net: emit error on invalid address family

This commit adds proper error handling to net.connect() when
a custom lookup() function returns an invalid address family.

PR-URL: nodejs#19415
Fixes: nodejs#19407
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Santiago Gimeno <santiago.gimeno@gmail.com>
Reviewed-By: Michaël Zasso <targos@protonmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Khaidi Chu <i@2333.moe>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/errors.md

@@ -973,6 +973,11 @@ The `inspector` module is not available for use.
 While using the `inspector` module, an attempt was made to use the inspector
 before it was connected.
 
+<a id="ERR_INVALID_ADDRESS_FAMILY"></a>
+### ERR_INVALID_ADDRESS_FAMILY
+
+The provided address family is not understood by the Node.js API.
+
 <a id="ERR_INVALID_ARG_TYPE"></a>
 ### ERR_INVALID_ARG_TYPE
 

lib/internal/errors.js

@@ -623,6 +623,7 @@ E('ERR_INSPECTOR_ALREADY_CONNECTED',
 E('ERR_INSPECTOR_CLOSED', 'Session was closed', Error);
 E('ERR_INSPECTOR_NOT_AVAILABLE', 'Inspector is not available', Error);
 E('ERR_INSPECTOR_NOT_CONNECTED', 'Session is not connected', Error);
+E('ERR_INVALID_ADDRESS_FAMILY', 'Invalid address family: %s', RangeError);
 E('ERR_INVALID_ARG_TYPE', invalidArgType, TypeError);
 E('ERR_INVALID_ARG_VALUE', (name, value, reason = 'is invalid') => {
   const util = lazyUtil();

lib/net.js

@@ -50,6 +50,9 @@ const { async_id_symbol } = process.binding('async_wrap');
 const { newUid, defaultTriggerAsyncIdScope } = require('internal/async_hooks');
 const { nextTick } = require('internal/process/next_tick');
 const errors = require('internal/errors');
+const {
+  ERR_INVALID_ADDRESS_FAMILY
+} = errors.codes;
 const dns = require('dns');
 
 const kLastWriteQueueSize = Symbol('lastWriteQueueSize');
@@ -1093,6 +1096,12 @@ function lookupAndConnect(self, options) {
         err.port = options.port;
         err.message = err.message + ' ' + options.host + ':' + options.port;
         process.nextTick(connectErrorNT, self, err);
+      } else if (addressType !== 4 && addressType !== 6) {
+        err = new ERR_INVALID_ADDRESS_FAMILY(addressType);
+        err.host = options.host;
+        err.port = options.port;
+        err.message = err.message + ' ' + options.host + ':' + options.port;
+        process.nextTick(connectErrorNT, self, err);
       } else {
         self._unrefTimer();
         defaultTriggerAsyncIdScope(

test/parallel/test-net-options-lookup.js

@@ -29,5 +29,14 @@ function connectDoesNotThrow(input) {
     lookup: input
   };
 
-  net.connect(opts);
+  return net.connect(opts);
+}
+
+{
+  // Verify that an error is emitted when an invalid address family is returned.
+  const s = connectDoesNotThrow((host, options, cb) => {
+    cb(null, '127.0.0.1', 100);
+  });
+
+  s.on('error', common.expectsError({ code: 'ERR_INVALID_ADDRESS_FAMILY' }));
 }