fix: add workaround for Origin header in sockjs

lib/Server.js

@@ -24,6 +24,22 @@ const webpackDevMiddleware = require('webpack-dev-middleware');
 const OptionsValidationError = require('./OptionsValidationError');
 const optionsSchema = require('./optionsSchema.json');
 
+// Workaround for sockjs@~0.3.19
+// sockjs will remove Origin header, however Origin header is required for checking host.
+// See https://github.com/webpack/webpack-dev-server/issues/1604 for more information
+{
+  // eslint-disable-next-line global-require
+  const SockjsSession = require('sockjs/lib/transport').Session;
+  const decorateConnection = SockjsSession.prototype.decorateConnection;
+  SockjsSession.prototype.decorateConnection = function(req) {
+    decorateConnection.call(this, req);
+    const connection = this.connection;
+    if (connection.headers && !('origin' in connection.headers) && 'origin' in req.headers) {
+      connection.headers.origin = req.headers.origin;
+    }
+  };
+}
+
 const clientStats = { errorDetails: false };
 const log = console.log; // eslint-disable-line no-console