net: added connection attempt events

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.

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);
@@ -1149,13 +1151,15 @@ 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);
   req.address = address;
   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) {

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,
 };

test/internet/test-net-autoselectfamily-events.js

@@ -0,0 +1,96 @@
+'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');
+
+// Test that all events are emitted when trying a single IP (which means autoselectfamily is bypassed)
+{
+  const connection = createConnection({
+    host: 'example.org',
+    port: 10,
+    lookup: createMockedLookup(INET4_IP),
+    autoSelectFamily: true,
+    autoSelectFamilyAttemptTimeout: 10,
+  });
+
+  connection.on('connectionAttempt', common.mustCall((address, port, family) => {
+    assert.strictEqual(address, INET4_IP);
+    assert.strictEqual(port, 10);
+    assert.strictEqual(family, 4);
+  }));
+
+  connection.on('connectionAttemptFailed', common.mustCall((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/));
+  }));
+
+  connection.on('ready', common.mustNotCall());
+  connection.on('error', common.mustCall());
+}
+
+// Test that all events are emitted when trying multiple IPs
+{
+  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', common.mustCall((address, port, family) => {
+    const expected = addresses.shift();
+
+    assert.strictEqual(address, expected.address);
+    assert.strictEqual(port, expected.port);
+    assert.strictEqual(family, expected.family);
+  }, 2));
+
+  connection.on('connectionAttemptFailed', common.mustCall((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|EHOSTUNREACH|ETIMEDOUT/), `Received unexpected error code ${error.code}`);
+  }, 2));
+
+  connection.on('ready', common.mustNotCall());
+  connection.on('error', common.mustCall());
+}
+
+// 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,
+  });
+
+  connection.on('connectionAttemptTimeout', common.mustCall((address, port, family) => {
+    assert.strictEqual(address, INET4_IP);
+    assert.strictEqual(port, 443);
+    assert.strictEqual(family, 4);
+    connection.destroy();
+  }));
+
+  connection.on('ready', common.mustNotCall());
+}

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({