Re: [PATCH v2 1/4][next] uapi: socket: Introduce struct sockaddr_legacy

[Johannes Berg <johannes@sipsolutions.net>]

On Mon, 2024-10-28 at 21:38 +0100, Andrew Lunn wrote:
> > As this new struct will live in UAPI, to avoid breaking user-space code
> > that expects `struct sockaddr`, the `__kernel_sockaddr_legacy` macro is
> > introduced. This macro allows us to use either `struct sockaddr` or
> > `struct sockaddr_legacy` depending on the context in which the code is
> > used: kernel-space or user-space.
> 
> Are there cases of userspace API structures where the flexiable array
> appears in the middle?

Clearly, it's the case for all the three other patches in this series.

> I assume this new compiler flag is not only for
> use in the kernel? When it gets turned on in user space, will the
> kernel headers will again produce warnings? Should we be considering
> allowing user space to opt in to using sockaddr_legacy?

For the userspace covered by patch 2 this will almost certainly never
happen, and I suspect that might also be true for the others (arp and
rtnetlink ioctls)? But it probably wouldn't be difficult either.

johannes