netdev - Re: [PATCH net-next 4/4] net/sched: act_mirred: Implement ingress actions

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Message-ID: <bd2b555f-cba2-b7bc-1fbe-663da288d8a3@mojatatu.com>
Date:   Sun, 25 Sep 2016 09:39:12 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Cong Wang <xiyou.wangcong@...il.com>,
        Shmulik Ladkani <shmulik.ladkani@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>,
        Florian Westphal <fw@...len.de>
Subject: Re: [PATCH net-next 4/4] net/sched: act_mirred: Implement ingress
 actions

On 16-09-24 08:07 PM, Cong Wang wrote:
> On Thu, Sep 22, 2016 at 10:11 PM, Shmulik Ladkani

>
> One problem to use your code for us is that, the RX side of veth
> is inside containers, not visible to outside, perhaps we need some
> more parameter to tell the netns before the device name/index?
> Thoughts?
>

Intriguing - but this would apply for only veth?

>>
>>> It may be around preventing loops maybe.
>>
>> Could be, but personally, I treat these constructs as (powerful)
>> building blocks, and "with great power comes great responsibility".
>>
>> Even today, one may create loops using existing 'egress redirect',
>> e.g. this rediculously errorneous construct:
>>
>>  # ip l add v0 type veth peer name v0p
>>  # tc filter add dev v0p parent ffff: basic \
>>     action mirred egress redirect dev v0
>
> Detecting such loops should not be hard technically, like we do
> for reclassification. We might need some bits in skb to detect
> this specific case.

Note my other email. We had the feature but we took it out to save bits
on the skb.


cheers,
jamal