linux-kernel - RE: selftests: net: l2tp.sh regression starting with 6.1-rc1

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Message-ID: <MW4PR11MB57763144FE1BE9756FD3176BFD899@MW4PR11MB5776.namprd11.prod.outlook.com>
Date:   Wed, 29 Mar 2023 14:16:37 +0000
From:   "Drewek, Wojciech" <wojciech.drewek@...el.com>
To:     Andrea Righi <andrea.righi@...onical.com>
CC:     "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, Shuah Khan <shuah@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kselftest@...r.kernel.org" <linux-kselftest@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: selftests: net: l2tp.sh regression starting with 6.1-rc1

Hi,

Modifying UAPI was not a good idea although the patch should not break userspace (related discussion [1]).
We could revert this patch with one additional change (include l2tp.h in net/sched/cls_flower.c) but then again,
modifying UAPI. This patch was mostly cosmetic anyway.
Second option is to try to fix the automatic load. I'm not an expert but I think
MODULE_ALIAS_NET_PF_PROTO macro is somehow responsible for that. I noticed some comments saying that
"__stringify doesn't like enums" (this macro is using _stringify) and my patch defined IPPROTO_L2TP in enum.
We can just replace IPPROTO_L2TP with 115 (where this macro is used) in order to fix this.
I'm going to give it a try and will let you know.

Regards,
Wojtek

[1] https://lore.kernel.org/netdev/Ywis3PYhKiATnzXB@nanopsycho/

> -----Original Message-----
> From: Andrea Righi <andrea.righi@...onical.com>
> Sent: środa, 29 marca 2023 14:24
> To: Drewek, Wojciech <wojciech.drewek@...el.com>
> Cc: David S. Miller <davem@...emloft.net>; Eric Dumazet <edumazet@...gle.com>; Jakub Kicinski <kuba@...nel.org>; Paolo Abeni
> <pabeni@...hat.com>; Shuah Khan <shuah@...nel.org>; netdev@...r.kernel.org; linux-kselftest@...r.kernel.org; linux-
> kernel@...r.kernel.org
> Subject: selftests: net: l2tp.sh regression starting with 6.1-rc1
> 
> I noticed that l2tp.sh net selftest is failing in recent kernels with
> the following error:
> 
>  RTNETLINK answers: Protocol not supported
> 
> See also: https://bugs.launchpad.net/bugs/2013014
> 
> Apprently the module lt2p_ipv6 is not automatically loaded when the test
> is trying to create an l2tp ipv6 tunnel.
> 
> I did a bisect and found that the offending commit is this one:
> 
>  65b32f801bfb ("uapi: move IPPROTO_L2TP to in.h")
> 
> I've temporarily reverted this commit for now, any suggestion on how to
> fix this properly?
> 
> Thanks,
> -Andrea