Re: [PATCH net-next 3/6] tools: ynl-gen: use uapi mask definition in NLA_POLICY_MASK

[Asbjørn Sloth Tønnesen]

On 10/14/25 12:59 AM, Jakub Kicinski wrote:
> On Mon, 13 Oct 2025 16:50:00 +0000 Asbjørn Sloth Tønnesen wrote:
> > Currently when generating policies using NLA_POLICY_MASK(), then
> > we emit a pre-computed decimal mask.
> >
> > When render-max is set, then we can re-use the mask definition,
> > that has been generated in the uapi header.
>
> This will encourage people to render masks in uAPI which just pollutes
> the uAPI files.

It might, but is that a problem, given that most flag-sets are rather small?

Example from include/uapi/linux/wireguard.h:
> enum wgpeer_flag {
>     WGPEER_F_REMOVE_ME = 1U << 0,
>     WGPEER_F_REPLACE_ALLOWEDIPS = 1U << 1,
>     WGPEER_F_UPDATE_ONLY = 1U << 2,
>     __WGPEER_F_ALL = WGPEER_F_REMOVE_ME | WGPEER_F_REPLACE_ALLOWEDIPS |
>                      WGPEER_F_UPDATE_ONLY
> };

I agree that a private "WGPEER_F_ALL" would be pollution, but "__WGPEER_F_ALL"
is less likely to accidentally be used by user-space.

I get why Jason likes having the __WGPEER_F_ALL in a place where it is easy
to review that it has contains all flags, and why he don't like a policy like
NLA_POLICY_MASK(.., 0x7).

We could do the mask definition in the kernel code, like many handwritten
netlink families does, but we still need to keep NETDEV_XDP_ACT_MASK in
netdev.h or remove it's YNL-GEN header for some time.