Extending EVFILT_NETDEV to support ip-address changes

[Fredrik Lindberg]

Julian Elischer wrote:
> 
> I may be wrong but doesn't an address change already trigger a routing 
> socket event?
> 

Yes, a routing message is sent on address addition/removal, but
the point (as I noted in my first mail) was to avoid the routing
socket-read-parse dance and provide a lightweight and direct
(the routing socket broadcasts events about all interfaces) mechanism
for address addition/removal events.
Also, the NOTE_ADDR{NEW,DEL} are sent AFTER interface configuration is
complete, at least RTM_DELADDR is broadcasted before the ip-address
actually is removed from the interface because it's sent from the
routing code and not the interface configuration code.

Fredrik Lindberg