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 * 3. All advertising materials mentioning features or use of this software
14 * must display the following acknowledgement:
15 * This product includes software developed by the University of
16 * California, Berkeley and its contributors.
17 * 4. Neither the name of the University nor the names of its contributors
18 * may be used to endorse or promote products derived from this software
19 * without specific prior written permission.
21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
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26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
33 * @(#)tcp_subr.c 8.2 (Berkeley) 5/24/95
34 * $FreeBSD: src/sys/netinet/tcp_subr.c,v 1.73.2.31 2003/01/24 05:11:34 sam Exp $
35 * $DragonFly: src/sys/netinet/tcp_subr.c,v 1.14 2004/03/08 19:44:32 hsu Exp $
38 #include "opt_compat.h"
39 #include "opt_inet6.h"
40 #include "opt_ipsec.h"
41 #include "opt_tcpdebug.h"
43 #include <sys/param.h>
44 #include <sys/systm.h>
45 #include <sys/callout.h>
46 #include <sys/kernel.h>
47 #include <sys/sysctl.h>
48 #include <sys/malloc.h>
51 #include <sys/domain.h>
54 #include <sys/socket.h>
55 #include <sys/socketvar.h>
56 #include <sys/protosw.h>
57 #include <sys/random.h>
58 #include <sys/in_cksum.h>
60 #include <vm/vm_zone.h>
62 #include <net/route.h>
66 #include <netinet/in.h>
67 #include <netinet/in_systm.h>
68 #include <netinet/ip.h>
70 #include <netinet/ip6.h>
72 #include <netinet/in_pcb.h>
74 #include <netinet6/in6_pcb.h>
76 #include <netinet/in_var.h>
77 #include <netinet/ip_var.h>
79 #include <netinet6/ip6_var.h>
81 #include <netinet/tcp.h>
82 #include <netinet/tcp_fsm.h>
83 #include <netinet/tcp_seq.h>
84 #include <netinet/tcp_timer.h>
85 #include <netinet/tcp_var.h>
87 #include <netinet6/tcp6_var.h>
89 #include <netinet/tcpip.h>
91 #include <netinet/tcp_debug.h>
93 #include <netinet6/ip6protosw.h>
96 #include <netinet6/ipsec.h>
98 #include <netinet6/ipsec6.h>
103 #include <netipsec/ipsec.h>
105 #include <netipsec/ipsec6.h>
108 #endif /*FAST_IPSEC*/
112 int tcp_mssdflt = TCP_MSS;
113 SYSCTL_INT(_net_inet_tcp, TCPCTL_MSSDFLT, mssdflt, CTLFLAG_RW,
114 &tcp_mssdflt , 0, "Default TCP Maximum Segment Size");
117 int tcp_v6mssdflt = TCP6_MSS;
118 SYSCTL_INT(_net_inet_tcp, TCPCTL_V6MSSDFLT, v6mssdflt,
119 CTLFLAG_RW, &tcp_v6mssdflt , 0,
120 "Default TCP Maximum Segment Size for IPv6");
124 static int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ;
125 SYSCTL_INT(_net_inet_tcp, TCPCTL_RTTDFLT, rttdflt, CTLFLAG_RW,
126 &tcp_rttdflt , 0, "Default maximum TCP Round Trip Time");
129 int tcp_do_rfc1323 = 1;
130 SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, CTLFLAG_RW,
131 &tcp_do_rfc1323 , 0, "Enable rfc1323 (high performance TCP) extensions");
133 int tcp_do_rfc1644 = 0;
134 SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1644, rfc1644, CTLFLAG_RW,
135 &tcp_do_rfc1644 , 0, "Enable rfc1644 (TTCP) extensions");
137 static int tcp_tcbhashsize = 0;
138 SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcbhashsize, CTLFLAG_RD,
139 &tcp_tcbhashsize, 0, "Size of TCP control-block hashtable");
141 static int do_tcpdrain = 1;
142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_tcpdrain, CTLFLAG_RW, &do_tcpdrain, 0,
143 "Enable tcp_drain routine for extra help when low on mbufs");
146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, pcbcount, CTLFLAG_RD,
147 &tcbinfo[0].ipi_count, 0, "Number of active PCBs");
149 static int icmp_may_rst = 1;
150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, icmp_may_rst, CTLFLAG_RW, &icmp_may_rst, 0,
151 "Certain ICMP unreachable messages may abort connections in SYN_SENT");
153 static int tcp_isn_reseed_interval = 0;
154 SYSCTL_INT(_net_inet_tcp, OID_AUTO, isn_reseed_interval, CTLFLAG_RW,
155 &tcp_isn_reseed_interval, 0, "Seconds between reseeding of ISN secret");
158 * TCP bandwidth limiting sysctls. Note that the default lower bound of
159 * 1024 exists only for debugging. A good production default would be
160 * something like 6100.
162 static int tcp_inflight_enable = 0;
163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, inflight_enable, CTLFLAG_RW,
164 &tcp_inflight_enable, 0, "Enable automatic TCP inflight data limiting");
166 static int tcp_inflight_debug = 0;
167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, inflight_debug, CTLFLAG_RW,
168 &tcp_inflight_debug, 0, "Debug TCP inflight calculations");
170 static int tcp_inflight_min = 6144;
171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, inflight_min, CTLFLAG_RW,
172 &tcp_inflight_min, 0, "Lower-bound for TCP inflight window");
174 static int tcp_inflight_max = TCP_MAXWIN << TCP_MAX_WINSHIFT;
175 SYSCTL_INT(_net_inet_tcp, OID_AUTO, inflight_max, CTLFLAG_RW,
176 &tcp_inflight_max, 0, "Upper-bound for TCP inflight window");
178 static int tcp_inflight_stab = 20;
179 SYSCTL_INT(_net_inet_tcp, OID_AUTO, inflight_stab, CTLFLAG_RW,
180 &tcp_inflight_stab, 0, "Slop in maximal packets / 10 (20 = 2 packets)");
182 static void tcp_cleartaocache (void);
183 static void tcp_notify (struct inpcb *, int);
186 * Target size of TCP PCB hash tables. Must be a power of two.
188 * Note that this can be overridden by the kernel environment
189 * variable net.inet.tcp.tcbhashsize
192 #define TCBHASHSIZE 512
196 * This is the actual shape of what we allocate using the zone
197 * allocator. Doing it this way allows us to protect both structures
198 * using the same generation count, and also eliminates the overhead
199 * of allocating tcpcbs separately. By hiding the structure here,
200 * we avoid changing most of the rest of the code (although it needs
201 * to be changed, eventually, for greater efficiency).
204 #define ALIGNM1 (ALIGNMENT - 1)
208 char align[(sizeof(struct inpcb) + ALIGNM1) & ~ALIGNM1];
211 struct callout inp_tp_rexmt, inp_tp_persist, inp_tp_keep, inp_tp_2msl;
212 struct callout inp_tp_delack;
223 struct inpcbporthead *porthashbase;
225 struct inpcbhead *bindhashbase;
227 struct vm_zone *ipi_zone;
228 int hashsize = TCBHASHSIZE;
234 tcp_delacktime = TCPTV_DELACK;
235 tcp_keepinit = TCPTV_KEEP_INIT;
236 tcp_keepidle = TCPTV_KEEP_IDLE;
237 tcp_keepintvl = TCPTV_KEEPINTVL;
238 tcp_maxpersistidle = TCPTV_KEEP_IDLE;
240 tcp_rexmit_min = TCPTV_MIN;
241 tcp_rexmit_slop = TCPTV_CPU_VAR;
243 TUNABLE_INT_FETCH("net.inet.tcp.tcbhashsize", &hashsize);
244 if (!powerof2(hashsize)) {
245 printf("WARNING: TCB hash size not a power of 2\n");
246 hashsize = 512; /* safe default */
248 tcp_tcbhashsize = hashsize;
249 porthashbase = hashinit(hashsize, M_PCB, &porthashmask);
250 bindhashbase = hashinit(hashsize, M_PCB, &bindhashmask);
251 ipi_zone = zinit("tcpcb", sizeof(struct inp_tp), maxsockets,
254 for (cpu = 0; cpu < ncpus2; cpu++) {
255 LIST_INIT(&tcbinfo[cpu].listhead);
256 tcbinfo[cpu].hashbase = hashinit(hashsize, M_PCB,
257 &tcbinfo[cpu].hashmask);
258 tcbinfo[cpu].porthashbase = porthashbase;
259 tcbinfo[cpu].porthashmask = porthashmask;
260 tcbinfo[cpu].bindhashbase = bindhashbase;
261 tcbinfo[cpu].bindhashmask = bindhashmask;
262 tcbinfo[cpu].ipi_zone = ipi_zone;
265 tcp_reass_maxseg = nmbclusters / 16;
266 TUNABLE_INT_FETCH("net.inet.tcp.reass.maxsegments",
270 #define TCP_MINPROTOHDR (sizeof(struct ip6_hdr) + sizeof(struct tcphdr))
272 #define TCP_MINPROTOHDR (sizeof(struct tcpiphdr))
274 if (max_protohdr < TCP_MINPROTOHDR)
275 max_protohdr = TCP_MINPROTOHDR;
276 if (max_linkhdr + TCP_MINPROTOHDR > MHLEN)
278 #undef TCP_MINPROTOHDR
285 * Fill in the IP and TCP headers for an outgoing packet, given the tcpcb.
286 * tcp_template used to store this data in mbufs, but we now recopy it out
287 * of the tcpcb each time to conserve mbufs.
290 tcp_fillheaders(tp, ip_ptr, tcp_ptr)
295 struct inpcb *inp = tp->t_inpcb;
296 struct tcphdr *tcp_hdr = (struct tcphdr *)tcp_ptr;
299 if ((inp->inp_vflag & INP_IPV6) != 0) {
302 ip6 = (struct ip6_hdr *)ip_ptr;
303 ip6->ip6_flow = (ip6->ip6_flow & ~IPV6_FLOWINFO_MASK) |
304 (inp->in6p_flowinfo & IPV6_FLOWINFO_MASK);
305 ip6->ip6_vfc = (ip6->ip6_vfc & ~IPV6_VERSION_MASK) |
306 (IPV6_VERSION & IPV6_VERSION_MASK);
307 ip6->ip6_nxt = IPPROTO_TCP;
308 ip6->ip6_plen = sizeof(struct tcphdr);
309 ip6->ip6_src = inp->in6p_laddr;
310 ip6->ip6_dst = inp->in6p_faddr;
315 struct ip *ip = (struct ip *) ip_ptr;
317 ip->ip_vhl = IP_VHL_BORING;
324 ip->ip_p = IPPROTO_TCP;
325 ip->ip_src = inp->inp_laddr;
326 ip->ip_dst = inp->inp_faddr;
327 tcp_hdr->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
328 htons(sizeof(struct tcphdr) + IPPROTO_TCP));
331 tcp_hdr->th_sport = inp->inp_lport;
332 tcp_hdr->th_dport = inp->inp_fport;
337 tcp_hdr->th_flags = 0;
343 * Create template to be used to send tcp packets on a connection.
344 * Allocates an mbuf and fills in a skeletal tcp/ip header. The only
345 * use for this function is in keepalives, which use tcp_respond.
354 m = m_get(M_DONTWAIT, MT_HEADER);
357 m->m_len = sizeof(struct tcptemp);
358 n = mtod(m, struct tcptemp *);
360 tcp_fillheaders(tp, (void *)&n->tt_ipgen, (void *)&n->tt_t);
365 * Send a single message to the TCP at address specified by
366 * the given TCP/IP header. If m == 0, then we make a copy
367 * of the tcpiphdr at ti and send directly to the addressed host.
368 * This is used to force keep alive messages out using the TCP
369 * template for a connection. If flags are given then we send
370 * a message back to the TCP which originated the * segment ti,
371 * and discard the mbuf containing it and any other attached mbufs.
373 * In any case the ack and sequence number of the transmitted
374 * segment are as specified by the parameters.
376 * NOTE: If m != NULL, then ti must point to *inside* the mbuf.
379 tcp_respond(tp, ipgen, th, m, ack, seq, flags)
389 struct route *ro = 0;
394 struct route_in6 *ro6 = 0;
395 struct route_in6 sro6;
402 isipv6 = IP_VHL_V(((struct ip *)ipgen)->ip_vhl) == 6;
408 if (!(flags & TH_RST)) {
409 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv);
410 if (win > (long)TCP_MAXWIN << tp->rcv_scale)
411 win = (long)TCP_MAXWIN << tp->rcv_scale;
415 ro6 = &tp->t_inpcb->in6p_route;
418 ro = &tp->t_inpcb->inp_route;
423 bzero(ro6, sizeof *ro6);
428 bzero(ro, sizeof *ro);
432 m = m_gethdr(M_DONTWAIT, MT_HEADER);
436 m->m_data += max_linkhdr;
439 bcopy((caddr_t)ip6, mtod(m, caddr_t),
440 sizeof(struct ip6_hdr));
441 ip6 = mtod(m, struct ip6_hdr *);
442 nth = (struct tcphdr *)(ip6 + 1);
446 bcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip));
447 ip = mtod(m, struct ip *);
448 nth = (struct tcphdr *)(ip + 1);
450 bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr));
455 m->m_data = (caddr_t)ipgen;
456 /* m_len is set later */
458 #define xchg(a,b,type) { type t; t=a; a=b; b=t; }
461 xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr);
462 nth = (struct tcphdr *)(ip6 + 1);
466 xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, n_long);
467 nth = (struct tcphdr *)(ip + 1);
471 * this is usually a case when an extension header
472 * exists between the IPv6 header and the
475 nth->th_sport = th->th_sport;
476 nth->th_dport = th->th_dport;
478 xchg(nth->th_dport, nth->th_sport, n_short);
484 ip6->ip6_vfc = IPV6_VERSION;
485 ip6->ip6_nxt = IPPROTO_TCP;
486 ip6->ip6_plen = htons((u_short)(sizeof (struct tcphdr) +
488 tlen += sizeof (struct ip6_hdr) + sizeof (struct tcphdr);
492 tlen += sizeof (struct tcpiphdr);
494 ip->ip_ttl = ip_defttl;
497 m->m_pkthdr.len = tlen;
498 m->m_pkthdr.rcvif = (struct ifnet *) 0;
499 nth->th_seq = htonl(seq);
500 nth->th_ack = htonl(ack);
502 nth->th_off = sizeof (struct tcphdr) >> 2;
503 nth->th_flags = flags;
505 nth->th_win = htons((u_short) (win >> tp->rcv_scale));
507 nth->th_win = htons((u_short)win);
512 nth->th_sum = in6_cksum(m, IPPROTO_TCP,
513 sizeof(struct ip6_hdr),
514 tlen - sizeof(struct ip6_hdr));
515 ip6->ip6_hlim = in6_selecthlim(tp ? tp->t_inpcb : NULL,
522 nth->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr,
523 htons((u_short)(tlen - sizeof(struct ip) + ip->ip_p)));
524 m->m_pkthdr.csum_flags = CSUM_TCP;
525 m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum);
528 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
529 tcp_trace(TA_OUTPUT, 0, tp, mtod(m, void *), th, 0);
533 (void)ip6_output(m, NULL, ro6, ipflags, NULL, NULL,
534 tp ? tp->t_inpcb : NULL);
535 if (ro6 == &sro6 && ro6->ro_rt) {
542 (void) ip_output(m, NULL, ro, ipflags, NULL, tp ? tp->t_inpcb : NULL);
543 if (ro == &sro && ro->ro_rt) {
551 * Create a new TCP control block, making an
552 * empty reassembly queue and hooking it to the argument
553 * protocol control block. The `inp' parameter must have
554 * come from the zone allocator set up in tcp_init().
563 int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
566 it = (struct inp_tp *)inp;
568 bzero((char *) tp, sizeof(struct tcpcb));
569 LIST_INIT(&tp->t_segq);
570 tp->t_maxseg = tp->t_maxopd =
572 isipv6 ? tcp_v6mssdflt :
576 /* Set up our timeouts. */
577 callout_init(tp->tt_rexmt = &it->inp_tp_rexmt);
578 callout_init(tp->tt_persist = &it->inp_tp_persist);
579 callout_init(tp->tt_keep = &it->inp_tp_keep);
580 callout_init(tp->tt_2msl = &it->inp_tp_2msl);
581 callout_init(tp->tt_delack = &it->inp_tp_delack);
584 tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP);
586 tp->t_flags |= TF_REQ_CC;
587 tp->t_inpcb = inp; /* XXX */
589 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no
590 * rtt estimate. Set rttvar so that srtt + 4 * rttvar gives
591 * reasonable initial retransmit time.
593 tp->t_srtt = TCPTV_SRTTBASE;
594 tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
595 tp->t_rttmin = tcp_rexmit_min;
596 tp->t_rxtcur = TCPTV_RTOBASE;
597 tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
598 tp->snd_bwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
599 tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
600 tp->t_rcvtime = ticks;
601 tp->t_bw_rtttime = ticks;
603 * IPv4 TTL initialization is necessary for an IPv6 socket as well,
604 * because the socket may be bound to an IPv6 wildcard address,
605 * which may match an IPv4-mapped IPv6 address.
607 inp->inp_ip_ttl = ip_defttl;
608 inp->inp_ppcb = (caddr_t)tp;
609 return (tp); /* XXX */
613 * Drop a TCP connection, reporting
614 * the specified error. If connection is synchronized,
615 * then send a RST to peer.
622 struct socket *so = tp->t_inpcb->inp_socket;
624 if (TCPS_HAVERCVDSYN(tp->t_state)) {
625 tp->t_state = TCPS_CLOSED;
626 (void) tcp_output(tp);
627 tcpstat.tcps_drops++;
629 tcpstat.tcps_conndrops++;
630 if (errno == ETIMEDOUT && tp->t_softerror)
631 errno = tp->t_softerror;
632 so->so_error = errno;
633 return (tcp_close(tp));
637 * Close a TCP control block:
638 * discard all space held by the tcp
639 * discard internet protocol block
640 * wake up any sleepers
647 struct inpcb *inp = tp->t_inpcb;
648 struct socket *so = inp->inp_socket;
650 int isipv6 = (inp->inp_vflag & INP_IPV6) != 0;
656 * Make sure that all of our timers are stopped before we
659 callout_stop(tp->tt_rexmt);
660 callout_stop(tp->tt_persist);
661 callout_stop(tp->tt_keep);
662 callout_stop(tp->tt_2msl);
663 callout_stop(tp->tt_delack);
666 * If we got enough samples through the srtt filter,
667 * save the rtt and rttvar in the routing entry.
668 * 'Enough' is arbitrarily defined as the 16 samples.
669 * 16 samples is enough for the srtt filter to converge
670 * to within 5% of the correct value; fewer samples and
671 * we could save a very bogus rtt.
673 * Don't update the default route's characteristics and don't
674 * update anything that the user "locked".
676 if (tp->t_rttupdated >= 16) {
680 struct sockaddr_in6 *sin6;
682 if ((rt = inp->in6p_route.ro_rt) == NULL)
684 sin6 = (struct sockaddr_in6 *)rt_key(rt);
685 if (IN6_IS_ADDR_UNSPECIFIED(&sin6->sin6_addr))
690 if ((rt = inp->inp_route.ro_rt) == NULL ||
691 ((struct sockaddr_in *)rt_key(rt))->sin_addr.s_addr
695 if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) {
697 (RTM_RTTUNIT / (hz * TCP_RTT_SCALE));
698 if (rt->rt_rmx.rmx_rtt && i)
700 * filter this update to half the old & half
701 * the new values, converting scale.
702 * See route.h and tcp_var.h for a
703 * description of the scaling constants.
706 (rt->rt_rmx.rmx_rtt + i) / 2;
708 rt->rt_rmx.rmx_rtt = i;
709 tcpstat.tcps_cachedrtt++;
711 if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) {
713 (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE));
714 if (rt->rt_rmx.rmx_rttvar && i)
715 rt->rt_rmx.rmx_rttvar =
716 (rt->rt_rmx.rmx_rttvar + i) / 2;
718 rt->rt_rmx.rmx_rttvar = i;
719 tcpstat.tcps_cachedrttvar++;
722 * The old comment here said:
723 * update the pipelimit (ssthresh) if it has been updated
724 * already or if a pipesize was specified & the threshhold
725 * got below half the pipesize. I.e., wait for bad news
726 * before we start updating, then update on both good
729 * But we want to save the ssthresh even if no pipesize is
730 * specified explicitly in the route, because such
731 * connections still have an implicit pipesize specified
732 * by the global tcp_sendspace. In the absence of a reliable
733 * way to calculate the pipesize, it will have to do.
735 i = tp->snd_ssthresh;
736 if (rt->rt_rmx.rmx_sendpipe != 0)
737 dosavessthresh = (i < rt->rt_rmx.rmx_sendpipe / 2);
739 dosavessthresh = (i < so->so_snd.sb_hiwat / 2);
740 if (((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 &&
741 i != 0 && rt->rt_rmx.rmx_ssthresh != 0)
744 * convert the limit from user data bytes to
745 * packets then to packet data bytes.
747 i = (i + tp->t_maxseg / 2) / tp->t_maxseg;
750 i *= (u_long)(tp->t_maxseg +
752 (isipv6 ? sizeof (struct ip6_hdr) +
753 sizeof (struct tcphdr) :
755 sizeof (struct tcpiphdr)
760 if (rt->rt_rmx.rmx_ssthresh)
761 rt->rt_rmx.rmx_ssthresh =
762 (rt->rt_rmx.rmx_ssthresh + i) / 2;
764 rt->rt_rmx.rmx_ssthresh = i;
765 tcpstat.tcps_cachedssthresh++;
769 /* free the reassembly queue, if any */
770 while((q = LIST_FIRST(&tp->t_segq)) != NULL) {
771 LIST_REMOVE(q, tqe_q);
776 inp->inp_ppcb = NULL;
777 soisdisconnected(so);
779 if (INP_CHECK_SOCKAF(so, AF_INET6))
784 tcpstat.tcps_closed++;
785 return ((struct tcpcb *)0);
793 struct tseg_qent *te;
800 * Walk the tcpbs, if existing, and flush the reassembly queue,
802 * XXX: The "Net/3" implementation doesn't imply that the TCP
803 * reassembly queue should be flushed, but in a situation
804 * where we're really low on mbufs, this is potentially
807 for (cpu = 0; cpu < ncpus2; cpu++) {
808 LIST_FOREACH(inpb, &tcbinfo[cpu].listhead, inp_list) {
809 if ((tcpb = intotcpcb(inpb))) {
810 while ((te = LIST_FIRST(&tcpb->t_segq))
812 LIST_REMOVE(te, tqe_q);
823 * Notify a tcp user of an asynchronous error;
824 * store error as soft error, but wake up user
825 * (for now, won't do anything until can select for soft error).
827 * Do not wake up user since there currently is no mechanism for
828 * reporting soft errors (yet - a kqueue filter may be added).
831 tcp_notify(inp, error)
835 struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb;
838 * Ignore some errors if we are hooked up.
839 * If connection hasn't completed, has retransmitted several times,
840 * and receives a second error, give up now. This is better
841 * than waiting a long time to establish a connection that
842 * can never complete.
844 if (tp->t_state == TCPS_ESTABLISHED &&
845 (error == EHOSTUNREACH || error == ENETUNREACH ||
846 error == EHOSTDOWN)) {
848 } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 &&
852 tp->t_softerror = error;
854 wakeup((caddr_t) &so->so_timeo);
861 tcp_pcblist(SYSCTL_HANDLER_ARGS)
864 struct inpcb *inp, **inp_list;
869 * The process of preparing the TCB list is too time-consuming and
870 * resource-intensive to repeat twice on every request.
872 if (req->oldptr == 0) {
873 n = tcbinfo[mycpu->gd_cpuid].ipi_count;
874 req->oldidx = 2 * (sizeof xig)
875 + (n + n/8) * sizeof(struct xtcpcb);
879 if (req->newptr != 0)
883 * OK, now we're committed to doing something.
886 gencnt = tcbinfo[mycpu->gd_cpuid].ipi_gencnt;
887 n = tcbinfo[mycpu->gd_cpuid].ipi_count;
890 xig.xig_len = sizeof xig;
892 xig.xig_gen = gencnt;
893 xig.xig_sogen = so_gencnt;
894 error = SYSCTL_OUT(req, &xig, sizeof xig);
898 inp_list = malloc(n * sizeof *inp_list, M_TEMP, M_WAITOK);
903 for (inp = LIST_FIRST(&tcbinfo[mycpu->gd_cpuid].listhead), i = 0;
904 inp && i < n; inp = LIST_NEXT(inp, inp_list)) {
905 if (inp->inp_gencnt <= gencnt && !prison_xinpcb(req->td, inp))
912 for (i = 0; i < n; i++) {
914 if (inp->inp_gencnt <= gencnt) {
917 xt.xt_len = sizeof xt;
918 /* XXX should avoid extra copy */
919 bcopy(inp, &xt.xt_inp, sizeof *inp);
920 inp_ppcb = inp->inp_ppcb;
921 if (inp_ppcb != NULL)
922 bcopy(inp_ppcb, &xt.xt_tp, sizeof xt.xt_tp);
924 bzero((char *) &xt.xt_tp, sizeof xt.xt_tp);
926 sotoxsocket(inp->inp_socket, &xt.xt_socket);
927 error = SYSCTL_OUT(req, &xt, sizeof xt);
932 * Give the user an updated idea of our state.
933 * If the generation differs from what we told
934 * her before, she knows that something happened
935 * while we were processing this request, and it
936 * might be necessary to retry.
939 xig.xig_gen = tcbinfo[mycpu->gd_cpuid].ipi_gencnt;
940 xig.xig_sogen = so_gencnt;
941 xig.xig_count = tcbinfo[mycpu->gd_cpuid].ipi_count;
943 error = SYSCTL_OUT(req, &xig, sizeof xig);
945 free(inp_list, M_TEMP);
949 SYSCTL_PROC(_net_inet_tcp, TCPCTL_PCBLIST, pcblist, CTLFLAG_RD, 0, 0,
950 tcp_pcblist, "S,xtcpcb", "List of active TCP connections");
953 tcp_getcred(SYSCTL_HANDLER_ARGS)
955 struct sockaddr_in addrs[2];
960 error = suser(req->td);
963 error = SYSCTL_IN(req, addrs, sizeof(addrs));
967 cpu = tcp_addrcpu(addrs[1].sin_addr.s_addr, addrs[1].sin_port,
968 addrs[0].sin_addr.s_addr, addrs[0].sin_port);
969 inp = in_pcblookup_hash(&tcbinfo[cpu], addrs[1].sin_addr,
970 addrs[1].sin_port, addrs[0].sin_addr, addrs[0].sin_port, 0, NULL);
971 if (inp == NULL || inp->inp_socket == NULL) {
975 error = SYSCTL_OUT(req, inp->inp_socket->so_cred, sizeof(struct ucred));
981 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, getcred, CTLTYPE_OPAQUE|CTLFLAG_RW,
982 0, 0, tcp_getcred, "S,ucred", "Get the ucred of a TCP connection");
986 tcp6_getcred(SYSCTL_HANDLER_ARGS)
988 struct sockaddr_in6 addrs[2];
990 int error, s, mapped = 0;
992 error = suser(req->td);
995 error = SYSCTL_IN(req, addrs, sizeof(addrs));
998 if (IN6_IS_ADDR_V4MAPPED(&addrs[0].sin6_addr)) {
999 if (IN6_IS_ADDR_V4MAPPED(&addrs[1].sin6_addr))
1006 inp = in_pcblookup_hash(&tcbinfo[0],
1007 *(struct in_addr *)&addrs[1].sin6_addr.s6_addr[12],
1009 *(struct in_addr *)&addrs[0].sin6_addr.s6_addr[12],
1013 inp = in6_pcblookup_hash(&tcbinfo[0],
1014 &addrs[1].sin6_addr, addrs[1].sin6_port,
1015 &addrs[0].sin6_addr, addrs[0].sin6_port,
1018 if (inp == NULL || inp->inp_socket == NULL) {
1022 error = SYSCTL_OUT(req, inp->inp_socket->so_cred,
1023 sizeof(struct ucred));
1029 SYSCTL_PROC(_net_inet6_tcp6, OID_AUTO, getcred, CTLTYPE_OPAQUE|CTLFLAG_RW,
1031 tcp6_getcred, "S,ucred", "Get the ucred of a TCP6 connection");
1036 tcp_ctlinput(cmd, sa, vip)
1038 struct sockaddr *sa;
1041 struct ip *ip = vip;
1043 struct in_addr faddr;
1046 void (*notify) (struct inpcb *, int) = tcp_notify;
1051 faddr = ((struct sockaddr_in *)sa)->sin_addr;
1052 if (sa->sa_family != AF_INET || faddr.s_addr == INADDR_ANY)
1055 if (cmd == PRC_QUENCH)
1056 notify = tcp_quench;
1057 else if (icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB ||
1058 cmd == PRC_UNREACH_PORT || cmd == PRC_TIMXCEED_INTRANS) && ip)
1059 notify = tcp_drop_syn_sent;
1060 else if (cmd == PRC_MSGSIZE)
1061 notify = tcp_mtudisc;
1062 else if (PRC_IS_REDIRECT(cmd)) {
1064 notify = in_rtchange;
1065 } else if (cmd == PRC_HOSTDEAD)
1067 else if ((unsigned)cmd > PRC_NCMDS || inetctlerrmap[cmd] == 0)
1071 th = (struct tcphdr *)((caddr_t)ip
1072 + (IP_VHL_HL(ip->ip_vhl) << 2));
1073 cpu = tcp_addrcpu(faddr.s_addr, th->th_dport,
1074 ip->ip_src.s_addr, th->th_sport);
1075 inp = in_pcblookup_hash(&tcbinfo[cpu], faddr, th->th_dport,
1076 ip->ip_src, th->th_sport, 0, NULL);
1077 if (inp != NULL && inp->inp_socket != NULL) {
1078 icmp_seq = htonl(th->th_seq);
1079 tp = intotcpcb(inp);
1080 if (SEQ_GEQ(icmp_seq, tp->snd_una) &&
1081 SEQ_LT(icmp_seq, tp->snd_max))
1082 (*notify)(inp, inetctlerrmap[cmd]);
1084 struct in_conninfo inc;
1086 inc.inc_fport = th->th_dport;
1087 inc.inc_lport = th->th_sport;
1088 inc.inc_faddr = faddr;
1089 inc.inc_laddr = ip->ip_src;
1093 syncache_unreach(&inc, th);
1097 for (cpu = 0; cpu < ncpus2; cpu++)
1098 in_pcbnotifyall(&tcbinfo[cpu].listhead, faddr,
1099 inetctlerrmap[cmd], notify);
1105 tcp6_ctlinput(cmd, sa, d)
1107 struct sockaddr *sa;
1111 void (*notify) (struct inpcb *, int) = tcp_notify;
1112 struct ip6_hdr *ip6;
1114 struct ip6ctlparam *ip6cp = NULL;
1115 const struct sockaddr_in6 *sa6_src = NULL;
1117 struct tcp_portonly {
1122 if (sa->sa_family != AF_INET6 ||
1123 sa->sa_len != sizeof(struct sockaddr_in6))
1126 if (cmd == PRC_QUENCH)
1127 notify = tcp_quench;
1128 else if (cmd == PRC_MSGSIZE)
1129 notify = tcp_mtudisc;
1130 else if (!PRC_IS_REDIRECT(cmd) &&
1131 ((unsigned)cmd > PRC_NCMDS || inet6ctlerrmap[cmd] == 0))
1134 /* if the parameter is from icmp6, decode it. */
1136 ip6cp = (struct ip6ctlparam *)d;
1138 ip6 = ip6cp->ip6c_ip6;
1139 off = ip6cp->ip6c_off;
1140 sa6_src = ip6cp->ip6c_src;
1144 off = 0; /* fool gcc */
1149 struct in_conninfo inc;
1151 * XXX: We assume that when IPV6 is non NULL,
1152 * M and OFF are valid.
1155 /* check if we can safely examine src and dst ports */
1156 if (m->m_pkthdr.len < off + sizeof(*thp))
1159 bzero(&th, sizeof(th));
1160 m_copydata(m, off, sizeof(*thp), (caddr_t)&th);
1162 in6_pcbnotify(&tcbinfo[0].listhead, sa, th.th_dport,
1163 (struct sockaddr *)ip6cp->ip6c_src,
1164 th.th_sport, cmd, notify);
1166 inc.inc_fport = th.th_dport;
1167 inc.inc_lport = th.th_sport;
1168 inc.inc6_faddr = ((struct sockaddr_in6 *)sa)->sin6_addr;
1169 inc.inc6_laddr = ip6cp->ip6c_src->sin6_addr;
1171 syncache_unreach(&inc, &th);
1173 in6_pcbnotify(&tcbinfo[0].listhead, sa, 0,
1174 (const struct sockaddr *)sa6_src, 0, cmd, notify);
1180 * Following is where TCP initial sequence number generation occurs.
1182 * There are two places where we must use initial sequence numbers:
1183 * 1. In SYN-ACK packets.
1184 * 2. In SYN packets.
1186 * All ISNs for SYN-ACK packets are generated by the syncache. See
1187 * tcp_syncache.c for details.
1189 * The ISNs in SYN packets must be monotonic; TIME_WAIT recycling
1190 * depends on this property. In addition, these ISNs should be
1191 * unguessable so as to prevent connection hijacking. To satisfy
1192 * the requirements of this situation, the algorithm outlined in
1193 * RFC 1948 is used to generate sequence numbers.
1195 * Implementation details:
1197 * Time is based off the system timer, and is corrected so that it
1198 * increases by one megabyte per second. This allows for proper
1199 * recycling on high speed LANs while still leaving over an hour
1202 * net.inet.tcp.isn_reseed_interval controls the number of seconds
1203 * between seeding of isn_secret. This is normally set to zero,
1204 * as reseeding should not be necessary.
1208 #define ISN_BYTES_PER_SECOND 1048576
1210 u_char isn_secret[32];
1211 int isn_last_reseed;
1218 u_int32_t md5_buffer[4];
1221 /* Seed if this is the first use, reseed if requested. */
1222 if ((isn_last_reseed == 0) || ((tcp_isn_reseed_interval > 0) &&
1223 (((u_int)isn_last_reseed + (u_int)tcp_isn_reseed_interval*hz)
1225 read_random_unlimited(&isn_secret, sizeof(isn_secret));
1226 isn_last_reseed = ticks;
1229 /* Compute the md5 hash and return the ISN. */
1231 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_fport, sizeof(u_short));
1232 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_lport, sizeof(u_short));
1234 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) {
1235 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_faddr,
1236 sizeof(struct in6_addr));
1237 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_laddr,
1238 sizeof(struct in6_addr));
1242 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_faddr,
1243 sizeof(struct in_addr));
1244 MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_laddr,
1245 sizeof(struct in_addr));
1247 MD5Update(&isn_ctx, (u_char *) &isn_secret, sizeof(isn_secret));
1248 MD5Final((u_char *) &md5_buffer, &isn_ctx);
1249 new_isn = (tcp_seq) md5_buffer[0];
1250 new_isn += ticks * (ISN_BYTES_PER_SECOND / hz);
1255 * When a source quench is received, close congestion window
1256 * to one segment. We will gradually open it again as we proceed.
1259 tcp_quench(inp, errno)
1263 struct tcpcb *tp = intotcpcb(inp);
1266 tp->snd_cwnd = tp->t_maxseg;
1270 * When a specific ICMP unreachable message is received and the
1271 * connection state is SYN-SENT, drop the connection. This behavior
1272 * is controlled by the icmp_may_rst sysctl.
1275 tcp_drop_syn_sent(inp, errno)
1279 struct tcpcb *tp = intotcpcb(inp);
1281 if (tp && tp->t_state == TCPS_SYN_SENT)
1282 tcp_drop(tp, errno);
1286 * When `need fragmentation' ICMP is received, update our idea of the MSS
1287 * based on the new value in the route. Also nudge TCP to send something,
1288 * since we know the packet we just sent was dropped.
1289 * This duplicates some code in the tcp_mss() function in tcp_input.c.
1292 tcp_mtudisc(inp, errno)
1296 struct tcpcb *tp = intotcpcb(inp);
1298 struct rmxp_tao *taop;
1299 struct socket *so = inp->inp_socket;
1303 int isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0;
1309 rt = tcp_rtlookup6(&inp->inp_inc);
1312 rt = tcp_rtlookup(&inp->inp_inc);
1313 if (!rt || !rt->rt_rmx.rmx_mtu) {
1314 tp->t_maxopd = tp->t_maxseg =
1316 isipv6 ? tcp_v6mssdflt :
1321 taop = rmx_taop(rt->rt_rmx);
1322 offered = taop->tao_mssopt;
1323 mss = rt->rt_rmx.rmx_mtu -
1326 sizeof(struct ip6_hdr) + sizeof(struct tcphdr) :
1328 sizeof(struct tcpiphdr)
1335 mss = min(mss, offered);
1337 * XXX - The above conditional probably violates the TCP
1338 * spec. The problem is that, since we don't know the
1339 * other end's MSS, we are supposed to use a conservative
1340 * default. But, if we do that, then MTU discovery will
1341 * never actually take place, because the conservative
1342 * default is much less than the MTUs typically seen
1343 * on the Internet today. For the moment, we'll sweep
1344 * this under the carpet.
1346 * The conservative default might not actually be a problem
1347 * if the only case this occurs is when sending an initial
1348 * SYN with options and data to a host we've never talked
1349 * to before. Then, they will reply with an MSS value which
1350 * will get recorded and the new parameters should get
1351 * recomputed. For Further Study.
1353 if (tp->t_maxopd <= mss)
1357 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
1358 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)
1359 mss -= TCPOLEN_TSTAMP_APPA;
1360 if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
1361 (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC)
1362 mss -= TCPOLEN_CC_APPA;
1363 #if (MCLBYTES & (MCLBYTES - 1)) == 0
1365 mss &= ~(MCLBYTES-1);
1368 mss = mss / MCLBYTES * MCLBYTES;
1370 if (so->so_snd.sb_hiwat < mss)
1371 mss = so->so_snd.sb_hiwat;
1375 tcpstat.tcps_mturesent++;
1377 tp->snd_nxt = tp->snd_una;
1383 * Look-up the routing entry to the peer of this inpcb. If no route
1384 * is found and it cannot be allocated the return NULL. This routine
1385 * is called by TCP routines that access the rmx structure and by tcp_mss
1386 * to get the interface MTU.
1390 struct in_conninfo *inc;
1395 ro = &inc->inc_route;
1397 if (rt == NULL || !(rt->rt_flags & RTF_UP)) {
1398 /* No route yet, so try to acquire one */
1399 if (inc->inc_faddr.s_addr != INADDR_ANY) {
1400 ro->ro_dst.sa_family = AF_INET;
1401 ro->ro_dst.sa_len = sizeof(struct sockaddr_in);
1402 ((struct sockaddr_in *) &ro->ro_dst)->sin_addr =
1414 struct in_conninfo *inc;
1416 struct route_in6 *ro6;
1419 ro6 = &inc->inc6_route;
1421 if (rt == NULL || !(rt->rt_flags & RTF_UP)) {
1422 /* No route yet, so try to acquire one */
1423 if (!IN6_IS_ADDR_UNSPECIFIED(&inc->inc6_faddr)) {
1424 ro6->ro_dst.sin6_family = AF_INET6;
1425 ro6->ro_dst.sin6_len = sizeof(struct sockaddr_in6);
1426 ro6->ro_dst.sin6_addr = inc->inc6_faddr;
1427 rtalloc((struct route *)ro6);
1436 /* compute ESP/AH header size for TCP, including outer IP header. */
1438 ipsec_hdrsiz_tcp(tp)
1446 struct ip6_hdr *ip6;
1450 if ((tp == NULL) || ((inp = tp->t_inpcb) == NULL))
1452 MGETHDR(m, M_DONTWAIT, MT_DATA);
1457 if ((inp->inp_vflag & INP_IPV6) != 0) {
1458 ip6 = mtod(m, struct ip6_hdr *);
1459 th = (struct tcphdr *)(ip6 + 1);
1460 m->m_pkthdr.len = m->m_len =
1461 sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
1462 tcp_fillheaders(tp, ip6, th);
1463 hdrsiz = ipsec6_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
1467 ip = mtod(m, struct ip *);
1468 th = (struct tcphdr *)(ip + 1);
1469 m->m_pkthdr.len = m->m_len = sizeof(struct tcpiphdr);
1470 tcp_fillheaders(tp, ip, th);
1471 hdrsiz = ipsec4_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp);
1480 * Return a pointer to the cached information about the remote host.
1481 * The cached information is stored in the protocol specific part of
1482 * the route metrics.
1485 tcp_gettaocache(inc)
1486 struct in_conninfo *inc;
1491 if (inc->inc_isipv6)
1492 rt = tcp_rtlookup6(inc);
1495 rt = tcp_rtlookup(inc);
1497 /* Make sure this is a host route and is up. */
1499 (rt->rt_flags & (RTF_UP|RTF_HOST)) != (RTF_UP|RTF_HOST))
1502 return rmx_taop(rt->rt_rmx);
1506 * Clear all the TAO cache entries, called from tcp_init.
1509 * This routine is just an empty one, because we assume that the routing
1510 * routing tables are initialized at the same time when TCP, so there is
1511 * nothing in the cache left over.
1519 * TCP BANDWIDTH DELAY PRODUCT WINDOW LIMITING
1521 * This code attempts to calculate the bandwidth-delay product as a
1522 * means of determining the optimal window size to maximize bandwidth,
1523 * minimize RTT, and avoid the over-allocation of buffers on interfaces and
1524 * routers. This code also does a fairly good job keeping RTTs in check
1525 * across slow links like modems. We implement an algorithm which is very
1526 * similar (but not meant to be) TCP/Vegas. The code operates on the
1527 * transmitter side of a TCP connection and so only effects the transmit
1528 * side of the connection.
1530 * BACKGROUND: TCP makes no provision for the management of buffer space
1531 * at the end points or at the intermediate routers and switches. A TCP
1532 * stream, whether using NewReno or not, will eventually buffer as
1533 * many packets as it is able and the only reason this typically works is
1534 * due to the fairly small default buffers made available for a connection
1535 * (typicaly 16K or 32K). As machines use larger windows and/or window
1536 * scaling it is now fairly easy for even a single TCP connection to blow-out
1537 * all available buffer space not only on the local interface, but on
1538 * intermediate routers and switches as well. NewReno makes a misguided
1539 * attempt to 'solve' this problem by waiting for an actual failure to occur,
1540 * then backing off, then steadily increasing the window again until another
1541 * failure occurs, ad-infinitum. This results in terrible oscillation that
1542 * is only made worse as network loads increase and the idea of intentionally
1543 * blowing out network buffers is, frankly, a terrible way to manage network
1546 * It is far better to limit the transmit window prior to the failure
1547 * condition being achieved. There are two general ways to do this: First
1548 * you can 'scan' through different transmit window sizes and locate the
1549 * point where the RTT stops increasing, indicating that you have filled the
1550 * pipe, then scan backwards until you note that RTT stops decreasing, then
1551 * repeat ad-infinitum. This method works in principle but has severe
1552 * implementation issues due to RTT variances, timer granularity, and
1553 * instability in the algorithm which can lead to many false positives and
1554 * create oscillations as well as interact badly with other TCP streams
1555 * implementing the same algorithm.
1557 * The second method is to limit the window to the bandwidth delay product
1558 * of the link. This is the method we implement. RTT variances and our
1559 * own manipulation of the congestion window, bwnd, can potentially
1560 * destabilize the algorithm. For this reason we have to stabilize the
1561 * elements used to calculate the window. We do this by using the minimum
1562 * observed RTT, the long term average of the observed bandwidth, and
1563 * by adding two segments worth of slop. It isn't perfect but it is able
1564 * to react to changing conditions and gives us a very stable basis on
1565 * which to extend the algorithm.
1568 tcp_xmit_bandwidth_limit(struct tcpcb *tp, tcp_seq ack_seq)
1575 * If inflight_enable is disabled in the middle of a tcp connection,
1576 * make sure snd_bwnd is effectively disabled.
1578 if (tcp_inflight_enable == 0) {
1579 tp->snd_bwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
1580 tp->snd_bandwidth = 0;
1585 * Figure out the bandwidth. Due to the tick granularity this
1586 * is a very rough number and it MUST be averaged over a fairly
1587 * long period of time. XXX we need to take into account a link
1588 * that is not using all available bandwidth, but for now our
1589 * slop will ramp us up if this case occurs and the bandwidth later
1592 * Note: if ticks rollover 'bw' may wind up negative. We must
1593 * effectively reset t_bw_rtttime for this case.
1596 if ((u_int)(save_ticks - tp->t_bw_rtttime) < 1)
1599 bw = (int64_t)(ack_seq - tp->t_bw_rtseq) * hz /
1600 (save_ticks - tp->t_bw_rtttime);
1601 tp->t_bw_rtttime = save_ticks;
1602 tp->t_bw_rtseq = ack_seq;
1603 if (tp->t_bw_rtttime == 0 || (int)bw < 0)
1605 bw = ((int64_t)tp->snd_bandwidth * 15 + bw) >> 4;
1607 tp->snd_bandwidth = bw;
1610 * Calculate the semi-static bandwidth delay product, plus two maximal
1611 * segments. The additional slop puts us squarely in the sweet
1612 * spot and also handles the bandwidth run-up case. Without the
1613 * slop we could be locking ourselves into a lower bandwidth.
1615 * Situations Handled:
1616 * (1) Prevents over-queueing of packets on LANs, especially on
1617 * high speed LANs, allowing larger TCP buffers to be
1618 * specified, and also does a good job preventing
1619 * over-queueing of packets over choke points like modems
1620 * (at least for the transmit side).
1622 * (2) Is able to handle changing network loads (bandwidth
1623 * drops so bwnd drops, bandwidth increases so bwnd
1626 * (3) Theoretically should stabilize in the face of multiple
1627 * connections implementing the same algorithm (this may need
1630 * (4) Stability value (defaults to 20 = 2 maximal packets) can
1631 * be adjusted with a sysctl but typically only needs to be on
1632 * very slow connections. A value no smaller then 5 should
1633 * be used, but only reduce this default if you have no other
1636 #define USERTT ((tp->t_srtt + tp->t_rttbest) / 2)
1637 bwnd = (int64_t)bw * USERTT / (hz << TCP_RTT_SHIFT) + tcp_inflight_stab * (int)tp->t_maxseg / 10;
1640 if (tcp_inflight_debug > 0) {
1642 if ((u_int)(ticks - ltime) >= hz / tcp_inflight_debug) {
1644 printf("%p bw %ld rttbest %d srtt %d bwnd %ld\n",
1653 if ((long)bwnd < tcp_inflight_min)
1654 bwnd = tcp_inflight_min;
1655 if (bwnd > tcp_inflight_max)
1656 bwnd = tcp_inflight_max;
1657 if ((long)bwnd < tp->t_maxseg * 2)
1658 bwnd = tp->t_maxseg * 2;
1659 tp->snd_bwnd = bwnd;