Re: [Contiki-developers] packet analyzer for ContikiMAC

[Chiara S. <chi...@un...>]

First of all thanks for the help in this post.
To complete this discussion, I now write what I had noticed that time...
  
In Contiki-conf should be added: 
+++ #define WITH_CONTIKIMAC_HEADER 0 
and not 
--- #define CONTIKIMAC_CONF_WITH_CONTIKIMAC_HEADER 0

This makes some errors rise. I solved them by commenting lines 90 and 97 in this way:
//#if WITH_CONTIKIMAC_HEADER 
#define CONTIKIMAC_ID 0x00
struct hdr {
  uint8_t id;
  uint8_t len;
};
//#endif /* WITH_CONTIKIMAC_HEADER */

And adding at 665 the following line: struct hdr *chdr;

I also noticed that - doing this way - packets are visible not only in Wireshark (even if I noticed a time-mismatch in it - anyway: packets are shown) but  also in Radio Logger (from which I could not get any information before). 
Hopefully this may be useful for someone ...
Regards,
Chiara

Message: 5
Date: Fri, 21 Oct 2011 06:34:51 -0400
From: "David Kopf" <da...@em...>
Subject: Re: [Contiki-developers] packet analyzer for ContikiMAC
To: <con...@li...>
Message-ID: <367060D30FA049D688C845D60BC906E3@Ginger>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original

Correct, wireshark does not understand the contikimac header so can not 
decode the packets. As far as I can tell the only reason for the header is 
to tell how much padding was added to short packets so the other side can 
remove it (the padding makes the impv6 checksum wrong so without recovering 
the original length, technically all the icmpv6 options should be ignored), 
in contikimac.c:
/* SHORTEST_PACKET_SIZE is the shortest packet that ContikiMAC
allows. Packets have to be a certain size to be able to be detected
by two consecutive CCA checks, and here is where we define this
shortest size. */
#define SHORTEST_PACKET_ SIZE 43

#define CONTIKIMAC_CONF_WITH_CONTIKIMAC_HEADER 0 in the contiki-conf.h file 
will remove it and wireshark will then be happy. The only problem I have run 
into is a bad checksum on the initial multicast DIS at startup which delays 
joining the network. Fix that with #define SHORTEST_PACKET_SIZE 
43-18//fix checksum on multicast RPL DIS

Of course any padded packets after that may take more strobes to wake the 
recipient, but I have not seen any in webserver or ping traffic. I don't 
understand the 43; the contikimac pdf says two CCAs are done "within 0.5 
msec" so the shortest packet length would seem to be 500usec/32usec = 15 
bytes
See 
http://www.jennic.com/files/support_files/JN-AN-1035%20Calculating%20802-15-4%20Data%20Rates-1v0.pdf



-----Original Message----- 
From: Chiara Sammarco
Sent: Friday, October 21, 2011 4:25 AM
To: con...@li...
Subject: [Contiki-developers] packet analyzer for ContikiMAC

Hi all,
So far I've used Cooja for emulating a network of Tmote Sky and I've 
analyzed the .pcap file (generated by the radio logger) with Wireshark 1.7.0 
Development Version.
I've noticed that if I use the ContikiMAC as RDC layer, Wireshark inspection 
with .pcap file does not work properly; instead using sicslowmac or nullrdc, 
It works (so I manage to the type and the content of the exchanged 
messages).
Does anyone know why this happens? Is there a way to inspect packet exchange 
for ContikiMAC as RDC layer?
Thank you in advance.
Regards,
Chiara

--------------------------------
Chiara Sammarco
PhD Student at ARTS Lab - DIMET
University of Reggio Calabria
Engineering Faculty
Via Graziella, loc. Feo di Vito
89122 Reggio Calabria - Italy
Tel/fax: +39 0965 875 276


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--------------------------------
Chiara Sammarco
PhD Student at ARTS Lab - DIMET
University of Reggio Calabria
Engineering Faculty
Via Graziella, loc. Feo di Vito
89122 Reggio Calabria - Italy
Tel/fax: +39 0965 875 276