test: cover cluster error during dgram socket bind

When a non-exclusive dgram socket is bound from a cluster
worker, a handle is requested from the cluster module. This
commit adds coverage for the case where an error occurs while
retrieving the handle.

PR-URL: #11295
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-dgram-cluster-bind-error.js

@@ -0,0 +1,29 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const cluster = require('cluster');
+const dgram = require('dgram');
+const { UV_UNKNOWN } = process.binding('uv');
+
+if (cluster.isMaster) {
+  cluster.fork();
+} else {
+  // When the socket attempts to bind, it requests a handle from the cluster.
+  // Force the cluster to send back an error code.
+  cluster._getServer = function(self, options, callback) {
+    callback(UV_UNKNOWN);
+  };
+
+  const socket = dgram.createSocket('udp4');
+
+  socket.on('error', common.mustCall((err) => {
+    assert(/^Error: bind UNKNOWN 0.0.0.0$/.test(err.toString()));
+    process.nextTick(common.mustCall(() => {
+      assert.strictEqual(socket._bindState, 0); // BIND_STATE_UNBOUND
+      socket.close();
+      cluster.worker.disconnect();
+    }));
+  }));
+
+  socket.bind(common.mustNotCall('Socket should not bind.'));
+}