Guy Harris schrieb: > On Mar 16, 2009, at 3:45 PM, Joerg Mayer wrote: > >> On Mon, Mar 16, 2009 at 09:40:03PM +0000, [email protected] wrote: >>> http://anonsvn.wireshark.org/viewvc/viewvc.cgi? >>> view=rev&revision=27748 >>> crc16 algorithm copied from Linux sources (GPL V2 only!) >> So far the wireshark sources are v2 or later - so adding a gplv2 >> only file >> is not something that should be done without asking *first*, because >> it >> has effects for all of Wireshark. Or maybe there already were files >> that >> are v2 only and I missed that? > > Is the only difference between the CRC16 in PROFINET and the ITU-T > CRC16 implemented in epan/crc16.c the polynomial? It looks as if the > algorithm is the same in the PROFINET CRC16 and the "reflected" ITU-T > CRC16: > > crc = initial value; > for (all bytes in the buffer) > crc = (crc >> 8) ^ table[(crc ^ byte from buffer) & 0xff]; > return crc; > > so it might just be the table. If so, could we just generate the > appropriate table for the PROFINET polynomial, have epan/crc16.c > export crc16_reflected(), and have the PROFINET CRC16 routine use > crc16_reflected() and the appropriate table?
To be honest I just don't have a clue. I did some experiments to use the existing CRC algorithms (trial and error based), but this is really no indication if it's possible or not ;-) If you would like to do some "more educated" experiments on this I could send you a capture file with some valid CRCs in PM. Regards, ULFL ___________________________________________________________________________ Sent via: Wireshark-dev mailing list <[email protected]> Archives: http://www.wireshark.org/lists/wireshark-dev Unsubscribe: https://wireshark.org/mailman/options/wireshark-dev mailto:[email protected]?subject=unsubscribe
