1 /*
2  *  Copyright (c) 2016 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 "modules/rtp_rtcp/source/rtcp_packet/common_header.h"
12 
13 #include "modules/rtp_rtcp/source/byte_io.h"
14 #include "rtc_base/logging.h"
15 
16 namespace webrtc {
17 namespace rtcp {
18 constexpr size_t CommonHeader::kHeaderSizeBytes;
19 //    0                   1           1       2                   3
20 //    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
21 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
22 // 0 |V=2|P|   C/F   |
23 //   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
24 // 1                 |  Packet Type  |
25 //   ----------------+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
26 // 2                                 |             length            |
27 //   --------------------------------+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 //
29 // Common header for all RTCP packets, 4 octets.
Parse(const uint8_t * buffer,size_t size_bytes)30 bool CommonHeader::Parse(const uint8_t* buffer, size_t size_bytes) {
31   const uint8_t kVersion = 2;
32 
33   if (size_bytes < kHeaderSizeBytes) {
34     RTC_LOG(LS_WARNING)
35         << "Too little data (" << size_bytes << " byte"
36         << (size_bytes != 1 ? "s" : "")
37         << ") remaining in buffer to parse RTCP header (4 bytes).";
38     return false;
39   }
40 
41   uint8_t version = buffer[0] >> 6;
42   if (version != kVersion) {
43     RTC_LOG(LS_WARNING) << "Invalid RTCP header: Version must be "
44                         << static_cast<int>(kVersion) << " but was "
45                         << static_cast<int>(version);
46     return false;
47   }
48 
49   bool has_padding = (buffer[0] & 0x20) != 0;
50   count_or_format_ = buffer[0] & 0x1F;
51   packet_type_ = buffer[1];
52   payload_size_ = ByteReader<uint16_t>::ReadBigEndian(&buffer[2]) * 4;
53   payload_ = buffer + kHeaderSizeBytes;
54   padding_size_ = 0;
55 
56   if (size_bytes < kHeaderSizeBytes + payload_size_) {
57     RTC_LOG(LS_WARNING) << "Buffer too small (" << size_bytes
58                         << " bytes) to fit an RtcpPacket with a header and "
59                         << payload_size_ << " bytes.";
60     return false;
61   }
62 
63   if (has_padding) {
64     if (payload_size_ == 0) {
65       RTC_LOG(LS_WARNING)
66           << "Invalid RTCP header: Padding bit set but 0 payload "
67              "size specified.";
68       return false;
69     }
70 
71     padding_size_ = payload_[payload_size_ - 1];
72     if (padding_size_ == 0) {
73       RTC_LOG(LS_WARNING)
74           << "Invalid RTCP header: Padding bit set but 0 padding "
75              "size specified.";
76       return false;
77     }
78     if (padding_size_ > payload_size_) {
79       RTC_LOG(LS_WARNING) << "Invalid RTCP header: Too many padding bytes ("
80                           << padding_size_ << ") for a packet payload size of "
81                           << payload_size_ << " bytes.";
82       return false;
83     }
84     payload_size_ -= padding_size_;
85   }
86   return true;
87 }
88 }  // namespace rtcp
89 }  // namespace webrtc
90