Wireshark-dev: Re: [Wireshark-dev] [PATCH] IEEE 802.15.4 dissectors and libpcap support.
Hi Richard,
> The ccitt crc16 routines are already in crc16.h - please could you
use them
> rather than reinventing this particular wheel?
When I first wrote the dissectors, I was having trouble finding a CRC
algorithm that would produce the right answer. IEEE 802.15.4 transmits
bytes in reflected bit-order, and calculates the CRC over those bits as
they are transmitted over the air. IEEE 802.15.4 also further violates
the CCITT specification by using initial and final values of 0x0000,
instead of 0xFFFF. I now know substantially more about CRC's than I did
when I first wrote those functions, and I really should have replaced
them with those already available in Wireshark. They have been fixed in
the attached patch.
> Your patch messes up the indentation in libpcap.c - please can you
sort it out?
My apologies about that, my editor mucked that up, and I thought I had
fixed the damage, but apparently I didn't. I should note that the
indentation in libpcap.c is inconsistent anyways (some parts use soft
tabs, others use hard tabs). Hopefully, the attached patch should
correct any out-of-place hard or soft tabs.
> I'm not generally a fan of 500-line functions - any chance the
offender could
> be split up a bit?
I assume you are referring to dissect_ieee802154_common()? Well, I have
taken the time to break that function down a bit, but it's still a bit
on the lengthy side (just over 300 lines). I also broke the command
dissector function down into a bunch of subroutines. Hopefully this is
more to your liking.
> Please could you create a Protocols/ieee802154 page on the wiki, and
add an
> example capture, so we can see what your dissector does?
Certainly, I would be more than happy to add a protocol Wiki page for
IEEE 802.15.4, is it a high priority, or can I get that done later this
week once I have some time?
Thanks,
Owen Kirby
Attachment:
ieee802154r3.patch.gz
Description: GNU Zip compressed data
