[Winpcap-users] About TCP/UDP/ICMP checksum

[James Garrison]

Try googling "tcp checksum" for a wealth of resources.

Also, remember that for gigabit ethernet, most drivers
offload checksum calculation to the adapter, and that happens long
after the packet has been captured by winpcap.  Try doing a capture
of traffic on a gigabit ethernet adapter... all outgoing packets
will be spuriously shown to have "invalid checksum".  In short, you
cannot validate checksums for outgoing traffic on gigabit ethernet.

ZhiyuHe wrote:
> I'm writing a simple protocol analyzer for my graduation project using
> WinPcap.This mailing list and Guy Harris has given me too much
> help,thanks very much.
> I should calculate the TCP/UDP checksum in my program,but it's so
> difficult for me.I have perused <<TCP/IP Illustracted Volume 1>>
> (Richard Stevens) and RFC1071,and have searched this topic in
> Google,WinPcap mailing list archive,and ethereal.com,but I still can't
> manage this.I don't understand how to process TCP/UDP psuedo
> header,and how to calculate.I need a demonstration.
> Thanks a lot!
> 
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-- 
James Garrison                                Athens Group, Inc.
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