dns: accept 'IPv4' and 'IPv6' as valid family values

Refs: nodejs#43014

doc/api/dns.md

@@ -179,6 +179,10 @@ section if a custom port is used.
 <!-- YAML
 added: v0.1.90
 changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/00000
+    description: For compatibility with `node:net`, when passing an option
+                 object the `family` option can be a string.
   - version: v18.0.0
     pr-url: https://github.com/nodejs/node/pull/41678
     description: Passing an invalid callback to the `callback` argument
@@ -197,7 +201,8 @@ changes:
 
 * `hostname` {string}
 * `options` {integer | Object}
-  * `family` {integer} The record family. Must be `4`, `6`, or `0`. The value
+  * `family` {integer|string} The record family. Must be `4`, `6`, or `0`.
+    `'IPv4'` is interpreted as `4`, and `'IPv6'` is interpreted as `6`. The value
     `0` indicates that IPv4 and IPv6 addresses are both returned. **Default:**
     `0`.
   * `hints` {number} One or more [supported `getaddrinfo` flags][]. Multiple

lib/dns.js

@@ -140,8 +140,18 @@ function lookup(hostname, options, callback) {
       validateHints(hints);
     }
     if (options?.family != null) {
-      validateOneOf(options.family, 'options.family', validFamilies, true);
-      family = options.family;
+      switch (options.family){
+        case 'IPv4':
+          family = 4;
+          break;
+        case 'IPv6':
+          family = 6;
+          break;
+        default:
+          validateOneOf(options.family, 'options.family', validFamilies, true);
+          family = options.family;
+          break;
+      }
     }
     if (options?.all != null) {
       validateBoolean(options.all, 'options.all');

test/internet/test-dns-lookup.js

@@ -47,7 +47,7 @@ dns.lookup(addresses.NOT_FOUND, {
 
 assert.throws(
   () => dnsPromises.lookup(addresses.NOT_FOUND, {
-    family: 'IPv4',
+    family: 'ipv4',
     all: 'all'
   }),
   { code: 'ERR_INVALID_ARG_VALUE' }