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Re: [tinydtls-dev] Feedback trying to use tinyDTLS with Contiki 2.7 
Hello,
I have new feedback. When sending, the node was crashing because of the watchdog because netq send_queue got corrupted. This was because a node was added many times which made the queue being an infinite loop.
I added a sanity check in netq for this so dtls does not crash. https://github.com/iot-lab/armour-tinydtls/commit/b276a3b6cafa82ace11bcfae170cc8378890d0d5
Now the reason why it was added twice, is because the contiki 'dtls_retransmit_process' implementation does not mimic the basic 'dtls_check_retransmit'. It was not removing the node of the queue but dtls_transmit is always re-adding it. I just duplicated the implementation, thinking of how to factorize it could prevent this problem. 
https://github.com/iot-lab/armour-tinydtls/commit/99ba634a03ebbb1692d5543569173a48643e2223
Also the node was freed while still in the queue. (this may be detectable by checking '->next' for null and setting next to null in 'netq_remove' or 'netq_pop_first') Also 'node_free' could memset the node to 0 to detect cases where its reused.
I think it only happen in my case because I'm currently loosing a lot of packets. 
If the packets always arrive, it must solve itself in some way.


Now after some time, the client and server get stuck I will try to see why.

Please let me know what you think of the changes.
I would better have them integrated in the main repository.


Regards,
Gaëtan


On 11/28/2016 05:26 PM, Gaëtan Harter wrote:

Hello,

for a research project, I need to make coap+dtls work on our hardware.
We already have a working Contiki port and I start by integrating tinyDTLS and validate as much as possible.
I started from a direct clone of the repository, added a shell app in my contiki repo to allow running test commands. My first goal was to run the unit tests provided in tinydtls/sha2 and tinydtls/ecc with every tests packaged in the same firmware. 

The first issues I encountered were:
* 'Makefile.tinydtls' still references 'debug.c' instead of 'dtls_debug.c' * Contiki 2.7 has different path for 'uip.h' and 'uip_debug.h' so I added a custom CONTIKI_2_7 define to know which one to use. 
* Name conflicts in 'testecc.c' and 'testfield.c'
* A boggus name: 'testfiled' instead of 'testfield'
* Some compilation warning

I fixed all of them here for the moment:

https://github.com/iot-lab/armour-tinydtls/compare/0016138fe3998552eee3987a1c09da43a23c9fb5...master

These were really easily fixed.
I will contribute that back to the main repository, but wanted to get some feedback here before going to gerrit. 


Now two other problems that occured:

Testing takes time on slow hardware
-----------------------------------
I execute the tests from testecc in another C file, (just call the test functions from another app). It crashed in edcsaTest, adding some prints showed it never crashed at the same time. After a lot of debugging I found that the watchdog was triggered and was rebooting the node.
It could be a good idea to add some `watchdog_periodic();` calls between each test. 
It's not in my clone as I am calling the function from another file.


After that, all tests are ok and working.


Include mess
------------
There is a bigger problem I have not written a solution to, I just fell on it right now.
I'm now at the level of trying to run a client and a server. I took the example files from here: 

   https://github.com/spark/tinydtls/tree/master/examples/contiki
The client was crashing because it accesses invalid addresses when using "dtls_security_params(peer)". I tried to print, its value was changing between 'dtls_new_peer' and just after returning its value to 'dtls_connect'. Using gdb I saw that in these two functions, the definition of a peer was different. One was built with UTASH support and not the other.
And in fact, not every header is including "dtls_config.h" and so "platform-specific/platform.h" This led to a type being defined differently in two C files from the library.
I quickly tried try removing the define NOHASH in "platform-specific/platform.h" 

   -#define DTLS_PEERS_NOHASH 1
   +//#define DTLS_PEERS_NOHASH 1

Then I got the following compilation warning:

   In file included from ../../../../apps/tinydtls/dtls_debug.h:24:0,
                     from ../../../../apps/tinydtls/dtls.c:39:
   ../../../../apps/tinydtls/global.h:139:0: warning: "uthash_fatal"
   redefined
     #define uthash_fatal(msg) return(-1) /* fatal error in uthash */
     ^
   In file included from ../../../../apps/tinydtls/dtls.c:36:0:
   ../../../../apps/tinydtls/uthash.h:70:0: note: this is the location
   of the previous definition
     #define uthash_fatal(msg) exit(-1)        /* fatal error (out of
   memory,etc) */

So it requires even more cleaning.
But at least the client is not crashing on the same problem.
(Currently it's rebooting because of the watchdog too, but I did not investigate.) 

What would be the idea to fix this include problem?
Also, currently both "tinydtls.h" and "dtls_config.h" are defining DTLS_ECC, DTLS_PSK and WITH_CONTIKI. 

I will keep working on this and give feedback.


Regards,
Gaëtan
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