RE: [PATCH] net/mlx5: fix maximum packet headers size for TSO

[Raslan Darawsheh <rasland@nvidia.com>]

Hi,

> -----Original Message-----
> From: Alexander Kozyrev <akozyrev@nvidia.com>
> Sent: Thursday, January 13, 2022 4:32 PM
> To: dev@dpdk.org
> Cc: stable@dpdk.org; Raslan Darawsheh <rasland@nvidia.com>; Slava
> Ovsiienko <viacheslavo@nvidia.com>; Matan Azrad <matan@nvidia.com>
> Subject: [PATCH] net/mlx5: fix maximum packet headers size for TSO
> 
> The maximum packet headers size for TSO is calculated as a sum of
> Ethernet, VLAN, IPv6 and TCP headers (plus inner headers).
> The rationale  behind choosing IPv6 and TCP is their headers
> are bigger than IPv4 and UDP respectively, giving us the maximum
> possible headers size. But it is not true for L3 headers.
> IPv4 header size (20 bytes) is smaller than IPv6 header size
> (40 bytes) only in the default case. There are up to 10
> optional header fields called Options in case IHL > 5.
> This means that the maximum size of the IPv4 header is 60 bytes.
> 
> Choosing the wrong maximum packets headers size causes inability
> to transmit multi-segment TSO packets with IPv4 Options present.
> PMD check that it is possible to inline all the packet headers
> and the packet headers size exceeds the expected maximum size.
> The maximum packet headers size was set to 192 bytes before,
> but its value has been reduced during Tx path refactor activity.
> Restore the proper maximum packet headers size for TSO.
> 
> Fixes: 50724e1 ("net/mlx5: update Tx definitions")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Alexander Kozyrev <akozyrev@nvidia.com>
> Acked-by: Viacheslav Ovsiienko <viacheslavo@nvidia.com>

Patch applied to next-net-mlx,

Kindest regards,
Raslan Darawsheh