fix: prefer IPv4 addresses when resolving domains

Node 17+ changed the DNS resolution (see nodejs/node#40702), so now it resolves `localhost` according to the OS settings instead of IPv4-address first. The Karma server only listens on IPv4 address (127.0.0.1) by default, but the requests are sent to `localhost` in several places and `localhost` is resolved into IPv6 address (`::`) in Node 17+. So the run/stop/proxy request is unable to reach the Karma server and produces an error. This commit configures karma to use the IPv4-address first approach in newer Node version as well.

In the future major release, we may consider changing defaults to listen on IPv6 address instead, but IPv6 is not supported in Docker on macOS and Windows, so I think we should not rush such a change to make sure karma works there out of the box.

Fixes karma-runner#3730

lib/middleware/proxy.js

@@ -3,6 +3,7 @@ const { Agent: httpAgent } = require('http')
 const { Agent: httpsAgent } = require('https')
 const httpProxy = require('http-proxy')
 const _ = require('lodash')
+const { lookup } = require('../utils/dns-utils')
 
 const log = require('../logger').create('proxy')
 
@@ -41,7 +42,10 @@ function parseProxyConfig (proxies, config) {
     const port = proxyDetails.port || defaultPorts[proxyDetails.protocol] || config.port
     const changeOrigin = proxyConfiguration.changeOrigin || false
     const Agent = protocol === 'https:' ? httpsAgent : httpAgent
-    const agent = new Agent({ keepAlive: true })
+    const agent = new Agent({
+      keepAlive: true,
+      lookup
+    })
     const proxy = httpProxy.createProxyServer({
       target: { host: hostname, port, protocol },
       xfwd: true,

lib/runner.js

@@ -7,6 +7,7 @@ const EventEmitter = require('events').EventEmitter
 const helper = require('./helper')
 const cfg = require('./config')
 const logger = require('./logger')
+const { lookup } = require('./utils/dns-utils')
 const log = logger.create('runner')
 
 function parseExitCode (buffer, defaultExitCode, failOnEmptyTestSuite) {
@@ -74,7 +75,8 @@ function run (cliOptionsOrConfig, done) {
     method: 'POST',
     headers: {
       'Content-Type': 'application/json'
-    }
+    },
+    lookup
   }
 
   const request = http.request(options, function (response) {

lib/stopper.js

@@ -2,6 +2,7 @@ const http = require('http')
 const cfg = require('./config')
 const logger = require('./logger')
 const helper = require('./helper')
+const { lookup } = require('./utils/dns-utils')
 
 exports.stop = function (cliOptionsOrConfig, done) {
   cliOptionsOrConfig = cliOptionsOrConfig || {}
@@ -42,7 +43,8 @@ exports.stop = function (cliOptionsOrConfig, done) {
     hostname: config.hostname,
     path: config.urlRoot + 'stop',
     port: config.port,
-    method: 'GET'
+    method: 'GET',
+    lookup
   })
 
   request.on('response', function (response) {

lib/utils/dns-utils.js

@@ -0,0 +1,11 @@
+const dns = require('dns')
+
+// Node >=17 has different DNS resolution (see
+// https://github.com/nodejs/node/issues/40702), it resolves domains
+// according to the OS settings instead of IPv4-address first. The Karma server
+// only listens on IPv4 address (127.0.0.1) by default, but the requests are
+// sent to `localhost` in several places and `localhost` is resolved into IPv6
+// address (`::`). So the run/stop/proxy request is unable to reach the Karma
+// server and produces an error. To mitigate this issue karma force the
+// IPv4-address first approach in Node >=17 as well.
+module.exports.lookup = (hostname, options, callback) => dns.lookup(hostname, { ...options, verbatim: false }, callback)

test/e2e/support/proxy.js

@@ -8,7 +8,7 @@ module.exports = class Proxy {
     this.proxyPathRegExp = null
 
     this.proxy = httpProxy.createProxyServer({
-      target: 'http://localhost:9876'
+      target: 'http://127.0.0.1:9876'
     })
 
     this.proxy.on('error', (err) => {