admin/webrtc_m130
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity
webrtc_m130/p2p/base/pseudo_tcp.cc
Tomas Gunnarsson 8e4cda7de0 Give PseudoTcp its own FifoBuffer. 
The PseudoTcp test class is being used outside of WebRTC in ways
that WebRTC itself doesn't, which caused this revert:
https://webrtc-review.googlesource.com/c/src/+/186564

As it happens though, PseudoTcp doesn't actually use the
StreamInterface part of FifoBuffer, so this CL cuts the dependency
from PseudoTcp on FifoBuffer.

Moving forward, we could just remove this class from WebRTC.

Bug: webrtc:11988
Change-Id: Id34a2a6305e8fe37d705ba5e8876dd6398515125
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/186665
Commit-Queue: Tommi <tommi@webrtc.org>
Reviewed-by: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32309}
2020-10-05 12:35:13 +00:00

1433 lines
42 KiB
C++
Raw Blame History

/*
* 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 "p2p/base/pseudo_tcp.h"
#include <errno.h>
#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <cstdint>
#include <memory>
#include <set>
#include "rtc_base/byte_buffer.h"
#include "rtc_base/byte_order.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "rtc_base/numerics/safe_minmax.h"
#include "rtc_base/socket.h"
#include "rtc_base/time_utils.h"
// The following logging is for detailed (packet-level) analysis only.
#define _DBG_NONE 0
#define _DBG_NORMAL 1
#define _DBG_VERBOSE 2
#define _DEBUGMSG _DBG_NONE
namespace cricket {
//////////////////////////////////////////////////////////////////////
// Network Constants
//////////////////////////////////////////////////////////////////////
// Standard MTUs
const uint16_t PACKET_MAXIMUMS[] = {
65535, // Theoretical maximum, Hyperchannel
32000, // Nothing
17914, // 16Mb IBM Token Ring
8166, // IEEE 802.4
// 4464, // IEEE 802.5 (4Mb max)
4352, // FDDI
// 2048, // Wideband Network
2002, // IEEE 802.5 (4Mb recommended)
// 1536, // Expermental Ethernet Networks
// 1500, // Ethernet, Point-to-Point (default)
1492, // IEEE 802.3
1006, // SLIP, ARPANET
// 576, // X.25 Networks
// 544, // DEC IP Portal
// 512, // NETBIOS
508, // IEEE 802/Source-Rt Bridge, ARCNET
296, // Point-to-Point (low delay)
// 68, // Official minimum
0, // End of list marker
};
const uint32_t MAX_PACKET = 65535;
// Note: we removed lowest level because packet overhead was larger!
const uint32_t MIN_PACKET = 296;
const uint32_t IP_HEADER_SIZE = 20; // (+ up to 40 bytes of options?)
const uint32_t UDP_HEADER_SIZE = 8;
// TODO(?): Make JINGLE_HEADER_SIZE transparent to this code?
const uint32_t JINGLE_HEADER_SIZE = 64; // when relay framing is in use
// Default size for receive and send buffer.
const uint32_t DEFAULT_RCV_BUF_SIZE = 60 * 1024;
const uint32_t DEFAULT_SND_BUF_SIZE = 90 * 1024;
//////////////////////////////////////////////////////////////////////
// Global Constants and Functions
//////////////////////////////////////////////////////////////////////
//
// 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
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 0 | Conversation Number |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 4 | Sequence Number |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 8 | Acknowledgment Number |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | | |U|A|P|R|S|F| |
// 12 | Control | |R|C|S|S|Y|I| Window |
// | | |G|K|H|T|N|N| |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 16 | Timestamp sending |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 20 | Timestamp receiving |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 24 | data |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//
//////////////////////////////////////////////////////////////////////
#define PSEUDO_KEEPALIVE 0
const uint32_t HEADER_SIZE = 24;
const uint32_t PACKET_OVERHEAD =
HEADER_SIZE + UDP_HEADER_SIZE + IP_HEADER_SIZE + JINGLE_HEADER_SIZE;
const uint32_t MIN_RTO =
250; // 250 ms (RFC1122, Sec 4.2.3.1 "fractions of a second")
const uint32_t DEF_RTO = 3000; // 3 seconds (RFC1122, Sec 4.2.3.1)
const uint32_t MAX_RTO = 60000; // 60 seconds
const uint32_t DEF_ACK_DELAY = 100; // 100 milliseconds
const uint8_t FLAG_CTL = 0x02;
const uint8_t FLAG_RST = 0x04;
const uint8_t CTL_CONNECT = 0;
// TCP options.
const uint8_t TCP_OPT_EOL = 0; // End of list.
const uint8_t TCP_OPT_NOOP = 1; // No-op.
const uint8_t TCP_OPT_MSS = 2; // Maximum segment size.
const uint8_t TCP_OPT_WND_SCALE = 3; // Window scale factor.
const long DEFAULT_TIMEOUT =
4000; // If there are no pending clocks, wake up every 4 seconds
const long CLOSED_TIMEOUT =
60 * 1000; // If the connection is closed, once per minute
#if PSEUDO_KEEPALIVE
// !?! Rethink these times
const uint32_t IDLE_PING =
20 *
1000; // 20 seconds (note: WinXP SP2 firewall udp timeout is 90 seconds)
const uint32_t IDLE_TIMEOUT = 90 * 1000; // 90 seconds;
#endif // PSEUDO_KEEPALIVE
//////////////////////////////////////////////////////////////////////
// Helper Functions
//////////////////////////////////////////////////////////////////////
inline void long_to_bytes(uint32_t val, void* buf) {
*static_cast<uint32_t*>(buf) = rtc::HostToNetwork32(val);
}
inline void short_to_bytes(uint16_t val, void* buf) {
*static_cast<uint16_t*>(buf) = rtc::HostToNetwork16(val);
}
inline uint32_t bytes_to_long(const void* buf) {
return rtc::NetworkToHost32(*static_cast<const uint32_t*>(buf));
}
inline uint16_t bytes_to_short(const void* buf) {
return rtc::NetworkToHost16(*static_cast<const uint16_t*>(buf));
}
//////////////////////////////////////////////////////////////////////
// Debugging Statistics
//////////////////////////////////////////////////////////////////////
#if 0 // Not used yet
enum Stat {
S_SENT_PACKET, // All packet sends
S_RESENT_PACKET, // All packet sends that are retransmits
S_RECV_PACKET, // All packet receives
S_RECV_NEW, // All packet receives that are too new
S_RECV_OLD, // All packet receives that are too old
S_NUM_STATS
};
const char* const STAT_NAMES[S_NUM_STATS] = {
"snt",
"snt-r",
"rcv"
"rcv-n",
"rcv-o"
};
int g_stats[S_NUM_STATS];
inline void Incr(Stat s) { ++g_stats[s]; }
void ReportStats() {
char buffer[256];
size_t len = 0;
for (int i = 0; i < S_NUM_STATS; ++i) {
len += snprintf(buffer, arraysize(buffer), "%s%s:%d",
(i == 0) ? "" : ",", STAT_NAMES[i], g_stats[i]);
g_stats[i] = 0;
}
RTC_LOG(LS_INFO) << "Stats[" << buffer << "]";
}
#endif
//////////////////////////////////////////////////////////////////////
// PseudoTcp
//////////////////////////////////////////////////////////////////////
uint32_t PseudoTcp::Now() {
#if 0 // Use this to synchronize timers with logging timestamps (easier debug)
return static_cast<uint32_t>(rtc::TimeSince(StartTime()));
#else
return rtc::Time32();
#endif
}
PseudoTcp::PseudoTcp(IPseudoTcpNotify* notify, uint32_t conv)
: m_notify(notify),
m_shutdown(SD_NONE),
m_error(0),
m_rbuf_len(DEFAULT_RCV_BUF_SIZE),
m_rbuf(m_rbuf_len),
m_sbuf_len(DEFAULT_SND_BUF_SIZE),
m_sbuf(m_sbuf_len) {
// Sanity check on buffer sizes (needed for OnTcpWriteable notification logic)
RTC_DCHECK(m_rbuf_len + MIN_PACKET < m_sbuf_len);
uint32_t now = Now();
m_state = TCP_LISTEN;
m_conv = conv;
m_rcv_wnd = m_rbuf_len;
m_rwnd_scale = m_swnd_scale = 0;
m_snd_nxt = 0;
m_snd_wnd = 1;
m_snd_una = m_rcv_nxt = 0;
m_bReadEnable = true;
m_bWriteEnable = false;
m_t_ack = 0;
m_msslevel = 0;
m_largest = 0;
RTC_DCHECK(MIN_PACKET > PACKET_OVERHEAD);
m_mss = MIN_PACKET - PACKET_OVERHEAD;
m_mtu_advise = MAX_PACKET;
m_rto_base = 0;
m_cwnd = 2 * m_mss;
m_ssthresh = m_rbuf_len;
m_lastrecv = m_lastsend = m_lasttraffic = now;
m_bOutgoing = false;
m_dup_acks = 0;
m_recover = 0;
m_ts_recent = m_ts_lastack = 0;
m_rx_rto = DEF_RTO;
m_rx_srtt = m_rx_rttvar = 0;
m_use_nagling = true;
m_ack_delay = DEF_ACK_DELAY;
m_support_wnd_scale = true;
}
PseudoTcp::~PseudoTcp() {}
int PseudoTcp::Connect() {
if (m_state != TCP_LISTEN) {
m_error = EINVAL;
return -1;
}
m_state = TCP_SYN_SENT;
RTC_LOG(LS_INFO) << "State: TCP_SYN_SENT";
queueConnectMessage();
attemptSend();
return 0;
}
void PseudoTcp::NotifyMTU(uint16_t mtu) {
m_mtu_advise = mtu;
if (m_state == TCP_ESTABLISHED) {
adjustMTU();
}
}
void PseudoTcp::NotifyClock(uint32_t now) {
if (m_state == TCP_CLOSED)
return;
// Check if it's time to retransmit a segment
if (m_rto_base && (rtc::TimeDiff32(m_rto_base + m_rx_rto, now) <= 0)) {
if (m_slist.empty()) {
RTC_NOTREACHED();
} else {
// Note: (m_slist.front().xmit == 0)) {
// retransmit segments
#if _DEBUGMSG >= _DBG_NORMAL
RTC_LOG(LS_INFO) << "timeout retransmit (rto: " << m_rx_rto
<< ") (rto_base: " << m_rto_base << ") (now: " << now
<< ") (dup_acks: " << static_cast<unsigned>(m_dup_acks)
<< ")";
#endif // _DEBUGMSG
if (!transmit(m_slist.begin(), now)) {
closedown(ECONNABORTED);
return;
}
uint32_t nInFlight = m_snd_nxt - m_snd_una;
m_ssthresh = std::max(nInFlight / 2, 2 * m_mss);
// RTC_LOG(LS_INFO) << "m_ssthresh: " << m_ssthresh << " nInFlight: " <<
// nInFlight << " m_mss: " << m_mss;
m_cwnd = m_mss;
// Back off retransmit timer. Note: the limit is lower when connecting.
uint32_t rto_limit = (m_state < TCP_ESTABLISHED) ? DEF_RTO : MAX_RTO;
m_rx_rto = std::min(rto_limit, m_rx_rto * 2);
m_rto_base = now;
}
}
// Check if it's time to probe closed windows
if ((m_snd_wnd == 0) && (rtc::TimeDiff32(m_lastsend + m_rx_rto, now) <= 0)) {
if (rtc::TimeDiff32(now, m_lastrecv) >= 15000) {
closedown(ECONNABORTED);
return;
}
// probe the window
packet(m_snd_nxt - 1, 0, 0, 0);
m_lastsend = now;
// back off retransmit timer
m_rx_rto = std::min(MAX_RTO, m_rx_rto * 2);
}
// Check if it's time to send delayed acks
if (m_t_ack && (rtc::TimeDiff32(m_t_ack + m_ack_delay, now) <= 0)) {
packet(m_snd_nxt, 0, 0, 0);
}
#if PSEUDO_KEEPALIVE
// Check for idle timeout
if ((m_state == TCP_ESTABLISHED) &&
(TimeDiff32(m_lastrecv + IDLE_TIMEOUT, now) <= 0)) {
closedown(ECONNABORTED);
return;
}
// Check for ping timeout (to keep udp mapping open)
if ((m_state == TCP_ESTABLISHED) &&
(TimeDiff32(m_lasttraffic + (m_bOutgoing ? IDLE_PING * 3 / 2 : IDLE_PING),
now) <= 0)) {
packet(m_snd_nxt, 0, 0, 0);
}
#endif // PSEUDO_KEEPALIVE
}
bool PseudoTcp::NotifyPacket(const char* buffer, size_t len) {
if (len > MAX_PACKET) {
RTC_LOG_F(WARNING) << "packet too large";
return false;
}
return parse(reinterpret_cast<const uint8_t*>(buffer), uint32_t(len));
}
bool PseudoTcp::GetNextClock(uint32_t now, long& timeout) {
return clock_check(now, timeout);
}
void PseudoTcp::GetOption(Option opt, int* value) {
if (opt == OPT_NODELAY) {
*value = m_use_nagling ? 0 : 1;
} else if (opt == OPT_ACKDELAY) {
*value = m_ack_delay;
} else if (opt == OPT_SNDBUF) {
*value = m_sbuf_len;
} else if (opt == OPT_RCVBUF) {
*value = m_rbuf_len;
} else {
RTC_NOTREACHED();
}
}
void PseudoTcp::SetOption(Option opt, int value) {
if (opt == OPT_NODELAY) {
m_use_nagling = value == 0;
} else if (opt == OPT_ACKDELAY) {
m_ack_delay = value;
} else if (opt == OPT_SNDBUF) {
RTC_DCHECK(m_state == TCP_LISTEN);
resizeSendBuffer(value);
} else if (opt == OPT_RCVBUF) {
RTC_DCHECK(m_state == TCP_LISTEN);
resizeReceiveBuffer(value);
} else {
RTC_NOTREACHED();
}
}
uint32_t PseudoTcp::GetCongestionWindow() const {
return m_cwnd;
}
uint32_t PseudoTcp::GetBytesInFlight() const {
return m_snd_nxt - m_snd_una;
}
uint32_t PseudoTcp::GetBytesBufferedNotSent() const {
return static_cast<uint32_t>(m_snd_una + m_sbuf.GetBuffered() - m_snd_nxt);
}
uint32_t PseudoTcp::GetRoundTripTimeEstimateMs() const {
return m_rx_srtt;
}
//
// IPStream Implementation
//
int PseudoTcp::Recv(char* buffer, size_t len) {
if (m_state != TCP_ESTABLISHED) {
m_error = ENOTCONN;
return SOCKET_ERROR;
}
size_t read = 0;
if (!m_rbuf.Read(buffer, len, &read)) {
m_bReadEnable = true;
m_error = EWOULDBLOCK;
return SOCKET_ERROR;
}
size_t available_space = 0;
m_rbuf.GetWriteRemaining(&available_space);
if (uint32_t(available_space) - m_rcv_wnd >=
std::min<uint32_t>(m_rbuf_len / 2, m_mss)) {
// TODO(jbeda): !?! Not sure about this was closed business
bool bWasClosed = (m_rcv_wnd == 0);
m_rcv_wnd = static_cast<uint32_t>(available_space);
if (bWasClosed) {
attemptSend(sfImmediateAck);
}
}
return static_cast<int>(read);
}
int PseudoTcp::Send(const char* buffer, size_t len) {
if (m_state != TCP_ESTABLISHED) {
m_error = ENOTCONN;
return SOCKET_ERROR;
}
size_t available_space = 0;
m_sbuf.GetWriteRemaining(&available_space);
if (!available_space) {
m_bWriteEnable = true;
m_error = EWOULDBLOCK;
return SOCKET_ERROR;
}
int written = queue(buffer, uint32_t(len), false);
attemptSend();
return written;
}
void PseudoTcp::Close(bool force) {
RTC_LOG_F(LS_VERBOSE) << "(" << (force ? "true" : "false") << ")";
m_shutdown = force ? SD_FORCEFUL : SD_GRACEFUL;
}
int PseudoTcp::GetError() {
return m_error;
}
//
// Internal Implementation
//
uint32_t PseudoTcp::queue(const char* data, uint32_t len, bool bCtrl) {
size_t available_space = 0;
m_sbuf.GetWriteRemaining(&available_space);
if (len > static_cast<uint32_t>(available_space)) {
RTC_DCHECK(!bCtrl);
len = static_cast<uint32_t>(available_space);
}
// We can concatenate data if the last segment is the same type
// (control v. regular data), and has not been transmitted yet
if (!m_slist.empty() && (m_slist.back().bCtrl == bCtrl) &&
(m_slist.back().xmit == 0)) {
m_slist.back().len += len;
} else {
SSegment sseg(static_cast<uint32_t>(m_snd_una + m_sbuf.GetBuffered()), len,
bCtrl);
m_slist.push_back(sseg);
}
size_t written = 0;
m_sbuf.Write(data, len, &written);
return static_cast<uint32_t>(written);
}
IPseudoTcpNotify::WriteResult PseudoTcp::packet(uint32_t seq,
uint8_t flags,
uint32_t offset,
uint32_t len) {
RTC_DCHECK(HEADER_SIZE + len <= MAX_PACKET);
uint32_t now = Now();
std::unique_ptr<uint8_t[]> buffer(new uint8_t[MAX_PACKET]);
long_to_bytes(m_conv, buffer.get());
long_to_bytes(seq, buffer.get() + 4);
long_to_bytes(m_rcv_nxt, buffer.get() + 8);
buffer[12] = 0;
buffer[13] = flags;
short_to_bytes(static_cast<uint16_t>(m_rcv_wnd >> m_rwnd_scale),
buffer.get() + 14);
// Timestamp computations
long_to_bytes(now, buffer.get() + 16);
long_to_bytes(m_ts_recent, buffer.get() + 20);
m_ts_lastack = m_rcv_nxt;
if (len) {
size_t bytes_read = 0;
bool result =
m_sbuf.ReadOffset(buffer.get() + HEADER_SIZE, len, offset, &bytes_read);
RTC_DCHECK(result);
RTC_DCHECK(static_cast<uint32_t>(bytes_read) == len);
}
#if _DEBUGMSG >= _DBG_VERBOSE
RTC_LOG(LS_INFO) << "<-- <CONV=" << m_conv
<< "><FLG=" << static_cast<unsigned>(flags)
<< "><SEQ=" << seq << ":" << seq + len
<< "><ACK=" << m_rcv_nxt << "><WND=" << m_rcv_wnd
<< "><TS=" << (now % 10000)
<< "><TSR=" << (m_ts_recent % 10000) << "><LEN=" << len
<< ">";
#endif // _DEBUGMSG
IPseudoTcpNotify::WriteResult wres = m_notify->TcpWritePacket(
this, reinterpret_cast<char*>(buffer.get()), len + HEADER_SIZE);
// Note: When len is 0, this is an ACK packet. We don't read the return value
// for those, and thus we won't retry. So go ahead and treat the packet as a
// success (basically simulate as if it were dropped), which will prevent our
// timers from being messed up.
if ((wres != IPseudoTcpNotify::WR_SUCCESS) && (0 != len))
return wres;
m_t_ack = 0;
if (len > 0) {
m_lastsend = now;
}
m_lasttraffic = now;
m_bOutgoing = true;
return IPseudoTcpNotify::WR_SUCCESS;
}
bool PseudoTcp::parse(const uint8_t* buffer, uint32_t size) {
if (size < HEADER_SIZE)
return false;
Segment seg;
seg.conv = bytes_to_long(buffer);
seg.seq = bytes_to_long(buffer + 4);
seg.ack = bytes_to_long(buffer + 8);
seg.flags = buffer[13];
seg.wnd = bytes_to_short(buffer + 14);
seg.tsval = bytes_to_long(buffer + 16);
seg.tsecr = bytes_to_long(buffer + 20);
seg.data = reinterpret_cast<const char*>(buffer) + HEADER_SIZE;
seg.len = size - HEADER_SIZE;
#if _DEBUGMSG >= _DBG_VERBOSE
RTC_LOG(LS_INFO) << "--> <CONV=" << seg.conv
<< "><FLG=" << static_cast<unsigned>(seg.flags)
<< "><SEQ=" << seg.seq << ":" << seg.seq + seg.len
<< "><ACK=" << seg.ack << "><WND=" << seg.wnd
<< "><TS=" << (seg.tsval % 10000)
<< "><TSR=" << (seg.tsecr % 10000) << "><LEN=" << seg.len
<< ">";
#endif // _DEBUGMSG
return process(seg);
}
bool PseudoTcp::clock_check(uint32_t now, long& nTimeout) {
if (m_shutdown == SD_FORCEFUL)
return false;
if ((m_shutdown == SD_GRACEFUL) &&
((m_state != TCP_ESTABLISHED) ||
((m_sbuf.GetBuffered() == 0) && (m_t_ack == 0)))) {
return false;
}
if (m_state == TCP_CLOSED) {
nTimeout = CLOSED_TIMEOUT;
return true;
}
nTimeout = DEFAULT_TIMEOUT;
if (m_t_ack) {
nTimeout = std::min<int32_t>(nTimeout,
rtc::TimeDiff32(m_t_ack + m_ack_delay, now));
}
if (m_rto_base) {
nTimeout = std::min<int32_t>(nTimeout,
rtc::TimeDiff32(m_rto_base + m_rx_rto, now));
}
if (m_snd_wnd == 0) {
nTimeout = std::min<int32_t>(nTimeout,
rtc::TimeDiff32(m_lastsend + m_rx_rto, now));
}
#if PSEUDO_KEEPALIVE
if (m_state == TCP_ESTABLISHED) {
nTimeout = std::min<int32_t>(
nTimeout,
rtc::TimeDiff32(
m_lasttraffic + (m_bOutgoing ? IDLE_PING * 3 / 2 : IDLE_PING),
now));
}
#endif // PSEUDO_KEEPALIVE
return true;
}
bool PseudoTcp::process(Segment& seg) {
// If this is the wrong conversation, send a reset!?! (with the correct
// conversation?)
if (seg.conv != m_conv) {
// if ((seg.flags & FLAG_RST) == 0) {
// packet(tcb, seg.ack, 0, FLAG_RST, 0, 0);
//}
RTC_LOG_F(LS_ERROR) << "wrong conversation";
return false;
}
uint32_t now = Now();
m_lasttraffic = m_lastrecv = now;
m_bOutgoing = false;
if (m_state == TCP_CLOSED) {
// !?! send reset?
RTC_LOG_F(LS_ERROR) << "closed";
return false;
}
// Check if this is a reset segment
if (seg.flags & FLAG_RST) {
closedown(ECONNRESET);
return false;
}
// Check for control data
bool bConnect = false;
if (seg.flags & FLAG_CTL) {
if (seg.len == 0) {
RTC_LOG_F(LS_ERROR) << "Missing control code";
return false;
} else if (seg.data[0] == CTL_CONNECT) {
bConnect = true;
// TCP options are in the remainder of the payload after CTL_CONNECT.
parseOptions(&seg.data[1], seg.len - 1);
if (m_state == TCP_LISTEN) {
m_state = TCP_SYN_RECEIVED;
RTC_LOG(LS_INFO) << "State: TCP_SYN_RECEIVED";
// m_notify->associate(addr);
queueConnectMessage();
} else if (m_state == TCP_SYN_SENT) {
m_state = TCP_ESTABLISHED;
RTC_LOG(LS_INFO) << "State: TCP_ESTABLISHED";
adjustMTU();
if (m_notify) {
m_notify->OnTcpOpen(this);
}
// notify(evOpen);
}
} else {
RTC_LOG_F(LS_WARNING) << "Unknown control code: " << seg.data[0];
return false;
}
}
// Update timestamp
if ((seg.seq <= m_ts_lastack) && (m_ts_lastack < seg.seq + seg.len)) {
m_ts_recent = seg.tsval;
}
// Check if this is a valuable ack
if ((seg.ack > m_snd_una) && (seg.ack <= m_snd_nxt)) {
// Calculate round-trip time
if (seg.tsecr) {
int32_t rtt = rtc::TimeDiff32(now, seg.tsecr);
if (rtt >= 0) {
if (m_rx_srtt == 0) {
m_rx_srtt = rtt;
m_rx_rttvar = rtt / 2;
} else {
uint32_t unsigned_rtt = static_cast<uint32_t>(rtt);
uint32_t abs_err = unsigned_rtt > m_rx_srtt
? unsigned_rtt - m_rx_srtt
: m_rx_srtt - unsigned_rtt;
m_rx_rttvar = (3 * m_rx_rttvar + abs_err) / 4;
m_rx_srtt = (7 * m_rx_srtt + rtt) / 8;
}
m_rx_rto = rtc::SafeClamp(m_rx_srtt + rtc::SafeMax(1, 4 * m_rx_rttvar),
MIN_RTO, MAX_RTO);
#if _DEBUGMSG >= _DBG_VERBOSE
RTC_LOG(LS_INFO) << "rtt: " << rtt << " srtt: " << m_rx_srtt
<< " rto: " << m_rx_rto;
#endif // _DEBUGMSG
} else {
RTC_LOG(LS_WARNING) << "rtt < 0";
}
}
m_snd_wnd = static_cast<uint32_t>(seg.wnd) << m_swnd_scale;
uint32_t nAcked = seg.ack - m_snd_una;
m_snd_una = seg.ack;
m_rto_base = (m_snd_una == m_snd_nxt) ? 0 : now;
m_sbuf.ConsumeReadData(nAcked);
for (uint32_t nFree = nAcked; nFree > 0;) {
RTC_DCHECK(!m_slist.empty());
if (nFree < m_slist.front().len) {
m_slist.front().len -= nFree;
nFree = 0;
} else {
if (m_slist.front().len > m_largest) {
m_largest = m_slist.front().len;
}
nFree -= m_slist.front().len;
m_slist.pop_front();
}
}
if (m_dup_acks >= 3) {
if (m_snd_una >= m_recover) { // NewReno
uint32_t nInFlight = m_snd_nxt - m_snd_una;
m_cwnd = std::min(m_ssthresh, nInFlight + m_mss); // (Fast Retransmit)
#if _DEBUGMSG >= _DBG_NORMAL
RTC_LOG(LS_INFO) << "exit recovery";
#endif // _DEBUGMSG
m_dup_acks = 0;
} else {
#if _DEBUGMSG >= _DBG_NORMAL
RTC_LOG(LS_INFO) << "recovery retransmit";
#endif // _DEBUGMSG
if (!transmit(m_slist.begin(), now)) {
closedown(ECONNABORTED);
return false;
}
m_cwnd += m_mss - std::min(nAcked, m_cwnd);
}
} else {
m_dup_acks = 0;
// Slow start, congestion avoidance
if (m_cwnd < m_ssthresh) {
m_cwnd += m_mss;
} else {
m_cwnd += std::max<uint32_t>(1, m_mss * m_mss / m_cwnd);
}
}
} else if (seg.ack == m_snd_una) {
// !?! Note, tcp says don't do this... but otherwise how does a closed
// window become open?
m_snd_wnd = static_cast<uint32_t>(seg.wnd) << m_swnd_scale;
// Check duplicate acks
if (seg.len > 0) {
// it's a dup ack, but with a data payload, so don't modify m_dup_acks
} else if (m_snd_una != m_snd_nxt) {
m_dup_acks += 1;
if (m_dup_acks == 3) { // (Fast Retransmit)
#if _DEBUGMSG >= _DBG_NORMAL
RTC_LOG(LS_INFO) << "enter recovery";
RTC_LOG(LS_INFO) << "recovery retransmit";
#endif // _DEBUGMSG
if (!transmit(m_slist.begin(), now)) {
closedown(ECONNABORTED);
return false;
}
m_recover = m_snd_nxt;
uint32_t nInFlight = m_snd_nxt - m_snd_una;
m_ssthresh = std::max(nInFlight / 2, 2 * m_mss);
// RTC_LOG(LS_INFO) << "m_ssthresh: " << m_ssthresh << " nInFlight: "
// << nInFlight << " m_mss: " << m_mss;
m_cwnd = m_ssthresh + 3 * m_mss;
} else if (m_dup_acks > 3) {
m_cwnd += m_mss;
}
} else {
m_dup_acks = 0;
}
}
// !?! A bit hacky
if ((m_state == TCP_SYN_RECEIVED) && !bConnect) {
m_state = TCP_ESTABLISHED;
RTC_LOG(LS_INFO) << "State: TCP_ESTABLISHED";
adjustMTU();
if (m_notify) {
m_notify->OnTcpOpen(this);
}
// notify(evOpen);
}
// If we make room in the send queue, notify the user
// The goal it to make sure we always have at least enough data to fill the
// window. We'd like to notify the app when we are halfway to that point.
const uint32_t kIdealRefillSize = (m_sbuf_len + m_rbuf_len) / 2;
if (m_bWriteEnable &&
static_cast<uint32_t>(m_sbuf.GetBuffered()) < kIdealRefillSize) {
m_bWriteEnable = false;
if (m_notify) {
m_notify->OnTcpWriteable(this);
}
// notify(evWrite);
}
// Conditions were acks must be sent:
// 1) Segment is too old (they missed an ACK) (immediately)
// 2) Segment is too new (we missed a segment) (immediately)
// 3) Segment has data (so we need to ACK!) (delayed)
// ... so the only time we don't need to ACK, is an empty segment that points
// to rcv_nxt!
SendFlags sflags = sfNone;
if (seg.seq != m_rcv_nxt) {
sflags = sfImmediateAck; // (Fast Recovery)
} else if (seg.len != 0) {
if (m_ack_delay == 0) {
sflags = sfImmediateAck;
} else {
sflags = sfDelayedAck;
}
}
#if _DEBUGMSG >= _DBG_NORMAL
if (sflags == sfImmediateAck) {
if (seg.seq > m_rcv_nxt) {
RTC_LOG_F(LS_INFO) << "too new";
} else if (seg.seq + seg.len <= m_rcv_nxt) {
RTC_LOG_F(LS_INFO) << "too old";
}
}
#endif // _DEBUGMSG
// Adjust the incoming segment to fit our receive buffer
if (seg.seq < m_rcv_nxt) {
uint32_t nAdjust = m_rcv_nxt - seg.seq;
if (nAdjust < seg.len) {
seg.seq += nAdjust;
seg.data += nAdjust;
seg.len -= nAdjust;
} else {
seg.len = 0;
}
}
size_t available_space = 0;
m_rbuf.GetWriteRemaining(&available_space);
if ((seg.seq + seg.len - m_rcv_nxt) >
static_cast<uint32_t>(available_space)) {
uint32_t nAdjust =
seg.seq + seg.len - m_rcv_nxt - static_cast<uint32_t>(available_space);
if (nAdjust < seg.len) {
seg.len -= nAdjust;
} else {
seg.len = 0;
}
}
bool bIgnoreData = (seg.flags & FLAG_CTL) || (m_shutdown != SD_NONE);
bool bNewData = false;
if (seg.len > 0) {
bool bRecover = false;
if (bIgnoreData) {
if (seg.seq == m_rcv_nxt) {
m_rcv_nxt += seg.len;
// If we received a data segment out of order relative to a control
// segment, then we wrote it into the receive buffer at an offset (see
// "WriteOffset") below. So we need to advance the position in the
// buffer to avoid corrupting data. See bugs.webrtc.org/9208
//
// We advance the position in the buffer by N bytes by acting like we
// wrote N bytes and then immediately read them. We can only do this if
// there's not already data ready to read, but this should always be
// true in the problematic scenario, since control frames are always
// sent first in the stream.
if (m_rbuf.GetBuffered() == 0) {
m_rbuf.ConsumeWriteBuffer(seg.len);
m_rbuf.ConsumeReadData(seg.len);
// After shifting the position in the buffer, we may have
// out-of-order packets ready to be recovered.
bRecover = true;
}
}
} else {
uint32_t nOffset = seg.seq - m_rcv_nxt;
if (!m_rbuf.WriteOffset(seg.data, seg.len, nOffset, NULL)) {
// Ignore incoming packets outside of the receive window.
return false;
}
if (seg.seq == m_rcv_nxt) {
m_rbuf.ConsumeWriteBuffer(seg.len);
m_rcv_nxt += seg.len;
m_rcv_wnd -= seg.len;
bNewData = true;
// May be able to recover packets previously received out-of-order
// now.
bRecover = true;
} else {
#if _DEBUGMSG >= _DBG_NORMAL
RTC_LOG(LS_INFO) << "Saving " << seg.len << " bytes (" << seg.seq
<< " -> " << seg.seq + seg.len << ")";
#endif // _DEBUGMSG
RSegment rseg;
rseg.seq = seg.seq;
rseg.len = seg.len;
RList::iterator it = m_rlist.begin();
while ((it != m_rlist.end()) && (it->seq < rseg.seq)) {
++it;
}
m_rlist.insert(it, rseg);
}
}
if (bRecover) {
RList::iterator it = m_rlist.begin();
while ((it != m_rlist.end()) && (it->seq <= m_rcv_nxt)) {
if (it->seq + it->len > m_rcv_nxt) {
sflags = sfImmediateAck; // (Fast Recovery)
uint32_t nAdjust = (it->seq + it->len) - m_rcv_nxt;
#if _DEBUGMSG >= _DBG_NORMAL
RTC_LOG(LS_INFO) << "Recovered " << nAdjust << " bytes (" << m_rcv_nxt
<< " -> " << m_rcv_nxt + nAdjust << ")";
#endif // _DEBUGMSG
m_rbuf.ConsumeWriteBuffer(nAdjust);
m_rcv_nxt += nAdjust;
m_rcv_wnd -= nAdjust;
bNewData = true;
}
it = m_rlist.erase(it);
}
}
}
attemptSend(sflags);
// If we have new data, notify the user
if (bNewData && m_bReadEnable) {
m_bReadEnable = false;
if (m_notify) {
m_notify->OnTcpReadable(this);
}
// notify(evRead);
}
return true;
}
bool PseudoTcp::transmit(const SList::iterator& seg, uint32_t now) {
if (seg->xmit >= ((m_state == TCP_ESTABLISHED) ? 15 : 30)) {
RTC_LOG_F(LS_VERBOSE) << "too many retransmits";
return false;
}
uint32_t nTransmit = std::min(seg->len, m_mss);
while (true) {
uint32_t seq = seg->seq;
uint8_t flags = (seg->bCtrl ? FLAG_CTL : 0);
IPseudoTcpNotify::WriteResult wres =
packet(seq, flags, seg->seq - m_snd_una, nTransmit);
if (wres == IPseudoTcpNotify::WR_SUCCESS)
break;
if (wres == IPseudoTcpNotify::WR_FAIL) {
RTC_LOG_F(LS_VERBOSE) << "packet failed";
return false;
}
RTC_DCHECK(wres == IPseudoTcpNotify::WR_TOO_LARGE);
while (true) {
if (PACKET_MAXIMUMS[m_msslevel + 1] == 0) {
RTC_LOG_F(LS_VERBOSE) << "MTU too small";
return false;
}
// !?! We need to break up all outstanding and pending packets and then
// retransmit!?!
m_mss = PACKET_MAXIMUMS[++m_msslevel] - PACKET_OVERHEAD;
m_cwnd = 2 * m_mss; // I added this... haven't researched actual formula
if (m_mss < nTransmit) {
nTransmit = m_mss;
break;
}
}
#if _DEBUGMSG >= _DBG_NORMAL
RTC_LOG(LS_INFO) << "Adjusting mss to " << m_mss << " bytes";
#endif // _DEBUGMSG
}
if (nTransmit < seg->len) {
RTC_LOG_F(LS_VERBOSE) << "mss reduced to " << m_mss;
SSegment subseg(seg->seq + nTransmit, seg->len - nTransmit, seg->bCtrl);
// subseg.tstamp = seg->tstamp;
subseg.xmit = seg->xmit;
seg->len = nTransmit;
SList::iterator next = seg;
m_slist.insert(++next, subseg);
}
if (seg->xmit == 0) {
m_snd_nxt += seg->len;
}
seg->xmit += 1;
// seg->tstamp = now;
if (m_rto_base == 0) {
m_rto_base = now;
}
return true;
}
void PseudoTcp::attemptSend(SendFlags sflags) {
uint32_t now = Now();
if (rtc::TimeDiff32(now, m_lastsend) > static_cast<long>(m_rx_rto)) {
m_cwnd = m_mss;
}
#if _DEBUGMSG
bool bFirst = true;
#endif // _DEBUGMSG
while (true) {
uint32_t cwnd = m_cwnd;
if ((m_dup_acks == 1) || (m_dup_acks == 2)) { // Limited Transmit
cwnd += m_dup_acks * m_mss;
}
uint32_t nWindow = std::min(m_snd_wnd, cwnd);
uint32_t nInFlight = m_snd_nxt - m_snd_una;
uint32_t nUseable = (nInFlight < nWindow) ? (nWindow - nInFlight) : 0;
size_t snd_buffered = m_sbuf.GetBuffered();
uint32_t nAvailable =
std::min(static_cast<uint32_t>(snd_buffered) - nInFlight, m_mss);
if (nAvailable > nUseable) {
if (nUseable * 4 < nWindow) {
// RFC 813 - avoid SWS
nAvailable = 0;
} else {
nAvailable = nUseable;
}
}
#if _DEBUGMSG >= _DBG_VERBOSE
if (bFirst) {
size_t available_space = 0;
m_sbuf.GetWriteRemaining(&available_space);
bFirst = false;
RTC_LOG(LS_INFO) << "[cwnd: " << m_cwnd << " nWindow: " << nWindow
<< " nInFlight: " << nInFlight
<< " nAvailable: " << nAvailable
<< " nQueued: " << snd_buffered
<< " nEmpty: " << available_space
<< " ssthresh: " << m_ssthresh << "]";
}
#endif // _DEBUGMSG
if (nAvailable == 0) {
if (sflags == sfNone)
return;
// If this is an immediate ack, or the second delayed ack
if ((sflags == sfImmediateAck) || m_t_ack) {
packet(m_snd_nxt, 0, 0, 0);
} else {
m_t_ack = Now();
}
return;
}
// Nagle's algorithm.
// If there is data already in-flight, and we haven't a full segment of
// data ready to send then hold off until we get more to send, or the
// in-flight data is acknowledged.
if (m_use_nagling && (m_snd_nxt > m_snd_una) && (nAvailable < m_mss)) {
return;
}
// Find the next segment to transmit
SList::iterator it = m_slist.begin();
while (it->xmit > 0) {
++it;
RTC_DCHECK(it != m_slist.end());
}
SList::iterator seg = it;
// If the segment is too large, break it into two
if (seg->len > nAvailable) {
SSegment subseg(seg->seq + nAvailable, seg->len - nAvailable, seg->bCtrl);
seg->len = nAvailable;
m_slist.insert(++it, subseg);
}
if (!transmit(seg, now)) {
RTC_LOG_F(LS_VERBOSE) << "transmit failed";
// TODO(?): consider closing socket
return;
}
sflags = sfNone;
}
}
void PseudoTcp::closedown(uint32_t err) {
RTC_LOG(LS_INFO) << "State: TCP_CLOSED";
m_state = TCP_CLOSED;
if (m_notify) {
m_notify->OnTcpClosed(this, err);
}
// notify(evClose, err);
}
void PseudoTcp::adjustMTU() {
// Determine our current mss level, so that we can adjust appropriately later
for (m_msslevel = 0; PACKET_MAXIMUMS[m_msslevel + 1] > 0; ++m_msslevel) {
if (static_cast<uint16_t>(PACKET_MAXIMUMS[m_msslevel]) <= m_mtu_advise) {
break;
}
}
m_mss = m_mtu_advise - PACKET_OVERHEAD;
// !?! Should we reset m_largest here?
#if _DEBUGMSG >= _DBG_NORMAL
RTC_LOG(LS_INFO) << "Adjusting mss to " << m_mss << " bytes";
#endif // _DEBUGMSG
// Enforce minimums on ssthresh and cwnd
m_ssthresh = std::max(m_ssthresh, 2 * m_mss);
m_cwnd = std::max(m_cwnd, m_mss);
}
bool PseudoTcp::isReceiveBufferFull() const {
size_t available_space = 0;
m_rbuf.GetWriteRemaining(&available_space);
return !available_space;
}
void PseudoTcp::disableWindowScale() {
m_support_wnd_scale = false;
}
void PseudoTcp::queueConnectMessage() {
rtc::ByteBufferWriter buf;
buf.WriteUInt8(CTL_CONNECT);
if (m_support_wnd_scale) {
buf.WriteUInt8(TCP_OPT_WND_SCALE);
buf.WriteUInt8(1);
buf.WriteUInt8(m_rwnd_scale);
}
m_snd_wnd = static_cast<uint32_t>(buf.Length());
queue(buf.Data(), static_cast<uint32_t>(buf.Length()), true);
}
void PseudoTcp::parseOptions(const char* data, uint32_t len) {
std::set<uint8_t> options_specified;
// See http://www.freesoft.org/CIE/Course/Section4/8.htm for
// parsing the options list.
rtc::ByteBufferReader buf(data, len);
while (buf.Length()) {
uint8_t kind = TCP_OPT_EOL;
buf.ReadUInt8(&kind);
if (kind == TCP_OPT_EOL) {
// End of option list.
break;
} else if (kind == TCP_OPT_NOOP) {
// No op.
continue;
}
// Length of this option.
RTC_DCHECK(len != 0);
uint8_t opt_len = 0;
buf.ReadUInt8(&opt_len);
// Content of this option.
if (opt_len <= buf.Length()) {
applyOption(kind, buf.Data(), opt_len);
buf.Consume(opt_len);
} else {
RTC_LOG(LS_ERROR) << "Invalid option length received.";
return;
}
options_specified.insert(kind);
}
if (options_specified.find(TCP_OPT_WND_SCALE) == options_specified.end()) {
RTC_LOG(LS_WARNING) << "Peer doesn't support window scaling";
if (m_rwnd_scale > 0) {
// Peer doesn't support TCP options and window scaling.
// Revert receive buffer size to default value.
resizeReceiveBuffer(DEFAULT_RCV_BUF_SIZE);
m_swnd_scale = 0;
}
}
}
void PseudoTcp::applyOption(char kind, const char* data, uint32_t len) {
if (kind == TCP_OPT_MSS) {
RTC_LOG(LS_WARNING) << "Peer specified MSS option which is not supported.";
// TODO(?): Implement.
} else if (kind == TCP_OPT_WND_SCALE) {
// Window scale factor.
// http://www.ietf.org/rfc/rfc1323.txt
if (len != 1) {
RTC_LOG_F(WARNING) << "Invalid window scale option received.";
return;
}
applyWindowScaleOption(data[0]);
}
}
void PseudoTcp::applyWindowScaleOption(uint8_t scale_factor) {
m_swnd_scale = scale_factor;
}
void PseudoTcp::resizeSendBuffer(uint32_t new_size) {
m_sbuf_len = new_size;
m_sbuf.SetCapacity(new_size);
}
void PseudoTcp::resizeReceiveBuffer(uint32_t new_size) {
uint8_t scale_factor = 0;
// Determine the scale factor such that the scaled window size can fit
// in a 16-bit unsigned integer.
while (new_size > 0xFFFF) {
++scale_factor;
new_size >>= 1;
}
// Determine the proper size of the buffer.
new_size <<= scale_factor;
bool result = m_rbuf.SetCapacity(new_size);
// Make sure the new buffer is large enough to contain data in the old
// buffer. This should always be true because this method is called either
// before connection is established or when peers are exchanging connect
// messages.
RTC_DCHECK(result);
m_rbuf_len = new_size;
m_rwnd_scale = scale_factor;
m_ssthresh = new_size;
size_t available_space = 0;
m_rbuf.GetWriteRemaining(&available_space);
m_rcv_wnd = static_cast<uint32_t>(available_space);
}
PseudoTcp::LockedFifoBuffer::LockedFifoBuffer(size_t size)
: buffer_(new char[size]),
buffer_length_(size),
data_length_(0),
read_position_(0) {}
PseudoTcp::LockedFifoBuffer::~LockedFifoBuffer() {}
size_t PseudoTcp::LockedFifoBuffer::GetBuffered() const {
webrtc::MutexLock lock(&mutex_);
return data_length_;
}
bool PseudoTcp::LockedFifoBuffer::SetCapacity(size_t size) {
webrtc::MutexLock lock(&mutex_);
if (data_length_ > size)
return false;
if (size != buffer_length_) {
char* buffer = new char[size];
const size_t copy = data_length_;
const size_t tail_copy = std::min(copy, buffer_length_ - read_position_);
memcpy(buffer, &buffer_[read_position_], tail_copy);
memcpy(buffer + tail_copy, &buffer_[0], copy - tail_copy);
buffer_.reset(buffer);
read_position_ = 0;
buffer_length_ = size;
}
return true;
}
bool PseudoTcp::LockedFifoBuffer::ReadOffset(void* buffer,
size_t bytes,
size_t offset,
size_t* bytes_read) {
webrtc::MutexLock lock(&mutex_);
return ReadOffsetLocked(buffer, bytes, offset, bytes_read);
}
bool PseudoTcp::LockedFifoBuffer::WriteOffset(const void* buffer,
size_t bytes,
size_t offset,
size_t* bytes_written) {
webrtc::MutexLock lock(&mutex_);
return WriteOffsetLocked(buffer, bytes, offset, bytes_written);
}
bool PseudoTcp::LockedFifoBuffer::Read(void* buffer,
size_t bytes,
size_t* bytes_read) {
webrtc::MutexLock lock(&mutex_);
size_t copy = 0;
if (!ReadOffsetLocked(buffer, bytes, 0, &copy))
return false;
// If read was successful then adjust the read position and number of
// bytes buffered.
read_position_ = (read_position_ + copy) % buffer_length_;
data_length_ -= copy;
if (bytes_read)
*bytes_read = copy;
return true;
}
bool PseudoTcp::LockedFifoBuffer::Write(const void* buffer,
size_t bytes,
size_t* bytes_written) {
webrtc::MutexLock lock(&mutex_);
size_t copy = 0;
if (!WriteOffsetLocked(buffer, bytes, 0, &copy))
return false;
// If write was successful then adjust the number of readable bytes.
data_length_ += copy;
if (bytes_written) {
*bytes_written = copy;
}
return true;
}
void PseudoTcp::LockedFifoBuffer::ConsumeReadData(size_t size) {
webrtc::MutexLock lock(&mutex_);
RTC_DCHECK(size <= data_length_);
read_position_ = (read_position_ + size) % buffer_length_;
data_length_ -= size;
}
void PseudoTcp::LockedFifoBuffer::ConsumeWriteBuffer(size_t size) {
webrtc::MutexLock lock(&mutex_);
RTC_DCHECK(size <= buffer_length_ - data_length_);
data_length_ += size;
}
bool PseudoTcp::LockedFifoBuffer::GetWriteRemaining(size_t* size) const {
webrtc::MutexLock lock(&mutex_);
*size = buffer_length_ - data_length_;
return true;
}
bool PseudoTcp::LockedFifoBuffer::ReadOffsetLocked(void* buffer,
size_t bytes,
size_t offset,
size_t* bytes_read) {
if (offset >= data_length_)
return false;
const size_t available = data_length_ - offset;
const size_t read_position = (read_position_ + offset) % buffer_length_;
const size_t copy = std::min(bytes, available);
const size_t tail_copy = std::min(copy, buffer_length_ - read_position);
char* const p = static_cast<char*>(buffer);
memcpy(p, &buffer_[read_position], tail_copy);
memcpy(p + tail_copy, &buffer_[0], copy - tail_copy);
if (bytes_read)
*bytes_read = copy;
return true;
}
bool PseudoTcp::LockedFifoBuffer::WriteOffsetLocked(const void* buffer,
size_t bytes,
size_t offset,
size_t* bytes_written) {
if (data_length_ + offset >= buffer_length_)
return false;
const size_t available = buffer_length_ - data_length_ - offset;
const size_t write_position =
(read_position_ + data_length_ + offset) % buffer_length_;
const size_t copy = std::min(bytes, available);
const size_t tail_copy = std::min(copy, buffer_length_ - write_position);
const char* const p = static_cast<const char*>(buffer);
memcpy(&buffer_[write_position], p, tail_copy);
memcpy(&buffer_[0], p + tail_copy, copy - tail_copy);
if (bytes_written)
*bytes_written = copy;
return true;
}
} // namespace cricket
Reference in New Issue View Git Blame Copy Permalink