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Commit 47aa262f authored by Jakub Pawlowski's avatar Jakub Pawlowski Committed by android-build-merger
Browse files

Advertisement parsing fix for zero padding 

am: 819b843f

Change-Id: I59bf8524b2c95c5f8c7f4261166057078dd25b7c
parents c1625851 819b843f

system/stack/btm/btm_ble_gap.cc

+5 −2
Original line number Diff line number Diff line
@@ -2017,11 +2017,14 @@ static void btm_ble_process_adv_pkt_cont( 
  bool is_scannable = ble_evt_type_is_scannable(evt_type);

  bool is_scan_resp = ble_evt_type_is_scan_resp(evt_type);



  bool is_start =

      ble_evt_type_is_legacy(evt_type) && is_scannable && !is_scan_resp;



  if (is_start) AdvertiseDataParser::RemoveTrailingZeros(tmp);



  // We might have send scan request to this device before, but didn't get the

  // response. In such case make sure data is put at start, not appended to

  // already existing data.

  bool is_start =

      ble_evt_type_is_legacy(evt_type) && is_scannable && !is_scan_resp;

  std::vector<uint8_t> const& adv_data =

      is_start ? cache.Set(addr_type, bda, std::move(tmp))

               : cache.Append(addr_type, bda, std::move(tmp));

system/stack/include/advertise_data_parser.h

+30 −0
Original line number Diff line number Diff line
@@ -44,6 +44,36 @@ class AdvertiseDataParser { 
  }



 public:

  static void RemoveTrailingZeros(std::vector<uint8_t>& ad) {

    size_t position = 0;



    size_t ad_len = ad.size();

    while (position != ad_len) {

      uint8_t len = ad[position];



      // A field length of 0 would be invalid as it should at least contain the

      // EIR field type. However, some existing devices send zero padding at the

      // end of advertisement. If this is the case, cut the zero padding from

      // end of the packet. Otherwise i.e. gluing scan response to advertise

      // data will result in data with zero padding in the middle.

      if (len == 0) {

        size_t zeros_start = position;

        for (size_t i = position + 1; i < ad_len; i++) {

          if (ad[i] != 0) return;

        }



        ad.erase(ad.begin() + zeros_start, ad.end());

        return;

      }



      if (position + len >= ad_len) {

        return;

      }



      position += len + 1;

    }

  }



  /**

   * Return true if this |ad| represent properly formatted advertising data.

   */

system/stack/test/ad_parser_unittest.cc

+21 −0
Original line number Diff line number Diff line
@@ -128,3 +128,24 @@ TEST(AdvertiseDataParserTest, GetFieldByType) { 
  EXPECT_EQ(nullptr, data);

  EXPECT_EQ(0, p_length);

}



// This test makes sure that RemoveTrailingZeros is working correctly. It does

// run the RemoveTrailingZeros for ad data, then glue scan response at end of

// it, and checks that the resulting data is good.

TEST(AdvertiseDataParserTest, RemoveTrailingZeros) {

  std::vector<uint8_t> podo_ad_data{

      0x02, 0x01, 0x02, 0x11, 0x06, 0x66, 0x9a, 0x0c, 0x20, 0x00, 0x08,

      0x37, 0xa8, 0xe5, 0x11, 0x81, 0x8b, 0xd0, 0xf0, 0xf0, 0xf0, 0x00,

      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};

  const std::vector<uint8_t> podo_scan_resp{

      0x03, 0x19, 0x00, 0x80, 0x09, 0x09, 0x50, 0x6f, 0x64, 0x6f, 0x51,

      0x35, 0x56, 0x47, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,

      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00};



  AdvertiseDataParser::RemoveTrailingZeros(podo_ad_data);



  std::vector<uint8_t> glued(podo_ad_data);

  glued.insert(glued.end(), podo_ad_data.begin(), podo_ad_data.end());



  EXPECT_TRUE(AdvertiseDataParser::IsValid(glued));

}
 
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