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-rw-r--r--cpukit/libnetworking/netinet/tcp_input.c2148
1 files changed, 2148 insertions, 0 deletions
diff --git a/cpukit/libnetworking/netinet/tcp_input.c b/cpukit/libnetworking/netinet/tcp_input.c
new file mode 100644
index 0000000000..6d75c5c841
--- /dev/null
+++ b/cpukit/libnetworking/netinet/tcp_input.c
@@ -0,0 +1,2148 @@
+/*
+ * 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.
+ * 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
+ * $Id$
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "opt_tcpdebug.h"
+
+#ifndef TUBA_INCLUDE
+#include <sys/param.h>
+#include <sys/queue.h>
+#include <sys/systm.h>
+#include <sys/kernel.h>
+#include <sys/sysctl.h>
+#include <sys/malloc.h>
+#include <sys/mbuf.h>
+#include <sys/protosw.h>
+#include <sys/socket.h>
+#include <sys/socketvar.h>
+#include <errno.h>
+#include <sys/syslog.h>
+
+#include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */
+
+#include <net/if.h>
+#include <net/route.h>
+
+#include <netinet/in.h>
+#include <netinet/in_systm.h>
+#include <netinet/ip.h>
+#include <netinet/in_pcb.h>
+#include <netinet/ip_var.h>
+#include <netinet/tcp.h>
+#include <netinet/tcp_fsm.h>
+#include <netinet/tcp_seq.h>
+#include <netinet/tcp_timer.h>
+#include <netinet/tcp_var.h>
+#include <netinet/tcpip.h>
+#ifdef TCPDEBUG
+#include <netinet/tcp_debug.h>
+static struct tcpiphdr tcp_saveti;
+#endif
+
+static int tcprexmtthresh = 3;
+tcp_seq tcp_iss;
+tcp_cc tcp_ccgen;
+
+struct tcpstat tcpstat;
+SYSCTL_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats,
+ CTLFLAG_RD, &tcpstat , tcpstat, "");
+
+static int log_in_vain = 0;
+SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
+ &log_in_vain, 0, "");
+
+u_long tcp_now;
+struct inpcbhead tcb;
+struct inpcbinfo tcbinfo;
+
+static void tcp_dooptions(struct tcpcb *,
+ u_char *, int, struct tcpiphdr *, struct tcpopt *);
+static void tcp_pulloutofband(struct socket *,
+ struct tcpiphdr *, struct mbuf *);
+static int tcp_reass(struct tcpcb *, struct tcpiphdr *, struct mbuf *);
+static void tcp_xmit_timer(struct tcpcb *, int);
+
+#endif /* TUBA_INCLUDE */
+
+/*
+ * 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).
+ */
+#ifdef TCP_ACK_HACK
+#define TCP_REASS(tp, ti, m, so, flags) { \
+ if ((ti)->ti_seq == (tp)->rcv_nxt && \
+ (tp)->seg_next == (struct tcpiphdr *)(tp) && \
+ (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; \
+ } \
+}
+#else
+#define TCP_REASS(tp, ti, m, so, flags) { \
+ if ((ti)->ti_seq == (tp)->rcv_nxt && \
+ (tp)->seg_next == (struct tcpiphdr *)(tp) && \
+ (tp)->t_state == TCPS_ESTABLISHED) { \
+ 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; \
+ } \
+}
+#endif
+#ifndef TUBA_INCLUDE
+
+static int
+tcp_reass(struct tcpcb *tp, struct tcpiphdr *ti, struct mbuf *m)
+{
+ register struct tcpiphdr *q;
+ 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;
+
+ /*
+ * Find a segment which begins after this one does.
+ */
+ for (q = tp->seg_next; q != (struct tcpiphdr *)tp;
+ q = (struct tcpiphdr *)q->ti_next)
+ if (SEQ_GT(q->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 ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) {
+ register int i;
+ q = (struct tcpiphdr *)q->ti_prev;
+ /* conversion to int (in i) handles seq wraparound */
+ i = q->ti_seq + q->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);
+ /*
+ * Try to present any queued data
+ * at the left window edge to the user.
+ * This is needed after the 3-WHS
+ * completes.
+ */
+ goto present; /* ??? */
+ }
+ m_adj(m, i);
+ ti->ti_len -= i;
+ ti->ti_seq += i;
+ }
+ q = (struct tcpiphdr *)(q->ti_next);
+ }
+ tcpstat.tcps_rcvoopack++;
+ tcpstat.tcps_rcvoobyte += ti->ti_len;
+#if (defined(__GNUC__) && (defined(__arm__) || defined(__mips__)))
+ STR32_UNALGN(ti,m);
+#else
+ REASS_MBUF(ti) = m; /* XXX */
+#endif
+ /*
+ * While we overlap succeeding segments trim them or,
+ * if they are completely covered, dequeue them.
+ */
+ while (q != (struct tcpiphdr *)tp) {
+ register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq;
+ if (i <= 0)
+ break;
+ if (i < q->ti_len) {
+ q->ti_seq += i;
+ q->ti_len -= i;
+#if (defined(__GNUC__) && (defined(__arm__) || defined(__mips__)))
+ LD32_UNALGN(q,m);
+ m_adj(m, i);
+#else
+ m_adj(REASS_MBUF(q), i);
+#endif
+ break;
+ }
+ q = (struct tcpiphdr *)q->ti_next;
+#if (defined(__GNUC__) && (defined(__arm__) || defined(__mips__)))
+ LD32_UNALGN((struct tcpiphdr *)q->ti_prev,m);
+#else
+ m = REASS_MBUF((struct tcpiphdr *)q->ti_prev);
+#endif
+ remque(q->ti_prev);
+ m_freem(m);
+ }
+
+ /*
+ * Stick new segment in its place.
+ */
+ insque(ti, q->ti_prev);
+
+present:
+ /*
+ * Present data to user, advancing rcv_nxt through
+ * completed sequence space.
+ */
+ if (!TCPS_HAVEESTABLISHED(tp->t_state))
+ return (0);
+ ti = tp->seg_next;
+ if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt)
+ return (0);
+ do {
+ tp->rcv_nxt += ti->ti_len;
+ flags = ti->ti_flags & TH_FIN;
+ remque(ti);
+#if (defined(__GNUC__) && (defined(__arm__) || defined(__mips__)))
+ LD32_UNALGN(ti,m);
+#else
+ m = REASS_MBUF(ti);
+#endif
+ ti = (struct tcpiphdr *)ti->ti_next;
+ if (so->so_state & SS_CANTRCVMORE)
+ m_freem(m);
+ else
+ sbappend(&so->so_rcv, m);
+ } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt);
+ sorwakeup(so);
+ return (flags);
+}
+
+/*
+ * TCP input routine, follows pages 65-76 of the
+ * protocol specification dated September, 1981 very closely.
+ */
+void
+tcp_input(struct mbuf *m, int iphlen)
+{
+ register struct tcpiphdr *ti;
+ register struct inpcb *inp;
+ u_char *optp = NULL;
+ int optlen = 0;
+ int len, tlen, off;
+ register struct tcpcb *tp = 0;
+ register int tiflags;
+ struct socket *so = 0;
+ int todrop, acked, ourfinisacked, needoutput = 0;
+ struct in_addr laddr;
+ int dropsocket = 0;
+ int iss = 0;
+ u_long tiwin;
+ struct tcpopt to; /* options in this segment */
+ struct rmxp_tao *taop; /* pointer to our TAO cache entry */
+ struct rmxp_tao tao_noncached; /* in case there's no cached entry */
+#ifdef TCPDEBUG
+ short ostate = 0;
+#endif
+
+ bzero((char *)&to, sizeof(to));
+
+ 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;
+ ti->ti_next = ti->ti_prev = 0;
+ ti->ti_x1 = 0;
+ ti->ti_len = (u_short)tlen;
+ HTONS(ti->ti_len);
+ ti->ti_sum = in_cksum(m, len);
+ if (ti->ti_sum) {
+ 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, u_char *) + sizeof (struct tcpiphdr);
+ }
+ 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);
+
+ /*
+ * 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);
+
+ /*
+ * Locate pcb for segment.
+ */
+findpcb:
+ inp = in_pcblookuphash(&tcbinfo, ti->ti_src, ti->ti_sport,
+ ti->ti_dst, ti->ti_dport, 1);
+
+ /*
+ * If the state is CLOSED (i.e., TCB does not exist) then
+ * all data in the incoming segment is discarded.
+ * If the TCB exists but is in CLOSED state, it is embryonic,
+ * but should either do a listen or a connect soon.
+ */
+ if (inp == NULL) {
+ if (log_in_vain && tiflags & TH_SYN) {
+ char buf[4*sizeof "123"];
+
+ strcpy(buf, inet_ntoa(ti->ti_dst));
+ log(LOG_INFO, "Connection attempt to TCP %s:%d"
+ " from %s:%d\n",
+ buf, ntohs(ti->ti_dport),
+ inet_ntoa(ti->ti_src), ntohs(ti->ti_sport));
+ }
+ 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)) {
+#ifdef TCPDEBUG
+ if (so->so_options & SO_DEBUG) {
+ ostate = tp->t_state;
+ tcp_saveti = *ti;
+ }
+#endif
+ if (so->so_options & SO_ACCEPTCONN) {
+ register struct tcpcb *tp0 = tp;
+ struct socket *so2;
+ if ((tiflags & (TH_RST|TH_ACK|TH_SYN)) != TH_SYN) {
+ /*
+ * Note: dropwithreset makes sure we don't
+ * send a RST in response to a RST.
+ */
+ if (tiflags & TH_ACK) {
+ tcpstat.tcps_badsyn++;
+ goto dropwithreset;
+ }
+ goto drop;
+ }
+ so2 = sonewconn(so, 0);
+ if (so2 == 0) {
+ tcpstat.tcps_listendrop++;
+ so2 = sodropablereq(so);
+ if (so2) {
+ tcp_drop(sototcpcb(so2), ETIMEDOUT);
+ so2 = sonewconn(so, 0);
+ }
+ if (!so2)
+ goto drop;
+ }
+ so = so2;
+ /*
+ * 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;
+ tp->t_flags |= tp0->t_flags & (TF_NOPUSH|TF_NOOPT);
+
+ /* 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 (TCPS_HAVEESTABLISHED(tp->t_state))
+ tp->t_timer[TCPT_KEEP] = tcp_keepidle;
+
+ /*
+ * Process options if not in LISTEN state,
+ * else do it below (after getting remote address).
+ */
+ if (tp->t_state != TCPS_LISTEN)
+ tcp_dooptions(tp, optp, optlen, ti, &to);
+
+ /*
+ * Header prediction: check for the two common cases
+ * of a uni-directional data xfer. If the packet has
+ * no control flags, is in-sequence, the window didn't
+ * change and we're not retransmitting, it's a
+ * candidate. If the length is zero and the ack moved
+ * forward, we're the sender side of the xfer. Just
+ * free the data acked & wake any higher level process
+ * that was blocked waiting for space. If the length
+ * is non-zero and the ack didn't move, we're the
+ * receiver side. If we're getting packets in-order
+ * (the reassembly queue is empty), add the data to
+ * the socket buffer and note that we need a delayed ack.
+ * Make sure that the hidden state-flags are also off.
+ * Since we check for TCPS_ESTABLISHED above, it can only
+ * be TH_NEEDSYN.
+ */
+ if (tp->t_state == TCPS_ESTABLISHED &&
+ (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
+ ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
+ ((to.to_flags & TOF_TS) == 0 ||
+ TSTMP_GEQ(to.to_tsval, tp->ts_recent)) &&
+ /*
+ * Using the CC option is compulsory if once started:
+ * the segment is OK if no T/TCP was negotiated or
+ * if the segment has a CC option equal to CCrecv
+ */
+ ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) != (TF_REQ_CC|TF_RCVD_CC) ||
+ ((to.to_flags & TOF_CC) != 0 && to.to_cc == tp->cc_recv)) &&
+ 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.
+ * NOTE that the test is modified according to the latest
+ * proposal of the tcplw@cray.com list (Braden 1993/04/26).
+ */
+ if ((to.to_flags & TOF_TS) != 0 &&
+ SEQ_LEQ(ti->ti_seq, tp->last_ack_sent)) {
+ tp->ts_recent_age = tcp_now;
+ tp->ts_recent = to.to_tsval;
+ }
+
+ 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 ((to.to_flags & TOF_TS) != 0)
+ tcp_xmit_timer(tp,
+ tcp_now - to.to_tsecr + 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)
+ tp->t_timer[TCPT_REXMT] = 0;
+ else if (tp->t_timer[TCPT_PERSIST] == 0)
+ tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
+
+ if (so->so_snd.sb_flags & SB_NOTIFY)
+ sowwakeup(so);
+ if (so->so_snd.sb_cc)
+ (void) tcp_output(tp);
+ return;
+ }
+ } else if (ti->ti_ack == tp->snd_una &&
+ tp->seg_next == (struct tcpiphdr *)tp &&
+ 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;
+ /*
+ * Add data to socket buffer.
+ */
+ sbappend(&so->so_rcv, m);
+ sorwakeup(so);
+#ifdef TCP_ACK_HACK
+ /*
+ * If this is a short packet, then ACK now - with Nagel
+ * congestion avoidance sender won't send more until
+ * he gets an ACK.
+ */
+ if (tiflags & TH_PUSH) {
+ tp->t_flags |= TF_ACKNOW;
+ tcp_output(tp);
+ } else {
+ tp->t_flags |= TF_DELACK;
+ }
+#else
+ tp->t_flags |= TF_DELACK;
+#endif
+ return;
+ }
+ }
+
+ /*
+ * 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:
+ * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK>
+ * 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;
+ /*
+ * 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(ntohl(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 ((taop = tcp_gettaocache(inp)) == NULL) {
+ taop = &tao_noncached;
+ bzero(taop, sizeof(*taop));
+ }
+ tcp_dooptions(tp, optp, optlen, ti, &to);
+ if (iss)
+ tp->iss = iss;
+ else
+ tp->iss = tcp_iss;
+ tcp_iss += TCP_ISSINCR/4;
+ tp->irs = ti->ti_seq;
+ tcp_sendseqinit(tp);
+ tcp_rcvseqinit(tp);
+ /*
+ * Initialization of the tcpcb for transaction;
+ * set SND.WND = SEG.WND,
+ * initialize CCsend and CCrecv.
+ */
+ tp->snd_wnd = tiwin; /* initial send-window */
+ tp->cc_send = CC_INC(tcp_ccgen);
+ tp->cc_recv = to.to_cc;
+ /*
+ * Perform TAO test on incoming CC (SEG.CC) option, if any.
+ * - compare SEG.CC against cached CC from the same host,
+ * if any.
+ * - if SEG.CC > chached value, SYN must be new and is accepted
+ * immediately: save new CC in the cache, mark the socket
+ * connected, enter ESTABLISHED state, turn on flag to
+ * send a SYN in the next segment.
+ * A virtual advertised window is set in rcv_adv to
+ * initialize SWS prevention. Then enter normal segment
+ * processing: drop SYN, process data and FIN.
+ * - otherwise do a normal 3-way handshake.
+ */
+ if ((to.to_flags & TOF_CC) != 0) {
+ if (taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) {
+ taop->tao_cc = to.to_cc;
+ tp->t_state = TCPS_ESTABLISHED;
+
+ /*
+ * If there is a FIN, or if there is data and the
+ * connection is local, then delay SYN,ACK(SYN) in
+ * the hope of piggy-backing it on a response
+ * segment. Otherwise must send ACK now in case
+ * the other side is slow starting.
+ */
+ if ((tiflags & TH_FIN) || (ti->ti_len != 0 &&
+ in_localaddr(inp->inp_faddr)))
+ tp->t_flags |= (TF_DELACK | TF_NEEDSYN);
+ else
+ tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
+
+ /*
+ * Limit the `virtual advertised window' to TCP_MAXWIN
+ * here. Even if we requested window scaling, it will
+ * become effective only later when our SYN is acked.
+ */
+ tp->rcv_adv += min(tp->rcv_wnd, TCP_MAXWIN);
+ tcpstat.tcps_connects++;
+ soisconnected(so);
+ tp->t_timer[TCPT_KEEP] = tcp_keepinit;
+ dropsocket = 0; /* committed to socket */
+ tcpstat.tcps_accepts++;
+ goto trimthenstep6;
+ }
+ /* else do standard 3-way handshake */
+ } else {
+ /*
+ * No CC option, but maybe CC.NEW:
+ * invalidate cached value.
+ */
+ taop->tao_cc = 0;
+ }
+ /*
+ * TAO test failed or there was no CC option,
+ * do a standard 3-way handshake.
+ */
+ tp->t_flags |= TF_ACKNOW;
+ tp->t_state = TCPS_SYN_RECEIVED;
+ tp->t_timer[TCPT_KEEP] = tcp_keepinit;
+ dropsocket = 0; /* committed to socket */
+ tcpstat.tcps_accepts++;
+ goto trimthenstep6;
+ }
+
+ /*
+ * If the state is SYN_RECEIVED:
+ * if seg contains SYN/ACK, send a RST.
+ * if seg contains an ACK, but not for our SYN/ACK, send a 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 ((taop = tcp_gettaocache(inp)) == NULL) {
+ taop = &tao_noncached;
+ bzero(taop, sizeof(*taop));
+ }
+
+ if ((tiflags & TH_ACK) &&
+ (SEQ_LEQ(ti->ti_ack, tp->iss) ||
+ SEQ_GT(ti->ti_ack, tp->snd_max))) {
+ /*
+ * If we have a cached CCsent for the remote host,
+ * hence we haven't just crashed and restarted,
+ * do not send a RST. This may be a retransmission
+ * from the other side after our earlier ACK was lost.
+ * Our new SYN, when it arrives, will serve as the
+ * needed ACK.
+ */
+ if (taop->tao_ccsent != 0)
+ goto drop;
+ else
+ goto dropwithreset;
+ }
+ if (tiflags & TH_RST) {
+ if (tiflags & TH_ACK)
+ tp = tcp_drop(tp, ECONNREFUSED);
+ goto drop;
+ }
+ if ((tiflags & TH_SYN) == 0)
+ goto drop;
+ tp->snd_wnd = ti->ti_win; /* initial send window */
+ tp->cc_recv = to.to_cc; /* foreign CC */
+
+ tp->irs = ti->ti_seq;
+ tcp_rcvseqinit(tp);
+ if (tiflags & TH_ACK) {
+ /*
+ * Our SYN was acked. If segment contains CC.ECHO
+ * option, check it to make sure this segment really
+ * matches our SYN. If not, just drop it as old
+ * duplicate, but send an RST if we're still playing
+ * by the old rules. If no CC.ECHO option, make sure
+ * we don't get fooled into using T/TCP.
+ */
+ if (to.to_flags & TOF_CCECHO) {
+ if (tp->cc_send != to.to_ccecho) {
+ if (taop->tao_ccsent != 0)
+ goto drop;
+ else
+ goto dropwithreset;
+ }
+ } else
+ tp->t_flags &= ~TF_RCVD_CC;
+ tcpstat.tcps_connects++;
+ soisconnected(so);
+ /* Do window scaling on this connection? */
+ if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
+ (TF_RCVD_SCALE|TF_REQ_SCALE)) {
+ tp->snd_scale = tp->requested_s_scale;
+ tp->rcv_scale = tp->request_r_scale;
+ }
+ /* Segment is acceptable, update cache if undefined. */
+ if (taop->tao_ccsent == 0)
+ taop->tao_ccsent = to.to_ccecho;
+
+ tp->rcv_adv += tp->rcv_wnd;
+ tp->snd_una++; /* SYN is acked */
+ /*
+ * If there's data, delay ACK; if there's also a FIN
+ * ACKNOW will be turned on later.
+ */
+ if (ti->ti_len != 0)
+ tp->t_flags |= TF_DELACK;
+ else
+ tp->t_flags |= TF_ACKNOW;
+ /*
+ * Received <SYN,ACK> in SYN_SENT[*] state.
+ * Transitions:
+ * SYN_SENT --> ESTABLISHED
+ * SYN_SENT* --> FIN_WAIT_1
+ */
+ if (tp->t_flags & TF_NEEDFIN) {
+ tp->t_state = TCPS_FIN_WAIT_1;
+ tp->t_flags &= ~TF_NEEDFIN;
+ tiflags &= ~TH_SYN;
+ } else {
+ tp->t_state = TCPS_ESTABLISHED;
+ tp->t_timer[TCPT_KEEP] = tcp_keepidle;
+ }
+ } else {
+ /*
+ * Received initial SYN in SYN-SENT[*] state => simul-
+ * taneous open. If segment contains CC option and there is
+ * a cached CC, apply TAO test; if it succeeds, connection is
+ * half-synchronized. Otherwise, do 3-way handshake:
+ * SYN-SENT -> SYN-RECEIVED
+ * SYN-SENT* -> SYN-RECEIVED*
+ * If there was no CC option, clear cached CC value.
+ */
+ tp->t_flags |= TF_ACKNOW;
+ tp->t_timer[TCPT_REXMT] = 0;
+ if (to.to_flags & TOF_CC) {
+ if (taop->tao_cc != 0 &&
+ CC_GT(to.to_cc, taop->tao_cc)) {
+ /*
+ * update cache and make transition:
+ * SYN-SENT -> ESTABLISHED*
+ * SYN-SENT* -> FIN-WAIT-1*
+ */
+ taop->tao_cc = to.to_cc;
+ if (tp->t_flags & TF_NEEDFIN) {
+ tp->t_state = TCPS_FIN_WAIT_1;
+ tp->t_flags &= ~TF_NEEDFIN;
+ } else {
+ tp->t_state = TCPS_ESTABLISHED;
+ tp->t_timer[TCPT_KEEP] = tcp_keepidle;
+ }
+ tp->t_flags |= TF_NEEDSYN;
+ } else
+ tp->t_state = TCPS_SYN_RECEIVED;
+ } else {
+ /* CC.NEW or no option => invalidate cache */
+ taop->tao_cc = 0;
+ 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;
+ /*
+ * Client side of transaction: already sent SYN and data.
+ * If the remote host used T/TCP to validate the SYN,
+ * our data will be ACK'd; if so, enter normal data segment
+ * processing in the middle of step 5, ack processing.
+ * Otherwise, goto step 6.
+ */
+ if (tiflags & TH_ACK)
+ goto process_ACK;
+ goto step6;
+ /*
+ * If the state is LAST_ACK or CLOSING or TIME_WAIT:
+ * if segment contains a SYN and CC [not CC.NEW] option:
+ * if state == TIME_WAIT and connection duration > MSL,
+ * drop packet and send RST;
+ *
+ * if SEG.CC > CCrecv then is new SYN, and can implicitly
+ * ack the FIN (and data) in retransmission queue.
+ * Complete close and delete TCPCB. Then reprocess
+ * segment, hoping to find new TCPCB in LISTEN state;
+ *
+ * else must be old SYN; drop it.
+ * else do normal processing.
+ */
+ case TCPS_LAST_ACK:
+ case TCPS_CLOSING:
+ case TCPS_TIME_WAIT:
+ if ((tiflags & TH_SYN) &&
+ (to.to_flags & TOF_CC) && tp->cc_recv != 0) {
+ if (tp->t_state == TCPS_TIME_WAIT &&
+ tp->t_duration > TCPTV_MSL)
+ goto dropwithreset;
+ if (CC_GT(to.to_cc, tp->cc_recv)) {
+ tp = tcp_close(tp);
+ goto findpcb;
+ }
+ else
+ goto drop;
+ }
+ break; /* continue normal processing */
+ }
+
+ /*
+ * States other than LISTEN or SYN_SENT.
+ * First check timestamp, if present.
+ * Then check the connection count, if present.
+ * Then check that at least some bytes of segment are within
+ * receive window. If segment begins before rcv_nxt,
+ * drop leading data (and SYN); if nothing left, just ack.
+ *
+ * RFC 1323 PAWS: If we have a timestamp reply on this segment
+ * and it's less than ts_recent, drop it.
+ */
+ if ((to.to_flags & TOF_TS) != 0 && (tiflags & TH_RST) == 0 &&
+ tp->ts_recent && TSTMP_LT(to.to_tsval, 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;
+ }
+ }
+
+ /*
+ * T/TCP mechanism
+ * If T/TCP was negotiated and the segment doesn't have CC,
+ * or if it's CC is wrong then drop the segment.
+ * RST segments do not have to comply with this.
+ */
+ if ((tp->t_flags & (TF_REQ_CC|TF_RCVD_CC)) == (TF_REQ_CC|TF_RCVD_CC) &&
+ ((to.to_flags & TOF_CC) == 0 || tp->cc_recv != to.to_cc) &&
+ (tiflags & TH_RST) == 0)
+ 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--;
+ }
+ /*
+ * Following if statement from Stevens, vol. 2, p. 960.
+ */
+ 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_rcvduppack++;
+ tcpstat.tcps_rcvdupbyte += todrop;
+ } 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.
+ * NOTE that the test is modified according to the latest
+ * proposal of the tcplw@cray.com list (Braden 1993/04/26).
+ */
+ if ((to.to_flags & TOF_TS) != 0 &&
+ SEQ_LEQ(ti->ti_seq, tp->last_ack_sent)) {
+ tp->ts_recent_age = tcp_now;
+ tp->ts_recent = to.to_tsval;
+ }
+
+ /*
+ * 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: if in SYN-RECEIVED state or SENDSYN
+ * flag is on (half-synchronized state), then queue data for
+ * later processing; else drop segment and return.
+ */
+ if ((tiflags & TH_ACK) == 0) {
+ if (tp->t_state == TCPS_SYN_RECEIVED ||
+ (tp->t_flags & TF_NEEDSYN))
+ goto step6;
+ else
+ goto drop;
+ }
+
+ /*
+ * Ack processing.
+ */
+ switch (tp->t_state) {
+
+ /*
+ * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
+ * ESTABLISHED state and continue processing.
+ * The ACK was checked above.
+ */
+ case TCPS_SYN_RECEIVED:
+
+ tcpstat.tcps_connects++;
+ soisconnected(so);
+ /* Do window scaling? */
+ if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
+ (TF_RCVD_SCALE|TF_REQ_SCALE)) {
+ tp->snd_scale = tp->requested_s_scale;
+ tp->rcv_scale = tp->request_r_scale;
+ }
+ /*
+ * Upon successful completion of 3-way handshake,
+ * update cache.CC if it was undefined, pass any queued
+ * data to the user, and advance state appropriately.
+ */
+ if ((taop = tcp_gettaocache(inp)) != NULL &&
+ taop->tao_cc == 0)
+ taop->tao_cc = tp->cc_recv;
+
+ /*
+ * Make transitions:
+ * SYN-RECEIVED -> ESTABLISHED
+ * SYN-RECEIVED* -> FIN-WAIT-1
+ */
+ if (tp->t_flags & TF_NEEDFIN) {
+ tp->t_state = TCPS_FIN_WAIT_1;
+ tp->t_flags &= ~TF_NEEDFIN;
+ } else {
+ tp->t_state = TCPS_ESTABLISHED;
+ tp->t_timer[TCPT_KEEP] = tcp_keepidle;
+ }
+ /*
+ * If segment contains data or ACK, will call tcp_reass()
+ * later; if not, do so now to pass queued data to user.
+ */
+ if (ti->ti_len == 0 && (tiflags & TH_FIN) == 0)
+ (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)) {
+ 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 (tp->t_timer[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_maxseg;
+
+ if (win < 2)
+ win = 2;
+ tp->snd_ssthresh = win * tp->t_maxseg;
+ tp->t_timer[TCPT_REXMT] = 0;
+ tp->t_rtt = 0;
+ tp->snd_nxt = ti->ti_ack;
+ tp->snd_cwnd = tp->t_maxseg;
+ (void) tcp_output(tp);
+ tp->snd_cwnd = tp->snd_ssthresh +
+ tp->t_maxseg * tp->t_dupacks;
+ if (SEQ_GT(onxt, tp->snd_nxt))
+ tp->snd_nxt = onxt;
+ goto drop;
+ } else if (tp->t_dupacks > tcprexmtthresh) {
+ tp->snd_cwnd += tp->t_maxseg;
+ (void) tcp_output(tp);
+ goto drop;
+ }
+ } else
+ tp->t_dupacks = 0;
+ break;
+ }
+ /*
+ * If the congestion window was inflated to account
+ * for the other side's cached packets, retract it.
+ */
+ if (tp->t_dupacks >= tcprexmtthresh &&
+ tp->snd_cwnd > tp->snd_ssthresh)
+ tp->snd_cwnd = tp->snd_ssthresh;
+ tp->t_dupacks = 0;
+ if (SEQ_GT(ti->ti_ack, tp->snd_max)) {
+ tcpstat.tcps_rcvacktoomuch++;
+ goto dropafterack;
+ }
+ /*
+ * If we reach this point, ACK is not a duplicate,
+ * i.e., it ACKs something we sent.
+ */
+ if (tp->t_flags & TF_NEEDSYN) {
+ /*
+ * T/TCP: Connection was half-synchronized, and our
+ * SYN has been ACK'd (so connection is now fully
+ * synchronized). Go to non-starred state,
+ * increment snd_una for ACK of SYN, and check if
+ * we can do window scaling.
+ */
+ tp->t_flags &= ~TF_NEEDSYN;
+ tp->snd_una++;
+ /* Do window scaling? */
+ if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
+ (TF_RCVD_SCALE|TF_REQ_SCALE)) {
+ tp->snd_scale = tp->requested_s_scale;
+ tp->rcv_scale = tp->request_r_scale;
+ }
+ }
+
+process_ACK:
+ 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 (to.to_flags & TOF_TS)
+ tcp_xmit_timer(tp, tcp_now - to.to_tsecr + 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;
+
+ /*
+ * If no data (only SYN) was ACK'd,
+ * skip rest of ACK processing.
+ */
+ if (acked == 0)
+ goto step6;
+
+ /*
+ * 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;
+ tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->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 (so->so_snd.sb_flags & SB_NOTIFY)
+ 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) {
+ /*
+ * 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);
+ /* Shorten TIME_WAIT [RFC-1644, p.28] */
+ if (tp->cc_recv != 0 &&
+ tp->t_duration < TCPTV_MSL)
+ tp->t_timer[TCPT_2MSL] =
+ tp->t_rxtcur * TCPTV_TWTRUNC;
+ else
+ 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_long)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.
+ */
+ if (tiflags & TH_FIN) {
+ if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
+ socantrcvmore(so);
+ /*
+ * If connection is half-synchronized
+ * (ie NEEDSYN flag on) then delay ACK,
+ * so it may be piggybacked when SYN is sent.
+ * Otherwise, since we received a FIN then no
+ * more input can be expected, send ACK now.
+ */
+ if (tp->t_flags & TF_NEEDSYN)
+ tp->t_flags |= TF_DELACK;
+ else
+ tp->t_flags |= TF_ACKNOW;
+ tp->rcv_nxt++;
+ }
+ switch (tp->t_state) {
+
+ /*
+ * In SYN_RECEIVED and ESTABLISHED STATES
+ * enter the CLOSE_WAIT state.
+ */
+ case TCPS_SYN_RECEIVED:
+ 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);
+ /* Shorten TIME_WAIT [RFC-1644, p.28] */
+ if (tp->cc_recv != 0 &&
+ tp->t_duration < TCPTV_MSL) {
+ tp->t_timer[TCPT_2MSL] =
+ tp->t_rxtcur * TCPTV_TWTRUNC;
+ /* For transaction client, force ACK now. */
+ tp->t_flags |= TF_ACKNOW;
+ }
+ else
+ 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;
+ }
+ }
+#ifdef TCPDEBUG
+ if (so->so_options & SO_DEBUG)
+ tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0);
+#endif
+
+ /*
+ * Return any desired output.
+ */
+ if (needoutput || (tp->t_flags & TF_ACKNOW))
+ (void) tcp_output(tp);
+ 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;
+#ifdef TCPDEBUG
+ if (so->so_options & SO_DEBUG)
+ tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0);
+#endif
+ 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(ntohl(ti->ti_dst.s_addr)))
+ goto drop;
+#ifdef TCPDEBUG
+ if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
+ tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0);
+#endif
+ 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.
+ */
+#ifdef TCPDEBUG
+ if (tp == 0 || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
+ tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0);
+#endif
+ m_freem(m);
+ /* destroy temporarily created socket */
+ if (dropsocket)
+ (void) soabort(so);
+ return;
+#ifndef TUBA_INCLUDE
+}
+
+static void
+tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, struct tcpiphdr *ti,
+ struct tcpopt *to)
+{
+ u_short 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;
+ to->to_flags |= TOF_TS;
+ bcopy((char *)cp + 2,
+ (char *)&to->to_tsval, sizeof(to->to_tsval));
+ NTOHL(to->to_tsval);
+ bcopy((char *)cp + 6,
+ (char *)&to->to_tsecr, sizeof(to->to_tsecr));
+ NTOHL(to->to_tsecr);
+
+ /*
+ * 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 = to->to_tsval;
+ tp->ts_recent_age = tcp_now;
+ }
+ break;
+ case TCPOPT_CC:
+ if (optlen != TCPOLEN_CC)
+ continue;
+ to->to_flags |= TOF_CC;
+ bcopy((char *)cp + 2,
+ (char *)&to->to_cc, sizeof(to->to_cc));
+ NTOHL(to->to_cc);
+ /*
+ * A CC or CC.new option received in a SYN makes
+ * it ok to send CC in subsequent segments.
+ */
+ if (ti->ti_flags & TH_SYN)
+ tp->t_flags |= TF_RCVD_CC;
+ break;
+ case TCPOPT_CCNEW:
+ if (optlen != TCPOLEN_CC)
+ continue;
+ if (!(ti->ti_flags & TH_SYN))
+ continue;
+ to->to_flags |= TOF_CCNEW;
+ bcopy((char *)cp + 2,
+ (char *)&to->to_cc, sizeof(to->to_cc));
+ NTOHL(to->to_cc);
+ /*
+ * A CC or CC.new option received in a SYN makes
+ * it ok to send CC in subsequent segments.
+ */
+ tp->t_flags |= TF_RCVD_CC;
+ break;
+ case TCPOPT_CCECHO:
+ if (optlen != TCPOLEN_CC)
+ continue;
+ if (!(ti->ti_flags & TH_SYN))
+ continue;
+ to->to_flags |= TOF_CCECHO;
+ bcopy((char *)cp + 2,
+ (char *)&to->to_ccecho, sizeof(to->to_ccecho));
+ NTOHL(to->to_ccecho);
+ break;
+ }
+ }
+ if (ti->ti_flags & TH_SYN)
+ tcp_mss(tp, mss); /* sets t_maxseg */
+}
+
+/*
+ * 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.
+ */
+static void
+tcp_pulloutofband(struct socket *so, struct tcpiphdr *ti, 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.
+ */
+static void
+tcp_xmit_timer(struct tcpcb *tp, int rtt)
+{
+ int delta;
+
+ tcpstat.tcps_rttupdated++;
+ tp->t_rttupdated++;
+ if (tp->t_srtt != 0) {
+ /*
+ * srtt is stored as fixed point with 5 bits after the
+ * binary point (i.e., scaled by 8). The following magic
+ * is equivalent to the smoothing algorithm in rfc793 with
+ * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
+ * point). Adjust rtt to origin 0.
+ */
+ delta = ((rtt - 1) << TCP_DELTA_SHIFT)
+ - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
+
+ if ((tp->t_srtt += delta) <= 0)
+ tp->t_srtt = 1;
+
+ /*
+ * We accumulate a smoothed rtt variance (actually, a
+ * smoothed mean difference), then set the retransmit
+ * timer to smoothed rtt + 4 times the smoothed variance.
+ * rttvar is stored as fixed point with 4 bits after the
+ * binary point (scaled by 16). The following is
+ * equivalent to rfc793 smoothing with an alpha of .75
+ * (rttvar = rttvar*3/4 + |delta| / 4). This replaces
+ * rfc793's wired-in beta.
+ */
+ if (delta < 0)
+ delta = -delta;
+ delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
+ if ((tp->t_rttvar += delta) <= 0)
+ tp->t_rttvar = 1;
+ } else {
+ /*
+ * No rtt measurement yet - use the unsmoothed rtt.
+ * Set the variance to half the rtt (so our first
+ * retransmit happens at 3*rtt).
+ */
+ tp->t_srtt = rtt << TCP_RTT_SHIFT;
+ tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
+ }
+ tp->t_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),
+ max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
+
+ /*
+ * We received an ack for a packet that wasn't retransmitted;
+ * it is probably safe to discard any error indications we've
+ * received recently. This isn't quite right, but close enough
+ * for now (a route might have failed after we sent a segment,
+ * and the return path might not be symmetrical).
+ */
+ tp->t_softerror = 0;
+}
+
+/*
+ * Determine a reasonable value for maxseg size.
+ * If the route is known, check route for mtu.
+ * If none, use an mss that can be handled on the outgoing
+ * interface without forcing IP to fragment; if bigger than
+ * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES
+ * to utilize large mbufs. If no route is found, route has no mtu,
+ * or the destination isn't local, use a default, hopefully conservative
+ * size (usually 512 or the default IP max size, but no more than the mtu
+ * of the interface), as we can't discover anything about intervening
+ * gateways or networks. We also initialize the congestion/slow start
+ * window to be a single segment if the destination isn't local.
+ * While looking at the routing entry, we also initialize other path-dependent
+ * parameters from pre-set or cached values in the routing entry.
+ *
+ * Also take into account the space needed for options that we
+ * send regularly. Make maxseg shorter by that amount to assure
+ * that we can send maxseg amount of data even when the options
+ * are present. Store the upper limit of the length of options plus
+ * data in maxopd.
+ *
+ * NOTE that this routine is only called when we process an incoming
+ * segment, for outgoing segments only tcp_mssopt is called.
+ *
+ * In case of T/TCP, we call this routine during implicit connection
+ * setup as well (offer = -1), to initialize maxseg from the cached
+ * MSS of our peer.
+ */
+void
+tcp_mss(struct tcpcb *tp, int offer)
+{
+ register struct rtentry *rt;
+ struct ifnet *ifp;
+ register int rtt, mss;
+ u_long bufsize;
+ struct inpcb *inp;
+ struct socket *so;
+ struct rmxp_tao *taop;
+ int origoffer = offer;
+
+ inp = tp->t_inpcb;
+ if ((rt = tcp_rtlookup(inp)) == NULL) {
+ tp->t_maxopd = tp->t_maxseg = tcp_mssdflt;
+ return;
+ }
+ ifp = rt->rt_ifp;
+ so = inp->inp_socket;
+
+ taop = rmx_taop(rt->rt_rmx);
+ /*
+ * Offer == -1 means that we didn't receive SYN yet,
+ * use cached value in that case;
+ */
+ if (offer == -1)
+ offer = taop->tao_mssopt;
+ /*
+ * Offer == 0 means that there was no MSS on the SYN segment,
+ * in this case we use tcp_mssdflt.
+ */
+ if (offer == 0)
+ offer = tcp_mssdflt;
+ else
+ /*
+ * Sanity check: make sure that maxopd will be large
+ * enough to allow some data on segments even is the
+ * all the option space is used (40bytes). Otherwise
+ * funny things may happen in tcp_output.
+ */
+ offer = max(offer, 64);
+ taop->tao_mssopt = offer;
+
+ /*
+ * While we're here, check if there's an initial rtt
+ * or rttvar. Convert from the route-table units
+ * to scaled multiples of the slow timeout timer.
+ */
+ if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) {
+ /*
+ * XXX the lock bit for RTT indicates that the value
+ * is also a minimum value; this is subject to time.
+ */
+ if (rt->rt_rmx.rmx_locks & RTV_RTT)
+ tp->t_rttmin = rtt / (RTM_RTTUNIT / PR_SLOWHZ);
+ tp->t_srtt = rtt / (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE));
+ tcpstat.tcps_usedrtt++;
+ if (rt->rt_rmx.rmx_rttvar) {
+ tp->t_rttvar = rt->rt_rmx.rmx_rttvar /
+ (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE));
+ tcpstat.tcps_usedrttvar++;
+ } else {
+ /* default variation is +- 1 rtt */
+ tp->t_rttvar =
+ tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
+ }
+ TCPT_RANGESET(tp->t_rxtcur,
+ ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
+ tp->t_rttmin, TCPTV_REXMTMAX);
+ }
+ /*
+ * if there's an mtu associated with the route, use it
+ */
+ if (rt->rt_rmx.rmx_mtu)
+ mss = rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr);
+ else
+ {
+ mss = ifp->if_mtu - sizeof(struct tcpiphdr);
+ if (!in_localaddr(inp->inp_faddr))
+ mss = min(mss, tcp_mssdflt);
+ }
+ mss = min(mss, offer);
+ /*
+ * maxopd stores the maximum length of data AND options
+ * in a segment; maxseg is the amount of data in a normal
+ * segment. We need to store this value (maxopd) apart
+ * from maxseg, because now every segment carries options
+ * and thus we normally have somewhat less data in segments.
+ */
+ tp->t_maxopd = mss;
+
+ /*
+ * In case of T/TCP, origoffer==-1 indicates, that no segments
+ * were received yet. In this case we just guess, otherwise
+ * we do the same as before T/TCP.
+ */
+ if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
+ (origoffer == -1 ||
+ (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
+ mss -= TCPOLEN_TSTAMP_APPA;
+ if ((tp->t_flags & (TF_REQ_CC|TF_NOOPT)) == TF_REQ_CC &&
+ (origoffer == -1 ||
+ (tp->t_flags & TF_RCVD_CC) == TF_RCVD_CC))
+ mss -= TCPOLEN_CC_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);
+ }
+ /*
+ * Don't force slow-start on local network.
+ */
+ if (!in_localaddr(inp->inp_faddr))
+ tp->snd_cwnd = mss;
+
+ if (rt->rt_rmx.rmx_ssthresh) {
+ /*
+ * There's some sort of gateway or interface
+ * buffer limit on the path. Use this to set
+ * the slow start threshhold, but set the
+ * threshold to no less than 2*mss.
+ */
+ tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh);
+ tcpstat.tcps_usedssthresh++;
+ }
+}
+
+/*
+ * Determine the MSS option to send on an outgoing SYN.
+ */
+int
+tcp_mssopt(struct tcpcb *tp)
+{
+ struct rtentry *rt;
+
+ rt = tcp_rtlookup(tp->t_inpcb);
+ if (rt == NULL)
+ return tcp_mssdflt;
+
+ return rt->rt_ifp->if_mtu - sizeof(struct tcpiphdr);
+}
+#endif /* TUBA_INCLUDE */