[RFC PATCH net-next 08/10] ipv6: Do not use inetpeer when creating RTF_CACHE route for /128 via gateway entry

[Martin KaFai Lau <kafai@fb.com>]

When there is a pmtu exception on /128 via gateway route, we need to
create a separate metrics copy for the newly created RTF_CACHE route instead
of reusing the inetpeer cache.  Otherwise, the original mtu will be
over-written and the mtu update will stay after the expiration.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Reviewed-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
---
 net/ipv6/route.c | 17 +++++++++++------
 1 file changed, 11 insertions(+), 6 deletions(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 91c80bc..61ce45e 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -322,8 +322,16 @@ static void ip6_dst_destroy(struct dst_entry *dst)
 	struct rt6_info *rt = (struct rt6_info *)dst;
 	struct inet6_dev *idev = rt->rt6i_idev;
 	struct dst_entry *from = dst->from;
+	unsigned long peer_metrics = 0;
 
-	if (!(rt->dst.flags & DST_HOST))
+	if (rt6_has_peer(rt)) {
+		struct inet_peer *peer = rt6_peer_ptr(rt);
+
+		peer_metrics = (unsigned long)peer->metrics;
+		inet_putpeer(peer);
+	}
+
+	if (peer_metrics != dst->_metrics)
 		dst_destroy_metrics_generic(dst);
 
 	if (idev) {
@@ -333,11 +341,6 @@ static void ip6_dst_destroy(struct dst_entry *dst)
 
 	dst->from = NULL;
 	dst_release(from);
-
-	if (rt6_has_peer(rt)) {
-		struct inet_peer *peer = rt6_peer_ptr(rt);
-		inet_putpeer(peer);
-	}
 }
 
 static void ip6_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
@@ -1956,6 +1959,8 @@ static struct rt6_info *ip6_rt_copy(struct rt6_info *ort,
 
 		rt->rt6i_dst.addr = *dest;
 		rt->rt6i_dst.plen = 128;
+		if (ort->dst.flags & DST_HOST)
+			dst_cow_metrics_generic(&rt->dst, rt->dst._metrics);
 		dst_copy_metrics(&rt->dst, &ort->dst);
 		rt->dst.error = ort->dst.error;
 		rt->rt6i_idev = ort->rt6i_idev;
-- 
1.8.1