protected bool check_checksum(UInt32 ip_source_in_network_order, UInt32 ip_destination_in_network_order, ref byte[] incoming_udp_data, int incoming_udp_data_size)
{
if (incoming_udp_data == null)
{
return(false);
}
if (incoming_udp_data_size < udp_header.size)
{
return(false);
}
UInt16 packet_checksum = System.BitConverter.ToUInt16(incoming_udp_data, 6);
byte[] udp_packet_and_pseudo_header = new byte[incoming_udp_data_size + udp_pseudo_header.size];
udp_pseudo_header uph = new udp_pseudo_header();
uph.destination_address = ip_source_in_network_order;
uph.source_address = ip_destination_in_network_order;
uph.protocol = easy_socket.ip_header.ipv4_header.protocol_udp;
uph.UdpLength = (ushort)incoming_udp_data_size;
byte[] encoded_pseudo_header = uph.encode();
System.Array.Copy(encoded_pseudo_header, 0, udp_packet_and_pseudo_header, 0, udp_pseudo_header.size);
System.Array.Copy(incoming_udp_data, 0, udp_packet_and_pseudo_header, udp_pseudo_header.size, incoming_udp_data_size);
// putting the checksum to 0
udp_packet_and_pseudo_header[6 + udp_pseudo_header.size] = 0;
udp_packet_and_pseudo_header[7 + udp_pseudo_header.size] = 0;
UInt16 computed_checksum = easy_socket.Cchecksum.checksum(udp_packet_and_pseudo_header, true);
return(computed_checksum == packet_checksum);
}
public byte[] encode(UInt32 ip_source_in_network_order, UInt32 ip_destination_in_network_order)
{
int data_size = 0;
if (data != null)
{
data_size = this.data.Length;
}
byte[] ret = new byte[udp_header.size + data_size];
System.Array.Copy(System.BitConverter.GetBytes(this.source_port), 0, ret, 0, 2);
System.Array.Copy(System.BitConverter.GetBytes(this.destination_port), 0, ret, 2, 2);
// if udp_length not set comput it if this.data
if (!this.b_udp_length_set)
{
this.UdpLength = (ushort)(udp_header.size + data_size);
}
System.Array.Copy(System.BitConverter.GetBytes(this.udp_length), 0, ret, 4, 2);
// if checksum not set put it to 0
if (!this.b_checksum_set)
{
this.checksum = 0;
}
System.Array.Copy(System.BitConverter.GetBytes(this.checksum), 0, ret, 6, 2);
// copy data
if (data_size > 0)
{
System.Array.Copy(this.data, 0, ret, 8, data_size);
}
if (!this.b_checksum_set)
{
// comput checksum
// create udp_pseudo_header
udp_pseudo_header udpph = new udp_pseudo_header();
udpph.destination_address = ip_destination_in_network_order;
udpph.source_address = ip_source_in_network_order;
udpph.udp_length = this.udp_length;
// create a byte array containing udp_pseudo_header and the datagram
byte[] full_array_for_checksum = new byte[udp_pseudo_header.size + udp_header.size + data_size];
System.Array.Copy(udpph.encode(), 0, full_array_for_checksum, 0, udp_pseudo_header.size);
System.Array.Copy(ret, 0, full_array_for_checksum, udp_pseudo_header.size, udp_header.size + data_size);
// comput checksum
this.checksum = easy_socket.Cchecksum.checksum(full_array_for_checksum, true);
// put new check some in udp datagram
System.Array.Copy(System.BitConverter.GetBytes(this.checksum), 0, ret, 6, 2);
}
return(ret);
}
