commit 8b774af641799a6c0c558719f95fe3e30928cf00
Author: Andrey Zonov <zont@FreeBSD.org>
Date:   Thu Sep 20 01:05:50 2012 +0400

    - Make TCP timers tunable.

diff --git a/sys/netinet/tcp_output.c b/sys/netinet/tcp_output.c
index 53a4ab4..e095af6 100644
--- a/sys/netinet/tcp_output.c
+++ b/sys/netinet/tcp_output.c
@@ -1375,7 +1375,7 @@ tcp_setpersist(struct tcpcb *tp)
 	 * Start/restart persistance timer.
 	 */
 	TCPT_RANGESET(tt, t * tcp_backoff[tp->t_rxtshift],
-		      TCPTV_PERSMIN, TCPTV_PERSMAX);
+		      tcp_persmin, tcp_persmax);
 	tcp_timer_activate(tp, TT_PERSIST, tt);
 	if (tp->t_rxtshift < TCP_MAXRXTSHIFT)
 		tp->t_rxtshift++;
diff --git a/sys/netinet/tcp_subr.c b/sys/netinet/tcp_subr.c
index 2662163..2e2c6c5 100644
--- a/sys/netinet/tcp_subr.c
+++ b/sys/netinet/tcp_subr.c
@@ -336,6 +336,9 @@ tcp_init(void)
 		tcp_rexmit_min = 1;
 	tcp_rexmit_slop = TCPTV_CPU_VAR;
 	tcp_finwait2_timeout = TCPTV_FINWAIT2_TIMEOUT;
+	tcp_rtobase = TCPTV_RTOBASE;
+	tcp_persmin = TCPTV_PERSMIN;
+	tcp_persmax = TCPTV_PERSMAX;
 	tcp_tcbhashsize = hashsize;
 
 	TUNABLE_INT_FETCH("net.inet.tcp.soreceive_stream", &tcp_soreceive_stream);
@@ -731,9 +734,9 @@ tcp_newtcpcb(struct inpcb *inp)
 	 * reasonable initial retransmit time.
 	 */
 	tp->t_srtt = TCPTV_SRTTBASE;
-	tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
+	tp->t_rttvar = ((tcp_rtobase - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
 	tp->t_rttmin = tcp_rexmit_min;
-	tp->t_rxtcur = TCPTV_RTOBASE;
+	tp->t_rxtcur = tcp_rtobase;
 	tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
 	tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
 	tp->t_rcvtime = ticks;
diff --git a/sys/netinet/tcp_syncache.c b/sys/netinet/tcp_syncache.c
index 55a782b..1d3ba9d 100644
--- a/sys/netinet/tcp_syncache.c
+++ b/sys/netinet/tcp_syncache.c
@@ -175,6 +175,11 @@ SYSCTL_VNET_INT(_net_inet_tcp_syncache, OID_AUTO, rst_on_sock_fail,
     CTLFLAG_RW, &VNET_NAME(tcp_sc_rst_sock_fail), 0,
     "Send reset on socket allocation failure");
 
+static int tcp_sc_rexmttime;
+SYSCTL_PROC(_net_inet_tcp_syncache, OID_AUTO, rexmttime, CTLTYPE_INT|CTLFLAG_RW,
+    &tcp_sc_rexmttime, 0, sysctl_msec_to_ticks, "I",
+    "SYN/ACK retransmit timeout");
+
 static MALLOC_DEFINE(M_SYNCACHE, "syncache", "TCP syncache");
 
 #define SYNCACHE_HASH(inc, mask)					\
@@ -225,6 +230,7 @@ syncache_init(void)
 {
 	int i;
 
+	tcp_sc_rexmttime = TCPTV_RTOBASE;
 	V_tcp_syncache.cache_count = 0;
 	V_tcp_syncache.hashsize = TCP_SYNCACHE_HASHSIZE;
 	V_tcp_syncache.bucket_limit = TCP_SYNCACHE_BUCKETLIMIT;
@@ -383,7 +389,7 @@ static void
 syncache_timeout(struct syncache *sc, struct syncache_head *sch, int docallout)
 {
 	sc->sc_rxttime = ticks +
-		TCPTV_RTOBASE * (tcp_backoff[sc->sc_rxmits]);
+		tcp_sc_rexmttime * (tcp_backoff[sc->sc_rxmits]);
 	sc->sc_rxmits++;
 	if (TSTMP_LT(sc->sc_rxttime, sch->sch_nextc)) {
 		sch->sch_nextc = sc->sc_rxttime;
diff --git a/sys/netinet/tcp_timer.c b/sys/netinet/tcp_timer.c
index 531899c..4510ad0 100644
--- a/sys/netinet/tcp_timer.c
+++ b/sys/netinet/tcp_timer.c
@@ -115,6 +115,18 @@ int	tcp_keepcnt = TCPTV_KEEPCNT;
 SYSCTL_INT(_net_inet_tcp, OID_AUTO, keepcnt, CTLFLAG_RW, &tcp_keepcnt, 0,
     "Number of keepalive probes to send");
 
+int	tcp_rtobase;
+SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rtobase, CTLTYPE_INT|CTLFLAG_RW,
+    &tcp_rtobase, 0, sysctl_msec_to_ticks, "I", "Initial retransmit timeout");
+
+int	tcp_persmin;
+SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmin, CTLTYPE_INT|CTLFLAG_RW,
+    &tcp_persmin, 0, sysctl_msec_to_ticks, "I", "Retransmit persistence");
+
+int	tcp_persmax;
+SYSCTL_PROC(_net_inet_tcp, OID_AUTO, persmax, CTLTYPE_INT|CTLFLAG_RW,
+    &tcp_persmax, 0, sysctl_msec_to_ticks, "I", "Maximum persist interval");
+
 	/* max idle probes */
 int	tcp_maxpersistidle;
 
diff --git a/sys/netinet/tcp_timer.h b/sys/netinet/tcp_timer.h
index 8a93da8..0be3e6a 100644
--- a/sys/netinet/tcp_timer.h
+++ b/sys/netinet/tcp_timer.h
@@ -173,6 +173,9 @@ extern int tcp_backoff[];
 
 extern int tcp_finwait2_timeout;
 extern int tcp_fast_finwait2_recycle;
+extern int tcp_rtobase;
+extern int tcp_persmin;
+extern int tcp_persmax;
 
 void	tcp_timer_init(void);
 void	tcp_timer_2msl(void *xtp);