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* Copyright 2004 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 <stddef.h>
#include <stdint.h>
#include <list>
#include <memory>
#include "rtc_base/synchronization/mutex.h"
#include "rtc_base/system/rtc_export.h"
namespace cricket {
// IPseudoTcpNotify
class PseudoTcp;
class IPseudoTcpNotify {
// Notification of tcp events
virtual void OnTcpOpen(PseudoTcp* tcp) = 0;
virtual void OnTcpReadable(PseudoTcp* tcp) = 0;
virtual void OnTcpWriteable(PseudoTcp* tcp) = 0;
virtual void OnTcpClosed(PseudoTcp* tcp, uint32_t error) = 0;
// Write the packet onto the network
enum WriteResult { WR_SUCCESS, WR_TOO_LARGE, WR_FAIL };
virtual WriteResult TcpWritePacket(PseudoTcp* tcp,
const char* buffer,
size_t len) = 0;
virtual ~IPseudoTcpNotify() {}
// PseudoTcp
class RTC_EXPORT PseudoTcp {
static uint32_t Now();
PseudoTcp(IPseudoTcpNotify* notify, uint32_t conv);
virtual ~PseudoTcp();
int Connect();
int Recv(char* buffer, size_t len);
int Send(const char* buffer, size_t len);
void Close(bool force);
int GetError();
enum TcpState {
TcpState State() const { return m_state; }
// Call this when the PMTU changes.
void NotifyMTU(uint16_t mtu);
// Call this based on timeout value returned from GetNextClock.
// It's ok to call this too frequently.
void NotifyClock(uint32_t now);
// Call this whenever a packet arrives.
// Returns true if the packet was processed successfully.
bool NotifyPacket(const char* buffer, size_t len);
// Call this to determine the next time NotifyClock should be called.
// Returns false if the socket is ready to be destroyed.
bool GetNextClock(uint32_t now, long& timeout);
// Call these to get/set option values to tailor this PseudoTcp
// instance's behaviour for the kind of data it will carry.
// If an unrecognized option is set or got, an assertion will fire.
// Setting options for OPT_RCVBUF or OPT_SNDBUF after Connect() is called
// will result in an assertion.
enum Option {
OPT_NODELAY, // Whether to enable Nagle's algorithm (0 == off)
OPT_ACKDELAY, // The Delayed ACK timeout (0 == off).
OPT_RCVBUF, // Set the receive buffer size, in bytes.
OPT_SNDBUF, // Set the send buffer size, in bytes.
void GetOption(Option opt, int* value);
void SetOption(Option opt, int value);
// Returns current congestion window in bytes.
uint32_t GetCongestionWindow() const;
// Returns amount of data in bytes that has been sent, but haven't
// been acknowledged.
uint32_t GetBytesInFlight() const;
// Returns number of bytes that were written in buffer and haven't
// been sent.
uint32_t GetBytesBufferedNotSent() const;
// Returns current round-trip time estimate in milliseconds.
uint32_t GetRoundTripTimeEstimateMs() const;
enum SendFlags { sfNone, sfDelayedAck, sfImmediateAck };
struct Segment {
uint32_t conv, seq, ack;
uint8_t flags;
uint16_t wnd;
const char* data;
uint32_t len;
uint32_t tsval, tsecr;
struct SSegment {
SSegment(uint32_t s, uint32_t l, bool c)
: seq(s), len(l), /*tstamp(0),*/ xmit(0), bCtrl(c) {}
uint32_t seq, len;
// uint32_t tstamp;
uint8_t xmit;
bool bCtrl;
typedef std::list<SSegment> SList;
struct RSegment {
uint32_t seq, len;
uint32_t queue(const char* data, uint32_t len, bool bCtrl);
// Creates a packet and submits it to the network. This method can either
// send payload or just an ACK packet.
// |seq| is the sequence number of this packet.
// |flags| is the flags for sending this packet.
// |offset| is the offset to read from |m_sbuf|.
// |len| is the number of bytes to read from |m_sbuf| as payload. If this
// value is 0 then this is an ACK packet, otherwise this packet has payload.
IPseudoTcpNotify::WriteResult packet(uint32_t seq,
uint8_t flags,
uint32_t offset,
uint32_t len);
bool parse(const uint8_t* buffer, uint32_t size);
void attemptSend(SendFlags sflags = sfNone);
void closedown(uint32_t err = 0);
bool clock_check(uint32_t now, long& nTimeout);
bool process(Segment& seg);
bool transmit(const SList::iterator& seg, uint32_t now);
void adjustMTU();
// This method is used in test only to query receive buffer state.
bool isReceiveBufferFull() const;
// This method is only used in tests, to disable window scaling
// support for testing backward compatibility.
void disableWindowScale();
// Queue the connect message with TCP options.
void queueConnectMessage();
// Parse TCP options in the header.
void parseOptions(const char* data, uint32_t len);
// Apply a TCP option that has been read from the header.
void applyOption(char kind, const char* data, uint32_t len);
// Apply window scale option.
void applyWindowScaleOption(uint8_t scale_factor);
// Resize the send buffer with |new_size| in bytes.
void resizeSendBuffer(uint32_t new_size);
// Resize the receive buffer with |new_size| in bytes. This call adjusts
// window scale factor |m_swnd_scale| accordingly.
void resizeReceiveBuffer(uint32_t new_size);
class LockedFifoBuffer final {
explicit LockedFifoBuffer(size_t size);
size_t GetBuffered() const;
bool SetCapacity(size_t size);
bool ReadOffset(void* buffer,
size_t bytes,
size_t offset,
size_t* bytes_read);
bool WriteOffset(const void* buffer,
size_t bytes,
size_t offset,
size_t* bytes_written);
bool Read(void* buffer, size_t bytes, size_t* bytes_read);
bool Write(const void* buffer, size_t bytes, size_t* bytes_written);
void ConsumeReadData(size_t size);
void ConsumeWriteBuffer(size_t size);
bool GetWriteRemaining(size_t* size) const;
bool ReadOffsetLocked(void* buffer,
size_t bytes,
size_t offset,
size_t* bytes_read)
bool WriteOffsetLocked(const void* buffer,
size_t bytes,
size_t offset,
size_t* bytes_written)
// the allocated buffer
std::unique_ptr<char[]> buffer_ RTC_GUARDED_BY(mutex_);
// size of the allocated buffer
size_t buffer_length_ RTC_GUARDED_BY(mutex_);
// amount of readable data in the buffer
size_t data_length_ RTC_GUARDED_BY(mutex_);
// offset to the readable data
size_t read_position_ RTC_GUARDED_BY(mutex_);
mutable webrtc::Mutex mutex_;
IPseudoTcpNotify* m_notify;
enum Shutdown { SD_NONE, SD_GRACEFUL, SD_FORCEFUL } m_shutdown;
int m_error;
// TCB data
TcpState m_state;
uint32_t m_conv;
bool m_bReadEnable, m_bWriteEnable, m_bOutgoing;
uint32_t m_lasttraffic;
// Incoming data
typedef std::list<RSegment> RList;
RList m_rlist;
uint32_t m_rbuf_len, m_rcv_nxt, m_rcv_wnd, m_lastrecv;
uint8_t m_rwnd_scale; // Window scale factor.
LockedFifoBuffer m_rbuf;
// Outgoing data
SList m_slist;
uint32_t m_sbuf_len, m_snd_nxt, m_snd_wnd, m_lastsend, m_snd_una;
uint8_t m_swnd_scale; // Window scale factor.
LockedFifoBuffer m_sbuf;
// Maximum segment size, estimated protocol level, largest segment sent
uint32_t m_mss, m_msslevel, m_largest, m_mtu_advise;
// Retransmit timer
uint32_t m_rto_base;
// Timestamp tracking
uint32_t m_ts_recent, m_ts_lastack;
// Round-trip calculation
uint32_t m_rx_rttvar, m_rx_srtt, m_rx_rto;
// Congestion avoidance, Fast retransmit/recovery, Delayed ACKs
uint32_t m_ssthresh, m_cwnd;
uint8_t m_dup_acks;
uint32_t m_recover;
uint32_t m_t_ack;
// Configuration options
bool m_use_nagling;
uint32_t m_ack_delay;
// This is used by unit tests to test backward compatibility of
// PseudoTcp implementations that don't support window scaling.
bool m_support_wnd_scale;
} // namespace cricket
#endif // P2P_BASE_PSEUDO_TCP_H_