Proxying UDP in HTTP

CONNECT-UDP (RFC 9298) enables the proxying of UDP packets over HTTP/3. It is implemented in masque-go.

Protocol Overview

A client establishes an HTTP/3 connection to a proxy. It requests the proxying of UDP packets to a remote server by sending an Extended CONNECT (RFC 9220) HTTP request. If the proxy accepts the proxying request, it opens a UDP socket to the target and forwards UDP packets between the client and the target. Between the client and the proxy, UDP datagrams are sent on the QUIC connection using HTTP Datagrams (RFC 9279).

sequenceDiagram
    participant Client
    participant Proxy
    participant Server as Target Server

    Client->>Proxy: Extended CONNECT Proxying Request
    Proxy-->>Proxy: Open UDP Socket to Server

    loop UDP Proxying
    Client->>Proxy: UDP payload sent in HTTP Datagram
    Proxy->>Server: UDP Packet
    Server-->>Proxy: UDP Packet
    Proxy->>Client: UDP payload sent in HTTP Datagram
    end