[BACKPORT] sys/net/nanocoap: align request handling with spec

[maribu]

Backport of sys/net/nanocoap: align request handling with spec #21163

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Contribution description

• Do not reply with a reset message to a reset or an ACK message
• Reply with a reset message when not able to process a CON/NON message (not even a suitable error reply)

Testing procedure

$ sudo ip tuntap add tap0 mode tap user $(whoami)
$ sudo ip link set tap0 up
$ make BOARD=native64 -C examples/nanocoap_server -j flash term

$ cat test.py                     
import socket, aiocoap
m = aiocoap.Message()
m.code = 0
m.mid = 0
m.mtype = aiocoap.RST
s = socket.socket(socket.AF_INET6, socket.SOCK_DGRAM)
s.connect(('fe80::9826:30ff:feb8:31f4', 5683, 0, socket.if_nametoindex('tap0')))
s.send(m.encode())
s.recv(1024)
$ python3 test.py

With master:

$ tshark -i tap0 -Y "coap"
Capturing on 'tap0'
    3 0.000397706 fe80::9826:30ff:feb8:31f3 56273 5683 fe80::9826:30ff:feb8:31f4 CoAP 66 RST, MID:0, Empty Message
    4 0.000675868 fe80::9826:30ff:feb8:31f4 5683 56273 fe80::9826:30ff:feb8:31f3 CoAP 66 RST, MID:0, Empty Message

Note the RST "reply" to the RST

With this PR:

$ tshark -i tap0 -Y "coap"
Capturing on 'tap0'
    7 3.994693734 fe80::9826:30ff:feb8:31f3 54684 5683 fe80::9826:30ff:feb8:31f4 CoAP 66 RST, MID:0, Empty Message

Note that no RST "reply" is send to the RST

Issues/PRs references

None

[maribu]

Tested:

First (packet 3) a RST injected to the server (correctly got no RST as reply), afterwards pings send and correctly got RSTs.

$ tshark -i tap0 -Y "coap"
Capturing on 'tap0'
    3 1.922254924 fe80::9826:30ff:feb8:31f3 48728 5683 fe80::9826:30ff:feb8:31f4 CoAP 66 RST, MID:0, Empty Message
    6 22.301734177 fe80::9826:30ff:feb8:31f3 58943 5683 fe80::9826:30ff:feb8:31f4 CoAP 66 CON, MID:17073, Empty Message
    7 22.302041251 fe80::9826:30ff:feb8:31f4 5683 58943 fe80::9826:30ff:feb8:31f3 CoAP 66 RST, MID:17073, Empty Message
    8 23.302259263 fe80::9826:30ff:feb8:31f3 58943 5683 fe80::9826:30ff:feb8:31f4 CoAP 66 CON, MID:17074, Empty Message
    9 23.302580815 fe80::9826:30ff:feb8:31f4 5683 58943 fe80::9826:30ff:feb8:31f3 CoAP 66 RST, MID:17074, Empty Message
   10 24.304082908 fe80::9826:30ff:feb8:31f3 58943 5683 fe80::9826:30ff:feb8:31f4 CoAP 66 CON, MID:17075, Empty Message
   11 24.304431790 fe80::9826:30ff:feb8:31f4 5683 58943 fe80::9826:30ff:feb8:31f3 CoAP 66 RST, MID:17075, Empty Message
   12 25.306029669 fe80::9826:30ff:feb8:31f3 58943 5683 fe80::9826:30ff:feb8:31f4 CoAP 66 CON, MID:17076, Empty Message
   13 25.306453672 fe80::9826:30ff:feb8:31f4 5683 58943 fe80::9826:30ff:feb8:31f3 CoAP 66 RST, MID:17076, Empty Message
   14 26.308035518 fe80::9826:30ff:feb8:31f3 58943 5683 fe80::9826:30ff:feb8:31f4 CoAP 66 CON, MID:17077, Empty Message
   15 26.308374502 fe80::9826:30ff:feb8:31f4 5683 58943 fe80::9826:30ff:feb8:31f3 CoAP 66 RST, MID:17077, Empty Message
   16 27.309967650 fe80::9826:30ff:feb8:31f3 58943 5683 fe80::9826:30ff:feb8:31f4 CoAP 66 CON, MID:17078, Empty Message
   17 27.310318876 fe80::9826:30ff:feb8:31f4 5683 58943 fe80::9826:30ff:feb8:31f3 CoAP 66 RST, MID:17078, Empty Message
   18 28.311765589 fe80::9826:30ff:feb8:31f3 58943 5683 fe80::9826:30ff:feb8:31f4 CoAP 66 CON, MID:17079, Empty Message
   19 28.312233154 fe80::9826:30ff:feb8:31f4 5683 58943 fe80::9826:30ff:feb8:31f3 CoAP 66 RST, MID:17079, Empty Message

[MrKevinWeiss]

Perfect, thanks for retesting (as this was not just a simple backport)! ACK!

[riot-ci]

Murdock results

✔️ PASSED

0d6cb6f sys/net/nanocoap: align request handling with spec

Success	Failures	Total	Runtime
10271	0	10271	09m:29s

Artifacts

• Documentation preview