linux-kernel - Re: [PATCH net-next v12 11/22] ovpn: implement TCP transport

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Message-ID: <8714deae-c1f7-42ff-9e76-fabd9ca5188b@openvpn.net>
Date: Wed, 4 Dec 2024 23:52:43 +0100
From: Antonio Quartulli <antonio@...nvpn.net>
To: Paolo Abeni <pabeni@...hat.com>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Donald Hunter <donald.hunter@...il.com>,
 Shuah Khan <shuah@...nel.org>, sd@...asysnail.net, ryazanov.s.a@...il.com,
 Andrew Lunn <andrew@...n.ch>
Cc: Simon Horman <horms@...nel.org>, netdev@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH net-next v12 11/22] ovpn: implement TCP transport

Paolo,

On 04/12/2024 12:15, Antonio Quartulli wrote:
[...]
>>> +        mutex_lock(&tcp6_prot_mutex);
>>> +        if (!ovpn_tcp6_prot.recvmsg)
>>> +            ovpn_tcp_build_protos(&ovpn_tcp6_prot, &ovpn_tcp6_ops,
>>> +                          sock->sk->sk_prot,
>>> +                          sock->sk->sk_socket->ops);
>>> +        mutex_unlock(&tcp6_prot_mutex);
>>
>> This looks like an hack to avoid a build dependency on IPV6, I think the
>> explicit
> 
> I happily copied this approach from espintcp.c:espintcp_init_sk() :-D
> 
>>
>> #if IS_ENABLED(CONFIG_IPV6)
>>
>> at init time should be preferable

To get this done at init time I need inet6_stream_ops to be accessible, 
but it seems there is no EXPORT_SYMBOL() for this object.

However, I see that mptcp/protocol.c is happily accessing it.
Any clue how this is possible?

If I try to access it within ovpn I get the usual error:
ERROR: modpost: "inet6_stream_ops" [drivers/net/ovpn/ovpn.ko] undefined!

but mptcp compiles just fine.

Any hint?

Regards,

-- 
Antonio Quartulli
OpenVPN Inc.