On Tue, Jan 20, 2026 at 03:20:18PM -0800, H. Peter Anvin wrote:

On 2026-01-20 14:31, Arnd Bergmann wrote:

quoted

quoted

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

This looks reasonable, but would only apply to future libc releases, no?

Adopting a new scheme for all types will be a larger undertaking. Today
'struct sockaddr' is the only type not using the current compatibility
mechanism. Could we first align 'struct sockaddr' as shown by the patch?
Whatever comes next can then build on a uniform base.

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.

Thomas