src/java.base/unix/native/libnet/portconfig.c

/*
 * Copyright (c) 2013, 2020, 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.
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>

#if defined(_ALLBSD_SOURCE)
#include <sys/sysctl.h>
#endif

#include "jni.h"
#include "net_util.h"
#include "sun_net_PortConfig.h"

#ifdef __cplusplus
extern "C" {
#endif

struct portrange {
    int lower;
    int higher;
};

static int getPortRange(struct portrange *range)
{
#ifdef __linux__
    {
        FILE *f;
        int ret;

        f = fopen("/proc/sys/net/ipv4/ip_local_port_range", "r");
        if (f != NULL) {
            ret = fscanf(f, "%d %d", &range->lower, &range->higher);
            fclose(f);
            return ret == 2 ? 0 : -1;
        }
        return -1;
    }
#elif defined(_ALLBSD_SOURCE)
    {
        int ret;
        size_t size = sizeof(range->lower);
        ret = sysctlbyname(
            "net.inet.ip.portrange.first", &range->lower, &size, 0, 0
        );
        if (ret == -1) {
            return -1;
        }
        size = sizeof(range->higher);
        ret = sysctlbyname(
            "net.inet.ip.portrange.last", &range->higher, &size, 0, 0
        );
        return ret;
    }
#else
    return -1;
#endif
}

/*
 * Class:     sun_net_PortConfig
 * Method:    getLower0
 * Signature: ()I
 */
JNIEXPORT jint JNICALL Java_sun_net_PortConfig_getLower0
  (JNIEnv *env, jclass clazz)
{
    struct portrange range;
    if (getPortRange(&range) < 0) {
        return -1;
    }
    return range.lower;
}

/*
 * Class:     sun_net_PortConfig
 * Method:    getUpper0
 * Signature: ()I
 */
JNIEXPORT jint JNICALL Java_sun_net_PortConfig_getUpper0
  (JNIEnv *env, jclass clazz)
{
    struct portrange range;
    if (getPortRange(&range) < 0) {
        return -1;
    }
    return range.higher;
}

#ifdef __cplusplus
}
#endif