From 732658e4cf0ab676040cdbad92f39b93fbacaa80 Mon Sep 17 00:00:00 2001
From: Anna Henningsen <anna@addaleax.net>
Date: Thu, 27 Jul 2017 19:03:11 +0200
Subject: [PATCH] dns: add channel.cancel()
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

This can be used to implement custom timeouts.

Fixes: https://github.com/nodejs/node/issues/7231
PR-URL: https://github.com/nodejs/node/pull/14518
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Tobias Nießen <tniessen@tnie.de>
---
 doc/api/dns.md                           |  8 +++++++
 lib/dns.js                               |  4 ++++
 src/cares_wrap.cc                        |  8 +++++++
 test/parallel/test-dns-channel-cancel.js | 29 ++++++++++++++++++++++++
 4 files changed, 49 insertions(+)
 create mode 100644 test/parallel/test-dns-channel-cancel.js

diff --git a/doc/api/dns.md b/doc/api/dns.md
index e9de95c118c573..5be30f22284b9c 100644
--- a/doc/api/dns.md
+++ b/doc/api/dns.md
@@ -95,6 +95,14 @@ The following methods from the `dns` module are available:
 * [`resolver.resolveTxt()`][`dns.resolveTxt()`]
 * [`resolver.reverse()`][`dns.reverse()`]
 
+### resolver.cancel()
+<!-- YAML
+added: REPLACEME
+-->
+
+Cancel all outstanding DNS queries made by this resolver. The corresponding
+callbacks will be called with an error with code `ECANCELLED`.
+
 ## dns.getServers()
 <!-- YAML
 added: v0.11.3
diff --git a/lib/dns.js b/lib/dns.js
index f79eb3bb14e9b2..90eaac312213d0 100644
--- a/lib/dns.js
+++ b/lib/dns.js
@@ -247,6 +247,10 @@ class Resolver {
   constructor() {
     this._handle = new ChannelWrap();
   }
+
+  cancel() {
+    this._handle.cancel();
+  }
 }
 
 function resolver(bindingName) {
diff --git a/src/cares_wrap.cc b/src/cares_wrap.cc
index a75da1f410ae1d..327d947f3aa1cf 100644
--- a/src/cares_wrap.cc
+++ b/src/cares_wrap.cc
@@ -2131,6 +2131,13 @@ void SetServers(const FunctionCallbackInfo<Value>& args) {
   args.GetReturnValue().Set(err);
 }
 
+void Cancel(const FunctionCallbackInfo<Value>& args) {
+  ChannelWrap* channel;
+  ASSIGN_OR_RETURN_UNWRAP(&channel, args.Holder());
+
+  ares_cancel(channel->cares_channel());
+}
+
 
 void StrError(const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);
@@ -2215,6 +2222,7 @@ void Initialize(Local<Object> target,
 
   env->SetProtoMethod(channel_wrap, "getServers", GetServers);
   env->SetProtoMethod(channel_wrap, "setServers", SetServers);
+  env->SetProtoMethod(channel_wrap, "cancel", Cancel);
 
   channel_wrap->SetClassName(
       FIXED_ONE_BYTE_STRING(env->isolate(), "ChannelWrap"));
diff --git a/test/parallel/test-dns-channel-cancel.js b/test/parallel/test-dns-channel-cancel.js
new file mode 100644
index 00000000000000..797d61efb40653
--- /dev/null
+++ b/test/parallel/test-dns-channel-cancel.js
@@ -0,0 +1,29 @@
+'use strict';
+const common = require('../common');
+const dnstools = require('../common/dns');
+const { Resolver } = require('dns');
+const assert = require('assert');
+const dgram = require('dgram');
+
+const server = dgram.createSocket('udp4');
+const resolver = new Resolver();
+
+server.bind(0, common.mustCall(() => {
+  resolver.setServers([`127.0.0.1:${server.address().port}`]);
+  resolver.resolve4('example.org', common.mustCall((err, res) => {
+    assert.strictEqual(err.code, 'ECANCELLED');
+    assert.strictEqual(err.errno, 'ECANCELLED');
+    assert.strictEqual(err.syscall, 'queryA');
+    assert.strictEqual(err.hostname, 'example.org');
+    server.close();
+  }));
+}));
+
+server.on('message', common.mustCall((msg, { address, port }) => {
+  const parsed = dnstools.parseDNSPacket(msg);
+  const domain = parsed.questions[0].domain;
+  assert.strictEqual(domain, 'example.org');
+
+  // Do not send a reply.
+  resolver.cancel();
+}));