Extending EVFILT_NETDEV to support ip-address changes

[Julian Elischer]

John-Mark Gurney wrote:

>Fredrik Lindberg wrote this message on Tue, Jul 25, 2006 at 14:54 +0200:
>  
>
>>I have a suggestion to add support for ip-address changes to the
>>kqueue (EVFILT_NETDEV) system.
>>The infrastructure for EVFILT_NETDEV is already in place and this
>>only introduce NOTE_NEWADDR and NOTE_DELADDR and minor modifications
>>to the interface ioctl handler.
>>
>>The purpose is not to replicate the functionality of the
>>routing socket, but to provide a low overhead mechanism for
>>monitoring a given interface for address changes.
>>No information about the event is sent through the kqueue system,
>>instead it will be up to the caller to query the system (if wanted)
>>to obtain information about the current state of the interface
>>that is being monitored.
>>
>>I have attached a suggested patch, any thoughts?
>>    
>>

I may be wrong but doesn't an address change already trigger a routing 
socket event?

>
>Looks basicly good, though you will need to rethink how the filt_netdev
>handles the hint.. since right now it just sets kn_data to whatever
>hint is..  This is fine when it was simply one of NOTE_LINK{UP,DOWN,INV},
>but now that you have an extra flag, the NOTE_DELADDR could make an
>app miss the LINK status if it was looking at data instead of fflags..
>
>Plus, are you sure everyone that is using NOTE_LINK* are treating them
>as a bit mask?  maybe we need to redefine NOTE_LINK* as a mask plus set
>of values, since each of the NOTE_LINK* can only be set once...  but
>the NOTE_ADDR{NEW,DEL} should probably be flags...
>
>We may want to reverse the naming to NOTE_ADDR{NEW,DEL} so that we have
>the more generic first before the more specific...  similar to NOTE_LINK*...
>
>Suffice it to say, this cannot be back ported to RELENG_6 due to API
>breakage...
>
>  
>