ipv6: Remove external dependency on rt6i_gateway and RTF_ANYCAST

When creating a RTF_CACHE route, RTF_ANYCAST is set based on rt6i_dst.
Also, rt6i_gateway is always set to the nexthop while the nexthop
could be a gateway or the rt6i_dst.addr.

After removing the rt6i_dst and rt6i_src dependency in the last patch,
we also need to stop the caller from depending on rt6i_gateway and
RTF_ANYCAST.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Cc: Hannes Frederic Sowa <hannes@stressinduktion.org>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: Julian Anastasov <ja@ssi.bg>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/ip6_route.h b/include/net/ip6_route.h
index 5e19206..4caf7d6 100644
--- a/include/net/ip6_route.h
+++ b/include/net/ip6_route.h
@@ -163,11 +163,14 @@
 	return rt->rt6i_flags & RTF_LOCAL;
 }
 
-static inline bool ipv6_anycast_destination(const struct sk_buff *skb)
+static inline bool ipv6_anycast_destination(const struct dst_entry *dst,
+					    const struct in6_addr *daddr)
 {
-	struct rt6_info *rt = (struct rt6_info *) skb_dst(skb);
+	struct rt6_info *rt = (struct rt6_info *)dst;
 
-	return rt->rt6i_flags & RTF_ANYCAST;
+	return rt->rt6i_flags & RTF_ANYCAST ||
+		(rt->rt6i_dst.plen != 128 &&
+		 ipv6_addr_equal(&rt->rt6i_dst.addr, daddr));
 }
 
 int ip6_fragment(struct sock *sk, struct sk_buff *skb,
@@ -194,9 +197,15 @@
 	       inet6_sk(sk)->pmtudisc == IPV6_PMTUDISC_OMIT;
 }
 
-static inline struct in6_addr *rt6_nexthop(struct rt6_info *rt)
+static inline struct in6_addr *rt6_nexthop(struct rt6_info *rt,
+					   struct in6_addr *daddr)
 {
-	return &rt->rt6i_gateway;
+	if (rt->rt6i_flags & RTF_GATEWAY)
+		return &rt->rt6i_gateway;
+	else if (rt->rt6i_flags & RTF_CACHE)
+		return &rt->rt6i_dst.addr;
+	else
+		return daddr;
 }
 
 #endif