Garrett D'Amore writes: > Andrew Gallatin wrote: > > Why don't you just fix the checksum by "subtracting" off the last 4 > > bytes of the expanded vlan header (bytes 14..17 of the frame). > > > > I had considered that, but done it mostly because I am not entirely sure > that this is universally "safe". (This is due to ignorance on my part, > and I'd love to be better informed.) > > There are two complexities in the checksum calculation that I'm > concerned about. The first is the inclusion of carry bits. The second > is the negation (~). I'm not entirely sure after these are done, that > the operation is reversible enough to safely subtract those bytes.
That shouldn't be an issue. It's just 1's complement math, not something exotic like a Galios field. The hard part is knowing which bytes are overhead and need to be removed. If the sender doesn't tell you, then you're probably sunk. -- James Carlson, Solaris Networking <[EMAIL PROTECTED]> Sun Microsystems / 1 Network Drive 71.232W Vox +1 781 442 2084 MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677 _______________________________________________ networking-discuss mailing list [email protected]
