1 /*
   2  * Copyright (c) 2011, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.  Oracle designates this
   8  * particular file as subject to the "Classpath" exception as provided
   9  * by Oracle in the LICENSE file that accompanied this code.
  10  *
  11  * This code is distributed in the hope that it will be useful, but WITHOUT
  12  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  13  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  14  * version 2 for more details (a copy is included in the LICENSE file that
  15  * accompanied this code).
  16  *
  17  * You should have received a copy of the GNU General Public License version
  18  * 2 along with this work; if not, write to the Free Software Foundation,
  19  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  20  *
  21  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  22  * or visit www.oracle.com if you need additional information or have any
  23  * questions.
  24  */
  25 
  26 package sun.net;
  27 
  28 import java.net.SocketException;
  29 import java.util.concurrent.atomic.AtomicInteger;
  30 import sun.security.action.GetPropertyAction;
  31 
  32 /**
  33  * Manages count of total number of UDP sockets and ensures
  34  * that exception is thrown if we try to create more than the
  35  * configured limit.
  36  *
  37  * This functionality could be put in NetHooks some time in future.
  38  */
  39 
  40 public class ResourceManager {
  41 
  42     /* default maximum number of udp sockets per VM
  43      * when a security manager is enabled.
  44      * The default is 25 which is high enough to be useful
  45      * but low enough to be well below the maximum number
  46      * of port numbers actually available on all OSes
  47      * when multiplied by the maximum feasible number of VM processes
  48      * that could practically be spawned.
  49      */
  50 
  51     private static final int DEFAULT_MAX_SOCKETS = 25;
  52     private static final int maxSockets;
  53     private static final AtomicInteger numSockets;
  54 
  55     static {
  56         String prop = java.security.AccessController.doPrivileged(
  57             new GetPropertyAction("sun.net.maxDatagramSockets")
  58         );
  59         int defmax = DEFAULT_MAX_SOCKETS;
  60         try {
  61             if (prop != null) {
  62                 defmax = Integer.parseInt(prop);
  63             }
  64         } catch (NumberFormatException e) {}
  65         maxSockets = defmax;
  66         numSockets = new AtomicInteger(0);
  67     }
  68 
  69     public static void beforeUdpCreate() throws SocketException {
  70         if (System.getSecurityManager() != null) {
  71             if (numSockets.incrementAndGet() > maxSockets) {
  72                 numSockets.decrementAndGet();
  73                 throw new SocketException("maximum number of DatagramSockets reached");
  74             }
  75         }
  76     }
  77 
  78     public static void afterUdpClose() {
  79         if (System.getSecurityManager() != null) {
  80             numSockets.decrementAndGet();
  81         }
  82     }
  83 }