Re: RE: RE: RE: [Freeipmi-devel] Using libfreeipmi interface

[Albert Chu]

Hi Andrew,

> Where did the 0x3f arbitrary sequence limit come from anyway?  I
> couldn't find any reference to sequence number limits in the IPMI spec
> or platform specs.

The 0x3f comes from the fact the requester sequence number is 6 bits
long.  You can see this in section 7.3, figure 7-1 of the IPMI 1.5 spec.
 (That section is pointed to by section 12.4, which discusses IPMI over
Lan).  

I get the feeling you are passing in session sequence numbers, which are
32 bits, in place of the requester sequence numbers, which are 6 bits
long.  The session sequence number is passed to the fill_hdr_session()
function when building a packet and the requester sequence number is
passed to fill_lan_msg_hdr().

Al

--
Albert Chu
address@hidden
Lawrence Livermore National Laboratory

----- Original Message -----
From: "Cress, Andrew R" <address@hidden>
Date: Friday, October 29, 2004 7:44 am
Subject: RE: RE: RE: [Freeipmi-devel] Using libfreeipmi interface

> 
> re: IPMI_LAN_SEQ_NUM_MAX (=0x3F)
> 
> As a use case, to understand the problem this causes, one of my
> applications 'showsel' allows reading the IPMI SEL.  This can be quite
> long on Intel platforms (e.g. 4032 record capacity on one test system
> here).  On one test system, with 257 SEL records, the sequence number
> increments to 267 (0x10B), and wrapping the sequence number during 
> thissession causes the IPMI chipset to ignore the command with a
> duplicate/lower sequence number (and the app/lib would hang).  This
> would also affect the fish/sel script/app similarly.  The sequence
> number is 32 bits, and incrementing up through that capacity is 
> allowed.My Tiger (ia64) system isn't up right now, but as I recall, 
> it behaves
> the same way.
> 
> Where did the 0x3f arbitrary sequence limit come from anyway?  I
> couldn't find any reference to sequence number limits in the IPMI spec
> or platform specs.
> 
> So, my position is that it is not just inappropriate to check sequence
> number bounds at 0x3f, but invalid for IPMI 1.5 platforms with LAN
> support (a bug).
> 
> Andy
> 
> -----Original Message-----
> From: Albert Chu [mailto:address@hidden 
> Sent: Thursday, October 28, 2004 8:04 PM
> To: Cress, Andrew R
> Cc: address@hidden
> Subject: Re: RE: RE: [Freeipmi-devel] Using libfreeipmi interface
> 
> 
> > I also found a problem with the  IPMI_LAN_SEQ_NUM_MAX (=0x3F).
> > There isn't any precedent in IPMI 1.5 for this, and limiting the 
> 32-
> > bitsequence number to 6 bits causes some problems, since the BMC 
> > LAN won't handle wrapping the sequence number back to 0 or 1 
> after 63 
> > (0x3f).
> 
> I'm not quite convinced this is a problem.  The bounds check makes the
> user knowledgeable to the fact that arbitrary sequence numbers aren't
> allowed.  I spoke to a few other developers I work with, and they feel
> that the bounds checking is more appropriate.  Ab, Ian, Bala, what are
> your thoughts??
> 
>