copy_to_cpu

Copy To Cpu

+--+      +--+     ++-+
|h1+------+s1+-----+h2+
+--+      +-++     +--+

Introduction

In this example we show how to send a copy of a packet to any port. However, in this very specific case we send it to a special port called cpu_port. The cpu_port is the port that connects the switch with an external controller. The extern clone egress to egress is used to send a copy of the egress packet to the buffer mechanism located between the ingress and egress pipeline.

In this simple program packets with IPv4 TOS field equal to 1 are sent to the cpu port (s1-cpu-eth1). You can use send.py to send packets with the tos field modified. And receive.py to receive the cpu packets. In addition to sending packets to the controller, this example shows how to add custom headers to a packet.

Note: that to add an extra port to each switch we added the attribute cpu_port to the p4app.json file.

How to run

Run the topology:

sudo p4run

Run the very small controller code that receives packets from the switch:

sudo python receive.py

Generate packets using the send.py script which sets the TOS field to 1.

mx h1
sudo python send.py 10.0.1.2