Commit b05229f442 ("gre6: Cleanup GREv6 transmit path,
call common GRE functions") moved dev->mtu initialization
from ip6gre_tunnel_setup() to ip6gre_tunnel_init(), as a
result, the previously set values, before ndo_init(), are
reset in the following cases:
* rtnl_create_link() can update dev->mtu from IFLA_MTU
parameter.
* ip6gre_tnl_link_config() is invoked before ndo_init() in
netlink and ioctl setup, so ndo_init() can reset MTU
adjustments with the lower device MTU as well, dev->mtu
and dev->hard_header_len.
Not applicable for ip6gretap because it has one more call
to ip6gre_tnl_link_config(tunnel, 1) in ip6gre_tap_init().
Fix the first case by updating dev->mtu with 'tb[IFLA_MTU]'
parameter if a user sets it manually on a device creation,
and fix the second one by moving ip6gre_tnl_link_config()
call after register_netdevice().
Fixes: b05229f442 ("gre6: Cleanup GREv6 transmit path, call common GRE functions")
Fixes: db2ec95d1b ("ip6_gre: Fix MTU setting")
Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
128bb975dc