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VPP's host stack is a user space implementation of a number of transport, session and application layer protocols that leverages VPP's existing protocol stack. It roughly consists of four major components:

  • Session Layer that accepts pluggable transport protocols
  • Shared memory mechanisms for pushing data between VPP and applications
  • Transport protocol implementations (e.g. TCP, SCTP, UDP)
  • Comms Library (VCL) and LD_PRELOAD Library
VPP HostStack Arch


Set Up Dev Environment - Explains how to set up a VPP development environment and the requirements for using the build tools

Session Layer Architecture - Goes over the main features of the session layer

TLS Application - Describes the TLS Application Layer protocol implementation

Getting Started

Applications can link against the following APIs for host-stack service:

  • Builtin C API. It can only be used by applications hosted within VPP
  • "Raw" session layer API. It does not offer any support for async communication
  • VCL API that offers a POSIX-like interface. It comes with its own epoll implementation.

A number of test applications can be used to exercise these APIs. For all the examples below, it is assumed that two VPP instances have been brought up and properly configured to ensure networking connectivity between them. To test that network connectivity is available, the builtin ping tool can be used. As a convention, we consider the first vpp instance (vpp1) to be the one the server is attached to and the second instance (vpp2) to be the one where the client application is attached. For illustrative purposes all examples use TCP as a transport protocol but other available protocols could be used.

Builtin Echo Server/Client

On vpp1, from the cli do:

# test echo server uri tcp://vpp1_ip/port

and on vpp2:

# test echo client uri tcp://vpp1_ip/port

For more details on how to further configure the client/server apps to do throughput and CPS testing see here

External Echo Server/Client

To build the external test echo apps first edit vnet.am to make test apps installable

# sed -i 's/noinst_PROGRAMS += tcp_echo udp_echo/bin_PROGRAMS += tcp_echo udp_echo/' src/vnet.am

then build vpp and the apps. Start vpp1 and attach the server application:

$ ./build-root/install-vpp_debug-native/vpp/bin/tcp_echo uri tcp://vpp1_ip/port

Then start vpp2 and attach the client:

$ ./build-root/install-vpp_debug-native/vpp/bin/tcp_echo slave uri tcp://vpp1_ip/port

VCL socket client/server

For more details see the tutorial here

Tutorials/Test Apps

Test HTTP Server App

Test Echo Client/Server Apps

Test Proxy App

Running List of Presentations