Re: [PATCH] Linux: Implement opensock using Netlink sockets

[Florian Weimer <fw@deneb.enyo.de>]

* Adhemerval Zanella:

>> Ahh, it's been fixed since then.  Netlink sockets were one of the
>> few which did not perform ENOIOCTLCMD fallback.  This was changed in
>> kernel 4.6:
>> 
>> commit 025c68186e07afaededa84143f1a22f273cd3f67
>> Author: David Decotigny <decot@googlers.com>
>> Date:   Mon Mar 21 10:15:35 2016 -0700
>> 
>>     netlink: add support for NIC driver ioctls
>> 
>>     By returning -ENOIOCTLCMD, sock_do_ioctl() falls back to calling
>>     dev_ioctl(), which provides support for NIC driver ioctls, which
>>     includes ethtool support. This is similar to the way ioctls are
>>     handled in udp.c or tcp.c.
>> 
>>     This removes the requirement that ethtool for example be tied to the
>>     support of a specific L3 protocol (ethtool uses an AF_INET socket
>>     today).
>> 
>> It's unfortunate that it took that long to make this change.
>> 
>> Thanks,
>> Florian
>
> Indeed, so I think we will need the fallback options (maybe we can restrict
> to some options).

The real question is whether it is important to avoid module loading.
If we could just try

AF_NETLINK
AF_UNIX
AF_INET
AF_INET6

in this order, irrespective of the module load status, the code would
already be much, much simpler.