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

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Date:   Sat, 24 Sep 2016 17:20:07 -0700
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Shmulik Ladkani <shmulik.ladkani@...il.com>
Cc:     Jamal Hadi Salim <jhs@...atatu.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next 4/4] net/sched: act_mirred: Implement ingress actions

On Fri, Sep 23, 2016 at 8:40 AM, Shmulik Ladkani
<shmulik.ladkani@...il.com> wrote:
> On Fri, 23 Sep 2016 08:48:33 -0400 Jamal Hadi Salim <jhs@...atatu.com> wrote:
>> > 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
>>
>> I think we actually recover from this one by eventually
>> dropping (theres a ttl field).
>
> [off topic]
>
> Don't know about that :) cpu fan got very noisy, 3 of 4 cores at 100%,
> and after one second I got:
>
> # ip -s l show type veth
> 16: v0p@v0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
>     link/ether a2:64:ff:10:dd:85 brd ff:ff:ff:ff:ff:ff
>     RX: bytes  packets  errors  dropped overrun mcast
>     71660305923 469890864 0       0       0       0
>     TX: bytes  packets  errors  dropped carrier collsns
>     3509       24       0       0       0       0
> 17: v0@v0p: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default qlen 1000
>     link/ether 52:a2:34:f6:7c:ec brd ff:ff:ff:ff:ff:ff
>     RX: bytes  packets  errors  dropped overrun mcast
>     3509       24       0       0       0       0
>     TX: bytes  packets  errors  dropped carrier collsns
>     71660713017 469893555 0       0       0       0

These ghost packets never enter IP stack, I don't think TTL
helps.