linux-kernel - [PATCH 4.14 033/115] ip_gre: remove the incorrect mtu limit for ipgre tap

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Date:   Fri,  2 Mar 2018 09:50:36 +0100
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Jianlin Shi <jishi@...hat.com>,
        Xin Long <lucien.xin@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Sasha Levin <alexander.levin@...izon.com>
Subject: [PATCH 4.14 033/115] ip_gre: remove the incorrect mtu limit for ipgre tap

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

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

From: Xin Long <lucien.xin@...il.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@...hat.com>
Signed-off-by: Xin Long <lucien.xin@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Sasha Levin <alexander.levin@...izon.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv4/ip_gre.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1274,6 +1274,7 @@ static const struct net_device_ops erspa
 static void ipgre_tap_setup(struct net_device *dev)
 {
 	ether_setup(dev);
+	dev->max_mtu = 0;
 	dev->netdev_ops	= &gre_tap_netdev_ops;
 	dev->priv_flags &= ~IFF_TX_SKB_SHARING;
 	dev->priv_flags	|= IFF_LIVE_ADDR_CHANGE;