# P4 Openflow Agent

***This repository is no longer maintained. If you want to integrate a P4
   dataplane with an SDN controller, you can take a look at the
   [ONOS](https://opennetworking.org/onos/) project.***

This is the controller-facing layer of a P4 agnostic Openflow 1.3 Agent.

    +-----------------------------------+
    |      Openflow Controller          | 
    |                                   |
    +-----------------------------------+
                     ^
                     |
                     |
                     v
    +-----------------------------------+
    |          Openflow Agent           |
    |                                   |
    |-----------------------------------|
    |      Openflow <-> P4 Mapping      |
    +-----------------------------------+
    |        Resource Mgmt. API         |
    |   (auto-gen. from p4 program)     |
    +-----------------------------------+
    |          Soft Switch              |
    |    (compiled from p4 program)     |
    +-----------------------------------+

## Building
To build, run

`git submodule update --init --recursive`

`./autogen.sh`

`./configure`

This generates a Makefile with target `p4ofagent` to be required by a
[p4factory](https://github.com/p4lang/p4factory) target Makefile.

For use with BMV2, the P4 Openflow Agent needs to be installed. First install
[BMV2](https://github.com/p4lang/behavioral-model), then follow the
above instructions for building, but with CPPFLAGS=-D_BMV2_ exported in your environment.
Note that when running `./configure` for bmv2, you need to provide the `--with-pdfixed`
option, as `p4ofagent` requires the PD library.

Then run `make p4ofagent` and `make install`.

## Features
The P4 Openflow Agent is P4-independent, so features vary with the
source P4 program. With everything enabled, the `openflow.p4` module supports:

1. Forwarding

2. Multicast (OFPGT_ALL) groups.

3. Vlan push/pop/set

4. MPLS push/pop/ttl-set

5. Network ttl set

6. Packet in, packet out

## Dependencies
#### PD
The P4 Openflow Agent depends on the PD (Protocol Dependent) API generated by
[the P4 compiler](https://github.com/p4lang/p4c-behavioral) when building a
p4factory target. It is intended to be used as a submodule to p4factory.

## Adding Openflow to a Behavioral Model target
#### The P4 Source
There is an `openflow.p4` file in the `p4src/` directory of this repo. A copy
of this file lives in the
[switch](https://github.com/p4lang/p4factory/tree/master/targets/switch)
target of p4factory, where Openflow integration is already done. But you will
probably have to edit it slightly for other targets. In particular, packet-in
and packet-out must be enabled by uncommenting the `OPENFLOW_PACKET_IN_OUT`
macro, which protects fabric header definitions and related parsers/actions.
This has been done for the
[l2_switch](https://github.com/p4lang/p4factory/tree/master/targets/l2_switch) 
target as an example.

`openflow.p4` defines two "public" actions, `openflow_apply` and `openflow_miss`. 
These must be included in an Openflow table's action set. The
`process_ofpat_ingress` control block must be called from within the target's
ingress control flow, and the `process_ofpat_egress` control block must be called
from within the target's egress control flow. Finally, the `packet_out` table 
should be applied appropriately in the ingress control flow with a definition of 
the `nop` action to take on a miss, but this is subject to programmer discretion.

Note that to enable features such as VLAN and MPLS, the header declarations must 
be added if not present, and modifications to the source program's parser must 
to be made to unpack these headers.

#### The Mapping File
When adding Openflow to a target, you must write a mapping file that tells the 
behavioral model which P4 tables to expose as Openflow tables. This keeps the 
P4 Openflow Agent P4-independent. The mapping file enumerates the tables to 
expose as Openflow tables and each tables' match fields, along with their 
corresponding Openflow types per the Openflow 1.3 specification.

#### Final steps
Edit the target Makefile to build and link this library, then add a call to
`p4ofagent_init` (defined in `p4ofagent.c`) to the `main.c` that is starting 
the behavioral model. This will start the P4 Openflow Agent as a thread in 
the behavioral model. Then you're done! Whew!

#### Example Ryu Controller App Integration

To play with a live example, see the
[mininet script](https://github.com/p4lang/p4factory/blob/master/mininet/openflow_l2.py)
written for use with the Ryu opensource openflow controller. To run it, build the switch
target with the Openflow Agent, then start a Ryu instance running the
[simple_switch_13](https://github.com/osrg/ryu/blob/master/ryu/app/simple_switch_13.py)
app in another window.