erspan: remove the incorrect mtu limit for erspan

[ Upstream commit 0e141f757b2c78c983df893e9993313e2dc21e38 ]

erspan 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 erspan device to not be greater
than 1500, this limit value is not correct for ipgre tap device.

Tested:
Before patch:
# ip link set erspan0 mtu 1600
Error: mtu greater than device maximum.
After patch:
# ip link set erspan0 mtu 1600
# ip -d link show erspan0
21: erspan0@NONE: <BROADCAST,MULTICAST> mtu 1600 qdisc noop state DOWN
mode DEFAULT group default qlen 1000
    link/ether 00:00:00:00:00:00 brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 68 maxmtu 0

Fixes: 61e84623ace3 ("net: centralize net_device min/max MTU checking")
Signed-off-by: Haishuang Yan <yanhaishuang@cmss.chinamobile.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 0fc499db6da23c47b511a5a62433907864198787..347be2ea78d4a4c9facecb084aeddaccff49612c 100644 (file)
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -1424,6 +1424,7 @@ nla_put_failure:
 static void erspan_setup(struct net_device *dev)
 {
        ether_setup(dev);
+       dev->max_mtu = 0;
        dev->netdev_ops = &erspan_netdev_ops;
        dev->priv_flags &= ~IFF_TX_SKB_SHARING;
        dev->priv_flags |= IFF_LIVE_ADDR_CHANGE;