1 /*-
2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
3 * The Regents of the University of California. All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 * notice, this list of conditions and the following disclaimer.
10 * 2. Redistributions in binary form must reproduce the above copyright
11 * notice, this list of conditions and the following disclaimer in the
12 * documentation and/or other materials provided with the distribution.
13 * 4. Neither the name of the University nor the names of its contributors
14 * may be used to endorse or promote products derived from this software
15 * without specific prior written permission.
16 *
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
27 * SUCH DAMAGE.
28 *
29 * @(#)tcp_subr.c 8.2 (Berkeley) 5/24/95
30 */
31
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
34
35 #include "opt_inet.h"
36 #include "opt_inet6.h"
37 #include "opt_mac.h"
38 #include "opt_tcpdebug.h"
39
40 #include <sys/param.h>
41 #include <sys/systm.h>
42 #include <sys/callout.h>
43 #include <sys/kernel.h>
44 #include <sys/sysctl.h>
45 #include <sys/malloc.h>
46 #include <sys/mbuf.h>
47 #include <sys/priv.h>
48 #include <sys/proc.h>
49 #include <sys/socket.h>
50 #include <sys/socketvar.h>
51 #include <sys/protosw.h>
52 #include <sys/random.h>
53
54 #include <vm/uma.h>
55
56 #include <net/route.h>
57 #include <net/if.h>
58
59 #include <netinet/in.h>
60 #include <netinet/in_systm.h>
61 #include <netinet/ip.h>
62 #ifdef INET6
63 #include <netinet/ip6.h>
64 #endif
65 #include <netinet/in_pcb.h>
66 #ifdef INET6
67 #include <netinet6/in6_pcb.h>
68 #endif
69 #include <netinet/in_var.h>
70 #include <netinet/ip_var.h>
71 #ifdef INET6
72 #include <netinet6/ip6_var.h>
73 #include <netinet6/scope6_var.h>
74 #include <netinet6/nd6.h>
75 #endif
76 #include <netinet/ip_icmp.h>
77 #include <netinet/tcp.h>
78 #include <netinet/tcp_fsm.h>
79 #include <netinet/tcp_seq.h>
80 #include <netinet/tcp_timer.h>
81 #include <netinet/tcp_var.h>
82 #ifdef INET6
83 #include <netinet6/tcp6_var.h>
84 #endif
85 #include <netinet/tcpip.h>
86 #ifdef TCPDEBUG
87 #include <netinet/tcp_debug.h>
88 #endif
89 #include <netinet6/ip6protosw.h>
90
91 #include <machine/in_cksum.h>
92
93 #include <security/mac/mac_framework.h>
94
95 static uma_zone_t tcptw_zone;
96 static int maxtcptw;
97
98 /*
99 * The timed wait queue contains references to each of the TCP sessions
100 * currently in the TIME_WAIT state. The queue pointers, including the
101 * queue pointers in each tcptw structure, are protected using the global
102 * tcbinfo lock, which must be held over queue iteration and modification.
103 */
104 static TAILQ_HEAD(, tcptw) twq_2msl;
105
106 static void tcp_tw_2msl_reset(struct tcptw *, int);
107 static void tcp_tw_2msl_stop(struct tcptw *);
108
109 static int
110 tcptw_auto_size(void)
111 {
112 int halfrange;
113
114 /*
115 * Max out at half the ephemeral port range so that TIME_WAIT
116 * sockets don't tie up too many ephemeral ports.
117 */
118 if (ipport_lastauto > ipport_firstauto)
119 halfrange = (ipport_lastauto - ipport_firstauto) / 2;
120 else
121 halfrange = (ipport_firstauto - ipport_lastauto) / 2;
122 /* Protect against goofy port ranges smaller than 32. */
123 return (imin(imax(halfrange, 32), maxsockets / 5));
124 }
125
126 static int
127 sysctl_maxtcptw(SYSCTL_HANDLER_ARGS)
128 {
129 int error, new;
130
131 if (maxtcptw == 0)
132 new = tcptw_auto_size();
133 else
134 new = maxtcptw;
135 error = sysctl_handle_int(oidp, &new, 0, req);
136 if (error == 0 && req->newptr)
137 if (new >= 32) {
138 maxtcptw = new;
139 uma_zone_set_max(tcptw_zone, maxtcptw);
140 }
141 return (error);
142 }
143
144 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxtcptw, CTLTYPE_INT|CTLFLAG_RW,
145 &maxtcptw, 0, sysctl_maxtcptw, "IU",
146 "Maximum number of compressed TCP TIME_WAIT entries");
147
148 static int nolocaltimewait = 0;
149 SYSCTL_INT(_net_inet_tcp, OID_AUTO, nolocaltimewait, CTLFLAG_RW,
150 &nolocaltimewait, 0,
151 "Do not create compressed TCP TIME_WAIT entries for local connections");
152
153 void
154 tcp_tw_zone_change(void)
155 {
156
157 if (maxtcptw == 0)
158 uma_zone_set_max(tcptw_zone, tcptw_auto_size());
159 }
160
161 void
162 tcp_tw_init(void)
163 {
164
165 tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw),
166 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
167 TUNABLE_INT_FETCH("net.inet.tcp.maxtcptw", &maxtcptw);
168 if (maxtcptw == 0)
169 uma_zone_set_max(tcptw_zone, tcptw_auto_size());
170 else
171 uma_zone_set_max(tcptw_zone, maxtcptw);
172 TAILQ_INIT(&twq_2msl);
173 }
174
175 /*
176 * Move a TCP connection into TIME_WAIT state.
177 * tcbinfo is locked.
178 * inp is locked, and is unlocked before returning.
179 */
180 void
181 tcp_twstart(struct tcpcb *tp)
182 {
183 struct tcptw *tw;
184 struct inpcb *inp = tp->t_inpcb;
185 int acknow;
186 struct socket *so;
187
188 INP_INFO_WLOCK_ASSERT(&tcbinfo); /* tcp_tw_2msl_reset(). */
189 INP_WLOCK_ASSERT(inp);
190
191 if (nolocaltimewait && in_localip(inp->inp_faddr)) {
192 tp = tcp_close(tp);
193 if (tp != NULL)
194 INP_WUNLOCK(inp);
195 return;
196 }
197
198 tw = uma_zalloc(tcptw_zone, M_NOWAIT);
199 if (tw == NULL) {
200 tw = tcp_tw_2msl_scan(1);
201 if (tw == NULL) {
202 tp = tcp_close(tp);
203 if (tp != NULL)
204 INP_WUNLOCK(inp);
205 return;
206 }
207 }
208 tw->tw_inpcb = inp;
209
210 /*
211 * Recover last window size sent.
212 */
213 tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale;
214
215 /*
216 * Set t_recent if timestamps are used on the connection.
217 */
218 if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) ==
219 (TF_REQ_TSTMP|TF_RCVD_TSTMP)) {
220 tw->t_recent = tp->ts_recent;
221 tw->ts_offset = tp->ts_offset;
222 } else {
223 tw->t_recent = 0;
224 tw->ts_offset = 0;
225 }
226
227 tw->snd_nxt = tp->snd_nxt;
228 tw->rcv_nxt = tp->rcv_nxt;
229 tw->iss = tp->iss;
230 tw->irs = tp->irs;
231 tw->t_starttime = tp->t_starttime;
232 tw->tw_time = 0;
233
234 /* XXX
235 * If this code will
236 * be used for fin-wait-2 state also, then we may need
237 * a ts_recent from the last segment.
238 */
239 acknow = tp->t_flags & TF_ACKNOW;
240
241 /*
242 * First, discard tcpcb state, which includes stopping its timers and
243 * freeing it. tcp_discardcb() used to also release the inpcb, but
244 * that work is now done in the caller.
245 *
246 * Note: soisdisconnected() call used to be made in tcp_discardcb(),
247 * and might not be needed here any longer.
248 */
249 tcp_discardcb(tp);
250 so = inp->inp_socket;
251 soisdisconnected(so);
252 tw->tw_cred = crhold(so->so_cred);
253 SOCK_LOCK(so);
254 tw->tw_so_options = so->so_options;
255 SOCK_UNLOCK(so);
256 if (acknow)
257 tcp_twrespond(tw, TH_ACK);
258 inp->inp_ppcb = tw;
259 inp->inp_flags |= INP_TIMEWAIT;
260 tcp_tw_2msl_reset(tw, 0);
261
262 /*
263 * If the inpcb owns the sole reference to the socket, then we can
264 * detach and free the socket as it is not needed in time wait.
265 */
266 if (inp->inp_flags & INP_SOCKREF) {
267 KASSERT(so->so_state & SS_PROTOREF,
268 ("tcp_twstart: !SS_PROTOREF"));
269 inp->inp_flags &= ~INP_SOCKREF;
270 INP_WUNLOCK(inp);
271 ACCEPT_LOCK();
272 SOCK_LOCK(so);
273 so->so_state &= ~SS_PROTOREF;
274 sofree(so);
275 } else
276 INP_WUNLOCK(inp);
277 }
278
279 #if 0
280 /*
281 * The appromixate rate of ISN increase of Microsoft TCP stacks;
282 * the actual rate is slightly higher due to the addition of
283 * random positive increments.
284 *
285 * Most other new OSes use semi-randomized ISN values, so we
286 * do not need to worry about them.
287 */
288 #define MS_ISN_BYTES_PER_SECOND 250000
289
290 /*
291 * Determine if the ISN we will generate has advanced beyond the last
292 * sequence number used by the previous connection. If so, indicate
293 * that it is safe to recycle this tw socket by returning 1.
294 */
295 int
296 tcp_twrecycleable(struct tcptw *tw)
297 {
298 tcp_seq new_iss = tw->iss;
299 tcp_seq new_irs = tw->irs;
300
301 INP_INFO_WLOCK_ASSERT(&tcbinfo);
302 new_iss += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz);
303 new_irs += (ticks - tw->t_starttime) * (MS_ISN_BYTES_PER_SECOND / hz);
304
305 if (SEQ_GT(new_iss, tw->snd_nxt) && SEQ_GT(new_irs, tw->rcv_nxt))
306 return (1);
307 else
308 return (0);
309 }
310 #endif
311
312 /*
313 * Returns 1 if the TIME_WAIT state was killed and we should start over,
314 * looking for a pcb in the listen state. Returns 0 otherwise.
315 */
316 int
317 tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th,
318 struct mbuf *m, int tlen)
319 {
320 struct tcptw *tw;
321 int thflags;
322 tcp_seq seq;
323
324 /* tcbinfo lock required for tcp_twclose(), tcp_tw_2msl_reset(). */
325 INP_INFO_WLOCK_ASSERT(&tcbinfo);
326 INP_WLOCK_ASSERT(inp);
327
328 /*
329 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is
330 * still present. This is undesirable, but temporarily necessary
331 * until we work out how to handle inpcb's who's timewait state has
332 * been removed.
333 */
334 tw = intotw(inp);
335 if (tw == NULL)
336 goto drop;
337
338 thflags = th->th_flags;
339
340 /*
341 * NOTE: for FIN_WAIT_2 (to be added later),
342 * must validate sequence number before accepting RST
343 */
344
345 /*
346 * If the segment contains RST:
347 * Drop the segment - see Stevens, vol. 2, p. 964 and
348 * RFC 1337.
349 */
350 if (thflags & TH_RST)
351 goto drop;
352
353 #if 0
354 /* PAWS not needed at the moment */
355 /*
356 * RFC 1323 PAWS: If we have a timestamp reply on this segment
357 * and it's less than ts_recent, drop it.
358 */
359 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
360 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
361 if ((thflags & TH_ACK) == 0)
362 goto drop;
363 goto ack;
364 }
365 /*
366 * ts_recent is never updated because we never accept new segments.
367 */
368 #endif
369
370 /*
371 * If a new connection request is received
372 * while in TIME_WAIT, drop the old connection
373 * and start over if the sequence numbers
374 * are above the previous ones.
375 */
376 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
377 tcp_twclose(tw, 0);
378 return (1);
379 }
380
381 /*
382 * Drop the the segment if it does not contain an ACK.
383 */
384 if ((thflags & TH_ACK) == 0)
385 goto drop;
386
387 /*
388 * Reset the 2MSL timer if this is a duplicate FIN.
389 */
390 if (thflags & TH_FIN) {
391 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
392 if (seq + 1 == tw->rcv_nxt)
393 tcp_tw_2msl_reset(tw, 1);
394 }
395
396 /*
397 * Acknowledge the segment if it has data or is not a duplicate ACK.
398 */
399 if (thflags != TH_ACK || tlen != 0 ||
400 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
401 tcp_twrespond(tw, TH_ACK);
402 drop:
403 INP_WUNLOCK(inp);
404 m_freem(m);
405 return (0);
406 }
407
408 void
409 tcp_twclose(struct tcptw *tw, int reuse)
410 {
411 struct socket *so;
412 struct inpcb *inp;
413
414 /*
415 * At this point, we are in one of two situations:
416 *
417 * (1) We have no socket, just an inpcb<->twtcp pair. We can free
418 * all state.
419 *
420 * (2) We have a socket -- if we own a reference, release it and
421 * notify the socket layer.
422 */
423 inp = tw->tw_inpcb;
424 KASSERT((inp->inp_flags & INP_TIMEWAIT), ("tcp_twclose: !timewait"));
425 KASSERT(intotw(inp) == tw, ("tcp_twclose: inp_ppcb != tw"));
426 INP_INFO_WLOCK_ASSERT(&tcbinfo); /* tcp_tw_2msl_stop(). */
427 INP_WLOCK_ASSERT(inp);
428
429 tw->tw_inpcb = NULL;
430 tcp_tw_2msl_stop(tw);
431 inp->inp_ppcb = NULL;
432 in_pcbdrop(inp);
433
434 so = inp->inp_socket;
435 if (so != NULL) {
436 /*
437 * If there's a socket, handle two cases: first, we own a
438 * strong reference, which we will now release, or we don't
439 * in which case another reference exists (XXXRW: think
440 * about this more), and we don't need to take action.
441 */
442 if (inp->inp_flags & INP_SOCKREF) {
443 inp->inp_flags &= ~INP_SOCKREF;
444 INP_WUNLOCK(inp);
445 ACCEPT_LOCK();
446 SOCK_LOCK(so);
447 KASSERT(so->so_state & SS_PROTOREF,
448 ("tcp_twclose: INP_SOCKREF && !SS_PROTOREF"));
449 so->so_state &= ~SS_PROTOREF;
450 sofree(so);
451 } else {
452 /*
453 * If we don't own the only reference, the socket and
454 * inpcb need to be left around to be handled by
455 * tcp_usr_detach() later.
456 */
457 INP_WUNLOCK(inp);
458 }
459 } else
460 in_pcbfree(inp);
461 tcpstat.tcps_closed++;
462 crfree(tw->tw_cred);
463 tw->tw_cred = NULL;
464 if (reuse)
465 return;
466 uma_zfree(tcptw_zone, tw);
467 }
468
469 int
470 tcp_twrespond(struct tcptw *tw, int flags)
471 {
472 struct inpcb *inp = tw->tw_inpcb;
473 struct tcphdr *th;
474 struct mbuf *m;
475 struct ip *ip = NULL;
476 u_int hdrlen, optlen;
477 int error;
478 struct tcpopt to;
479 #ifdef INET6
480 struct ip6_hdr *ip6 = NULL;
481 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
482 #endif
483
484 INP_WLOCK_ASSERT(inp);
485
486 m = m_gethdr(M_DONTWAIT, MT_DATA);
487 if (m == NULL)
488 return (ENOBUFS);
489 m->m_data += max_linkhdr;
490
491 #ifdef MAC
492 mac_create_mbuf_from_inpcb(inp, m);
493 #endif
494
495 #ifdef INET6
496 if (isipv6) {
497 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
498 ip6 = mtod(m, struct ip6_hdr *);
499 th = (struct tcphdr *)(ip6 + 1);
500 tcpip_fillheaders(inp, ip6, th);
501 } else
502 #endif
503 {
504 hdrlen = sizeof(struct tcpiphdr);
505 ip = mtod(m, struct ip *);
506 th = (struct tcphdr *)(ip + 1);
507 tcpip_fillheaders(inp, ip, th);
508 }
509 to.to_flags = 0;
510
511 /*
512 * Send a timestamp and echo-reply if both our side and our peer
513 * have sent timestamps in our SYN's and this is not a RST.
514 */
515 if (tw->t_recent && flags == TH_ACK) {
516 to.to_flags |= TOF_TS;
517 to.to_tsval = ticks + tw->ts_offset;
518 to.to_tsecr = tw->t_recent;
519 }
520 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
521
522 m->m_len = hdrlen + optlen;
523 m->m_pkthdr.len = m->m_len;
524
525 KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small"));
526
527 th->th_seq = htonl(tw->snd_nxt);
528 th->th_ack = htonl(tw->rcv_nxt);
529 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
530 th->th_flags = flags;
531 th->th_win = htons(tw->last_win);
532
533 #ifdef INET6
534 if (isipv6) {
535 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr),
536 sizeof(struct tcphdr) + optlen);
537 ip6->ip6_hlim = in6_selecthlim(inp, NULL);
538 error = ip6_output(m, inp->in6p_outputopts, NULL,
539 (tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp);
540 } else
541 #endif
542 {
543 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
544 htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP));
545 m->m_pkthdr.csum_flags = CSUM_TCP;
546 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
547 ip->ip_len = m->m_pkthdr.len;
548 if (path_mtu_discovery)
549 ip->ip_off |= IP_DF;
550 error = ip_output(m, inp->inp_options, NULL,
551 ((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
552 NULL, inp);
553 }
554 if (flags & TH_ACK)
555 tcpstat.tcps_sndacks++;
556 else
557 tcpstat.tcps_sndctrl++;
558 tcpstat.tcps_sndtotal++;
559 return (error);
560 }
561
562 static void
563 tcp_tw_2msl_reset(struct tcptw *tw, int rearm)
564 {
565
566 INP_INFO_WLOCK_ASSERT(&tcbinfo);
567 INP_WLOCK_ASSERT(tw->tw_inpcb);
568 if (rearm)
569 TAILQ_REMOVE(&twq_2msl, tw, tw_2msl);
570 tw->tw_time = ticks + 2 * tcp_msl;
571 TAILQ_INSERT_TAIL(&twq_2msl, tw, tw_2msl);
572 }
573
574 static void
575 tcp_tw_2msl_stop(struct tcptw *tw)
576 {
577
578 INP_INFO_WLOCK_ASSERT(&tcbinfo);
579 TAILQ_REMOVE(&twq_2msl, tw, tw_2msl);
580 }
581
582 struct tcptw *
583 tcp_tw_2msl_scan(int reuse)
584 {
585 struct tcptw *tw;
586
587 INP_INFO_WLOCK_ASSERT(&tcbinfo);
588 for (;;) {
589 tw = TAILQ_FIRST(&twq_2msl);
590 if (tw == NULL || (!reuse && tw->tw_time > ticks))
591 break;
592 INP_WLOCK(tw->tw_inpcb);
593 tcp_twclose(tw, reuse);
594 if (reuse)
595 return (tw);
596 }
597 return (NULL);
598 }
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