private static IPv4Packet BuildDhcpDiscoverMessage(NetworkInterface inter, ushort packetId, uint dhcpTransactionId)
{
var hardwareAddress = new HardwareAddress(HardwareAddressType.Ethernet,
inter.GetPhysicalAddress().GetAddressBytes());
var dhcpPacket = new DhcpPacket();
dhcpPacket.Operation = DhcpOperation.Request;
dhcpPacket.MessageType = DhcpMessageType.Discover;
dhcpPacket.TransactionId = dhcpTransactionId;
dhcpPacket.HardwareAddress = hardwareAddress;
var dhcpUdpPacket = new UdpPacket();
dhcpUdpPacket.SourcePort = 68;
dhcpUdpPacket.DestinationPort = 67;
dhcpUdpPacket.Payload = dhcpPacket;
var dhcpIpPacket = new IPv4Packet();
dhcpIpPacket.Source = IPAddress.Any;
dhcpIpPacket.Destination = IPAddress.Broadcast;
dhcpIpPacket.Identifiation = packetId;
dhcpIpPacket.Payload = dhcpUdpPacket;
return(dhcpIpPacket);
}
private static IPv4Packet BuildDhcpRebindMessage(DhcpOffer offer, NetworkInterface inter, ushort packetId, uint dhcpTransactionId)
{
var hardwareAddress = new HardwareAddress(HardwareAddressType.Ethernet,
inter.GetPhysicalAddress().GetAddressBytes());
var dhcpPacket = new DhcpPacket();
dhcpPacket.Operation = DhcpOperation.Request;
dhcpPacket.MessageType = DhcpMessageType.Request;
dhcpPacket.TransactionId = dhcpTransactionId;
dhcpPacket.HardwareAddress = hardwareAddress;
dhcpPacket.ClientAddress = offer.ClientAddress;
dhcpPacket.Options.Add(new DhcpClientIdentifier(hardwareAddress));
var dhcpUdpPacket = new UdpPacket();
dhcpUdpPacket.SourcePort = 68;
dhcpUdpPacket.DestinationPort = 67;
dhcpUdpPacket.Payload = dhcpPacket;
var dhcpIpPacket = new IPv4Packet();
dhcpIpPacket.Source = offer.ClientAddress;
dhcpIpPacket.Destination = offer.DhcpServer;
dhcpIpPacket.Identifiation = packetId;
dhcpIpPacket.Payload = dhcpUdpPacket;
return(dhcpIpPacket);
}
public static DhcpPacket CreateFromRaw(byte[] rawPacket)
{
DhcpPacket packet = new DhcpPacket();
using (var reader = new BinaryReader(new MemoryStream(rawPacket)))
{
packet.MessageType = (DhcpMessageType)reader.ReadByte();
HardwareAddressType hardwareAddressType = (HardwareAddressType)reader.ReadByte();
byte hardwareAddressLength = reader.ReadByte();
packet.Hops = reader.ReadByte();
packet.TransactionId = (uint)IPAddress.NetworkToHostOrder(reader.ReadInt32());
packet.SecondsElapsed = (ushort)IPAddress.NetworkToHostOrder(reader.ReadInt16());
packet.Flags = (ushort)IPAddress.NetworkToHostOrder(reader.ReadInt16());
packet.ClientAddress = new IPAddress(reader.ReadBytes(4));
packet.YourClientAddress = new IPAddress(reader.ReadBytes(4));
packet.NextServerAddress = new IPAddress(reader.ReadBytes(4));
packet.RelayAgentAddress = new IPAddress(reader.ReadBytes(4));
packet.HardwareAddress = new HardwareAddress(hardwareAddressType,
reader.ReadBytes(hardwareAddressLength));
reader.ReadBytes(16 - hardwareAddressLength); // padding
packet.ServerName = Encoding.ASCII.GetString(reader.ReadBytes(64));
packet.BootFileName = Encoding.ASCII.GetString(reader.ReadBytes(128));
int packetMagicCookie = IPAddress.NetworkToHostOrder(reader.ReadInt32());
if (packetMagicCookie != MagicCookie)
{
throw new InvalidDataException("Magic cookie not found!");
}
byte messageType = reader.ReadByte();
if (messageType != 53)
{
throw new InvalidDataException("Options should start with Message type!");
}
reader.ReadByte(); // length
packet.MessageType = (DhcpMessageType)reader.ReadByte();
var optionFactory = new DhcpOptionFactory();
byte optionType = reader.ReadByte();
while (optionType != 255)
{
DhcpOptionType type = (DhcpOptionType)optionType;
byte length = reader.ReadByte();
byte[] optionData = reader.ReadBytes(length);
DhcpOption option = optionFactory.CreateFromRaw(type, optionData);
if (option != null)
{
packet.Options.Add(option);
}
else
{
Console.WriteLine($"WARN: Unsupported option type: {type}");
}
optionType = reader.ReadByte();
}
}
return(packet);
}
public IApplicationPacket CreateFromRaw(ushort port, byte[] rawPacket)
{
switch (port)
{
case 68:
return(DhcpPacket.CreateFromRaw(rawPacket));
default:
return(new UnknownPayload(rawPacket));
}
}
public static DhcpOffer FromDhcpPacket(DhcpPacket packet)
{
if (packet.MessageType != DhcpMessageType.Offer)
{
return(null);
}
return(new DhcpOffer
{
DhcpServer = packet.GetOption <DhcpServerIdentifierOption>().ServerAddress,
ClientAddress = packet.YourClientAddress,
Gateway = packet.GetOption <DhcpRouterOption>()?.Routers[0],
DnsServer = packet.GetOption <DhcpDomainNameServerOption>()?.DomainNameServers[0],
Domain = packet.GetOption <DhcpDomainNameOption>()?.DomainName,
SubnetMask = packet.GetOption <DhcpSubnetMaskOption>()?.Mask,
RelayAgnetAddress = packet.RelayAgentAddress
});
}
