/* $OpenBSD: tcp_input.c,v 1.22 1998/11/25 05:44:36 millert Exp $ */ /* $NetBSD: tcp_input.c,v 1.23 1996/02/13 23:43:44 christos Exp $ */ /* * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994 * The Regents of the University of California. All rights reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, this list of conditions and the following disclaimer. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. 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 8.5 (Berkeley) 4/10/94 */ #ifndef TUBA_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 #include int tcprexmtthresh = 3; struct tcpiphdr tcp_saveti; int tcptv_keep_init = TCPTV_KEEP_INIT; extern u_long sb_max; #endif /* TUBA_INCLUDE */ #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) #ifdef TCPCOOKIE /* * Code originally by Matt Blaze and John Ioannidis. This code implements * a cookie-like extension for TCP. Adapted to OpenBSD by Angelos D. * Keromytis. */ #ifndef TCK_NFRIENDS #define TCK_NFRIENDS 16 #endif /* TCK_NFRIENDS */ static struct in_addr tck_friends[TCK_NFRIENDS]; static int tck_nfriends = 0; static int tck_initialized = 0; #define TCK_PORT 333 /* Unused port! */ static int tck_isafriend(struct in_addr f) { register int i; for (i = tck_nfriends - 1; i >= 0; i--) if (tck_friends[i].s_addr == f.s_addr) return 1; return 0; } static void tck_delat(int n) { int i; if ((n >= tck_nfriends) || (tck_nfriends == 0)) return; for (i = n + 1; i < tck_nfriends ; i++) tck_friends[i - 1] = tck_friends[i]; tck_nfriends--; } static void tck_addfriend(struct in_addr f) { #ifdef DEBUG_TCPCOOKIE printf("tck_addfriend: 0x%08x\n", ntohl(f.s_addr)); #endif /* DEBUG_TCPCOOKIE */ if (tck_isafriend(f)) return; if (tck_nfriends == TCK_NFRIENDS) tck_delat(0); tck_friends[tck_nfriends++] = f; } /* * static void * tck_delfriend(struct in_addr f) * { * int i; * * for (i = tck_nfriends - 1; i >= 0; i--) * if (tck_friends[i].s_addr == f.s_addr) * goto found1; * * return; * * found1: * tck_delat(i); * } */ static u_int32_t tck_makecookie(f) struct in_addr f; { static MD5_CTX ctx; u_int8_t buf[16]; MD5_CTX ctx2; if (tck_initialized == 0) { /* This only happens once per reboot */ tck_initialized = 1; get_random_bytes((void *) buf, 16); MD5Init(&ctx); MD5Update(&ctx, buf, 16); } ctx2 = ctx; MD5Update(&ctx2, (void *) &f, sizeof(f)); MD5Final(buf, &ctx2); /* This may not be necessary */ return ((buf[0] << 24) | (buf[1] << 16) | (buf[2] << 8) | buf[3]); } static int tck_chkcookie(ti) struct tcpiphdr *ti; { #ifdef DEBUG_TCPCOOKIE printf("tck_chkcookie: src = 0x%08x, cookie = 0x%08x, seq = 0x%08x, ack = 0x%08x\n", ntohl(ti->ti_src.s_addr), tck_makecookie(ti->ti_src), ti->ti_seq, ti->ti_ack); #endif /* DEBUG_TCPCOOKIE */ if (tck_makecookie(ti->ti_src) == ti->ti_seq) { /* seq in host order */ tck_addfriend(ti->ti_src); return 1; } return 0; } #endif /* TCPCOOKIE */ /* * 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) { \ if ((ti)->ti_seq == (tp)->rcv_nxt && \ (tp)->segq.lh_first == NULL && \ (tp)->t_state == TCPS_ESTABLISHED) { \ if ((ti)->ti_flags & TH_PUSH) \ tp->t_flags |= TF_ACKNOW; \ else \ tp->t_flags |= TF_DELACK; \ (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; \ } \ } #ifndef TUBA_INCLUDE int tcp_reass(tp, ti, m) register struct tcpcb *tp; register struct tcpiphdr *ti; struct mbuf *m; { register struct ipqent *p, *q, *nq, *tiqe; struct socket *so = tp->t_inpcb->inp_socket; int flags; /* * Call with ti==0 after become established to * force pre-ESTABLISHED data up to user socket. */ if (ti == 0) goto present; /* * Allocate a new queue entry, before we throw away any data. * If we can't, just drop the packet. XXX */ MALLOC(tiqe, struct ipqent *, sizeof (struct ipqent), M_IPQ, M_NOWAIT); if (tiqe == NULL) { tcpstat.tcps_rcvmemdrop++; m_freem(m); return (0); } /* * Find a segment which begins after this one does. */ for (p = NULL, q = tp->segq.lh_first; q != NULL; p = q, q = q->ipqe_q.le_next) if (SEQ_GT(q->ipqe_tcp->ti_seq, ti->ti_seq)) break; /* * If there is a preceding segment, it may provide some of * our data already. If so, drop the data from the incoming * segment. If it provides all of our data, drop us. */ if (p != NULL) { register struct tcpiphdr *phdr = p->ipqe_tcp; register int i; /* conversion to int (in i) handles seq wraparound */ i = phdr->ti_seq + phdr->ti_len - ti->ti_seq; if (i > 0) { if (i >= ti->ti_len) { tcpstat.tcps_rcvduppack++; tcpstat.tcps_rcvdupbyte += ti->ti_len; m_freem(m); FREE(tiqe, M_IPQ); return (0); } m_adj(m, i); ti->ti_len -= i; ti->ti_seq += i; } } tcpstat.tcps_rcvoopack++; tcpstat.tcps_rcvoobyte += ti->ti_len; /* * While we overlap succeeding segments trim them or, * if they are completely covered, dequeue them. */ for (; q != NULL; q = nq) { register struct tcpiphdr *qhdr = q->ipqe_tcp; register int i = (ti->ti_seq + ti->ti_len) - qhdr->ti_seq; if (i <= 0) break; if (i < qhdr->ti_len) { qhdr->ti_seq += i; qhdr->ti_len -= i; m_adj(q->ipqe_m, i); break; } nq = q->ipqe_q.le_next; m_freem(q->ipqe_m); LIST_REMOVE(q, ipqe_q); FREE(q, M_IPQ); } /* Insert the new fragment queue entry into place. */ tiqe->ipqe_m = m; tiqe->ipqe_tcp = ti; if (p == NULL) { LIST_INSERT_HEAD(&tp->segq, tiqe, ipqe_q); } else { LIST_INSERT_AFTER(p, tiqe, ipqe_q); } 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_tcp->ti_seq != tp->rcv_nxt) return (0); if (tp->t_state == TCPS_SYN_RECEIVED && q->ipqe_tcp->ti_len) return (0); do { tp->rcv_nxt += q->ipqe_tcp->ti_len; flags = q->ipqe_tcp->ti_flags & TH_FIN; nq = q->ipqe_q.le_next; LIST_REMOVE(q, ipqe_q); if (so->so_state & SS_CANTRCVMORE) m_freem(q->ipqe_m); else sbappend(&so->so_rcv, q->ipqe_m); FREE(q, M_IPQ); q = nq; } while (q != NULL && q->ipqe_tcp->ti_seq == tp->rcv_nxt); sorwakeup(so); return (flags); } /* * First check for a port-specific bomb. We do not want to drop half-opens * for other ports if this is the only port being bombed. We only check * the bottom 40 half open connections, to avoid wasting too much time. * * Or, otherwise it is more likely a generic syn bomb, so delete the oldest * half-open connection. */ void tcpdropoldhalfopen(avoidtp, port) struct tcpcb *avoidtp; u_int16_t port; { register struct inpcb *inp; register struct tcpcb *tp; int ncheck = 40; int s; s = splnet(); inp = tcbtable.inpt_queue.cqh_first; if (inp) /* XXX */ for (; inp != (struct inpcb *)&tcbtable.inpt_queue && --ncheck; inp = inp->inp_queue.cqe_prev) { if ((tp = (struct tcpcb *)inp->inp_ppcb) && tp != avoidtp && tp->t_state == TCPS_SYN_RECEIVED && port == inp->inp_lport) { tcp_close(tp); goto done; } } inp = tcbtable.inpt_queue.cqh_first; if (inp) /* XXX */ for (; inp != (struct inpcb *)&tcbtable.inpt_queue; inp = inp->inp_queue.cqe_prev) { if ((tp = (struct tcpcb *)inp->inp_ppcb) && tp != avoidtp && tp->t_state == TCPS_SYN_RECEIVED) { tcp_close(tp); goto done; } } done: splx(s); } /* * 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; register struct tcpcb *tp = 0; register int tiflags; struct socket *so = NULL; int todrop, acked, ourfinisacked, needoutput = 0; short ostate = 0; struct in_addr laddr; int dropsocket = 0; int iss = 0; u_long tiwin; u_int32_t ts_val, ts_ecr; int ts_present = 0; int iphlen; va_list ap; va_start(ap, m); iphlen = va_arg(ap, int); va_end(ap); tcpstat.tcps_rcvtotal++; /* * 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. */ tlen = ((struct ip *)ti)->ip_len; len = sizeof (struct ip) + tlen; bzero(ti->ti_x1, sizeof ti->ti_x1); ti->ti_len = (u_int16_t)tlen; HTONS(ti->ti_len); if ((ti->ti_sum = in_cksum(m, len)) != 0) { tcpstat.tcps_rcvbadsum++; goto drop; } #endif /* TUBA_INCLUDE */ /* * 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) { ts_present = 1; ts_val = ntohl(*(u_int32_t *)(optp + 4)); 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); #ifdef TCPCOOKIE /* * If this looks like a cookie response, check it. * If it is, the check routine also adds the source * of the packet to the friends list. */ if ((tiflags & TH_RST) && (ntohs(ti->ti_dport) == TCK_PORT)) if (tck_chkcookie(ti)) goto drop; /* RST is no longer needed */ #endif /* TCPCOOKIE */ /* * Locate pcb for segment. */ findpcb: inp = in_pcbhashlookup(&tcbtable, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport); if (inp == 0) { ++tcpstat.tcps_pcbhashmiss; inp = in_pcblookup(&tcbtable, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport, INPLOOKUP_WILDCARD); /* * 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 == 0) { ++tcpstat.tcps_noport; goto dropwithreset; } } 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) { struct socket *so1; so1 = sonewconn(so, 0); if (so1 == NULL) { tcpdropoldhalfopen(tp, ti->ti_dport); so1 = sonewconn(so, 0); if (so1 == NULL) goto drop; } so = so1; /* * This is ugly, but .... * * Mark socket as temporary until we're * committed to keeping it. The code at * ``drop'' and ``dropwithreset'' check the * flag dropsocket to see if the temporary * socket created here should be discarded. * We mark the socket as discardable until * we're committed to it below in TCPS_LISTEN. */ dropsocket++; inp = (struct inpcb *)so->so_pcb; inp->inp_laddr = ti->ti_dst; inp->inp_lport = ti->ti_dport; in_pcbrehash(inp); #if BSD>=43 inp->inp_options = ip_srcroute(); #endif tp = intotcpcb(inp); tp->t_state = TCPS_LISTEN; /* Compute proper scaling value from buffer space */ while (tp->request_r_scale < TCP_MAX_WINSHIFT && TCP_MAXWIN << tp->request_r_scale < so->so_rcv.sb_hiwat) tp->request_r_scale++; } } /* * Segment received on connection. * Reset idle time and keep-alive timer. */ tp->t_idle = 0; if (tp->t_state != TCPS_SYN_RECEIVED) tp->t_timer[TCPT_KEEP] = tcp_keepidle; #ifdef TCP_SACK if (!tp->sack_disable) tcp_del_sackholes(tp, ti); /* Delete stale SACK holes */ #endif /* TCP_SACK */ /* * Process options if not in LISTEN state, * else do it below (after getting remote address). */ if (optp && tp->t_state != TCPS_LISTEN) tcp_dooptions(tp, optp, optlen, ti, &ts_present, &ts_val, &ts_ecr); #ifdef TCP_SACK if (!tp->sack_disable) { tp->rcv_laststart = ti->ti_seq; /* last rec'vd segment*/ tp->rcv_lastend = ti->ti_seq + ti->ti_len; } #endif /* TCP_SACK */ /* * 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 && (!ts_present || TSTMP_GEQ(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. * Fix from Braden, see Stevens p. 870 */ if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent)) { tp->ts_recent_age = tcp_now; tp->ts_recent = 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 == 0) { /* * this is a pure ack for outstanding data. */ ++tcpstat.tcps_predack; if (ts_present) tcp_xmit_timer(tp, tcp_now-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; #if defined(TCP_SACK) && defined(TCP_FACK) tp->snd_fack = tp->snd_una; tp->retran_data = 0; #endif /* TCP_FACK */ 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) tp->t_timer[TCPT_REXMT] = 0; else if (tp->t_timer[TCPT_PERSIST] == 0) tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; if (sb_notify(&so->so_snd)) 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. */ #ifdef TCP_SACK /* Clean receiver SACK report if present */ if (!tp->sack_disable && tp->rcv_numsacks) tcp_clean_sackreport(tp); #endif /* TCP_SACK */ ++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); if (ti->ti_flags & TH_PUSH) tp->t_flags |= TF_ACKNOW; else tp->t_flags |= TF_DELACK; return; } } /* * Drop TCP, IP headers and TCP options. */ m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); /* * Calculate amount of space in receive window, * and then do TCP input processing. * Receive window is amount of space in rcv queue, * but not less than advertised window. */ { int win; win = sbspace(&so->so_rcv); if (win < 0) win = 0; tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); } switch (tp->t_state) { /* * If the state is LISTEN then ignore segment if it contains an RST. * If the segment contains an ACK then it is bad and send a RST. * If it does not contain a SYN then it is not interesting; drop it. * If it is from this socket, drop it, it must be forged. * Don't bother responding if the destination was a broadcast. * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial * tp->iss, and send a segment: * * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. * Fill in remote peer address fields if not previously specified. * Enter SYN_RECEIVED state, and process any other fields of this * segment in this state. */ case TCPS_LISTEN: { struct mbuf *am; register struct sockaddr_in *sin; if (tiflags & TH_RST) goto drop; if (tiflags & TH_ACK) goto dropwithreset; if ((tiflags & TH_SYN) == 0) goto drop; if ((ti->ti_dport == ti->ti_sport) && (ti->ti_dst.s_addr == ti->ti_src.s_addr)) goto drop; #ifdef TCPCOOKIE /* * If source address is on friends list, proceed, otherwise * try to obtain a cookie and drop the frame. */ if (!tck_isafriend(ti->ti_src)) { u_int32_t acookie; acookie = tck_makecookie(ti->ti_src); ti->ti_dport = htons(TCK_PORT); tcp_respond(tp, ti, m, acookie, acookie, TH_ACK); /* destroy temporarily created socket */ if (dropsocket) (void) soabort(so); return; } #endif /* TCPCOOKIE */ /* * 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_dst.s_addr)) goto drop; am = m_get(M_DONTWAIT, MT_SONAME); /* XXX */ if (am == NULL) goto drop; 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 = ti->ti_src; sin->sin_port = ti->ti_sport; bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); laddr = inp->inp_laddr; if (inp->inp_laddr.s_addr == INADDR_ANY) inp->inp_laddr = ti->ti_dst; if (in_pcbconnect(inp, am)) { inp->inp_laddr = laddr; (void) m_free(am); goto drop; } (void) m_free(am); tp->t_template = tcp_template(tp); if (tp->t_template == 0) { tp = tcp_drop(tp, ENOBUFS); dropsocket = 0; /* socket is already gone */ goto drop; } if (optp) tcp_dooptions(tp, optp, optlen, ti, &ts_present, &ts_val, &ts_ecr); #ifdef TCP_SACK /* * If peer did not send a SACK_PERMITTED option (i.e., if * tcp_dooptions() did not set TF_SACK_PERMIT), set * sack_disable to 1 if it is currently 0. */ if (!tp->sack_disable) if ((tp->t_flags & TF_SACK_PERMIT) == 0) tp->sack_disable = 1; #endif if (iss) tp->iss = iss; else tp->iss = tcp_iss; #ifdef TCP_COMPAT_42 tcp_iss += TCP_ISSINCR/2; #else /* TCP_COMPAT_42 */ tcp_iss += arc4random() % (TCP_ISSINCR / 2) + 1; #endif /* !TCP_COMPAT_42 */ tp->irs = ti->ti_seq; tcp_sendseqinit(tp); #if defined (TCP_SACK) || defined (TCP_NEWRENO) tp->snd_last = tp->snd_una; #endif /* TCP_SACK || TCP_NEWRENO */ #if defined(TCP_SACK) && defined(TCP_FACK) tp->snd_fack = tp->snd_una; tp->retran_data = 0; tp->snd_awnd = 0; #endif /* TCP_FACK */ tcp_rcvseqinit(tp); tp->t_flags |= TF_ACKNOW; tp->t_state = TCPS_SYN_RECEIVED; tp->t_timer[TCPT_KEEP] = tcptv_keep_init; dropsocket = 0; /* committed to socket */ tcpstat.tcps_accepts++; goto trimthenstep6; } /* * If the state is SYN_RECEIVED: * if seg contains SYN/ACK, send an RST. * if seg contains an ACK, but not for our SYN/ACK, send an RST */ case TCPS_SYN_RECEIVED: if (tiflags & TH_ACK) { if (tiflags & TH_SYN) { tcpstat.tcps_badsyn++; goto dropwithreset; } if (SEQ_LEQ(ti->ti_ack, tp->snd_una) || SEQ_GT(ti->ti_ack, tp->snd_max)) goto dropwithreset; } break; /* * If the state is SYN_SENT: * if seg contains an ACK, but not for our SYN, drop the input. * if seg contains a RST, then drop the connection. * if seg does not contain SYN, then drop it. * Otherwise this is an acceptable SYN segment * initialize tp->rcv_nxt and tp->irs * if seg contains ack then advance tp->snd_una * if SYN has been acked change to ESTABLISHED else SYN_RCVD state * arrange for segment to be acked (eventually) * continue processing rest of data/controls, beginning with URG */ case TCPS_SYN_SENT: if ((tiflags & TH_ACK) && (SEQ_LEQ(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; } tp->t_timer[TCPT_REXMT] = 0; tp->irs = ti->ti_seq; tcp_rcvseqinit(tp); tp->t_flags |= TF_ACKNOW; #ifdef TCP_SACK /* * If we've sent a SACK_PERMITTED option, and the peer * also replied with one, then TF_SACK_PERMIT should have * been set in tcp_dooptions(). If it was not, disable SACKs. */ if (!tp->sack_disable) if ((tp->t_flags & TF_SACK_PERMIT) == 0) tp->sack_disable = 1; #endif if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) { tcpstat.tcps_connects++; soisconnected(so); tp->t_state = TCPS_ESTABLISHED; /* 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; } (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0); /* * 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); /* * Since new data was acked (the SYN), open the * congestion window by one MSS. We do this * here, because we won't go through the normal * ACK processing below. And since this is the * start of the connection, we know we are in * the exponential phase of slow-start. */ tp->snd_cwnd += tp->t_maxseg; } else tp->t_state = TCPS_SYN_RECEIVED; trimthenstep6: /* * 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; } /* * 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 (ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent && TSTMP_LT(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; 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, FIN must be a * duplicate or out-of-sequence, so drop it. */ tiflags &= ~TH_FIN; /* * Send ACK to resynchronize, and drop any data, * but keep on processing for RST or ACK. */ tp->t_flags |= TF_ACKNOW; tcpstat.tcps_rcvdupbyte += todrop = ti->ti_len; 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 = tp->rcv_nxt + TCP_ISSINCR; tp = tcp_close(tp); goto findpcb; } /* * If window is closed can only take segments at * window edge, and have to drop data and PUSH from * incoming segments. Continue processing, but * remember to ack. Otherwise, drop segment * and ack. */ if (tp->rcv_wnd == 0 && 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, * record its timestamp. * Fix from Braden, see Stevens p. 870 */ if (ts_present && TSTMP_GEQ(ts_val, tp->ts_recent) && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent)) { tp->ts_recent_age = tcp_now; tp->ts_recent = ts_val; } /* * If the RST bit is set examine the state: * SYN_RECEIVED STATE: * If passive open, return to LISTEN state. * If active open, inform user that connection was refused. * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: * Inform user that connection was reset, and close tcb. * CLOSING, LAST_ACK, TIME_WAIT STATES * Close the tcb. */ if (tiflags & TH_RST) { if ((ti->ti_seq != tp->rcv_nxt) && (ti->ti_ack && ((SEQ_GT(ti->ti_ack, tp->snd_nxt) || SEQ_LT(ti->ti_ack, (tp->snd_nxt - tp->snd_wnd)))))) goto drop; 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, the ack ACKs our SYN, so enter * ESTABLISHED state and continue processing. * The ACK was checked above. */ case TCPS_SYN_RECEIVED: tcpstat.tcps_connects++; soisconnected(so); tp->t_state = TCPS_ESTABLISHED; /* 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; } (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0); 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)) { /* * Duplicate/old ACK processing. * Increments t_dupacks: * Pure duplicate (same seq/ack/window, no data) * Doesn't affect t_dupacks: * Data packets. * Normal window updates (window opens) * Resets t_dupacks: * New data ACKed. * Window shrinks * Old ACK */ if (ti->ti_len) break; /* * If we get an old ACK, there is probably packet * reordering going on. Be conservative and reset * t_dupacks so that we are less agressive in * doing a fast retransmit. */ if (ti->ti_ack != tp->snd_una) { tp->t_dupacks = 0; break; } if (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 (tp->t_timer[TCPT_REXMT] == 0) tp->t_dupacks = 0; #if defined(TCP_SACK) && defined(TCP_FACK) /* * In FACK, can enter fast rec. if the receiver * reports a reass. queue longer than 3 segs. */ else if (++tp->t_dupacks == tcprexmtthresh || ((SEQ_GT(tp->snd_fack, tcprexmtthresh * tp->t_maxseg + tp->snd_una)) && SEQ_GT(tp->snd_una, tp->snd_last))) { #else else if (++tp->t_dupacks == tcprexmtthresh) { #endif /* TCP_FACK */ tcp_seq onxt = tp->snd_nxt; u_long win = ulmin(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg; #if defined(TCP_SACK) || defined(TCP_NEWRENO) if (SEQ_LT(ti->ti_ack, tp->snd_last)){ /* * False fast retx after * timeout. Do not cut window. */ tp->snd_cwnd += tp->t_maxseg; tp->t_dupacks = 0; (void) tcp_output(tp); goto drop; } #endif if (win < 2) win = 2; tp->snd_ssthresh = win * tp->t_maxseg; #if defined(TCP_SACK) || defined(TCP_NEWRENO) tp->snd_last = tp->snd_max; #endif #ifdef TCP_SACK if (!tp->sack_disable) { tp->t_timer[TCPT_REXMT] = 0; tp->t_rtt = 0; tcpstat.tcps_sndrexmitfast++; #if defined(TCP_SACK) && defined(TCP_FACK) (void) tcp_output(tp); /* * During FR, snd_cwnd is held * constant for FACK. */ tp->snd_cwnd = tp->snd_ssthresh; tp->t_dupacks = tcprexmtthresh; #else /* * tcp_output() will send * oldest SACK-eligible rtx. */ (void) tcp_output(tp); tp->snd_cwnd = tp->snd_ssthresh+ tp->t_maxseg * tp->t_dupacks; #endif /* TCP_FACK */ /* * It is possible for * tcp_output to fail to send * a segment. If so, make * sure that REMXT timer is set. */ if (SEQ_GT(tp->snd_max, tp->snd_una) && tp->t_timer[TCPT_REXMT] == 0 && tp->t_timer[TCPT_PERSIST] == 0) tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; goto drop; } #endif /* TCP_SACK */ tp->t_timer[TCPT_REXMT] = 0; tp->t_rtt = 0; tp->snd_nxt = ti->ti_ack; tp->snd_cwnd = tp->t_maxseg; tcpstat.tcps_sndrexmitfast++; (void) tcp_output(tp); tp->snd_cwnd = tp->snd_ssthresh + tp->t_maxseg * tp->t_dupacks; if (SEQ_GT(onxt, tp->snd_nxt)) tp->snd_nxt = onxt; goto drop; } else if (tp->t_dupacks > tcprexmtthresh) { #if defined(TCP_SACK) && defined(TCP_FACK) /* * while (awnd < cwnd) * sendsomething(); */ if (!tp->sack_disable) { if (tp->snd_awnd < tp->snd_cwnd) tcp_output(tp); goto drop; } #endif /* TCP_FACK */ tp->snd_cwnd += tp->t_maxseg; (void) tcp_output(tp); goto drop; } } else if (tiwin < tp->snd_wnd) { /* * The window was retracted! Previous dup * ACKs may have been due to packets arriving * after the shrunken window, not a missing * packet, so play it safe and reset t_dupacks */ tp->t_dupacks = 0; } break; } /* * If the congestion window was inflated to account * for the other side's cached packets, retract it. */ #ifdef TCP_NEWRENO if (tp->t_dupacks >= tcprexmtthresh && !tcp_newreno(tp, ti)) { /* Out of fast recovery */ 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 (tcp_seq_subtract(tp->snd_max, ti->ti_ack) < tp->snd_ssthresh) tp->snd_cwnd = tcp_seq_subtract(tp->snd_max, ti->ti_ack) + tp->t_maxseg; tp->t_dupacks = 0; } #elif defined(TCP_SACK) if (!tp->sack_disable) { if (tp->t_dupacks >= tcprexmtthresh) { /* Check for a partial ACK */ if (tcp_sack_partialack(tp, ti)) { #if defined(TCP_SACK) && defined(TCP_FACK) /* Force call to tcp_output */ if (tp->snd_awnd < tp->snd_cwnd) needoutput = 1; #else tp->snd_cwnd += tp->t_maxseg; needoutput = 1; #endif /* TCP_FACK */ } else { /* Out of fast recovery */ tp->snd_cwnd = tp->snd_ssthresh; if (tcp_seq_subtract(tp->snd_max, ti->ti_ack) < tp->snd_ssthresh) tp->snd_cwnd = tcp_seq_subtract(tp->snd_max, ti->ti_ack) + tp->t_maxseg; tp->t_dupacks = 0; #if defined(TCP_SACK) && defined(TCP_FACK) if (SEQ_GT(ti->ti_ack, tp->snd_fack)) tp->snd_fack = ti->ti_ack; #endif /* TCP_FACK */ } } } else { if (tp->t_dupacks >= tcprexmtthresh && !tcp_newreno(tp, ti)) { /* Out of fast recovery */ tp->snd_cwnd = tp->snd_ssthresh; if (tcp_seq_subtract(tp->snd_max, ti->ti_ack) < tp->snd_ssthresh) tp->snd_cwnd = tcp_seq_subtract(tp->snd_max, ti->ti_ack) + tp->t_maxseg; tp->t_dupacks = 0; } } #else /* else neither TCP_NEWRENO nor TCP_SACK */ if (tp->t_dupacks >= tcprexmtthresh && tp->snd_cwnd > tp->snd_ssthresh) tp->snd_cwnd = tp->snd_ssthresh; tp->t_dupacks = 0; #endif 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 (ts_present) tcp_xmit_timer(tp, tcp_now-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) { tp->t_timer[TCPT_REXMT] = 0; needoutput = 1; } else if (tp->t_timer[TCPT_PERSIST] == 0) tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; /* * When new data is acked, open the congestion window. * If the window gives us less than ssthresh packets * in flight, open exponentially (maxseg per packet). * Otherwise open linearly: maxseg per window * (maxseg^2 / cwnd per packet). */ { register u_int cw = tp->snd_cwnd; register u_int incr = tp->t_maxseg; if (cw > tp->snd_ssthresh) incr = incr * incr / cw; #if defined (TCP_NEWRENO) || defined (TCP_SACK) if (SEQ_GEQ(ti->ti_ack, tp->snd_last)) #endif 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; } if (sb_notify(&so->so_snd)) sowwakeup(so); tp->snd_una = ti->ti_ack; if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; #if defined (TCP_SACK) && defined (TCP_FACK) if (SEQ_GT(tp->snd_una, tp->snd_fack)) tp->snd_fack = tp->snd_una; #endif 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); tp->t_timer[TCPT_2MSL] = tcp_maxidle; } tp->t_state = TCPS_FIN_WAIT_2; } break; /* * In CLOSING STATE in addition to the processing for * the ESTABLISHED state if the ACK acknowledges our FIN * then enter the TIME-WAIT state, otherwise ignore * the segment. */ case TCPS_CLOSING: if (ourfinisacked) { tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); tp->t_timer[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: tp->t_timer[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); #ifdef TCP_SACK if (!tp->sack_disable) tcp_update_sack_list(tp); #endif /* * 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); tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; soisdisconnected(so); break; /* * In TIME_WAIT state restart the 2 MSL time_wait timer. */ case TCPS_TIME_WAIT: tp->t_timer[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); #ifdef TCP_SACK /* * In SACK, it is possible for tcp_output() to fail to send a segment * after the retransmission timer has been turned off. Make sure that * the retransmission timer is set if we are in fast recovery. */ if (needoutput && SEQ_GT(tp->snd_max, tp->snd_una) && tp->t_timer[TCPT_REXMT] == 0 && tp->t_timer[TCPT_PERSIST] == 0) tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; #endif } return; 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) tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST); else { if (tiflags & TH_SYN) ti->ti_len++; tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0, TH_RST|TH_ACK); } /* destroy temporarily created socket */ if (dropsocket) (void) soabort(so); return; drop: /* * Drop space held by incoming segment and return. */ if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); m_freem(m); /* destroy temporarily created socket */ if (dropsocket) (void) soabort(so); return; #ifndef TUBA_INCLUDE } void tcp_dooptions(tp, cp, cnt, ti, ts_present, ts_val, ts_ecr) struct tcpcb *tp; u_char *cp; int cnt; struct tcpiphdr *ti; int *ts_present; u_int32_t *ts_val, *ts_ecr; { u_int16_t mss = 0; int opt, optlen; for (; cnt > 0; cnt -= optlen, cp += optlen) { opt = cp[0]; if (opt == TCPOPT_EOL) break; if (opt == TCPOPT_NOP) optlen = 1; else { optlen = cp[1]; if (optlen <= 0) break; } switch (opt) { default: continue; case TCPOPT_MAXSEG: if (optlen != TCPOLEN_MAXSEG) continue; if (!(ti->ti_flags & TH_SYN)) continue; bcopy((char *) cp + 2, (char *) &mss, sizeof(mss)); 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 = min(cp[2], TCP_MAX_WINSHIFT); break; case TCPOPT_TIMESTAMP: if (optlen != TCPOLEN_TIMESTAMP) continue; *ts_present = 1; bcopy((char *)cp + 2, (char *) ts_val, sizeof(*ts_val)); NTOHL(*ts_val); bcopy((char *)cp + 6, (char *) ts_ecr, sizeof(*ts_ecr)); NTOHL(*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 = *ts_val; tp->ts_recent_age = tcp_now; } break; #ifdef TCP_SACK case TCPOPT_SACK_PERMITTED: if (tp->sack_disable || optlen!=TCPOLEN_SACK_PERMITTED) continue; if (ti->ti_flags & TH_SYN) /* MUST only be set on SYN */ tp->t_flags |= TF_SACK_PERMIT; break; case TCPOPT_SACK: if (tcp_sack_option(tp, ti, cp, optlen)) continue; break; #endif } } /* Update t_maxopd and t_maxseg after all options are processed */ if (ti->ti_flags & TH_SYN) (void) tcp_mss(tp, mss); /* sets t_maxseg */ } #if defined(TCP_SACK) || defined(TCP_NEWRENO) u_long tcp_seq_subtract(a, b) u_long a, b; { return ((long)(a - b)); } #endif #ifdef TCP_SACK /* * This function is called upon receipt of new valid data (while not in header * prediction mode), and it updates the ordered list of sacks. */ void tcp_update_sack_list(tp) struct tcpcb *tp; { /* * First reported block MUST be the most recent one. Subsequent * blocks SHOULD be in the order in which they arrived at the * receiver. These two conditions make the implementation fully * compliant with RFC 2018. */ int i, j = 0, count = 0, lastpos = -1; struct sackblk sack, firstsack, temp[MAX_SACK_BLKS]; /* First clean up current list of sacks */ for (i = 0; i < tp->rcv_numsacks; i++) { sack = tp->sackblks[i]; if (sack.start == 0 && sack.end == 0) { count++; /* count = number of blocks to be discarded */ continue; } if (SEQ_LEQ(sack.end, tp->rcv_nxt)) { tp->sackblks[i].start = tp->sackblks[i].end = 0; count++; } else { temp[j].start = tp->sackblks[i].start; temp[j++].end = tp->sackblks[i].end; } } tp->rcv_numsacks -= count; if (tp->rcv_numsacks == 0) { /* no sack blocks currently (fast path) */ tcp_clean_sackreport(tp); if (SEQ_LT(tp->rcv_nxt, tp->rcv_laststart)) { /* ==> need first sack block */ tp->sackblks[0].start = tp->rcv_laststart; tp->sackblks[0].end = tp->rcv_lastend; tp->rcv_numsacks = 1; } return; } /* Otherwise, sack blocks are already present. */ for (i = 0; i < tp->rcv_numsacks; i++) tp->sackblks[i] = temp[i]; /* first copy back sack list */ if (SEQ_GEQ(tp->rcv_nxt, tp->rcv_lastend)) return; /* sack list remains unchanged */ /* * From here, segment just received should be (part of) the 1st sack. * Go through list, possibly coalescing sack block entries. */ firstsack.start = tp->rcv_laststart; firstsack.end = tp->rcv_lastend; for (i = 0; i < tp->rcv_numsacks; i++) { sack = tp->sackblks[i]; if (SEQ_LT(sack.end, firstsack.start) || SEQ_GT(sack.start, firstsack.end)) continue; /* no overlap */ if (sack.start == firstsack.start && sack.end == firstsack.end){ /* * identical block; delete it here since we will * move it to the front of the list. */ tp->sackblks[i].start = tp->sackblks[i].end = 0; lastpos = i; /* last posn with a zero entry */ continue; } if (SEQ_LEQ(sack.start, firstsack.start)) firstsack.start = sack.start; /* merge blocks */ if (SEQ_GEQ(sack.end, firstsack.end)) firstsack.end = sack.end; /* merge blocks */ tp->sackblks[i].start = tp->sackblks[i].end = 0; lastpos = i; /* last posn with a zero entry */ } if (lastpos != -1) { /* at least one merge */ for (i = 0, j = 1; i < tp->rcv_numsacks; i++) { sack = tp->sackblks[i]; if (sack.start == 0 && sack.end == 0) continue; temp[j++] = sack; } tp->rcv_numsacks = j; /* including first blk (added later) */ for (i = 1; i < tp->rcv_numsacks; i++) /* now copy back */ tp->sackblks[i] = temp[i]; } else { /* no merges -- shift sacks by 1 */ if (tp->rcv_numsacks < MAX_SACK_BLKS) tp->rcv_numsacks++; for (i = tp->rcv_numsacks-1; i > 0; i--) tp->sackblks[i] = tp->sackblks[i-1]; } tp->sackblks[0] = firstsack; return; } /* * Process the TCP SACK option. Returns 1 if tcp_dooptions() should continue, * and 0 otherwise, if the option was fine. tp->snd_holes is an ordered list * of holes (oldest to newest, in terms of the sequence space). */ int tcp_sack_option(tp, ti, cp, optlen) struct tcpcb *tp; struct tcpiphdr *ti; u_char *cp; int optlen; { int tmp_olen; u_char *tmp_cp; struct sackhole *cur, *p, *temp; if (tp->sack_disable) return 1; /* Note: TCPOLEN_SACK must be 2*sizeof(tcp_seq) */ if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) return 1; tmp_cp = cp + 2; tmp_olen = optlen - 2; if (tp->snd_numholes < 0) tp->snd_numholes = 0; if (tp->t_maxseg == 0) panic("tcp_sack_option"); /* Should never happen */ while (tmp_olen > 0) { struct sackblk sack; bcopy((char *) tmp_cp, (char *) &(sack.start), sizeof(tcp_seq)); NTOHL(sack.start); bcopy((char *) tmp_cp + sizeof(tcp_seq), (char *) &(sack.end), sizeof(tcp_seq)); NTOHL(sack.end); tmp_olen -= TCPOLEN_SACK; tmp_cp += TCPOLEN_SACK; if (SEQ_LEQ(sack.end, sack.start)) continue; /* bad SACK fields */ if (SEQ_LEQ(sack.end, tp->snd_una)) continue; /* old block */ #if defined(TCP_SACK) && defined(TCP_FACK) /* Updates snd_fack. */ if (SEQ_GEQ(sack.end, tp->snd_fack)) tp->snd_fack = sack.end; #endif /* TCP_FACK */ if (tp->snd_holes == 0) { /* first hole */ tp->snd_holes = (struct sackhole *) malloc(sizeof(struct sackhole), M_PCB, M_NOWAIT); cur = tp->snd_holes; cur->start = ti->ti_ack; cur->end = sack.start; cur->rxmit = cur->start; cur->next = 0; tp->snd_numholes = 1; tp->rcv_lastsack = sack.end; /* * dups is at least one. If more data has been * SACKed, it can be greater than one. */ cur->dups = min(tcprexmtthresh, ((sack.end - cur->end)/tp->t_maxseg)); if (cur->dups < 1) cur->dups = 1; continue; /* with next sack block */ } /* Go thru list of holes: p = previous, cur = current */ p = cur = tp->snd_holes; while (cur) { if (SEQ_LEQ(sack.end, cur->start)) /* SACKs data before the current hole */ break; /* no use going through more holes */ if (SEQ_GEQ(sack.start, cur->end)) { /* SACKs data beyond the current hole */ cur->dups++; if ( ((sack.end - cur->end)/tp->t_maxseg) >= tcprexmtthresh) cur->dups = tcprexmtthresh; p = cur; cur = cur->next; continue; } if (SEQ_LEQ(sack.start, cur->start)) { /* Data acks at least the beginning of hole */ #if defined(TCP_SACK) && defined(TCP_FACK) if (SEQ_GT(sack.end, cur->rxmit)) tp->retran_data -= tcp_seq_subtract(cur->rxmit, cur->start); else tp->retran_data -= tcp_seq_subtract(sack.end, cur->start); #endif /* TCP_FACK */ if (SEQ_GEQ(sack.end,cur->end)){ /* Acks entire hole, so delete hole */ if (p != cur) { p->next = cur->next; free(cur, M_PCB); cur = p->next; } else { cur=cur->next; free(p, M_PCB); p = cur; tp->snd_holes = p; } tp->snd_numholes--; continue; } /* otherwise, move start of hole forward */ cur->start = sack.end; cur->rxmit = max (cur->rxmit, cur->start); p = cur; cur = cur->next; continue; } /* move end of hole backward */ if (SEQ_GEQ(sack.end, cur->end)) { #if defined(TCP_SACK) && defined(TCP_FACK) if (SEQ_GT(cur->rxmit, sack.start)) tp->retran_data -= tcp_seq_subtract(cur->rxmit, sack.start); #endif /* TCP_FACK */ cur->end = sack.start; cur->rxmit = min (cur->rxmit, cur->end); cur->dups++; if ( ((sack.end - cur->end)/tp->t_maxseg) >= tcprexmtthresh) cur->dups = tcprexmtthresh; p = cur; cur = cur->next; continue; } if (SEQ_LT(cur->start, sack.start) && SEQ_GT(cur->end, sack.end)) { /* * ACKs some data in middle of a hole; need to * split current hole */ #if defined(TCP_SACK) && defined(TCP_FACK) if (SEQ_GT(cur->rxmit, sack.end)) tp->retran_data -= tcp_seq_subtract(sack.end, sack.start); else if (SEQ_GT(cur->rxmit, sack.start)) tp->retran_data -= tcp_seq_subtract(cur->rxmit, sack.start); #endif /* TCP_FACK */ temp = (struct sackhole *)malloc(sizeof(*temp), M_PCB,M_NOWAIT); temp->next = cur->next; temp->start = sack.end; temp->end = cur->end; temp->dups = cur->dups; temp->rxmit = max (cur->rxmit, temp->start); cur->end = sack.start; cur->rxmit = min (cur->rxmit, cur->end); cur->dups++; if ( ((sack.end - cur->end)/tp->t_maxseg) >= tcprexmtthresh) cur->dups = tcprexmtthresh; cur->next = temp; p = temp; cur = p->next; tp->snd_numholes++; } } /* At this point, p points to the last hole on the list */ if (SEQ_LT(tp->rcv_lastsack, sack.start)) { /* * Need to append new hole at end. * Last hole is p (and it's not NULL). */ temp = (struct sackhole *) malloc(sizeof(*temp), M_PCB, M_NOWAIT); temp->start = tp->rcv_lastsack; temp->end = sack.start; temp->dups = min(tcprexmtthresh, ((sack.end - sack.start)/tp->t_maxseg)); if (temp->dups < 1) temp->dups = 1; temp->rxmit = temp->start; temp->next = 0; p->next = temp; tp->rcv_lastsack = sack.end; tp->snd_numholes++; } } #if defined(TCP_SACK) && defined(TCP_FACK) /* * Update retran_data, snd_fack, and snd_awnd. Go through the list of * holes. Increment retran_data by (hole->rxmit - hole->start). * snd_fack gets the highest value of hole->end. */ tp->retran_data = 0; cur = tp->snd_holes; while (cur) { tp->retran_data += cur->rxmit - cur->start; cur = cur->next; } tp->snd_awnd = tcp_seq_subtract(tp->snd_nxt, tp->snd_fack) + tp->retran_data; #endif /* TCP_FACK */ return 0; } /* * Delete stale (i.e, cumulatively ack'd) holes. Hole is deleted only if * it is completely acked; otherwise, tcp_sack_option(), called from * tcp_dooptions(), will fix up the hole. */ void tcp_del_sackholes(tp, ti) struct tcpcb *tp; struct tcpiphdr *ti; { if (!tp->sack_disable && tp->t_state != TCPS_LISTEN) { /* max because this could be an older ack just arrived */ tcp_seq lastack = max(ti->ti_ack, tp->snd_una); struct sackhole *cur = tp->snd_holes; struct sackhole *prev = cur; while (cur) if (SEQ_LEQ(cur->end, lastack)) { cur = cur->next; free(prev, M_PCB); prev = cur; tp->snd_numholes--; } else if (SEQ_LT(cur->start, lastack)) { cur->start = lastack; break; } else break; tp->snd_holes = cur; } } /* * Delete all receiver-side SACK information. */ void tcp_clean_sackreport(tp) struct tcpcb *tp; { int i; tp->rcv_numsacks = 0; for (i = 0; i < MAX_SACK_BLKS; i++) tp->sackblks[i].start = tp->sackblks[i].end=0; } /* * Checks for partial ack. If partial ack arrives, turn off retransmission * timer, deflate the window, do not clear tp->t_dupacks, and return 1. * If the ack advances at least to tp->snd_last, return 0. */ int tcp_sack_partialack(tp, ti) struct tcpcb *tp; struct tcpiphdr *ti; { if (SEQ_LT(ti->ti_ack, tp->snd_last)) { /* Turn off retx. timer (will start again next segment) */ tp->t_timer[TCPT_REXMT] = 0; tp->t_rtt = 0; #ifndef TCP_FACK /* * Partial window deflation. This statement relies on the * fact that tp->snd_una has not been updated yet. In FACK * hold snd_cwnd constant during fast recovery. */ tp->snd_cwnd -= (ti->ti_ack - tp->snd_una - tp->t_maxseg); #endif return 1; } return 0; } #endif TCP_SACK /* * 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; 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; /* * 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; } 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). */ TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), rtt + 2, TCPTV_REXMTMAX); /* * We received an ack for a packet that wasn't retransmitted; * it is probably safe to discard any error indications we've * received recently. This isn't quite right, but close enough * for now (a route might have failed after we sent a segment, * and the return path might not be symmetrical). */ tp->t_softerror = 0; } /* * Determine a reasonable value for maxseg size. * If the route is known, check route for mtu. * If none, use an mss that can be handled on the outgoing * interface without forcing IP to fragment; if bigger than * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES * to utilize large mbufs. If no route is found, route has no mtu, * or the destination isn't local, use a default, hopefully conservative * size (usually 512 or the default IP max size, but no more than the mtu * of the interface), as we can't discover anything about intervening * gateways or networks. We also initialize the congestion/slow start * window to be a single segment if the destination isn't local. * While looking at the routing entry, we also initialize other path-dependent * parameters from pre-set or cached values in the routing entry. * * Also take into account the space needed for options that we * send regularly. Make maxseg shorter by that amount to assure * that we can send maxseg amount of data even when the options * are present. Store the upper limit of the length of options plus * data in maxopd. */ int tcp_mss(tp, offer) register struct tcpcb *tp; u_int offer; { struct route *ro; register struct rtentry *rt; struct ifnet *ifp; register int rtt, mss; u_long bufsize; struct inpcb *inp; struct socket *so; inp = tp->t_inpcb; ro = &inp->inp_route; if ((rt = ro->ro_rt) == (struct rtentry *)0) { /* No route yet, so try to acquire one */ if (inp->inp_faddr.s_addr != INADDR_ANY) { ro->ro_dst.sa_family = AF_INET; ro->ro_dst.sa_len = sizeof(ro->ro_dst); satosin(&ro->ro_dst)->sin_addr = inp->inp_faddr; rtalloc(ro); } if ((rt = ro->ro_rt) == (struct rtentry *)0) { tp->t_maxopd = tp->t_maxseg = tcp_mssdflt; return (tcp_mssdflt); } } ifp = rt->rt_ifp; so = inp->inp_socket; #ifdef RTV_MTU /* if route characteristics exist ... */ /* * 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 MTU 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 / PR_SLOWHZ); tp->t_srtt = rtt / (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); if (rt->rt_rmx.rmx_rttvar) tp->t_rttvar = rt->rt_rmx.rmx_rttvar / (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); else /* default variation is +- 1 rtt */ tp->t_rttvar = tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; TCPT_RANGESET((long) 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 */ if (rt->rt_rmx.rmx_mtu) mss = rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr); else #endif /* RTV_MTU */ { mss = ifp->if_mtu - sizeof(struct tcpiphdr); if (!in_localaddr(inp->inp_faddr)) mss = min(mss, tcp_mssdflt); } /* * The current mss, t_maxseg, is initialized to the default value. * If we compute a smaller value, reduce the current mss. * If we compute a larger value, return it for use in sending * a max seg size option, but don't store it for use * unless we received an offer at least that large from peer. * However, do not accept offers under 32 bytes. */ if (offer) mss = min(mss, offer); mss = max(mss, 64); /* sanity - at least max opt. space */ /* * 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.sb_hiwat; if (bufsize < mss) mss = bufsize; else { bufsize = roundup(bufsize, mss); if (bufsize > sb_max) bufsize = sb_max; (void)sbreserve(&so->so_snd, bufsize); } tp->t_maxseg = mss; #ifdef RTV_RPIPE if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) #endif bufsize = so->so_rcv.sb_hiwat; if (bufsize > mss) { bufsize = roundup(bufsize, mss); if (bufsize > sb_max) bufsize = sb_max; (void)sbreserve(&so->so_rcv, bufsize); } tp->snd_cwnd = mss; #ifdef RTV_SSTHRESH 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); } #endif /* RTV_MTU */ return (mss); } #endif /* TUBA_INCLUDE */ #if defined(TCP_NEWRENO) || defined (TCP_SACK) /* * 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_last, return 0. */ int tcp_newreno(tp, ti) struct tcpcb *tp; struct tcpiphdr *ti; { if (SEQ_LT(ti->ti_ack, tp->snd_last)) { tcp_seq onxt = tp->snd_nxt; tcp_seq ouna = tp->snd_una; /* snd_una not yet updated */ u_long ocwnd = tp->snd_cwnd; tp->t_timer[TCPT_REXMT] = 0; tp->t_rtt = 0; tp->snd_nxt = ti->ti_ack; tp->snd_cwnd = tp->t_maxseg; 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_maxseg); return 1; } return 0; } #endif /* TCP_NEWRENO || TCP_SACK */