svn commit: r184720 - head/sys/netinet

[Bjoern A. Zeeb]

Author: bz
Date: Thu Nov  6 12:33:33 2008
New Revision: 184720
URL: http://svn.freebsd.org/changeset/base/184720

Log:
  Fix a bug introduced with r182851 splitting tcp_mss() into
  tcp_mss() and tcp_mss_update() so that tcp_mtudisc() could
  re-use the same code.
  
  In case we return early and got a metricptr to pass the hostcache
  info back to the caller we need to initialize the data to a defined
  state (zero it) as tcp_hc_get() would do if there was no hit.
  Without that the caller would check on random stack garbage which
  could lead to undefined results.
  
  This only affected tcp_mss() if there was no routing entry for the peer,
  tcp_mtudisc() was not affected.
  
  MFC after:	2 months (along with r182851)

Modified:
  head/sys/netinet/tcp_input.c

Modified: head/sys/netinet/tcp_input.c
==============================================================================
--- head/sys/netinet/tcp_input.c	Thu Nov  6 11:43:49 2008	(r184719)
+++ head/sys/netinet/tcp_input.c	Thu Nov  6 12:33:33 2008	(r184720)
@@ -2847,8 +2847,16 @@ tcp_mss_update(struct tcpcb *tp, int off
 	/*
 	 * No route to sender, stay with default mss and return.
 	 */
-	if (maxmtu == 0)
+	if (maxmtu == 0) {
+		/*
+		 * In case we return early we need to intialize metrics
+		 * to a defined state as tcp_hc_get() would do for us
+		 * if there was no cache hit.
+		 */
+		if (metricptr != NULL)
+			bzero(metricptr, sizeof(struct hc_metrics_lite));
 		return;
+	}
 
 	/* Check the interface for TSO capabilities. */
 	if (mtuflags & CSUM_TSO)