Merge branch 'tls-device-offload-for-bond'

Tariq Toukan says:

====================
TLS device offload for Bond

This series opens TX and RX TLS device offload for bond interfaces.
This allows bond interfaces to benefit from capable lower devices.

We add a new ndo_sk_get_lower_dev() to be used to get the lower dev that
corresponds to a given socket.
The TLS module uses it to interact directly with the lowest device in
chain, and invoke the control operations in tlsdev_ops. This means that the
bond interface doesn't have his own struct tlsdev_ops instance and
derived logic/callbacks.

To keep simple track of the HW and SW TLS contexts, we bind each socket to
a specific lower device for the socket's whole lifetime. This is logically
valid (and similar to the SW kTLS behavior) in the following bond configuration,
so we restrict the offload support to it:

((mode == balance-xor) or (mode == 802.3ad))
and xmit_hash_policy == layer3+4.

In this design, TLS TX/RX offload feature flags of the bond device are
independent from the lower devices. They reflect the current features state,
but are not directly controllable.
This is because the bond driver is bypassed by the call to
ndo_sk_get_lower_dev(), without him knowing who the caller is.
The bond TLS feature flags are set/cleared only according to the configuration
of the mode and xmit_hash_policy.

Bypass is true only for the control flow. Packets in fast path still go through
the bond logic.

The design here differs from the xfrm/ipsec offload, where the bond driver
has his own copy of struct xfrmdev_ops and callbacks.
====================

Link: https://lore.kernel.org/r/20210117145949.8632-1-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>