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

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Date:   Mon, 28 Jan 2019 20:09:34 +0800
From:   Tonghao Zhang <xiangxia.m.yue@...il.com>
To:     Or Gerlitz <gerlitz.or@...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 Mon, Jan 28, 2019 at 12:40 AM Or Gerlitz <gerlitz.or@...il.com> wrote:
>
> 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?
Because we use the num_mod_hdr_actions to store the number of actions
we have parsed,
and when we alloc it, we init it 0 as default.

> 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.
The patch does't break the cache, I think that different matching may
share the same set of
pedit actions.

I use the tc filters to test it: only one same pedit actions in hw,
and after deleting one tc filter, other filter work fine.

tc filter add dev eth4_0 parent ffff: protocol ip prio 1  \
        flower skip_sw ip_proto icmp dst_ip 3.3.3.3                     \
        action pedit ex munge ip dst set 192.168.1.100 pipe             \
        action pedit ex munge eth src set 00:00:00:00:00:01 pipe        \
        action pedit ex munge eth dst set 00:00:00:00:00:02 pipe        \
        action csum ip pipe                                             \
        action tunnel_key set src_ip 192.168.6.2 dst_ip 192.168.10.2
dst_port 4789 id 100 \
        action mirred egress redirect dev vxlan0

note: match 3.3.3.3, vxlan id 100

tc filter add dev eth4_0 parent ffff: protocol ip prio 1  \
        flower skip_sw ip_proto icmp dst_ip 3.3.3.4                     \
        action pedit ex munge ip dst set 192.168.1.100 pipe             \
        action pedit ex munge eth src set 00:00:00:00:00:01 pipe        \
        action pedit ex munge eth dst set 00:00:00:00:00:02 pipe        \
        action csum ip pipe                                             \
        action tunnel_key set src_ip 192.168.6.2 dst_ip 192.168.10.2
dst_port 4789 id 200 \
        action mirred egress redirect dev vxlan0

note: match 3.3.3.4, vxlan id 200