netdev - [RFC PATCH net-next] ipv6: fix ipv6_cow_metrics for non DST

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Message-ID: <1423771650-870555-1-git-send-email-kafai@fb.com>
Date:	Thu, 12 Feb 2015 12:07:30 -0800
From:	Martin KaFai Lau <kafai@...com>
To:	<netdev@...r.kernel.org>
CC:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	<davem@...emloft.net>, Kernel Team <kernel-team@...com>
Subject: [RFC PATCH net-next] ipv6: fix ipv6_cow_metrics for non DST_HOST case

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@...u1 ~]# 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@...u1 ~]# 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

Signed-off-by: Martin KaFai Lau <kafai@...com>
---
 net/ipv6/route.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 98565ce..4688bd4 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -141,7 +141,7 @@ static u32 *ipv6_cow_metrics(struct dst_entry *dst, unsigned long old)
 	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) {
-- 
1.8.1

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