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Dragos Tatulea 083dbb54c4 net/mlx5e: SHAMPO, Disable gso_size for non GRO packets
When HW GRO is enabled, forwarding of packets is broken due to gso_size
being set incorrectly on non GRO packets.

Non GRO packets have a skb GRO count of 1. mlx5 always sets gso_size on
the skb, even for non GRO packets. It leans on the fact that gso_size is
normally reset in napi_gro_complete(). But this happens only for packets
from GRO'able protocols (TCP/UDP) that have a gro_receive() handler.

The problematic scenarios are:

1) Non GRO protocol packets are received, validate_xmit_skb() will drop
   them (see EPROTONOSUPPORT in skb_mac_gso_segment()). The fix for
   this case would be to not set gso_size at all for SHAMPO packets with
   header size 0.

2) Packets from a GRO'ed protocol (TCP) are received but immediately
   flushed because they are not GRO'able (TCP SYN for example).
   mlx5e_shampo_update_hdr(), which updates the remaining GRO state on
   the skb, is not called because skb GRO count is 1. The fix here would
   be to always call mlx5e_shampo_update_hdr(), regardless of skb GRO
   count. But this call is expensive

The unified fix for both cases is to reset gso_size before calling
napi_gro_receive(). It is a change that is more effective (no call to
mlx5e_shampo_update_hdr() necessary) and simple (smallest code
footprint).

Signed-off-by: Dragos Tatulea <dtatulea@nvidia.com>
Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
Link: https://lore.kernel.org/r/20240603212219.1037656-6-tariqt@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
History 2024-06-05 20:20:46 -07:00
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Linux kernel
============

There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.

In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``.  The formatted documentation can also be read online at:

    https://www.kernel.org/doc/html/latest/

There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.

Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.