curl/lib/capsule.h
Aritra Basu e78b1b3ecc
HTTP/3: add proxy CONNECT and MASQUE CONNECT-UDP support (ngtcp2 QUIC)
This patch adds two major proxy capabilities to curl (ngtcp2 QUIC):
- HTTP/3 Proxy CONNECT: Tunnel HTTP/1.1 or HTTP/2 traffic through an
  HTTPS proxy that speaks HTTP/3 (QUIC) using the standard CONNECT
  method over an HTTP/3 connection.
- MASQUE CONNECT-UDP: Tunnel HTTP/3 (QUIC) traffic through an HTTP
  proxy (speaking HTTP/1.1, HTTP/2, or HTTP/3) using the extended
  CONNECT method with the CONNECT-UDP protocol (RFC9297 & RFC9298).

Public API additions:
- `CURLPROXY_HTTPS3`: new proxy type constant for HTTP/3 proxy
- `--proxy-http3`: new CLI flag to negotiate HTTP/3 with HTTPS proxy

The implementation adds two new filters:
- `H3-PROXY` - enables negotiating HTTP/3 (QUIC) to the proxy and
  running CONNECT/CONNECT-UDP through that proxy transport.
- `CAPSULE` - dedicated filter inserted between QUIC transport and
  HTTP-PROXY to handle datagram capsule encapsulation/decapsulation.

Here is how the curl filter chaining looks in different scenarios:
- HTTP/3 Proxy CONNECT (tunneling TCP protocols over QUIC proxy):
  conn -> HTTP/1.1 or HTTP/2  -> SSL -> HTTP-PROXY ->
                                 H3-PROXY -> HAPPY-EYEBALLS -> UDP
- MASQUE CONNECT-UDP (tunneling QUIC over any proxy):
  conn -> HTTP/3 -> CAPSULE -> HTTP-PROXY -> H3-PROXY ->
                               HAPPY-EYEBALLS -> UDP
  conn -> HTTP/3 -> CAPSULE -> HTTP-PROXY -> H1-PROXY or H2-PROXY ->
                               SSL -> HAPPY-EYEBALLS -> TCP

- Both features currently require the ngtcp2 QUIC backend.
- Both features are experimental (disabled by default). Enable with
  `--enable-proxy-http3`(autotools) or `-DUSE_PROXY_HTTP3=ON`(CMake).

Tests:
- tests/unit/unit3400.c: Unit tests for capsule protocol encode/decode
- tests/http/test_60_h3_proxy.py: Comprehensive pytest integration suite
- tests/http/testenv/h2o.py: Managing h2o instances with HTTP/1.1, HTTP/2,
  and HTTP/3 (QUIC) listeners, proxy.connect and proxy.connect-udp enabled.

References:
  RFC 9297 - HTTP Datagrams and the Capsule Protocol
  RFC 9298 - Proxying UDP in HTTP
  RFC 9000 §16 — Variable-Length Integer Encoding

Signed-off-by: Aritra Basu <aritrbas+gh@cisco.com>

Closes #21153
2026-05-27 08:49:53 +02:00

77 lines
2.9 KiB
C

#ifndef HEADER_CURL_CAPSULE_H
#define HEADER_CURL_CAPSULE_H
/***************************************************************************
* _ _ ____ _
* Project ___| | | | _ \| |
* / __| | | | |_) | |
* | (__| |_| | _ <| |___
* \___|\___/|_| \_\_____|
*
* Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
*
* This software is licensed as described in the file COPYING, which
* you should have received as part of this distribution. The terms
* are also available at https://curl.se/docs/copyright.html.
*
* You may opt to use, copy, modify, merge, publish, distribute and/or sell
* copies of the Software, and permit persons to whom the Software is
* furnished to do so, under the terms of the COPYING file.
*
* This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
* KIND, either express or implied.
*
* SPDX-License-Identifier: curl
*
***************************************************************************/
#include "curl_setup.h"
#if !defined(CURL_DISABLE_PROXY) && !defined(CURL_DISABLE_HTTP)
#include "curlx/dynbuf.h"
#include "bufq.h"
/* HTTP Capsule constants */
#define HTTP_CAPSULE_HEADER_MAX_SIZE 10
/* HTTP Capsule function prototypes */
/**
* Write the capsule header (type + varint length + context ID) into `hdr`.
* @param hdr Output buffer (must be >= HTTP_CAPSULE_HEADER_MAX_SIZE)
* @param hdrlen Size of `hdr` in bytes
* @param payload_len Length of the UDP payload that follows
* @return Number of header bytes written, or 0 on error
*/
size_t Curl_capsule_encap_udp_hdr(uint8_t *hdr, size_t hdrlen,
size_t payload_len);
/**
* Encapsulate UDP payload into HTTP Datagram capsule format
* @param dyn Dynamic buffer to write capsule to
* @param buf Payload buffer
* @param blen Payload buffer length
* @return CURLE_OK on success, error code on failure
*/
CURLcode Curl_capsule_encap_udp_datagram(struct dynbuf *dyn,
const void *buf, size_t blen);
/**
* Process one UDP capsule from buffer into raw datagram payload bytes.
* @param cf Connection filter
* @param data Easy handle
* @param recvbufq Buffer queue containing capsule data
* @param buf Output buffer for one datagram payload
* @param len Size of output buffer in bytes
* @param err Error code output
* @return Number of payload bytes written. Check `err` for status.
*/
size_t Curl_capsule_process_udp_raw(struct Curl_cfilter *cf,
struct Curl_easy *data,
struct bufq *recvbufq,
unsigned char *buf, size_t len,
CURLcode *err);
#endif /* !CURL_DISABLE_PROXY && !CURL_DISABLE_HTTP */
#endif /* HEADER_CURL_CAPSULE_H */