netdev - Re: Linux kernel error stack

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Date:   Mon, 6 Aug 2018 02:06:45 +0200
From:   Michal Kubecek <mkubecek@...e.cz>
To:     Florian Westphal <fw@...len.de>
Cc:     Satish Patel <satish.txt@...il.com>, netdev@...r.kernel.org
Subject: Re: Linux kernel error stack

On Mon, Aug 06, 2018 at 01:15:37AM +0200, Florian Westphal wrote:
> Michal Kubecek <mkubecek@...e.cz> wrote:
> > Oops, exactly this issue was already discussed almost a year ago:
> > 
> >   http://lkml.kernel.org/r/20170824104824.2C318A0F3A@unicorn.suse.cz
> > 
> > But something more urgent came and I forgot to get back to it. :-(
> 
> I did not even remeber, thanks for the pointer.
> So I think best course of action is to update man page to clearly
> say this only works in postrouting and with udp, and is ONLY
> intended for working around old dhcp software.

As GSO for UDP is on its way to mainline, one might get into trouble
even with UDP if the rule is not specific enough.
 
> From kernel, have checkentry emit a warning
> when this is used for protocols other than udp,
> and make this a no-op for everything else.
> 
> Same for postrouting: warn from checkentry if the hook is something
> else, and have target function not do anything for !postrouting.
> 
> Does that make sense?

It sounds reasonable to me.

> I can work on a patch later this week if needed.

I'll be on vacation until Sunday so that I certainly won't get to it
earlier than next week.

Michal Kubecek