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| 1 // Copyright (c) 2012 The Chromium Authors. All rights reserved. | |
| 2 // Use of this source code is governed by a BSD-style license that can be | |
| 3 // found in the LICENSE file. | |
| 4 | |
| 5 #include "net/quic/quic_fec_group.h" | |
| 6 | |
| 7 #include <limits> | |
| 8 | |
| 9 #include "base/basictypes.h" | |
| 10 #include "base/logging.h" | |
| 11 #include "base/stl_util.h" | |
| 12 | |
| 13 using base::StringPiece; | |
| 14 using std::numeric_limits; | |
| 15 using std::set; | |
| 16 | |
| 17 namespace net { | |
| 18 | |
| 19 namespace { | |
| 20 const QuicPacketSequenceNumber kNoSequenceNumber = kuint64max; | |
| 21 } // namespace | |
| 22 | |
| 23 QuicFecGroup::QuicFecGroup() | |
| 24 : min_protected_packet_(kNoSequenceNumber), | |
| 25 max_protected_packet_(kNoSequenceNumber), | |
| 26 payload_parity_len_(0), | |
| 27 effective_encryption_level_(NUM_ENCRYPTION_LEVELS) { | |
| 28 } | |
| 29 | |
| 30 QuicFecGroup::~QuicFecGroup() {} | |
| 31 | |
| 32 bool QuicFecGroup::Update(EncryptionLevel encryption_level, | |
| 33 const QuicPacketHeader& header, | |
| 34 StringPiece decrypted_payload) { | |
| 35 if (ContainsKey(received_packets_, header.packet_sequence_number)) { | |
| 36 return false; | |
| 37 } | |
| 38 if (min_protected_packet_ != kNoSequenceNumber && | |
| 39 max_protected_packet_ != kNoSequenceNumber && | |
| 40 (header.packet_sequence_number < min_protected_packet_ || | |
| 41 header.packet_sequence_number > max_protected_packet_)) { | |
| 42 DLOG(ERROR) << "FEC group does not cover received packet: " | |
| 43 << header.packet_sequence_number; | |
| 44 return false; | |
| 45 } | |
| 46 if (!UpdateParity(decrypted_payload)) { | |
| 47 return false; | |
| 48 } | |
| 49 received_packets_.insert(header.packet_sequence_number); | |
| 50 if (encryption_level < effective_encryption_level_) { | |
| 51 effective_encryption_level_ = encryption_level; | |
| 52 } | |
| 53 return true; | |
| 54 } | |
| 55 | |
| 56 bool QuicFecGroup::UpdateFec( | |
| 57 EncryptionLevel encryption_level, | |
| 58 QuicPacketSequenceNumber fec_packet_sequence_number, | |
| 59 const QuicFecData& fec) { | |
| 60 if (min_protected_packet_ != kNoSequenceNumber) { | |
| 61 return false; | |
| 62 } | |
| 63 SequenceNumberSet::const_iterator it = received_packets_.begin(); | |
| 64 while (it != received_packets_.end()) { | |
| 65 if ((*it < fec.fec_group) || (*it >= fec_packet_sequence_number)) { | |
| 66 DLOG(ERROR) << "FEC group does not cover received packet: " << *it; | |
| 67 return false; | |
| 68 } | |
| 69 ++it; | |
| 70 } | |
| 71 if (!UpdateParity(fec.redundancy)) { | |
| 72 return false; | |
| 73 } | |
| 74 min_protected_packet_ = fec.fec_group; | |
| 75 max_protected_packet_ = fec_packet_sequence_number - 1; | |
| 76 if (encryption_level < effective_encryption_level_) { | |
| 77 effective_encryption_level_ = encryption_level; | |
| 78 } | |
| 79 return true; | |
| 80 } | |
| 81 | |
| 82 bool QuicFecGroup::CanRevive() const { | |
| 83 // We can revive if we're missing exactly 1 packet. | |
| 84 return NumMissingPackets() == 1; | |
| 85 } | |
| 86 | |
| 87 bool QuicFecGroup::IsFinished() const { | |
| 88 // We are finished if we are not missing any packets. | |
| 89 return NumMissingPackets() == 0; | |
| 90 } | |
| 91 | |
| 92 size_t QuicFecGroup::Revive(QuicPacketHeader* header, | |
| 93 char* decrypted_payload, | |
| 94 size_t decrypted_payload_len) { | |
| 95 if (!CanRevive()) { | |
| 96 return 0; | |
| 97 } | |
| 98 | |
| 99 // Identify the packet sequence number to be resurrected. | |
| 100 QuicPacketSequenceNumber missing = kNoSequenceNumber; | |
| 101 for (QuicPacketSequenceNumber i = min_protected_packet_; | |
| 102 i <= max_protected_packet_; ++i) { | |
| 103 // Is this packet missing? | |
| 104 if (received_packets_.count(i) == 0) { | |
| 105 missing = i; | |
| 106 break; | |
| 107 } | |
| 108 } | |
| 109 DCHECK_NE(kNoSequenceNumber, missing); | |
| 110 | |
| 111 DCHECK_LE(payload_parity_len_, decrypted_payload_len); | |
| 112 if (payload_parity_len_ > decrypted_payload_len) { | |
| 113 return 0; | |
| 114 } | |
| 115 for (size_t i = 0; i < payload_parity_len_; ++i) { | |
| 116 decrypted_payload[i] = payload_parity_[i]; | |
| 117 } | |
| 118 | |
| 119 header->packet_sequence_number = missing; | |
| 120 header->entropy_flag = false; // Unknown entropy. | |
| 121 | |
| 122 received_packets_.insert(missing); | |
| 123 return payload_parity_len_; | |
| 124 } | |
| 125 | |
| 126 bool QuicFecGroup::ProtectsPacketsBefore(QuicPacketSequenceNumber num) const { | |
| 127 if (max_protected_packet_ != kNoSequenceNumber) { | |
| 128 return max_protected_packet_ < num; | |
| 129 } | |
| 130 // Since we might not yet have received the FEC packet, we must check | |
| 131 // the packets we have received. | |
| 132 return *received_packets_.begin() < num; | |
| 133 } | |
| 134 | |
| 135 bool QuicFecGroup::UpdateParity(StringPiece payload) { | |
| 136 DCHECK_LE(payload.size(), kMaxPacketSize); | |
| 137 if (payload.size() > kMaxPacketSize) { | |
| 138 DLOG(ERROR) << "Illegal payload size: " << payload.size(); | |
| 139 return false; | |
| 140 } | |
| 141 if (payload_parity_len_ < payload.size()) { | |
| 142 payload_parity_len_ = payload.size(); | |
| 143 } | |
| 144 DCHECK_LE(payload.size(), kMaxPacketSize); | |
| 145 if (received_packets_.empty() && | |
| 146 min_protected_packet_ == kNoSequenceNumber) { | |
| 147 // Initialize the parity to the value of this payload | |
| 148 memcpy(payload_parity_, payload.data(), payload.size()); | |
| 149 if (payload.size() < kMaxPacketSize) { | |
| 150 // TODO(rch): expand as needed. | |
| 151 memset(payload_parity_ + payload.size(), 0, | |
| 152 kMaxPacketSize - payload.size()); | |
| 153 } | |
| 154 return true; | |
| 155 } | |
| 156 // Update the parity by XORing in the data (padding with 0s if necessary). | |
| 157 for (size_t i = 0; i < kMaxPacketSize; ++i) { | |
| 158 uint8 byte = i < payload.size() ? payload[i] : 0x00; | |
| 159 payload_parity_[i] ^= byte; | |
| 160 } | |
| 161 return true; | |
| 162 } | |
| 163 | |
| 164 size_t QuicFecGroup::NumMissingPackets() const { | |
| 165 if (min_protected_packet_ == kNoSequenceNumber) | |
| 166 return numeric_limits<size_t>::max(); | |
| 167 return static_cast<size_t>( | |
| 168 (max_protected_packet_ - min_protected_packet_ + 1) - | |
| 169 received_packets_.size()); | |
| 170 } | |
| 171 | |
| 172 } // namespace net | |
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