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Re: Patch to implement SIOCGIFINDEX
On Apr 2, 2013, at 4:55 PM, Lloyd Parkes
> On 3/04/2013, at 5:52 AM, Ty Sarna <ty%sarna.org@localhost> wrote:
>> Still, what I've done now is to add an "ifname" field as well. By default
>> ignored and so the interface is backwards compatible, but I allow setting the
>> index to -1, in which case the name is used instead.
> I'm pretty sure that ifname isn't especially useful.
It's really the most useful thing for this use (sockaddr_can), because it's
stable across the attachment life of an interface, and it's the only identifier
a user knows for an interface anyway -- so it makes the most sense to use it
directly rather than indirecting through index numbers, which only add fragility
anyway, as we've seen.
> Something working as a VPN concentrator for remote users will have a lot of
> churn and a lot of reused interfaces names. I would look at using a
> generation number, an unsigned 32 bit number that is incremented every time
> an interface is added or removed. Maybe we even have one already? That way
> someone who really cares can just check the generation number and the people
> that don't care can ignore it.
That's a completely different use case. But, I think there is indeed a
number within the interface system, though I don't know if it's exposed outside
the kernel or not.
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