Introduce a pointer to const variable gw, which points either at the

same place as dst, or to the sockaddr in the routing table.

The const constraint of gw makes us safe from modifing routing table
accidentially. And "onstantness" of dst allows us to remove several
bandaids, when we switched it back at &ro->ro_dst, now it always
points there.

Reviewed by:	rrs

1 files changed, 6 insertions, 13 deletions

diff --git a/sys/netinet/ip_output.c b/sys/netinet/ip_output.c
index 120fe22..5770ae7 100644
--- a/sys/netinet/ip_output.c
+++ b/sys/netinet/ip_output.c
@@ -123,6 +123,7 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro, int flags,
 	int n;	/* scratchpad */
 	int error = 0;
 	struct sockaddr_in *dst;
+	const struct sockaddr_in *gw;
 	struct in_ifaddr *ia;
 	int isbroadcast;
 	uint16_t ip_len, ip_off;
@@ -196,8 +197,8 @@ ip_output(struct mbuf *m, struct mbuf *opt, struct route *ro, int flags,
 		hlen = ip->ip_hl << 2;
 	}
 
+	gw = dst = (struct sockaddr_in *)&ro->ro_dst;
 again:
-	dst = (struct sockaddr_in *)&ro->ro_dst;
 	ia = NULL;
 	/*
 	 * If there is a cached route,
@@ -297,11 +298,11 @@ again:
 		ifp = rte->rt_ifp;
 		rte->rt_rmx.rmx_pksent++;
 		if (rte->rt_flags & RTF_GATEWAY)
-			dst = (struct sockaddr_in *)rte->rt_gateway;
+			gw = (struct sockaddr_in *)rte->rt_gateway;
 		if (rte->rt_flags & RTF_HOST)
 			isbroadcast = (rte->rt_flags & RTF_BROADCAST);
 		else
-			isbroadcast = in_broadcast(dst->sin_addr, ifp);
+			isbroadcast = in_broadcast(gw->sin_addr, ifp);
 	}
 	/*
 	 * Calculate MTU.  If we have a route that is up, use that,
@@ -327,12 +328,6 @@ again:
 	if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr))) {
 		m->m_flags |= M_MCAST;
 		/*
-		 * IP destination address is multicast.  Make sure "dst"
-		 * still points to the address in "ro".  (It may have been
-		 * changed to point to a gateway address, above.)
-		 */
-		dst = (struct sockaddr_in *)&ro->ro_dst;
-		/*
 		 * See if the caller provided any multicast options
 		 */
 		if (imo != NULL) {
@@ -559,7 +554,6 @@ sendit:
 	/* Or forward to some other address? */
 	if ((m->m_flags & M_IP_NEXTHOP) &&
 	    (fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL)) != NULL) {
-		dst = (struct sockaddr_in *)&ro->ro_dst;
 		bcopy((fwd_tag+1), dst, sizeof(struct sockaddr_in));
 		m->m_flags |= M_SKIP_FIREWALL;
 		m->m_flags &= ~M_IP_NEXTHOP;
@@ -628,8 +622,7 @@ passout:
 		 * to avoid confusing lower layers.
 		 */
 		m->m_flags &= ~(M_PROTOFLAGS);
-		error = (*ifp->if_output)(ifp, m,
-		    		(struct sockaddr *)dst, ro);
+		error = (*ifp->if_output)(ifp, m, (struct sockaddr *)gw, ro);
 		goto done;
 	}
 
@@ -663,7 +656,7 @@ passout:
 			m->m_flags &= ~(M_PROTOFLAGS);
 
 			error = (*ifp->if_output)(ifp, m,
-			    (struct sockaddr *)dst, ro);
+			    (struct sockaddr *)gw, ro);
 		} else
 			m_freem(m);
 	}