[PATCH 0/3] [netifd] support external device handlers

[arne.kappen at hhi.fraunhofer.de]

From: Arne Kappen <arne.kappen at hhi.fraunhofer.de>

This extension is based on an idea by Felix Fietkau which I implemented as part
of a student project at TU Berlin in 2015 and during Google Summer of Code 2016
for Freifunk. I've since been using this prototype  to allow for native UCI
configuration of Open vSwitch devices through /etc/config/network - to add wifi
interfaces to it, configure OpenFlow controllers etc. The project recently got
some attention and I was asked to publish it. The concept is as follows:
Add an interface to netifd which allows other programs to fulfill the device
handler function (struct device_type) for a certain device class (ovs in my
case). The communication happens over ubus and thus device handling logic for a
specific type of devices can evolve independently from netifd. To realize this
netifd generates device handler stubs from JSON descriptions which simply relay
calls against the device handler API to the external device configuration
daemon over ubus. The JSON file also contains the UCI config options for the
device class. That way, netifd can create a blobmsg_policy to parse config
options that are unknown at compile time. As a convention I had to add the UCI
option 'depends_on' for expressing dependencies between devices.
There are 2 general external device types: regular devices and bridge devices.
Since my use case with Open vSwitch only involved bridge devices the regular
device part is untested. It is a lot less complex than the bridge part, though.
For the bridge part I followed the structure in bridge.c as much as possible
and it works with Open vSwitch but I don't know if it is generic enough for
other bridge device classes. I was hoping to get some feedback on that.

I've broken down my work into 3 patches. Unfortunately almost the entire thing
comes as a huge block in patch 3. Patch 1 just cleans up an irrelevant comment
on a line which I contributed in 2016 in preparation for publication of this
extension which eventually didn't happen. Patch 2 prepares the device handler
stub generation using a mechanism similar to how proto handlers are
constructed. Patch 3 adds extdev.c which is the meat of the extension.

If you want to test it with Open vSwitch these are the repositories for
my external device handler 'ovsd' and its package feed:
 - https://github.com/arkap/package-ovsd.git
 - https://github.com/arkap/ovsd.git


Arne Kappen (3):
  device: remove left-over comment
  handler: add mechanism to generate external device handler stubs
  extdev: add support for external device handlers

 CMakeLists.txt |    3 +-
 device.c       |    3 -
 extdev.c       | 1383 ++++++++++++++++++++++++++++++++++++++++++++++++
 extdev.h       |   20 +
 handler.c      |  114 ++++
 handler.h      |    5 +
 main.c         |    2 +
 ubus.c         |    7 +
 ubus.h         |    3 +
 9 files changed, 1536 insertions(+), 4 deletions(-)
 create mode 100644 extdev.c
 create mode 100644 extdev.h

-- 
2.29.2