internal void OnPingAckReceived(long payload, Http2Connection connection)
{
if (_state != State.PingSent && _state != State.TerminatingMayReceivePingAck)
{
if (NetEventSource.Log.IsEnabled())
{
connection.Trace($"[FlowControl] Unexpected PING ACK in state {_state}");
}
ThrowProtocolError();
}
if (_state == State.TerminatingMayReceivePingAck)
{
_state = State.Disabled;
return;
}
// RTT PINGs always carry negative payload, positive values indicate a response to KeepAlive PING.
Debug.Assert(payload < 0);
if (_pingCounter != payload)
{
if (NetEventSource.Log.IsEnabled())
{
connection.Trace($"[FlowControl] Unexpected RTT PING ACK payload {payload}, should be {_pingCounter}.");
}
ThrowProtocolError();
}
RefreshRtt(connection);
_state = State.Waiting;
}
internal void OnDataOrHeadersReceived(Http2Connection connection)
{
if (_state != State.Waiting)
{
return;
}
long now = Stopwatch.GetTimestamp();
bool initial = _initialBurst > 0;
if (initial || now - _pingSentTimestamp > PingIntervalInTicks)
{
if (initial)
{
_initialBurst--;
}
// Send a PING
_pingCounter--;
if (NetEventSource.Log.IsEnabled())
{
connection.Trace($"[FlowControl] Sending RTT PING with payload {_pingCounter}");
}
connection.LogExceptions(connection.SendPingAsync(_pingCounter, isAck: false));
_pingSentTimestamp = now;
_state = State.PingSent;
}
}
private void RefreshRtt(Http2Connection connection)
{
long prevRtt = _minRtt == 0 ? long.MaxValue : _minRtt;
TimeSpan currentRtt = Stopwatch.GetElapsedTime(_pingSentTimestamp);
long minRtt = Math.Min(prevRtt, currentRtt.Ticks);
Interlocked.Exchange(ref _minRtt, minRtt); // MinRtt is being queried from another thread
if (NetEventSource.Log.IsEnabled())
{
connection.Trace($"[FlowControl] Updated MinRtt: {MinRtt.TotalMilliseconds} ms");
}
}
