Re: Network Interface Daemon

[Dan Williams <dcbw redhat com>]

On Wed, 2005-04-06 at 14:39 +0100, Rui Campos wrote:
> Hi all,
> Does anybody know about some reference(s) explaining in detail how
> Network Interface Daemon (nifd) works?
> 
> At this time, I am just aware that nifd monitors the network
> interfaces on a host and triggers autoipd and mDNSResponder when link
> change is detected, for example. However, I was interested in learning
> a bit more about it. Can anybody give me some pointers?

That's exactly what it does.  Its only purpose is to make these two
daemons respond to network interface events by sending them signals (HUP
I think).  AFAIK, no other daemons that could benefit from this service
actually do (like sshd).  NetworkManager provides the same functionality
that nifd does, albeit in a more intelligent format:

Network drivers, especially wireless drivers, are quite simplistic about
when they signal that the interface is up or down.  For example, the
Orinoco driver will send the netlink "up" event even when you cannot
exchange traffic with the access point.  Its purely a "did I receive the
last handshake packet from the access point" thing for Orinoco.
However, that does not in any way imply that you can pass _traffic_ back
and forth with the AP.  NetworkManager implements a much more
intelligent set of criteria for wireless devices being "up", including
whether or not you can actually talk to devices behind that access
point, ie you have an IP address.

NetworkManager itself kicks mDNSResponder, but ideally mDNSResponder
would use dbus and receive NetworkManager's "interface changed" events
by itself.

NetworkManager also subsumes the operation of autoipd, and gives an
autoip address where appropriate.

Dan