/* * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)tcp_subr.c 8.2 (Berkeley) 5/24/95 * $FreeBSD: src/sys/netinet/tcp_subr.c,v 1.73.2.31 2003/01/24 05:11:34 sam Exp $ * $DragonFly: src/sys/netinet/tcp_subr.c,v 1.9 2003/11/08 07:57:51 dillon Exp $ */ #include "opt_compat.h" #include "opt_inet6.h" #include "opt_ipsec.h" #include "opt_tcpdebug.h" #include #include #include #include #include #include #include #ifdef INET6 #include #endif #include #include #include #include #include #include #include #include #define _IP_VHL #include #include #include #ifdef INET6 #include #endif #include #ifdef INET6 #include #endif #include #include #ifdef INET6 #include #endif #include #include #include #include #include #ifdef INET6 #include #endif #include #ifdef TCPDEBUG #include #endif #include #ifdef IPSEC #include #ifdef INET6 #include #endif #endif /*IPSEC*/ #ifdef FAST_IPSEC #include #ifdef INET6 #include #endif #define IPSEC #endif /*FAST_IPSEC*/ #include #include int tcp_mssdflt = TCP_MSS; SYSCTL_INT(_net_inet_tcp, TCPCTL_MSSDFLT, mssdflt, CTLFLAG_RW, &tcp_mssdflt , 0, "Default TCP Maximum Segment Size"); #ifdef INET6 int tcp_v6mssdflt = TCP6_MSS; SYSCTL_INT(_net_inet_tcp, TCPCTL_V6MSSDFLT, v6mssdflt, CTLFLAG_RW, &tcp_v6mssdflt , 0, "Default TCP Maximum Segment Size for IPv6"); #endif #if 0 static int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ; SYSCTL_INT(_net_inet_tcp, TCPCTL_RTTDFLT, rttdflt, CTLFLAG_RW, &tcp_rttdflt , 0, "Default maximum TCP Round Trip Time"); #endif int tcp_do_rfc1323 = 1; SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1323, rfc1323, CTLFLAG_RW, &tcp_do_rfc1323 , 0, "Enable rfc1323 (high performance TCP) extensions"); int tcp_do_rfc1644 = 0; SYSCTL_INT(_net_inet_tcp, TCPCTL_DO_RFC1644, rfc1644, CTLFLAG_RW, &tcp_do_rfc1644 , 0, "Enable rfc1644 (TTCP) extensions"); static int tcp_tcbhashsize = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, tcbhashsize, CTLFLAG_RD, &tcp_tcbhashsize, 0, "Size of TCP control-block hashtable"); static int do_tcpdrain = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, do_tcpdrain, CTLFLAG_RW, &do_tcpdrain, 0, "Enable tcp_drain routine for extra help when low on mbufs"); SYSCTL_INT(_net_inet_tcp, OID_AUTO, pcbcount, CTLFLAG_RD, &tcbinfo.ipi_count, 0, "Number of active PCBs"); static int icmp_may_rst = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, icmp_may_rst, CTLFLAG_RW, &icmp_may_rst, 0, "Certain ICMP unreachable messages may abort connections in SYN_SENT"); static int tcp_isn_reseed_interval = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, isn_reseed_interval, CTLFLAG_RW, &tcp_isn_reseed_interval, 0, "Seconds between reseeding of ISN secret"); /* * TCP bandwidth limiting sysctls. Note that the default lower bound of * 1024 exists only for debugging. A good production default would be * something like 6100. */ static int tcp_inflight_enable = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, inflight_enable, CTLFLAG_RW, &tcp_inflight_enable, 0, "Enable automatic TCP inflight data limiting"); static int tcp_inflight_debug = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, inflight_debug, CTLFLAG_RW, &tcp_inflight_debug, 0, "Debug TCP inflight calculations"); static int tcp_inflight_min = 6144; SYSCTL_INT(_net_inet_tcp, OID_AUTO, inflight_min, CTLFLAG_RW, &tcp_inflight_min, 0, "Lower-bound for TCP inflight window"); static int tcp_inflight_max = TCP_MAXWIN << TCP_MAX_WINSHIFT; SYSCTL_INT(_net_inet_tcp, OID_AUTO, inflight_max, CTLFLAG_RW, &tcp_inflight_max, 0, "Upper-bound for TCP inflight window"); static int tcp_inflight_stab = 20; SYSCTL_INT(_net_inet_tcp, OID_AUTO, inflight_stab, CTLFLAG_RW, &tcp_inflight_stab, 0, "Slop in maximal packets / 10 (20 = 2 packets)"); static void tcp_cleartaocache (void); static void tcp_notify (struct inpcb *, int); /* * Target size of TCP PCB hash tables. Must be a power of two. * * Note that this can be overridden by the kernel environment * variable net.inet.tcp.tcbhashsize */ #ifndef TCBHASHSIZE #define TCBHASHSIZE 512 #endif /* * This is the actual shape of what we allocate using the zone * allocator. Doing it this way allows us to protect both structures * using the same generation count, and also eliminates the overhead * of allocating tcpcbs separately. By hiding the structure here, * we avoid changing most of the rest of the code (although it needs * to be changed, eventually, for greater efficiency). */ #define ALIGNMENT 32 #define ALIGNM1 (ALIGNMENT - 1) struct inp_tp { union { struct inpcb inp; char align[(sizeof(struct inpcb) + ALIGNM1) & ~ALIGNM1]; } inp_tp_u; struct tcpcb tcb; struct callout inp_tp_rexmt, inp_tp_persist, inp_tp_keep, inp_tp_2msl; struct callout inp_tp_delack; }; #undef ALIGNMENT #undef ALIGNM1 /* * Tcp initialization */ void tcp_init() { int hashsize = TCBHASHSIZE; tcp_ccgen = 1; tcp_cleartaocache(); tcp_delacktime = TCPTV_DELACK; tcp_keepinit = TCPTV_KEEP_INIT; tcp_keepidle = TCPTV_KEEP_IDLE; tcp_keepintvl = TCPTV_KEEPINTVL; tcp_maxpersistidle = TCPTV_KEEP_IDLE; tcp_msl = TCPTV_MSL; tcp_rexmit_min = TCPTV_MIN; tcp_rexmit_slop = TCPTV_CPU_VAR; LIST_INIT(&tcb); tcbinfo.listhead = &tcb; TUNABLE_INT_FETCH("net.inet.tcp.tcbhashsize", &hashsize); if (!powerof2(hashsize)) { printf("WARNING: TCB hash size not a power of 2\n"); hashsize = 512; /* safe default */ } tcp_tcbhashsize = hashsize; tcbinfo.hashbase = hashinit(hashsize, M_PCB, &tcbinfo.hashmask); tcbinfo.porthashbase = hashinit(hashsize, M_PCB, &tcbinfo.porthashmask); tcbinfo.ipi_zone = zinit("tcpcb", sizeof(struct inp_tp), maxsockets, ZONE_INTERRUPT, 0); #ifdef INET6 #define TCP_MINPROTOHDR (sizeof(struct ip6_hdr) + sizeof(struct tcphdr)) #else /* INET6 */ #define TCP_MINPROTOHDR (sizeof(struct tcpiphdr)) #endif /* INET6 */ if (max_protohdr < TCP_MINPROTOHDR) max_protohdr = TCP_MINPROTOHDR; if (max_linkhdr + TCP_MINPROTOHDR > MHLEN) panic("tcp_init"); #undef TCP_MINPROTOHDR syncache_init(); tcp_thread_init(); } /* * Fill in the IP and TCP headers for an outgoing packet, given the tcpcb. * tcp_template used to store this data in mbufs, but we now recopy it out * of the tcpcb each time to conserve mbufs. */ void tcp_fillheaders(tp, ip_ptr, tcp_ptr) struct tcpcb *tp; void *ip_ptr; void *tcp_ptr; { struct inpcb *inp = tp->t_inpcb; struct tcphdr *tcp_hdr = (struct tcphdr *)tcp_ptr; #ifdef INET6 if ((inp->inp_vflag & INP_IPV6) != 0) { struct ip6_hdr *ip6; ip6 = (struct ip6_hdr *)ip_ptr; ip6->ip6_flow = (ip6->ip6_flow & ~IPV6_FLOWINFO_MASK) | (inp->in6p_flowinfo & IPV6_FLOWINFO_MASK); ip6->ip6_vfc = (ip6->ip6_vfc & ~IPV6_VERSION_MASK) | (IPV6_VERSION & IPV6_VERSION_MASK); ip6->ip6_nxt = IPPROTO_TCP; ip6->ip6_plen = sizeof(struct tcphdr); ip6->ip6_src = inp->in6p_laddr; ip6->ip6_dst = inp->in6p_faddr; tcp_hdr->th_sum = 0; } else #endif { struct ip *ip = (struct ip *) ip_ptr; ip->ip_vhl = IP_VHL_BORING; ip->ip_tos = 0; ip->ip_len = 0; ip->ip_id = 0; ip->ip_off = 0; ip->ip_ttl = 0; ip->ip_sum = 0; ip->ip_p = IPPROTO_TCP; ip->ip_src = inp->inp_laddr; ip->ip_dst = inp->inp_faddr; tcp_hdr->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, htons(sizeof(struct tcphdr) + IPPROTO_TCP)); } tcp_hdr->th_sport = inp->inp_lport; tcp_hdr->th_dport = inp->inp_fport; tcp_hdr->th_seq = 0; tcp_hdr->th_ack = 0; tcp_hdr->th_x2 = 0; tcp_hdr->th_off = 5; tcp_hdr->th_flags = 0; tcp_hdr->th_win = 0; tcp_hdr->th_urp = 0; } /* * Create template to be used to send tcp packets on a connection. * Allocates an mbuf and fills in a skeletal tcp/ip header. The only * use for this function is in keepalives, which use tcp_respond. */ struct tcptemp * tcp_maketemplate(tp) struct tcpcb *tp; { struct mbuf *m; struct tcptemp *n; m = m_get(M_DONTWAIT, MT_HEADER); if (m == NULL) return (0); m->m_len = sizeof(struct tcptemp); n = mtod(m, struct tcptemp *); tcp_fillheaders(tp, (void *)&n->tt_ipgen, (void *)&n->tt_t); return (n); } /* * Send a single message to the TCP at address specified by * the given TCP/IP header. If m == 0, then we make a copy * of the tcpiphdr at ti and send directly to the addressed host. * This is used to force keep alive messages out using the TCP * template for a connection. If flags are given then we send * a message back to the TCP which originated the * segment ti, * and discard the mbuf containing it and any other attached mbufs. * * In any case the ack and sequence number of the transmitted * segment are as specified by the parameters. * * NOTE: If m != NULL, then ti must point to *inside* the mbuf. */ void tcp_respond(tp, ipgen, th, m, ack, seq, flags) struct tcpcb *tp; void *ipgen; struct tcphdr *th; struct mbuf *m; tcp_seq ack, seq; int flags; { int tlen; int win = 0; struct route *ro = 0; struct route sro; struct ip *ip; struct tcphdr *nth; #ifdef INET6 struct route_in6 *ro6 = 0; struct route_in6 sro6; struct ip6_hdr *ip6; int isipv6; #endif /* INET6 */ int ipflags = 0; #ifdef INET6 isipv6 = IP_VHL_V(((struct ip *)ipgen)->ip_vhl) == 6; ip6 = ipgen; #endif /* INET6 */ ip = ipgen; if (tp) { if (!(flags & TH_RST)) { win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); if (win > (long)TCP_MAXWIN << tp->rcv_scale) win = (long)TCP_MAXWIN << tp->rcv_scale; } #ifdef INET6 if (isipv6) ro6 = &tp->t_inpcb->in6p_route; else #endif /* INET6 */ ro = &tp->t_inpcb->inp_route; } else { #ifdef INET6 if (isipv6) { ro6 = &sro6; bzero(ro6, sizeof *ro6); } else #endif /* INET6 */ { ro = &sro; bzero(ro, sizeof *ro); } } if (m == 0) { m = m_gethdr(M_DONTWAIT, MT_HEADER); if (m == NULL) return; tlen = 0; m->m_data += max_linkhdr; #ifdef INET6 if (isipv6) { bcopy((caddr_t)ip6, mtod(m, caddr_t), sizeof(struct ip6_hdr)); ip6 = mtod(m, struct ip6_hdr *); nth = (struct tcphdr *)(ip6 + 1); } else #endif /* INET6 */ { bcopy((caddr_t)ip, mtod(m, caddr_t), sizeof(struct ip)); ip = mtod(m, struct ip *); nth = (struct tcphdr *)(ip + 1); } bcopy((caddr_t)th, (caddr_t)nth, sizeof(struct tcphdr)); flags = TH_ACK; } else { m_freem(m->m_next); m->m_next = 0; m->m_data = (caddr_t)ipgen; /* m_len is set later */ tlen = 0; #define xchg(a,b,type) { type t; t=a; a=b; b=t; } #ifdef INET6 if (isipv6) { xchg(ip6->ip6_dst, ip6->ip6_src, struct in6_addr); nth = (struct tcphdr *)(ip6 + 1); } else #endif /* INET6 */ { xchg(ip->ip_dst.s_addr, ip->ip_src.s_addr, n_long); nth = (struct tcphdr *)(ip + 1); } if (th != nth) { /* * this is usually a case when an extension header * exists between the IPv6 header and the * TCP header. */ nth->th_sport = th->th_sport; nth->th_dport = th->th_dport; } xchg(nth->th_dport, nth->th_sport, n_short); #undef xchg } #ifdef INET6 if (isipv6) { ip6->ip6_flow = 0; ip6->ip6_vfc = IPV6_VERSION; ip6->ip6_nxt = IPPROTO_TCP; ip6->ip6_plen = htons((u_short)(sizeof (struct tcphdr) + tlen)); tlen += sizeof (struct ip6_hdr) + sizeof (struct tcphdr); } else #endif { tlen += sizeof (struct tcpiphdr); ip->ip_len = tlen; ip->ip_ttl = ip_defttl; } m->m_len = tlen; m->m_pkthdr.len = tlen; m->m_pkthdr.rcvif = (struct ifnet *) 0; nth->th_seq = htonl(seq); nth->th_ack = htonl(ack); nth->th_x2 = 0; nth->th_off = sizeof (struct tcphdr) >> 2; nth->th_flags = flags; if (tp) nth->th_win = htons((u_short) (win >> tp->rcv_scale)); else nth->th_win = htons((u_short)win); nth->th_urp = 0; #ifdef INET6 if (isipv6) { nth->th_sum = 0; nth->th_sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), tlen - sizeof(struct ip6_hdr)); ip6->ip6_hlim = in6_selecthlim(tp ? tp->t_inpcb : NULL, ro6 && ro6->ro_rt ? ro6->ro_rt->rt_ifp : NULL); } else #endif /* INET6 */ { nth->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, htons((u_short)(tlen - sizeof(struct ip) + ip->ip_p))); m->m_pkthdr.csum_flags = CSUM_TCP; m->m_pkthdr.csum_data = offsetof(struct tcphdr, th_sum); } #ifdef TCPDEBUG if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) tcp_trace(TA_OUTPUT, 0, tp, mtod(m, void *), th, 0); #endif #ifdef INET6 if (isipv6) { (void)ip6_output(m, NULL, ro6, ipflags, NULL, NULL, tp ? tp->t_inpcb : NULL); if (ro6 == &sro6 && ro6->ro_rt) { RTFREE(ro6->ro_rt); ro6->ro_rt = NULL; } } else #endif /* INET6 */ { (void) ip_output(m, NULL, ro, ipflags, NULL, tp ? tp->t_inpcb : NULL); if (ro == &sro && ro->ro_rt) { RTFREE(ro->ro_rt); ro->ro_rt = NULL; } } } /* * Create a new TCP control block, making an * empty reassembly queue and hooking it to the argument * protocol control block. The `inp' parameter must have * come from the zone allocator set up in tcp_init(). */ struct tcpcb * tcp_newtcpcb(inp) struct inpcb *inp; { struct inp_tp *it; struct tcpcb *tp; #ifdef INET6 int isipv6 = (inp->inp_vflag & INP_IPV6) != 0; #endif /* INET6 */ it = (struct inp_tp *)inp; tp = &it->tcb; bzero((char *) tp, sizeof(struct tcpcb)); LIST_INIT(&tp->t_segq); tp->t_maxseg = tp->t_maxopd = #ifdef INET6 isipv6 ? tcp_v6mssdflt : #endif /* INET6 */ tcp_mssdflt; /* Set up our timeouts. */ callout_init(tp->tt_rexmt = &it->inp_tp_rexmt); callout_init(tp->tt_persist = &it->inp_tp_persist); callout_init(tp->tt_keep = &it->inp_tp_keep); callout_init(tp->tt_2msl = &it->inp_tp_2msl); callout_init(tp->tt_delack = &it->inp_tp_delack); if (tcp_do_rfc1323) tp->t_flags = (TF_REQ_SCALE|TF_REQ_TSTMP); if (tcp_do_rfc1644) tp->t_flags |= TF_REQ_CC; tp->t_inpcb = inp; /* XXX */ /* * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no * rtt estimate. Set rttvar so that srtt + 4 * rttvar gives * reasonable initial retransmit time. */ tp->t_srtt = TCPTV_SRTTBASE; tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4; tp->t_rttmin = tcp_rexmit_min; tp->t_rxtcur = TCPTV_RTOBASE; tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT; tp->snd_bwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT; tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT; tp->t_rcvtime = ticks; tp->t_bw_rtttime = ticks; /* * IPv4 TTL initialization is necessary for an IPv6 socket as well, * because the socket may be bound to an IPv6 wildcard address, * which may match an IPv4-mapped IPv6 address. */ inp->inp_ip_ttl = ip_defttl; inp->inp_ppcb = (caddr_t)tp; return (tp); /* XXX */ } /* * Drop a TCP connection, reporting * the specified error. If connection is synchronized, * then send a RST to peer. */ struct tcpcb * tcp_drop(tp, errno) struct tcpcb *tp; int errno; { struct socket *so = tp->t_inpcb->inp_socket; if (TCPS_HAVERCVDSYN(tp->t_state)) { tp->t_state = TCPS_CLOSED; (void) tcp_output(tp); tcpstat.tcps_drops++; } else tcpstat.tcps_conndrops++; if (errno == ETIMEDOUT && tp->t_softerror) errno = tp->t_softerror; so->so_error = errno; return (tcp_close(tp)); } /* * Close a TCP control block: * discard all space held by the tcp * discard internet protocol block * wake up any sleepers */ struct tcpcb * tcp_close(tp) struct tcpcb *tp; { struct tseg_qent *q; struct inpcb *inp = tp->t_inpcb; struct socket *so = inp->inp_socket; #ifdef INET6 int isipv6 = (inp->inp_vflag & INP_IPV6) != 0; #endif /* INET6 */ struct rtentry *rt; int dosavessthresh; /* * Make sure that all of our timers are stopped before we * delete the PCB. */ callout_stop(tp->tt_rexmt); callout_stop(tp->tt_persist); callout_stop(tp->tt_keep); callout_stop(tp->tt_2msl); callout_stop(tp->tt_delack); /* * If we got enough samples through the srtt filter, * save the rtt and rttvar in the routing entry. * 'Enough' is arbitrarily defined as the 16 samples. * 16 samples is enough for the srtt filter to converge * to within 5% of the correct value; fewer samples and * we could save a very bogus rtt. * * Don't update the default route's characteristics and don't * update anything that the user "locked". */ if (tp->t_rttupdated >= 16) { u_long i = 0; #ifdef INET6 if (isipv6) { struct sockaddr_in6 *sin6; if ((rt = inp->in6p_route.ro_rt) == NULL) goto no_valid_rt; sin6 = (struct sockaddr_in6 *)rt_key(rt); if (IN6_IS_ADDR_UNSPECIFIED(&sin6->sin6_addr)) goto no_valid_rt; } else #endif /* INET6 */ if ((rt = inp->inp_route.ro_rt) == NULL || ((struct sockaddr_in *)rt_key(rt))->sin_addr.s_addr == INADDR_ANY) goto no_valid_rt; if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) { i = tp->t_srtt * (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); if (rt->rt_rmx.rmx_rtt && i) /* * filter this update to half the old & half * the new values, converting scale. * See route.h and tcp_var.h for a * description of the scaling constants. */ rt->rt_rmx.rmx_rtt = (rt->rt_rmx.rmx_rtt + i) / 2; else rt->rt_rmx.rmx_rtt = i; tcpstat.tcps_cachedrtt++; } if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) { i = tp->t_rttvar * (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); if (rt->rt_rmx.rmx_rttvar && i) rt->rt_rmx.rmx_rttvar = (rt->rt_rmx.rmx_rttvar + i) / 2; else rt->rt_rmx.rmx_rttvar = i; tcpstat.tcps_cachedrttvar++; } /* * The old comment here said: * update the pipelimit (ssthresh) if it has been updated * already or if a pipesize was specified & the threshhold * got below half the pipesize. I.e., wait for bad news * before we start updating, then update on both good * and bad news. * * But we want to save the ssthresh even if no pipesize is * specified explicitly in the route, because such * connections still have an implicit pipesize specified * by the global tcp_sendspace. In the absence of a reliable * way to calculate the pipesize, it will have to do. */ i = tp->snd_ssthresh; if (rt->rt_rmx.rmx_sendpipe != 0) dosavessthresh = (i < rt->rt_rmx.rmx_sendpipe / 2); else dosavessthresh = (i < so->so_snd.sb_hiwat / 2); if (((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 && i != 0 && rt->rt_rmx.rmx_ssthresh != 0) || dosavessthresh) { /* * convert the limit from user data bytes to * packets then to packet data bytes. */ i = (i + tp->t_maxseg / 2) / tp->t_maxseg; if (i < 2) i = 2; i *= (u_long)(tp->t_maxseg + #ifdef INET6 (isipv6 ? sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : #endif sizeof (struct tcpiphdr) #ifdef INET6 ) #endif ); if (rt->rt_rmx.rmx_ssthresh) rt->rt_rmx.rmx_ssthresh = (rt->rt_rmx.rmx_ssthresh + i) / 2; else rt->rt_rmx.rmx_ssthresh = i; tcpstat.tcps_cachedssthresh++; } } no_valid_rt: /* free the reassembly queue, if any */ while((q = LIST_FIRST(&tp->t_segq)) != NULL) { LIST_REMOVE(q, tqe_q); m_freem(q->tqe_m); FREE(q, M_TSEGQ); } inp->inp_ppcb = NULL; soisdisconnected(so); #ifdef INET6 if (INP_CHECK_SOCKAF(so, AF_INET6)) in6_pcbdetach(inp); else #endif /* INET6 */ in_pcbdetach(inp); tcpstat.tcps_closed++; return ((struct tcpcb *)0); } void tcp_drain() { if (do_tcpdrain) { struct inpcb *inpb; struct tcpcb *tcpb; struct tseg_qent *te; /* * Walk the tcpbs, if existing, and flush the reassembly queue, * if there is one... * XXX: The "Net/3" implementation doesn't imply that the TCP * reassembly queue should be flushed, but in a situation * where we're really low on mbufs, this is potentially * usefull. */ LIST_FOREACH(inpb, tcbinfo.listhead, inp_list) { if ((tcpb = intotcpcb(inpb))) { while ((te = LIST_FIRST(&tcpb->t_segq)) != NULL) { LIST_REMOVE(te, tqe_q); m_freem(te->tqe_m); FREE(te, M_TSEGQ); } } } } } /* * Notify a tcp user of an asynchronous error; * store error as soft error, but wake up user * (for now, won't do anything until can select for soft error). * * Do not wake up user since there currently is no mechanism for * reporting soft errors (yet - a kqueue filter may be added). */ static void tcp_notify(inp, error) struct inpcb *inp; int error; { struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb; /* * Ignore some errors if we are hooked up. * If connection hasn't completed, has retransmitted several times, * and receives a second error, give up now. This is better * than waiting a long time to establish a connection that * can never complete. */ if (tp->t_state == TCPS_ESTABLISHED && (error == EHOSTUNREACH || error == ENETUNREACH || error == EHOSTDOWN)) { return; } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 && tp->t_softerror) tcp_drop(tp, error); else tp->t_softerror = error; #if 0 wakeup((caddr_t) &so->so_timeo); sorwakeup(so); sowwakeup(so); #endif } static int tcp_pcblist(SYSCTL_HANDLER_ARGS) { int error, i, n, s; struct inpcb *inp, **inp_list; inp_gen_t gencnt; struct xinpgen xig; /* * The process of preparing the TCB list is too time-consuming and * resource-intensive to repeat twice on every request. */ if (req->oldptr == 0) { n = tcbinfo.ipi_count; req->oldidx = 2 * (sizeof xig) + (n + n/8) * sizeof(struct xtcpcb); return 0; } if (req->newptr != 0) return EPERM; /* * OK, now we're committed to doing something. */ s = splnet(); gencnt = tcbinfo.ipi_gencnt; n = tcbinfo.ipi_count; splx(s); xig.xig_len = sizeof xig; xig.xig_count = n; xig.xig_gen = gencnt; xig.xig_sogen = so_gencnt; error = SYSCTL_OUT(req, &xig, sizeof xig); if (error) return error; inp_list = malloc(n * sizeof *inp_list, M_TEMP, M_WAITOK); if (inp_list == 0) return ENOMEM; s = splnet(); for (inp = LIST_FIRST(tcbinfo.listhead), i = 0; inp && i < n; inp = LIST_NEXT(inp, inp_list)) { if (inp->inp_gencnt <= gencnt && !prison_xinpcb(req->td, inp)) inp_list[i++] = inp; } splx(s); n = i; error = 0; for (i = 0; i < n; i++) { inp = inp_list[i]; if (inp->inp_gencnt <= gencnt) { struct xtcpcb xt; caddr_t inp_ppcb; xt.xt_len = sizeof xt; /* XXX should avoid extra copy */ bcopy(inp, &xt.xt_inp, sizeof *inp); inp_ppcb = inp->inp_ppcb; if (inp_ppcb != NULL) bcopy(inp_ppcb, &xt.xt_tp, sizeof xt.xt_tp); else bzero((char *) &xt.xt_tp, sizeof xt.xt_tp); if (inp->inp_socket) sotoxsocket(inp->inp_socket, &xt.xt_socket); error = SYSCTL_OUT(req, &xt, sizeof xt); } } if (!error) { /* * Give the user an updated idea of our state. * If the generation differs from what we told * her before, she knows that something happened * while we were processing this request, and it * might be necessary to retry. */ s = splnet(); xig.xig_gen = tcbinfo.ipi_gencnt; xig.xig_sogen = so_gencnt; xig.xig_count = tcbinfo.ipi_count; splx(s); error = SYSCTL_OUT(req, &xig, sizeof xig); } free(inp_list, M_TEMP); return error; } SYSCTL_PROC(_net_inet_tcp, TCPCTL_PCBLIST, pcblist, CTLFLAG_RD, 0, 0, tcp_pcblist, "S,xtcpcb", "List of active TCP connections"); static int tcp_getcred(SYSCTL_HANDLER_ARGS) { struct sockaddr_in addrs[2]; struct inpcb *inp; int error, s; error = suser(req->td); if (error) return (error); error = SYSCTL_IN(req, addrs, sizeof(addrs)); if (error) return (error); s = splnet(); inp = in_pcblookup_hash(&tcbinfo, addrs[1].sin_addr, addrs[1].sin_port, addrs[0].sin_addr, addrs[0].sin_port, 0, NULL); if (inp == NULL || inp->inp_socket == NULL) { error = ENOENT; goto out; } error = SYSCTL_OUT(req, inp->inp_socket->so_cred, sizeof(struct ucred)); out: splx(s); return (error); } SYSCTL_PROC(_net_inet_tcp, OID_AUTO, getcred, CTLTYPE_OPAQUE|CTLFLAG_RW, 0, 0, tcp_getcred, "S,ucred", "Get the ucred of a TCP connection"); #ifdef INET6 static int tcp6_getcred(SYSCTL_HANDLER_ARGS) { struct sockaddr_in6 addrs[2]; struct inpcb *inp; int error, s, mapped = 0; error = suser(req->td); if (error) return (error); error = SYSCTL_IN(req, addrs, sizeof(addrs)); if (error) return (error); if (IN6_IS_ADDR_V4MAPPED(&addrs[0].sin6_addr)) { if (IN6_IS_ADDR_V4MAPPED(&addrs[1].sin6_addr)) mapped = 1; else return (EINVAL); } s = splnet(); if (mapped == 1) inp = in_pcblookup_hash(&tcbinfo, *(struct in_addr *)&addrs[1].sin6_addr.s6_addr[12], addrs[1].sin6_port, *(struct in_addr *)&addrs[0].sin6_addr.s6_addr[12], addrs[0].sin6_port, 0, NULL); else inp = in6_pcblookup_hash(&tcbinfo, &addrs[1].sin6_addr, addrs[1].sin6_port, &addrs[0].sin6_addr, addrs[0].sin6_port, 0, NULL); if (inp == NULL || inp->inp_socket == NULL) { error = ENOENT; goto out; } error = SYSCTL_OUT(req, inp->inp_socket->so_cred, sizeof(struct ucred)); out: splx(s); return (error); } SYSCTL_PROC(_net_inet6_tcp6, OID_AUTO, getcred, CTLTYPE_OPAQUE|CTLFLAG_RW, 0, 0, tcp6_getcred, "S,ucred", "Get the ucred of a TCP6 connection"); #endif void tcp_ctlinput(cmd, sa, vip) int cmd; struct sockaddr *sa; void *vip; { struct ip *ip = vip; struct tcphdr *th; struct in_addr faddr; struct inpcb *inp; struct tcpcb *tp; void (*notify) (struct inpcb *, int) = tcp_notify; tcp_seq icmp_seq; int s; faddr = ((struct sockaddr_in *)sa)->sin_addr; if (sa->sa_family != AF_INET || faddr.s_addr == INADDR_ANY) return; if (cmd == PRC_QUENCH) notify = tcp_quench; else if (icmp_may_rst && (cmd == PRC_UNREACH_ADMIN_PROHIB || cmd == PRC_UNREACH_PORT || cmd == PRC_TIMXCEED_INTRANS) && ip) notify = tcp_drop_syn_sent; else if (cmd == PRC_MSGSIZE) notify = tcp_mtudisc; else if (PRC_IS_REDIRECT(cmd)) { ip = 0; notify = in_rtchange; } else if (cmd == PRC_HOSTDEAD) ip = 0; else if ((unsigned)cmd > PRC_NCMDS || inetctlerrmap[cmd] == 0) return; if (ip) { s = splnet(); th = (struct tcphdr *)((caddr_t)ip + (IP_VHL_HL(ip->ip_vhl) << 2)); inp = in_pcblookup_hash(&tcbinfo, faddr, th->th_dport, ip->ip_src, th->th_sport, 0, NULL); if (inp != NULL && inp->inp_socket != NULL) { icmp_seq = htonl(th->th_seq); tp = intotcpcb(inp); if (SEQ_GEQ(icmp_seq, tp->snd_una) && SEQ_LT(icmp_seq, tp->snd_max)) (*notify)(inp, inetctlerrmap[cmd]); } else { struct in_conninfo inc; inc.inc_fport = th->th_dport; inc.inc_lport = th->th_sport; inc.inc_faddr = faddr; inc.inc_laddr = ip->ip_src; #ifdef INET6 inc.inc_isipv6 = 0; #endif syncache_unreach(&inc, th); } splx(s); } else in_pcbnotifyall(&tcb, faddr, inetctlerrmap[cmd], notify); } #ifdef INET6 void tcp6_ctlinput(cmd, sa, d) int cmd; struct sockaddr *sa; void *d; { struct tcphdr th; void (*notify) (struct inpcb *, int) = tcp_notify; struct ip6_hdr *ip6; struct mbuf *m; struct ip6ctlparam *ip6cp = NULL; const struct sockaddr_in6 *sa6_src = NULL; int off; struct tcp_portonly { u_int16_t th_sport; u_int16_t th_dport; } *thp; if (sa->sa_family != AF_INET6 || sa->sa_len != sizeof(struct sockaddr_in6)) return; if (cmd == PRC_QUENCH) notify = tcp_quench; else if (cmd == PRC_MSGSIZE) notify = tcp_mtudisc; else if (!PRC_IS_REDIRECT(cmd) && ((unsigned)cmd > PRC_NCMDS || inet6ctlerrmap[cmd] == 0)) return; /* if the parameter is from icmp6, decode it. */ if (d != NULL) { ip6cp = (struct ip6ctlparam *)d; m = ip6cp->ip6c_m; ip6 = ip6cp->ip6c_ip6; off = ip6cp->ip6c_off; sa6_src = ip6cp->ip6c_src; } else { m = NULL; ip6 = NULL; off = 0; /* fool gcc */ sa6_src = &sa6_any; } if (ip6) { struct in_conninfo inc; /* * XXX: We assume that when IPV6 is non NULL, * M and OFF are valid. */ /* check if we can safely examine src and dst ports */ if (m->m_pkthdr.len < off + sizeof(*thp)) return; bzero(&th, sizeof(th)); m_copydata(m, off, sizeof(*thp), (caddr_t)&th); in6_pcbnotify(&tcb, sa, th.th_dport, (struct sockaddr *)ip6cp->ip6c_src, th.th_sport, cmd, notify); inc.inc_fport = th.th_dport; inc.inc_lport = th.th_sport; inc.inc6_faddr = ((struct sockaddr_in6 *)sa)->sin6_addr; inc.inc6_laddr = ip6cp->ip6c_src->sin6_addr; inc.inc_isipv6 = 1; syncache_unreach(&inc, &th); } else in6_pcbnotify(&tcb, sa, 0, (const struct sockaddr *)sa6_src, 0, cmd, notify); } #endif /* INET6 */ /* * Following is where TCP initial sequence number generation occurs. * * There are two places where we must use initial sequence numbers: * 1. In SYN-ACK packets. * 2. In SYN packets. * * All ISNs for SYN-ACK packets are generated by the syncache. See * tcp_syncache.c for details. * * The ISNs in SYN packets must be monotonic; TIME_WAIT recycling * depends on this property. In addition, these ISNs should be * unguessable so as to prevent connection hijacking. To satisfy * the requirements of this situation, the algorithm outlined in * RFC 1948 is used to generate sequence numbers. * * Implementation details: * * Time is based off the system timer, and is corrected so that it * increases by one megabyte per second. This allows for proper * recycling on high speed LANs while still leaving over an hour * before rollover. * * net.inet.tcp.isn_reseed_interval controls the number of seconds * between seeding of isn_secret. This is normally set to zero, * as reseeding should not be necessary. * */ #define ISN_BYTES_PER_SECOND 1048576 u_char isn_secret[32]; int isn_last_reseed; MD5_CTX isn_ctx; tcp_seq tcp_new_isn(tp) struct tcpcb *tp; { u_int32_t md5_buffer[4]; tcp_seq new_isn; /* Seed if this is the first use, reseed if requested. */ if ((isn_last_reseed == 0) || ((tcp_isn_reseed_interval > 0) && (((u_int)isn_last_reseed + (u_int)tcp_isn_reseed_interval*hz) < (u_int)ticks))) { read_random_unlimited(&isn_secret, sizeof(isn_secret)); isn_last_reseed = ticks; } /* Compute the md5 hash and return the ISN. */ MD5Init(&isn_ctx); MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_fport, sizeof(u_short)); MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_lport, sizeof(u_short)); #ifdef INET6 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) { MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_faddr, sizeof(struct in6_addr)); MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->in6p_laddr, sizeof(struct in6_addr)); } else #endif { MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_faddr, sizeof(struct in_addr)); MD5Update(&isn_ctx, (u_char *) &tp->t_inpcb->inp_laddr, sizeof(struct in_addr)); } MD5Update(&isn_ctx, (u_char *) &isn_secret, sizeof(isn_secret)); MD5Final((u_char *) &md5_buffer, &isn_ctx); new_isn = (tcp_seq) md5_buffer[0]; new_isn += ticks * (ISN_BYTES_PER_SECOND / hz); return new_isn; } /* * When a source quench is received, close congestion window * to one segment. We will gradually open it again as we proceed. */ void tcp_quench(inp, errno) struct inpcb *inp; int errno; { struct tcpcb *tp = intotcpcb(inp); if (tp) tp->snd_cwnd = tp->t_maxseg; } /* * When a specific ICMP unreachable message is received and the * connection state is SYN-SENT, drop the connection. This behavior * is controlled by the icmp_may_rst sysctl. */ void tcp_drop_syn_sent(inp, errno) struct inpcb *inp; int errno; { struct tcpcb *tp = intotcpcb(inp); if (tp && tp->t_state == TCPS_SYN_SENT) tcp_drop(tp, errno); } /* * When `need fragmentation' ICMP is received, update our idea of the MSS * based on the new value in the route. Also nudge TCP to send something, * since we know the packet we just sent was dropped. * This duplicates some code in the tcp_mss() function in tcp_input.c. */ void tcp_mtudisc(inp, errno) struct inpcb *inp; int errno; { struct tcpcb *tp = intotcpcb(inp); struct rtentry *rt; struct rmxp_tao *taop; struct socket *so = inp->inp_socket; int offered; int mss; #ifdef INET6 int isipv6 = (tp->t_inpcb->inp_vflag & INP_IPV6) != 0; #endif /* INET6 */ if (tp) { #ifdef INET6 if (isipv6) rt = tcp_rtlookup6(&inp->inp_inc); else #endif /* INET6 */ rt = tcp_rtlookup(&inp->inp_inc); if (!rt || !rt->rt_rmx.rmx_mtu) { tp->t_maxopd = tp->t_maxseg = #ifdef INET6 isipv6 ? tcp_v6mssdflt : #endif /* INET6 */ tcp_mssdflt; return; } taop = rmx_taop(rt->rt_rmx); offered = taop->tao_mssopt; mss = rt->rt_rmx.rmx_mtu - #ifdef INET6 (isipv6 ? sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : #endif /* INET6 */ sizeof(struct tcpiphdr) #ifdef INET6 ) #endif /* INET6 */ ; if (offered) mss = min(mss, offered); /* * XXX - The above conditional probably violates the TCP * spec. The problem is that, since we don't know the * other end's MSS, we are supposed to use a conservative * default. But, if we do that, then MTU discovery will * never actually take place, because the conservative * default is much less than the MTUs typically seen * on the Internet today. For the moment, we'll sweep * this under the carpet. * * The conservative default might not actually be a problem * if the only case this occurs is when sending an initial * SYN with options and data to a host we've never talked * to before. Then, they will reply with an MSS value which * will get recorded and the new parameters should get * recomputed. For Further Study. */ if (tp->t_maxopd <= mss) return; tp->t_maxopd = mss; if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP) mss -= TCPOLEN_TSTAMP_APPA; if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC && (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC) mss -= TCPOLEN_CC_APPA; #if (MCLBYTES & (MCLBYTES - 1)) == 0 if (mss > MCLBYTES) mss &= ~(MCLBYTES-1); #else if (mss > MCLBYTES) mss = mss / MCLBYTES * MCLBYTES; #endif if (so->so_snd.sb_hiwat < mss) mss = so->so_snd.sb_hiwat; tp->t_maxseg = mss; tcpstat.tcps_mturesent++; tp->t_rtttime = 0; tp->snd_nxt = tp->snd_una; tcp_output(tp); } } /* * Look-up the routing entry to the peer of this inpcb. If no route * is found and it cannot be allocated the return NULL. This routine * is called by TCP routines that access the rmx structure and by tcp_mss * to get the interface MTU. */ struct rtentry * tcp_rtlookup(inc) struct in_conninfo *inc; { struct route *ro; struct rtentry *rt; ro = &inc->inc_route; rt = ro->ro_rt; if (rt == NULL || !(rt->rt_flags & RTF_UP)) { /* No route yet, so try to acquire one */ if (inc->inc_faddr.s_addr != INADDR_ANY) { ro->ro_dst.sa_family = AF_INET; ro->ro_dst.sa_len = sizeof(struct sockaddr_in); ((struct sockaddr_in *) &ro->ro_dst)->sin_addr = inc->inc_faddr; rtalloc(ro); rt = ro->ro_rt; } } return rt; } #ifdef INET6 struct rtentry * tcp_rtlookup6(inc) struct in_conninfo *inc; { struct route_in6 *ro6; struct rtentry *rt; ro6 = &inc->inc6_route; rt = ro6->ro_rt; if (rt == NULL || !(rt->rt_flags & RTF_UP)) { /* No route yet, so try to acquire one */ if (!IN6_IS_ADDR_UNSPECIFIED(&inc->inc6_faddr)) { ro6->ro_dst.sin6_family = AF_INET6; ro6->ro_dst.sin6_len = sizeof(struct sockaddr_in6); ro6->ro_dst.sin6_addr = inc->inc6_faddr; rtalloc((struct route *)ro6); rt = ro6->ro_rt; } } return rt; } #endif /* INET6 */ #ifdef IPSEC /* compute ESP/AH header size for TCP, including outer IP header. */ size_t ipsec_hdrsiz_tcp(tp) struct tcpcb *tp; { struct inpcb *inp; struct mbuf *m; size_t hdrsiz; struct ip *ip; #ifdef INET6 struct ip6_hdr *ip6; #endif /* INET6 */ struct tcphdr *th; if ((tp == NULL) || ((inp = tp->t_inpcb) == NULL)) return 0; MGETHDR(m, M_DONTWAIT, MT_DATA); if (!m) return 0; #ifdef INET6 if ((inp->inp_vflag & INP_IPV6) != 0) { ip6 = mtod(m, struct ip6_hdr *); th = (struct tcphdr *)(ip6 + 1); m->m_pkthdr.len = m->m_len = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); tcp_fillheaders(tp, ip6, th); hdrsiz = ipsec6_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp); } else #endif /* INET6 */ { ip = mtod(m, struct ip *); th = (struct tcphdr *)(ip + 1); m->m_pkthdr.len = m->m_len = sizeof(struct tcpiphdr); tcp_fillheaders(tp, ip, th); hdrsiz = ipsec4_hdrsiz(m, IPSEC_DIR_OUTBOUND, inp); } m_free(m); return hdrsiz; } #endif /*IPSEC*/ /* * Return a pointer to the cached information about the remote host. * The cached information is stored in the protocol specific part of * the route metrics. */ struct rmxp_tao * tcp_gettaocache(inc) struct in_conninfo *inc; { struct rtentry *rt; #ifdef INET6 if (inc->inc_isipv6) rt = tcp_rtlookup6(inc); else #endif /* INET6 */ rt = tcp_rtlookup(inc); /* Make sure this is a host route and is up. */ if (rt == NULL || (rt->rt_flags & (RTF_UP|RTF_HOST)) != (RTF_UP|RTF_HOST)) return NULL; return rmx_taop(rt->rt_rmx); } /* * Clear all the TAO cache entries, called from tcp_init. * * XXX * This routine is just an empty one, because we assume that the routing * routing tables are initialized at the same time when TCP, so there is * nothing in the cache left over. */ static void tcp_cleartaocache() { } /* * TCP BANDWIDTH DELAY PRODUCT WINDOW LIMITING * * This code attempts to calculate the bandwidth-delay product as a * means of determining the optimal window size to maximize bandwidth, * minimize RTT, and avoid the over-allocation of buffers on interfaces and * routers. This code also does a fairly good job keeping RTTs in check * across slow links like modems. We implement an algorithm which is very * similar (but not meant to be) TCP/Vegas. The code operates on the * transmitter side of a TCP connection and so only effects the transmit * side of the connection. * * BACKGROUND: TCP makes no provision for the management of buffer space * at the end points or at the intermediate routers and switches. A TCP * stream, whether using NewReno or not, will eventually buffer as * many packets as it is able and the only reason this typically works is * due to the fairly small default buffers made available for a connection * (typicaly 16K or 32K). As machines use larger windows and/or window * scaling it is now fairly easy for even a single TCP connection to blow-out * all available buffer space not only on the local interface, but on * intermediate routers and switches as well. NewReno makes a misguided * attempt to 'solve' this problem by waiting for an actual failure to occur, * then backing off, then steadily increasing the window again until another * failure occurs, ad-infinitum. This results in terrible oscillation that * is only made worse as network loads increase and the idea of intentionally * blowing out network buffers is, frankly, a terrible way to manage network * resources. * * It is far better to limit the transmit window prior to the failure * condition being achieved. There are two general ways to do this: First * you can 'scan' through different transmit window sizes and locate the * point where the RTT stops increasing, indicating that you have filled the * pipe, then scan backwards until you note that RTT stops decreasing, then * repeat ad-infinitum. This method works in principle but has severe * implementation issues due to RTT variances, timer granularity, and * instability in the algorithm which can lead to many false positives and * create oscillations as well as interact badly with other TCP streams * implementing the same algorithm. * * The second method is to limit the window to the bandwidth delay product * of the link. This is the method we implement. RTT variances and our * own manipulation of the congestion window, bwnd, can potentially * destabilize the algorithm. For this reason we have to stabilize the * elements used to calculate the window. We do this by using the minimum * observed RTT, the long term average of the observed bandwidth, and * by adding two segments worth of slop. It isn't perfect but it is able * to react to changing conditions and gives us a very stable basis on * which to extend the algorithm. */ void tcp_xmit_bandwidth_limit(struct tcpcb *tp, tcp_seq ack_seq) { u_long bw; u_long bwnd; int save_ticks; /* * If inflight_enable is disabled in the middle of a tcp connection, * make sure snd_bwnd is effectively disabled. */ if (tcp_inflight_enable == 0) { tp->snd_bwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT; tp->snd_bandwidth = 0; return; } /* * Figure out the bandwidth. Due to the tick granularity this * is a very rough number and it MUST be averaged over a fairly * long period of time. XXX we need to take into account a link * that is not using all available bandwidth, but for now our * slop will ramp us up if this case occurs and the bandwidth later * increases. * * Note: if ticks rollover 'bw' may wind up negative. We must * effectively reset t_bw_rtttime for this case. */ save_ticks = ticks; if ((u_int)(save_ticks - tp->t_bw_rtttime) < 1) return; bw = (int64_t)(ack_seq - tp->t_bw_rtseq) * hz / (save_ticks - tp->t_bw_rtttime); tp->t_bw_rtttime = save_ticks; tp->t_bw_rtseq = ack_seq; if (tp->t_bw_rtttime == 0 || (int)bw < 0) return; bw = ((int64_t)tp->snd_bandwidth * 15 + bw) >> 4; tp->snd_bandwidth = bw; /* * Calculate the semi-static bandwidth delay product, plus two maximal * segments. The additional slop puts us squarely in the sweet * spot and also handles the bandwidth run-up case. Without the * slop we could be locking ourselves into a lower bandwidth. * * Situations Handled: * (1) Prevents over-queueing of packets on LANs, especially on * high speed LANs, allowing larger TCP buffers to be * specified, and also does a good job preventing * over-queueing of packets over choke points like modems * (at least for the transmit side). * * (2) Is able to handle changing network loads (bandwidth * drops so bwnd drops, bandwidth increases so bwnd * increases). * * (3) Theoretically should stabilize in the face of multiple * connections implementing the same algorithm (this may need * a little work). * * (4) Stability value (defaults to 20 = 2 maximal packets) can * be adjusted with a sysctl but typically only needs to be on * very slow connections. A value no smaller then 5 should * be used, but only reduce this default if you have no other * choice. */ #define USERTT ((tp->t_srtt + tp->t_rttbest) / 2) bwnd = (int64_t)bw * USERTT / (hz << TCP_RTT_SHIFT) + tcp_inflight_stab * (int)tp->t_maxseg / 10; #undef USERTT if (tcp_inflight_debug > 0) { static int ltime; if ((u_int)(ticks - ltime) >= hz / tcp_inflight_debug) { ltime = ticks; printf("%p bw %ld rttbest %d srtt %d bwnd %ld\n", tp, bw, tp->t_rttbest, tp->t_srtt, bwnd ); } } if ((long)bwnd < tcp_inflight_min) bwnd = tcp_inflight_min; if (bwnd > tcp_inflight_max) bwnd = tcp_inflight_max; if ((long)bwnd < tp->t_maxseg * 2) bwnd = tp->t_maxseg * 2; tp->snd_bwnd = bwnd; }