Re: Checksum

[Guy Harris <guy () alum mit edu>]

Luis Del Pino wrote:
> When I capture an UDP datagram from a well-known source, Could the checksum
> be incorrect?

Yes, if the packet was corrupted.  (I assume you're capturing with libpcap.)

> do I have to calculate it?

If you want to check whether the packet was corrupted, yes.  See 
tcpdump's print-udp.c for an example of how to check the checksum. 
(Note that a checksum value of 0 means "no checksum".)
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