OPEN QUESTION: Can srsRAN (4G) trigger specific EMM Cause on demand?

[robert-r-colvin]

Hi all!

firstly apologies if this is the wrong place to ask this question. I didn't find a better place, but please feel free to send me somewhere else if I should!

I am looking into srsRAN 4G to test devices and specifically would like to test the devices response to specific EMM Cause codes - is it possible in srsRAN to reject attach attempts with a specific cause code? I have searched the code base and documentation but haven't found any references (yet!)

... though I haven't seen anyone else trying or wanting to do it either!

thanks!

[andrepuschmann]

Hey - You mean RRC reject or attach reject? I don't think you can dynamically select the cause in an RRC message. But take a look at e.g. send_connection_reject(procedure_result_code::error_mme_not_connected); and manually code the cause you want to test. If you refer to EPC attach reject you'd need to hard-code the response there.
Hope that helps.

[robert-r-colvin]

cheers mate will take a look;

things like "IMSI unknown in HSS" are easy enough, and maybe most of the causes related to UE identification.

Subscription related is very interesting, so Cause #11 - PLMN not allowed, #12 - TA not allowed, #13 Roaming not Allowed, etc. #15 No suitable cells in tracking area! .... these all seem to be defined here:

srsRAN_4G/lib/include/srsran/asn1/liblte_mme.h

Line 647 in 6bcbd9e

#define LIBLTE_MME_EMM_CAUSE_IMSI_UNKNOWN_IN_HSS 0x02

so find a way to, through a config file or similar, set the reject cause I want to trigger