public DHCPPacketView(DHCPMessageType messageType)
{
Packet = new DHCPPacket();
DHCPMessageType = messageType;
Hops = 0;
TimeElapsed = TimeSpan.Zero;
BroadcastFlag = false;
Packet.sname = string.Empty;
Packet.file = string.Empty;
Packet.magicNumber = DHCPPacket.DHCPMagicNumber;
ClientIP = IPAddress.Any;
YourIP = IPAddress.Any;
NextServerIP = IPAddress.Any;
RelayAgentIP = IPAddress.Any;
}
public DHCPPacketView(DHCPPacket packet)
{
Packet = packet;
}
public DHCPPacketView(byte[] buffer)
{
Packet = DHCPPacketParser.Parse(buffer);
}
/// <summary>
/// DHCP packet parser based on RFC2131 (https://tools.ietf.org/html/rfc2131)
/// </summary>
/// <param name="buffer">The input buffer to parse.</param>
/// <returns>A parsed packet structure or null</returns>
public static DHCPPacket Parse(byte[] buffer)
{
if (buffer.Length < 240)
{
throw new ArgumentException("The minimum DHCP packet size if 236 bytes", "buffer");
}
// Parse BOOTP Options
var result = new DHCPPacket
{
op = (MessageOpCode)buffer[0],
htype = (HardwareAddressType)buffer[1],
hlen = Convert.ToInt32(buffer[2]),
hops = Convert.ToInt32(buffer[3]),
xid = Read32UnsignedBE(buffer, 4),
secs = Convert.ToInt32(Read16UnsignedBE(buffer, 8)),
flags = Convert.ToInt32(Read16UnsignedBE(buffer, 10)),
ciaddr = ReadIPAddress(buffer, 12),
yiaddr = ReadIPAddress(buffer, 16),
siaddr = ReadIPAddress(buffer, 20),
giaddr = ReadIPAddress(buffer, 24),
chaddr = ReadClientHardwareAddress((HardwareAddressType)buffer[1], buffer, 28),
sname = Encoding.ASCII.GetString(buffer, 44, 64).Trim(),
file = Encoding.ASCII.GetString(buffer, 108, 128).Trim(),
magicNumber = Read32UnsignedBE(buffer, 236)
};
if (result.magicNumber != DHCPPacket.DHCPMagicNumber)
{
throw new Exception("Received packet may be a BOOTP packet but is not a valid DHCP packet as it is missing the magic number at offset 236.");
}
var index = 240;
while (index < buffer.Length)
{
int optionCode = Convert.ToInt32(buffer[index++]);
if ((DHCPOptionType)optionCode == DHCPOptionType.End)
{
break;
}
int length = Convert.ToInt32(buffer[index++]);
// Parse the new option and add it to the list
var dhcpOption = ParseDHCPOption(optionCode, length, buffer, index);
result.options.Add(dhcpOption);
index += length;
// For option 43 (Vendor Specific Information) and 60 (Vendor Class Id),
// there is a "chicken and egg" possibility. As such, if 43 is seen before
// 60 is seen, then the suboptions will be parsed before knowing the vendor class.
// Then when option 60 is seen, option 43 will be reprocessed to find the right suboptions.
if (dhcpOption is DHCPOptionVendorSpecificInformation)
{
(dhcpOption as DHCPOptionVendorSpecificInformation).VendorClassId = GetVendorClassId(result.options);
}
else if (dhcpOption is DHCPOptionClassId)
{
SetVendorClassId(result.options, (dhcpOption as DHCPOptionClassId).ClassId);
}
}
return(result);
}
