stop(struct tcpcb * tp)950 tcp_timer_stop(struct tcpcb *tp)
951 {
952
953 INP_WLOCK_ASSERT(tptoinpcb(tp));
954
955 /*
956 * We don't check return value from callout_stop(). There are two
957 * reasons why it can return 0. First, a legitimate one: we could have
958 * been called from the callout itself. Second, callout(9) has a bug.
959 * It can race internally in softclock_call_cc(), when callout has
960 * already completed, but cc_exec_curr still points at the callout.
961 */
962 (void )callout_stop(&tp->t_callout);
963 /*
964 * In case of being called from callout itself, we must make sure that
965 * we don't reschedule.
966 */
967 for (tt_which i = 0; i < TT_N; i++)
968 tp->t_timers[i] = SBT_MAX;
969 }
970