TUN-6929: Use same protocol for other connections as first one

This PR changes protocol initialization of the other N connections to be
the same as the one we know the initial tunnel connected with. This is
so we homogenize connections and not lead to some connections being
QUIC-able and the others not.

There's also an improvement to the connection registered log so we know
what protocol every individual connection connected with from the
cloudflared side.

Author: sudarshan-reddy

connection/control.go

@@ -85,7 +85,7 @@ func (c *controlStream) ServeControlStream(
 		return err
 	}
 
-	c.observer.logServerInfo(c.connIndex, registrationDetails.Location, c.edgeAddress, fmt.Sprintf("Connection %s registered", registrationDetails.UUID))
+	c.observer.logServerInfo(c.connIndex, registrationDetails.Location, c.edgeAddress, fmt.Sprintf("Connection %s registered with protocol: %s", registrationDetails.UUID, c.protocol))
 	c.observer.sendConnectedEvent(c.connIndex, c.protocol, registrationDetails.Location)
 	c.connectedFuse.Connected()
 

supervisor/supervisor.go

@@ -45,7 +45,7 @@ type Supervisor struct {
 	config                  *TunnelConfig
 	orchestrator            *orchestration.Orchestrator
 	edgeIPs                 *edgediscovery.Edge
-	edgeTunnelServer        *EdgeTunnelServer
+	edgeTunnelServer        TunnelServer
 	tunnelErrors            chan tunnelError
 	tunnelsConnecting       map[int]chan struct{}
 	tunnelsProtocolFallback map[int]*protocolFallback
@@ -285,7 +285,8 @@ func (s *Supervisor) initialize(
 	for i := 1; i < s.config.HAConnections; i++ {
 		s.tunnelsProtocolFallback[i] = &protocolFallback{
 			retry.BackoffHandler{MaxRetries: s.config.Retries, RetryForever: true},
-			s.config.ProtocolSelector.Current(),
+			// Set the protocol we know the first tunnel connected with.
+			s.tunnelsProtocolFallback[0].protocol,
 			false,
 		}
 		go s.startTunnel(ctx, i, s.newConnectedTunnelSignal(i))

supervisor/supervisor_test.go

@@ -0,0 +1,74 @@
+package supervisor
+
+import (
+	"context"
+	"testing"
+
+	"github.com/rs/zerolog"
+	"github.com/stretchr/testify/assert"
+
+	"github.com/cloudflare/cloudflared/connection"
+	"github.com/cloudflare/cloudflared/edgediscovery"
+	"github.com/cloudflare/cloudflared/edgediscovery/allregions"
+	"github.com/cloudflare/cloudflared/signal"
+)
+
+type mockProtocolSelector struct {
+	protocols []connection.Protocol
+	index     int
+}
+
+func (m *mockProtocolSelector) Current() connection.Protocol {
+	return m.protocols[m.index]
+}
+
+func (m *mockProtocolSelector) Fallback() (connection.Protocol, bool) {
+	m.index++
+	if m.index == len(m.protocols) {
+		return m.protocols[len(m.protocols)-1], false
+	}
+
+	return m.protocols[m.index], true
+}
+
+type mockEdgeTunnelServer struct {
+	config *TunnelConfig
+}
+
+func (m *mockEdgeTunnelServer) Serve(ctx context.Context, connIndex uint8, protocolFallback *protocolFallback, connectedSignal *signal.Signal) error {
+	// This is to mock the first connection falling back because of connectivity issues.
+	protocolFallback.protocol, _ = m.config.ProtocolSelector.Fallback()
+	connectedSignal.Notify()
+	return nil
+}
+
+// Test to check if initialize sets all the different connections to the same protocol should the first
+// tunnel fall back.
+func Test_Initialize_Same_Protocol(t *testing.T) {
+	edgeIPs, err := edgediscovery.ResolveEdge(&zerolog.Logger{}, "us", allregions.Auto)
+	assert.Nil(t, err)
+	s := Supervisor{
+		edgeIPs: edgeIPs,
+		config: &TunnelConfig{
+			ProtocolSelector: &mockProtocolSelector{protocols: []connection.Protocol{connection.QUIC, connection.HTTP2, connection.H2mux}},
+		},
+		tunnelsProtocolFallback: make(map[int]*protocolFallback),
+		edgeTunnelServer: &mockEdgeTunnelServer{
+			config: &TunnelConfig{
+				ProtocolSelector: &mockProtocolSelector{protocols: []connection.Protocol{connection.QUIC, connection.HTTP2, connection.H2mux}},
+			},
+		},
+	}
+
+	ctx := context.Background()
+	connectedSignal := signal.New(make(chan struct{}))
+	s.initialize(ctx, connectedSignal)
+
+	// Make sure we fell back to http2 as the mock Serve is wont to do.
+	assert.Equal(t, s.tunnelsProtocolFallback[0].protocol, connection.HTTP2)
+
+	// Ensure all the protocols we set to try are the same as what the first tunnel has fallen back to.
+	for _, protocolFallback := range s.tunnelsProtocolFallback {
+		assert.Equal(t, protocolFallback.protocol, s.tunnelsProtocolFallback[0].protocol)
+	}
+}

supervisor/tunnel.go

@@ -206,6 +206,10 @@ type EdgeTunnelServer struct {
 	connAwareLogger *ConnAwareLogger
 }
 
+type TunnelServer interface {
+	Serve(ctx context.Context, connIndex uint8, protocolFallback *protocolFallback, connectedSignal *signal.Signal) error
+}
+
 func (e *EdgeTunnelServer) Serve(ctx context.Context, connIndex uint8, protocolFallback *protocolFallback, connectedSignal *signal.Signal) error {
 	haConnections.Inc()
 	defer haConnections.Dec()