Add scope zone index to host cache.

--- sys/netinet/tcp_hostcache.h	(svn+ssh://svn.freebsd.org/base/head)	(revision 261548)
+++ sys/netinet/tcp_hostcache.h	(working copy)
@@ -51,6 +51,7 @@ struct hc_metrics {
 	struct	hc_head *rmx_head; /* head of bucket tail queue */
 	struct	in_addr ip4;	/* IP address */
 	struct	in6_addr ip6;	/* IP6 address */
+	uint32_t ip6_zoneid;	/* IPv6 scope zone id */
 	/* endpoint specific values for tcp */
 	u_long	rmx_mtu;	/* MTU for this path */
 	u_long	rmx_ssthresh;	/* outbound gateway buffer limit */