tonic: Introduce a new method on Endpoint to override the origin

tests/integration_tests/tests/origin.rs

@@ -0,0 +1,100 @@
+use futures::future::BoxFuture;
+use futures_util::FutureExt;
+use integration_tests::pb::test_client;
+use integration_tests::pb::{test_server, Input, Output};
+use std::task::Context;
+use std::task::Poll;
+use std::time::Duration;
+use tokio::sync::oneshot;
+use tonic::codegen::http::Request;
+use tonic::{
+    transport::{Endpoint, Server},
+    Response, Status,
+};
+use tower::Layer;
+use tower::Service;
+
+#[tokio::test]
+async fn writes_origin_header() {
+    struct Svc;
+
+    #[tonic::async_trait]
+    impl test_server::Test for Svc {
+        async fn unary_call(
+            &self,
+            _req: tonic::Request<Input>,
+        ) -> Result<Response<Output>, Status> {
+            Ok(Response::new(Output {}))
+        }
+    }
+
+    let svc = test_server::TestServer::new(Svc);
+
+    let (tx, rx) = oneshot::channel::<()>();
+
+    let jh = tokio::spawn(async move {
+        Server::builder()
+            .layer(OriginLayer {})
+            .add_service(svc)
+            .serve_with_shutdown("127.0.0.1:1442".parse().unwrap(), rx.map(drop))
+            .await
+            .unwrap();
+    });
+
+    tokio::time::sleep(Duration::from_millis(100)).await;
+
+    let channel = Endpoint::from_static("http://127.0.0.1:1442")
+        .origin("https://docs.rs".parse().expect("valid uri"))
+        .connect()
+        .await
+        .unwrap();
+
+    let mut client = test_client::TestClient::new(channel);
+
+    match client.unary_call(Input {}).await {
+        Ok(_) => {}
+        Err(status) => panic!("{}", status.message()),
+    }
+
+    tx.send(()).unwrap();
+
+    jh.await.unwrap();
+}
+
+#[derive(Clone)]
+struct OriginLayer {}
+
+impl<S> Layer<S> for OriginLayer {
+    type Service = OriginService<S>;
+
+    fn layer(&self, inner: S) -> Self::Service {
+        OriginService { inner }
+    }
+}
+
+#[derive(Clone)]
+struct OriginService<S> {
+    inner: S,
+}
+
+impl<T> Service<Request<tonic::transport::Body>> for OriginService<T>
+where
+    T: Service<Request<tonic::transport::Body>>,
+    T::Future: Send + 'static,
+    T::Error: Into<Box<dyn std::error::Error + Send + Sync>>,
+{
+    type Response = T::Response;
+    type Error = Box<dyn std::error::Error + Send + Sync>;
+    type Future = BoxFuture<'static, Result<Self::Response, Self::Error>>;
+
+    fn poll_ready(&mut self, cx: &mut Context<'_>) -> Poll<Result<(), Self::Error>> {
+        self.inner.poll_ready(cx).map_err(Into::into)
+    }
+
+    fn call(&mut self, req: Request<tonic::transport::Body>) -> Self::Future {
+        assert_eq!(req.uri().host(), Some("docs.rs"));
+        let fut = self.inner.call(req);
+
+        Box::pin(async move { fut.await.map_err(Into::into) })
+    }
+}

tonic/src/transport/channel/endpoint.rs

@@ -24,6 +24,7 @@ use tower::make::MakeConnection;
 #[derive(Clone)]
 pub struct Endpoint {
     pub(crate) uri: Uri,
+    pub(crate) origin: Option<Uri>,
     pub(crate) user_agent: Option<HeaderValue>,
     pub(crate) timeout: Option<Duration>,
     pub(crate) concurrency_limit: Option<usize>,
@@ -106,6 +107,25 @@ impl Endpoint {
             .map_err(|_| Error::new_invalid_user_agent())
     }
 
+    /// Set a custom origin.
+    ///
+    /// Override the `origin`, mainly useful when you are reaching a Server/LoadBalancer
+    /// which serves multiple services at the same time.
+    /// It will play the role of SNI (Server Name Indication).
+    ///
+    /// ```
+    /// # use tonic::transport::Endpoint;
+    /// # let mut builder = Endpoint::from_static("https://proxy.com");
+    /// builder.origin("https://example.com".parse().expect("http://example.com must be a valid URI"));
+    /// // origin: "https://example.com"
+    /// ```
+    pub fn origin(self, origin: Uri) -> Self {
+        Endpoint {
+            origin: Some(origin),
+            ..self
+        }
+    }
+
     /// Apply a timeout to each request.
     ///
     /// ```
@@ -395,6 +415,7 @@ impl From<Uri> for Endpoint {
     fn from(uri: Uri) -> Self {
         Self {
             uri,
+            origin: None,
             user_agent: None,
             concurrency_limit: None,
             rate_limit: None,

tonic/src/transport/service/add_origin.rs

@@ -1,17 +1,28 @@
 use futures_core::future::BoxFuture;
+use http::uri::Authority;
+use http::uri::Scheme;
 use http::{Request, Uri};
 use std::task::{Context, Poll};
 use tower_service::Service;
 
 #[derive(Debug)]
 pub(crate) struct AddOrigin<T> {
     inner: T,
-    origin: Uri,
+    scheme: Option<Scheme>,
+    authority: Option<Authority>,
 }
 
 impl<T> AddOrigin<T> {
     pub(crate) fn new(inner: T, origin: Uri) -> Self {
-        Self { inner, origin }
+        let http::uri::Parts {
+            scheme, authority, ..
+        } = origin.into_parts();
+
+        Self {
+            inner,
+            scheme,
+            authority,
+        }
     }
 }
 
@@ -30,24 +41,24 @@ where
     }
 
     fn call(&mut self, req: Request<ReqBody>) -> Self::Future {
-        // Split the request into the head and the body.
-        let (mut head, body) = req.into_parts();
-
-        // Split the request URI into parts.
-        let mut uri: http::uri::Parts = head.uri.into();
-        let set_uri = self.origin.clone().into_parts();
-
-        if set_uri.scheme.is_none() || set_uri.authority.is_none() {
+        if self.scheme.is_none() || self.authority.is_none() {
             let err = crate::transport::Error::new_invalid_uri();
             return Box::pin(async move { Err::<Self::Response, _>(err.into()) });
         }
 
-        // Update the URI parts, setting hte scheme and authority
-        uri.scheme = Some(set_uri.scheme.expect("expected scheme"));
-        uri.authority = Some(set_uri.authority.expect("expected authority"));
+        // Split the request into the head and the body.
+        let (mut head, body) = req.into_parts();
 
         // Update the the request URI
-        head.uri = http::Uri::from_parts(uri).expect("valid uri");
+        head.uri = {
+            // Split the request URI into parts.
+            let mut uri: http::uri::Parts = head.uri.into();
+            // Update the URI parts, setting hte scheme and authority
+            uri.scheme = self.scheme.clone();
+            uri.authority = self.authority.clone();
+
+            http::Uri::from_parts(uri).expect("valid uri")
+        };
 
         let request = Request::from_parts(head, body);
 

tonic/src/transport/service/connection.rs

@@ -55,7 +55,11 @@ impl Connection {
         }
 
         let stack = ServiceBuilder::new()
-            .layer_fn(|s| AddOrigin::new(s, endpoint.uri.clone()))
+            .layer_fn(|s| {
+                let origin = endpoint.origin.as_ref().unwrap_or(&endpoint.uri).clone();
+
+                AddOrigin::new(s, origin)
+            })
             .layer_fn(|s| UserAgent::new(s, endpoint.user_agent.clone()))
             .layer_fn(|s| GrpcTimeout::new(s, endpoint.timeout))
             .option_layer(endpoint.concurrency_limit.map(ConcurrencyLimitLayer::new))