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tcp: Update handling of CWR state

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* CWR state should be left when a RTT is observed, not by noticing
  the lack of ECE ACKs
* Ensure that PktsAcked() is called during CWR
This commit is contained in:
Tom Henderson
2020-11-25 14:18:14 -08:00
parent 8e5d2165c1
commit 12b82f2c5d
1 changed files with 23 additions and 9 deletions
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32
src/internet/model/tcp-socket-base.cc
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@@ -1578,11 +1578,17 @@ TcpSocketBase::EnterCwr (uint32_t currentDelivered)
NS_ASSERT (m_tcb->m_congState != TcpSocketState::CA_CWR);
NS_LOG_DEBUG (TcpSocketState::TcpCongStateName[m_tcb->m_congState] << " -> CA_CWR");
m_tcb->m_congState = TcpSocketState::CA_CWR;
// CWR state will be exited when the ack exceeds the m_recover variable.
// Do not set m_recoverActive (which applies to a loss-based recovery)
// m_recover corresponds to Linux tp->high_seq
m_recover = m_tcb->m_highTxMark;
if (!m_congestionControl->HasCongControl ())
{
// If there is a recovery algorithm, invoke it.
m_recoveryOps->EnterRecovery (m_tcb, m_dupAckCount, UnAckDataCount (), currentDelivered);
NS_LOG_INFO ("Enter CWR recovery mode; reset cwnd to " << m_tcb->m_cWnd
<< ", ssthresh to " << m_tcb->m_ssThresh);
NS_LOG_INFO ("Enter CWR recovery mode; set cwnd to " << m_tcb->m_cWnd
<< ", ssthresh to " << m_tcb->m_ssThresh
<< ", recover to " << m_recover);
}
}
@@ -1801,6 +1807,20 @@ TcpSocketBase::ReceivedAck (Ptr<Packet> packet, const TcpHeader& tcpHeader)
uint32_t currentDelivered = static_cast<uint32_t> (m_rateOps->GetConnectionRate ().m_delivered - previousDelivered);
if (m_tcb->m_congState == TcpSocketState::CA_CWR && (ackNumber > m_recover))
{
// Recovery is over after the window exceeds m_recover
// (although it may be re-entered below if ECE is still set)
NS_LOG_DEBUG (TcpSocketState::TcpCongStateName[m_tcb->m_congState] << " -> CA_OPEN");
m_tcb->m_congState = TcpSocketState::CA_OPEN;
if (!m_congestionControl->HasCongControl ())
{
m_tcb->m_cWnd = m_tcb->m_ssThresh.Get ();
m_recoveryOps->ExitRecovery (m_tcb);
m_congestionControl->CwndEvent (m_tcb, TcpSocketState::CA_EVENT_COMPLETE_CWR);
}
}
if (ackNumber > oldHeadSequence && (m_tcb->m_ecnState != TcpSocketState::ECN_DISABLED) && (tcpHeader.GetFlags () & TcpHeader::ECE))
{
if (m_ecnEchoSeq < ackNumber)
@@ -1817,14 +1837,7 @@ TcpSocketBase::ReceivedAck (Ptr<Packet> packet, const TcpHeader& tcpHeader)
}
else if (m_tcb->m_ecnState == TcpSocketState::ECN_ECE_RCVD && !(tcpHeader.GetFlags () & TcpHeader::ECE))
{
// When the receiver stops sending ECE, the recovery is over
m_tcb->m_ecnState = TcpSocketState::ECN_IDLE;
NS_ASSERT (m_tcb->m_congState == TcpSocketState::CA_CWR);
NS_LOG_DEBUG (TcpSocketState::TcpCongStateName[m_tcb->m_congState] << " -> CA_OPEN");
m_tcb->m_congState = TcpSocketState::CA_OPEN;
m_tcb->m_cWnd = m_tcb->m_ssThresh.Get ();
m_recoveryOps->ExitRecovery (m_tcb);
m_congestionControl->CwndEvent (m_tcb, TcpSocketState::CA_EVENT_COMPLETE_CWR);
}
// Update bytes in flight before processing the ACK for proper calculation of congestion window
@@ -2038,6 +2051,7 @@ TcpSocketBase::ProcessAck(const SequenceNumber32 &ackNumber, bool scoreboardUpda
}
else if (m_tcb->m_congState == TcpSocketState::CA_CWR)
{
m_congestionControl->PktsAcked (m_tcb, segsAcked, m_tcb->m_lastRtt);
// TODO: need to check behavior if marking is compounded by loss
// and/or packet reordering
if (!m_congestionControl->HasCongControl () && segsAcked >= 1)