if_link_state_change() patch for review

[Sam Leffler]

Gleb Smirnoff wrote:
> On Tue, Apr 19, 2005 at 08:27:19AM -0700, Sam Leffler wrote:
> S> >change message will report either all state changes or those where at
> S> >the time of reporting the state changed relative to the last report.
> S> >The same assumption is true for the OpenIGPd we are working on at the
> S> >moment.
> S>
> S> It is possible with the change to defer the messages to have multiple 
> S> changes coalesced.  If an app is written to assume it receives notice of 
> S> every change and it uses this to track internal state then it can get 
> S> confused.  The issue was whether or not to communicate any coalescing to 
> S> applications so they can recognize that it's happened.  In lieu of doing 
> S> that I asked for a console printf so we could see if it ever happened in 
> S> practice.
> 
> Yes, all the time we are speaking about a theoretical issue. Let's see
> whether it can happen or not. I decided to go ahead with this change.
> 
> S> >From an (routing) application point of view only effective state changes
> S> >are interesting and only those should be provided.
> S> >
> S> 
> S> If an inteface does down, moves network, then comes back up and you only 
> S> get the up event then you will likely do the wrong thing unless you have 
> S> some other way of identifying what happened.  I'm not convinced (yet) 
> S> this cannot happen so am being cautious.
> 
> In this case you will receive additional messages, not only RTM_IFINFO.
> Move network will also generate RTM_NEWADDR and RTM_DELADDR
> 

Only if someone sets the address which won't be true in the case I'm 
thinking of: dhclient handling a wireless nic that re-associates with a 
different ap.  But since the dhclient I'm thinking of isn't in the tree 
yet I'll look at the problem myself.

	Sam