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      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 }
     84