linux-kernel - Re: [PATCH bpf-next v3 2/7] net: export inet_lookup_reuseport and inet6_lookup

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Message-ID: <CAN+4W8hnPzhuKPorSjHeOQHFgAuk=A9oa1hW5jckUPoF=5zEQQ@mail.gmail.com>
Date:   Tue, 27 Jun 2023 09:56:42 +0100
From:   Lorenz Bauer <lmb@...valent.com>
To:     Kuniyuki Iwashima <kuniyu@...zon.com>
Cc:     andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
        daniel@...earbox.net, davem@...emloft.net, dsahern@...nel.org,
        edumazet@...gle.com, haoluo@...gle.com, hemanthmalla@...il.com,
        joe@...d.net.nz, john.fastabend@...il.com, jolsa@...nel.org,
        kpsingh@...nel.org, kuba@...nel.org, linux-kernel@...r.kernel.org,
        linux-kselftest@...r.kernel.org, martin.lau@...ux.dev,
        mykolal@...com, netdev@...r.kernel.org, pabeni@...hat.com,
        sdf@...gle.com, shuah@...nel.org, song@...nel.org,
        willemdebruijn.kernel@...il.com, yhs@...com
Subject: Re: [PATCH bpf-next v3 2/7] net: export inet_lookup_reuseport and inet6_lookup_reuseport

On Mon, Jun 26, 2023 at 6:33 PM Kuniyuki Iwashima <kuniyu@...zon.com> wrote:
>
> From: Lorenz Bauer <lmb@...valent.com>
> Date: Mon, 26 Jun 2023 16:08:59 +0100
> > Rename the existing reuseport helpers for IPv4 and IPv6 so that they
> > can be invoked in the follow up commit. Export them so that DCCP which
> > may be built as a module can access them.
>
> We need not export the functions unless there is a real user.
>
> I added a deprecation notice for DCCP recently, so I bet DCCP
> will not get SO_REUSEPORT support.
> https://git.kernel.org/pub/scm/linux/kernel/git/netdev/net.git/commit/?id=b144fcaf46d4

Misleading commit message, it turns out that ipv6 as a module also
needs (the v6 functions at least) to be EXPORT_SYMBOL'd. That's
because of some special shenanigans where inet6_hashtables.c is linked
into vmlinux even when CONFIG_IPV6=m.

Also not sure how to work around this: DCCP may be deprecated but
without the export a module build of it fails.