From 71a85602783f10eb3eb2ed5aab6218701901c8d8 Mon Sep 17 00:00:00 2001
From: lazerg <lazerg2@gmail.com>
Date: Tue, 27 Oct 2026 09:03:48 +0500
Subject: [PATCH] dns: propagate ares_dns_write() failure status

Assisted-by: Claude Code
Signed-off-by: lazerg <lazerg2@gmail.com>
---
 src/cares_wrap.h                              |  2 +-
 .../test-dns-resolve-unwritable-reply.js      | 35 +++++++++++++++++++
 2 files changed, 36 insertions(+), 1 deletion(-)
 create mode 100644 test/parallel/test-dns-resolve-unwritable-reply.js

diff --git a/src/cares_wrap.h b/src/cares_wrap.h
index fd66a67164b3..7f297e74d9a7 100644
--- a/src/cares_wrap.h
+++ b/src/cares_wrap.h
@@ -336,7 +336,7 @@ class QueryWrap final : public AsyncWrap {
       // No need to explicitly call ares_free_string here,
       // as it is a wrapper around free, which is already
       // invoked when MallocedBuffer is destructed.
-      ares_dns_write(dnsrec, &buf_copy, &answer_len);
+      status = ares_dns_write(dnsrec, &buf_copy, &answer_len);
     }
 
     wrap->response_data_ = std::make_unique<ResponseData>();
diff --git a/test/parallel/test-dns-resolve-unwritable-reply.js b/test/parallel/test-dns-resolve-unwritable-reply.js
new file mode 100644
index 000000000000..f8c2a666840d
--- /dev/null
+++ b/test/parallel/test-dns-resolve-unwritable-reply.js
@@ -0,0 +1,35 @@
+'use strict';
+const common = require('../common');
+const dnstools = require('../common/dns');
+const assert = require('assert');
+const dgram = require('dgram');
+const dns = require('dns');
+
+const server = dgram.createSocket('udp4');
+
+server.on('message', common.mustCall((msg, { address, port }) => {
+  const parsed = dnstools.parseDNSPacket(msg);
+  const domain = parsed.questions[0].domain;
+  assert.strictEqual(domain, 'example.org');
+
+  server.send(dnstools.writeDNSPacket({
+    id: parsed.id,
+    questions: parsed.questions,
+    answers: [{ type: 'A', address: '1.2.3.4', ttl: 123, domain }],
+    additionalRecords: [
+      { type: 'A', address: '1.2.3.4', ttl: 123, domain: 'x y.example.org' },
+    ],
+  }), port, address);
+}));
+
+server.bind(0, common.mustCall(() => {
+  const resolver = new dns.Resolver({ timeout: 1000, tries: 1 });
+  resolver.setServers([`127.0.0.1:${server.address().port}`]);
+
+  resolver.resolve4('example.org', common.mustCall((err) => {
+    assert.strictEqual(err.code, 'EBADNAME');
+    assert.strictEqual(err.syscall, 'queryA');
+    assert.strictEqual(err.hostname, 'example.org');
+    server.close();
+  }));
+}));