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

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Date:   Wed, 29 Mar 2023 15:39:13 +0000
From:   "Drewek, Wojciech" <wojciech.drewek@...el.com>
To:     Guillaume Nault <gnault@...hat.com>
CC:     Andrea Righi <andrea.righi@...onical.com>,
        "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



> -----Original Message-----
> From: Guillaume Nault <gnault@...hat.com>
> Sent: środa, 29 marca 2023 17:26
> To: Drewek, Wojciech <wojciech.drewek@...el.com>
> Cc: Andrea Righi <andrea.righi@...onical.com>; 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: Re: selftests: net: l2tp.sh regression starting with 6.1-rc1
> 
> On Wed, Mar 29, 2023 at 02:16:37PM +0000, Drewek, Wojciech wrote:
> > 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.
> 
> Yes, the modules aliases now have symbolic names:
> 
> $ modinfo l2tp_ip l2tp_ip6 | grep alias
> alias:          net-pf-2-proto-IPPROTO_L2TP
> alias:          net-pf-2-proto-2-type-IPPROTO_L2TP
> alias:          net-pf-10-proto-IPPROTO_L2TP
> alias:          net-pf-10-proto-2-type-IPPROTO_L2TP
> 
> Therefore, 'request_module("net-pf-%d-proto-%d-type-%d")' can't find
> them.
> 
> My personal preference is for the second option: fix module loading by
> using plain numbers in MODULE_ALIAS_*. We can always keep the symbolic
> names in comments.
> 
> ---- >8 ----
> 
> diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
> index 4db5a554bdbd..afe94a390ef0 100644
> --- a/net/l2tp/l2tp_ip.c
> +++ b/net/l2tp/l2tp_ip.c
> @@ -680,5 +680,5 @@ MODULE_VERSION("1.0");
>  /* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like
>   * enums
>   */
> -MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 2, IPPROTO_L2TP);
> -MODULE_ALIAS_NET_PF_PROTO(PF_INET, IPPROTO_L2TP);
> +MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET, 2, 115 /* IPPROTO_L2TP */);
> +MODULE_ALIAS_NET_PF_PROTO(PF_INET, 115 /* IPPROTO_L2TP */);
> diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
> index 2478aa60145f..65d106b41951 100644
> --- a/net/l2tp/l2tp_ip6.c
> +++ b/net/l2tp/l2tp_ip6.c
> @@ -809,5 +809,5 @@ MODULE_VERSION("1.0");
>  /* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like
>   * enums
>   */
> -MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET6, 2, IPPROTO_L2TP);
> -MODULE_ALIAS_NET_PF_PROTO(PF_INET6, IPPROTO_L2TP);
> +MODULE_ALIAS_NET_PF_PROTO_TYPE(PF_INET6, 2, 115 /* IPPROTO_L2TP */);
> +MODULE_ALIAS_NET_PF_PROTO(PF_INET6, 115 /* IPPROTO_L2TP */);

Btw, am I blind or the alias with type was wrong the whole time?
pf goes first, then proto and type at the end according to the definition of MODULE_ALIAS_NET_PF_PROTO_TYPE
and here type (2) is 2nd and proto (115) is 3rd