1 /****************************************************************************** 2 * 3 * Copyright (C) 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 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 (std::equal(data_start, data_start + 3, trx_quirk.begin()) && 38 std::equal(data_start + 5, data_start + 11, trx_quirk.begin() + 5) && 39 std::equal(data_start + 12, data_start + 18, trx_quirk.begin() + 12)) { 40 return true; 41 } 42 43 return false; 44 } 45 46 public: 47 static void RemoveTrailingZeros(std::vector<uint8_t>& ad) { 48 size_t position = 0; 49 50 size_t ad_len = ad.size(); 51 while (position != ad_len) { 52 uint8_t len = ad[position]; 53 54 // A field length of 0 would be invalid as it should at least contain the 55 // EIR field type. However, some existing devices send zero padding at the 56 // end of advertisement. If this is the case, cut the zero padding from 57 // end of the packet. Otherwise i.e. gluing scan response to advertise 58 // data will result in data with zero padding in the middle. 59 if (len == 0) { 60 size_t zeros_start = position; 61 for (size_t i = position + 1; i < ad_len; i++) { 62 if (ad[i] != 0) return; 63 } 64 65 ad.erase(ad.begin() + zeros_start, ad.end()); 66 return; 67 } 68 69 if (position + len >= ad_len) { 70 return; 71 } 72 73 position += len + 1; 74 } 75 } 76 77 /** 78 * Return true if this |ad| represent properly formatted advertising data. 79 */ 80 static bool IsValid(const std::vector<uint8_t>& ad) { 81 size_t position = 0; 82 83 size_t ad_len = ad.size(); 84 while (position != ad_len) { 85 uint8_t len = ad[position]; 86 87 // A field length of 0 would be invalid as it should at least contain the 88 // EIR field type. However, some existing devices send zero padding at the 89 // end of advertisement. If this is the case, treat the packet as valid. 90 if (len == 0) { 91 for (size_t i = position + 1; i < ad_len; i++) { 92 if (ad[i] != 0) return false; 93 } 94 return true; 95 } 96 97 // If the length of the current field would exceed the total data length, 98 // then the data is badly formatted. 99 if (position + len >= ad_len) { 100 if (MalformedPacketQuirk(ad, position)) return true; 101 102 return false; 103 } 104 105 position += len + 1; 106 } 107 108 return true; 109 } 110 111 /** 112 * This function returns a pointer inside the |ad| array of length |ad_len| 113 * where a field of |type| is located, together with its length in |p_length| 114 */ 115 static const uint8_t* GetFieldByType(const uint8_t* ad, size_t ad_len, 116 uint8_t type, uint8_t* p_length) { 117 size_t position = 0; 118 119 while (position != ad_len) { 120 uint8_t len = ad[position]; 121 122 if (len == 0) break; 123 if (position + len >= ad_len) break; 124 125 uint8_t adv_type = ad[position + 1]; 126 127 if (adv_type == type) { 128 /* length doesn't include itself */ 129 *p_length = len - 1; /* minus the length of type */ 130 return ad + position + 2; 131 } 132 133 position += len + 1; /* skip the length of data */ 134 } 135 136 *p_length = 0; 137 return NULL; 138 } 139 140 /** 141 * This function returns a pointer inside the |adv| where a field of |type| is 142 * located, together with it' length in |p_length| 143 */ 144 static const uint8_t* GetFieldByType(std::vector<uint8_t> const& ad, 145 uint8_t type, uint8_t* p_length) { 146 return GetFieldByType(ad.data(), ad.size(), type, p_length); 147 } 148 }; 149
