cluster: propagate bind errors

This commit fixes a bug where the cluster module fails to propagate
EADDRINUSE errors.

When a worker starts a (net, http) server, it requests the listen socket
from its master who then creates and binds the socket.

Now, OS X and Windows don't always signal EADDRINUSE from bind() but
instead defer the error until a later syscall. libuv mimics this
behaviour to provide consistent behaviour across platforms but that
means the worker could end up with a socket that is not actually bound
to the requested addresss.

That's why the worker now checks if the socket is bound, raising
EADDRINUSE if that's not the case.

Fixes #2721.

1 files changed, 18 insertions, 6 deletions

diff --git a/lib/net.js b/lib/net.js
index c8d7f60913..38985214d6 100644
--- a/lib/net.js
+++ b/lib/net.js
@@ -928,14 +928,26 @@ Server.prototype._listen2 = function(address, port, addressType, backlog, fd) {
 function listen(self, address, port, addressType, backlog, fd) {
   if (!cluster) cluster = require('cluster');
 
-  if (cluster.isWorker) {
-    cluster._getServer(self, address, port, addressType, fd, function(handle) {
-      self._handle = handle;
-      self._listen2(address, port, addressType, backlog, fd);
-    });
-  } else {
+  if (cluster.isMaster) {
     self._listen2(address, port, addressType, backlog, fd);
+    return;
   }
+
+  cluster._getServer(self, address, port, addressType, fd, function(handle) {
+    // Some operating systems (notably OS X and Solaris) don't report EADDRINUSE
+    // errors right away. libuv mimics that behavior for the sake of platform
+    // consistency but that means we have have a socket on our hands that is
+    // not actually bound. That's why we check if the actual port matches what
+    // we requested and if not, raise an error. The exception is when port == 0
+    // because that means "any random port".
+    if (port && handle.getsockname && port != handle.getsockname().port) {
+      self.emit('error', errnoException('EADDRINUSE', 'bind'));
+      return;
+    }
+
+    self._handle = handle;
+    self._listen2(address, port, addressType, backlog, fd);
+  });
 }