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Date:   Tue, 2 Nov 2021 09:40:58 +0800
From:   Tonghao Zhang <xiangxia.m.yue@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     Cong Wang <xiyou.wangcong@...il.com>, ast@...nel.org,
        andrii@...nel.org, songliubraving@...com, yhs@...com,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: bpf redirect will loop the packets

On Mon, Nov 1, 2021 at 10:41 PM Daniel Borkmann <daniel@...earbox.net> wrote:
>
> On 11/1/21 7:32 AM, Tonghao Zhang wrote:
> > Hi
> > I found the issue,
> > if we use the bpf_redirect to the same netdevice in the ingress path.
> > the packet loop.
> > and now linux doesn't check that. In tx path,
> > softnet_data.xmit.recursion will limit the recursion.
> > I think we should check that in ingress. any thoughts?
>
> Nope, since this is xmit, not receive. This goes through a rescheduling
> point and could end up on a different CPU potentially. This is not any
> different in than how other infra handles this case. Point here is that
> it's not freezing the box, so admin can react to misconfig and then undo
> it again.
Yes, Should we print a warning msg when packets loop in ingress. in
__dev_queue_xmit
we print an msg, and admin may find that issue.

Thanks Daniel



-- 
Best regards, Tonghao

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