[PATCH 4.9 18/66] ipvlan: fix IFLA_MTU ignored on NEWLINK

[Greg Kroah-Hartman]

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

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

From: Xin Long <lucien.xin@xxxxxxxxx>

[ Upstream commit 30877961b1cdd6fdca783c2e8c4f0f47e95dc58c ]

Commit 296d48568042 ("ipvlan: inherit MTU from master device") adjusted
the mtu from the master device when creating a ipvlan device, but it
would also override the mtu value set in rtnl_create_link. It causes
IFLA_MTU param not to take effect.

So this patch is to not adjust the mtu if IFLA_MTU param is set when
creating a ipvlan device.

Fixes: 296d48568042 ("ipvlan: inherit MTU from master device")
Reported-by: Jianlin Shi <jishi@xxxxxxxxxx>
Signed-off-by: Xin Long <lucien.xin@xxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 drivers/net/ipvlan/ipvlan_main.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/net/ipvlan/ipvlan_main.c
+++ b/drivers/net/ipvlan/ipvlan_main.c
@@ -525,7 +525,8 @@ static int ipvlan_link_new(struct net *s
 	ipvlan->dev = dev;
 	ipvlan->port = port;
 	ipvlan->sfeatures = IPVLAN_FEATURES;
-	ipvlan_adjust_mtu(ipvlan, phy_dev);
+	if (!tb[IFLA_MTU])
+		ipvlan_adjust_mtu(ipvlan, phy_dev);
 	INIT_LIST_HEAD(&ipvlan->addrs);
 
 	/* TODO Probably put random address here to be presented to the