Re: [PATCH net-next v2 1/4] selftests: net: Move some UAPI header inclusions after libc ones

[Matthieu Baerts <matttbe@kernel.org>]

Hi Thomas,

On 20/01/2026 15:10, Thomas Weißschuh wrote:
> Interleaving inclusions of UAPI headers and libc headers is problematic.
> Both sets of headers define conflicting symbols. To enable their
> coexistence a compatibility-mechanism is in place.
> 
> An upcoming change will define 'struct sockaddr' from linux/socket.h.
> However sys/socket.h from libc does not yet handle this case and a
> symbol conflict will arise.
> 
> Furthermore libc-compat.h evaluates the state of the libc
> inclusions only once, at the point it is included first. If another
> problematic header from libc is included later, symbol conflicts arise.
> This will trigger other duplicate definitions when linux/libc-compat.h
> is added to linux/socket.h
> 
> Move the inclusion of UAPI headers after the inclusion of the glibc
> ones, so the libc-compat.h continues to work correctly.

Thank you for looking at this!

Here is my (late, sorry) review for the modifications related to MPTCP:
> diff --git a/tools/testing/selftests/net/mptcp/mptcp_diag.c b/tools/testing/selftests/net/mptcp/mptcp_diag.c
> index 8e0b1b8d84b6..af25ebfd2915 100644
> --- a/tools/testing/selftests/net/mptcp/mptcp_diag.c
> +++ b/tools/testing/selftests/net/mptcp/mptcp_diag.c
> @@ -1,11 +1,6 @@
>  // SPDX-License-Identifier: GPL-2.0
>  /* Copyright (c) 2025, Kylin Software */
>  
> -#include <linux/sock_diag.h>
> -#include <linux/rtnetlink.h>
> -#include <linux/inet_diag.h>
> -#include <linux/netlink.h>
> -#include <linux/compiler.h>
>  #include <sys/socket.h>
>  #include <netinet/in.h>
>  #include <linux/tcp.h>

There is a remaining one (linux/tcp.h) here that you might want to move
below too.

> @@ -17,6 +12,12 @@
>  #include <errno.h>
>  #include <stdio.h>
>  
> +#include <linux/sock_diag.h>
> +#include <linux/rtnetlink.h>
> +#include <linux/inet_diag.h>
> +#include <linux/netlink.h>
> +#include <linux/compiler.h>

Note that I just noticed this is the only file from this directory where
the "includes" are not sorted by type and alphabetical order, see
pm_nl_ctl.c as an example. A bit of a detail, but if you plan to send a
v2, do you mind doing that too here while at it, please?

If not, I can look at that later, but better to avoid doing that in
parallel.

Cheers,
Matt
-- 
Sponsored by the NGI0 Core fund.