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
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
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_pcb.h>
61 #include <netinet/in_systm.h>
62 #include <netinet/in_var.h>
63 #include <netinet/ip.h>
64 #include <netinet/ip_icmp.h>
65 #include <netinet/ip_var.h>
67 #include <netinet/ip6.h>
68 #include <netinet6/in6_pcb.h>
69 #include <netinet6/ip6_var.h>
70 #include <netinet6/scope6_var.h>
71 #include <netinet6/nd6.h>
73 #include <netinet/tcp.h>
74 #include <netinet/tcp_fsm.h>
75 #include <netinet/tcp_seq.h>
76 #include <netinet/tcp_timer.h>
77 #include <netinet/tcp_var.h>
79 #include <netinet6/tcp6_var.h>
81 #include <netinet/tcpip.h>
83 #include <netinet/tcp_debug.h>
86 #include <netinet6/ip6protosw.h>
89 #include <machine/in_cksum.h>
91 #include <security/mac/mac_framework.h>
93 static VNET_DEFINE(uma_zone_t, tcptw_zone);
94 #define V_tcptw_zone VNET(tcptw_zone)
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(TAILQ_HEAD(, tcptw), twq_2msl);
104 #define V_twq_2msl VNET(twq_2msl)
106 static void tcp_tw_2msl_reset(struct tcptw *, int);
107 static void tcp_tw_2msl_stop(struct tcptw *);
110 tcptw_auto_size(void)
115 * Max out at half the ephemeral port range so that TIME_WAIT
116 * sockets don't tie up too many ephemeral ports.
118 if (V_ipport_lastauto > V_ipport_firstauto)
119 halfrange = (V_ipport_lastauto - V_ipport_firstauto) / 2;
121 halfrange = (V_ipport_firstauto - V_ipport_lastauto) / 2;
122 /* Protect against goofy port ranges smaller than 32. */
123 return (imin(imax(halfrange, 32), maxsockets / 5));
127 sysctl_maxtcptw(SYSCTL_HANDLER_ARGS)
132 new = tcptw_auto_size();
135 error = sysctl_handle_int(oidp, &new, 0, req);
136 if (error == 0 && req->newptr)
139 uma_zone_set_max(V_tcptw_zone, maxtcptw);
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");
148 VNET_DEFINE(int, nolocaltimewait) = 0;
149 #define V_nolocaltimewait VNET(nolocaltimewait)
150 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, nolocaltimewait, CTLFLAG_RW,
151 &VNET_NAME(nolocaltimewait), 0,
152 "Do not create compressed TCP TIME_WAIT entries for local connections");
155 tcp_tw_zone_change(void)
159 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
166 V_tcptw_zone = uma_zcreate("tcptw", sizeof(struct tcptw),
167 NULL, NULL, NULL, NULL, UMA_ALIGN_PTR, UMA_ZONE_NOFREE);
168 TUNABLE_INT_FETCH("net.inet.tcp.maxtcptw", &maxtcptw);
170 uma_zone_set_max(V_tcptw_zone, tcptw_auto_size());
172 uma_zone_set_max(V_tcptw_zone, maxtcptw);
173 TAILQ_INIT(&V_twq_2msl);
182 INP_INFO_WLOCK(&V_tcbinfo);
183 while((tw = TAILQ_FIRST(&V_twq_2msl)) != NULL)
185 INP_INFO_WUNLOCK(&V_tcbinfo);
187 uma_zdestroy(V_tcptw_zone);
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 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
207 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); /* tcp_tw_2msl_reset(). */
208 INP_WLOCK_ASSERT(inp);
210 if (V_nolocaltimewait) {
214 error = in6_localaddr(&inp->in6p_faddr);
216 #if defined(INET6) && defined(INET)
220 error = in_localip(inp->inp_faddr);
230 tw = uma_zalloc(V_tcptw_zone, M_NOWAIT);
232 tw = tcp_tw_2msl_scan(1);
243 * Recover last window size sent.
245 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
246 tw->last_win = (tp->rcv_adv - tp->rcv_nxt) >> tp->rcv_scale;
251 * Set t_recent if timestamps are used on the connection.
253 if ((tp->t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP|TF_NOOPT)) ==
254 (TF_REQ_TSTMP|TF_RCVD_TSTMP)) {
255 tw->t_recent = tp->ts_recent;
256 tw->ts_offset = tp->ts_offset;
262 tw->snd_nxt = tp->snd_nxt;
263 tw->rcv_nxt = tp->rcv_nxt;
266 tw->t_starttime = tp->t_starttime;
271 * be used for fin-wait-2 state also, then we may need
272 * a ts_recent from the last segment.
274 acknow = tp->t_flags & TF_ACKNOW;
277 * First, discard tcpcb state, which includes stopping its timers and
278 * freeing it. tcp_discardcb() used to also release the inpcb, but
279 * that work is now done in the caller.
281 * Note: soisdisconnected() call used to be made in tcp_discardcb(),
282 * and might not be needed here any longer.
285 so = inp->inp_socket;
286 soisdisconnected(so);
287 tw->tw_cred = crhold(so->so_cred);
289 tw->tw_so_options = so->so_options;
292 tcp_twrespond(tw, TH_ACK);
294 inp->inp_flags |= INP_TIMEWAIT;
295 tcp_tw_2msl_reset(tw, 0);
298 * If the inpcb owns the sole reference to the socket, then we can
299 * detach and free the socket as it is not needed in time wait.
301 if (inp->inp_flags & INP_SOCKREF) {
302 KASSERT(so->so_state & SS_PROTOREF,
303 ("tcp_twstart: !SS_PROTOREF"));
304 inp->inp_flags &= ~INP_SOCKREF;
308 so->so_state &= ~SS_PROTOREF;
316 * The appromixate rate of ISN increase of Microsoft TCP stacks;
317 * the actual rate is slightly higher due to the addition of
318 * random positive increments.
320 * Most other new OSes use semi-randomized ISN values, so we
321 * do not need to worry about them.
323 #define MS_ISN_BYTES_PER_SECOND 250000
326 * Determine if the ISN we will generate has advanced beyond the last
327 * sequence number used by the previous connection. If so, indicate
328 * that it is safe to recycle this tw socket by returning 1.
331 tcp_twrecycleable(struct tcptw *tw)
333 tcp_seq new_iss = tw->iss;
334 tcp_seq new_irs = tw->irs;
336 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
337 new_iss += (ticks - tw->t_starttime) * (ISN_BYTES_PER_SECOND / hz);
338 new_irs += (ticks - tw->t_starttime) * (MS_ISN_BYTES_PER_SECOND / hz);
340 if (SEQ_GT(new_iss, tw->snd_nxt) && SEQ_GT(new_irs, tw->rcv_nxt))
348 * Returns 1 if the TIME_WAIT state was killed and we should start over,
349 * looking for a pcb in the listen state. Returns 0 otherwise.
352 tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th,
353 struct mbuf *m, int tlen)
359 /* tcbinfo lock required for tcp_twclose(), tcp_tw_2msl_reset(). */
360 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
361 INP_WLOCK_ASSERT(inp);
364 * XXXRW: Time wait state for inpcb has been recycled, but inpcb is
365 * still present. This is undesirable, but temporarily necessary
366 * until we work out how to handle inpcb's who's timewait state has
373 thflags = th->th_flags;
376 * NOTE: for FIN_WAIT_2 (to be added later),
377 * must validate sequence number before accepting RST
381 * If the segment contains RST:
382 * Drop the segment - see Stevens, vol. 2, p. 964 and
385 if (thflags & TH_RST)
389 /* PAWS not needed at the moment */
391 * RFC 1323 PAWS: If we have a timestamp reply on this segment
392 * and it's less than ts_recent, drop it.
394 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent &&
395 TSTMP_LT(to.to_tsval, tp->ts_recent)) {
396 if ((thflags & TH_ACK) == 0)
401 * ts_recent is never updated because we never accept new segments.
406 * If a new connection request is received
407 * while in TIME_WAIT, drop the old connection
408 * and start over if the sequence numbers
409 * are above the previous ones.
411 if ((thflags & TH_SYN) && SEQ_GT(th->th_seq, tw->rcv_nxt)) {
417 * Drop the segment if it does not contain an ACK.
419 if ((thflags & TH_ACK) == 0)
423 * Reset the 2MSL timer if this is a duplicate FIN.
425 if (thflags & TH_FIN) {
426 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0);
427 if (seq + 1 == tw->rcv_nxt)
428 tcp_tw_2msl_reset(tw, 1);
432 * Acknowledge the segment if it has data or is not a duplicate ACK.
434 if (thflags != TH_ACK || tlen != 0 ||
435 th->th_seq != tw->rcv_nxt || th->th_ack != tw->snd_nxt)
436 tcp_twrespond(tw, TH_ACK);
444 tcp_twclose(struct tcptw *tw, int reuse)
450 * At this point, we are in one of two situations:
452 * (1) We have no socket, just an inpcb<->twtcp pair. We can free
455 * (2) We have a socket -- if we own a reference, release it and
456 * notify the socket layer.
459 KASSERT((inp->inp_flags & INP_TIMEWAIT), ("tcp_twclose: !timewait"));
460 KASSERT(intotw(inp) == tw, ("tcp_twclose: inp_ppcb != tw"));
461 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); /* tcp_tw_2msl_stop(). */
462 INP_WLOCK_ASSERT(inp);
465 tcp_tw_2msl_stop(tw);
466 inp->inp_ppcb = NULL;
469 so = inp->inp_socket;
472 * If there's a socket, handle two cases: first, we own a
473 * strong reference, which we will now release, or we don't
474 * in which case another reference exists (XXXRW: think
475 * about this more), and we don't need to take action.
477 if (inp->inp_flags & INP_SOCKREF) {
478 inp->inp_flags &= ~INP_SOCKREF;
482 KASSERT(so->so_state & SS_PROTOREF,
483 ("tcp_twclose: INP_SOCKREF && !SS_PROTOREF"));
484 so->so_state &= ~SS_PROTOREF;
488 * If we don't own the only reference, the socket and
489 * inpcb need to be left around to be handled by
490 * tcp_usr_detach() later.
496 TCPSTAT_INC(tcps_closed);
501 uma_zfree(V_tcptw_zone, tw);
505 tcp_twrespond(struct tcptw *tw, int flags)
507 struct inpcb *inp = tw->tw_inpcb;
508 #if defined(INET6) || defined(INET)
509 struct tcphdr *th = NULL;
513 struct ip *ip = NULL;
515 u_int hdrlen, optlen;
516 int error = 0; /* Keep compiler happy */
519 struct ip6_hdr *ip6 = NULL;
520 int isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6;
522 hdrlen = 0; /* Keep compiler happy */
524 INP_WLOCK_ASSERT(inp);
526 m = m_gethdr(M_NOWAIT, MT_DATA);
529 m->m_data += max_linkhdr;
532 mac_inpcb_create_mbuf(inp, m);
537 hdrlen = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
538 ip6 = mtod(m, struct ip6_hdr *);
539 th = (struct tcphdr *)(ip6 + 1);
540 tcpip_fillheaders(inp, ip6, th);
543 #if defined(INET6) && defined(INET)
548 hdrlen = sizeof(struct tcpiphdr);
549 ip = mtod(m, struct ip *);
550 th = (struct tcphdr *)(ip + 1);
551 tcpip_fillheaders(inp, ip, th);
557 * Send a timestamp and echo-reply if both our side and our peer
558 * have sent timestamps in our SYN's and this is not a RST.
560 if (tw->t_recent && flags == TH_ACK) {
561 to.to_flags |= TOF_TS;
562 to.to_tsval = tcp_ts_getticks() + tw->ts_offset;
563 to.to_tsecr = tw->t_recent;
565 optlen = tcp_addoptions(&to, (u_char *)(th + 1));
567 m->m_len = hdrlen + optlen;
568 m->m_pkthdr.len = m->m_len;
570 KASSERT(max_linkhdr + m->m_len <= MHLEN, ("tcptw: mbuf too small"));
572 th->th_seq = htonl(tw->snd_nxt);
573 th->th_ack = htonl(tw->rcv_nxt);
574 th->th_off = (sizeof(struct tcphdr) + optlen) >> 2;
575 th->th_flags = flags;
576 th->th_win = htons(tw->last_win);
578 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
581 m->m_pkthdr.csum_flags = CSUM_TCP_IPV6;
582 th->th_sum = in6_cksum_pseudo(ip6,
583 sizeof(struct tcphdr) + optlen, IPPROTO_TCP, 0);
584 ip6->ip6_hlim = in6_selecthlim(inp, NULL);
585 error = ip6_output(m, inp->in6p_outputopts, NULL,
586 (tw->tw_so_options & SO_DONTROUTE), NULL, NULL, inp);
589 #if defined(INET6) && defined(INET)
594 m->m_pkthdr.csum_flags = CSUM_TCP;
595 th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
596 htons(sizeof(struct tcphdr) + optlen + IPPROTO_TCP));
597 ip->ip_len = htons(m->m_pkthdr.len);
598 if (V_path_mtu_discovery)
599 ip->ip_off |= htons(IP_DF);
600 error = ip_output(m, inp->inp_options, NULL,
601 ((tw->tw_so_options & SO_DONTROUTE) ? IP_ROUTETOIF : 0),
606 TCPSTAT_INC(tcps_sndacks);
608 TCPSTAT_INC(tcps_sndctrl);
609 TCPSTAT_INC(tcps_sndtotal);
614 tcp_tw_2msl_reset(struct tcptw *tw, int rearm)
617 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
618 INP_WLOCK_ASSERT(tw->tw_inpcb);
620 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
621 tw->tw_time = ticks + 2 * tcp_msl;
622 TAILQ_INSERT_TAIL(&V_twq_2msl, tw, tw_2msl);
626 tcp_tw_2msl_stop(struct tcptw *tw)
629 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
630 TAILQ_REMOVE(&V_twq_2msl, tw, tw_2msl);
634 tcp_tw_2msl_scan(int reuse)
638 INP_INFO_WLOCK_ASSERT(&V_tcbinfo);
640 tw = TAILQ_FIRST(&V_twq_2msl);
641 if (tw == NULL || (!reuse && (tw->tw_time - ticks) > 0))
643 INP_WLOCK(tw->tw_inpcb);
644 tcp_twclose(tw, reuse);