Hello,
I try to implement a UDP checksum routine. Unfortunately it calculates a
completely different value than Wireshark does. I don't known what I am
doing wrong. Can you help me?
The calculation is done using a UDP pseudo header with the structure
struct pseudo
{
uint32 source;
uint32 destination;
uint8 zero;
uint8 protocol;
uint16 udp_length;
};
When I have a UDP frame with IP source = "192.168.100.132" and IP
destination = "192.168.144.255", and UDP Length = 66 (IP Total_Length = 86)
I get this data in the pseudo header:
c0 a8 64 84
c0 a8 90 ff
00 11 00 42
The sum is 0x32874 which is must be folded to 0x2874+0x0003 = 0x8277. The
complement is 0xd788.
But Wireshark detects an error and says the checksum must be 0x5528. Can
anybody give me a hint what's wrong?
--
Andy
