2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995
3 * The Regents of the University of California. All rights reserved.
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
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.
17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
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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
29 * @(#)tcp_subr.c 8.2 (Berkeley) 5/24/95
32 #include <sys/cdefs.h>
33 __FBSDID("$FreeBSD$");
36 #include "opt_inet6.h"
37 #include "opt_tcpdebug.h"
39 #include <sys/param.h>
40 #include <sys/systm.h>
41 #include <sys/callout.h>
42 #include <sys/kernel.h>
43 #include <sys/sysctl.h>
44 #include <sys/malloc.h>
48 #include <sys/socket.h>
49 #include <sys/socketvar.h>
50 #include <sys/protosw.h>
51 #include <sys/random.h>
55 #include <net/route.h>
59 #include <netinet/in.h>
60 #include <netinet/in_systm.h>
61 #include <netinet/ip.h>
63 #include <netinet/ip6.h>
65 #include <netinet/in_pcb.h>
67 #include <netinet6/in6_pcb.h>
69 #include <netinet/in_var.h>
70 #include <netinet/ip_var.h>
72 #include <netinet6/ip6_var.h>
73 #include <netinet6/scope6_var.h>
74 #include <netinet6/nd6.h>
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>
83 #include <netinet6/tcp6_var.h>
85 #include <netinet/tcpip.h>
87 #include <netinet/tcp_debug.h>
89 #include <netinet6/ip6protosw.h>
91 #include <machine/in_cksum.h>
93 #include <security/mac/mac_framework.h>
98 * The timed wait queue contains references to each of the TCP sessions
99 * currently in the TIME_WAIT state. The queue pointers, including the
100 * queue pointers in each tcptw structure, are protected using the global
101 * tcbinfo lock, which must be held over queue iteration and modification.
103 static VNET_DEFINE(uma_zone_t, tcptw_zone);
104 static VNET_DEFINE(TAILQ_HEAD(, tcptw), twq_2msl);
105 VNET_DEFINE(int, nolocaltimewait);
107 #define V_tcptw_zone VNET(tcptw_zone)
108 #define V_twq_2msl VNET(twq_2msl)
110 static void tcp_tw_2msl_reset(struct tcptw *, int);
111 static void tcp_tw_2msl_stop(struct tcptw *);
114 tcptw_auto_size(void)
119 * Max out at half the ephemeral port range so that TIME_WAIT
120 * sockets don't tie up too many ephemeral ports.
122 if (V_ipport_lastauto > V_ipport_firstauto)
123 halfrange = (V_ipport_lastauto - V_ipport_firstauto) / 2;
125 halfrange = (V_ipport_firstauto - V_ipport_lastauto) / 2;
126 /* Protect against goofy port ranges smaller than 32. */
127 return (imin(imax(halfrange, 32), maxsockets / 5));
131 sysctl_maxtcptw(SYSCTL_HANDLER_ARGS)
136 new = tcptw_auto_size();
139 error = sysctl_handle_int(oidp, &new, 0, req);
140 if (error == 0 && req->newptr)
143 uma_zone_set_max(V_tcptw_zone, maxtcptw);
148 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, maxtcptw, CTLTYPE_INT|CTLFLAG_RW,
149 &maxtcptw, 0, sysctl_maxtcptw, "IU",
150 "Maximum number of compressed TCP TIME_WAIT entries");
152 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, nolocaltimewait, CTLFLAG_RW,
153 &VNET_NAME(nolocaltimewait), 0,
154 "Do not create compressed TCP TIME_WAIT entries for local connections");
157 tcp_tw_zone_change(void)
161 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
168 V_tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw),
169 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
170 TUNABLE_INT_FETCH("net.inet.tcp.maxtcptw", &maxtcptw);
172 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
174 uma_zone_set_max(V_tcptw_zone, maxtcptw);
175 TAILQ_INIT(&V_twq_2msl);
184 INP_INFO_WLOCK(&V_tcbinfo);
185 while((tw = TAILQ_FIRST(&V_twq_2msl)) != NULL)
187 INP_INFO_WUNLOCK(&V_tcbinfo);
192 * Move a TCP connection into TIME_WAIT state.
194 * inp is locked, and is unlocked before returning.
197 tcp_twstart(struct tcpcb *tp)
200 struct inpcb *inp = tp->t_inpcb;
204 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); /* tcp_tw_2msl_reset(). */
205 INP_WLOCK_ASSERT(inp);
207 if (V_nolocaltimewait && in_localip(inp->inp_faddr)) {
214 tw = uma_zalloc(V_tcptw_zone, M_NOWAIT);
216 tw = tcp_tw_2msl_scan(1);
227 * Recover last window size sent.
229 tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale;
232 * Set t_recent if timestamps are used on the connection.
234 if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) ==
235 (TF_REQ_TSTMP|TF_RCVD_TSTMP)) {
236 tw->t_recent = tp->ts_recent;
237 tw->ts_offset = tp->ts_offset;
243 tw->snd_nxt = tp->snd_nxt;
244 tw->rcv_nxt = tp->rcv_nxt;
247 tw->t_starttime = tp->t_starttime;
252 * be used for fin-wait-2 state also, then we may need
253 * a ts_recent from the last segment.
255 acknow = tp->t_flags & TF_ACKNOW;
258 * First, discard tcpcb state, which includes stopping its timers and
259 * freeing it. tcp_discardcb() used to also release the inpcb, but
260 * that work is now done in the caller.
262 * Note: soisdisconnected() call used to be made in tcp_discardcb(),
263 * and might not be needed here any longer.
266 so = inp->inp_socket;
267 soisdisconnected(so);
268 tw->tw_cred = crhold(so->so_cred);
270 tw->tw_so_options = so->so_options;
273 tcp_twrespond(tw, TH_ACK);
275 inp->inp_flags |= INP_TIMEWAIT;
276 tcp_tw_2msl_reset(tw, 0);
279 * If the inpcb owns the sole reference to the socket, then we can
280 * detach and free the socket as it is not needed in time wait.
282 if (inp->inp_flags & INP_SOCKREF) {
283 KASSERT(so->so_state & SS_PROTOREF,
284 ("tcp_twstart: !SS_PROTOREF"));
285 inp->inp_flags &= ~INP_SOCKREF;
289 so->so_state &= ~SS_PROTOREF;
297 * The appromixate rate of ISN increase of Microsoft TCP stacks;
298 * the actual rate is slightly higher due to the addition of
299 * random positive increments.
301 * Most other new OSes use semi-randomized ISN values, so we
302 * do not need to worry about them.
304 #define MS_ISN_BYTES_PER_SECOND 250000
307 * Determine if the ISN we will generate has advanced beyond the last
308 * sequence number used by the previous connection. If so, indicate
309 * that it is safe to recycle this tw socket by returning 1.
312 tcp_twrecycleable(struct tcptw *tw)
314 tcp_seq new_iss = tw->iss;
315 tcp_seq new_irs = tw->irs;
317 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
318 new_iss += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz);
319 new_irs += (ticks - tw->t_starttime) * (MS_ISN_BYTES_PER_SECOND / hz);
321 if (SEQ_GT(new_iss, tw->snd_nxt) && SEQ_GT(new_irs, tw->rcv_nxt))
329 * Returns 1 if the TIME_WAIT state was killed and we should start over,
330 * looking for a pcb in the listen state. Returns 0 otherwise.
333 tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th,
334 struct mbuf *m, int tlen)
340 /* tcbinfo lock required for tcp_twclose(), tcp_tw_2msl_reset(). */
341 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
342 INP_WLOCK_ASSERT(inp);
345 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is
346 * still present. This is undesirable, but temporarily necessary
347 * until we work out how to handle inpcb's who's timewait state has
354 thflags = th->th_flags;
357 * NOTE: for FIN_WAIT_2 (to be added later),
358 * must validate sequence number before accepting RST
362 * If the segment contains RST:
363 * Drop the segment - see Stevens, vol. 2, p. 964 and
366 if (thflags & TH_RST)
370 /* PAWS not needed at the moment */
372 * RFC 1323 PAWS: If we have a timestamp reply on this segment
373 * and it's less than ts_recent, drop it.
375 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
376 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
377 if ((thflags & TH_ACK) == 0)
382 * ts_recent is never updated because we never accept new segments.
387 * If a new connection request is received
388 * while in TIME_WAIT, drop the old connection
389 * and start over if the sequence numbers
390 * are above the previous ones.
392 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
398 * Drop the the segment if it does not contain an ACK.
400 if ((thflags & TH_ACK) == 0)
404 * Reset the 2MSL timer if this is a duplicate FIN.
406 if (thflags & TH_FIN) {
407 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
408 if (seq + 1 == tw->rcv_nxt)
409 tcp_tw_2msl_reset(tw, 1);
413 * Acknowledge the segment if it has data or is not a duplicate ACK.
415 if (thflags != TH_ACK || tlen != 0 ||
416 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
417 tcp_twrespond(tw, TH_ACK);
425 tcp_twclose(struct tcptw *tw, int reuse)
431 * At this point, we are in one of two situations:
433 * (1) We have no socket, just an inpcb<->twtcp pair. We can free
436 * (2) We have a socket -- if we own a reference, release it and
437 * notify the socket layer.
440 KASSERT((inp->inp_flags & INP_TIMEWAIT), ("tcp_twclose: !timewait"));
441 KASSERT(intotw(inp) == tw, ("tcp_twclose: inp_ppcb != tw"));
442 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); /* tcp_tw_2msl_stop(). */
443 INP_WLOCK_ASSERT(inp);
446 tcp_tw_2msl_stop(tw);
447 inp->inp_ppcb = NULL;
450 so = inp->inp_socket;
453 * If there's a socket, handle two cases: first, we own a
454 * strong reference, which we will now release, or we don't
455 * in which case another reference exists (XXXRW: think
456 * about this more), and we don't need to take action.
458 if (inp->inp_flags & INP_SOCKREF) {
459 inp->inp_flags &= ~INP_SOCKREF;
463 KASSERT(so->so_state & SS_PROTOREF,
464 ("tcp_twclose: INP_SOCKREF && !SS_PROTOREF"));
465 so->so_state &= ~SS_PROTOREF;
469 * If we don't own the only reference, the socket and
470 * inpcb need to be left around to be handled by
471 * tcp_usr_detach() later.
477 TCPSTAT_INC(tcps_closed);
482 uma_zfree(V_tcptw_zone, tw);
486 tcp_twrespond(struct tcptw *tw, int flags)
488 struct inpcb *inp = tw->tw_inpcb;
491 struct ip *ip = NULL;
492 u_int hdrlen, optlen;
496 struct ip6_hdr *ip6 = NULL;
497 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
500 INP_WLOCK_ASSERT(inp);
502 m = m_gethdr(M_DONTWAIT, MT_DATA);
505 m->m_data += max_linkhdr;
508 mac_inpcb_create_mbuf(inp, m);
513 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
514 ip6 = mtod(m, struct ip6_hdr *);
515 th = (struct tcphdr *)(ip6 + 1);
516 tcpip_fillheaders(inp, ip6, th);
520 hdrlen = sizeof(struct tcpiphdr);
521 ip = mtod(m, struct ip *);
522 th = (struct tcphdr *)(ip + 1);
523 tcpip_fillheaders(inp, ip, th);
528 * Send a timestamp and echo-reply if both our side and our peer
529 * have sent timestamps in our SYN's and this is not a RST.
531 if (tw->t_recent && flags == TH_ACK) {
532 to.to_flags |= TOF_TS;
533 to.to_tsval = ticks + tw->ts_offset;
534 to.to_tsecr = tw->t_recent;
536 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
538 m->m_len = hdrlen + optlen;
539 m->m_pkthdr.len = m->m_len;
541 KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small"));
543 th->th_seq = htonl(tw->snd_nxt);
544 th->th_ack = htonl(tw->rcv_nxt);
545 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
546 th->th_flags = flags;
547 th->th_win = htons(tw->last_win);
551 th->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr),
552 sizeof(struct tcphdr) + optlen);
553 ip6->ip6_hlim = in6_selecthlim(inp, NULL);
554 error = ip6_output(m, inp->in6p_outputopts, NULL,
555 (tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp);
559 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
560 htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP));
561 m->m_pkthdr.csum_flags = CSUM_TCP;
562 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
563 ip->ip_len = m->m_pkthdr.len;
564 if (V_path_mtu_discovery)
566 error = ip_output(m, inp->inp_options, NULL,
567 ((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
571 TCPSTAT_INC(tcps_sndacks);
573 TCPSTAT_INC(tcps_sndctrl);
574 TCPSTAT_INC(tcps_sndtotal);
579 tcp_tw_2msl_reset(struct tcptw *tw, int rearm)
582 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
583 INP_WLOCK_ASSERT(tw->tw_inpcb);
585 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
586 tw->tw_time = ticks + 2 * tcp_msl;
587 TAILQ_INSERT_TAIL(&V_twq_2msl, tw, tw_2msl);
591 tcp_tw_2msl_stop(struct tcptw *tw)
594 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
595 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
599 tcp_tw_2msl_scan(int reuse)
603 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
605 tw = TAILQ_FIRST(&V_twq_2msl);
606 if (tw == NULL || (!reuse && (tw->tw_time - ticks) > 0))
608 INP_WLOCK(tw->tw_inpcb);
609 tcp_twclose(tw, reuse);