Hard coded context ID of 0 in the Serial LTE Modem application (nRF SDK 2.0.0)

RE: Hard coded context ID of 0 in the Serial LTE Modem application (nRF SDK 2.0.0)

dejans — Tue, 28 Jun 2022 13:30:39 GMT

Hi Hans Jørgen,

It is good to hear that the issue has been resolved.

Best regards,
Dejan

RE: Hard coded context ID of 0 in the Serial LTE Modem application (nRF SDK 2.0.0)

dejans — Thu, 23 Jun 2022 08:39:15 GMT

Hi Hans Jørgen,

You could apply these changes. This should work regardless if your network allows non-zero primary context or not. Cid 0 is assumed as primary context (in init state), but it can be overridden with <cid> parameter in AT command.

Best regards,
Dejan

RE: Hard coded context ID of 0 in the Serial LTE Modem application (nRF SDK 2.0.0)

Hans Jorgen Grimstad — Wed, 22 Jun 2022 11:49:27 GMT

Hi !

It seems that the best solution for me was to add the following configs to the prj.conf (instead of defining the context with +CGDCONT, activating with +CGACT and then deactivating the default with +CGACT)

CONFIG_PDN=y

CONFIG_PDN_DEFAULTS_OVERRIDE=y

CONFIG_PDN_SYS_INIT=y

CONFIG_PDN_DEFAULT_APN="<our APN>"

CONFIG_PDN_DEFAULT_FAM_IPV4V6=y

Best Regards

Hans Jørgen Grimstad

Lab5e AS

RE: Hard coded context ID of 0 in the Serial LTE Modem application (nRF SDK 2.0.0)

Hans Jorgen Grimstad — Tue, 21 Jun 2022 18:36:32 GMT

Hi !

I am not trying to use multiple PDP contexts.

I created a new one using +CGDCONT and then deactivated the default context with +CGACT. I then ended up with a single active context with a context id == 1. The non-zero id breaks any attempts to use the context to transfer data in the SLM code.

The SLM code works just fine for AT#XSENDTO and AT#XRECVFROM if the correct (non-zero) cid is transferred in the calls to util_get_ip_addr and util_resolve_host, so I don't quite understand why it isn't supported.

The source code documentation for these two functions is also clear about this:

* @param[in] cid PDP Context ID as defined in "+CGDCONT" command (0~10).

If it's the case that only a single context with an id of 0 is permitted in this version of SLM, maybe it would have been better to:

Explicitly include the CONFIG_PDN_DEFAULT_APN and CONFIG_PDN_DEFAULTS_OVERRIDE configs (along with maybe a comment or two) in the SLM prj.conf, since this would make it a bit more explicit (I guess that by using these I can specify my own default context that will end up with a cid == 0 ?)
Disallow creation of PDP contexts with a non-zero id in the +CGDCONT command, since being able to create a seemingly ok PDP context that can't be used for sending data is a somewhat confusing user experience.

> For socket send and receive, previously mentioned socket option can be used to bind secondary PDP context.

Which socket option are you referring to ?

Best Regards

Hans Jørgen

RE: Hard coded context ID of 0 in the Serial LTE Modem application (nRF SDK 2.0.0)

dejans — Tue, 21 Jun 2022 14:43:55 GMT

Hi Hans Jørgen,

Currently, multiple PDP contexts are supported only by ICMP echo request #XPING and socket #XSOCKET. For socket send and receive, previously mentioned socket option can be used to bind secondary PDP context.

Best regards,
Dejan

RE: Hard coded context ID of 0 in the Serial LTE Modem application (nRF SDK 2.0.0)

Hans Jorgen Grimstad — Tue, 21 Jun 2022 11:10:20 GMT

Hi !

It seems that the same hardcoded cid is present in calls to :

void util_get_ip_addr(int cid, char *addr4, char *addr6)

Running AT#XBIND will result in:

<err> slm_sock: Get local IPv4 address failed

If I tweak the SLM source code and pass the correct cid, then AT#XBIND and AT#XRECVFROM behaves as expected.

Regards

Hans Jørgen

RE: Hard coded context ID of 0 in the Serial LTE Modem application (nRF SDK 2.0.0)

dejans — Mon, 20 Jun 2022 15:11:11 GMT

Hi,

I have reported your finding internally. I'll get back to you when I get new information, possibly till the end of this week.

Best regards,
Dejan