Merge branch 'macsec-offload-mlx5'

Saeed Mahameed says:

====================
Introduce MACsec skb_metadata_dst and mlx5 macsec offload

v1->v2:
   - attach mlx5 implementation patches.

This patchset introduces MACsec skb_metadata_dst to lay the ground
for MACsec HW offload.

MACsec is an IEEE standard (IEEE 802.1AE) for MAC security.
It defines a way to establish a protocol independent connection
between two hosts with data confidentiality, authenticity and/or
integrity, using GCM-AES. MACsec operates on the Ethernet layer and
as such is a layer 2 protocol, which means it’s designed to secure
traffic within a layer 2 network, including DHCP or ARP requests.

Linux has a software implementation of the MACsec standard and
HW offloading support.
The offloading is re-using the logic, netlink API and data
structures of the existing MACsec software implementation.

For Tx:
In the current MACsec offload implementation, MACsec interfaces shares
the same MAC address by default.
Therefore, HW can't distinguish from which MACsec interface the traffic
originated from.

MACsec stack will use skb_metadata_dst to store the SCI value, which is
unique per MACsec interface, skb_metadat_dst will be used later by the
offloading device driver to associate the SKB with the corresponding
offloaded interface (SCI) to facilitate HW MACsec offload.

For Rx:
Like in the Tx changes, if there are more than one MACsec device with
the same MAC address as in the packet's destination MAC, the packet will
be forward only to one of the devices and not neccessarly to the desired one.

Offloading device driver sets the MACsec skb_metadata_dst sci
field with the appropriaate Rx SCI for each SKB so the MACsec rx handler
will know to which port to divert those skbs, instead of wrongly solely
relaying on dst MAC address comparison.

1) patch 1,2, Add support to skb_metadata_dst in MACsec code:
net/macsec: Add MACsec skb_metadata_dst Tx Data path support
net/macsec: Add MACsec skb_metadata_dst Rx Data path support

2) patch 3, Move some MACsec driver code for sharing with various
drivers that implements offload:
net/macsec: Move some code for sharing with various drivers that
implements offload

3) The rest of the patches introduce mlx5 implementation for macsec
offloads TX and RX via steering tables.
  a) TX, intercept skbs with macsec offlad mark in skb_metadata_dst and mark
the descriptor for offload.
  b) RX, intercept offloaded frames and prepare the proper
skb_metadata_dst to mark offloaded rx frames.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>