Can now reconcile

clitools/pkg/node/prereqs.go

@@ -2,6 +2,7 @@ package node
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net"
 	"strings"
@@ -106,7 +107,85 @@ func ValidateNodeIPAndAPIServerReachability(ctx context.Context, nct *NodeContex
 	return nil
 }
 
-func CheckUpgradePrereqs(context.Context, *NodeContext) error {
-	klog.Info("check_upgrade_prereqs: TODO implement kubeadm version / skew checks")
+func CheckForVersionSkew(ctx context.Context, nctx *NodeContext) error {
+	if nctx.BootstrapState == nil {
+		return errors.New("BootstrapState is nil, call ClassifyBootstrapAction() first")
+	}
+
+	role := strings.TrimSpace(nctx.Config.Spec.ClusterRole)
+	wantVersion := normalizeKubeVersion(strings.TrimSpace(nctx.Config.Spec.KubernetesVersion))
+	if wantVersion == "" {
+		return errors.New("spec.kubernetesVersion is required")
+	}
+
+	switch nctx.LocalClusterState.MembershipKind {
+	case LocalMembershipFresh:
+		// Nothing to compare for fresh nodes.
+		return nil
+	case LocalMembershipPartial:
+		return fmt.Errorf("cannot check version skew with partial local cluster state")
+	}
+
+	versionKubeconfig := chooseVersionKubeconfig(nctx.LocalClusterState)
+	if versionKubeconfig == "" {
+		return fmt.Errorf("no kubeconfig available for version detection")
+	}
+
+	currentVersion, err := getServerVersion(ctx, versionKubeconfig)
+	if err != nil {
+		if role == "control-plane" {
+			return fmt.Errorf("existing control-plane state found, but cluster version could not be determined: %w", err)
+		}
+
+		// Worker path stays permissive.
+		nctx.BootstrapState.UnsupportedWorkerVersionSkew = true
+		nctx.BootstrapState.VersionSkewReason = "cluster version could not be determined"
+
+		if nctx.BootstrapState.Action == BootstrapActionManageWorker {
+			nctx.BootstrapState.Action = BootstrapActionReconcileWorker
+		}
+		return nil
+	}
+
+	nctx.BootstrapState.DetectedClusterVersion = currentVersion
+
+	switch role {
+	case "control-plane":
+		if !isSupportedControlPlaneSkew(currentVersion, wantVersion) {
+			return fmt.Errorf(
+				"unsupported control-plane version skew: cluster=%s node=%s",
+				currentVersion, wantVersion,
+			)
+		}
+
+		if nctx.BootstrapState.Action == BootstrapActionManageControlPlane {
+			if versionEq(currentVersion, wantVersion) {
+				nctx.BootstrapState.Action = BootstrapActionReconcileControlPlane
+			} else {
+				nctx.BootstrapState.Action = BootstrapActionUpgradeControlPlane
+			}
+		}
+
+	case "worker":
+		if !isSupportedWorkerSkew(currentVersion, wantVersion) {
+			nctx.BootstrapState.UnsupportedWorkerVersionSkew = true
+			nctx.BootstrapState.VersionSkewReason = fmt.Sprintf(
+				"unsupported worker version skew: cluster=%s node=%s",
+				currentVersion, wantVersion,
+			)
+		}
+
+		if nctx.BootstrapState.Action == BootstrapActionManageWorker {
+			if versionEq(currentVersion, wantVersion) {
+				nctx.BootstrapState.Action = BootstrapActionReconcileWorker
+			} else {
+				nctx.BootstrapState.Action = BootstrapActionUpgradeWorker
+			}
+		}
+
+	default:
+		return fmt.Errorf("unsupported cluster role %q", role)
+	}
+
 	return nil
 }