TUN-3490: Make sure OriginClient implementation doesn't write after Proxy return

origin/proxy.go

@@ -5,6 +5,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"net"
 	"net/http"
 	"strconv"
 	"strings"
@@ -124,19 +125,31 @@ func (c *client) proxyWebsocket(w connection.ResponseWriter, req *http.Request,
 	}
 
 	serveCtx, cancel := context.WithCancel(req.Context())
-	defer cancel()
+	connClosedChan := make(chan struct{})
 	go func() {
+		// serveCtx is done if req is cancelled, or streamWebsocket returns
 		<-serveCtx.Done()
 		conn.Close()
+		close(connClosedChan)
 	}()
-	err = w.WriteRespHeaders(resp)
-	if err != nil {
-		return nil, errors.Wrap(err, "Error writing response header")
-	}
+
 	// Copy to/from stream to the undelying connection. Use the underlying
 	// connection because cloudflared doesn't operate on the message themselves
-	websocket.Stream(conn.UnderlyingConn(), w)
-	return resp, nil
+	err = c.streamWebsocket(w, conn.UnderlyingConn(), resp)
+	cancel()
+
+	// We need to make sure conn is closed before returning, otherwise we might write to conn after Proxy returns
+	<-connClosedChan
+	return resp, err
+}
+
+func (c *client) streamWebsocket(w connection.ResponseWriter, conn net.Conn, resp *http.Response) error {
+	err := w.WriteRespHeaders(resp)
+	if err != nil {
+		return errors.Wrap(err, "Error writing websocket response header")
+	}
+	websocket.Stream(conn, w)
+	return nil
 }
 
 func (c *client) writeEventStream(w connection.ResponseWriter, respBody io.ReadCloser) {

origin/proxy_test.go

@@ -49,6 +49,7 @@ func (w *mockHTTPRespWriter) WriteRespHeaders(resp *http.Response) error {
 
 func (w *mockHTTPRespWriter) WriteErrorResponse() {
 	w.WriteHeader(http.StatusBadGateway)
+	w.Write([]byte("http response error"))
 }
 
 func (w *mockHTTPRespWriter) Read(data []byte) (int, error) {
@@ -315,3 +316,37 @@ func (ma mockAPI) ServeHTTP(w http.ResponseWriter, r *http.Request) {
 	w.WriteHeader(http.StatusCreated)
 	w.Write([]byte("Created"))
 }
+
+type errorOriginTransport struct{}
+
+func (errorOriginTransport) RoundTrip(*http.Request) (*http.Response, error) {
+	return nil, fmt.Errorf("Proxy error")
+}
+
+func TestProxyError(t *testing.T) {
+	ingress := ingress.Ingress{
+		Rules: []ingress.Rule{
+			{
+				Hostname: "*",
+				Path:     nil,
+				Service: ingress.MockOriginService{
+					Transport: errorOriginTransport{},
+				},
+			},
+		},
+	}
+
+	logger, err := logger.New()
+	require.NoError(t, err)
+
+	client := NewClient(ingress, testTags, logger)
+
+	respWriter := newMockHTTPRespWriter()
+	req, err := http.NewRequest(http.MethodGet, "http://127.0.0.1", nil)
+	assert.NoError(t, err)
+
+	err = client.Proxy(respWriter, req, false)
+	assert.Error(t, err)
+	assert.Equal(t, http.StatusBadGateway, respWriter.Code)
+	assert.Equal(t, "http response error", respWriter.Body.String())
+}