openairinterface5g/openair2/LAYER2/PDCP_v10.1.0/pdcp_sequence_manager.c

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/*! \file pdcp_sequence_manager.c
* \brief PDCP Sequence Numbering Methods
* \author Baris Demiray
* \date 2011
*/

#include "pdcp_sequence_manager.h"
#include "UTIL/LOG/log_if.h"
#include "pdcp_util.h"

/*
 * Initializes sequence numbering state
 * @param pdcp_entity The PDCP entity to be initialized
 * @return boolean_t TRUE on success, FALSE otherwise
 */
boolean_t pdcp_init_seq_numbers(pdcp_t* pdcp_entity)
{
  if (pdcp_entity == NULL)
    return FALSE;

  /* Sequence number state variables */

  // TX and RX window
  pdcp_entity->next_pdcp_tx_sn = 0;
  pdcp_entity->next_pdcp_rx_sn = 0;

  // TX and RX Hyper Frame Numbers
  pdcp_entity->tx_hfn = 0;
  pdcp_entity->rx_hfn = 0;

  // SN of the last PDCP SDU delivered to upper layers
  // Shall UE and eNB behave differently on initialization? (see 7.1.e)
  pdcp_entity->last_submitted_pdcp_rx_sn = 4095;

  return TRUE;
}

boolean_t pdcp_is_seq_num_size_valid(pdcp_t* pdcp_entity)
{
  if (pdcp_entity == NULL)
    return FALSE;

  // Check if the size of SN is valid (see 3GPP TS 36.323 v10.1.0 item 6.3.2)
  if (pdcp_entity->seq_num_size != 5 && pdcp_entity->seq_num_size != 7 && pdcp_entity->seq_num_size != 12) {
    LOG_W(PDCP, "Incoming SN size is invalid! (Expected: {5 | 7 | 12}, Received: %d\n", pdcp_entity->seq_num_size);
    return FALSE;
  }

  return TRUE;
}

/**
 * Check if SN number is in the range according to SN size
 */
boolean_t pdcp_is_seq_num_valid(uint16_t seq_num, uint8_t seq_num_size)
{
  if (seq_num >= 0 && seq_num <= pdcp_calculate_max_seq_num_for_given_size(seq_num_size))
    return TRUE;

  return FALSE;
}

uint16_t pdcp_calculate_max_seq_num_for_given_size(uint8_t seq_num_size)
{
  uint16_t max_seq_num = 1;

  max_seq_num <<= seq_num_size;

  return max_seq_num - 1;
}

uint16_t pdcp_get_next_tx_seq_number(pdcp_t* pdcp_entity)
{
  if (pdcp_is_seq_num_size_valid(pdcp_entity) == FALSE)
    return -1;

  // Sequence number should be incremented after it is assigned for a PDU
  uint16_t pdcp_seq_num = pdcp_entity->next_pdcp_tx_sn;

  /*
   * Update sequence numbering state and Hyper Frame Number if SN has already reached
   * its max value (see 5.1 PDCP Data Transfer Procedures)
   */
  if (pdcp_entity->next_pdcp_tx_sn == pdcp_calculate_max_seq_num_for_given_size(pdcp_entity->seq_num_size)) {
    pdcp_entity->next_pdcp_tx_sn = 0;
    pdcp_entity->tx_hfn++;
    LOG_D(PDCP,"Reseting the PDCP sequence number\n");
  } else {
    pdcp_entity->next_pdcp_tx_sn++;
  }

  return pdcp_seq_num;
}

boolean_t pdcp_advance_rx_window(pdcp_t* pdcp_entity)
{
  if (pdcp_is_seq_num_size_valid(pdcp_entity) == FALSE)
    return FALSE;

  /*
   * Update sequence numbering state and Hyper Frame Number if SN has already reached
   * its max value (see 5.1 PDCP Data Transfer Procedures)
   */
  LOG_I(PDCP, "Advancing RX window...\n");
  if (pdcp_entity->next_pdcp_rx_sn == pdcp_calculate_max_seq_num_for_given_size(pdcp_entity->seq_num_size)) {
    pdcp_entity->next_pdcp_rx_sn = 0;
    pdcp_entity->rx_hfn++;
  } else {
    pdcp_entity->next_pdcp_rx_sn++;
  }

  return TRUE;
}

/**
 * Checks if incoming PDU has a sequence number in accordance with the RX window
 * @return 1 if SN is okay, 0 otherwise
 * XXX Reordering window should also be handled here
 */
boolean_t pdcp_is_rx_seq_number_valid(uint16_t seq_num, pdcp_t* pdcp_entity)
{
  LOG_D(PDCP, "Incoming RX Seq # is %04d\n", seq_num);

  if (pdcp_is_seq_num_size_valid(pdcp_entity) == FALSE || pdcp_is_seq_num_valid(seq_num, pdcp_entity->seq_num_size) == FALSE)
    return FALSE;

  /*
   * Mark received sequence numbers to keep track of missing ones
   * (and to build PDCP Control PDU for PDCP status report)
   */
  if (pdcp_mark_current_pdu_as_received(seq_num, pdcp_entity) == TRUE) {
    LOG_I(PDCP, "Received sequence number successfuly marked\n");
  } else {
    LOG_W(PDCP, "Cannot mark received sequence number on the bitmap!\n");
  }

  /*
   * XXX Since we do not implement reordering window yet we expect to receive
   * exactly the next SN from lower layer. When reordering window is implemented
   * the operator utilized here should be >= as stated in 5.1.2.1.2
   */
  if (seq_num == pdcp_entity->next_pdcp_rx_sn) {
    LOG_I(PDCP, "Next expected SN (%d) arrived, advancing RX window\n", seq_num);

    return pdcp_advance_rx_window(pdcp_entity);
  } else {
    LOG_E(PDCP, "D'oh! Incoming SN is not the one we expected to receive! (Incoming:%d, Expected:%d)\n", \
        seq_num, pdcp_entity->next_pdcp_rx_sn);

    /*
     * Update first missing PDU (used in PDCP Control PDU for 
     * PDCP status report, see 6.2.6)
     */
    if (pdcp_entity->first_missing_pdu != -1)
      pdcp_entity->first_missing_pdu = pdcp_entity->next_pdcp_rx_sn;

    return FALSE;
  }
}

boolean_t pdcp_mark_current_pdu_as_received(uint16_t seq_num, pdcp_t* pdcp_entity)
{
  /*
   * Incoming sequence number and PDCP entity were already
   * validated in pdcp_is_rx_seq_number_valid() so we don't 
   * check here
   */

  /*
   * Find relevant octet
   */
  uint16_t octet_index = seq_num / 8;
  /*
   * Set relevant bit
   */
  LOG_D(PDCP, "Marking %d. bit of %d. octet of status bitmap\n", (seq_num % 8) + 1, octet_index);
  util_mark_nth_bit_of_octet(&pdcp_entity->missing_pdu_bitmap[octet_index], seq_num % 8); 
  util_print_binary_representation((uint8_t*)"Current state of relevant octet: ", pdcp_entity->missing_pdu_bitmap[octet_index]);

  return TRUE;
}