node: relax websocket connection header check (ethereum#21646)

This makes it accept the "upgrade,keep-alive" header value, which
apparently is a thing.

node/rpcstack.go

@@ -313,7 +313,7 @@ func (h *httpServer) wsAllowed() bool {
 // isWebsocket checks the header of an http request for a websocket upgrade request.
 func isWebsocket(r *http.Request) bool {
 	return strings.ToLower(r.Header.Get("Upgrade")) == "websocket" &&
-		strings.ToLower(r.Header.Get("Connection")) == "upgrade"
+		strings.Contains(strings.ToLower(r.Header.Get("Connection")), "upgrade")
 }
 
 // NewHTTPHandlerStack returns wrapped http-related handlers

node/rpcstack_test.go

@@ -73,6 +73,21 @@ func TestWebsocketOrigins(t *testing.T) {
 	assert.Error(t, err)
 }
 
+// TestIsWebsocket tests if an incoming websocket upgrade request is handled properly.
+func TestIsWebsocket(t *testing.T) {
+	r, _ := http.NewRequest("GET", "/", nil)
+
+	assert.False(t, isWebsocket(r))
+	r.Header.Set("upgrade", "websocket")
+	assert.False(t, isWebsocket(r))
+	r.Header.Set("connection", "upgrade")
+	assert.True(t, isWebsocket(r))
+	r.Header.Set("connection", "upgrade,keep-alive")
+	assert.True(t, isWebsocket(r))
+	r.Header.Set("connection", " UPGRADE,keep-alive")
+	assert.True(t, isWebsocket(r))
+}
+
 func createAndStartServer(t *testing.T, conf httpConfig, ws bool, wsConf wsConfig) *httpServer {
 	t.Helper()