ln.dhcp/DHCPListener.cs

using System;
using System.Net.Sockets;
using ln.types.net;
using System.Net;
using System.Net.NetworkInformation;
using System.Threading;
using ln.logging;
using System.Text;
namespace ln.dhcp
{
    public class DHCPListener
    {
        public DHCPServer DHCPServer { get; private set; }
        public DHCPServerInterface ServerInterface { get; private set; }
        public IPv4 InterfaceAddress => ServerInterface.InterfaceAddress;

        public InterfaceConfiguration ListeningInterfaceConfiguration { get; private set; }
        public IPv4 ListeningAddress { get; private set; }

        UdpClient udpClient;
        Thread listenerThread;

        public DHCPListener(DHCPServer dhcpServer,DHCPServerInterface serverInterface)
        {
            DHCPServer = dhcpServer;
            ServerInterface = serverInterface;
            ListeningInterfaceConfiguration = FindNetworkInterface(InterfaceAddress);

            if (Environment.OSVersion.Platform == PlatformID.Win32NT)
                SetupWindows();
            else
                SetupLinux();
        }

        public void Start()
        {
            if (((listenerThread == null) || !listenerThread.IsAlive) && (ListeningInterfaceConfiguration != null))
            {
                listenerThread = new Thread(() => InterfaceListener());
                listenerThread.Start();
            }
        }
        public void Close()
        {
            udpClient.Close();
        }

        public InterfaceConfiguration FindNetworkInterface(IPv4 interfaceAddr)
        {
            NetworkInterface[] networkInterfaces = System.Net.NetworkInformation.NetworkInterface.GetAllNetworkInterfaces();
            foreach (NetworkInterface networkInterface in networkInterfaces)
            {
                foreach (UnicastIPAddressInformation addressInformation in networkInterface.GetIPProperties().UnicastAddresses)
                {
                    if (interfaceAddr.Equals(addressInformation.Address))
                    {
                        return new InterfaceConfiguration(networkInterface.Name, addressInformation.Address, addressInformation.IPv4Mask);
                    }
                }
            }
            return null;
        }

        private void SetupWindows()
        {
            if (ListeningInterfaceConfiguration == null)
                return;

            ListeningAddress = ListeningInterfaceConfiguration.BroadcastAddress;
        }
        private void SetupLinux()
        {
            if (ListeningInterfaceConfiguration == null)
                return;

            ListeningAddress = IPAddress.Any;
        }

        private void FixupSocket()
        {
            if (Environment.OSVersion.Platform != PlatformID.Win32NT)
            {
                IntPtr socket = udpClient.Client.Handle;
                byte[] ifName = Encoding.ASCII.GetBytes(ListeningInterfaceConfiguration.Name);

                int result = Mono.Unix.Native.Syscall.setsockopt(
                    (int)socket,
                    Mono.Unix.Native.UnixSocketProtocol.SOL_SOCKET,
                    Mono.Unix.Native.UnixSocketOptionName.SO_BINDTODEVICE,
                    ifName,
                    ifName.Length
                    );
            }
        }

        private void InterfaceListener()
        {
            udpClient = new UdpClient(new IPEndPoint(ListeningAddress, 67));
            udpClient.EnableBroadcast = true;

            FixupSocket();

            try
            {
                Logging.Log(LogLevel.INFO, "InterfaceListener started: {0}", ServerInterface.InterfaceAddress);

                while (true)
                {
                    IPEndPoint remoteEndpoint = new IPEndPoint(IPAddress.Any, 0);
                    byte[] rxBytes = udpClient.Receive(ref remoteEndpoint);
                    Logging.Log(LogLevel.INFO, "RX: {0} {1}", ServerInterface.InterfaceAddress,BitConverter.ToString(rxBytes));
                    BootPPacket bootPPacket = new BootPPacket(rxBytes, remoteEndpoint);
                    Logging.Log(LogLevel.INFO, "RX: {0} {1}", ServerInterface.InterfaceAddress, bootPPacket);
                    DHCPServer.Pool.Enqueue(() => DHCPServer.Received(ServerInterface, bootPPacket));
                }
            }
            catch (Exception e)
            {
                Logging.Log(LogLevel.WARNING, "DHCPServer.InterfaceListener(): Caught exception: {0}", e);
            }

            Logging.Log(LogLevel.INFO, "InterfaceListener stopped: {0}", ServerInterface.InterfaceAddress);

            lock (this)
            {
                udpClient.Dispose();
                listenerThread = null;
            }
        }

        public void Send(byte[] packet,IPEndPoint remoteEndpoint)
        {
            Logging.Log(LogLevel.INFO, "DHCPListener: Send(): {0} {1}", remoteEndpoint, BitConverter.ToString(packet));
            udpClient.Send(packet, packet.Length, remoteEndpoint);
        }

        public class InterfaceConfiguration
        {
            public String Name;
            public IPv4 Address;
            public IPv4 Netmask;
            public Network4 Network => new Network4(Address, Netmask);

            public IPv4 BroadcastAddress => Network.Last;

            public InterfaceConfiguration(String name,IPv4 address,IPv4 netmask)
            {
                Name = name;
                Address = address;
                Netmask = netmask;
            }
        }

    }
}