bonding: Fix feature propagation of NETIF_F_GSO_ENCAP_ALL

bonding: Fix feature propagation of NETIF_F_GSO_ENCAP_ALL

Drivers like mlx5 expose NIC's vlan_features such as
NETIF_F_GSO_UDP_TUNNEL & NETIF_F_GSO_UDP_TUNNEL_CSUM which are
later not propagated when the underlying devices are bonded and
a vlan device created on top of the bond.

Right now, the more cumbersome workaround for this is to create
the vlan on top of the mlx5 and then enslave the vlan devices
to a bond.

To fix this, add NETIF_F_GSO_ENCAP_ALL to BOND_VLAN_FEATURES
such that bond_compute_features() can probe and propagate the
vlan_features from the slave devices up to the vlan device.

Given the following bond:

  # ethtool -i enp2s0f{0,1}np{0,1}
  driver: mlx5_core
  [...]

  # ethtool -k enp2s0f0np0 | grep udp
  tx-udp_tnl-segmentation: on
  tx-udp_tnl-csum-segmentation: on
  tx-udp-segmentation: on
  rx-udp_tunnel-port-offload: on
  rx-udp-gro-forwarding: off

  # ethtool -k enp2s0f1np1 | grep udp
  tx-udp_tnl-segmentation: on
  tx-udp_tnl-csum-segmentation: on
  tx-udp-segmentation: on
  rx-udp_tunnel-port-offload: on
  rx-udp-gro-forwarding: off

  # ethtool -k bond0 | grep udp
  tx-udp_tnl-segmentation: on
  tx-udp_tnl-csum-segmentation: on
  tx-udp-segmentation: on
  rx-udp_tunnel-port-offload: off [fixed]
  rx-udp-gro-forwarding: off

Before:

  # ethtool -k bond0.100 | grep udp
  tx-udp_tnl-segmentation: off [requested on]
  tx-udp_tnl-csum-segmentation: off [requested on]
  tx-udp-segmentation: on
  rx-udp_tunnel-port-offload: off [fixed]
  rx-udp-gro-forwarding: off

After:

  # ethtool -k bond0.100 | grep udp
  tx-udp_tnl-segmentation: on
  tx-udp_tnl-csum-segmentation: on
  tx-udp-segmentation: on
  rx-udp_tunnel-port-offload: off [fixed]
  rx-udp-gro-forwarding: off

Various users have run into this reporting performance issues when
configuring Cilium in vxlan tunneling mode and having the combination
of bond & vlan for the core devices connecting the Kubernetes cluster
to the outside world.

Fixes: a9b3ace44c7d ("bonding: fix vlan_features computing")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Nikolay Aleksandrov <razor@blackwall.org>
Cc: Ido Schimmel <idosch@idosch.org>
Cc: Jiri Pirko <jiri@nvidia.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Reviewed-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://patch.msgid.link/20241210141245.327886-3-daniel@iogearbox.net
Signed-off-by: Paolo Abeni <pabeni@redhat.com>