Hello Jakub

On Fri, 8 Sep 2023 08:41:08 -0700
Jakub Kicinski [off-list ref] wrote:

On Thu,  7 Sep 2023 11:23:58 +0200 Maxime Chevallier wrote:

quoted

 - the netlink API would need polishing, I struggle a bit with finding
   the correct netlink design pattern to return variale-length list of u32.  

Think of them as a list, not an array.

Dump them one by one, don't try to wrap them in any way:
https://docs.kernel.org/next/userspace-api/netlink/specs.html#multi-attr-arrays
People have tried other things in the past:
https://docs.kernel.org/next/userspace-api/netlink/genetlink-legacy.html#attribute-type-nests
but in the end they add constraints and pain for little benefit.

Thanks for the pointers, this makes much more sense than my attempt at
creating an array.

This and your other comment on the .do vs .dump is exactly what I was
missing in my understanding of netlink.

Maxime