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

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Date:   Thu, 30 Mar 2023 08:45:15 +0200
From:   Andrea Righi <andrea.righi@...onical.com>
To:     Guillaume Nault <gnault@...hat.com>
Cc:     "Drewek, Wojciech" <wojciech.drewek@...el.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

On Wed, Mar 29, 2023 at 06:52:20PM +0200, Guillaume Nault wrote:
> On Wed, Mar 29, 2023 at 03:39:13PM +0000, Drewek, Wojciech wrote:
> > 
> > 
> > > -----Original Message-----
> > > -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
> 
> You're not blind :). The MODULE_ALIAS_NET_PF_PROTO_TYPE(...) is indeed
> wrong. Auto-loading the l2tp_ip and l2tp_ip6 modules only worked
> because of the extra MODULE_ALIAS_NET_PF_PROTO() declaration (as
> inet_create() and inet6_create() fallback to "net-pf-%d-proto-%d" if
> "net-pf-%d-proto-%d-type-%d" fails).

At this point I think using 115 directly is probably the best solution,
that is also what we do already with SOCK_DGRAM, but I would just update
the comment up above, instead of adding the inline comments.

Something like this maybe:

---

From: Andrea Righi <andrea.righi@...onical.com>
Subject: [PATCH] l2tp: generate correct module alias strings

Commit 65b32f801bfb ("uapi: move IPPROTO_L2TP to in.h") moved the
definition of IPPROTO_L2TP from a define to an enum, but since
__stringify doesn't work properly with enums, we ended up breaking the
modalias strings for the l2tp modules:

 $ 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

Use the resolved number directly in MODULE_ALIAS_*() macros (as we
already do with SOCK_DGRAM) to fix the alias strings:

$ modinfo l2tp_ip l2tp_ip6 | grep alias
alias:          net-pf-2-proto-115
alias:          net-pf-2-proto-115-type-2
alias:          net-pf-10-proto-115
alias:          net-pf-10-proto-115-type-2

Moreover, fix the ordering of the parameters passed to
MODULE_ALIAS_NET_PF_PROTO_TYPE() by switching proto and type.

Fixes: 65b32f801bfb ("uapi: move IPPROTO_L2TP to in.h")
Signed-off-by: Guillaume Nault <gnault@...hat.com>
Signed-off-by: Andrea Righi <andrea.righi@...onical.com>
---
 net/l2tp/l2tp_ip.c  | 8 ++++----
 net/l2tp/l2tp_ip6.c | 8 ++++----
 2 files changed, 8 insertions(+), 8 deletions(-)

diff --git a/net/l2tp/l2tp_ip.c b/net/l2tp/l2tp_ip.c
index 4db5a554bdbd..41a74fc84ca1 100644
--- a/net/l2tp/l2tp_ip.c
+++ b/net/l2tp/l2tp_ip.c
@@ -677,8 +677,8 @@ MODULE_AUTHOR("James Chapman <jchapman@...alix.com>");
 MODULE_DESCRIPTION("L2TP over IP");
 MODULE_VERSION("1.0");
 
-/* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like
- * enums
+/* Use the values of SOCK_DGRAM (2) as type and IPPROTO_L2TP (115) as protocol,
+ * 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, 115, 2);
+MODULE_ALIAS_NET_PF_PROTO(PF_INET, 115);
diff --git a/net/l2tp/l2tp_ip6.c b/net/l2tp/l2tp_ip6.c
index 2478aa60145f..5137ea1861ce 100644
--- a/net/l2tp/l2tp_ip6.c
+++ b/net/l2tp/l2tp_ip6.c
@@ -806,8 +806,8 @@ MODULE_AUTHOR("Chris Elston <celston@...alix.com>");
 MODULE_DESCRIPTION("L2TP IP encapsulation for IPv6");
 MODULE_VERSION("1.0");
 
-/* Use the value of SOCK_DGRAM (2) directory, because __stringify doesn't like
- * enums
+/* Use the values of SOCK_DGRAM (2) as type and IPPROTO_L2TP (115) as protocol,
+ * 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, 115, 2);
+MODULE_ALIAS_NET_PF_PROTO(PF_INET6, 115);
-- 
2.39.2