/* $NetBSD: tcp_input.c,v 1.77 1999/02/05 22:37:24 matt Exp $ */ /*- * Copyright (c) 1997, 1998, 1999 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation * by Jason R. Thorpe and Kevin M. Lahey of the Numerical Aerospace Simulation * Facility, NASA Ames Research Center. * * 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 NetBSD * Foundation, Inc. and its contributors. * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE * POSSIBILITY OF SUCH DAMAGE. */ /* * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. 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 */ /* * TODO list for SYN cache stuff: * * Find room for a "state" field, which is needed to keep a * compressed state for TIME_WAIT TCBs. It's been noted already * that this is fairly important for very high-volume web and * mail servers, which use a large number of short-lived * connections. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include int tcprexmtthresh = 3; struct tcpiphdr tcp_saveti; extern u_long sb_max; #define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ) /* for modulo comparisons of timestamps */ #define TSTMP_LT(a,b) ((int)((a)-(b)) < 0) #define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0) /* * Macro to compute ACK transmission behavior. Delay the ACK unless * we have already delayed an ACK (must send an ACK every two segments). * We also ACK immediately if we received a PUSH and the ACK-on-PUSH * option is enabled. */ #define TCP_SETUP_ACK(tp, ti) \ do { \ if ((tp)->t_flags & TF_DELACK || \ (tcp_ack_on_push && (ti)->ti_flags & TH_PUSH)) \ tp->t_flags |= TF_ACKNOW; \ else \ TCP_SET_DELACK(tp); \ } while (0) /* * Insert segment ti into reassembly queue of tcp with * control block tp. Return TH_FIN if reassembly now includes * a segment with FIN. The macro form does the common case inline * (segment is the next to be received on an established connection, * and the queue is empty), avoiding linkage into and removal * from the queue and repetition of various conversions. * Set DELACK for segments received in order, but ack immediately * when segments are out of order (so fast retransmit can work). */ #define TCP_REASS(tp, ti, m, so, flags) { \ TCP_REASS_LOCK((tp)); \ if ((ti)->ti_seq == (tp)->rcv_nxt && \ (tp)->segq.lh_first == NULL && \ (tp)->t_state == TCPS_ESTABLISHED) { \ TCP_SETUP_ACK(tp, ti); \ (tp)->rcv_nxt += (ti)->ti_len; \ flags = (ti)->ti_flags & TH_FIN; \ tcpstat.tcps_rcvpack++;\ tcpstat.tcps_rcvbyte += (ti)->ti_len;\ sbappend(&(so)->so_rcv, (m)); \ sorwakeup(so); \ } else { \ (flags) = tcp_reass((tp), (ti), (m)); \ tp->t_flags |= TF_ACKNOW; \ } \ TCP_REASS_UNLOCK((tp)); \ } int tcp_reass(tp, ti, m) register struct tcpcb *tp; register struct tcpiphdr *ti; struct mbuf *m; { register struct ipqent *p, *q, *nq, *tiqe = NULL; struct socket *so = tp->t_inpcb->inp_socket; int pkt_flags; tcp_seq pkt_seq; unsigned pkt_len; u_long rcvpartdupbyte = 0; u_long rcvoobyte; TCP_REASS_LOCK_CHECK(tp); /* * Call with ti==0 after become established to * force pre-ESTABLISHED data up to user socket. */ if (ti == 0) goto present; rcvoobyte = ti->ti_len; /* * Copy these to local variables because the tcpiphdr * gets munged while we are collapsing mbufs. */ pkt_seq = ti->ti_seq; pkt_len = ti->ti_len; pkt_flags = ti->ti_flags; /* * Find a segment which begins after this one does. */ for (p = NULL, q = tp->segq.lh_first; q != NULL; q = nq) { nq = q->ipqe_q.le_next; /* * If the received segment is just right after this * fragment, merge the two together and then check * for further overlaps. */ if (q->ipqe_seq + q->ipqe_len == pkt_seq) { #ifdef TCPREASS_DEBUG printf("tcp_reass[%p]: concat %u:%u(%u) to %u:%u(%u)\n", tp, pkt_seq, pkt_seq + pkt_len, pkt_len, q->ipqe_seq, q->ipqe_seq + q->ipqe_len, q->ipqe_len); #endif pkt_len += q->ipqe_len; pkt_flags |= q->ipqe_flags; pkt_seq = q->ipqe_seq; m_cat(q->ipqe_m, m); m = q->ipqe_m; goto free_ipqe; } /* * If the received segment is completely past this * fragment, we need to go the next fragment. */ if (SEQ_LT(q->ipqe_seq + q->ipqe_len, pkt_seq)) { p = q; continue; } /* * If the fragment is past the received segment, * it (or any following) can't be concatenated. */ if (SEQ_GT(q->ipqe_seq, pkt_seq + pkt_len)) break; /* * We've received all the data in this segment before. * mark it as a duplicate and return. */ if (SEQ_LEQ(q->ipqe_seq, pkt_seq) && SEQ_GEQ(q->ipqe_seq + q->ipqe_len, pkt_seq + pkt_len)) { tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += pkt_len; m_freem(m); if (tiqe != NULL) pool_put(&ipqent_pool, tiqe); return (0); } /* * Received segment completely overlaps this fragment * so we drop the fragment (this keeps the temporal * ordering of segments correct). */ if (SEQ_GEQ(q->ipqe_seq, pkt_seq) && SEQ_LEQ(q->ipqe_seq + q->ipqe_len, pkt_seq + pkt_len)) { rcvpartdupbyte += q->ipqe_len; m_freem(q->ipqe_m); goto free_ipqe; } /* * RX'ed segment extends past the end of the * fragment. Drop the overlapping bytes. Then * merge the fragment and segment then treat as * a longer received packet. */ if (SEQ_LT(q->ipqe_seq, pkt_seq) && SEQ_GT(q->ipqe_seq + q->ipqe_len, pkt_seq)) { int overlap = q->ipqe_seq + q->ipqe_len - pkt_seq; #ifdef TCPREASS_DEBUG printf("tcp_reass[%p]: trim starting %d bytes of %u:%u(%u)\n", tp, overlap, pkt_seq, pkt_seq + pkt_len, pkt_len); #endif m_adj(m, overlap); rcvpartdupbyte += overlap; m_cat(q->ipqe_m, m); m = q->ipqe_m; pkt_seq = q->ipqe_seq; pkt_len += q->ipqe_len - overlap; rcvoobyte -= overlap; goto free_ipqe; } /* * RX'ed segment extends past the front of the * fragment. Drop the overlapping bytes on the * received packet. The packet will then be * contatentated with this fragment a bit later. */ if (SEQ_GT(q->ipqe_seq, pkt_seq) && SEQ_LT(q->ipqe_seq, pkt_seq + pkt_len)) { int overlap = pkt_seq + pkt_len - q->ipqe_seq; #ifdef TCPREASS_DEBUG printf("tcp_reass[%p]: trim trailing %d bytes of %u:%u(%u)\n", tp, overlap, pkt_seq, pkt_seq + pkt_len, pkt_len); #endif m_adj(m, -overlap); pkt_len -= overlap; rcvpartdupbyte += overlap; rcvoobyte -= overlap; } /* * If the received segment immediates precedes this * fragment then tack the fragment onto this segment * and reinsert the data. */ if (q->ipqe_seq == pkt_seq + pkt_len) { #ifdef TCPREASS_DEBUG printf("tcp_reass[%p]: append %u:%u(%u) to %u:%u(%u)\n", tp, q->ipqe_seq, q->ipqe_seq + q->ipqe_len, q->ipqe_len, pkt_seq, pkt_seq + pkt_len, pkt_len); #endif pkt_len += q->ipqe_len; pkt_flags |= q->ipqe_flags; m_cat(m, q->ipqe_m); LIST_REMOVE(q, ipqe_q); LIST_REMOVE(q, ipqe_timeq); if (tiqe == NULL) { tiqe = q; } else { pool_put(&ipqent_pool, q); } break; } /* * If the fragment is before the segment, remember it. * When this loop is terminated, p will contain the * pointer to fragment that is right before the received * segment. */ if (SEQ_LEQ(q->ipqe_seq, pkt_seq)) p = q; continue; /* * This is a common operation. It also will allow * to save doing a malloc/free in most instances. */ free_ipqe: LIST_REMOVE(q, ipqe_q); LIST_REMOVE(q, ipqe_timeq); if (tiqe == NULL) { tiqe = q; } else { pool_put(&ipqent_pool, q); } } /* * Allocate a new queue entry since the received segment did not * collapse onto any other out-of-order block; thus we are allocating * a new block. If it had collapsed, tiqe would not be NULL and * we would be reusing it. * XXX If we can't, just drop the packet. XXX */ if (tiqe == NULL) { tiqe = pool_get(&ipqent_pool, PR_NOWAIT); if (tiqe == NULL) { tcpstat.tcps_rcvmemdrop++; m_freem(m); return (0); } } /* * Update the counters. */ tcpstat.tcps_rcvoopack++; tcpstat.tcps_rcvoobyte += rcvoobyte; if (rcvpartdupbyte) { tcpstat.tcps_rcvpartduppack++; tcpstat.tcps_rcvpartdupbyte += rcvpartdupbyte; } /* * Insert the new fragment queue entry into both queues. */ tiqe->ipqe_m = m; tiqe->ipqe_seq = pkt_seq; tiqe->ipqe_len = pkt_len; tiqe->ipqe_flags = pkt_flags; if (p == NULL) { LIST_INSERT_HEAD(&tp->segq, tiqe, ipqe_q); #ifdef TCPREASS_DEBUG if (tiqe->ipqe_seq != tp->rcv_nxt) printf("tcp_reass[%p]: insert %u:%u(%u) at front\n", tp, pkt_seq, pkt_seq + pkt_len, pkt_len); #endif } else { LIST_INSERT_AFTER(p, tiqe, ipqe_q); #ifdef TCPREASS_DEBUG printf("tcp_reass[%p]: insert %u:%u(%u) after %u:%u(%u)\n", tp, pkt_seq, pkt_seq + pkt_len, pkt_len, p->ipqe_seq, p->ipqe_seq + p->ipqe_len, p->ipqe_len); #endif } LIST_INSERT_HEAD(&tp->timeq, tiqe, ipqe_timeq); present: /* * Present data to user, advancing rcv_nxt through * completed sequence space. */ if (TCPS_HAVEESTABLISHED(tp->t_state) == 0) return (0); q = tp->segq.lh_first; if (q == NULL || q->ipqe_seq != tp->rcv_nxt) return (0); if (tp->t_state == TCPS_SYN_RECEIVED && q->ipqe_len) return (0); tp->rcv_nxt += q->ipqe_len; pkt_flags = q->ipqe_flags & TH_FIN; LIST_REMOVE(q, ipqe_q); LIST_REMOVE(q, ipqe_timeq); if (so->so_state & SS_CANTRCVMORE) m_freem(q->ipqe_m); else sbappend(&so->so_rcv, q->ipqe_m); pool_put(&ipqent_pool, q); sorwakeup(so); return (pkt_flags); } /* * TCP input routine, follows pages 65-76 of the * protocol specification dated September, 1981 very closely. */ void #if __STDC__ tcp_input(struct mbuf *m, ...) #else tcp_input(m, va_alist) register struct mbuf *m; #endif { register struct tcpiphdr *ti; register struct inpcb *inp; caddr_t optp = NULL; int optlen = 0; int len, tlen, off, hdroptlen; register struct tcpcb *tp = 0; register int tiflags; struct socket *so = NULL; int todrop, acked, ourfinisacked, needoutput = 0; short ostate = 0; int iss = 0; u_long tiwin; struct tcp_opt_info opti; int iphlen; va_list ap; va_start(ap, m); iphlen = va_arg(ap, int); va_end(ap); tcpstat.tcps_rcvtotal++; opti.ts_present = 0; opti.maxseg = 0; /* * Get IP and TCP header together in first mbuf. * Note: IP leaves IP header in first mbuf. */ ti = mtod(m, struct tcpiphdr *); if (iphlen > sizeof (struct ip)) ip_stripoptions(m, (struct mbuf *)0); if (m->m_len < sizeof (struct tcpiphdr)) { if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { tcpstat.tcps_rcvshort++; return; } ti = mtod(m, struct tcpiphdr *); } /* * Checksum extended TCP header and data. */ len = ((struct ip *)ti)->ip_len; tlen = len - sizeof (struct ip); bzero(ti->ti_x1, sizeof ti->ti_x1); ti->ti_len = (u_int16_t)tlen; HTONS(ti->ti_len); if (in_cksum(m, len) != 0) { tcpstat.tcps_rcvbadsum++; goto drop; } /* * Check that TCP offset makes sense, * pull out TCP options and adjust length. XXX */ off = ti->ti_off << 2; if (off < sizeof (struct tcphdr) || off > tlen) { tcpstat.tcps_rcvbadoff++; goto drop; } tlen -= off; ti->ti_len = tlen; if (off > sizeof (struct tcphdr)) { if (m->m_len < sizeof(struct ip) + off) { if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { tcpstat.tcps_rcvshort++; return; } ti = mtod(m, struct tcpiphdr *); } optlen = off - sizeof (struct tcphdr); optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr); /* * Do quick retrieval of timestamp options ("options * prediction?"). If timestamp is the only option and it's * formatted as recommended in RFC 1323 appendix A, we * quickly get the values now and not bother calling * tcp_dooptions(), etc. */ if ((optlen == TCPOLEN_TSTAMP_APPA || (optlen > TCPOLEN_TSTAMP_APPA && optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) && *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) && (ti->ti_flags & TH_SYN) == 0) { opti.ts_present = 1; opti.ts_val = ntohl(*(u_int32_t *)(optp + 4)); opti.ts_ecr = ntohl(*(u_int32_t *)(optp + 8)); optp = NULL; /* we've parsed the options */ } } tiflags = ti->ti_flags; /* * Convert TCP protocol specific fields to host format. */ NTOHL(ti->ti_seq); NTOHL(ti->ti_ack); NTOHS(ti->ti_win); NTOHS(ti->ti_urp); /* * Locate pcb for segment. */ findpcb: inp = in_pcblookup_connect(&tcbtable, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport); if (inp == 0) { ++tcpstat.tcps_pcbhashmiss; inp = in_pcblookup_bind(&tcbtable, ti->ti_dst, ti->ti_dport); if (inp == 0) { ++tcpstat.tcps_noport; goto dropwithreset; } } /* * If the state is CLOSED (i.e., TCB does not exist) then * all data in the incoming segment is discarded. * If the TCB exists but is in CLOSED state, it is embryonic, * but should either do a listen or a connect soon. */ tp = intotcpcb(inp); if (tp == 0) goto dropwithreset; if (tp->t_state == TCPS_CLOSED) goto drop; /* Unscale the window into a 32-bit value. */ if ((tiflags & TH_SYN) == 0) tiwin = ti->ti_win << tp->snd_scale; else tiwin = ti->ti_win; so = inp->inp_socket; if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { if (so->so_options & SO_DEBUG) { ostate = tp->t_state; tcp_saveti = *ti; } if (so->so_options & SO_ACCEPTCONN) { if ((tiflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) { if (tiflags & TH_RST) { syn_cache_reset(ti); } else if ((tiflags & (TH_ACK|TH_SYN)) == (TH_ACK|TH_SYN)) { /* * Received a SYN,ACK. This should * never happen while we are in * LISTEN. Send an RST. */ goto badsyn; } else if (tiflags & TH_ACK) { so = syn_cache_get(so, m); if (so == NULL) { /* * We don't have a SYN for * this ACK; send an RST. */ goto badsyn; } else if (so == (struct socket *)(-1)) { /* * We were unable to create * the connection. If the * 3-way handshake was * completed, and RST has * been sent to the peer. * Since the mbuf might be * in use for the reply, * do not free it. */ m = NULL; } else { /* * We have created a * full-blown connection. */ inp = sotoinpcb(so); tp = intotcpcb(inp); tiwin <<= tp->snd_scale; goto after_listen; } } else { /* * None of RST, SYN or ACK was set. * This is an invalid packet for a * TCB in LISTEN state. Send a RST. */ goto badsyn; } } else { /* * Received a SYN. */ if (in_hosteq(ti->ti_src, ti->ti_dst) && ti->ti_sport == ti->ti_dport) { /* * LISTEN socket received a SYN * from itself? This can't possibly * be valid; drop the packet. */ tcpstat.tcps_badsyn++; goto drop; } /* * SYN looks ok; create compressed TCP * state for it. */ if (so->so_qlen <= so->so_qlimit && syn_cache_add(so, m, optp, optlen, &opti)) m = NULL; } goto drop; } } after_listen: #ifdef DIAGNOSTIC /* * Should not happen now that all embryonic connections * are handled with compressed state. */ if (tp->t_state == TCPS_LISTEN) panic("tcp_input: TCPS_LISTEN"); #endif /* * Segment received on connection. * Reset idle time and keep-alive timer. */ tp->t_idle = 0; if (TCPS_HAVEESTABLISHED(tp->t_state)) TCP_TIMER_ARM(tp, TCPT_KEEP, tcp_keepidle); /* * Process options. */ if (optp) tcp_dooptions(tp, optp, optlen, ti, &opti); /* * Header prediction: check for the two common cases * of a uni-directional data xfer. If the packet has * no control flags, is in-sequence, the window didn't * change and we're not retransmitting, it's a * candidate. If the length is zero and the ack moved * forward, we're the sender side of the xfer. Just * free the data acked & wake any higher level process * that was blocked waiting for space. If the length * is non-zero and the ack didn't move, we're the * receiver side. If we're getting packets in-order * (the reassembly queue is empty), add the data to * the socket buffer and note that we need a delayed ack. */ if (tp->t_state == TCPS_ESTABLISHED && (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && (!opti.ts_present || TSTMP_GEQ(opti.ts_val, tp->ts_recent)) && ti->ti_seq == tp->rcv_nxt && tiwin && tiwin == tp->snd_wnd && tp->snd_nxt == tp->snd_max) { /* * If last ACK falls within this segment's sequence numbers, * record the timestamp. */ if (opti.ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) && SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) { tp->ts_recent_age = tcp_now; tp->ts_recent = opti.ts_val; } if (ti->ti_len == 0) { if (SEQ_GT(ti->ti_ack, tp->snd_una) && SEQ_LEQ(ti->ti_ack, tp->snd_max) && tp->snd_cwnd >= tp->snd_wnd && tp->t_dupacks < tcprexmtthresh) { /* * this is a pure ack for outstanding data. */ ++tcpstat.tcps_predack; if (opti.ts_present) tcp_xmit_timer(tp, tcp_now-opti.ts_ecr+1); else if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) tcp_xmit_timer(tp, tp->t_rtt); acked = ti->ti_ack - tp->snd_una; tcpstat.tcps_rcvackpack++; tcpstat.tcps_rcvackbyte += acked; sbdrop(&so->so_snd, acked); tp->snd_una = ti->ti_ack; m_freem(m); /* * If all outstanding data are acked, stop * retransmit timer, otherwise restart timer * using current (possibly backed-off) value. * If process is waiting for space, * wakeup/selwakeup/signal. If data * are ready to send, let tcp_output * decide between more output or persist. */ if (tp->snd_una == tp->snd_max) TCP_TIMER_DISARM(tp, TCPT_REXMT); else if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); sowwakeup(so); if (so->so_snd.sb_cc) (void) tcp_output(tp); return; } } else if (ti->ti_ack == tp->snd_una && tp->segq.lh_first == NULL && ti->ti_len <= sbspace(&so->so_rcv)) { /* * this is a pure, in-sequence data packet * with nothing on the reassembly queue and * we have enough buffer space to take it. */ ++tcpstat.tcps_preddat; tp->rcv_nxt += ti->ti_len; tcpstat.tcps_rcvpack++; tcpstat.tcps_rcvbyte += ti->ti_len; /* * Drop TCP, IP headers and TCP options then add data * to socket buffer. */ m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); sbappend(&so->so_rcv, m); sorwakeup(so); TCP_SETUP_ACK(tp, ti); if (tp->t_flags & TF_ACKNOW) (void) tcp_output(tp); return; } } /* * Drop TCP, IP headers and TCP options. */ hdroptlen = sizeof(struct tcpiphdr) + off - sizeof(struct tcphdr); m->m_data += hdroptlen; m->m_len -= hdroptlen; /* * Calculate amount of space in receive window, * and then do TCP input processing. * Receive window is amount of space in rcv queue, * but not less than advertised window. */ { int win; win = sbspace(&so->so_rcv); if (win < 0) win = 0; tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); } switch (tp->t_state) { /* * If the state is SYN_SENT: * if seg contains an ACK, but not for our SYN, drop the input. * if seg contains a RST, then drop the connection. * if seg does not contain SYN, then drop it. * Otherwise this is an acceptable SYN segment * initialize tp->rcv_nxt and tp->irs * if seg contains ack then advance tp->snd_una * if SYN has been acked change to ESTABLISHED else SYN_RCVD state * arrange for segment to be acked (eventually) * continue processing rest of data/controls, beginning with URG */ case TCPS_SYN_SENT: if ((tiflags & TH_ACK) && (SEQ_LEQ(ti->ti_ack, tp->iss) || SEQ_GT(ti->ti_ack, tp->snd_max))) goto dropwithreset; if (tiflags & TH_RST) { if (tiflags & TH_ACK) tp = tcp_drop(tp, ECONNREFUSED); goto drop; } if ((tiflags & TH_SYN) == 0) goto drop; if (tiflags & TH_ACK) { tp->snd_una = ti->ti_ack; if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; } TCP_TIMER_DISARM(tp, TCPT_REXMT); tp->irs = ti->ti_seq; tcp_rcvseqinit(tp); tp->t_flags |= TF_ACKNOW; tcp_mss_from_peer(tp, opti.maxseg); /* * Initialize the initial congestion window. If we * had to retransmit the SYN, we must initialize cwnd * to 1 segment (i.e. the Loss Window). */ if (tp->t_flags & TF_SYN_REXMT) tp->snd_cwnd = tp->t_peermss; else tp->snd_cwnd = TCP_INITIAL_WINDOW(tcp_init_win, tp->t_peermss); tcp_rmx_rtt(tp); if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) { #ifdef ORIG tcpstat.tcps_connects++; soisconnected(so); #else /* ORIG */ soisconnected(so); tcpstat.tcps_connects++; #endif /* ORIG */ tcp_established(tp); /* Do window scaling on this connection? */ if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == (TF_RCVD_SCALE|TF_REQ_SCALE)) { tp->snd_scale = tp->requested_s_scale; tp->rcv_scale = tp->request_r_scale; } TCP_REASS_LOCK(tp); (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0); TCP_REASS_UNLOCK(tp); /* * if we didn't have to retransmit the SYN, * use its rtt as our initial srtt & rtt var. */ if (tp->t_rtt) tcp_xmit_timer(tp, tp->t_rtt); } else tp->t_state = TCPS_SYN_RECEIVED; /* * Advance ti->ti_seq to correspond to first data byte. * If data, trim to stay within window, * dropping FIN if necessary. */ ti->ti_seq++; if (ti->ti_len > tp->rcv_wnd) { todrop = ti->ti_len - tp->rcv_wnd; m_adj(m, -todrop); ti->ti_len = tp->rcv_wnd; tiflags &= ~TH_FIN; tcpstat.tcps_rcvpackafterwin++; tcpstat.tcps_rcvbyteafterwin += todrop; } tp->snd_wl1 = ti->ti_seq - 1; tp->rcv_up = ti->ti_seq; goto step6; /* * If the state is SYN_RECEIVED: * If seg contains an ACK, but not for our SYN, drop the input * and generate an RST. See page 36, rfc793 */ case TCPS_SYN_RECEIVED: if ((tiflags & TH_ACK) && (SEQ_LEQ(ti->ti_ack, tp->iss) || SEQ_GT(ti->ti_ack, tp->snd_max))) goto dropwithreset; break; } /* * States other than LISTEN or SYN_SENT. * First check timestamp, if present. * Then check that at least some bytes of segment are within * receive window. If segment begins before rcv_nxt, * drop leading data (and SYN); if nothing left, just ack. * * RFC 1323 PAWS: If we have a timestamp reply on this segment * and it's less than ts_recent, drop it. */ if (opti.ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent && TSTMP_LT(opti.ts_val, tp->ts_recent)) { /* Check to see if ts_recent is over 24 days old. */ if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) { /* * Invalidate ts_recent. If this segment updates * ts_recent, the age will be reset later and ts_recent * will get a valid value. If it does not, setting * ts_recent to zero will at least satisfy the * requirement that zero be placed in the timestamp * echo reply when ts_recent isn't valid. The * age isn't reset until we get a valid ts_recent * because we don't want out-of-order segments to be * dropped when ts_recent is old. */ tp->ts_recent = 0; } else { tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += ti->ti_len; tcpstat.tcps_pawsdrop++; goto dropafterack; } } todrop = tp->rcv_nxt - ti->ti_seq; if (todrop > 0) { if (tiflags & TH_SYN) { tiflags &= ~TH_SYN; ti->ti_seq++; if (ti->ti_urp > 1) ti->ti_urp--; else { tiflags &= ~TH_URG; ti->ti_urp = 0; } todrop--; } if (todrop > ti->ti_len || (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) { /* * Any valid FIN must be to the left of the window. * At this point the FIN must be a duplicate or * out of sequence; drop it. */ tiflags &= ~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 = ti->ti_len; tcpstat.tcps_rcvdupbyte += todrop; tcpstat.tcps_rcvduppack++; } else { tcpstat.tcps_rcvpartduppack++; tcpstat.tcps_rcvpartdupbyte += todrop; } m_adj(m, todrop); ti->ti_seq += todrop; ti->ti_len -= todrop; if (ti->ti_urp > todrop) ti->ti_urp -= todrop; else { tiflags &= ~TH_URG; ti->ti_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 && ti->ti_len) { tp = tcp_close(tp); tcpstat.tcps_rcvafterclose++; goto dropwithreset; } /* * If segment ends after window, drop trailing data * (and PUSH and FIN); if nothing left, just ACK. */ todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); if (todrop > 0) { tcpstat.tcps_rcvpackafterwin++; if (todrop >= ti->ti_len) { tcpstat.tcps_rcvbyteafterwin += ti->ti_len; /* * If a new connection request is received * while in TIME_WAIT, drop the old connection * and start over if the sequence numbers * are above the previous ones. */ if (tiflags & TH_SYN && tp->t_state == TCPS_TIME_WAIT && SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { iss = tcp_new_iss(tp, sizeof(struct tcpcb), tp->snd_nxt); tp = tcp_close(tp); /* * We have already advanced the mbuf * pointers past the IP+TCP headers and * options. Restore those pointers before * attempting to use the TCP header again. */ m->m_data -= hdroptlen; m->m_len += hdroptlen; 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 && ti->ti_seq == tp->rcv_nxt) { tp->t_flags |= TF_ACKNOW; tcpstat.tcps_rcvwinprobe++; } else goto dropafterack; } else tcpstat.tcps_rcvbyteafterwin += todrop; m_adj(m, -todrop); ti->ti_len -= todrop; tiflags &= ~(TH_PUSH|TH_FIN); } /* * If last ACK falls within this segment's sequence numbers, * and the timestamp is newer, record it. */ if (opti.ts_present && TSTMP_GEQ(opti.ts_val, tp->ts_recent) && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) && SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len + ((tiflags & (TH_SYN|TH_FIN)) != 0))) { tp->ts_recent_age = tcp_now; tp->ts_recent = opti.ts_val; } /* * If the RST bit is set examine the state: * SYN_RECEIVED STATE: * If passive open, return to LISTEN state. * If active open, inform user that connection was refused. * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: * Inform user that connection was reset, and close tcb. * CLOSING, LAST_ACK, TIME_WAIT STATES * Close the tcb. */ if (tiflags&TH_RST) 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); goto drop; case TCPS_CLOSING: case TCPS_LAST_ACK: case TCPS_TIME_WAIT: tp = tcp_close(tp); goto drop; } /* * If a SYN is in the window, then this is an * error and we send an RST and drop the connection. */ if (tiflags & TH_SYN) { tp = tcp_drop(tp, ECONNRESET); goto dropwithreset; } /* * If the ACK bit is off we drop the segment and return. */ if ((tiflags & TH_ACK) == 0) goto drop; /* * Ack processing. */ switch (tp->t_state) { /* * In SYN_RECEIVED state if the ack ACKs our SYN then enter * ESTABLISHED state and continue processing, otherwise * send an RST. */ case TCPS_SYN_RECEIVED: if (SEQ_GT(tp->snd_una, ti->ti_ack) || SEQ_GT(ti->ti_ack, tp->snd_max)) goto dropwithreset; tcpstat.tcps_connects++; soisconnected(so); tcp_established(tp); /* Do window scaling? */ if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == (TF_RCVD_SCALE|TF_REQ_SCALE)) { tp->snd_scale = tp->requested_s_scale; tp->rcv_scale = tp->request_r_scale; } TCP_REASS_LOCK(tp); (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0); TCP_REASS_UNLOCK(tp); tp->snd_wl1 = ti->ti_seq - 1; /* fall into ... */ /* * In ESTABLISHED state: drop duplicate ACKs; ACK out of range * ACKs. If the ack is in the range * tp->snd_una < ti->ti_ack <= tp->snd_max * then advance tp->snd_una to ti->ti_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(ti->ti_ack, tp->snd_una)) { if (ti->ti_len == 0 && tiwin == tp->snd_wnd) { tcpstat.tcps_rcvdupack++; /* * If we have outstanding data (other than * a window probe), this is a completely * duplicate ack (ie, window info didn't * change), the ack is the biggest we've * seen and we've seen exactly our rexmt * threshhold of them, assume a packet * has been dropped and retransmit it. * Kludge snd_nxt & the congestion * window so we send only this one * packet. * * We know we're losing at the current * window size so do congestion avoidance * (set ssthresh to half the current window * and pull our congestion window back to * the new ssthresh). * * Dup acks mean that packets have left the * network (they're now cached at the receiver) * so bump cwnd by the amount in the receiver * to keep a constant cwnd packets in the * network. */ if (TCP_TIMER_ISARMED(tp, TCPT_REXMT) == 0 || ti->ti_ack != tp->snd_una) tp->t_dupacks = 0; else if (++tp->t_dupacks == tcprexmtthresh) { tcp_seq onxt = tp->snd_nxt; u_int win = min(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_segsz; if (SEQ_LT(ti->ti_ack, tp->snd_recover)) { /* * False fast retransmit after * timeout. Do not cut window. */ tp->snd_cwnd += tp->t_segsz; tp->t_dupacks = 0; (void) tcp_output(tp); goto drop; } if (win < 2) win = 2; tp->snd_ssthresh = win * tp->t_segsz; tp->snd_recover = tp->snd_max; TCP_TIMER_DISARM(tp, TCPT_REXMT); tp->t_rtt = 0; tp->snd_nxt = ti->ti_ack; tp->snd_cwnd = tp->t_segsz; (void) tcp_output(tp); tp->snd_cwnd = tp->snd_ssthresh + tp->t_segsz * tp->t_dupacks; if (SEQ_GT(onxt, tp->snd_nxt)) tp->snd_nxt = onxt; goto drop; } else if (tp->t_dupacks > tcprexmtthresh) { tp->snd_cwnd += tp->t_segsz; (void) tcp_output(tp); goto drop; } } else tp->t_dupacks = 0; break; } /* * If the congestion window was inflated to account * for the other side's cached packets, retract it. */ if (!tcp_do_newreno) { if (tp->t_dupacks >= tcprexmtthresh && tp->snd_cwnd > tp->snd_ssthresh) tp->snd_cwnd = tp->snd_ssthresh; tp->t_dupacks = 0; } else if (tp->t_dupacks >= tcprexmtthresh && !tcp_newreno(tp, ti)) { tp->snd_cwnd = tp->snd_ssthresh; /* * Window inflation should have left us with approx. * snd_ssthresh outstanding data. But in case we * would be inclined to send a burst, better to do * it via the slow start mechanism. */ if (SEQ_SUB(tp->snd_max, ti->ti_ack) < tp->snd_ssthresh) tp->snd_cwnd = SEQ_SUB(tp->snd_max, ti->ti_ack) + tp->t_segsz; tp->t_dupacks = 0; } if (SEQ_GT(ti->ti_ack, tp->snd_max)) { tcpstat.tcps_rcvacktoomuch++; goto dropafterack; } acked = ti->ti_ack - tp->snd_una; tcpstat.tcps_rcvackpack++; tcpstat.tcps_rcvackbyte += acked; /* * If we have a timestamp reply, update smoothed * round trip time. If no timestamp is present but * transmit timer is running and timed sequence * number was acked, update smoothed round trip time. * Since we now have an rtt measurement, cancel the * timer backoff (cf., Phil Karn's retransmit alg.). * Recompute the initial retransmit timer. */ if (opti.ts_present) tcp_xmit_timer(tp, tcp_now - opti.ts_ecr + 1); else if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) tcp_xmit_timer(tp,tp->t_rtt); /* * 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 (ti->ti_ack == tp->snd_max) { TCP_TIMER_DISARM(tp, TCPT_REXMT); needoutput = 1; } else if (TCP_TIMER_ISARMED(tp, TCPT_PERSIST) == 0) TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); /* * When new data is acked, open the congestion window. * If the window gives us less than ssthresh packets * in flight, open exponentially (segsz per packet). * Otherwise open linearly: segsz per window * (segsz^2 / cwnd per packet), plus a constant * fraction of a packet (segsz/8) to help larger windows * open quickly enough. */ { register u_int cw = tp->snd_cwnd; register u_int incr = tp->t_segsz; if (cw > tp->snd_ssthresh) incr = incr * incr / cw; if (!tcp_do_newreno || SEQ_GEQ(ti->ti_ack, tp->snd_recover)) tp->snd_cwnd = min(cw + incr,TCP_MAXWIN<snd_scale); } if (acked > so->so_snd.sb_cc) { tp->snd_wnd -= so->so_snd.sb_cc; sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); ourfinisacked = 1; } else { sbdrop(&so->so_snd, acked); tp->snd_wnd -= acked; ourfinisacked = 0; } sowwakeup(so); tp->snd_una = ti->ti_ack; if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; switch (tp->t_state) { /* * In FIN_WAIT_1 STATE in addition to the processing * for the ESTABLISHED state if our FIN is now acknowledged * then enter FIN_WAIT_2. */ case TCPS_FIN_WAIT_1: if (ourfinisacked) { #ifdef ORIG /* * If we can't receive any more * data, then closing user can proceed. * Starting the timer is contrary to the * specification, but if we don't get a FIN * we'll hang forever. */ if (so->so_state & SS_CANTRCVMORE) { soisdisconnected(so); if (tcp_maxidle > 0) TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_maxidle); } tp->t_state = TCPS_FIN_WAIT_2; #else /* ORIG */ tp->t_state = TCPS_FIN_WAIT_2; if (so->so_state & SS_CANTRCVMORE) { soisdisconnected(so); if (tcp_maxidle > 0) TCP_TIMER_ARM(tp, TCPT_2MSL, tcp_maxidle); } #endif /* ORIG */ } break; /* * In CLOSING STATE in addition to the processing for * the ESTABLISHED state if the ACK acknowledges our FIN * then enter the TIME-WAIT state, otherwise ignore * the segment. */ case TCPS_CLOSING: if (ourfinisacked) { tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * TCPTV_MSL); soisdisconnected(so); } break; /* * In LAST_ACK, we may still be waiting for data to drain * and/or to be acked, as well as for the ack of our FIN. * If our FIN is now acknowledged, delete the TCB, * enter the closed state and return. */ case TCPS_LAST_ACK: if (ourfinisacked) { tp = tcp_close(tp); goto drop; } break; /* * In TIME_WAIT state the only thing that should arrive * is a retransmission of the remote FIN. Acknowledge * it and restart the finack timer. */ case TCPS_TIME_WAIT: TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * TCPTV_MSL); goto dropafterack; } } step6: /* * Update window information. * Don't look at window if no ACK: TAC's send garbage on first SYN. */ if ((tiflags & TH_ACK) && (SEQ_LT(tp->snd_wl1, ti->ti_seq) || (tp->snd_wl1 == ti->ti_seq && SEQ_LT(tp->snd_wl2, ti->ti_ack)) || (tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))) { /* keep track of pure window updates */ if (ti->ti_len == 0 && tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd) tcpstat.tcps_rcvwinupd++; tp->snd_wnd = tiwin; tp->snd_wl1 = ti->ti_seq; tp->snd_wl2 = ti->ti_ack; if (tp->snd_wnd > tp->max_sndwnd) tp->max_sndwnd = tp->snd_wnd; needoutput = 1; } /* * Process segments with URG. */ if ((tiflags & TH_URG) && ti->ti_urp && TCPS_HAVERCVDFIN(tp->t_state) == 0) { /* * This is a kludge, but if we receive and accept * random urgent pointers, we'll crash in * soreceive. It's hard to imagine someone * actually wanting to send this much urgent data. */ if (ti->ti_urp + so->so_rcv.sb_cc > sb_max) { ti->ti_urp = 0; /* XXX */ tiflags &= ~TH_URG; /* XXX */ goto dodata; /* XXX */ } /* * If this segment advances the known urgent pointer, * then mark the data stream. This should not happen * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since * a FIN has been received from the remote side. * In these states we ignore the URG. * * According to RFC961 (Assigned Protocols), * the urgent pointer points to the last octet * of urgent data. We continue, however, * to consider it to indicate the first octet * of data past the urgent section as the original * spec states (in one of two places). */ if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { tp->rcv_up = ti->ti_seq + ti->ti_urp; so->so_oobmark = so->so_rcv.sb_cc + (tp->rcv_up - tp->rcv_nxt) - 1; if (so->so_oobmark == 0) so->so_state |= SS_RCVATMARK; sohasoutofband(so); tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); } /* * Remove out of band data so doesn't get presented to user. * This can happen independent of advancing the URG pointer, * but if two URG's are pending at once, some out-of-band * data may creep in... ick. */ if (ti->ti_urp <= (u_int16_t) ti->ti_len #ifdef SO_OOBINLINE && (so->so_options & SO_OOBINLINE) == 0 #endif ) tcp_pulloutofband(so, ti, m); } 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 ((ti->ti_len || (tiflags & TH_FIN)) && TCPS_HAVERCVDFIN(tp->t_state) == 0) { TCP_REASS(tp, ti, m, so, tiflags); /* * Note the amount of data that peer has sent into * our window, in order to estimate the sender's * buffer size. */ len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); } else { m_freem(m); tiflags &= ~TH_FIN; } /* * If FIN is received ACK the FIN and let the user know * that the connection is closing. Ignore a FIN received before * the connection is fully established. */ if ((tiflags & TH_FIN) && TCPS_HAVEESTABLISHED(tp->t_state)) { if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { socantrcvmore(so); tp->t_flags |= TF_ACKNOW; tp->rcv_nxt++; } switch (tp->t_state) { /* * In ESTABLISHED STATE enter the CLOSE_WAIT state. */ case TCPS_ESTABLISHED: tp->t_state = TCPS_CLOSE_WAIT; break; /* * If still in FIN_WAIT_1 STATE FIN has not been acked so * enter the CLOSING state. */ case TCPS_FIN_WAIT_1: tp->t_state = TCPS_CLOSING; break; /* * In FIN_WAIT_2 state enter the TIME_WAIT state, * starting the time-wait timer, turning off the other * standard timers. */ case TCPS_FIN_WAIT_2: tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * TCPTV_MSL); soisdisconnected(so); break; /* * In TIME_WAIT state restart the 2 MSL time_wait timer. */ case TCPS_TIME_WAIT: TCP_TIMER_ARM(tp, TCPT_2MSL, 2 * TCPTV_MSL); break; } } if (so->so_options & SO_DEBUG) tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); /* * Return any desired output. */ if (needoutput || (tp->t_flags & TF_ACKNOW)) (void) tcp_output(tp); return; badsyn: /* * Received a bad SYN. Increment counters and dropwithreset. */ tcpstat.tcps_badsyn++; tp = NULL; goto dropwithreset; dropafterack: /* * Generate an ACK dropping incoming segment if it occupies * sequence space, where the ACK reflects our state. */ if (tiflags & TH_RST) goto drop; m_freem(m); tp->t_flags |= TF_ACKNOW; (void) tcp_output(tp); return; 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 ((tiflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST) || IN_MULTICAST(ti->ti_dst.s_addr)) goto drop; if (tiflags & TH_ACK) (void)tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST); else { if (tiflags & TH_SYN) ti->ti_len++; (void)tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0, TH_RST|TH_ACK); } return; drop: /* * Drop space held by incoming segment and return. */ if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); m_freem(m); return; } void tcp_dooptions(tp, cp, cnt, ti, oi) struct tcpcb *tp; u_char *cp; int cnt; struct tcpiphdr *ti; struct tcp_opt_info *oi; { u_int16_t mss; int opt, optlen; for (; cnt > 0; cnt -= optlen, cp += optlen) { opt = cp[0]; if (opt == TCPOPT_EOL) break; if (opt == TCPOPT_NOP) optlen = 1; else { optlen = cp[1]; if (optlen <= 0) break; } switch (opt) { default: continue; case TCPOPT_MAXSEG: if (optlen != TCPOLEN_MAXSEG) continue; if (!(ti->ti_flags & TH_SYN)) continue; bcopy(cp + 2, &mss, sizeof(mss)); oi->maxseg = ntohs(mss); break; case TCPOPT_WINDOW: if (optlen != TCPOLEN_WINDOW) continue; if (!(ti->ti_flags & TH_SYN)) continue; tp->t_flags |= TF_RCVD_SCALE; tp->requested_s_scale = cp[2]; if (tp->requested_s_scale > TCP_MAX_WINSHIFT) { log(LOG_ERR, "TCP: invalid wscale %d from " "0x%08x, assuming %d\n", tp->requested_s_scale, ntohl(ti->ti_src.s_addr), TCP_MAX_WINSHIFT); tp->requested_s_scale = TCP_MAX_WINSHIFT; } break; case TCPOPT_TIMESTAMP: if (optlen != TCPOLEN_TIMESTAMP) continue; oi->ts_present = 1; bcopy(cp + 2, &oi->ts_val, sizeof(oi->ts_val)); NTOHL(oi->ts_val); bcopy(cp + 6, &oi->ts_ecr, sizeof(oi->ts_ecr)); NTOHL(oi->ts_ecr); /* * A timestamp received in a SYN makes * it ok to send timestamp requests and replies. */ if (ti->ti_flags & TH_SYN) { tp->t_flags |= TF_RCVD_TSTMP; tp->ts_recent = oi->ts_val; tp->ts_recent_age = tcp_now; } break; case TCPOPT_SACK_PERMITTED: if (optlen != TCPOLEN_SACK_PERMITTED) continue; if (!(ti->ti_flags & TH_SYN)) continue; tp->t_flags &= ~TF_CANT_TXSACK; break; case TCPOPT_SACK: if (tp->t_flags & TF_IGNR_RXSACK) continue; if (optlen % 8 != 2 || optlen < 10) continue; cp += 2; optlen -= 2; for (; optlen > 0; cp -= 8, optlen -= 8) { tcp_seq lwe, rwe; bcopy((char *)cp, (char *) &lwe, sizeof(lwe)); NTOHL(lwe); bcopy((char *)cp, (char *) &rwe, sizeof(rwe)); NTOHL(rwe); /* tcp_mark_sacked(tp, lwe, rwe); */ } break; } } } /* * Pull out of band byte out of a segment so * it doesn't appear in the user's data queue. * It is still reflected in the segment length for * sequencing purposes. */ void tcp_pulloutofband(so, ti, m) struct socket *so; struct tcpiphdr *ti; register struct mbuf *m; { int cnt = ti->ti_urp - 1; while (cnt >= 0) { if (m->m_len > cnt) { char *cp = mtod(m, caddr_t) + cnt; struct tcpcb *tp = sototcpcb(so); tp->t_iobc = *cp; tp->t_oobflags |= TCPOOB_HAVEDATA; bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); m->m_len--; return; } cnt -= m->m_len; m = m->m_next; if (m == 0) break; } panic("tcp_pulloutofband"); } /* * Collect new round-trip time estimate * and update averages and current timeout. */ void tcp_xmit_timer(tp, rtt) register struct tcpcb *tp; short rtt; { register short delta; short rttmin; tcpstat.tcps_rttupdated++; --rtt; if (tp->t_srtt != 0) { /* * srtt is stored as fixed point with 3 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 << 2) - (tp->t_srtt >> TCP_RTT_SHIFT); if ((tp->t_srtt += delta) <= 0) tp->t_srtt = 1 << 2; /* * 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 2 bits after the * binary point (scaled by 4). The following is * equivalent to rfc793 smoothing with an alpha of .75 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces * rfc793's wired-in beta. */ if (delta < 0) delta = -delta; delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT); if ((tp->t_rttvar += delta) <= 0) tp->t_rttvar = 1 << 2; } 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 + 2); tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT + 2 - 1); } tp->t_rtt = 0; tp->t_rxtshift = 0; /* * the retransmit should happen at rtt + 4 * rttvar. * Because of the way we do the smoothing, srtt and rttvar * will each average +1/2 tick of bias. When we compute * the retransmit timer, we want 1/2 tick of rounding and * 1 extra tick because of +-1/2 tick uncertainty in the * firing of the timer. The bias will give us exactly the * 1.5 tick we need. But, because the bias is * statistical, we have to test that we don't drop below * the minimum feasible timer (which is 2 ticks). */ if (tp->t_rttmin > rtt + 2) rttmin = tp->t_rttmin; else rttmin = rtt + 2; TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), rttmin, TCPTV_REXMTMAX); /* * We received an ack for a packet that wasn't retransmitted; * it is probably safe to discard any error indications we've * received recently. This isn't quite right, but close enough * for now (a route might have failed after we sent a segment, * and the return path might not be symmetrical). */ tp->t_softerror = 0; } /* * Checks for partial ack. If partial ack arrives, force the retransmission * of the next unacknowledged segment, do not clear tp->t_dupacks, and return * 1. By setting snd_nxt to ti_ack, this forces retransmission timer to * be started again. If the ack advances at least to tp->snd_recover, return 0. */ int tcp_newreno(tp, ti) struct tcpcb *tp; struct tcpiphdr *ti; { if (SEQ_LT(ti->ti_ack, tp->snd_recover)) { tcp_seq onxt = tp->snd_nxt; tcp_seq ouna = tp->snd_una; /* Haven't updated snd_una yet*/ u_long ocwnd = tp->snd_cwnd; TCP_TIMER_DISARM(tp, TCPT_REXMT); tp->t_rtt = 0; tp->snd_nxt = ti->ti_ack; tp->snd_cwnd = tp->t_segsz; tp->snd_una = ti->ti_ack; (void) tcp_output(tp); tp->snd_cwnd = ocwnd; tp->snd_una = ouna; if (SEQ_GT(onxt, tp->snd_nxt)) tp->snd_nxt = onxt; /* * Partial window deflation. Relies on fact that tp->snd_una * not updated yet. */ tp->snd_cwnd -= (ti->ti_ack - tp->snd_una - tp->t_segsz); return 1; } return 0; } /* * TCP compressed state engine. Currently used to hold compressed * state for SYN_RECEIVED. */ u_long syn_cache_count; u_int32_t syn_hash1, syn_hash2; #define SYN_HASH(sa, sp, dp) \ ((((sa)->s_addr^syn_hash1)*(((((u_int32_t)(dp))<<16) + \ ((u_int32_t)(sp)))^syn_hash2))) LIST_HEAD(, syn_cache_head) tcp_syn_cache_queue; #define SYN_CACHE_RM(sc, scp) \ do { \ TAILQ_REMOVE(&(scp)->sch_queue, (sc), sc_queue); \ if (--(scp)->sch_length == 0) \ LIST_REMOVE((scp), sch_headq); \ syn_cache_count--; \ } while (0) #define SYN_CACHE_PUT(sc) \ do { \ if ((sc)->sc_ipopts) \ (void) m_free((sc)->sc_ipopts); \ if ((sc)->sc_route.ro_rt != NULL) \ RTFREE((sc)->sc_route.ro_rt); \ pool_put(&syn_cache_pool, (sc)); \ } while (0) struct pool syn_cache_pool; void syn_cache_init() { int i; /* Initialize the hash bucket queues. */ for (i = 0; i < tcp_syn_cache_size; i++) TAILQ_INIT(&tcp_syn_cache[i].sch_queue); /* Initialize the active hash bucket cache. */ LIST_INIT(&tcp_syn_cache_queue); /* Initialize the syn cache pool. */ pool_init(&syn_cache_pool, sizeof(struct syn_cache), 0, 0, 0, "synpl", 0, NULL, NULL, M_PCB); } void syn_cache_insert(sc) struct syn_cache *sc; { struct syn_cache_head *scp, *scp2, *sce; struct syn_cache *sc2; int s; /* * If there are no entries in the hash table, reinitialize * the hash secrets. */ if (syn_cache_count == 0) { struct timeval tv; microtime(&tv); syn_hash1 = random() ^ (u_long)≻ syn_hash2 = random() ^ tv.tv_usec; } sc->sc_hash = SYN_HASH(&sc->sc_src, sc->sc_sport, sc->sc_dport); scp = &tcp_syn_cache[sc->sc_hash % tcp_syn_cache_size]; /* * Make sure that we don't overflow the per-bucket * limit or the total cache size limit. */ s = splsoftnet(); if (scp->sch_length >= tcp_syn_bucket_limit) { tcpstat.tcps_sc_bucketoverflow++; /* * The bucket is full. Toss the first (i.e. oldest) * element in this bucket. */ sc2 = TAILQ_FIRST(&scp->sch_queue); SYN_CACHE_RM(sc2, scp); SYN_CACHE_PUT(sc2); } else if (syn_cache_count >= tcp_syn_cache_limit) { tcpstat.tcps_sc_overflowed++; /* * The cache is full. Toss the first (i.e. oldest) * element in the first non-empty bucket we can find. */ scp2 = scp; if (TAILQ_FIRST(&scp2->sch_queue) == NULL) { sce = &tcp_syn_cache[tcp_syn_cache_size]; for (++scp2; scp2 != scp; scp2++) { if (scp2 >= sce) scp2 = &tcp_syn_cache[0]; if (TAILQ_FIRST(&scp2->sch_queue) != NULL) break; } } sc2 = TAILQ_FIRST(&scp2->sch_queue); if (sc2 == NULL) { SYN_CACHE_PUT(sc); return; } SYN_CACHE_RM(sc2, scp2); SYN_CACHE_PUT(sc2); } /* Set entry's timer. */ PRT_SLOW_ARM(sc->sc_timer, tcp_syn_cache_timeo); /* Put it into the bucket. */ TAILQ_INSERT_TAIL(&scp->sch_queue, sc, sc_queue); if (++scp->sch_length == 1) LIST_INSERT_HEAD(&tcp_syn_cache_queue, scp, sch_headq); syn_cache_count++; tcpstat.tcps_sc_added++; splx(s); } /* * Walk down the cache list, looking for expired entries in each bucket. */ void syn_cache_timer() { struct syn_cache_head *scp, *nscp; struct syn_cache *sc, *nsc; int s; s = splsoftnet(); for (scp = LIST_FIRST(&tcp_syn_cache_queue); scp != NULL; scp = nscp) { #ifdef DIAGNOSTIC if (TAILQ_FIRST(&scp->sch_queue) == NULL) panic("syn_cache_timer: queue inconsistency"); #endif nscp = LIST_NEXT(scp, sch_headq); for (sc = TAILQ_FIRST(&scp->sch_queue); sc != NULL && PRT_SLOW_ISEXPIRED(sc->sc_timer); sc = nsc) { nsc = TAILQ_NEXT(sc, sc_queue); tcpstat.tcps_sc_timed_out++; SYN_CACHE_RM(sc, scp); SYN_CACHE_PUT(sc); } } splx(s); } /* * Find an entry in the syn cache. */ struct syn_cache * syn_cache_lookup(ti, headp) struct tcpiphdr *ti; struct syn_cache_head **headp; { struct syn_cache *sc; struct syn_cache_head *scp; u_int32_t hash; int s; hash = SYN_HASH(&ti->ti_src, ti->ti_sport, ti->ti_dport); scp = &tcp_syn_cache[hash % tcp_syn_cache_size]; *headp = scp; s = splsoftnet(); for (sc = TAILQ_FIRST(&scp->sch_queue); sc != NULL; sc = TAILQ_NEXT(sc, sc_queue)) { if (sc->sc_hash != hash) continue; if (sc->sc_src.s_addr == ti->ti_src.s_addr && sc->sc_sport == ti->ti_sport && sc->sc_dport == ti->ti_dport && sc->sc_dst.s_addr == ti->ti_dst.s_addr) { splx(s); return (sc); } } splx(s); return (NULL); } /* * This function gets called when we receive an ACK for a * socket in the LISTEN state. We look up the connection * in the syn cache, and if its there, we pull it out of * the cache and turn it into a full-blown connection in * the SYN-RECEIVED state. * * The return values may not be immediately obvious, and their effects * can be subtle, so here they are: * * NULL SYN was not found in cache; caller should drop the * packet and send an RST. * * -1 We were unable to create the new connection, and are * aborting it. An ACK,RST is being sent to the peer * (unless we got screwey sequence numbners; see below), * because the 3-way handshake has been completed. Caller * should not free the mbuf, since we may be using it. If * we are not, we will free it. * * Otherwise, the return value is a pointer to the new socket * associated with the connection. */ struct socket * syn_cache_get(so, m) struct socket *so; struct mbuf *m; { struct syn_cache *sc; struct syn_cache_head *scp; register struct inpcb *inp; register struct tcpcb *tp = 0; register struct tcpiphdr *ti; struct sockaddr_in *sin; struct mbuf *am; long win; int s; ti = mtod(m, struct tcpiphdr *); s = splsoftnet(); if ((sc = syn_cache_lookup(ti, &scp)) == NULL) { splx(s); return (NULL); } win = sbspace(&so->so_rcv); if (win > TCP_MAXWIN) win = TCP_MAXWIN; /* * Verify the sequence and ack numbers. Try getting the correct * response again. */ if ((ti->ti_ack != sc->sc_iss + 1) || SEQ_LEQ(ti->ti_seq, sc->sc_irs) || SEQ_GT(ti->ti_seq, sc->sc_irs + 1 + win)) { (void) syn_cache_respond(sc, m, win, 0); splx(s); return ((struct socket *)(-1)); } /* Remove this cache entry */ SYN_CACHE_RM(sc, scp); splx(s); /* * Ok, create the full blown connection, and set things up * as they would have been set up if we had created the * connection when the SYN arrived. If we can't create * the connection, abort it. */ so = sonewconn(so, SS_ISCONNECTED); if (so == NULL) goto resetandabort; inp = sotoinpcb(so); inp->inp_laddr = sc->sc_dst; inp->inp_lport = sc->sc_dport; in_pcbstate(inp, INP_BOUND); inp->inp_options = ip_srcroute(); if (inp->inp_options == NULL) { inp->inp_options = sc->sc_ipopts; sc->sc_ipopts = NULL; } /* * Give the new socket our cached route reference. */ inp->inp_route = sc->sc_route; /* struct assignment */ sc->sc_route.ro_rt = NULL; am = m_get(M_DONTWAIT, MT_SONAME); /* XXX */ if (am == NULL) goto resetandabort; am->m_len = sizeof(struct sockaddr_in); sin = mtod(am, struct sockaddr_in *); sin->sin_family = AF_INET; sin->sin_len = sizeof(*sin); sin->sin_addr = sc->sc_src; sin->sin_port = sc->sc_sport; bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); if (in_pcbconnect(inp, am)) { (void) m_free(am); goto resetandabort; } (void) m_free(am); tp = intotcpcb(inp); if (sc->sc_request_r_scale != 15) { tp->requested_s_scale = sc->sc_requested_s_scale; tp->request_r_scale = sc->sc_request_r_scale; tp->snd_scale = sc->sc_requested_s_scale; tp->rcv_scale = sc->sc_request_r_scale; tp->t_flags |= TF_RCVD_SCALE; } if (sc->sc_flags & SCF_TIMESTAMP) tp->t_flags |= TF_RCVD_TSTMP; tp->t_template = tcp_template(tp); if (tp->t_template == 0) { tp = tcp_drop(tp, ENOBUFS); /* destroys socket */ so = NULL; m_freem(m); goto abort; } tp->iss = sc->sc_iss; tp->irs = sc->sc_irs; tcp_sendseqinit(tp); tcp_rcvseqinit(tp); tp->t_state = TCPS_SYN_RECEIVED; TCP_TIMER_ARM(tp, TCPT_KEEP, TCPTV_KEEP_INIT); tcpstat.tcps_accepts++; /* Initialize tp->t_ourmss before we deal with the peer's! */ tp->t_ourmss = sc->sc_ourmaxseg; tcp_mss_from_peer(tp, sc->sc_peermaxseg); /* * Initialize the initial congestion window. If we * had to retransmit the SYN,ACK, we must initialize cwnd * to 1 segment (i.e. the Loss Window). */ if (sc->sc_rexmt_count) tp->snd_cwnd = tp->t_peermss; else tp->snd_cwnd = TCP_INITIAL_WINDOW(tcp_init_win, tp->t_peermss); tcp_rmx_rtt(tp); tp->snd_wl1 = sc->sc_irs; tp->rcv_up = sc->sc_irs + 1; /* * This is what whould have happened in tcp_ouput() when * the SYN,ACK was sent. */ tp->snd_up = tp->snd_una; tp->snd_max = tp->snd_nxt = tp->iss+1; TCP_TIMER_ARM(tp, TCPT_REXMT, tp->t_rxtcur); if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) tp->rcv_adv = tp->rcv_nxt + win; tp->last_ack_sent = tp->rcv_nxt; tcpstat.tcps_sc_completed++; SYN_CACHE_PUT(sc); return (so); resetandabort: (void) tcp_respond(NULL, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0, TH_RST|TH_ACK); abort: if (so != NULL) (void) soabort(so); SYN_CACHE_PUT(sc); tcpstat.tcps_sc_aborted++; return ((struct socket *)(-1)); } /* * This function is called when we get a RST for a * non-existant connection, so that we can see if the * connection is in the syn cache. If it is, zap it. */ void syn_cache_reset(ti) register struct tcpiphdr *ti; { struct syn_cache *sc; struct syn_cache_head *scp; int s = splsoftnet(); if ((sc = syn_cache_lookup(ti, &scp)) == NULL) { splx(s); return; } if (SEQ_LT(ti->ti_seq,sc->sc_irs) || SEQ_GT(ti->ti_seq, sc->sc_irs+1)) { splx(s); return; } SYN_CACHE_RM(sc, scp); splx(s); tcpstat.tcps_sc_reset++; SYN_CACHE_PUT(sc); } void syn_cache_unreach(ip, th) struct ip *ip; struct tcphdr *th; { struct syn_cache *sc; struct syn_cache_head *scp; struct tcpiphdr ti2; int s; ti2.ti_src.s_addr = ip->ip_dst.s_addr; ti2.ti_dst.s_addr = ip->ip_src.s_addr; ti2.ti_sport = th->th_dport; ti2.ti_dport = th->th_sport; s = splsoftnet(); if ((sc = syn_cache_lookup(&ti2, &scp)) == NULL) { splx(s); return; } /* If the sequence number != sc_iss, then it's a bogus ICMP msg */ if (ntohl (th->th_seq) != sc->sc_iss) { splx(s); return; } /* * If we've rertransmitted 3 times and this is our second error, * we remove the entry. Otherwise, we allow it to continue on. * This prevents us from incorrectly nuking an entry during a * spurious network outage. * * See tcp_notify(). */ if ((sc->sc_flags & SCF_UNREACH) == 0 || sc->sc_rexmt_count < 3) { sc->sc_flags |= SCF_UNREACH; splx(s); return; } SYN_CACHE_RM(sc, scp); splx(s); tcpstat.tcps_sc_unreach++; SYN_CACHE_PUT(sc); } /* * Given a LISTEN socket and an inbound SYN request, add * this to the syn cache, and send back a segment: * * to the source. * * IMPORTANT NOTE: We do _NOT_ ACK data that might accompany the SYN. * Doing so would require that we hold onto the data and deliver it * to the application. However, if we are the target of a SYN-flood * DoS attack, an attacker could send data which would eventually * consume all available buffer space if it were ACKed. By not ACKing * the data, we avoid this DoS scenario. */ int syn_cache_add(so, m, optp, optlen, oi) struct socket *so; struct mbuf *m; u_char *optp; int optlen; struct tcp_opt_info *oi; { register struct tcpiphdr *ti; struct tcpcb tb, *tp; long win; struct syn_cache *sc; struct syn_cache_head *scp; struct mbuf *ipopts; tp = sototcpcb(so); ti = mtod(m, struct tcpiphdr *); /* * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN * in_broadcast() should never return true on a received * packet with M_BCAST not set. */ if (m->m_flags & (M_BCAST|M_MCAST) || IN_MULTICAST(ti->ti_src.s_addr) || IN_MULTICAST(ti->ti_dst.s_addr)) return (0); /* * Initialize some local state. */ win = sbspace(&so->so_rcv); if (win > TCP_MAXWIN) win = TCP_MAXWIN; /* * Remember the IP options, if any. */ ipopts = ip_srcroute(); if (optp) { tb.t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; tcp_dooptions(&tb, optp, optlen, ti, oi); } else tb.t_flags = 0; /* * See if we already have an entry for this connection. * If we do, resend the SYN,ACK, and remember since the * initial congestion window must be initialized to 1 * segment when the connection completes. */ if ((sc = syn_cache_lookup(ti, &scp)) != NULL) { tcpstat.tcps_sc_dupesyn++; sc->sc_rexmt_count++; if (sc->sc_rexmt_count == 0) { /* * Eeek! We rolled the counter. Just set it * to the max value. This shouldn't ever happen, * but there's no real reason to panic here, since * the count doesn't have to be very precise. */ sc->sc_rexmt_count = USHRT_MAX; } if (ipopts) { /* * If we were remembering a previous source route, * forget it and use the new one we've been given. */ if (sc->sc_ipopts) (void) m_free(sc->sc_ipopts); sc->sc_ipopts = ipopts; } if (syn_cache_respond(sc, m, win, tb.ts_recent) == 0) { tcpstat.tcps_sndacks++; tcpstat.tcps_sndtotal++; } return (1); } sc = pool_get(&syn_cache_pool, PR_NOWAIT); if (sc == NULL) { if (ipopts) (void) m_free(ipopts); return (0); } /* * Fill in the cache, and put the necessary IP and TCP * options into the reply. */ memset(&sc->sc_route, 0, sizeof(sc->sc_route)); sc->sc_src.s_addr = ti->ti_src.s_addr; sc->sc_dst.s_addr = ti->ti_dst.s_addr; sc->sc_sport = ti->ti_sport; sc->sc_dport = ti->ti_dport; sc->sc_flags = 0; sc->sc_ipopts = ipopts; sc->sc_irs = ti->ti_seq; sc->sc_iss = tcp_new_iss(sc, sizeof(struct syn_cache), 0); sc->sc_peermaxseg = oi->maxseg; sc->sc_ourmaxseg = tcp_mss_to_advertise(m->m_flags & M_PKTHDR ? m->m_pkthdr.rcvif : NULL); if (tcp_do_rfc1323 && (tb.t_flags & TF_RCVD_TSTMP)) sc->sc_flags |= SCF_TIMESTAMP; if ((tb.t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == (TF_RCVD_SCALE|TF_REQ_SCALE)) { sc->sc_requested_s_scale = tb.requested_s_scale; sc->sc_request_r_scale = 0; while (sc->sc_request_r_scale < TCP_MAX_WINSHIFT && TCP_MAXWIN << sc->sc_request_r_scale < so->so_rcv.sb_hiwat) sc->sc_request_r_scale++; } else { sc->sc_requested_s_scale = 15; sc->sc_request_r_scale = 15; } if (syn_cache_respond(sc, m, win, tb.ts_recent) == 0) { syn_cache_insert(sc); tcpstat.tcps_sndacks++; tcpstat.tcps_sndtotal++; } else { SYN_CACHE_PUT(sc); tcpstat.tcps_sc_dropped++; } return (1); } int syn_cache_respond(sc, m, win, ts) struct syn_cache *sc; struct mbuf *m; long win; u_long ts; { struct route *ro = &sc->sc_route; struct rtentry *rt; struct sockaddr_in *dst; struct tcpiphdr *ti; u_int8_t *optp; int optlen, error; u_int16_t tlen; /* Compute the size of the TCP options. */ optlen = 4 + (sc->sc_request_r_scale != 15 ? 4 : 0) + ((sc->sc_flags & SCF_TIMESTAMP) ? TCPOLEN_TSTAMP_APPA : 0); tlen = sizeof(struct tcpiphdr) + optlen; /* * Create the IP+TCP header from scratch. Reuse the received mbuf * if possible. */ if (m != NULL) { m_freem(m->m_next); m->m_next = NULL; MRESETDATA(m); } else { MGETHDR(m, M_DONTWAIT, MT_DATA); if (m == NULL) return (ENOBUFS); } /* Fixup the mbuf. */ m->m_data += max_linkhdr; m->m_len = m->m_pkthdr.len = tlen; m->m_pkthdr.rcvif = NULL; ti = mtod(m, struct tcpiphdr *); memset(ti, 0, tlen); ti->ti_dst = sc->sc_src; ti->ti_src = sc->sc_dst; ti->ti_sport = sc->sc_dport; ti->ti_dport = sc->sc_sport; ti->ti_pr = IPPROTO_TCP; ti->ti_len = htons(tlen - sizeof(struct ip)); /* ti_x1 already 0'd */ ti->ti_seq = htonl(sc->sc_iss); ti->ti_ack = htonl(sc->sc_irs + 1); /* ti_x2 already 0 */ ti->ti_off = (sizeof(struct tcphdr) + optlen) >> 2; ti->ti_flags = TH_SYN|TH_ACK; ti->ti_win = htons(win); /* ti_sum already 0 */ /* ti_urp already 0 */ /* Tack on the TCP options. */ optp = (u_int8_t *)(ti + 1); *optp++ = TCPOPT_MAXSEG; *optp++ = 4; *optp++ = (sc->sc_ourmaxseg >> 8) & 0xff; *optp++ = sc->sc_ourmaxseg & 0xff; if (sc->sc_request_r_scale != 15) { *((u_int32_t *)optp) = htonl(TCPOPT_NOP << 24 | TCPOPT_WINDOW << 16 | TCPOLEN_WINDOW << 8 | sc->sc_request_r_scale); optp += 4; } if (sc->sc_flags & SCF_TIMESTAMP) { u_int32_t *lp = (u_int32_t *)(optp); /* Form timestamp option as shown in appendix A of RFC 1323. */ *lp++ = htonl(TCPOPT_TSTAMP_HDR); *lp++ = htonl(tcp_now); *lp = htonl(ts); optp += TCPOLEN_TSTAMP_APPA; } /* Compute the packet's checksum. */ ti->ti_sum = in_cksum(m, tlen); /* * Fill in some straggling IP bits. Note the stack expects * ip_len to be in host order, for convenience. */ ((struct ip *)ti)->ip_len = tlen; ((struct ip *)ti)->ip_ttl = ip_defttl; /* XXX tos? */ /* * If we're doing Path MTU discovery, we need to set DF unless * the route's MTU is locked. If we don't yet know the route, * look it up now. We will copy this reference to the inpcb * when we finish creating the connection. */ if ((rt = ro->ro_rt) == NULL || (rt->rt_flags & RTF_UP) == 0) { if (ro->ro_rt != NULL) { RTFREE(ro->ro_rt); ro->ro_rt = NULL; } dst = satosin(&ro->ro_dst); dst->sin_family = AF_INET; dst->sin_len = sizeof(*dst); dst->sin_addr = ti->ti_dst; rtalloc(ro); if ((rt = ro->ro_rt) == NULL) { m_freem(m); ipstat.ips_noroute++; return (EHOSTUNREACH); } } if (ip_mtudisc != 0 && (rt->rt_rmx.rmx_locks & RTV_MTU) == 0) ((struct ip *)ti)->ip_off |= IP_DF; /* ...and send it off! */ error = ip_output(m, sc->sc_ipopts, ro, 0, NULL); return (error); }