ipv4/ipv6: Prepare for new route gateway semantics.

In the future the ipv4/ipv6 route gateway will take on two types
of values:

1) INADDR_ANY/IN6ADDR_ANY, for local network routes, and in this case
   the neighbour must be obtained using the destination address in
   ipv4/ipv6 header as the lookup key.

2) Everything else, the actual nexthop route address.

So if the gateway is not inaddr-any we use it, otherwise we must use
the packet's destination address.

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 20 insertions, 1 deletions

diff --git a/net/ipv4/route.c b/net/ipv4/route.c
index bcacf54e5418..4eeb8ce856e2 100644
--- a/net/ipv4/route.c
+++ b/net/ipv4/route.c
@@ -1117,10 +1117,15 @@ static struct neighbour *ipv4_neigh_lookup(const struct dst_entry *dst, const vo
         static const __be32 inaddr_any = 0;
         struct net_device *dev = dst->dev;
         const __be32 *pkey = daddr;
+        const struct rtable *rt;
         struct neighbour *n;
 
+        rt = (const struct rtable *) dst;
+
         if (dev->flags & (IFF_LOOPBACK | IFF_POINTOPOINT))
                 pkey = &inaddr_any;
+        else if (rt->rt_gateway)
+                pkey = (const __be32 *) &rt->rt_gateway;
 
         n = __ipv4_neigh_lookup(&arp_tbl, dev, *(__force u32 *)pkey);
         if (n)
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 8c2e3ab58f2a..7d7f30697ead 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -121,9 +121,23 @@ static u32 *ipv6_cow_metrics(struct dst_entry *dst, unsigned long old)
         return p;
 }
 
+static inline const void *choose_neigh_daddr(struct rt6_info *rt, const void *daddr)
+{
+        struct in6_addr *p = &rt->rt6i_gateway;
+
+        if (p->s6_addr32[0] | p->s6_addr32[1] |
+            p->s6_addr32[2] | p->s6_addr32[3])
+                return (const void *) p;
+        return daddr;
+}
+
 static struct neighbour *ip6_neigh_lookup(const struct dst_entry *dst, const void *daddr)
 {
-        struct neighbour *n = __ipv6_neigh_lookup(&nd_tbl, dst->dev, daddr);
+        struct rt6_info *rt = (struct rt6_info *) dst;
+        struct neighbour *n;
+
+        daddr = choose_neigh_daddr(rt, daddr);
+        n = __ipv6_neigh_lookup(&nd_tbl, dst->dev, daddr);
         if (n)
                 return n;
         return neigh_create(&nd_tbl, daddr, dst->dev);