/*
 * Copyright (c) 1998, 2010, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package sun.net;


public final class InetAddressCachePolicy {

    // Controls the cache policy for successful lookups only
    private static final String cachePolicyProp = "networkaddress.cache.ttl";
    private static final String cachePolicyPropFallback =
        "sun.net.inetaddr.ttl";

    // Controls the cache policy for negative lookups only
    private static final String negativeCachePolicyProp =
        "networkaddress.cache.negative.ttl";
    private static final String negativeCachePolicyPropFallback =
        "sun.net.inetaddr.negative.ttl";

    public static final int FOREVER = -1;
    public static final int NEVER = 0;

    /* default value for positive lookups */
    public static final int DEFAULT_POSITIVE = 30;

    /* The Java-level namelookup cache policy for successful lookups:
     *
     * -1: caching forever
     * any positive value: the number of seconds to cache an address for
     *
     * default value is forever (FOREVER), as we let the platform do the
     * caching. For security reasons, this caching is made forever when
     * a security manager is set.
     */
    private static int cachePolicy = FOREVER;

    /* The Java-level namelookup cache policy for negative lookups:
     *
     * -1: caching forever
     * any positive value: the number of seconds to cache an address for
     *
     * default value is 0. It can be set to some other value for
     * performance reasons.
     */
    private static int negativeCachePolicy = NEVER;

    /*
     * Whether or not the cache policy for successful lookups was set
     * using a property (cmd line).
     */
    private static boolean propertySet;

    /*
     * Whether or not the cache policy for negative lookups was set
     * using a property (cmd line).
     */
    private static boolean propertyNegativeSet;

    /*
     * Initialize
     */
    static {

        /* NANITE: Security is not supported */
        cachePolicy = DEFAULT_POSITIVE;
        propertySet = false;
        negativeCachePolicy = FOREVER;
        propertyNegativeSet = true;

    }

    public static synchronized int get() {
        return cachePolicy;
    }

    public static synchronized int getNegative() {
        return negativeCachePolicy;
    }

    /**
     * Sets the cache policy for successful lookups if the user has not
     * already specified a cache policy for it using a
     * command-property.
     * @param newPolicy the value in seconds for how long the lookup
     * should be cached
     */
    public static synchronized void setIfNotSet(int newPolicy) {
        /*
         * When setting the new value we may want to signal that the
         * cache should be flushed, though this doesn't seem strictly
         * necessary.
         */
        if (!propertySet) {
            checkValue(newPolicy, cachePolicy);
            cachePolicy = newPolicy;
        }
    }

    /**
     * Sets the cache policy for negative lookups if the user has not
     * already specified a cache policy for it using a
     * command-property.
     * @param newPolicy the value in seconds for how long the lookup
     * should be cached
     */
    public static synchronized void setNegativeIfNotSet(int newPolicy) {
        /*
         * When setting the new value we may want to signal that the
         * cache should be flushed, though this doesn't seem strictly
         * necessary.
         */
        if (!propertyNegativeSet) {
            // Negative caching does not seem to have any security
            // implications.
            // checkValue(newPolicy, negativeCachePolicy);
            negativeCachePolicy = newPolicy;
        }
    }

    private static void checkValue(int newPolicy, int oldPolicy) {
        /*
         * If malicious code gets a hold of this method, prevent
         * setting the cache policy to something laxer or some
         * invalid negative value.
         */
        if (newPolicy == FOREVER)
            return;

        if ((oldPolicy == FOREVER) ||
            (newPolicy < oldPolicy) ||
            (newPolicy < FOREVER)) {

            throw new
                SecurityException("can't make InetAddress cache more lax");
        }
    }
}
