QUIC HostStack

The quic plugin provides an IETF QUIC protocol implementation. It is based on the quicly library.

This plugin adds the QUIC protocol to VPP's Host Stack. As a result QUIC is usable both in internal VPP applications and in external apps.


  • This plugin is under current development: it should mostly work, but has not been thoroughly tested and should not be used in production.

  • Only bidirectional streams are supported currently.

Getting started

  • A common sample setup is with two vpp instances interconnected #twovppinstances

  • Ensure your vpp configuration file contains session { evt_qs_memfd_seg }

  • Then run session enable in the debug cli (vppctl)

This plugin can be tested in the following cases.

Internal client

This application is a simple command to be run on the debug cli to test connectivity & throughput on QUIC over the debug cli (vppctl). It does not reflect reality and is mostly used for internal tests.

  • Run test echo server uri quic:// on your first instance

  • Then test echo client uri quic:// on the second one

Source for the internal client lives in src/plugins/hs_apps/echo_client.c

External client

This setup reflects the use case of an app developer using vpp to create a quic client / server. The application is an external binary that connects to VPP via its binary API.

After having setup two interconnected vpps, you can attach the quic_echo binary to each of them.

  • The binary can be found in ./build-root/build-vpp[_debug]-native/vpp/bin/quic_echo

  • To run the client & server use quic_echo socket-name /vpp.sock client|server uri quic://

  • Several options are available to customize the amount of data sent, number of threads, logging and timing.

The behavior of this app when run with nclient 2/4 is two first establish 2 connections with the given peer, and once everything has been opened start opening 4 quic streams, and transmit data. Flow is as follows.


This allows timing of either the whole setup & teardown or specific phases in assessing the protocol's performance

Source for the internal client lives in src/plugins/hs_apps/sapi/quic_echo.c

VCL client

The hoststack exposes a simplified API call the VCL (blocking posix like calls), this API is used by a sample client & server implementation that supports QUIC, TCP and UDP.

  • The binaries can be found in ./build-root/build-vpp[_debug]-native/vpp/bin/

  • Create the VCL conf files echo "vcl { api-socket-name /vpp.sock }" | tee /tmp/vcl.conf]

  • For the server VCL_CONFIG=/tmp/vcl.conf ; vcl_test_server -p QUIC 1234"

  • For the client VCL_CONFIG=/tmp/vcl.conf ; vcl_test_client -p QUIC 1234"

Source for the internal client lives in src/plugins/hs_apps/vcl/vcl_test_client.c

A basic usage is the following client side

#include <vcl/vppcom.h>
int fd = vppcom_session_create (VPPCOM_PROTO_QUIC);
vppcom_session_tls_add_cert (/* args */);
vppcom_session_tls_add_key (/* args */);
vppcom_session_connect (fd, "quic://"); /* create a quic connection */
int sfd = vppcom_session_create (VPPCOM_PROTO_QUIC);
vppcom_session_stream_connect (sfd, fd); /* open a quic stream on the connection*/
vppcom_session_write (sfd, buf, n);

Server side

#include <vcl/vppcom.h>
int lfd = vppcom_session_create (VPPCOM_PROTO_QUIC);
vppcom_session_tls_add_cert (/* args */);
vppcom_session_tls_add_key (/* args */);
vppcom_session_bind (fd, "quic://");
vppcom_session_listen (fd);
int fd = vppcom_session_accept (lfd); /* accept quic connection*/
vppcom_session_is_connectable_listener (fd); /* is true */
int sfd = vppcom_session_accept (fd); /* accept quic stream */
vppcom_session_is_connectable_listener (sfd); /* is false */
vppcom_session_read (sfd, buf, n);

Internal Mechanics

QUIC constructs are exposed as follows:

  • QUIC connections and streams are both regular host stack session, exposed via the API with their 64bits handle.

  • QUIC connections can be created and destroyed with regular connect and close calls with TRANSPORT_PROTO_QUIC.

  • Streams can be opened in a connection by calling connect again and passing the handle of the connection to which the new stream should belong.

  • Streams can be closed with a regular close call.

  • Streams opened by peers can be accepted from the sessions corresponding to QUIC connections.

  • Data can ba exchanged by using the regular send and recv calls on the stream sessions.

Data structures

Quic relies on the hoststack constructs, namely applications, sessions, transport_connections, and app_listeners. When listening on a port with the quic protocol, an external application :

  • Attaches to vpp and register an application

  • It creates an app_listener and a quic_listen_session.

  • The quic_listen_session relies on a transport_connection (lctx) to access the underlying udp_listen_session that will receive packets.

  • Upon connection request, we create the same data structure (quic_session, qctx, udp_session) and pass a handle to the quic_session in the accept callback to acknowledge the creation of a quic connection. All further UDP datagrams for the peers at each end of the connection will be exchanged through the udp_session

  • Upon receiving a Stream opening request, we create the stream_session and its transport sctx and pass the handle to the stream_session back to the app. Here we don't have any UDP datastructures, as all datagrams are bound to the connection.

Those structures are linked as follows :