if_link_state_change() patch for review

[Gleb Smirnoff]

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

-- 
Totus tuus, Glebius.
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