Update if.h to match Linux kernel headers?

[Florian Weimer]

On 06/23/2016 05:57 PM, David Miller wrote:
> From: Florian Weimer <fweimer@redhat.com>
> Date: Thu, 23 Jun 2016 17:10:54 +0200
>
>> On 06/17/2016 11:12 AM, Joseph Myers wrote:
>>> On Thu, 16 Jun 2016, Carlos O'Donell wrote:
>>>
>>>> I'm not entirely sure if userspace can make use of these flags, but
>>>> one
>>>> could conceivably write userspace tools and drivers that would.
>>>
>>> In <https://sourceware.org/ml/libc-alpha/2014-06/msg00413.html> I
>>> noted
>>> that I presumed the exclusion of IFF_* values not fitting in a "short"
>>> flags field was deliberate.
>>
>> Can you elaborate way?  Do you fear that we might end up with an ABI
>> change if the enum promotes to int, not short?  But doesn't do it that
>> already, due to the value IFF_DYNAMIC = 0x8000?
>
> Because ifr_flags in struct ifreq is 16-bit.

But these flags are also used for ifr_flags?

So maybe we should put them into a separate enum block and point to 
struct ifaddrs and getifaddrs?

Thanks,
Florian