From ad2da1fb3cf6a0b03bc14495ebb3bb173a4fcebd Mon Sep 17 00:00:00 2001
From: "jiahao.si" <sijiahao0839@gmail.com>
Date: Sun, 24 Jul 2022 18:18:20 +0800
Subject: [PATCH] dns: fix getServers return undefined

PR-URL: https://github.com/nodejs/node/pull/43922
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
---
 lib/internal/dns/utils.js            |  4 ++--
 test/parallel/test-dns-get-server.js | 11 +++++++++++
 2 files changed, 13 insertions(+), 2 deletions(-)
 create mode 100644 test/parallel/test-dns-get-server.js

diff --git a/lib/internal/dns/utils.js b/lib/internal/dns/utils.js
index 26949a028d89c7..511be2bb457b34 100644
--- a/lib/internal/dns/utils.js
+++ b/lib/internal/dns/utils.js
@@ -61,7 +61,7 @@ class Resolver {
   }
 
   getServers() {
-    return ArrayPrototypeMap(this._handle.getServers(), (val) => {
+    return ArrayPrototypeMap(this._handle.getServers() || [], (val) => {
       if (!val[1] || val[1] === IANA_DNS_PORT)
         return val[0];
 
@@ -76,7 +76,7 @@ class Resolver {
     // Cache the original servers because in the event of an error while
     // setting the servers, c-ares won't have any servers available for
     // resolution.
-    const orig = this._handle.getServers();
+    const orig = this._handle.getServers() || [];
     const newSet = [];
 
     ArrayPrototypeForEach(servers, (serv, index) => {
diff --git a/test/parallel/test-dns-get-server.js b/test/parallel/test-dns-get-server.js
new file mode 100644
index 00000000000000..24c01218fad519
--- /dev/null
+++ b/test/parallel/test-dns-get-server.js
@@ -0,0 +1,11 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+
+const { Resolver } = require('dns');
+
+const resolver = new Resolver();
+assert(resolver.getServers().length > 0);
+// return undefined
+resolver._handle.getServers = common.mustCall(() => {});
+assert.strictEqual(resolver.getServers().length, 0);