svn commit: r261545 - stable/10/sys/netinet

[Andrey V. Elsukov]

Author: ae
Date: Thu Feb  6 10:48:55 2014
New Revision: 261545
URL: http://svnweb.freebsd.org/changeset/base/261545

Log:
  MFC r260702 (by melifaro):
    Fix ipfw fwd for IPv4 traffic broken by r249894.
  
    Problem case:
    Original lookup returns route with GW set, so gw points to
    rte->rt_gateway.
    After that we're changing dst and performing lookup another time.
    Since fwd host is most probably directly reachable, resulting
    rte does not contain rt_gateway, so gw is not set. Finally, we
    end with packet transmitted to proper interface but wrong
    link-layer address.

Modified:
  stable/10/sys/netinet/ip_output.c
Directory Properties:
  stable/10/   (props changed)

Modified: stable/10/sys/netinet/ip_output.c
==============================================================================
--- stable/10/sys/netinet/ip_output.c	Thu Feb  6 10:47:47 2014	(r261544)
+++ stable/10/sys/netinet/ip_output.c	Thu Feb  6 10:48:55 2014	(r261545)
@@ -200,6 +200,13 @@ ip_output(struct mbuf *m, struct mbuf *o
 		hlen = ip->ip_hl << 2;
 	}
 
+	/*
+	 * dst/gw handling:
+	 *
+	 * dst can be rewritten but always point to &ro->ro_dst
+	 * gw is readonly but can be pointed either to dst OR rt_gatewy
+	 * therefore we need restore GW if we're re-doing lookup
+	 */
 	gw = dst = (struct sockaddr_in *)&ro->ro_dst;
 again:
 	ia = NULL;
@@ -219,6 +226,7 @@ again:
 		RO_RTFREE(ro);
 		ro->ro_lle = NULL;
 		rte = NULL;
+		gw = dst;
 	}
 	if (rte == NULL && fwd_tag == NULL) {
 		bzero(dst, sizeof(*dst));