On Wed, Apr 24, 2013 at 06:30:32PM +0000, Randall Stewart wrote:
> Author: rrs
> Date: Wed Apr 24 18:30:32 2013
> New Revision: 249848
> URL: http://svnweb.freebsd.org/changeset/base/249848
>
> Log:
> This fixes the issue with the "randomly changing" default
> route. What it was is there are two places in ip_output.c
> where we do a goto again. One place was fine, it
> copies out the new address and then resets dst = ro->rt_dst;
> But the other place does *not* do that, which means earlier
> when we found the gateway, we have dst pointing there
> aka dst = ro->rt_gateway is done.. then we do a
> goto again.. bam now we clobber the default route.
>
> The fix is just to move the again so we are always
> doing dst = &ro->rt_dst; in the again loop.
Hi Randall,
>From my reading of ip6_output() it seems as though a similar bug exists
in the IPv6 case. It's not as bad though: the clobbering write to *dst
only happens if the route lookup of the rewritten destination address
doesn't return anything. So we'd need to have an IPv6 packet match a
gateway route and then be diverted by a pfil hook to a destination for
which selectroute() returns a NULL route. In this case we'll see the
same problem as in the IPv4 case - the original gateway route will be
clobbered.
Would you (or anyone familiar with the code in question) be able to take
a look and confirm whether this is the case? The fix would be the same I
think (patch below).
Thanks!
-Mark
Index: ip6_output.c
===================================================================
--- ip6_output.c (revision 249866)
+++ ip6_output.c (working copy)
@@ -519,7 +519,6 @@
ro_pmtu = ro;
if (opt && opt->ip6po_rthdr)
ro = &opt->ip6po_route;
- dst = (struct sockaddr_in6 *)&ro->ro_dst;
#ifdef FLOWTABLE
if (ro->ro_rt == NULL) {
struct flentry *fle;
@@ -536,6 +535,8 @@
}
#endif
again:
+ dst = (struct sockaddr_in6 *)&ro->ro_dst;
+
/*
* if specified, try to fill in the traffic class field.
* do not override if a non-zero value is already set.
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