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Date:   Thu, 7 Oct 2021 11:29:56 +0200
From:   Florian Westphal <fw@strlen.de>
To:     Eugene Crosser <crosser@average.org>
Cc:     Florian Westphal <fw@strlen.de>, netfilter-devel@vger.kernel.org
Subject: Re: In raw prerouting, `iif` matches different interfaces in
 different kernels when enslaved in a vrf
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Eugene Crosser <crosser@average.org> wrote:
> It would seem that you have an existing filter that drops packets and
> prevents creation of conntrack entries? I can reproduce the behaviour on
> freshly installed Debian and Ubuntu VMs without any modifications, with and
> without `unshare`.

FWIW, this was due to different default setting of rp_filter.
Adding
sysctl net.ipv4.conf.all.rp_filter=0
sysctl net.ipv4.conf.default.rp_filter=0

to start of script makes it work on my side too.