TUN-6720: Remove forcibly closing connection during reconnect signal

Previously allowing the reconnect signal forcibly close the connection
caused a race condition on which error was returned by the errgroup
in the tunnel connection. Allowing the signal to return and provide
a context cancel to the connection provides a safer shutdown of the
tunnel for this test-only scenario.

cmd/cloudflared/tunnel/cmd.go

@@ -375,7 +375,7 @@ func StartServer(
 		errC <- metrics.ServeMetrics(metricsListener, ctx.Done(), readinessServer, quickTunnelURL, orchestrator, log)
 	}()
 
-	reconnectCh := make(chan supervisor.ReconnectSignal, 1)
+	reconnectCh := make(chan supervisor.ReconnectSignal, c.Int("ha-connections"))
 	if c.IsSet("stdin-control") {
 		log.Info().Msg("Enabling control through stdin")
 		go stdinControl(reconnectCh, log)

component-tests/test_reconnect.py

@@ -47,17 +47,12 @@ class TestReconnect:
         cloudflared.stdin.flush()
 
     def assert_reconnect(self, config, cloudflared, repeat):
-        wait_tunnel_ready(tunnel_url=config.get_url(), require_min_connections=self.default_ha_conns)
+        wait_tunnel_ready(tunnel_url=config.get_url(),
+                          require_min_connections=self.default_ha_conns)
         for _ in range(repeat):
-            for i in range(self.default_ha_conns):
+            for _ in range(self.default_ha_conns):
                 self.send_reconnect(cloudflared, self.default_reconnect_secs)
-                expect_connections = self.default_ha_conns-i-1
-                if expect_connections > 0:
-                    # Don't check if tunnel returns 200 here because there is a race condition between wait_tunnel_ready
-                    # retrying to get 200 response and reconnecting
-                    wait_tunnel_ready(require_min_connections=expect_connections)
-                else:
-                    check_tunnel_not_connected()
-
+            check_tunnel_not_connected()
             sleep(self.default_reconnect_secs * 2)
-            wait_tunnel_ready(tunnel_url=config.get_url(), require_min_connections=self.default_ha_conns)
+            wait_tunnel_ready(tunnel_url=config.get_url(),
+                              require_min_connections=self.default_ha_conns)

component-tests/util.py

@@ -15,6 +15,7 @@ from constants import METRICS_PORT, MAX_RETRIES, BACKOFF_SECS
 
 LOGGER = logging.getLogger(__name__)
 
+
 def select_platform(plat):
     return pytest.mark.skipif(
         platform.system() != plat, reason=f"Only runs on {plat}")
@@ -108,13 +109,15 @@ def _log_cloudflared_logs(cfd_logs):
             LOGGER.warning(line)
 
 
-@retry(stop_max_attempt_number=MAX_RETRIES * BACKOFF_SECS, wait_fixed=1000)
+@retry(stop_max_attempt_number=MAX_RETRIES, wait_fixed=BACKOFF_SECS * 1000)
 def check_tunnel_not_connected():
     url = f'http://localhost:{METRICS_PORT}/ready'
 
     try:
-        resp = requests.get(url, timeout=1)
+        resp = requests.get(url, timeout=BACKOFF_SECS)
         assert resp.status_code == 503, f"Expect {url} returns 503, got {resp.status_code}"
+        assert resp.json()[
+            "readyConnections"] == 0, "Expected all connections to be terminated (pending reconnect)"
     # cloudflared might already terminate
     except requests.exceptions.ConnectionError as e:
         LOGGER.warning(f"Failed to connect to {url}, error: {e}")

supervisor/supervisor.go

@@ -295,8 +295,7 @@ func (s *Supervisor) initialize(
 			s.config.ProtocolSelector.Current(),
 			false,
 		}
-		ch := signal.New(make(chan struct{}))
-		go s.startTunnel(ctx, i, ch)
+		go s.startTunnel(ctx, i, s.newConnectedTunnelSignal(i))
 		time.Sleep(registrationInterval)
 	}
 	return nil

supervisor/tunnel.go

@@ -546,7 +546,13 @@ func (e *EdgeTunnelServer) serveH2mux(
 	})
 
 	errGroup.Go(func() error {
-		return listenReconnect(serveCtx, e.reconnectCh, e.gracefulShutdownC)
+		err := listenReconnect(serveCtx, e.reconnectCh, e.gracefulShutdownC)
+		if err != nil {
+			// forcefully break the connection (this is only used for testing)
+			// errgroup will return context canceled for the handler.ServeClassicTunnel
+			connLog.Logger().Debug().Msg("Forcefully breaking h2mux connection")
+		}
+		return err
 	})
 
 	return errGroup.Wait()
@@ -580,8 +586,8 @@ func (e *EdgeTunnelServer) serveHTTP2(
 		err := listenReconnect(serveCtx, e.reconnectCh, e.gracefulShutdownC)
 		if err != nil {
 			// forcefully break the connection (this is only used for testing)
+			// errgroup will return context canceled for the h2conn.Serve
 			connLog.Logger().Debug().Msg("Forcefully breaking http2 connection")
-			_ = tlsServerConn.Close()
 		}
 		return err
 	})
@@ -636,8 +642,8 @@ func (e *EdgeTunnelServer) serveQUIC(
 		err := listenReconnect(serveCtx, e.reconnectCh, e.gracefulShutdownC)
 		if err != nil {
 			// forcefully break the connection (this is only used for testing)
+			// errgroup will return context canceled for the quicConn.Serve
 			connLogger.Logger().Debug().Msg("Forcefully breaking quic connection")
-			quicConn.Close()
 		}
 		return err
 	})