Add a bandaid for a long-standing race condition during route entry

un-expiring.

The previous version of code have no locking when testing rt_refcnt.
The result of the lack of locking may result in a condition where
a routing entry have a reference count but at the same time have
RTPRF_OURS bit set and an expiration timer.  These would eventually
lead to a panic:

	panic: rtqkill route really not free

When the system have ICMP redirects accepted from local gateway
in a moderate frequency, for instance.

Commit this workaround for now until we have some better solution.

PR:		kern/149804
Reviewed by:	bz
Tested by:	Zhao Xin, Pete French
MFC after:	2 weeks

1 files changed, 3 insertions, 1 deletions

diff --git a/sys/netinet6/in6_rmx.c b/sys/netinet6/in6_rmx.c
index 8927a17..2a13646 100644
--- a/sys/netinet6/in6_rmx.c
+++ b/sys/netinet6/in6_rmx.c
@@ -193,11 +193,13 @@ in6_matroute(void *v_arg, struct radix_node_head *head)
 	struct radix_node *rn = rn_match(v_arg, head);
 	struct rtentry *rt = (struct rtentry *)rn;
 
-	if (rt && rt->rt_refcnt == 0) { /* this is first reference */
+	if (rt) {
+		RT_LOCK(rt);
 		if (rt->rt_flags & RTPRF_OURS) {
 			rt->rt_flags &= ~RTPRF_OURS;
 			rt->rt_rmx.rmx_expire = 0;
 		}
+		RT_UNLOCK(rt);
 	}
 	return rn;
 }