From 108df27c0bffca8c218246141129c5f1ce2b36b6 Mon Sep 17 00:00:00 2001
From: Randall Stewart <rrs@FreeBSD.org>
Date: Fri, 8 Jun 2007 10:57:11 +0000
Subject: [PATCH] - RTO was not being initialized to 0, thus the rtt
 calculation   algoritm would not go through the proper initialization. - The
 initialization was incorrect as well, causing problems in   sat networks with
 > 1sec RTT - Get rid of magic numbers in RTT calculations.

---
 sys/netinet/sctp_asconf.c |  2 +-
 sys/netinet/sctp_input.c  |  2 +-
 sys/netinet/sctp_pcb.c    |  6 +++++-
 sys/netinet/sctp_timer.h  |  3 +++
 sys/netinet/sctputil.c    | 19 +++++++++++++------
 5 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/sys/netinet/sctp_asconf.c b/sys/netinet/sctp_asconf.c
index 932ba5a84ece..b2c932c02693 100644
--- a/sys/netinet/sctp_asconf.c
+++ b/sys/netinet/sctp_asconf.c
@@ -1794,7 +1794,7 @@ sctp_iterator_stcb(struct sctp_inpcb *inp, struct sctp_tcb *stcb, void *ptr,
 					 * address?
 					 */
 					sctp_set_initial_cc_param(stcb, net);
-					net->RTO = stcb->asoc.initial_rto;
+					net->RTO = 0;
 
 				}
 			}
diff --git a/sys/netinet/sctp_input.c b/sys/netinet/sctp_input.c
index 85cfeed5d7ae..adc4ce900fab 100644
--- a/sys/netinet/sctp_input.c
+++ b/sys/netinet/sctp_input.c
@@ -2319,7 +2319,7 @@ sctp_handle_ecn_echo(struct sctp_ecne_chunk *cp,
 		if (net->ssthresh < net->mtu) {
 			net->ssthresh = net->mtu;
 			/* here back off the timer as well, to slow us down */
-			net->RTO <<= 2;
+			net->RTO <<= 1;
 		}
 		net->cwnd = net->ssthresh;
 #ifdef SCTP_CWND_MONITOR
diff --git a/sys/netinet/sctp_pcb.c b/sys/netinet/sctp_pcb.c
index 50369c45e201..a803eca1c38b 100644
--- a/sys/netinet/sctp_pcb.c
+++ b/sys/netinet/sctp_pcb.c
@@ -3064,7 +3064,11 @@ sctp_add_remote_addr(struct sctp_tcb *stcb, struct sockaddr *newaddr,
 			net->dest_state = SCTP_ADDR_REACHABLE |
 			    SCTP_ADDR_UNCONFIRMED;
 	}
-	net->RTO = stcb->asoc.initial_rto;
+	/*
+	 * We set this to 0, the timer code knows that this means its an
+	 * initial value
+	 */
+	net->RTO = 0;
 	stcb->asoc.numnets++;
 	*(&net->ref_count) = 1;
 	net->tos_flowlabel = 0;
diff --git a/sys/netinet/sctp_timer.h b/sys/netinet/sctp_timer.h
index 15a7f08b2703..e28408453bc8 100644
--- a/sys/netinet/sctp_timer.h
+++ b/sys/netinet/sctp_timer.h
@@ -37,6 +37,9 @@ __FBSDID("$FreeBSD$");
 
 #if defined(_KERNEL)
 
+#define SCTP_RTT_SHIFT 3
+#define SCTP_RTT_VAR_SHIFT 2
+
 void
 sctp_early_fr_timer(struct sctp_inpcb *inp, struct sctp_tcb *stcb,
     struct sctp_nets *net);
diff --git a/sys/netinet/sctputil.c b/sys/netinet/sctputil.c
index ee39de53770f..2afafccaebae 100644
--- a/sys/netinet/sctputil.c
+++ b/sys/netinet/sctputil.c
@@ -2577,24 +2577,31 @@ sctp_calculate_rto(struct sctp_tcb *stcb,
 	o_calctime = calc_time;
 	/* this is Van Jacobson's integer version */
 	if (net->RTO) {
-		calc_time -= (net->lastsa >> 3);
+		calc_time -= (net->lastsa >> SCTP_RTT_SHIFT);	/* take away 1/8th when
+								 * shift=3 */
 #ifdef SCTP_RTTVAR_LOGGING
 		rto_logging(net, SCTP_LOG_RTTVAR);
 #endif
 		net->prev_rtt = o_calctime;
-		net->lastsa += calc_time;
+		net->lastsa += calc_time;	/* add 7/8th into sa when
+						 * shift=3 */
 		if (calc_time < 0) {
 			calc_time = -calc_time;
 		}
-		calc_time -= (net->lastsv >> 2);
+		calc_time -= (net->lastsv >> SCTP_RTT_VAR_SHIFT);	/* take away 1/4 when
+									 * VAR shift=2 */
 		net->lastsv += calc_time;
 		if (net->lastsv == 0) {
 			net->lastsv = SCTP_CLOCK_GRANULARITY;
 		}
 	} else {
 		/* First RTO measurment */
-		net->lastsa = calc_time;
-		net->lastsv = calc_time >> 1;
+		net->lastsa = calc_time << SCTP_RTT_SHIFT;	/* Multiply by 8 when
+								 * shift=3 */
+		net->lastsv = calc_time;
+		if (net->lastsv == 0) {
+			net->lastsv = SCTP_CLOCK_GRANULARITY;
+		}
 		first_measure = 1;
 		net->prev_rtt = o_calctime;
 #ifdef SCTP_RTTVAR_LOGGING
@@ -2602,7 +2609,7 @@ sctp_calculate_rto(struct sctp_tcb *stcb,
 #endif
 	}
 calc_rto:
-	new_rto = ((net->lastsa >> 2) + net->lastsv) >> 1;
+	new_rto = (net->lastsa >> SCTP_RTT_SHIFT) + net->lastsv;
 	if ((new_rto > SCTP_SAT_NETWORK_MIN) &&
 	    (stcb->asoc.sat_network_lockout == 0)) {
 		stcb->asoc.sat_network = 1;