DTLS PSK CoAP Client

RE: DTLS PSK CoAP Client

ced27 — Fri, 22 Oct 2021 08:41:07 GMT

Hi Dennis,

i am trying to add dtls to coap client, please can you help me with some advise on how to go about it. I am really stuck right now.

Thanks

Cedric

RE: DTLS PSK CoAP Client

Giang — Thu, 22 Aug 2019 08:24:54 GMT

Hi Dennis ,

Can you give me some advise about how to add dtls library to simple_coap_client or server ?

Thank !!

RE: DTLS PSK CoAP Client

[Stihl] Dennis — Tue, 20 Aug 2019 05:20:18 GMT

Hello,

i was able to implement the new coap library into our project now. During a short test there were no problems and also no memory overflows. The updated library solved my problems, thanks.

Best regards,

Dennis B.

RE: DTLS PSK CoAP Client

[Stihl] Dennis — Thu, 04 Jul 2019 14:29:00 GMT

Hi Martin,

i was already notified this morning by Thomas that the new version is available. So I tried my code directly. Unfortunately I had to adjust some things to make it work with the new version (I used version v0.4.0 before). The CoAP library seems to have been completely revised. This also changed the API. So a migration is not possible so easily. Because of this I currently use the old coap library. The first look at the reworked coap library suggests that the problems have been fixed.

I also updated the modem firmware to 1.0.0. unfortunately i had more problems with connecting via nb-iot during the day than with the old firmware. Sometimes i had to reboot the board 2 times until it was able to establish the connection. But it could also be due to the base station...

Best regards,

Dennis B.

RE: DTLS PSK CoAP Client

Martin Lesund — Thu, 04 Jul 2019 13:31:00 GMT

Hi Dennis,
I am sincerely sorry for the delay.

I suppose that there are some updates regarding this issue?

I would like you to upgrade to v1.0.0 if you already haven't which has introduced a lot of fixes.

RE: DTLS PSK CoAP Client

[Stihl] Dennis — Thu, 16 May 2019 08:05:56 GMT

Hi Martin,

I have logged the dynamic memory allocation of the coap client and displayed it in an Excel table.

as you can see not all allocated memory areas are released again. Is there a function in the coab lib that releases the memory or can a variable be set that releases the memory after use?

I have already written a function that allocates the memory. This function is passed with the function coap_init(). I use a buffer according to the FIFO principle which automatically releases the oldest memory area. An empty function was passed as free function, because the memory is now released automatically. This method works without problems so far.

Best regards,

Dennis B.

RE: DTLS PSK CoAP Client

[Stihl] Dennis — Wed, 15 May 2019 15:05:36 GMT

Hi Martin,

i have already set the varable CONFIG_HEAP_MEM_POOL_SIZE=16384 in the prj.conf. As I understand it, 16384 is the largest possible number (see: zephyr_doc). Also increasing the CONFIG_MAIN_STACK_SIZE did not bring any improvement. After the successful exchange of several coap messages, the function coap_message_new from the library returns the error code 12.

Best regards,

Dennis B.

RE: DTLS PSK CoAP Client

Martin Lesund — Wed, 15 May 2019 13:11:08 GMT

Hi Dennis,

Great work that you found out the issue.

Could you try to increase the memory in the prj.conf file?

RE: DTLS PSK CoAP Client

[Stihl] Dennis — Wed, 15 May 2019 09:16:47 GMT

Hi,

after long debunging sessions i found out how to get the coap client to run with dtls:

If the parameter CONFIG_NRF_COAP_PORT_COUNT is set to 0 (the default value is 1), it is possible to exchange more than one data using dtls + coap.

But now I've got a new problem:

After the successful exchange of several coap messages, the function coap_message_new from the library returns the error code 12 (Not enough core) when creating a new get request message (because no new memory can be allocated). Even a longer wait and a new coap_message_new() request throw this error. Only a complete restart can solve the problem!

How can I solve this problem, without making a restart? Do I have to provide my own function for allocating the memory and empty this pool accordingly or is there a better solution?

Best regards,

Dennis B.

RE: DTLS PSK CoAP Client

Martin Lesund — Wed, 15 May 2019 06:06:40 GMT

Hi Dennis,

Is it possible for you to share the capture file and PSK so we could analyze it?

(We can make this case private if there is some sensitive information.)

Best regards,

Martin L.

RE: DTLS PSK CoAP Client

Achim Kraus — Tue, 14 May 2019 20:21:03 GMT

Just, if it's possible:

Can you capture without decrypting the dtls records?

If "e958..." is the raw/encrypted "fragment" (part after the length field, see RFC6347, 4.3.1) of dtls record and your using TLS_PSK_WITH_AES_128_CCM_8 then the record seems to be wrong, it should start with the "epoch:seqn" . May be you can show the working records also without decryption.

RE: DTLS PSK CoAP Client

[Stihl] Dennis — Thu, 09 May 2019 13:13:34 GMT

Hi Martin

ah, now I get it 😆. Yes I am using version 3.0.1

Best Regards,

Dennis B.

RE: DTLS PSK CoAP Client

Martin Lesund — Thu, 09 May 2019 13:05:09 GMT

Hi Dennis,
I was talking about the latest stable Wireshark version 3.0.x.

Best Regards,

Martin L.

RE: DTLS PSK CoAP Client

[Stihl] Dennis — Thu, 09 May 2019 12:49:57 GMT

Hi Martin,

# If both connections use the same PSK, then this could be a Wireshark issue.

Unfortunately, I can't follow them mentally. As I already wrote Wireshark is able to decrypt all messages even after the first data exchange during a test setup from Californium DTLS Server + Californium DTLS Client. So the function PSK decryption with Wireshark works without problme. That's why it shouldn't be a problem for Wireshark, or should it? When using the nRF9160 Modem + Californium DTLS Server, the message cannot be decrypted after the first data exchange (see Wireshark screenshot). The 18.197.48.88 ip is the nRF9160 DK.

# I cannot see which version you are using, but I would recommend either way to update to the latest 3.0 release to see if that makes a difference.

Do you mean version v0.3.0? -> if yes: i've already written above that i used version v0.4.0-c1 and other untagged versions.

I think version 0.3.0 doesn't fully support coap. (the coap files don't exist - compare with v0.4.0-rc1)

Best Regards

Dennis B.

RE: DTLS PSK CoAP Client

Martin Lesund — Thu, 09 May 2019 12:19:31 GMT

Hi Dennis,

If both connections use the same PSK, then this could be a Wireshark issue.

I cannot see which version you are using, but I would recommend either way to update to the latest 3.0 release to see if that makes a difference.

Best Regards,
Martin L.

RE: DTLS PSK CoAP Client

[Stihl] Dennis — Thu, 09 May 2019 05:49:44 GMT

Hi Martin,

we have also tested the code with the latest firmware. The program still has the same behavior.

One indicator for the behavior of the program is that it hangs after the first data exchange. (See timestamp between package 15 and 16 in Wireshark screenshot)

Best Regards

Dennis B.

RE: DTLS PSK CoAP Client

Martin Lesund — Wed, 08 May 2019 14:23:31 GMT

Hi Dennis,
Are you using the newest modem firmware?

if not, please upgrade: https://www.nordicsemi.com/Products/Low-power-cellular-IoT/nRF9160/Download#infotabs

I would need some more time to look into this, since there is nothing that comes to my mind right away.

Thank you for your patience.

Best Regards,

Martin L.