Handle zombie streams, when sending rst

[martenrichter]

If QuicSession::OnStreamClosed is called on a stream with a pending outgoing fin, a zombie stream will be created. A call to QuicStream::OnStopSending afterward, which in turn calls QuicStream::MaybeSendRstStream should kill the zombie finally. But this route misses a call to session's session_->MaybeCloseZombieStream, so the stream is not removed from active streams. This triggers a quic_bug_12435_2 when OnConnectionClosed is finally called on session close. This commit adds the missing call to the MaybeCloseZombieStream.

[yangfanud]

Thank you for reporting the issue!
To make sure I understand the scenario correctly:

QuicSession::OnStreamClosed is called on a stream with a pending outgoing fin
Do you mean the stream has consumed fin, and sent fin but waiting for all data get acknowledged?
QuicStream::OnStopSending afterward
Is a STOP_SENDING frame gets received for this stream?

[martenrichter]

Thank you for reporting the issue! To make sure I understand the scenario correctly:

QuicSession::OnStreamClosed is called on a stream with a pending outgoing fin
Do you mean the stream has consumed fin, and sent fin but waiting for all data get acknowledged?
QuicStream::OnStopSending afterward
No the other way round, a fin is outstanding but all data is received. And with fin outstanding I mean the the flag which is checked here:

quiche/quiche/quic/core/quic_stream.cc

Line 1195 in 42b2e66

bool QuicStream::IsWaitingForAcks() const {

Test code is on the firefox side:
https://github.com/fails-components/webtransport/blob/0bbe8abd1cc9016d902812823f9ac5a502f4385a/test/stream-limits.spec.js#L117
and on the server side.

Is a STOP_SENDING frame gets received for this stream?
I do not know. I have just put print outs on all code points, that change variables checked at

quiche/quiche/quic/core/quic_stream.cc

Line 1195 in 42b2e66

bool QuicStream::IsWaitingForAcks() const {

and I have seen that a to QuicStream::OnStopSending change the variables, so that the Zooombietest reports false and that on this route session_->MaybeCloseZombieStream, was not called.

[yangfanud]

Thanks for the details. In addition to your PR in flight, it is a bug that session does not deliver RESET or STOP_SENDING to zombie streams. I am going to land a fix internally, if that sounds good to you?
Again, thanks for reporting the issue!

[martenrichter]

Yes, this sounds good. All I care about is that it is fixed in quiche.

[yangfanud]

Thank you! I landed the fix in https://quiche.googlesource.com/quiche/+/93f3b29187f44d10a0b2563fb0a7b6b21e21b682