quiche: fix quiche being unable to handle timeout events properly

[oldduckruirui]

According to quiche's document, it is essential to invoke quiche_conn_on_timeout when a timer expires. Failing to call this function can result in quiche being unable to manage various timeout events, including scenarios like retransmitting lost packets and handling idle timeout events.

When packets are sent, the application is responsible for maintaining a timer to react to time-based connection events. The timer expiration can be obtained using the connection's timeout() method.

The application is responsible for providing a timer implementation, which can be specific to the operating system or networking framework used. When a timer expires, the connection's on_timeout() method should be called, after which additional packets might need to be sent on the network:

[icing]

This PR goes in the right direction. But needs to be built on to invoke quiche_conn_on_timeout() only in case the timeout really did happen.

[icing]

This calls the function unconditionally on every egress handling. Which is not what the quiche example seem to mandate (guessing through their lack of documentation).

I think we need to handle timeouts more elaborate here. But we can do this based on this PR.

[oldduckruirui]

Thanks! I have made additional modifications to the code. Please check it. :)

[bagder]

@LPardue @ghedo you think this makes sense?

[LPardue]

Few things:

• Calling quiche_conn_on_timeout() before any timeout elapsed is fine, there is no harm other than wasted cycles.
• It would be better to grab the timeout value once and only fire when expires, than query it every time and check for 0 (optimization)
• its not clear to me how this relates to the existing timeout_ns that also reads quiche_conn_timeout() for setting a Curl_expire

[oldduckruirui]

• That's right, using a variable to record the value of timeout can improve performance. However, in order to remain consistent with curl_ngtcp2.c and minimize code modifications, I chose not to do this. Maybe we can consider optimizing the implementations of curl_ngtcp2 and curl_quiche together in the future.

• Reading quiche_conn_timeout again is to promptly update the timing for the next timeout. After processing with quiche_conn_on_timeout, the timeout duration might change. Perhaps I can make a small optimization by placing the update of timeout and the setting of a Curl_expire after calling quiche_conn_on_timeout, which would require querying quiche_conn_timeout only when necessary. But this may cause a little more code modifications.

[bagder]

@icing you think we should merge this as-is and consider further improvements later? It seems like a step in the right direction at least to me.

[icing]

@icing you think we should merge this as-is and consider further improvements later? It seems like a step in the right direction at least to me.

I agree. Let's merge it.

[bagder]

Thanks!