path: root/media/cast/net/rtcp/rtcp_utility.cc

// Copyright 2014 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "media/cast/net/rtcp/rtcp_utility.h"

#include "base/logging.h"
#include "media/cast/net/cast_transport_defines.h"

namespace media {
namespace cast {

RtcpParser::RtcpParser(uint32 local_ssrc, uint32 remote_ssrc) :
    local_ssrc_(local_ssrc),
    remote_ssrc_(remote_ssrc),
    has_sender_report_(false),
    has_last_report_(false),
    has_cast_message_(false),
    has_receiver_reference_time_report_(false) {
}

RtcpParser::~RtcpParser() {}

bool RtcpParser::Parse(base::BigEndianReader* reader) {
  while (reader->remaining()) {
    RtcpCommonHeader header;
    if (!ParseCommonHeader(reader, &header))
      return false;

    base::StringPiece tmp;
    if (!reader->ReadPiece(&tmp, header.length_in_octets - 4))
      return false;
    base::BigEndianReader chunk(tmp.data(), tmp.size());

    switch (header.PT) {
      case kPacketTypeSenderReport:
        if (!ParseSR(&chunk, header))
          return false;
        break;

      case kPacketTypeReceiverReport:
        if (!ParseRR(&chunk, header))
          return false;
        break;

      case kPacketTypeApplicationDefined:
        if (!ParseApplicationDefined(&chunk, header))
          return false;
        break;

      case kPacketTypePayloadSpecific:
        if (!ParseFeedbackCommon(&chunk, header))
          return false;
        break;

      case kPacketTypeXr:
        if (!ParseExtendedReport(&chunk, header))
          return false;
        break;
    }
  }
  return true;
}

bool RtcpParser::ParseCommonHeader(base::BigEndianReader* reader,
                                   RtcpCommonHeader* parsed_header) {
  //  0                   1                   2                   3
  //  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
  // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  // |V=2|P|    IC   |      PT       |             length            |
  // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
  //
  // Common header for all Rtcp packets, 4 octets.

  uint8 byte;
  if (!reader->ReadU8(&byte))
    return false;
  parsed_header->V = byte >> 6;
  parsed_header->P = ((byte & 0x20) == 0) ? false : true;

  // Check if RTP version field == 2.
  if (parsed_header->V != 2)
    return false;

  parsed_header->IC = byte & 0x1f;
  if (!reader->ReadU8(&parsed_header->PT))
    return false;

  uint16 bytes;
  if (!reader->ReadU16(&bytes))
    return false;

  parsed_header->length_in_octets = (static_cast<size_t>(bytes) + 1) * 4;

  if (parsed_header->length_in_octets == 0)
    return false;

  return true;
}

bool RtcpParser::ParseSR(base::BigEndianReader* reader,
                         const RtcpCommonHeader& header) {
  uint32 sender_ssrc;
  if (!reader->ReadU32(&sender_ssrc))
    return false;

  if (sender_ssrc != remote_ssrc_)
    return true;

  uint32 tmp;
  if (!reader->ReadU32(&sender_report_.ntp_seconds) ||
      !reader->ReadU32(&sender_report_.ntp_fraction) ||
      !reader->ReadU32(&sender_report_.rtp_timestamp) ||
      !reader->ReadU32(&sender_report_.send_packet_count) ||
      !reader->ReadU32(&tmp))
    return false;
  sender_report_.send_octet_count = tmp;
  has_sender_report_ = true;

  for (size_t block = 0; block < header.IC; block++)
    if (!ParseReportBlock(reader))
      return false;

  return true;
}

bool RtcpParser::ParseRR(base::BigEndianReader* reader,
                         const RtcpCommonHeader& header) {
  uint32 receiver_ssrc;
  if (!reader->ReadU32(&receiver_ssrc))
    return false;

  if (receiver_ssrc != remote_ssrc_)
    return true;

  for (size_t block = 0; block < header.IC; block++)
    if (!ParseReportBlock(reader))
      return false;

  return true;
}

bool RtcpParser::ParseReportBlock(base::BigEndianReader* reader) {
  uint32 ssrc, last_report, delay;
  if (!reader->ReadU32(&ssrc) ||
      !reader->Skip(12) ||
      !reader->ReadU32(&last_report) ||
      !reader->ReadU32(&delay))
    return false;

  if (ssrc == local_ssrc_) {
    last_report_ = last_report;
    delay_since_last_report_ = delay;
    has_last_report_ = true;
  }

  return true;
}

bool RtcpParser::ParseApplicationDefined(base::BigEndianReader* reader,
                                         const RtcpCommonHeader& header) {
  uint32 sender_ssrc;
  uint32 name;
  if (!reader->ReadU32(&sender_ssrc) ||
      !reader->ReadU32(&name))
    return false;

  if (sender_ssrc != remote_ssrc_)
    return true;

  if (name != kCast)
    return false;

  switch (header.IC /* subtype */ ) {
    case kReceiverLogSubtype:
      if (!ParseCastReceiverLogFrameItem(reader))
        return false;
      break;
  }
  return true;
}

bool RtcpParser::ParseCastReceiverLogFrameItem(
    base::BigEndianReader* reader) {

  while (reader->remaining()) {
    uint32 rtp_timestamp;
    uint32 data;
    if (!reader->ReadU32(&rtp_timestamp) ||
        !reader->ReadU32(&data))
      return false;

    // We have 24 LSB of the event timestamp base on the wire.
    base::TimeTicks event_timestamp_base = base::TimeTicks() +
        base::TimeDelta::FromMilliseconds(data & 0xffffff);

    size_t num_events = 1 + static_cast<uint8>(data >> 24);

    RtcpReceiverFrameLogMessage frame_log(rtp_timestamp);
    for (size_t event = 0; event < num_events; event++) {
      uint16 delay_delta_or_packet_id;
      uint16 event_type_and_timestamp_delta;
      if (!reader->ReadU16(&delay_delta_or_packet_id) ||
          !reader->ReadU16(&event_type_and_timestamp_delta))
        return false;

      RtcpReceiverEventLogMessage event_log;
      event_log.type = TranslateToLogEventFromWireFormat(
          static_cast<uint8>(event_type_and_timestamp_delta >> 12));
      event_log.event_timestamp =
          event_timestamp_base +
          base::TimeDelta::FromMilliseconds(
              event_type_and_timestamp_delta & 0xfff);
      if (event_log.type == PACKET_RECEIVED) {
        event_log.packet_id = delay_delta_or_packet_id;
      } else {
        event_log.delay_delta = base::TimeDelta::FromMilliseconds(
            static_cast<int16>(delay_delta_or_packet_id));
      }
      frame_log.event_log_messages_.push_back(event_log);
    }

    receiver_log_.push_back(frame_log);
  }

  return true;
}

// RFC 4585.
bool RtcpParser::ParseFeedbackCommon(base::BigEndianReader* reader,
                                     const RtcpCommonHeader& header) {
  // See RTC 4585 Section 6.4 for application specific feedback messages.
  if (header.IC != 15) {
    return true;
  }
  uint32 remote_ssrc;
  uint32 media_ssrc;
  if (!reader->ReadU32(&remote_ssrc) ||
      !reader->ReadU32(&media_ssrc))
    return false;

  if (remote_ssrc != remote_ssrc_)
    return true;

  uint32 name;
  if (!reader->ReadU32(&name))
    return false;

  if (name != kCast) {
    return true;
  }

  cast_message_.media_ssrc = remote_ssrc;

  uint8 last_frame_id;
  uint8 number_of_lost_fields;
  if (!reader->ReadU8(&last_frame_id) ||
      !reader->ReadU8(&number_of_lost_fields) ||
      !reader->ReadU16(&cast_message_.target_delay_ms))
    return false;

  // Please note, this frame_id is still only 8-bit!
  cast_message_.ack_frame_id = last_frame_id;

  for (size_t i = 0; i < number_of_lost_fields; i++) {
    uint8 frame_id;
    uint16 packet_id;
    uint8 bitmask;
    if (!reader->ReadU8(&frame_id) ||
        !reader->ReadU16(&packet_id) ||
        !reader->ReadU8(&bitmask))
      return false;
    cast_message_.missing_frames_and_packets[frame_id].insert(packet_id);
    if (packet_id != kRtcpCastAllPacketsLost) {
      while (bitmask) {
        packet_id++;
        if (bitmask & 1)
          cast_message_.missing_frames_and_packets[frame_id].insert(packet_id);
        bitmask >>= 1;
      }
    }
  }

  has_cast_message_ = true;
  return true;
}

bool RtcpParser::ParseExtendedReport(base::BigEndianReader* reader,
                                     const RtcpCommonHeader& header) {
  uint32 remote_ssrc;
  if (!reader->ReadU32(&remote_ssrc))
    return false;

  // Is it for us?
  if (remote_ssrc != remote_ssrc_)
    return true;

  while (reader->remaining()) {
    uint8 block_type;
    uint16 block_length;
    if (!reader->ReadU8(&block_type) ||
        !reader->Skip(1) ||
        !reader->ReadU16(&block_length))
      return false;

    switch (block_type) {
      case 4:  // RRTR. RFC3611 Section 4.4.
        if (block_length != 2)
          return false;
        if (!ParseExtendedReportReceiverReferenceTimeReport(reader,
                                                            remote_ssrc))
          return false;
        break;

      default:
        // Skip unknown item.
        if (!reader->Skip(block_length * 4))
          return false;
    }
  }

  return true;
}

bool RtcpParser::ParseExtendedReportReceiverReferenceTimeReport(
    base::BigEndianReader* reader,
    uint32 remote_ssrc) {
  receiver_reference_time_report_.remote_ssrc = remote_ssrc;
  if(!reader->ReadU32(&receiver_reference_time_report_.ntp_seconds) ||
     !reader->ReadU32(&receiver_reference_time_report_.ntp_fraction))
    return false;

  has_receiver_reference_time_report_ = true;
  return true;
}

// Converts a log event type to an integer value.
// NOTE: We have only allocated 4 bits to represent the type of event over the
// wire. Therefore, this function can only return values from 0 to 15.
uint8 ConvertEventTypeToWireFormat(CastLoggingEvent event) {
  switch (event) {
    case FRAME_ACK_SENT:
      return 11;
    case FRAME_PLAYOUT:
      return 12;
    case FRAME_DECODED:
      return 13;
    case PACKET_RECEIVED:
      return 14;
    default:
      return 0;  // Not an interesting event.
  }
}

CastLoggingEvent TranslateToLogEventFromWireFormat(uint8 event) {
  // TODO(imcheng): Remove the old mappings once they are no longer used.
  switch (event) {
    case 1:  // AudioAckSent
    case 5:  // VideoAckSent
    case 11:  // Unified
      return FRAME_ACK_SENT;
    case 2:  // AudioPlayoutDelay
    case 7:  // VideoRenderDelay
    case 12:  // Unified
      return FRAME_PLAYOUT;
    case 3:  // AudioFrameDecoded
    case 6:  // VideoFrameDecoded
    case 13:  // Unified
      return FRAME_DECODED;
    case 4:  // AudioPacketReceived
    case 8:  // VideoPacketReceived
    case 14:  // Unified
      return PACKET_RECEIVED;
    case 9:  // DuplicateAudioPacketReceived
    case 10:  // DuplicateVideoPacketReceived
    default:
      // If the sender adds new log messages we will end up here until we add
      // the new messages in the receiver.
      VLOG(1) << "Unexpected log message received: " << static_cast<int>(event);
      return UNKNOWN;
  }
}

}  // namespace cast
}  // namespace media