BSD: Fix netmask family and length for incoming route msgs

Netmask family and length are ignored by traditional
userland tools such as route and netstat and are assumed
to match the destination sockaddr.
This is fortunate because BSD kernels use a radix tree
to store routes which adjusts the netmask at the point
of insertion where this information is lost.
We can just sub in the values from the destination address.

This is currently true for all BSD kernels.

Author: rsmarples

src/if-bsd.c

@@ -887,10 +887,22 @@ if_copyrt(struct dhcpcd_ctx *ctx, struct rt *rt, const struct rt_msghdr *rtm)
 
 	rt->rt_flags = (unsigned int)rtm->rtm_flags;
 	if_copysa(&rt->rt_dest, rti_info[RTAX_DST]);
+
 	if (rtm->rtm_addrs & RTA_NETMASK) {
 		if_copysa(&rt->rt_netmask, rti_info[RTAX_NETMASK]);
-		if (rt->rt_netmask.sa_family == 255) /* Why? */
-			rt->rt_netmask.sa_family = rt->rt_dest.sa_family;
+		/*
+		 * Netmask family and length are ignored by traditional
+		 * userland tools such as route and netstat and are assumed
+		 * to match the destination sockaddr.
+		 * This is fortunate because BSD kernels use a radix tree
+		 * to store routes which adjusts the netmask at the point
+		 * of insertion where this information is lost.
+		 * We can just sub in the values from the destination address.
+		 *
+		 * This is currently true for all BSD kernels.
+		 */
+		rt->rt_netmask.sa_family = rt->rt_dest.sa_family;
+		rt->rt_netmask.sa_len = rt->rt_dest.sa_len;
 	}
 
 	/* dhcpcd likes an unspecified gateway to indicate via the link.

src/sa.c

@@ -419,11 +419,6 @@ sa_cmp(const struct sockaddr *sa1, const struct sockaddr *sa2)
 	assert(sa1 != NULL);
 	assert(sa2 != NULL);
 
-	/* Treat AF_UNSPEC as the unspecified address. */
-	if ((sa1->sa_family == AF_UNSPEC || sa2->sa_family == AF_UNSPEC) &&
-	    sa_is_unspecified(sa1) && sa_is_unspecified(sa2))
-		return 0;
-
 	if (sa1->sa_family != sa2->sa_family)
 		return sa1->sa_family - sa2->sa_family;