/* $NetBSD: tcp_input.c,v 1.414.2.4 2020/09/13 12:18:16 martin Exp $ */ /* * Copyright (C) 1995, 1996, 1997, and 1998 WIDE Project. * 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 project 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 PROJECT 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 PROJECT 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). */ /*- * Copyright (c) 1997, 1998, 1999, 2001, 2005, 2006, * 2011 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Coyote Point Systems, Inc. * This code is derived from software contributed to The NetBSD Foundation * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation * Facility, NASA Ames Research Center. * This code is derived from software contributed to The NetBSD Foundation * by Charles M. Hannum. * This code is derived from software contributed to The NetBSD Foundation * by Rui Paulo. * * 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. * * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. 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 FOUNDATION 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 (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 */ /* * TODO list for SYN cache stuff: * * Find room for a "state" field, which is needed to keep a * compressed state for TIME_WAIT TCBs. It's been noted already * that this is fairly important for very high-volume web and * mail servers, which use a large number of short-lived * connections. */ #include __KERNEL_RCSID(0, "$NetBSD: tcp_input.c,v 1.414.2.4 2020/09/13 12:18:16 martin Exp $"); #ifdef _KERNEL_OPT #include "opt_inet.h" #include "opt_ipsec.h" #include "opt_inet_csum.h" #include "opt_tcp_debug.h" #endif #include #include #include #include #include #include #include #include #include #include #include #include #ifdef TCP_SIGNATURE #include #endif #include /* for lwp0 */ #include #include #include #include #include #include #include #include #include #include #ifdef INET6 #include #include #include #include #include #include #include #ifdef TCP_SIGNATURE #include #endif #endif #ifndef INET6 #include #endif #include #include #include #include #include #include #include #include #ifdef INET6 #include "faith.h" #if defined(NFAITH) && NFAITH > 0 #include #endif #endif #ifdef IPSEC #include #include #ifdef INET6 #include #endif #endif /* IPSEC*/ #include int tcprexmtthresh = 3; int tcp_log_refused; int tcp_do_autorcvbuf = 1; int tcp_autorcvbuf_inc = 16 * 1024; int tcp_autorcvbuf_max = 256 * 1024; int tcp_msl = (TCPTV_MSL / PR_SLOWHZ); static int tcp_rst_ppslim_count = 0; static struct timeval tcp_rst_ppslim_last; static int tcp_ackdrop_ppslim_count = 0; static struct timeval tcp_ackdrop_ppslim_last; static void syn_cache_timer(void *); #define TCP_PAWS_IDLE (24U * 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) /* * Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ #ifdef INET6 static inline void nd6_hint(struct tcpcb *tp) { struct rtentry *rt = NULL; if (tp != NULL && tp->t_in6pcb != NULL && tp->t_family == AF_INET6 && (rt = rtcache_validate(&tp->t_in6pcb->in6p_route)) != NULL) nd6_nud_hint(rt); rtcache_unref(rt, &tp->t_in6pcb->in6p_route); } #else static inline void nd6_hint(struct tcpcb *tp) { } #endif /* * 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. */ static void tcp_setup_ack(struct tcpcb *tp, const struct tcphdr *th) { if (tp->t_flags & TF_DELACK || (tcp_ack_on_push && th->th_flags & TH_PUSH)) tp->t_flags |= TF_ACKNOW; else TCP_SET_DELACK(tp); } static void icmp_check(struct tcpcb *tp, const struct tcphdr *th, int 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; } /* * Convert TCP protocol fields to host order for easier processing. */ static void tcp_fields_to_host(struct tcphdr *th) { NTOHL(th->th_seq); NTOHL(th->th_ack); NTOHS(th->th_win); NTOHS(th->th_urp); } /* * ... and reverse the above. */ static void tcp_fields_to_net(struct tcphdr *th) { HTONL(th->th_seq); HTONL(th->th_ack); HTONS(th->th_win); HTONS(th->th_urp); } static void tcp_urp_drop(struct tcphdr *th, int todrop, int *tiflags) { if (th->th_urp > todrop) { th->th_urp -= todrop; } else { *tiflags &= ~TH_URG; th->th_urp = 0; } } #ifdef TCP_CSUM_COUNTERS #include extern struct evcnt tcp_hwcsum_ok; extern struct evcnt tcp_hwcsum_bad; extern struct evcnt tcp_hwcsum_data; extern struct evcnt tcp_swcsum; #if defined(INET6) extern struct evcnt tcp6_hwcsum_ok; extern struct evcnt tcp6_hwcsum_bad; extern struct evcnt tcp6_hwcsum_data; extern struct evcnt tcp6_swcsum; #endif /* defined(INET6) */ #define TCP_CSUM_COUNTER_INCR(ev) (ev)->ev_count++ #else #define TCP_CSUM_COUNTER_INCR(ev) /* nothing */ #endif /* TCP_CSUM_COUNTERS */ #ifdef TCP_REASS_COUNTERS #include extern struct evcnt tcp_reass_; extern struct evcnt tcp_reass_empty; extern struct evcnt tcp_reass_iteration[8]; extern struct evcnt tcp_reass_prependfirst; extern struct evcnt tcp_reass_prepend; extern struct evcnt tcp_reass_insert; extern struct evcnt tcp_reass_inserttail; extern struct evcnt tcp_reass_append; extern struct evcnt tcp_reass_appendtail; extern struct evcnt tcp_reass_overlaptail; extern struct evcnt tcp_reass_overlapfront; extern struct evcnt tcp_reass_segdup; extern struct evcnt tcp_reass_fragdup; #define TCP_REASS_COUNTER_INCR(ev) (ev)->ev_count++ #else #define TCP_REASS_COUNTER_INCR(ev) /* nothing */ #endif /* TCP_REASS_COUNTERS */ static int tcp_reass(struct tcpcb *, const struct tcphdr *, struct mbuf *, int); static int tcp_dooptions(struct tcpcb *, const u_char *, int, struct tcphdr *, struct mbuf *, int, struct tcp_opt_info *); static void tcp4_log_refused(const struct ip *, const struct tcphdr *); #ifdef INET6 static void tcp6_log_refused(const struct ip6_hdr *, const struct tcphdr *); #endif #if defined(MBUFTRACE) struct mowner tcp_reass_mowner = MOWNER_INIT("tcp", "reass"); #endif /* defined(MBUFTRACE) */ static struct pool tcpipqent_pool; void tcpipqent_init(void) { pool_init(&tcpipqent_pool, sizeof(struct ipqent), 0, 0, 0, "tcpipqepl", NULL, IPL_VM); } struct ipqent * tcpipqent_alloc(void) { struct ipqent *ipqe; int s; s = splvm(); ipqe = pool_get(&tcpipqent_pool, PR_NOWAIT); splx(s); return ipqe; } void tcpipqent_free(struct ipqent *ipqe) { int s; s = splvm(); pool_put(&tcpipqent_pool, ipqe); splx(s); } /* * Insert segment ti into reassembly queue of tcp with * control block tp. Return TH_FIN if reassembly now includes * a segment with FIN. */ static int tcp_reass(struct tcpcb *tp, const struct tcphdr *th, struct mbuf *m, int tlen) { struct ipqent *p, *q, *nq, *tiqe = NULL; struct socket *so = NULL; int pkt_flags; tcp_seq pkt_seq; unsigned pkt_len; u_long rcvpartdupbyte = 0; u_long rcvoobyte; #ifdef TCP_REASS_COUNTERS u_int count = 0; #endif uint64_t *tcps; if (tp->t_inpcb) so = tp->t_inpcb->inp_socket; #ifdef INET6 else if (tp->t_in6pcb) so = tp->t_in6pcb->in6p_socket; #endif TCP_REASS_LOCK_CHECK(tp); /* * Call with th==NULL after become established to * force pre-ESTABLISHED data up to user socket. */ if (th == NULL) goto present; m_claimm(m, &tcp_reass_mowner); rcvoobyte = tlen; /* * Copy these to local variables because the TCP header gets munged * while we are collapsing mbufs. */ pkt_seq = th->th_seq; pkt_len = tlen; pkt_flags = th->th_flags; TCP_REASS_COUNTER_INCR(&tcp_reass_); if ((p = TAILQ_LAST(&tp->segq, ipqehead)) != NULL) { /* * When we miss a packet, the vast majority of time we get * packets that follow it in order. So optimize for that. */ if (pkt_seq == p->ipqe_seq + p->ipqe_len) { p->ipqe_len += pkt_len; p->ipqe_flags |= pkt_flags; m_cat(p->ipqe_m, m); m = NULL; tiqe = p; TAILQ_REMOVE(&tp->timeq, p, ipqe_timeq); TCP_REASS_COUNTER_INCR(&tcp_reass_appendtail); goto skip_replacement; } /* * While we're here, if the pkt is completely beyond * anything we have, just insert it at the tail. */ if (SEQ_GT(pkt_seq, p->ipqe_seq + p->ipqe_len)) { TCP_REASS_COUNTER_INCR(&tcp_reass_inserttail); goto insert_it; } } q = TAILQ_FIRST(&tp->segq); if (q != NULL) { /* * If this segment immediately precedes the first out-of-order * block, simply slap the segment in front of it and (mostly) * skip the complicated logic. */ if (pkt_seq + pkt_len == q->ipqe_seq) { q->ipqe_seq = pkt_seq; q->ipqe_len += pkt_len; q->ipqe_flags |= pkt_flags; m_cat(m, q->ipqe_m); q->ipqe_m = m; tiqe = q; TAILQ_REMOVE(&tp->timeq, q, ipqe_timeq); TCP_REASS_COUNTER_INCR(&tcp_reass_prependfirst); goto skip_replacement; } } else { TCP_REASS_COUNTER_INCR(&tcp_reass_empty); } /* * Find a segment which begins after this one does. */ for (p = NULL; q != NULL; q = nq) { nq = TAILQ_NEXT(q, ipqe_q); #ifdef TCP_REASS_COUNTERS count++; #endif /* * If the received segment is just right after this * fragment, merge the two together and then check * for further overlaps. */ if (q->ipqe_seq + q->ipqe_len == pkt_seq) { pkt_len += q->ipqe_len; pkt_flags |= q->ipqe_flags; pkt_seq = q->ipqe_seq; m_cat(q->ipqe_m, m); m = q->ipqe_m; TCP_REASS_COUNTER_INCR(&tcp_reass_append); goto free_ipqe; } /* * If the received segment is completely past this * fragment, we need to go to the next fragment. */ if (SEQ_LT(q->ipqe_seq + q->ipqe_len, pkt_seq)) { p = q; continue; } /* * If the fragment is past the received segment, * it (or any following) can't be concatenated. */ if (SEQ_GT(q->ipqe_seq, pkt_seq + pkt_len)) { TCP_REASS_COUNTER_INCR(&tcp_reass_insert); break; } /* * We've received all the data in this segment before. * Mark it as a duplicate and return. */ if (SEQ_LEQ(q->ipqe_seq, pkt_seq) && SEQ_GEQ(q->ipqe_seq + q->ipqe_len, pkt_seq + pkt_len)) { tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_RCVDUPPACK]++; tcps[TCP_STAT_RCVDUPBYTE] += pkt_len; TCP_STAT_PUTREF(); tcp_new_dsack(tp, pkt_seq, pkt_len); m_freem(m); if (tiqe != NULL) { tcpipqent_free(tiqe); } TCP_REASS_COUNTER_INCR(&tcp_reass_segdup); goto out; } /* * Received segment completely overlaps this fragment * so we drop the fragment (this keeps the temporal * ordering of segments correct). */ if (SEQ_GEQ(q->ipqe_seq, pkt_seq) && SEQ_LEQ(q->ipqe_seq + q->ipqe_len, pkt_seq + pkt_len)) { rcvpartdupbyte += q->ipqe_len; m_freem(q->ipqe_m); TCP_REASS_COUNTER_INCR(&tcp_reass_fragdup); goto free_ipqe; } /* * Received segment extends past the end of the fragment. * Drop the overlapping bytes, merge the fragment and * segment, and treat as a longer received packet. */ if (SEQ_LT(q->ipqe_seq, pkt_seq) && SEQ_GT(q->ipqe_seq + q->ipqe_len, pkt_seq)) { int overlap = q->ipqe_seq + q->ipqe_len - pkt_seq; m_adj(m, overlap); rcvpartdupbyte += overlap; m_cat(q->ipqe_m, m); m = q->ipqe_m; pkt_seq = q->ipqe_seq; pkt_len += q->ipqe_len - overlap; rcvoobyte -= overlap; TCP_REASS_COUNTER_INCR(&tcp_reass_overlaptail); goto free_ipqe; } /* * Received segment extends past the front of the fragment. * Drop the overlapping bytes on the received packet. The * packet will then be concatenated with this fragment a * bit later. */ if (SEQ_GT(q->ipqe_seq, pkt_seq) && SEQ_LT(q->ipqe_seq, pkt_seq + pkt_len)) { int overlap = pkt_seq + pkt_len - q->ipqe_seq; m_adj(m, -overlap); pkt_len -= overlap; rcvpartdupbyte += overlap; TCP_REASS_COUNTER_INCR(&tcp_reass_overlapfront); rcvoobyte -= overlap; } /* * If the received segment immediately precedes this * fragment then tack the fragment onto this segment * and reinsert the data. */ if (q->ipqe_seq == pkt_seq + pkt_len) { pkt_len += q->ipqe_len; pkt_flags |= q->ipqe_flags; m_cat(m, q->ipqe_m); TAILQ_REMOVE(&tp->segq, q, ipqe_q); TAILQ_REMOVE(&tp->timeq, q, ipqe_timeq); tp->t_segqlen--; KASSERT(tp->t_segqlen >= 0); KASSERT(tp->t_segqlen != 0 || (TAILQ_EMPTY(&tp->segq) && TAILQ_EMPTY(&tp->timeq))); if (tiqe == NULL) { tiqe = q; } else { tcpipqent_free(q); } TCP_REASS_COUNTER_INCR(&tcp_reass_prepend); break; } /* * If the fragment is before the segment, remember it. * When this loop is terminated, p will contain the * pointer to the fragment that is right before the * received segment. */ if (SEQ_LEQ(q->ipqe_seq, pkt_seq)) p = q; continue; /* * This is a common operation. It also will allow * to save doing a malloc/free in most instances. */ free_ipqe: TAILQ_REMOVE(&tp->segq, q, ipqe_q); TAILQ_REMOVE(&tp->timeq, q, ipqe_timeq); tp->t_segqlen--; KASSERT(tp->t_segqlen >= 0); KASSERT(tp->t_segqlen != 0 || (TAILQ_EMPTY(&tp->segq) && TAILQ_EMPTY(&tp->timeq))); if (tiqe == NULL) { tiqe = q; } else { tcpipqent_free(q); } } #ifdef TCP_REASS_COUNTERS if (count > 7) TCP_REASS_COUNTER_INCR(&tcp_reass_iteration[0]); else if (count > 0) TCP_REASS_COUNTER_INCR(&tcp_reass_iteration[count]); #endif insert_it: /* * Allocate a new queue entry (block) since the received segment * did not collapse onto any other out-of-order block. If it had * collapsed, tiqe would not be NULL and we would be reusing it. * * If the allocation fails, drop the packet. */ if (tiqe == NULL) { tiqe = tcpipqent_alloc(); if (tiqe == NULL) { TCP_STATINC(TCP_STAT_RCVMEMDROP); m_freem(m); goto out; } } /* * Update the counters. */ tp->t_rcvoopack++; tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_RCVOOPACK]++; tcps[TCP_STAT_RCVOOBYTE] += rcvoobyte; if (rcvpartdupbyte) { tcps[TCP_STAT_RCVPARTDUPPACK]++; tcps[TCP_STAT_RCVPARTDUPBYTE] += rcvpartdupbyte; } TCP_STAT_PUTREF(); /* * Insert the new fragment queue entry into both queues. */ tiqe->ipqe_m = m; tiqe->ipqe_seq = pkt_seq; tiqe->ipqe_len = pkt_len; tiqe->ipqe_flags = pkt_flags; if (p == NULL) { TAILQ_INSERT_HEAD(&tp->segq, tiqe, ipqe_q); } else { TAILQ_INSERT_AFTER(&tp->segq, p, tiqe, ipqe_q); } tp->t_segqlen++; skip_replacement: TAILQ_INSERT_HEAD(&tp->timeq, tiqe, ipqe_timeq); present: /* * Present data to user, advancing rcv_nxt through * completed sequence space. */ if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) goto out; q = TAILQ_FIRST(&tp->segq); if (q == NULL || q->ipqe_seq != tp->rcv_nxt) goto out; if (tp->t_state == TCPS_SYN_RECEIVED && q->ipqe_len) goto out; tp->rcv_nxt += q->ipqe_len; pkt_flags = q->ipqe_flags & TH_FIN; nd6_hint(tp); TAILQ_REMOVE(&tp->segq, q, ipqe_q); TAILQ_REMOVE(&tp->timeq, q, ipqe_timeq); tp->t_segqlen--; KASSERT(tp->t_segqlen >= 0); KASSERT(tp->t_segqlen != 0 || (TAILQ_EMPTY(&tp->segq) && TAILQ_EMPTY(&tp->timeq))); if (so->so_state & SS_CANTRCVMORE) m_freem(q->ipqe_m); else sbappendstream(&so->so_rcv, q->ipqe_m); tcpipqent_free(q); TCP_REASS_UNLOCK(tp); sorwakeup(so); return pkt_flags; out: TCP_REASS_UNLOCK(tp); return 0; } #ifdef INET6 int tcp6_input(struct mbuf **mp, int *offp, int proto) { struct mbuf *m = *mp; /* * draft-itojun-ipv6-tcp-to-anycast * better place to put this in? */ if (m->m_flags & M_ANYCAST6) { struct ip6_hdr *ip6; if (m->m_len < sizeof(struct ip6_hdr)) { if ((m = m_pullup(m, sizeof(struct ip6_hdr))) == NULL) { TCP_STATINC(TCP_STAT_RCVSHORT); return IPPROTO_DONE; } } ip6 = mtod(m, struct ip6_hdr *); icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, (char *)&ip6->ip6_dst - (char *)ip6); return IPPROTO_DONE; } tcp_input(m, *offp, proto); return IPPROTO_DONE; } #endif static void tcp4_log_refused(const struct ip *ip, const struct tcphdr *th) { char src[INET_ADDRSTRLEN]; char dst[INET_ADDRSTRLEN]; if (ip) { in_print(src, sizeof(src), &ip->ip_src); in_print(dst, sizeof(dst), &ip->ip_dst); } else { strlcpy(src, "(unknown)", sizeof(src)); strlcpy(dst, "(unknown)", sizeof(dst)); } log(LOG_INFO, "Connection attempt to TCP %s:%d from %s:%d\n", dst, ntohs(th->th_dport), src, ntohs(th->th_sport)); } #ifdef INET6 static void tcp6_log_refused(const struct ip6_hdr *ip6, const struct tcphdr *th) { char src[INET6_ADDRSTRLEN]; char dst[INET6_ADDRSTRLEN]; if (ip6) { in6_print(src, sizeof(src), &ip6->ip6_src); in6_print(dst, sizeof(dst), &ip6->ip6_dst); } else { strlcpy(src, "(unknown v6)", sizeof(src)); strlcpy(dst, "(unknown v6)", sizeof(dst)); } log(LOG_INFO, "Connection attempt to TCP [%s]:%d from [%s]:%d\n", dst, ntohs(th->th_dport), src, ntohs(th->th_sport)); } #endif /* * Checksum extended TCP header and data. */ int tcp_input_checksum(int af, struct mbuf *m, const struct tcphdr *th, int toff, int off, int tlen) { struct ifnet *rcvif; int s; /* * XXX it's better to record and check if this mbuf is * already checked. */ rcvif = m_get_rcvif(m, &s); if (__predict_false(rcvif == NULL)) goto badcsum; /* XXX */ switch (af) { case AF_INET: switch (m->m_pkthdr.csum_flags & ((rcvif->if_csum_flags_rx & M_CSUM_TCPv4) | M_CSUM_TCP_UDP_BAD | M_CSUM_DATA)) { case M_CSUM_TCPv4|M_CSUM_TCP_UDP_BAD: TCP_CSUM_COUNTER_INCR(&tcp_hwcsum_bad); goto badcsum; case M_CSUM_TCPv4|M_CSUM_DATA: { u_int32_t hw_csum = m->m_pkthdr.csum_data; TCP_CSUM_COUNTER_INCR(&tcp_hwcsum_data); if (m->m_pkthdr.csum_flags & M_CSUM_NO_PSEUDOHDR) { const struct ip *ip = mtod(m, const struct ip *); hw_csum = in_cksum_phdr(ip->ip_src.s_addr, ip->ip_dst.s_addr, htons(hw_csum + tlen + off + IPPROTO_TCP)); } if ((hw_csum ^ 0xffff) != 0) goto badcsum; break; } case M_CSUM_TCPv4: /* Checksum was okay. */ TCP_CSUM_COUNTER_INCR(&tcp_hwcsum_ok); break; default: /* * Must compute it ourselves. Maybe skip checksum * on loopback interfaces. */ if (__predict_true(!(rcvif->if_flags & IFF_LOOPBACK) || tcp_do_loopback_cksum)) { TCP_CSUM_COUNTER_INCR(&tcp_swcsum); if (in4_cksum(m, IPPROTO_TCP, toff, tlen + off) != 0) goto badcsum; } break; } break; #ifdef INET6 case AF_INET6: switch (m->m_pkthdr.csum_flags & ((rcvif->if_csum_flags_rx & M_CSUM_TCPv6) | M_CSUM_TCP_UDP_BAD | M_CSUM_DATA)) { case M_CSUM_TCPv6|M_CSUM_TCP_UDP_BAD: TCP_CSUM_COUNTER_INCR(&tcp6_hwcsum_bad); goto badcsum; #if 0 /* notyet */ case M_CSUM_TCPv6|M_CSUM_DATA: #endif case M_CSUM_TCPv6: /* Checksum was okay. */ TCP_CSUM_COUNTER_INCR(&tcp6_hwcsum_ok); break; default: /* * Must compute it ourselves. Maybe skip checksum * on loopback interfaces. */ if (__predict_true((m->m_flags & M_LOOP) == 0 || tcp_do_loopback_cksum)) { TCP_CSUM_COUNTER_INCR(&tcp6_swcsum); if (in6_cksum(m, IPPROTO_TCP, toff, tlen + off) != 0) goto badcsum; } } break; #endif /* INET6 */ } m_put_rcvif(rcvif, &s); return 0; badcsum: m_put_rcvif(rcvif, &s); TCP_STATINC(TCP_STAT_RCVBADSUM); return -1; } /* * When a packet arrives addressed to a vestigial tcpbp, we * nevertheless have to respond to it per the spec. * * This code is duplicated from the one in tcp_input(). */ static void tcp_vtw_input(struct tcphdr *th, vestigial_inpcb_t *vp, struct mbuf *m, int tlen) { int tiflags; int todrop; uint32_t t_flags = 0; uint64_t *tcps; tiflags = th->th_flags; todrop = vp->rcv_nxt - th->th_seq; if (todrop > 0) { if (tiflags & TH_SYN) { tiflags &= ~TH_SYN; th->th_seq++; tcp_urp_drop(th, 1, &tiflags); todrop--; } if (todrop > tlen || (todrop == tlen && (tiflags & TH_FIN) == 0)) { /* * Any valid FIN or RST must be to the left of the * window. At this point the FIN or RST must be a * duplicate or out of sequence; drop it. */ if (tiflags & TH_RST) goto drop; tiflags &= ~(TH_FIN|TH_RST); /* * Send an ACK to resynchronize and drop any data. * But keep on processing for RST or ACK. */ t_flags |= TF_ACKNOW; todrop = tlen; tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_RCVDUPPACK] += 1; tcps[TCP_STAT_RCVDUPBYTE] += todrop; TCP_STAT_PUTREF(); } else if ((tiflags & TH_RST) && th->th_seq != vp->rcv_nxt) { /* * Test for reset before adjusting the sequence * number for overlapping data. */ goto dropafterack_ratelim; } else { tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_RCVPARTDUPPACK] += 1; tcps[TCP_STAT_RCVPARTDUPBYTE] += todrop; TCP_STAT_PUTREF(); } // tcp_new_dsack(tp, th->th_seq, todrop); // hdroptlen += todrop; /*drop from head afterwards*/ th->th_seq += todrop; tlen -= todrop; tcp_urp_drop(th, todrop, &tiflags); } /* * If new data are received on a connection after the * user processes are gone, then RST the other end. */ if (tlen) { TCP_STATINC(TCP_STAT_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) - (vp->rcv_nxt + vp->rcv_wnd); if (todrop > 0) { TCP_STATINC(TCP_STAT_RCVPACKAFTERWIN); if (todrop >= tlen) { /* * The segment actually starts after the window. * th->th_seq + tlen - vp->rcv_nxt - vp->rcv_wnd >= tlen * th->th_seq - vp->rcv_nxt - vp->rcv_wnd >= 0 * th->th_seq >= vp->rcv_nxt + vp->rcv_wnd */ TCP_STATADD(TCP_STAT_RCVBYTEAFTERWIN, tlen); /* * If a new connection request is received * while in TIME_WAIT, drop the old connection * and start over if the sequence numbers * are above the previous ones. */ if ((tiflags & TH_SYN) && SEQ_GT(th->th_seq, vp->rcv_nxt)) { /* * We only support this in the !NOFDREF case, which * is to say: not here. */ goto dropwithreset; } /* * 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 (if not RST) ack. */ if (vp->rcv_wnd == 0 && th->th_seq == vp->rcv_nxt) { t_flags |= TF_ACKNOW; TCP_STATINC(TCP_STAT_RCVWINPROBE); } else { goto dropafterack; } } else { TCP_STATADD(TCP_STAT_RCVBYTEAFTERWIN, todrop); } m_adj(m, -todrop); tlen -= todrop; tiflags &= ~(TH_PUSH|TH_FIN); } if (tiflags & TH_RST) { if (th->th_seq != vp->rcv_nxt) goto dropafterack_ratelim; vtw_del(vp->ctl, vp->vtw); goto drop; } /* * If the ACK bit is off we drop the segment and return. */ if ((tiflags & TH_ACK) == 0) { if (t_flags & TF_ACKNOW) goto dropafterack; goto drop; } /* * In TIME_WAIT state the only thing that should arrive * is a retransmission of the remote FIN. Acknowledge * it and restart the finack timer. */ vtw_restart(vp); goto 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; goto dropafterack2; dropafterack_ratelim: /* * We may want to rate-limit ACKs against SYN/RST attack. */ if (ppsratecheck(&tcp_ackdrop_ppslim_last, &tcp_ackdrop_ppslim_count, tcp_ackdrop_ppslim) == 0) { /* XXX stat */ goto drop; } /* ...fall into dropafterack2... */ dropafterack2: (void)tcp_respond(0, m, m, th, th->th_seq + tlen, th->th_ack, TH_ACK); return; dropwithreset: /* * Generate a RST, dropping incoming segment. * Make ACK acceptable to originator of segment. */ if (tiflags & TH_RST) goto drop; if (tiflags & TH_ACK) { tcp_respond(0, m, m, th, (tcp_seq)0, th->th_ack, TH_RST); } else { if (tiflags & TH_SYN) ++tlen; (void)tcp_respond(0, m, m, th, th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); } return; drop: m_freem(m); } /* * TCP input routine, follows pages 65-76 of RFC 793 very closely. */ void tcp_input(struct mbuf *m, int off, int proto) { struct tcphdr *th; struct ip *ip; struct inpcb *inp; #ifdef INET6 struct ip6_hdr *ip6; struct in6pcb *in6p; #endif u_int8_t *optp = NULL; int optlen = 0; int len, tlen, hdroptlen = 0; struct tcpcb *tp = NULL; int tiflags; struct socket *so = NULL; int todrop, acked, ourfinisacked, needoutput = 0; bool dupseg; #ifdef TCP_DEBUG short ostate = 0; #endif u_long tiwin; struct tcp_opt_info opti; int thlen, iphlen; int af; /* af on the wire */ struct mbuf *tcp_saveti = NULL; uint32_t ts_rtt; uint8_t iptos; uint64_t *tcps; vestigial_inpcb_t vestige; vestige.valid = 0; MCLAIM(m, &tcp_rx_mowner); TCP_STATINC(TCP_STAT_RCVTOTAL); memset(&opti, 0, sizeof(opti)); opti.ts_present = 0; opti.maxseg = 0; /* * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN. * * TCP is, by definition, unicast, so we reject all * multicast outright. * * Note, there are additional src/dst address checks in * the AF-specific code below. */ if (m->m_flags & (M_BCAST|M_MCAST)) { /* XXX stat */ goto drop; } #ifdef INET6 if (m->m_flags & M_ANYCAST6) { /* XXX stat */ goto drop; } #endif M_REGION_GET(th, struct tcphdr *, m, off, sizeof(struct tcphdr)); if (th == NULL) { TCP_STATINC(TCP_STAT_RCVSHORT); return; } /* * Enforce alignment requirements that are violated in * some cases, see kern/50766 for details. */ if (TCP_HDR_ALIGNED_P(th) == 0) { m = m_copyup(m, off + sizeof(struct tcphdr), 0); if (m == NULL) { TCP_STATINC(TCP_STAT_RCVSHORT); return; } th = (struct tcphdr *)(mtod(m, char *) + off); } KASSERT(TCP_HDR_ALIGNED_P(th)); /* * Get IP and TCP header. * Note: IP leaves IP header in first mbuf. */ ip = mtod(m, struct ip *); #ifdef INET6 ip6 = mtod(m, struct ip6_hdr *); #endif switch (ip->ip_v) { case 4: af = AF_INET; iphlen = sizeof(struct ip); if (IN_MULTICAST(ip->ip_dst.s_addr) || in_broadcast(ip->ip_dst, m_get_rcvif_NOMPSAFE(m))) goto drop; /* We do the checksum after PCB lookup... */ len = ntohs(ip->ip_len); tlen = len - off; iptos = ip->ip_tos; break; #ifdef INET6 case 6: iphlen = sizeof(struct ip6_hdr); af = AF_INET6; /* * 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; } /* * Make sure destination address is not multicast. * Source address checked in ip6_input(). */ if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst)) { /* XXX stat */ goto drop; } /* We do the checksum after PCB lookup... */ len = m->m_pkthdr.len; tlen = len - off; iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; break; #endif default: m_freem(m); return; } /* * Check that TCP offset makes sense, pull out TCP options and * adjust length. */ thlen = th->th_off << 2; if (thlen < sizeof(struct tcphdr) || thlen > tlen) { TCP_STATINC(TCP_STAT_RCVBADOFF); goto drop; } tlen -= thlen; if (thlen > sizeof(struct tcphdr)) { M_REGION_GET(th, struct tcphdr *, m, off, thlen); if (th == NULL) { TCP_STATINC(TCP_STAT_RCVSHORT); return; } KASSERT(TCP_HDR_ALIGNED_P(th)); optlen = thlen - sizeof(struct tcphdr); optp = ((u_int8_t *)th) + sizeof(struct tcphdr); /* * Do quick retrieval of timestamp options. * * If timestamp is the only option and it's formatted as * recommended in RFC 1323 appendix A, we quickly get the * values now and don't bother calling tcp_dooptions(), * etc. */ if ((optlen == TCPOLEN_TSTAMP_APPA || (optlen > TCPOLEN_TSTAMP_APPA && optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) && be32dec(optp) == TCPOPT_TSTAMP_HDR && (th->th_flags & TH_SYN) == 0) { opti.ts_present = 1; opti.ts_val = be32dec(optp + 4); opti.ts_ecr = be32dec(optp + 8); optp = NULL; /* we've parsed the options */ } } tiflags = th->th_flags; /* * Checksum extended TCP header and data */ if (tcp_input_checksum(af, m, th, off, thlen, tlen)) goto badcsum; /* * Locate pcb for segment. */ findpcb: inp = NULL; #ifdef INET6 in6p = NULL; #endif switch (af) { case AF_INET: inp = in_pcblookup_connect(&tcbtable, ip->ip_src, th->th_sport, ip->ip_dst, th->th_dport, &vestige); if (inp == NULL && !vestige.valid) { TCP_STATINC(TCP_STAT_PCBHASHMISS); inp = in_pcblookup_bind(&tcbtable, ip->ip_dst, th->th_dport); } #ifdef INET6 if (inp == NULL && !vestige.valid) { struct in6_addr s, d; /* mapped addr case */ in6_in_2_v4mapin6(&ip->ip_src, &s); in6_in_2_v4mapin6(&ip->ip_dst, &d); in6p = in6_pcblookup_connect(&tcbtable, &s, th->th_sport, &d, th->th_dport, 0, &vestige); if (in6p == 0 && !vestige.valid) { TCP_STATINC(TCP_STAT_PCBHASHMISS); in6p = in6_pcblookup_bind(&tcbtable, &d, th->th_dport, 0); } } #endif #ifndef INET6 if (inp == NULL && !vestige.valid) #else if (inp == NULL && in6p == NULL && !vestige.valid) #endif { TCP_STATINC(TCP_STAT_NOPORT); if (tcp_log_refused && (tiflags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN) { tcp4_log_refused(ip, th); } tcp_fields_to_host(th); goto dropwithreset_ratelim; } #if defined(IPSEC) if (ipsec_used) { if (inp && ipsec_in_reject(m, inp)) { goto drop; } #ifdef INET6 else if (in6p && ipsec_in_reject(m, in6p)) { goto drop; } #endif } #endif /*IPSEC*/ break; #ifdef INET6 case AF_INET6: { int faith; #if defined(NFAITH) && NFAITH > 0 faith = faithprefix(&ip6->ip6_dst); #else faith = 0; #endif in6p = in6_pcblookup_connect(&tcbtable, &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, faith, &vestige); if (!in6p && !vestige.valid) { TCP_STATINC(TCP_STAT_PCBHASHMISS); in6p = in6_pcblookup_bind(&tcbtable, &ip6->ip6_dst, th->th_dport, faith); } if (!in6p && !vestige.valid) { TCP_STATINC(TCP_STAT_NOPORT); if (tcp_log_refused && (tiflags & (TH_RST|TH_ACK|TH_SYN)) == TH_SYN) { tcp6_log_refused(ip6, th); } tcp_fields_to_host(th); goto dropwithreset_ratelim; } #if defined(IPSEC) if (ipsec_used && in6p && ipsec_in_reject(m, in6p)) { goto drop; } #endif break; } #endif } tcp_fields_to_host(th); /* * 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. */ tp = NULL; so = NULL; if (inp) { /* Check the minimum TTL for socket. */ if (ip->ip_ttl < inp->inp_ip_minttl) goto drop; tp = intotcpcb(inp); so = inp->inp_socket; } #ifdef INET6 else if (in6p) { tp = in6totcpcb(in6p); so = in6p->in6p_socket; } #endif else if (vestige.valid) { /* We do not support the resurrection of vtw tcpcps. */ tcp_vtw_input(th, &vestige, m, tlen); m = NULL; goto drop; } if (tp == NULL) goto dropwithreset_ratelim; if (tp->t_state == TCPS_CLOSED) goto drop; KASSERT(so->so_lock == softnet_lock); KASSERT(solocked(so)); /* 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; #ifdef INET6 /* save packet options if user wanted */ if (in6p && (in6p->in6p_flags & IN6P_CONTROLOPTS)) { if (in6p->in6p_options) { m_freem(in6p->in6p_options); in6p->in6p_options = NULL; } ip6_savecontrol(in6p, &in6p->in6p_options, ip6, m); } #endif if (so->so_options & SO_DEBUG) { #ifdef TCP_DEBUG ostate = tp->t_state; #endif tcp_saveti = NULL; if (iphlen + sizeof(struct tcphdr) > MHLEN) goto nosave; if (m->m_len > iphlen && (m->m_flags & M_EXT) == 0) { tcp_saveti = m_copym(m, 0, iphlen, M_DONTWAIT); if (tcp_saveti == NULL) goto nosave; } else { MGETHDR(tcp_saveti, M_DONTWAIT, MT_HEADER); if (tcp_saveti == NULL) goto nosave; MCLAIM(m, &tcp_mowner); tcp_saveti->m_len = iphlen; m_copydata(m, 0, iphlen, mtod(tcp_saveti, void *)); } if (M_TRAILINGSPACE(tcp_saveti) < sizeof(struct tcphdr)) { m_freem(tcp_saveti); tcp_saveti = NULL; } else { tcp_saveti->m_len += sizeof(struct tcphdr); memcpy(mtod(tcp_saveti, char *) + iphlen, th, sizeof(struct tcphdr)); } nosave:; } if (so->so_options & SO_ACCEPTCONN) { union syn_cache_sa src; union syn_cache_sa dst; KASSERT(tp->t_state == TCPS_LISTEN); memset(&src, 0, sizeof(src)); memset(&dst, 0, 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 } if ((tiflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { if (tiflags & TH_RST) { syn_cache_reset(&src.sa, &dst.sa, th); } else if ((tiflags & (TH_ACK|TH_SYN)) == (TH_ACK|TH_SYN)) { /* * Received a SYN,ACK. This should never * happen while we are in LISTEN. Send an RST. */ goto badsyn; } else if (tiflags & TH_ACK) { so = syn_cache_get(&src.sa, &dst.sa, th, 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 = NULL; } else { /* * We have created a full-blown * connection. */ tp = NULL; inp = NULL; #ifdef INET6 in6p = NULL; #endif switch (so->so_proto->pr_domain->dom_family) { case AF_INET: inp = sotoinpcb(so); tp = intotcpcb(inp); break; #ifdef INET6 case AF_INET6: in6p = sotoin6pcb(so); tp = in6totcpcb(in6p); break; #endif } if (tp == NULL) goto badsyn; /*XXX*/ tiwin <<= tp->snd_scale; goto after_listen; } } else { /* * None of RST, SYN or ACK was set. * This is an invalid packet for a * TCB in LISTEN state. Send a RST. */ goto badsyn; } } else { /* * 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 (af == AF_INET6 && !ip6_use_deprecated) { struct in6_ifaddr *ia6; int s; struct ifnet *rcvif = m_get_rcvif(m, &s); if (rcvif == NULL) goto dropwithreset; /* XXX */ if ((ia6 = in6ifa_ifpwithaddr(rcvif, &ip6->ip6_dst)) && (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { tp = NULL; m_put_rcvif(rcvif, &s); goto dropwithreset; } m_put_rcvif(rcvif, &s); } #endif /* * LISTEN socket received a SYN from itself? This * can't possibly be valid; drop the packet. */ if (th->th_sport == th->th_dport) { int eq = 0; switch (af) { case AF_INET: eq = in_hosteq(ip->ip_src, ip->ip_dst); break; #ifdef INET6 case AF_INET6: eq = IN6_ARE_ADDR_EQUAL(&ip6->ip6_src, &ip6->ip6_dst); break; #endif } if (eq) { TCP_STATINC(TCP_STAT_BADSYN); goto drop; } } /* * SYN looks ok; create compressed TCP * state for it. */ if (so->so_qlen <= so->so_qlimit && syn_cache_add(&src.sa, &dst.sa, th, off, so, m, optp, optlen, &opti)) m = NULL; } goto drop; } after_listen: /* * From here on, we're dealing with !LISTEN. */ KASSERT(tp->t_state != TCPS_LISTEN); /* * 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, tp->t_keepidle); /* * Process options. */ #ifdef TCP_SIGNATURE if (optp || (tp->t_flags & TF_SIGNATURE)) #else if (optp) #endif if (tcp_dooptions(tp, optp, optlen, th, m, off, &opti) < 0) goto drop; if (TCP_SACK_ENABLED(tp)) { tcp_del_sackholes(tp, th); } if (TCP_ECN_ALLOWED(tp)) { if (tiflags & TH_CWR) { tp->t_flags &= ~TF_ECN_SND_ECE; } switch (iptos & IPTOS_ECN_MASK) { case IPTOS_ECN_CE: tp->t_flags |= TF_ECN_SND_ECE; TCP_STATINC(TCP_STAT_ECN_CE); break; case IPTOS_ECN_ECT0: TCP_STATINC(TCP_STAT_ECN_ECT); break; case IPTOS_ECN_ECT1: /* XXX: ignore for now -- rpaulo */ break; } /* * Congestion experienced. * Ignore if we are already trying to recover. */ if ((tiflags & TH_ECE) && SEQ_GEQ(tp->snd_una, tp->snd_recover)) tp->t_congctl->cong_exp(tp); } if (opti.ts_present && opti.ts_ecr) { /* * Calculate the RTT from the returned time stamp and the * connection's time base. If the time stamp is later than * the current time, or is extremely old, fall back to non-1323 * RTT calculation. Since ts_rtt is unsigned, we can test both * at the same time. * * Note that ts_rtt is in units of slow ticks (500 * ms). Since most earthbound RTTs are < 500 ms, * observed values will have large quantization noise. * Our smoothed RTT is then the fraction of observed * samples that are 1 tick instead of 0 (times 500 * ms). * * ts_rtt is increased by 1 to denote a valid sample, * with 0 indicating an invalid measurement. This * extra 1 must be removed when ts_rtt is used, or * else an erroneous extra 500 ms will result. */ ts_rtt = TCP_TIMESTAMP(tp) - opti.ts_ecr + 1; if (ts_rtt > TCP_PAWS_IDLE) ts_rtt = 0; } else { ts_rtt = 0; } /* * Fast path: check for the two common cases of a uni-directional * data transfer. If: * o We are in the ESTABLISHED state, and * o The packet has no control flags, and * o The packet is in-sequence, and * o The window didn't change, and * o We are not retransmitting * It's a candidate. * * If the length (tlen) is zero and the ack moved forward, we're * the sender side of the transfer. Just free the data acked and * 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 && (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ECE|TH_CWR|TH_ACK)) == TH_ACK && (!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. * NOTE that the test is modified according to the latest * proposal of the tcplw@cray.com list (Braden 1993/04/26). * * note that we already know * TSTMP_GEQ(opti.ts_val, tp->ts_recent) */ 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) { /* Ack prediction. */ 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_partialacks < 0) { /* * this is a pure ack for outstanding data. */ if (ts_rtt) tcp_xmit_timer(tp, ts_rtt - 1); 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; tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_PREDACK]++; tcps[TCP_STAT_RCVACKPACK]++; tcps[TCP_STAT_RCVACKBYTE] += acked; TCP_STAT_PUTREF(); nd6_hint(tp); if (acked > (tp->t_lastoff - tp->t_inoff)) tp->t_lastm = NULL; sbdrop(&so->so_snd, acked); tp->t_lastoff -= acked; icmp_check(tp, th, acked); tp->snd_una = th->th_ack; tp->snd_fack = tp->snd_una; if (SEQ_LT(tp->snd_high, tp->snd_una)) tp->snd_high = tp->snd_una; /* * drag snd_wl2 along so only newer * ACKs can update the window size. * also avoids the state where snd_wl2 * is eventually larger than th_ack and thus * blocking the window update mechanism and * the connection gets stuck for a loooong * time in the zero sized send window state. * * see PR/kern 55567 */ tp->snd_wl2 = 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/selnotify/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); sowwakeup(so); if (so->so_snd.sb_cc) { KERNEL_LOCK(1, NULL); (void)tcp_output(tp); KERNEL_UNLOCK_ONE(NULL); } if (tcp_saveti) m_freem(tcp_saveti); return; } } else if (th->th_ack == tp->snd_una && TAILQ_FIRST(&tp->segq) == NULL && tlen <= sbspace(&so->so_rcv)) { int newsize = 0; /* * this is a pure, in-sequence data packet * with nothing on the reassembly queue and * we have enough buffer space to take it. */ tp->rcv_nxt += tlen; /* * Pull rcv_up up to prevent seq wrap relative to * rcv_nxt. */ tp->rcv_up = tp->rcv_nxt; /* * Pull snd_wl1 up to prevent seq wrap relative to * th_seq. */ tp->snd_wl1 = th->th_seq; tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_PREDDAT]++; tcps[TCP_STAT_RCVPACK]++; tcps[TCP_STAT_RCVBYTE] += tlen; TCP_STAT_PUTREF(); nd6_hint(tp); /* * Automatic sizing enables the performance of large buffers * and most of the efficiency of small ones by only allocating * space when it is needed. * * On the receive side the socket buffer memory is only rarely * used to any significant extent. This allows us to be much * more aggressive in scaling the receive socket buffer. For * the case that the buffer space is actually used to a large * extent and we run out of kernel memory we can simply drop * the new segments; TCP on the sender will just retransmit it * later. Setting the buffer size too big may only consume too * much kernel memory if the application doesn't read() from * the socket or packet loss or reordering makes use of the * reassembly queue. * * The criteria to step up the receive buffer one notch are: * 1. the number of bytes received during the time it takes * one timestamp to be reflected back to us (the RTT); * 2. received bytes per RTT is within seven eighth of the * current socket buffer size; * 3. receive buffer size has not hit maximal automatic size; * * This algorithm does one step per RTT at most and only if * we receive a bulk stream w/o packet losses or reorderings. * Shrinking the buffer during idle times is not necessary as * it doesn't consume any memory when idle. * * TODO: Only step up if the application is actually serving * the buffer to better manage the socket buffer resources. */ if (tcp_do_autorcvbuf && opti.ts_ecr && (so->so_rcv.sb_flags & SB_AUTOSIZE)) { if (opti.ts_ecr > tp->rfbuf_ts && opti.ts_ecr - tp->rfbuf_ts < PR_SLOWHZ) { if (tp->rfbuf_cnt > (so->so_rcv.sb_hiwat / 8 * 7) && so->so_rcv.sb_hiwat < tcp_autorcvbuf_max) { newsize = uimin(so->so_rcv.sb_hiwat + tcp_autorcvbuf_inc, tcp_autorcvbuf_max); } /* Start over with next RTT. */ tp->rfbuf_ts = 0; tp->rfbuf_cnt = 0; } else tp->rfbuf_cnt += tlen; /* add up */ } /* * Drop TCP, IP headers and TCP options then add data * to socket buffer. */ if (so->so_state & SS_CANTRCVMORE) { m_freem(m); } else { /* * Set new socket buffer size. * Give up when limit is reached. */ if (newsize) if (!sbreserve(&so->so_rcv, newsize, so)) so->so_rcv.sb_flags &= ~SB_AUTOSIZE; m_adj(m, off + thlen); sbappendstream(&so->so_rcv, m); } sorwakeup(so); tcp_setup_ack(tp, th); if (tp->t_flags & TF_ACKNOW) { KERNEL_LOCK(1, NULL); (void)tcp_output(tp); KERNEL_UNLOCK_ONE(NULL); } if (tcp_saveti) m_freem(tcp_saveti); return; } } /* * Compute mbuf offset to TCP data segment. */ hdroptlen = off + thlen; /* * Calculate amount of space in receive window. Receive window is * amount of space in rcv queue, but not less than advertised * window. */ { int win; win = sbspace(&so->so_rcv); if (win < 0) win = 0; tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); } /* Reset receive buffer auto scaling when not in bulk receive mode. */ tp->rfbuf_ts = 0; tp->rfbuf_cnt = 0; switch (tp->t_state) { /* * 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 seg contains a ECE and ECN support is enabled, the stream * is ECN capable. * 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) { 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; if (SEQ_LT(tp->snd_high, tp->snd_una)) tp->snd_high = tp->snd_una; TCP_TIMER_DISARM(tp, TCPT_REXMT); if ((tiflags & TH_ECE) && tcp_do_ecn) { tp->t_flags |= TF_ECN_PERMIT; TCP_STATINC(TCP_STAT_ECN_SHS); } } tp->irs = th->th_seq; tcp_rcvseqinit(tp); tp->t_flags |= TF_ACKNOW; tcp_mss_from_peer(tp, opti.maxseg); /* * Initialize the initial congestion window. If we * had to retransmit the SYN, we must initialize cwnd * to 1 segment (i.e. the Loss Window). */ if (tp->t_flags & TF_SYN_REXMT) tp->snd_cwnd = tp->t_peermss; else { int ss = tcp_init_win; if (inp != NULL && in_localaddr(inp->inp_faddr)) ss = tcp_init_win_local; #ifdef INET6 if (in6p != NULL && in6_localaddr(&in6p->in6p_faddr)) ss = tcp_init_win_local; #endif tp->snd_cwnd = TCP_INITIAL_WINDOW(ss, tp->t_peermss); } tcp_rmx_rtt(tp); if (tiflags & TH_ACK) { TCP_STATINC(TCP_STAT_CONNECTS); /* * move tcp_established before soisconnected * because upcall handler can drive tcp_output * functionality. * XXX we might call soisconnected at the end of * all processing */ tcp_established(tp); soisconnected(so); /* Do window scaling on this connection? */ if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == (TF_RCVD_SCALE|TF_REQ_SCALE)) { tp->snd_scale = tp->requested_s_scale; tp->rcv_scale = tp->request_r_scale; } TCP_REASS_LOCK(tp); (void)tcp_reass(tp, NULL, NULL, tlen); /* * 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); } else { tp->t_state = TCPS_SYN_RECEIVED; } /* * 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; tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_RCVPACKAFTERWIN]++; tcps[TCP_STAT_RCVBYTEAFTERWIN] += todrop; TCP_STAT_PUTREF(); } tp->snd_wl1 = th->th_seq - 1; tp->rcv_up = th->th_seq; goto step6; /* * If the state is SYN_RECEIVED: * If seg contains an ACK, but not for our SYN, drop the input * and generate an RST. See page 36, rfc793 */ case TCPS_SYN_RECEIVED: if ((tiflags & TH_ACK) && (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) goto dropwithreset; break; } /* * From here on, we're dealing with !LISTEN and !SYN_SENT. */ KASSERT(tp->t_state != TCPS_LISTEN && tp->t_state != TCPS_SYN_SENT); /* * RFC1323 PAWS: if we have a timestamp reply on this segment and * it's less than 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 (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 { tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_RCVDUPPACK]++; tcps[TCP_STAT_RCVDUPBYTE] += tlen; tcps[TCP_STAT_PAWSDROP]++; TCP_STAT_PUTREF(); tcp_new_dsack(tp, th->th_seq, tlen); goto dropafterack; } } /* * Check that at least some bytes of the segment are within the * receive window. If segment begins before rcv_nxt, drop leading * data (and SYN); if nothing left, just ack. */ todrop = tp->rcv_nxt - th->th_seq; dupseg = false; if (todrop > 0) { if (tiflags & TH_SYN) { tiflags &= ~TH_SYN; th->th_seq++; tcp_urp_drop(th, 1, &tiflags); todrop--; } if (todrop > tlen || (todrop == tlen && (tiflags & TH_FIN) == 0)) { /* * Any valid FIN or RST must be to the left of the * window. At this point the FIN or RST must be a * duplicate or out of sequence; drop it. */ if (tiflags & TH_RST) goto drop; tiflags &= ~(TH_FIN|TH_RST); /* * Send an ACK to resynchronize and drop any data. * But keep on processing for RST or ACK. */ tp->t_flags |= TF_ACKNOW; todrop = tlen; dupseg = true; tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_RCVDUPPACK]++; tcps[TCP_STAT_RCVDUPBYTE] += todrop; TCP_STAT_PUTREF(); } else if ((tiflags & TH_RST) && th->th_seq != tp->rcv_nxt) { /* * Test for reset before adjusting the sequence * number for overlapping data. */ goto dropafterack_ratelim; } else { tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_RCVPARTDUPPACK]++; tcps[TCP_STAT_RCVPARTDUPBYTE] += todrop; TCP_STAT_PUTREF(); } tcp_new_dsack(tp, th->th_seq, todrop); hdroptlen += todrop; /* drop from head afterwards (m_adj) */ th->th_seq += todrop; tlen -= todrop; tcp_urp_drop(th, todrop, &tiflags); } /* * If new data is 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); TCP_STATINC(TCP_STAT_RCVAFTERCLOSE); goto dropwithreset; } /* * If the segment ends after the 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) { TCP_STATINC(TCP_STAT_RCVPACKAFTERWIN); if (todrop >= tlen) { /* * The segment actually starts after the window. * th->th_seq + tlen - tp->rcv_nxt - tp->rcv_wnd >= tlen * th->th_seq - tp->rcv_nxt - tp->rcv_wnd >= 0 * th->th_seq >= tp->rcv_nxt + tp->rcv_wnd */ TCP_STATADD(TCP_STAT_RCVBYTEAFTERWIN, tlen); /* * If a new connection request is received while in * TIME_WAIT, drop the old connection and start over * if the sequence numbers are above the previous * ones. * * NOTE: We need to put the header fields back into * network order. */ if ((tiflags & TH_SYN) && tp->t_state == TCPS_TIME_WAIT && SEQ_GT(th->th_seq, tp->rcv_nxt)) { tp = tcp_close(tp); tcp_fields_to_net(th); m_freem(tcp_saveti); tcp_saveti = NULL; goto findpcb; } /* * If window is closed can only take segments at * window edge, and have to drop data and PUSH from * incoming segments. Continue processing, but * remember to ack. Otherwise, drop segment * and (if not RST) ack. */ if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { KASSERT(todrop == tlen); tp->t_flags |= TF_ACKNOW; TCP_STATINC(TCP_STAT_RCVWINPROBE); } else { goto dropafterack; } } else { TCP_STATADD(TCP_STAT_RCVBYTEAFTERWIN, todrop); } m_adj(m, -todrop); tlen -= todrop; tiflags &= ~(TH_PUSH|TH_FIN); } /* * If last ACK falls within this segment's sequence numbers, * record the timestamp. * NOTE: * 1) That the test incorporates suggestions from the latest * proposal of the tcplw@cray.com list (Braden 1993/04/26). * 2) That updating only on newer timestamps interferes with * our earlier PAWS tests, so this check should be solely * predicated on the sequence space of this segment. * 3) That we modify the segment boundary check to be * Last.ACK.Sent <= SEG.SEQ + SEG.Len * instead of RFC1323's * Last.ACK.Sent < SEG.SEQ + SEG.Len, * This modified check allows us to overcome RFC1323's * limitations as described in Stevens TCP/IP Illustrated * Vol. 2 p.869. In such cases, we can still calculate the * RTT correctly when RCV.NXT == Last.ACK.Sent. */ if (opti.ts_present && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + ((tiflags & (TH_SYN|TH_FIN)) != 0))) { tp->ts_recent_age = tcp_now; tp->ts_recent = opti.ts_val; } /* * If the RST bit is set examine the state: * 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->rcv_nxt) goto dropafterack_ratelim; switch (tp->t_state) { case TCPS_SYN_RECEIVED: so->so_error = ECONNREFUSED; goto close; case TCPS_ESTABLISHED: case TCPS_FIN_WAIT_1: case TCPS_FIN_WAIT_2: case TCPS_CLOSE_WAIT: so->so_error = ECONNRESET; close: tp->t_state = TCPS_CLOSED; TCP_STATINC(TCP_STAT_DROPS); tp = tcp_close(tp); goto drop; case TCPS_CLOSING: case TCPS_LAST_ACK: case TCPS_TIME_WAIT: tp = tcp_close(tp); goto drop; } } /* * Since we've covered the SYN-SENT and SYN-RECEIVED states above * we must be in a synchronized state. RFC791 states (under RST * generation) that any unacceptable segment (an out-of-order SYN * qualifies) received in a synchronized state must elicit only an * empty acknowledgment segment ... and the connection remains in * the same state. */ if (tiflags & TH_SYN) { if (tp->rcv_nxt == th->th_seq) { tcp_respond(tp, m, m, th, (tcp_seq)0, th->th_ack - 1, TH_ACK); if (tcp_saveti) m_freem(tcp_saveti); return; } 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; goto drop; } /* * From here on, we're doing ACK processing. */ switch (tp->t_state) { /* * In SYN_RECEIVED state if the ack ACKs our SYN then enter * ESTABLISHED state and continue processing, otherwise * send an RST. */ case TCPS_SYN_RECEIVED: if (SEQ_GT(tp->snd_una, th->th_ack) || SEQ_GT(th->th_ack, tp->snd_max)) goto dropwithreset; TCP_STATINC(TCP_STAT_CONNECTS); soisconnected(so); tcp_established(tp); /* 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; } TCP_REASS_LOCK(tp); (void)tcp_reass(tp, NULL, NULL, tlen); tp->snd_wl1 = th->th_seq - 1; /* FALLTHROUGH */ /* * In ESTABLISHED state: drop duplicate ACKs; ACK out of range * ACKs. If the ack is in the range * tp->snd_una < th->th_ack <= tp->snd_max * then advance tp->snd_una to th->th_ack and drop * data from the retransmission queue. If this ACK reflects * more up to date window information we update our window information. */ case TCPS_ESTABLISHED: case TCPS_FIN_WAIT_1: case TCPS_FIN_WAIT_2: case TCPS_CLOSE_WAIT: case TCPS_CLOSING: case TCPS_LAST_ACK: case TCPS_TIME_WAIT: if (SEQ_LEQ(th->th_ack, tp->snd_una)) { if (tlen == 0 && !dupseg && tiwin == tp->snd_wnd) { TCP_STATINC(TCP_STAT_RCVDUPACK); /* * If we have outstanding data (other than * a window probe), this is a completely * duplicate ack (ie, window info didn't * change), the ack is the biggest we've * seen and we've seen exactly our rexmt * threshhold of them, assume a packet * has been dropped and retransmit it. * Kludge snd_nxt & the congestion * window so we send only this one * packet. */ if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 || th->th_ack != tp->snd_una) tp->t_dupacks = 0; else if (tp->t_partialacks < 0 && (++tp->t_dupacks == tcprexmtthresh || TCP_FACK_FASTRECOV(tp))) { /* * Do the fast retransmit, and adjust * congestion control paramenters. */ if (tp->t_congctl->fast_retransmit(tp, th)) { /* False fast retransmit */ break; } goto drop; } else if (tp->t_dupacks > tcprexmtthresh) { tp->snd_cwnd += tp->t_segsz; KERNEL_LOCK(1, NULL); (void)tcp_output(tp); KERNEL_UNLOCK_ONE(NULL); goto drop; } } else { /* * If the ack appears to be very old, only * allow data that is in-sequence. This * makes it somewhat more difficult to insert * forged data by guessing sequence numbers. * Sent an ack to try to update the send * sequence number on the other side. */ if (tlen && th->th_seq != tp->rcv_nxt && SEQ_LT(th->th_ack, tp->snd_una - tp->max_sndwnd)) goto dropafterack; } break; } /* * If the congestion window was inflated to account * for the other side's cached packets, retract it. */ tp->t_congctl->fast_retransmit_newack(tp, th); if (SEQ_GT(th->th_ack, tp->snd_max)) { TCP_STATINC(TCP_STAT_RCVACKTOOMUCH); goto dropafterack; } acked = th->th_ack - tp->snd_una; tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_RCVACKPACK]++; tcps[TCP_STAT_RCVACKBYTE] += acked; TCP_STAT_PUTREF(); /* * 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 (ts_rtt) tcp_xmit_timer(tp, ts_rtt - 1); 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); needoutput = 1; } else if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); /* * New data has been acked, adjust the congestion window. */ tp->t_congctl->newack(tp, th); nd6_hint(tp); if (acked > so->so_snd.sb_cc) { tp->snd_wnd -= so->so_snd.sb_cc; sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); ourfinisacked = 1; } else { if (acked > (tp->t_lastoff - tp->t_inoff)) tp->t_lastm = NULL; sbdrop(&so->so_snd, acked); tp->t_lastoff -= acked; if (tp->snd_wnd > acked) tp->snd_wnd -= acked; else tp->snd_wnd = 0; ourfinisacked = 0; } sowwakeup(so); icmp_check(tp, th, acked); tp->snd_una = th->th_ack; if (SEQ_GT(tp->snd_una, tp->snd_fack)) tp->snd_fack = tp->snd_una; if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; if (SEQ_LT(tp->snd_high, tp->snd_una)) tp->snd_high = tp->snd_una; switch (tp->t_state) { /* * In FIN_WAIT_1 STATE in addition to the processing * for the ESTABLISHED state if our FIN is now acknowledged * then enter FIN_WAIT_2. */ case TCPS_FIN_WAIT_1: if (ourfinisacked) { /* * If we can't receive any more * data, then closing user can proceed. * Starting the timer is contrary to the * specification, but if we don't get a FIN * we'll hang forever. */ if (so->so_state & SS_CANTRCVMORE) { soisdisconnected(so); if (tp->t_maxidle > 0) TCP_TIMER_ARM(tp, TCPT_2MSL, tp->t_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 * tp->t_msl); soisdisconnected(so); } break; /* * In LAST_ACK, we may still be waiting for data to drain * and/or to be acked, as well as for the ack of our FIN. * If our FIN is now acknowledged, delete the TCB, * enter the closed state and return. */ case TCPS_LAST_ACK: if (ourfinisacked) { tp = tcp_close(tp); goto drop; } break; /* * In TIME_WAIT state the only thing that should arrive * is a retransmission of the remote FIN. Acknowledge * it and restart the finack timer. */ case TCPS_TIME_WAIT: TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * tp->t_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) TCP_STATINC(TCP_STAT_RCVWINUPD); tp->snd_wnd = tiwin; tp->snd_wl1 = th->th_seq; tp->snd_wl2 = th->th_ack; if (tp->snd_wnd > tp->max_sndwnd) tp->max_sndwnd = tp->snd_wnd; needoutput = 1; } /* * Process segments with URG. */ if ((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, 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: /* * Process the segment text, merging it into the TCP sequencing queue, * and arranging for acknowledgement 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, * tcp_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) { /* * Handle the common case: * o Segment is the next to be received, and * o The queue is empty, and * o The connection is established * In this case, we avoid calling tcp_reass. * * tcp_setup_ack: set DELACK for segments received in order, * but ack immediately when segments are out of order (so that * fast retransmit can work). */ TCP_REASS_LOCK(tp); if (th->th_seq == tp->rcv_nxt && TAILQ_FIRST(&tp->segq) == NULL && tp->t_state == TCPS_ESTABLISHED) { tcp_setup_ack(tp, th); tp->rcv_nxt += tlen; tiflags = th->th_flags & TH_FIN; tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_RCVPACK]++; tcps[TCP_STAT_RCVBYTE] += tlen; TCP_STAT_PUTREF(); nd6_hint(tp); if (so->so_state & SS_CANTRCVMORE) { m_freem(m); } else { m_adj(m, hdroptlen); sbappendstream(&(so)->so_rcv, m); } TCP_REASS_UNLOCK(tp); sorwakeup(so); } else { m_adj(m, hdroptlen); tiflags = tcp_reass(tp, th, m, tlen); tp->t_flags |= TF_ACKNOW; } /* * Note the amount of data that peer has sent into * our window, in order to estimate the sender's * buffer size. */ len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); } else { m_freem(m); m = NULL; 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) { socantrcvmore(so); 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 * tp->t_msl); soisdisconnected(so); break; /* * In TIME_WAIT state restart the 2 MSL time_wait timer. */ case TCPS_TIME_WAIT: TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * tp->t_msl); break; } } #ifdef TCP_DEBUG if (so->so_options & SO_DEBUG) tcp_trace(TA_INPUT, ostate, tp, tcp_saveti, 0); #endif /* * Return any desired output. */ if (needoutput || (tp->t_flags & TF_ACKNOW)) { KERNEL_LOCK(1, NULL); (void)tcp_output(tp); KERNEL_UNLOCK_ONE(NULL); } if (tcp_saveti) m_freem(tcp_saveti); if (tp->t_state == TCPS_TIME_WAIT && (so->so_state & SS_NOFDREF) && (tp->t_inpcb || af != AF_INET) && (tp->t_in6pcb || af != AF_INET6) && ((af == AF_INET ? tcp4_vtw_enable : tcp6_vtw_enable) & 1) != 0 && TAILQ_EMPTY(&tp->segq) && vtw_add(af, tp)) { ; } return; badsyn: /* * Received a bad SYN. Increment counters and dropwithreset. */ TCP_STATINC(TCP_STAT_BADSYN); tp = NULL; goto dropwithreset; dropafterack: /* * Generate an ACK dropping incoming segment if it occupies * sequence space, where the ACK reflects our state. */ if (tiflags & TH_RST) goto drop; goto dropafterack2; dropafterack_ratelim: /* * We may want to rate-limit ACKs against SYN/RST attack. */ if (ppsratecheck(&tcp_ackdrop_ppslim_last, &tcp_ackdrop_ppslim_count, tcp_ackdrop_ppslim) == 0) { /* XXX stat */ goto drop; } dropafterack2: m_freem(m); tp->t_flags |= TF_ACKNOW; KERNEL_LOCK(1, NULL); (void)tcp_output(tp); KERNEL_UNLOCK_ONE(NULL); if (tcp_saveti) m_freem(tcp_saveti); return; 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; } dropwithreset: /* * Generate a RST, dropping incoming segment. * Make ACK acceptable to originator of segment. */ if (tiflags & TH_RST) goto drop; if (tiflags & TH_ACK) { (void)tcp_respond(tp, m, m, th, (tcp_seq)0, th->th_ack, TH_RST); } else { if (tiflags & TH_SYN) tlen++; (void)tcp_respond(tp, m, m, th, th->th_seq + tlen, (tcp_seq)0, TH_RST|TH_ACK); } if (tcp_saveti) m_freem(tcp_saveti); return; badcsum: drop: /* * Drop space held by incoming segment and return. */ if (tp) { if (tp->t_inpcb) so = tp->t_inpcb->inp_socket; #ifdef INET6 else if (tp->t_in6pcb) so = tp->t_in6pcb->in6p_socket; #endif else so = NULL; #ifdef TCP_DEBUG if (so && (so->so_options & SO_DEBUG) != 0) tcp_trace(TA_DROP, ostate, tp, tcp_saveti, 0); #endif } if (tcp_saveti) m_freem(tcp_saveti); m_freem(m); return; } #ifdef TCP_SIGNATURE int tcp_signature_apply(void *fstate, void *data, u_int len) { MD5Update(fstate, (u_char *)data, len); return (0); } struct secasvar * tcp_signature_getsav(struct mbuf *m) { struct ip *ip; struct ip6_hdr *ip6; ip = mtod(m, struct ip *); switch (ip->ip_v) { case 4: ip = mtod(m, struct ip *); ip6 = NULL; break; case 6: ip = NULL; ip6 = mtod(m, struct ip6_hdr *); break; default: return (NULL); } #ifdef IPSEC union sockaddr_union dst; /* Extract the destination from the IP header in the mbuf. */ memset(&dst, 0, sizeof(union sockaddr_union)); if (ip != NULL) { dst.sa.sa_len = sizeof(struct sockaddr_in); dst.sa.sa_family = AF_INET; dst.sin.sin_addr = ip->ip_dst; } else { dst.sa.sa_len = sizeof(struct sockaddr_in6); dst.sa.sa_family = AF_INET6; dst.sin6.sin6_addr = ip6->ip6_dst; } /* * Look up an SADB entry which matches the address of the peer. */ return KEY_LOOKUP_SA(&dst, IPPROTO_TCP, htonl(TCP_SIG_SPI), 0, 0); #else return NULL; #endif } int tcp_signature(struct mbuf *m, struct tcphdr *th, int thoff, struct secasvar *sav, char *sig) { MD5_CTX ctx; struct ip *ip; struct ipovly *ipovly; #ifdef INET6 struct ip6_hdr *ip6; struct ip6_hdr_pseudo ip6pseudo; #endif struct ippseudo ippseudo; struct tcphdr th0; int l, tcphdrlen; if (sav == NULL) return (-1); tcphdrlen = th->th_off * 4; switch (mtod(m, struct ip *)->ip_v) { case 4: MD5Init(&ctx); ip = mtod(m, struct ip *); memset(&ippseudo, 0, sizeof(ippseudo)); ipovly = (struct ipovly *)ip; ippseudo.ippseudo_src = ipovly->ih_src; ippseudo.ippseudo_dst = ipovly->ih_dst; ippseudo.ippseudo_pad = 0; ippseudo.ippseudo_p = IPPROTO_TCP; ippseudo.ippseudo_len = htons(m->m_pkthdr.len - thoff); MD5Update(&ctx, (char *)&ippseudo, sizeof(ippseudo)); break; #if INET6 case 6: MD5Init(&ctx); ip6 = mtod(m, struct ip6_hdr *); memset(&ip6pseudo, 0, sizeof(ip6pseudo)); ip6pseudo.ip6ph_src = ip6->ip6_src; in6_clearscope(&ip6pseudo.ip6ph_src); ip6pseudo.ip6ph_dst = ip6->ip6_dst; in6_clearscope(&ip6pseudo.ip6ph_dst); ip6pseudo.ip6ph_len = htons(m->m_pkthdr.len - thoff); ip6pseudo.ip6ph_nxt = IPPROTO_TCP; MD5Update(&ctx, (char *)&ip6pseudo, sizeof(ip6pseudo)); break; #endif default: return (-1); } th0 = *th; th0.th_sum = 0; MD5Update(&ctx, (char *)&th0, sizeof(th0)); l = m->m_pkthdr.len - thoff - tcphdrlen; if (l > 0) m_apply(m, thoff + tcphdrlen, m->m_pkthdr.len - thoff - tcphdrlen, tcp_signature_apply, &ctx); MD5Update(&ctx, _KEYBUF(sav->key_auth), _KEYLEN(sav->key_auth)); MD5Final(sig, &ctx); return (0); } #endif /* * Parse and process tcp options. * * Returns -1 if this segment should be dropped. (eg. wrong signature) * Otherwise returns 0. */ static int tcp_dooptions(struct tcpcb *tp, const u_char *cp, int cnt, struct tcphdr *th, struct mbuf *m, int toff, struct tcp_opt_info *oi) { u_int16_t mss; int opt, optlen = 0; #ifdef TCP_SIGNATURE void *sigp = NULL; char sigbuf[TCP_SIGLEN]; struct secasvar *sav = NULL; #endif 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)); oi->maxseg = ntohs(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 = cp[2]; if (tp->requested_s_scale > TCP_MAX_WINSHIFT) { char buf[INET6_ADDRSTRLEN]; struct ip *ip = mtod(m, struct ip *); #ifdef INET6 struct ip6_hdr *ip6 = mtod(m, struct ip6_hdr *); #endif switch (ip->ip_v) { case 4: in_print(buf, sizeof(buf), &ip->ip_src); break; #ifdef INET6 case 6: in6_print(buf, sizeof(buf), &ip6->ip6_src); break; #endif default: strlcpy(buf, "(unknown)", sizeof(buf)); break; } log(LOG_ERR, "TCP: invalid wscale %d from %s, " "assuming %d\n", tp->requested_s_scale, buf, TCP_MAX_WINSHIFT); tp->requested_s_scale = 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)); NTOHL(oi->ts_val); memcpy(&oi->ts_ecr, cp + 6, sizeof(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 (optlen != TCPOLEN_SACK_PERMITTED) continue; if (!(th->th_flags & TH_SYN)) continue; if (TCPS_HAVERCVDSYN(tp->t_state)) continue; if (tcp_do_sack) { tp->t_flags |= TF_SACK_PERMIT; tp->t_flags |= TF_WILL_SACK; } 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 && !consttime_memequal(sigp, cp + 2, TCP_SIGLEN)) return (-1); sigp = sigbuf; memcpy(sigbuf, cp + 2, TCP_SIGLEN); tp->t_flags |= TF_SIGNATURE; break; #endif } } #ifndef TCP_SIGNATURE return 0; #else if (tp->t_flags & TF_SIGNATURE) { sav = tcp_signature_getsav(m); if (sav == NULL && tp->t_state == TCPS_LISTEN) return (-1); } if ((sigp ? TF_SIGNATURE : 0) ^ (tp->t_flags & TF_SIGNATURE)) goto out; if (sigp) { char sig[TCP_SIGLEN]; tcp_fields_to_net(th); if (tcp_signature(m, th, toff, sav, sig) < 0) { tcp_fields_to_host(th); goto out; } tcp_fields_to_host(th); if (!consttime_memequal(sig, sigp, TCP_SIGLEN)) { TCP_STATINC(TCP_STAT_BADSIG); goto out; } else TCP_STATINC(TCP_STAT_GOODSIG); key_sa_recordxfer(sav, m); KEY_SA_UNREF(&sav); } return 0; out: if (sav != NULL) KEY_SA_UNREF(&sav); return -1; #endif } /* * 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, struct tcphdr *th, struct mbuf *m, int off) { int cnt = off + th->th_urp - 1; while (cnt >= 0) { if (m->m_len > cnt) { char *cp = mtod(m, char *) + cnt; struct tcpcb *tp = sototcpcb(so); tp->t_iobc = *cp; tp->t_oobflags |= TCPOOB_HAVEDATA; memmove(cp, cp + 1, (unsigned)(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. * * rtt is in units of slow ticks (typically 500 ms) -- essentially the * difference of two timestamps. */ void tcp_xmit_timer(struct tcpcb *tp, uint32_t rtt) { int32_t delta; TCP_STATINC(TCP_STAT_RTTUPDATED); if (tp->t_srtt != 0) { /* * Compute the amount to add to srtt for smoothing, * *alpha, or 2^(-TCP_RTT_SHIFT). Because * srtt is stored in 1/32 slow ticks, we conceptually * shift left 5 bits, subtract srtt to get the * diference, and then shift right by TCP_RTT_SHIFT * (3) to obtain 1/8 of the difference. */ delta = (rtt << 2) - (tp->t_srtt >> TCP_RTT_SHIFT); /* * This can never happen, because delta's lowest * possible value is 1/8 of t_srtt. But if it does, * set srtt to some reasonable value, here chosen * as 1/8 tick. */ if ((tp->t_srtt += delta) <= 0) tp->t_srtt = 1 << 2; /* * RFC2988 requires that rttvar be updated first. * This code is compliant because "delta" is the old * srtt minus the new observation (scaled). * * RFC2988 says: * rttvar = (1-beta) * rttvar + beta * |srtt-observed| * * delta is in units of 1/32 ticks, and has then been * divided by 8. This is equivalent to being in 1/16s * units and divided by 4. Subtract from it 1/4 of * the existing rttvar to form the (signed) amount to * adjust. */ if (delta < 0) delta = -delta; delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT); /* * As with srtt, this should never happen. There is * no support in RFC2988 for this operation. But 1/4s * as rttvar when faced with something arguably wrong * is ok. */ if ((tp->t_rttvar += delta) <= 0) tp->t_rttvar = 1 << 2; /* * If srtt exceeds .01 second, ensure we use the 'remote' MSL * Problem is: it doesn't work. Disabled by defaulting * tcp_rttlocal to 0; see corresponding code in * tcp_subr that selects local vs remote in a different way. * * The static branch prediction hint here should be removed * when the rtt estimator is fixed and the rtt_enable code * is turned back on. */ if (__predict_false(tcp_rttlocal) && tcp_msl_enable && tp->t_srtt > tcp_msl_remote_threshold && tp->t_msl < tcp_msl_remote) { tp->t_msl = MIN(tcp_msl_remote, TCP_MAXMSL); } } else { /* * This is the first measurement. Per RFC2988, 2.2, * set rtt=R and srtt=R/2. * For srtt, storage representation is 1/32 ticks, * so shift left by 5. * For rttvar, storage representation is 1/16 ticks, * So shift left by 4, but then right by 1 to halve. */ tp->t_srtt = rtt << (TCP_RTT_SHIFT + 2); tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT + 2 - 1); } tp->t_rtttime = 0; tp->t_rxtshift = 0; /* * the retransmit should happen at rtt + 4 * rttvar. * Because of the way we do the smoothing, srtt and rttvar * will each average +1/2 tick of bias. When we compute * the retransmit timer, we want 1/2 tick of rounding and * 1 extra tick because of +-1/2 tick uncertainty in the * firing of the timer. The bias will give us exactly the * 1.5 tick we need. But, because the bias is * statistical, we have to test that we don't drop below * the minimum feasible timer (which is 2 ticks). */ TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), uimax(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); /* * We received an ack for a packet that wasn't retransmitted; * it is probably safe to discard any error indications we've * received recently. This isn't quite right, but close enough * for now (a route might have failed after we sent a segment, * and the return path might not be symmetrical). */ tp->t_softerror = 0; } /* * TCP compressed state engine. Currently used to hold compressed * state for SYN_RECEIVED. */ u_long syn_cache_count; u_int32_t syn_hash1, syn_hash2; #define SYN_HASH(sa, sp, dp) \ ((((sa)->s_addr^syn_hash1)*(((((u_int32_t)(dp))<<16) + \ ((u_int32_t)(sp)))^syn_hash2))) #ifndef INET6 #define SYN_HASHALL(hash, src, dst) \ do { \ hash = SYN_HASH(&((const struct sockaddr_in *)(src))->sin_addr, \ ((const struct sockaddr_in *)(src))->sin_port, \ ((const struct sockaddr_in *)(dst))->sin_port); \ } while (/*CONSTCOND*/ 0) #else #define SYN_HASH6(sa, sp, dp) \ ((((sa)->s6_addr32[0] ^ (sa)->s6_addr32[3] ^ syn_hash1) * \ (((((u_int32_t)(dp))<<16) + ((u_int32_t)(sp)))^syn_hash2)) \ & 0x7fffffff) #define SYN_HASHALL(hash, src, dst) \ do { \ switch ((src)->sa_family) { \ case AF_INET: \ hash = SYN_HASH(&((const struct sockaddr_in *)(src))->sin_addr, \ ((const struct sockaddr_in *)(src))->sin_port, \ ((const struct sockaddr_in *)(dst))->sin_port); \ break; \ case AF_INET6: \ hash = SYN_HASH6(&((const struct sockaddr_in6 *)(src))->sin6_addr, \ ((const struct sockaddr_in6 *)(src))->sin6_port, \ ((const struct sockaddr_in6 *)(dst))->sin6_port); \ break; \ default: \ hash = 0; \ } \ } while (/*CONSTCOND*/0) #endif /* INET6 */ static 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. */ static inline void syn_cache_timer_arm(struct syn_cache *sc) { TCPT_RANGESET(sc->sc_rxtcur, TCPTV_SRTTDFLT * tcp_backoff[sc->sc_rxtshift], TCPTV_MIN, TCPTV_REXMTMAX); callout_reset(&sc->sc_timer, sc->sc_rxtcur * (hz / PR_SLOWHZ), syn_cache_timer, sc); } #define SYN_CACHE_TIMESTAMP(sc) (tcp_now - (sc)->sc_timebase) static inline void syn_cache_rm(struct syn_cache *sc) { TAILQ_REMOVE(&tcp_syn_cache[sc->sc_bucketidx].sch_bucket, sc, sc_bucketq); sc->sc_tp = NULL; LIST_REMOVE(sc, sc_tpq); tcp_syn_cache[sc->sc_bucketidx].sch_length--; callout_stop(&sc->sc_timer); syn_cache_count--; } static inline void syn_cache_put(struct syn_cache *sc) { if (sc->sc_ipopts) (void) m_free(sc->sc_ipopts); rtcache_free(&sc->sc_route); sc->sc_flags |= SCF_DEAD; if (!callout_invoking(&sc->sc_timer)) callout_schedule(&(sc)->sc_timer, 1); } void syn_cache_init(void) { int i; pool_init(&syn_cache_pool, sizeof(struct syn_cache), 0, 0, 0, "synpl", NULL, IPL_SOFTNET); /* Initialize the hash buckets. */ for (i = 0; i < tcp_syn_cache_size; i++) TAILQ_INIT(&tcp_syn_cache[i].sch_bucket); } void syn_cache_insert(struct syn_cache *sc, struct tcpcb *tp) { struct syn_cache_head *scp; struct syn_cache *sc2; int s; /* * If there are no entries in the hash table, reinitialize * the hash secrets. */ if (syn_cache_count == 0) { syn_hash1 = cprng_fast32(); syn_hash2 = cprng_fast32(); } SYN_HASHALL(sc->sc_hash, &sc->sc_src.sa, &sc->sc_dst.sa); sc->sc_bucketidx = sc->sc_hash % tcp_syn_cache_size; scp = &tcp_syn_cache[sc->sc_bucketidx]; /* * Make sure that we don't overflow the per-bucket * limit or the total cache size limit. */ s = splsoftnet(); if (scp->sch_length >= tcp_syn_bucket_limit) { TCP_STATINC(TCP_STAT_SC_BUCKETOVERFLOW); /* * 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("syn_cache_insert: bucketoverflow: impossible"); #endif syn_cache_rm(sc2); syn_cache_put(sc2); /* calls pool_put but see spl above */ } else if (syn_cache_count >= tcp_syn_cache_limit) { struct syn_cache_head *scp2, *sce; TCP_STATINC(TCP_STAT_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 = &tcp_syn_cache[tcp_syn_cache_size]; for (++scp2; scp2 != scp; scp2++) { if (scp2 >= sce) scp2 = &tcp_syn_cache[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("syn_cache_insert: cacheoverflow: " "impossible"); #endif } sc2 = TAILQ_FIRST(&scp2->sch_bucket); syn_cache_rm(sc2); syn_cache_put(sc2); /* calls pool_put but see spl above */ } /* * 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++; syn_cache_count++; TCP_STATINC(TCP_STAT_SC_ADDED); splx(s); } /* * 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. */ static void syn_cache_timer(void *arg) { struct syn_cache *sc = arg; mutex_enter(softnet_lock); KERNEL_LOCK(1, NULL); callout_ack(&sc->sc_timer); if (__predict_false(sc->sc_flags & SCF_DEAD)) { TCP_STATINC(TCP_STAT_SC_DELAYED_FREE); goto free; } 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 >= MIN(tcp_keepinit, TCP_TIMER_MAXTICKS)) goto dropit; TCP_STATINC(TCP_STAT_SC_RETRANSMITTED); (void)syn_cache_respond(sc); /* Advance the timer back-off. */ sc->sc_rxtshift++; syn_cache_timer_arm(sc); goto out; dropit: TCP_STATINC(TCP_STAT_SC_TIMED_OUT); syn_cache_rm(sc); if (sc->sc_ipopts) (void) m_free(sc->sc_ipopts); rtcache_free(&sc->sc_route); free: callout_destroy(&sc->sc_timer); pool_put(&syn_cache_pool, sc); out: KERNEL_UNLOCK_ONE(NULL); mutex_exit(softnet_lock); } /* * 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; int s; s = splsoftnet(); for (sc = LIST_FIRST(&tp->t_sc); sc != NULL; sc = nsc) { nsc = LIST_NEXT(sc, sc_tpq); #ifdef DIAGNOSTIC if (sc->sc_tp != tp) panic("invalid sc_tp in syn_cache_cleanup"); #endif syn_cache_rm(sc); syn_cache_put(sc); /* calls pool_put but see spl above */ } /* just for safety */ LIST_INIT(&tp->t_sc); splx(s); } /* * Find an entry in the syn cache. */ struct syn_cache * syn_cache_lookup(const struct sockaddr *src, const struct sockaddr *dst, struct syn_cache_head **headp) { struct syn_cache *sc; struct syn_cache_head *scp; u_int32_t hash; int s; SYN_HASHALL(hash, src, dst); scp = &tcp_syn_cache[hash % tcp_syn_cache_size]; *headp = scp; s = splsoftnet(); for (sc = TAILQ_FIRST(&scp->sch_bucket); sc != NULL; sc = TAILQ_NEXT(sc, sc_bucketq)) { if (sc->sc_hash != hash) continue; if (!memcmp(&sc->sc_src, src, src->sa_len) && !memcmp(&sc->sc_dst, dst, dst->sa_len)) { splx(s); return (sc); } } splx(s); 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 it's * 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 numbers; 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, struct socket *so, struct mbuf *m) { struct syn_cache *sc; struct syn_cache_head *scp; struct inpcb *inp = NULL; #ifdef INET6 struct in6pcb *in6p = NULL; #endif struct tcpcb *tp; int s; struct socket *oso; s = splsoftnet(); if ((sc = syn_cache_lookup(src, dst, &scp)) == NULL) { splx(s); 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)) { m_freem(m); (void)syn_cache_respond(sc); splx(s); return ((struct socket *)(-1)); } /* Remove this cache entry */ syn_cache_rm(sc); splx(s); /* * 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. */ /* * inp still has the OLD in_pcb stuff, set the * v6-related flags on the new guy, too. This is * done particularly for the case where an AF_INET6 * socket is bound only to a port, and a v4 connection * comes in on that port. * we also copy the flowinfo from the original pcb * to the new one. */ oso = so; so = sonewconn(so, true); if (so == NULL) goto resetandabort; switch (so->so_proto->pr_domain->dom_family) { case AF_INET: inp = sotoinpcb(so); break; #ifdef INET6 case AF_INET6: in6p = sotoin6pcb(so); break; #endif } switch (src->sa_family) { case AF_INET: if (inp) { inp->inp_laddr = ((struct sockaddr_in *)dst)->sin_addr; inp->inp_lport = ((struct sockaddr_in *)dst)->sin_port; inp->inp_options = ip_srcroute(m); in_pcbstate(inp, INP_BOUND); if (inp->inp_options == NULL) { inp->inp_options = sc->sc_ipopts; sc->sc_ipopts = NULL; } } #ifdef INET6 else if (in6p) { /* IPv4 packet to AF_INET6 socket */ memset(&in6p->in6p_laddr, 0, sizeof(in6p->in6p_laddr)); in6p->in6p_laddr.s6_addr16[5] = htons(0xffff); bcopy(&((struct sockaddr_in *)dst)->sin_addr, &in6p->in6p_laddr.s6_addr32[3], sizeof(((struct sockaddr_in *)dst)->sin_addr)); in6p->in6p_lport = ((struct sockaddr_in *)dst)->sin_port; in6totcpcb(in6p)->t_family = AF_INET; if (sotoin6pcb(oso)->in6p_flags & IN6P_IPV6_V6ONLY) in6p->in6p_flags |= IN6P_IPV6_V6ONLY; else in6p->in6p_flags &= ~IN6P_IPV6_V6ONLY; in6_pcbstate(in6p, IN6P_BOUND); } #endif break; #ifdef INET6 case AF_INET6: if (in6p) { in6p->in6p_laddr = ((struct sockaddr_in6 *)dst)->sin6_addr; in6p->in6p_lport = ((struct sockaddr_in6 *)dst)->sin6_port; in6_pcbstate(in6p, IN6P_BOUND); } break; #endif } #ifdef INET6 if (in6p && in6totcpcb(in6p)->t_family == AF_INET6 && sotoinpcb(oso)) { struct in6pcb *oin6p = sotoin6pcb(oso); /* inherit socket options from the listening socket */ in6p->in6p_flags |= (oin6p->in6p_flags & IN6P_CONTROLOPTS); if (in6p->in6p_flags & IN6P_CONTROLOPTS) { m_freem(in6p->in6p_options); in6p->in6p_options = NULL; } ip6_savecontrol(in6p, &in6p->in6p_options, mtod(m, struct ip6_hdr *), m); } #endif /* * Give the new socket our cached route reference. */ if (inp) { rtcache_copy(&inp->inp_route, &sc->sc_route); rtcache_free(&sc->sc_route); } #ifdef INET6 else { rtcache_copy(&in6p->in6p_route, &sc->sc_route); rtcache_free(&sc->sc_route); } #endif if (inp) { struct sockaddr_in sin; memcpy(&sin, src, src->sa_len); if (in_pcbconnect(inp, &sin, &lwp0)) { goto resetandabort; } } #ifdef INET6 else if (in6p) { struct sockaddr_in6 sin6; memcpy(&sin6, src, src->sa_len); if (src->sa_family == AF_INET) { /* IPv4 packet to AF_INET6 socket */ in6_sin_2_v4mapsin6((struct sockaddr_in *)src, &sin6); } if (in6_pcbconnect(in6p, &sin6, NULL)) { goto resetandabort; } } #endif else { goto resetandabort; } if (inp) tp = intotcpcb(inp); #ifdef INET6 else if (in6p) tp = in6totcpcb(in6p); #endif else tp = NULL; tp->t_flags = sototcpcb(oso)->t_flags & 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->snd_scale = sc->sc_requested_s_scale; tp->rcv_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->ts_timebase = sc->sc_timebase; tp->t_template = tcp_template(tp); if (tp->t_template == 0) { tp = tcp_drop(tp, ENOBUFS); /* destroys socket */ so = NULL; m_freem(m); goto abort; } tp->iss = sc->sc_iss; tp->irs = sc->sc_irs; tcp_sendseqinit(tp); tcp_rcvseqinit(tp); tp->t_state = TCPS_SYN_RECEIVED; TCP_TIMER_ARM(tp, TCPT_KEEP, tp->t_keepinit); TCP_STATINC(TCP_STAT_ACCEPTS); if ((sc->sc_flags & SCF_SACK_PERMIT) && tcp_do_sack) tp->t_flags |= TF_WILL_SACK; if ((sc->sc_flags & SCF_ECN_PERMIT) && tcp_do_ecn) tp->t_flags |= TF_ECN_PERMIT; #ifdef TCP_SIGNATURE if (sc->sc_flags & SCF_SIGNATURE) tp->t_flags |= TF_SIGNATURE; #endif /* Initialize tp->t_ourmss before we deal with the peer's! */ tp->t_ourmss = sc->sc_ourmaxseg; tcp_mss_from_peer(tp, sc->sc_peermaxseg); /* * Initialize the initial congestion window. If we * had to retransmit the SYN,ACK, we must initialize cwnd * to 1 segment (i.e. the Loss Window). */ if (sc->sc_rxtshift) tp->snd_cwnd = tp->t_peermss; else { int ss = tcp_init_win; if (inp != NULL && in_localaddr(inp->inp_faddr)) ss = tcp_init_win_local; #ifdef INET6 if (in6p != NULL && in6_localaddr(&in6p->in6p_faddr)) ss = tcp_init_win_local; #endif tp->snd_cwnd = TCP_INITIAL_WINDOW(ss, tp->t_peermss); } tcp_rmx_rtt(tp); tp->snd_wl1 = sc->sc_irs; tp->rcv_up = sc->sc_irs + 1; /* * This is what whould 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; tp->t_partialacks = -1; tp->t_dupacks = 0; TCP_STATINC(TCP_STAT_SC_COMPLETED); s = splsoftnet(); syn_cache_put(sc); splx(s); return so; resetandabort: (void)tcp_respond(NULL, m, m, th, (tcp_seq)0, th->th_ack, TH_RST); abort: if (so != NULL) { (void) soqremque(so, 1); (void) soabort(so); mutex_enter(softnet_lock); } s = splsoftnet(); syn_cache_put(sc); splx(s); TCP_STATINC(TCP_STAT_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) { struct syn_cache *sc; struct syn_cache_head *scp; int s = splsoftnet(); if ((sc = syn_cache_lookup(src, dst, &scp)) == NULL) { splx(s); return; } if (SEQ_LT(th->th_seq, sc->sc_irs) || SEQ_GT(th->th_seq, sc->sc_irs+1)) { splx(s); return; } syn_cache_rm(sc); TCP_STATINC(TCP_STAT_SC_RESET); syn_cache_put(sc); /* calls pool_put but see spl above */ splx(s); } void syn_cache_unreach(const struct sockaddr *src, const struct sockaddr *dst, struct tcphdr *th) { struct syn_cache *sc; struct syn_cache_head *scp; int s; s = splsoftnet(); if ((sc = syn_cache_lookup(src, dst, &scp)) == NULL) { splx(s); return; } /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ if (ntohl(th->th_seq) != sc->sc_iss) { splx(s); 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; splx(s); return; } syn_cache_rm(sc); TCP_STATINC(TCP_STAT_SC_UNREACH); syn_cache_put(sc); /* calls pool_put but see spl above */ splx(s); } /* * 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, unsigned int toff, struct socket *so, struct mbuf *m, u_char *optp, int optlen, struct tcp_opt_info *oi) { struct tcpcb tb, *tp; long win; struct syn_cache *sc; struct syn_cache_head *scp; struct mbuf *ipopts; int s; tp = sototcpcb(so); /* * Initialize some local state. */ win = sbspace(&so->so_rcv); if (win > TCP_MAXWIN) win = TCP_MAXWIN; #ifdef TCP_SIGNATURE if (optp || (tp->t_flags & TF_SIGNATURE)) #else if (optp) #endif { tb.t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; #ifdef TCP_SIGNATURE tb.t_flags |= (tp->t_flags & TF_SIGNATURE); #endif tb.t_state = TCPS_LISTEN; if (tcp_dooptions(&tb, optp, optlen, th, m, toff, oi) < 0) return 0; } else tb.t_flags = 0; 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). */ if ((sc = syn_cache_lookup(src, dst, &scp)) != NULL) { TCP_STATINC(TCP_STAT_SC_DUPESYN); if (ipopts) { /* * If we were remembering a previous source route, * forget it and use the new one we've been given. */ if (sc->sc_ipopts) (void)m_free(sc->sc_ipopts); sc->sc_ipopts = ipopts; } sc->sc_timestamp = tb.ts_recent; m_freem(m); if (syn_cache_respond(sc) == 0) { uint64_t *tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_SNDACKS]++; tcps[TCP_STAT_SNDTOTAL]++; TCP_STAT_PUTREF(); } return 1; } s = splsoftnet(); sc = pool_get(&syn_cache_pool, PR_NOWAIT); splx(s); if (sc == NULL) { if (ipopts) (void)m_free(ipopts); return 0; } /* * Fill in the cache, and put the necessary IP and TCP * options into the reply. */ memset(sc, 0, sizeof(struct syn_cache)); callout_init(&sc->sc_timer, CALLOUT_MPSAFE); memcpy(&sc->sc_src, src, src->sa_len); memcpy(&sc->sc_dst, dst, dst->sa_len); sc->sc_flags = 0; sc->sc_ipopts = ipopts; sc->sc_irs = th->th_seq; switch (src->sa_family) { case AF_INET: { struct sockaddr_in *srcin = (void *)src; struct sockaddr_in *dstin = (void *)dst; sc->sc_iss = tcp_new_iss1(&dstin->sin_addr, &srcin->sin_addr, dstin->sin_port, srcin->sin_port, sizeof(dstin->sin_addr), 0); break; } #ifdef INET6 case AF_INET6: { struct sockaddr_in6 *srcin6 = (void *)src; struct sockaddr_in6 *dstin6 = (void *)dst; sc->sc_iss = tcp_new_iss1(&dstin6->sin6_addr, &srcin6->sin6_addr, dstin6->sin6_port, srcin6->sin6_port, sizeof(dstin6->sin6_addr), 0); break; } #endif } sc->sc_peermaxseg = oi->maxseg; sc->sc_ourmaxseg = tcp_mss_to_advertise(m->m_flags & M_PKTHDR ? m_get_rcvif_NOMPSAFE(m) : NULL, sc->sc_src.sa.sa_family); sc->sc_win = win; sc->sc_timebase = tcp_now - 1; /* see tcp_newtcpcb() */ 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; 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 compatiblity 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; } if ((tb.t_flags & TF_SACK_PERMIT) && tcp_do_sack) sc->sc_flags |= SCF_SACK_PERMIT; /* * ECN setup packet received. */ if ((th->th_flags & (TH_ECE|TH_CWR)) && tcp_do_ecn) sc->sc_flags |= SCF_ECN_PERMIT; #ifdef TCP_SIGNATURE if (tb.t_flags & TF_SIGNATURE) sc->sc_flags |= SCF_SIGNATURE; #endif sc->sc_tp = tp; m_freem(m); if (syn_cache_respond(sc) == 0) { uint64_t *tcps = TCP_STAT_GETREF(); tcps[TCP_STAT_SNDACKS]++; tcps[TCP_STAT_SNDTOTAL]++; TCP_STAT_PUTREF(); syn_cache_insert(sc, tp); } else { s = splsoftnet(); /* * syn_cache_put() will try to schedule the timer, so * we need to initialize it */ syn_cache_timer_arm(sc); syn_cache_put(sc); splx(s); TCP_STATINC(TCP_STAT_SC_DROPPED); } return 1; } /* * syn_cache_respond: (re)send SYN+ACK. * * Returns 0 on success. */ int syn_cache_respond(struct syn_cache *sc) { #ifdef INET6 struct rtentry *rt = NULL; #endif struct route *ro; u_int8_t *optp; int optlen, error; u_int16_t tlen; struct ip *ip = NULL; #ifdef INET6 struct ip6_hdr *ip6 = NULL; #endif struct tcpcb *tp; struct tcphdr *th; struct mbuf *m; u_int hlen; #ifdef TCP_SIGNATURE struct secasvar *sav = NULL; u_int8_t *sigp = NULL; #endif ro = &sc->sc_route; 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: return EAFNOSUPPORT; } /* Worst case scanario, since we don't know the option size yet. */ tlen = hlen + sizeof(struct tcphdr) + MAX_TCPOPTLEN; KASSERT(max_linkhdr + tlen <= MCLBYTES); /* * Create the IP+TCP header from scratch. */ 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; MCLAIM(m, &tcp_tx_mowner); tp = sc->sc_tp; /* Fixup the mbuf. */ m->m_data += max_linkhdr; m_reset_rcvif(m); memset(mtod(m, void *), 0, tlen); switch (sc->sc_src.sa.sa_family) { case AF_INET: ip = mtod(m, struct ip *); ip->ip_v = 4; 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_vfc = IPV6_VERSION; 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: panic("%s: impossible (1)", __func__); } th->th_seq = htonl(sc->sc_iss); th->th_ack = htonl(sc->sc_irs + 1); th->th_flags = TH_SYN|TH_ACK; th->th_win = htons(sc->sc_win); /* th_x2, th_sum, th_urp already 0 from memset */ /* Tack on the TCP options. */ optp = (u_int8_t *)(th + 1); optlen = 0; *optp++ = TCPOPT_MAXSEG; *optp++ = TCPOLEN_MAXSEG; *optp++ = (sc->sc_ourmaxseg >> 8) & 0xff; *optp++ = sc->sc_ourmaxseg & 0xff; optlen += TCPOLEN_MAXSEG; 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 += TCPOLEN_WINDOW + TCPOLEN_NOP; optlen += TCPOLEN_WINDOW + TCPOLEN_NOP; } if (sc->sc_flags & SCF_SACK_PERMIT) { /* Let the peer know that we will SACK. */ *optp++ = TCPOPT_SACK_PERMITTED; *optp++ = TCPOLEN_SACK_PERMITTED; optlen += TCPOLEN_SACK_PERMITTED; } if (sc->sc_flags & SCF_TIMESTAMP) { while (optlen % 4 != 2) { optlen += TCPOLEN_NOP; *optp++ = TCPOPT_NOP; } *optp++ = TCPOPT_TIMESTAMP; *optp++ = TCPOLEN_TIMESTAMP; u_int32_t *lp = (u_int32_t *)(optp); /* Form timestamp option as shown in appendix A of RFC 1323. */ *lp++ = htonl(SYN_CACHE_TIMESTAMP(sc)); *lp = htonl(sc->sc_timestamp); optp += TCPOLEN_TIMESTAMP - 2; optlen += TCPOLEN_TIMESTAMP; } #ifdef TCP_SIGNATURE if (sc->sc_flags & SCF_SIGNATURE) { sav = tcp_signature_getsav(m); if (sav == NULL) { m_freem(m); return EPERM; } *optp++ = TCPOPT_SIGNATURE; *optp++ = TCPOLEN_SIGNATURE; sigp = optp; memset(optp, 0, TCP_SIGLEN); optp += TCP_SIGLEN; optlen += TCPOLEN_SIGNATURE; } #endif /* * Terminate and pad TCP options to a 4 byte boundary. * * According to RFC793: "The content of the header beyond the * End-of-Option option must be header padding (i.e., zero)." * And later: "The padding is composed of zeros." */ if (optlen % 4) { optlen += TCPOLEN_EOL; *optp++ = TCPOPT_EOL; } while (optlen % 4) { optlen += TCPOLEN_PAD; *optp++ = TCPOPT_PAD; } /* Compute the actual values now that we've added the options. */ tlen = hlen + sizeof(struct tcphdr) + optlen; m->m_len = m->m_pkthdr.len = tlen; th->th_off = (sizeof(struct tcphdr) + optlen) >> 2; #ifdef TCP_SIGNATURE if (sav) { (void)tcp_signature(m, th, hlen, sav, sigp); key_sa_recordxfer(sav, m); KEY_SA_UNREF(&sav); } #endif /* * Send ECN SYN-ACK setup packet. * Routes can be asymetric, so, even if we receive a packet * with ECE and CWR set, we must not assume no one will block * the ECE packet we are about to send. */ if ((sc->sc_flags & SCF_ECN_PERMIT) && tp && SEQ_GEQ(tp->snd_nxt, tp->snd_max)) { th->th_flags |= TH_ECE; TCP_STATINC(TCP_STAT_ECN_SHS); /* * draft-ietf-tcpm-ecnsyn-00.txt * * "[...] a TCP node MAY respond to an ECN-setup * SYN packet by setting ECT in the responding * ECN-setup SYN/ACK packet, indicating to routers * that the SYN/ACK packet is ECN-Capable. * This allows a congested router along the path * to mark the packet instead of dropping the * packet as an indication of congestion." * * "[...] There can be a great benefit in setting * an ECN-capable codepoint in SYN/ACK packets [...] * Congestion is most likely to occur in * the server-to-client direction. As a result, * setting an ECN-capable codepoint in SYN/ACK * packets can reduce the occurence of three-second * retransmit timeouts resulting from the drop * of SYN/ACK packets." * * Page 4 and 6, January 2006. */ switch (sc->sc_src.sa.sa_family) { case AF_INET: ip->ip_tos |= IPTOS_ECN_ECT0; break; #ifdef INET6 case AF_INET6: ip6->ip6_flow |= htonl(IPTOS_ECN_ECT0 << 20); break; #endif } TCP_STATINC(TCP_STAT_ECN_ECT); } /* * Compute the packet's checksum. * * 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 - hlen); th->th_sum = 0; th->th_sum = in4_cksum(m, IPPROTO_TCP, hlen, tlen - hlen); ip->ip_len = htons(tlen); ip->ip_ttl = ip_defttl; /* XXX tos? */ 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); ip6->ip6_vfc &= ~IPV6_VERSION_MASK; ip6->ip6_vfc |= IPV6_VERSION; ip6->ip6_plen = htons(tlen - hlen); /* ip6_hlim will be initialized afterwards */ /* XXX flowlabel? */ break; #endif } /* XXX use IPsec policy on listening socket, on SYN ACK */ tp = sc->sc_tp; switch (sc->sc_src.sa.sa_family) { case AF_INET: error = ip_output(m, sc->sc_ipopts, ro, (ip_mtudisc ? IP_MTUDISC : 0), NULL, tp ? tp->t_inpcb : NULL); break; #ifdef INET6 case AF_INET6: ip6->ip6_hlim = in6_selecthlim(NULL, (rt = rtcache_validate(ro)) != NULL ? rt->rt_ifp : NULL); rtcache_unref(rt, ro); error = ip6_output(m, NULL /*XXX*/, ro, 0, NULL, tp ? tp->t_in6pcb : NULL, NULL); break; #endif default: panic("%s: impossible (2)", __func__); } return error; }