On 10/30/2018 9:57 AM, Eric Dumazet wrote:

As shown by Dmitris, we need to use csum_block_add() instead of csum_add()
when adding the FCS contribution to skb csum.

Before 4.18 (more exactly commit 88078d98d1bb "net: pskb_trim_rcsum()
and CHECKSUM_COMPLETE are friends"), the whole skb csum was thrown away,
so RXFCS changes were ignored.

Then before commit d55bef5059dd ("net: fix pskb_trim_rcsum_slow() with
odd trim offset") both mlx5 and pskb_trim_rcsum_slow() bugs were canceling
each other.

Now we fixed pskb_trim_rcsum_slow() we need to fix mlx5.

Note that this patch also rewrites mlx5e_get_fcs() to :

- Use skb_header_pointer() instead of reinventing it.
- Use __get_unaligned_cpu32() to avoid possible non aligned accesses
   as Dmitris pointed out.

Fixes: 902a545904c7 ("net/mlx5e: When RXFCS is set, add FCS data into checksum calculation")
Reported-by: Paweł Staszewski <redacted>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Eran Ben Elisha <redacted>
Cc: Saeed Mahameed <redacted>
Cc: Dimitris Michailidis <redacted>
Cc: Cong Wang <redacted>
Cc: Paweł Staszewski <redacted>
---
  .../net/ethernet/mellanox/mlx5/core/en_rx.c   | 45 ++++---------------
  1 file changed, 9 insertions(+), 36 deletions(-)

Thanks for the modification!
We run a direct test we had for this scenario and it passed.

Reviewed-by: Eran Ben Elisha <redacted>
Tested-By: Maria Pasechnik <redacted>