I am not quite sure what the motivation behind this module (in the current form) is. Is this intended to act as central registry for network devices, as alternative to including the handling of these also into netreg?

The motivation is to have a central registry of interfaces, that can be returned via the FIB. The reason I did not put it into netreg is two-fold:

1. Nostalgia: this module is pretty much the ng version of net_if
2. I don't see much connection in the functionality, other than registering PIDs somewhere. netreg is more a "I'm interested in packets of a certain type", netif is more "I want to be an endpoint for routing. Network layer what do you need of me." (Last sentence reflects the add/remove callbacks).

See it this way: you can leave netif out if you don't want routing in theory, but you can not leave out netreg, since it is integral to the inter-layer communication.

ERROR: The following new files generate doxygen warnings: sys/include/net/ng_netif.h

Fixed

I think I understand. So this module would also be used when I want to get a list of network devices for implementing shell commands, right?

Yes.

just this one thing about the return value and the ng_netreg/Makefile that has nothing to do with this PR... I will ack once this is fixed.

Addressed comments

looks good to me -> ACK when squashed and Travis is happy.

kicked Travis

Squashed