[openib-general] Re: RMPP Message Format Errors

[Hal Rosenstock]

Hi Eitan,

On Sat, 2005-08-27 at 11:14, Eitan Zahavi wrote:
> Sean Hefty wrote:
> 
> > 
> > I believe that the 220 byte payload length is for all RMPP MADs.  Only the
> > common and RMPP header lengths are ignored.
> Yes.
> > 
> > 
> > 
> >>Doesn't it need to account for a "partial" rather than full last segment
> >>transferred data in the first segment length ?
> Yes I think it needs to use the partial length.

Agreed.
 
> > What I couldn't easily tell from the spec is whether a partial last segment is
> > included in the initial payload length or not.  I read it as: "PayloadLength
> > counts all the bytes in the TransferredData field of the DATA packet format."
> > In my interpretation, partial data is indicated by the PayloadLength field in
> > the last segment only.  It's quite possible that my interpretation is incorrect,
> > in which case the calculation in the RMPP code is off.
> I agree the text might be missing an example or two for clarification.
> Anyway, we probably can use the IB Analyzer as the ultimate 
> interpretation test. Note that there are IB implementations that uses 
> the first segment payload length as the source of packet length and 
> count on it to represent the correct DATA length.
> 
> We can take your interpretation to discussion in the IBTA MGTWG for 
> further discussion.

I think the spec wording is ambiguous and we should take it to the
MgtWG. I believe your interpretation is the intent but could not find
any specific language other than the valid bytes in terms of the last
segment. The first segment length references transferred data which is
the whole segment. I'll send something to MgtWG on this and copy
openib-general.

> Is the effort for fixing it big?

It's a one line patch. I sent it previously.

-- Hal