From cb5e7a029ba11acff4eb36433c7c58b4bf9513ca Mon Sep 17 00:00:00 2001
From: Jon Seager <jon@sgrs.uk>
Date: Thu, 1 Aug 2024 17:00:36 +0100
Subject: [PATCH] build: use `resolve4`/`resolve6` in `build:dns-fallback`.

`dns.lookup` relies on making syscalls to the underlying
system using `getaddrinfo`, which can sometimes fail in
proxy situations.

This is an equivalent implementation using the native
NodeJS DNS functions.
---
 ts/scripts/generate-dns-fallback.ts | 58 ++++++++++++++---------------
 1 file changed, 27 insertions(+), 31 deletions(-)

diff --git a/ts/scripts/generate-dns-fallback.ts b/ts/scripts/generate-dns-fallback.ts
index 39f442f4b9e1..f204fe7843c3 100644
--- a/ts/scripts/generate-dns-fallback.ts
+++ b/ts/scripts/generate-dns-fallback.ts
@@ -1,15 +1,15 @@
 // Copyright 2024 Signal Messenger, LLC
 // SPDX-License-Identifier: AGPL-3.0-only
 
-import { join } from 'path';
-import { lookup as lookupCb } from 'dns';
+import { resolve4 as resolve4Cb, resolve6 as resolve6Cb } from 'dns';
 import { writeFile } from 'fs/promises';
+import { join } from 'path';
 import { promisify } from 'util';
-import type { ResolvedEndpoint } from 'electron';
 
 import { isNotNil } from '../util/isNotNil';
 
-const lookup = promisify(lookupCb);
+const resolve4 = promisify(resolve4Cb);
+const resolve6 = promisify(resolve6Cb);
 
 const FALLBACK_DOMAINS = [
   'chat.signal.org',
@@ -25,35 +25,31 @@ const FALLBACK_DOMAINS = [
 async function main() {
   const config = await Promise.all(
     FALLBACK_DOMAINS.sort().map(async domain => {
-      const addresses = await lookup(domain, { all: true });
 
-      const endpoints = addresses
-        .map(({ address, family }): ResolvedEndpoint | null => {
-          if (family === 4) {
-            return { family: 'ipv4', address };
-          }
-          if (family === 6) {
-            return { family: 'ipv6', address };
-          }
-          return null;
-        })
-        .filter(isNotNil)
-        .sort((a, b) => {
-          if (a.family < b.family) {
-            return -1;
-          }
-          if (a.family > b.family) {
-            return 1;
-          }
+      const ipv4endpoints = (await resolve4(domain))
+        .map(a => ({"family": "ipv4", "address": a}))
 
-          if (a.address < b.address) {
-            return -1;
-          }
-          if (a.address > b.address) {
-            return 1;
-          }
-          return 0;
-        });
+      const ipv6endpoints = (await resolve6(domain))
+        .map(a => ({"family": "ipv6", "address": a}))
+
+      const endpoints = [...ipv4endpoints, ...ipv6endpoints]
+      .filter(isNotNil)
+      .sort((a, b) => {
+        if (a.family < b.family) {
+          return -1;
+        }
+        if (a.family > b.family) {
+          return 1;
+        }
+
+        if (a.address < b.address) {
+          return -1;
+        }
+        if (a.address > b.address) {
+          return 1;
+        }
+        return 0;
+      })
 
       return { domain, endpoints };
     })