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Requirement

  • Basic Linux/Unix knowledge
  • Basic networking knowledge

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Overview

However, XDP model was not complete enough in order to compile router.p4 and we could not generate the corresponding kernel bypass code with ELTE T4P4S based on BMv2 V1Model.p4. (A GitHub issue is still pending). In that context, Csaba freeRouter lead developer decided to develop P4Emu a software dataplane that has the particularity to:

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  • had a demonstration of how to integrate freeRouter into a local area network (Similar to article #002)
  • However instead of using bmv2 or TOFINO we used a P4Emu/pcap dataplane
  • communication between freeRouter control plane and P4Emu/pcapis ensured by pcapInt via veth pair [ veth250 - veth251 ]
  • In this example the freeRouter with P4Emu/pcap has only 1 dataplane interface that is bound to enp0s3 VM interface exposed to the local network as a bridged interface
Tip
title[ #004 #005 ] RARE/FreeRouter-101 - key take-away
  • FreeRouter is using UNIX socket in order to forward packet dedicated to control plane + dataplane communication.

This essential paradigm is used to ensure communication between freeRouter and P4Emu/pcap dataplane. It is ensured by pcapInt binary from freeRouter net-tools that will bind freeRouter socket (veth251@locathost:22710) to a virtual network interface (veth250@localhost:22709)  connected to CPU_PORT 64.

  • freeRouter is the control plane for P4Emu/pcap dataplane

freeRouter is doing all the control plane route computation and write/modify/remove message entry P4 entries are created/modified/removed accordingly from P4Emu/pcap tables. Although the name is P4Emu, it does not emulate BMv2 V1Model.p4, but rather forwarder.p4

  • In this setup the combination of freeRouter/pcap deliver a solution for SOHO network having 1GE links

However, 1GE traffic rate require 50% of one CPU thread. Nevertheless, traffic rate achieved is higher with P4Emu/pcap than freeRouter native software packet forwarding software.

Note

In subsequent article we will see how we can improve the latter requirement implied by P4Emu/pcap.


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