fix(server): Drain requests on drop.

If a client sent an illegal request (like a GET request with a message
body), or if there was a legal request with a body but the Handler
didn't read all of it, the remaining bytes would be left in the stream.
The next request to come from the same client would error, as the server
would confuse the remaining bytes, and think the request was malformed.

Fixes #197
Fixes #309

src/server/request.rs

@@ -2,7 +2,7 @@
 //!
 //! These are requests that a `hyper::Server` receives, and include its method,
 //! target URI, headers, and message body.
-use std::old_io::IoResult;
+use std::old_io::{self, IoResult};
 use std::old_io::net::ip::SocketAddr;
 
 use {HttpResult};
@@ -11,7 +11,7 @@ use method::Method::{self, Get, Head};
 use header::{Headers, ContentLength, TransferEncoding};
 use http::{read_request_line};
 use http::HttpReader;
-use http::HttpReader::{SizedReader, ChunkedReader, EmptyReader};
+use http::HttpReader::{SizedReader, ChunkedReader};
 use uri::RequestUri;
 
 /// A request bundles several parts of an incoming `NetworkStream`, given to a `Handler`.
@@ -26,7 +26,7 @@ pub struct Request<'a> {
     pub uri: RequestUri,
     /// The version of HTTP for this request.
     pub version: HttpVersion,
-    body: HttpReader<&'a mut (Reader + 'a)>
+    body: Body<HttpReader<&'a mut (Reader + 'a)>>
 }
 
 
@@ -39,18 +39,19 @@ impl<'a> Request<'a> {
         let headers = try!(Headers::from_raw(&mut stream));
         debug!("{:?}", headers);
 
-        let body = if method == Get || method == Head {
-            EmptyReader(stream)
-        } else if headers.has::<ContentLength>() {
-            match headers.get::<ContentLength>() {
-                Some(&ContentLength(len)) => SizedReader(stream, len),
-                None => unreachable!()
-            }
+        let body = if let Some(len) = headers.get::<ContentLength>() {
+            SizedReader(stream, **len)
         } else if headers.has::<TransferEncoding>() {
             todo!("check for Transfer-Encoding: chunked");
             ChunkedReader(stream, None)
         } else {
-            EmptyReader(stream)
+            SizedReader(stream, 0)
+        };
+
+        let body = if method == Get || method == Head {
+            Body::Empty(body)
+        } else {
+            Body::NonEmpty(body)
         };
 
         Ok(Request {
@@ -68,13 +69,31 @@ impl<'a> Request<'a> {
                                  RequestUri, HttpVersion,
                                  HttpReader<&'a mut (Reader + 'a)>,) {
         (self.remote_addr, self.method, self.headers,
-         self.uri, self.version, self.body)
+         self.uri, self.version, self.body.into_inner())
     }
 }
 
 impl<'a> Reader for Request<'a> {
+    #[inline]
     fn read(&mut self, buf: &mut [u8]) -> IoResult<usize> {
-        self.body.read(buf)
+        match self.body {
+            Body::Empty(..) => Err(old_io::standard_error(old_io::EndOfFile)),
+            Body::NonEmpty(ref mut r) => r.read(buf)
+        }
+    }
+}
+
+enum Body<R> {
+    Empty(R),
+    NonEmpty(R),
+}
+
+impl<R> Body<R> {
+    fn into_inner(self) -> R {
+        match self {
+            Body::Empty(r) => r,
+            Body::NonEmpty(r) => r
+        }
     }
 }
 
@@ -95,8 +114,9 @@ mod tests {
         let mut stream = MockStream::with_input(b"\
             GET / HTTP/1.1\r\n\
             Host: example.domain\r\n\
+            Content-Length: 18\r\n\
             \r\n\
-            I'm a bad request.\r\n\
+            I'm a bad request.\
         ");
 
         let mut req = Request::new(&mut stream, sock("127.0.0.1:80")).unwrap();
@@ -108,8 +128,9 @@ mod tests {
         let mut stream = MockStream::with_input(b"\
             HEAD / HTTP/1.1\r\n\
             Host: example.domain\r\n\
+            Content-Length: 18\r\n\
             \r\n\
-            I'm a bad request.\r\n\
+            I'm a bad request.\
         ");
 
         let mut req = Request::new(&mut stream, sock("127.0.0.1:80")).unwrap();
@@ -117,7 +138,7 @@ mod tests {
     }
 
     #[test]
-    fn test_post_empty_body() {
+    fn test_post_body_with_no_content_length() {
         let mut stream = MockStream::with_input(b"\
             POST / HTTP/1.1\r\n\
             Host: example.domain\r\n\
@@ -129,6 +150,20 @@ mod tests {
         assert_eq!(req.read_to_string(), Ok("".to_string()));
     }
 
+    #[test]
+    fn test_unexpected_body_drains_upon_drop() {
+        let mut stream = MockStream::with_input(b"\
+            GET / HTTP/1.1\r\n\
+            Host: example.domain\r\n\
+            Content-Length: 18\r\n\
+            \r\n\
+            I'm a bad request.\
+        ");
+
+        Request::new(&mut stream, sock("127.0.0.1:80")).unwrap().read_to_string().unwrap();
+        assert!(stream.read.eof());
+    }
+
     #[test]
     fn test_parse_chunked_request() {
         let mut stream = MockStream::with_input(b"\