stack/gatt/gatt_db.cc

/******************************************************************************
 *
 *  Copyright 2009-2012 Broadcom Corporation
 *
 *  Licensed under the Apache License, Version 2.0 (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.apache.org/licenses/LICENSE-2.0
 *
 *  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.
 *
 ******************************************************************************/

/******************************************************************************
 *
 *  this file contains GATT database building and query functions
 *
 ******************************************************************************/

#include <bluetooth/log.h>
#include <string.h>

#include "gatt_int.h"
#include "stack/include/bt_hdr.h"
#include "stack/include/bt_types.h"
#include "stack/include/l2cap_types.h"
#include "types/bluetooth/uuid.h"

using bluetooth::Uuid;
using namespace bluetooth;

/*******************************************************************************
 *             L O C A L    F U N C T I O N     P R O T O T Y P E S            *
 ******************************************************************************/
static tGATT_ATTR& allocate_attr_in_db(tGATT_SVC_DB& db, const Uuid& uuid, tGATT_PERM perm);
static tGATT_STATUS gatts_send_app_read_request(tGATT_TCB& tcb, uint16_t cid, uint8_t op_code,
                                                uint16_t handle, uint16_t offset, uint32_t trans_id,
                                                bt_gatt_db_attribute_type_t gatt_type);

/**
 * Initialize a memory space to be a service database.
 */
void gatts_init_service_db(tGATT_SVC_DB& db, const Uuid& service_uuid, bool is_pri, uint16_t s_hdl,
                           uint16_t num_handle) {
  db.attr_list.reserve(num_handle);

  log::verbose("s_hdl= {} num_handle= {}", s_hdl, num_handle);

  /* update service database information */
  db.next_handle = s_hdl;
  db.end_handle = s_hdl + num_handle;

  /* add service declaration record */
  Uuid uuid = Uuid::From16Bit(is_pri ? GATT_UUID_PRI_SERVICE : GATT_UUID_SEC_SERVICE);
  tGATT_ATTR& attr = allocate_attr_in_db(db, uuid, GATT_PERM_READ);
  attr.p_value.reset(new tGATT_ATTR_VALUE);
  attr.p_value->uuid = service_uuid;
}

Uuid* gatts_get_service_uuid(tGATT_SVC_DB* p_db) {
  if (!p_db || p_db->attr_list.empty()) {
    log::error("service DB empty");
    return NULL;
  } else {
    return &p_db->attr_list[0].p_value->uuid;
  }
}

/** Check attribute readability. Returns status of operation. */
static tGATT_STATUS gatts_check_attr_readability(const tGATT_ATTR& attr, uint16_t /* offset */,
                                                 bool read_long, tGATT_SEC_FLAG sec_flag,
                                                 uint8_t key_size) {
  uint16_t min_key_size;
  tGATT_PERM perm = attr.permission;

  min_key_size = ((perm & GATT_ENCRYPT_KEY_SIZE_MASK) >> 12);
  if (min_key_size != 0) {
    min_key_size += 6;
  }

  if (!(perm & GATT_READ_ALLOWED)) {
    log::error("GATT_READ_NOT_PERMIT");
    return GATT_READ_NOT_PERMIT;
  }

  if ((perm & GATT_READ_AUTH_REQUIRED) && !sec_flag.is_link_key_known && !sec_flag.is_encrypted) {
    log::error("GATT_INSUF_AUTHENTICATION");
    return GATT_INSUF_AUTHENTICATION;
  }

  if ((perm & GATT_READ_MITM_REQUIRED) && !sec_flag.is_link_key_authed) {
    log::error("GATT_INSUF_AUTHENTICATION: MITM Required");
    return GATT_INSUF_AUTHENTICATION;
  }

  if ((perm & GATT_READ_ENCRYPTED_REQUIRED) && !sec_flag.is_encrypted) {
    log::error("GATT_INSUF_ENCRYPTION");
    return GATT_INSUF_ENCRYPTION;
  }

  if ((perm & GATT_READ_ENCRYPTED_REQUIRED) && sec_flag.is_encrypted && (key_size < min_key_size)) {
    log::error("GATT_INSUF_KEY_SIZE");
    return GATT_INSUF_KEY_SIZE;
  }

  if (perm & GATT_PERM_READ_IF_ENCRYPTED_OR_DISCOVERABLE) {
    if (sec_flag.can_read_discoverable_characteristics) {
      // no checks here
    } else {
      if (!sec_flag.is_link_key_known || !sec_flag.is_encrypted) {
        return GATT_INSUF_AUTHENTICATION;
      }
      if (key_size < min_key_size) {
        return GATT_INSUF_KEY_SIZE;
      }
    }
  }

  if (read_long && attr.uuid.Is16Bit()) {
    switch (attr.uuid.As16Bit()) {
      case GATT_UUID_PRI_SERVICE:
      case GATT_UUID_SEC_SERVICE:
      case GATT_UUID_CHAR_DECLARE:
      case GATT_UUID_INCLUDE_SERVICE:
      case GATT_UUID_CHAR_EXT_PROP:
      case GATT_UUID_CHAR_CLIENT_CONFIG:
      case GATT_UUID_CHAR_SRVR_CONFIG:
      case GATT_UUID_CHAR_PRESENT_FORMAT:
        log::error("GATT_NOT_LONG");
        return GATT_NOT_LONG;

      default:
        break;
    }
  }

  return GATT_SUCCESS;
}

/*******************************************************************************
 *
 * Function         read_attr_value
 *
 * Description      Utility function to read an attribute value.
 *
 * Parameter        attr16: pointer to the attribute to read.
 *                  offset: read offset.
 *                  p_data: output parameter to carry out the attribute value.
 *                  read_long: this is a read blob request.
 *                  mtu: MTU
 *                  p_len: output parameter to carry out the attribute length.
 *                   sec_flag: current link security status.
 *                  key_size: encryption key size.
 *
 * Returns          status of operation.
 *
 ******************************************************************************/
static tGATT_STATUS read_attr_value(tGATT_ATTR& attr16, uint16_t offset, uint8_t** p_data,
                                    bool read_long, uint16_t mtu, uint16_t* p_len,
                                    tGATT_SEC_FLAG sec_flag, uint8_t key_size) {
  uint8_t* p = *p_data;

  log::verbose("uuid={} perm=0x{:02x} offset={} read_long={}", attr16.uuid, attr16.permission,
               offset, read_long);

  tGATT_STATUS status = gatts_check_attr_readability(attr16, offset, read_long, sec_flag, key_size);
  if (status != GATT_SUCCESS) {
    return status;
  }

  if (!attr16.uuid.Is16Bit()) {
    /* characteristic description or characteristic value */
    return GATT_PENDING;
  }

  uint16_t uuid16 = attr16.uuid.As16Bit();

  if (uuid16 == GATT_UUID_PRI_SERVICE || uuid16 == GATT_UUID_SEC_SERVICE) {
    *p_len = gatt_build_uuid_to_stream_len(attr16.p_value->uuid);
    if (mtu < *p_len) {
      return GATT_NO_RESOURCES;
    }

    gatt_build_uuid_to_stream(&p, attr16.p_value->uuid);
    *p_data = p;
    return GATT_SUCCESS;
  }

  if (uuid16 == GATT_UUID_CHAR_DECLARE) {
    tGATT_ATTR* val_attr = &attr16 + 1;
    uint8_t val_len = val_attr->uuid.GetShortestRepresentationSize();
    *p_len = (val_len == Uuid::kNumBytes16) ? 5 : 19;

    if (mtu < *p_len) {
      return GATT_NO_RESOURCES;
    }

    UINT8_TO_STREAM(p, attr16.p_value->char_decl.property);
    UINT16_TO_STREAM(p, attr16.p_value->char_decl.char_val_handle);

    if (val_len == Uuid::kNumBytes16) {
      UINT16_TO_STREAM(p, val_attr->uuid.As16Bit());
    } else {
      /* if 32 bit UUID, convert to 128 bit */
      ARRAY_TO_STREAM(p, val_attr->uuid.To128BitLE(), (int)Uuid::kNumBytes128);
    }
    *p_data = p;
    return GATT_SUCCESS;
  }

  if (uuid16 == GATT_UUID_INCLUDE_SERVICE) {
    tGATT_INCL_SRVC& incl_handle = attr16.p_value->incl_handle;
    if (incl_handle.service_type.Is16Bit()) {
      *p_len = 6;
    } else {
      *p_len = 4;
    }

    if (mtu < *p_len) {
      return GATT_NO_RESOURCES;
    }

    UINT16_TO_STREAM(p, incl_handle.s_handle);
    UINT16_TO_STREAM(p, incl_handle.e_handle);

    if (incl_handle.service_type.Is16Bit()) {
      UINT16_TO_STREAM(p, incl_handle.service_type.As16Bit());
    }
    *p_data = p;
    return GATT_SUCCESS;
  }

  if (uuid16 == GATT_UUID_CHAR_EXT_PROP) {
    // sometimes this descriptor is added by users manually, we need to check if
    // the p_value is nullptr.
    uint16_t char_ext_prop = attr16.p_value ? attr16.p_value->char_ext_prop : 0x0000;
    *p_len = 2;

    if (mtu < *p_len) {
      return GATT_NO_RESOURCES;
    }

    UINT16_TO_STREAM(p, char_ext_prop);
    *p_data = p;
    return GATT_SUCCESS;
  }

  /* characteristic descriptor or characteristic value (again) */
  return GATT_PENDING;
}

/*******************************************************************************
 *
 * Function         gatts_db_read_attr_value_by_type
 *
 * Description      Query attribute value by attribute type.
 *
 * Parameter        p_db: pointer to the attribute database.
 *                  p_rsp: Read By type response data.
 *                  s_handle: starting handle of the range we are looking for.
 *                  e_handle: ending handle of the range we are looking for.
 *                  type: Attribute type.
 *                  mtu: MTU.
 *                  sec_flag: current link security status.
 *                  key_size: encryption key size.
 *
 * Returns          Status of the operation.
 *
 ******************************************************************************/
tGATT_STATUS gatts_db_read_attr_value_by_type(tGATT_TCB& tcb, uint16_t cid, tGATT_SVC_DB* p_db,
                                              uint8_t op_code, BT_HDR* p_rsp, uint16_t s_handle,
                                              uint16_t /* e_handle */, const Uuid& type,
                                              uint16_t* p_len, tGATT_SEC_FLAG sec_flag,
                                              uint8_t key_size, uint32_t trans_id,
                                              uint16_t* p_cur_handle) {
  tGATT_STATUS status = GATT_NOT_FOUND;
  uint16_t len = 0;
  uint8_t* p = (uint8_t*)(p_rsp + 1) + p_rsp->len + L2CAP_MIN_OFFSET;

  if (p_db) {
    for (tGATT_ATTR& attr : p_db->attr_list) {
      if (attr.handle >= s_handle && type == attr.uuid) {
        if (*p_len <= 2) {
          status = GATT_NO_RESOURCES;
          break;
        }

        UINT16_TO_STREAM(p, attr.handle);

        status = read_attr_value(attr, 0, &p, false, (uint16_t)(*p_len - 2), &len, sec_flag,
                                 key_size);

        if (status == GATT_PENDING) {
          status = gatts_send_app_read_request(tcb, cid, op_code, attr.handle, 0, trans_id,
                                               attr.gatt_type);

          /* one callback at a time */
          break;
        } else if (status == GATT_SUCCESS) {
          if (p_rsp->offset == 0) {
            p_rsp->offset = len + 2;
          }

          if (p_rsp->offset == len + 2) {
            p_rsp->len += (len + 2);
            *p_len -= (len + 2);
          } else {
            log::error("format mismatch");
            status = GATT_NO_RESOURCES;
            break;
          }
        } else {
          *p_cur_handle = attr.handle;
          break;
        }
      }
    }
  }

  return status;
}

/**
 * This function adds an included service into a database.
 *
 * Parameter        db: database pointer.
 *                  inc_srvc_type: included service type.
 *
 * Returns          Status of the operation.
 *
 */
uint16_t gatts_add_included_service(tGATT_SVC_DB& db, uint16_t s_handle, uint16_t e_handle,
                                    const Uuid& service) {
  Uuid uuid = Uuid::From16Bit(GATT_UUID_INCLUDE_SERVICE);

  log::verbose("s_hdl=0x{:04x} e_hdl=0x{:04x} service uuid = {}", s_handle, e_handle, service);

  if (service.IsEmpty() || s_handle == 0 || e_handle == 0) {
    log::error("Illegal Params.");
    return 0;
  }

  tGATT_ATTR& attr = allocate_attr_in_db(db, uuid, GATT_PERM_READ);

  attr.p_value.reset(new tGATT_ATTR_VALUE);
  attr.p_value->incl_handle.s_handle = s_handle;
  attr.p_value->incl_handle.e_handle = e_handle;
  attr.p_value->incl_handle.service_type = service;

  return attr.handle;
}

/*******************************************************************************
 *
 * Function         gatts_add_characteristic
 *
 * Description      This function add a characteristics and its descriptor into
 *                  a service identified by the service database pointer.
 *
 * Parameter        db: database.
 *                  perm: permission (authentication and key size requirements)
 *                  property: property of the characteristic.
 *                  extended_properties: characteristic extended properties.
 *                  p_char: characteristic value information.
 *
 * Returns          Status of te operation.
 *
 ******************************************************************************/
uint16_t gatts_add_characteristic(tGATT_SVC_DB& db, tGATT_PERM perm, tGATT_CHAR_PROP property,
                                  const Uuid& char_uuid) {
  Uuid uuid = Uuid::From16Bit(GATT_UUID_CHAR_DECLARE);

  log::verbose("perm=0x{:0x} property=0x{:0x}", perm, property);

  tGATT_ATTR& char_decl = allocate_attr_in_db(db, uuid, GATT_PERM_READ);
  tGATT_ATTR& char_val = allocate_attr_in_db(db, char_uuid, perm);

  char_decl.p_value.reset(new tGATT_ATTR_VALUE);
  char_decl.p_value->char_decl.property = property;
  char_decl.p_value->char_decl.char_val_handle = char_val.handle;
  char_val.gatt_type = BTGATT_DB_CHARACTERISTIC;

  return char_val.handle;
}

/*******************************************************************************
 *
 * Function         gatts_add_char_ext_prop_descr
 *
 * Description      add a characteristics extended properties descriptor.
 *
 * Parameter        db: database pointer.
 *                  extended_properties: characteristic descriptors values.
 *
 * Returns          Status of the operation.
 *
 ******************************************************************************/
uint16_t gatts_add_char_ext_prop_descr(tGATT_SVC_DB& db, uint16_t extended_properties) {
  Uuid descr_uuid = Uuid::From16Bit(GATT_UUID_CHAR_EXT_PROP);

  log::verbose("gatts_add_char_ext_prop_descr uuid={}", descr_uuid.ToString());

  tGATT_ATTR& char_dscptr = allocate_attr_in_db(db, descr_uuid, GATT_PERM_READ);
  char_dscptr.gatt_type = BTGATT_DB_DESCRIPTOR;
  char_dscptr.p_value.reset(new tGATT_ATTR_VALUE);
  char_dscptr.p_value->char_ext_prop = extended_properties;

  return char_dscptr.handle;
}

/*******************************************************************************
 *
 * Function         gatts_add_char_descr
 *
 * Description      This function add a characteristics descriptor.
 *
 * Parameter        p_db: database pointer.
 *                  perm: characteristic descriptor permission type.
 *                  char_dscp_type: the characteristic descriptor masks.
 *                  p_dscp_params: characteristic descriptors values.
 *
 * Returns          Status of the operation.
 *
 ******************************************************************************/
uint16_t gatts_add_char_descr(tGATT_SVC_DB& db, tGATT_PERM perm, const Uuid& descr_uuid) {
  log::verbose("gatts_add_char_descr uuid={}", descr_uuid.ToString());

  /* Add characteristic descriptors */
  tGATT_ATTR& char_dscptr = allocate_attr_in_db(db, descr_uuid, perm);
  char_dscptr.gatt_type = BTGATT_DB_DESCRIPTOR;
  return char_dscptr.handle;
}

/******************************************************************************/
/* Service Attribute Database Query Utility Functions */
/******************************************************************************/
static tGATT_ATTR* find_attr_by_handle(tGATT_SVC_DB* p_db, uint16_t handle) {
  if (!p_db) {
    return nullptr;
  }

  for (auto& attr : p_db->attr_list) {
    if (attr.handle == handle) {
      return &attr;
    }
    if (attr.handle > handle) {
      return nullptr;
    }
  }

  return nullptr;
}

/*******************************************************************************
 *
 * Function         gatts_read_attr_value_by_handle
 *
 * Description      Query attribute value by attribute handle.
 *
 * Parameter        p_db: pointer to the attribute database.
 *                  handle: Attribute handle to read.
 *                  offset: Read offset.
 *                  p_value: output parameter to carry out the attribute value.
 *                  p_len: output parameter as attribute length read.
 *                  read_long: this is a read blob request.
 *                  mtu: MTU.
 *                  sec_flag: current link security status.
 *                  key_size: encryption key size
 *
 * Returns          Status of operation.
 *
 ******************************************************************************/
tGATT_STATUS gatts_read_attr_value_by_handle(tGATT_TCB& tcb, uint16_t cid, tGATT_SVC_DB* p_db,
                                             uint8_t op_code, uint16_t handle, uint16_t offset,
                                             uint8_t* p_value, uint16_t* p_len, uint16_t mtu,
                                             tGATT_SEC_FLAG sec_flag, uint8_t key_size,
                                             uint32_t trans_id) {
  tGATT_ATTR* p_attr = find_attr_by_handle(p_db, handle);
  if (!p_attr) {
    return GATT_NOT_FOUND;
  }

  uint8_t* pp = p_value;
  tGATT_STATUS status = read_attr_value(*p_attr, offset, &pp, (bool)(op_code == GATT_REQ_READ_BLOB),
                                        mtu, p_len, sec_flag, key_size);

  if (status == GATT_PENDING) {
    status = gatts_send_app_read_request(tcb, cid, op_code, p_attr->handle, offset, trans_id,
                                         p_attr->gatt_type);
  }
  return status;
}

/*******************************************************************************
 *
 * Function         gatts_read_attr_perm_check
 *
 * Description      Check attribute readability.
 *
 * Parameter        p_db: pointer to the attribute database.
 *                  handle: Attribute handle to read.
 *                  offset: Read offset.
 *                  p_value: output parameter to carry out the attribute value.
 *                  p_len: output parameter as attribute length read.
 *                  read_long: this is a read blob request.
 *                  mtu: MTU.
 *                  sec_flag: current link security status.
 *                  key_size: encryption key size
 *
 * Returns          Status of operation.
 *
 ******************************************************************************/
tGATT_STATUS gatts_read_attr_perm_check(tGATT_SVC_DB* p_db, bool is_long, uint16_t handle,
                                        tGATT_SEC_FLAG sec_flag, uint8_t key_size) {
  tGATT_ATTR* p_attr = find_attr_by_handle(p_db, handle);
  if (!p_attr) {
    return GATT_NOT_FOUND;
  }

  return gatts_check_attr_readability(*p_attr, 0, is_long, sec_flag, key_size);
}

/*******************************************************************************
 *
 * Function         gatts_write_attr_perm_check
 *
 * Description      Write attribute value into database.
 *
 * Parameter        p_db: pointer to the attribute database.
 *                  op_code:op code of this write.
 *                  handle: handle of the attribute to write.
 *                  offset: Write offset if write op code is write blob.
 *                  p_data: Attribute value to write.
 *                  len: attribute data length.
 *                  sec_flag: current link security status.
 *                  key_size: encryption key size
 *
 * Returns          Status of the operation.
 *
 ******************************************************************************/
tGATT_STATUS gatts_write_attr_perm_check(tGATT_SVC_DB* p_db, uint8_t op_code, uint16_t handle,
                                         uint16_t offset, uint8_t* p_data, uint16_t len,
                                         tGATT_SEC_FLAG sec_flag, uint8_t key_size) {
  log::verbose("op_code=0x{:x} handle=0x{:04x} offset={} len={} key_size={}", op_code, handle,
               offset, len, key_size);

  tGATT_ATTR* p_attr = find_attr_by_handle(p_db, handle);
  if (!p_attr) {
    return GATT_NOT_FOUND;
  }

  tGATT_PERM perm = p_attr->permission;
  uint16_t min_key_size = ((perm & GATT_ENCRYPT_KEY_SIZE_MASK) >> 12);
  if (min_key_size != 0) {
    min_key_size += 6;
  }
  log::verbose("p_attr->permission =0x{:04x} min_key_size==0x{:04x}", p_attr->permission,
               min_key_size);

  if ((op_code == GATT_CMD_WRITE || op_code == GATT_REQ_WRITE) && (perm & GATT_WRITE_SIGNED_PERM)) {
    /* use the rules for the mixed security see section 10.2.3*/
    /* use security mode 1 level 2 when the following condition follows */
    /* LE security mode 2 level 1 and LE security mode 1 level 2 */
    if ((perm & GATT_PERM_WRITE_SIGNED) && (perm & GATT_PERM_WRITE_ENCRYPTED)) {
      perm = GATT_PERM_WRITE_ENCRYPTED;
    } else if (((perm & GATT_PERM_WRITE_SIGNED_MITM) && (perm & GATT_PERM_WRITE_ENCRYPTED)) ||
               ((perm & GATT_WRITE_SIGNED_PERM) && (perm & GATT_PERM_WRITE_ENC_MITM))) {
      /* use security mode 1 level 3 when the following condition follows */
      /* LE security mode 2 level 2 and security mode 1 and LE */
      /* LE security mode 2 and security mode 1 level 3 */
      perm = GATT_PERM_WRITE_ENC_MITM;
    }
  }

  tGATT_STATUS status = GATT_NOT_FOUND;
  if ((op_code == GATT_SIGN_CMD_WRITE) && !(perm & GATT_WRITE_SIGNED_PERM)) {
    status = GATT_WRITE_NOT_PERMIT;
    log::verbose("sign cmd write not allowed");
  }
  if ((op_code == GATT_SIGN_CMD_WRITE) && sec_flag.is_encrypted) {
    status = GATT_INVALID_PDU;
    log::error("Error!! sign cmd write sent on a encrypted link");
  } else if (!(perm & GATT_WRITE_ALLOWED)) {
    status = GATT_WRITE_NOT_PERMIT;
    log::error("GATT_WRITE_NOT_PERMIT");
  } else if ((perm & GATT_WRITE_AUTH_REQUIRED) && !sec_flag.is_link_key_known) {
    /* require authentication, but not been authenticated */
    status = GATT_INSUF_AUTHENTICATION;
    log::error("GATT_INSUF_AUTHENTICATION");
  } else if ((perm & GATT_WRITE_MITM_REQUIRED) && !sec_flag.is_link_key_authed) {
    status = GATT_INSUF_AUTHENTICATION;
    log::error("GATT_INSUF_AUTHENTICATION: MITM required");
  } else if ((perm & GATT_WRITE_ENCRYPTED_PERM) && !sec_flag.is_encrypted) {
    status = GATT_INSUF_ENCRYPTION;
    log::error("GATT_INSUF_ENCRYPTION");
  } else if ((perm & GATT_WRITE_ENCRYPTED_PERM) && sec_flag.is_encrypted &&
             (key_size < min_key_size)) {
    status = GATT_INSUF_KEY_SIZE;
    log::error("GATT_INSUF_KEY_SIZE");
  } else if (perm & GATT_WRITE_SIGNED_PERM && op_code != GATT_SIGN_CMD_WRITE &&
             !sec_flag.is_encrypted && (perm & GATT_WRITE_ALLOWED) == 0) {
    /* LE security mode 2 attribute  */
    status = GATT_INSUF_AUTHENTICATION;
    log::error("GATT_INSUF_AUTHENTICATION: LE security mode 2 required");
  } else {
    /* writable: must be char value declaration or char descriptors */
    uint16_t max_size = 0;

    if (p_attr->uuid.IsEmpty()) {
      status = GATT_INVALID_PDU;
    } else if (p_attr->uuid.Is16Bit()) {
      switch (p_attr->uuid.As16Bit()) {
        case GATT_UUID_CHAR_PRESENT_FORMAT: /* should be readable only */
        case GATT_UUID_CHAR_EXT_PROP:       /* should be readable only */
        case GATT_UUID_CHAR_AGG_FORMAT:     /* should be readable only */
        case GATT_UUID_CHAR_VALID_RANGE:
          status = GATT_WRITE_NOT_PERMIT;
          break;

        case GATT_UUID_CHAR_CLIENT_CONFIG:
          FALLTHROUGH_INTENDED; /* FALLTHROUGH */
        case GATT_UUID_CHAR_SRVR_CONFIG:
          max_size = 2;
          FALLTHROUGH_INTENDED; /* FALLTHROUGH */
        case GATT_UUID_CHAR_DESCRIPTION:
        default: /* any other must be character value declaration */
          status = GATT_SUCCESS;
          break;
      }
    } else {  // 32 or 128 bit UUID
      status = GATT_SUCCESS;
    }

    if (p_data == NULL && len > 0) {
      return GATT_INVALID_PDU;
    }

    /* these attribute does not allow write blob */
    if (p_attr->uuid.Is16Bit() && (p_attr->uuid.As16Bit() == GATT_UUID_CHAR_CLIENT_CONFIG ||
                                   p_attr->uuid.As16Bit() == GATT_UUID_CHAR_SRVR_CONFIG)) {
      if (op_code == GATT_REQ_PREPARE_WRITE && offset != 0) {
        /* does not allow write blob */
        status = GATT_NOT_LONG;
        log::error("GATT_NOT_LONG");
      } else if (len != max_size) {
        /* data does not match the required format */
        status = GATT_INVALID_ATTR_LEN;
        log::error("GATT_INVALID_PDU");
      } else {
        return GATT_SUCCESS;
      }
    }
  }

  return status;
}

/**
 * Description      Allocate a memory space for a new attribute, and link this
 *                  attribute into the database attribute list.
 *
 *
 * Parameter        p_db    : database pointer.
 *                  uuid:     attribute UUID
 *
 * Returns          pointer to the newly allocated attribute.
 *
 */
static tGATT_ATTR& allocate_attr_in_db(tGATT_SVC_DB& db, const Uuid& uuid, tGATT_PERM perm) {
  if (db.next_handle >= db.end_handle) {
    log::fatal("wrong number of handles! handle_max = {}, next_handle = {}", db.end_handle,
               db.next_handle);
  }

  db.attr_list.emplace_back();
  tGATT_ATTR& attr = db.attr_list.back();
  attr.handle = db.next_handle++;
  attr.uuid = uuid;
  attr.permission = perm;
  return attr;
}

/*******************************************************************************
 *
 * Function         gatts_send_app_read_request
 *
 * Description      Send application read request callback
 *
 * Returns          status of operation.
 *
 ******************************************************************************/
static tGATT_STATUS gatts_send_app_read_request(tGATT_TCB& tcb, uint16_t cid, uint8_t op_code,
                                                uint16_t handle, uint16_t offset, uint32_t trans_id,
                                                bt_gatt_db_attribute_type_t gatt_type) {
  tGATT_SRV_LIST_ELEM& el = *gatt_sr_find_i_rcb_by_handle(handle);
  tCONN_ID conn_id = gatt_create_conn_id(tcb.tcb_idx, el.gatt_if);

  if (trans_id == 0) {
    trans_id = gatt_sr_enqueue_cmd(tcb, cid, op_code, handle);
    gatt_sr_update_cback_cnt(tcb, cid, el.gatt_if, true, true);
  }

  if (trans_id != 0) {
    tGATTS_DATA sr_data;
    memset(&sr_data, 0, sizeof(tGATTS_DATA));

    sr_data.read_req.handle = handle;
    sr_data.read_req.is_long = (bool)(op_code == GATT_REQ_READ_BLOB);
    sr_data.read_req.offset = offset;

    uint8_t opcode;
    if (gatt_type == BTGATT_DB_DESCRIPTOR) {
      opcode = GATTS_REQ_TYPE_READ_DESCRIPTOR;
    } else if (gatt_type == BTGATT_DB_CHARACTERISTIC) {
      opcode = GATTS_REQ_TYPE_READ_CHARACTERISTIC;
    } else {
      log::error(
              "Attempt to read attribute that's not tied with characteristic or descriptor value.");
      return GATT_ERROR;
    }

    gatt_sr_send_req_callback(conn_id, trans_id, opcode, &sr_data);
    return (tGATT_STATUS)GATT_PENDING;
  } else {
    return (tGATT_STATUS)GATT_BUSY; /* max pending command, application error */
  }
}