feat(client): implement the HTTP/2 extended CONNECT protocol from RFC 8441 (#2682)

src/client/conn.rs

@@ -487,6 +487,23 @@ where
             Poll::Ready(Ok(conn.take().unwrap().into_parts()))
         })
     }
+
+    /// Returns whether the [extended CONNECT protocol][1] is enabled or not.
+    ///
+    /// This setting is configured by the server peer by sending the
+    /// [`SETTINGS_ENABLE_CONNECT_PROTOCOL` parameter][2] in a `SETTINGS` frame.
+    /// This method returns the currently acknowledged value recieved from the
+    /// remote.
+    ///
+    /// [1]: https://datatracker.ietf.org/doc/html/rfc8441#section-4
+    /// [2]: https://datatracker.ietf.org/doc/html/rfc8441#section-3
+    #[cfg(feature = "http2")]
+    pub fn http2_is_extended_connect_protocol_enabled(&self) -> bool {
+        match self.inner.as_ref().unwrap() {
+            ProtoClient::H1 { .. } => false,
+            ProtoClient::H2 { h2 } => h2.is_extended_connect_protocol_enabled(),
+        }
+    }
 }
 
 impl<T, B> Future for Connection<T, B>

src/ext.rs

@@ -1,9 +1,67 @@
-//! HTTP extensions
+//! HTTP extensions.
 
 use bytes::Bytes;
 #[cfg(feature = "http1")]
 use http::header::{HeaderName, IntoHeaderName, ValueIter};
 use http::HeaderMap;
+#[cfg(feature = "http2")]
+use std::fmt;
+
+#[cfg(feature = "http2")]
+/// Represents the `:protocol` pseudo-header used by
+/// the [Extended CONNECT Protocol].
+///
+/// [Extended CONNECT Protocol]: https://datatracker.ietf.org/doc/html/rfc8441#section-4
+#[derive(Clone, Eq, PartialEq)]
+pub struct Protocol {
+    inner: h2::ext::Protocol,
+}
+
+#[cfg(feature = "http2")]
+impl Protocol {
+    /// Converts a static string to a protocol name.
+    pub const fn from_static(value: &'static str) -> Self {
+        Self {
+            inner: h2::ext::Protocol::from_static(value),
+        }
+    }
+
+    /// Returns a str representation of the header.
+    pub fn as_str(&self) -> &str {
+        self.inner.as_str()
+    }
+
+    pub(crate) fn from_inner(inner: h2::ext::Protocol) -> Self {
+        Self { inner }
+    }
+
+    pub(crate) fn into_inner(self) -> h2::ext::Protocol {
+        self.inner
+    }
+}
+
+#[cfg(feature = "http2")]
+impl<'a> From<&'a str> for Protocol {
+    fn from(value: &'a str) -> Self {
+        Self {
+            inner: h2::ext::Protocol::from(value),
+        }
+    }
+}
+
+#[cfg(feature = "http2")]
+impl AsRef<[u8]> for Protocol {
+    fn as_ref(&self) -> &[u8] {
+        self.inner.as_ref()
+    }
+}
+
+#[cfg(feature = "http2")]
+impl fmt::Debug for Protocol {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        self.inner.fmt(f)
+    }
+}
 
 /// A map from header names to their original casing as received in an HTTP message.
 ///

src/lib.rs

@@ -76,7 +76,7 @@ mod cfg;
 mod common;
 pub mod body;
 mod error;
-mod ext;
+pub mod ext;
 #[cfg(test)]
 mod mock;
 pub mod rt;

src/proto/h2/client.rs

@@ -14,6 +14,7 @@ use tracing::{debug, trace, warn};
 use super::{ping, H2Upgraded, PipeToSendStream, SendBuf};
 use crate::body::HttpBody;
 use crate::common::{exec::Exec, task, Future, Never, Pin, Poll};
+use crate::ext::Protocol;
 use crate::headers;
 use crate::proto::h2::UpgradedSendStream;
 use crate::proto::Dispatched;
@@ -204,6 +205,15 @@ where
     req_rx: ClientRx<B>,
 }
 
+impl<B> ClientTask<B>
+where
+    B: HttpBody + 'static,
+{
+    pub(crate) fn is_extended_connect_protocol_enabled(&self) -> bool {
+        self.h2_tx.is_extended_connect_protocol_enabled()
+    }
+}
+
 impl<B> Future for ClientTask<B>
 where
     B: HttpBody + Send + 'static,
@@ -260,6 +270,10 @@ where
                         }
                     }
 
+                    if let Some(protocol) = req.extensions_mut().remove::<Protocol>() {
+                        req.extensions_mut().insert(protocol.into_inner());
+                    }
+
                     let (fut, body_tx) = match self.h2_tx.send_request(req, !is_connect && eos) {
                         Ok(ok) => ok,
                         Err(err) => {

src/proto/h2/server.rs

@@ -15,6 +15,7 @@ use super::{ping, PipeToSendStream, SendBuf};
 use crate::body::HttpBody;
 use crate::common::exec::ConnStreamExec;
 use crate::common::{date, task, Future, Pin, Poll};
+use crate::ext::Protocol;
 use crate::headers;
 use crate::proto::h2::ping::Recorder;
 use crate::proto::h2::{H2Upgraded, UpgradedSendStream};
@@ -41,6 +42,7 @@ pub(crate) struct Config {
     pub(crate) initial_conn_window_size: u32,
     pub(crate) initial_stream_window_size: u32,
     pub(crate) max_frame_size: u32,
+    pub(crate) enable_connect_protocol: bool,
     pub(crate) max_concurrent_streams: Option<u32>,
     #[cfg(feature = "runtime")]
     pub(crate) keep_alive_interval: Option<Duration>,
@@ -56,6 +58,7 @@ impl Default for Config {
             initial_conn_window_size: DEFAULT_CONN_WINDOW,
             initial_stream_window_size: DEFAULT_STREAM_WINDOW,
             max_frame_size: DEFAULT_MAX_FRAME_SIZE,
+            enable_connect_protocol: false,
             max_concurrent_streams: None,
             #[cfg(feature = "runtime")]
             keep_alive_interval: None,
@@ -117,6 +120,9 @@ where
         if let Some(max) = config.max_concurrent_streams {
             builder.max_concurrent_streams(max);
         }
+        if config.enable_connect_protocol {
+            builder.enable_connect_protocol();
+        }
         let handshake = builder.handshake(io);
 
         let bdp = if config.adaptive_window {
@@ -280,7 +286,7 @@ where
 
                         let is_connect = req.method() == Method::CONNECT;
                         let (mut parts, stream) = req.into_parts();
-                        let (req, connect_parts) = if !is_connect {
+                        let (mut req, connect_parts) = if !is_connect {
                             (
                                 Request::from_parts(
                                     parts,
@@ -307,6 +313,10 @@ where
                             )
                         };
 
+                        if let Some(protocol) = req.extensions_mut().remove::<h2::ext::Protocol>() {
+                            req.extensions_mut().insert(Protocol::from_inner(protocol));
+                        }
+
                         let fut = H2Stream::new(service.call(req), connect_parts, respond);
                         exec.execute_h2stream(fut);
                     }

src/server/conn.rs

@@ -558,6 +558,15 @@ impl<E> Http<E> {
         self
     }
 
+    /// Enables the [extended CONNECT protocol].
+    ///
+    /// [extended CONNECT protocol]: https://datatracker.ietf.org/doc/html/rfc8441#section-4
+    #[cfg(feature = "http2")]
+    pub fn http2_enable_connect_protocol(&mut self) -> &mut Self {
+        self.h2_builder.enable_connect_protocol = true;
+        self
+    }
+
     /// Set the maximum buffer size for the connection.
     ///
     /// Default is ~400kb.

src/server/server.rs

@@ -453,6 +453,15 @@ impl<I, E> Builder<I, E> {
         self
     }
 
+    /// Enables the [extended CONNECT protocol].
+    ///
+    /// [extended CONNECT protocol]: https://datatracker.ietf.org/doc/html/rfc8441#section-4
+    #[cfg(feature = "http2")]
+    pub fn http2_enable_connect_protocol(mut self) -> Self {
+        self.protocol.http2_enable_connect_protocol();
+        self
+    }
+
     /// Sets the `Executor` to deal with connection tasks.
     ///
     /// Default is `tokio::spawn`.