initial user mode network support

git-svn-id: svn://svn.savannah.nongnu.org/qemu/trunk@733 c046a42c-6fe2-441c-8c8c-71466251a162

1 files changed, 1733 insertions, 0 deletions

diff --git a/tcp_input.c b/tcp_input.c
new file mode 100644
index 0000000..c21f97b
--- /dev/null
+++ b/tcp_input.c
@@ -0,0 +1,1733 @@
+/*
+ * 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
+ * tcp_input.c,v 1.10 1994/10/13 18:36:32 wollman Exp
+ */
+
+/*
+ * Changes and additions relating to SLiRP
+ * Copyright (c) 1995 Danny Gasparovski.
+ *
+ * Please read the file COPYRIGHT for the
+ * terms and conditions of the copyright.
+ */
+
+#include <slirp.h>
+#include "ip_icmp.h"
+
+struct socket tcb;
+
+#define min(x, y) ((x) < (y) ? (x) : (y))
+#define max(x, y) ((x) > (y) ? (x) : (y))
+
+int tcprexmtthresh = 3;
+struct socket *tcp_last_so = &tcb;
+
+tcp_seq tcp_iss; /* tcp initial send seq # */
+
+#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)
+
+/*
+ * 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 == (tcpiphdrp_32)(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;   \
+            if (so->so_emu) {                       \
+                if (tcp_emu((so), (m)))             \
+                    sbappend((so), (m));            \
+            } else                                  \
+                sbappend((so), (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 == (tcpiphdrp_32)(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;   \
+            if (so->so_emu) {                       \
+                if (tcp_emu((so), (m)))             \
+                    sbappend(so, (m));              \
+            } else                                  \
+                sbappend((so), (m));                \
+            /*		sorwakeup(so); */                   \
+        } else {                                    \
+            (flags) = tcp_reass((tp), (ti), (m));   \
+            tp->t_flags |= TF_ACKNOW;               \
+        }                                           \
+    }
+#endif
+
+int tcp_reass(tp, ti, m) register struct tcpcb *tp;
+register struct tcpiphdr *ti;
+struct mbuf *m;
+{
+    register struct tcpiphdr *q;
+    struct socket *so = tp->t_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 = (struct tcpiphdr *)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;
+    REASS_MBUF(ti) = (mbufp_32)m; /* XXX */
+
+    /*
+     * 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;
+            m_adj((struct mbuf *)REASS_MBUF(q), i);
+            break;
+        }
+        q = (struct tcpiphdr *)q->ti_next;
+        m = (struct mbuf *)REASS_MBUF((struct tcpiphdr *)q->ti_prev);
+        remque_32((void *)(q->ti_prev));
+        m_freem(m);
+    }
+
+    /*
+     * Stick new segment in its place.
+     */
+    insque_32(ti, (void *)(q->ti_prev));
+
+present:
+    /*
+     * Present data to user, advancing rcv_nxt through
+     * completed sequence space.
+     */
+    if (!TCPS_HAVEESTABLISHED(tp->t_state))
+        return (0);
+    ti = (struct tcpiphdr *)tp->seg_next;
+    if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt)
+        return (0);
+    if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len)
+        return (0);
+    do {
+        tp->rcv_nxt += ti->ti_len;
+        flags = ti->ti_flags & TH_FIN;
+        remque_32(ti);
+        m = (struct mbuf *)REASS_MBUF(ti); /* XXX */
+        ti = (struct tcpiphdr *)ti->ti_next;
+        /*		if (so->so_state & SS_FCANTRCVMORE) */
+        if (so->so_state & SS_FCANTSENDMORE)
+            m_freem(m);
+        else {
+            if (so->so_emu) {
+                if (tcp_emu(so, m))
+                    sbappend(so, m);
+            } else
+                sbappend(so, 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(m, iphlen, inso) register struct mbuf *m;
+int iphlen;
+struct socket *inso;
+{
+    struct ip save_ip, *ip;
+    register struct tcpiphdr *ti;
+    caddr_t 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;
+    /*	int dropsocket = 0; */
+    int iss = 0;
+    u_long tiwin;
+    int ret;
+    /*	int ts_present = 0; */
+
+    DEBUG_CALL("tcp_input");
+    DEBUG_ARGS((dfd, " m = %8lx  iphlen = %2d  inso = %lx\n", (long)m, iphlen,
+                (long)inso));
+
+    /*
+     * If called with m == 0, then we're continuing the connect
+     */
+    if (m == NULL) {
+        so = inso;
+
+        /* Re-set a few variables */
+        tp = sototcpcb(so);
+        m = so->so_m;
+        so->so_m = 0;
+        ti = so->so_ti;
+        tiwin = ti->ti_win;
+        tiflags = ti->ti_flags;
+
+        goto cont_conn;
+    }
+
+
+    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);
+        iphlen = sizeof(struct ip);
+    }
+    /* XXX Check if too short */
+
+
+    /*
+     * Save a copy of the IP header in case we want restore it
+     * for sending an ICMP error message in response.
+     */
+    ip = mtod(m, struct ip *);
+    save_ip = *ip;
+    save_ip.ip_len += iphlen;
+
+    /*
+     * Checksum extended TCP header and data.
+     */
+    tlen = ((struct ip *)ti)->ip_len;
+    ti->ti_next = ti->ti_prev = 0;
+    ti->ti_x1 = 0;
+    ti->ti_len = htons((u_int16_t)tlen);
+    len = sizeof(struct ip) + tlen;
+    /* keep checksum for ICMP reply
+     * ti->ti_sum = cksum(m, len);
+     * if (ti->ti_sum) { */
+    if (cksum(m, len)) {
+        tcpstat.tcps_rcvbadsum++;
+        goto drop;
+    }
+
+    /*
+     * Check that TCP offset makes sense,
+     * pull out TCP options and adjust length.		XXX
+     */
+    off = ti->ti_off << 2;
+    if (off < sizeof(struct tcphdr) || off > tlen) {
+        tcpstat.tcps_rcvbadoff++;
+        goto drop;
+    }
+    tlen -= off;
+    ti->ti_len = tlen;
+    if (off > sizeof(struct tcphdr)) {
+        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);
+
+    /*
+     * 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.
+     */
+findso:
+    so = tcp_last_so;
+    if (so->so_fport != ti->ti_dport || so->so_lport != ti->ti_sport ||
+        so->so_laddr.s_addr != ti->ti_src.s_addr ||
+        so->so_faddr.s_addr != ti->ti_dst.s_addr) {
+        so = solookup(&tcb, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport);
+        if (so)
+            tcp_last_so = so;
+        ++tcpstat.tcps_socachemiss;
+    }
+
+    /*
+     * 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.
+     *
+     * state == CLOSED means we've done socreate() but haven't
+     * attached it to a protocol yet...
+     *
+     * XXX If a TCB does not exist, and the TH_SYN flag is
+     * the only flag set, then create a session, mark it
+     * as if it was LISTENING, and continue...
+     */
+    if (so == 0) {
+        if ((tiflags & (TH_SYN | TH_FIN | TH_RST | TH_URG | TH_ACK)) != TH_SYN)
+            goto dropwithreset;
+
+        if ((so = socreate()) == NULL)
+            goto dropwithreset;
+        if (tcp_attach(so) < 0) {
+            free(so); /* Not sofree (if it failed, it's not insqued) */
+            goto dropwithreset;
+        }
+
+        sbreserve(&so->so_snd, tcp_sndspace);
+        sbreserve(&so->so_rcv, tcp_rcvspace);
+
+        /*		tcp_last_so = so; */ /* XXX ? */
+        /*		tp = sototcpcb(so);    */
+
+        so->so_laddr = ti->ti_src;
+        so->so_lport = ti->ti_sport;
+        so->so_faddr = ti->ti_dst;
+        so->so_fport = ti->ti_dport;
+
+        if ((so->so_iptos = tcp_tos(so)) == 0)
+            so->so_iptos = ((struct ip *)ti)->ip_tos;
+
+        tp = sototcpcb(so);
+        tp->t_state = TCPS_LISTEN;
+    }
+
+    /*
+     * If this is a still-connecting socket, this probably
+     * a retransmit of the SYN.  Whether it's a retransmit SYN
+     * or something else, we nuke it.
+     */
+    if (so->so_state & SS_ISFCONNECTING)
+        goto drop;
+
+    tp = sototcpcb(so);
+
+    /* XXX Should never fail */
+    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;
+
+    /*
+     * Segment received on connection.
+     * Reset idle time and keep-alive timer.
+     */
+    tp->t_idle = 0;
+    if (so_options)
+        tp->t_timer[TCPT_KEEP] = tcp_keepintvl;
+    else
+        tp->t_timer[TCPT_KEEP] = tcp_keepidle;
+
+    /*
+     * 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, (u_char *)optp, optlen, ti);
+    /* , */
+    /*			&ts_present, &ts_val, &ts_ecr); */
+
+    /*
+     * 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.
+     *
+     * XXX Some of these tests are not needed
+     * eg: the tiwin == tp->snd_wnd prevents many more
+     * predictions.. with no *real* advantage..
+     */
+    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.
+         */
+        /*		if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent)
+         *&& SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) {
+         *			tp->ts_recent_age = tcp_now;
+         *			tp->ts_recent = 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) {
+                /*
+                 * 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;
+                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;
+
+                /*
+                 * There's room in so_snd, sowwakup will read()
+                 * from the socket if we can
+                 */
+                /*				if (so->so_snd.sb_flags &
+                 *SB_NOTIFY) sowwakeup(so);
+                 */
+                /*
+                 * This is called because sowwakeup might have
+                 * put data into so_snd.  Since we don't so sowwakeup,
+                 * we don't need this.. XXX???
+                 */
+                if (so->so_snd.sb_cc)
+                    (void)tcp_output(tp);
+
+                return;
+            }
+        } else if (ti->ti_ack == tp->snd_una &&
+                   tp->seg_next == (tcpiphdrp_32)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.
+             */
+            if (so->so_emu) {
+                if (tcp_emu(so, m))
+                    sbappend(so, m);
+            } else
+                sbappend(so, m);
+
+            /*
+             * XXX This is called when data arrives.  Later, check
+             * if we can actually write() to the socket
+             * XXX Need to check? It's be NON_BLOCKING
+             */
+            /*			sorwakeup(so); */
+
+            /*
+             * If this is a short packet, then ACK now - with Nagel
+             *	congestion avoidance sender won't send more until
+             *	he gets an ACK.
+             *
+             * Here are 3 interpretations of what should happen.
+             * The best (for me) is to delay-ack everything except
+             * if it's a one-byte packet containing an ESC
+             * (this means it's an arrow key (or similar) sent using
+             * Nagel, hence there will be no echo)
+             * The first of these is the original, the second is the
+             * middle ground between the other 2
+             */
+            /*			if (((unsigned)ti->ti_len < tp->t_maxseg)) {
+             */
+            /*			if (((unsigned)ti->ti_len < tp->t_maxseg &&
+             *			     (so->so_iptos & IPTOS_LOWDELAY) == 0) ||
+             *			    ((so->so_iptos & IPTOS_LOWDELAY) &&
+             *			     ((struct tcpiphdr_2 *)ti)->first_char == (char)27))
+             *{
+             */
+            if ((unsigned)ti->ti_len == 1 &&
+                ((struct tcpiphdr_2 *)ti)->first_char == (char)27) {
+                tp->t_flags |= TF_ACKNOW;
+                tcp_output(tp);
+            } else {
+                tp->t_flags |= TF_DELACK;
+            }
+            return;
+        }
+    } /* header prediction */
+    /*
+     * 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 = max(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.
+     * 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: {
+        if (tiflags & TH_RST)
+            goto drop;
+        if (tiflags & TH_ACK)
+            goto dropwithreset;
+        if ((tiflags & TH_SYN) == 0)
+            goto drop;
+
+        /*
+         * This has way too many gotos...
+         * But a bit of spaghetti code never hurt anybody :)
+         */
+
+        /*
+         * If this is destined for the control address, then flag to
+         * tcp_ctl once connected, otherwise connect
+         */
+        if ((so->so_faddr.s_addr & htonl(0xffffff00)) == special_addr.s_addr) {
+            int lastbyte = ntohl(so->so_faddr.s_addr) & 0xff;
+            if (lastbyte != CTL_ALIAS && lastbyte != CTL_DNS) {
+#if 0
+	      if(lastbyte==CTL_CMD || lastbyte==CTL_EXEC) {
+		/* Command or exec adress */
+		so->so_state |= SS_CTL;
+	      } else {
+		/* May be an add exec */
+		struct ex_list *ex_ptr;
+
+		for(ex_ptr = exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) {
+		  if(ex_ptr->ex_fport == so->so_fport && 
+		     lastbyte == ex_ptr->ex_addr) {
+		    so->so_state |= SS_CTL;
+		    break;
+		  }
+		}
+	      }
+	      if(so->so_state & SS_CTL) goto cont_input;
+#endif
+            }
+            /* CTL_ALIAS: Do nothing, tcp_fconnect will be called on it */
+        }
+
+        if (so->so_emu & EMU_NOCONNECT) {
+            so->so_emu &= ~EMU_NOCONNECT;
+            goto cont_input;
+        }
+
+        if (tcp_fconnect(so) == -1 && errno != EINPROGRESS) {
+            u_char code = ICMP_UNREACH_NET;
+            DEBUG_MISC(
+                (dfd, " tcp fconnect errno = %d-%s\n", errno, strerror(errno)));
+            if (errno == ECONNREFUSED) {
+                /* ACK the SYN, send RST to refuse the connection */
+                tcp_respond(tp, ti, m, ti->ti_seq + 1, (tcp_seq)0,
+                            TH_RST | TH_ACK);
+            } else {
+                if (errno == EHOSTUNREACH)
+                    code = ICMP_UNREACH_HOST;
+                HTONL(ti->ti_seq); /* restore tcp header */
+                HTONL(ti->ti_ack);
+                HTONS(ti->ti_win);
+                HTONS(ti->ti_urp);
+                m->m_data -=
+                    sizeof(struct tcpiphdr) + off - sizeof(struct tcphdr);
+                m->m_len +=
+                    sizeof(struct tcpiphdr) + off - sizeof(struct tcphdr);
+                *ip = save_ip;
+                icmp_error(m, ICMP_UNREACH, code, 0, strerror(errno));
+            }
+            tp = tcp_close(tp);
+            m_free(m);
+        } else {
+            /*
+             * Haven't connected yet, save the current mbuf
+             * and ti, and return
+             * XXX Some OS's don't tell us whether the connect()
+             * succeeded or not.  So we must time it out.
+             */
+            so->so_m = m;
+            so->so_ti = ti;
+            tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
+            tp->t_state = TCPS_SYN_RECEIVED;
+        }
+        return;
+
+    cont_conn:
+        /* m==NULL
+         * Check if the connect succeeded
+         */
+        if (so->so_state & SS_NOFDREF) {
+            tp = tcp_close(tp);
+            goto dropwithreset;
+        }
+    cont_input:
+        tcp_template(tp);
+
+        if (optp)
+            tcp_dooptions(tp, (u_char *)optp, optlen, ti);
+        /* , */
+        /*				&ts_present, &ts_val, &ts_ecr); */
+
+        if (iss)
+            tp->iss = iss;
+        else
+            tp->iss = tcp_iss;
+        tcp_iss += TCP_ISSINCR / 2;
+        tp->irs = ti->ti_seq;
+        tcp_sendseqinit(tp);
+        tcp_rcvseqinit(tp);
+        tp->t_flags |= TF_ACKNOW;
+        tp->t_state = TCPS_SYN_RECEIVED;
+        tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT;
+        tcpstat.tcps_accepts++;
+        goto trimthenstep6;
+    } /* case TCPS_LISTEN */
+
+    /*
+     * 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, 0); /* XXX Check t_softerror! */
+            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;
+        if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) {
+            tcpstat.tcps_connects++;
+            soisfconnected(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);
+        } 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;
+    } /* switch tp->t_state */
+    /*
+     * 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--;
+        }
+        /*
+         * 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 findso;
+            }
+            /*
+             * 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.
+     */
+    /*	if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) &&
+     *	    SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len +
+     *		   ((tiflags & (TH_SYN|TH_FIN)) != 0))) {
+     *		tp->ts_recent_age = tcp_now;
+     *		tp->ts_recent = ts_val;
+     *	}
+     */
+
+    /*
+     * If the RST bit is set examine the state:
+     *    SYN_RECEIVED STATE:
+     *	If passive open, return to LISTEN state.
+     *	If active open, inform user that connection was refused.
+     *    ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES:
+     *	Inform user that connection was reset, and close tcb.
+     *    CLOSING, LAST_ACK, TIME_WAIT STATES
+     *	Close the tcb.
+     */
+    if (tiflags & TH_RST)
+        switch (tp->t_state) {
+        case TCPS_SYN_RECEIVED:
+            /*		so->so_error = ECONNREFUSED; */
+            goto close;
+
+        case TCPS_ESTABLISHED:
+        case TCPS_FIN_WAIT_1:
+        case TCPS_FIN_WAIT_2:
+        case TCPS_CLOSE_WAIT:
+            /*		so->so_error = ECONNRESET; */
+        close:
+            tp->t_state = TCPS_CLOSED;
+            tcpstat.tcps_drops++;
+            tp = tcp_close(tp);
+            goto drop;
+
+        case TCPS_CLOSING:
+        case TCPS_LAST_ACK:
+        case TCPS_TIME_WAIT:
+            tp = tcp_close(tp);
+            goto drop;
+        }
+
+    /*
+     * If a SYN is in the window, then this is an
+     * error and we send an RST and drop the connection.
+     */
+    if (tiflags & TH_SYN) {
+        tp = tcp_drop(tp, 0);
+        goto dropwithreset;
+    }
+
+    /*
+     * If the ACK bit is off we drop the segment and return.
+     */
+    if ((tiflags & TH_ACK) == 0)
+        goto drop;
+
+    /*
+     * Ack processing.
+     */
+    switch (tp->t_state) {
+    /*
+     * In SYN_RECEIVED state if the ack ACKs our SYN then enter
+     * ESTABLISHED state and continue processing, otherwise
+     * send an RST.  una<=ack<=max
+     */
+    case TCPS_SYN_RECEIVED:
+
+        if (SEQ_GT(tp->snd_una, ti->ti_ack) || SEQ_GT(ti->ti_ack, tp->snd_max))
+            goto dropwithreset;
+        tcpstat.tcps_connects++;
+        tp->t_state = TCPS_ESTABLISHED;
+        /*
+         * The sent SYN is ack'ed with our sequence number +1
+         * The first data byte already in the buffer will get
+         * lost if no correction is made.  This is only needed for
+         * SS_CTL since the buffer is empty otherwise.
+         * tp->snd_una++; or:
+         */
+        tp->snd_una = ti->ti_ack;
+        if (so->so_state & SS_CTL) {
+            /* So tcp_ctl reports the right state */
+            ret = tcp_ctl(so);
+            if (ret == 1) {
+                soisfconnected(so);
+                so->so_state &= ~SS_CTL; /* success XXX */
+            } else if (ret == 2) {
+                so->so_state = SS_NOFDREF; /* CTL_CMD */
+            } else {
+                needoutput = 1;
+                tp->t_state = TCPS_FIN_WAIT_1;
+            }
+        } else {
+            soisfconnected(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;
+         *		}
+         */
+        (void)tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0);
+        tp->snd_wl1 = ti->ti_seq - 1;
+        /* Avoid ack processing; snd_una==ti_ack  =>  dup ack */
+        goto synrx_to_est;
+        /* 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++;
+                DEBUG_MISC(
+                    (dfd, " dup ack  m = %lx  so = %lx \n", (long)m, (long)so));
+                /*
+                 * 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
+                 * threshold 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;
+        }
+    synrx_to_est:
+        /*
+         * 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;
+        }
+        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;
+            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;
+        }
+        /*
+         * XXX sowwakup is called when data is acked and there's room for
+         * for more data... it should read() the socket
+         */
+        /*		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_FCANTRCVMORE) {
+                    soisfdisconnected(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;
+                soisfdisconnected(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;
+        }
+    } /* switch(tp->t_state) */
+
+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 > so->so_rcv.sb_datalen) {
+            ti->ti_urp = 0;
+            tiflags &= ~TH_URG;
+            goto dodata;
+        }
+        /*
+         * 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_urgc =
+                so->so_rcv.sb_cc + (tp->rcv_up - tp->rcv_nxt); /* -1; */
+            tp->rcv_up = ti->ti_seq + ti->ti_urp;
+        }
+    } else
+        /*
+         * If no out of band data is expected,
+         * pull receive urgent pointer along
+         * with the receive window.
+         */
+        if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
+        tp->rcv_up = tp->rcv_nxt;
+dodata:
+
+    /*
+     * Process the segment text, merging it into the TCP sequencing queue,
+     * and arranging for 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_datalen - (tp->rcv_adv - tp->rcv_nxt);
+    } else {
+        m_free(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) {
+            /*
+             * If we receive a FIN we can't send more data,
+             * set it SS_FDRAIN
+             * Shutdown the socket if there is no rx data in the
+             * buffer.
+             * soread() is called on completion of shutdown() and
+             * will got to TCPS_LAST_ACK, and use tcp_output()
+             * to send the FIN.
+             */
+            /*			sofcantrcvmore(so); */
+            sofwdrain(so);
+
+            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:
+            if (so->so_emu == EMU_CTL) /* no shutdown on socket */
+                tp->t_state = TCPS_LAST_ACK;
+            else
+                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;
+            soisfdisconnected(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 this is a small packet, then ACK now - with Nagel
+     *      congestion avoidance sender won't send more until
+     *      he gets an ACK.
+     *
+     * See above.
+     */
+    /*	if (ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg) {
+     */
+    /*	if ((ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg &&
+     *		(so->so_iptos & IPTOS_LOWDELAY) == 0) ||
+     *	       ((so->so_iptos & IPTOS_LOWDELAY) &&
+     *	       ((struct tcpiphdr_2 *)ti)->first_char == (char)27)) {
+     */
+    if (ti->ti_len && (unsigned)ti->ti_len <= 5 &&
+        ((struct tcpiphdr_2 *)ti)->first_char == (char)27) {
+        tp->t_flags |= TF_ACKNOW;
+    }
+
+    /*
+     * 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;
+    m_freem(m);
+    tp->t_flags |= TF_ACKNOW;
+    (void)tcp_output(tp);
+    return;
+
+dropwithreset:
+    /* reuses m if m!=NULL, m_free() unnecessary */
+    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);
+    }
+
+    return;
+
+drop:
+    /*
+     * Drop space held by incoming segment and return.
+     */
+    m_free(m);
+
+    return;
+}
+
+/* , ts_present, ts_val, ts_ecr) */
+/*	int *ts_present;
+ *	u_int32_t *ts_val, *ts_ecr;
+ */
+void tcp_dooptions(tp, cp, cnt, ti) struct tcpcb *tp;
+u_char *cp;
+int cnt;
+struct tcpiphdr *ti;
+{
+    u_int16_t mss;
+    int opt, optlen;
+
+    DEBUG_CALL("tcp_dooptions");
+    DEBUG_ARGS((dfd, " tp = %lx  cnt=%i \n", (long)tp, cnt));
+
+    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;
+            memcpy((char *)&mss, (char *)cp + 2, sizeof(mss));
+            NTOHS(mss);
+            (void)tcp_mss(tp, mss); /* sets t_maxseg */
+            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;
+             *			memcpy((char *) ts_val, (char *)cp + 2,
+             *sizeof(*ts_val)); NTOHL(*ts_val); memcpy((char *) ts_ecr, (char
+             **)cp + 6, 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;
+        }
+    }
+}
+
+
+/*
+ * 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.
+ */
+
+#ifdef notdef
+
+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;
+            memcpy(sp, cp + 1, (unsigned)(m->m_len - cnt - 1));
+            m->m_len--;
+            return;
+        }
+        cnt -= m->m_len;
+        m = m->m_next; /* XXX WRONG! Fix it! */
+        if (m == 0)
+            break;
+    }
+    panic("tcp_pulloutofband");
+}
+
+#endif /* notdef */
+
+/*
+ * Collect new round-trip time estimate
+ * and update averages and current timeout.
+ */
+
+void tcp_xmit_timer(tp, rtt) register struct tcpcb *tp;
+int rtt;
+{
+    register short delta;
+
+    DEBUG_CALL("tcp_xmit_timer");
+    DEBUG_ARG("tp = %lx", (long)tp);
+    DEBUG_ARG("rtt = %d", rtt);
+
+    tcpstat.tcps_rttupdated++;
+    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 - 1 - (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;
+        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), (short)tp->t_rttmin,
+                  TCPTV_REXMTMAX); /* XXX */
+
+    /*
+     * 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.
+ */
+
+int tcp_mss(tp, offer) register struct tcpcb *tp;
+u_int offer;
+{
+    struct socket *so = tp->t_socket;
+    int mss;
+
+    DEBUG_CALL("tcp_mss");
+    DEBUG_ARG("tp = %lx", (long)tp);
+    DEBUG_ARG("offer = %d", offer);
+
+    mss = min(if_mtu, if_mru) - sizeof(struct tcpiphdr);
+    if (offer)
+        mss = min(mss, offer);
+    mss = max(mss, 32);
+    if (mss < tp->t_maxseg || offer != 0)
+        tp->t_maxseg = mss;
+
+    tp->snd_cwnd = mss;
+
+    sbreserve(&so->so_snd,
+              tcp_sndspace +
+                  ((tcp_sndspace % mss) ? (mss - (tcp_sndspace % mss)) : 0));
+    sbreserve(&so->so_rcv,
+              tcp_rcvspace +
+                  ((tcp_rcvspace % mss) ? (mss - (tcp_rcvspace % mss)) : 0));
+
+    DEBUG_MISC((dfd, " returning mss = %d\n", mss));
+
+    return mss;
+}