pkg/tinydtls: DTLS handshake does not work

[jia200x]

Description

The DTLS handshake does not work anymore since 2023.01.
I'm currently running examples/gcoap_dtls and see that the client sends "Client Hello" but gets no response from the server. After some seconds the node generates an Alert, probably as a result of a failed handshake.

DTLS seems to be working fine on 2022.10.

Steps to reproduce the issue

Try examples/gcoap_dtls with the default settings and perform a GET request using DTLS (port 5684).

Expected results

> coap get fe80::804e:b4ff:fe15:3164 5684 /.well-known/core
coap get fe80::804e:b4ff:fe15:3164 5684 /.well-known/core
gcoap_cli: sending msg ID 26500, 23 bytes
> gcoap: response Success, code 2.05, 46 bytes
</cli/stats>;ct=0;rt="count";obs,</riot/board>

Actual results

> coap get [fe80::804e:b4ff:fe15:3164]:5684 /.well-known/core
coap get [fe80::804e:b4ff:fe15:3164]:5684 /.well-known/core
gcoap_cli: sending msg ID 12284, 23 bytes

Versions

Operating System Environment
----------------------------
         Operating System: "Arch Linux" 
                   Kernel: Linux 6.2.9-arch1-1 x86_64 unknown
             System shell: GNU bash, version 5.1.16(1)-release (x86_64-pc-linux-gnu)
             make's shell: GNU bash, version 5.1.16(1)-release (x86_64-pc-linux-gnu)

Installed compiler toolchains
-----------------------------
               native gcc: gcc (GCC) 12.2.1 20230201
        arm-none-eabi-gcc: arm-none-eabi-gcc (GNU Tools for Arm Embedded Processors 7-2017-q4-major) 7.2.1 20170904 (release) [ARM/embedded-7-branch revision 255204]
                  avr-gcc: avr-gcc (GCC) 12.2.0
           msp430-elf-gcc: missing
       riscv-none-elf-gcc: missing
  riscv64-unknown-elf-gcc: missing
     riscv-none-embed-gcc: missing
     xtensa-esp32-elf-gcc: missing
   xtensa-esp8266-elf-gcc: missing
                    clang: clang version 15.0.7

Installed compiler libs
-----------------------
     arm-none-eabi-newlib: "2.5.0"
        msp430-elf-newlib: missing
    riscv-none-elf-newlib: missing
riscv64-unknown-elf-newlib: missing
  riscv-none-embed-newlib: missing
  xtensa-esp32-elf-newlib: missing
xtensa-esp8266-elf-newlib: missing
                 avr-libc: "2.1.0" ("20220128")

Installed development tools
---------------------------
                   ccache: ccache version 4.8
                    cmake: cmake version 3.26.2
                 cppcheck: missing
                  doxygen: 1.9.6
                      git: git version 2.40.0
                     make: GNU Make 4.4.1
                  openocd: Open On-Chip Debugger 0.11.0
                   python: Python 3.10.10
                  python2: Python 2.7.18
                  python3: Python 3.10.10
                   flake8: 6.0.0 (mccabe: 0.7.0, pycodestyle: 2.10.0, pyflakes: 3.0.1) CPython 3.10.10 on
               coccinelle: missing

[LizzieDE110]

Hello, any news?

I am trying to run examples/gcoap_dtls on native board and when I am trying a Get request, I have:

> coap get [fe80::6c47:25ff:fe32:5271%tap1]:5684 /riot/board 
coap get [fe80::6c47:25ff:fe32:5271%tap1]:5684 /riot/board 
gcoap_cli: sending msg ID 16874, 17 bytes
gcoap_cli: no observer for /cli/stats

Expected result:

> coap get [fe80::6c47:25ff:fe32:5271%6]:5683 /riot/board
coap get [fe80::6c47:25ff:fe32:5271%6]:5683 /riot/board
gcoap_cli: sending msg ID 13924, 17 bytes
gcoap: response Success, code 2.05, 6 bytes
native

Thanks in advance