BSD 4_3_Tahoe release

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

diff --git a/usr/src/sys/netinet/tcp_timer.c b/usr/src/sys/netinet/tcp_timer.c
index 4d63bfe..45f827f 100644 (file)
--- a/usr/src/sys/netinet/tcp_timer.c
+++ b/usr/src/sys/netinet/tcp_timer.c
@@ -1,9 +1,20 @@
 /*
 /*

- * Copyright (c) 1982 Regents of the University of California.
- * All rights reserved.  The Berkeley software License Agreement
- * specifies the terms and conditions for redistribution.
+ * Copyright (c) 1982, 1986 Regents of the University of California.
+ * All rights reserved.

  *
  *

- *     @(#)tcp_timer.c 6.13 (Berkeley) %G%
+ * Redistribution and use in source and binary forms are permitted
+ * provided that the above copyright notice and this paragraph are
+ * duplicated in all such forms and that any documentation,
+ * advertising materials, and other materials related to such
+ * distribution and use acknowledge that the software was developed
+ * by the University of California, Berkeley.  The name of the
+ * University may not be used to endorse or promote products derived
+ * from this software without specific prior written permission.
+ * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED
+ * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ *     @(#)tcp_timer.c 7.14 (Berkeley) 6/29/88

  */
 
 #include "param.h"
  */
 
 #include "param.h"


@@ -29,7 +40,9 @@
 #include "tcp_var.h"
 #include "tcpip.h"
 
 #include "tcp_var.h"
 #include "tcpip.h"
 

-int    tcpnodelack = 0;
+int    tcp_keepidle = TCPTV_KEEP_IDLE;
+int    tcp_keepintvl = TCPTV_KEEPINTVL;
+int    tcp_maxidle;

 /*
  * Fast timeout routine for processing delayed acks
  */
 /*
  * Fast timeout routine for processing delayed acks
  */


@@ -46,6 +59,7 @@ tcp_fasttimo()
                    (tp->t_flags & TF_DELACK)) {
                        tp->t_flags &= ~TF_DELACK;
                        tp->t_flags |= TF_ACKNOW;
                    (tp->t_flags & TF_DELACK)) {
                        tp->t_flags &= ~TF_DELACK;
                        tp->t_flags |= TF_ACKNOW;

+                       tcpstat.tcps_delack++;

                        (void) tcp_output(tp);
                }
        splx(s);
                        (void) tcp_output(tp);
                }
        splx(s);


@@ -63,6 +77,7 @@ tcp_slowtimo()
        int s = splnet();
        register int i;
 
        int s = splnet();
        register int i;
 

+       tcp_maxidle = TCPTV_KEEPCNT * tcp_keepintvl;

        /*
         * Search through tcb's and update active timers.
         */
        /*
         * Search through tcb's and update active timers.
         */


@@ -111,8 +126,9 @@ tcp_canceltimers(tp)
                tp->t_timer[i] = 0;
 }
 
                tp->t_timer[i] = 0;
 }
 

-int    tcp_backoff[TCP_MAXRXTSHIFT+1] =
-    { 1, 2, 4, 6, 8, 10, 15, 20, 30, 30, 30, 30, 30 };
+int    tcp_backoff[TCP_MAXRXTSHIFT + 1] =
+    { 1, 2, 4, 8, 16, 32, 64, 64, 64, 64, 64, 64, 64 };
+

 /*
  * TCP timer processing.
  */
 /*
  * TCP timer processing.
  */


@@ -133,8 +149,8 @@ tcp_timers(tp, timer)
         */
        case TCPT_2MSL:
                if (tp->t_state != TCPS_TIME_WAIT &&
         */
        case TCPT_2MSL:
                if (tp->t_state != TCPS_TIME_WAIT &&

-                   tp->t_idle <= TCPTV_MAXIDLE)
-                       tp->t_timer[TCPT_2MSL] = TCPTV_KEEP;
+                   tp->t_idle <= tcp_maxidle)
+                       tp->t_timer[TCPT_2MSL] = tcp_keepintvl;

                else
                        tp = tcp_close(tp);
                break;
                else
                        tp = tcp_close(tp);
                break;


@@ -145,33 +161,66 @@ tcp_timers(tp, timer)
         * to a longer retransmit interval and retransmit one segment.
         */
        case TCPT_REXMT:
         * to a longer retransmit interval and retransmit one segment.
         */
        case TCPT_REXMT:

-               tp->t_rxtshift++;
-               if (tp->t_rxtshift > TCP_MAXRXTSHIFT) {
+               if (++tp->t_rxtshift > TCP_MAXRXTSHIFT) {
+                       tp->t_rxtshift = TCP_MAXRXTSHIFT;
+                       tcpstat.tcps_timeoutdrop++;

                        tp = tcp_drop(tp, ETIMEDOUT);
                        break;
                }
                        tp = tcp_drop(tp, ETIMEDOUT);
                        break;
                }

-               if (tp->t_srtt == 0)
-                       rexmt = tcp_beta * TCPTV_SRTTDFLT;
-               else
-                       rexmt = (int)(tcp_beta * tp->t_srtt);
-               rexmt *= tcp_backoff[tp->t_rxtshift - 1];
-               TCPT_RANGESET(tp->t_timer[TCPT_REXMT], rexmt,
-                           TCPTV_MIN, TCPTV_MAX);
+               tcpstat.tcps_rexmttimeo++;
+               rexmt = ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1;
+               rexmt *= tcp_backoff[tp->t_rxtshift];
+               TCPT_RANGESET(tp->t_rxtcur, rexmt, TCPTV_MIN, TCPTV_REXMTMAX);
+               tp->t_timer[TCPT_REXMT] = tp->t_rxtcur;

                /*
                /*

-                * If losing, let the lower level know
-                * and try for a better route.
+                * If losing, let the lower level know and try for
+                * a better route.  Also, if we backed off this far,
+                * our srtt estimate is probably bogus.  Clobber it
+                * so we'll take the next rtt measurement as our srtt;
+                * move the current srtt into rttvar to keep the current
+                * retransmit times until then.

                 */
                 */

-               if (tp->t_rxtshift >= TCP_MAXRXTSHIFT / 4 ||
-                   rexmt >= 10 * PR_SLOWHZ)
+               if (tp->t_rxtshift > TCP_MAXRXTSHIFT / 4) {

                        in_losing(tp->t_inpcb);
                        in_losing(tp->t_inpcb);

+                       tp->t_rttvar += (tp->t_srtt >> 2);
+                       tp->t_srtt = 0;
+               }

                tp->snd_nxt = tp->snd_una;
                /*
                tp->snd_nxt = tp->snd_una;
                /*

-                * If timing a segment in this window,
-                * and we have already gotten some timing estimate,
-                * stop the timer.
+                * If timing a segment in this window, stop the timer.
+                */
+               tp->t_rtt = 0;
+               /*
+                * Close the congestion window down to one segment
+                * (we'll open it by one segment for each ack we get).
+                * Since we probably have a window's worth of unacked
+                * data accumulated, this "slow start" keeps us from
+                * dumping all that data as back-to-back packets (which
+                * might overwhelm an intermediate gateway).
+                *
+                * There are two phases to the opening: Initially we
+                * open by one mss on each ack.  This makes the window
+                * size increase exponentially with time.  If the
+                * window is larger than the path can handle, this
+                * exponential growth results in dropped packet(s)
+                * almost immediately.  To get more time between 
+                * drops but still "push" the network to take advantage
+                * of improving conditions, we switch from exponential
+                * to linear window opening at some threshhold size.
+                * For a threshhold, we use half the current window
+                * size, truncated to a multiple of the mss.
+                *
+                * (the minimum cwnd that will give us exponential
+                * growth is 2 mss.  We don't allow the threshhold
+                * to go below this.)

                 */
                 */

-               if (tp->t_rtt && tp->t_srtt)
-                       tp->t_rtt = 0;
+               {
+               u_int win = MIN(tp->snd_wnd, tp->snd_cwnd) / 2 / tp->t_maxseg;
+               if (win < 2)
+                       win = 2;
+               tp->snd_cwnd = tp->t_maxseg;
+               tp->snd_ssthresh = win * tp->t_maxseg;
+               }

                (void) tcp_output(tp);
                break;
 
                (void) tcp_output(tp);
                break;
 


@@ -180,6 +229,7 @@ tcp_timers(tp, timer)
         * Force a byte to be output, if possible.
         */
        case TCPT_PERSIST:
         * Force a byte to be output, if possible.
         */
        case TCPT_PERSIST:

+               tcpstat.tcps_persisttimeo++;

                tcp_setpersist(tp);
                tp->t_force = 1;
                (void) tcp_output(tp);
                tcp_setpersist(tp);
                tp->t_force = 1;
                (void) tcp_output(tp);


@@ -191,28 +241,43 @@ tcp_timers(tp, timer)
         * or drop connection if idle for too long.
         */
        case TCPT_KEEP:
         * or drop connection if idle for too long.
         */
        case TCPT_KEEP:

+               tcpstat.tcps_keeptimeo++;

                if (tp->t_state < TCPS_ESTABLISHED)
                        goto dropit;
                if (tp->t_state < TCPS_ESTABLISHED)
                        goto dropit;

-               if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE) {
-                       if (tp->t_idle >= TCPTV_MAXIDLE)
+               if (tp->t_inpcb->inp_socket->so_options & SO_KEEPALIVE &&
+                   tp->t_state <= TCPS_CLOSE_WAIT) {
+                       if (tp->t_idle >= tcp_keepidle + tcp_maxidle)

                                goto dropit;
                        /*
                                goto dropit;
                        /*

-                        * Saying tp->rcv_nxt-1 lies about what
-                        * we have received, and by the protocol spec
-                        * requires the correspondent TCP to respond.
-                        * Saying tp->snd_una-1 causes the transmitted
-                        * byte to lie outside the receive window; this
-                        * is important because we don't necessarily
-                        * have a byte in the window to send (consider
-                        * a one-way stream!)
+                        * Send a packet designed to force a response
+                        * if the peer is up and reachable:
+                        * either an ACK if the connection is still alive,
+                        * or an RST if the peer has closed the connection
+                        * due to timeout or reboot.
+                        * Using sequence number tp->snd_una-1
+                        * causes the transmitted zero-length segment
+                        * to lie outside the receive window;
+                        * by the protocol spec, this requires the
+                        * correspondent TCP to respond.

                         */
                         */

-                       tcp_respond(tp,
-                           tp->t_template, tp->rcv_nxt-1, tp->snd_una-1, 0);
+                       tcpstat.tcps_keepprobe++;
+#ifdef TCP_COMPAT_42
+                       /*
+                        * The keepalive packet must have nonzero length
+                        * to get a 4.2 host to respond.
+                        */
+                       tcp_respond(tp, tp->t_template,
+                           tp->rcv_nxt - 1, tp->snd_una - 1, 0);
+#else
+                       tcp_respond(tp, tp->t_template,
+                           tp->rcv_nxt, tp->snd_una - 1, 0);
+#endif
+                       tp->t_timer[TCPT_KEEP] = tcp_keepintvl;

                } else
                } else

-                       tp->t_idle = 0;
-               tp->t_timer[TCPT_KEEP] = TCPTV_KEEP;
+                       tp->t_timer[TCPT_KEEP] = tcp_keepidle;

                break;
        dropit:
                break;
        dropit:

+               tcpstat.tcps_keepdrops++;

                tp = tcp_drop(tp, ETIMEDOUT);
                break;
        }
                tp = tcp_drop(tp, ETIMEDOUT);
                break;
        }