netdev - Re: [PATCH nf-next v5 0/4] netfilter: flowtable: add indr-block offload

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Message-ID: <20200315212800.j45jg3s4gbpiql53@salvia>
Date:   Sun, 15 Mar 2020 22:28:00 +0100
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     wenxu <wenxu@...oud.cn>
Cc:     netfilter-devel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH nf-next v5 0/4] netfilter: flowtable: add indr-block
 offload

On Wed, Mar 04, 2020 at 08:54:25PM +0800, wenxu wrote:
> 
> 在 2020/3/4 5:53, Pablo Neira Ayuso 写道:
[...]
> The indirect block infrastructure is designed by the driver guys. The callbacks
> is used for building and finishing relationship between the tunnel device and
> the hardware devices. Such as the tunnel device come in and go away and the hardware
> device come in and go away. The relationship between the tunnel device and the
> hardware devices is so subtle.

I understand that this mechanism provides a way for the driver to
subscribe to tunnel devices that might be offloaded.

> > Probably not a requirement in your case, but the same net_device might
> > be used in several flowtables. Your patch is flawed there and I don't
> > see an easy way to fix this.
> 
> The same tunnel device can only be added to one offloaded flowtables.

This is a limitation that needs to be removed. There are requirements
to allow to make the same tunnel device be part of another flowtable.

> The tunnel device can build the relationship with the hardware
> devices one time in the dirver. This is protected by
> flow_block_cb_is_busy and xxx_indr_block_cb_priv in driver.
>
> > I know there is no way to use ->ndo_setup_tc for tunnel devices, but
> > you could have just make it work making it look consistent to the
> > ->ndo_setup_tc logic.
> 
> I think the difficulty is how to find the hardware device for tunnel
> device to set the rule to the hardware.

Right, this is the problem that the infrastructure is solving,
however, it's a bit of a twisty way to address the problem.

> > I'm inclined to apply this patch though, in the hope that this all can
> > be revisited later to get it in line with the ->ndo_setup_tc approach.
> > However, probably I'm hoping for too much.

I have applied this patchset to nf-next.

Probably, there might be a chance to revisit this indirect block
infrastructure.

Thank you.