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Date: Thu, 8 Jun 2000 01:27:00 -0700
From: William Carrel <william.a@carrel.org>
To: freebsd-gnats-submit@Carrel.ORG, william.a@carrel.org,
	freebsd-hackers@freebsd.org
Subject: Re: kern/16318: Fix for wrong interface when adding new routes
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This problem still affects the FreeBSD kernel in 4.0 and 5.0.

A patch file for 4.0-STABLE follows, I've tested this on 4.0-RELEASE and
4.0-STABLE (incl. SMP for what it's worth).

There is no difference between route.c at HEAD(5.0-current) and 
RELENG_4(4.0-stable) so this patch should work effectively in both of
the aforementioned.  And it does still fix my routing troubles.

--- route.c.orig	Sat May 27 14:48:42 2000
+++ route.c	Sat May 27 15:01:43 2000
@@ -400,6 +400,9 @@
 	struct sockaddr	*dst, *gateway;
 {
 	register struct ifaddr *ifa;
+	struct rtentry *rt;
+
+	ifa = 0;
 	if ((flags & RTF_GATEWAY) == 0) {
 		/*
 		 * If we are adding a route to an interface,
@@ -408,7 +411,6 @@
 		 * as our clue to the interface.  Otherwise
 		 * we can use the local address.
 		 */
-		ifa = 0;
 		if (flags & RTF_HOST) {
 			ifa = ifa_ifwithdstaddr(dst);
 		}
@@ -425,18 +427,33 @@
 	if (ifa == 0)
 		ifa = ifa_ifwithnet(gateway);
 	if (ifa == 0) {
-		struct rtentry *rt = rtalloc1(dst, 0, 0UL);
-		if (rt == 0)
-			return (0);
-		rt->rt_refcnt--;
-		if ((ifa = rt->rt_ifa) == 0)
-			return (0);
+		rt = rtalloc1(dst, 0, 0UL);
+		if (rt) {
+			rt->rt_refcnt--;
+			if (rt->rt_ifa)
+				ifa = rt->rt_ifa;
+		}
 	}
-	if (ifa->ifa_addr->sa_family != dst->sa_family) {
+	if ((ifa) && (ifa->ifa_addr->sa_family != dst->sa_family)) {
 		struct ifaddr *oifa = ifa;
 		ifa = ifaof_ifpforaddr(dst, ifa->ifa_ifp);
 		if (ifa == 0)
 			ifa = oifa;
+	}
+	/* 
+	 * If we are adding a gateway, it is quite
+	 * possible that the routing table has a static
+	 * entry in place for the gateway, that may
+	 * not agree with the info from the interfaces.
+	 * The routing table should carry more precedence
+	 * than the interfaces in this matter.
+	 * Must be careful not to stomp on new entries from 
+	 * rtinit, hence (ifa->ifa_addr !=gateway).
+	 */
+	if ((ifa == 0 || ifa->ifa_addr != gateway) &&
+			(rt = rtalloc1(gateway,0,0UL))) {
+		rt->rt_refcnt--;
+		ifa = rt->rt_ifa;
 	}
 	return (ifa);
 }


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