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

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Date: Tue, 27 Jun 2023 12:19:41 +0200
From: Daniel Borkmann <daniel@...earbox.net>
To: Lorenz Bauer <lmb@...valent.com>, Kuniyuki Iwashima <kuniyu@...zon.com>
Cc: andrii@...nel.org, ast@...nel.org, bpf@...r.kernel.org,
 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 6/27/23 10:56 AM, Lorenz Bauer wrote:
> 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.

If it breaks the build, then we need to export it.