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 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 ad.erase(ad.begin() + position, ad.end()); 61 return; 62 } 63 64 if (position + len >= ad_len) { 65 return; 66 } 67 68 position += len + 1; 69 } 70 } 71 72 /** 73 * Return true if this |ad| represent properly formatted advertising data. 74 */ 75 static bool IsValid(const std::vector<uint8_t>& ad) { 76 size_t position = 0; 77 78 size_t ad_len = ad.size(); 79 while (position != ad_len) { 80 uint8_t len = ad[position]; 81 82 // A field length of 0 would be invalid as it should at least contain the 83 // EIR field type. However, some existing devices send zero padding at the 84 // end of advertisement. If this is the case, treat the packet as valid. 85 if (len == 0) { 86 for (size_t i = position + 1; i < ad_len; i++) { 87 if (ad[i] != 0) return false; 88 } 89 return true; 90 } 91 92 // If the length of the current field would exceed the total data length, 93 // then the data is badly formatted. 94 if (position + len >= ad_len) { 95 if (MalformedPacketQuirk(ad, position)) return true; 96 97 return false; 98 } 99 100 position += len + 1; 101 } 102 103 return true; 104 } 105 106 /** 107 * This function returns a pointer inside the |ad| array of length |ad_len| 108 * where a field of |type| is located, together with its length in |p_length| 109 */ 110 static const uint8_t* GetFieldByType(const uint8_t* ad, size_t ad_len, 111 uint8_t type, uint8_t* p_length) { 112 size_t position = 0; 113 114 while (position != ad_len) { 115 uint8_t len = ad[position]; 116 117 if (len == 0) break; 118 if (position + len >= ad_len) break; 119 120 uint8_t adv_type = ad[position + 1]; 121 122 if (adv_type == type) { 123 /* length doesn't include itself */ 124 *p_length = len - 1; /* minus the length of type */ 125 return ad + position + 2; 126 } 127 128 position += len + 1; /* skip the length of data */ 129 } 130 131 *p_length = 0; 132 return NULL; 133 } 134 135 /** 136 * This function returns a pointer inside the |adv| where a field of |type| is 137 * located, together with it' length in |p_length| 138 */ 139 static const uint8_t* GetFieldByType(std::vector<uint8_t> const& ad, 140 uint8_t type, uint8_t* p_length) { 141 return GetFieldByType(ad.data(), ad.size(), type, p_length); 142 } 143 }; 144
