fix: upgrade headers if hop headers are removed (zalando#3553)

fix: upgrade headers if hop headers are removed

fix: zalando#3548

Signed-off-by: Sandor Szücs <[email protected]>

Author: szuecs

proxy/proxy.go

@@ -967,6 +967,8 @@ func (p *Proxy) makeUpgradeRequest(ctx *context, req *http.Request) {
 }
 
 func (p *Proxy) makeBackendRequest(ctx *context, requestContext stdlibcontext.Context) (*http.Response, *proxyError) {
+	payloadProtocol := getUpgradeRequest(ctx.Request())
+
 	req, endpointMetrics, err := p.mapRequest(ctx, requestContext)
 	if err != nil {
 		return nil, &proxyError{err: fmt.Errorf("could not map backend request: %w", err)}
@@ -981,7 +983,10 @@ func (p *Proxy) makeBackendRequest(ctx *context, requestContext stdlibcontext.Co
 		defer endpointMetrics.DecInflightRequest()
 	}
 
-	if p.experimentalUpgrade && isUpgradeRequest(req) {
+	if p.experimentalUpgrade && payloadProtocol != "" {
+		// see also https://github.com/golang/go/blob/9159cd4ec6b0e9475dc9c71c830035c1c4c13483/src/net/http/httputil/reverseproxy.go#L423-L428
+		req.Header.Set("Connection", "Upgrade")
+		req.Header.Set("Upgrade", payloadProtocol)
 		p.makeUpgradeRequest(ctx, req)
 
 		// We are not owner of the connection anymore.

proxy/upgrade_test.go

@@ -95,6 +95,7 @@ func TestServeHTTP(t *testing.T) {
 		backendClosesConnection    bool
 		backendHangs               bool
 		noBackend                  bool
+		dropHopHeaders             bool
 		backendStatusCode          int
 		expectedResponseStatusCode int
 		expectedResponseBody       string
@@ -112,6 +113,13 @@ func TestServeHTTP(t *testing.T) {
 			method:            http.MethodGet,
 			backendStatusCode: http.StatusSwitchingProtocols,
 		},
+		{
+			msg:               "Simple route with hop-headers dropped",
+			route:             `route: Path("/ws") -> "%s";`,
+			method:            http.MethodGet,
+			dropHopHeaders:    true,
+			backendStatusCode: http.StatusSwitchingProtocols,
+		},
 		{
 			msg:               "Wrong method",
 			route:             `route: Path("/ws") -> "%s";`,
@@ -247,7 +255,14 @@ func TestServeHTTP(t *testing.T) {
 				defer backend.Close()
 			}
 
-			tp, err := newTestProxyWithParams(routes, Params{ExperimentalUpgrade: true})
+			flags := FlagsNone
+			if ti.dropHopHeaders {
+				flags = HopHeadersRemoval
+			}
+			tp, err := newTestProxyWithParams(routes, Params{
+				ExperimentalUpgrade: true,
+				Flags:               flags,
+			})
 			require.NoError(t, err)
 
 			defer tp.close()