pc/sctp_utils.cc

/*
 *  Copyright 2013 The WebRTC project authors. All Rights Reserved.
 *
 *  Use of this source code is governed by a BSD-style license
 *  that can be found in the LICENSE file in the root of the source
 *  tree. An additional intellectual property rights grant can be found
 *  in the file PATENTS.  All contributing project authors may
 *  be found in the AUTHORS file in the root of the source tree.
 */

#include "pc/sctp_utils.h"

#include <stddef.h>

#include <cstdint>

#include "absl/types/optional.h"
#include "api/priority.h"
#include "rtc_base/byte_buffer.h"
#include "rtc_base/copy_on_write_buffer.h"
#include "rtc_base/logging.h"

namespace webrtc {

// Format defined at
// http://tools.ietf.org/html/draft-ietf-rtcweb-data-protocol-01#section

static const uint8_t DATA_CHANNEL_OPEN_MESSAGE_TYPE = 0x03;
static const uint8_t DATA_CHANNEL_OPEN_ACK_MESSAGE_TYPE = 0x02;

enum DataChannelOpenMessageChannelType {
  DCOMCT_ORDERED_RELIABLE = 0x00,
  DCOMCT_ORDERED_PARTIAL_RTXS = 0x01,
  DCOMCT_ORDERED_PARTIAL_TIME = 0x02,
  DCOMCT_UNORDERED_RELIABLE = 0x80,
  DCOMCT_UNORDERED_PARTIAL_RTXS = 0x81,
  DCOMCT_UNORDERED_PARTIAL_TIME = 0x82,
};

// Values of priority in the DC open protocol message.
// These are compared against an integer, so are enum, not enum class.
enum DataChannelPriority {
  DCO_PRIORITY_VERY_LOW = 128,
  DCO_PRIORITY_LOW = 256,
  DCO_PRIORITY_MEDIUM = 512,
  DCO_PRIORITY_HIGH = 1024,
};

bool IsOpenMessage(const rtc::CopyOnWriteBuffer& payload) {
  // Format defined at
  // https://www.rfc-editor.org/rfc/rfc8832#section-5.1
  if (payload.size() < 1) {
    RTC_DLOG(LS_WARNING) << "Could not read OPEN message type.";
    return false;
  }

  uint8_t message_type = payload[0];
  return message_type == DATA_CHANNEL_OPEN_MESSAGE_TYPE;
}

bool ParseDataChannelOpenMessage(const rtc::CopyOnWriteBuffer& payload,
                                 std::string* label,
                                 DataChannelInit* config) {
  // Format defined at
  // http://tools.ietf.org/html/draft-jesup-rtcweb-data-protocol-04

  rtc::ByteBufferReader buffer(payload);
  uint8_t message_type;
  if (!buffer.ReadUInt8(&message_type)) {
    RTC_LOG(LS_WARNING) << "Could not read OPEN message type.";
    return false;
  }
  if (message_type != DATA_CHANNEL_OPEN_MESSAGE_TYPE) {
    RTC_LOG(LS_WARNING) << "Data Channel OPEN message of unexpected type: "
                        << message_type;
    return false;
  }

  uint8_t channel_type;
  if (!buffer.ReadUInt8(&channel_type)) {
    RTC_LOG(LS_WARNING) << "Could not read OPEN message channel type.";
    return false;
  }

  uint16_t priority;
  if (!buffer.ReadUInt16(&priority)) {
    RTC_LOG(LS_WARNING)
        << "Could not read OPEN message reliabilility prioirty.";
    return false;
  }
  // Parse priority as defined in
  // https://w3c.github.io/webrtc-priority/#rtcdatachannel-processing-steps
  if (priority <= DCO_PRIORITY_VERY_LOW) {
    config->priority = Priority::kVeryLow;
  } else if (priority <= DCO_PRIORITY_LOW) {
    config->priority = Priority::kLow;
  } else if (priority <= DCO_PRIORITY_MEDIUM) {
    config->priority = Priority::kMedium;
  } else {
    config->priority = Priority::kHigh;
  }

  uint32_t reliability_param;
  if (!buffer.ReadUInt32(&reliability_param)) {
    RTC_LOG(LS_WARNING) << "Could not read OPEN message reliabilility param.";
    return false;
  }
  uint16_t label_length;
  if (!buffer.ReadUInt16(&label_length)) {
    RTC_LOG(LS_WARNING) << "Could not read OPEN message label length.";
    return false;
  }
  uint16_t protocol_length;
  if (!buffer.ReadUInt16(&protocol_length)) {
    RTC_LOG(LS_WARNING) << "Could not read OPEN message protocol length.";
    return false;
  }
  if (!buffer.ReadString(label, (size_t)label_length)) {
    RTC_LOG(LS_WARNING) << "Could not read OPEN message label";
    return false;
  }
  if (!buffer.ReadString(&config->protocol, protocol_length)) {
    RTC_LOG(LS_WARNING) << "Could not read OPEN message protocol.";
    return false;
  }

  config->ordered = true;
  switch (channel_type) {
    case DCOMCT_UNORDERED_RELIABLE:
    case DCOMCT_UNORDERED_PARTIAL_RTXS:
    case DCOMCT_UNORDERED_PARTIAL_TIME:
      config->ordered = false;
  }

  config->maxRetransmits = absl::nullopt;
  config->maxRetransmitTime = absl::nullopt;
  switch (channel_type) {
    case DCOMCT_ORDERED_PARTIAL_RTXS:
    case DCOMCT_UNORDERED_PARTIAL_RTXS:
      config->maxRetransmits = reliability_param;
      break;
    case DCOMCT_ORDERED_PARTIAL_TIME:
    case DCOMCT_UNORDERED_PARTIAL_TIME:
      config->maxRetransmitTime = reliability_param;
      break;
  }
  return true;
}

bool ParseDataChannelOpenAckMessage(const rtc::CopyOnWriteBuffer& payload) {
  if (payload.size() < 1) {
    RTC_LOG(LS_WARNING) << "Could not read OPEN_ACK message type.";
    return false;
  }

  uint8_t message_type = payload[0];
  if (message_type != DATA_CHANNEL_OPEN_ACK_MESSAGE_TYPE) {
    RTC_LOG(LS_WARNING) << "Data Channel OPEN_ACK message of unexpected type: "
                        << message_type;
    return false;
  }
  return true;
}

bool WriteDataChannelOpenMessage(const std::string& label,
                                 const DataChannelInit& config,
                                 rtc::CopyOnWriteBuffer* payload) {
  return WriteDataChannelOpenMessage(label, config.protocol, config.priority,
                                     config.ordered, config.maxRetransmits,
                                     config.maxRetransmitTime, payload);
}

bool WriteDataChannelOpenMessage(const std::string& label,
                                 const std::string& protocol,
                                 absl::optional<Priority> opt_priority,
                                 bool ordered,
                                 absl::optional<int> max_retransmits,
                                 absl::optional<int> max_retransmit_time,
                                 rtc::CopyOnWriteBuffer* payload) {
  // Format defined at
  // http://tools.ietf.org/html/draft-ietf-rtcweb-data-protocol-09#section-5.1
  uint8_t channel_type = 0;
  uint32_t reliability_param = 0;
  uint16_t priority = 0;
  // Set priority according to
  // https://tools.ietf.org/html/draft-ietf-rtcweb-data-channel-12#section-6.4
  if (opt_priority) {
    switch (*opt_priority) {
      case Priority::kVeryLow:
        priority = DCO_PRIORITY_VERY_LOW;
        break;
      case Priority::kLow:
        priority = DCO_PRIORITY_LOW;
        break;
      case Priority::kMedium:
        priority = DCO_PRIORITY_MEDIUM;
        break;
      case Priority::kHigh:
        priority = DCO_PRIORITY_HIGH;
        break;
    }
  }
  if (ordered) {
    if (max_retransmits) {
      channel_type = DCOMCT_ORDERED_PARTIAL_RTXS;
      reliability_param = *max_retransmits;
    } else if (max_retransmit_time) {
      channel_type = DCOMCT_ORDERED_PARTIAL_TIME;
      reliability_param = *max_retransmit_time;
    } else {
      channel_type = DCOMCT_ORDERED_RELIABLE;
    }
  } else {
    if (max_retransmits) {
      channel_type = DCOMCT_UNORDERED_PARTIAL_RTXS;
      reliability_param = *max_retransmits;
    } else if (max_retransmit_time) {
      channel_type = DCOMCT_UNORDERED_PARTIAL_TIME;
      reliability_param = *max_retransmit_time;
    } else {
      channel_type = DCOMCT_UNORDERED_RELIABLE;
    }
  }

  rtc::ByteBufferWriter buffer(NULL, 20 + label.length() + protocol.length());
  // TODO(tommi): Add error handling and check resulting length.
  buffer.WriteUInt8(DATA_CHANNEL_OPEN_MESSAGE_TYPE);
  buffer.WriteUInt8(channel_type);
  buffer.WriteUInt16(priority);
  buffer.WriteUInt32(reliability_param);
  buffer.WriteUInt16(static_cast<uint16_t>(label.length()));
  buffer.WriteUInt16(static_cast<uint16_t>(protocol.length()));
  buffer.WriteString(label);
  buffer.WriteString(protocol);
  payload->SetData(buffer.Data(), buffer.Length());
  return true;
}

void WriteDataChannelOpenAckMessage(rtc::CopyOnWriteBuffer* payload) {
  uint8_t data = DATA_CHANNEL_OPEN_ACK_MESSAGE_TYPE;
  payload->SetData(&data, sizeof(data));
}

}  // namespace webrtc