TUN-6740: Detect no UDP packets allowed and fallback from QUIC in that case

connection/errors.go

@@ -27,6 +27,10 @@ func (e *EdgeQuicDialError) Error() string {
 	return "failed to dial to edge with quic: " + e.Cause.Error()
 }
 
+func (e *EdgeQuicDialError) Unwrap() error {
+	return e.Cause
+}
+
 // RegisterTunnel error from server
 type ServerRegisterTunnelError struct {
 	Cause     error

ingress/origin_icmp_proxy_test.go

@@ -23,6 +23,10 @@ var (
 
 // TestICMPProxyEcho makes sure we can send ICMP echo via the Request method and receives response via the
 // ListenResponse method
+//
+// Note: if this test fails on your device under Linux, then most likely you need to make sure that your user
+// is allowed in ping_group_range. See the following gist for how to do that:
+// https://github.com/ValentinBELYN/icmplib/blob/main/docs/6-use-icmplib-without-privileges.md
 func TestICMPProxyEcho(t *testing.T) {
 	onlyDarwinOrLinux(t)
 	const (

supervisor/tunnel.go

@@ -317,16 +317,11 @@ func selectNextProtocol(
 	selector connection.ProtocolSelector,
 	cause error,
 ) bool {
-	var idleTimeoutError *quic.IdleTimeoutError
+	isQuicBroken := isQuicBroken(cause)
-	isNetworkActivityTimeout := errors.As(cause, &idleTimeoutError)
-	edgeQuicDialError, ok := cause.(*connection.EdgeQuicDialError)
-	if !isNetworkActivityTimeout && ok {
-		isNetworkActivityTimeout = errors.As(edgeQuicDialError.Cause, &idleTimeoutError)
-	}
 	_, hasFallback := selector.Fallback()
 
-	if protocolBackoff.ReachedMaxRetries() || (hasFallback && isNetworkActivityTimeout) {
+	if protocolBackoff.ReachedMaxRetries() || (hasFallback && isQuicBroken) {
-		if isNetworkActivityTimeout {
+		if isQuicBroken {
 			connLog.Warn().Msg("If this log occurs persistently, and cloudflared is unable to connect to " +
 				"Cloudflare Network with `quic` protocol, then most likely your machine/network is getting its egress " +
 				"UDP to port 7844 (or others) blocked or dropped. Make sure to allow egress connectivity as per " +
@@ -355,6 +350,20 @@ func selectNextProtocol(
 	return true
 }
 
+func isQuicBroken(cause error) bool {
+	var idleTimeoutError *quic.IdleTimeoutError
+	if errors.As(cause, &idleTimeoutError) {
+		return true
+	}
+
+	var transportError *quic.TransportError
+	if errors.As(cause, &transportError) && strings.Contains(cause.Error(), "operation not permitted") {
+		return true
+	}
+
+	return false
+}
+
 // ServeTunnel runs a single tunnel connection, returns nil on graceful shutdown,
 // on error returns a flag indicating if error can be retried
 func (e *EdgeTunnelServer) serveTunnel(