Wireshark · Ethereal-dev: [Ethereal-dev] Re: BACnet packet-bacapp corrections

[Steve Karg <skarg@xxxxxxxxxxxxxxxxxxxxx>]

Hi Jaap,

> How about lvt == 0? Is that an allowed value?

The BACnet standard states:
"The encoding of an unsigned integer value shall be primitive, with at 
least one contents octet." and "The encoding of a signed integer value 
shall be primitive, with at least one contents octet."

So zero is not allowed.  Attached is a patch replacing the first two.

Patch summary:

1) BACnet signed values were being decoded incorrectly for negative 
values since BACnet tries to be clever and minimizes the number of bytes 
sent on the wire and drops the leading FF on negative values.  For 
example, -200 is passed as FF 38 on the wire, but would display as 65336.

2) Since the BACnet unsigned values were decoded using a 64-bit entity, 
I changed the decoding such that allows all 8 bytes to be decoded.  The 
function can now decode 5, 6, and 7 byte values.

3) Corrected warning about signed/unsigned in a pointer parameter.

Thanks for being picky and reveiwing the code!

Best Regards,

Steve

Attachment: bacapp.patch.gz
Description: GNU Zip compressed data