[srslte-users] Follow-up on "Tracking Area Update Reject" by Daly Dylanger in January 2018

[Patrik]

Nope, not a single response yet here on the forum. As far as I have understood TAU reject is not supported.

/Patrik

> 4 dec. 2019 kl. 11:58 skrev Johann T. <johann.tzt at gmail.com>:
> 
> 
> Hi Patrik,
> 
> Did you receive any response on your question?
> 
> I am also interested in the TAU Reject function. Though I haven't yet tried the code from Daly.
> 
> Regards,
> Johann
> 
> 
> 
>> On Mon, Nov 4, 2019 at 7:09 PM Patrik <pdjdev at gmail.com> wrote:
>> Hello!
>> 
>> This is my first post in this forum, and I hope that you could help me out here. 
>> 
>> I was looking into the older posts and found a question (from January 2018) where Daly Dylanger asked about Tracking Area Update Reject, and I am curious about knowing if there is an update on this issue (for example that this issue was resolved in any recent releases).
>> 
>> My understanding is that the reject was (still is) not implemented in srsLTE and the coding efforts to include the reject handling by Daly resulted in a conclusion that his code does not work in srsLTE while working fine in OpenLTE, suggesting that there is a problem in srsenb? 
>> 
>> See also below. The original post is included below for your convenience.
>> 
>> The reason for asking about this is that we would like to do some tests on TAU reject and attach rejects.
>> 
>> Thanks in advance.
>> 
>> BR, Patrik
>> 
>> 
>> ____
>> "Hey Guys,
>> 
>> I'm trying to issue a TAU Reject directly after an incoming INITIAL
>> Tracking Area Update Request.
>> 
>> This is what I have so far
>> 
>> bool
>> s1ap_nas_transport::pack_tracking_area_update_reject(srslte::byte_buffer_t
>> *reply_msg, uint32_t enb_ue_s1ap_id)
>> {
>>   srslte::byte_buffer_t *nas_buffer = m_pool->allocate();
>> 
>>   uint8 sec_hdr_type;
>> 
>>   m_s1ap_log->console("Packing TAU Reject...\n");
>> 
>>   //Setup initiating message
>>   LIBLTE_S1AP_S1AP_PDU_STRUCT tx_pdu;
>>   bzero(&tx_pdu, sizeof(LIBLTE_S1AP_S1AP_PDU_STRUCT));
>> 
>>   tx_pdu.ext          = false;
>>   tx_pdu.choice_type  = LIBLTE_S1AP_S1AP_PDU_CHOICE_INITIATINGMESSAGE;
>> 
>>   LIBLTE_S1AP_INITIATINGMESSAGE_STRUCT *init =
>> &tx_pdu.choice.initiatingMessage;
>>   init->procedureCode = LIBLTE_S1AP_PROC_ID_DOWNLINKNASTRANSPORT;
>>   init->choice_type   =
>> LIBLTE_S1AP_INITIATINGMESSAGE_CHOICE_DOWNLINKNASTRANSPORT;
>> 
>>   //Setup Dw NAS structure
>>   LIBLTE_S1AP_MESSAGE_DOWNLINKNASTRANSPORT_STRUCT *dw_nas =
>> &init->choice.DownlinkNASTransport;
>>   dw_nas->ext=false;
>>   dw_nas->MME_UE_S1AP_ID.MME_UE_S1AP_ID = m_s1ap->get_next_mme_ue_s1ap_id();
>>   dw_nas->eNB_UE_S1AP_ID.ENB_UE_S1AP_ID = enb_ue_s1ap_id;
>>   dw_nas->HandoverRestrictionList_present=false;
>>   dw_nas->SubscriberProfileIDforRFP_present=false;
>> 
>>   // Set things here
>>   LIBLTE_MME_TRACKING_AREA_UPDATE_REJECT_MSG_STRUCT track_rej;
>>   track_rej.emm_cause = LIBLTE_MME_EMM_CAUSE_IMPLICITLY_DETACHED;
>>   track_rej.t3446_present = false;
>>   sec_hdr_type = LIBLTE_MME_MSG_TYPE_TRACKING_AREA_UPDATE_REJECT;
>> 
>>   LIBLTE_ERROR_ENUM err =
>> liblte_mme_pack_tracking_area_update_reject_msg(&track_rej, sec_hdr_type,
>> NULL, (LIBLTE_BYTE_MSG_STRUCT *) nas_buffer);
>>   if(err != LIBLTE_SUCCESS)
>>   {
>>     m_s1ap_log->error("Error packing TAU Reject\n");
>>     m_s1ap_log->console("Error packing TAU Reject\n");
>>     return false;
>>   }
>> 
>>   //Copy NAS PDU to Downlink NAS Trasport message buffer
>>   memcpy(dw_nas->NAS_PDU.buffer, nas_buffer->msg, nas_buffer->N_bytes);
>>   dw_nas->NAS_PDU.n_octets = nas_buffer->N_bytes;
>> 
>>   //Pack Downlink NAS Transport Message
>>   err = liblte_s1ap_pack_s1ap_pdu(&tx_pdu, (LIBLTE_BYTE_MSG_STRUCT *)
>> reply_msg);
>>   if(err != LIBLTE_SUCCESS)
>>   {
>>     m_s1ap_log->error("Error packing Dw NAS Transport: Authentication
>> Reject\n");
>>     m_s1ap_log->console("Error packing Downlink NAS Transport:
>> Authentication Reject\n");
>>     return false;
>>   }
>> 
>>   m_pool->deallocate(nas_buffer);
>>   return true;
>> }
>> 
>> However, after receiving the TAU Request, my reject is never sent, I had to
>> remove some TMSI Checks, for it to execute, there appears to be some
>> confusion with Security Context, I need to provide nas_dl_count, however
>> this is only possible with a Security Context, that doesen't exist yet,
>> I've successfully done this on OpenLTE, it appears to be a srsENB specific
>> issue.
>> 
>> Setting it to NULL or 0 dosen't help.
>> 
>> What am I missing?
>> 
>> Any help would be greatly appreciated!"
>> _______________________________________________
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>> srslte-users at lists.softwareradiosystems.com
>> http://www.softwareradiosystems.com/mailman/listinfo/srslte-users
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