keep USETRAILERS from SIOCSARP

[unix-history] / usr / src / sys / netinet / tcp_output.c

diff --git a/usr/src/sys/netinet/tcp_output.c b/usr/src/sys/netinet/tcp_output.c
index 2c762fd..4d150a4 100644 (file)
--- a/usr/src/sys/netinet/tcp_output.c
+++ b/usr/src/sys/netinet/tcp_output.c
@@ -1,38 +1,39 @@
-/*     tcp_output.c    4.32    82/03/12        */
+/*
+ * Copyright (c) 1982, 1986 Regents of the University of California.
+ * All rights reserved.  The Berkeley software License Agreement
+ * specifies the terms and conditions for redistribution.
+ *
+ *     @(#)tcp_output.c        7.10 (Berkeley) %G%
+ */

 
 

-#include "../h/param.h"
-#include "../h/systm.h"
-#include "../h/mbuf.h"
-#include "../h/protosw.h"
-#include "../h/socket.h"
-#include "../h/socketvar.h"
-#include "../net/in.h"
-#include "../net/in_pcb.h"
-#include "../net/in_systm.h"
-#include "../net/ip.h"
-#include "../net/ip_var.h"
-#include "../net/tcp.h"
-#define        TCPOUTFLAGS
-#include "../net/tcp_fsm.h"
-#include "../net/tcp_seq.h"
-#include "../net/tcp_timer.h"
-#include "../net/tcp_var.h"
-#include "../net/tcpip.h"
-#include "../net/tcp_debug.h"
-#include "../errno.h"
+#include "param.h"
+#include "systm.h"
+#include "mbuf.h"
+#include "protosw.h"
+#include "socket.h"
+#include "socketvar.h"
+#include "errno.h"

 
 

-char *tcpstates[]; /* XXX */
+#include "../net/route.h"
+
+#include "in.h"
+#include "in_pcb.h"
+#include "in_systm.h"
+#include "ip.h"
+#include "ip_var.h"
+#include "tcp.h"
+#define        TCPOUTFLAGS
+#include "tcp_fsm.h"
+#include "tcp_seq.h"
+#include "tcp_timer.h"
+#include "tcp_var.h"
+#include "tcpip.h"
+#include "tcp_debug.h"

 
 /*
 
 /*

- * Initial options: indicate max segment length 1/2 of space
- * allocated for receive; if TCPTRUEOOB is defined, indicate
- * willingness to do true out-of-band.
+ * Initial options.

  */
  */

-#ifndef TCPTRUEOOB

 u_char tcp_initopt[4] = { TCPOPT_MAXSEG, 4, 0x0, 0x0, };
 u_char tcp_initopt[4] = { TCPOPT_MAXSEG, 4, 0x0, 0x0, };

-#else
-u_char tcp_initopt[6] = { TCPOPT_MAXSEG, 4, 0x0, 0x0, TCPOPT_WILLOOB, 2 };
-#endif

 
 /*
  * Tcp output routine: figure out what should be sent and send it.
 
 /*
  * Tcp output routine: figure out what should be sent and send it.


@@ -41,58 +42,162 @@ tcp_output(tp)
        register struct tcpcb *tp;
 {
        register struct socket *so = tp->t_inpcb->inp_socket;
        register struct tcpcb *tp;
 {
        register struct socket *so = tp->t_inpcb->inp_socket;

-       register int len;
+       register int len, win;

        struct mbuf *m0;
        struct mbuf *m0;

-       int off, flags, win;
+       int off, flags, error;

        register struct mbuf *m;
        register struct tcpiphdr *ti;
        u_char *opt;
        unsigned optlen = 0;
        register struct mbuf *m;
        register struct tcpiphdr *ti;
        u_char *opt;
        unsigned optlen = 0;

-
-COUNT(TCP_OUTPUT);
+       int idle, sendalot;

 
        /*
 
        /*

-        * Determine length of data that can be transmitted,
+        * Determine length of data that should be transmitted,

         * and flags that will be used.
         * If there is some data or critical controls (SYN, RST)
         * to send, then transmit; otherwise, investigate further.
         */
         * and flags that will be used.
         * If there is some data or critical controls (SYN, RST)
         * to send, then transmit; otherwise, investigate further.
         */

+       idle = (tp->snd_max == tp->snd_una);
+again:
+       sendalot = 0;

        off = tp->snd_nxt - tp->snd_una;
        off = tp->snd_nxt - tp->snd_una;

-       len = MIN(so->so_snd.sb_cc, tp->snd_wnd+tp->t_force) - off;
-       if (len < 0)
-               return (0);                     /* past FIN */
-       if (len > tp->t_maxseg)
-               len = tp->t_maxseg;
+       win = MIN(tp->snd_wnd, tp->snd_cwnd);
+
+       /*
+        * If in persist timeout with window of 0, send 1 byte.
+        * Otherwise, if window is small but nonzero
+        * and timer expired, we will send what we can
+        * and go to transmit state.
+        */
+       if (tp->t_force) {
+               if (win == 0)
+                       win = 1;
+               else {
+                       tp->t_timer[TCPT_PERSIST] = 0;
+                       tp->t_rxtshift = 0;
+               }
+       }
+
+       len = MIN(so->so_snd.sb_cc, win) - off;

        flags = tcp_outflags[tp->t_state];
        flags = tcp_outflags[tp->t_state];

-       if (tp->snd_nxt + len < tp->snd_una + so->so_snd.sb_cc)
+
+       if (len < 0) {
+               /*
+                * If FIN has been sent but not acked,
+                * but we haven't been called to retransmit,
+                * len will be -1; transmit if acking, otherwise no need.
+                * Otherwise, window shrank after we sent into it.
+                * If window shrank to 0, cancel pending retransmit
+                * and pull snd_nxt back to (closed) window.
+                * We will enter persist state below.
+                * If the window didn't close completely,
+                * just wait for an ACK.
+                */
+               if (flags & TH_FIN) {
+                       if (tp->t_flags & TF_ACKNOW)
+                               len = 0;
+                       else
+                               return (0);
+               } else if (win == 0) {
+                       tp->t_timer[TCPT_REXMT] = 0;
+                       tp->snd_nxt = tp->snd_una;
+                       len = 0;
+               } else
+                       return (0);
+       }
+       if (len > tp->t_maxseg) {
+               len = tp->t_maxseg;
+               sendalot = 1;
+       }
+       if (SEQ_LT(tp->snd_nxt + len, tp->snd_una + so->so_snd.sb_cc))

                flags &= ~TH_FIN;
                flags &= ~TH_FIN;

-       if (len || (flags & (TH_SYN|TH_RST|TH_FIN)))
-               goto send;
+       win = sbspace(&so->so_rcv);
+

 
 

+       /*
+        * If our state indicates that FIN should be sent
+        * and we have not yet done so, or we're retransmitting the FIN,
+        * then we need to send.
+        */
+       if (flags & TH_FIN &&
+           ((tp->t_flags & TF_SENTFIN) == 0 || tp->snd_nxt == tp->snd_una))
+               goto send;

        /*
         * Send if we owe peer an ACK.
         */
        /*
         * Send if we owe peer an ACK.
         */

-       if (tp->t_flags&TF_ACKNOW)
+       if (tp->t_flags & TF_ACKNOW)
+               goto send;
+       if (flags & (TH_SYN|TH_RST))
+               goto send;
+       if (SEQ_GT(tp->snd_up, tp->snd_una))

                goto send;
 
                goto send;
 

-#ifdef TCPTRUEOOB

        /*
        /*

-        * Send if an out of band data or ack should be transmitted.
+        * Sender silly window avoidance.  If connection is idle
+        * and can send all data, a maximum segment,
+        * at least a maximum default-size segment do it,
+        * or are forced, do it; otherwise don't bother.
+        * If peer's buffer is tiny, then send
+        * when window is at least half open.
+        * If retransmitting (possibly after persist timer forced us
+        * to send into a small window), then must resend.

         */
         */

-       if (tp->t_oobflags&(TCPOOB_OWEACK|TCPOOB_NEEDACK)))
-               goto send;
-#endif
+       if (len) {
+               if (len == tp->t_maxseg)
+                       goto send;
+               if ((idle || tp->t_flags & TF_NODELAY) &&
+                   len + off >= so->so_snd.sb_cc)
+                       goto send;
+               if (tp->t_force)
+                       goto send;
+               if (len >= tp->max_sndwnd / 2)
+                       goto send;
+               if (SEQ_LT(tp->snd_nxt, tp->snd_max))
+                       goto send;
+       }

 
        /*
 
        /*

-        * Calculate available window in i, and also amount
-        * of window known to peer (as advertised window less
-        * next expected input.)  If this is 35% or more of the
-        * maximum possible window, then want to send a segment to peer.
+        * Compare available window to amount of window
+        * known to peer (as advertised window less
+        * next expected input.)  If the difference is 35% or more of the
+        * maximum possible window, then want to send a window update to peer.

         */
         */

-       win = sbspace(&so->so_rcv);
-       if (win > 0 &&
-           ((100*(win-(tp->rcv_adv-tp->rcv_nxt))/so->so_rcv.sb_hiwat) >= 35))
-               goto send;
+       if (win > 0) {
+               int adv = win - (tp->rcv_adv - tp->rcv_nxt);
+
+               if (100 * adv / so->so_rcv.sb_hiwat >= 35)
+                       goto send;
+               if (adv >= 2 * tp->t_maxseg && so->so_rcv.sb_cc == 0)
+                       goto send;
+       }
+
+       /*
+        * TCP window updates are not reliable, rather a polling protocol
+        * using ``persist'' packets is used to insure receipt of window
+        * updates.  The three ``states'' for the output side are:
+        *      idle                    not doing retransmits or persists
+        *      persisting              to move a small or zero window
+        *      (re)transmitting        and thereby not persisting
+        *
+        * tp->t_timer[TCPT_PERSIST]
+        *      is set when we are in persist state.
+        * tp->t_force
+        *      is set when we are called to send a persist packet.
+        * tp->t_timer[TCPT_REXMT]
+        *      is set when we are retransmitting
+        * The output side is idle when both timers are zero.
+        *
+        * If send window is too small, there is data to transmit, and no
+        * retransmit or persist is pending, then go to persist state.
+        * If nothing happens soon, send when timer expires:
+        * if window is nonzero, transmit what we can,
+        * otherwise force out a byte.
+        */
+       if (so->so_snd.sb_cc && tp->t_timer[TCPT_REXMT] == 0 &&
+           tp->t_timer[TCPT_PERSIST] == 0) {
+               tp->t_rxtshift = 0;
+               tcp_setpersist(tp);
+       }

 
        /*
         * No reason to send a segment, just return.
 
        /*
         * No reason to send a segment, just return.


@@ -105,16 +210,33 @@ send:
         * be transmitted, and initialize the header from
         * the template for sends on this connection.
         */
         * be transmitted, and initialize the header from
         * the template for sends on this connection.
         */

-       MGET(m, 0);
-       if (m == 0)
-               return (0);
+       MGET(m, M_DONTWAIT, MT_HEADER);
+       if (m == NULL)
+               return (ENOBUFS);

        m->m_off = MMAXOFF - sizeof (struct tcpiphdr);
        m->m_len = sizeof (struct tcpiphdr);
        if (len) {
        m->m_off = MMAXOFF - sizeof (struct tcpiphdr);
        m->m_len = sizeof (struct tcpiphdr);
        if (len) {

+               if (tp->t_force && len == 1)
+                       tcpstat.tcps_sndprobe++;
+               else if (SEQ_LT(tp->snd_nxt, tp->snd_max)) {
+                       tcpstat.tcps_sndrexmitpack++;
+                       tcpstat.tcps_sndrexmitbyte += len;
+               } else {
+                       tcpstat.tcps_sndpack++;
+                       tcpstat.tcps_sndbyte += len;
+               }

                m->m_next = m_copy(so->so_snd.sb_mb, off, len);
                if (m->m_next == 0)
                        len = 0;
                m->m_next = m_copy(so->so_snd.sb_mb, off, len);
                if (m->m_next == 0)
                        len = 0;

-       }
+       } else if (tp->t_flags & TF_ACKNOW)
+               tcpstat.tcps_sndacks++;
+       else if (flags & (TH_SYN|TH_FIN|TH_RST))
+               tcpstat.tcps_sndctrl++;
+       else if (SEQ_GT(tp->snd_up, tp->snd_una))
+               tcpstat.tcps_sndurg++;
+       else
+               tcpstat.tcps_sndwinup++;
+

        ti = mtod(m, struct tcpiphdr *);
        if (tp->t_template == 0)
                panic("tcp_output");
        ti = mtod(m, struct tcpiphdr *);
        if (tp->t_template == 0)
                panic("tcp_output");


@@ -123,76 +245,41 @@ send:
        /*
         * Fill in fields, remembering maximum advertised
         * window for use in delaying messages about window sizes.
        /*
         * Fill in fields, remembering maximum advertised
         * window for use in delaying messages about window sizes.

+        * If resending a FIN, be sure not to use a new sequence number.

         */
         */

-       ti->ti_seq = tp->snd_nxt;
-       ti->ti_ack = tp->rcv_nxt;
-#if vax
-       ti->ti_seq = htonl(ti->ti_seq);
-       ti->ti_ack = htonl(ti->ti_ack);
-#endif
+       if (flags & TH_FIN && tp->t_flags & TF_SENTFIN && 
+           tp->snd_nxt == tp->snd_max)
+               tp->snd_nxt--;
+       ti->ti_seq = htonl(tp->snd_nxt);
+       ti->ti_ack = htonl(tp->rcv_nxt);

        /*
         * Before ESTABLISHED, force sending of initial options
         * unless TCP set to not do any options.
         */
        /*
         * Before ESTABLISHED, force sending of initial options
         * unless TCP set to not do any options.
         */

-       if (tp->t_state < TCPS_ESTABLISHED) {
-               if (tp->t_flags&TF_NOOPT)
-                       goto noopt;
-               opt = tcp_initopt;
-               optlen = sizeof (tcp_initopt);
-               *(u_short *)(opt + 2) = so->so_rcv.sb_hiwat / 2;
-#if vax
-               *(u_short *)(opt + 2) = htons(*(u_short *)(opt + 2));
-#endif
-       } else {
-               if (tp->t_tcpopt == 0)
-                       goto noopt;
-               opt = mtod(tp->t_tcpopt, u_char *);
-               optlen = tp->t_tcpopt->m_len;
+       opt = NULL;
+       if (flags & TH_SYN && (tp->t_flags & TF_NOOPT) == 0) {
+               u_short mss;
+
+               mss = MIN(so->so_rcv.sb_hiwat / 2, tcp_mss(tp));
+               if (mss > IP_MSS - sizeof(struct tcpiphdr)) {
+                       opt = tcp_initopt;
+                       optlen = sizeof (tcp_initopt);
+                       *(u_short *)(opt + 2) = htons(mss);
+               }

        }
        }

-#ifndef TCPTRUEOOB
-       if (opt)
-#else
-       if (opt || (tp->t_oobflags&(TCPOOB_OWEACK|TCPOOB_NEEDACK)))
-#endif
-       {
+       if (opt) {

                m0 = m->m_next;
                m0 = m->m_next;

-               m->m_next = m_get(M_DONTWAIT);
+               m->m_next = m_get(M_DONTWAIT, MT_DATA);

                if (m->m_next == 0) {
                        (void) m_free(m);
                        m_freem(m0);
                if (m->m_next == 0) {
                        (void) m_free(m);
                        m_freem(m0);

-                       return (0);
+                       return (ENOBUFS);

                }
                m->m_next->m_next = m0;
                m0 = m->m_next;
                }
                m->m_next->m_next = m0;
                m0 = m->m_next;

-               m0->m_off = MMINOFF;

                m0->m_len = optlen;
                m0->m_len = optlen;

-               bcopy(opt, mtod(m0, caddr_t), optlen);
+               bcopy((caddr_t)opt, mtod(m0, caddr_t), optlen);

                opt = (u_char *)(mtod(m0, caddr_t) + optlen);
                opt = (u_char *)(mtod(m0, caddr_t) + optlen);

-#ifdef TCPTRUEOOB
-               if (tp->t_oobflags&TCPOOB_OWEACK) {
-printf("tp %x send OOBACK for %x\n", tp->t_iobseq);
-                       *opt++ = TCPOPT_OOBACK;
-                       *opt++ = 3;
-                       *opt++ = tp->t_iobseq;
-                       m0->m_len += 3;
-                       tp->t_oobflags &= ~TCPOOB_OWEACK;
-                       /* sender should rexmt oob to force ack repeat */
-               }
-               if (tp->t_oobflags&TCPOOB_NEEDACK) {
-printf("tp %x send OOBDATA seq %x data %x\n", tp->t_oobseq, tp->t_oobc);
-                       *opt++ = TCPOPT_OOBDATA;
-                       *opt++ = 8;
-                       *opt++ = tp->t_oobseq;
-                       *opt++ = tp->t_oobc;
-                       *(tcp_seq *)opt = tp->t_oobmark - tp->snd_nxt;
-#ifdef vax
-                       *(tcp_seq *)opt = htonl((unsigned)*(tcp_seq *)opt);
-#endif
-                       m0->m_len += 8;
-                       TCPT_RANGESET(tp->t_timer[TCPT_OOBREXMT],
-                           tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX);
-               }
-#endif

                while (m0->m_len & 0x3) {
                        *opt++ = TCPOPT_EOL;
                        m0->m_len++;
                while (m0->m_len & 0x3) {
                        *opt++ = TCPOPT_EOL;
                        m0->m_len++;


@@ -200,16 +287,18 @@ printf("tp %x send OOBDATA seq %x data %x\n", tp->t_oobseq, tp->t_oobc);
                optlen = m0->m_len;
                ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2;
        }
                optlen = m0->m_len;
                ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2;
        }

-noopt:

        ti->ti_flags = flags;
        ti->ti_flags = flags;

-       win = sbspace(&so->so_rcv);
-       if (win > 0)
-               ti->ti_win = htons((u_short)win);
+       /*
+        * Calculate receive window.  Don't shrink window,
+        * but avoid silly window syndrome.
+        */
+       if (win < so->so_rcv.sb_hiwat / 4 && win < tp->t_maxseg)
+               win = 0;
+       if (win < (int)(tp->rcv_adv - tp->rcv_nxt))
+               win = (int)(tp->rcv_adv - tp->rcv_nxt);
+       ti->ti_win = htons((u_short)win);

        if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {
        if (SEQ_GT(tp->snd_up, tp->snd_nxt)) {

-               ti->ti_urp = tp->snd_up - tp->snd_nxt;
-#if vax
-               ti->ti_urp = htons(ti->ti_urp);
-#endif
+               ti->ti_urp = htons((u_short)(tp->snd_up - tp->snd_nxt));

                ti->ti_flags |= TH_URG;
        } else
                /*
                ti->ti_flags |= TH_URG;
        } else
                /*


@@ -219,64 +308,77 @@ noopt:
                 * number wraparound.
                 */
                tp->snd_up = tp->snd_una;               /* drag it along */
                 * number wraparound.
                 */
                tp->snd_up = tp->snd_una;               /* drag it along */

-       /* PUSH */
-

        /*
        /*

-        * Put TCP length in extended header, and then
-        * checksum extended header and data.
+        * If anything to send and we can send it all, set PUSH.
+        * (This will keep happy those implementations which only
+        * give data to the user when a buffer fills or a PUSH comes in.)

         */
         */

-       if (len + optlen) {
-               ti->ti_len = sizeof (struct tcphdr) + optlen + len;
-#if vax
-               ti->ti_len = htons((u_short)ti->ti_len);
-#endif
-       }
-       ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + optlen + len);
+       if (len && off+len == so->so_snd.sb_cc)
+               ti->ti_flags |= TH_PUSH;

 
        /*
 
        /*

-        * Advance snd_nxt over sequence space of this segment
+        * Put TCP length in extended header, and then
+        * checksum extended header and data.

         */
         */

-       if (flags & (TH_SYN|TH_FIN))
-               tp->snd_nxt++;
-       tp->snd_nxt += len;
+       if (len + optlen)
+               ti->ti_len = htons((u_short)(sizeof(struct tcphdr) +
+                   optlen + len));
+       ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + (int)optlen + len);

 
        /*
 
        /*

-        * If this transmission closes the window,
-        * start persistance timer at 2 round trip times
-        * but at least TCPTV_PERSMIN ticks.
+        * In transmit state, time the transmission and arrange for
+        * the retransmit.  In persist state, just set snd_max.

         */
         */

-       if (TCPS_HAVERCVDSYN(tp->t_state) &&
-           SEQ_GEQ(tp->snd_nxt, tp->snd_una+tp->snd_wnd) &&
-           tp->t_timer[TCPT_PERSIST] == 0)
-               TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
-                   2 * tp->t_srtt, TCPTV_PERSMIN, TCPTV_MAX);
+       if (tp->t_force == 0 || tp->t_timer[TCPT_PERSIST] == 0) {
+               tcp_seq startseq = tp->snd_nxt;

 
 

-       /*
-        * Time this transmission if not a retransmission and
-        * not currently timing anything.
-        */
-       if (SEQ_GT(tp->snd_nxt, tp->snd_max) && tp->t_rtt == 0) {
-               tp->t_rtt = 1;
-               tp->t_rtseq = tp->snd_nxt - len;
-       }
+               /*
+                * Advance snd_nxt over sequence space of this segment.
+                */
+               if (flags & TH_SYN)
+                       tp->snd_nxt++;
+               if (flags & TH_FIN) {
+                       tp->snd_nxt++;
+                       tp->t_flags |= TF_SENTFIN;
+               }
+               tp->snd_nxt += len;
+               if (SEQ_GT(tp->snd_nxt, tp->snd_max)) {
+                       tp->snd_max = tp->snd_nxt;
+                       /*
+                        * Time this transmission if not a retransmission and
+                        * not currently timing anything.
+                        */
+                       if (tp->t_rtt == 0) {
+                               tp->t_rtt = 1;
+                               tp->t_rtseq = startseq;
+                               tcpstat.tcps_segstimed++;
+                       }
+               }

 
 

-       /*
-        * Set retransmit timer if not currently set.
-        * Initial value for retransmit timer to tcp_beta*tp->t_srtt.
-        * Initialize shift counter which is used for exponential
-        * backoff of retransmit time.
-        */
-       if (tp->t_timer[TCPT_REXMT] == 0 && tp->snd_nxt != tp->snd_una) {
-               TCPT_RANGESET(tp->t_timer[TCPT_REXMT],
-                   tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX);
-               tp->t_rtt = 0;
-               tp->t_rxtshift = 0;
-       }
+               /*
+                * Set retransmit timer if not currently set,
+                * and not doing an ack or a keep-alive probe.
+                * Initial value for retransmit timer is smoothed
+                * round-trip time + 2 * round-trip time variance.
+                * Initialize shift counter which is used for backoff
+                * of retransmit time.
+                */
+               if (tp->t_timer[TCPT_REXMT] == 0 &&
+                   tp->snd_nxt != tp->snd_una) {
+                       tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;
+                       if (tp->t_timer[TCPT_PERSIST]) {
+                               tp->t_timer[TCPT_PERSIST] = 0;
+                               tp->t_rxtshift = 0;
+                       }
+               }
+       } else
+               if (SEQ_GT(tp->snd_nxt + len, tp->snd_max))
+                       tp->snd_max = tp->snd_nxt + len;

 
        /*
         * Trace.
         */
 
        /*
         * Trace.
         */

-       if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)
+       if (so->so_options & SO_DEBUG)

                tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0);
 
        /*
                tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0);
 
        /*


@@ -285,19 +387,39 @@ noopt:
         */
        ((struct ip *)ti)->ip_len = sizeof (struct tcpiphdr) + optlen + len;
        ((struct ip *)ti)->ip_ttl = TCP_TTL;
         */
        ((struct ip *)ti)->ip_len = sizeof (struct tcpiphdr) + optlen + len;
        ((struct ip *)ti)->ip_ttl = TCP_TTL;

-       if (ip_output(m, tp->t_ipopt) == 0)
-               return (0);
+       error = ip_output(m, tp->t_inpcb->inp_options, &tp->t_inpcb->inp_route,
+           so->so_options & SO_DONTROUTE);
+       if (error)
+               return (error);
+       tcpstat.tcps_sndtotal++;

 
        /*
         * Data sent (as far as we can tell).
         * If this advertises a larger window than any other segment,
         * then remember the size of the advertised window.
 
        /*
         * Data sent (as far as we can tell).
         * If this advertises a larger window than any other segment,
         * then remember the size of the advertised window.

-        * Drop send for purpose of ACK requirements.
+        * Any pending ACK has now been sent.

         */
        if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
                tp->rcv_adv = tp->rcv_nxt + win;
        tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
         */
        if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv))
                tp->rcv_adv = tp->rcv_nxt + win;
        tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);

-       if (SEQ_GT(tp->snd_nxt, tp->snd_max))
-               tp->snd_max = tp->snd_nxt;
-       return (1);
+       if (sendalot)
+               goto again;
+       return (0);
+}
+
+tcp_setpersist(tp)
+       register struct tcpcb *tp;
+{
+       register t = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
+
+       if (tp->t_timer[TCPT_REXMT])
+               panic("tcp_output REXMT");
+       /*
+        * Start/restart persistance timer.
+        */
+       TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
+           t * tcp_backoff[tp->t_rxtshift],
+           TCPTV_PERSMIN, TCPTV_PERSMAX);
+       if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
+               tp->t_rxtshift++;

 }
 }