Hi,
have a raspberry pi equipped with a MRF24j40 RF module. raspberry pi has
6lowpan stack installed.
I also have a telosb node install
with contiki/examples/ipv6/rpl-udp/udp-server.c
Communication between two linux node has no probelm. I am trying to make
contiki node and linux node communicate with each other.
In the test
I try to ping the address of the telosb node from raspberry pi like below
ping6 fe80::212:7400:1333:9d90%lowpan0
PING fe80::212:7400:1333:9d90%lowpan0(fe80::212:7400:1333:9d90) 56 data
bytes
64 bytes from fe80::212:7400:1333:9d90: icmp_seq=1 ttl=64 time=39.1 ms
64 bytes from fe80::212:7400:1333:9d90: icmp_seq=2 ttl=64 time=25.8 ms
64 bytes from fe80::212:7400:1333:9d90: icmp_seq=2 ttl=64 time=275 ms
it works fine
But when I increase the package size of the ping6 like
ping6 fe80::212:7400:1333:9d90%lowpan0 -s 200
Then I can not get any response from Contiki node.
I think it has something to to with the fragmentation on contiki
implemation and linux implemention, that they are somehow not compatible
By doing a tcpdump and analyze the result using wireshark, I can see that
when ping with -s 80, sender send 1 package, contiki repy with 2 fragmented
package, but rpi is unable to reassemble it. When ping with -s 200, sender
send several fragmented package, then contiki does not reply any thing.
What I also find out is that when the linux node sends 2 fragmented data,
the first fragment has a payload from 0-92, the second from 88-142, so they
have a overlap, it also causes the checksum of this package to be
wrong(link here is the wireshark screenshot
https://docs.google.com/document/d/1MtXeP1xHWuHZSAX1OHBTj465jjUnHdhyMvJrWM1kUCo/edit?usp=sharing
).
So I don't think it is correctly implemented. I think it is the reason that
make contiki node unable to reassemble them.
I am not good at kernel programming, and I can not pinpoint the place where
goes wrong.
Could anyone help me solve this issue?
Best Regards
Xeonqq
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