From 159f874f1f01529510754c1124523cd8ba7dcb8e Mon Sep 17 00:00:00 2001
From: Paolo Insogna <paolo@cowtech.it>
Date: Mon, 4 Dec 2023 16:46:49 +0100
Subject: [PATCH] net: add connection attempt events

---
 doc/api/net.md                                |  44 ++-
 lib/net.js                                    |  31 +-
 test/common/dns.js                            |  21 +
 ...est-net-autoselectfamily-events-failure.js | 128 ++++++
 ...est-net-autoselectfamily-events-timeout.js |  54 +++
 ...test-net-autoselectfamily-timeout-close.js |   9 +
 ...net-autoselectfamily-commandline-option.js | 116 ++----
 .../test-net-autoselectfamily-default.js      | 169 +++-----
 .../test-net-autoselectfamily-ipv4first.js    | 117 ++----
 test/parallel/test-net-autoselectfamily.js    | 374 +++++++-----------
 10 files changed, 549 insertions(+), 514 deletions(-)
 create mode 100644 test/internet/test-net-autoselectfamily-events-failure.js
 create mode 100644 test/internet/test-net-autoselectfamily-events-timeout.js

diff --git a/doc/api/net.md b/doc/api/net.md
index fc260b9f636266..8a66a0a68b4c60 100644
--- a/doc/api/net.md
+++ b/doc/api/net.md
@@ -691,6 +691,47 @@ added: v0.1.90
 Emitted when a socket connection is successfully established.
 See [`net.createConnection()`][].
 
+### Event: `'connectionAttempt'`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `ip` {number} The IP which the socket is attempting to connect to.
+* `port` {number} The port which the socket is attempting to connect to.
+* `family` {number} The family of the IP. It can be `6` for IPv6 or `4` for IPv4.
+
+Emitted when a new connection attempt is started. This may be emitted multiple times
+if the family autoselection algorithm is enabled in [`socket.connect(options)`][].
+
+### Event: `'connectionAttemptFailed'`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `ip` {number} The IP which the socket attempted to connect to.
+* `port` {number} The port which the socket attempted to connect to.
+* `family` {number} The family of the IP. It can be `6` for IPv6 or `4` for IPv4.
+  \* `error` {Error} The error associated with the failure.
+
+Emitted when a connection attempt failed. This may be emitted multiple times
+if the family autoselection algorithm is enabled in [`socket.connect(options)`][].
+
+### Event: `'connectionAttemptTimeout'`
+
+<!-- YAML
+added: REPLACEME
+-->
+
+* `ip` {number} The IP which the socket attempted to connect to.
+* `port` {number} The port which the socket attempted to connect to.
+* `family` {number} The family of the IP. It can be `6` for IPv6 or `4` for IPv4.
+
+Emitted when a connection attempt timed out. This is only emitted (and may be
+emitted multiple times) if the family autoselection algorithm is enabled
+in [`socket.connect(options)`][].
+
 ### Event: `'data'`
 
 <!-- YAML
@@ -963,8 +1004,7 @@ For TCP connections, available `options` are:
   obtained IPv6 and IPv4 addresses, in sequence, until a connection is established.
   The first returned AAAA address is tried first, then the first returned A address,
   then the second returned AAAA address and so on.
-  Each connection attempt is given the amount of time specified by the `autoSelectFamilyAttemptTimeout`
-  option before timing out and trying the next address.
+  Each connection attempt (but the last one) is given the amount of time specified by the `autoSelectFamilyAttemptTimeout` 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.
   If all connections attempts fails, a single `AggregateError` with all failed attempts is emitted.
diff --git a/lib/net.js b/lib/net.js
index a7e1dbb3f524a5..fa470dbb060455 100644
--- a/lib/net.js
+++ b/lib/net.js
@@ -1058,6 +1058,7 @@ function internalConnect(
   }
 
   debug('connect: attempting to connect to %s:%d (addressType: %d)', address, port, addressType);
+  self.emit('connectionAttempt', address, port, addressType);
 
   if (addressType === 6 || addressType === 4) {
     const req = new TCPConnectWrap();
@@ -1066,6 +1067,7 @@ function internalConnect(
     req.port = port;
     req.localAddress = localAddress;
     req.localPort = localPort;
+    req.addressType = addressType;
 
     if (addressType === 4)
       err = self._handle.connect(req, address, port);
@@ -1149,6 +1151,7 @@ function internalConnectMultiple(context, canceled) {
   }
 
   debug('connect/multiple: attempting to connect to %s:%d (addressType: %d)', address, port, addressType);
+  self.emit('connectionAttempt', address, port, addressType);
 
   const req = new TCPConnectWrap();
   req.oncomplete = FunctionPrototypeBind(afterConnectMultiple, undefined, context, current);
@@ -1156,6 +1159,7 @@ function internalConnectMultiple(context, canceled) {
   req.port = port;
   req.localAddress = localAddress;
   req.localPort = localPort;
+  req.addressType = addressType;
 
   ArrayPrototypePush(self.autoSelectFamilyAttemptedAddresses, `${address}:${port}`);
 
@@ -1173,7 +1177,10 @@ function internalConnectMultiple(context, canceled) {
       details = sockname.address + ':' + sockname.port;
     }
 
-    ArrayPrototypePush(context.errors, new ExceptionWithHostPort(err, 'connect', address, port, details));
+    const ex = new ExceptionWithHostPort(err, 'connect', address, port, details);
+    ArrayPrototypePush(context.errors, ex);
+
+    self.emit('connectionAttemptFailed', address, port, addressType, ex);
     internalConnectMultiple(context);
     return;
   }
@@ -1601,6 +1608,8 @@ function afterConnect(status, handle, req, readable, writable) {
       ex.localAddress = req.localAddress;
       ex.localPort = req.localPort;
     }
+
+    self.emit('connectionAttemptFailed', req.address, req.port, req.addressType, ex);
     self.destroy(ex);
   }
 }
@@ -1661,10 +1670,16 @@ function afterConnectMultiple(context, current, status, handle, req, readable, w
 
   // Some error occurred, add to the list of exceptions
   if (status !== 0) {
-    ArrayPrototypePush(context.errors, createConnectionError(req, status));
+    const ex = createConnectionError(req, status);
+    ArrayPrototypePush(context.errors, ex);
+
+    self.emit('connectionAttemptFailed', req.address, req.port, req.addressType, ex);
+
+    // Try the next address, unless we were aborted
+    if (context.socket.connecting) {
+      internalConnectMultiple(context, status === UV_ECANCELED);
+    }
 
-    // Try the next address
-    internalConnectMultiple(context, status === UV_ECANCELED);
     return;
   }
 
@@ -1681,10 +1696,16 @@ function afterConnectMultiple(context, current, status, handle, req, readable, w
 
 function internalConnectMultipleTimeout(context, req, handle) {
   debug('connect/multiple: connection to %s:%s timed out', req.address, req.port);
+  context.socket.emit('connectionAttemptTimeout', req.address, req.port, req.addressType);
+
   req.oncomplete = undefined;
   ArrayPrototypePush(context.errors, createConnectionError(req, UV_ETIMEDOUT));
   handle.close();
-  internalConnectMultiple(context);
+
+  // Try the next address, unless we were aborted
+  if (context.socket.connecting) {
+    internalConnectMultiple(context);
+  }
 }
 
 function addServerAbortSignalOption(self, options) {
diff --git a/test/common/dns.js b/test/common/dns.js
index 2ee4bff5182699..578f823684bbf9 100644
--- a/test/common/dns.js
+++ b/test/common/dns.js
@@ -2,6 +2,7 @@
 
 const assert = require('assert');
 const os = require('os');
+const { isIP } = require('net');
 
 const types = {
   A: 1,
@@ -309,6 +310,25 @@ function errorLookupMock(code = mockedErrorCode, syscall = mockedSysCall) {
   };
 }
 
+function createMockedLookup(...addresses) {
+  addresses = addresses.map((address) => ({ address: address, family: isIP(address) }));
+
+  // Create a DNS server which replies with a AAAA and a A record for the same host
+  return function lookup(hostname, options, cb) {
+    if (options.all === true) {
+      process.nextTick(() => {
+        cb(null, addresses);
+      });
+
+      return;
+    }
+
+    process.nextTick(() => {
+      cb(null, addresses[0].address, addresses[0].family);
+    });
+  };
+}
+
 module.exports = {
   types,
   classes,
@@ -317,4 +337,5 @@ module.exports = {
   errorLookupMock,
   mockedErrorCode,
   mockedSysCall,
+  createMockedLookup,
 };
diff --git a/test/internet/test-net-autoselectfamily-events-failure.js b/test/internet/test-net-autoselectfamily-events-failure.js
new file mode 100644
index 00000000000000..a1d1930a9b4907
--- /dev/null
+++ b/test/internet/test-net-autoselectfamily-events-failure.js
@@ -0,0 +1,128 @@
+'use strict';
+
+const common = require('../common');
+const { addresses: { INET6_IP, INET4_IP } } = require('../common/internet');
+const { createMockedLookup } = require('../common/dns');
+
+const assert = require('assert');
+const { createConnection } = require('net');
+
+//
+// When testing this is MacOS, remember that the last connection will have no timeout at Node.js
+// level but only at operating system one.
+//
+// The default for MacOS is 75 seconds. It can be changed by doing:
+//
+// sudo sysctl net.inet.tcp.keepinit=VALUE_IN_MS
+//
+
+// Test that all failure events are emitted when trying a single IP (which means autoselectfamily is bypassed)
+{
+  const pass = common.mustCallAtLeast(1);
+
+  const connection = createConnection({
+    host: 'example.org',
+    port: 10,
+    lookup: createMockedLookup(INET4_IP),
+    autoSelectFamily: true,
+    autoSelectFamilyAttemptTimeout: 10,
+  });
+
+  connection.on('connectionAttempt', (address, port, family) => {
+    assert.strictEqual(address, INET4_IP);
+    assert.strictEqual(port, 10);
+    assert.strictEqual(family, 4);
+
+    pass();
+  });
+
+  connection.on('connectionAttemptFailed', (address, port, family, error) => {
+    assert.strictEqual(address, INET4_IP);
+    assert.strictEqual(port, 10);
+    assert.strictEqual(family, 4);
+
+    assert.ok(
+      error.code.match(/ECONNREFUSED|ENETUNREACH|EHOSTUNREACH|ETIMEDOUT/),
+      `Received unexpected error code ${error.code}`,
+    );
+
+    pass();
+  });
+
+  connection.on('ready', () => {
+    pass();
+    connection.destroy();
+  });
+
+  connection.on('error', () => {
+    pass();
+    connection.destroy();
+  });
+
+  setTimeout(() => {
+    pass();
+    process.exit(0);
+  }, 5000).unref();
+
+}
+
+// Test that all events are emitted when trying multiple IPs
+{
+  const pass = common.mustCallAtLeast(1);
+
+  const connection = createConnection({
+    host: 'example.org',
+    port: 10,
+    lookup: createMockedLookup(INET6_IP, INET4_IP),
+    autoSelectFamily: true,
+    autoSelectFamilyAttemptTimeout: 10,
+  });
+
+  const addresses = [
+    { address: INET6_IP, port: 10, family: 6 },
+    { address: INET6_IP, port: 10, family: 6 },
+    { address: INET4_IP, port: 10, family: 4 },
+    { address: INET4_IP, port: 10, family: 4 },
+  ];
+
+  connection.on('connectionAttempt', (address, port, family) => {
+    const expected = addresses.shift();
+
+    assert.strictEqual(address, expected.address);
+    assert.strictEqual(port, expected.port);
+    assert.strictEqual(family, expected.family);
+
+    pass();
+  });
+
+  connection.on('connectionAttemptFailed', (address, port, family, error) => {
+    const expected = addresses.shift();
+
+    assert.strictEqual(address, expected.address);
+    assert.strictEqual(port, expected.port);
+    assert.strictEqual(family, expected.family);
+
+    assert.ok(
+      error.code.match(/ECONNREFUSED|ENETUNREACH|EHOSTUNREACH|ETIMEDOUT/),
+      `Received unexpected error code ${error.code}`,
+    );
+
+    pass();
+  });
+
+  connection.on('ready', () => {
+    pass();
+    connection.destroy();
+  });
+
+  connection.on('error', () => {
+    pass();
+    connection.destroy();
+  });
+
+  setTimeout(() => {
+    pass();
+    process.exit(0);
+  }, 5000).unref();
+
+}
diff --git a/test/internet/test-net-autoselectfamily-events-timeout.js b/test/internet/test-net-autoselectfamily-events-timeout.js
new file mode 100644
index 00000000000000..5968b68afd037e
--- /dev/null
+++ b/test/internet/test-net-autoselectfamily-events-timeout.js
@@ -0,0 +1,54 @@
+'use strict';
+
+const common = require('../common');
+const { addresses: { INET6_IP, INET4_IP } } = require('../common/internet');
+const { createMockedLookup } = require('../common/dns');
+
+const assert = require('assert');
+const { createConnection } = require('net');
+
+//
+// When testing this is MacOS, remember that the last connection will have no timeout at Node.js
+// level but only at operating system one.
+//
+// The default for MacOS is 75 seconds. It can be changed by doing:
+//
+// sudo sysctl net.inet.tcp.keepinit=VALUE_IN_MS
+//
+// Depending on the network, it might be impossible to obtain a timeout in 10ms,
+// which is the minimum value allowed by network family autoselection.
+// At the time of writing (Dec 2023), the network times out on local machine and in the Node CI,
+// but it does not on GitHub actions runner.
+// Therefore, after five seconds we just consider this test as passed.
+
+// Test that if a connection attempt times out and the socket is destroyed before the
+// next attempt starts then the process does not crash
+{
+  const connection = createConnection({
+    host: 'example.org',
+    port: 443,
+    lookup: createMockedLookup(INET4_IP, INET6_IP),
+    autoSelectFamily: true,
+    autoSelectFamilyAttemptTimeout: 10,
+  });
+
+  const pass = common.mustCall();
+
+  connection.on('connectionAttemptTimeout', (address, port, family) => {
+    assert.strictEqual(address, INET4_IP);
+    assert.strictEqual(port, 443);
+    assert.strictEqual(family, 4);
+    connection.destroy();
+    pass();
+  });
+
+  connection.on('ready', () => {
+    pass();
+    connection.destroy();
+  });
+
+  setTimeout(() => {
+    pass();
+    process.exit(0);
+  }, 5000).unref();
+}
diff --git a/test/internet/test-net-autoselectfamily-timeout-close.js b/test/internet/test-net-autoselectfamily-timeout-close.js
index b93bbc546d24e9..e2d0945cb43b1d 100644
--- a/test/internet/test-net-autoselectfamily-timeout-close.js
+++ b/test/internet/test-net-autoselectfamily-timeout-close.js
@@ -6,6 +6,15 @@ const { addresses } = require('../common/internet');
 const assert = require('assert');
 const { connect } = require('net');
 
+//
+// When testing this is MacOS, remember that the last connection will have no timeout at Node.js
+// level but only at operating system one.
+//
+// The default for MacOS is 75 seconds. It can be changed by doing:
+//
+// sudo sysctl net.inet.tcp.keepinit=VALUE_IN_MS
+//
+
 // Test that when all errors are returned when no connections succeeded and that the close event is emitted
 {
   const connection = connect({
diff --git a/test/parallel/test-net-autoselectfamily-commandline-option.js b/test/parallel/test-net-autoselectfamily-commandline-option.js
index 47ad69566d5c16..bf98d5f756e427 100644
--- a/test/parallel/test-net-autoselectfamily-commandline-option.js
+++ b/test/parallel/test-net-autoselectfamily-commandline-option.js
@@ -3,100 +3,46 @@
 // Flags: --no-network-family-autoselection
 
 const common = require('../common');
-const { parseDNSPacket, writeDNSPacket } = require('../common/dns');
+const { createMockedLookup } = 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.
-
-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 NOT reached if IPV6 is not reachable and the option has been disabled via command line
 {
-  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,
-        lookup,
-      });
+  const ipv4Server = createServer((socket) => {
+    socket.on('data', common.mustCall(() => {
+      socket.write('response-ipv4');
+      socket.end();
+    }));
+  });
 
-      connection.on('ready', common.mustNotCall());
-      connection.on('error', common.mustCall((error) => {
-        assert.strictEqual(connection.autoSelectFamilyAttemptedAddresses, undefined);
+  ipv4Server.listen(0, '127.0.0.1', common.mustCall(() => {
+    const port = ipv4Server.address().port;
 
-        if (common.hasIPv6) {
-          assert.strictEqual(error.code, 'ECONNREFUSED');
-          assert.strictEqual(error.message, `connect ECONNREFUSED ::1:${port}`);
-        } else if (error.code === 'EAFNOSUPPORT') {
-          assert.strictEqual(error.message, `connect EAFNOSUPPORT ::1:${port} - Local (undefined:undefined)`);
-        } else if (error.code === 'EUNATCH') {
-          assert.strictEqual(error.message, `connect EUNATCH ::1:${port} - Local (:::0)`);
-        } else {
-          assert.strictEqual(error.code, 'EADDRNOTAVAIL');
-          assert.strictEqual(error.message, `connect EADDRNOTAVAIL ::1:${port} - Local (:::0)`);
-        }
+    const connection = createConnection({
+      host: 'example.org',
+      port,
+      lookup: createMockedLookup('::1', '127.0.0.1'),
+    });
 
-        ipv4Server.close();
-        dnsServer.close();
-      }));
+    connection.on('ready', common.mustNotCall());
+    connection.on('error', common.mustCall((error) => {
+      assert.strictEqual(connection.autoSelectFamilyAttemptedAddresses, undefined);
+
+      if (common.hasIPv6) {
+        assert.strictEqual(error.code, 'ECONNREFUSED');
+        assert.strictEqual(error.message, `connect ECONNREFUSED ::1:${port}`);
+      } else if (error.code === 'EAFNOSUPPORT') {
+        assert.strictEqual(error.message, `connect EAFNOSUPPORT ::1:${port} - Local (undefined:undefined)`);
+      } else if (error.code === 'EUNATCH') {
+        assert.strictEqual(error.message, `connect EUNATCH ::1:${port} - Local (:::0)`);
+      } else {
+        assert.strictEqual(error.code, 'EADDRNOTAVAIL');
+        assert.strictEqual(error.message, `connect EADDRNOTAVAIL ::1:${port} - Local (:::0)`);
+      }
+
+      ipv4Server.close();
     }));
   }));
 }
diff --git a/test/parallel/test-net-autoselectfamily-default.js b/test/parallel/test-net-autoselectfamily-default.js
index 3fb95a08313c6c..b0b41fb7037d2f 100644
--- a/test/parallel/test-net-autoselectfamily-default.js
+++ b/test/parallel/test-net-autoselectfamily-default.js
@@ -1,140 +1,83 @@
 'use strict';
 
 const common = require('../common');
-const { parseDNSPacket, writeDNSPacket } = require('../common/dns');
+const { createMockedLookup } = require('../common/dns');
 
 const assert = require('assert');
-const dgram = require('dgram');
-const { Resolver } = require('dns');
 const { createConnection, createServer, setDefaultAutoSelectFamily } = require('net');
 
-// Test that the default for happy eyeballs algorithm is properly respected.
-
 const autoSelectFamilyAttemptTimeout = common.defaultAutoSelectFamilyAttemptTimeout;
 
-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 by default if IPV6 is not reachable and the default is enabled
 {
-  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(() => {
-      setDefaultAutoSelectFamily(true);
+  const ipv4Server = createServer((socket) => {
+    socket.on('data', common.mustCall(() => {
+      socket.write('response-ipv4');
+      socket.end();
+    }));
+  });
 
-      const connection = createConnection({
-        host: 'example.org',
-        port: ipv4Server.address().port,
-        lookup,
-        autoSelectFamilyAttemptTimeout,
-      });
+  ipv4Server.listen(0, '127.0.0.1', common.mustCall(() => {
+    setDefaultAutoSelectFamily(true);
 
-      let response = '';
-      connection.setEncoding('utf-8');
+    const connection = createConnection({
+      host: 'example.org',
+      port: ipv4Server.address().port,
+      lookup: createMockedLookup('::1', '127.0.0.1'),
+      autoSelectFamilyAttemptTimeout,
+    });
 
-      connection.on('data', (chunk) => {
-        response += chunk;
-      });
+    let response = '';
+    connection.setEncoding('utf-8');
 
-      connection.on('end', common.mustCall(() => {
-        assert.strictEqual(response, 'response-ipv4');
-        ipv4Server.close();
-        dnsServer.close();
-      }));
+    connection.on('data', (chunk) => {
+      response += chunk;
+    });
 
-      connection.write('request');
+    connection.on('end', common.mustCall(() => {
+      assert.strictEqual(response, 'response-ipv4');
+      ipv4Server.close();
     }));
+
+    connection.write('request');
   }));
 }
 
 // Test that IPV4 is not reached by default if IPV6 is not reachable and the default is disabled
 {
-  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();
-      }));
+  const ipv4Server = createServer((socket) => {
+    socket.on('data', common.mustCall(() => {
+      socket.write('response-ipv4');
+      socket.end();
+    }));
+  });
+
+  ipv4Server.listen(0, '127.0.0.1', common.mustCall(() => {
+    setDefaultAutoSelectFamily(false);
+
+    const port = ipv4Server.address().port;
+
+    const connection = createConnection({
+      host: 'example.org',
+      port,
+      lookup: createMockedLookup('::1', '127.0.0.1'),
     });
 
-    ipv4Server.listen(0, '127.0.0.1', common.mustCall(() => {
-      setDefaultAutoSelectFamily(false);
-
-      const port = ipv4Server.address().port;
-
-      const connection = createConnection({
-        host: 'example.org',
-        port,
-        lookup,
-      });
-
-      connection.on('ready', common.mustNotCall());
-      connection.on('error', common.mustCall((error) => {
-        if (common.hasIPv6) {
-          assert.strictEqual(error.code, 'ECONNREFUSED');
-          assert.strictEqual(error.message, `connect ECONNREFUSED ::1:${port}`);
-        } else if (error.code === 'EAFNOSUPPORT') {
-          assert.strictEqual(error.message, `connect EAFNOSUPPORT ::1:${port} - Local (undefined:undefined)`);
-        } else if (error.code === 'EUNATCH') {
-          assert.strictEqual(error.message, `connect EUNATCH ::1:${port} - Local (:::0)`);
-        } else {
-          assert.strictEqual(error.code, 'EADDRNOTAVAIL');
-          assert.strictEqual(error.message, `connect EADDRNOTAVAIL ::1:${port} - Local (:::0)`);
-        }
-
-        ipv4Server.close();
-        dnsServer.close();
-      }));
+    connection.on('ready', common.mustNotCall());
+    connection.on('error', common.mustCall((error) => {
+      if (common.hasIPv6) {
+        assert.strictEqual(error.code, 'ECONNREFUSED');
+        assert.strictEqual(error.message, `connect ECONNREFUSED ::1:${port}`);
+      } else if (error.code === 'EAFNOSUPPORT') {
+        assert.strictEqual(error.message, `connect EAFNOSUPPORT ::1:${port} - Local (undefined:undefined)`);
+      } else if (error.code === 'EUNATCH') {
+        assert.strictEqual(error.message, `connect EUNATCH ::1:${port} - Local (:::0)`);
+      } else {
+        assert.strictEqual(error.code, 'EADDRNOTAVAIL');
+        assert.strictEqual(error.message, `connect EADDRNOTAVAIL ::1:${port} - Local (:::0)`);
+      }
+
+      ipv4Server.close();
     }));
   }));
 }
diff --git a/test/parallel/test-net-autoselectfamily-ipv4first.js b/test/parallel/test-net-autoselectfamily-ipv4first.js
index 7c2e10213c4d28..f94af0d9eeeb81 100644
--- a/test/parallel/test-net-autoselectfamily-ipv4first.js
+++ b/test/parallel/test-net-autoselectfamily-ipv4first.js
@@ -1,105 +1,52 @@
 'use strict';
 
 const common = require('../common');
-const { parseDNSPacket, writeDNSPacket } = require('../common/dns');
+const { createMockedLookup } = 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 is properly implemented when a A record is returned first.
-
-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 }));
-
-    if (options.all === true) {
-      return cb(null, hosts);
-    }
-
-    return cb(null, hosts[0].address, hosts[0].family);
+if (common.hasIPv6) {
+  const ipv4Server = createServer((socket) => {
+    socket.on('data', common.mustCall(() => {
+      socket.write('response-ipv4');
+      socket.end();
+    }));
   });
-}
-
-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: 'A', address: ipv4Addr, ttl: 123, domain: 'example.org' },
-        { type: 'AAAA', address: ipv6Addr, 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) });
+  const ipv6Server = createServer((socket) => {
+    socket.on('data', common.mustNotCall(() => {
+      socket.write('response-ipv6');
+      socket.end();
+    }));
   });
-}
 
-// Test that IPV6 is NOT reached if IPV4 is sorted first
-if (common.hasIPv6) {
-  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 ipv6Server = createServer((socket) => {
-      socket.on('data', common.mustNotCall(() => {
-        socket.write('response-ipv6');
-        socket.end();
-      }));
-    });
-
-    ipv4Server.listen(0, '127.0.0.1', common.mustCall(() => {
-      const port = ipv4Server.address().port;
-
-      ipv6Server.listen(port, '::1', common.mustCall(() => {
-        const connection = createConnection({
-          host: 'example.org',
-          port,
-          lookup,
-          autoSelectFamily: true,
-        });
+    ipv6Server.listen(port, '::1', common.mustCall(() => {
+      const connection = createConnection({
+        host: 'example.org',
+        port,
+        lookup: createMockedLookup('127.0.0.1', '::1'),
+        autoSelectFamily: true,
+      });
 
-        let response = '';
-        connection.setEncoding('utf-8');
+      let response = '';
+      connection.setEncoding('utf-8');
 
-        connection.on('data', (chunk) => {
-          response += chunk;
-        });
+      connection.on('data', (chunk) => {
+        response += chunk;
+      });
 
-        connection.on('end', common.mustCall(() => {
-          assert.strictEqual(response, 'response-ipv4');
-          ipv4Server.close();
-          ipv6Server.close();
-          dnsServer.close();
-        }));
-
-        connection.write('request');
+      connection.on('end', common.mustCall(() => {
+        assert.strictEqual(response, 'response-ipv4');
+        ipv4Server.close();
+        ipv6Server.close();
       }));
+
+      connection.write('request');
     }));
   }));
 }
diff --git a/test/parallel/test-net-autoselectfamily.js b/test/parallel/test-net-autoselectfamily.js
index f4b696fd192828..180ec9073eac89 100644
--- a/test/parallel/test-net-autoselectfamily.js
+++ b/test/parallel/test-net-autoselectfamily.js
@@ -1,93 +1,136 @@
 'use strict';
 
 const common = require('../common');
-const { parseDNSPacket, writeDNSPacket } = require('../common/dns');
+const { createMockedLookup } = 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 is properly implemented.
 
 // Purposely not using setDefaultAutoSelectFamilyAttemptTimeout here to test the
 // parameter is correctly used in options.
-//
+
 // Some of the machines in the CI need more time to establish connection
 const autoSelectFamilyAttemptTimeout = common.defaultAutoSelectFamilyAttemptTimeout;
 
-function _lookup(resolver, hostname, options, cb) {
-  resolver.resolve(hostname, 'ANY', (err, replies) => {
-    assert.notStrictEqual(options.family, 4);
+// Test that IPV4 is reached if IPV6 is not reachable
+{
+  const ipv4Server = createServer((socket) => {
+    socket.on('data', common.mustCall(() => {
+      socket.write('response-ipv4');
+      socket.end();
+    }));
+  });
 
-    if (err) {
-      return cb(err);
-    }
+  ipv4Server.listen(0, '127.0.0.1', common.mustCall(() => {
+    const port = ipv4Server.address().port;
 
-    const hosts = replies
-      .map((r) => ({ address: r.address, family: r.type === 'AAAA' ? 6 : 4 }))
-      .sort((a, b) => b.family - a.family);
+    const connection = createConnection({
+      host: 'example.org',
+      port: port,
+      lookup: createMockedLookup('::1', '127.0.0.1'),
+      autoSelectFamily: true,
+      autoSelectFamilyAttemptTimeout,
+    });
 
-    if (options.all === true) {
-      return cb(null, hosts);
-    }
+    let response = '';
+    connection.setEncoding('utf-8');
 
-    return cb(null, hosts[0].address, hosts[0].family);
-  });
-}
+    connection.on('ready', common.mustCall(() => {
+      assert.deepStrictEqual(connection.autoSelectFamilyAttemptedAddresses, [`::1:${port}`, `127.0.0.1:${port}`]);
+    }));
 
-function createDnsServer(ipv6Addrs, ipv4Addrs, cb) {
-  if (!Array.isArray(ipv6Addrs)) {
-    ipv6Addrs = [ipv6Addrs];
-  }
-
-  if (!Array.isArray(ipv4Addrs)) {
-    ipv4Addrs = [ipv4Addrs];
-  }
-
-  // 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: [
-        ...ipv6Addrs.map((address) => ({ type: 'AAAA', address, ttl: 123, domain: 'example.org' })),
-        ...ipv4Addrs.map((address) => ({ type: 'A', address, ttl: 123, domain: 'example.org' })),
-      ]
-    }), port, address);
-  }));
+    connection.on('data', (chunk) => {
+      response += chunk;
+    });
 
-  socket.bind(0, () => {
-    const resolver = new Resolver();
-    resolver.setServers([`127.0.0.1:${socket.address().port}`]);
+    connection.on('end', common.mustCall(() => {
+      assert.strictEqual(response, 'response-ipv4');
+      ipv4Server.close();
+    }));
 
-    cb({ dnsServer: socket, lookup: _lookup.bind(null, resolver) });
-  });
+    connection.write('request');
+  }));
 }
 
-// Test that IPV4 is reached if IPV6 is not reachable
+// Test that only the last successful connection is established.
 {
-  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();
-      }));
+  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: createMockedLookup(
+        '2606:4700::6810:85e5', '2606:4700::6810:84e5', '::1',
+        '104.20.22.46', '104.20.23.46', '127.0.0.1',
+      ),
+      autoSelectFamily: true,
+      autoSelectFamilyAttemptTimeout,
+    });
+
+    let response = '';
+    connection.setEncoding('utf-8');
+
+    connection.on('ready', common.mustCall(() => {
+      assert.deepStrictEqual(
+        connection.autoSelectFamilyAttemptedAddresses,
+        [
+          `2606:4700::6810:85e5:${port}`,
+          `104.20.22.46:${port}`,
+          `2606:4700::6810:84e5:${port}`,
+          `104.20.23.46:${port}`,
+          `::1:${port}`,
+          `127.0.0.1:${port}`,
+        ]
+      );
+    }));
+
+    connection.on('data', (chunk) => {
+      response += chunk;
     });
 
-    ipv4Server.listen(0, '127.0.0.1', common.mustCall(() => {
-      const port = ipv4Server.address().port;
+    connection.on('end', common.mustCall(() => {
+      assert.strictEqual(response, 'response-ipv4');
+      ipv4Server.close();
+    }));
+
+    connection.write('request');
+  }));
+}
+
+// Test that IPV4 is NOT reached if IPV6 is reachable
+if (common.hasIPv6) {
+  const ipv4Server = createServer((socket) => {
+    socket.on('data', common.mustNotCall(() => {
+      socket.write('response-ipv4');
+      socket.end();
+    }));
+  });
+
+  const ipv6Server = createServer((socket) => {
+    socket.on('data', common.mustCall(() => {
+      socket.write('response-ipv6');
+      socket.end();
+    }));
+  });
+
+  ipv4Server.listen(0, '127.0.0.1', common.mustCall(() => {
+    const port = ipv4Server.address().port;
 
+    ipv6Server.listen(port, '::1', common.mustCall(() => {
       const connection = createConnection({
         host: 'example.org',
-        port: port,
-        lookup,
+        port,
+        lookup: createMockedLookup('::1', '127.0.0.1'),
         autoSelectFamily: true,
         autoSelectFamilyAttemptTimeout,
       });
@@ -96,7 +139,7 @@ function createDnsServer(ipv6Addrs, ipv4Addrs, cb) {
       connection.setEncoding('utf-8');
 
       connection.on('ready', common.mustCall(() => {
-        assert.deepStrictEqual(connection.autoSelectFamilyAttemptedAddresses, [`::1:${port}`, `127.0.0.1:${port}`]);
+        assert.deepStrictEqual(connection.autoSelectFamilyAttemptedAddresses, [`::1:${port}`]);
       }));
 
       connection.on('data', (chunk) => {
@@ -104,9 +147,9 @@ function createDnsServer(ipv6Addrs, ipv4Addrs, cb) {
       });
 
       connection.on('end', common.mustCall(() => {
-        assert.strictEqual(response, 'response-ipv4');
+        assert.strictEqual(response, 'response-ipv6');
         ipv4Server.close();
-        dnsServer.close();
+        ipv6Server.close();
       }));
 
       connection.write('request');
@@ -114,184 +157,67 @@ function createDnsServer(ipv6Addrs, ipv4Addrs, cb) {
   }));
 }
 
-// Test that only the last successful connection is established.
+// Test that when all errors are returned when no connections succeeded
 {
-  createDnsServer(
-    ['2606:4700::6810:85e5', '2606:4700::6810:84e5', '::1'],
-    ['104.20.22.46', '104.20.23.46', '127.0.0.1'],
-    common.mustCall(function({ dnsServer, lookup }) {
-      const ipv4Server = createServer((socket) => {
-        socket.on('data', common.mustCall(() => {
-          socket.write('response-ipv4');
-          socket.end();
-        }));
-      });
+  const connection = createConnection({
+    host: 'example.org',
+    port: 10,
+    lookup: createMockedLookup('::1', '127.0.0.1'),
+    autoSelectFamily: true,
+    autoSelectFamilyAttemptTimeout,
+  });
 
-      ipv4Server.listen(0, '127.0.0.1', common.mustCall(() => {
-        const port = ipv4Server.address().port;
-
-        const connection = createConnection({
-          host: 'example.org',
-          port: port,
-          lookup,
-          autoSelectFamily: true,
-          autoSelectFamilyAttemptTimeout,
-        });
-
-        let response = '';
-        connection.setEncoding('utf-8');
-
-        connection.on('ready', common.mustCall(() => {
-          assert.deepStrictEqual(
-            connection.autoSelectFamilyAttemptedAddresses,
-            [
-              `2606:4700::6810:85e5:${port}`,
-              `104.20.22.46:${port}`,
-              `2606:4700::6810:84e5:${port}`,
-              `104.20.23.46:${port}`,
-              `::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');
-      }));
-    })
-  );
-}
+  connection.on('ready', common.mustNotCall());
+  connection.on('error', common.mustCall((error) => {
+    assert.deepStrictEqual(connection.autoSelectFamilyAttemptedAddresses, ['::1:10', '127.0.0.1:10']);
+    assert.strictEqual(error.constructor.name, 'AggregateError');
+    assert.strictEqual(error.errors.length, 2);
 
-// Test that IPV4 is NOT reached if IPV6 is reachable
-if (common.hasIPv6) {
-  createDnsServer('::1', '127.0.0.1', common.mustCall(function({ dnsServer, lookup }) {
-    const ipv4Server = createServer((socket) => {
-      socket.on('data', common.mustNotCall(() => {
-        socket.write('response-ipv4');
-        socket.end();
-      }));
-    });
-
-    const ipv6Server = createServer((socket) => {
-      socket.on('data', common.mustCall(() => {
-        socket.write('response-ipv6');
-        socket.end();
-      }));
-    });
+    const errors = error.errors.map((e) => e.message);
+    assert.ok(errors.includes('connect ECONNREFUSED 127.0.0.1:10'));
 
-    ipv4Server.listen(0, '127.0.0.1', common.mustCall(() => {
-      const port = ipv4Server.address().port;
-
-      ipv6Server.listen(port, '::1', common.mustCall(() => {
-        const connection = createConnection({
-          host: 'example.org',
-          port,
-          lookup,
-          autoSelectFamily: true,
-          autoSelectFamilyAttemptTimeout,
-        });
-
-        let response = '';
-        connection.setEncoding('utf-8');
-
-        connection.on('ready', common.mustCall(() => {
-          assert.deepStrictEqual(connection.autoSelectFamilyAttemptedAddresses, [`::1:${port}`]);
-        }));
-
-        connection.on('data', (chunk) => {
-          response += chunk;
-        });
-
-        connection.on('end', common.mustCall(() => {
-          assert.strictEqual(response, 'response-ipv6');
-          ipv4Server.close();
-          ipv6Server.close();
-          dnsServer.close();
-        }));
-
-        connection.write('request');
-      }));
-    }));
+    if (common.hasIPv6) {
+      assert.ok(errors.includes('connect ECONNREFUSED ::1:10'));
+    }
   }));
 }
 
-// Test that when all errors are returned when no connections succeeded
+// Test that the option can be disabled
 {
-  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: 10,
-      lookup,
-      autoSelectFamily: true,
-      autoSelectFamilyAttemptTimeout,
+      port,
+      lookup: createMockedLookup('::1', '127.0.0.1'),
+      autoSelectFamily: false,
     });
 
     connection.on('ready', common.mustNotCall());
     connection.on('error', common.mustCall((error) => {
-      assert.deepStrictEqual(connection.autoSelectFamilyAttemptedAddresses, ['::1:10', '127.0.0.1:10']);
-      assert.strictEqual(error.constructor.name, 'AggregateError');
-      assert.strictEqual(error.errors.length, 2);
-
-      const errors = error.errors.map((e) => e.message);
-      assert.ok(errors.includes('connect ECONNREFUSED 127.0.0.1:10'));
+      assert.strictEqual(connection.autoSelectFamilyAttemptedAddresses, undefined);
 
       if (common.hasIPv6) {
-        assert.ok(errors.includes('connect ECONNREFUSED ::1:10'));
+        assert.strictEqual(error.code, 'ECONNREFUSED');
+        assert.strictEqual(error.message, `connect ECONNREFUSED ::1:${port}`);
+      } else if (error.code === 'EAFNOSUPPORT') {
+        assert.strictEqual(error.message, `connect EAFNOSUPPORT ::1:${port} - Local (undefined:undefined)`);
+      } else if (error.code === 'EUNATCH') {
+        assert.strictEqual(error.message, `connect EUNATCH ::1:${port} - Local (:::0)`);
+      } else {
+        assert.strictEqual(error.code, 'EADDRNOTAVAIL');
+        assert.strictEqual(error.message, `connect EADDRNOTAVAIL ::1:${port} - Local (:::0)`);
       }
 
-      dnsServer.close();
-    }));
-  }));
-}
-
-// Test that the option can be disabled
-{
-  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,
-        lookup,
-        autoSelectFamily: false,
-      });
-
-      connection.on('ready', common.mustNotCall());
-      connection.on('error', common.mustCall((error) => {
-        assert.strictEqual(connection.autoSelectFamilyAttemptedAddresses, undefined);
-
-        if (common.hasIPv6) {
-          assert.strictEqual(error.code, 'ECONNREFUSED');
-          assert.strictEqual(error.message, `connect ECONNREFUSED ::1:${port}`);
-        } else if (error.code === 'EAFNOSUPPORT') {
-          assert.strictEqual(error.message, `connect EAFNOSUPPORT ::1:${port} - Local (undefined:undefined)`);
-        } else if (error.code === 'EUNATCH') {
-          assert.strictEqual(error.message, `connect EUNATCH ::1:${port} - Local (:::0)`);
-        } else {
-          assert.strictEqual(error.code, 'EADDRNOTAVAIL');
-          assert.strictEqual(error.message, `connect EADDRNOTAVAIL ::1:${port} - Local (:::0)`);
-        }
-
-        ipv4Server.close();
-        dnsServer.close();
-      }));
+      ipv4Server.close();
     }));
   }));
 }