Add some helping logs to avoid wrong configs

pkg/agent/run.go

@@ -25,6 +25,7 @@ import (
 	cp "github.com/k3s-io/k3s/pkg/cloudprovider"
 	"github.com/k3s-io/k3s/pkg/daemons/agent"
 	daemonconfig "github.com/k3s-io/k3s/pkg/daemons/config"
+	types "github.com/k3s-io/k3s/pkg/daemons/config"
 	"github.com/k3s-io/k3s/pkg/daemons/executor"
 	"github.com/k3s-io/k3s/pkg/nodeconfig"
 	"github.com/k3s-io/k3s/pkg/rootless"
@@ -97,6 +98,11 @@ func run(ctx context.Context, cfg cmds.Agent, proxy proxy.Proxy) error {
 	}
 
 	if !nodeConfig.NoFlannel {
+		if (nodeConfig.FlannelExternalIP) && (len(nodeConfig.AgentConfig.NodeExternalIPs) == 0) {
+			logrus.Warnf("Server has flannel-external-ip flag set but this node does not set node-external-ip. Flannel will use internal address when connecting to this node.")
+		} else if (nodeConfig.FlannelBackend != types.FlannelBackendWireguardNative) && (nodeConfig.FlannelBackend != types.FlannelBackendIPSEC) {
+			logrus.Warnf("Flannel is using external addresses with an insecure backend: %v. Please consider using an encrypting flannel backend.", nodeConfig.FlannelBackend)
+		}
 		if err := flannel.Prepare(ctx, nodeConfig); err != nil {
 			return err
 		}