svn commit: r216672 - head/sys/netinet

[Michael Tuexen]

Author: tuexen
Date: Wed Dec 22 19:04:14 2010
New Revision: 216672
URL: http://svn.freebsd.org/changeset/base/216672

Log:
  Provide a possibility to configure the inital congestion window to the
  value defined in RFC 4960.
  
  MFC after: 3 months.

Modified:
  head/sys/netinet/sctp_cc_functions.c
  head/sys/netinet/sctp_sysctl.h

Modified: head/sys/netinet/sctp_cc_functions.c
==============================================================================
--- head/sys/netinet/sctp_cc_functions.c	Wed Dec 22 19:01:48 2010	(r216671)
+++ head/sys/netinet/sctp_cc_functions.c	Wed Dec 22 19:04:14 2010	(r216672)
@@ -53,15 +53,19 @@ sctp_set_initial_cc_param(struct sctp_tc
 	uint32_t cwnd_in_mtu;
 
 	assoc = &stcb->asoc;
-	/*
-	 * We take the minimum of the burst limit and the initial congestion
-	 * window. The initial congestion window is at least two times the
-	 * MTU.
-	 */
 	cwnd_in_mtu = SCTP_BASE_SYSCTL(sctp_initial_cwnd);
-	if ((assoc->max_burst > 0) && (cwnd_in_mtu > assoc->max_burst))
-		cwnd_in_mtu = assoc->max_burst;
-	net->cwnd = (net->mtu - sizeof(struct sctphdr)) * cwnd_in_mtu;
+	if (cwnd_in_mtu == 0) {
+		/* Using 0 means that the value of RFC 4960 is used. */
+		net->cwnd = min((net->mtu * 4), max((2 * net->mtu), SCTP_INITIAL_CWND));
+	} else {
+		/*
+		 * We take the minimum of the burst limit and the initial
+		 * congestion window.
+		 */
+		if ((assoc->max_burst > 0) && (cwnd_in_mtu > assoc->max_burst))
+			cwnd_in_mtu = assoc->max_burst;
+		net->cwnd = (net->mtu - sizeof(struct sctphdr)) * cwnd_in_mtu;
+	}
 	net->ssthresh = assoc->peers_rwnd;
 
 	SDT_PROBE(sctp, cwnd, net, init,

Modified: head/sys/netinet/sctp_sysctl.h
==============================================================================
--- head/sys/netinet/sctp_sysctl.h	Wed Dec 22 19:01:48 2010	(r216671)
+++ head/sys/netinet/sctp_sysctl.h	Wed Dec 22 19:04:14 2010	(r216672)
@@ -500,7 +500,7 @@ struct sctp_sysctl {
 
 /* Initial congestion window in MTU */
 #define SCTPCTL_INITIAL_CWND_DESC	"Initial congestion window in MTUs"
-#define SCTPCTL_INITIAL_CWND_MIN	1
+#define SCTPCTL_INITIAL_CWND_MIN	0
 #define SCTPCTL_INITIAL_CWND_MAX	0xffffffff
 #define SCTPCTL_INITIAL_CWND_DEFAULT	3