/* $OpenBSD: tcp_input.c,v 1.368 2021/04/16 12:08:25 bluhm Exp $ */ /* $NetBSD: tcp_input.c,v 1.23 1996/02/13 23:43:44 christos Exp $ */ /* * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994 * 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. 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. * * @(#)COPYRIGHT 1.1 (NRL) 17 January 1995 * * NRL grants permission for redistribution and use in source and binary * forms, with or without modification, of the software and documentation * created at NRL 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 acknowledgements: * This product includes software developed by the University of * California, Berkeley and its contributors. * This product includes software developed at the Information * Technology Division, US Naval Research Laboratory. * 4. Neither the name of the NRL nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THE SOFTWARE PROVIDED BY NRL IS PROVIDED BY NRL 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 NRL 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. * * The views and conclusions contained in the software and documentation * are those of the authors and should not be interpreted as representing * official policies, either expressed or implied, of the US Naval * Research Laboratory (NRL). */ #include "pf.h" #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #if NPF > 0 #include #endif struct tcpiphdr tcp_saveti; int tcp_mss_adv(struct mbuf *, int); int tcp_flush_queue(struct tcpcb *); #ifdef INET6 #include #include struct tcpipv6hdr tcp_saveti6; /* for the packet header length in the mbuf */ #define M_PH_LEN(m) (((struct mbuf *)(m))->m_pkthdr.len) #define M_V6_LEN(m) (M_PH_LEN(m) - sizeof(struct ip6_hdr)) #define M_V4_LEN(m) (M_PH_LEN(m) - sizeof(struct ip)) #endif /* INET6 */ int tcprexmtthresh = 3; int tcptv_keep_init = TCPTV_KEEP_INIT; int tcp_rst_ppslim = 100; /* 100pps */ int tcp_rst_ppslim_count = 0; struct timeval tcp_rst_ppslim_last; int tcp_ackdrop_ppslim = 100; /* 100pps */ int tcp_ackdrop_ppslim_count = 0; struct timeval tcp_ackdrop_ppslim_last; #define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ) /* for modulo comparisons of timestamps */ #define TSTMP_LT(a,b) ((int)((a)-(b)) < 0) #define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0) /* for TCP SACK comparisons */ #define SEQ_MIN(a,b) (SEQ_LT(a,b) ? (a) : (b)) #define SEQ_MAX(a,b) (SEQ_GT(a,b) ? (a) : (b)) /* * Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ #ifdef INET6 #define ND6_HINT(tp) \ do { \ if (tp && tp->t_inpcb && (tp->t_inpcb->inp_flags & INP_IPV6) && \ rtisvalid(tp->t_inpcb->inp_route6.ro_rt)) { \ nd6_nud_hint(tp->t_inpcb->inp_route6.ro_rt); \ } \ } while (0) #else #define ND6_HINT(tp) #endif #ifdef TCP_ECN /* * ECN (Explicit Congestion Notification) support based on RFC3168 * implementation note: * snd_last is used to track a recovery phase. * when cwnd is reduced, snd_last is set to snd_max. * while snd_last > snd_una, the sender is in a recovery phase and * its cwnd should not be reduced again. * snd_last follows snd_una when not in a recovery phase. */ #endif /* * Macro to compute ACK transmission behavior. Delay the ACK unless * we have already delayed an ACK (must send an ACK every two segments). * We also ACK immediately if we received a PUSH and the ACK-on-PUSH * option is enabled or when the packet is coming from a loopback * interface. */ #define TCP_SETUP_ACK(tp, tiflags, m) \ do { \ struct ifnet *ifp = NULL; \ if (m && (m->m_flags & M_PKTHDR)) \ ifp = if_get(m->m_pkthdr.ph_ifidx); \ if (TCP_TIMER_ISARMED(tp, TCPT_DELACK) || \ (tcp_ack_on_push && (tiflags) & TH_PUSH) || \ (ifp && (ifp->if_flags & IFF_LOOPBACK))) \ tp->t_flags |= TF_ACKNOW; \ else \ TCP_TIMER_ARM_MSEC(tp, TCPT_DELACK, tcp_delack_msecs); \ if_put(ifp); \ } while (0) void tcp_sack_partialack(struct tcpcb *, struct tcphdr *); void tcp_newreno_partialack(struct tcpcb *, struct tcphdr *); void syn_cache_put(struct syn_cache *); void syn_cache_rm(struct syn_cache *); int syn_cache_respond(struct syn_cache *, struct mbuf *); void syn_cache_timer(void *); void syn_cache_reaper(void *); void syn_cache_insert(struct syn_cache *, struct tcpcb *); void syn_cache_reset(struct sockaddr *, struct sockaddr *, struct tcphdr *, u_int); int syn_cache_add(struct sockaddr *, struct sockaddr *, struct tcphdr *, unsigned int, struct socket *, struct mbuf *, u_char *, int, struct tcp_opt_info *, tcp_seq *); struct socket *syn_cache_get(struct sockaddr *, struct sockaddr *, struct tcphdr *, unsigned int, unsigned int, struct socket *, struct mbuf *); struct syn_cache *syn_cache_lookup(struct sockaddr *, struct sockaddr *, struct syn_cache_head **, u_int); /* * Insert segment ti 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). */ int tcp_reass(struct tcpcb *tp, struct tcphdr *th, struct mbuf *m, int *tlen) { struct tcpqent *p, *q, *nq, *tiqe; /* * Allocate a new queue entry, before we throw away any data. * If we can't, just drop the packet. XXX */ tiqe = pool_get(&tcpqe_pool, PR_NOWAIT); if (tiqe == NULL) { tiqe = TAILQ_LAST(&tp->t_segq, tcpqehead); if (tiqe != NULL && th->th_seq == tp->rcv_nxt) { /* Reuse last entry since new segment fills a hole */ m_freem(tiqe->tcpqe_m); TAILQ_REMOVE(&tp->t_segq, tiqe, tcpqe_q); } if (tiqe == NULL || th->th_seq != tp->rcv_nxt) { /* Flush segment queue for this connection */ tcp_freeq(tp); tcpstat_inc(tcps_rcvmemdrop); m_freem(m); return (0); } } /* * Find a segment which begins after this one does. */ for (p = NULL, q = TAILQ_FIRST(&tp->t_segq); q != NULL; p = q, q = TAILQ_NEXT(q, tcpqe_q)) if (SEQ_GT(q->tcpqe_tcp->th_seq, th->th_seq)) break; /* * 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) { struct tcphdr *phdr = p->tcpqe_tcp; int i; /* conversion to int (in i) handles seq wraparound */ i = phdr->th_seq + phdr->th_reseqlen - th->th_seq; if (i > 0) { if (i >= *tlen) { tcpstat_pkt(tcps_rcvduppack, tcps_rcvdupbyte, *tlen); m_freem(m); pool_put(&tcpqe_pool, tiqe); return (0); } m_adj(m, i); *tlen -= i; th->th_seq += i; } } tcpstat_pkt(tcps_rcvoopack, tcps_rcvoobyte, *tlen); /* * While we overlap succeeding segments trim them or, * if they are completely covered, dequeue them. */ for (; q != NULL; q = nq) { struct tcphdr *qhdr = q->tcpqe_tcp; int i = (th->th_seq + *tlen) - qhdr->th_seq; if (i <= 0) break; if (i < qhdr->th_reseqlen) { qhdr->th_seq += i; qhdr->th_reseqlen -= i; m_adj(q->tcpqe_m, i); break; } nq = TAILQ_NEXT(q, tcpqe_q); m_freem(q->tcpqe_m); TAILQ_REMOVE(&tp->t_segq, q, tcpqe_q); pool_put(&tcpqe_pool, q); } /* Insert the new segment queue entry into place. */ tiqe->tcpqe_m = m; th->th_reseqlen = *tlen; tiqe->tcpqe_tcp = th; if (p == NULL) { TAILQ_INSERT_HEAD(&tp->t_segq, tiqe, tcpqe_q); } else { TAILQ_INSERT_AFTER(&tp->t_segq, p, tiqe, tcpqe_q); } if (th->th_seq != tp->rcv_nxt) return (0); return (tcp_flush_queue(tp)); } int tcp_flush_queue(struct tcpcb *tp) { struct socket *so = tp->t_inpcb->inp_socket; struct tcpqent *q, *nq; int flags; /* * Present data to user, advancing rcv_nxt through * completed sequence space. */ if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) return (0); q = TAILQ_FIRST(&tp->t_segq); if (q == NULL || q->tcpqe_tcp->th_seq != tp->rcv_nxt) return (0); if (tp->t_state == TCPS_SYN_RECEIVED && q->tcpqe_tcp->th_reseqlen) return (0); do { tp->rcv_nxt += q->tcpqe_tcp->th_reseqlen; flags = q->tcpqe_tcp->th_flags & TH_FIN; nq = TAILQ_NEXT(q, tcpqe_q); TAILQ_REMOVE(&tp->t_segq, q, tcpqe_q); ND6_HINT(tp); if (so->so_state & SS_CANTRCVMORE) m_freem(q->tcpqe_m); else sbappendstream(so, &so->so_rcv, q->tcpqe_m); pool_put(&tcpqe_pool, q); q = nq; } while (q != NULL && q->tcpqe_tcp->th_seq == tp->rcv_nxt); tp->t_flags |= TF_BLOCKOUTPUT; sorwakeup(so); tp->t_flags &= ~TF_BLOCKOUTPUT; return (flags); } /* * TCP input routine, follows pages 65-76 of the * protocol specification dated September, 1981 very closely. */ int tcp_input(struct mbuf **mp, int *offp, int proto, int af) { struct mbuf *m = *mp; int iphlen = *offp; struct ip *ip = NULL; struct inpcb *inp = NULL; u_int8_t *optp = NULL; int optlen = 0; int tlen, off; struct tcpcb *otp = NULL, *tp = NULL; int tiflags; struct socket *so = NULL; int todrop, acked, ourfinisacked; int hdroptlen = 0; short ostate; caddr_t saveti; tcp_seq iss, *reuse = NULL; u_long tiwin; struct tcp_opt_info opti; struct tcphdr *th; #ifdef INET6 struct ip6_hdr *ip6 = NULL; #endif /* INET6 */ #ifdef IPSEC struct m_tag *mtag; struct tdb_ident *tdbi; struct tdb *tdb; int error; #endif /* IPSEC */ #ifdef TCP_ECN u_char iptos; #endif tcpstat_inc(tcps_rcvtotal); opti.ts_present = 0; opti.maxseg = 0; /* * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN */ if (m->m_flags & (M_BCAST|M_MCAST)) goto drop; /* * Get IP and TCP header together in first mbuf. * Note: IP leaves IP header in first mbuf. */ IP6_EXTHDR_GET(th, struct tcphdr *, m, iphlen, sizeof(*th)); if (!th) { tcpstat_inc(tcps_rcvshort); return IPPROTO_DONE; } tlen = m->m_pkthdr.len - iphlen; switch (af) { case AF_INET: ip = mtod(m, struct ip *); #ifdef TCP_ECN /* save ip_tos before clearing it for checksum */ iptos = ip->ip_tos; #endif break; #ifdef INET6 case AF_INET6: ip6 = mtod(m, struct ip6_hdr *); #ifdef TCP_ECN iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; #endif /* * Be proactive about unspecified IPv6 address in source. * As we use all-zero to indicate unbounded/unconnected pcb, * unspecified IPv6 address can be used to confuse us. * * Note that packets with unspecified IPv6 destination is * already dropped in ip6_input. */ if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { /* XXX stat */ goto drop; } /* Discard packets to multicast */ if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) { /* XXX stat */ goto drop; } break; #endif default: unhandled_af(af); } /* * Checksum extended TCP header and data. */ if ((m->m_pkthdr.csum_flags & M_TCP_CSUM_IN_OK) == 0) { int sum; if (m->m_pkthdr.csum_flags & M_TCP_CSUM_IN_BAD) { tcpstat_inc(tcps_rcvbadsum); goto drop; } tcpstat_inc(tcps_inswcsum); switch (af) { case AF_INET: sum = in4_cksum(m, IPPROTO_TCP, iphlen, tlen); break; #ifdef INET6 case AF_INET6: sum = in6_cksum(m, IPPROTO_TCP, sizeof(struct ip6_hdr), tlen); break; #endif } if (sum != 0) { tcpstat_inc(tcps_rcvbadsum); goto drop; } } /* * 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_inc(tcps_rcvbadoff); goto drop; } tlen -= off; if (off > sizeof(struct tcphdr)) { IP6_EXTHDR_GET(th, struct tcphdr *, m, iphlen, off); if (!th) { tcpstat_inc(tcps_rcvshort); return IPPROTO_DONE; } optlen = off - sizeof(struct tcphdr); optp = (u_int8_t *)(th + 1); /* * Do quick retrieval of timestamp options ("options * prediction?"). If timestamp is the only option and it's * formatted as recommended in RFC 1323 appendix A, we * quickly get the values now and not bother calling * tcp_dooptions(), etc. */ if ((optlen == TCPOLEN_TSTAMP_APPA || (optlen > TCPOLEN_TSTAMP_APPA && optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) && *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) && (th->th_flags & TH_SYN) == 0) { opti.ts_present = 1; opti.ts_val = ntohl(*(u_int32_t *)(optp + 4)); opti.ts_ecr = ntohl(*(u_int32_t *)(optp + 8)); optp = NULL; /* we've parsed the options */ } } tiflags = th->th_flags; /* * Convert TCP protocol specific fields to host format. */ th->th_seq = ntohl(th->th_seq); th->th_ack = ntohl(th->th_ack); th->th_win = ntohs(th->th_win); th->th_urp = ntohs(th->th_urp); /* * Locate pcb for segment. */ #if NPF > 0 inp = pf_inp_lookup(m); #endif findpcb: if (inp == NULL) { switch (af) { #ifdef INET6 case AF_INET6: inp = in6_pcbhashlookup(&tcbtable, &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, m->m_pkthdr.ph_rtableid); break; #endif case AF_INET: inp = in_pcbhashlookup(&tcbtable, ip->ip_src, th->th_sport, ip->ip_dst, th->th_dport, m->m_pkthdr.ph_rtableid); break; } } if (inp == NULL) { tcpstat_inc(tcps_pcbhashmiss); switch (af) { #ifdef INET6 case AF_INET6: inp = in6_pcblookup_listen(&tcbtable, &ip6->ip6_dst, th->th_dport, m, m->m_pkthdr.ph_rtableid); break; #endif /* INET6 */ case AF_INET: inp = in_pcblookup_listen(&tcbtable, ip->ip_dst, th->th_dport, m, m->m_pkthdr.ph_rtableid); break; } /* * 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. */ } #ifdef IPSEC if (ipsec_in_use) { /* Find most recent IPsec tag */ mtag = m_tag_find(m, PACKET_TAG_IPSEC_IN_DONE, NULL); if (mtag != NULL) { tdbi = (struct tdb_ident *)(mtag + 1); tdb = gettdb(tdbi->rdomain, tdbi->spi, &tdbi->dst, tdbi->proto); } else tdb = NULL; ipsp_spd_lookup(m, af, iphlen, &error, IPSP_DIRECTION_IN, tdb, inp, 0); if (error) { tcpstat_inc(tcps_rcvnosec); goto drop; } } #endif /* IPSEC */ if (inp == NULL) { tcpstat_inc(tcps_noport); goto dropwithreset_ratelim; } KASSERT(sotoinpcb(inp->inp_socket) == inp); KASSERT(intotcpcb(inp) == NULL || intotcpcb(inp)->t_inpcb == inp); soassertlocked(inp->inp_socket); /* Check the minimum TTL for socket. */ switch (af) { case AF_INET: if (inp->inp_ip_minttl && inp->inp_ip_minttl > ip->ip_ttl) goto drop; break; #ifdef INET6 case AF_INET6: if (inp->inp_ip6_minhlim && inp->inp_ip6_minhlim > ip6->ip6_hlim) goto drop; break; #endif } tp = intotcpcb(inp); if (tp == NULL) goto dropwithreset_ratelim; if (tp->t_state == TCPS_CLOSED) goto drop; /* Unscale the window into a 32-bit value. */ if ((tiflags & TH_SYN) == 0) tiwin = th->th_win << tp->snd_scale; else tiwin = th->th_win; so = inp->inp_socket; if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { union syn_cache_sa src; union syn_cache_sa dst; bzero(&src, sizeof(src)); bzero(&dst, sizeof(dst)); switch (af) { case AF_INET: src.sin.sin_len = sizeof(struct sockaddr_in); src.sin.sin_family = AF_INET; src.sin.sin_addr = ip->ip_src; src.sin.sin_port = th->th_sport; dst.sin.sin_len = sizeof(struct sockaddr_in); dst.sin.sin_family = AF_INET; dst.sin.sin_addr = ip->ip_dst; dst.sin.sin_port = th->th_dport; break; #ifdef INET6 case AF_INET6: src.sin6.sin6_len = sizeof(struct sockaddr_in6); src.sin6.sin6_family = AF_INET6; src.sin6.sin6_addr = ip6->ip6_src; src.sin6.sin6_port = th->th_sport; dst.sin6.sin6_len = sizeof(struct sockaddr_in6); dst.sin6.sin6_family = AF_INET6; dst.sin6.sin6_addr = ip6->ip6_dst; dst.sin6.sin6_port = th->th_dport; break; #endif /* INET6 */ } if (so->so_options & SO_DEBUG) { otp = tp; ostate = tp->t_state; switch (af) { #ifdef INET6 case AF_INET6: saveti = (caddr_t) &tcp_saveti6; memcpy(&tcp_saveti6.ti6_i, ip6, sizeof(*ip6)); memcpy(&tcp_saveti6.ti6_t, th, sizeof(*th)); break; #endif case AF_INET: saveti = (caddr_t) &tcp_saveti; memcpy(&tcp_saveti.ti_i, ip, sizeof(*ip)); memcpy(&tcp_saveti.ti_t, th, sizeof(*th)); break; } } if (so->so_options & SO_ACCEPTCONN) { switch (tiflags & (TH_RST|TH_SYN|TH_ACK)) { case TH_SYN|TH_ACK|TH_RST: case TH_SYN|TH_RST: case TH_ACK|TH_RST: case TH_RST: syn_cache_reset(&src.sa, &dst.sa, th, inp->inp_rtableid); goto drop; case TH_SYN|TH_ACK: /* * Received a SYN,ACK. This should * never happen while we are in * LISTEN. Send an RST. */ goto badsyn; case TH_ACK: so = syn_cache_get(&src.sa, &dst.sa, th, iphlen, tlen, so, m); if (so == NULL) { /* * We don't have a SYN for * this ACK; send an RST. */ goto badsyn; } else if (so == (struct socket *)(-1)) { /* * We were unable to create * the connection. If the * 3-way handshake was * completed, and RST has * been sent to the peer. * Since the mbuf might be * in use for the reply, * do not free it. */ m = *mp = NULL; goto drop; } else { /* * We have created a * full-blown connection. */ tp = NULL; inp = sotoinpcb(so); tp = intotcpcb(inp); if (tp == NULL) goto badsyn; /*XXX*/ } break; default: /* * None of RST, SYN or ACK was set. * This is an invalid packet for a * TCB in LISTEN state. Send a RST. */ goto badsyn; case TH_SYN: /* * Received a SYN. */ #ifdef INET6 /* * If deprecated address is forbidden, we do * not accept SYN to deprecated interface * address to prevent any new inbound * connection from getting established. * When we do not accept SYN, we send a TCP * RST, with deprecated source address (instead * of dropping it). We compromise it as it is * much better for peer to send a RST, and * RST will be the final packet for the * exchange. * * If we do not forbid deprecated addresses, we * accept the SYN packet. RFC2462 does not * suggest dropping SYN in this case. * If we decipher RFC2462 5.5.4, it says like * this: * 1. use of deprecated addr with existing * communication is okay - "SHOULD continue * to be used" * 2. use of it with new communication: * (2a) "SHOULD NOT be used if alternate * address with sufficient scope is * available" * (2b) nothing mentioned otherwise. * Here we fall into (2b) case as we have no * choice in our source address selection - we * must obey the peer. * * The wording in RFC2462 is confusing, and * there are multiple description text for * deprecated address handling - worse, they * are not exactly the same. I believe 5.5.4 * is the best one, so we follow 5.5.4. */ if (ip6 && !ip6_use_deprecated) { struct in6_ifaddr *ia6; struct ifnet *ifp = if_get(m->m_pkthdr.ph_ifidx); if (ifp && (ia6 = in6ifa_ifpwithaddr(ifp, &ip6->ip6_dst)) && (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { tp = NULL; if_put(ifp); goto dropwithreset; } if_put(ifp); } #endif /* * LISTEN socket received a SYN * from itself? This can't possibly * be valid; drop the packet. */ if (th->th_dport == th->th_sport) { switch (af) { #ifdef INET6 case AF_INET6: if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &ip6->ip6_dst)) { tcpstat_inc(tcps_badsyn); goto drop; } break; #endif /* INET6 */ case AF_INET: if (ip->ip_dst.s_addr == ip->ip_src.s_addr) { tcpstat_inc(tcps_badsyn); goto drop; } break; } } /* * SYN looks ok; create compressed TCP * state for it. */ if (so->so_qlen > so->so_qlimit || syn_cache_add(&src.sa, &dst.sa, th, iphlen, so, m, optp, optlen, &opti, reuse) == -1) { tcpstat_inc(tcps_dropsyn); goto drop; } return IPPROTO_DONE; } } } #ifdef DIAGNOSTIC /* * Should not happen now that all embryonic connections * are handled with compressed state. */ if (tp->t_state == TCPS_LISTEN) panic("tcp_input: TCPS_LISTEN"); #endif #if NPF > 0 pf_inp_link(m, inp); #endif /* * Segment received on connection. * Reset idle time and keep-alive timer. */ tp->t_rcvtime = tcp_now; if (TCPS_HAVEESTABLISHED(tp->t_state)) TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle); if (tp->sack_enable) tcp_del_sackholes(tp, th); /* Delete stale SACK holes */ /* * Process options. */ #ifdef TCP_SIGNATURE if (optp || (tp->t_flags & TF_SIGNATURE)) #else if (optp) #endif if (tcp_dooptions(tp, optp, optlen, th, m, iphlen, &opti, m->m_pkthdr.ph_rtableid)) goto drop; if (opti.ts_present && opti.ts_ecr) { int rtt_test; /* subtract out the tcp timestamp modulator */ opti.ts_ecr -= tp->ts_modulate; /* make sure ts_ecr is sensible */ rtt_test = tcp_now - opti.ts_ecr; if (rtt_test < 0 || rtt_test > TCP_RTT_MAX) opti.ts_ecr = 0; } #ifdef TCP_ECN /* if congestion experienced, set ECE bit in subsequent packets. */ if ((iptos & IPTOS_ECN_MASK) == IPTOS_ECN_CE) { tp->t_flags |= TF_RCVD_CE; tcpstat_inc(tcps_ecn_rcvce); } #endif /* * 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. */ if (tp->t_state == TCPS_ESTABLISHED && #ifdef TCP_ECN (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ECE|TH_CWR|TH_ACK)) == TH_ACK && #else (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && #endif (!opti.ts_present || TSTMP_GEQ(opti.ts_val, tp->ts_recent)) && 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. * Fix from Braden, see Stevens p. 870 */ if (opti.ts_present && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { tp->ts_recent_age = tcp_now; tp->ts_recent = opti.ts_val; } 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 == 0) { /* * this is a pure ack for outstanding data. */ tcpstat_inc(tcps_predack); if (opti.ts_present && opti.ts_ecr) tcp_xmit_timer(tp, tcp_now - opti.ts_ecr); else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) tcp_xmit_timer(tp, tcp_now - tp->t_rtttime); acked = th->th_ack - tp->snd_una; tcpstat_pkt(tcps_rcvackpack, tcps_rcvackbyte, acked); ND6_HINT(tp); sbdrop(so, &so->so_snd, acked); /* * If we had a pending ICMP message that * refers to data that have just been * acknowledged, disregard the recorded ICMP * message. */ if ((tp->t_flags & TF_PMTUD_PEND) && SEQ_GT(th->th_ack, tp->t_pmtud_th_seq)) tp->t_flags &= ~TF_PMTUD_PEND; /* * Keep track of the largest chunk of data * acknowledged since last PMTU update */ if (tp->t_pmtud_mss_acked < acked) tp->t_pmtud_mss_acked = acked; tp->snd_una = th->th_ack; /* * We want snd_last to track snd_una so * as to avoid sequence wraparound problems * for very large transfers. */ #ifdef TCP_ECN if (SEQ_GT(tp->snd_una, tp->snd_last)) #endif tp->snd_last = tp->snd_una; m_freem(m); /* * 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) TCP_TIMER_DISARM(tp, TCPT_REXMT); else if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); tcp_update_sndspace(tp); if (sb_notify(so, &so->so_snd)) { tp->t_flags |= TF_BLOCKOUTPUT; sowwakeup(so); tp->t_flags &= ~TF_BLOCKOUTPUT; } if (so->so_snd.sb_cc || tp->t_flags & TF_NEEDOUTPUT) (void) tcp_output(tp); return IPPROTO_DONE; } } else if (th->th_ack == tp->snd_una && TAILQ_EMPTY(&tp->t_segq) && tlen <= sbspace(so, &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. */ /* Clean receiver SACK report if present */ if (tp->sack_enable && tp->rcv_numsacks) tcp_clean_sackreport(tp); tcpstat_inc(tcps_preddat); tp->rcv_nxt += tlen; tcpstat_pkt(tcps_rcvpack, tcps_rcvbyte, tlen); ND6_HINT(tp); TCP_SETUP_ACK(tp, tiflags, m); /* * Drop TCP, IP headers and TCP options then add data * to socket buffer. */ if (so->so_state & SS_CANTRCVMORE) m_freem(m); else { if (opti.ts_present && opti.ts_ecr) { if (tp->rfbuf_ts < opti.ts_ecr && opti.ts_ecr - tp->rfbuf_ts < hz) { tcp_update_rcvspace(tp); /* Start over with next RTT. */ tp->rfbuf_cnt = 0; tp->rfbuf_ts = 0; } else tp->rfbuf_cnt += tlen; } m_adj(m, iphlen + off); sbappendstream(so, &so->so_rcv, m); } tp->t_flags |= TF_BLOCKOUTPUT; sorwakeup(so); tp->t_flags &= ~TF_BLOCKOUTPUT; if (tp->t_flags & (TF_ACKNOW|TF_NEEDOUTPUT)) (void) tcp_output(tp); return IPPROTO_DONE; } } /* * Compute mbuf offset to TCP data segment. */ hdroptlen = iphlen + off; /* * 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->so_rcv); if (win < 0) win = 0; tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); } /* Reset receive buffer auto scaling when not in bulk receive mode. */ tp->rfbuf_cnt = 0; tp->rfbuf_ts = 0; switch (tp->t_state) { /* * If the state is SYN_RECEIVED: * if seg contains SYN/ACK, send an RST. * if seg contains an ACK, but not for our SYN/ACK, send an RST */ case TCPS_SYN_RECEIVED: if (tiflags & TH_ACK) { if (tiflags & TH_SYN) { tcpstat_inc(tcps_badsyn); goto dropwithreset; } if (SEQ_LEQ(th->th_ack, tp->snd_una) || SEQ_GT(th->th_ack, tp->snd_max)) goto dropwithreset; } 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 ((tiflags & TH_ACK) && (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) goto dropwithreset; if (tiflags & TH_RST) { #ifdef TCP_ECN /* if ECN is enabled, fall back to non-ecn at rexmit */ if (tcp_do_ecn && !(tp->t_flags & TF_DISABLE_ECN)) goto drop; #endif if (tiflags & TH_ACK) tp = tcp_drop(tp, ECONNREFUSED); goto drop; } if ((tiflags & TH_SYN) == 0) goto drop; if (tiflags & TH_ACK) { tp->snd_una = th->th_ack; if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; } TCP_TIMER_DISARM(tp, TCPT_REXMT); tp->irs = th->th_seq; tcp_mss(tp, opti.maxseg); /* Reset initial window to 1 segment for retransmit */ if (tp->t_rxtshift > 0) tp->snd_cwnd = tp->t_maxseg; tcp_rcvseqinit(tp); tp->t_flags |= TF_ACKNOW; /* * If we've sent a SACK_PERMITTED option, and the peer * also replied with one, then TF_SACK_PERMIT should have * been set in tcp_dooptions(). If it was not, disable SACKs. */ if (tp->sack_enable) tp->sack_enable = tp->t_flags & TF_SACK_PERMIT; #ifdef TCP_ECN /* * if ECE is set but CWR is not set for SYN-ACK, or * both ECE and CWR are set for simultaneous open, * peer is ECN capable. */ if (tcp_do_ecn) { switch (tiflags & (TH_ACK|TH_ECE|TH_CWR)) { case TH_ACK|TH_ECE: case TH_ECE|TH_CWR: tp->t_flags |= TF_ECN_PERMIT; tiflags &= ~(TH_ECE|TH_CWR); tcpstat_inc(tcps_ecn_accepts); } } #endif if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) { tcpstat_inc(tcps_connects); tp->t_flags |= TF_BLOCKOUTPUT; soisconnected(so); tp->t_flags &= ~TF_BLOCKOUTPUT; tp->t_state = TCPS_ESTABLISHED; TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle); /* 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; } tcp_flush_queue(tp); /* * if we didn't have to retransmit the SYN, * use its rtt as our initial srtt & rtt var. */ if (tp->t_rtttime) tcp_xmit_timer(tp, tcp_now - tp->t_rtttime); /* * Since new data was acked (the SYN), open the * congestion window by one MSS. We do this * here, because we won't go through the normal * ACK processing below. And since this is the * start of the connection, we know we are in * the exponential phase of slow-start. */ tp->snd_cwnd += tp->t_maxseg; } else tp->t_state = TCPS_SYN_RECEIVED; #if 0 trimthenstep6: #endif /* * 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; tiflags &= ~TH_FIN; tcpstat_pkt(tcps_rcvpackafterwin, tcps_rcvbyteafterwin, todrop); } tp->snd_wl1 = th->th_seq - 1; tp->rcv_up = th->th_seq; goto step6; /* * If a new connection request is received while in TIME_WAIT, * drop the old connection and start over if the if the * timestamp or the sequence numbers are above the previous * ones. */ case TCPS_TIME_WAIT: if (((tiflags & (TH_SYN|TH_ACK)) == TH_SYN) && ((opti.ts_present && TSTMP_LT(tp->ts_recent, opti.ts_val)) || SEQ_GT(th->th_seq, tp->rcv_nxt))) { #if NPF > 0 /* * The socket will be recreated but the new state * has already been linked to the socket. Remove the * link between old socket and new state. */ pf_inp_unlink(inp); #endif /* * Advance the iss by at least 32768, but * clear the msb in order to make sure * that SEG_LT(snd_nxt, iss). */ iss = tp->snd_nxt + ((arc4random() & 0x7fffffff) | 0x8000); reuse = &iss; tp = tcp_close(tp); inp = NULL; goto findpcb; } } /* * States other than LISTEN or SYN_SENT. * First check timestamp, 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. * * RFC 1323 PAWS: If we have a timestamp reply on this segment * and it's less than opti.ts_recent, drop it. */ if (opti.ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent && TSTMP_LT(opti.ts_val, tp->ts_recent)) { /* Check to see if ts_recent is over 24 days old. */ if ((int)(tcp_now - 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_pkt(tcps_rcvduppack, tcps_rcvdupbyte, tlen); tcpstat_inc(tcps_pawsdrop); if (tlen) goto dropafterack; goto drop; } } todrop = tp->rcv_nxt - th->th_seq; if (todrop > 0) { if (tiflags & TH_SYN) { tiflags &= ~TH_SYN; th->th_seq++; if (th->th_urp > 1) th->th_urp--; else tiflags &= ~TH_URG; todrop--; } if (todrop > tlen || (todrop == tlen && (tiflags & TH_FIN) == 0)) { /* * Any valid FIN must be to the left of the * window. At this point, FIN must be a * duplicate or out-of-sequence, so drop it. */ tiflags &= ~TH_FIN; /* * Send ACK to resynchronize, and drop any data, * but keep on processing for RST or ACK. */ tp->t_flags |= TF_ACKNOW; todrop = tlen; tcpstat_pkt(tcps_rcvduppack, tcps_rcvdupbyte, todrop); } else { tcpstat_pkt(tcps_rcvpartduppack, tcps_rcvpartdupbyte, todrop); } hdroptlen += todrop; /* drop from head afterwards */ th->th_seq += todrop; tlen -= todrop; if (th->th_urp > todrop) th->th_urp -= todrop; else { tiflags &= ~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_inc(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_inc(tcps_rcvpackafterwin); if (todrop >= tlen) { tcpstat_add(tcps_rcvbyteafterwin, tlen); /* * 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_inc(tcps_rcvwinprobe); } else goto dropafterack; } else tcpstat_add(tcps_rcvbyteafterwin, todrop); m_adj(m, -todrop); tlen -= todrop; tiflags &= ~(TH_PUSH|TH_FIN); } /* * If last ACK falls within this segment's sequence numbers, * record its timestamp if it's more recent. * NOTE that the test is modified according to the latest * proposal of the tcplw@cray.com list (Braden 1993/04/26). */ if (opti.ts_present && TSTMP_GEQ(opti.ts_val, tp->ts_recent) && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { tp->ts_recent_age = tcp_now; tp->ts_recent = opti.ts_val; } /* * If the RST bit is set 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, TIME_WAIT STATES * Close the tcb. */ if (tiflags & TH_RST) { if (th->th_seq != tp->last_ack_sent && th->th_seq != tp->rcv_nxt && th->th_seq != (tp->rcv_nxt + 1)) goto drop; switch (tp->t_state) { case TCPS_SYN_RECEIVED: #ifdef TCP_ECN /* if ECN is enabled, fall back to non-ecn at rexmit */ if (tcp_do_ecn && !(tp->t_flags & TF_DISABLE_ECN)) goto drop; #endif 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_inc(tcps_drops); tp = tcp_close(tp); goto drop; case TCPS_CLOSING: case TCPS_LAST_ACK: case TCPS_TIME_WAIT: tp = tcp_close(tp); goto drop; } } /* * If a SYN is in the window, then this is an * error and we ACK and drop the packet. */ if (tiflags & TH_SYN) goto dropafterack_ratelim; /* * If the ACK bit is off we drop the segment and return. */ if ((tiflags & TH_ACK) == 0) { if (tp->t_flags & TF_ACKNOW) goto dropafterack; 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_inc(tcps_connects); tp->t_flags |= TF_BLOCKOUTPUT; soisconnected(so); tp->t_flags &= ~TF_BLOCKOUTPUT; tp->t_state = TCPS_ESTABLISHED; TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle); /* 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; tiwin = th->th_win << tp->snd_scale; } tcp_flush_queue(tp); 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: #ifdef TCP_ECN /* * if we receive ECE and are not already in recovery phase, * reduce cwnd by half but don't slow-start. * advance snd_last to snd_max not to reduce cwnd again * until all outstanding packets are acked. */ if (tcp_do_ecn && (tiflags & TH_ECE)) { if ((tp->t_flags & TF_ECN_PERMIT) && SEQ_GEQ(tp->snd_una, tp->snd_last)) { u_int win; win = min(tp->snd_wnd, tp->snd_cwnd) / tp->t_maxseg; if (win > 1) { tp->snd_ssthresh = win / 2 * tp->t_maxseg; tp->snd_cwnd = tp->snd_ssthresh; tp->snd_last = tp->snd_max; tp->t_flags |= TF_SEND_CWR; tcpstat_inc(tcps_cwr_ecn); } } tcpstat_inc(tcps_ecn_rcvece); } /* * if we receive CWR, we know that the peer has reduced * its congestion window. stop sending ecn-echo. */ if ((tiflags & TH_CWR)) { tp->t_flags &= ~TF_RCVD_CE; tcpstat_inc(tcps_ecn_rcvcwr); } #endif /* TCP_ECN */ if (SEQ_LEQ(th->th_ack, tp->snd_una)) { /* * Duplicate/old ACK processing. * Increments t_dupacks: * Pure duplicate (same seq/ack/window, no data) * Doesn't affect t_dupacks: * Data packets. * Normal window updates (window opens) * Resets t_dupacks: * New data ACKed. * Window shrinks * Old ACK */ if (tlen) { /* Drop very old ACKs unless th_seq matches */ if (th->th_seq != tp->rcv_nxt && SEQ_LT(th->th_ack, tp->snd_una - tp->max_sndwnd)) { tcpstat_inc(tcps_rcvacktooold); goto drop; } break; } /* * If we get an old ACK, there is probably packet * reordering going on. Be conservative and reset * t_dupacks so that we are less aggressive in * doing a fast retransmit. */ if (th->th_ack != tp->snd_una) { tp->t_dupacks = 0; break; } if (tiwin == tp->snd_wnd) { tcpstat_inc(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 * threshold 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 (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0) tp->t_dupacks = 0; else if (++tp->t_dupacks == tcprexmtthresh) { tcp_seq onxt = tp->snd_nxt; u_long win = ulmin(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; if (SEQ_LT(th->th_ack, tp->snd_last)){ /* * False fast retx after * timeout. Do not cut window. */ tp->t_dupacks = 0; goto drop; } if (win < 2) win = 2; tp->snd_ssthresh = win * tp->t_maxseg; tp->snd_last = tp->snd_max; if (tp->sack_enable) { TCP_TIMER_DISARM(tp, TCPT_REXMT); tp->t_rtttime = 0; #ifdef TCP_ECN tp->t_flags |= TF_SEND_CWR; #endif tcpstat_inc(tcps_cwr_frecovery); tcpstat_inc(tcps_sack_recovery_episode); /* * tcp_output() will send * oldest SACK-eligible rtx. */ (void) tcp_output(tp); tp->snd_cwnd = tp->snd_ssthresh+ tp->t_maxseg * tp->t_dupacks; goto drop; } TCP_TIMER_DISARM(tp, TCPT_REXMT); tp->t_rtttime = 0; tp->snd_nxt = th->th_ack; tp->snd_cwnd = tp->t_maxseg; #ifdef TCP_ECN tp->t_flags |= TF_SEND_CWR; #endif tcpstat_inc(tcps_cwr_frecovery); tcpstat_inc(tcps_sndrexmitfast); (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 if (tiwin < tp->snd_wnd) { /* * The window was retracted! Previous dup * ACKs may have been due to packets arriving * after the shrunken window, not a missing * packet, so play it safe and reset t_dupacks */ 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) { /* Check for a partial ACK */ if (SEQ_LT(th->th_ack, tp->snd_last)) { if (tp->sack_enable) tcp_sack_partialack(tp, th); else tcp_newreno_partialack(tp, th); } else { /* Out of fast recovery */ tp->snd_cwnd = tp->snd_ssthresh; if (tcp_seq_subtract(tp->snd_max, th->th_ack) < tp->snd_ssthresh) tp->snd_cwnd = tcp_seq_subtract(tp->snd_max, th->th_ack); tp->t_dupacks = 0; } } else { /* * Reset the duplicate ACK counter if we * were not in fast recovery. */ tp->t_dupacks = 0; } if (SEQ_GT(th->th_ack, tp->snd_max)) { tcpstat_inc(tcps_rcvacktoomuch); goto dropafterack_ratelim; } acked = th->th_ack - tp->snd_una; tcpstat_pkt(tcps_rcvackpack, tcps_rcvackbyte, acked); /* * 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 (opti.ts_present && opti.ts_ecr) tcp_xmit_timer(tp, tcp_now - opti.ts_ecr); else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) tcp_xmit_timer(tp, tcp_now - 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) { TCP_TIMER_DISARM(tp, TCPT_REXMT); tp->t_flags |= TF_NEEDOUTPUT; } else if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); /* * 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). */ { u_int cw = tp->snd_cwnd; u_int incr = tp->t_maxseg; if (cw > tp->snd_ssthresh) incr = max(incr * incr / cw, 1); if (tp->t_dupacks < tcprexmtthresh) tp->snd_cwnd = ulmin(cw + incr, TCP_MAXWIN << tp->snd_scale); } ND6_HINT(tp); if (acked > so->so_snd.sb_cc) { if (tp->snd_wnd > so->so_snd.sb_cc) tp->snd_wnd -= so->so_snd.sb_cc; else tp->snd_wnd = 0; sbdrop(so, &so->so_snd, (int)so->so_snd.sb_cc); ourfinisacked = 1; } else { sbdrop(so, &so->so_snd, acked); if (tp->snd_wnd > acked) tp->snd_wnd -= acked; else tp->snd_wnd = 0; ourfinisacked = 0; } tcp_update_sndspace(tp); if (sb_notify(so, &so->so_snd)) { tp->t_flags |= TF_BLOCKOUTPUT; sowwakeup(so); tp->t_flags &= ~TF_BLOCKOUTPUT; } /* * If we had a pending ICMP message that referred to data * that have just been acknowledged, disregard the recorded * ICMP message. */ if ((tp->t_flags & TF_PMTUD_PEND) && SEQ_GT(th->th_ack, tp->t_pmtud_th_seq)) tp->t_flags &= ~TF_PMTUD_PEND; /* * Keep track of the largest chunk of data acknowledged * since last PMTU update */ if (tp->t_pmtud_mss_acked < acked) tp->t_pmtud_mss_acked = acked; tp->snd_una = th->th_ack; #ifdef TCP_ECN /* sync snd_last with snd_una */ if (SEQ_GT(tp->snd_una, tp->snd_last)) tp->snd_last = tp->snd_una; #endif 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) { tp->t_flags |= TF_BLOCKOUTPUT; soisdisconnected(so); tp->t_flags &= ~TF_BLOCKOUTPUT; TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_maxidle); } 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); TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * TCPTV_MSL); tp->t_flags |= TF_BLOCKOUTPUT; soisdisconnected(so); tp->t_flags &= ~TF_BLOCKOUTPUT; } 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: TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * TCPTV_MSL); goto dropafterack; } } step6: /* * Update window information. * Don't look at window if no ACK: TAC's send garbage on first SYN. */ if ((tiflags & 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_inc(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; tp->t_flags |= TF_NEEDOUTPUT; } /* * Process segments with URG. */ if ((tiflags & 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 */ tiflags &= ~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_int16_t) tlen && (so->so_options & SO_OOBINLINE) == 0) tcp_pulloutofband(so, th->th_urp, m, hdroptlen); } 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 || (tiflags & TH_FIN)) && TCPS_HAVERCVDFIN(tp->t_state) == 0) { tcp_seq laststart = th->th_seq; tcp_seq lastend = th->th_seq + tlen; if (th->th_seq == tp->rcv_nxt && TAILQ_EMPTY(&tp->t_segq) && tp->t_state == TCPS_ESTABLISHED) { TCP_SETUP_ACK(tp, tiflags, m); tp->rcv_nxt += tlen; tiflags = th->th_flags & TH_FIN; tcpstat_pkt(tcps_rcvpack, tcps_rcvbyte, tlen); ND6_HINT(tp); if (so->so_state & SS_CANTRCVMORE) m_freem(m); else { m_adj(m, hdroptlen); sbappendstream(so, &so->so_rcv, m); } tp->t_flags |= TF_BLOCKOUTPUT; sorwakeup(so); tp->t_flags &= ~TF_BLOCKOUTPUT; } else { m_adj(m, hdroptlen); tiflags = tcp_reass(tp, th, m, &tlen); tp->t_flags |= TF_ACKNOW; } if (tp->sack_enable) tcp_update_sack_list(tp, laststart, lastend); /* * variable len never referenced again in modern BSD, * so why bother computing it ?? */ #if 0 /* * 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); #endif /* 0 */ } else { m_freem(m); tiflags &= ~TH_FIN; } /* * If FIN is received ACK the FIN and let the user know * that the connection is closing. Ignore a FIN received before * the connection is fully established. */ if ((tiflags & TH_FIN) && TCPS_HAVEESTABLISHED(tp->t_state)) { if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { tp->t_flags |= TF_BLOCKOUTPUT; socantrcvmore(so); tp->t_flags &= ~TF_BLOCKOUTPUT; tp->t_flags |= TF_ACKNOW; tp->rcv_nxt++; } switch (tp->t_state) { /* * In ESTABLISHED STATE enter the CLOSE_WAIT state. */ 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); TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * TCPTV_MSL); tp->t_flags |= TF_BLOCKOUTPUT; soisdisconnected(so); tp->t_flags &= ~TF_BLOCKOUTPUT; break; /* * In TIME_WAIT state restart the 2 MSL time_wait timer. */ case TCPS_TIME_WAIT: TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * TCPTV_MSL); break; } } if (otp) tcp_trace(TA_INPUT, ostate, tp, otp, saveti, 0, tlen); /* * Return any desired output. */ if (tp->t_flags & (TF_ACKNOW|TF_NEEDOUTPUT)) (void) tcp_output(tp); return IPPROTO_DONE; badsyn: /* * Received a bad SYN. Increment counters and dropwithreset. */ tcpstat_inc(tcps_badsyn); tp = NULL; goto dropwithreset; dropafterack_ratelim: if (ppsratecheck(&tcp_ackdrop_ppslim_last, &tcp_ackdrop_ppslim_count, tcp_ackdrop_ppslim) == 0) { /* XXX stat */ goto drop; } /* ...fall into dropafterack... */ dropafterack: /* * Generate an ACK dropping incoming segment if it occupies * sequence space, where the ACK reflects our state. */ if (tiflags & TH_RST) goto drop; m_freem(m); tp->t_flags |= TF_ACKNOW; (void) tcp_output(tp); return IPPROTO_DONE; dropwithreset_ratelim: /* * We may want to rate-limit RSTs in certain situations, * particularly if we are sending an RST in response to * an attempt to connect to or otherwise communicate with * a port for which we have no socket. */ if (ppsratecheck(&tcp_rst_ppslim_last, &tcp_rst_ppslim_count, tcp_rst_ppslim) == 0) { /* XXX stat */ goto drop; } /* ...fall into dropwithreset... */ dropwithreset: /* * Generate a RST, dropping incoming segment. * Make ACK acceptable to originator of segment. * Don't bother to respond to RST. */ if (tiflags & TH_RST) goto drop; if (tiflags & TH_ACK) { tcp_respond(tp, mtod(m, caddr_t), th, (tcp_seq)0, th->th_ack, TH_RST, m->m_pkthdr.ph_rtableid); } else { if (tiflags & TH_SYN) tlen++; tcp_respond(tp, mtod(m, caddr_t), th, th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK, m->m_pkthdr.ph_rtableid); } m_freem(m); return IPPROTO_DONE; drop: /* * Drop space held by incoming segment and return. */ if (otp) tcp_trace(TA_DROP, ostate, tp, otp, saveti, 0, tlen); m_freem(m); return IPPROTO_DONE; } int tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, struct tcphdr *th, struct mbuf *m, int iphlen, struct tcp_opt_info *oi, u_int rtableid) { u_int16_t mss = 0; int opt, optlen; #ifdef TCP_SIGNATURE caddr_t sigp = NULL; struct tdb *tdb = NULL; #endif /* TCP_SIGNATURE */ for (; cp && cnt > 0; cnt -= optlen, cp += optlen) { opt = cp[0]; if (opt == TCPOPT_EOL) break; if (opt == TCPOPT_NOP) optlen = 1; else { if (cnt < 2) break; optlen = cp[1]; if (optlen < 2 || optlen > cnt) break; } switch (opt) { default: continue; case TCPOPT_MAXSEG: if (optlen != TCPOLEN_MAXSEG) continue; if (!(th->th_flags & TH_SYN)) continue; if (TCPS_HAVERCVDSYN(tp->t_state)) continue; memcpy(&mss, cp + 2, sizeof(mss)); mss = ntohs(mss); oi->maxseg = mss; break; case TCPOPT_WINDOW: if (optlen != TCPOLEN_WINDOW) continue; if (!(th->th_flags & TH_SYN)) continue; if (TCPS_HAVERCVDSYN(tp->t_state)) 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; oi->ts_present = 1; memcpy(&oi->ts_val, cp + 2, sizeof(oi->ts_val)); oi->ts_val = ntohl(oi->ts_val); memcpy(&oi->ts_ecr, cp + 6, sizeof(oi->ts_ecr)); oi->ts_ecr = ntohl(oi->ts_ecr); if (!(th->th_flags & TH_SYN)) continue; if (TCPS_HAVERCVDSYN(tp->t_state)) continue; /* * A timestamp received in a SYN makes * it ok to send timestamp requests and replies. */ tp->t_flags |= TF_RCVD_TSTMP; tp->ts_recent = oi->ts_val; tp->ts_recent_age = tcp_now; break; case TCPOPT_SACK_PERMITTED: if (!tp->sack_enable || optlen!=TCPOLEN_SACK_PERMITTED) continue; if (!(th->th_flags & TH_SYN)) continue; if (TCPS_HAVERCVDSYN(tp->t_state)) continue; /* MUST only be set on SYN */ tp->t_flags |= TF_SACK_PERMIT; break; case TCPOPT_SACK: tcp_sack_option(tp, th, cp, optlen); break; #ifdef TCP_SIGNATURE case TCPOPT_SIGNATURE: if (optlen != TCPOLEN_SIGNATURE) continue; if (sigp && timingsafe_bcmp(sigp, cp + 2, 16)) return (-1); sigp = cp + 2; break; #endif /* TCP_SIGNATURE */ } } #ifdef TCP_SIGNATURE if (tp->t_flags & TF_SIGNATURE) { union sockaddr_union src, dst; memset(&src, 0, sizeof(union sockaddr_union)); memset(&dst, 0, sizeof(union sockaddr_union)); switch (tp->pf) { case 0: case AF_INET: src.sa.sa_len = sizeof(struct sockaddr_in); src.sa.sa_family = AF_INET; src.sin.sin_addr = mtod(m, struct ip *)->ip_src; dst.sa.sa_len = sizeof(struct sockaddr_in); dst.sa.sa_family = AF_INET; dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst; break; #ifdef INET6 case AF_INET6: src.sa.sa_len = sizeof(struct sockaddr_in6); src.sa.sa_family = AF_INET6; src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src; dst.sa.sa_len = sizeof(struct sockaddr_in6); dst.sa.sa_family = AF_INET6; dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst; break; #endif /* INET6 */ } tdb = gettdbbysrcdst(rtable_l2(rtableid), 0, &src, &dst, IPPROTO_TCP); /* * We don't have an SA for this peer, so we turn off * TF_SIGNATURE on the listen socket */ if (tdb == NULL && tp->t_state == TCPS_LISTEN) tp->t_flags &= ~TF_SIGNATURE; } if ((sigp ? TF_SIGNATURE : 0) ^ (tp->t_flags & TF_SIGNATURE)) { tcpstat_inc(tcps_rcvbadsig); return (-1); } if (sigp) { char sig[16]; if (tdb == NULL) { tcpstat_inc(tcps_rcvbadsig); return (-1); } if (tcp_signature(tdb, tp->pf, m, th, iphlen, 1, sig) < 0) return (-1); if (timingsafe_bcmp(sig, sigp, 16)) { tcpstat_inc(tcps_rcvbadsig); return (-1); } tcpstat_inc(tcps_rcvgoodsig); } #endif /* TCP_SIGNATURE */ return (0); } u_long tcp_seq_subtract(u_long a, u_long b) { return ((long)(a - b)); } /* * This function is called upon receipt of new valid data (while not in header * prediction mode), and it updates the ordered list of sacks. */ void tcp_update_sack_list(struct tcpcb *tp, tcp_seq rcv_laststart, tcp_seq rcv_lastend) { /* * First reported block MUST be the most recent one. Subsequent * blocks SHOULD be in the order in which they arrived at the * receiver. These two conditions make the implementation fully * compliant with RFC 2018. */ int i, j = 0, count = 0, lastpos = -1; struct sackblk sack, firstsack, temp[MAX_SACK_BLKS]; /* First clean up current list of sacks */ for (i = 0; i < tp->rcv_numsacks; i++) { sack = tp->sackblks[i]; if (sack.start == 0 && sack.end == 0) { count++; /* count = number of blocks to be discarded */ continue; } if (SEQ_LEQ(sack.end, tp->rcv_nxt)) { tp->sackblks[i].start = tp->sackblks[i].end = 0; count++; } else { temp[j].start = tp->sackblks[i].start; temp[j++].end = tp->sackblks[i].end; } } tp->rcv_numsacks -= count; if (tp->rcv_numsacks == 0) { /* no sack blocks currently (fast path) */ tcp_clean_sackreport(tp); if (SEQ_LT(tp->rcv_nxt, rcv_laststart)) { /* ==> need first sack block */ tp->sackblks[0].start = rcv_laststart; tp->sackblks[0].end = rcv_lastend; tp->rcv_numsacks = 1; } return; } /* Otherwise, sack blocks are already present. */ for (i = 0; i < tp->rcv_numsacks; i++) tp->sackblks[i] = temp[i]; /* first copy back sack list */ if (SEQ_GEQ(tp->rcv_nxt, rcv_lastend)) return; /* sack list remains unchanged */ /* * From here, segment just received should be (part of) the 1st sack. * Go through list, possibly coalescing sack block entries. */ firstsack.start = rcv_laststart; firstsack.end = rcv_lastend; for (i = 0; i < tp->rcv_numsacks; i++) { sack = tp->sackblks[i]; if (SEQ_LT(sack.end, firstsack.start) || SEQ_GT(sack.start, firstsack.end)) continue; /* no overlap */ if (sack.start == firstsack.start && sack.end == firstsack.end){ /* * identical block; delete it here since we will * move it to the front of the list. */ tp->sackblks[i].start = tp->sackblks[i].end = 0; lastpos = i; /* last posn with a zero entry */ continue; } if (SEQ_LEQ(sack.start, firstsack.start)) firstsack.start = sack.start; /* merge blocks */ if (SEQ_GEQ(sack.end, firstsack.end)) firstsack.end = sack.end; /* merge blocks */ tp->sackblks[i].start = tp->sackblks[i].end = 0; lastpos = i; /* last posn with a zero entry */ } if (lastpos != -1) { /* at least one merge */ for (i = 0, j = 1; i < tp->rcv_numsacks; i++) { sack = tp->sackblks[i]; if (sack.start == 0 && sack.end == 0) continue; temp[j++] = sack; } tp->rcv_numsacks = j; /* including first blk (added later) */ for (i = 1; i < tp->rcv_numsacks; i++) /* now copy back */ tp->sackblks[i] = temp[i]; } else { /* no merges -- shift sacks by 1 */ if (tp->rcv_numsacks < MAX_SACK_BLKS) tp->rcv_numsacks++; for (i = tp->rcv_numsacks-1; i > 0; i--) tp->sackblks[i] = tp->sackblks[i-1]; } tp->sackblks[0] = firstsack; return; } /* * Process the TCP SACK option. tp->snd_holes is an ordered list * of holes (oldest to newest, in terms of the sequence space). */ void tcp_sack_option(struct tcpcb *tp, struct tcphdr *th, u_char *cp, int optlen) { int tmp_olen; u_char *tmp_cp; struct sackhole *cur, *p, *temp; if (!tp->sack_enable) return; /* SACK without ACK doesn't make sense. */ if ((th->th_flags & TH_ACK) == 0) return; /* Make sure the ACK on this segment is in [snd_una, snd_max]. */ if (SEQ_LT(th->th_ack, tp->snd_una) || SEQ_GT(th->th_ack, tp->snd_max)) return; /* Note: TCPOLEN_SACK must be 2*sizeof(tcp_seq) */ if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) return; /* Note: TCPOLEN_SACK must be 2*sizeof(tcp_seq) */ tmp_cp = cp + 2; tmp_olen = optlen - 2; tcpstat_inc(tcps_sack_rcv_opts); if (tp->snd_numholes < 0) tp->snd_numholes = 0; if (tp->t_maxseg == 0) panic("tcp_sack_option"); /* Should never happen */ while (tmp_olen > 0) { struct sackblk sack; memcpy(&sack.start, tmp_cp, sizeof(tcp_seq)); sack.start = ntohl(sack.start); memcpy(&sack.end, tmp_cp + sizeof(tcp_seq), sizeof(tcp_seq)); sack.end = ntohl(sack.end); tmp_olen -= TCPOLEN_SACK; tmp_cp += TCPOLEN_SACK; if (SEQ_LEQ(sack.end, sack.start)) continue; /* bad SACK fields */ if (SEQ_LEQ(sack.end, tp->snd_una)) continue; /* old block */ if (SEQ_GT(th->th_ack, tp->snd_una)) { if (SEQ_LT(sack.start, th->th_ack)) continue; } if (SEQ_GT(sack.end, tp->snd_max)) continue; if (tp->snd_holes == NULL) { /* first hole */ tp->snd_holes = (struct sackhole *) pool_get(&sackhl_pool, PR_NOWAIT); if (tp->snd_holes == NULL) { /* ENOBUFS, so ignore SACKed block for now */ goto dropped; } cur = tp->snd_holes; cur->start = th->th_ack; cur->end = sack.start; cur->rxmit = cur->start; cur->next = NULL; tp->snd_numholes = 1; tp->rcv_lastsack = sack.end; /* * dups is at least one. If more data has been * SACKed, it can be greater than one. */ cur->dups = min(tcprexmtthresh, ((sack.end - cur->end)/tp->t_maxseg)); if (cur->dups < 1) cur->dups = 1; continue; /* with next sack block */ } /* Go thru list of holes: p = previous, cur = current */ p = cur = tp->snd_holes; while (cur) { if (SEQ_LEQ(sack.end, cur->start)) /* SACKs data before the current hole */ break; /* no use going through more holes */ if (SEQ_GEQ(sack.start, cur->end)) { /* SACKs data beyond the current hole */ cur->dups++; if (((sack.end - cur->end)/tp->t_maxseg) >= tcprexmtthresh) cur->dups = tcprexmtthresh; p = cur; cur = cur->next; continue; } if (SEQ_LEQ(sack.start, cur->start)) { /* Data acks at least the beginning of hole */ if (SEQ_GEQ(sack.end, cur->end)) { /* Acks entire hole, so delete hole */ if (p != cur) { p->next = cur->next; pool_put(&sackhl_pool, cur); cur = p->next; } else { cur = cur->next; pool_put(&sackhl_pool, p); p = cur; tp->snd_holes = p; } tp->snd_numholes--; continue; } /* otherwise, move start of hole forward */ cur->start = sack.end; cur->rxmit = SEQ_MAX(cur->rxmit, cur->start); p = cur; cur = cur->next; continue; } /* move end of hole backward */ if (SEQ_GEQ(sack.end, cur->end)) { cur->end = sack.start; cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); cur->dups++; if (((sack.end - cur->end)/tp->t_maxseg) >= tcprexmtthresh) cur->dups = tcprexmtthresh; p = cur; cur = cur->next; continue; } if (SEQ_LT(cur->start, sack.start) && SEQ_GT(cur->end, sack.end)) { /* * ACKs some data in middle of a hole; need to * split current hole */ if (tp->snd_numholes >= TCP_SACKHOLE_LIMIT) goto dropped; temp = (struct sackhole *) pool_get(&sackhl_pool, PR_NOWAIT); if (temp == NULL) goto dropped; /* ENOBUFS */ temp->next = cur->next; temp->start = sack.end; temp->end = cur->end; temp->dups = cur->dups; temp->rxmit = SEQ_MAX(cur->rxmit, temp->start); cur->end = sack.start; cur->rxmit = SEQ_MIN(cur->rxmit, cur->end); cur->dups++; if (((sack.end - cur->end)/tp->t_maxseg) >= tcprexmtthresh) cur->dups = tcprexmtthresh; cur->next = temp; p = temp; cur = p->next; tp->snd_numholes++; } } /* At this point, p points to the last hole on the list */ if (SEQ_LT(tp->rcv_lastsack, sack.start)) { /* * Need to append new hole at end. * Last hole is p (and it's not NULL). */ if (tp->snd_numholes >= TCP_SACKHOLE_LIMIT) goto dropped; temp = (struct sackhole *) pool_get(&sackhl_pool, PR_NOWAIT); if (temp == NULL) goto dropped; /* ENOBUFS */ temp->start = tp->rcv_lastsack; temp->end = sack.start; temp->dups = min(tcprexmtthresh, ((sack.end - sack.start)/tp->t_maxseg)); if (temp->dups < 1) temp->dups = 1; temp->rxmit = temp->start; temp->next = 0; p->next = temp; tp->rcv_lastsack = sack.end; tp->snd_numholes++; } } return; dropped: tcpstat_inc(tcps_sack_drop_opts); } /* * Delete stale (i.e, cumulatively ack'd) holes. Hole is deleted only if * it is completely acked; otherwise, tcp_sack_option(), called from * tcp_dooptions(), will fix up the hole. */ void tcp_del_sackholes(struct tcpcb *tp, struct tcphdr *th) { if (tp->sack_enable && tp->t_state != TCPS_LISTEN) { /* max because this could be an older ack just arrived */ tcp_seq lastack = SEQ_GT(th->th_ack, tp->snd_una) ? th->th_ack : tp->snd_una; struct sackhole *cur = tp->snd_holes; struct sackhole *prev; while (cur) if (SEQ_LEQ(cur->end, lastack)) { prev = cur; cur = cur->next; pool_put(&sackhl_pool, prev); tp->snd_numholes--; } else if (SEQ_LT(cur->start, lastack)) { cur->start = lastack; if (SEQ_LT(cur->rxmit, cur->start)) cur->rxmit = cur->start; break; } else break; tp->snd_holes = cur; } } /* * Delete all receiver-side SACK information. */ void tcp_clean_sackreport(struct tcpcb *tp) { int i; tp->rcv_numsacks = 0; for (i = 0; i < MAX_SACK_BLKS; i++) tp->sackblks[i].start = tp->sackblks[i].end=0; } /* * Partial ack handling within a sack recovery episode. When a partial ack * arrives, turn off retransmission timer, deflate the window, do not clear * tp->t_dupacks. */ void tcp_sack_partialack(struct tcpcb *tp, struct tcphdr *th) { /* Turn off retx. timer (will start again next segment) */ TCP_TIMER_DISARM(tp, TCPT_REXMT); tp->t_rtttime = 0; /* * Partial window deflation. This statement relies on the * fact that tp->snd_una has not been updated yet. */ if (tp->snd_cwnd > (th->th_ack - tp->snd_una)) { tp->snd_cwnd -= th->th_ack - tp->snd_una; tp->snd_cwnd += tp->t_maxseg; } else tp->snd_cwnd = tp->t_maxseg; tp->snd_cwnd += tp->t_maxseg; tp->t_flags |= TF_NEEDOUTPUT; } /* * 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. */ void tcp_pulloutofband(struct socket *so, u_int urgent, struct mbuf *m, int off) { int cnt = off + urgent - 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; memmove(cp, cp + 1, m->m_len - cnt - 1); m->m_len--; return; } cnt -= m->m_len; m = m->m_next; if (m == NULL) break; } panic("tcp_pulloutofband"); } /* * Collect new round-trip time estimate * and update averages and current timeout. */ void tcp_xmit_timer(struct tcpcb *tp, int rtt) { short delta; short rttmin; if (rtt < 0) rtt = 0; else if (rtt > TCP_RTT_MAX) rtt = TCP_RTT_MAX; tcpstat_inc(tcps_rttupdated); if (tp->t_srtt != 0) { /* * delta is fixed point with 2 (TCP_RTT_BASE_SHIFT) bits * after the binary point (scaled by 4), whereas * srtt is stored as fixed point with 5 bits after the * binary point (i.e., scaled by 32). 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). */ delta = (rtt << TCP_RTT_BASE_SHIFT) - (tp->t_srtt >> TCP_RTT_SHIFT); if ((tp->t_srtt += delta) <= 0) tp->t_srtt = 1 << TCP_RTT_BASE_SHIFT; /* * 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); if ((tp->t_rttvar += delta) <= 0) tp->t_rttvar = 1 << TCP_RTT_BASE_SHIFT; } 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 + 1) << (TCP_RTT_SHIFT + TCP_RTT_BASE_SHIFT); tp->t_rttvar = (rtt + 1) << (TCP_RTTVAR_SHIFT + TCP_RTT_BASE_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). */ rttmin = min(max(rtt + 2, tp->t_rttmin), TCPTV_REXMTMAX); TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), rttmin, 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: offer == -1 indicates that the maxseg size changed due to * Path MTU discovery. */ int tcp_mss(struct tcpcb *tp, int offer) { struct rtentry *rt; struct ifnet *ifp = NULL; int mss, mssopt; int iphlen; struct inpcb *inp; inp = tp->t_inpcb; mssopt = mss = tcp_mssdflt; rt = in_pcbrtentry(inp); if (rt == NULL) goto out; ifp = if_get(rt->rt_ifidx); if (ifp == NULL) goto out; switch (tp->pf) { #ifdef INET6 case AF_INET6: iphlen = sizeof(struct ip6_hdr); break; #endif case AF_INET: iphlen = sizeof(struct ip); break; default: /* the family does not support path MTU discovery */ goto out; } /* * if there's an mtu associated with the route and we support * path MTU discovery for the underlying protocol family, use it. */ if (rt->rt_mtu) { /* * One may wish to lower MSS to take into account options, * especially security-related options. */ if (tp->pf == AF_INET6 && rt->rt_mtu < IPV6_MMTU) { /* * RFC2460 section 5, last paragraph: if path MTU is * smaller than 1280, use 1280 as packet size and * attach fragment header. */ mss = IPV6_MMTU - iphlen - sizeof(struct ip6_frag) - sizeof(struct tcphdr); } else { mss = rt->rt_mtu - iphlen - sizeof(struct tcphdr); } } else if (ifp->if_flags & IFF_LOOPBACK) { mss = ifp->if_mtu - iphlen - sizeof(struct tcphdr); } else if (tp->pf == AF_INET) { if (ip_mtudisc) mss = ifp->if_mtu - iphlen - sizeof(struct tcphdr); } #ifdef INET6 else if (tp->pf == AF_INET6) { /* * for IPv6, path MTU discovery is always turned on, * or the node must use packet size <= 1280. */ mss = ifp->if_mtu - iphlen - sizeof(struct tcphdr); } #endif /* INET6 */ /* Calculate the value that we offer in TCPOPT_MAXSEG */ if (offer != -1) { mssopt = ifp->if_mtu - iphlen - sizeof(struct tcphdr); mssopt = max(tcp_mssdflt, mssopt); } out: if_put(ifp); /* * The current mss, t_maxseg, is initialized to the default value. * If we compute a smaller value, reduce the current mss. * If we compute a larger value, return it for use in sending * a max seg size option, but don't store it for use * unless we received an offer at least that large from peer. * * However, do not accept offers lower than the minimum of * the interface MTU and 216. */ if (offer > 0) tp->t_peermss = offer; if (tp->t_peermss) mss = min(mss, max(tp->t_peermss, 216)); /* sanity - at least max opt. space */ mss = max(mss, 64); /* * 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; 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; #ifdef TCP_SIGNATURE if (tp->t_flags & TF_SIGNATURE) mss -= TCPOLEN_SIGLEN; #endif if (offer == -1) { /* mss changed due to Path MTU discovery */ tp->t_flags &= ~TF_PMTUD_PEND; tp->t_pmtud_mtu_sent = 0; tp->t_pmtud_mss_acked = 0; if (mss < tp->t_maxseg) { /* * Follow suggestion in RFC 2414 to reduce the * congestion window by the ratio of the old * segment size to the new segment size. */ tp->snd_cwnd = ulmax((tp->snd_cwnd / tp->t_maxseg) * mss, mss); } } else if (tcp_do_rfc3390 == 2) { /* increase initial window */ tp->snd_cwnd = ulmin(10 * mss, ulmax(2 * mss, 14600)); } else if (tcp_do_rfc3390) { /* increase initial window */ tp->snd_cwnd = ulmin(4 * mss, ulmax(2 * mss, 4380)); } else tp->snd_cwnd = mss; tp->t_maxseg = mss; return (offer != -1 ? mssopt : mss); } u_int tcp_hdrsz(struct tcpcb *tp) { u_int hlen; switch (tp->pf) { #ifdef INET6 case AF_INET6: hlen = sizeof(struct ip6_hdr); break; #endif case AF_INET: hlen = sizeof(struct ip); break; default: hlen = 0; break; } hlen += sizeof(struct tcphdr); if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP) hlen += TCPOLEN_TSTAMP_APPA; #ifdef TCP_SIGNATURE if (tp->t_flags & TF_SIGNATURE) hlen += TCPOLEN_SIGLEN; #endif return (hlen); } /* * Set connection variables based on the effective MSS. * We are passed the TCPCB for the actual connection. If we * are the server, we are called by the compressed state engine * when the 3-way handshake is complete. If we are the client, * we are called when we receive the SYN,ACK from the server. * * NOTE: The t_maxseg value must be initialized in the TCPCB * before this routine is called! */ void tcp_mss_update(struct tcpcb *tp) { int mss; u_long bufsize; struct rtentry *rt; struct socket *so; so = tp->t_inpcb->inp_socket; mss = tp->t_maxseg; rt = in_pcbrtentry(tp->t_inpcb); if (rt == NULL) return; bufsize = so->so_snd.sb_hiwat; if (bufsize < mss) { mss = bufsize; /* Update t_maxseg and t_maxopd */ tcp_mss(tp, mss); } else { bufsize = roundup(bufsize, mss); if (bufsize > sb_max) bufsize = sb_max; (void)sbreserve(so, &so->so_snd, bufsize); } bufsize = so->so_rcv.sb_hiwat; if (bufsize > mss) { bufsize = roundup(bufsize, mss); if (bufsize > sb_max) bufsize = sb_max; (void)sbreserve(so, &so->so_rcv, bufsize); } } /* * When a partial ack arrives, force the retransmission of the * next unacknowledged segment. Do not clear tp->t_dupacks. * By setting snd_nxt to ti_ack, this forces retransmission timer * to be started again. */ void tcp_newreno_partialack(struct tcpcb *tp, struct tcphdr *th) { /* * snd_una has not been updated and the socket send buffer * not yet drained of the acked data, so we have to leave * snd_una as it was to get the correct data offset in * tcp_output(). */ tcp_seq onxt = tp->snd_nxt; u_long ocwnd = tp->snd_cwnd; TCP_TIMER_DISARM(tp, TCPT_REXMT); tp->t_rtttime = 0; tp->snd_nxt = th->th_ack; /* * Set snd_cwnd to one segment beyond acknowledged offset * (tp->snd_una not yet updated when this function is called) */ tp->snd_cwnd = tp->t_maxseg + (th->th_ack - tp->snd_una); (void)tcp_output(tp); tp->snd_cwnd = ocwnd; if (SEQ_GT(onxt, tp->snd_nxt)) tp->snd_nxt = onxt; /* * Partial window deflation. Relies on fact that tp->snd_una * not updated yet. */ if (tp->snd_cwnd > th->th_ack - tp->snd_una) tp->snd_cwnd -= th->th_ack - tp->snd_una; else tp->snd_cwnd = 0; tp->snd_cwnd += tp->t_maxseg; } int tcp_mss_adv(struct mbuf *m, int af) { int mss = 0; int iphlen; struct ifnet *ifp = NULL; if (m && (m->m_flags & M_PKTHDR)) ifp = if_get(m->m_pkthdr.ph_ifidx); switch (af) { case AF_INET: if (ifp != NULL) mss = ifp->if_mtu; iphlen = sizeof(struct ip); break; #ifdef INET6 case AF_INET6: if (ifp != NULL) mss = ifp->if_mtu; iphlen = sizeof(struct ip6_hdr); break; #endif default: unhandled_af(af); } if_put(ifp); mss = mss - iphlen - sizeof(struct tcphdr); return (max(mss, tcp_mssdflt)); } /* * TCP compressed state engine. Currently used to hold compressed * state for SYN_RECEIVED. */ /* syn hash parameters */ int tcp_syn_hash_size = TCP_SYN_HASH_SIZE; int tcp_syn_cache_limit = TCP_SYN_HASH_SIZE*TCP_SYN_BUCKET_SIZE; int tcp_syn_bucket_limit = 3*TCP_SYN_BUCKET_SIZE; int tcp_syn_use_limit = 100000; struct syn_cache_set tcp_syn_cache[2]; int tcp_syn_cache_active; #define SYN_HASH(sa, sp, dp, rand) \ (((sa)->s_addr ^ (rand)[0]) * \ (((((u_int32_t)(dp))<<16) + ((u_int32_t)(sp))) ^ (rand)[4])) #ifndef INET6 #define SYN_HASHALL(hash, src, dst, rand) \ do { \ hash = SYN_HASH(&satosin(src)->sin_addr, \ satosin(src)->sin_port, \ satosin(dst)->sin_port, (rand)); \ } while (/*CONSTCOND*/ 0) #else #define SYN_HASH6(sa, sp, dp, rand) \ (((sa)->s6_addr32[0] ^ (rand)[0]) * \ ((sa)->s6_addr32[1] ^ (rand)[1]) * \ ((sa)->s6_addr32[2] ^ (rand)[2]) * \ ((sa)->s6_addr32[3] ^ (rand)[3]) * \ (((((u_int32_t)(dp))<<16) + ((u_int32_t)(sp))) ^ (rand)[4])) #define SYN_HASHALL(hash, src, dst, rand) \ do { \ switch ((src)->sa_family) { \ case AF_INET: \ hash = SYN_HASH(&satosin(src)->sin_addr, \ satosin(src)->sin_port, \ satosin(dst)->sin_port, (rand)); \ break; \ case AF_INET6: \ hash = SYN_HASH6(&satosin6(src)->sin6_addr, \ satosin6(src)->sin6_port, \ satosin6(dst)->sin6_port, (rand)); \ break; \ default: \ hash = 0; \ } \ } while (/*CONSTCOND*/0) #endif /* INET6 */ void syn_cache_rm(struct syn_cache *sc) { sc->sc_flags |= SCF_DEAD; TAILQ_REMOVE(&sc->sc_buckethead->sch_bucket, sc, sc_bucketq); sc->sc_tp = NULL; LIST_REMOVE(sc, sc_tpq); sc->sc_buckethead->sch_length--; timeout_del(&sc->sc_timer); sc->sc_set->scs_count--; } void syn_cache_put(struct syn_cache *sc) { m_free(sc->sc_ipopts); if (sc->sc_route4.ro_rt != NULL) { rtfree(sc->sc_route4.ro_rt); sc->sc_route4.ro_rt = NULL; } timeout_set(&sc->sc_timer, syn_cache_reaper, sc); timeout_add(&sc->sc_timer, 0); } struct pool syn_cache_pool; /* * We don't estimate RTT with SYNs, so each packet starts with the default * RTT and each timer step has a fixed timeout value. */ #define SYN_CACHE_TIMER_ARM(sc) \ do { \ TCPT_RANGESET((sc)->sc_rxtcur, \ TCPTV_SRTTDFLT * tcp_backoff[(sc)->sc_rxtshift], TCPTV_MIN, \ TCPTV_REXMTMAX); \ if (!timeout_initialized(&(sc)->sc_timer)) \ timeout_set_proc(&(sc)->sc_timer, syn_cache_timer, (sc)); \ timeout_add(&(sc)->sc_timer, (sc)->sc_rxtcur * (hz / PR_SLOWHZ)); \ } while (/*CONSTCOND*/0) #define SYN_CACHE_TIMESTAMP(sc) tcp_now + (sc)->sc_modulate void syn_cache_init(void) { int i; /* Initialize the hash buckets. */ tcp_syn_cache[0].scs_buckethead = mallocarray(tcp_syn_hash_size, sizeof(struct syn_cache_head), M_SYNCACHE, M_WAITOK|M_ZERO); tcp_syn_cache[1].scs_buckethead = mallocarray(tcp_syn_hash_size, sizeof(struct syn_cache_head), M_SYNCACHE, M_WAITOK|M_ZERO); tcp_syn_cache[0].scs_size = tcp_syn_hash_size; tcp_syn_cache[1].scs_size = tcp_syn_hash_size; for (i = 0; i < tcp_syn_hash_size; i++) { TAILQ_INIT(&tcp_syn_cache[0].scs_buckethead[i].sch_bucket); TAILQ_INIT(&tcp_syn_cache[1].scs_buckethead[i].sch_bucket); } /* Initialize the syn cache pool. */ pool_init(&syn_cache_pool, sizeof(struct syn_cache), 0, IPL_SOFTNET, 0, "syncache", NULL); } void syn_cache_insert(struct syn_cache *sc, struct tcpcb *tp) { struct syn_cache_set *set = &tcp_syn_cache[tcp_syn_cache_active]; struct syn_cache_head *scp; struct syn_cache *sc2; int i; NET_ASSERT_LOCKED(); /* * If there are no entries in the hash table, reinitialize * the hash secrets. To avoid useless cache swaps and * reinitialization, use it until the limit is reached. * An empty cache is also the opportunity to resize the hash. */ if (set->scs_count == 0 && set->scs_use <= 0) { set->scs_use = tcp_syn_use_limit; if (set->scs_size != tcp_syn_hash_size) { scp = mallocarray(tcp_syn_hash_size, sizeof(struct syn_cache_head), M_SYNCACHE, M_NOWAIT|M_ZERO); if (scp == NULL) { /* Try again next time. */ set->scs_use = 0; } else { free(set->scs_buckethead, M_SYNCACHE, set->scs_size * sizeof(struct syn_cache_head)); set->scs_buckethead = scp; set->scs_size = tcp_syn_hash_size; for (i = 0; i < tcp_syn_hash_size; i++) TAILQ_INIT(&scp[i].sch_bucket); } } arc4random_buf(set->scs_random, sizeof(set->scs_random)); tcpstat_inc(tcps_sc_seedrandom); } SYN_HASHALL(sc->sc_hash, &sc->sc_src.sa, &sc->sc_dst.sa, set->scs_random); scp = &set->scs_buckethead[sc->sc_hash % set->scs_size]; sc->sc_buckethead = scp; /* * Make sure that we don't overflow the per-bucket * limit or the total cache size limit. */ if (scp->sch_length >= tcp_syn_bucket_limit) { tcpstat_inc(tcps_sc_bucketoverflow); /* * Someone might attack our bucket hash function. Reseed * with random as soon as the passive syn cache gets empty. */ set->scs_use = 0; /* * The bucket is full. Toss the oldest element in the * bucket. This will be the first entry in the bucket. */ sc2 = TAILQ_FIRST(&scp->sch_bucket); #ifdef DIAGNOSTIC /* * This should never happen; we should always find an * entry in our bucket. */ if (sc2 == NULL) panic("%s: bucketoverflow: impossible", __func__); #endif syn_cache_rm(sc2); syn_cache_put(sc2); } else if (set->scs_count >= tcp_syn_cache_limit) { struct syn_cache_head *scp2, *sce; tcpstat_inc(tcps_sc_overflowed); /* * The cache is full. Toss the oldest entry in the * first non-empty bucket we can find. * * XXX We would really like to toss the oldest * entry in the cache, but we hope that this * condition doesn't happen very often. */ scp2 = scp; if (TAILQ_EMPTY(&scp2->sch_bucket)) { sce = &set->scs_buckethead[set->scs_size]; for (++scp2; scp2 != scp; scp2++) { if (scp2 >= sce) scp2 = &set->scs_buckethead[0]; if (! TAILQ_EMPTY(&scp2->sch_bucket)) break; } #ifdef DIAGNOSTIC /* * This should never happen; we should always find a * non-empty bucket. */ if (scp2 == scp) panic("%s: cacheoverflow: impossible", __func__); #endif } sc2 = TAILQ_FIRST(&scp2->sch_bucket); syn_cache_rm(sc2); syn_cache_put(sc2); } /* * Initialize the entry's timer. */ sc->sc_rxttot = 0; sc->sc_rxtshift = 0; SYN_CACHE_TIMER_ARM(sc); /* Link it from tcpcb entry */ LIST_INSERT_HEAD(&tp->t_sc, sc, sc_tpq); /* Put it into the bucket. */ TAILQ_INSERT_TAIL(&scp->sch_bucket, sc, sc_bucketq); scp->sch_length++; sc->sc_set = set; set->scs_count++; set->scs_use--; tcpstat_inc(tcps_sc_added); /* * If the active cache has exceeded its use limit and * the passive syn cache is empty, exchange their roles. */ if (set->scs_use <= 0 && tcp_syn_cache[!tcp_syn_cache_active].scs_count == 0) tcp_syn_cache_active = !tcp_syn_cache_active; } /* * Walk the timer queues, looking for SYN,ACKs that need to be retransmitted. * If we have retransmitted an entry the maximum number of times, expire * that entry. */ void syn_cache_timer(void *arg) { struct syn_cache *sc = arg; NET_LOCK(); if (sc->sc_flags & SCF_DEAD) goto out; if (__predict_false(sc->sc_rxtshift == TCP_MAXRXTSHIFT)) { /* Drop it -- too many retransmissions. */ goto dropit; } /* * Compute the total amount of time this entry has * been on a queue. If this entry has been on longer * than the keep alive timer would allow, expire it. */ sc->sc_rxttot += sc->sc_rxtcur; if (sc->sc_rxttot >= tcptv_keep_init) goto dropit; tcpstat_inc(tcps_sc_retransmitted); (void) syn_cache_respond(sc, NULL); /* Advance the timer back-off. */ sc->sc_rxtshift++; SYN_CACHE_TIMER_ARM(sc); out: NET_UNLOCK(); return; dropit: tcpstat_inc(tcps_sc_timed_out); syn_cache_rm(sc); syn_cache_put(sc); NET_UNLOCK(); } void syn_cache_reaper(void *arg) { struct syn_cache *sc = arg; pool_put(&syn_cache_pool, (sc)); return; } /* * Remove syn cache created by the specified tcb entry, * because this does not make sense to keep them * (if there's no tcb entry, syn cache entry will never be used) */ void syn_cache_cleanup(struct tcpcb *tp) { struct syn_cache *sc, *nsc; NET_ASSERT_LOCKED(); LIST_FOREACH_SAFE(sc, &tp->t_sc, sc_tpq, nsc) { #ifdef DIAGNOSTIC if (sc->sc_tp != tp) panic("invalid sc_tp in syn_cache_cleanup"); #endif syn_cache_rm(sc); syn_cache_put(sc); } /* just for safety */ LIST_INIT(&tp->t_sc); } /* * Find an entry in the syn cache. */ struct syn_cache * syn_cache_lookup(struct sockaddr *src, struct sockaddr *dst, struct syn_cache_head **headp, u_int rtableid) { struct syn_cache_set *sets[2]; struct syn_cache *sc; struct syn_cache_head *scp; u_int32_t hash; int i; NET_ASSERT_LOCKED(); /* Check the active cache first, the passive cache is likely empty. */ sets[0] = &tcp_syn_cache[tcp_syn_cache_active]; sets[1] = &tcp_syn_cache[!tcp_syn_cache_active]; for (i = 0; i < 2; i++) { if (sets[i]->scs_count == 0) continue; SYN_HASHALL(hash, src, dst, sets[i]->scs_random); scp = &sets[i]->scs_buckethead[hash % sets[i]->scs_size]; *headp = scp; TAILQ_FOREACH(sc, &scp->sch_bucket, sc_bucketq) { if (sc->sc_hash != hash) continue; if (!bcmp(&sc->sc_src, src, src->sa_len) && !bcmp(&sc->sc_dst, dst, dst->sa_len) && rtable_l2(rtableid) == rtable_l2(sc->sc_rtableid)) return (sc); } } return (NULL); } /* * This function gets called when we receive an ACK for a * socket in the LISTEN state. We look up the connection * in the syn cache, and if its there, we pull it out of * the cache and turn it into a full-blown connection in * the SYN-RECEIVED state. * * The return values may not be immediately obvious, and their effects * can be subtle, so here they are: * * NULL SYN was not found in cache; caller should drop the * packet and send an RST. * * -1 We were unable to create the new connection, and are * aborting it. An ACK,RST is being sent to the peer * (unless we got screwey sequence numbners; see below), * because the 3-way handshake has been completed. Caller * should not free the mbuf, since we may be using it. If * we are not, we will free it. * * Otherwise, the return value is a pointer to the new socket * associated with the connection. */ struct socket * syn_cache_get(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th, u_int hlen, u_int tlen, struct socket *so, struct mbuf *m) { struct syn_cache *sc; struct syn_cache_head *scp; struct inpcb *inp, *oldinp; struct tcpcb *tp = NULL; struct mbuf *am; struct socket *oso; NET_ASSERT_LOCKED(); sc = syn_cache_lookup(src, dst, &scp, sotoinpcb(so)->inp_rtableid); if (sc == NULL) return (NULL); /* * Verify the sequence and ack numbers. Try getting the correct * response again. */ if ((th->th_ack != sc->sc_iss + 1) || SEQ_LEQ(th->th_seq, sc->sc_irs) || SEQ_GT(th->th_seq, sc->sc_irs + 1 + sc->sc_win)) { (void) syn_cache_respond(sc, m); return ((struct socket *)(-1)); } /* Remove this cache entry */ syn_cache_rm(sc); /* * Ok, create the full blown connection, and set things up * as they would have been set up if we had created the * connection when the SYN arrived. If we can't create * the connection, abort it. */ oso = so; so = sonewconn(so, SS_ISCONNECTED); if (so == NULL) goto resetandabort; oldinp = sotoinpcb(oso); inp = sotoinpcb(so); #ifdef IPSEC /* * We need to copy the required security levels * from the old pcb. Ditto for any other * IPsec-related information. */ memcpy(inp->inp_seclevel, oldinp->inp_seclevel, sizeof(oldinp->inp_seclevel)); #endif /* IPSEC */ #ifdef INET6 /* * inp still has the OLD in_pcb stuff, set the * v6-related flags on the new guy, too. */ inp->inp_flags |= (oldinp->inp_flags & INP_IPV6); if (inp->inp_flags & INP_IPV6) { inp->inp_ipv6.ip6_hlim = oldinp->inp_ipv6.ip6_hlim; inp->inp_hops = oldinp->inp_hops; } else #endif /* INET6 */ { inp->inp_ip.ip_ttl = oldinp->inp_ip.ip_ttl; } #if NPF > 0 if (m->m_pkthdr.pf.flags & PF_TAG_DIVERTED) { struct pf_divert *divert; divert = pf_find_divert(m); KASSERT(divert != NULL); inp->inp_rtableid = divert->rdomain; } else #endif /* inherit rtable from listening socket */ inp->inp_rtableid = sc->sc_rtableid; inp->inp_lport = th->th_dport; switch (src->sa_family) { #ifdef INET6 case AF_INET6: inp->inp_laddr6 = satosin6(dst)->sin6_addr; break; #endif /* INET6 */ case AF_INET: inp->inp_laddr = satosin(dst)->sin_addr; inp->inp_options = ip_srcroute(m); if (inp->inp_options == NULL) { inp->inp_options = sc->sc_ipopts; sc->sc_ipopts = NULL; } break; } in_pcbrehash(inp); /* * Give the new socket our cached route reference. */ if (src->sa_family == AF_INET) inp->inp_route = sc->sc_route4; /* struct assignment */ #ifdef INET6 else inp->inp_route6 = sc->sc_route6; #endif sc->sc_route4.ro_rt = NULL; am = m_get(M_DONTWAIT, MT_SONAME); /* XXX */ if (am == NULL) goto resetandabort; am->m_len = src->sa_len; memcpy(mtod(am, caddr_t), src, src->sa_len); if (in_pcbconnect(inp, am)) { (void) m_free(am); goto resetandabort; } (void) m_free(am); tp = intotcpcb(inp); tp->t_flags = sototcpcb(oso)->t_flags & (TF_NOPUSH|TF_NODELAY); if (sc->sc_request_r_scale != 15) { tp->requested_s_scale = sc->sc_requested_s_scale; tp->request_r_scale = sc->sc_request_r_scale; tp->t_flags |= TF_REQ_SCALE|TF_RCVD_SCALE; } if (sc->sc_flags & SCF_TIMESTAMP) tp->t_flags |= TF_REQ_TSTMP|TF_RCVD_TSTMP; tp->t_template = tcp_template(tp); if (tp->t_template == 0) { tp = tcp_drop(tp, ENOBUFS); /* destroys socket */ so = NULL; goto abort; } tp->sack_enable = sc->sc_flags & SCF_SACK_PERMIT; tp->ts_modulate = sc->sc_modulate; tp->ts_recent = sc->sc_timestamp; tp->iss = sc->sc_iss; tp->irs = sc->sc_irs; tcp_sendseqinit(tp); tp->snd_last = tp->snd_una; #ifdef TCP_ECN if (sc->sc_flags & SCF_ECN_PERMIT) { tp->t_flags |= TF_ECN_PERMIT; tcpstat_inc(tcps_ecn_accepts); } #endif if (sc->sc_flags & SCF_SACK_PERMIT) tp->t_flags |= TF_SACK_PERMIT; #ifdef TCP_SIGNATURE if (sc->sc_flags & SCF_SIGNATURE) tp->t_flags |= TF_SIGNATURE; #endif tcp_rcvseqinit(tp); tp->t_state = TCPS_SYN_RECEIVED; tp->t_rcvtime = tcp_now; TCP_TIMER_ARM(tp, TCPT_KEEP, tcptv_keep_init); tcpstat_inc(tcps_accepts); tcp_mss(tp, sc->sc_peermaxseg); /* sets t_maxseg */ if (sc->sc_peermaxseg) tcp_mss_update(tp); /* Reset initial window to 1 segment for retransmit */ if (sc->sc_rxtshift > 0) tp->snd_cwnd = tp->t_maxseg; tp->snd_wl1 = sc->sc_irs; tp->rcv_up = sc->sc_irs + 1; /* * This is what would have happened in tcp_output() when * the SYN,ACK was sent. */ tp->snd_up = tp->snd_una; tp->snd_max = tp->snd_nxt = tp->iss+1; TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); if (sc->sc_win > 0 && SEQ_GT(tp->rcv_nxt + sc->sc_win, tp->rcv_adv)) tp->rcv_adv = tp->rcv_nxt + sc->sc_win; tp->last_ack_sent = tp->rcv_nxt; tcpstat_inc(tcps_sc_completed); syn_cache_put(sc); return (so); resetandabort: tcp_respond(NULL, mtod(m, caddr_t), th, (tcp_seq)0, th->th_ack, TH_RST, m->m_pkthdr.ph_rtableid); abort: m_freem(m); if (so != NULL) (void) soabort(so); syn_cache_put(sc); tcpstat_inc(tcps_sc_aborted); return ((struct socket *)(-1)); } /* * This function is called when we get a RST for a * non-existent connection, so that we can see if the * connection is in the syn cache. If it is, zap it. */ void syn_cache_reset(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th, u_int rtableid) { struct syn_cache *sc; struct syn_cache_head *scp; NET_ASSERT_LOCKED(); if ((sc = syn_cache_lookup(src, dst, &scp, rtableid)) == NULL) return; if (SEQ_LT(th->th_seq, sc->sc_irs) || SEQ_GT(th->th_seq, sc->sc_irs + 1)) return; syn_cache_rm(sc); tcpstat_inc(tcps_sc_reset); syn_cache_put(sc); } void syn_cache_unreach(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th, u_int rtableid) { struct syn_cache *sc; struct syn_cache_head *scp; NET_ASSERT_LOCKED(); if ((sc = syn_cache_lookup(src, dst, &scp, rtableid)) == NULL) return; /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ if (ntohl (th->th_seq) != sc->sc_iss) { return; } /* * If we've retransmitted 3 times and this is our second error, * we remove the entry. Otherwise, we allow it to continue on. * This prevents us from incorrectly nuking an entry during a * spurious network outage. * * See tcp_notify(). */ if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rxtshift < 3) { sc->sc_flags |= SCF_UNREACH; return; } syn_cache_rm(sc); tcpstat_inc(tcps_sc_unreach); syn_cache_put(sc); } /* * Given a LISTEN socket and an inbound SYN request, add * this to the syn cache, and send back a segment: * * to the source. * * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. * Doing so would require that we hold onto the data and deliver it * to the application. However, if we are the target of a SYN-flood * DoS attack, an attacker could send data which would eventually * consume all available buffer space if it were ACKed. By not ACKing * the data, we avoid this DoS scenario. */ int syn_cache_add(struct sockaddr *src, struct sockaddr *dst, struct tcphdr *th, u_int iphlen, struct socket *so, struct mbuf *m, u_char *optp, int optlen, struct tcp_opt_info *oi, tcp_seq *issp) { struct tcpcb tb, *tp; long win; struct syn_cache *sc; struct syn_cache_head *scp; struct mbuf *ipopts; tp = sototcpcb(so); /* * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN * * Note this check is performed in tcp_input() very early on. */ /* * Initialize some local state. */ win = sbspace(so, &so->so_rcv); if (win > TCP_MAXWIN) win = TCP_MAXWIN; bzero(&tb, sizeof(tb)); #ifdef TCP_SIGNATURE if (optp || (tp->t_flags & TF_SIGNATURE)) { #else if (optp) { #endif tb.pf = tp->pf; tb.sack_enable = tp->sack_enable; tb.t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; #ifdef TCP_SIGNATURE if (tp->t_flags & TF_SIGNATURE) tb.t_flags |= TF_SIGNATURE; #endif tb.t_state = TCPS_LISTEN; if (tcp_dooptions(&tb, optp, optlen, th, m, iphlen, oi, sotoinpcb(so)->inp_rtableid)) return (-1); } switch (src->sa_family) { case AF_INET: /* * Remember the IP options, if any. */ ipopts = ip_srcroute(m); break; default: ipopts = NULL; } /* * See if we already have an entry for this connection. * If we do, resend the SYN,ACK. We do not count this * as a retransmission (XXX though maybe we should). */ sc = syn_cache_lookup(src, dst, &scp, sotoinpcb(so)->inp_rtableid); if (sc != NULL) { tcpstat_inc(tcps_sc_dupesyn); if (ipopts) { /* * If we were remembering a previous source route, * forget it and use the new one we've been given. */ m_free(sc->sc_ipopts); sc->sc_ipopts = ipopts; } sc->sc_timestamp = tb.ts_recent; if (syn_cache_respond(sc, m) == 0) { tcpstat_inc(tcps_sndacks); tcpstat_inc(tcps_sndtotal); } return (0); } sc = pool_get(&syn_cache_pool, PR_NOWAIT|PR_ZERO); if (sc == NULL) { m_free(ipopts); return (-1); } /* * Fill in the cache, and put the necessary IP and TCP * options into the reply. */ memcpy(&sc->sc_src, src, src->sa_len); memcpy(&sc->sc_dst, dst, dst->sa_len); sc->sc_rtableid = sotoinpcb(so)->inp_rtableid; sc->sc_flags = 0; sc->sc_ipopts = ipopts; sc->sc_irs = th->th_seq; sc->sc_iss = issp ? *issp : arc4random(); sc->sc_peermaxseg = oi->maxseg; sc->sc_ourmaxseg = tcp_mss_adv(m, sc->sc_src.sa.sa_family); sc->sc_win = win; sc->sc_timestamp = tb.ts_recent; if ((tb.t_flags & (TF_REQ_TSTMP|TF_RCVD_TSTMP)) == (TF_REQ_TSTMP|TF_RCVD_TSTMP)) { sc->sc_flags |= SCF_TIMESTAMP; sc->sc_modulate = arc4random(); } if ((tb.t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == (TF_RCVD_SCALE|TF_REQ_SCALE)) { sc->sc_requested_s_scale = tb.requested_s_scale; sc->sc_request_r_scale = 0; /* * Pick the smallest possible scaling factor that * will still allow us to scale up to sb_max. * * We do this because there are broken firewalls that * will corrupt the window scale option, leading to * the other endpoint believing that our advertised * window is unscaled. At scale factors larger than * 5 the unscaled window will drop below 1500 bytes, * leading to serious problems when traversing these * broken firewalls. * * With the default sbmax of 256K, a scale factor * of 3 will be chosen by this algorithm. Those who * choose a larger sbmax should watch out * for the compatibility problems mentioned above. * * RFC1323: The Window field in a SYN (i.e., a * or ) segment itself is never scaled. */ while (sc->sc_request_r_scale < TCP_MAX_WINSHIFT && (TCP_MAXWIN << sc->sc_request_r_scale) < sb_max) sc->sc_request_r_scale++; } else { sc->sc_requested_s_scale = 15; sc->sc_request_r_scale = 15; } #ifdef TCP_ECN /* * if both ECE and CWR flag bits are set, peer is ECN capable. */ if (tcp_do_ecn && (th->th_flags & (TH_ECE|TH_CWR)) == (TH_ECE|TH_CWR)) sc->sc_flags |= SCF_ECN_PERMIT; #endif /* * Set SCF_SACK_PERMIT if peer did send a SACK_PERMITTED option * (i.e., if tcp_dooptions() did set TF_SACK_PERMIT). */ if (tb.sack_enable && (tb.t_flags & TF_SACK_PERMIT)) sc->sc_flags |= SCF_SACK_PERMIT; #ifdef TCP_SIGNATURE if (tb.t_flags & TF_SIGNATURE) sc->sc_flags |= SCF_SIGNATURE; #endif sc->sc_tp = tp; if (syn_cache_respond(sc, m) == 0) { syn_cache_insert(sc, tp); tcpstat_inc(tcps_sndacks); tcpstat_inc(tcps_sndtotal); } else { syn_cache_put(sc); tcpstat_inc(tcps_sc_dropped); } return (0); } int syn_cache_respond(struct syn_cache *sc, struct mbuf *m) { u_int8_t *optp; int optlen, error; u_int16_t tlen; struct ip *ip = NULL; #ifdef INET6 struct ip6_hdr *ip6 = NULL; #endif struct tcphdr *th; u_int hlen; struct inpcb *inp; switch (sc->sc_src.sa.sa_family) { case AF_INET: hlen = sizeof(struct ip); break; #ifdef INET6 case AF_INET6: hlen = sizeof(struct ip6_hdr); break; #endif default: m_freem(m); return (EAFNOSUPPORT); } /* Compute the size of the TCP options. */ optlen = 4 + (sc->sc_request_r_scale != 15 ? 4 : 0) + ((sc->sc_flags & SCF_SACK_PERMIT) ? 4 : 0) + #ifdef TCP_SIGNATURE ((sc->sc_flags & SCF_SIGNATURE) ? TCPOLEN_SIGLEN : 0) + #endif ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0); tlen = hlen + sizeof(struct tcphdr) + optlen; /* * Create the IP+TCP header from scratch. */ m_freem(m); #ifdef DIAGNOSTIC if (max_linkhdr + tlen > MCLBYTES) return (ENOBUFS); #endif MGETHDR(m, M_DONTWAIT, MT_DATA); if (m && max_linkhdr + tlen > MHLEN) { MCLGET(m, M_DONTWAIT); if ((m->m_flags & M_EXT) == 0) { m_freem(m); m = NULL; } } if (m == NULL) return (ENOBUFS); /* Fixup the mbuf. */ m->m_data += max_linkhdr; m->m_len = m->m_pkthdr.len = tlen; m->m_pkthdr.ph_ifidx = 0; m->m_pkthdr.ph_rtableid = sc->sc_rtableid; memset(mtod(m, u_char *), 0, tlen); switch (sc->sc_src.sa.sa_family) { case AF_INET: ip = mtod(m, struct ip *); ip->ip_dst = sc->sc_src.sin.sin_addr; ip->ip_src = sc->sc_dst.sin.sin_addr; ip->ip_p = IPPROTO_TCP; th = (struct tcphdr *)(ip + 1); th->th_dport = sc->sc_src.sin.sin_port; th->th_sport = sc->sc_dst.sin.sin_port; break; #ifdef INET6 case AF_INET6: ip6 = mtod(m, struct ip6_hdr *); ip6->ip6_dst = sc->sc_src.sin6.sin6_addr; ip6->ip6_src = sc->sc_dst.sin6.sin6_addr; ip6->ip6_nxt = IPPROTO_TCP; /* ip6_plen will be updated in ip6_output() */ th = (struct tcphdr *)(ip6 + 1); th->th_dport = sc->sc_src.sin6.sin6_port; th->th_sport = sc->sc_dst.sin6.sin6_port; break; #endif default: unhandled_af(sc->sc_src.sa.sa_family); } th->th_seq = htonl(sc->sc_iss); th->th_ack = htonl(sc->sc_irs + 1); th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; th->th_flags = TH_SYN|TH_ACK; #ifdef TCP_ECN /* Set ECE for SYN-ACK if peer supports ECN. */ if (tcp_do_ecn && (sc->sc_flags & SCF_ECN_PERMIT)) th->th_flags |= TH_ECE; #endif th->th_win = htons(sc->sc_win); /* th_sum already 0 */ /* th_urp already 0 */ /* Tack on the TCP options. */ optp = (u_int8_t *)(th + 1); *optp++ = TCPOPT_MAXSEG; *optp++ = 4; *optp++ = (sc->sc_ourmaxseg >> 8) & 0xff; *optp++ = sc->sc_ourmaxseg & 0xff; /* Include SACK_PERMIT_HDR option if peer has already done so. */ if (sc->sc_flags & SCF_SACK_PERMIT) { *((u_int32_t *)optp) = htonl(TCPOPT_SACK_PERMIT_HDR); optp += 4; } if (sc->sc_request_r_scale != 15) { *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | sc->sc_request_r_scale); optp += 4; } if (sc->sc_flags & SCF_TIMESTAMP) { u_int32_t *lp = (u_int32_t *)(optp); /* Form timestamp option as shown in appendix A of RFC 1323. */ *lp++ = htonl(TCPOPT_TSTAMP_HDR); *lp++ = htonl(SYN_CACHE_TIMESTAMP(sc)); *lp = htonl(sc->sc_timestamp); optp += TCPOLEN_TSTAMP_APPA; } #ifdef TCP_SIGNATURE if (sc->sc_flags & SCF_SIGNATURE) { union sockaddr_union src, dst; struct tdb *tdb; bzero(&src, sizeof(union sockaddr_union)); bzero(&dst, sizeof(union sockaddr_union)); src.sa.sa_len = sc->sc_src.sa.sa_len; src.sa.sa_family = sc->sc_src.sa.sa_family; dst.sa.sa_len = sc->sc_dst.sa.sa_len; dst.sa.sa_family = sc->sc_dst.sa.sa_family; switch (sc->sc_src.sa.sa_family) { case 0: /*default to PF_INET*/ case AF_INET: src.sin.sin_addr = mtod(m, struct ip *)->ip_src; dst.sin.sin_addr = mtod(m, struct ip *)->ip_dst; break; #ifdef INET6 case AF_INET6: src.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_src; dst.sin6.sin6_addr = mtod(m, struct ip6_hdr *)->ip6_dst; break; #endif /* INET6 */ } tdb = gettdbbysrcdst(rtable_l2(sc->sc_rtableid), 0, &src, &dst, IPPROTO_TCP); if (tdb == NULL) { m_freem(m); return (EPERM); } /* Send signature option */ *(optp++) = TCPOPT_SIGNATURE; *(optp++) = TCPOLEN_SIGNATURE; if (tcp_signature(tdb, sc->sc_src.sa.sa_family, m, th, hlen, 0, optp) < 0) { m_freem(m); return (EINVAL); } optp += 16; /* Pad options list to the next 32 bit boundary and * terminate it. */ *optp++ = TCPOPT_NOP; *optp++ = TCPOPT_EOL; } #endif /* TCP_SIGNATURE */ /* Compute the packet's checksum. */ switch (sc->sc_src.sa.sa_family) { case AF_INET: ip->ip_len = htons(tlen - hlen); th->th_sum = 0; th->th_sum = in_cksum(m, tlen); break; #ifdef INET6 case AF_INET6: ip6->ip6_plen = htons(tlen - hlen); th->th_sum = 0; th->th_sum = in6_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); break; #endif } /* use IPsec policy and ttl from listening socket, on SYN ACK */ inp = sc->sc_tp ? sc->sc_tp->t_inpcb : NULL; /* * Fill in some straggling IP bits. Note the stack expects * ip_len to be in host order, for convenience. */ switch (sc->sc_src.sa.sa_family) { case AF_INET: ip->ip_len = htons(tlen); ip->ip_ttl = inp ? inp->inp_ip.ip_ttl : ip_defttl; if (inp != NULL) ip->ip_tos = inp->inp_ip.ip_tos; break; #ifdef INET6 case AF_INET6: ip6->ip6_vfc &= ~IPV6_VERSION_MASK; ip6->ip6_vfc |= IPV6_VERSION; ip6->ip6_plen = htons(tlen - hlen); /* ip6_hlim will be initialized afterwards */ /* leave flowlabel = 0, it is legal and require no state mgmt */ break; #endif } switch (sc->sc_src.sa.sa_family) { case AF_INET: error = ip_output(m, sc->sc_ipopts, &sc->sc_route4, (ip_mtudisc ? IP_MTUDISC : 0), NULL, inp, 0); break; #ifdef INET6 case AF_INET6: ip6->ip6_hlim = in6_selecthlim(inp); error = ip6_output(m, NULL /*XXX*/, &sc->sc_route6, 0, NULL, NULL); break; #endif default: error = EAFNOSUPPORT; break; } return (error); }