ifnet: Move SIOCSIFVNET from ifhwioctl() to ifioctl()

[zlei]

Summary

SIOCSIFVNET is not a hardware ioctl. Move it to where it belongs.

Where here, rewrite the logic of checking whether we are moving the
interface from and to the same vnet or not, since it is obviously not
safe to access the members of an interface until the interface is
proven to be on the "active" list.

MFC after: 2 weeks

[zlei]

sys/net/if.c

1199

The error ENXIO means the interface does not exists. Should choose a better error to distinguish that with the case not found child prison / vnet.

[glebius]

Correct me if I am wrong, but this seems to be two separate changes. Can this be split please?

[zlei]

In D55880#1278503, @glebius wrote:

Correct me if I am wrong, but this seems to be two separate changes. Can this be split please?

Ah I mixed the changes to the comments into this revision. I'll update.

[zlei]

Removed the changes to comments.

[zlei]

sys/net/if.c

1192

This revision is based on latest main, so this removal is competing with D55875 .

I'd personally prefer to land this first. With this change it is more robust to check "the moving between the same vnet".