Petr says:

When offloading GRE tunnels, the MTU setting is kept fixed after the
initial offload even as the slow-path configuration changed. Worse: the
offloaded MTU setting is actually just a transient value set at the time
of NETDEV_REGISTER of the tunnel. As of commit ffc2b6ee4174 ("ip_gre:
fix IFLA_MTU ignored on NEWLINK"), that transient value is zero, and
unless there's e.g. a VRF migration that prompts re-offload, it stays at
zero, and all GRE packets end up trapping.

Thus, in patch #1, change the way the MTU is changed post-registration,
so that the full event protocol is observed. That way the drivers get to
see the change and have a chance to react.

In the remaining two patches, implement support for MTU change in mlxsw
driver.

Petr Machata (3):
  ip_tunnel: Emit events for post-register MTU changes
  mlxsw: spectrum_router: Move mlxsw_sp_rif_ipip_lb_op()
  mlxsw: spectrum_router: Handle MTU change of GRE netdevs

 .../net/ethernet/mellanox/mlxsw/spectrum_router.c  | 78 ++++++++++++++--------
 net/ipv4/ip_tunnel.c                               | 26 ++++++--
 2 files changed, 72 insertions(+), 32 deletions(-)

-- 
2.14.3

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