Add support for WebSocket protocol negotiation. (#83)

CHANGELOG.md

@@ -8,6 +8,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 # Unreleased
 
 - Fix stripping prefix when nesting services at `/` ([#91](https://github.com/tokio-rs/axum/pull/91))
+- Add support for WebSocket protocol negotiation. ([#83](https://github.com/tokio-rs/axum/pull/83))
 
 ## Breaking changes
 

src/ws/mod.rs

@@ -73,6 +73,7 @@ use http_body::Full;
 use hyper::upgrade::{OnUpgrade, Upgraded};
 use sha1::{Digest, Sha1};
 use std::pin::Pin;
+use std::sync::Arc;
 use std::{
     borrow::Cow, convert::Infallible, fmt, future::Future, marker::PhantomData, task::Context,
     task::Poll,
@@ -96,6 +97,7 @@ where
     WebSocketUpgrade {
         callback,
         config: WebSocketConfig::default(),
+        protocols: Vec::new().into(),
         _request_body: PhantomData,
     }
 }
@@ -169,6 +171,7 @@ impl_ws_handler!(T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T1
 pub struct WebSocketUpgrade<F, B, T> {
     callback: F,
     config: WebSocketConfig,
+    protocols: Arc<[Cow<'static, str>]>,
     _request_body: PhantomData<fn() -> (B, T)>,
 }
 
@@ -180,6 +183,7 @@ where
         Self {
             callback: self.callback.clone(),
             config: self.config,
+            protocols: self.protocols.clone(),
             _request_body: PhantomData,
         }
     }
@@ -212,6 +216,47 @@ impl<F, B, T> WebSocketUpgrade<F, B, T> {
         self.config.max_frame_size = Some(max);
         self
     }
+
+    /// Set the known protocols.
+    ///
+    /// If the protocol name specified by `Sec-WebSocket-Protocol` header
+    /// to match any of them, the upgrade response will include `Sec-WebSocket-Protocol` header and return the protocol name.
+    ///
+    /// # Examples
+    ///
+    /// ```no_run
+    /// # use axum::prelude::*;
+    /// # use axum::ws::{ws, WebSocket};
+    /// # use std::net::SocketAddr;
+    /// #
+    /// # async fn handle_socket(socket: WebSocket) {
+    /// #     todo!()
+    /// # }
+    /// #
+    /// # #[tokio::main]
+    /// # async fn main() {
+    /// let app = route("/ws", ws(handle_socket).protocols(["graphql-ws", "graphql-transport-ws"]));
+    /// #
+    /// #   let addr = SocketAddr::from(([127, 0, 0, 1], 3000));
+    /// #   hyper::Server::bind(&addr)
+    /// #       .serve(app.into_make_service())
+    /// #       .await
+    /// #       .unwrap();
+    /// # }
+    ///
+    /// ```
+    pub fn protocols<I>(mut self, protocols: I) -> Self
+    where
+        I: IntoIterator,
+        I::Item: Into<Cow<'static, str>>,
+    {
+        self.protocols = protocols
+            .into_iter()
+            .map(Into::into)
+            .collect::<Vec<_>>()
+            .into();
+        self
+    }
 }
 
 impl<ReqBody, F, T> Service<Request<ReqBody>> for WebSocketUpgrade<F, ReqBody, T>
@@ -230,6 +275,7 @@ where
 
     fn call(&mut self, mut req: Request<ReqBody>) -> Self::Future {
         let this = self.clone();
+        let protocols = self.protocols.clone();
 
         ResponseFuture(Box::pin(async move {
             if req.method() != http::Method::GET {
@@ -257,6 +303,31 @@ where
                 );
             }
 
+            // check requested protocols
+            let protocol =
+                req.headers()
+                    .get(&header::SEC_WEBSOCKET_PROTOCOL)
+                    .and_then(|req_protocols| {
+                        let req_protocols = req_protocols.to_str().ok()?;
+                        req_protocols
+                            .split(',')
+                            .map(|req_p| req_p.trim())
+                            .find(|req_p| protocols.iter().any(|p| p == req_p))
+                    });
+            let protocol = match protocol {
+                Some(protocol) => {
+                    if let Ok(protocol) = HeaderValue::from_str(protocol) {
+                        Some(protocol)
+                    } else {
+                        return response(
+                            StatusCode::BAD_REQUEST,
+                            "`Sec-Websocket-Protocol` header is invalid",
+                        );
+                    }
+                }
+                None => None,
+            };
+
             let key = if let Some(key) = req.headers_mut().remove(header::SEC_WEBSOCKET_KEY) {
                 key
             } else {
@@ -292,7 +363,7 @@ where
                 callback.call(socket, input).await;
             });
 
-            let res = Response::builder()
+            let mut builder = Response::builder()
                 .status(StatusCode::SWITCHING_PROTOCOLS)
                 .header(
                     http::header::CONNECTION,
@@ -302,9 +373,11 @@ where
                     http::header::UPGRADE,
                     HeaderValue::from_str("websocket").unwrap(),
                 )
-                .header(http::header::SEC_WEBSOCKET_ACCEPT, sign(key.as_bytes()))
-                .body(box_body(Full::new(Bytes::new())))
-                .unwrap();
+                .header(http::header::SEC_WEBSOCKET_ACCEPT, sign(key.as_bytes()));
+            if let Some(protocol) = protocol {
+                builder = builder.header(http::header::SEC_WEBSOCKET_PROTOCOL, protocol);
+            }
+            let res = builder.body(box_body(Full::new(Bytes::new()))).unwrap();
 
             Ok(res)
         }))