This PR implements all the dialers and resolvers needed to make pre-checks happen. So this task focuses on the following:
1. Implement the DNS probe: call DNSResolver.Resolve(region)
2. Implement the QUIC probe: call QUICDialer.DialQuic (handshake only, no stream opened) and record the result.
3. Implement the HTTP/2 probe: call TCPDialer.DialEdge (TCP + TLS handshake only, no frames sent) and record the result.
4. Implement the Management API probe: call ManagementDialer.DialContext to api.cloudflare.com:443 and record the result.
5. Export edgeDiscovery as EdgeDiscovery in edgediscovery/allregions/discovery.go so the pre-check can reuse the production DNS path.
This sets up the main components to implement the checker.
Some more legacy h2mux code to be cleaned up and moved out of the way.
The h2mux.Header used in the serialization for http2 proxied headers is moved to connection module. Additionally, the booleanfuse structure is also moved to supervisor as it is also needed. Both of these structures could be evaluated later for removal/updates, however, the intent of the proposed changes here is to remove the dependencies on the h2mux code and removal.
Approved-by: Chung-Ting Huang <chungting@cloudflare.com>
Approved-by: Luis Neto <lneto@cloudflare.com>
Approved-by: Gonçalo Garcia <ggarcia@cloudflare.com>
MR: https://gitlab.cfdata.org/cloudflare/tun/cloudflared/-/merge_requests/1576
Going forward, the only protocols supported will be QUIC and HTTP2,
defaulting to QUIC for "auto". Selecting h2mux protocol will be forcibly
upgraded to http2 internally.
We previously always preferred region2 as the first region to connect
to if both the regions cloudflared connects to have the same number of
availabe addresses. This change randomises that choice. The first
connection, conn index: 0, can now either connect to region 1 or region
2.
More importantly, conn 0 and 2 and 1 and 3 need not belong to the same
region.
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.
Miguel da Costa Martins Marcelino
Devin Carr
iBug
Sudarsan Reddy
Areg Harutyunyan
Nuno Diegues
Igor Postelnik
cthuang
Dalton
Adam Chalmers