net/mlx5: Change TTC rules to match on undecrypted ESP packets

net/mlx5: Change TTC rules to match on undecrypted ESP packets

The TTC (Traffic Type Classifier) table classifies the traffic and
steers packet to TIRs, where RSS works based on the hash calculated
from the selected packet fields. For AH/ESP packets, SPI and IP
addresses are the fields used to calculate the hash value for RSS. So,
it's hard to distribute packets to different receiving queues as there
is usually only one SPI in that direction.

IPSec hardware offloads, crypto offload and full (packet) offload were
introduced later. For crypto offload, hardware does encryption,
decryption and authentication, kernel does the others. Kernel always
sends/receives formatted ESP packets with plaintext data instead of
the ciphertext data, all other fields are unmodified. For full
offload, hardware will take care of almost everything, kernel just
sends/receives packets without any IPSec headers.

Currently, all packets with ESP protocols are forwarded to IPSec
offload tables if IPSec rules are configured. In a downstream patch,
the decrypted packets will be recirculated to TTC table, in order to
use RSS, which does the hash on L4 fields after IPSec headers are
stripped by full offload. So those packets handled by crypto offload
must filtered out, as they still have the ESP headers, but apparently
no need to be decrypted again. To do that, ipsec_next_header is added
for the packet matching, as it is valid only after passing through
IPSec decryption.

Signed-off-by: Jianbo Liu <jianbol@nvidia.com>
Reviewed-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://patch.msgid.link/1758179963-649455-2-git-send-email-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>