RE: [Freeipmi-devel] Using libfreeipmi interface

[Cress, Andrew R]

Ian,

In IPMI 1.5 sections 6.11.8 through 6.11.11 it describes sequence number
handling for outbound and inbound.
Regarding wrapping, the spec clearly says that FFFF_FFFFh wraps to
0000_0000h, but otherwise packets with lower sequence numbers than the
current seqnum shall be "silently discarded".

Andy

-----Original Message-----
From: address@hidden
[mailto:address@hidden On
Behalf Of Ian Zimmerman
Sent: Thursday, October 28, 2004 9:00 PM
To: address@hidden
Subject: Re: [Freeipmi-devel] Using libfreeipmi interface



Andrew> I also found a problem with the IPMI_LAN_SEQ_NUM_MAX (=0x3F).
Andrew> There isn't any precedent in IPMI 1.5 for this, and limiting the
Andrew> 32- bitsequence number to 6 bits causes some problems, since the
Andrew> BMC LAN won't handle wrapping the sequence number back to 0 or 1
Andrew> after 63 (0x3f).

Al> I'm not quite convinced this is a problem.  The bounds check makes
Al> the user knowledgeable to the fact that arbitrary sequence numbers
Al> aren't allowed.  I spoke to a few other developers I work with, and
Al> they feel that the bounds checking is more appropriate.  Ab, Ian,
Al> Bala, what are your thoughts??

Ian> Hmm, where is the sequence number field specified?  The closest I
Ian> see is Figure 12-4 which is unfortunately quite unclear (to me at
Ian> least).  It doesn't say how many bits are taken by the LUN and how
Ian> many by Rqseq.  How have we come by tmpl_lan_msg_hdr_r[sq] - by
Ian> experiment?

Sorry for replying to myself :-)  Regardless of the spec, just the fact
that the number is going to be stuffed into a 6 bit field justifies the
check, IMHO.


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