1 /****************************************************************************** 2 * 3 * Copyright 2017 The Android Open Source Project 4 * 5 * Licensed under the Apache License, Version 2.0 (the "License"); 6 * you may not use this file except in compliance with the License. 7 * You may obtain a copy of the License at: 8 * 9 * http://www.apache.org/licenses/LICENSE-2.0 10 * 11 * Unless required by applicable law or agreed to in writing, software 12 * distributed under the License is distributed on an "AS IS" BASIS, 13 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14 * See the License for the specific language governing permissions and 15 * limitations under the License. 16 * 17 ******************************************************************************/ 18 19 #pragma once 20 21 #include <array> 22 #include <vector> 23 24 // Scan Response data from Traxxas 25 static constexpr std::array<uint8_t, 18> trx_quirk{ 26 {0x14, 0x09, 0x54, 0xFF, 0xFF, 0x20, 0x42, 0x4C, 0x45, 0x05, 0x12, 0xFF, 27 0x00, 0xE8, 0x03, 0x02, 0x0A, 0x00}}; 28 29 class AdvertiseDataParser { 30 // Return true if the packet is malformed, but should be considered valid for 31 // compatibility with already existing devices MalformedPacketQuirk(const std::vector<uint8_t> & ad,size_t position)32 static bool MalformedPacketQuirk(const std::vector<uint8_t>& ad, 33 size_t position) { 34 auto data_start = ad.begin() + position; 35 36 // Traxxas - bad name length 37 if ((ad.size() - position) >= 18 && 38 std::equal(data_start, data_start + 3, trx_quirk.begin()) && 39 std::equal(data_start + 5, data_start + 11, trx_quirk.begin() + 5) && 40 std::equal(data_start + 12, data_start + 18, trx_quirk.begin() + 12)) { 41 return true; 42 } 43 44 return false; 45 } 46 47 public: RemoveTrailingZeros(std::vector<uint8_t> & ad)48 static void RemoveTrailingZeros(std::vector<uint8_t>& ad) { 49 size_t position = 0; 50 51 size_t ad_len = ad.size(); 52 while (position != ad_len) { 53 uint8_t len = ad[position]; 54 55 // A field length of 0 would be invalid as it should at least contain the 56 // EIR field type. However, some existing devices send zero padding at the 57 // end of advertisement. If this is the case, cut the zero padding from 58 // end of the packet. Otherwise i.e. gluing scan response to advertise 59 // data will result in data with zero padding in the middle. 60 if (len == 0) { 61 ad.erase(ad.begin() + position, ad.end()); 62 return; 63 } 64 65 if (position + len >= ad_len) { 66 return; 67 } 68 69 position += len + 1; 70 } 71 } 72 73 /** 74 * Return true if this |ad| represent properly formatted advertising data. 75 */ IsValid(const std::vector<uint8_t> & ad)76 static bool IsValid(const std::vector<uint8_t>& ad) { 77 size_t position = 0; 78 79 size_t ad_len = ad.size(); 80 while (position != ad_len) { 81 uint8_t len = ad[position]; 82 83 // A field length of 0 would be invalid as it should at least contain the 84 // EIR field type. However, some existing devices send zero padding at the 85 // end of advertisement. If this is the case, treat the packet as valid. 86 if (len == 0) { 87 for (size_t i = position + 1; i < ad_len; i++) { 88 if (ad[i] != 0) return false; 89 } 90 return true; 91 } 92 93 // If the length of the current field would exceed the total data length, 94 // then the data is badly formatted. 95 if (position + len >= ad_len) { 96 if (MalformedPacketQuirk(ad, position)) return true; 97 98 return false; 99 } 100 101 position += len + 1; 102 } 103 104 return true; 105 } 106 107 /** 108 * This function returns a pointer inside the |ad| array of length |ad_len| 109 * where a field of |type| is located, together with its length in |p_length| 110 */ GetFieldByType(const uint8_t * ad,size_t ad_len,uint8_t type,uint8_t * p_length)111 static const uint8_t* GetFieldByType(const uint8_t* ad, size_t ad_len, 112 uint8_t type, uint8_t* p_length) { 113 size_t position = 0; 114 115 while (position != ad_len) { 116 uint8_t len = ad[position]; 117 118 if (len == 0) break; 119 if (position + len >= ad_len) break; 120 121 uint8_t adv_type = ad[position + 1]; 122 123 if (adv_type == type) { 124 /* length doesn't include itself */ 125 *p_length = len - 1; /* minus the length of type */ 126 return ad + position + 2; 127 } 128 129 position += len + 1; /* skip the length of data */ 130 } 131 132 *p_length = 0; 133 return NULL; 134 } 135 136 /** 137 * This function returns a pointer inside the |adv| where a field of |type| is 138 * located, together with it' length in |p_length| 139 */ GetFieldByType(std::vector<uint8_t> const & ad,uint8_t type,uint8_t * p_length)140 static const uint8_t* GetFieldByType(std::vector<uint8_t> const& ad, 141 uint8_t type, uint8_t* p_length) { 142 return GetFieldByType(ad.data(), ad.size(), type, p_length); 143 } 144 }; 145