http: handle unchunked, un-lengthed HTTP/1.1 responses

Fixes #716

This CL simply resumes the previous CL in-flight at
https://golang.org/cl/906042/

R=rsc, petar-m, dsymonds
CC=golang-dev
https://golang.org/cl/4157042

src/pkg/http/response_test.go

@@ -44,6 +44,47 @@ var respTests = []respTest{
 		"Body here\n",
 	},
 
+	// Unchunked HTTP/1.1 response without Content-Length or
+	// Connection headers.
+	{
+		"HTTP/1.1 200 OK\r\n" +
+			"\r\n" +
+			"Body here\n",
+
+		Response{
+			Status:        "200 OK",
+			StatusCode:    200,
+			Proto:         "HTTP/1.1",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			RequestMethod: "GET",
+			Close:         true,
+			ContentLength: -1,
+		},
+
+		"Body here\n",
+	},
+
+	// Unchunked HTTP/1.1 204 response without Content-Length.
+	{
+		"HTTP/1.1 204 No Content\r\n" +
+			"\r\n" +
+			"Body should not be read!\n",
+
+		Response{
+			Status:        "204 No Content",
+			StatusCode:    204,
+			Proto:         "HTTP/1.1",
+			ProtoMajor:    1,
+			ProtoMinor:    1,
+			RequestMethod: "GET",
+			Close:         false,
+			ContentLength: 0,
+		},
+
+		"",
+	},
+
 	// Unchunked response with Content-Length.
 	{
 		"HTTP/1.0 200 OK\r\n" +

src/pkg/http/transfer.go

@@ -172,6 +172,20 @@ type transferReader struct {
 	Trailer          map[string]string
 }
 
+// bodyAllowedForStatus returns whether a given response status code
+// permits a body.  See RFC2616, section 4.4.
+func bodyAllowedForStatus(status int) bool {
+	switch {
+	case status >= 100 && status <= 199:
+		return false
+	case status == 204:
+		return false
+	case status == 304:
+		return false
+	}
+	return true
+}
+
 // msg is *Request or *Response.
 func readTransfer(msg interface{}, r *bufio.Reader) (err os.Error) {
 	t := &transferReader{}
@@ -217,6 +231,19 @@ func readTransfer(msg interface{}, r *bufio.Reader) (err os.Error) {
 		return err
 	}
 
+	// If there is no Content-Length or chunked Transfer-Encoding on a *Response
+	// and the status is not 1xx, 204 or 304, then the body is unbounded.
+	// See RFC2616, section 4.4.
+	switch msg.(type) {
+	case *Response:
+		if t.ContentLength == -1 &&
+			!chunked(t.TransferEncoding) &&
+			bodyAllowedForStatus(t.StatusCode) {
+			// Unbounded body.
+			t.Close = true
+		}
+	}
+
 	// Prepare body reader.  ContentLength < 0 means chunked encoding
 	// or close connection when finished, since multipart is not supported yet
 	switch {