/*
 * Licensed to the OpenAirInterface (OAI) Software Alliance under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The OpenAirInterface Software Alliance licenses this file to You under
 * the OAI Public License, Version 1.0  (the "License"); you may not use this file
 * except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.openairinterface.org/?page_id=698
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *-------------------------------------------------------------------------------
 * For more information about the OpenAirInterface (OAI) Software Alliance:
 *      contact@openairinterface.org
 */

/*****************************************************************************
Source      Detach.c

Version     0.1

Date        2013/05/07

Product     NAS stack

Subsystem   EPS Mobility Management

Author      Frederic Maurel

Description Defines the detach related EMM procedure executed by the
        Non-Access Stratum.

        The detach procedure is used by the UE to detach for EPS servi-
        ces, to disconnect from the last PDN it is connected to; by the
        network to inform the UE that it is detached for EPS services
        or non-EPS services or both, to disconnect the UE from the last
        PDN to which it is connected and to inform the UE to re-attach
        to the network and re-establish all PDN connections.

*****************************************************************************/

#include "emm_proc.h"
#include "nas_log.h"
#include "nas_timer.h"

#include "emmData.h"

#include "emm_sap.h"
#include "esm_sap.h"
#include "msc.h"

#include <stdlib.h> // free

/****************************************************************************/
/****************  E X T E R N A L    D E F I N I T I O N S  ****************/
/****************************************************************************/

/****************************************************************************/
/*******************  L O C A L    D E F I N I T I O N S  *******************/
/****************************************************************************/

/* String representation of the detach type */
static const char *_emm_detach_type_str[] = {
  "EPS", "IMSI", "EPS/IMSI",
  "RE-ATTACH REQUIRED", "RE-ATTACH NOT REQUIRED", "RESERVED"
};

/*
 * --------------------------------------------------------------------------
 *      Internal data handled by the detach procedure in the UE
 * --------------------------------------------------------------------------
 */
/*
 * Timer handlers
 */
void *_emm_detach_t3421_handler(void *);

/*
 * Abnormal case detach procedures
 */
static int _emm_detach_abort(emm_proc_detach_type_t type);

/*
 * Internal data used for detach procedure
 */
static struct {
#define EMM_DETACH_COUNTER_MAX  5
  unsigned int count;      /* Counter used to limit the number of
                  * subsequently detach attempts    */
  int switch_off;      /* UE switch-off indicator     */
  emm_proc_detach_type_t type; /* Type of the detach procedure
                  * currently in progress       */
} _emm_detach_data = {0, FALSE, EMM_DETACH_TYPE_RESERVED};



/****************************************************************************/
/******************  E X P O R T E D    F U N C T I O N S  ******************/
/****************************************************************************/

/*
 * --------------------------------------------------------------------------
 *          Detach procedure executed by the UE
 * --------------------------------------------------------------------------
 */
/****************************************************************************
 **                                                                        **
 ** Name:    emm_proc_detach()                                         **
 **                                                                        **
 ** Description: Initiates the detach procedure in order for the UE to de- **
 **      tach for EPS services.                                    **
 **                                                                        **
 **              3GPP TS 24.301, section 5.5.2.2.1                         **
 **      In state EMM-REGISTERED or EMM-REGISTERED-INITIATED, the  **
 **      UE initiates the detach procedure by sending a DETACH RE- **
 **      QUEST message to the network, starting timer T3421 and    **
 **      entering state EMM-DEREGISTERED-INITIATED.                **
 **                                                                        **
 ** Inputs:  type:      Type of the requested detach               **
 **      switch_off:    Indicates whether the detach is required   **
 **             because the UE is switched off or not      **
 **      Others:    _emm_data                                  **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    _emm_detach_data                           **
 **                                                                        **
 ***************************************************************************/
int emm_proc_detach(emm_proc_detach_type_t type, int switch_off)
{
  LOG_FUNC_IN;

  emm_sap_t emm_sap;
  emm_as_data_t *emm_as = &emm_sap.u.emm_as.u.data;
  int rc;

  LOG_TRACE(INFO, "EMM-PROC  - Initiate EPS detach type = %s (%d)",
            _emm_detach_type_str[type], type);

  /* Initialize the detach procedure internal data */
  _emm_detach_data.count = 0;
  _emm_detach_data.switch_off = switch_off;
  _emm_detach_data.type = type;

  /* Setup EMM procedure handler to be executed upon receiving
   * lower layer notification */
  rc = emm_proc_lowerlayer_initialize(emm_proc_detach_request,
                                      emm_proc_detach_failure,
                                      emm_proc_detach_release, NULL);

  if (rc != RETURNok) {
    LOG_TRACE(WARNING, "Failed to initialize EMM procedure handler");
    LOG_FUNC_RETURN (RETURNerror);
  }

  /* Setup NAS information message to transfer */
  emm_as->NASinfo = EMM_AS_NAS_INFO_DETACH;
  emm_as->NASmsg.length = 0;
  emm_as->NASmsg.value = NULL;
  /* Set the detach type */
  emm_as->type = type;
  /* Set the switch-off indicator */
  emm_as->switch_off = switch_off;
  /* Set the EPS mobile identity */
  emm_as->guti = _emm_data.guti;
  emm_as->ueid = 0;
  /* Setup EPS NAS security data */
  emm_as_set_security_data(&emm_as->sctx, _emm_data.security, FALSE, TRUE);

  /*
   * Notify EMM-AS SAP that Detach Request message has to
   * be sent to the network
   */
  emm_sap.primitive = EMMAS_DATA_REQ;
  rc = emm_sap_send(&emm_sap);

  LOG_FUNC_RETURN(rc);
}

/****************************************************************************
 **                                                                        **
 ** Name:    emm_proc_detach_request()                                 **
 **                                                                        **
 ** Description: Performs the detach procedure upon receipt of indication  **
 **      from lower layers that Detach Request message has been    **
 **      successfully delivered to the network.                    **
 **                                                                        **
 ** Inputs:  args:      Not used                                   **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    T3421                                      **
 **                                                                        **
 ***************************************************************************/
int emm_proc_detach_request(void *args)
{
  LOG_FUNC_IN;

  emm_sap_t emm_sap;
  int rc;

  if ( !_emm_detach_data.switch_off ) {
    /* Start T3421 timer */
    T3421.id = nas_timer_start(T3421.sec, _emm_detach_t3421_handler, NULL);
    LOG_TRACE(INFO, "EMM-PROC  - Timer T3421 (%d) expires in %ld seconds",
              T3421.id, T3421.sec);
  }

  /*
   * Notify EMM that Detach Request has been sent to the network
   */
  emm_sap.primitive = EMMREG_DETACH_REQ;
  rc = emm_sap_send(&emm_sap);

  LOG_FUNC_RETURN(rc);
}

/****************************************************************************
 **                                                                        **
 ** Name:    emm_proc_detach_accept()                                  **
 **                                                                        **
 ** Description: Performs the UE initiated detach procedure for EPS servi- **
 **      ces only When the DETACH ACCEPT message is received from  **
 **      the network.                                              **
 **                                                                        **
 **              3GPP TS 24.301, section 5.5.2.2.2                         **
 **              Upon receiving the DETACH ACCEPT message, the UE shall    **
 **      stop timer T3421, locally deactivate all EPS bearer con-  **
 **      texts without peer-to-peer signalling and enter state EMM-**
 **      DEREGISTERED.                                             **
 **                                                                        **
 ** Inputs:  None                                                      **
 **      Others:    None                                       **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    T3421                                      **
 **                                                                        **
 ***************************************************************************/
int emm_proc_detach_accept(void)
{
  LOG_FUNC_IN;

  int rc;

  LOG_TRACE(INFO, "EMM-PROC  - UE initiated detach procedure completion");

  /* Reset EMM procedure handler */
  (void) emm_proc_lowerlayer_initialize(NULL, NULL, NULL, NULL);

  /* Stop timer T3421 */
  T3421.id = nas_timer_stop(T3421.id);

  /*
   * Notify ESM that all EPS bearer contexts have to be locally deactivated
   */
  esm_sap_t esm_sap;
  esm_sap.primitive = ESM_EPS_BEARER_CONTEXT_DEACTIVATE_REQ;
  esm_sap.data.eps_bearer_context_deactivate.ebi = ESM_SAP_ALL_EBI;
  rc = esm_sap_send(&esm_sap);

  /*
   * XXX - Upon receiving notification from ESM that all EPS bearer
   * contexts are locally deactivated, the UE is considered as
   * detached from the network and is entered state EMM-DEREGISTERED
   */
  LOG_FUNC_RETURN(rc);
}

/****************************************************************************
 **                                                                        **
 ** Name:    emm_proc_detach_failure()                                 **
 **                                                                        **
 ** Description: Performs the detach procedure abnormal case upon receipt  **
 **          of transmission failure of Detach Request message.        **
 **                                                                        **
 **              3GPP TS 24.301, section 5.5.2.2.4, case h                 **
 **      The UE shall restart the detach procedure.                **
 **                                                                        **
 ** Inputs:  is_initial:    Not used                                   **
 **          args:      Not used                                   **
 **      Others:    _emm_detach_data                           **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    None                                       **
 **                                                                        **
 ***************************************************************************/
int emm_proc_detach_failure(int is_initial, void *args)
{
  LOG_FUNC_IN;

  emm_sap_t emm_sap;
  int rc;

  LOG_TRACE(WARNING, "EMM-PROC  - Network detach failure");

  /* Reset EMM procedure handler */
  (void) emm_proc_lowerlayer_initialize(NULL, NULL, NULL, NULL);

  /* Stop timer T3421 */
  T3421.id = nas_timer_stop(T3421.id);

  /*
   * Notify EMM that detach procedure has to be restarted
   */
  emm_sap.primitive = EMMREG_DETACH_INIT;
  emm_sap.u.emm_reg.u.detach.switch_off = _emm_detach_data.switch_off;
  rc = emm_sap_send(&emm_sap);

  LOG_FUNC_RETURN(rc);
}

/****************************************************************************
 **                                                                        **
 ** Name:    emm_proc_detach_release()                                 **
 **                                                                        **
 ** Description: Performs the detach procedure abnormal case upon receipt  **
 **          of NAS signalling connection release indication before    **
 **      reception of Detach Accept message.                       **
 **                                                                        **
 **              3GPP TS 24.301, section 5.5.2.2.4, case b                 **
 **      The  detach procedure shall be aborted.                   **
 **                                                                        **
 ** Inputs:  args:      not used                                   **
 **      Others:    _emm_detach_data                           **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    None                                       **
 **                                                                        **
 ***************************************************************************/
int emm_proc_detach_release(void *args)
{
  LOG_FUNC_IN;

  LOG_TRACE(WARNING, "EMM-PROC  - NAS signalling connection released");

  /* Abort the detach procedure */
  int rc = _emm_detach_abort(_emm_detach_data.type);

  LOG_FUNC_RETURN(rc);
}


/****************************************************************************/
/*********************  L O C A L    F U N C T I O N S  *********************/
/****************************************************************************/

/*
 * --------------------------------------------------------------------------
 *              Timer handlers
 * --------------------------------------------------------------------------
 */

/****************************************************************************
 **                                                                        **
 ** Name:    _emm_detach_t3421_handler()                               **
 **                                                                        **
 ** Description: T3421 timeout handler                                     **
 **                                                                        **
 **              3GPP TS 24.301, section 5.5.2.2.4 case c                  **
 **      On the first four expiries of the timer, the UE shall re- **
 **      transmit the DETACH REQUEST message and shall reset and   **
 **      restart timer T3421. On the fifth expiry of timer T3421,  **
 **      the detach procedure shall be aborted.                    **
 **                                                                        **
 ** Inputs:  args:      handler parameters                         **
 **      Others:    _emm_detach_data                           **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    None                                       **
 **      Others:    None                                       **
 **                                                                        **
 ***************************************************************************/
void *_emm_detach_t3421_handler(void *args)
{
  LOG_FUNC_IN;

  int rc;

  /* Increment the retransmission counter */
  _emm_detach_data.count += 1;

  LOG_TRACE(WARNING, "EMM-PROC  - T3421 timer expired, "
            "retransmission counter = %d", _emm_detach_data.count);

  if (_emm_detach_data.count < EMM_DETACH_COUNTER_MAX) {
    /* Retransmit the Detach Request message */
    emm_sap_t emm_sap;
    emm_as_data_t *emm_as = &emm_sap.u.emm_as.u.data;

    /* Stop timer T3421 */
    T3421.id = nas_timer_stop(T3421.id);

    /* Setup NAS information message to transfer */
    emm_as->NASinfo = EMM_AS_NAS_INFO_DETACH;
    emm_as->NASmsg.length = 0;
    emm_as->NASmsg.value = NULL;
    /* Set the detach type */
    emm_as->type = _emm_detach_data.type;
    /* Set the switch-off indicator */
    emm_as->switch_off = _emm_detach_data.switch_off;
    /* Set the EPS mobile identity */
    emm_as->guti = _emm_data.guti;
    emm_as->ueid = 0;
    /* Setup EPS NAS security data */
    emm_as_set_security_data(&emm_as->sctx, _emm_data.security,
                             FALSE, TRUE);

    /*
     * Notify EMM-AS SAP that Detach Request message has to
     * be sent to the network
     */
    emm_sap.primitive = EMMAS_DATA_REQ;
    rc = emm_sap_send(&emm_sap);

    if (rc != RETURNerror) {
      /* Start T3421 timer */
      T3421.id = nas_timer_start(T3421.sec, _emm_detach_t3421_handler, NULL);
      LOG_TRACE(INFO, "EMM-PROC  - Timer T3421 (%d) expires in %ld "
                "seconds", T3421.id, T3421.sec);
    }
  } else {
    /* Abort the detach procedure */
    rc = _emm_detach_abort(_emm_detach_data.type);
  }

  LOG_FUNC_RETURN(NULL);
}

/*
 * --------------------------------------------------------------------------
 *              Abnormal cases in the UE
 * --------------------------------------------------------------------------
 */

/****************************************************************************
 **                                                                        **
 ** Name:    _emm_detach_abort()                                       **
 **                                                                        **
 ** Description: Aborts the detach procedure                               **
 **                                                                        **
 ** Inputs:  type:      not used                                   **
 **      Others:    _emm_detach_data                           **
 **                                                                        **
 ** Outputs:     None                                                      **
 **      Return:    RETURNok, RETURNerror                      **
 **      Others:    T3421                                      **
 **                                                                        **
 ***************************************************************************/
static int _emm_detach_abort(emm_proc_detach_type_t type)
{
  LOG_FUNC_IN;

  emm_sap_t emm_sap;
  int rc ;

  LOG_TRACE(WARNING, "EMM-PROC  - Abort the detach procedure");

  /* Reset EMM procedure handler */
  (void) emm_proc_lowerlayer_initialize(NULL, NULL, NULL, NULL);

  /* Stop timer T3421 */
  T3421.id = nas_timer_stop(T3421.id);

  /*
   * Notify EMM that detach procedure failed
   */
  emm_sap.primitive = EMMREG_DETACH_FAILED;
  emm_sap.u.emm_reg.u.detach.type = type;
  rc = emm_sap_send(&emm_sap);

  LOG_FUNC_RETURN (rc);
}
