cloudflared falls back aggressively to HTTP/2 protocol if a connection
attempt with QUIC failed. This was done to ensure that machines with UDP
egress disabled did not stop clients from connecting to the cloudlfare
edge. This PR improves on that experience by having cloudflared remember
if a QUIC connection was successful which implies UDP egress works. In
this case, cloudflared does not fallback to HTTP/2 and keeps trying to
connect to the edge with QUIC.
The idle period is set to 5sec.
We now also ping every second since last activity.
This makes the quic.Connection less prone to being closed with
no network activity, since we send multiple pings per idle
period, and thus a single packet loss cannot cause the problem.
Errors that are non-recoverable can lead to one of two things happening:
1. That connection lying dead and cloudflared not retrying to make that
connection.
2. cloudflared resolving to a different edge addr to retry connection.
We should subject these errors to a backoff as well. This will result in
us introducing a backoff for 1. When we are going to let the connection
become stale anyway and 2. When we are about to try a different edge
addr.
cthuang
Sudarsan Reddy
Devin Carr
João Oliveirinha
Nuno Diegues