From: Xin Long <lucien.xin@gmail.com>
Date: Thu, 21 Jun 2018 12:56:04 +0800
Subject: ipvlan: fix IFLA_MTU ignored on NEWLINK
Git-commit: 30877961b1cdd6fdca783c2e8c4f0f47e95dc58c
Patch-mainline: v4.18-rc3
References: networking-stable-18_07_19

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@redhat.com>
Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 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
@@ -556,7 +556,8 @@ int ipvlan_link_new(struct net *src_net,
 	ipvlan->phy_dev = phy_dev;
 	ipvlan->dev = dev;
 	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);
 	spin_lock_init(&ipvlan->addrs_lock);