fix(electron): 🩹 fix connection issue of domain name keys (#1763)

src/electron/connectivity.ts

@@ -0,0 +1,39 @@
+// Copyright 2019 The Outline Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import * as dns from 'dns';
+
+import {timeoutPromise} from '../infrastructure/timeout_promise';
+import * as errors from '../www/model/errors';
+
+const DNS_LOOKUP_TIMEOUT_MS = 10000;
+
+// Uses the OS' built-in functions, i.e. /etc/hosts, et al.:
+// https://nodejs.org/dist/latest-v10.x/docs/api/dns.html#dns_dns
+//
+// Effectively a no-op if hostname is already an IP.
+export function lookupIp(hostname: string): Promise<string> {
+  return timeoutPromise(
+    new Promise<string>((fulfill, reject) => {
+      dns.lookup(hostname, 4, (e, address) => {
+        if (e) {
+          return reject(new errors.ServerUnreachable('could not resolve proxy server hostname'));
+        }
+        fulfill(address);
+      });
+    }),
+    DNS_LOOKUP_TIMEOUT_MS,
+    'DNS lookup'
+  );
+}

src/electron/index.ts

@@ -31,6 +31,7 @@ import {GoVpnTunnel} from './go_vpn_tunnel';
 import {installRoutingServices, RoutingDaemon} from './routing_service';
 import {TunnelStore, SerializableTunnel} from './tunnel_store';
 import {VpnTunnel} from './vpn_tunnel';
+import {lookupIp} from './connectivity';
 
 // TODO: can we define these macros in other .d.ts files with default values?
 // Build-time macros injected by webpack's DefinePlugin:
@@ -466,6 +467,12 @@ function main() {
       console.log(`connecting to ${args.id}...`);
 
       try {
+        // We must convert the host from a potential "hostname" to an "IP" address
+        // because startVpn will add a routing table entry that prefixed with this
+        // host (e.g. "<host>/32"), therefore <host> must be an IP address.
+        // TODO: make sure we resolve it in the native code
+        args.config.host = await lookupIp(args.config.host || '');
+
         await startVpn(args.config, args.id);
         console.log(`connected to ${args.id}`);
         await setupAutoLaunch(args);