ln.dhcp/Option.cs

using System;
using ln.types;
using System.Collections.Generic;
using ln.types.net;
using System.Linq;
using System.Text;
using System.IO;
namespace ln.dhcp
{
    public delegate Option OptionFactory(byte tag, byte[] bytes);

    public class Option
    {
        public byte Tag { get; }
        public virtual byte[] Bytes { get; set; }

        public Option(byte tag)
        {
            Tag = tag;
        }
        public Option(byte tag, byte[] bytes)
        {
            Tag = tag;
            Bytes = bytes;
        }

        public override string ToString()
        {
            return String.Format("[Option TAG={0} Bytes={1}]", Tag, BitConverter.ToString(Bytes));
        }

        static Dictionary<byte, OptionFactory> factories = new Dictionary<byte, OptionFactory>();
        static void AddFactory(byte tag, OptionFactory factory) => factories.Add(tag, factory);

        public static Option[] ParseOptions(byte[] bytes, int offset)
        {
            List<Option> options = new List<Option>();
            while ((offset < bytes.Length) && (bytes[offset] != 0xff))
                if (bytes[offset] != 0x00)
                    options.Add(Option.Parse(bytes, ref offset));
                else
                    offset++;

            return options.ToArray();
        }
        public static Option Parse(byte[] bytes, ref int offset)
        {
            Console.WriteLine("OFFSET: {0}", offset);
            switch (bytes[offset])
            {
                case 0:
                case 255:
                    return new Option(bytes[offset++]);
                default:
                    byte tag = bytes[offset++];
                    byte len = bytes[offset++];
                    byte[] slice = bytes.Slice(offset, len);
                    offset += len;

                    if (factories.ContainsKey(tag))
                        return factories[tag](tag, slice);
                    else
                        return new Option(tag, slice);
            }
        }

        public static byte[] ToBytes(IEnumerable<Option> options)
        {
            MemoryStream memoryStream = new MemoryStream();
            foreach(Option option in options)
            {
                byte[] b = option.Bytes;
                memoryStream.WriteByte(option.Tag);
                memoryStream.WriteByte((byte)(b.Length));
                memoryStream.Write(b, 0, b.Length);
            }
            memoryStream.WriteByte(0xff);
            return memoryStream.ToArray();
        }

        static Option()
        {
            AddFactory(0x01, (tag, bytes) => new NetmaskOption(bytes));   // Netmask
            AddFactory(0x03, (tag, bytes) => new GatewaysOption(bytes));   // Gateways
            AddFactory(0x0C, (tag, bytes) => new TextOption(tag, bytes));   // Host Name
            AddFactory(0x0F, (tag, bytes) => new TextOption(tag, bytes));   // Domain Name

            AddFactory(0x32, (tag, bytes) => new DHCPRequestedIPOption(bytes));   // Requested IP
            AddFactory(0x33, (tag, bytes) => new DHCPLeaseTimeOption(bytes));// Lease Time

            AddFactory(0x35, (tag, bytes) => new DHCPMessageTypeOption(bytes[0]));   // DHCP Message Type
            AddFactory(0x36, (tag, bytes) => new DHCPServerIdentifierOption(bytes));   // Server ID

        }
    }
    public class IPv4ListOption : Option
    {
        public IPv4[] IPs { get; set; }
        public override byte[] Bytes
        {
            get => IPs.SelectMany(ip => ip.IPBytes).ToArray();
            set
            {
                IPs = new IPv4[value.Length / 4];
                for (int n = 0; n < value.Length / 4; n++)
                    IPs[n] = new IPv4(value.Slice(n * 4, 4));
            }
        }
        public IPv4ListOption(byte tag)
            :base(tag)
        {
            IPs = new IPv4[0];
        }
        public IPv4ListOption(byte tag, IPv4[] ips)
            : base(tag)
        {
            IPs = ips.Slice(0);
        }
        public IPv4ListOption(byte tag, byte[] bytes)
            : base(tag)
        {
            IPs = new IPv4[] { new IPv4(bytes) };
        }
    }
    public class GatewaysOption : IPv4ListOption
    {
        public GatewaysOption()
            : base(0x03,new byte[0])
        {
        }
        public GatewaysOption(byte[] bytes)
            : base(0x03,bytes)
        {
        }
        public GatewaysOption(IEnumerable<IPv4> gateways)
            : base(0x03)
        {
            IPs = gateways.ToArray();
        }
    }


    public class IPv4Option : Option
    {
        public IPv4 IP { get; set; }
        public override byte[] Bytes
        {
            get => IP.IPBytes;
            set => IP = new IPv4(value);

        }
        public IPv4Option(byte tag)
            : base(tag)
        { }
        public IPv4Option(byte tag, IPv4 ip)
            : base(tag)
        {
            IP = ip;
        }
        public IPv4Option(byte tag, byte[] bytes)
            : base(tag)
        {
            Bytes = bytes;
        }
    }
    public class NetmaskOption : IPv4Option
    {
        public NetmaskOption()
            : base(0x01)
        { }
        public NetmaskOption(byte[] bytes)
            : base(0x01)
        {
            Bytes = bytes;
        }
        public NetmaskOption(IPv4 ip)
            : base(0x01, ip)
        { }
    }
    public class DHCPRequestedIPOption : IPv4Option
    {
        public DHCPRequestedIPOption()
            : base(0x32)
        { }
        public DHCPRequestedIPOption(byte[] bytes)
            : base(0x32)
        {
            Bytes = bytes;
        }
        public DHCPRequestedIPOption(IPv4 ip)
            : base(0x32, ip)
        { }

        public override string ToString()
        {
            return string.Format("DHCPRequestedIP={0}",IP);
        }
    }


    public class DHCPServerIdentifierOption : IPv4Option
    {
        public DHCPServerIdentifierOption()
            : base(0x36)
        { }
        public DHCPServerIdentifierOption(byte[] bytes)
            : base(0x36)
        {
            IP = new IPv4(bytes);
        }
        public DHCPServerIdentifierOption(IPv4 ip)
            : base(0x36, ip)
        { }

        public override string ToString()
        {
            return string.Format("DHCPServerIdentifier={0}",IP);
        }
    }

    public class TextOption : Option
    {
        public String Text { get; set; }
        public override byte[] Bytes
        {
            get => Encoding.UTF8.GetBytes(Text);
            set => Text = Encoding.UTF8.GetString(value);
        }
        public TextOption(byte tag)
            : base(tag)
        { }
        public TextOption(byte tag, byte[] bytes)
            : base(tag)
        {
            Bytes = bytes;
        }
        public TextOption(byte tag, string text)
            : this(tag)
        {
            Text = text;
        }
    }
    public class IntegerOption : Option
    {
        public int Integer { get; set; }
        public override byte[] Bytes
        {
            get => Integer.GetBytes(true);
            set => Integer = value.GetInt(true);
        }
        public IntegerOption(byte tag)
            : base(tag)
        { }
        public IntegerOption(byte tag, byte[] bytes)
            : base(tag)
        {
            Bytes = bytes;
        }
        public IntegerOption(byte tag, int i)
            : this(tag)
        {
            Integer = i;
        }
    }
    public class DHCPLeaseTimeOption : IntegerOption
    {
        public DHCPLeaseTimeOption(byte[] val)
            : base(0x33, val)
        {}
        public DHCPLeaseTimeOption(int leaseTime)
            : base(0x33)
        {
            Integer = leaseTime;
        }
        public DHCPLeaseTimeOption(DateTimeOffset validThrough)
            :base(0x33)
        {
            Integer = (int)(validThrough - DateTimeOffset.Now).TotalSeconds;
        }

        public override string ToString()
        {
            return String.Format("DHCPLeaseTime={0}s",Integer);
        }
    }

    public class DHCPMessageTypeOption : Option
    {
        public DHCPMessageType DHCPMessageType { get; set; }
        public override byte[] Bytes
        {
            get => new byte[] { (byte)DHCPMessageType };
            set => DHCPMessageType = value.Length > 0 ? (DHCPMessageType)value[0] : DHCPMessageType.DISCOVER;
        }
        public DHCPMessageTypeOption()
            : base(0x35)
        {
        }
        public DHCPMessageTypeOption(DHCPMessageType messageType)
            : base(0x35)
        {
            DHCPMessageType = messageType;
        }
        public DHCPMessageTypeOption(byte value)
            : this()
        {
            DHCPMessageType = (DHCPMessageType)value;
        }

        public override string ToString()
        {
            return string.Format("DHCPMessageType={0}",DHCPMessageType);
        }
    }

}