1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright (c) 2010, Oracle and/or its affiliates. All rights reserved.
24 * Copyright (c) 2011 Nexenta Systems, Inc. All rights reserved.
25 * Copyright 2011 Joyent, Inc. All rights reserved.
26 * Copyright (c) 2014, 2016 by Delphix. All rights reserved.
27 */
28
29 #include <sys/types.h>
30 #include <sys/strlog.h>
31 #include <sys/strsun.h>
32 #include <sys/squeue_impl.h>
33 #include <sys/squeue.h>
34 #include <sys/callo.h>
35 #include <sys/strsubr.h>
36
37 #include <inet/common.h>
38 #include <inet/ip.h>
39 #include <inet/ip_ire.h>
40 #include <inet/ip_rts.h>
41 #include <inet/tcp.h>
42 #include <inet/tcp_impl.h>
43
44 /*
45 * Implementation of TCP Timers.
46 * =============================
47 *
48 * INTERFACE:
49 *
50 * There are two basic functions dealing with tcp timers:
51 *
52 * timeout_id_t tcp_timeout(connp, func, time)
53 * clock_t tcp_timeout_cancel(connp, timeout_id)
54 * TCP_TIMER_RESTART(tcp, intvl)
55 *
56 * tcp_timeout() starts a timer for the 'tcp' instance arranging to call 'func'
57 * after 'time' ticks passed. The function called by timeout() must adhere to
58 * the same restrictions as a driver soft interrupt handler - it must not sleep
59 * or call other functions that might sleep. The value returned is the opaque
60 * non-zero timeout identifier that can be passed to tcp_timeout_cancel() to
61 * cancel the request. The call to tcp_timeout() may fail in which case it
62 * returns zero. This is different from the timeout(9F) function which never
63 * fails.
64 *
65 * The call-back function 'func' always receives 'connp' as its single
66 * argument. It is always executed in the squeue corresponding to the tcp
67 * structure. The tcp structure is guaranteed to be present at the time the
68 * call-back is called.
69 *
70 * NOTE: The call-back function 'func' is never called if tcp is in
71 * the TCPS_CLOSED state.
72 *
73 * tcp_timeout_cancel() attempts to cancel a pending tcp_timeout()
74 * request. locks acquired by the call-back routine should not be held across
75 * the call to tcp_timeout_cancel() or a deadlock may result.
76 *
77 * tcp_timeout_cancel() returns -1 if the timeout request is invalid.
78 * Otherwise, it returns an integer value greater than or equal to 0.
79 *
80 * NOTE: both tcp_timeout() and tcp_timeout_cancel() should always be called
81 * within squeue context corresponding to the tcp instance. Since the
82 * call-back is also called via the same squeue, there are no race
83 * conditions described in untimeout(9F) manual page since all calls are
84 * strictly serialized.
85 *
86 * TCP_TIMER_RESTART() is a macro that attempts to cancel a pending timeout
87 * stored in tcp_timer_tid and starts a new one using
88 * MSEC_TO_TICK(intvl). It always uses tcp_timer() function as a call-back
89 * and stores the return value of tcp_timeout() in the tcp->tcp_timer_tid
90 * field.
91 *
92 * IMPLEMENTATION:
93 *
94 * TCP timers are implemented using three-stage process. The call to
95 * tcp_timeout() uses timeout(9F) function to call tcp_timer_callback() function
96 * when the timer expires. The tcp_timer_callback() arranges the call of the
97 * tcp_timer_handler() function via squeue corresponding to the tcp
98 * instance. The tcp_timer_handler() calls actual requested timeout call-back
99 * and passes tcp instance as an argument to it. Information is passed between
100 * stages using the tcp_timer_t structure which contains the connp pointer, the
101 * tcp call-back to call and the timeout id returned by the timeout(9F).
102 *
103 * The tcp_timer_t structure is not used directly, it is embedded in an mblk_t -
104 * like structure that is used to enter an squeue. The mp->b_rptr of this pseudo
105 * mblk points to the beginning of tcp_timer_t structure. The tcp_timeout()
106 * returns the pointer to this mblk.
107 *
108 * The pseudo mblk is allocated from a special tcp_timer_cache kmem cache. It
109 * looks like a normal mblk without actual dblk attached to it.
110 *
111 * To optimize performance each tcp instance holds a small cache of timer
112 * mblocks. In the current implementation it caches up to two timer mblocks per
113 * tcp instance. The cache is preserved over tcp frees and is only freed when
114 * the whole tcp structure is destroyed by its kmem destructor. Since all tcp
115 * timer processing happens on a corresponding squeue, the cache manipulation
116 * does not require any locks. Experiments show that majority of timer mblocks
117 * allocations are satisfied from the tcp cache and do not involve kmem calls.
118 *
119 * The tcp_timeout() places a refhold on the connp instance which guarantees
120 * that it will be present at the time the call-back function fires. The
121 * tcp_timer_handler() drops the reference after calling the call-back, so the
122 * call-back function does not need to manipulate the references explicitly.
123 */
124
125 kmem_cache_t *tcp_timercache;
126
127 static void tcp_ip_notify(tcp_t *);
128 static void tcp_timer_callback(void *);
129 static void tcp_timer_free(tcp_t *, mblk_t *);
130 static void tcp_timer_handler(void *, mblk_t *, void *, ip_recv_attr_t *);
131
132 /*
133 * tim is in millisec.
134 */
135 timeout_id_t
136 tcp_timeout(conn_t *connp, void (*f)(void *), hrtime_t tim)
137 {
138 mblk_t *mp;
139 tcp_timer_t *tcpt;
140 tcp_t *tcp = connp->conn_tcp;
141
142 ASSERT(connp->conn_sqp != NULL);
143
144 TCP_DBGSTAT(tcp->tcp_tcps, tcp_timeout_calls);
145
146 if (tcp->tcp_timercache == NULL) {
147 mp = tcp_timermp_alloc(KM_NOSLEEP | KM_PANIC);
148 } else {
149 TCP_DBGSTAT(tcp->tcp_tcps, tcp_timeout_cached_alloc);
150 mp = tcp->tcp_timercache;
151 tcp->tcp_timercache = mp->b_next;
152 mp->b_next = NULL;
153 ASSERT(mp->b_wptr == NULL);
154 }
155
156 CONN_INC_REF(connp);
157 tcpt = (tcp_timer_t *)mp->b_rptr;
158 tcpt->connp = connp;
159 tcpt->tcpt_proc = f;
160 /*
161 * TCP timers are normal timeouts. Plus, they do not require more than
162 * a 10 millisecond resolution. By choosing a coarser resolution and by
163 * rounding up the expiration to the next resolution boundary, we can
164 * batch timers in the callout subsystem to make TCP timers more
165 * efficient. The roundup also protects short timers from expiring too
166 * early before they have a chance to be cancelled.
167 */
168 tcpt->tcpt_tid = timeout_generic(CALLOUT_NORMAL, tcp_timer_callback, mp,
169 tim * MICROSEC, CALLOUT_TCP_RESOLUTION, CALLOUT_FLAG_ROUNDUP);
170 VERIFY(!(tcpt->tcpt_tid & CALLOUT_ID_FREE));
171
172 return ((timeout_id_t)mp);
173 }
174
175 static void
176 tcp_timer_callback(void *arg)
177 {
178 mblk_t *mp = (mblk_t *)arg;
179 tcp_timer_t *tcpt;
180 conn_t *connp;
181
182 tcpt = (tcp_timer_t *)mp->b_rptr;
183 connp = tcpt->connp;
184 SQUEUE_ENTER_ONE(connp->conn_sqp, mp, tcp_timer_handler, connp,
185 NULL, SQ_FILL, SQTAG_TCP_TIMER);
186 }
187
188 /* ARGSUSED */
189 static void
190 tcp_timer_handler(void *arg, mblk_t *mp, void *arg2, ip_recv_attr_t *dummy)
191 {
192 tcp_timer_t *tcpt;
193 conn_t *connp = (conn_t *)arg;
194 tcp_t *tcp = connp->conn_tcp;
195
196 tcpt = (tcp_timer_t *)mp->b_rptr;
197 ASSERT(connp == tcpt->connp);
198 ASSERT((squeue_t *)arg2 == connp->conn_sqp);
199
200 if (tcpt->tcpt_tid & CALLOUT_ID_FREE) {
201 /*
202 * This timeout was cancelled after it was enqueued to the
203 * squeue; free the timer and return.
204 */
205 tcp_timer_free(connp->conn_tcp, mp);
206 return;
207 }
208
209 /*
210 * If the TCP has reached the closed state, don't proceed any
211 * further. This TCP logically does not exist on the system.
212 * tcpt_proc could for example access queues, that have already
213 * been qprocoff'ed off.
214 */
215 if (tcp->tcp_state != TCPS_CLOSED) {
216 (*tcpt->tcpt_proc)(connp);
217 } else {
218 tcp->tcp_timer_tid = 0;
219 }
220
221 tcp_timer_free(connp->conn_tcp, mp);
222 }
223
224 /*
225 * There is potential race with untimeout and the handler firing at the same
226 * time. The mblock may be freed by the handler while we are trying to use
227 * it. But since both should execute on the same squeue, this race should not
228 * occur.
229 */
230 clock_t
231 tcp_timeout_cancel(conn_t *connp, timeout_id_t id)
232 {
233 mblk_t *mp = (mblk_t *)id;
234 tcp_timer_t *tcpt;
235 clock_t delta;
236
237 TCP_DBGSTAT(connp->conn_tcp->tcp_tcps, tcp_timeout_cancel_reqs);
238
239 if (mp == NULL)
240 return (-1);
241
242 tcpt = (tcp_timer_t *)mp->b_rptr;
243 ASSERT(tcpt->connp == connp);
244
245 delta = untimeout_default(tcpt->tcpt_tid, 0);
246
247 if (delta >= 0) {
248 TCP_DBGSTAT(connp->conn_tcp->tcp_tcps, tcp_timeout_canceled);
249 tcp_timer_free(connp->conn_tcp, mp);
250 CONN_DEC_REF(connp);
251 } else {
252 /*
253 * If we were unable to untimeout successfully, it has already
254 * been enqueued on the squeue; mark the ID with the free
255 * bit. This bit can never be set in a valid identifier, and
256 * we'll use it to prevent the timeout from being executed.
257 * And note that we're within the squeue perimeter here, so
258 * we don't need to worry about racing with timer handling
259 * (which also executes within the perimeter).
260 */
261 tcpt->tcpt_tid |= CALLOUT_ID_FREE;
262 delta = 0;
263 }
264
265 return (TICK_TO_MSEC(delta));
266 }
267
268 /*
269 * Allocate space for the timer event. The allocation looks like mblk, but it is
270 * not a proper mblk. To avoid confusion we set b_wptr to NULL.
271 *
272 * Dealing with failures: If we can't allocate from the timer cache we try
273 * allocating from dblock caches using allocb_tryhard(). In this case b_wptr
274 * points to b_rptr.
275 * If we can't allocate anything using allocb_tryhard(), we perform a last
276 * attempt and use kmem_alloc_tryhard(). In this case we set b_wptr to -1 and
277 * save the actual allocation size in b_datap.
278 */
279 mblk_t *
280 tcp_timermp_alloc(int kmflags)
281 {
282 mblk_t *mp = (mblk_t *)kmem_cache_alloc(tcp_timercache,
283 kmflags & ~KM_PANIC);
284
285 if (mp != NULL) {
286 mp->b_next = mp->b_prev = NULL;
287 mp->b_rptr = (uchar_t *)(&mp[1]);
288 mp->b_wptr = NULL;
289 mp->b_datap = NULL;
290 mp->b_queue = NULL;
291 mp->b_cont = NULL;
292 } else if (kmflags & KM_PANIC) {
293 /*
294 * Failed to allocate memory for the timer. Try allocating from
295 * dblock caches.
296 */
297 /* ipclassifier calls this from a constructor - hence no tcps */
298 TCP_G_STAT(tcp_timermp_allocfail);
299 mp = allocb_tryhard(sizeof (tcp_timer_t));
300 if (mp == NULL) {
301 size_t size = 0;
302 /*
303 * Memory is really low. Try tryhard allocation.
304 *
305 * ipclassifier calls this from a constructor -
306 * hence no tcps
307 */
308 TCP_G_STAT(tcp_timermp_allocdblfail);
309 mp = kmem_alloc_tryhard(sizeof (mblk_t) +
310 sizeof (tcp_timer_t), &size, kmflags);
311 mp->b_rptr = (uchar_t *)(&mp[1]);
312 mp->b_next = mp->b_prev = NULL;
313 mp->b_wptr = (uchar_t *)-1;
314 mp->b_datap = (dblk_t *)size;
315 mp->b_queue = NULL;
316 mp->b_cont = NULL;
317 }
318 ASSERT(mp->b_wptr != NULL);
319 }
320 /* ipclassifier calls this from a constructor - hence no tcps */
321 TCP_G_DBGSTAT(tcp_timermp_alloced);
322
323 return (mp);
324 }
325
326 /*
327 * Free per-tcp timer cache.
328 * It can only contain entries from tcp_timercache.
329 */
330 void
331 tcp_timermp_free(tcp_t *tcp)
332 {
333 mblk_t *mp;
334
335 while ((mp = tcp->tcp_timercache) != NULL) {
336 ASSERT(mp->b_wptr == NULL);
337 tcp->tcp_timercache = tcp->tcp_timercache->b_next;
338 kmem_cache_free(tcp_timercache, mp);
339 }
340 }
341
342 /*
343 * Free timer event. Put it on the per-tcp timer cache if there is not too many
344 * events there already (currently at most two events are cached).
345 * If the event is not allocated from the timer cache, free it right away.
346 */
347 static void
348 tcp_timer_free(tcp_t *tcp, mblk_t *mp)
349 {
350 mblk_t *mp1 = tcp->tcp_timercache;
351
352 if (mp->b_wptr != NULL) {
353 /*
354 * This allocation is not from a timer cache, free it right
355 * away.
356 */
357 if (mp->b_wptr != (uchar_t *)-1)
358 freeb(mp);
359 else
360 kmem_free(mp, (size_t)mp->b_datap);
361 } else if (mp1 == NULL || mp1->b_next == NULL) {
362 /* Cache this timer block for future allocations */
363 mp->b_rptr = (uchar_t *)(&mp[1]);
364 mp->b_next = mp1;
365 tcp->tcp_timercache = mp;
366 } else {
367 kmem_cache_free(tcp_timercache, mp);
368 TCP_DBGSTAT(tcp->tcp_tcps, tcp_timermp_freed);
369 }
370 }
371
372 /*
373 * Stop all TCP timers.
374 */
375 void
376 tcp_timers_stop(tcp_t *tcp)
377 {
378 if (tcp->tcp_timer_tid != 0) {
379 (void) TCP_TIMER_CANCEL(tcp, tcp->tcp_timer_tid);
380 tcp->tcp_timer_tid = 0;
381 }
382 if (tcp->tcp_ka_tid != 0) {
383 (void) TCP_TIMER_CANCEL(tcp, tcp->tcp_ka_tid);
384 tcp->tcp_ka_tid = 0;
385 }
386 if (tcp->tcp_ack_tid != 0) {
387 (void) TCP_TIMER_CANCEL(tcp, tcp->tcp_ack_tid);
388 tcp->tcp_ack_tid = 0;
389 }
390 if (tcp->tcp_push_tid != 0) {
391 (void) TCP_TIMER_CANCEL(tcp, tcp->tcp_push_tid);
392 tcp->tcp_push_tid = 0;
393 }
394 if (tcp->tcp_reass_tid != 0) {
395 (void) TCP_TIMER_CANCEL(tcp, tcp->tcp_reass_tid);
396 tcp->tcp_reass_tid = 0;
397 }
398 }
399
400 /*
401 * Timer callback routine for keepalive probe. We do a fake resend of
402 * last ACKed byte. Then set a timer using RTO. When the timer expires,
403 * check to see if we have heard anything from the other end for the last
404 * RTO period. If we have, set the timer to expire for another
405 * tcp_keepalive_intrvl and check again. If we have not, set a timer using
406 * RTO << 1 and check again when it expires. Keep exponentially increasing
407 * the timeout if we have not heard from the other side. If for more than
408 * (tcp_ka_interval + tcp_ka_abort_thres) we have not heard anything,
409 * kill the connection unless the keepalive abort threshold is 0. In
410 * that case, we will probe "forever."
411 * If tcp_ka_cnt and tcp_ka_rinterval are non-zero, then we do not follow
412 * the exponential backoff, but send probes tcp_ka_cnt times in regular
413 * intervals of tcp_ka_rinterval milliseconds until we hear back from peer.
414 * Kill the connection if we don't hear back from peer after tcp_ka_cnt
415 * probes are sent.
416 */
417 void
418 tcp_keepalive_timer(void *arg)
419 {
420 mblk_t *mp;
421 conn_t *connp = (conn_t *)arg;
422 tcp_t *tcp = connp->conn_tcp;
423 int32_t firetime;
424 int32_t idletime;
425 int32_t ka_intrvl;
426 tcp_stack_t *tcps = tcp->tcp_tcps;
427
428 tcp->tcp_ka_tid = 0;
429
430 if (tcp->tcp_fused)
431 return;
432
433 TCPS_BUMP_MIB(tcps, tcpTimKeepalive);
434 ka_intrvl = tcp->tcp_ka_interval;
435
436 /*
437 * Keepalive probe should only be sent if the application has not
438 * done a close on the connection.
439 */
440 if (tcp->tcp_state > TCPS_CLOSE_WAIT) {
441 return;
442 }
443 /* Timer fired too early, restart it. */
444 if (tcp->tcp_state < TCPS_ESTABLISHED) {
445 tcp->tcp_ka_tid = TCP_TIMER(tcp, tcp_keepalive_timer,
446 ka_intrvl);
447 return;
448 }
449
450 idletime = TICK_TO_MSEC(ddi_get_lbolt() - tcp->tcp_last_recv_time);
451 /*
452 * If we have not heard from the other side for a long
453 * time, kill the connection unless the keepalive abort
454 * threshold is 0. In that case, we will probe "forever."
455 */
456 if (tcp->tcp_ka_abort_thres != 0 &&
457 idletime > (ka_intrvl + tcp->tcp_ka_abort_thres)) {
458 TCPS_BUMP_MIB(tcps, tcpTimKeepaliveDrop);
459 (void) tcp_clean_death(tcp, tcp->tcp_client_errno ?
460 tcp->tcp_client_errno : ETIMEDOUT);
461 return;
462 }
463
464 if (tcp->tcp_snxt == tcp->tcp_suna &&
465 idletime >= ka_intrvl) {
466 /* Fake resend of last ACKed byte. */
467 mblk_t *mp1 = allocb(1, BPRI_LO);
468
469 if (mp1 != NULL) {
470 *mp1->b_wptr++ = '\0';
471 mp = tcp_xmit_mp(tcp, mp1, 1, NULL, NULL,
472 tcp->tcp_suna - 1, B_FALSE, NULL, B_TRUE);
473 freeb(mp1);
474 /*
475 * if allocation failed, fall through to start the
476 * timer back.
477 */
478 if (mp != NULL) {
479 tcp_send_data(tcp, mp);
480 TCPS_BUMP_MIB(tcps, tcpTimKeepaliveProbe);
481 if (tcp->tcp_ka_rinterval) {
482 firetime = tcp->tcp_ka_rinterval;
483 } else if (tcp->tcp_ka_last_intrvl != 0) {
484 int max;
485 /*
486 * We should probe again at least
487 * in ka_intrvl, but not more than
488 * tcp_rto_max.
489 */
490 max = tcp->tcp_rto_max;
491 firetime = MIN(ka_intrvl - 1,
492 tcp->tcp_ka_last_intrvl << 1);
493 if (firetime > max)
494 firetime = max;
495 } else {
496 firetime = tcp->tcp_rto;
497 }
498 tcp->tcp_ka_tid = TCP_TIMER(tcp,
499 tcp_keepalive_timer, firetime);
500 tcp->tcp_ka_last_intrvl = firetime;
501 return;
502 }
503 }
504 } else {
505 tcp->tcp_ka_last_intrvl = 0;
506 }
507
508 /* firetime can be negative if (mp1 == NULL || mp == NULL) */
509 if ((firetime = ka_intrvl - idletime) < 0) {
510 firetime = ka_intrvl;
511 }
512 tcp->tcp_ka_tid = TCP_TIMER(tcp, tcp_keepalive_timer, firetime);
513 }
514
515 void
516 tcp_reass_timer(void *arg)
517 {
518 conn_t *connp = (conn_t *)arg;
519 tcp_t *tcp = connp->conn_tcp;
520
521 tcp->tcp_reass_tid = 0;
522 if (tcp->tcp_reass_head == NULL)
523 return;
524 ASSERT(tcp->tcp_reass_tail != NULL);
525 if (tcp->tcp_snd_sack_ok && tcp->tcp_num_sack_blk > 0) {
526 tcp_sack_remove(tcp->tcp_sack_list,
527 TCP_REASS_END(tcp->tcp_reass_tail), &tcp->tcp_num_sack_blk);
528 }
529 tcp_close_mpp(&tcp->tcp_reass_head);
530 tcp->tcp_reass_tail = NULL;
531 TCP_STAT(tcp->tcp_tcps, tcp_reass_timeout);
532 }
533
534 /* This function handles the push timeout. */
535 void
536 tcp_push_timer(void *arg)
537 {
538 conn_t *connp = (conn_t *)arg;
539 tcp_t *tcp = connp->conn_tcp;
540
541 TCP_DBGSTAT(tcp->tcp_tcps, tcp_push_timer_cnt);
542
543 ASSERT(tcp->tcp_listener == NULL);
544
545 ASSERT(!IPCL_IS_NONSTR(connp));
546
547 tcp->tcp_push_tid = 0;
548
549 if (tcp->tcp_rcv_list != NULL &&
550 tcp_rcv_drain(tcp) == TH_ACK_NEEDED)
551 tcp_xmit_ctl(NULL, tcp, tcp->tcp_snxt, tcp->tcp_rnxt, TH_ACK);
552 }
553
554 /*
555 * This function handles delayed ACK timeout.
556 */
557 void
558 tcp_ack_timer(void *arg)
559 {
560 conn_t *connp = (conn_t *)arg;
561 tcp_t *tcp = connp->conn_tcp;
562 mblk_t *mp;
563 tcp_stack_t *tcps = tcp->tcp_tcps;
564
565 TCP_DBGSTAT(tcps, tcp_ack_timer_cnt);
566
567 tcp->tcp_ack_tid = 0;
568
569 if (tcp->tcp_fused)
570 return;
571
572 /*
573 * Do not send ACK if there is no outstanding unack'ed data.
574 */
575 if (tcp->tcp_rnxt == tcp->tcp_rack) {
576 return;
577 }
578
579 if ((tcp->tcp_rnxt - tcp->tcp_rack) > tcp->tcp_mss) {
580 /*
581 * Make sure we don't allow deferred ACKs to result in
582 * timer-based ACKing. If we have held off an ACK
583 * when there was more than an mss here, and the timer
584 * goes off, we have to worry about the possibility
585 * that the sender isn't doing slow-start, or is out
586 * of step with us for some other reason. We fall
587 * permanently back in the direction of
588 * ACK-every-other-packet as suggested in RFC 1122.
589 */
590 if (tcp->tcp_rack_abs_max > 2)
591 tcp->tcp_rack_abs_max--;
592 tcp->tcp_rack_cur_max = 2;
593 }
594 mp = tcp_ack_mp(tcp);
595
596 if (mp != NULL) {
597 TCPS_BUMP_MIB(tcps, tcpHCOutSegs);
598 TCPS_BUMP_MIB(tcps, tcpOutAck);
599 TCPS_BUMP_MIB(tcps, tcpOutAckDelayed);
600 tcp_send_data(tcp, mp);
601 }
602 }
603
604 /*
605 * Notify IP that we are having trouble with this connection. IP should
606 * make note so it can potentially use a different IRE.
607 */
608 static void
609 tcp_ip_notify(tcp_t *tcp)
610 {
611 conn_t *connp = tcp->tcp_connp;
612 ire_t *ire;
613
614 /*
615 * Note: in the case of source routing we want to blow away the
616 * route to the first source route hop.
617 */
618 ire = connp->conn_ixa->ixa_ire;
619 if (ire != NULL && !(ire->ire_flags & (RTF_REJECT|RTF_BLACKHOLE))) {
620 if (ire->ire_ipversion == IPV4_VERSION) {
621 /*
622 * As per RFC 1122, we send an RTM_LOSING to inform
623 * routing protocols.
624 */
625 ip_rts_change(RTM_LOSING, ire->ire_addr,
626 ire->ire_gateway_addr, ire->ire_mask,
627 connp->conn_laddr_v4, 0, 0, 0,
628 (RTA_DST | RTA_GATEWAY | RTA_NETMASK | RTA_IFA),
629 ire->ire_ipst);
630 }
631 (void) ire_no_good(ire);
632 }
633 }
634
635 /*
636 * tcp_timer is the timer service routine. It handles the retransmission,
637 * FIN_WAIT_2 flush, and zero window probe timeout events. It figures out
638 * from the state of the tcp instance what kind of action needs to be done
639 * at the time it is called.
640 */
641 void
642 tcp_timer(void *arg)
643 {
644 mblk_t *mp;
645 clock_t first_threshold;
646 clock_t second_threshold;
647 clock_t ms;
648 uint32_t mss;
649 conn_t *connp = (conn_t *)arg;
650 tcp_t *tcp = connp->conn_tcp;
651 tcp_stack_t *tcps = tcp->tcp_tcps;
652 boolean_t dont_timeout = B_FALSE;
653
654 tcp->tcp_timer_tid = 0;
655
656 if (tcp->tcp_fused)
657 return;
658
659 first_threshold = tcp->tcp_first_timer_threshold;
660 second_threshold = tcp->tcp_second_timer_threshold;
661 switch (tcp->tcp_state) {
662 case TCPS_IDLE:
663 case TCPS_BOUND:
664 case TCPS_LISTEN:
665 return;
666 case TCPS_SYN_RCVD: {
667 tcp_t *listener = tcp->tcp_listener;
668
669 if (tcp->tcp_syn_rcvd_timeout == 0 && (listener != NULL)) {
670 /* it's our first timeout */
671 tcp->tcp_syn_rcvd_timeout = 1;
672 mutex_enter(&listener->tcp_eager_lock);
673 listener->tcp_syn_rcvd_timeout++;
674 if (!tcp->tcp_dontdrop && !tcp->tcp_closemp_used) {
675 /*
676 * Make this eager available for drop if we
677 * need to drop one to accomodate a new
678 * incoming SYN request.
679 */
680 MAKE_DROPPABLE(listener, tcp);
681 }
682 if (!listener->tcp_syn_defense &&
683 (listener->tcp_syn_rcvd_timeout >
684 (tcps->tcps_conn_req_max_q0 >> 2)) &&
685 (tcps->tcps_conn_req_max_q0 > 200)) {
686 /* We may be under attack. Put on a defense. */
687 listener->tcp_syn_defense = B_TRUE;
688 cmn_err(CE_WARN, "High TCP connect timeout "
689 "rate! System (port %d) may be under a "
690 "SYN flood attack!",
691 ntohs(listener->tcp_connp->conn_lport));
692
693 listener->tcp_ip_addr_cache = kmem_zalloc(
694 IP_ADDR_CACHE_SIZE * sizeof (ipaddr_t),
695 KM_NOSLEEP);
696 }
697 mutex_exit(&listener->tcp_eager_lock);
698 } else if (listener != NULL) {
699 mutex_enter(&listener->tcp_eager_lock);
700 tcp->tcp_syn_rcvd_timeout++;
701 if (tcp->tcp_syn_rcvd_timeout > 1 &&
702 !tcp->tcp_closemp_used) {
703 /*
704 * This is our second timeout. Put the tcp in
705 * the list of droppable eagers to allow it to
706 * be dropped, if needed. We don't check
707 * whether tcp_dontdrop is set or not to
708 * protect ourselve from a SYN attack where a
709 * remote host can spoof itself as one of the
710 * good IP source and continue to hold
711 * resources too long.
712 */
713 MAKE_DROPPABLE(listener, tcp);
714 }
715 mutex_exit(&listener->tcp_eager_lock);
716 }
717 }
718 /* FALLTHRU */
719 case TCPS_SYN_SENT:
720 first_threshold = tcp->tcp_first_ctimer_threshold;
721 second_threshold = tcp->tcp_second_ctimer_threshold;
722
723 /*
724 * If an app has set the second_threshold to 0, it means that
725 * we need to retransmit forever, unless this is a passive
726 * open. We need to set second_threshold back to a normal
727 * value such that later comparison with it still makes
728 * sense. But we set dont_timeout to B_TRUE so that we will
729 * never time out.
730 */
731 if (second_threshold == 0) {
732 second_threshold = tcps->tcps_ip_abort_linterval;
733 if (tcp->tcp_active_open)
734 dont_timeout = B_TRUE;
735 }
736 break;
737 case TCPS_ESTABLISHED:
738 case TCPS_CLOSE_WAIT:
739 /*
740 * If the end point has not been closed, TCP can retransmit
741 * forever. But if the end point is closed, the normal
742 * timeout applies.
743 */
744 if (second_threshold == 0) {
745 second_threshold = tcps->tcps_ip_abort_linterval;
746 dont_timeout = B_TRUE;
747 }
748 /* FALLTHRU */
749 case TCPS_FIN_WAIT_1:
750 case TCPS_CLOSING:
751 case TCPS_LAST_ACK:
752 /* If we have data to rexmit */
753 if (tcp->tcp_suna != tcp->tcp_snxt) {
754 clock_t time_to_wait;
755
756 TCPS_BUMP_MIB(tcps, tcpTimRetrans);
757 if (!tcp->tcp_xmit_head)
758 break;
759 time_to_wait = NSEC2MSEC(gethrtime() -
760 (hrtime_t)(intptr_t)tcp->tcp_xmit_head->b_prev);
761 time_to_wait = tcp->tcp_rto - time_to_wait;
762 /*
763 * If the timer fires too early, 1 clock tick earlier,
764 * restart the timer.
765 */
766 if (time_to_wait > msec_per_tick) {
767 TCP_STAT(tcps, tcp_timer_fire_early);
768 TCP_TIMER_RESTART(tcp, time_to_wait);
769 return;
770 }
771 /*
772 * When we probe zero windows, we force the swnd open.
773 * If our peer acks with a closed window swnd will be
774 * set to zero by tcp_rput(). As long as we are
775 * receiving acks tcp_rput will
776 * reset 'tcp_ms_we_have_waited' so as not to trip the
777 * first and second interval actions. NOTE: the timer
778 * interval is allowed to continue its exponential
779 * backoff.
780 */
781 if (tcp->tcp_swnd == 0 || tcp->tcp_zero_win_probe) {
782 if (connp->conn_debug) {
783 (void) strlog(TCP_MOD_ID, 0, 1,
784 SL_TRACE, "tcp_timer: zero win");
785 }
786 } else {
787 /*
788 * After retransmission, we need to do
789 * slow start. Set the ssthresh to one
790 * half of current effective window and
791 * cwnd to one MSS. Also reset
792 * tcp_cwnd_cnt.
793 *
794 * Note that if tcp_ssthresh is reduced because
795 * of ECN, do not reduce it again unless it is
796 * already one window of data away (tcp_cwr
797 * should then be cleared) or this is a
798 * timeout for a retransmitted segment.
799 */
800 uint32_t npkt;
801
802 if (!tcp->tcp_cwr || tcp->tcp_rexmit) {
803 npkt = ((tcp->tcp_timer_backoff ?
804 tcp->tcp_cwnd_ssthresh :
805 tcp->tcp_snxt -
806 tcp->tcp_suna) >> 1) / tcp->tcp_mss;
807 tcp->tcp_cwnd_ssthresh = MAX(npkt, 2) *
808 tcp->tcp_mss;
809 }
810 tcp->tcp_cwnd = tcp->tcp_mss;
811 tcp->tcp_cwnd_cnt = 0;
812 if (tcp->tcp_ecn_ok) {
813 tcp->tcp_cwr = B_TRUE;
814 tcp->tcp_cwr_snd_max = tcp->tcp_snxt;
815 tcp->tcp_ecn_cwr_sent = B_FALSE;
816 }
817 }
818 break;
819 }
820 /*
821 * We have something to send yet we cannot send. The
822 * reason can be:
823 *
824 * 1. Zero send window: we need to do zero window probe.
825 * 2. Zero cwnd: because of ECN, we need to "clock out
826 * segments.
827 * 3. SWS avoidance: receiver may have shrunk window,
828 * reset our knowledge.
829 *
830 * Note that condition 2 can happen with either 1 or
831 * 3. But 1 and 3 are exclusive.
832 */
833 if (tcp->tcp_unsent != 0) {
834 /*
835 * Should not hold the zero-copy messages for too long.
836 */
837 if (tcp->tcp_snd_zcopy_aware && !tcp->tcp_xmit_zc_clean)
838 tcp->tcp_xmit_head = tcp_zcopy_backoff(tcp,
839 tcp->tcp_xmit_head, B_TRUE);
840
841 if (tcp->tcp_cwnd == 0) {
842 /*
843 * Set tcp_cwnd to 1 MSS so that a
844 * new segment can be sent out. We
845 * are "clocking out" new data when
846 * the network is really congested.
847 */
848 ASSERT(tcp->tcp_ecn_ok);
849 tcp->tcp_cwnd = tcp->tcp_mss;
850 }
851 if (tcp->tcp_swnd == 0) {
852 /* Extend window for zero window probe */
853 tcp->tcp_swnd++;
854 tcp->tcp_zero_win_probe = B_TRUE;
855 TCPS_BUMP_MIB(tcps, tcpOutWinProbe);
856 tcp->tcp_cs.tcp_out_zwnd_probes++;
857 } else {
858 /*
859 * Handle timeout from sender SWS avoidance.
860 * Reset our knowledge of the max send window
861 * since the receiver might have reduced its
862 * receive buffer. Avoid setting tcp_max_swnd
863 * to one since that will essentially disable
864 * the SWS checks.
865 *
866 * Note that since we don't have a SWS
867 * state variable, if the timeout is set
868 * for ECN but not for SWS, this
869 * code will also be executed. This is
870 * fine as tcp_max_swnd is updated
871 * constantly and it will not affect
872 * anything.
873 */
874 tcp->tcp_max_swnd = MAX(tcp->tcp_swnd, 2);
875 }
876 tcp_wput_data(tcp, NULL, B_FALSE);
877 return;
878 }
879 /* Is there a FIN that needs to be to re retransmitted? */
880 if ((tcp->tcp_valid_bits & TCP_FSS_VALID) &&
881 !tcp->tcp_fin_acked)
882 break;
883 /* Nothing to do, return without restarting timer. */
884 TCP_STAT(tcps, tcp_timer_fire_miss);
885 return;
886 case TCPS_FIN_WAIT_2:
887 /*
888 * User closed the TCP endpoint and peer ACK'ed our FIN.
889 * We waited some time for for peer's FIN, but it hasn't
890 * arrived. We flush the connection now to avoid
891 * case where the peer has rebooted.
892 */
893 if (TCP_IS_DETACHED(tcp)) {
894 (void) tcp_clean_death(tcp, 0);
895 } else {
896 TCP_TIMER_RESTART(tcp,
897 tcp->tcp_fin_wait_2_flush_interval);
898 }
899 return;
900 case TCPS_TIME_WAIT:
901 (void) tcp_clean_death(tcp, 0);
902 return;
903 default:
904 if (connp->conn_debug) {
905 (void) strlog(TCP_MOD_ID, 0, 1, SL_TRACE|SL_ERROR,
906 "tcp_timer: strange state (%d) %s",
907 tcp->tcp_state, tcp_display(tcp, NULL,
908 DISP_PORT_ONLY));
909 }
910 return;
911 }
912
913 /*
914 * If the system is under memory pressure or the max number of
915 * connections have been established for the listener, be more
916 * aggressive in aborting connections.
917 */
918 if (tcps->tcps_reclaim || (tcp->tcp_listen_cnt != NULL &&
919 tcp->tcp_listen_cnt->tlc_cnt > tcp->tcp_listen_cnt->tlc_max)) {
920 second_threshold = tcp_early_abort * SECONDS;
921
922 /* We will ignore the never timeout promise in this case... */
923 dont_timeout = B_FALSE;
924 }
925
926 ASSERT(second_threshold != 0);
927
928 if ((ms = tcp->tcp_ms_we_have_waited) > second_threshold) {
929 /*
930 * Should not hold the zero-copy messages for too long.
931 */
932 if (tcp->tcp_snd_zcopy_aware && !tcp->tcp_xmit_zc_clean)
933 tcp->tcp_xmit_head = tcp_zcopy_backoff(tcp,
934 tcp->tcp_xmit_head, B_TRUE);
935
936 if (dont_timeout) {
937 /*
938 * Reset tcp_ms_we_have_waited to avoid overflow since
939 * we are going to retransmit forever.
940 */
941 tcp->tcp_ms_we_have_waited = second_threshold;
942 goto timer_rexmit;
943 }
944
945 /*
946 * For zero window probe, we need to send indefinitely,
947 * unless we have not heard from the other side for some
948 * time...
949 */
950 if ((tcp->tcp_zero_win_probe == 0) ||
951 (TICK_TO_MSEC(ddi_get_lbolt() - tcp->tcp_last_recv_time) >
952 second_threshold)) {
953 TCPS_BUMP_MIB(tcps, tcpTimRetransDrop);
954 /*
955 * If TCP is in SYN_RCVD state, send back a
956 * RST|ACK as BSD does. Note that tcp_zero_win_probe
957 * should be zero in TCPS_SYN_RCVD state.
958 */
959 if (tcp->tcp_state == TCPS_SYN_RCVD) {
960 tcp_xmit_ctl("tcp_timer: RST sent on timeout "
961 "in SYN_RCVD",
962 tcp, tcp->tcp_snxt,
963 tcp->tcp_rnxt, TH_RST | TH_ACK);
964 }
965 (void) tcp_clean_death(tcp,
966 tcp->tcp_client_errno ?
967 tcp->tcp_client_errno : ETIMEDOUT);
968 return;
969 } else {
970 /*
971 * If the system is under memory pressure, we also
972 * abort connection in zero window probing.
973 */
974 if (tcps->tcps_reclaim) {
975 (void) tcp_clean_death(tcp,
976 tcp->tcp_client_errno ?
977 tcp->tcp_client_errno : ETIMEDOUT);
978 TCP_STAT(tcps, tcp_zwin_mem_drop);
979 return;
980 }
981 /*
982 * Set tcp_ms_we_have_waited to second_threshold
983 * so that in next timeout, we will do the above
984 * check (ddi_get_lbolt() - tcp_last_recv_time).
985 * This is also to avoid overflow.
986 *
987 * We don't need to decrement tcp_timer_backoff
988 * to avoid overflow because it will be decremented
989 * later if new timeout value is greater than
990 * tcp_rto_max. In the case when tcp_rto_max is
991 * greater than second_threshold, it means that we
992 * will wait longer than second_threshold to send
993 * the next
994 * window probe.
995 */
996 tcp->tcp_ms_we_have_waited = second_threshold;
997 }
998 } else if (ms > first_threshold) {
999 /*
1000 * Should not hold the zero-copy messages for too long.
1001 */
1002 if (tcp->tcp_snd_zcopy_aware && !tcp->tcp_xmit_zc_clean)
1003 tcp->tcp_xmit_head = tcp_zcopy_backoff(tcp,
1004 tcp->tcp_xmit_head, B_TRUE);
1005
1006 /*
1007 * We have been retransmitting for too long... The RTT
1008 * we calculated is probably incorrect. Reinitialize it.
1009 * Need to compensate for 0 tcp_rtt_sa. Reset
1010 * tcp_rtt_update so that we won't accidentally cache a
1011 * bad value. But only do this if this is not a zero
1012 * window probe.
1013 */
1014 if (tcp->tcp_rtt_sa != 0 && tcp->tcp_zero_win_probe == 0) {
1015 tcp->tcp_rtt_sd += tcp->tcp_rtt_sa >> 3 +
1016 tcp->tcp_rtt_sa >> 5;
1017 tcp->tcp_rtt_sa = 0;
1018 tcp_ip_notify(tcp);
1019 tcp->tcp_rtt_update = 0;
1020 }
1021 }
1022
1023 timer_rexmit:
1024 tcp->tcp_timer_backoff++;
1025 /*
1026 * Calculate the backed off retransmission timeout. If the shift brings
1027 * us back over the max, then we repin the value, and decrement the
1028 * backoff to avoid overflow.
1029 */
1030 ms = tcp_calculate_rto(tcp, tcps, 0) << tcp->tcp_timer_backoff;
1031 if (ms > tcp->tcp_rto_max) {
1032 ms = tcp->tcp_rto_max;
1033 tcp->tcp_timer_backoff--;
1034 }
1035 tcp->tcp_ms_we_have_waited += ms;
1036 if (tcp->tcp_zero_win_probe == 0) {
1037 tcp->tcp_rto = ms;
1038 }
1039 TCP_TIMER_RESTART(tcp, ms);
1040 /*
1041 * This is after a timeout and tcp_rto is backed off. Set
1042 * tcp_set_timer to 1 so that next time RTO is updated, we will
1043 * restart the timer with a correct value.
1044 */
1045 tcp->tcp_set_timer = 1;
1046 mss = tcp->tcp_snxt - tcp->tcp_suna;
1047 if (mss > tcp->tcp_mss)
1048 mss = tcp->tcp_mss;
1049 if (mss > tcp->tcp_swnd && tcp->tcp_swnd != 0)
1050 mss = tcp->tcp_swnd;
1051
1052 if ((mp = tcp->tcp_xmit_head) != NULL) {
1053 mp->b_prev = (mblk_t *)(intptr_t)gethrtime();
1054 }
1055 mp = tcp_xmit_mp(tcp, mp, mss, NULL, NULL, tcp->tcp_suna, B_TRUE, &mss,
1056 B_TRUE);
1057
1058 /*
1059 * When slow start after retransmission begins, start with
1060 * this seq no. tcp_rexmit_max marks the end of special slow
1061 * start phase.
1062 */
1063 tcp->tcp_rexmit_nxt = tcp->tcp_suna;
1064 if ((tcp->tcp_valid_bits & TCP_FSS_VALID) &&
1065 (tcp->tcp_unsent == 0)) {
1066 tcp->tcp_rexmit_max = tcp->tcp_fss;
1067 } else {
1068 tcp->tcp_rexmit_max = tcp->tcp_snxt;
1069 }
1070 tcp->tcp_rexmit = B_TRUE;
1071 tcp->tcp_dupack_cnt = 0;
1072
1073 /*
1074 * Remove all rexmit SACK blk to start from fresh.
1075 */
1076 if (tcp->tcp_snd_sack_ok)
1077 TCP_NOTSACK_REMOVE_ALL(tcp->tcp_notsack_list, tcp);
1078 if (mp == NULL) {
1079 return;
1080 }
1081
1082 tcp->tcp_csuna = tcp->tcp_snxt;
1083 TCPS_BUMP_MIB(tcps, tcpRetransSegs);
1084 TCPS_UPDATE_MIB(tcps, tcpRetransBytes, mss);
1085 tcp->tcp_cs.tcp_out_retrans_segs++;
1086 tcp->tcp_cs.tcp_out_retrans_bytes += mss;
1087 tcp_send_data(tcp, mp);
1088
1089 }
1090
1091 /*
1092 * Handle lingering timeouts. This function is called when the SO_LINGER timeout
1093 * expires.
1094 */
1095 void
1096 tcp_close_linger_timeout(void *arg)
1097 {
1098 conn_t *connp = (conn_t *)arg;
1099 tcp_t *tcp = connp->conn_tcp;
1100
1101 tcp->tcp_client_errno = ETIMEDOUT;
1102 tcp_stop_lingering(tcp);
1103 }