fix(server): error if Response code is 1xx

Returning a Response from a Service with a 1xx StatusCode is not
currently supported in hyper. It has always resulted in broken
semantics. This patch simply errors better.

- A Response with 1xx status is converted into a 500 response with no body.
- An error is returned from the `server::Connection` to alert about the
  bad response.

src/proto/conn.rs

@@ -40,6 +40,7 @@ where I: AsyncRead + AsyncWrite,
         Conn {
             io: Buffered::new(io),
             state: State {
+                error: None,
                 keep_alive: keep_alive,
                 method: None,
                 read_task: None,
@@ -437,11 +438,18 @@ where I: AsyncRead + AsyncWrite,
                 buf.extend_from_slice(pending.buf());
             }
         }
-        let encoder = T::encode(head, body, &mut self.state.method, buf);
-        self.state.writing = if !encoder.is_eof() {
-            Writing::Body(encoder, None)
-        } else {
-            Writing::KeepAlive
+        self.state.writing = match T::encode(head, body, &mut self.state.method, buf) {
+            Ok(encoder) => {
+                if !encoder.is_eof() {
+                    Writing::Body(encoder, None)
+                } else {
+                    Writing::KeepAlive
+                }
+            },
+            Err(err) => {
+                self.state.error = Some(err);
+                Writing::Closed
+            }
         };
     }
 
@@ -626,6 +634,14 @@ where I: AsyncRead + AsyncWrite,
             self.state.disable_keep_alive();
         }
     }
+
+    pub fn take_error(&mut self) -> ::Result<()> {
+        if let Some(err) = self.state.error.take() {
+            Err(err)
+        } else {
+            Ok(())
+        }
+    }
 }
 
 // ==== tokio_proto impl ====
@@ -736,6 +752,7 @@ impl<I, B: AsRef<[u8]>, T, K: KeepAlive> fmt::Debug for Conn<I, B, T, K> {
 }
 
 struct State<B, K> {
+    error: Option<::Error>,
     keep_alive: K,
     method: Option<Method>,
     read_task: Option<Task>,
@@ -767,6 +784,7 @@ impl<B: AsRef<[u8]>, K: KeepAlive> fmt::Debug for State<B, K> {
             .field("reading", &self.reading)
             .field("writing", &self.writing)
             .field("keep_alive", &self.keep_alive.status())
+            .field("error", &self.error)
             //.field("method", &self.method)
             .field("read_task", &self.read_task)
             .finish()

src/proto/dispatch.rs

@@ -73,6 +73,7 @@ where
 
         if self.is_done() {
             try_ready!(self.conn.shutdown());
+            self.conn.take_error()?;
             trace!("Dispatch::poll done");
             Ok(Async::Ready(()))
         } else {

src/proto/h1/parse.rs

@@ -111,10 +111,23 @@ impl Http1Transaction for ServerTransaction {
     }
 
 
-    fn encode(mut head: MessageHead<Self::Outgoing>, has_body: bool, method: &mut Option<Method>, dst: &mut Vec<u8>) -> Encoder {
+    fn encode(mut head: MessageHead<Self::Outgoing>, has_body: bool, method: &mut Option<Method>, dst: &mut Vec<u8>) -> ::Result<Encoder> {
         trace!("ServerTransaction::encode has_body={}, method={:?}", has_body, method);
 
-        let body = ServerTransaction::set_length(&mut head, has_body, method.as_ref());
+        // hyper currently doesn't support returning 1xx status codes as a Response
+        // This is because Service only allows returning a single Response, and
+        // so if you try to reply with a e.g. 100 Continue, you have no way of
+        // replying with the latter status code response.
+        let ret = if head.subject.is_informational() {
+            error!("response with 1xx status code not supported");
+            head = MessageHead::default();
+            head.subject = ::StatusCode::InternalServerError;
+            head.headers.set(ContentLength(0));
+            Err(::Error::Status)
+        } else {
+            Ok(ServerTransaction::set_length(&mut head, has_body, method.as_ref()))
+        };
+
 
         let init_cap = 30 + head.headers.len() * AVERAGE_HEADER_SIZE;
         dst.reserve(init_cap);
@@ -133,7 +146,8 @@ impl Http1Transaction for ServerTransaction {
             extend(dst, b"\r\n");
         }
         extend(dst, b"\r\n");
-        body
+
+        ret
     }
 
     fn should_error_on_parse_eof() -> bool {
@@ -289,7 +303,7 @@ impl Http1Transaction for ClientTransaction {
         }
     }
 
-    fn encode(mut head: MessageHead<Self::Outgoing>, has_body: bool, method: &mut Option<Method>, dst: &mut Vec<u8>) -> Encoder {
+    fn encode(mut head: MessageHead<Self::Outgoing>, has_body: bool, method: &mut Option<Method>, dst: &mut Vec<u8>) -> ::Result<Encoder> {
         trace!("ClientTransaction::encode has_body={}, method={:?}", has_body, method);
 
         *method = Some(head.subject.0.clone());
@@ -300,7 +314,7 @@ impl Http1Transaction for ClientTransaction {
         dst.reserve(init_cap);
         let _ = write!(FastWrite(dst), "{} {}\r\n{}\r\n", head.subject, head.version, head.headers);
 
-        body
+        Ok(body)
     }
 
     fn should_error_on_parse_eof() -> bool {
@@ -645,7 +659,7 @@ mod tests {
 
         b.iter(|| {
             let mut vec = Vec::new();
-            ServerTransaction::encode(head.clone(), true, &mut None, &mut vec);
+            ServerTransaction::encode(head.clone(), true, &mut None, &mut vec).unwrap();
             assert_eq!(vec.len(), len);
             ::test::black_box(vec);
         })

src/proto/mod.rs

@@ -148,7 +148,7 @@ pub trait Http1Transaction {
     type Outgoing: Default;
     fn parse(bytes: &mut BytesMut) -> ParseResult<Self::Incoming>;
     fn decoder(head: &MessageHead<Self::Incoming>, method: &mut Option<::Method>) -> ::Result<Option<h1::Decoder>>;
-    fn encode(head: MessageHead<Self::Outgoing>, has_body: bool, method: &mut Option<Method>, dst: &mut Vec<u8>) -> h1::Encoder;
+    fn encode(head: MessageHead<Self::Outgoing>, has_body: bool, method: &mut Option<Method>, dst: &mut Vec<u8>) -> ::Result<h1::Encoder>;
 
     fn should_error_on_parse_eof() -> bool;
     fn should_read_first() -> bool;