eswifi recvfrom() not properly implemented on disco_l475_iot1

[panekk]

Describe the bug
Zephyr's LwM2M client uses recvfrom function with non-NULL from and fromlen arguments, but eswifi_socket_recvfrom() doesn't support them. Is there any chance to run the LwM2M client on B-L475E-IOT01A board?

To Reproduce
Run LwM2M client on B-L475E-IOT01A and try to register to the LwM2M Server.

Expected behavior
Successful registration to the server.

Impact
LwM2M client is unusable when eswifi modem is used.

Logs and console output

[00:00:04.848,000] <inf> net_lwm2m_rd_client: RD Client started with endpoint 'zephyr-test' with client lifetime 30
[00:00:05.412,000] <err> net_lwm2m_engine: Error reading response: 134

Environment (please complete the following information):

• OS: Ubuntu 20.04
• Toolchain: Zephyr SDK
• Version used: Zephyr OS build zephyr-v2.3.0-599-g1105aa521c29

[jukkar]

Hmm, I wonder why eswifi does not support this.

cc: @rlubos & @loicpoulain

[rlubos]

Well I'm a bit confused with this driver in general, since it seems to implement both, net offloading and socket offloading. Which one is used in this case?

As for socket offloading approach, it's clear that the recvfrom() implementation is incomplete:
https://github.com/zephyrproject-rtos/zephyr/blob/master/drivers/wifi/eswifi/eswifi_socket_offload.c#L349

[panekk]

CONFIG_WIFI_ESWIFI selects NET_SOCKETS_OFFLOAD by default, so I wonder if it's even possible to disable the offloading. Setting CONFIG_NET_SOCKETS_OFFLOAD, CONFIG_NET_OFFLOAD and CONFIG_WIFI_OFFLOAD to n doesn't help anyway, with warnings printed for the second two ((...) was assigned the value 'n' but got the value 'y'). It isn't possible to disable the offloading using menuconfig too.

[rlubos]

@nashif I'm not the one who should work on this one, It's not an LwM2M issue but a faulty/incomplete wifi driver implementation.

@panekk If eswifi does select NET_SOCKETS_OFFLOAD it means it uses socket offloading, hence the above answer explains the behaviour (the recvfrom implementation is incomplete). Unfortunately it seems the original author is not reachable through github anymore, I'm not sure who should be notified about this.
BTW, if some module uses select on certain symbol in Kconfig, it's not possible to "deselect" it.

[loicpoulain]

@jukkar, @rlubos, I'm going to have a look at this by the end of the week

[loicpoulain]

So, looking at eswifi behavior, to support that we need to handle 'UDP SVR' events which are on the below form:
[UDP SVR] Accepted 192.168.1.23:4242[EOMA]

We need to save ip/port so that it can be passed back in recvfrom. Seems only one UDP client can be handled at a time, we need to stop/restart UDP 'accept' after each client... will try to implement something.

I've started #29898 to address UDP server issue(s).

[github-actions]

This issue has been marked as stale because it has been open (more than) 60 days with no activity. Remove the stale label or add a comment saying that you would like to have the label removed otherwise this issue will automatically be closed in 14 days. Note, that you can always re-open a closed issue at any time.