netdev - Re: b118509076b3 (probably) breaks my firewall

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Message-ID: <20220908214859.GD16543@breakpoint.cc>
Date:   Thu, 8 Sep 2022 23:48:59 +0200
From:   Florian Westphal <fw@...len.de>
To:     Chris Clayton <chris2553@...glemail.com>
Cc:     Florian Westphal <fw@...len.de>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        Pablo Neira Ayuso <pablo@...filter.org>
Subject: Re: b118509076b3 (probably) breaks my firewall

Chris Clayton <chris2553@...glemail.com> wrote:

[ CC Pablo ]

> On 08/09/2022 20:19, Florian Westphal wrote:
> > Chris Clayton <chris2553@...glemail.com> wrote:
> >> Just a heads up and a question...
> >>
> >> I've pulled the latest and greatest from Linus' tree and built and installed the kernel. git describe gives
> >> v6.0-rc4-126-g26b1224903b3.
> >>
> >> I find that my firewall is broken because /proc/sys/net/netfilter/nf_conntrack_helper no longer exists. It existed on an
> >> -rc4 kernel. Are changes like this supposed to be introduced at this stage of the -rc cycle?
> > 
> > The problem is that the default-autoassign (nf_conntrack_helper=1) has
> > side effects that most people are not aware of.
> > 
> > The bug that propmpted this toggle from getting axed was that the irc (dcc) helper allowed
> > a remote client to create a port forwarding to the local client.
> 
> 
> Ok, but I still think it's not the sort of change that should be introduced at this stage of the -rc cycle.
> The other problem is that the documentation (Documentation/networking/nf_conntrack-sysctl.rst) hasn't been updated. So I
> know my firewall is broken but there's nothing I can find that tells me how to fix it.

Pablo, I don't think revert+move the 'next' will avoid this kinds of
problems, but at least the nf_conntrack-sysctl.rst should be amended to
reflect that this was removed.

I'd keep it though because people that see an error wrt. this might be
looking at nf_conntrack-sysctl.rst.

Maybe just a link to
https://home.regit.org/netfilter-en/secure-use-of-helpers/?

What do you think?