[AFS3-std] rxgk key version number of value zero

[Michael Meffie]

On Tue, 27 Nov 2012 11:37:05 -0500
Benjamin Kaduk <kaduk@MIT.EDU> wrote:

> We say that the connection's key number starts at zero, and is stored in 
> the checksum field of the rx header.
> 
> I was rereading kolya's rx-spec, and noticed that "a zero checksum field 
> value means that checksums are not being computed".
> 
> Given that we also say that this field is a spare field of the rx header, 
> I suspect that we don't care, but might as well double-check.  (It seems 
> like it would not be hard to start at 1 and skip multiples of 2^16 in the 
> 32-bit space.)
> 
> -Ben

Hello Ben,

I'm looking at section 3 of Kolya's document, and see:

   The Checksum field allows for an optional packet checksum.  A zero 
   checksum field value means that checksums are not being computed.  An
   Rx security protocol (identified by the security field, described
   below) may choose to use this field to transport some checksum of the
   packet that is computed and verified by it (for example, rxkad uses 
   this field for a cryptographic header checksum).  Rx itself makes no
   use of the checksum field.

So, yes, this is a bit confusing, because the second sentence "A zero
checksum field value means..." is not consistent with the ones that
follow, especially the last "Rx itself maks no use of the checksum field".

It looks to me like it is fine for rxgk to set the checksum field to 0,
and have that be a valid value.

Thanks,
Mike


-- 
Michael Meffie <mmeffie@sinenomine.net>