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
17using webrtc::RTCPUtility::RtcpCommonHeader;
18
19namespace webrtc {
20namespace 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//       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
34Bye::Bye() : sender_ssrc_(0) {}
35
36bool 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
76bool 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
112bool 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
121void Bye::WithReason(const std::string& reason) {
122  RTC_DCHECK_LE(reason.size(), 0xffu);
123  reason_ = reason;
124}
125
126size_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