Pass the HTTP host header to webpack-dev-server

lib/gitlab/webpack/dev_server_middleware.rb

@@ -16,14 +16,14 @@ module Gitlab
         super(app, backend: "#{@proxy_scheme}://#{@proxy_host}:#{@proxy_port}", **opts)
       end
 
-      # disable SSL check since any cert used here will likely be self-signed
-      def rewrite_env(env)
-        env["rack.ssl_verify_none"] = true
-        env
-      end
-
       def perform_request(env)
         if @proxy_path && env['PATH_INFO'].start_with?("/#{@proxy_path}")
+          # disable SSL check since any cert used here will likely be self-signed
+          env['rack.ssl_verify_none'] = true
+
+          # ensure we pass the expected Host header so webpack-dev-server doesn't complain
+          env['HTTP_HOST'] = "#{@proxy_host}:#{@proxy_port}"
+
           if relative_url_root = Rails.application.config.relative_url_root
             env['SCRIPT_NAME'] = ""
             env['REQUEST_PATH'].sub!(/\A#{Regexp.escape(relative_url_root)}/, '')