Invalidate cached forwarding route (ipforward_rt) whenever a new route

is added to the routing table, otherwise we may end up using the wrong
route when forwarding.

PR:		kern/10778
Reviewed by:	silence on -net

3 files changed, 14 insertions, 1 deletions

diff --git a/sys/netinet/in_rmx.c b/sys/netinet/in_rmx.c
index 51a5846..16ea5be 100644
--- a/sys/netinet/in_rmx.c
+++ b/sys/netinet/in_rmx.c
@@ -54,6 +54,7 @@
 #include <net/route.h>
 #include <netinet/in.h>
 #include <netinet/in_var.h>
+#include <netinet/ip_var.h>
 
 extern int	in_inithead __P((void **head, int off));
 
@@ -137,6 +138,17 @@ in_addroute(void *v_arg, void *n_arg, struct radix_node_head *head,
 			RTFREE(rt2);
 		}
 	}
+
+	/*
+	 * If the new route created successfully, and we are forwarding,
+	 * and there is a cached route, free it.  Otherwise, we may end
+	 * up using the wrong route.
+	 */
+	if (ret != NULL && ipforwarding && ipforward_rt.ro_rt) {
+		RTFREE(ipforward_rt.ro_rt);
+		ipforward_rt.ro_rt = 0;
+	}
+
 	return ret;
 }
 
diff --git a/sys/netinet/ip_input.c b/sys/netinet/ip_input.c
index 7ee78dd..0963a0a 100644
--- a/sys/netinet/ip_input.c
+++ b/sys/netinet/ip_input.c
@@ -257,7 +257,7 @@ ip_init()
 }
 
 static struct	sockaddr_in ipaddr = { sizeof(ipaddr), AF_INET };
-static struct	route ipforward_rt;
+struct	route ipforward_rt;
 
 /*
  * Ip input routine.  Checksum and byte swap header.  If fragmented
diff --git a/sys/netinet/ip_var.h b/sys/netinet/ip_var.h
index e821f0a..bc8b797 100644
--- a/sys/netinet/ip_var.h
+++ b/sys/netinet/ip_var.h
@@ -141,6 +141,7 @@ extern struct	ipstat	ipstat;
 extern u_short	ip_id;				/* ip packet ctr, for ids */
 extern int	ip_defttl;			/* default IP ttl */
 extern int	ipforwarding;			/* ip forwarding */
+extern struct route ipforward_rt;		/* ip forwarding cached route */
 extern u_char	ip_protox[];
 extern struct socket *ip_rsvpd;	/* reservation protocol daemon */
 extern struct socket *ip_mrouter; /* multicast routing daemon */