Crate quiche

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🥧 Savoury implementation of the QUIC transport protocol and HTTP/3.

quiche is an implementation of the QUIC transport protocol and HTTP/3 as specified by the IETF. It provides a low level API for processing QUIC packets and handling connection state. The application is responsible for providing I/O (e.g. sockets handling) as well as an event loop with support for timers.

Connection setup

The first step in establishing a QUIC connection using quiche is creating a configuration object:

let config = quiche::Config::new(quiche::PROTOCOL_VERSION)?;

This is shared among multiple connections and can be used to configure a QUIC endpoint.

On the client-side the connect() utility function can be used to create a new connection, while accept() is for servers:

// Client connection.
let conn = quiche::connect(Some(&server_name), &scid, to, &mut config)?;

// Server connection.
let conn = quiche::accept(&scid, None, from, &mut config)?;

In both cases, the application is responsible for generating a new source connection ID that will be used to identify the new connection.

The application also need to pass the address of the remote peer of the connection: in the case of a client that would be the address of the server it is trying to connect to, and for a server that is the address of the client that initiated the connection.

Handling incoming packets

Using the connection’s recv() method the application can process incoming packets that belong to that connection from the network:

loop {
    let (read, from) = socket.recv_from(&mut buf).unwrap();

    let recv_info = quiche::RecvInfo { from };

    let read = match conn.recv(&mut buf[..read], recv_info) {
        Ok(v) => v,

        Err(quiche::Error::Done) => {
            // Done reading.
            break;
        },

        Err(e) => {
            // An error occurred, handle it.
            break;
        },
    };
}

The application has to pass a RecvInfo structure in order to provide additional information about the received packet (such as the address it was received from).

Generating outgoing packets

Outgoing packet are generated using the connection’s send() method instead:

loop {
    let (write, send_info) = match conn.send(&mut out) {
        Ok(v) => v,

        Err(quiche::Error::Done) => {
            // Done writing.
            break;
        },

        Err(e) => {
            // An error occurred, handle it.
            break;
        },
    };

    socket.send_to(&out[..write], &send_info.to).unwrap();
}

The application will be provided with a SendInfo structure providing additional information about the newly created packet (such as the address the packet should be sent to).

When packets are sent, the application is responsible for maintaining a timer to react to time-based connection events. The timer expiration can be obtained using the connection’s timeout() method.

let timeout = conn.timeout();

The application is responsible for providing a timer implementation, which can be specific to the operating system or networking framework used. When a timer expires, the connection’s on_timeout() method should be called, after which additional packets might need to be sent on the network:

// Timeout expired, handle it.
conn.on_timeout();

// Send more packets as needed after timeout.
loop {
    let (write, send_info) = match conn.send(&mut out) {
        Ok(v) => v,

        Err(quiche::Error::Done) => {
            // Done writing.
            break;
        },

        Err(e) => {
            // An error occurred, handle it.
            break;
        },
    };

    socket.send_to(&out[..write], &send_info.to).unwrap();
}

Pacing

It is recommended that applications pace sending of outgoing packets to avoid creating packet bursts that could cause short-term congestion and losses in the network.

quiche exposes pacing hints for outgoing packets through the at field of the SendInfo structure that is returned by the send() method. This field represents the time when a specific packet should be sent into the network.

Applications can use these hints by artificially delaying the sending of packets through platform-specific mechanisms (such as the SO_TXTIME socket option on Linux), or custom methods (for example by using user-space timers).

Sending and receiving stream data

After some back and forth, the connection will complete its handshake and will be ready for sending or receiving application data.

Data can be sent on a stream by using the stream_send() method:

if conn.is_established() {
    // Handshake completed, send some data on stream 0.
    conn.stream_send(0, b"hello", true)?;
}

The application can check whether there are any readable streams by using the connection’s readable() method, which returns an iterator over all the streams that have outstanding data to read.

The stream_recv() method can then be used to retrieve the application data from the readable stream:

if conn.is_established() {
    // Iterate over readable streams.
    for stream_id in conn.readable() {
        // Stream is readable, read until there's no more data.
        while let Ok((read, fin)) = conn.stream_recv(stream_id, &mut buf) {
            println!("Got {} bytes on stream {}", read, stream_id);
        }
    }
}

HTTP/3

The quiche HTTP/3 module provides a high level API for sending and receiving HTTP requests and responses on top of the QUIC transport protocol.

Congestion Control

The quiche library provides a high-level API for configuring which congestion control algorithm to use throughout the QUIC connection.

When a QUIC connection is created, the application can optionally choose which CC algorithm to use. See CongestionControlAlgorithm for currently available congestion control algorithms.

For example:

let mut config = quiche::Config::new(quiche::PROTOCOL_VERSION).unwrap();
config.set_cc_algorithm(quiche::CongestionControlAlgorithm::Reno);

Alternatively, you can configure the congestion control algorithm to use by its name.

let mut config = quiche::Config::new(quiche::PROTOCOL_VERSION).unwrap();
config.set_cc_algorithm_name("reno").unwrap();

Note that the CC algorithm should be configured before calling connect() or accept(). Otherwise the connection will use a default CC algorithm.

Feature flags

quiche defines a number of feature flags to reduce the amount of compiled code and dependencies:

  • boringssl-vendored (default): Build the vendored BoringSSL library.

  • boringssl-boring-crate: Use the BoringSSL library provided by the boring crate. It takes precedence over boringssl-vendored if both features are enabled.

  • pkg-config-meta: Generate pkg-config metadata file for libquiche.

  • ffi: Build and expose the FFI API.

  • qlog: Enable support for the qlog logging format.

Modules

HTTP/3 wire protocol and QPACK implementation.

Structs

Stores configuration shared between multiple connections.

A QUIC connection.

Represents information carried by CONNECTION_CLOSE frames.

A QUIC connection ID.

A QUIC packet’s header.

Ancillary information about incoming packets.

Ancillary information about outgoing packets.

Statistics about the connection.

An iterator over QUIC streams.

Enums

Available congestion control algorithms.

A QUIC error.

Qlog logging level.

The stream’s side to shutdown.

QUIC packet type.

Constants

The maximum length of a connection ID.

The minimum length of Initial packets sent by a client.

The current QUIC wire version.

Functions

Creates a new server-side connection.

Creates a new client-side connection.

Writes a version negotiation packet.

Writes a stateless retry packet.

Returns true if the given protocol version is supported.

Type Definitions

A specialized Result type for quiche operations.