Provide fallback IP addrs for core services

ts/util/dns.ts

@@ -8,11 +8,40 @@ import type {
   lookup as nodeLookup,
 } from 'dns';
 import { ipcRenderer, net } from 'electron';
-import type { ResolvedHost } from 'electron';
+import type { ResolvedHost, ResolvedEndpoint } from 'electron';
 
 import { strictAssert } from './assert';
 import { drop } from './drop';
 
+const FALLBACK_ADDRS: ReadonlyMap<
+  string,
+  ReadonlyArray<ResolvedEndpoint>
+> = new Map([
+  [
+    'cdsi.signal.org',
+    [
+      { family: 'ipv4', address: '40.122.45.194' },
+      { family: 'ipv6', address: '2603:1030:7::1' },
+    ],
+  ],
+  [
+    'chat.signal.org',
+    [
+      { family: 'ipv4', address: '13.248.212.111' },
+      { family: 'ipv4', address: '76.223.92.165' },
+      { family: 'ipv6', address: '2600:9000:a507:ab6d:4ce3:2f58:25d7:9cbf' },
+      { family: 'ipv6', address: '2600:9000:a61f:527c:d5eb:a431:5239:3232' },
+    ],
+  ],
+  [
+    'sfu.voip.signal.org',
+    [
+      { family: 'ipv4', address: '34.49.5.136' },
+      { family: 'ipv6', address: '2600:1901:0:9c39::' },
+    ],
+  ],
+]);
+
 function lookupAll(
   hostname: string,
   opts: LookupOneOptions | LookupAllOptions,
@@ -27,9 +56,8 @@ function lookupAll(
   strictAssert(typeof callback === 'function', 'missing callback');
 
   async function run() {
-    let result: ResolvedHost;
+    let result: Pick<ResolvedHost, 'endpoints'>;
 
-    try {
     let queryType: 'A' | 'AAAA' | undefined;
     if (opts.family === 4) {
       queryType = 'A';
@@ -37,6 +65,7 @@ function lookupAll(
       queryType = 'AAAA';
     }
 
+    try {
       if (net) {
         // Main process
         result = await net.resolveHost(hostname, {
@@ -50,6 +79,16 @@ function lookupAll(
           queryType
         );
       }
+    } catch (error) {
+      const fallback = FALLBACK_ADDRS.get(hostname);
+      if (fallback) {
+        result = { endpoints: fallback.slice() };
+      } else {
+        callback(error, []);
+        return;
+      }
+    }
+
     const addresses = result.endpoints.map(({ address, family }) => {
       let numericFamily = -1;
       if (family === 'ipv4') {
@@ -64,15 +103,9 @@ function lookupAll(
     });
 
     if (!opts.all) {
-        const random = addresses.at(
+      const random = addresses.at(Math.floor(Math.random() * addresses.length));
-          Math.floor(Math.random() * addresses.length)
-        );
       if (random === undefined) {
-          callback(
+        callback(new Error(`Hostname: ${hostname} cannot be resolved`), '', -1);
-            new Error(`Hostname: ${hostname} cannot be resolved`),
-            '',
-            -1
-          );
         return;
       }
       callback(null, random.address, random.family);
@@ -80,9 +113,6 @@ function lookupAll(
     }
 
     callback(null, addresses);
-    } catch (error) {
-      callback(error, []);
-    }
   }
 
   drop(run());