Re: iSCSI v8 CRC32C

[Paul Koning <ni1d@arrl.net>]

Excerpt of message (sent 20 November 2001) by Luben Tuikov:
> Hello,
> 
> I've been trying to get CRC32C working. I read a few papers,
> derived the equations myself, etc, etc, but still cannot get
> CRC32C to work...

A good paper to read is the classic Ethernet spec (V1, not 802.3).  In
particular, see appendix C.
 
> My basic framework is: (not precomputing a table -- just force):
> 
> poly= 1edc6f41;
> crc = all 1's;
> while more bits in message do
> 	crc shift left, adding the next message bit at right;
> 	if carry then
> 		crc = crc XOR poly;
That looks wrong; the Ethernet spec as I read it seems to say you need
"if (carry xor messagebit)"
> 	end if;
> end while;
> crc = NOT crc; (e.g. complement the register)

Re your later note: if you get a 0 remainder, you're missing
something.  Probably the fact that the initial all 1 value is
mathematically equivalent to complementing the initial 32 bits of the
message. 

	 paul