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Date: Tue, 22 Apr 2025 13:43:52 +0200
From: Florian Westphal <fw@strlen.de>
To: Slavko <linux@slavino.sk>
Cc: netfilter ML <netfilter@vger.kernel.org>
Subject: Re: nftables RP filter and loopback
Message-ID: <20250422114352.GA2092@breakpoint.cc>
References: <905173BB-6745-4B59-8795-F9AC1E063A38@slavino.sk>
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Slavko <linux@slavino.sk> wrote:
> Hi all,
> 
> i encounter strange problem with reverse path filter in nftables,
> which i don't understand, thus i ask for help.
> 
> Some background -- for long time i have on my desktop (with
> some bridges/veths for LXC, VirtualBox ifaces, and one dummy
> iface) this prerouting chain (to shorten it i removed counter and
> log parts):
> 
>     chain r_prerouting {
>         type filter hook input priority raw; policy accept;
                           ~~~~~

This is an input chain.  The loopback bypass is restricted
to PRE_ROUTING before v6.15-rc1.

(This is an oversight, originally fib was rejected in input chain, and
when that restriction got lifted the lo bypass check wasn't adjusted).