Re: [Contiki-developers] Two bytes between 802.15.4 header and 6LoWPANheader

[David K. <da...@em...>]

I suspect your link level header length is too long by two bytes.
Why I don't know, have you changed  UIP_CONF_LLH_LEN or UIP_LLH_LEN defines?
The uip stack uses that to place the 6lowpan data at the end of the low 
level header, see uip.h and uipopt.h.
You could try defining that as 12 instead of 14.

-----Original Message----- 
From: Timo Boettcher
Sent: Monday, June 20, 2011 10:17 AM
To: Contiki developer mailing list
Subject: [Contiki-developers] Two bytes between 802.15.4 header and 
6LoWPANheader

Hi!

During testing the examples/ipv6/rpl-udp/udp-client.c example (using
contiki from current git), I noticed two bytes between the 802.15.4
header and the 6LoWPAN header.
The attached .pcap file contains a packet from cooja radiologger with
the encapsulation removed using scapy. The first packet in the .pcap
is unchanged, the second packet in the .pcap is the same packet with
the additional two bytes removed. These are bytes numbered 22 and 23 of
the first packet, with values 0x00 and 0x29, just before the 6LoWPAN
dispatch bits (011xxxxx for IPHC, 0x7e in this case).
I could not find any part of the 6LoWPAN (or any other) specification
that explains the meaning of those bytes. Did I miss anything there, or
is this a bug?
When these bytes are removed, current Wireshark (tested with Wireshark
svn 37373) and scapy can recognize and dissect the 6LoWPAN header.