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From:   Sasha Levin <Alexander.Levin@microsoft.com>
To:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "stable@vger.kernel.org" <stable@vger.kernel.org>
CC:     Xin Long <lucien.xin@gmail.com>,
        "David S . Miller" <davem@davemloft.net>,
        Sasha Levin <Alexander.Levin@microsoft.com>
Subject: [PATCH AUTOSEL for 4.14 036/110] ip_gre: remove the incorrect mtu
 limit for ipgre tap
Thread-Topic: [PATCH AUTOSEL for 4.14 036/110] ip_gre: remove the incorrect
 mtu limit for ipgre tap
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Date:   Sat, 3 Feb 2018 18:00:46 +0000
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From: Xin Long <lucien.xin@gmail.com>

[ Upstream commit cfddd4c33c254954927942599d299b3865743146 ]

ipgre tap driver calls ether_setup(), after commit 61e84623ace3
("net: centralize net_device min/max MTU checking"), the range
of mtu is [min_mtu, max_mtu], which is [68, 1500] by default.

It causes the dev mtu of the ipgre tap device to not be greater
than 1500, this limit value is not correct for ipgre tap device.

Besides, it's .change_mtu already does the right check. So this
patch is just to set max_mtu as 0, and leave the check to it's
.change_mtu.

Fixes: 61e84623ace3 ("net: centralize net_device min/max MTU checking")
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: Sasha Levin <alexander.levin@microsoft.com>
---
 net/ipv4/ip_gre.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 045331204097..1933654007c4 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1274,6 +1274,7 @@ static const struct net_device_ops erspan_netdev_ops =
=3D {
 static void ipgre_tap_setup(struct net_device *dev)
 {
 	ether_setup(dev);
+	dev->max_mtu =3D 0;
 	dev->netdev_ops	=3D &gre_tap_netdev_ops;
 	dev->priv_flags &=3D ~IFF_TX_SKB_SHARING;
 	dev->priv_flags	|=3D IFF_LIVE_ADDR_CHANGE;
--=20
2.11.0