if_flags usage etc.

[Brooks Davis]

On Wed, Jan 25, 2006 at 04:14:52PM -0800, Sam Leffler wrote:
> Robert Watson wrote:
> >
> >On Tue, 24 Jan 2006, John-Mark Gurney wrote:
> >
> >>sthaug at nethelp.no wrote this message on Tue, Jan 24, 2006 at 23:15 +0100:
> >>
> >>>>We should probably better document the interface "interface". if we are
> >>>>going to (as Sam suggests)
> >>>>do some cleanups we might as well consider what other changes should be
> >>>>put in at the same time.
> >>>
> >>>
> >>>A couple of other suggestions:
> >>>
> >>>- For software routers (quagga, zebra etc.) it would be very nice to
> >>>have "link up" / "link down" notifications to the routing process(es).
> >>
> >>
> >>already supported, either through kqueue, routing socket, or devd (I 
> >>believe)...
> >
> >
> >However, I believe some interface drivers don't generate these events. 
> >Drivers not supporting a specific event delivered by an interrupt 
> >probably need to learn to poll for state changes so that they can 
> >generate an event.
> 
> I am not aware of any drivers that do not generate the events; only 
> drivers that do not properly detect link status changes.

We do have some pseudo devices that could simulate a link and don't
appear to.  For instance tap could pretend to have media and produce
notifications based on whether the /dev/tap# device is open.  It seems
like that could be useful in some scenarios where you're hanging a
virtual machine off the other end.

-- Brooks

-- 
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