Chunked responses does not have a Content-Length header

Co-authored-by: Romain <rtribotte@users.noreply.github.com>

pkg/proxy/fast/connpool.go

@@ -215,34 +215,20 @@ func (c *conn) handleResponse(r rwWithUpgrade) error {
 		return nil
 	}
 
-	hasContentLength := len(res.Header.Peek("Content-Length")) > 0
-
-	if hasContentLength && res.Header.ContentLength() == 0 {
-		return nil
-	}
-
 	// When a body is not allowed for a given status code the body is ignored.
 	// The connection will be marked as broken by the next Peek in the readloop.
 	if !isBodyAllowedForStatus(res.StatusCode()) {
 		return nil
 	}
 
-	if !hasContentLength {
-		b := c.bufferPool.Get()
-		if b == nil {
-			b = make([]byte, bufferSize)
-		}
-		defer c.bufferPool.Put(b)
-
-		if _, err := io.CopyBuffer(r.RW, c.br, b); err != nil {
-			return err
-		}
+	contentLength := res.Header.ContentLength()
 
+	if contentLength == 0 {
 		return nil
 	}
 
 	// Chunked response, Content-Length is set to -1 by FastProxy when "Transfer-Encoding: chunked" header is received.
-	if res.Header.ContentLength() == -1 {
+	if contentLength == -1 {
 		cbr := httputil.NewChunkedReader(c.br)
 
 		b := c.bufferPool.Get()
@@ -282,6 +268,23 @@ func (c *conn) handleResponse(r rwWithUpgrade) error {
 		return nil
 	}
 
+	// Response without Content-Length header.
+	// The message body length is determined by the number of bytes received prior to the server closing the connection.
+	if contentLength == -2 {
+		b := c.bufferPool.Get()
+		if b == nil {
+			b = make([]byte, bufferSize)
+		}
+		defer c.bufferPool.Put(b)
+
+		if _, err := io.CopyBuffer(r.RW, c.br, b); err != nil {
+			return err
+		}
+
+		return nil
+	}
+
+	// Response with a valid Content-Length header.
 	brl := c.limitedReaderPool.Get()
 	if brl == nil {
 		brl = &io.LimitedReader{}

pkg/proxy/fast/proxy_test.go

@@ -306,7 +306,7 @@ func TestHeadRequest(t *testing.T) {
 	assert.Equal(t, http.StatusOK, res.Code)
 }
 
-func TestNoContentLengthResponse(t *testing.T) {
+func TestNoContentLength(t *testing.T) {
 	backendListener, err := net.Listen("tcp", ":0")
 	require.NoError(t, err)
 
@@ -346,6 +346,45 @@ func TestNoContentLengthResponse(t *testing.T) {
 	assert.Equal(t, "foo", res.Body.String())
 }
 
+func TestTransferEncodingChunked(t *testing.T) {
+	backendServer := httptest.NewServer(http.HandlerFunc(func(rw http.ResponseWriter, req *http.Request) {
+		flusher, ok := rw.(http.Flusher)
+		require.True(t, ok)
+
+		for i := range 3 {
+			_, err := rw.Write([]byte(fmt.Sprintf("chunk %d\n", i)))
+			require.NoError(t, err)
+
+			flusher.Flush()
+		}
+	}))
+	t.Cleanup(backendServer.Close)
+
+	builder := NewProxyBuilder(&transportManagerMock{}, static.FastProxyConfig{})
+
+	proxyHandler, err := builder.Build("", testhelpers.MustParseURL(backendServer.URL), true, true)
+	require.NoError(t, err)
+
+	proxyServer := httptest.NewServer(proxyHandler)
+	t.Cleanup(proxyServer.Close)
+
+	req, err := http.NewRequest(http.MethodGet, proxyServer.URL, http.NoBody)
+	require.NoError(t, err)
+
+	res, err := http.DefaultClient.Do(req)
+	require.NoError(t, err)
+
+	t.Cleanup(func() { _ = res.Body.Close() })
+
+	assert.Equal(t, http.StatusOK, res.StatusCode)
+	assert.Equal(t, []string{"chunked"}, res.TransferEncoding)
+
+	body, err := io.ReadAll(res.Body)
+	require.NoError(t, err)
+
+	assert.Equal(t, "chunk 0\nchunk 1\nchunk 2\n", string(body))
+}
+
 func newCertificate(t *testing.T, domain string) *tls.Certificate {
 	t.Helper()