[NaCl SDK] nacl_io: Auto-bind UDP socket on first sendto().

native_client_sdk/src/libraries/nacl_io/mount_node_socket.cc

Index: native_client_sdk/src/libraries/nacl_io/mount_node_socket.cc
diff --git a/native_client_sdk/src/libraries/nacl_io/mount_node_socket.cc b/native_client_sdk/src/libraries/nacl_io/mount_node_socket.cc
index 1d8ac375d88004d53f1f5b9ad38593e155949c09..f5c20c1b0a5092cb1d370db4f7415a16bb9b892f 100644
--- a/native_client_sdk/src/libraries/nacl_io/mount_node_socket.cc
+++ b/native_client_sdk/src/libraries/nacl_io/mount_node_socket.cc
@@ -462,12 +462,15 @@ Error MountNodeSocket::GetSockName(struct sockaddr* addr, socklen_t* len) {
     return EFAULT;
 
   AUTO_LOCK(node_lock_);
-  if (local_addr_ != 0) {
-    *len = ResourceToSockAddr(local_addr_, *len, addr);
+  if (local_addr_ == 0) {
+    // getsockname succeeds even if the socket is not bound. In this case,
+    // just return address 0, port 0.
+    memset(addr, 0, *len);
     return 0;
   }
 
-  return ENOTCONN;
+  *len = ResourceToSockAddr(local_addr_, *len, addr);
+  return 0;
 }
 
 }  // namespace nacl_io