netdev - Re: [PATCH net v4 2/2] net/mlx5e: Don't overwrite pedit action when multiple pedit used

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Message-ID: <CAJ3xEMjrLgJspjY-Aqd68GzWMrFuHHiAOjoazi9p1T8BhuPP=w@mail.gmail.com>
Date:   Sun, 27 Jan 2019 18:39:51 +0200
From:   Or Gerlitz <gerlitz.or@...il.com>
To:     Tonghao Zhang <xiangxia.m.yue@...il.com>
Cc:     Saeed Mahameed <saeedm@...lanox.com>,
        Linux Netdev List <netdev@...r.kernel.org>,
        Or Gerlitz <ogerlitz@...lanox.com>
Subject: Re: [PATCH net v4 2/2] net/mlx5e: Don't overwrite pedit action when
 multiple pedit used

On Sun, Jan 27, 2019 at 1:06 PM <xiangxia.m.yue@...il.com> wrote:
> From: Tonghao Zhang <xiangxia.m.yue@...il.com>
>
> In some case, we may use multiple pedit actions to modify packets.
> The command shown as below: the last pedit action is effective.

> @@ -2073,7 +2076,8 @@ static int alloc_mod_hdr_actions(struct mlx5e_priv *priv,
>         if (!parse_attr->mod_hdr_actions)
>                 return -ENOMEM;
>
> -       parse_attr->num_mod_hdr_actions = max_actions;
> +       parse_attr->max_mod_hdr_actions = max_actions;
> +       parse_attr->num_mod_hdr_actions = 0;

why would we want to do this zeroing? what purpose does it serve?

On a probably related note, I suspect that the patch broke the caching
we do for modify header contexts, see mlx5e_attach_mod_hdr where we
look if a given set of modify header operations already has hw modify header
context and we use it.

To test that, put two tc rules with different matching but same set of
modify header
(pedit) actions and see that only one modify header context is used.