feat(client): add Config::set_host option

If set to false, the `Client` will no longer automatically set the
`Host` header if absent.

src/client/mod.rs

@@ -46,6 +46,7 @@ pub struct Client<C, B = proto::Body> {
     h1_writev: bool,
     pool: Pool<HyperClient<B>>,
     retry_canceled_requests: bool,
+    set_host: bool,
 }
 
 impl Client<HttpConnector, proto::Body> {
@@ -101,6 +102,7 @@ impl<C, B> Client<C, B> {
             h1_writev: config.h1_writev,
             pool: Pool::new(config.keep_alive, config.keep_alive_timeout),
             retry_canceled_requests: config.retry_canceled_requests,
+            set_host: config.set_host,
         }
     }
 }
@@ -147,7 +149,7 @@ where C: Connect,
                 ))));
             }
         };
-        if !req.headers().has::<Host>() {
+        if self.set_host && !req.headers().has::<Host>() {
             let host = Host::new(
                 domain.host().expect("authority implies host").to_owned(),
                 domain.port(),
@@ -289,6 +291,7 @@ impl<C, B> Clone for Client<C, B> {
             h1_writev: self.h1_writev,
             pool: self.pool.clone(),
             retry_canceled_requests: self.retry_canceled_requests,
+            set_host: self.set_host,
         }
     }
 }
@@ -413,6 +416,7 @@ pub struct Config<C, B> {
     //TODO: make use of max_idle config
     max_idle: usize,
     retry_canceled_requests: bool,
+    set_host: bool,
 }
 
 /// Phantom type used to signal that `Config` should create a `HttpConnector`.
@@ -429,6 +433,7 @@ impl Default for Config<UseDefaultConnector, proto::Body> {
             h1_writev: true,
             max_idle: 5,
             retry_canceled_requests: true,
+            set_host: true,
         }
     }
 }
@@ -453,6 +458,7 @@ impl<C, B> Config<C, B> {
             h1_writev: self.h1_writev,
             max_idle: self.max_idle,
             retry_canceled_requests: self.retry_canceled_requests,
+            set_host: self.set_host,
         }
     }
 
@@ -467,6 +473,7 @@ impl<C, B> Config<C, B> {
             h1_writev: self.h1_writev,
             max_idle: self.max_idle,
             retry_canceled_requests: self.retry_canceled_requests,
+            set_host: self.set_host,
         }
     }
 
@@ -521,6 +528,18 @@ impl<C, B> Config<C, B> {
         self
     }
 
+    /// Set whether to automatically add the `Host` header to requests.
+    ///
+    /// If true, and a request does not include a `Host` header, one will be
+    /// added automatically, derived from the authority of the `Uri`.
+    ///
+    /// Default is `true`.
+    #[inline]
+    pub fn set_host(mut self, val: bool) -> Config<C, B> {
+        self.set_host = val;
+        self
+    }
+
     #[doc(hidden)]
     #[deprecated(since="0.11.11", note="no_proto is always enabled")]
     pub fn no_proto(self) -> Config<C, B> {
@@ -573,6 +592,7 @@ impl<C, B> fmt::Debug for Config<C, B> {
             .field("keep_alive_timeout", &self.keep_alive_timeout)
             .field("http1_writev", &self.h1_writev)
             .field("max_idle", &self.max_idle)
+            .field("set_host", &self.set_host)
             .finish()
     }
 }

tests/client.rs

@@ -45,6 +45,45 @@ macro_rules! test {
                 headers: [ $($response_headers:expr,)* ],
                 body: $response_body:expr,
     ) => (
+        test! {
+            name: $name,
+            server:
+                expected: $server_expected,
+                reply: $server_reply,
+            client:
+                set_host: true,
+                request:
+                    method: $client_method,
+                    url: $client_url,
+                    headers: [ $($request_headers,)* ],
+                    body: $request_body,
+                    proxy: $request_proxy,
+
+                response:
+                    status: $client_status,
+                    headers: [ $($response_headers,)* ],
+                    body: $response_body,
+        }
+    );
+    (
+        name: $name:ident,
+        server:
+            expected: $server_expected:expr,
+            reply: $server_reply:expr,
+        client:
+            set_host: $set_host:expr,
+            request:
+                method: $client_method:ident,
+                url: $client_url:expr,
+                headers: [ $($request_headers:expr,)* ],
+                body: $request_body:expr,
+                proxy: $request_proxy:expr,
+
+            response:
+                status: $client_status:ident,
+                headers: [ $($response_headers:expr,)* ],
+                body: $response_body:expr,
+    ) => (
         #[test]
         fn $name() {
             #![allow(unused)]
@@ -60,6 +99,7 @@ macro_rules! test {
                     expected: $server_expected,
                     reply: $server_reply,
                 client:
+                    set_host: $set_host,
                     request:
                         method: $client_method,
                         url: $client_url,
@@ -111,6 +151,7 @@ macro_rules! test {
                     expected: $server_expected,
                     reply: $server_reply,
                 client:
+                    set_host: true,
                     request:
                         method: $client_method,
                         url: $client_url,
@@ -132,6 +173,7 @@ macro_rules! test {
             expected: $server_expected:expr,
             reply: $server_reply:expr,
         client:
+            set_host: $set_host:expr,
             request:
                 method: $client_method:ident,
                 url: $client_url:expr,
@@ -142,7 +184,12 @@ macro_rules! test {
         let server = TcpListener::bind("127.0.0.1:0").unwrap();
         let addr = server.local_addr().unwrap();
         let mut core = $core;
-        let client = client(&core.handle());
+
+        let mut config = Client::configure();
+        if !$set_host {
+            config = config.set_host(false);
+        }
+        let client = config.build(&core.handle());
         let mut req = Request::new(Method::$client_method, format!($client_url, addr=addr).parse().unwrap());
         $(
             req.headers_mut().set($request_headers);
@@ -545,6 +592,35 @@ test! {
 
 }
 
+test! {
+    name: client_set_host_false,
+
+    server:
+        // {addr} is here because format! requires it to exist in the string
+        expected: "\
+            GET /no-host/{addr} HTTP/1.1\r\n\
+            \r\n\
+            ",
+        reply: "\
+            HTTP/1.1 200 OK\r\n\
+            Content-Length: 0\r\n\
+            \r\n\
+            ",
+
+    client:
+        set_host: false,
+        request:
+            method: Get,
+            url: "http://{addr}/no-host/{addr}",
+            headers: [],
+            body: None,
+            proxy: false,
+        response:
+            status: Ok,
+            headers: [],
+            body: None,
+}
+
 #[test]
 fn client_keep_alive() {
     let server = TcpListener::bind("127.0.0.1:0").unwrap();