/* * Copyright (c) 2002, 2003, 2004 Jeffrey M. Hsu. All rights reserved. * Copyright (c) 2002, 2003, 2004 The DragonFly Project. All rights reserved. * * This code is derived from software contributed to The DragonFly Project * by Jeffrey M. Hsu. * * 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 DragonFly 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 COPYRIGHT HOLDERS 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 * COPYRIGHT HOLDERS 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. All advertising materials mentioning features or use of this software * must display the following acknowledgement: * This product includes software developed by the University of * California, Berkeley and its contributors. * 4. Neither the name of the University nor the names of its contributors * may be used to endorse or promote products derived from this software * without specific prior written permission. * * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF * SUCH DAMAGE. * * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 * $FreeBSD: src/sys/netinet/tcp_input.c,v 1.107.2.38 2003/05/21 04:46:41 cjc Exp $ */ #include "opt_inet.h" #include "opt_inet6.h" #include "opt_ipsec.h" #include "opt_tcpdebug.h" #include "opt_tcp_input.h" #include #include #include #include #include #include #include /* for proc0 declaration */ #include #include #include #include #include #include #include /* before tcp_seq.h, for tcp_random18() */ #include #include #include #include #include #include #include /* for ICMP_BANDLIM */ #include #include /* for ICMP_BANDLIM */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #ifdef TCPDEBUG #include u_char tcp_saveipgen[40]; /* the size must be of max ip header, now IPv6 */ struct tcphdr tcp_savetcp; #endif #ifdef FAST_IPSEC #include #include #endif #ifdef IPSEC #include #include #include #endif MALLOC_DEFINE(M_TSEGQ, "tseg_qent", "TCP segment queue entry"); static int log_in_vain = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, &log_in_vain, 0, "Log all incoming TCP connections"); static int blackhole = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, &blackhole, 0, "Do not send RST when dropping refused connections"); int tcp_delack_enabled = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, &tcp_delack_enabled, 0, "Delay ACK to try and piggyback it onto a data packet"); #ifdef TCP_DROP_SYNFIN static int drop_synfin = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, &drop_synfin, 0, "Drop TCP packets with SYN+FIN set"); #endif static int tcp_do_limitedtransmit = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, limitedtransmit, CTLFLAG_RW, &tcp_do_limitedtransmit, 0, "Enable RFC 3042 (Limited Transmit)"); static int tcp_do_early_retransmit = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, earlyretransmit, CTLFLAG_RW, &tcp_do_early_retransmit, 0, "Early retransmit"); int tcp_aggregate_acks = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, aggregate_acks, CTLFLAG_RW, &tcp_aggregate_acks, 0, "Aggregate built-up acks into one ack"); static int tcp_do_eifel_detect = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, eifel, CTLFLAG_RW, &tcp_do_eifel_detect, 0, "Eifel detection algorithm (RFC 3522)"); static int tcp_do_abc = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc, CTLFLAG_RW, &tcp_do_abc, 0, "TCP Appropriate Byte Counting (RFC 3465)"); /* * Define as tunable for easy testing with SACK on and off. * Warning: do not change setting in the middle of an existing active TCP flow, * else strange things might happen to that flow. */ int tcp_do_sack = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, sack, CTLFLAG_RW, &tcp_do_sack, 0, "Enable SACK Algorithms"); int tcp_do_smartsack = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, smartsack, CTLFLAG_RW, &tcp_do_smartsack, 0, "Enable Smart SACK Algorithms"); int tcp_do_rescuesack = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack, CTLFLAG_RW, &tcp_do_rescuesack, 0, "Rescue retransmission for SACK"); int tcp_aggressive_rescuesack = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, rescuesack_agg, CTLFLAG_RW, &tcp_aggressive_rescuesack, 0, "Aggressive rescue retransmission for SACK"); int tcp_do_rfc3517bis = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3517bis, CTLFLAG_RW, &tcp_do_rfc3517bis, 0, "Enable RFC3517 update"); int tcp_rfc3517bis_rxt = 0; SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3517bis_rxt, CTLFLAG_RW, &tcp_rfc3517bis_rxt, 0, "Enable RFC3517 retransmit update"); SYSCTL_NODE(_net_inet_tcp, OID_AUTO, reass, CTLFLAG_RW, 0, "TCP Segment Reassembly Queue"); int tcp_reass_maxseg = 0; SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, maxsegments, CTLFLAG_RD, &tcp_reass_maxseg, 0, "Global maximum number of TCP Segments in Reassembly Queue"); int tcp_reass_qsize = 0; SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, cursegments, CTLFLAG_RD, &tcp_reass_qsize, 0, "Global number of TCP Segments currently in Reassembly Queue"); static int tcp_reass_overflows = 0; SYSCTL_INT(_net_inet_tcp_reass, OID_AUTO, overflows, CTLFLAG_RD, &tcp_reass_overflows, 0, "Global number of TCP Segment Reassembly Queue Overflows"); int tcp_do_autorcvbuf = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, &tcp_do_autorcvbuf, 0, "Enable automatic receive buffer sizing"); int tcp_autorcvbuf_inc = 16*1024; SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, &tcp_autorcvbuf_inc, 0, "Incrementor step size of automatic receive buffer"); int tcp_autorcvbuf_max = 2*1024*1024; SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, &tcp_autorcvbuf_max, 0, "Max size of automatic receive buffer"); int tcp_sosend_agglim = 2; SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_agglim, CTLFLAG_RW, &tcp_sosend_agglim, 0, "TCP sosend mbuf aggregation limit"); int tcp_sosend_async = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, sosend_async, CTLFLAG_RW, &tcp_sosend_async, 0, "TCP asynchronized pru_send"); static int tcp_ignore_redun_dsack = 1; SYSCTL_INT(_net_inet_tcp, OID_AUTO, ignore_redun_dsack, CTLFLAG_RW, &tcp_ignore_redun_dsack, 0, "Ignore redundant DSACK"); static void tcp_dooptions(struct tcpopt *, u_char *, int, boolean_t, tcp_seq); static void tcp_pulloutofband(struct socket *, struct tcphdr *, struct mbuf *, int); static int tcp_reass(struct tcpcb *, struct tcphdr *, int *, struct mbuf *); static void tcp_xmit_timer(struct tcpcb *, int, tcp_seq); static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *, int); static void tcp_sack_rexmt(struct tcpcb *, struct tcphdr *); static boolean_t tcp_sack_limitedxmit(struct tcpcb *); static int tcp_rmx_msl(const struct tcpcb *); static void tcp_established(struct tcpcb *); /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ #ifdef INET6 #define ND6_HINT(tp) \ do { \ if ((tp) && (tp)->t_inpcb && \ ((tp)->t_inpcb->inp_vflag & INP_IPV6) && \ (tp)->t_inpcb->in6p_route.ro_rt) \ nd6_nud_hint((tp)->t_inpcb->in6p_route.ro_rt, NULL, 0); \ } while (0) #else #define ND6_HINT(tp) #endif /* * Indicate whether this ack should be delayed. We can delay the ack if * - delayed acks are enabled and * - there is no delayed ack timer in progress and * - our last ack wasn't a 0-sized window. We never want to delay * the ack that opens up a 0-sized window. */ #define DELAY_ACK(tp) \ (tcp_delack_enabled && !tcp_callout_pending(tp, tp->tt_delack) && \ !(tp->t_flags & TF_RXWIN0SENT)) #define acceptable_window_update(tp, th, tiwin) \ (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)))) #define iceildiv(n, d) (((n)+(d)-1) / (d)) #define need_early_retransmit(tp, ownd) \ (tcp_do_early_retransmit && \ (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) && \ ownd < ((tp->t_rxtthresh + 1) * tp->t_maxseg) && \ tp->t_dupacks + 1 >= iceildiv(ownd, tp->t_maxseg) && \ (!TCP_DO_SACK(tp) || ownd <= tp->t_maxseg || \ tcp_sack_has_sacked(&tp->scb, ownd - tp->t_maxseg))) static int tcp_reass(struct tcpcb *tp, struct tcphdr *th, int *tlenp, struct mbuf *m) { struct tseg_qent *q; struct tseg_qent *p = NULL; struct tseg_qent *te; struct socket *so = tp->t_inpcb->inp_socket; int flags; /* * Call with th == NULL after become established to * force pre-ESTABLISHED data up to user socket. */ if (th == NULL) goto present; /* * Limit the number of segments in the reassembly queue to prevent * holding on to too many segments (and thus running out of mbufs). * Make sure to let the missing segment through which caused this * queue. Always keep one global queue entry spare to be able to * process the missing segment. */ if (th->th_seq != tp->rcv_nxt && tcp_reass_qsize + 1 >= tcp_reass_maxseg) { tcp_reass_overflows++; tcpstat.tcps_rcvmemdrop++; m_freem(m); /* no SACK block to report */ tp->reportblk.rblk_start = tp->reportblk.rblk_end; return (0); } /* Allocate a new queue entry. */ te = kmalloc(sizeof(struct tseg_qent), M_TSEGQ, M_INTWAIT | M_NULLOK); if (te == NULL) { tcpstat.tcps_rcvmemdrop++; m_freem(m); /* no SACK block to report */ tp->reportblk.rblk_start = tp->reportblk.rblk_end; return (0); } atomic_add_int(&tcp_reass_qsize, 1); /* * Find a segment which begins after this one does. */ LIST_FOREACH(q, &tp->t_segq, tqe_q) { if (SEQ_GT(q->tqe_th->th_seq, th->th_seq)) break; p = q; } /* * If there is a preceding segment, it may provide some of * our data already. If so, drop the data from the incoming * segment. If it provides all of our data, drop us. */ if (p != NULL) { tcp_seq_diff_t i; /* conversion to int (in i) handles seq wraparound */ i = p->tqe_th->th_seq + p->tqe_len - th->th_seq; if (i > 0) { /* overlaps preceding segment */ tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG); /* enclosing block starts w/ preceding segment */ tp->encloseblk.rblk_start = p->tqe_th->th_seq; if (i >= *tlenp) { /* preceding encloses incoming segment */ tp->encloseblk.rblk_end = TCP_SACK_BLKEND( p->tqe_th->th_seq + p->tqe_len, p->tqe_th->th_flags); tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += *tlenp; m_freem(m); kfree(te, M_TSEGQ); atomic_add_int(&tcp_reass_qsize, -1); /* * Try to present any queued data * at the left window edge to the user. * This is needed after the 3-WHS * completes. */ goto present; /* ??? */ } m_adj(m, i); *tlenp -= i; th->th_seq += i; /* incoming segment end is enclosing block end */ tp->encloseblk.rblk_end = TCP_SACK_BLKEND( th->th_seq + *tlenp, th->th_flags); /* trim end of reported D-SACK block */ tp->reportblk.rblk_end = th->th_seq; } } tcpstat.tcps_rcvoopack++; tcpstat.tcps_rcvoobyte += *tlenp; /* * While we overlap succeeding segments trim them or, * if they are completely covered, dequeue them. */ while (q) { tcp_seq_diff_t i = (th->th_seq + *tlenp) - q->tqe_th->th_seq; tcp_seq qend = q->tqe_th->th_seq + q->tqe_len; tcp_seq qend_sack = TCP_SACK_BLKEND(qend, q->tqe_th->th_flags); struct tseg_qent *nq; if (i <= 0) break; if (!(tp->sack_flags & TSACK_F_DUPSEG)) { /* first time through */ tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_ENCLOSESEG); tp->encloseblk = tp->reportblk; /* report trailing duplicate D-SACK segment */ tp->reportblk.rblk_start = q->tqe_th->th_seq; } if ((tp->sack_flags & TSACK_F_ENCLOSESEG) && SEQ_GT(qend_sack, tp->encloseblk.rblk_end)) { /* extend enclosing block if one exists */ tp->encloseblk.rblk_end = qend_sack; } if (i < q->tqe_len) { q->tqe_th->th_seq += i; q->tqe_len -= i; m_adj(q->tqe_m, i); break; } nq = LIST_NEXT(q, tqe_q); LIST_REMOVE(q, tqe_q); m_freem(q->tqe_m); kfree(q, M_TSEGQ); atomic_add_int(&tcp_reass_qsize, -1); q = nq; } /* Insert the new segment queue entry into place. */ te->tqe_m = m; te->tqe_th = th; te->tqe_len = *tlenp; /* check if can coalesce with following segment */ if (q != NULL && (th->th_seq + *tlenp == q->tqe_th->th_seq)) { tcp_seq tend = te->tqe_th->th_seq + te->tqe_len; tcp_seq tend_sack = TCP_SACK_BLKEND(tend, te->tqe_th->th_flags); te->tqe_len += q->tqe_len; if (q->tqe_th->th_flags & TH_FIN) te->tqe_th->th_flags |= TH_FIN; m_cat(te->tqe_m, q->tqe_m); tp->encloseblk.rblk_end = tend_sack; /* * When not reporting a duplicate segment, use * the larger enclosing block as the SACK block. */ if (!(tp->sack_flags & TSACK_F_DUPSEG)) tp->reportblk.rblk_end = tend_sack; LIST_REMOVE(q, tqe_q); kfree(q, M_TSEGQ); atomic_add_int(&tcp_reass_qsize, -1); } if (p == NULL) { LIST_INSERT_HEAD(&tp->t_segq, te, tqe_q); } else { /* check if can coalesce with preceding segment */ if (p->tqe_th->th_seq + p->tqe_len == th->th_seq) { p->tqe_len += te->tqe_len; m_cat(p->tqe_m, te->tqe_m); tp->encloseblk.rblk_start = p->tqe_th->th_seq; /* * When not reporting a duplicate segment, use * the larger enclosing block as the SACK block. */ if (!(tp->sack_flags & TSACK_F_DUPSEG)) tp->reportblk.rblk_start = p->tqe_th->th_seq; kfree(te, M_TSEGQ); atomic_add_int(&tcp_reass_qsize, -1); } else { LIST_INSERT_AFTER(p, te, tqe_q); } } present: /* * Present data to user, advancing rcv_nxt through * completed sequence space. */ if (!TCPS_HAVEESTABLISHED(tp->t_state)) return (0); q = LIST_FIRST(&tp->t_segq); if (q == NULL || q->tqe_th->th_seq != tp->rcv_nxt) return (0); tp->rcv_nxt += q->tqe_len; if (!(tp->sack_flags & TSACK_F_DUPSEG)) { /* no SACK block to report since ACK advanced */ tp->reportblk.rblk_start = tp->reportblk.rblk_end; } /* no enclosing block to report since ACK advanced */ tp->sack_flags &= ~TSACK_F_ENCLOSESEG; flags = q->tqe_th->th_flags & TH_FIN; LIST_REMOVE(q, tqe_q); KASSERT(LIST_EMPTY(&tp->t_segq) || LIST_FIRST(&tp->t_segq)->tqe_th->th_seq != tp->rcv_nxt, ("segment not coalesced")); if (so->so_state & SS_CANTRCVMORE) { m_freem(q->tqe_m); } else { lwkt_gettoken(&so->so_rcv.ssb_token); ssb_appendstream(&so->so_rcv, q->tqe_m); lwkt_reltoken(&so->so_rcv.ssb_token); } kfree(q, M_TSEGQ); atomic_add_int(&tcp_reass_qsize, -1); ND6_HINT(tp); sorwakeup(so); return (flags); } /* * TCP input routine, follows pages 65-76 of the * protocol specification dated September, 1981 very closely. */ #ifdef INET6 int tcp6_input(struct mbuf **mp, int *offp, int proto) { struct mbuf *m = *mp; struct in6_ifaddr *ia6; IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); /* * draft-itojun-ipv6-tcp-to-anycast * better place to put this in? */ ia6 = ip6_getdstifaddr(m); if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { struct ip6_hdr *ip6; ip6 = mtod(m, struct ip6_hdr *); icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, offsetof(struct ip6_hdr, ip6_dst)); return (IPPROTO_DONE); } tcp_input(mp, offp, proto); return (IPPROTO_DONE); } #endif int tcp_input(struct mbuf **mp, int *offp, int proto) { int off0; struct tcphdr *th; struct ip *ip = NULL; struct ipovly *ipov; struct inpcb *inp = NULL; u_char *optp = NULL; int optlen = 0; int tlen, off; int len = 0; int drop_hdrlen; struct tcpcb *tp = NULL; int thflags; struct socket *so = NULL; int todrop, acked; boolean_t ourfinisacked, needoutput = FALSE; u_long tiwin; int recvwin; struct tcpopt to; /* options in this segment */ struct sockaddr_in *next_hop = NULL; int rstreason; /* For badport_bandlim accounting purposes */ int cpu; struct ip6_hdr *ip6 = NULL; struct mbuf *m; #ifdef INET6 boolean_t isipv6; #else const boolean_t isipv6 = FALSE; #endif #ifdef TCPDEBUG short ostate = 0; #endif off0 = *offp; m = *mp; *mp = NULL; tcpstat.tcps_rcvtotal++; if (m->m_pkthdr.fw_flags & IPFORWARD_MBUF_TAGGED) { struct m_tag *mtag; mtag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); KKASSERT(mtag != NULL); next_hop = m_tag_data(mtag); } #ifdef INET6 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? TRUE : FALSE; #endif if (isipv6) { /* IP6_EXTHDR_CHECK() is already done at tcp6_input() */ ip6 = mtod(m, struct ip6_hdr *); tlen = (sizeof *ip6) + ntohs(ip6->ip6_plen) - off0; if (in6_cksum(m, IPPROTO_TCP, off0, tlen)) { tcpstat.tcps_rcvbadsum++; goto drop; } th = (struct tcphdr *)((caddr_t)ip6 + off0); /* * 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; } } else { /* * Get IP and TCP header together in first mbuf. * Note: IP leaves IP header in first mbuf. */ if (off0 > sizeof(struct ip)) { ip_stripoptions(m); off0 = sizeof(struct ip); } /* already checked and pulled up in ip_demux() */ KASSERT(m->m_len >= sizeof(struct tcpiphdr), ("TCP header not in one mbuf: m->m_len %d", m->m_len)); ip = mtod(m, struct ip *); ipov = (struct ipovly *)ip; th = (struct tcphdr *)((caddr_t)ip + off0); tlen = ip->ip_len; if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) th->th_sum = m->m_pkthdr.csum_data; else th->th_sum = in_pseudo(ip->ip_src.s_addr, ip->ip_dst.s_addr, htonl(m->m_pkthdr.csum_data + ip->ip_len + IPPROTO_TCP)); th->th_sum ^= 0xffff; } else { /* * Checksum extended TCP header and data. */ len = sizeof(struct ip) + tlen; bzero(ipov->ih_x1, sizeof ipov->ih_x1); ipov->ih_len = (u_short)tlen; ipov->ih_len = htons(ipov->ih_len); th->th_sum = in_cksum(m, len); } if (th->th_sum) { tcpstat.tcps_rcvbadsum++; goto drop; } #ifdef INET6 /* Re-initialization for later version check */ ip->ip_v = IPVERSION; #endif } /* * Check that TCP offset makes sense, * pull out TCP options and adjust length. XXX */ off = th->th_off << 2; /* already checked and pulled up in ip_demux() */ KASSERT(off >= sizeof(struct tcphdr) && off <= tlen, ("bad TCP data offset %d (tlen %d)", off, tlen)); tlen -= off; /* tlen is used instead of ti->ti_len */ if (off > sizeof(struct tcphdr)) { if (isipv6) { IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); ip6 = mtod(m, struct ip6_hdr *); th = (struct tcphdr *)((caddr_t)ip6 + off0); } else { /* already pulled up in ip_demux() */ KASSERT(m->m_len >= sizeof(struct ip) + off, ("TCP header and options not in one mbuf: " "m_len %d, off %d", m->m_len, off)); } optlen = off - sizeof(struct tcphdr); optp = (u_char *)(th + 1); } thflags = th->th_flags; #ifdef TCP_DROP_SYNFIN /* * If the drop_synfin option is enabled, drop all packets with * both the SYN and FIN bits set. This prevents e.g. nmap from * identifying the TCP/IP stack. * * This is a violation of the TCP specification. */ if (drop_synfin && (thflags & (TH_SYN | TH_FIN)) == (TH_SYN | TH_FIN)) goto drop; #endif /* * Convert TCP protocol specific fields to host format. */ th->th_seq = ntohl(th->th_seq); th->th_ack = ntohl(th->th_ack); th->th_win = ntohs(th->th_win); th->th_urp = ntohs(th->th_urp); /* * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options, * until after ip6_savecontrol() is called and before other functions * which don't want those proto headers. * Because ip6_savecontrol() is going to parse the mbuf to * search for data to be passed up to user-land, it wants mbuf * parameters to be unchanged. * XXX: the call of ip6_savecontrol() has been obsoleted based on * latest version of the advanced API (20020110). */ drop_hdrlen = off0 + off; /* * Locate pcb for segment. */ findpcb: /* IPFIREWALL_FORWARD section */ if (next_hop != NULL && !isipv6) { /* IPv6 support is not there yet */ /* * Transparently forwarded. Pretend to be the destination. * already got one like this? */ cpu = mycpu->gd_cpuid; inp = in_pcblookup_hash(&tcbinfo[cpu], ip->ip_src, th->th_sport, ip->ip_dst, th->th_dport, 0, m->m_pkthdr.rcvif); if (!inp) { /* * It's new. Try to find the ambushing socket. */ /* * The rest of the ipfw code stores the port in * host order. XXX * (The IP address is still in network order.) */ in_port_t dport = next_hop->sin_port ? htons(next_hop->sin_port) : th->th_dport; cpu = tcp_addrcpu(ip->ip_src.s_addr, th->th_sport, next_hop->sin_addr.s_addr, dport); inp = in_pcblookup_hash(&tcbinfo[cpu], ip->ip_src, th->th_sport, next_hop->sin_addr, dport, 1, m->m_pkthdr.rcvif); } } else { if (isipv6) { inp = in6_pcblookup_hash(&tcbinfo[0], &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 1, m->m_pkthdr.rcvif); } else { cpu = mycpu->gd_cpuid; inp = in_pcblookup_hash(&tcbinfo[cpu], ip->ip_src, th->th_sport, ip->ip_dst, th->th_dport, 1, m->m_pkthdr.rcvif); } } /* * If the state is CLOSED (i.e., TCB does not exist) then * all data in the incoming segment is discarded. * If the TCB exists but is in CLOSED state, it is embryonic, * but should either do a listen or a connect soon. */ if (inp == NULL) { if (log_in_vain) { #ifdef INET6 char dbuf[INET6_ADDRSTRLEN+2], sbuf[INET6_ADDRSTRLEN+2]; #else char dbuf[sizeof "aaa.bbb.ccc.ddd"]; char sbuf[sizeof "aaa.bbb.ccc.ddd"]; #endif if (isipv6) { strcpy(dbuf, "["); strcat(dbuf, ip6_sprintf(&ip6->ip6_dst)); strcat(dbuf, "]"); strcpy(sbuf, "["); strcat(sbuf, ip6_sprintf(&ip6->ip6_src)); strcat(sbuf, "]"); } else { strcpy(dbuf, inet_ntoa(ip->ip_dst)); strcpy(sbuf, inet_ntoa(ip->ip_src)); } switch (log_in_vain) { case 1: if (!(thflags & TH_SYN)) break; case 2: log(LOG_INFO, "Connection attempt to TCP %s:%d " "from %s:%d flags:0x%02x\n", dbuf, ntohs(th->th_dport), sbuf, ntohs(th->th_sport), thflags); break; default: break; } } if (blackhole) { switch (blackhole) { case 1: if (thflags & TH_SYN) goto drop; break; case 2: goto drop; default: goto drop; } } rstreason = BANDLIM_RST_CLOSEDPORT; goto dropwithreset; } #ifdef IPSEC if (isipv6) { if (ipsec6_in_reject_so(m, inp->inp_socket)) { ipsec6stat.in_polvio++; goto drop; } } else { if (ipsec4_in_reject_so(m, inp->inp_socket)) { ipsecstat.in_polvio++; goto drop; } } #endif #ifdef FAST_IPSEC if (isipv6) { if (ipsec6_in_reject(m, inp)) goto drop; } else { if (ipsec4_in_reject(m, inp)) goto drop; } #endif /* Check the minimum TTL for socket. */ #ifdef INET6 if ((isipv6 ? ip6->ip6_hlim : ip->ip_ttl) < inp->inp_ip_minttl) goto drop; #endif tp = intotcpcb(inp); if (tp == NULL) { rstreason = BANDLIM_RST_CLOSEDPORT; goto dropwithreset; } if (tp->t_state <= TCPS_CLOSED) goto drop; so = inp->inp_socket; #ifdef TCPDEBUG if (so->so_options & SO_DEBUG) { ostate = tp->t_state; if (isipv6) bcopy(ip6, tcp_saveipgen, sizeof(*ip6)); else bcopy(ip, tcp_saveipgen, sizeof(*ip)); tcp_savetcp = *th; } #endif bzero(&to, sizeof to); if (so->so_options & SO_ACCEPTCONN) { struct in_conninfo inc; #ifdef INET6 inc.inc_isipv6 = (isipv6 == TRUE); #endif if (isipv6) { inc.inc6_faddr = ip6->ip6_src; inc.inc6_laddr = ip6->ip6_dst; inc.inc6_route.ro_rt = NULL; /* XXX */ } else { inc.inc_faddr = ip->ip_src; inc.inc_laddr = ip->ip_dst; inc.inc_route.ro_rt = NULL; /* XXX */ } inc.inc_fport = th->th_sport; inc.inc_lport = th->th_dport; /* * If the state is LISTEN then ignore segment if it contains * a RST. If the segment contains an ACK then it is bad and * send a RST. If it does not contain a SYN then it is not * interesting; drop it. * * If the state is SYN_RECEIVED (syncache) and seg contains * an ACK, but not for our SYN/ACK, send a RST. If the seg * contains a RST, check the sequence number to see if it * is a valid reset segment. */ if ((thflags & (TH_RST | TH_ACK | TH_SYN)) != TH_SYN) { if ((thflags & (TH_RST | TH_ACK | TH_SYN)) == TH_ACK) { if (!syncache_expand(&inc, th, &so, m)) { /* * No syncache entry, or ACK was not * for our SYN/ACK. Send a RST. */ tcpstat.tcps_badsyn++; rstreason = BANDLIM_RST_OPENPORT; goto dropwithreset; } /* * Could not complete 3-way handshake, * connection is being closed down, and * syncache will free mbuf. */ if (so == NULL) return(IPPROTO_DONE); /* * We must be in the correct protocol thread * for this connection. */ KKASSERT(so->so_port == &curthread->td_msgport); /* * Socket is created in state SYN_RECEIVED. * Continue processing segment. */ inp = so->so_pcb; tp = intotcpcb(inp); /* * This is what would have happened in * tcp_output() when the SYN,ACK was sent. */ tp->snd_up = tp->snd_una; tp->snd_max = tp->snd_nxt = tp->iss + 1; tp->last_ack_sent = tp->rcv_nxt; goto after_listen; } if (thflags & TH_RST) { syncache_chkrst(&inc, th); goto drop; } if (thflags & TH_ACK) { syncache_badack(&inc); tcpstat.tcps_badsyn++; rstreason = BANDLIM_RST_OPENPORT; goto dropwithreset; } goto drop; } /* * Segment's flags are (SYN) or (SYN | FIN). */ #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 (isipv6 && !ip6_use_deprecated) { struct in6_ifaddr *ia6; if ((ia6 = ip6_getdstifaddr(m)) && (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { tp = NULL; rstreason = BANDLIM_RST_OPENPORT; goto dropwithreset; } } #endif /* * If it is from this socket, drop it, it must be forged. * Don't bother responding if the destination was a broadcast. */ if (th->th_dport == th->th_sport) { if (isipv6) { if (IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) goto drop; } else { if (ip->ip_dst.s_addr == ip->ip_src.s_addr) goto drop; } } /* * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN * * Note that it is quite possible to receive unicast * link-layer packets with a broadcast IP address. Use * in_broadcast() to find them. */ if (m->m_flags & (M_BCAST | M_MCAST)) goto drop; if (isipv6) { if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) goto drop; } else { if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) goto drop; } /* * SYN appears to be valid; create compressed TCP state * for syncache, or perform t/tcp connection. */ if (so->so_qlen <= so->so_qlimit) { tcp_dooptions(&to, optp, optlen, TRUE, th->th_ack); if (!syncache_add(&inc, &to, th, so, m)) goto drop; /* * Entry added to syncache, mbuf used to * send SYN,ACK packet. */ return(IPPROTO_DONE); } goto drop; } after_listen: /* * Should not happen - syncache should pick up these connections. * * Once we are past handling listen sockets we must be in the * correct protocol processing thread. */ KASSERT(tp->t_state != TCPS_LISTEN, ("tcp_input: TCPS_LISTEN state")); KKASSERT(so->so_port == &curthread->td_msgport); /* Unscale the window into a 32-bit value. */ if (!(thflags & TH_SYN)) tiwin = th->th_win << tp->snd_scale; else tiwin = th->th_win; /* * This is the second part of the MSS DoS prevention code (after * minmss on the sending side) and it deals with too many too small * tcp packets in a too short timeframe (1 second). * * XXX Removed. This code was crap. It does not scale to network * speed, and default values break NFS. Gone. */ /* REMOVED */ /* * Segment received on connection. * * Reset idle time and keep-alive timer. Don't waste time if less * then a second has elapsed. */ if ((int)(ticks - tp->t_rcvtime) > hz) tcp_timer_keep_activity(tp, thflags); /* * Process options. * XXX this is tradtitional behavior, may need to be cleaned up. */ tcp_dooptions(&to, optp, optlen, (thflags & TH_SYN) != 0, th->th_ack); if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { if ((to.to_flags & TOF_SCALE) && (tp->t_flags & TF_REQ_SCALE)) { tp->t_flags |= TF_RCVD_SCALE; tp->snd_scale = to.to_requested_s_scale; } /* * Initial send window; will be updated upon next ACK */ tp->snd_wnd = th->th_win; if (to.to_flags & TOF_TS) { tp->t_flags |= TF_RCVD_TSTMP; tp->ts_recent = to.to_tsval; tp->ts_recent_age = ticks; } if (!(to.to_flags & TOF_MSS)) to.to_mss = 0; tcp_mss(tp, to.to_mss); /* * Only set the TF_SACK_PERMITTED per-connection flag * if we got a SACK_PERMITTED option from the other side * and the global tcp_do_sack variable is true. */ if (tcp_do_sack && (to.to_flags & TOF_SACK_PERMITTED)) tp->t_flags |= TF_SACK_PERMITTED; } /* * Header prediction: check for the two common cases * of a uni-directional data xfer. If the packet has * no control flags, is in-sequence, the window didn't * change and we're not retransmitting, it's a * candidate. If the length is zero and the ack moved * forward, we're the sender side of the xfer. Just * free the data acked & wake any higher level process * that was blocked waiting for space. If the length * is non-zero and the ack didn't move, we're the * receiver side. If we're getting packets in-order * (the reassembly queue is empty), add the data to * the socket buffer and note that we need a delayed ack. * Make sure that the hidden state-flags are also off. * Since we check for TCPS_ESTABLISHED above, it can only * be TH_NEEDSYN. */ if (tp->t_state == TCPS_ESTABLISHED && (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && !(tp->t_flags & (TF_NEEDSYN | TF_NEEDFIN)) && (!(to.to_flags & TOF_TS) || TSTMP_GEQ(to.to_tsval, tp->ts_recent)) && th->th_seq == tp->rcv_nxt && tp->snd_nxt == tp->snd_max) { /* * If last ACK falls within this segment's sequence numbers, * record the timestamp. * NOTE that the test is modified according to the latest * proposal of the tcplw@cray.com list (Braden 1993/04/26). */ if ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { tp->ts_recent_age = ticks; tp->ts_recent = to.to_tsval; } if (tlen == 0) { if (SEQ_GT(th->th_ack, tp->snd_una) && SEQ_LEQ(th->th_ack, tp->snd_max) && tp->snd_cwnd >= tp->snd_wnd && !IN_FASTRECOVERY(tp)) { /* * This is a pure ack for outstanding data. */ ++tcpstat.tcps_predack; /* * "bad retransmit" recovery * * If Eifel detection applies, then * it is deterministic, so use it * unconditionally over the old heuristic. * Otherwise, fall back to the old heuristic. */ if (tcp_do_eifel_detect && (to.to_flags & TOF_TS) && to.to_tsecr && (tp->rxt_flags & TRXT_F_FIRSTACCACK)) { /* Eifel detection applicable. */ if (to.to_tsecr < tp->t_rexmtTS) { tcp_revert_congestion_state(tp); ++tcpstat.tcps_eifeldetected; if (tp->t_rxtshift != 1 || ticks >= tp->t_badrxtwin) ++tcpstat.tcps_rttcantdetect; } } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { tcp_revert_congestion_state(tp); ++tcpstat.tcps_rttdetected; } tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK | TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT); /* * Recalculate the retransmit timer / rtt. * * Some machines (certain windows boxes) * send broken timestamp replies during the * SYN+ACK phase, ignore timestamps of 0. */ if ((to.to_flags & TOF_TS) && to.to_tsecr) { tcp_xmit_timer(tp, ticks - to.to_tsecr + 1, th->th_ack); } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { tcp_xmit_timer(tp, ticks - tp->t_rtttime, th->th_ack); } tcp_xmit_bandwidth_limit(tp, th->th_ack); acked = th->th_ack - tp->snd_una; tcpstat.tcps_rcvackpack++; tcpstat.tcps_rcvackbyte += acked; sbdrop(&so->so_snd.sb, acked); tp->snd_recover = th->th_ack - 1; tp->snd_una = th->th_ack; tp->t_dupacks = 0; /* * Update window information. */ if (tiwin != tp->snd_wnd && acceptable_window_update(tp, th, tiwin)) { /* keep track of pure window updates */ if (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) tcpstat.tcps_rcvwinupd++; tp->snd_wnd = tiwin; tp->snd_wl1 = th->th_seq; tp->snd_wl2 = th->th_ack; if (tp->snd_wnd > tp->max_sndwnd) tp->max_sndwnd = tp->snd_wnd; } m_freem(m); ND6_HINT(tp); /* some progress has been done */ /* * If all outstanding data are acked, stop * retransmit timer, otherwise restart timer * using current (possibly backed-off) value. * If process is waiting for space, * wakeup/selwakeup/signal. If data * are ready to send, let tcp_output * decide between more output or persist. */ if (tp->snd_una == tp->snd_max) { tcp_callout_stop(tp, tp->tt_rexmt); } else if (!tcp_callout_active(tp, tp->tt_persist)) { tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, tcp_timer_rexmt); } sowwakeup(so); if (so->so_snd.ssb_cc > 0) tcp_output(tp); return(IPPROTO_DONE); } } else if (tiwin == tp->snd_wnd && th->th_ack == tp->snd_una && LIST_EMPTY(&tp->t_segq) && tlen <= ssb_space(&so->so_rcv)) { u_long newsize = 0; /* automatic sockbuf scaling */ /* * This is a pure, in-sequence data packet * with nothing on the reassembly queue and * we have enough buffer space to take it. */ ++tcpstat.tcps_preddat; tp->rcv_nxt += tlen; tcpstat.tcps_rcvpack++; tcpstat.tcps_rcvbyte += tlen; ND6_HINT(tp); /* some progress has been done */ /* * Automatic sizing of receive socket buffer. Often the send * buffer size is not optimally adjusted to the actual network * conditions at hand (delay bandwidth product). Setting the * buffer size too small limits throughput on links with high * bandwidth and high delay (eg. trans-continental/oceanic links). * * 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 && to.to_tsecr && (so->so_rcv.ssb_flags & SSB_AUTOSIZE)) { if (to.to_tsecr > tp->rfbuf_ts && to.to_tsecr - tp->rfbuf_ts < hz) { if (tp->rfbuf_cnt > (so->so_rcv.ssb_hiwat / 8 * 7) && so->so_rcv.ssb_hiwat < tcp_autorcvbuf_max) { newsize = ulmin(so->so_rcv.ssb_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 */ } /* * 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. * * Adjusting the size can mess up ACK * sequencing when pure window updates are * being avoided (which is the default), * so force an ack. */ lwkt_gettoken(&so->so_rcv.ssb_token); if (newsize) { tp->t_flags |= TF_RXRESIZED; if (!ssb_reserve(&so->so_rcv, newsize, so, NULL)) { atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); } if (newsize >= (TCP_MAXWIN << tp->rcv_scale)) { atomic_clear_int(&so->so_rcv.ssb_flags, SSB_AUTOSIZE); } } m_adj(m, drop_hdrlen); /* delayed header drop */ ssb_appendstream(&so->so_rcv, m); lwkt_reltoken(&so->so_rcv.ssb_token); } sorwakeup(so); /* * This code is responsible for most of the ACKs * the TCP stack sends back after receiving a data * packet. Note that the DELAY_ACK check fails if * the delack timer is already running, which results * in an ack being sent every other packet (which is * what we want). * * We then further aggregate acks by not actually * sending one until the protocol thread has completed * processing the current backlog of packets. This * does not delay the ack any further, but allows us * to take advantage of the packet aggregation that * high speed NICs do (usually blocks of 8-10 packets) * to send a single ack rather then four or five acks, * greatly reducing the ack rate, the return channel * bandwidth, and the protocol overhead on both ends. * * Since this also has the effect of slowing down * the exponential slow-start ramp-up, systems with * very large bandwidth-delay products might want * to turn the feature off. */ if (DELAY_ACK(tp)) { tcp_callout_reset(tp, tp->tt_delack, tcp_delacktime, tcp_timer_delack); } else if (tcp_aggregate_acks) { tp->t_flags |= TF_ACKNOW; if (!(tp->t_flags & TF_ONOUTPUTQ)) { tp->t_flags |= TF_ONOUTPUTQ; tp->tt_cpu = mycpu->gd_cpuid; TAILQ_INSERT_TAIL( &tcpcbackq[tp->tt_cpu], tp, t_outputq); } } else { tp->t_flags |= TF_ACKNOW; tcp_output(tp); } return(IPPROTO_DONE); } } /* * Calculate amount of space in receive window, * and then do TCP input processing. * Receive window is amount of space in rcv queue, * but not less than advertised window. */ recvwin = ssb_space(&so->so_rcv); if (recvwin < 0) recvwin = 0; tp->rcv_wnd = imax(recvwin, (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_RECEIVED: * if seg contains an ACK, but not for our SYN/ACK, send a RST. */ case TCPS_SYN_RECEIVED: if ((thflags & TH_ACK) && (SEQ_LEQ(th->th_ack, tp->snd_una) || SEQ_GT(th->th_ack, tp->snd_max))) { rstreason = BANDLIM_RST_OPENPORT; goto dropwithreset; } break; /* * If the state is SYN_SENT: * if seg contains an ACK, but not for our SYN, drop the input. * if seg contains a RST, then drop the connection. * if seg does not contain SYN, then drop it. * Otherwise this is an acceptable SYN segment * initialize tp->rcv_nxt and tp->irs * if seg contains ack then advance tp->snd_una * if SYN has been acked change to ESTABLISHED else SYN_RCVD state * arrange for segment to be acked (eventually) * continue processing rest of data/controls, beginning with URG */ case TCPS_SYN_SENT: if ((thflags & TH_ACK) && (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) { rstreason = BANDLIM_UNLIMITED; goto dropwithreset; } if (thflags & TH_RST) { if (thflags & TH_ACK) tp = tcp_drop(tp, ECONNREFUSED); goto drop; } if (!(thflags & TH_SYN)) goto drop; tp->irs = th->th_seq; tcp_rcvseqinit(tp); if (thflags & TH_ACK) { /* Our SYN was acked. */ tcpstat.tcps_connects++; soisconnected(so); /* Do window scaling on this connection? */ if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == (TF_RCVD_SCALE | TF_REQ_SCALE)) tp->rcv_scale = tp->request_r_scale; tp->rcv_adv += tp->rcv_wnd; tp->snd_una++; /* SYN is acked */ tcp_callout_stop(tp, tp->tt_rexmt); /* * If there's data, delay ACK; if there's also a FIN * ACKNOW will be turned on later. */ if (DELAY_ACK(tp) && tlen != 0) { tcp_callout_reset(tp, tp->tt_delack, tcp_delacktime, tcp_timer_delack); } else { tp->t_flags |= TF_ACKNOW; } /* * Received in SYN_SENT[*] state. * Transitions: * SYN_SENT --> ESTABLISHED * SYN_SENT* --> FIN_WAIT_1 */ tp->t_starttime = ticks; if (tp->t_flags & TF_NEEDFIN) { tp->t_state = TCPS_FIN_WAIT_1; tp->t_flags &= ~TF_NEEDFIN; thflags &= ~TH_SYN; } else { tcp_established(tp); } } else { /* * Received initial SYN in SYN-SENT[*] state => * simultaneous open. * Do 3-way handshake: * SYN-SENT -> SYN-RECEIVED * SYN-SENT* -> SYN-RECEIVED* */ tp->t_flags |= TF_ACKNOW; tcp_callout_stop(tp, tp->tt_rexmt); 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; thflags &= ~TH_FIN; tcpstat.tcps_rcvpackafterwin++; tcpstat.tcps_rcvbyteafterwin += todrop; } tp->snd_wl1 = th->th_seq - 1; tp->rcv_up = th->th_seq; /* * Client side of transaction: already sent SYN and data. * If the remote host used T/TCP to validate the SYN, * our data will be ACK'd; if so, enter normal data segment * processing in the middle of step 5, ack processing. * Otherwise, goto step 6. */ if (thflags & TH_ACK) goto process_ACK; goto step6; /* * If the state is LAST_ACK or CLOSING or TIME_WAIT: * do normal processing (we no longer bother with T/TCP). */ case TCPS_LAST_ACK: case TCPS_CLOSING: case TCPS_TIME_WAIT: break; /* continue normal processing */ } /* * States other than LISTEN or SYN_SENT. * First check the RST flag and sequence number since reset segments * are exempt from the timestamp and connection count tests. This * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix * below which allowed reset segments in half the sequence space * to fall though and be processed (which gives forged reset * segments with a random sequence number a 50 percent chance of * killing a connection). * Then check timestamp, if present. * Then check the connection count, if present. * Then check that at least some bytes of segment are within * receive window. If segment begins before rcv_nxt, * drop leading data (and SYN); if nothing left, just ack. * * * If the RST bit is set, check the sequence number to see * if this is a valid reset segment. * RFC 793 page 37: * In all states except SYN-SENT, all reset (RST) segments * are validated by checking their SEQ-fields. A reset is * valid if its sequence number is in the window. * Note: this does not take into account delayed ACKs, so * we should test against last_ack_sent instead of rcv_nxt. * The sequence number in the reset segment is normally an * echo of our outgoing acknowledgement numbers, but some hosts * send a reset with the sequence number at the rightmost edge * of our receive window, and we have to handle this case. * If we have multiple segments in flight, the intial reset * segment sequence numbers will be to the left of last_ack_sent, * but they will eventually catch up. * In any case, it never made sense to trim reset segments to * fit the receive window since RFC 1122 says: * 4.2.2.12 RST Segment: RFC-793 Section 3.4 * * A TCP SHOULD allow a received RST segment to include data. * * DISCUSSION * It has been suggested that a RST segment could contain * ASCII text that encoded and explained the cause of the * RST. No standard has yet been established for such * data. * * If the reset segment passes the sequence number test examine * the state: * SYN_RECEIVED STATE: * If passive open, return to LISTEN state. * If active open, inform user that connection was refused. * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: * Inform user that connection was reset, and close tcb. * CLOSING, LAST_ACK STATES: * Close the tcb. * TIME_WAIT STATE: * Drop the segment - see Stevens, vol. 2, p. 964 and * RFC 1337. */ if (thflags & TH_RST) { if (SEQ_GEQ(th->th_seq, tp->last_ack_sent) && SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { switch (tp->t_state) { case TCPS_SYN_RECEIVED: so->so_error = ECONNREFUSED; goto close; case TCPS_ESTABLISHED: case TCPS_FIN_WAIT_1: case TCPS_FIN_WAIT_2: case TCPS_CLOSE_WAIT: so->so_error = ECONNRESET; close: tp->t_state = TCPS_CLOSED; tcpstat.tcps_drops++; tp = tcp_close(tp); break; case TCPS_CLOSING: case TCPS_LAST_ACK: tp = tcp_close(tp); break; case TCPS_TIME_WAIT: break; } } goto drop; } /* * RFC 1323 PAWS: If we have a timestamp reply on this segment * and it's less than ts_recent, drop it. */ if ((to.to_flags & TOF_TS) && tp->ts_recent != 0 && TSTMP_LT(to.to_tsval, tp->ts_recent)) { /* Check to see if ts_recent is over 24 days old. */ if ((int)(ticks - tp->ts_recent_age) > TCP_PAWS_IDLE) { /* * Invalidate ts_recent. If this segment updates * ts_recent, the age will be reset later and ts_recent * will get a valid value. If it does not, setting * ts_recent to zero will at least satisfy the * requirement that zero be placed in the timestamp * echo reply when ts_recent isn't valid. The * age isn't reset until we get a valid ts_recent * because we don't want out-of-order segments to be * dropped when ts_recent is old. */ tp->ts_recent = 0; } else { tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += tlen; tcpstat.tcps_pawsdrop++; if (tlen) goto dropafterack; goto drop; } } /* * In the SYN-RECEIVED state, validate that the packet belongs to * this connection before trimming the data to fit the receive * window. Check the sequence number versus IRS since we know * the sequence numbers haven't wrapped. This is a partial fix * for the "LAND" DoS attack. */ if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { rstreason = BANDLIM_RST_OPENPORT; goto dropwithreset; } todrop = tp->rcv_nxt - th->th_seq; if (todrop > 0) { if (TCP_DO_SACK(tp)) { /* Report duplicate segment at head of packet. */ tp->reportblk.rblk_start = th->th_seq; tp->reportblk.rblk_end = TCP_SACK_BLKEND( th->th_seq + tlen, thflags); if (SEQ_GT(tp->reportblk.rblk_end, tp->rcv_nxt)) tp->reportblk.rblk_end = tp->rcv_nxt; tp->sack_flags |= (TSACK_F_DUPSEG | TSACK_F_SACKLEFT); tp->t_flags |= TF_ACKNOW; } if (thflags & TH_SYN) { thflags &= ~TH_SYN; th->th_seq++; if (th->th_urp > 1) th->th_urp--; else thflags &= ~TH_URG; todrop--; } /* * Following if statement from Stevens, vol. 2, p. 960. */ if (todrop > tlen || (todrop == tlen && !(thflags & TH_FIN))) { /* * Any valid FIN must be to the left of the window. * At this point the FIN must be a duplicate or out * of sequence; drop it. */ thflags &= ~TH_FIN; /* * Send an ACK to resynchronize and drop any data. * But keep on processing for RST or ACK. */ tp->t_flags |= TF_ACKNOW; todrop = tlen; tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += todrop; } else { tcpstat.tcps_rcvpartduppack++; tcpstat.tcps_rcvpartdupbyte += todrop; } drop_hdrlen += todrop; /* drop from the top afterwards */ th->th_seq += todrop; tlen -= todrop; if (th->th_urp > todrop) th->th_urp -= todrop; else { thflags &= ~TH_URG; th->th_urp = 0; } } /* * If new data are received on a connection after the * user processes are gone, then RST the other end. */ if ((so->so_state & SS_NOFDREF) && tp->t_state > TCPS_CLOSE_WAIT && tlen) { tp = tcp_close(tp); tcpstat.tcps_rcvafterclose++; rstreason = BANDLIM_UNLIMITED; goto dropwithreset; } /* * If segment ends after window, drop trailing data * (and PUSH and FIN); if nothing left, just ACK. */ todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); if (todrop > 0) { tcpstat.tcps_rcvpackafterwin++; if (todrop >= tlen) { tcpstat.tcps_rcvbyteafterwin += tlen; /* * If a new connection request is received * while in TIME_WAIT, drop the old connection * and start over if the sequence numbers * are above the previous ones. */ if (thflags & TH_SYN && tp->t_state == TCPS_TIME_WAIT && SEQ_GT(th->th_seq, tp->rcv_nxt)) { tp = tcp_close(tp); goto findpcb; } /* * If window is closed can only take segments at * window edge, and have to drop data and PUSH from * incoming segments. Continue processing, but * remember to ack. Otherwise, drop segment * and ack. */ if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { tp->t_flags |= TF_ACKNOW; tcpstat.tcps_rcvwinprobe++; } else goto dropafterack; } else tcpstat.tcps_rcvbyteafterwin += todrop; m_adj(m, -todrop); tlen -= todrop; thflags &= ~(TH_PUSH | TH_FIN); } /* * If last ACK falls within this segment's sequence numbers, * record its timestamp. * NOTE: * 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 ((to.to_flags & TOF_TS) && SEQ_LEQ(th->th_seq, tp->last_ack_sent) && SEQ_LEQ(tp->last_ack_sent, (th->th_seq + tlen + ((thflags & TH_SYN) != 0) + ((thflags & TH_FIN) != 0)))) { tp->ts_recent_age = ticks; tp->ts_recent = to.to_tsval; } /* * If a SYN is in the window, then this is an * error and we send an RST and drop the connection. */ if (thflags & TH_SYN) { tp = tcp_drop(tp, ECONNRESET); rstreason = BANDLIM_UNLIMITED; goto dropwithreset; } /* * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN * flag is on (half-synchronized state), then queue data for * later processing; else drop segment and return. */ if (!(thflags & TH_ACK)) { if (tp->t_state == TCPS_SYN_RECEIVED || (tp->t_flags & TF_NEEDSYN)) goto step6; else goto drop; } /* * Ack processing. */ switch (tp->t_state) { /* * In SYN_RECEIVED state, the ACK acknowledges our SYN, so enter * ESTABLISHED state and continue processing. * The ACK was checked above. */ case TCPS_SYN_RECEIVED: tcpstat.tcps_connects++; soisconnected(so); /* Do window scaling? */ if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == (TF_RCVD_SCALE | TF_REQ_SCALE)) tp->rcv_scale = tp->request_r_scale; /* * Make transitions: * SYN-RECEIVED -> ESTABLISHED * SYN-RECEIVED* -> FIN-WAIT-1 */ tp->t_starttime = ticks; if (tp->t_flags & TF_NEEDFIN) { tp->t_state = TCPS_FIN_WAIT_1; tp->t_flags &= ~TF_NEEDFIN; } else { tcp_established(tp); } /* * If segment contains data or ACK, will call tcp_reass() * later; if not, do so now to pass queued data to user. */ if (tlen == 0 && !(thflags & TH_FIN)) tcp_reass(tp, NULL, NULL, NULL); /* fall into ... */ /* * In ESTABLISHED state: drop duplicate ACKs; ACK out of range * ACKs. If the ack is in the range * tp->snd_una < th->th_ack <= tp->snd_max * then advance tp->snd_una to th->th_ack and drop * data from the retransmission queue. If this ACK reflects * more up to date window information we update our window information. */ case TCPS_ESTABLISHED: case TCPS_FIN_WAIT_1: case TCPS_FIN_WAIT_2: case TCPS_CLOSE_WAIT: case TCPS_CLOSING: case TCPS_LAST_ACK: case TCPS_TIME_WAIT: if (SEQ_LEQ(th->th_ack, tp->snd_una)) { if (TCP_DO_SACK(tp)) tcp_sack_update_scoreboard(tp, &to); if (!tcp_callout_active(tp, tp->tt_rexmt) || th->th_ack != tp->snd_una) { if (tlen == 0 && tiwin == tp->snd_wnd) tcpstat.tcps_rcvdupack++; tp->t_dupacks = 0; break; } if (tlen != 0 || tiwin != tp->snd_wnd) { if (!tcp_do_rfc3517bis || !TCP_DO_SACK(tp) || (to.to_flags & (TOF_SACK | TOF_SACK_REDUNDANT)) != TOF_SACK) { tp->t_dupacks = 0; break; } /* * Update window information. */ if (tiwin != tp->snd_wnd && acceptable_window_update(tp, th, tiwin)) { /* keep track of pure window updates */ if (tlen == 0 && tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) tcpstat.tcps_rcvwinupd++; tp->snd_wnd = tiwin; tp->snd_wl1 = th->th_seq; tp->snd_wl2 = th->th_ack; if (tp->snd_wnd > tp->max_sndwnd) tp->max_sndwnd = tp->snd_wnd; } } tcpstat.tcps_rcvdupack++; /* * 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, so assume a packet * has been dropped and retransmit it. * Kludge snd_nxt & the congestion * window so we send only this one * packet. */ if (IN_FASTRECOVERY(tp)) { if (TCP_DO_SACK(tp)) { /* No artifical cwnd inflation. */ tcp_sack_rexmt(tp, th); } else { /* * Dup acks mean that packets * have left the network * (they're now cached at the * receiver) so bump cwnd by * the amount in the receiver * to keep a constant cwnd * packets in the network. */ tp->snd_cwnd += tp->t_maxseg; tcp_output(tp); } } else if (SEQ_LT(th->th_ack, tp->snd_recover)) { tp->t_dupacks = 0; break; } else if (tcp_ignore_redun_dsack && TCP_DO_SACK(tp) && (to.to_flags & (TOF_DSACK | TOF_SACK_REDUNDANT)) == (TOF_DSACK | TOF_SACK_REDUNDANT)) { /* * If the ACK carries DSACK and other * SACK blocks carry information that * we have already known, don't count * this ACK as duplicate ACK. This * prevents spurious early retransmit * and fast retransmit. This also * meets the requirement of RFC3042 * that new segments should not be sent * if the SACK blocks do not contain * new information (XXX we actually * loosen the requirment that only DSACK * is checked here). * * This kind of ACKs are usually sent * after spurious retransmit. */ /* Do nothing; don't change t_dupacks */ } else if (++tp->t_dupacks == tp->t_rxtthresh) { tcp_seq old_snd_nxt; u_int win; fastretransmit: if (tcp_do_eifel_detect && (tp->t_flags & TF_RCVD_TSTMP)) { tcp_save_congestion_state(tp); tp->rxt_flags |= TRXT_F_FASTREXMT; } /* * We know we're losing at the current * window size, so do congestion avoidance: * set ssthresh to half the current window * and pull our congestion window back to the * new ssthresh. */ win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; if (win < 2) win = 2; tp->snd_ssthresh = win * tp->t_maxseg; ENTER_FASTRECOVERY(tp); tp->snd_recover = tp->snd_max; tcp_callout_stop(tp, tp->tt_rexmt); tp->t_rtttime = 0; old_snd_nxt = tp->snd_nxt; tp->snd_nxt = th->th_ack; tp->snd_cwnd = tp->t_maxseg; tcp_output(tp); ++tcpstat.tcps_sndfastrexmit; tp->snd_cwnd = tp->snd_ssthresh; tp->rexmt_high = tp->snd_nxt; tp->sack_flags &= ~TSACK_F_SACKRESCUED; if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) tp->snd_nxt = old_snd_nxt; KASSERT(tp->snd_limited <= 2, ("tp->snd_limited too big")); if (TCP_DO_SACK(tp)) tcp_sack_rexmt(tp, th); else tp->snd_cwnd += tp->t_maxseg * (tp->t_dupacks - tp->snd_limited); } else if (tcp_do_rfc3517bis && TCP_DO_SACK(tp)) { if (tcp_rfc3517bis_rxt && tcp_sack_islost(&tp->scb, tp->snd_una)) goto fastretransmit; if (tcp_do_limitedtransmit) { /* outstanding data */ uint32_t ownd = tp->snd_max - tp->snd_una; if (!tcp_sack_limitedxmit(tp) && need_early_retransmit(tp, ownd)) { ++tcpstat.tcps_sndearlyrexmit; tp->rxt_flags |= TRXT_F_EARLYREXMT; goto fastretransmit; } } } else if (tcp_do_limitedtransmit) { u_long oldcwnd = tp->snd_cwnd; tcp_seq oldsndmax = tp->snd_max; tcp_seq oldsndnxt = tp->snd_nxt; /* outstanding data */ uint32_t ownd = tp->snd_max - tp->snd_una; u_int sent; KASSERT(tp->t_dupacks == 1 || tp->t_dupacks == 2, ("dupacks not 1 or 2")); if (tp->t_dupacks == 1) tp->snd_limited = 0; tp->snd_nxt = tp->snd_max; tp->snd_cwnd = ownd + (tp->t_dupacks - tp->snd_limited) * tp->t_maxseg; tcp_output(tp); if (SEQ_LT(oldsndnxt, oldsndmax)) { KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), ("snd_una moved in other threads")); tp->snd_nxt = oldsndnxt; } tp->snd_cwnd = oldcwnd; sent = tp->snd_max - oldsndmax; if (sent > tp->t_maxseg) { KASSERT((tp->t_dupacks == 2 && tp->snd_limited == 0) || (sent == tp->t_maxseg + 1 && tp->t_flags & TF_SENTFIN), ("sent too much")); KASSERT(sent <= tp->t_maxseg * 2, ("sent too many segments")); tp->snd_limited = 2; tcpstat.tcps_sndlimited += 2; } else if (sent > 0) { ++tp->snd_limited; ++tcpstat.tcps_sndlimited; } else if (need_early_retransmit(tp, ownd)) { ++tcpstat.tcps_sndearlyrexmit; tp->rxt_flags |= TRXT_F_EARLYREXMT; goto fastretransmit; } } if (tlen != 0) break; else goto drop; } KASSERT(SEQ_GT(th->th_ack, tp->snd_una), ("th_ack <= snd_una")); tp->t_dupacks = 0; if (SEQ_GT(th->th_ack, tp->snd_max)) { /* * Detected optimistic ACK attack. * Force slow-start to de-synchronize attack. */ tp->snd_cwnd = tp->t_maxseg; tp->snd_wacked = 0; tcpstat.tcps_rcvacktoomuch++; goto dropafterack; } /* * If we reach this point, ACK is not a duplicate, * i.e., it ACKs something we sent. */ if (tp->t_flags & TF_NEEDSYN) { /* * T/TCP: Connection was half-synchronized, and our * SYN has been ACK'd (so connection is now fully * synchronized). Go to non-starred state, * increment snd_una for ACK of SYN, and check if * we can do window scaling. */ tp->t_flags &= ~TF_NEEDSYN; tp->snd_una++; /* Do window scaling? */ if ((tp->t_flags & (TF_RCVD_SCALE | TF_REQ_SCALE)) == (TF_RCVD_SCALE | TF_REQ_SCALE)) tp->rcv_scale = tp->request_r_scale; } process_ACK: acked = th->th_ack - tp->snd_una; tcpstat.tcps_rcvackpack++; tcpstat.tcps_rcvackbyte += acked; if (tcp_do_eifel_detect && acked > 0 && (to.to_flags & TOF_TS) && (to.to_tsecr != 0) && (tp->rxt_flags & TRXT_F_FIRSTACCACK)) { /* Eifel detection applicable. */ if (to.to_tsecr < tp->t_rexmtTS) { ++tcpstat.tcps_eifeldetected; tcp_revert_congestion_state(tp); if (tp->t_rxtshift != 1 || ticks >= tp->t_badrxtwin) ++tcpstat.tcps_rttcantdetect; } } else if (tp->t_rxtshift == 1 && ticks < tp->t_badrxtwin) { /* * If we just performed our first retransmit, * and the ACK arrives within our recovery window, * then it was a mistake to do the retransmit * in the first place. Recover our original cwnd * and ssthresh, and proceed to transmit where we * left off. */ tcp_revert_congestion_state(tp); ++tcpstat.tcps_rttdetected; } /* * 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. * * Some machines (certain windows boxes) send broken * timestamp replies during the SYN+ACK phase, ignore * timestamps of 0. */ if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) tcp_xmit_timer(tp, ticks - to.to_tsecr + 1, th->th_ack); else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) tcp_xmit_timer(tp, ticks - tp->t_rtttime, th->th_ack); tcp_xmit_bandwidth_limit(tp, th->th_ack); /* * If no data (only SYN) was ACK'd, * skip rest of ACK processing. */ if (acked == 0) goto step6; /* Stop looking for an acceptable ACK since one was received. */ tp->rxt_flags &= ~(TRXT_F_FIRSTACCACK | TRXT_F_FASTREXMT | TRXT_F_EARLYREXMT); if (acked > so->so_snd.ssb_cc) { tp->snd_wnd -= so->so_snd.ssb_cc; sbdrop(&so->so_snd.sb, (int)so->so_snd.ssb_cc); ourfinisacked = TRUE; } else { sbdrop(&so->so_snd.sb, acked); tp->snd_wnd -= acked; ourfinisacked = FALSE; } sowwakeup(so); /* * Update window information. */ if (acceptable_window_update(tp, th, tiwin)) { /* keep track of pure window updates */ if (tlen == 0 && tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) tcpstat.tcps_rcvwinupd++; tp->snd_wnd = tiwin; tp->snd_wl1 = th->th_seq; tp->snd_wl2 = th->th_ack; if (tp->snd_wnd > tp->max_sndwnd) tp->max_sndwnd = tp->snd_wnd; needoutput = TRUE; } tp->snd_una = th->th_ack; if (TCP_DO_SACK(tp)) tcp_sack_update_scoreboard(tp, &to); if (IN_FASTRECOVERY(tp)) { if (SEQ_GEQ(th->th_ack, tp->snd_recover)) { EXIT_FASTRECOVERY(tp); needoutput = TRUE; /* * If the congestion window was inflated * to account for the other side's * cached packets, retract it. */ if (!TCP_DO_SACK(tp)) tp->snd_cwnd = tp->snd_ssthresh; /* * Window inflation should have left us * with approximately snd_ssthresh outstanding * data. But, in case we would be inclined * to send a burst, better do it using * slow start. */ if (SEQ_GT(th->th_ack + tp->snd_cwnd, tp->snd_max + 2 * tp->t_maxseg)) tp->snd_cwnd = (tp->snd_max - tp->snd_una) + 2 * tp->t_maxseg; tp->snd_wacked = 0; } else { if (TCP_DO_SACK(tp)) { tp->snd_max_rexmt = tp->snd_max; tcp_sack_rexmt(tp, th); } else { tcp_newreno_partial_ack(tp, th, acked); } needoutput = FALSE; } } else { /* * Open the congestion window. When in slow-start, * open exponentially: maxseg per packet. Otherwise, * open linearly: maxseg per window. */ if (tp->snd_cwnd <= tp->snd_ssthresh) { u_int abc_sslimit = (SEQ_LT(tp->snd_nxt, tp->snd_max) ? tp->t_maxseg : 2 * tp->t_maxseg); /* slow-start */ tp->snd_cwnd += tcp_do_abc ? min(acked, abc_sslimit) : tp->t_maxseg; } else { /* linear increase */ tp->snd_wacked += tcp_do_abc ? acked : tp->t_maxseg; if (tp->snd_wacked >= tp->snd_cwnd) { tp->snd_wacked -= tp->snd_cwnd; tp->snd_cwnd += tp->t_maxseg; } } tp->snd_cwnd = min(tp->snd_cwnd, TCP_MAXWIN << tp->snd_scale); tp->snd_recover = th->th_ack - 1; } if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; /* * 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_callout_stop(tp, tp->tt_rexmt); needoutput = TRUE; } else if (!tcp_callout_active(tp, tp->tt_persist)) { tcp_callout_reset(tp, tp->tt_rexmt, tp->t_rxtcur, tcp_timer_rexmt); } 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); tcp_callout_reset(tp, tp->tt_2msl, tp->t_maxidle, tcp_timer_2msl); } 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_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), tcp_timer_2msl); 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_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), tcp_timer_2msl); goto dropafterack; } } step6: /* * Update window information. * Don't look at window if no ACK: TAC's send garbage on first SYN. */ if ((thflags & TH_ACK) && acceptable_window_update(tp, th, tiwin)) { /* keep track of pure window updates */ if (tlen == 0 && tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) tcpstat.tcps_rcvwinupd++; tp->snd_wnd = tiwin; tp->snd_wl1 = th->th_seq; tp->snd_wl2 = th->th_ack; if (tp->snd_wnd > tp->max_sndwnd) tp->max_sndwnd = tp->snd_wnd; needoutput = TRUE; } /* * Process segments with URG. */ if ((thflags & TH_URG) && th->th_urp && !TCPS_HAVERCVDFIN(tp->t_state)) { /* * 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.ssb_cc > sb_max) { th->th_urp = 0; /* XXX */ thflags &= ~TH_URG; /* XXX */ goto dodata; /* XXX */ } /* * If this segment advances the known urgent pointer, * then mark the data stream. This should not happen * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since * a FIN has been received from the remote side. * In these states we ignore the URG. * * According to RFC961 (Assigned Protocols), * the urgent pointer points to the last octet * of urgent data. We continue, however, * to consider it to indicate the first octet * of data past the urgent section as the original * spec states (in one of two places). */ if (SEQ_GT(th->th_seq + th->th_urp, tp->rcv_up)) { tp->rcv_up = th->th_seq + th->th_urp; so->so_oobmark = so->so_rcv.ssb_cc + (tp->rcv_up - tp->rcv_nxt) - 1; if (so->so_oobmark == 0) sosetstate(so, SS_RCVATMARK); sohasoutofband(so); tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); } /* * Remove out of band data so doesn't get presented to user. * This can happen independent of advancing the URG pointer, * but if two URG's are pending at once, some out-of-band * data may creep in... ick. */ if (th->th_urp <= (u_long)tlen && !(so->so_options & SO_OOBINLINE)) { /* hdr drop is delayed */ tcp_pulloutofband(so, th, m, drop_hdrlen); } } else { /* * If no out of band data is expected, * pull receive urgent pointer along * with the receive window. */ if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) tp->rcv_up = tp->rcv_nxt; } dodata: /* XXX */ /* * Process the segment text, merging it into the TCP sequencing queue, * and arranging for acknowledgment of receipt if necessary. * This process logically involves adjusting tp->rcv_wnd as data * is presented to the user (this happens in tcp_usrreq.c, * case PRU_RCVD). If a FIN has already been received on this * connection then we just ignore the text. */ if ((tlen || (thflags & TH_FIN)) && !TCPS_HAVERCVDFIN(tp->t_state)) { m_adj(m, drop_hdrlen); /* delayed header drop */ /* * Insert segment which includes th into TCP reassembly queue * with control block tp. Set thflags to whether reassembly now * includes a segment with FIN. This handles the common case * inline (segment is the next to be received on an established * connection, and the queue is empty), avoiding linkage into * and removal from the queue and repetition of various * conversions. * Set DELACK for segments received in order, but ack * immediately when segments are out of order (so * fast retransmit can work). */ if (th->th_seq == tp->rcv_nxt && LIST_EMPTY(&tp->t_segq) && TCPS_HAVEESTABLISHED(tp->t_state)) { if (DELAY_ACK(tp)) { tcp_callout_reset(tp, tp->tt_delack, tcp_delacktime, tcp_timer_delack); } else { tp->t_flags |= TF_ACKNOW; } tp->rcv_nxt += tlen; thflags = th->th_flags & TH_FIN; tcpstat.tcps_rcvpack++; tcpstat.tcps_rcvbyte += tlen; ND6_HINT(tp); if (so->so_state & SS_CANTRCVMORE) { m_freem(m); } else { lwkt_gettoken(&so->so_rcv.ssb_token); ssb_appendstream(&so->so_rcv, m); lwkt_reltoken(&so->so_rcv.ssb_token); } sorwakeup(so); } else { if (!(tp->sack_flags & TSACK_F_DUPSEG)) { /* Initialize SACK report block. */ tp->reportblk.rblk_start = th->th_seq; tp->reportblk.rblk_end = TCP_SACK_BLKEND( th->th_seq + tlen, thflags); } thflags = tcp_reass(tp, th, &tlen, m); 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.ssb_hiwat - (tp->rcv_adv - tp->rcv_nxt); } else { m_freem(m); thflags &= ~TH_FIN; } /* * If FIN is received ACK the FIN and let the user know * that the connection is closing. */ if (thflags & TH_FIN) { if (!TCPS_HAVERCVDFIN(tp->t_state)) { socantrcvmore(so); /* * If connection is half-synchronized * (ie NEEDSYN flag on) then delay ACK, * so it may be piggybacked when SYN is sent. * Otherwise, since we received a FIN then no * more input can be expected, send ACK now. */ if (DELAY_ACK(tp) && (tp->t_flags & TF_NEEDSYN)) { tcp_callout_reset(tp, tp->tt_delack, tcp_delacktime, tcp_timer_delack); } else { tp->t_flags |= TF_ACKNOW; } tp->rcv_nxt++; } switch (tp->t_state) { /* * In SYN_RECEIVED and ESTABLISHED STATES * enter the CLOSE_WAIT state. */ case TCPS_SYN_RECEIVED: tp->t_starttime = ticks; /*FALLTHROUGH*/ case TCPS_ESTABLISHED: tp->t_state = TCPS_CLOSE_WAIT; break; /* * If still in FIN_WAIT_1 STATE FIN has not been acked so * enter the CLOSING state. */ case TCPS_FIN_WAIT_1: tp->t_state = TCPS_CLOSING; break; /* * In FIN_WAIT_2 state enter the TIME_WAIT state, * starting the time-wait timer, turning off the other * standard timers. */ case TCPS_FIN_WAIT_2: tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), tcp_timer_2msl); soisdisconnected(so); break; /* * In TIME_WAIT state restart the 2 MSL time_wait timer. */ case TCPS_TIME_WAIT: tcp_callout_reset(tp, tp->tt_2msl, 2 * tcp_rmx_msl(tp), tcp_timer_2msl); break; } } #ifdef TCPDEBUG if (so->so_options & SO_DEBUG) tcp_trace(TA_INPUT, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); #endif /* * Return any desired output. */ if (needoutput || (tp->t_flags & TF_ACKNOW)) tcp_output(tp); tcp_sack_report_cleanup(tp); return(IPPROTO_DONE); dropafterack: /* * Generate an ACK dropping incoming segment if it occupies * sequence space, where the ACK reflects our state. * * We can now skip the test for the RST flag since all * paths to this code happen after packets containing * RST have been dropped. * * In the SYN-RECEIVED state, don't send an ACK unless the * segment we received passes the SYN-RECEIVED ACK test. * If it fails send a RST. This breaks the loop in the * "LAND" DoS attack, and also prevents an ACK storm * between two listening ports that have been sent forged * SYN segments, each with the source address of the other. */ if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && (SEQ_GT(tp->snd_una, th->th_ack) || SEQ_GT(th->th_ack, tp->snd_max)) ) { rstreason = BANDLIM_RST_OPENPORT; goto dropwithreset; } #ifdef TCPDEBUG if (so->so_options & SO_DEBUG) tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); #endif m_freem(m); tp->t_flags |= TF_ACKNOW; tcp_output(tp); tcp_sack_report_cleanup(tp); return(IPPROTO_DONE); dropwithreset: /* * Generate a RST, dropping incoming segment. * Make ACK acceptable to originator of segment. * Don't bother to respond if destination was broadcast/multicast. */ if ((thflags & TH_RST) || m->m_flags & (M_BCAST | M_MCAST)) goto drop; if (isipv6) { if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) goto drop; } else { if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) goto drop; } /* IPv6 anycast check is done at tcp6_input() */ /* * Perform bandwidth limiting. */ #ifdef ICMP_BANDLIM if (badport_bandlim(rstreason) < 0) goto drop; #endif #ifdef TCPDEBUG if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); #endif if (thflags & TH_ACK) /* mtod() below is safe as long as hdr dropping is delayed */ tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, th->th_ack, TH_RST); else { if (thflags & TH_SYN) tlen++; /* mtod() below is safe as long as hdr dropping is delayed */ tcp_respond(tp, mtod(m, void *), th, m, th->th_seq + tlen, (tcp_seq)0, TH_RST | TH_ACK); } if (tp != NULL) tcp_sack_report_cleanup(tp); return(IPPROTO_DONE); drop: /* * Drop space held by incoming segment and return. */ #ifdef TCPDEBUG if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) tcp_trace(TA_DROP, ostate, tp, tcp_saveipgen, &tcp_savetcp, 0); #endif m_freem(m); if (tp != NULL) tcp_sack_report_cleanup(tp); return(IPPROTO_DONE); } /* * Parse TCP options and place in tcpopt. */ static void tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, boolean_t is_syn, tcp_seq ack) { int opt, optlen, i; to->to_flags = 0; for (; 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) { case TCPOPT_MAXSEG: if (optlen != TCPOLEN_MAXSEG) continue; if (!is_syn) continue; to->to_flags |= TOF_MSS; bcopy(cp + 2, &to->to_mss, sizeof to->to_mss); to->to_mss = ntohs(to->to_mss); break; case TCPOPT_WINDOW: if (optlen != TCPOLEN_WINDOW) continue; if (!is_syn) continue; to->to_flags |= TOF_SCALE; to->to_requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); break; case TCPOPT_TIMESTAMP: if (optlen != TCPOLEN_TIMESTAMP) continue; to->to_flags |= TOF_TS; bcopy(cp + 2, &to->to_tsval, sizeof to->to_tsval); to->to_tsval = ntohl(to->to_tsval); bcopy(cp + 6, &to->to_tsecr, sizeof to->to_tsecr); to->to_tsecr = ntohl(to->to_tsecr); /* * If echoed timestamp is later than the current time, * fall back to non RFC1323 RTT calculation. */ if (to->to_tsecr != 0 && TSTMP_GT(to->to_tsecr, ticks)) to->to_tsecr = 0; break; case TCPOPT_SACK_PERMITTED: if (optlen != TCPOLEN_SACK_PERMITTED) continue; if (!is_syn) continue; to->to_flags |= TOF_SACK_PERMITTED; break; case TCPOPT_SACK: if ((optlen - 2) & 0x07) /* not multiple of 8 */ continue; to->to_nsackblocks = (optlen - 2) / 8; to->to_sackblocks = (struct raw_sackblock *) (cp + 2); to->to_flags |= TOF_SACK; for (i = 0; i < to->to_nsackblocks; i++) { struct raw_sackblock *r = &to->to_sackblocks[i]; r->rblk_start = ntohl(r->rblk_start); r->rblk_end = ntohl(r->rblk_end); if (SEQ_LEQ(r->rblk_end, r->rblk_start)) { /* * Invalid SACK block; discard all * SACK blocks */ tcpstat.tcps_rcvbadsackopt++; to->to_nsackblocks = 0; to->to_sackblocks = NULL; to->to_flags &= ~TOF_SACK; break; } } if ((to->to_flags & TOF_SACK) && tcp_sack_ndsack_blocks(to->to_sackblocks, to->to_nsackblocks, ack)) to->to_flags |= TOF_DSACK; break; #ifdef TCP_SIGNATURE /* * XXX In order to reply to a host which has set the * TCP_SIGNATURE option in its initial SYN, we have to * record the fact that the option was observed here * for the syncache code to perform the correct response. */ case TCPOPT_SIGNATURE: if (optlen != TCPOLEN_SIGNATURE) continue; to->to_flags |= (TOF_SIGNATURE | TOF_SIGLEN); break; #endif /* TCP_SIGNATURE */ default: continue; } } } /* * 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. * "off" is the delayed to be dropped hdrlen. */ static 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, caddr_t) + cnt; struct tcpcb *tp = sototcpcb(so); tp->t_iobc = *cp; tp->t_oobflags |= TCPOOB_HAVEDATA; bcopy(cp + 1, cp, m->m_len - cnt - 1); m->m_len--; if (m->m_flags & M_PKTHDR) m->m_pkthdr.len--; return; } cnt -= m->m_len; m = m->m_next; if (m == NULL) break; } panic("tcp_pulloutofband"); } /* * Collect new round-trip time estimate * and update averages and current timeout. */ static void tcp_xmit_timer(struct tcpcb *tp, int rtt, tcp_seq ack) { int rebaserto = 0; tcpstat.tcps_rttupdated++; tp->t_rttupdated++; if ((tp->rxt_flags & TRXT_F_REBASERTO) && SEQ_GT(ack, tp->snd_max_prev)) { #ifdef DEBUG_EIFEL_RESPONSE kprintf("srtt/rttvar, prev %d/%d, cur %d/%d, ", tp->t_srtt_prev, tp->t_rttvar_prev, tp->t_srtt, tp->t_rttvar); #endif tcpstat.tcps_eifelresponse++; rebaserto = 1; tp->rxt_flags &= ~TRXT_F_REBASERTO; tp->t_srtt = max(tp->t_srtt_prev, (rtt << TCP_RTT_SHIFT)); tp->t_rttvar = max(tp->t_rttvar_prev, (rtt << (TCP_RTTVAR_SHIFT - 1))); if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) tp->t_rttbest = tp->t_srtt + tp->t_rttvar; #ifdef DEBUG_EIFEL_RESPONSE kprintf("new %d/%d ", tp->t_srtt, tp->t_rttvar); #endif } else if (tp->t_srtt != 0) { int delta; /* * srtt is stored as fixed point with 5 bits after the * binary point (i.e., scaled by 8). The following magic * is equivalent to the smoothing algorithm in rfc793 with * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed * point). Adjust rtt to origin 0. */ delta = ((rtt - 1) << TCP_DELTA_SHIFT) - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); if ((tp->t_srtt += delta) <= 0) tp->t_srtt = 1; /* * We accumulate a smoothed rtt variance (actually, a * smoothed mean difference), then set the retransmit * timer to smoothed rtt + 4 times the smoothed variance. * rttvar is stored as fixed point with 4 bits after the * binary point (scaled by 16). The following is * equivalent to rfc793 smoothing with an alpha of .75 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces * rfc793's wired-in beta. */ if (delta < 0) delta = -delta; delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); if ((tp->t_rttvar += delta) <= 0) tp->t_rttvar = 1; if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) tp->t_rttbest = tp->t_srtt + tp->t_rttvar; } else { /* * No rtt measurement yet - use the unsmoothed rtt. * Set the variance to half the rtt (so our first * retransmit happens at 3*rtt). */ tp->t_srtt = rtt << TCP_RTT_SHIFT; tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); tp->t_rttbest = tp->t_srtt + tp->t_rttvar; } tp->t_rtttime = 0; tp->t_rxtshift = 0; #ifdef DEBUG_EIFEL_RESPONSE if (rebaserto) { kprintf("| rxtcur prev %d, old %d, ", tp->t_rxtcur_prev, tp->t_rxtcur); } #endif /* * the retransmit should happen at rtt + 4 * rttvar. * Because of the way we do the smoothing, srtt and rttvar * will each average +1/2 tick of bias. When we compute * the retransmit timer, we want 1/2 tick of rounding and * 1 extra tick because of +-1/2 tick uncertainty in the * firing of the timer. The bias will give us exactly the * 1.5 tick we need. But, because the bias is * statistical, we have to test that we don't drop below * the minimum feasible timer (which is 2 ticks). */ TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); if (rebaserto) { if (tp->t_rxtcur < tp->t_rxtcur_prev + tcp_eifel_rtoinc) { /* * RFC4015 requires that the new RTO is at least * 2*G (tcp_eifel_rtoinc) greater then the RTO * (t_rxtcur_prev) when the spurious retransmit * timeout happens. * * The above condition could be true, if the SRTT * and RTTVAR used to calculate t_rxtcur_prev * resulted in a value less than t_rttmin. So * simply increasing SRTT by tcp_eifel_rtoinc when * preparing for the Eifel response in * tcp_save_congestion_state() could not ensure * that the new RTO will be tcp_eifel_rtoinc greater * t_rxtcur_prev. */ tp->t_rxtcur = tp->t_rxtcur_prev + tcp_eifel_rtoinc; } #ifdef DEBUG_EIFEL_RESPONSE kprintf("new %d\n", tp->t_rxtcur); #endif } /* * We received an ack for a packet that wasn't retransmitted; * it is probably safe to discard any error indications we've * received recently. This isn't quite right, but close enough * for now (a route might have failed after we sent a segment, * and the return path might not be symmetrical). */ tp->t_softerror = 0; } /* * Determine a reasonable value for maxseg size. * If the route is known, check route for mtu. * If none, use an mss that can be handled on the outgoing * interface without forcing IP to fragment; if bigger than * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES * to utilize large mbufs. If no route is found, route has no mtu, * or the destination isn't local, use a default, hopefully conservative * size (usually 512 or the default IP max size, but no more than the mtu * of the interface), as we can't discover anything about intervening * gateways or networks. We also initialize the congestion/slow start * window to be a single segment if the destination isn't local. * While looking at the routing entry, we also initialize other path-dependent * parameters from pre-set or cached values in the routing entry. * * Also take into account the space needed for options that we * send regularly. Make maxseg shorter by that amount to assure * that we can send maxseg amount of data even when the options * are present. Store the upper limit of the length of options plus * data in maxopd. * * NOTE that this routine is only called when we process an incoming * segment, for outgoing segments only tcp_mssopt is called. */ void tcp_mss(struct tcpcb *tp, int offer) { struct rtentry *rt; struct ifnet *ifp; int rtt, mss; u_long bufsize; struct inpcb *inp = tp->t_inpcb; struct socket *so; #ifdef INET6 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); size_t min_protoh = isipv6 ? sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : sizeof(struct tcpiphdr); #else const boolean_t isipv6 = FALSE; const size_t min_protoh = sizeof(struct tcpiphdr); #endif if (isipv6) rt = tcp_rtlookup6(&inp->inp_inc); else rt = tcp_rtlookup(&inp->inp_inc); if (rt == NULL) { tp->t_maxopd = tp->t_maxseg = (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); return; } ifp = rt->rt_ifp; so = inp->inp_socket; /* * Offer == 0 means that there was no MSS on the SYN segment, * in this case we use either the interface mtu or tcp_mssdflt. * * An offer which is too large will be cut down later. */ if (offer == 0) { if (isipv6) { if (in6_localaddr(&inp->in6p_faddr)) { offer = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; } else { offer = tcp_v6mssdflt; } } else { if (in_localaddr(inp->inp_faddr)) offer = ifp->if_mtu - min_protoh; else offer = tcp_mssdflt; } } /* * Prevent DoS attack with too small MSS. Round up * to at least minmss. * * Sanity check: make sure that maxopd will be large * enough to allow some data on segments even is the * all the option space is used (40bytes). Otherwise * funny things may happen in tcp_output. */ offer = max(offer, tcp_minmss); offer = max(offer, 64); rt->rt_rmx.rmx_mssopt = offer; /* * While we're here, check if there's an initial rtt * or rttvar. Convert from the route-table units * to scaled multiples of the slow timeout timer. */ if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { /* * XXX the lock bit for RTT indicates that the value * is also a minimum value; this is subject to time. */ if (rt->rt_rmx.rmx_locks & RTV_RTT) tp->t_rttmin = rtt / (RTM_RTTUNIT / hz); tp->t_srtt = rtt / (RTM_RTTUNIT / (hz * TCP_RTT_SCALE)); tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; tcpstat.tcps_usedrtt++; if (rt->rt_rmx.rmx_rttvar) { tp->t_rttvar = rt->rt_rmx.rmx_rttvar / (RTM_RTTUNIT / (hz * TCP_RTTVAR_SCALE)); tcpstat.tcps_usedrttvar++; } else { /* default variation is +- 1 rtt */ tp->t_rttvar = tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; } TCPT_RANGESET(tp->t_rxtcur, ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, tp->t_rttmin, TCPTV_REXMTMAX); } /* * if there's an mtu associated with the route, use it * else, use the link mtu. Take the smaller of mss or offer * as our final mss. */ if (rt->rt_rmx.rmx_mtu) { mss = rt->rt_rmx.rmx_mtu - min_protoh; } else { if (isipv6) mss = ND_IFINFO(rt->rt_ifp)->linkmtu - min_protoh; else mss = ifp->if_mtu - min_protoh; } mss = min(mss, offer); /* * maxopd stores the maximum length of data AND options * in a segment; maxseg is the amount of data in a normal * segment. We need to store this value (maxopd) apart * from maxseg, because now every segment carries options * and thus we normally have somewhat less data in segments. */ tp->t_maxopd = mss; if ((tp->t_flags & (TF_REQ_TSTMP | TF_NOOPT)) == TF_REQ_TSTMP && ((tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) mss -= TCPOLEN_TSTAMP_APPA; #if (MCLBYTES & (MCLBYTES - 1)) == 0 if (mss > MCLBYTES) mss &= ~(MCLBYTES-1); #else if (mss > MCLBYTES) mss = mss / MCLBYTES * MCLBYTES; #endif /* * If there's a pipesize, change the socket buffer * to that size. Make the socket buffers an integral * number of mss units; if the mss is larger than * the socket buffer, decrease the mss. */ #ifdef RTV_SPIPE if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) #endif bufsize = so->so_snd.ssb_hiwat; if (bufsize < mss) mss = bufsize; else { bufsize = roundup(bufsize, mss); if (bufsize > sb_max) bufsize = sb_max; if (bufsize > so->so_snd.ssb_hiwat) ssb_reserve(&so->so_snd, bufsize, so, NULL); } tp->t_maxseg = mss; #ifdef RTV_RPIPE if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) #endif bufsize = so->so_rcv.ssb_hiwat; if (bufsize > mss) { bufsize = roundup(bufsize, mss); if (bufsize > sb_max) bufsize = sb_max; if (bufsize > so->so_rcv.ssb_hiwat) { lwkt_gettoken(&so->so_rcv.ssb_token); ssb_reserve(&so->so_rcv, bufsize, so, NULL); lwkt_reltoken(&so->so_rcv.ssb_token); } } /* * Set the slow-start flight size * * NOTE: t_maxseg must have been configured! */ tp->snd_cwnd = tcp_initial_window(tp); if (rt->rt_rmx.rmx_ssthresh) { /* * There's some sort of gateway or interface * buffer limit on the path. Use this to set * the slow start threshhold, but set the * threshold to no less than 2*mss. */ tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); tcpstat.tcps_usedssthresh++; } } /* * Determine the MSS option to send on an outgoing SYN. */ int tcp_mssopt(struct tcpcb *tp) { struct rtentry *rt; #ifdef INET6 boolean_t isipv6 = ((tp->t_inpcb->inp_vflag & INP_IPV6) ? TRUE : FALSE); int min_protoh = isipv6 ? sizeof(struct ip6_hdr) + sizeof(struct tcphdr) : sizeof(struct tcpiphdr); #else const boolean_t isipv6 = FALSE; const size_t min_protoh = sizeof(struct tcpiphdr); #endif if (isipv6) rt = tcp_rtlookup6(&tp->t_inpcb->inp_inc); else rt = tcp_rtlookup(&tp->t_inpcb->inp_inc); if (rt == NULL) return (isipv6 ? tcp_v6mssdflt : tcp_mssdflt); return (rt->rt_ifp->if_mtu - min_protoh); } /* * When a partial ack arrives, force the retransmission of the * next unacknowledged segment. Do not exit Fast Recovery. * * Implement the Slow-but-Steady variant of NewReno by restarting the * the retransmission timer. Turn it off here so it can be restarted * later in tcp_output(). */ static void tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th, int acked) { tcp_seq old_snd_nxt = tp->snd_nxt; u_long ocwnd = tp->snd_cwnd; tcp_callout_stop(tp, tp->tt_rexmt); tp->t_rtttime = 0; tp->snd_nxt = th->th_ack; /* Set snd_cwnd to one segment beyond acknowledged offset. */ tp->snd_cwnd = tp->t_maxseg; tp->t_flags |= TF_ACKNOW; tcp_output(tp); if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) tp->snd_nxt = old_snd_nxt; /* partial window deflation */ if (ocwnd > acked) tp->snd_cwnd = ocwnd - acked + tp->t_maxseg; else tp->snd_cwnd = tp->t_maxseg; } /* * In contrast to the Slow-but-Steady NewReno variant, * we do not reset the retransmission timer for SACK retransmissions, * except when retransmitting snd_una. */ static void tcp_sack_rexmt(struct tcpcb *tp, struct tcphdr *th) { tcp_seq old_snd_nxt = tp->snd_nxt; u_long ocwnd = tp->snd_cwnd; uint32_t pipe; int nseg = 0; /* consecutive new segments */ int nseg_rexmt = 0; /* retransmitted segments */ #define MAXBURST 4 /* limit burst of new packets on partial ack */ tp->t_rtttime = 0; pipe = tcp_sack_compute_pipe(tp); while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg && (!tcp_do_smartsack || nseg < MAXBURST)) { tcp_seq old_snd_max, old_rexmt_high, nextrexmt; uint32_t sent, seglen; boolean_t rescue; int error; old_rexmt_high = tp->rexmt_high; if (!tcp_sack_nextseg(tp, &nextrexmt, &seglen, &rescue)) { tp->rexmt_high = old_rexmt_high; break; } /* * If the next tranmission is a rescue retranmission, * we check whether we have already sent some data * (either new segments or retransmitted segments) * into the the network or not. Since the idea of rescue * retransmission is to sustain ACK clock, as long as * some segments are in the network, ACK clock will be * kept ticking. */ if (rescue && (nseg_rexmt > 0 || nseg > 0)) { tp->rexmt_high = old_rexmt_high; break; } if (nextrexmt == tp->snd_max) ++nseg; else ++nseg_rexmt; tp->snd_nxt = nextrexmt; tp->snd_cwnd = nextrexmt - tp->snd_una + seglen; old_snd_max = tp->snd_max; if (nextrexmt == tp->snd_una) tcp_callout_stop(tp, tp->tt_rexmt); error = tcp_output(tp); if (error != 0) { tp->rexmt_high = old_rexmt_high; break; } sent = tp->snd_nxt - nextrexmt; if (sent <= 0) { tp->rexmt_high = old_rexmt_high; break; } pipe += sent; tcpstat.tcps_sndsackpack++; tcpstat.tcps_sndsackbyte += sent; if (rescue) { tcpstat.tcps_sackrescue++; tp->rexmt_rescue = tp->snd_nxt; tp->sack_flags |= TSACK_F_SACKRESCUED; break; } if (SEQ_LT(nextrexmt, old_snd_max) && SEQ_LT(tp->rexmt_high, tp->snd_nxt)) { tp->rexmt_high = seq_min(tp->snd_nxt, old_snd_max); if (tcp_aggressive_rescuesack && (tp->sack_flags & TSACK_F_SACKRESCUED) && SEQ_LT(tp->rexmt_rescue, tp->rexmt_high)) { /* Drag RescueRxt along with HighRxt */ tp->rexmt_rescue = tp->rexmt_high; } } } if (SEQ_GT(old_snd_nxt, tp->snd_nxt)) tp->snd_nxt = old_snd_nxt; tp->snd_cwnd = ocwnd; } static boolean_t tcp_sack_limitedxmit(struct tcpcb *tp) { tcp_seq oldsndnxt = tp->snd_nxt; tcp_seq oldsndmax = tp->snd_max; u_long ocwnd = tp->snd_cwnd; uint32_t pipe; boolean_t ret = FALSE; tp->rexmt_high = tp->snd_una - 1; pipe = tcp_sack_compute_pipe(tp); while ((tcp_seq_diff_t)(ocwnd - pipe) >= (tcp_seq_diff_t)tp->t_maxseg) { uint32_t sent; tcp_seq next; int error; next = tp->snd_nxt = tp->snd_max; tp->snd_cwnd = tp->snd_nxt - tp->snd_una + tp->t_maxseg; error = tcp_output(tp); if (error) break; sent = tp->snd_nxt - next; if (sent <= 0) break; pipe += sent; ++tcpstat.tcps_sndlimited; ret = TRUE; } if (SEQ_LT(oldsndnxt, oldsndmax)) { KASSERT(SEQ_GEQ(oldsndnxt, tp->snd_una), ("snd_una moved in other threads")); tp->snd_nxt = oldsndnxt; } tp->snd_cwnd = ocwnd; return ret; } /* * Reset idle time and keep-alive timer, typically called when a valid * tcp packet is received but may also be called when FASTKEEP is set * to prevent the previous long-timeout from calculating to a drop. * * Only update t_rcvtime for non-SYN packets. * * Handle the case where one side thinks the connection is established * but the other side has, say, rebooted without cleaning out the * connection. The SYNs could be construed as an attack and wind * up ignored, but in case it isn't an attack we can validate the * connection by forcing a keepalive. */ void tcp_timer_keep_activity(struct tcpcb *tp, int thflags) { if (TCPS_HAVEESTABLISHED(tp->t_state)) { if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) { tp->t_flags |= TF_KEEPALIVE; tcp_callout_reset(tp, tp->tt_keep, hz / 2, tcp_timer_keep); } else { tp->t_rcvtime = ticks; tp->t_flags &= ~TF_KEEPALIVE; tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep); } } } static int tcp_rmx_msl(const struct tcpcb *tp) { struct rtentry *rt; struct inpcb *inp = tp->t_inpcb; int msl; #ifdef INET6 boolean_t isipv6 = ((inp->inp_vflag & INP_IPV6) ? TRUE : FALSE); #else const boolean_t isipv6 = FALSE; #endif if (isipv6) rt = tcp_rtlookup6(&inp->inp_inc); else rt = tcp_rtlookup(&inp->inp_inc); if (rt == NULL || rt->rt_rmx.rmx_msl == 0) return tcp_msl; msl = (rt->rt_rmx.rmx_msl * hz) / 1000; if (msl == 0) msl = 1; return msl; } static void tcp_established(struct tcpcb *tp) { tp->t_state = TCPS_ESTABLISHED; tcp_callout_reset(tp, tp->tt_keep, tp->t_keepidle, tcp_timer_keep); if (tp->t_rxtsyn > 0) { /* * RFC6298: * "If the timer expires awaiting the ACK of a SYN segment * and the TCP implementation is using an RTO less than 3 * seconds, the RTO MUST be re-initialized to 3 seconds * when data transmission begins" */ if (tp->t_rxtcur < TCPTV_RTOBASE3) tp->t_rxtcur = TCPTV_RTOBASE3; } }