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Date: Wed, 4 Mar 2026 18:50:56 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Daniel Borkmann <daniel@iogearbox.net>
Cc: Fernando Fernandez Mancera <fmancera@suse.de>, David Ahern
 <dsahern@kernel.org>, "Ricardo B. =?UTF-8?B?TWFybGnDqHJl?=" <rbm@suse.com>,
 Martin KaFai Lau <martin.lau@linux.dev>, John Fastabend
 <john.fastabend@gmail.com>, Stanislav Fomichev <sdf@fomichev.me>, Alexei
 Starovoitov <ast@kernel.org>, Andrii Nakryiko <andrii@kernel.org>, Eduard
 Zingerman <eddyz87@gmail.com>, Song Liu <song@kernel.org>, Yonghong Song
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 <davem@davemloft.net>, Eric Dumazet <edumazet@google.com>, Paolo Abeni
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 =?UTF-8?B?aWxhbmQtSsO4cmdlbnNlbg==?= <toke@redhat.com>, Jay Vosburgh
 <jv@jvosburgh.net>, Andrew Lunn <andrew+netdev@lunn.ch>, Hangbin Liu
 <liuhangbin@gmail.com>, bpf@vger.kernel.org, netdev@vger.kernel.org,
 linux-kernel@vger.kernel.org
Subject: Re: [PATCH net 1/3] bpf: bpf_out_neigh_v4: Fix nd_tbl NULL
 dereference when IPv6 is disabled
Message-ID: <20260304185056.4ef945d4@kernel.org>
In-Reply-To: <ec1fdead-8a2b-475b-a786-846b81234b74@iogearbox.net>
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On Thu, 5 Mar 2026 02:59:27 +0100 Daniel Borkmann wrote:
> >> I presume you mean disable_ipv6_mod which then bails out during the module
> >> load process without error, right? It could be deprecated with a warning so
> >> that it turns into a no-op:  
> > 
> > I believe disabling ipv6 may be legit. Some admins on ipv4 networks may
> > be paranoid and not want to allow any ipv6 traffic if their "firewalls"
> > can only understand IPv6? This is just a guess on my side, but I'm less
> > confident of deprecating the disable knob than =m. I'd be happy if I'm
> > wrong.
> > 
> > To answer the earlier question -- I would prefer to take the fixes now
> > and make IPv6 bool in net-next, feels like too big of a change for rc3
> > :(  
> 
> Makes sense, I think starting this process via net-next is fine and can be
> better justified. Fernando, maybe in that case resend with the unlikely()
> added.

I think Fernando was chiming in because he sent similar patches.
Ricardo, please respin checking ipv6_mod_disabled() ?