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

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Date:   Sun, 25 Sep 2016 21:15:52 -0400
From:   Jamal Hadi Salim <jhs@...atatu.com>
To:     Florian Westphal <fw@...len.de>,
        Shmulik Ladkani <shmulik.ladkani@...il.com>
Cc:     "David S. Miller" <davem@...emloft.net>,
        WANG Cong <xiyou.wangcong@...il.com>,
        Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH net-next 4/4] net/sched: act_mirred: Implement ingress
 actions

On 16-09-25 02:31 PM, Florian Westphal wrote:
> Shmulik Ladkani <shmulik.ladkani@...il.com> wrote:
>> We can later address any loop-detection improvements in mirred.
>> WDYT?
>
> You can address this after fixing infamous spinlock recursion hard
> lockup (which has existed forever):
>
> tc qdisc add dev eth0 root handle 1: prio
> tc filter add dev eth0 parent 1: protocol ip u32 match u32 0 0 flowid
> 1:2 action mirred egress redirect dev eth0
>
> (only do this on toy vm)
>

Realize didnt respond to this. Seems very simple to fix:
if skb->dev->ifindex and m->tcfm_dev->ifindex are the
same, then you can drop the packet.
But it may be possible to reject earlier the policy
entirely earlier.
And true given this is egress->egress redirection
one could also check with xmit_recursion check.


cheers,
jamal