fixes to persist timer handling

SCCS-vsn: sys/netinet/tcp_output.c 4.39

diff --git a/usr/src/sys/netinet/tcp_output.c b/usr/src/sys/netinet/tcp_output.c
index 49d701f..c0699a0 100644 (file)
--- a/usr/src/sys/netinet/tcp_output.c
+++ b/usr/src/sys/netinet/tcp_output.c
@@ -1,4 +1,4 @@
-/*     tcp_output.c    4.39    82/06/06        */
+/*     tcp_output.c    4.39    82/06/08        */

 
 #include "../h/param.h"
 #include "../h/systm.h"
 
 #include "../h/param.h"
 #include "../h/systm.h"


@@ -49,6 +49,7 @@ tcp_output(tp)
        register struct tcpiphdr *ti;
        u_char *opt;
        unsigned optlen = 0;
        register struct tcpiphdr *ti;
        u_char *opt;
        unsigned optlen = 0;

+       int sendalot;

 
 COUNT(TCP_OUTPUT);
 
 
 COUNT(TCP_OUTPUT);
 


@@ -58,12 +59,16 @@ COUNT(TCP_OUTPUT);
         * If there is some data or critical controls (SYN, RST)
         * to send, then transmit; otherwise, investigate further.
         */
         * If there is some data or critical controls (SYN, RST)
         * to send, then transmit; otherwise, investigate further.
         */

+again:
+       sendalot = 0;

        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 */
        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)
+       if (len > tp->t_maxseg) {

                len = tp->t_maxseg;
                len = tp->t_maxseg;

+               sendalot = 1;
+       }

 
        flags = tcp_outflags[tp->t_state];
        if (tp->snd_nxt + len < tp->snd_una + so->so_snd.sb_cc)
 
        flags = tcp_outflags[tp->t_state];
        if (tp->snd_nxt + len < tp->snd_una + so->so_snd.sb_cc)


@@ -112,6 +117,33 @@ COUNT(TCP_OUTPUT);
            ((100*(win-(tp->rcv_adv-tp->rcv_nxt))/so->so_rcv.sb_hiwat) >= 35))
                goto send;
 
            ((100*(win-(tp->rcv_adv-tp->rcv_nxt))/so->so_rcv.sb_hiwat) >= 35))
                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 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 closed, there is data to transmit, and no
+        * retransmit or persist is pending, then go to persist state,
+        * arranging to force out a byte to get more current window information
+        * if nothing happens soon.
+        */
+       if (tp->snd_wnd == 0 && 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.
         */


@@ -258,44 +290,43 @@ noopt:
        ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + (int)optlen + len);
 
        /*
        ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + (int)optlen + len);
 
        /*

-        * Advance snd_nxt over sequence space of this segment
-        */
-       if (flags & (TH_SYN|TH_FIN))
-               tp->snd_nxt++;
-       tp->snd_nxt += 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, reset persist time for
+        * next persist.

         */
         */

-       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) {
+               /*
+                * Advance snd_nxt over sequence space of this segment
+                */
+               if (flags & (TH_SYN|TH_FIN))
+                       tp->snd_nxt++;
+               tp->snd_nxt += len;

 
 

-       /*
-        * 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;
-       }
+               /*
+                * 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;
+               }

 
 

-       /*
-        * 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.
+                * 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;
+               }
+               tp->t_timer[TCPT_PERSIST] = 0;
+       } else
+               tcp_setpersist(tp);

 
        /*
         * Trace.
 
        /*
         * Trace.


@@ -323,5 +354,24 @@ noopt:
        tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
        if (SEQ_GT(tp->snd_nxt, tp->snd_max))
                tp->snd_max = tp->snd_nxt;
        tp->t_flags &= ~(TF_ACKNOW|TF_DELACK);
        if (SEQ_GT(tp->snd_nxt, tp->snd_max))
                tp->snd_max = tp->snd_nxt;

+       if (sendalot && tp->t_force == 0)
+               goto again;

        return (0);
 }
        return (0);
 }

+
+tcp_setpersist(tp)
+       register struct tcpcb *tp;
+{
+
+       if (tp->t_timer[TCPT_REXMT])
+               panic("tcp_output REXMT");
+       /*
+        * Start/restart persistance timer.
+        */
+       TCPT_RANGESET(tp->t_timer[TCPT_PERSIST],
+           ((int)(tcp_beta * tp->t_srtt)) << tp->t_rxtshift,
+           TCPTV_PERSMIN, TCPTV_MAX);
+       tp->t_rxtshift++;
+       if (tp->t_rxtshift >= TCP_MAXRXTSHIFT)
+               tp->t_rxtshift = 0;
+}