ipv6: use net->rt_genid to check dst validity

IPv6 dst should take care of rt_genid too. When a xfrm policy is inserted or
deleted, all dst should be invalidated.
To force the validation, dst entries should be created with ->obsolete set to
DST_OBSOLETE_FORCE_CHK. This was already the case for all functions calling
ip6_dst_alloc(), except for ip6_rt_copy().

As a consequence, we can remove the specific code in inet6_connection_sock.

Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 8e80fd2..fb29e22 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -281,13 +281,14 @@
 					     struct fib6_table *table)
 {
 	struct rt6_info *rt = dst_alloc(&net->ipv6.ip6_dst_ops, dev,
-					0, DST_OBSOLETE_NONE, flags);
+					0, DST_OBSOLETE_FORCE_CHK, flags);
 
 	if (rt) {
 		struct dst_entry *dst = &rt->dst;
 
 		memset(dst + 1, 0, sizeof(*rt) - sizeof(*dst));
 		rt6_init_peer(rt, table ? &table->tb6_peers : net->ipv6.peers);
+		rt->rt6i_genid = rt_genid(net);
 	}
 	return rt;
 }
@@ -1031,6 +1032,13 @@
 
 	rt = (struct rt6_info *) dst;
 
+	/* All IPV6 dsts are created with ->obsolete set to the value
+	 * DST_OBSOLETE_FORCE_CHK which forces validation calls down
+	 * into this function always.
+	 */
+	if (rt->rt6i_genid != rt_genid(dev_net(rt->dst.dev)))
+		return NULL;
+
 	if (rt->rt6i_node && (rt->rt6i_node->fn_sernum == cookie)) {
 		if (rt->rt6i_peer_genid != rt6_peer_genid()) {
 			if (!rt6_has_peer(rt))
@@ -1397,8 +1405,6 @@
 		goto out;
 	}
 
-	rt->dst.obsolete = -1;
-
 	if (cfg->fc_flags & RTF_EXPIRES)
 		rt6_set_expires(rt, jiffies +
 				clock_t_to_jiffies(cfg->fc_expires));
@@ -2080,7 +2086,6 @@
 	rt->dst.input = ip6_input;
 	rt->dst.output = ip6_output;
 	rt->rt6i_idev = idev;
-	rt->dst.obsolete = -1;
 
 	rt->rt6i_flags = RTF_UP | RTF_NONEXTHOP;
 	if (anycast)