netdev - Re: [PATCH net-next v2 0/4] net: uapi: Provide an UAPI definition of 'struct sockaddr'

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Message-ID: <20260209143003-80d3cb63-38c6-4280-a319-ee6879eeab11@linutronix.de>
Date: Mon, 9 Feb 2026 14:34:09 +0100
From: Thomas Weißschuh <thomas.weissschuh@...utronix.de>
To: Jakub Kicinski <kuba@...nel.org>
Cc: Eric Dumazet <edumazet@...gle.com>, 
	Kuniyuki Iwashima <kuniyu@...gle.com>, Paolo Abeni <pabeni@...hat.com>, 
	Willem de Bruijn <willemb@...gle.com>, "David S. Miller" <davem@...emloft.net>, 
	Simon Horman <horms@...nel.org>, Shuah Khan <shuah@...nel.org>, 
	Matthieu Baerts <matttbe@...nel.org>, Mat Martineau <martineau@...nel.org>, 
	Geliang Tang <geliang@...nel.org>, Mickaël Salaün <mic@...ikod.net>, 
	Günther Noack <gnoack@...gle.com>, Alexei Starovoitov <ast@...nel.org>, 
	Daniel Borkmann <daniel@...earbox.net>, Jesper Dangaard Brouer <hawk@...nel.org>, 
	John Fastabend <john.fastabend@...il.com>, Stanislav Fomichev <sdf@...ichev.me>, 
	Andrii Nakryiko <andrii@...nel.org>, Martin KaFai Lau <martin.lau@...ux.dev>, 
	Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>, 
	Yonghong Song <yonghong.song@...ux.dev>, KP Singh <kpsingh@...nel.org>, Hao Luo <haoluo@...gle.com>, 
	Jiri Olsa <jolsa@...nel.org>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, 
	linux-api@...r.kernel.org, Arnd Bergmann <arnd@...db.de>, linux-kselftest@...r.kernel.org, 
	mptcp@...ts.linux.dev, linux-security-module@...r.kernel.org, bpf@...r.kernel.org, 
	libc-alpha@...rceware.org, Carlos O'Donell <carlos@...hat.com>, 
	Adhemerval Zanella <adhemerval.zanella@...aro.org>, Rich Felker <dalias@...c.org>, klibc@...or.com, 
	Florian Weimer <fweimer@...hat.com>
Subject: Re: [PATCH net-next v2 0/4] net: uapi: Provide an UAPI definition of
 'struct sockaddr'

On Wed, Feb 04, 2026 at 05:55:16PM -0800, Jakub Kicinski wrote:
> On Wed, 4 Feb 2026 06:51:46 +0100 Thomas Weißschuh wrote:
> > > make -j16 O="$kobj" INSTALL_HDR_PATH="${kobj}/hdr" headers_install
> > > popd
> > > 
> > > pushd uapi
> > > find . -type f -name '*.h' -exec cp -v "${kobj}/hdr/include/{}" {} \;  
> > 
> > Here only those headers which already exist in ethtool's uapi/ directory
> > are copied. As linux/typelimits.h is new, it is now missing.
> > Honestly, if a user fiddles with the internals of the UAPI headers like
> > this, it is on them to update their code if the internal structure
> > changes. In your case a simple 'touch uapi/linux/typelimits.h'
> > before running the script will be enough. Also internal.h now requires
> > an explicit inclusion of <limits.h>, as that is not satisfied by the
> > UAPI anymore.
> 
> Hopefully you understand that while due to uapi header copy this is not
> a huge issue for ethtool itself, but it is a proof that your changes
> can break normal user space applications which do not vendor in uapi.

A regular application which uses a full UAPI headers tree will get
access to the new header automatically.
If the application uses symbols from <limits.h> without including <limits.h>
on its own, it is broken.


Thomas