linux-kernel - Re: [klibc] [PATCH net-next] net: uapi: Provide an UAPI definition of 'struct sockaddr'

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Message-ID: <0f257cd0-27cf-4c11-b79c-724f4e22c4bf@zytor.com>
Date: Tue, 20 Jan 2026 15:20:18 -0800
From: "H. Peter Anvin" <hpa@...or.com>
To: Arnd Bergmann <arnd@...db.de>,
        Thomas Weißschuh <thomas.weissschuh@...utronix.de>,
        Eric Dumazet <edumazet@...gle.com>,
        Kuniyuki Iwashima <kuniyu@...gle.com>, Paolo Abeni <pabeni@...hat.com>,
        Willem de Bruijn <willemb@...gle.com>,
        Xi Ruoyao <libc-alpha@...rceware.org>,
        "Carlos O'Donell" <carlos@...hat.com>,
        Adhemerval Zanella Netto <adhemerval.zanella@...aro.org>,
        Rich Felker <dalias@...c.org>
Cc: Netdev <netdev@...r.kernel.org>, linux-kernel@...r.kernel.org,
        linux-api@...r.kernel.org, klibc@...or.com
Subject: Re: [klibc] [PATCH net-next] net: uapi: Provide an UAPI definition of
 'struct sockaddr'

On 2026-01-20 14:31, Arnd Bergmann wrote:
>> 
> I must have accidentally cut that from my reply, sorry.
> Looking at it again now, I think I ran into problems with the
> flexible array that was removed from the in-kernel sockaddr
> structure in commit 2b5e9f9b7e41 ("net: Convert struct sockaddr
> to fixed-size "sa_data[14]""), so there is a good chance it works
> now with the (once more) fixed-size version.
> 
> The other problem is that the structures that embed 'sockaddr'
> are used a lot inside of the kernel, in particular in 'ifreq',
> so changing the uapi sockaddr to __kernel_sockaddr requires
> additional changes wherever the struct members are passed
> by reference.
>

Well, the kernel should do what opting-in libcs do:

#define sockaddr __kernel_sockaddr

or

struct sockaddr { struct __kernel_sockaddr; };

... now when we have ms extensions turned on. Unfortunately gcc/clang don't
support them without the option even with __extension__, so user space is
limited to using macros.

	-hpa