/*
 * Copyright 2012 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.dropwizard.jetty;

import java.io.BufferedReader;
import java.io.File;
import java.io.FileReader;
import java.io.IOException;
import java.net.InetAddress;
import java.net.NetworkInterface;
import java.net.SocketException;
import java.security.AccessController;
import java.security.PrivilegedAction;
import java.util.ArrayList;
import java.util.Collection;
import java.util.Enumeration;
import java.util.List;
import java.util.Locale;
import java.util.concurrent.atomic.AtomicReference;

import static java.util.Objects.requireNonNull;

This class is taken from the Netty project, and all credit goes to them. It has been modified, to remove dependencies on other classes, and to convert to methods, rather than a static value. The getAllLocalIPs() method was taken from the Apache Curator project which is also under the Apache 2.0 license. /**
 * This class is taken from the Netty project, and all credit goes to them.
 * It has been modified, to remove dependencies on other classes, and to convert to methods, rather than a
 * static value.
 *
 * The {@link #getAllLocalIPs()} method was taken from the Apache Curator project
 * which is also under the Apache 2.0 license.
 */
public class NetUtil {
    public static final int DEFAULT_TCP_BACKLOG_WINDOWS = 200;
    public static final int DEFAULT_TCP_BACKLOG_LINUX = 128;
    public static final String TCP_BACKLOG_SETTING_LOCATION = "/proc/sys/net/core/somaxconn";

    private static final AtomicReference<LocalIpFilter> LOCAL_IP_FILTER = new AtomicReference<>((nif, adr) ->
        (adr != null) && !adr.isLoopbackAddress() && (nif.isPointToPoint() || !adr.isLinkLocalAddress())
    );

    
The SOMAXCONN value of the current machine. If failed to get the value, 200 is used as a default value for Windows or 128 for others. /**
     * The SOMAXCONN value of the current machine.  If failed to get the value,  {@code 200}  is used as a
     * default value for Windows or {@code 128} for others.
     */
    public static int getTcpBacklog() {
        return getTcpBacklog(getDefaultTcpBacklog());
    }

    
The SOMAXCONN value of the current machine.  If failed to get the value, defaultBacklog argument is
used
/**
     * The SOMAXCONN value of the current machine.  If failed to get the value, <code>defaultBacklog</code> argument is
     * used
     */
    public static int getTcpBacklog(int tcpBacklog) {
        // Taken from netty.

        // As a SecurityManager may prevent reading the somaxconn file we wrap this in a privileged block.
        //
        // See https://github.com/netty/netty/issues/3680
        return AccessController.doPrivileged((PrivilegedAction<Integer>) () -> {
            // Determine the default somaxconn (server socket backlog) value of the platform.
            // The known defaults:
            // - Windows NT Server 4.0+: 200
            // - Linux and Mac OS X: 128
            final File file = new File(TCP_BACKLOG_SETTING_LOCATION);
            try (BufferedReader in = new BufferedReader(new FileReader(file))) {
                return Integer.parseInt(in.readLine().trim());
            } catch (SecurityException | IOException | NumberFormatException | NullPointerException e) {
                return tcpBacklog;
            }
        });

    }

    public static boolean isWindows() {
        final boolean windows = System.getProperty("os.name", "").toLowerCase(Locale.US).contains("win");
        return windows;
    }

    public static int getDefaultTcpBacklog() {
        return isWindows() ? DEFAULT_TCP_BACKLOG_WINDOWS : DEFAULT_TCP_BACKLOG_LINUX;
    }

    
Replace the default local ip filter used by getAllLocalIPs() 
Params:
newLocalIpFilter – the new local ip filter/**
     * Replace the default local ip filter used by {@link #getAllLocalIPs()}
     *
     * @param newLocalIpFilter the new local ip filter
     */
    public static void setLocalIpFilter(LocalIpFilter newLocalIpFilter) {
        requireNonNull(newLocalIpFilter);
        LOCAL_IP_FILTER.set(newLocalIpFilter);
    }

    
Return the current local ip filter used by getAllLocalIPs() 
Returns:
ip filter/**
     * Return the current local ip filter used by {@link #getAllLocalIPs()}
     *
     * @return ip filter
     */
    public static LocalIpFilter getLocalIpFilter() {
        return requireNonNull(LOCAL_IP_FILTER.get());
    }

    
based on http://pastebin.com/5X073pUc

Returns all available IP addresses.

In error case or if no network connection is established, we return
an empty list here.

Loopback addresses are excluded - so 127.0.0.1 will not be never
returned.

The "primary" IP might not be the first one in the returned list.
Throws:
SocketException – errors
See Also:
getAllLocalIPs
ServiceInstanceBuilder.java
Returns:
 Returns all IP addresses (can be an empty list in error case
         or if network connection is missing)./**
     * based on http://pastebin.com/5X073pUc
     * <p>
     *
     * Returns all available IP addresses.
     * <p>
     * In error case or if no network connection is established, we return
     * an empty list here.
     * <p>
     * Loopback addresses are excluded - so 127.0.0.1 will not be never
     * returned.
     * <p>
     * The "primary" IP might not be the first one in the returned list.
     *
     * @return  Returns all IP addresses (can be an empty list in error case
     *          or if network connection is missing).
     * @see <a href="http://pastebin.com/5X073pUc">getAllLocalIPs</a>
     * @see <a href="https://github.com/apache/curator/blob/master/curator-x-discovery/src/main/java/org/apache/curator/x/discovery/ServiceInstanceBuilder.java">ServiceInstanceBuilder.java</a>
     * @throws SocketException errors
     */
    public static Collection<InetAddress> getAllLocalIPs() throws SocketException {
        final List<InetAddress> listAdr = new ArrayList<>();
        final Enumeration<NetworkInterface> nifs = NetworkInterface.getNetworkInterfaces();
        if (nifs == null) {
            return listAdr;
        }

        while (nifs.hasMoreElements()) {
            final NetworkInterface nif = nifs.nextElement();
            // We ignore subinterfaces - as not yet needed.

            final Enumeration<InetAddress> adrs = nif.getInetAddresses();
            while (adrs.hasMoreElements()) {
                final InetAddress adr = adrs.nextElement();
                if (getLocalIpFilter().use(nif, adr)) {
                    listAdr.add(adr);
                }
            }
        }
        return listAdr;
    }
}