QuicStreams Zero-Copy

[Nacho-Neko]

Is it possible to achieve zero-copy packet forwarding between multiple QuicStreams? Linux itself supports zero-copy between sockets, but msquic adds multiple layers of wrappers, making it impossible to access the underlying sockets. Can an efficient method be implemented for mutual copying between QUIC Streams?

[anrossi]

Can you explain the use case a little further? Do you mean a situation like a QUIC forwarder where data received from stream 1 on connection 1 is immediately queued to be sent on stream 1 on connection 2?

[Nacho-Neko]

You are absolutely right. I am indeed implementing bidirectional forwarding between Quic Stream1 and Quic Stream2. We previously used KCP to achieve this. However, KCP is not a standardized or specification-based protocol, and its implementation varies across different programming languages ​​and environments. QUIC, on the other hand, is a standardized and specification-based protocol. But it seems that the msquic wrapper cannot accomplish this.

[guhetier]

You can minimize the number of copies by making by using non-buffered sends and passing the QUIC_BUFFER from the receive notification to the send call directly. I am not sure if it will be optimal from the point of view of performances though.

There will still be one copy involved to reassemble the stream data on the receive path, I don't think you can go around that one. Even with an exposed socket, it would take a very specialized QUIC implementation to do a zero-copy reassembly.

[Nacho-Neko]

How can I implement this functionality? Can you help me?

[guhetier]

I expect forwarder.cpp will be a good starting point if you want to give a try with MsQuic and accept one copy.

[Nacho-Neko]

Yes, I'd like to give it a try.