/* * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 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_input.c 8.12 (Berkeley) 5/24/95 * $FreeBSD$ */ #include "opt_ipfw.h" /* for ipfw_fwd */ #include "opt_inet6.h" #include "opt_ipsec.h" #include "opt_tcpdebug.h" #include "opt_tcp_input.h" #include #include #include #include #include #include #include /* for proc0 declaration */ #include #include #include #include #include /* before tcp_seq.h, for tcp_random18() */ #include #include #include #include #include #include /* for ICMP_BANDLIM */ #ifdef INET6 #include #include #include #include #endif #include #ifdef INET6 #include #endif #include #ifdef INET6 #include #endif #include /* for ICMP_BANDLIM */ #include #include #include #include #include #ifdef INET6 #include #endif #include #ifdef TCPDEBUG #include u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ struct tcphdr tcp_savetcp; #endif /* TCPDEBUG */ #ifdef IPSEC #include #ifdef INET6 #include #endif #include #endif /*IPSEC*/ #include MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); static int tcprexmtthresh = 3; tcp_seq tcp_iss; tcp_cc tcp_ccgen; struct tcpstat tcpstat; SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RD, &tcpstat , tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); static int log_in_vain = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, &log_in_vain, 0, "Log all incoming TCP connections"); static int blackhole = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, &blackhole, 0, "Do not send RST when dropping refused connections"); int tcp_delack_enabled = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, &tcp_delack_enabled, 0, "Delay ACK to try and piggyback it onto a data packet"); #ifdef TCP_DROP_SYNFIN static int drop_synfin = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); #endif #ifdef TCP_RESTRICT_RST static int restrict_rst = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, restrict_rst, CTLFLAG_RW, &restrict_rst, 0, "Restrict RST emission"); #endif struct inpcbhead tcb; #define tcb6 tcb /* for KAME src sync over BSD*'s */ struct inpcbinfo tcbinfo; static void tcp_dooptions __P((struct tcpcb *, u_char *, int, struct tcphdr *, struct tcpopt *)); static void tcp_pulloutofband __P((struct socket *, struct tcphdr *, struct mbuf *, int)); static int tcp_reass __P((struct tcpcb *, struct tcphdr *, int *, struct mbuf *)); static void tcp_xmit_timer __P((struct tcpcb *, int)); /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ #ifdef INET6 #define ND6_HINT(tp) \ do { \ if ((tp) && (tp)->t_inpcb && \ ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0 && \ (tp)->t_inpcb->in6p_route.ro_rt) \ nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL); \ } while (0) #else #define ND6_HINT(tp) #endif /* * Insert segment which inludes th into reassembly queue of tcp with * control block tp. Return TH_FIN if reassembly now includes * a segment with FIN. The macro form does the common case inline * (segment is the next to be received on an established connection, * and the queue is empty), avoiding linkage into and removal * from the queue and repetition of various conversions. * Set DELACK for segments received in order, but ack immediately * when segments are out of order (so fast retransmit can work). */ #define TCP_REASS(tp, th, tlenp, m, so, flags) { \ if ((th)->th_seq == (tp)->rcv_nxt && \ LIST_EMPTY(&(tp)->t_segq) && \ (tp)->t_state == TCPS_ESTABLISHED) { \ if (tcp_delack_enabled) \ callout_reset(tp->tt_delack, tcp_delacktime, \ tcp_timer_delack, tp); \ else \ tp->t_flags |= TF_ACKNOW; \ (tp)->rcv_nxt += *(tlenp); \ flags = (th)->th_flags & TH_FIN; \ tcpstat.tcps_rcvpack++;\ tcpstat.tcps_rcvbyte += *(tlenp);\ ND6_HINT(tp); \ sbappend(&(so)->so_rcv, (m)); \ sorwakeup(so); \ } else { \ (flags) = tcp_reass((tp), (th), (tlenp), (m)); \ tp->t_flags |= TF_ACKNOW; \ } \ } static int tcp_reass(tp, th, tlenp, m) register struct tcpcb *tp; register struct tcphdr *th; int *tlenp; struct mbuf *m; { struct tseg_qent *q; struct tseg_qent *p = NULL; struct tseg_qent *nq; struct tseg_qent *te; struct socket *so = tp->t_inpcb->inp_socket; int flags; /* * Call with th==0 after become established to * force pre-ESTABLISHED data up to user socket. */ if (th == 0) goto present; /* Allocate a new queue entry. If we can't, just drop the pkt. XXX */ MALLOC(te, struct tseg_qent *, sizeof (struct tseg_qent), M_TSEGQ, M_NOWAIT); if (te == NULL) { tcpstat.tcps_rcvmemdrop++; m_freem(m); return (0); } /* * Find a segment which begins after this one does. */ LIST_FOREACH(q, &tp->t_segq, tqe_q) { if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) break; p = q; } /* * If there is a preceding segment, it may provide some of * our data already. If so, drop the data from the incoming * segment. If it provides all of our data, drop us. */ if (p != NULL) { register int i; /* conversion to int (in i) handles seq wraparound */ i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; if (i > 0) { if (i >= *tlenp) { tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += *tlenp; m_freem(m); FREE(te, M_TSEGQ); /* * Try to present any queued data * at the left window edge to the user. * This is needed after the 3-WHS * completes. */ goto present; /* ??? */ } m_adj(m, i); *tlenp -= i; th->th_seq += i; } } tcpstat.tcps_rcvoopack++; tcpstat.tcps_rcvoobyte += *tlenp; /* * While we overlap succeeding segments trim them or, * if they are completely covered, dequeue them. */ while (q) { register int i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; if (i <= 0) break; if (i < q->tqe_len) { q->tqe_th->th_seq += i; q->tqe_len -= i; m_adj(q->tqe_m, i); break; } nq = LIST_NEXT(q, tqe_q); LIST_REMOVE(q, tqe_q); m_freem(q->tqe_m); FREE(q, M_TSEGQ); q = nq; } /* Insert the new segment queue entry into place. */ te->tqe_m = m; te->tqe_th = th; te->tqe_len = *tlenp; if (p == NULL) { LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); } else { LIST_INSERT_AFTER(p, te, tqe_q); } present: /* * Present data to user, advancing rcv_nxt through * completed sequence space. */ if (!TCPS_HAVEESTABLISHED(tp->t_state)) return (0); q = LIST_FIRST(&tp->t_segq); if (!q || q->tqe_th->th_seq != tp->rcv_nxt) return (0); do { tp->rcv_nxt += q->tqe_len; flags = q->tqe_th->th_flags & TH_FIN; nq = LIST_NEXT(q, tqe_q); LIST_REMOVE(q, tqe_q); if (so->so_state & SS_CANTRCVMORE) m_freem(q->tqe_m); else sbappend(&so->so_rcv, q->tqe_m); FREE(q, M_TSEGQ); q = nq; } while (q && q->tqe_th->th_seq == tp->rcv_nxt); ND6_HINT(tp); sorwakeup(so); return (flags); } /* * TCP input routine, follows pages 65-76 of the * protocol specification dated September, 1981 very closely. */ #ifdef INET6 int tcp6_input(mp, offp, proto) struct mbuf **mp; int *offp, proto; { register struct mbuf *m = *mp; IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); /* * draft-itojun-ipv6-tcp-to-anycast * better place to put this in? */ if (m->m_flags & M_ANYCAST6) { struct ip6_hdr *ip6; ip6 = mtod(m, struct ip6_hdr *); icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); return IPPROTO_DONE; } tcp_input(m, *offp, proto); return IPPROTO_DONE; } #endif void tcp_input(m, off0, proto) register struct mbuf *m; int off0, proto; { register struct tcphdr *th; register struct ip *ip = NULL; register struct ipovly *ipov; register struct inpcb *inp; u_char *optp = NULL; int optlen = 0; int len, tlen, off; int drop_hdrlen; register struct tcpcb *tp = 0; register int thflags; struct socket *so = 0; int todrop, acked, ourfinisacked, needoutput = 0; struct in_addr laddr; #ifdef INET6 struct in6_addr laddr6; #endif int dropsocket = 0; int iss = 0; u_long tiwin; struct tcpopt to; /* options in this segment */ struct rmxp_tao *taop; /* pointer to our TAO cache entry */ struct rmxp_tao tao_noncached; /* in case there's no cached entry */ #ifdef TCPDEBUG short ostate = 0; #endif #ifdef INET6 struct ip6_hdr *ip6 = NULL; int isipv6; #endif /* INET6 */ #ifdef INET6 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; #endif bzero((char *)&to, sizeof(to)); tcpstat.tcps_rcvtotal++; #ifdef INET6 if (isipv6) { /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ ip6 = mtod(m, struct ip6_hdr *); tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { tcpstat.tcps_rcvbadsum++; goto drop; } th = (struct tcphdr *)((caddr_t)ip6 + off0); } else #endif /* INET6 */ { /* * Get IP and TCP header together in first mbuf. * Note: IP leaves IP header in first mbuf. */ if (off0 > sizeof (struct ip)) { ip_stripoptions(m, (struct mbuf *)0); off0 = sizeof(struct ip); } if (m->m_len < sizeof (struct tcpiphdr)) { if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { tcpstat.tcps_rcvshort++; return; } } ip = mtod(m, struct ip *); ipov = (struct ipovly *)ip; th = (struct tcphdr *)((caddr_t)ip + off0); tlen = ip->ip_len; if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) th->th_sum = m->m_pkthdr.csum_data; else th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, htonl(m->m_pkthdr.csum_data + ip->ip_len + IPPROTO_TCP)); th->th_sum ^= 0xffff; } else { /* * Checksum extended TCP header and data. */ len = sizeof (struct ip) + tlen; bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); ipov->ih_len = (u_short)tlen; HTONS(ipov->ih_len); th->th_sum = in_cksum(m, len); } if (th->th_sum) { tcpstat.tcps_rcvbadsum++; goto drop; } #ifdef INET6 /* Re-initialization for later version check */ ip->ip_v = IPVERSION; #endif } /* * Check that TCP offset makes sense, * pull out TCP options and adjust length. XXX */ off = th->th_off << 2; if (off < sizeof (struct tcphdr) || off > tlen) { tcpstat.tcps_rcvbadoff++; goto drop; } tlen -= off; /* tlen is used instead of ti->ti_len */ if (off > sizeof (struct tcphdr)) { #ifdef INET6 if (isipv6) { IP6_EXTHDR_CHECK(m, off0, off, ); ip6 = mtod(m, struct ip6_hdr *); th = (struct tcphdr *)((caddr_t)ip6 + off0); } else #endif /* INET6 */ { if (m->m_len < sizeof(struct ip) + off) { if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { tcpstat.tcps_rcvshort++; return; } ip = mtod(m, struct ip *); ipov = (struct ipovly *)ip; th = (struct tcphdr *)((caddr_t)ip + off0); } } optlen = off - sizeof (struct tcphdr); optp = (u_char *)(th + 1); } thflags = th->th_flags; #ifdef TCP_DROP_SYNFIN /* * If the drop_synfin option is enabled, drop all packets with * both the SYN and FIN bits set. This prevents e.g. nmap from * identifying the TCP/IP stack. * * This is incompatible with RFC1644 extensions (T/TCP). */ if (drop_synfin && (thflags & (TH_SYN|TH_FIN)) == (TH_SYN|TH_FIN)) goto drop; #endif /* * Convert TCP protocol specific fields to host format. */ NTOHL(th->th_seq); NTOHL(th->th_ack); NTOHS(th->th_win); NTOHS(th->th_urp); /* * Delay droping TCP, IP headers, IPv6 ext headers, and TCP options, * until after ip6_savecontrol() is called and before other functions * which don't want those proto headers. * Because ip6_savecontrol() is going to parse the mbuf to * search for data to be passed up to user-land, it wants mbuf * parameters to be unchanged. */ drop_hdrlen = off0 + off; /* * Locate pcb for segment. */ findpcb: #ifdef IPFIREWALL_FORWARD if (ip_fw_fwd_addr != NULL #ifdef INET6 && isipv6 == NULL /* IPv6 support is not yet */ #endif /* INET6 */ ) { /* * Diverted. Pretend to be the destination. * already got one like this? */ inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, ip->ip_dst, th->th_dport, 0, m->m_pkthdr.rcvif); if (!inp) { /* * No, then it's new. Try find the ambushing socket */ if (!ip_fw_fwd_addr->sin_port) { inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, ip_fw_fwd_addr->sin_addr, th->th_dport, 1, m->m_pkthdr.rcvif); } else { inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, ip_fw_fwd_addr->sin_addr, ntohs(ip_fw_fwd_addr->sin_port), 1, m->m_pkthdr.rcvif); } } ip_fw_fwd_addr = NULL; } else #endif /* IPFIREWALL_FORWARD */ { #ifdef INET6 if (isipv6) inp = in6_pcblookup_hash(&tcbinfo, &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 1, m->m_pkthdr.rcvif); else #endif /* INET6 */ inp = in_pcblookup_hash(&tcbinfo, ip->ip_src, th->th_sport, ip->ip_dst, th->th_dport, 1, m->m_pkthdr.rcvif); } #ifdef IPSEC #ifdef INET6 if (isipv6) { if (inp != NULL && ipsec6_in_reject_so(m, inp->inp_socket)) { ipsec6stat.in_polvio++; goto drop; } } else #endif /* INET6 */ if (inp != NULL && ipsec4_in_reject_so(m, inp->inp_socket)) { ipsecstat.in_polvio++; goto drop; } #endif /*IPSEC*/ /* * If the state is CLOSED (i.e., TCB does not exist) then * all data in the incoming segment is discarded. * If the TCB exists but is in CLOSED state, it is embryonic, * but should either do a listen or a connect soon. */ if (inp == NULL) { if (log_in_vain) { #ifdef INET6 char dbuf[INET6_ADDRSTRLEN], sbuf[INET6_ADDRSTRLEN]; #else /* INET6 */ char dbuf[4*sizeof "123"], sbuf[4*sizeof "123"]; #endif /* INET6 */ #ifdef INET6 if (isipv6) { strcpy(dbuf, ip6_sprintf(&ip6->ip6_dst)); strcpy(sbuf, ip6_sprintf(&ip6->ip6_src)); } else #endif { strcpy(dbuf, inet_ntoa(ip->ip_dst)); strcpy(sbuf, inet_ntoa(ip->ip_src)); } switch (log_in_vain) { case 1: if(thflags & TH_SYN) log(LOG_INFO, "Connection attempt to TCP %s:%d from %s:%d\n", dbuf, ntohs(th->th_dport), sbuf, ntohs(th->th_sport)); break; case 2: log(LOG_INFO, "Connection attempt to TCP %s:%d from %s:%d flags:0x%x\n", dbuf, ntohs(th->th_dport), sbuf, ntohs(th->th_sport), thflags); break; default: break; } } if (blackhole) { switch (blackhole) { case 1: if (thflags & TH_SYN) goto drop; break; case 2: goto drop; default: goto drop; } } goto maybedropwithreset; } tp = intotcpcb(inp); if (tp == 0) goto maybedropwithreset; if (tp->t_state == TCPS_CLOSED) goto drop; /* Unscale the window into a 32-bit value. */ if ((thflags & TH_SYN) == 0) tiwin = th->th_win << tp->snd_scale; else tiwin = th->th_win; #ifdef INET6 /* save packet options if user wanted */ if (isipv6 && inp->in6p_flags & INP_CONTROLOPTS) { if (inp->in6p_options) { m_freem(inp->in6p_options); inp->in6p_options = 0; } ip6_savecontrol(inp, &inp->in6p_options, ip6, m); } /* else, should also do ip_srcroute() here? */ #endif /* INET6 */ so = inp->inp_socket; if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { #ifdef TCPDEBUG if (so->so_options & SO_DEBUG) { ostate = tp->t_state; #ifdef INET6 if (isipv6) bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); else #endif /* INET6 */ bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); tcp_savetcp = *th; } #endif if (so->so_options & SO_ACCEPTCONN) { register struct tcpcb *tp0 = tp; struct socket *so2; #ifdef IPSEC struct socket *oso; #endif #ifdef INET6 struct inpcb *oinp = sotoinpcb(so); #endif /* INET6 */ #ifndef IPSEC /* * Current IPsec implementation makes incorrect IPsec * cache if this check is done here. * So delay this until duplicated socket is created. */ if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { /* * Note: dropwithreset makes sure we don't * send a RST in response to a RST. */ if (thflags & TH_ACK) { tcpstat.tcps_badsyn++; goto maybedropwithreset; } goto drop; } #endif so2 = sonewconn(so, 0); if (so2 == 0) { tcpstat.tcps_listendrop++; so2 = sodropablereq(so); if (so2) { tcp_drop(sototcpcb(so2), ETIMEDOUT); so2 = sonewconn(so, 0); } if (!so2) goto drop; } #ifdef IPSEC oso = so; #endif so = so2; /* * This is ugly, but .... * * Mark socket as temporary until we're * committed to keeping it. The code at * ``drop'' and ``dropwithreset'' check the * flag dropsocket to see if the temporary * socket created here should be discarded. * We mark the socket as discardable until * we're committed to it below in TCPS_LISTEN. */ dropsocket++; inp = (struct inpcb *)so->so_pcb; #ifdef INET6 if (isipv6) inp->in6p_laddr = ip6->ip6_dst; else { if ((inp->inp_flags & IN6P_BINDV6ONLY) == 0) { inp->inp_vflag &= ~INP_IPV6; inp->inp_vflag |= INP_IPV4; } #endif /* INET6 */ inp->inp_laddr = ip->ip_dst; #ifdef INET6 } #endif /* INET6 */ inp->inp_lport = th->th_dport; if (in_pcbinshash(inp) != 0) { /* * Undo the assignments above if we failed to * put the PCB on the hash lists. */ #ifdef INET6 if (isipv6) inp->in6p_laddr = in6addr_any; else #endif /* INET6 */ inp->inp_laddr.s_addr = INADDR_ANY; inp->inp_lport = 0; goto drop; } #ifdef IPSEC /* * To avoid creating incorrectly cached IPsec * association, this is need to be done here. * * Subject: (KAME-snap 748) * From: Wayne Knowles * ftp://ftp.kame.net/pub/mail-list/snap-users/748 */ if ((thflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { /* * Note: dropwithreset makes sure we don't * send a RST in response to a RST. */ if (thflags & TH_ACK) { tcpstat.tcps_badsyn++; goto maybedropwithreset; } goto drop; } #endif #ifdef INET6 if (isipv6) { /* * inherit socket options from the listening * socket. */ inp->inp_flags |= oinp->inp_flags & INP_CONTROLOPTS; if (inp->inp_flags & INP_CONTROLOPTS) { if (inp->in6p_options) { m_freem(inp->in6p_options); inp->in6p_options = 0; } ip6_savecontrol(inp, &inp->in6p_options, ip6, m); } } else #endif /* INET6 */ inp->inp_options = ip_srcroute(); #ifdef IPSEC /* copy old policy into new socket's */ if (ipsec_copy_policy(sotoinpcb(oso)->inp_sp, inp->inp_sp)) printf("tcp_input: could not copy policy\n"); #endif tp = intotcpcb(inp); tp->t_state = TCPS_LISTEN; tp->t_flags |= tp0->t_flags & (TF_NOPUSH|TF_NOOPT); /* Compute proper scaling value from buffer space */ while (tp->request_r_scale < TCP_MAX_WINSHIFT && TCP_MAXWIN << tp->request_r_scale < so->so_rcv.sb_hiwat) tp->request_r_scale++; } } /* * Segment received on connection. * Reset idle time and keep-alive timer. */ tp->t_rcvtime = ticks; if (TCPS_HAVEESTABLISHED(tp->t_state)) callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); /* * Process options if not in LISTEN state, * else do it below (after getting remote address). */ if (tp->t_state != TCPS_LISTEN) tcp_dooptions(tp, optp, optlen, th, &to); /* * Header prediction: check for the two common cases * of a uni-directional data xfer. If the packet has * no control flags, is in-sequence, the window didn't * change and we're not retransmitting, it's a * candidate. If the length is zero and the ack moved * forward, we're the sender side of the xfer. Just * free the data acked & wake any higher level process * that was blocked waiting for space. If the length * is non-zero and the ack didn't move, we're the * receiver side. If we're getting packets in-order * (the reassembly queue is empty), add the data to * the socket buffer and note that we need a delayed ack. * Make sure that the hidden state-flags are also off. * Since we check for TCPS_ESTABLISHED above, it can only * be TH_NEEDSYN. */ if (tp->t_state == TCPS_ESTABLISHED && (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && ((to.to_flag & TOF_TS) == 0 || TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && /* * Using the CC option is compulsory if once started: * the segment is OK if no T/TCP was negotiated or * if the segment has a CC option equal to CCrecv */ ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) || ((to.to_flag & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) && th->th_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd && tp->snd_nxt == tp->snd_max) { /* * If last ACK falls within this segment's sequence numbers, * record the timestamp. * NOTE that the test is modified according to the latest * proposal of the tcplw@cray.com list (Braden 1993/04/26). */ if ((to.to_flag & TOF_TS) != 0 && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { tp->ts_recent_age = ticks; tp->ts_recent = to.to_tsval; } if (tlen == 0) { if (SEQ_GT(th->th_ack, tp->snd_una) && SEQ_LEQ(th->th_ack, tp->snd_max) && tp->snd_cwnd >= tp->snd_wnd && tp->t_dupacks < tcprexmtthresh) { /* * this is a pure ack for outstanding data. */ ++tcpstat.tcps_predack; /* * "bad retransmit" recovery */ if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { tp->snd_cwnd = tp->snd_cwnd_prev; tp->snd_ssthresh = tp->snd_ssthresh_prev; tp->snd_nxt = tp->snd_max; tp->t_badrxtwin = 0; } if ((to.to_flag & TOF_TS) != 0) tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) tcp_xmit_timer(tp, ticks - tp->t_rtttime); acked = th->th_ack - tp->snd_una; tcpstat.tcps_rcvackpack++; tcpstat.tcps_rcvackbyte += acked; sbdrop(&so->so_snd, acked); tp->snd_una = th->th_ack; m_freem(m); ND6_HINT(tp); /* some progress has been done */ /* * If all outstanding data are acked, stop * retransmit timer, otherwise restart timer * using current (possibly backed-off) value. * If process is waiting for space, * wakeup/selwakeup/signal. If data * are ready to send, let tcp_output * decide between more output or persist. */ if (tp->snd_una == tp->snd_max) callout_stop(tp->tt_rexmt); else if (!callout_active(tp->tt_persist)) callout_reset(tp->tt_rexmt, tp->t_rxtcur, tcp_timer_rexmt, tp); sowwakeup(so); if (so->so_snd.sb_cc) (void) tcp_output(tp); return; } } else if (th->th_ack == tp->snd_una && LIST_EMPTY(&tp->t_segq) && tlen <= sbspace(&so->so_rcv)) { /* * this is a pure, in-sequence data packet * with nothing on the reassembly queue and * we have enough buffer space to take it. */ ++tcpstat.tcps_preddat; tp->rcv_nxt += tlen; tcpstat.tcps_rcvpack++; tcpstat.tcps_rcvbyte += tlen; ND6_HINT(tp); /* some progress has been done */ /* * Add data to socket buffer. */ m_adj(m, drop_hdrlen); /* delayed header drop */ sbappend(&so->so_rcv, m); sorwakeup(so); if (tcp_delack_enabled) { callout_reset(tp->tt_delack, tcp_delacktime, tcp_timer_delack, tp); } else { tp->t_flags |= TF_ACKNOW; tcp_output(tp); } return; } } /* * Calculate amount of space in receive window, * and then do TCP input processing. * Receive window is amount of space in rcv queue, * but not less than advertised window. */ { int win; win = sbspace(&so->so_rcv); if (win < 0) win = 0; tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); } switch (tp->t_state) { /* * If the state is LISTEN then ignore segment if it contains an RST. * If the segment contains an ACK then it is bad and send a RST. * If it does not contain a SYN then it is not interesting; drop it. * If it is from this socket, drop it, it must be forged. * Don't bother responding if the destination was a broadcast. * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial * tp->iss, and send a segment: * * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. * Fill in remote peer address fields if not previously specified. * Enter SYN_RECEIVED state, and process any other fields of this * segment in this state. */ case TCPS_LISTEN: { register struct sockaddr_in *sin; #ifdef INET6 register struct sockaddr_in6 *sin6; #endif if (thflags & TH_RST) goto drop; if (thflags & TH_ACK) goto maybedropwithreset; if ((thflags & TH_SYN) == 0) goto drop; if (th->th_dport == th->th_sport) { #ifdef INET6 if (isipv6) { if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) goto drop; } else #endif /* INET6 */ if (ip->ip_dst.s_addr == ip->ip_src.s_addr) goto drop; } /* * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN * in_broadcast() should never return true on a received * packet with M_BCAST not set. * * Packets with a multicast source address should also * be discarded. */ if (m->m_flags & (M_BCAST|M_MCAST)) goto drop; #ifdef INET6 if (isipv6) { if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) goto drop; } else #endif if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || ip->ip_src.s_addr == htonl(INADDR_BROADCAST)) goto drop; #ifdef INET6 if (isipv6) { MALLOC(sin6, struct sockaddr_in6 *, sizeof *sin6, M_SONAME, M_NOWAIT); if (sin6 == NULL) goto drop; bzero(sin6, sizeof(*sin6)); sin6->sin6_family = AF_INET6; sin6->sin6_len = sizeof(*sin6); sin6->sin6_addr = ip6->ip6_src; sin6->sin6_port = th->th_sport; laddr6 = inp->in6p_laddr; if (IN6_IS_ADDR_UNSPECIFIED(&inp->in6p_laddr)) inp->in6p_laddr = ip6->ip6_dst; if (in6_pcbconnect(inp, (struct sockaddr *)sin6, &proc0)) { inp->in6p_laddr = laddr6; FREE(sin6, M_SONAME); goto drop; } FREE(sin6, M_SONAME); } else #endif { MALLOC(sin, struct sockaddr_in *, sizeof *sin, M_SONAME, M_NOWAIT); if (sin == NULL) goto drop; sin->sin_family = AF_INET; sin->sin_len = sizeof(*sin); sin->sin_addr = ip->ip_src; sin->sin_port = th->th_sport; bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); laddr = inp->inp_laddr; if (inp->inp_laddr.s_addr == INADDR_ANY) inp->inp_laddr = ip->ip_dst; if (in_pcbconnect(inp, (struct sockaddr *)sin, &proc0)) { inp->inp_laddr = laddr; FREE(sin, M_SONAME); goto drop; } FREE(sin, M_SONAME); } tp->t_template = tcp_template(tp); if (tp->t_template == 0) { tp = tcp_drop(tp, ENOBUFS); dropsocket = 0; /* socket is already gone */ goto drop; } if ((taop = tcp_gettaocache(inp)) == NULL) { taop = &tao_noncached; bzero(taop, sizeof(*taop)); } tcp_dooptions(tp, optp, optlen, th, &to); if (iss) tp->iss = iss; else tp->iss = tcp_iss; tcp_iss += TCP_ISSINCR/4; tp->irs = th->th_seq; tcp_sendseqinit(tp); tcp_rcvseqinit(tp); /* * Initialization of the tcpcb for transaction; * set SND.WND = SEG.WND, * initialize CCsend and CCrecv. */ tp->snd_wnd = tiwin; /* initial send-window */ tp->cc_send = CC_INC(tcp_ccgen); tp->cc_recv = to.to_cc; /* * Perform TAO test on incoming CC (SEG.CC) option, if any. * - compare SEG.CC against cached CC from the same host, * if any. * - if SEG.CC > chached value, SYN must be new and is accepted * immediately: save new CC in the cache, mark the socket * connected, enter ESTABLISHED state, turn on flag to * send a SYN in the next segment. * A virtual advertised window is set in rcv_adv to * initialize SWS prevention. Then enter normal segment * processing: drop SYN, process data and FIN. * - otherwise do a normal 3-way handshake. */ if ((to.to_flag & TOF_CC) != 0) { if (((tp->t_flags & TF_NOPUSH) != 0) && taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) { taop->tao_cc = to.to_cc; tp->t_starttime = ticks; tp->t_state = TCPS_ESTABLISHED; /* * If there is a FIN, or if there is data and the * connection is local, then delay SYN,ACK(SYN) in * the hope of piggy-backing it on a response * segment. Otherwise must send ACK now in case * the other side is slow starting. */ if (tcp_delack_enabled && ((thflags & TH_FIN) || (tlen != 0 && #ifdef INET6 ((isipv6 && in6_localaddr(&inp->in6p_faddr)) || (!isipv6 && #endif in_localaddr(inp->inp_faddr) #ifdef INET6 )) #endif ))) { callout_reset(tp->tt_delack, tcp_delacktime, tcp_timer_delack, tp); tp->t_flags |= TF_NEEDSYN; } else tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); /* * Limit the `virtual advertised window' to TCP_MAXWIN * here. Even if we requested window scaling, it will * become effective only later when our SYN is acked. */ tp->rcv_adv += min(tp->rcv_wnd, TCP_MAXWIN); tcpstat.tcps_connects++; soisconnected(so); callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); dropsocket = 0; /* committed to socket */ tcpstat.tcps_accepts++; goto trimthenstep6; } /* else do standard 3-way handshake */ } else { /* * No CC option, but maybe CC.NEW: * invalidate cached value. */ taop->tao_cc = 0; } /* * TAO test failed or there was no CC option, * do a standard 3-way handshake. */ tp->t_flags |= TF_ACKNOW; tp->t_state = TCPS_SYN_RECEIVED; callout_reset(tp->tt_keep, tcp_keepinit, tcp_timer_keep, tp); dropsocket = 0; /* committed to socket */ tcpstat.tcps_accepts++; ND6_HINT((struct tcpcb *)inp->inp_ppcb); goto trimthenstep6; } /* * If the state is SYN_RECEIVED: * if seg contains an ACK, but not for our SYN/ACK, send a RST. */ case TCPS_SYN_RECEIVED: if ((thflags & TH_ACK) && (SEQ_LEQ(th->th_ack, tp->snd_una) || SEQ_GT(th->th_ack, tp->snd_max))) goto maybedropwithreset; break; /* * If the state is SYN_SENT: * if seg contains an ACK, but not for our SYN, drop the input. * if seg contains a RST, then drop the connection. * if seg does not contain SYN, then drop it. * Otherwise this is an acceptable SYN segment * initialize tp->rcv_nxt and tp->irs * if seg contains ack then advance tp->snd_una * if SYN has been acked change to ESTABLISHED else SYN_RCVD state * arrange for segment to be acked (eventually) * continue processing rest of data/controls, beginning with URG */ case TCPS_SYN_SENT: if ((taop = tcp_gettaocache(inp)) == NULL) { taop = &tao_noncached; bzero(taop, sizeof(*taop)); } if ((thflags & TH_ACK) && (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) { /* * If we have a cached CCsent for the remote host, * hence we haven't just crashed and restarted, * do not send a RST. This may be a retransmission * from the other side after our earlier ACK was lost. * Our new SYN, when it arrives, will serve as the * needed ACK. */ if (taop->tao_ccsent != 0) goto drop; else goto dropwithreset; } if (thflags & TH_RST) { if (thflags & TH_ACK) tp = tcp_drop(tp, ECONNREFUSED); goto drop; } if ((thflags & TH_SYN) == 0) goto drop; tp->snd_wnd = th->th_win; /* initial send window */ tp->cc_recv = to.to_cc; /* foreign CC */ tp->irs = th->th_seq; tcp_rcvseqinit(tp); if (thflags & TH_ACK) { /* * Our SYN was acked. If segment contains CC.ECHO * option, check it to make sure this segment really * matches our SYN. If not, just drop it as old * duplicate, but send an RST if we're still playing * by the old rules. If no CC.ECHO option, make sure * we don't get fooled into using T/TCP. */ if (to.to_flag & TOF_CCECHO) { if (tp->cc_send != to.to_ccecho) { if (taop->tao_ccsent != 0) goto drop; else goto dropwithreset; } } else tp->t_flags &= ~TF_RCVD_CC; tcpstat.tcps_connects++; soisconnected(so); /* Do window scaling on this connection? */ if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == (TF_RCVD_SCALE|TF_REQ_SCALE)) { tp->snd_scale = tp->requested_s_scale; tp->rcv_scale = tp->request_r_scale; } /* Segment is acceptable, update cache if undefined. */ if (taop->tao_ccsent == 0) taop->tao_ccsent = to.to_ccecho; tp->rcv_adv += tp->rcv_wnd; tp->snd_una++; /* SYN is acked */ /* * If there's data, delay ACK; if there's also a FIN * ACKNOW will be turned on later. */ if (tcp_delack_enabled && tlen != 0) callout_reset(tp->tt_delack, tcp_delacktime, tcp_timer_delack, tp); else tp->t_flags |= TF_ACKNOW; /* * Received in SYN_SENT[*] state. * Transitions: * SYN_SENT --> ESTABLISHED * SYN_SENT* --> FIN_WAIT_1 */ tp->t_starttime = ticks; if (tp->t_flags & TF_NEEDFIN) { tp->t_state = TCPS_FIN_WAIT_1; tp->t_flags &= ~TF_NEEDFIN; thflags &= ~TH_SYN; } else { tp->t_state = TCPS_ESTABLISHED; callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); } } else { /* * Received initial SYN in SYN-SENT[*] state => simul- * taneous open. If segment contains CC option and there is * a cached CC, apply TAO test; if it succeeds, connection is * half-synchronized. Otherwise, do 3-way handshake: * SYN-SENT -> SYN-RECEIVED * SYN-SENT* -> SYN-RECEIVED* * If there was no CC option, clear cached CC value. */ tp->t_flags |= TF_ACKNOW; callout_stop(tp->tt_rexmt); if (to.to_flag & TOF_CC) { if (taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) { /* * update cache and make transition: * SYN-SENT -> ESTABLISHED* * SYN-SENT* -> FIN-WAIT-1* */ taop->tao_cc = to.to_cc; tp->t_starttime = ticks; if (tp->t_flags & TF_NEEDFIN) { tp->t_state = TCPS_FIN_WAIT_1; tp->t_flags &= ~TF_NEEDFIN; } else { tp->t_state = TCPS_ESTABLISHED; callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); } tp->t_flags |= TF_NEEDSYN; } else tp->t_state = TCPS_SYN_RECEIVED; } else { /* CC.NEW or no option => invalidate cache */ taop->tao_cc = 0; tp->t_state = TCPS_SYN_RECEIVED; } } trimthenstep6: /* * Advance th->th_seq to correspond to first data byte. * If data, trim to stay within window, * dropping FIN if necessary. */ th->th_seq++; if (tlen > tp->rcv_wnd) { todrop = tlen - tp->rcv_wnd; m_adj(m, -todrop); tlen = tp->rcv_wnd; thflags &= ~TH_FIN; tcpstat.tcps_rcvpackafterwin++; tcpstat.tcps_rcvbyteafterwin += todrop; } tp->snd_wl1 = th->th_seq - 1; tp->rcv_up = th->th_seq; /* * Client side of transaction: already sent SYN and data. * If the remote host used T/TCP to validate the SYN, * our data will be ACK'd; if so, enter normal data segment * processing in the middle of step 5, ack processing. * Otherwise, goto step 6. */ if (thflags & TH_ACK) goto process_ACK; goto step6; /* * If the state is LAST_ACK or CLOSING or TIME_WAIT: * if segment contains a SYN and CC [not CC.NEW] option: * if state == TIME_WAIT and connection duration > MSL, * drop packet and send RST; * * if SEG.CC > CCrecv then is new SYN, and can implicitly * ack the FIN (and data) in retransmission queue. * Complete close and delete TCPCB. Then reprocess * segment, hoping to find new TCPCB in LISTEN state; * * else must be old SYN; drop it. * else do normal processing. */ case TCPS_LAST_ACK: case TCPS_CLOSING: case TCPS_TIME_WAIT: if ((thflags & TH_SYN) && (to.to_flag & TOF_CC) && tp->cc_recv != 0) { if (tp->t_state == TCPS_TIME_WAIT && (ticks - tp->t_starttime) > tcp_msl) goto dropwithreset; if (CC_GT(to.to_cc, tp->cc_recv)) { tp = tcp_close(tp); goto findpcb; } else goto drop; } break; /* continue normal processing */ } /* * States other than LISTEN or SYN_SENT. * First check the RST flag and sequence number since reset segments * are exempt from the timestamp and connection count tests. This * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix * below which allowed reset segments in half the sequence space * to fall though and be processed (which gives forged reset * segments with a random sequence number a 50 percent chance of * killing a connection). * Then check timestamp, if present. * Then check the connection count, if present. * Then check that at least some bytes of segment are within * receive window. If segment begins before rcv_nxt, * drop leading data (and SYN); if nothing left, just ack. * * * If the RST bit is set, check the sequence number to see * if this is a valid reset segment. * RFC 793 page 37: * In all states except SYN-SENT, all reset (RST) segments * are validated by checking their SEQ-fields. A reset is * valid if its sequence number is in the window. * Note: this does not take into account delayed ACKs, so * we should test against last_ack_sent instead of rcv_nxt. * The sequence number in the reset segment is normally an * echo of our outgoing acknowlegement numbers, but some hosts * send a reset with the sequence number at the rightmost edge * of our receive window, and we have to handle this case. * If we have multiple segments in flight, the intial reset * segment sequence numbers will be to the left of last_ack_sent, * but they will eventually catch up. * In any case, it never made sense to trim reset segments to * fit the receive window since RFC 1122 says: * 4.2.2.12 RST Segment: RFC-793 Section 3.4 * * A TCP SHOULD allow a received RST segment to include data. * * DISCUSSION * It has been suggested that a RST segment could contain * ASCII text that encoded and explained the cause of the * RST. No standard has yet been established for such * data. * * If the reset segment passes the sequence number test examine * the state: * SYN_RECEIVED STATE: * If passive open, return to LISTEN state. * If active open, inform user that connection was refused. * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: * Inform user that connection was reset, and close tcb. * CLOSING, LAST_ACK STATES: * Close the tcb. * TIME_WAIT STATE: * Drop the segment - see Stevens, vol. 2, p. 964 and * RFC 1337. */ if (thflags & TH_RST) { if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { switch (tp->t_state) { case TCPS_SYN_RECEIVED: so->so_error = ECONNREFUSED; goto close; case TCPS_ESTABLISHED: case TCPS_FIN_WAIT_1: case TCPS_FIN_WAIT_2: case TCPS_CLOSE_WAIT: so->so_error = ECONNRESET; close: tp->t_state = TCPS_CLOSED; tcpstat.tcps_drops++; tp = tcp_close(tp); break; case TCPS_CLOSING: case TCPS_LAST_ACK: tp = tcp_close(tp); break; case TCPS_TIME_WAIT: break; } } goto drop; } /* * RFC 1323 PAWS: If we have a timestamp reply on this segment * and it's less than ts_recent, drop it. */ if ((to.to_flag & TOF_TS) != 0 && tp->ts_recent && TSTMP_LT(to.to_tsval, tp->ts_recent)) { /* Check to see if ts_recent is over 24 days old. */ if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { /* * Invalidate ts_recent. If this segment updates * ts_recent, the age will be reset later and ts_recent * will get a valid value. If it does not, setting * ts_recent to zero will at least satisfy the * requirement that zero be placed in the timestamp * echo reply when ts_recent isn't valid. The * age isn't reset until we get a valid ts_recent * because we don't want out-of-order segments to be * dropped when ts_recent is old. */ tp->ts_recent = 0; } else { tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += tlen; tcpstat.tcps_pawsdrop++; goto dropafterack; } } /* * T/TCP mechanism * If T/TCP was negotiated and the segment doesn't have CC, * or if its CC is wrong then drop the segment. * RST segments do not have to comply with this. */ if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) && ((to.to_flag & TOF_CC) == 0 || tp->cc_recv != to.to_cc)) goto dropafterack; /* * In the SYN-RECEIVED state, validate that the packet belongs to * this connection before trimming the data to fit the receive * window. Check the sequence number versus IRS since we know * the sequence numbers haven't wrapped. This is a partial fix * for the "LAND" DoS attack. */ if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) goto maybedropwithreset; todrop = tp->rcv_nxt - th->th_seq; if (todrop > 0) { if (thflags & TH_SYN) { thflags &= ~TH_SYN; th->th_seq++; if (th->th_urp > 1) th->th_urp--; else thflags &= ~TH_URG; todrop--; } /* * Following if statement from Stevens, vol. 2, p. 960. */ if (todrop > tlen || (todrop == tlen && (thflags & TH_FIN) == 0)) { /* * Any valid FIN must be to the left of the window. * At this point the FIN must be a duplicate or out * of sequence; drop it. */ thflags &= ~TH_FIN; /* * Send an ACK to resynchronize and drop any data. * But keep on processing for RST or ACK. */ tp->t_flags |= TF_ACKNOW; todrop = tlen; tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += todrop; } else { tcpstat.tcps_rcvpartduppack++; tcpstat.tcps_rcvpartdupbyte += todrop; } drop_hdrlen += todrop; /* drop from the top afterwards */ th->th_seq += todrop; tlen -= todrop; if (th->th_urp > todrop) th->th_urp -= todrop; else { thflags &= ~TH_URG; th->th_urp = 0; } } /* * If new data are received on a connection after the * user processes are gone, then RST the other end. */ if ((so->so_state & SS_NOFDREF) && tp->t_state > TCPS_CLOSE_WAIT && tlen) { tp = tcp_close(tp); tcpstat.tcps_rcvafterclose++; goto dropwithreset; } /* * If segment ends after window, drop trailing data * (and PUSH and FIN); if nothing left, just ACK. */ todrop = (th->th_seq+tlen) - (tp->rcv_nxt+tp->rcv_wnd); if (todrop > 0) { tcpstat.tcps_rcvpackafterwin++; if (todrop >= tlen) { tcpstat.tcps_rcvbyteafterwin += tlen; /* * If a new connection request is received * while in TIME_WAIT, drop the old connection * and start over if the sequence numbers * are above the previous ones. */ if (thflags & TH_SYN && tp->t_state == TCPS_TIME_WAIT && SEQ_GT(th->th_seq, tp->rcv_nxt)) { iss = tp->snd_nxt + TCP_ISSINCR; tp = tcp_close(tp); goto findpcb; } /* * If window is closed can only take segments at * window edge, and have to drop data and PUSH from * incoming segments. Continue processing, but * remember to ack. Otherwise, drop segment * and ack. */ if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { tp->t_flags |= TF_ACKNOW; tcpstat.tcps_rcvwinprobe++; } else goto dropafterack; } else tcpstat.tcps_rcvbyteafterwin += todrop; m_adj(m, -todrop); tlen -= todrop; thflags &= ~(TH_PUSH|TH_FIN); } /* * If last ACK falls within this segment's sequence numbers, * record its timestamp. * NOTE that the test is modified according to the latest * proposal of the tcplw@cray.com list (Braden 1993/04/26). */ if ((to.to_flag & TOF_TS) != 0 && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { tp->ts_recent_age = ticks; tp->ts_recent = to.to_tsval; } /* * If a SYN is in the window, then this is an * error and we send an RST and drop the connection. */ if (thflags & TH_SYN) { tp = tcp_drop(tp, ECONNRESET); goto dropwithreset; } /* * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN * flag is on (half-synchronized state), then queue data for * later processing; else drop segment and return. */ if ((thflags & TH_ACK) == 0) { if (tp->t_state == TCPS_SYN_RECEIVED || (tp->t_flags & TF_NEEDSYN)) goto step6; else goto drop; } /* * Ack processing. */ switch (tp->t_state) { /* * In SYN_RECEIVED state, the ack ACKs our SYN, so enter * ESTABLISHED state and continue processing. * The ACK was checked above. */ case TCPS_SYN_RECEIVED: tcpstat.tcps_connects++; soisconnected(so); /* Do window scaling? */ if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == (TF_RCVD_SCALE|TF_REQ_SCALE)) { tp->snd_scale = tp->requested_s_scale; tp->rcv_scale = tp->request_r_scale; } /* * Upon successful completion of 3-way handshake, * update cache.CC if it was undefined, pass any queued * data to the user, and advance state appropriately. */ if ((taop = tcp_gettaocache(inp)) != NULL && taop->tao_cc == 0) taop->tao_cc = tp->cc_recv; /* * Make transitions: * SYN-RECEIVED -> ESTABLISHED * SYN-RECEIVED* -> FIN-WAIT-1 */ tp->t_starttime = ticks; if (tp->t_flags & TF_NEEDFIN) { tp->t_state = TCPS_FIN_WAIT_1; tp->t_flags &= ~TF_NEEDFIN; } else { tp->t_state = TCPS_ESTABLISHED; callout_reset(tp->tt_keep, tcp_keepidle, tcp_timer_keep, tp); } /* * If segment contains data or ACK, will call tcp_reass() * later; if not, do so now to pass queued data to user. */ if (tlen == 0 && (thflags & TH_FIN) == 0) (void) tcp_reass(tp, (struct tcphdr *)0, 0, (struct mbuf *)0); tp->snd_wl1 = th->th_seq - 1; /* fall into ... */ /* * In ESTABLISHED state: drop duplicate ACKs; ACK out of range * ACKs. If the ack is in the range * tp->snd_una < th->th_ack <= tp->snd_max * then advance tp->snd_una to th->th_ack and drop * data from the retransmission queue. If this ACK reflects * more up to date window information we update our window information. */ case TCPS_ESTABLISHED: case TCPS_FIN_WAIT_1: case TCPS_FIN_WAIT_2: case TCPS_CLOSE_WAIT: case TCPS_CLOSING: case TCPS_LAST_ACK: case TCPS_TIME_WAIT: if (SEQ_LEQ(th->th_ack, tp->snd_una)) { if (tlen == 0 && tiwin == tp->snd_wnd) { tcpstat.tcps_rcvdupack++; /* * If we have outstanding data (other than * a window probe), this is a completely * duplicate ack (ie, window info didn't * change), the ack is the biggest we've * seen and we've seen exactly our rexmt * threshhold of them, assume a packet * has been dropped and retransmit it. * Kludge snd_nxt & the congestion * window so we send only this one * packet. * * We know we're losing at the current * window size so do congestion avoidance * (set ssthresh to half the current window * and pull our congestion window back to * the new ssthresh). * * Dup acks mean that packets have left the * network (they're now cached at the receiver) * so bump cwnd by the amount in the receiver * to keep a constant cwnd packets in the * network. */ if (!callout_active(tp->tt_rexmt) || th->th_ack != tp->snd_una) tp->t_dupacks = 0; else if (++tp->t_dupacks == tcprexmtthresh) { tcp_seq onxt = tp->snd_nxt; u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; if (win < 2) win = 2; tp->snd_ssthresh = win * tp->t_maxseg; callout_stop(tp->tt_rexmt); tp->t_rtttime = 0; tp->snd_nxt = th->th_ack; tp->snd_cwnd = tp->t_maxseg; (void) tcp_output(tp); tp->snd_cwnd = tp->snd_ssthresh + tp->t_maxseg * tp->t_dupacks; if (SEQ_GT(onxt, tp->snd_nxt)) tp->snd_nxt = onxt; goto drop; } else if (tp->t_dupacks > tcprexmtthresh) { tp->snd_cwnd += tp->t_maxseg; (void) tcp_output(tp); goto drop; } } else tp->t_dupacks = 0; break; } /* * If the congestion window was inflated to account * for the other side's cached packets, retract it. */ if (tp->t_dupacks >= tcprexmtthresh && tp->snd_cwnd > tp->snd_ssthresh) tp->snd_cwnd = tp->snd_ssthresh; tp->t_dupacks = 0; if (SEQ_GT(th->th_ack, tp->snd_max)) { tcpstat.tcps_rcvacktoomuch++; goto dropafterack; } /* * If we reach this point, ACK is not a duplicate, * i.e., it ACKs something we sent. */ if (tp->t_flags & TF_NEEDSYN) { /* * T/TCP: Connection was half-synchronized, and our * SYN has been ACK'd (so connection is now fully * synchronized). Go to non-starred state, * increment snd_una for ACK of SYN, and check if * we can do window scaling. */ tp->t_flags &= ~TF_NEEDSYN; tp->snd_una++; /* Do window scaling? */ if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == (TF_RCVD_SCALE|TF_REQ_SCALE)) { tp->snd_scale = tp->requested_s_scale; tp->rcv_scale = tp->request_r_scale; } } process_ACK: acked = th->th_ack - tp->snd_una; tcpstat.tcps_rcvackpack++; tcpstat.tcps_rcvackbyte += acked; /* * If we just performed our first retransmit, and the ACK * arrives within our recovery window, then it was a mistake * to do the retransmit in the first place. Recover our * original cwnd and ssthresh, and proceed to transmit where * we left off. */ if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { tp->snd_cwnd = tp->snd_cwnd_prev; tp->snd_ssthresh = tp->snd_ssthresh_prev; tp->snd_nxt = tp->snd_max; tp->t_badrxtwin = 0; /* XXX probably not required */ } /* * If we have a timestamp reply, update smoothed * round trip time. If no timestamp is present but * transmit timer is running and timed sequence * number was acked, update smoothed round trip time. * Since we now have an rtt measurement, cancel the * timer backoff (cf., Phil Karn's retransmit alg.). * Recompute the initial retransmit timer. */ if (to.to_flag & TOF_TS) tcp_xmit_timer(tp, ticks - to.to_tsecr + 1); else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) tcp_xmit_timer(tp, ticks - tp->t_rtttime); /* * If all outstanding data is acked, stop retransmit * timer and remember to restart (more output or persist). * If there is more data to be acked, restart retransmit * timer, using current (possibly backed-off) value. */ if (th->th_ack == tp->snd_max) { callout_stop(tp->tt_rexmt); needoutput = 1; } else if (!callout_active(tp->tt_persist)) callout_reset(tp->tt_rexmt, tp->t_rxtcur, tcp_timer_rexmt, tp); /* * If no data (only SYN) was ACK'd, * skip rest of ACK processing. */ if (acked == 0) goto step6; /* * When new data is acked, open the congestion window. * If the window gives us less than ssthresh packets * in flight, open exponentially (maxseg per packet). * Otherwise open linearly: maxseg per window * (maxseg^2 / cwnd per packet). */ { register u_int cw = tp->snd_cwnd; register u_int incr = tp->t_maxseg; if (cw > tp->snd_ssthresh) incr = incr * incr / cw; tp->snd_cwnd = min(cw + incr, TCP_MAXWIN << tp->snd_scale); } if (acked > so->so_snd.sb_cc) { tp->snd_wnd -= so->so_snd.sb_cc; sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); ourfinisacked = 1; } else { sbdrop(&so->so_snd, acked); tp->snd_wnd -= acked; ourfinisacked = 0; } sowwakeup(so); tp->snd_una = th->th_ack; if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; switch (tp->t_state) { /* * In FIN_WAIT_1 STATE in addition to the processing * for the ESTABLISHED state if our FIN is now acknowledged * then enter FIN_WAIT_2. */ case TCPS_FIN_WAIT_1: if (ourfinisacked) { /* * If we can't receive any more * data, then closing user can proceed. * Starting the timer is contrary to the * specification, but if we don't get a FIN * we'll hang forever. */ if (so->so_state & SS_CANTRCVMORE) { soisdisconnected(so); callout_reset(tp->tt_2msl, tcp_maxidle, tcp_timer_2msl, tp); } tp->t_state = TCPS_FIN_WAIT_2; } break; /* * In CLOSING STATE in addition to the processing for * the ESTABLISHED state if the ACK acknowledges our FIN * then enter the TIME-WAIT state, otherwise ignore * the segment. */ case TCPS_CLOSING: if (ourfinisacked) { tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); /* Shorten TIME_WAIT [RFC-1644, p.28] */ if (tp->cc_recv != 0 && (ticks - tp->t_starttime) < tcp_msl) callout_reset(tp->tt_2msl, tp->t_rxtcur * TCPTV_TWTRUNC, tcp_timer_2msl, tp); else callout_reset(tp->tt_2msl, 2 * tcp_msl, tcp_timer_2msl, tp); soisdisconnected(so); } break; /* * In LAST_ACK, we may still be waiting for data to drain * and/or to be acked, as well as for the ack of our FIN. * If our FIN is now acknowledged, delete the TCB, * enter the closed state and return. */ case TCPS_LAST_ACK: if (ourfinisacked) { tp = tcp_close(tp); goto drop; } break; /* * In TIME_WAIT state the only thing that should arrive * is a retransmission of the remote FIN. Acknowledge * it and restart the finack timer. */ case TCPS_TIME_WAIT: callout_reset(tp->tt_2msl, 2 * tcp_msl, tcp_timer_2msl, tp); goto dropafterack; } } step6: /* * Update window information. * Don't look at window if no ACK: TAC's send garbage on first SYN. */ if ((thflags & TH_ACK) && (SEQ_LT(tp->snd_wl1, th->th_seq) || (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { /* keep track of pure window updates */ if (tlen == 0 && tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) tcpstat.tcps_rcvwinupd++; tp->snd_wnd = tiwin; tp->snd_wl1 = th->th_seq; tp->snd_wl2 = th->th_ack; if (tp->snd_wnd > tp->max_sndwnd) tp->max_sndwnd = tp->snd_wnd; needoutput = 1; } /* * Process segments with URG. */ if ((thflags & TH_URG) && th->th_urp && TCPS_HAVERCVDFIN(tp->t_state) == 0) { /* * This is a kludge, but if we receive and accept * random urgent pointers, we'll crash in * soreceive. It's hard to imagine someone * actually wanting to send this much urgent data. */ if (th->th_urp + so->so_rcv.sb_cc > sb_max) { th->th_urp = 0; /* XXX */ thflags &= ~TH_URG; /* XXX */ goto dodata; /* XXX */ } /* * If this segment advances the known urgent pointer, * then mark the data stream. This should not happen * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since * a FIN has been received from the remote side. * In these states we ignore the URG. * * According to RFC961 (Assigned Protocols), * the urgent pointer points to the last octet * of urgent data. We continue, however, * to consider it to indicate the first octet * of data past the urgent section as the original * spec states (in one of two places). */ if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { tp->rcv_up = th->th_seq + th->th_urp; so->so_oobmark = so->so_rcv.sb_cc + (tp->rcv_up - tp->rcv_nxt) - 1; if (so->so_oobmark == 0) so->so_state |= SS_RCVATMARK; sohasoutofband(so); tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); } /* * Remove out of band data so doesn't get presented to user. * This can happen independent of advancing the URG pointer, * but if two URG's are pending at once, some out-of-band * data may creep in... ick. */ if (th->th_urp <= (u_long)tlen #ifdef SO_OOBINLINE && (so->so_options & SO_OOBINLINE) == 0 #endif ) tcp_pulloutofband(so, th, m, drop_hdrlen); /* hdr drop is delayed */ } else /* * If no out of band data is expected, * pull receive urgent pointer along * with the receive window. */ if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) tp->rcv_up = tp->rcv_nxt; dodata: /* XXX */ /* * Process the segment text, merging it into the TCP sequencing queue, * and arranging for acknowledgment of receipt if necessary. * This process logically involves adjusting tp->rcv_wnd as data * is presented to the user (this happens in tcp_usrreq.c, * case PRU_RCVD). If a FIN has already been received on this * connection then we just ignore the text. */ if ((tlen || (thflags&TH_FIN)) && TCPS_HAVERCVDFIN(tp->t_state) == 0) { m_adj(m, drop_hdrlen); /* delayed header drop */ TCP_REASS(tp, th, &tlen, m, so, thflags); /* * Note the amount of data that peer has sent into * our window, in order to estimate the sender's * buffer size. */ len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); } else { m_freem(m); thflags &= ~TH_FIN; } /* * If FIN is received ACK the FIN and let the user know * that the connection is closing. */ if (thflags & TH_FIN) { if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { socantrcvmore(so); /* * If connection is half-synchronized * (ie NEEDSYN flag on) then delay ACK, * so it may be piggybacked when SYN is sent. * Otherwise, since we received a FIN then no * more input can be expected, send ACK now. */ if (tcp_delack_enabled && (tp->t_flags & TF_NEEDSYN)) callout_reset(tp->tt_delack, tcp_delacktime, tcp_timer_delack, tp); else tp->t_flags |= TF_ACKNOW; tp->rcv_nxt++; } switch (tp->t_state) { /* * In SYN_RECEIVED and ESTABLISHED STATES * enter the CLOSE_WAIT state. */ case TCPS_SYN_RECEIVED: tp->t_starttime = ticks; /*FALLTHROUGH*/ case TCPS_ESTABLISHED: tp->t_state = TCPS_CLOSE_WAIT; break; /* * If still in FIN_WAIT_1 STATE FIN has not been acked so * enter the CLOSING state. */ case TCPS_FIN_WAIT_1: tp->t_state = TCPS_CLOSING; break; /* * In FIN_WAIT_2 state enter the TIME_WAIT state, * starting the time-wait timer, turning off the other * standard timers. */ case TCPS_FIN_WAIT_2: tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); /* Shorten TIME_WAIT [RFC-1644, p.28] */ if (tp->cc_recv != 0 && (ticks - tp->t_starttime) < tcp_msl) { callout_reset(tp->tt_2msl, tp->t_rxtcur * TCPTV_TWTRUNC, tcp_timer_2msl, tp); /* For transaction client, force ACK now. */ tp->t_flags |= TF_ACKNOW; } else callout_reset(tp->tt_2msl, 2 * tcp_msl, tcp_timer_2msl, tp); soisdisconnected(so); break; /* * In TIME_WAIT state restart the 2 MSL time_wait timer. */ case TCPS_TIME_WAIT: callout_reset(tp->tt_2msl, 2 * tcp_msl, tcp_timer_2msl, tp); break; } } #ifdef TCPDEBUG if (so->so_options & SO_DEBUG) tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, &tcp_savetcp, 0); #endif /* * Return any desired output. */ if (needoutput || (tp->t_flags & TF_ACKNOW)) (void) tcp_output(tp); return; dropafterack: /* * Generate an ACK dropping incoming segment if it occupies * sequence space, where the ACK reflects our state. * * We can now skip the test for the RST flag since all * paths to this code happen after packets containing * RST have been dropped. * * In the SYN-RECEIVED state, don't send an ACK unless the * segment we received passes the SYN-RECEIVED ACK test. * If it fails send a RST. This breaks the loop in the * "LAND" DoS attack, and also prevents an ACK storm * between two listening ports that have been sent forged * SYN segments, each with the source address of the other. */ if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && (SEQ_GT(tp->snd_una, th->th_ack) || SEQ_GT(th->th_ack, tp->snd_max)) ) goto maybedropwithreset; #ifdef TCPDEBUG if (so->so_options & SO_DEBUG) tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, &tcp_savetcp, 0); #endif m_freem(m); tp->t_flags |= TF_ACKNOW; (void) tcp_output(tp); return; /* * Conditionally drop with reset or just drop depending on whether * we think we are under attack or not. */ maybedropwithreset: #ifdef ICMP_BANDLIM if (badport_bandlim(1) < 0) goto drop; #endif /* fall through */ dropwithreset: #ifdef TCP_RESTRICT_RST if (restrict_rst) goto drop; #endif /* * Generate a RST, dropping incoming segment. * Make ACK acceptable to originator of segment. * Don't bother to respond if destination was broadcast/multicast. */ if ((thflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) goto drop; #ifdef INET6 if (isipv6) { if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) goto drop; } else #endif /* INET6 */ if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || ip->ip_src.s_addr == htonl(INADDR_BROADCAST)) goto drop; /* IPv6 anycast check is done at tcp6_input() */ #ifdef TCPDEBUG if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, &tcp_savetcp, 0); #endif if (thflags & TH_ACK) /* mtod() below is safe as long as hdr dropping is delayed */ tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, TH_RST); else { if (thflags & TH_SYN) tlen++; /* mtod() below is safe as long as hdr dropping is delayed */ tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, (tcp_seq)0, TH_RST|TH_ACK); } /* destroy temporarily created socket */ if (dropsocket) (void) soabort(so); return; drop: /* * Drop space held by incoming segment and return. */ #ifdef TCPDEBUG if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, &tcp_savetcp, 0); #endif m_freem(m); /* destroy temporarily created socket */ if (dropsocket) (void) soabort(so); return; } static void tcp_dooptions(tp, cp, cnt, th, to) struct tcpcb *tp; u_char *cp; int cnt; struct tcphdr *th; struct tcpopt *to; { u_short mss = 0; int opt, optlen; for (; cnt > 0; cnt -= optlen, cp += optlen) { opt = cp[0]; if (opt == TCPOPT_EOL) break; if (opt == TCPOPT_NOP) optlen = 1; else { optlen = cp[1]; if (optlen <= 0) break; } switch (opt) { default: continue; case TCPOPT_MAXSEG: if (optlen != TCPOLEN_MAXSEG) continue; if (!(th->th_flags & TH_SYN)) continue; bcopy((char *) cp + 2, (char *) &mss, sizeof(mss)); NTOHS(mss); break; case TCPOPT_WINDOW: if (optlen != TCPOLEN_WINDOW) continue; if (!(th->th_flags & TH_SYN)) continue; tp->t_flags |= TF_RCVD_SCALE; tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); break; case TCPOPT_TIMESTAMP: if (optlen != TCPOLEN_TIMESTAMP) continue; to->to_flag |= TOF_TS; bcopy((char *)cp + 2, (char *)&to->to_tsval, sizeof(to->to_tsval)); NTOHL(to->to_tsval); bcopy((char *)cp + 6, (char *)&to->to_tsecr, sizeof(to->to_tsecr)); NTOHL(to->to_tsecr); /* * A timestamp received in a SYN makes * it ok to send timestamp requests and replies. */ if (th->th_flags & TH_SYN) { tp->t_flags |= TF_RCVD_TSTMP; tp->ts_recent = to->to_tsval; tp->ts_recent_age = ticks; } break; case TCPOPT_CC: if (optlen != TCPOLEN_CC) continue; to->to_flag |= TOF_CC; bcopy((char *)cp + 2, (char *)&to->to_cc, sizeof(to->to_cc)); NTOHL(to->to_cc); /* * A CC or CC.new option received in a SYN makes * it ok to send CC in subsequent segments. */ if (th->th_flags & TH_SYN) tp->t_flags |= TF_RCVD_CC; break; case TCPOPT_CCNEW: if (optlen != TCPOLEN_CC) continue; if (!(th->th_flags & TH_SYN)) continue; to->to_flag |= TOF_CCNEW; bcopy((char *)cp + 2, (char *)&to->to_cc, sizeof(to->to_cc)); NTOHL(to->to_cc); /* * A CC or CC.new option received in a SYN makes * it ok to send CC in subsequent segments. */ tp->t_flags |= TF_RCVD_CC; break; case TCPOPT_CCECHO: if (optlen != TCPOLEN_CC) continue; if (!(th->th_flags & TH_SYN)) continue; to->to_flag |= TOF_CCECHO; bcopy((char *)cp + 2, (char *)&to->to_ccecho, sizeof(to->to_ccecho)); NTOHL(to->to_ccecho); break; } } if (th->th_flags & TH_SYN) tcp_mss(tp, mss); /* sets t_maxseg */ } /* * Pull out of band byte out of a segment so * it doesn't appear in the user's data queue. * It is still reflected in the segment length for * sequencing purposes. */ static void tcp_pulloutofband(so, th, m, off) struct socket *so; struct tcphdr *th; register struct mbuf *m; int off; /* delayed to be droped hdrlen */ { int cnt = off + th->th_urp - 1; while (cnt >= 0) { if (m->m_len > cnt) { char *cp = mtod(m, caddr_t) + cnt; struct tcpcb *tp = sototcpcb(so); tp->t_iobc = *cp; tp->t_oobflags |= TCPOOB_HAVEDATA; bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); m->m_len--; if (m->m_flags & M_PKTHDR) m->m_pkthdr.len--; return; } cnt -= m->m_len; m = m->m_next; if (m == 0) break; } panic("tcp_pulloutofband"); } /* * Collect new round-trip time estimate * and update averages and current timeout. */ static void tcp_xmit_timer(tp, rtt) register struct tcpcb *tp; int rtt; { register int delta; tcpstat.tcps_rttupdated++; tp->t_rttupdated++; if (tp->t_srtt != 0) { /* * srtt is stored as fixed point with 5 bits after the * binary point (i.e., scaled by 8). The following magic * is equivalent to the smoothing algorithm in rfc793 with * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed * point). Adjust rtt to origin 0. */ delta = ((rtt - 1) << TCP_DELTA_SHIFT) - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); if ((tp->t_srtt += delta) <= 0) tp->t_srtt = 1; /* * We accumulate a smoothed rtt variance (actually, a * smoothed mean difference), then set the retransmit * timer to smoothed rtt + 4 times the smoothed variance. * rttvar is stored as fixed point with 4 bits after the * binary point (scaled by 16). The following is * equivalent to rfc793 smoothing with an alpha of .75 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces * rfc793's wired-in beta. */ if (delta < 0) delta = -delta; delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); if ((tp->t_rttvar += delta) <= 0) tp->t_rttvar = 1; } else { /* * No rtt measurement yet - use the unsmoothed rtt. * Set the variance to half the rtt (so our first * retransmit happens at 3*rtt). */ tp->t_srtt = rtt << TCP_RTT_SHIFT; tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); } tp->t_rtttime = 0; tp->t_rxtshift = 0; /* * the retransmit should happen at rtt + 4 * rttvar. * Because of the way we do the smoothing, srtt and rttvar * will each average +1/2 tick of bias. When we compute * the retransmit timer, we want 1/2 tick of rounding and * 1 extra tick because of +-1/2 tick uncertainty in the * firing of the timer. The bias will give us exactly the * 1.5 tick we need. But, because the bias is * statistical, we have to test that we don't drop below * the minimum feasible timer (which is 2 ticks). */ TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); /* * We received an ack for a packet that wasn't retransmitted; * it is probably safe to discard any error indications we've * received recently. This isn't quite right, but close enough * for now (a route might have failed after we sent a segment, * and the return path might not be symmetrical). */ tp->t_softerror = 0; } /* * Determine a reasonable value for maxseg size. * If the route is known, check route for mtu. * If none, use an mss that can be handled on the outgoing * interface without forcing IP to fragment; if bigger than * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES * to utilize large mbufs. If no route is found, route has no mtu, * or the destination isn't local, use a default, hopefully conservative * size (usually 512 or the default IP max size, but no more than the mtu * of the interface), as we can't discover anything about intervening * gateways or networks. We also initialize the congestion/slow start * window to be a single segment if the destination isn't local. * While looking at the routing entry, we also initialize other path-dependent * parameters from pre-set or cached values in the routing entry. * * Also take into account the space needed for options that we * send regularly. Make maxseg shorter by that amount to assure * that we can send maxseg amount of data even when the options * are present. Store the upper limit of the length of options plus * data in maxopd. * * NOTE that this routine is only called when we process an incoming * segment, for outgoing segments only tcp_mssopt is called. * * In case of T/TCP, we call this routine during implicit connection * setup as well (offer = -1), to initialize maxseg from the cached * MSS of our peer. */ void tcp_mss(tp, offer) struct tcpcb *tp; int offer; { register struct rtentry *rt; struct ifnet *ifp; register int rtt, mss; u_long bufsize; struct inpcb *inp; struct socket *so; struct rmxp_tao *taop; int origoffer = offer; #ifdef INET6 int isipv6; int min_protoh; #endif inp = tp->t_inpcb; #ifdef INET6 isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; min_protoh = isipv6 ? sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : sizeof (struct tcpiphdr); #else #define min_protoh (sizeof (struct tcpiphdr)) #endif #ifdef INET6 if (isipv6) rt = tcp_rtlookup6(inp); else #endif rt = tcp_rtlookup(inp); if (rt == NULL) { tp->t_maxopd = tp->t_maxseg = #ifdef INET6 isipv6 ? tcp_v6mssdflt : #endif /* INET6 */ tcp_mssdflt; return; } ifp = rt->rt_ifp; so = inp->inp_socket; taop = rmx_taop(rt->rt_rmx); /* * Offer == -1 means that we didn't receive SYN yet, * use cached value in that case; */ if (offer == -1) offer = taop->tao_mssopt; /* * Offer == 0 means that there was no MSS on the SYN segment, * in this case we use tcp_mssdflt. */ if (offer == 0) offer = #ifdef INET6 isipv6 ? tcp_v6mssdflt : #endif /* INET6 */ tcp_mssdflt; else /* * Sanity check: make sure that maxopd will be large * enough to allow some data on segments even is the * all the option space is used (40bytes). Otherwise * funny things may happen in tcp_output. */ offer = max(offer, 64); taop->tao_mssopt = offer; /* * While we're here, check if there's an initial rtt * or rttvar. Convert from the route-table units * to scaled multiples of the slow timeout timer. */ if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { /* * XXX the lock bit for RTT indicates that the value * is also a minimum value; this is subject to time. */ if (rt->rt_rmx.rmx_locks & RTV_RTT) tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); tcpstat.tcps_usedrtt++; if (rt->rt_rmx.rmx_rttvar) { tp->t_rttvar = rt->rt_rmx.rmx_rttvar / (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); tcpstat.tcps_usedrttvar++; } else { /* default variation is +- 1 rtt */ tp->t_rttvar = tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; } TCPT_RANGESET(tp->t_rxtcur, ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, tp->t_rttmin, TCPTV_REXMTMAX); } /* * if there's an mtu associated with the route, use it * else, use the link mtu. */ if (rt->rt_rmx.rmx_mtu) mss = rt->rt_rmx.rmx_mtu - min_protoh; else { mss = #ifdef INET6 (isipv6 ? nd_ifinfo[rt->rt_ifp->if_index].linkmtu : #endif ifp->if_mtu #ifdef INET6 ) #endif - min_protoh; #ifdef INET6 if (isipv6) { if (!in6_localaddr(&inp->in6p_faddr)) mss = min(mss, tcp_v6mssdflt); } else #endif if (!in_localaddr(inp->inp_faddr)) mss = min(mss, tcp_mssdflt); } mss = min(mss, offer); /* * maxopd stores the maximum length of data AND options * in a segment; maxseg is the amount of data in a normal * segment. We need to store this value (maxopd) apart * from maxseg, because now every segment carries options * and thus we normally have somewhat less data in segments. */ tp->t_maxopd = mss; /* * In case of T/TCP, origoffer==-1 indicates, that no segments * were received yet. In this case we just guess, otherwise * we do the same as before T/TCP. */ if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && (origoffer == -1 || (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 && (origoffer == -1 || (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 there's a pipesize, change the socket buffer * to that size. Make the socket buffers an integral * number of mss units; if the mss is larger than * the socket buffer, decrease the mss. */ #ifdef RTV_SPIPE if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) #endif bufsize = so->so_snd.sb_hiwat; if (bufsize < mss) mss = bufsize; else { bufsize = roundup(bufsize, mss); if (bufsize > sb_max) bufsize = sb_max; (void)sbreserve(&so->so_snd, bufsize, so, NULL); } tp->t_maxseg = mss; #ifdef RTV_RPIPE if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) #endif bufsize = so->so_rcv.sb_hiwat; if (bufsize > mss) { bufsize = roundup(bufsize, mss); if (bufsize > sb_max) bufsize = sb_max; (void)sbreserve(&so->so_rcv, bufsize, so, NULL); } /* * Set the slow-start flight size depending on whether this * is a local network or not. */ if ( #ifdef INET6 (isipv6 && in6_localaddr(&inp->in6p_faddr)) || (!isipv6 && #endif in_localaddr(inp->inp_faddr) #ifdef INET6 ) #endif ) tp->snd_cwnd = mss * ss_fltsz_local; else tp->snd_cwnd = mss * ss_fltsz; if (rt->rt_rmx.rmx_ssthresh) { /* * There's some sort of gateway or interface * buffer limit on the path. Use this to set * the slow start threshhold, but set the * threshold to no less than 2*mss. */ tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); tcpstat.tcps_usedssthresh++; } } /* * Determine the MSS option to send on an outgoing SYN. */ int tcp_mssopt(tp) struct tcpcb *tp; { struct rtentry *rt; #ifdef INET6 int isipv6; int min_protoh; #endif #ifdef INET6 isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) ? 1 : 0; min_protoh = isipv6 ? sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : sizeof (struct tcpiphdr); #else #define min_protoh (sizeof (struct tcpiphdr)) #endif #ifdef INET6 if (isipv6) rt = tcp_rtlookup6(tp->t_inpcb); else #endif /* INET6 */ rt = tcp_rtlookup(tp->t_inpcb); if (rt == NULL) return #ifdef INET6 isipv6 ? tcp_v6mssdflt : #endif /* INET6 */ tcp_mssdflt; return rt->rt_ifp->if_mtu - min_protoh; }