From 2efd7979b78bce5624d800b18a80acd9f9b804e4 Mon Sep 17 00:00:00 2001
From: Paolo Insogna <paolo@cowtech.it>
Date: Thu, 8 Dec 2022 12:06:48 +0100
Subject: [PATCH] http: add --enable-network-family-autoselection command line
 option

---
 doc/api/cli.md                                |  10 ++
 doc/api/net.md                                |   6 +-
 lib/net.js                                    |   3 +-
 src/node_options.cc                           |   4 +
 src/node_options.h                            |   1 +
 ...net-autoselectfamily-commandline-option.js | 108 ++++++++++++++++++
 6 files changed, 129 insertions(+), 3 deletions(-)
 create mode 100644 test/parallel/test-net-autoselectfamily-commandline-option.js

diff --git a/doc/api/cli.md b/doc/api/cli.md
index c09066a29a1dec..23b5f0eecd5e25 100644
--- a/doc/api/cli.md
+++ b/doc/api/cli.md
@@ -314,6 +314,15 @@ added: v6.0.0
 Enable FIPS-compliant crypto at startup. (Requires Node.js to be built
 against FIPS-compatible OpenSSL.)
 
+### `--enable-network-family-autoselection`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+Enables the family autoselection algorithm unless connection options explicitly
+disables it.
+
 ### `--enable-source-maps`
 
 <!-- YAML
@@ -1840,6 +1849,7 @@ Node.js options that are allowed are:
 * `--disable-proto`
 * `--dns-result-order`
 * `--enable-fips`
+* `--enable-network-family-autoselection`
 * `--enable-source-maps`
 * `--experimental-abortcontroller`
 * `--experimental-import-meta-resolve`
diff --git a/doc/api/net.md b/doc/api/net.md
index 06296b5eadb00f..92d65aa91c813b 100644
--- a/doc/api/net.md
+++ b/doc/api/net.md
@@ -873,7 +873,8 @@ changes:
   - version: REPLACEME
     pr-url: https://github.com/nodejs/node/pull/45777
     description: The default value for autoSelectFamily option can be changed
-                 at runtime using `setDefaultAutoSelectFamily`.
+                 at runtime using `setDefaultAutoSelectFamily` or via the
+                 command line option `--enable-network-family-autoselection`.
   - version: REPLACEME
     pr-url: https://github.com/nodejs/node/pull/44731
     description: Added the `autoSelectFamily` option.
@@ -933,7 +934,8 @@ For TCP connections, available `options` are:
   option before timing out and trying the next address.
   Ignored if the `family` option is not `0` or if `localAddress` is set.
   Connection errors are not emitted if at least one connection succeeds.
-  **Default:** initially `false`, but it can be changed at runtime using [`net.setDefaultAutoSelectFamily(value)`][].
+  **Default:** initially `false`, but it can be changed at runtime using [`net.setDefaultAutoSelectFamily(value)`][]
+  or via the command line option `--enable-network-family-autoselection`.
 * `autoSelectFamilyAttemptTimeout` {number}: The amount of time in milliseconds to wait
   for a connection attempt to finish before trying the next address when using the `autoSelectFamily` option.
   If set to a positive integer less than `10`, then the value `10` will be used instead.
diff --git a/lib/net.js b/lib/net.js
index 941636729c5c5e..fd76c565b1f2aa 100644
--- a/lib/net.js
+++ b/lib/net.js
@@ -118,13 +118,14 @@ const {
   validateString
 } = require('internal/validators');
 const kLastWriteQueueSize = Symbol('lastWriteQueueSize');
+const { getOptionValue } = require('internal/options');
 
 // Lazy loaded to improve startup performance.
 let cluster;
 let dns;
 let BlockList;
 let SocketAddress;
-let autoSelectFamilyDefault = false;
+let autoSelectFamilyDefault = getOptionValue('--enable-network-family-autoselection');
 
 const { clearTimeout, setTimeout } = require('timers');
 const { kTimeout } = require('internal/timers');
diff --git a/src/node_options.cc b/src/node_options.cc
index a5365987129ac7..83904f95261b35 100644
--- a/src/node_options.cc
+++ b/src/node_options.cc
@@ -346,6 +346,10 @@ EnvironmentOptionsParser::EnvironmentOptionsParser() {
             "returned)",
             &EnvironmentOptions::dns_result_order,
             kAllowedInEnvvar);
+  AddOption("--enable-network-family-autoselection",
+            "Enable network address family autodetection algorithm",
+            &EnvironmentOptions::enable_network_family_autoselection,
+            kAllowedInEnvvar);
   AddOption("--enable-source-maps",
             "Source Map V3 support for stack traces",
             &EnvironmentOptions::enable_source_maps,
diff --git a/src/node_options.h b/src/node_options.h
index 02beddccdf01c8..fc1fcda5620a04 100644
--- a/src/node_options.h
+++ b/src/node_options.h
@@ -127,6 +127,7 @@ class EnvironmentOptions : public Options {
   bool frozen_intrinsics = false;
   int64_t heap_snapshot_near_heap_limit = 0;
   std::string heap_snapshot_signal;
+  bool enable_network_family_autoselection = false;
   uint64_t max_http_header_size = 16 * 1024;
   bool deprecation = true;
   bool force_async_hooks_checks = true;
diff --git a/test/parallel/test-net-autoselectfamily-commandline-option.js b/test/parallel/test-net-autoselectfamily-commandline-option.js
new file mode 100644
index 00000000000000..78c8a81b0ef126
--- /dev/null
+++ b/test/parallel/test-net-autoselectfamily-commandline-option.js
@@ -0,0 +1,108 @@
+'use strict';
+
+// Flags: --enable-network-family-autoselection
+
+const common = require('../common');
+const { parseDNSPacket, writeDNSPacket } = require('../common/dns');
+
+const assert = require('assert');
+const dgram = require('dgram');
+const { Resolver } = require('dns');
+const { createConnection, createServer } = require('net');
+
+// Test that happy eyeballs algorithm can be enable from command line.
+
+let autoSelectFamilyAttemptTimeout = common.platformTimeout(250);
+if (common.isWindows) {
+  // Some of the windows machines in the CI need more time to establish connection
+  autoSelectFamilyAttemptTimeout = common.platformTimeout(1500);
+}
+
+function _lookup(resolver, hostname, options, cb) {
+  resolver.resolve(hostname, 'ANY', (err, replies) => {
+    assert.notStrictEqual(options.family, 4);
+
+    if (err) {
+      return cb(err);
+    }
+
+    const hosts = replies
+      .map((r) => ({ address: r.address, family: r.type === 'AAAA' ? 6 : 4 }))
+      .sort((a, b) => b.family - a.family);
+
+    if (options.all === true) {
+      return cb(null, hosts);
+    }
+
+    return cb(null, hosts[0].address, hosts[0].family);
+  });
+}
+
+function createDnsServer(ipv6Addr, ipv4Addr, cb) {
+  // Create a DNS server which replies with a AAAA and a A record for the same host
+  const socket = dgram.createSocket('udp4');
+
+  socket.on('message', common.mustCall((msg, { address, port }) => {
+    const parsed = parseDNSPacket(msg);
+    const domain = parsed.questions[0].domain;
+    assert.strictEqual(domain, 'example.org');
+
+    socket.send(writeDNSPacket({
+      id: parsed.id,
+      questions: parsed.questions,
+      answers: [
+        { type: 'AAAA', address: ipv6Addr, ttl: 123, domain: 'example.org' },
+        { type: 'A', address: ipv4Addr, ttl: 123, domain: 'example.org' },
+      ]
+    }), port, address);
+  }));
+
+  socket.bind(0, () => {
+    const resolver = new Resolver();
+    resolver.setServers([`127.0.0.1:${socket.address().port}`]);
+
+    cb({ dnsServer: socket, lookup: _lookup.bind(null, resolver) });
+  });
+}
+
+// Test that IPV4 is reached if IPV6 is not reachable
+{
+  createDnsServer('::1', '127.0.0.1', common.mustCall(function({ dnsServer, lookup }) {
+    const ipv4Server = createServer((socket) => {
+      socket.on('data', common.mustCall(() => {
+        socket.write('response-ipv4');
+        socket.end();
+      }));
+    });
+
+    ipv4Server.listen(0, '127.0.0.1', common.mustCall(() => {
+      const port = ipv4Server.address().port;
+
+      const connection = createConnection({
+        host: 'example.org',
+        port: port,
+        lookup,
+        autoSelectFamilyAttemptTimeout,
+      });
+
+      let response = '';
+      connection.setEncoding('utf-8');
+
+      connection.on('ready', common.mustCall(() => {
+        assert.deepStrictEqual(connection.autoSelectFamilyAttemptedAddresses, [`::1:${port}`, `127.0.0.1:${port}`]);
+      }));
+
+      connection.on('data', (chunk) => {
+        response += chunk;
+      });
+
+      connection.on('end', common.mustCall(() => {
+        assert.strictEqual(response, 'response-ipv4');
+        ipv4Server.close();
+        dnsServer.close();
+      }));
+
+      connection.write('request');
+    }));
+  }));
+}