test_vendor: Implement packet assembly for SDUs

        "src/event_packet.cc",

        "src/packet.cc",

        "src/packet_stream.cc",

        "src/l2cap.cc",

        "src/l2cap_sdu.cc",

        "test/async_manager_unittest.cc",

        "test/bt_address_unittest.cc",

        "test/packet_stream_unittest.cc",

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

 *

 *  Copyright (C) 2017 Google, Inc.

 *

 *  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.

 *

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

#pragma once

#include <cstdint>

#include <iterator>

#include <memory>

#include <vector>

#include "base/macros.h"

#include "l2cap_sdu.h"

namespace test_vendor_lib {

const int kSduHeaderLength = 4;

class L2cap {

 public:

  // Returns an assembled L2cap object if successful, nullptr if failure.

  static std::unique_ptr<L2cap> assemble(

      const std::vector<L2capSdu>& sdu_packet);

  // Construct a vector of just the L2CAP payload. This essentially

  // will remove the L2CAP header from the private member variable.

  std::vector<uint8_t> get_l2cap_payload() const;

  uint16_t get_l2cap_cid() const;

 private:

  L2cap() = default;

  // Entire L2CAP packet: length, CID, and payload in that order.

  std::vector<uint8_t> l2cap_packet_;

  // Returns an iterator to the beginning of the L2CAP payload on success.

  auto get_l2cap_payload_begin() const {

    return std::next(l2cap_packet_.begin(), kSduHeaderLength);

  }

  // Returns true if the SDU control sequence for Segmentation and

  // Reassembly is 00b, false otherwise.

  static bool check_if_only_sdu(const uint8_t bytes);

  // Returns true if the SDU control sequence for Segmentation and

  // Reassembly is 01b, false otherwise.

  static bool check_if_starting_sdu(const uint8_t bytes);

  // Returns true if the SDU control sequence for Segmentation and

  // Reasembly is 10b, false otherwise.

  static bool check_if_ending_sdu(const uint8_t bytes);

  DISALLOW_COPY_AND_ASSIGN(L2cap);

};  // L2cap

}  // namespace test_vendor_lib

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

 *

 *  Copyright (C) 2017 Google, Inc.

 *

 *  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.

 *

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

#pragma once

#include <cstdint>

#include <iterator>

#include <vector>

namespace test_vendor_lib {

// Abstract representation of an SDU packet that contains an L2CAP

// payload. This class is meant to be used in collaboration with

// the L2cap class defined in l2cap.h. For example, an SDU packet

// may look as follows:

//

// vector<uint8_t> sdu = {0x04, 0x00, 0x48, 0x00, 0x04, 0x00, 0xab,

//                       0xcd, 0x78, 0x56}

//

// The first two bytes (in little endian) should be read as 0x0004

// and is the length of the payload of the SDU packet.

//

// The next two bytes (also in little endian) are the channel ID

// and should be read as 0x0048. These should remain the same for

// any number of SDUs that are a part of the same packet stream.

//

// Following the CID bytes, are the total length bytes. Since this

// SDU only requires a single packet, the length here is the same

// as the length in the first two bytes of the packet. Again stored

// in little endian.

//

// Next comes the two control bytes. These begin the L2CAP payload

// of the SDU packet; however, they will not be added to the L2CAP

// packet that is being constructed in the assemble function that

// will be creating an L2CAP packet from a stream of L2capSdu

// objects.

//

// The final two bytes are the frame check sequence that should be

// calculated from the start of the vector to the end of the

// payload.

//

// Thus, calling assemble on this example would create a

// zero-length L2CAP packet because the information payload of the

// L2CAP packet will not include either of the control or FCS

// bytes.

//

class L2capSdu {

 public:

  // Returns a completed L2capSdu object.

  L2capSdu(std::vector<uint8_t> create_from);

  // Get a vector iterator that points to the first byte of the

  // L2CAP payload within an SDU. The offset parameter will be the

  // number of bytes that are in the SDU header. This should always

  // be 6 bytes with the exception being the first SDU of a stream

  // of SDU packets where the first SDU packet will have an extra

  // two bytes and the offset should be 8 bytes.

  auto get_payload_begin(const unsigned int offset) const {

    return std::next(sdu_data_.begin(), offset);

  }

  // Get a vector iterator that points to the last bytes of the

  // L2CAP payload within an SDU packet. There is no offset

  // parameter for this function because there will always be two

  // FCS bytes and nothing else at the end of each SDU.

  auto get_payload_end() const { return std::prev(sdu_data_.end(), 2); }

  // Get the FCS bytes from the end of the L2CAP payload of an SDU

  // packet.

  uint16_t get_fcs() const;

  uint16_t get_payload_length() const;

  uint16_t calculate_fcs() const;

  // Get the two control bytes that begin the L2CAP payload. These

  // bytes will contain information such as the Segmentation and

  // Reassembly bits, and the TxSeq/ReqSeq numbers.

  uint16_t get_controls() const;

  uint16_t get_total_l2cap_length() const;

  size_t get_vector_size() const;

  uint16_t get_channel_id() const;

 private:

  // This is the SDU packet in bytes.

  std::vector<uint8_t> sdu_data_;

  // Table for precalculated lfsr values.

  static const uint16_t lfsr_table_[256];

  uint16_t convert_from_little_endian(const unsigned int starting_index) const;

};  // L2capSdu

}  // namespace test_vendor_lib

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

 *

 *  Copyright (C) 2017 Google, Inc.

 *

 *  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.

 *

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

#define LOG_TAG "l2cap_assemble"

#include "l2cap.h"

#include <algorithm>

#include "osi/include/log.h"

namespace test_vendor_lib {

const int kL2capHeaderLength = 4;

const uint16_t kSduSarBits = 0xe000;

const uint16_t kSduTxSeqBits = 0x007e;

const int kSduStandardHeaderLength = 6;

const int kSduFirstHeaderLength = 8;

std::unique_ptr<L2cap> L2cap::assemble(

    const std::vector<L2capSdu>& sdu_packets) {

  std::unique_ptr<L2cap> built_l2cap_packet(new L2cap());

  uint16_t l2cap_payload_length = 0;

  uint16_t first_packet_channel_id = 0;

  uint8_t txseq_start;

  if (sdu_packets.size() == 0) {

    return nullptr;

  }

  first_packet_channel_id = sdu_packets[0].get_channel_id();

  built_l2cap_packet->l2cap_packet_.resize(kL2capHeaderLength);

  for (size_t i = 0; i < sdu_packets.size(); i++) {

    uint16_t payload_length = sdu_packets[i].get_payload_length();

    // TODO(jruthe): Remove these checks when ACL packets have been

    // implemented. Once those are done, that will be the only way to create

    // L2capSdu objects and these checks will be moved there instead.

    //

    // Check the integrity of the packet length, if it is zero, it is invalid.

    // The maximum size of a single, partial L2CAP payload is 1016 bytes.

    if ((payload_length <= 0) ||

        (payload_length != sdu_packets[i].get_vector_size() - 4)) {

      return nullptr;

    }

    uint16_t fcs_check = sdu_packets[i].get_fcs();

    if (sdu_packets[i].calculate_fcs() != fcs_check) {

      return nullptr;

    }

    uint16_t controls = sdu_packets[i].get_controls();

    uint16_t continuation_bits = controls & kSduSarBits;

    continuation_bits = continuation_bits >> 12;

    if (sdu_packets[i].get_channel_id() != first_packet_channel_id) {

      return nullptr;

    }

    if (i == 0) txseq_start = controls & kSduTxSeqBits;

    // Bluetooth Specification version 4.2 volume 3 part A 3.3.2:

    // If there is only a single SDU, the first two bits of the control must be

    // set to 00b, representing an unsegmented SDU. If the SDU is segmented,

    // there is a begin and an end. The first segment must have the first two

    // control bits set to 01b and the ending segment must have them set to 10b.

    // Meanwhile all segments in between the start and end must have the bits

    // set to 11b.

    uint16_t starting_index;

    uint16_t total_expected_l2cap_length;

    uint8_t txseq = controls & kSduTxSeqBits;

    if (sdu_packets.size() == 1 && !check_if_only_sdu(continuation_bits)) {

      return nullptr;

    } else if (sdu_packets.size() > 1 && i == 0 &&

               !check_if_starting_sdu(continuation_bits)) {

      return nullptr;

    } else if (i != 0 && check_if_starting_sdu(continuation_bits)) {

      return nullptr;

    } else if (txseq != (txseq_start + (static_cast<uint8_t>(i) << 1))) {

      return nullptr;

    } else if (sdu_packets.size() > 1 && i == sdu_packets.size() - 1 &&

               !check_if_ending_sdu(continuation_bits)) {

      return nullptr;

    } else if (check_if_starting_sdu(continuation_bits)) {

      starting_index = kSduFirstHeaderLength;

      total_expected_l2cap_length = sdu_packets[i].get_total_l2cap_length();

    } else {

      starting_index = kSduStandardHeaderLength;

    }

    l2cap_payload_length += (payload_length - 2);

    auto payload_begin = sdu_packets[i].get_payload_begin(starting_index);

    auto payload_end = sdu_packets[i].get_payload_end();

    built_l2cap_packet->l2cap_packet_.insert(

        built_l2cap_packet->l2cap_packet_.end(), payload_begin, payload_end);

  }

  built_l2cap_packet->l2cap_packet_[0] = l2cap_payload_length & 0xff;

  built_l2cap_packet->l2cap_packet_[1] = (l2cap_payload_length & 0xff00) >> 8;

  built_l2cap_packet->l2cap_packet_[2] = first_packet_channel_id & 0xff;

  built_l2cap_packet->l2cap_packet_[3] =

      (first_packet_channel_id & 0xff00) >> 8;

  return built_l2cap_packet;

}  // Assemble

std::vector<uint8_t> L2cap::get_l2cap_payload() const {

  std::vector<uint8_t> payload_sub_vector;

  payload_sub_vector.clear();

  auto begin_payload_iter = get_l2cap_payload_begin();

  payload_sub_vector.insert(payload_sub_vector.end(), begin_payload_iter,

                            l2cap_packet_.end());

  return payload_sub_vector;

}

uint16_t L2cap::get_l2cap_cid() const {

  return ((l2cap_packet_[3] << 8) | l2cap_packet_[2]);

}

bool L2cap::check_if_only_sdu(const uint8_t bits) {

  return ((bits & 0xc) == 0x0);

}

bool L2cap::check_if_starting_sdu(const uint8_t bits) {

  return ((bits & 0xc) == 0x4);

}

bool L2cap::check_if_ending_sdu(const uint8_t bits) {

  return ((bits & 0xc) == 0x8);

}

}  // namespace test_vendor_lib

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

 *

 *  Copyright (C) 2017 Google, Inc.

 *

 *  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.

 *

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

#include "l2cap_sdu.h"

#include <base/logging.h>

namespace test_vendor_lib {

// Define the LFSR table of precalculated values defined by the

// Bluetooth specification version 4.2 volume 3 part A section 3.3.5.

const uint16_t L2capSdu::lfsr_table_[256] = {

    0x0000, 0xc0c1, 0xc181, 0x0140, 0xc301, 0x03c0, 0x0280, 0xc241, 0xc601,

    0x06c0, 0x0780, 0xc741, 0x0500, 0xc5c1, 0xc481, 0x0440, 0xcc01, 0x0cc0,

    0x0d80, 0xcd41, 0x0f00, 0xcfc1, 0xce81, 0x0e40, 0x0a00, 0xcac1, 0xcb81,

    0x0b40, 0xc901, 0x09c0, 0x0880, 0xc841, 0xd801, 0x18c0, 0x1980, 0xd941,

    0x1b00, 0xdbc1, 0xda81, 0x1a40, 0x1e00, 0xdec1, 0xdf81, 0x1f40, 0xdd01,

    0x1dc0, 0x1c80, 0xdc41, 0x1400, 0xd4c1, 0xd581, 0x1540, 0xd701, 0x17c0,

    0x1680, 0xd641, 0xd201, 0x12c0, 0x1380, 0xd341, 0x1100, 0xd1c1, 0xd081,

    0x1040, 0xf001, 0x30c0, 0x3180, 0xf141, 0x3300, 0xf3c1, 0xf281, 0x3240,

    0x3600, 0xf6c1, 0xf781, 0x3740, 0xf501, 0x35c0, 0x3480, 0xf441, 0x3c00,

    0xfcc1, 0xfd81, 0x3d40, 0xff01, 0x3fc0, 0x3e80, 0xfe41, 0xfa01, 0x3ac0,

    0x3b80, 0xfb41, 0x3900, 0xf9c1, 0xf881, 0x3840, 0x2800, 0xe8c1, 0xe981,

    0x2940, 0xeb01, 0x2bc0, 0x2a80, 0xea41, 0xee01, 0x2ec0, 0x2f80, 0xef41,

    0x2d00, 0xedc1, 0xec81, 0x2c40, 0xe401, 0x24c0, 0x2580, 0xe541, 0x2700,

    0xe7c1, 0xe681, 0x2640, 0x2200, 0xe2c1, 0xe381, 0x2340, 0xe101, 0x21c0,

    0x2080, 0xe041, 0xa001, 0x60c0, 0x6180, 0xa141, 0x6300, 0xa3c1, 0xa281,

    0x6240, 0x6600, 0xa6c1, 0xa781, 0x6740, 0xa501, 0x65c0, 0x6480, 0xa441,

    0x6c00, 0xacc1, 0xad81, 0x6d40, 0xaf01, 0x6fc0, 0x6e80, 0xae41, 0xaa01,

    0x6ac0, 0x6b80, 0xab41, 0x6900, 0xa9c1, 0xa881, 0x6840, 0x7800, 0xb8c1,

    0xb981, 0x7940, 0xbb01, 0x7bc0, 0x7a80, 0xba41, 0xbe01, 0x7ec0, 0x7f80,

    0xbf41, 0x7d00, 0xbdc1, 0xbc81, 0x7c40, 0xb401, 0x74c0, 0x7580, 0xb541,

    0x7700, 0xb7c1, 0xb681, 0x7640, 0x7200, 0xb2c1, 0xb381, 0x7340, 0xb101,

    0x71c0, 0x7080, 0xb041, 0x5000, 0x90c1, 0x9181, 0x5140, 0x9301, 0x53c0,

    0x5280, 0x9241, 0x9601, 0x56c0, 0x5780, 0x9741, 0x5500, 0x95c1, 0x9481,

    0x5440, 0x9c01, 0x5cc0, 0x5d80, 0x9d41, 0x5f00, 0x9fc1, 0x9e81, 0x5e40,

    0x5a00, 0x9ac1, 0x9b81, 0x5b40, 0x9901, 0x59c0, 0x5880, 0x9841, 0x8801,

    0x48c0, 0x4980, 0x8941, 0x4b00, 0x8bc1, 0x8a81, 0x4a40, 0x4e00, 0x8ec1,

    0x8f81, 0x4f40, 0x8d01, 0x4dc0, 0x4c80, 0x8c41, 0x4400, 0x84c1, 0x8581,

    0x4540, 0x8701, 0x47c0, 0x4680, 0x8641, 0x8201, 0x42c0, 0x4380, 0x8341,

    0x4100, 0x81c1, 0x8081, 0x4040,

};  // lfsr_table

L2capSdu::L2capSdu(std::vector<uint8_t> create_from) {

  sdu_data_.clear();

  sdu_data_.insert(sdu_data_.end(), create_from.begin(), create_from.end());

}

uint16_t L2capSdu::convert_from_little_endian(

    const unsigned int starting_index) const {

  uint16_t convert = sdu_data_[starting_index + 1];

  convert = convert << 8;

  convert = convert | sdu_data_[starting_index];

  return convert;

}

uint16_t L2capSdu::calculate_fcs() const {

  // Starting state as directed by Bluetooth specification version 4.2 volume 3

  // part A 3.3.5.

  uint16_t lfsr = 0x0000;

  for (size_t i = 0; i < sdu_data_.size() - 2; i++) {

    uint8_t current_byte = sdu_data_[i];

    lfsr = ((lfsr >> 8) & 0xff) ^ lfsr_table_[(lfsr & 0xff) ^ current_byte];

  }

  return lfsr;

}

uint16_t L2capSdu::get_payload_length() const {

  return convert_from_little_endian(0);

}

uint16_t L2capSdu::get_fcs() const {

  return convert_from_little_endian(sdu_data_.size() - 2);

}

uint16_t L2capSdu::get_controls() const {

  return convert_from_little_endian(4);

}

uint16_t L2capSdu::get_total_l2cap_length() const {

  return convert_from_little_endian(6);

}

uint16_t L2capSdu::get_channel_id() const {

  return convert_from_little_endian(2);

}

size_t L2capSdu::get_vector_size() const { return sdu_data_.size(); }

}  // namespace test_vendor_lib