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      1 /*
      2  *  Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
      3  *
      4  *  Use of this source code is governed by a BSD-style license
      5  *  that can be found in the LICENSE file in the root of the source
      6  *  tree. An additional intellectual property rights grant can be found
      7  *  in the file PATENTS.  All contributing project authors may
      8  *  be found in the AUTHORS file in the root of the source tree.
      9  */
     10 
     11 #include "webrtc/modules/rtp_rtcp/source/rtcp_packet/bye.h"
     12 
     13 #include "webrtc/base/checks.h"
     14 #include "webrtc/base/logging.h"
     15 #include "webrtc/modules/rtp_rtcp/source/byte_io.h"
     16 
     17 using webrtc::RTCPUtility::RtcpCommonHeader;
     18 
     19 namespace webrtc {
     20 namespace rtcp {
     21 
     22 // Bye packet (BYE) (RFC 3550).
     23 //
     24 //        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     25 //       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     26 //       |V=2|P|    SC   |   PT=BYE=203  |             length            |
     27 //       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     28 //       |                           SSRC/CSRC                           |
     29 //       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     30 //       :                              ...                              :
     31 //       +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
     32 // (opt) |     length    |               reason for leaving            ...
     33 //       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     34 Bye::Bye() : sender_ssrc_(0) {}
     35 
     36 bool Bye::Parse(const RtcpCommonHeader& header, const uint8_t* payload) {
     37   RTC_DCHECK(header.packet_type == kPacketType);
     38 
     39   const uint8_t src_count = header.count_or_format;
     40   // Validate packet.
     41   if (header.payload_size_bytes < 4u * src_count) {
     42     LOG(LS_WARNING)
     43         << "Packet is too small to contain CSRCs it promise to have.";
     44     return false;
     45   }
     46   bool has_reason = (header.payload_size_bytes > 4u * src_count);
     47   uint8_t reason_length = 0;
     48   if (has_reason) {
     49     reason_length = payload[4u * src_count];
     50     if (header.payload_size_bytes - 4u * src_count < 1u + reason_length) {
     51       LOG(LS_WARNING) << "Invalid reason length: " << reason_length;
     52       return false;
     53     }
     54   }
     55   // Once sure packet is valid, copy values.
     56   if (src_count == 0) {  // A count value of zero is valid, but useless.
     57     sender_ssrc_ = 0;
     58     csrcs_.clear();
     59   } else {
     60     sender_ssrc_ = ByteReader<uint32_t>::ReadBigEndian(payload);
     61     csrcs_.resize(src_count - 1);
     62     for (size_t i = 1; i < src_count; ++i)
     63       csrcs_[i - 1] = ByteReader<uint32_t>::ReadBigEndian(&payload[4 * i]);
     64   }
     65 
     66   if (has_reason) {
     67     reason_.assign(reinterpret_cast<const char*>(&payload[4u * src_count + 1]),
     68                    reason_length);
     69   } else {
     70     reason_.clear();
     71   }
     72 
     73   return true;
     74 }
     75 
     76 bool Bye::Create(uint8_t* packet,
     77                  size_t* index,
     78                  size_t max_length,
     79                  RtcpPacket::PacketReadyCallback* callback) const {
     80   while (*index + BlockLength() > max_length) {
     81     if (!OnBufferFull(packet, index, callback))
     82       return false;
     83   }
     84   const size_t index_end = *index + BlockLength();
     85 
     86   CreateHeader(1 + csrcs_.size(), kPacketType, HeaderLength(), packet, index);
     87   // Store srcs of the leaving clients.
     88   ByteWriter<uint32_t>::WriteBigEndian(&packet[*index], sender_ssrc_);
     89   *index += sizeof(uint32_t);
     90   for (uint32_t csrc : csrcs_) {
     91     ByteWriter<uint32_t>::WriteBigEndian(&packet[*index], csrc);
     92     *index += sizeof(uint32_t);
     93   }
     94   // Store the reason to leave.
     95   if (!reason_.empty()) {
     96     uint8_t reason_length = reason_.size();
     97     packet[(*index)++] = reason_length;
     98     memcpy(&packet[*index], reason_.data(), reason_length);
     99     *index += reason_length;
    100     // Add padding bytes if needed.
    101     size_t bytes_to_pad = index_end - *index;
    102     RTC_DCHECK_LE(bytes_to_pad, 3u);
    103     if (bytes_to_pad > 0) {
    104       memset(&packet[*index], 0, bytes_to_pad);
    105       *index += bytes_to_pad;
    106     }
    107   }
    108   RTC_DCHECK_EQ(index_end, *index);
    109   return true;
    110 }
    111 
    112 bool Bye::WithCsrc(uint32_t csrc) {
    113   if (csrcs_.size() >= kMaxNumberOfCsrcs) {
    114     LOG(LS_WARNING) << "Max CSRC size reached.";
    115     return false;
    116   }
    117   csrcs_.push_back(csrc);
    118   return true;
    119 }
    120 
    121 void Bye::WithReason(const std::string& reason) {
    122   RTC_DCHECK_LE(reason.size(), 0xffu);
    123   reason_ = reason;
    124 }
    125 
    126 size_t Bye::BlockLength() const {
    127   size_t src_count = (1 + csrcs_.size());
    128   size_t reason_size_in_32bits = reason_.empty() ? 0 : (reason_.size() / 4 + 1);
    129   return kHeaderLength + 4 * (src_count + reason_size_in_32bits);
    130 }
    131 
    132 }  // namespace rtcp
    133 }  // namespace webrtc
    134