[PATCH 3.19 008/177] ipv6: fix ipv6_cow_metrics for non DST_HOST case

[Greg Kroah-Hartman]

3.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Martin KaFai Lau <kafai@xxxxxx>

[ Upstream commit 3b4711757d7903ab6fa88a9e7ab8901b8227da60 ]

ipv6_cow_metrics() currently assumes only DST_HOST routes require
dynamic metrics allocation from inetpeer.  The assumption breaks
when ndisc discovered router with RTAX_MTU and RTAX_HOPLIMIT metric.
Refer to ndisc_router_discovery() in ndisc.c and note that dst_metric_set()
is called after the route is created.

This patch creates the metrics array (by calling dst_cow_metrics_generic) in
ipv6_cow_metrics().

Test:
radvd.conf:
interface qemubr0
{
	AdvLinkMTU 1300;
	AdvCurHopLimit 30;

	prefix fd00:face:face:face::/64
	{
		AdvOnLink on;
		AdvAutonomous on;
		AdvRouterAddr off;
	};
};

Before:
[root@qemu1 ~]# ip -6 r show | egrep -v unreachable
fd00:face:face:face::/64 dev eth0  proto kernel  metric 256  expires 27sec
fe80::/64 dev eth0  proto kernel  metric 256
default via fe80::74df:d0ff:fe23:8ef2 dev eth0  proto ra  metric 1024  expires 27sec

After:
[root@qemu1 ~]# ip -6 r show | egrep -v unreachable
fd00:face:face:face::/64 dev eth0  proto kernel  metric 256  expires 27sec mtu 1300
fe80::/64 dev eth0  proto kernel  metric 256  mtu 1300
default via fe80::74df:d0ff:fe23:8ef2 dev eth0  proto ra  metric 1024  expires 27sec mtu 1300 hoplimit 30

Fixes: 8e2ec639173f325 (ipv6: don't use inetpeer to store metrics for routes.)
Signed-off-by: Martin KaFai Lau <kafai@xxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/ipv6/route.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -141,7 +141,7 @@ static u32 *ipv6_cow_metrics(struct dst_
 	u32 *p = NULL;
 
 	if (!(rt->dst.flags & DST_HOST))
-		return NULL;
+		return dst_cow_metrics_generic(dst, old);
 
 	peer = rt6_get_peer_create(rt);
 	if (peer) {


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