feat(api): Add kubernetes version to coredns version mapping

Added script and makefile target to update coredns version mapping.
`make coredns.sync` will fetch the list of releases from upstream
release branches and create a mapping k8s releases to coredns
versions.

Author: thunderboltsid

api/versions/coredns.go

@@ -0,0 +1,331 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"errors"
+	"flag"
+	"fmt"
+	"go/format"
+	"io"
+	"net/http"
+	"os"
+	"path"
+	"regexp"
+	"sort"
+	"strings"
+	"text/template"
+)
+
+var (
+	// Command-line flags
+	outputFile           = flag.String("output", "api/versions/coredns.go", "Output file path")
+	minKubernetesVersion = flag.String("min-kubernetes-version", "1.22", "Minimum Kubernetes version to include")
+)
+
+const (
+	constantsURLTemplate = "https://raw.githubusercontent.com/kubernetes/kubernetes/%s/cmd/kubeadm/app/constants/constants.go"
+	branchesAPIURL       = "https://api.github.com/repos/kubernetes/kubernetes/branches?per_page=100&page=%d"
+)
+
+var goTemplate = `// Code generated by script; DO NOT EDIT. Run 'make coredns.sync' instead
+
+package versions
+
+// Kubernetes versions
+const (
+{{- range .KubernetesConstants }}
+	{{ .Name }} = "{{ .Version }}"
+{{- end }}
+)
+
+// CoreDNS versions
+const (
+{{- range .CoreDNSConstants }}
+	{{ .Name }} = "{{ .Version }}"
+{{- end }}
+)
+
+// KubernetesToCoreDNSVersion maps Kubernetes versions to CoreDNS versions.
+var KubernetesToCoreDNSVersion = map[string]string{
+{{- range .VersionMap }}
+	{{ .KubernetesConst }}: {{ .CoreDNSConst }},
+{{- end }}
+}
+`
+
+func main() {
+	flag.Parse()
+
+	versions, err := fetchKubernetesVersions(*minKubernetesVersion)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error fetching Kubernetes versions: %v\n", err)
+		os.Exit(1)
+	}
+
+	versionMap, err := fetchCoreDNSVersions(versions)
+	if err != nil {
+		fmt.Fprintf(os.Stderr, "Error fetching CoreDNS versions: %v\n", err)
+		os.Exit(1)
+	}
+
+	if err := generateGoFile(versionMap, *outputFile); err != nil {
+		fmt.Fprintf(os.Stderr, "Error generating Go file: %v\n", err)
+		os.Exit(1)
+	}
+
+	fmt.Printf("Successfully generated %s\n", *outputFile)
+}
+
+// Fetch Kubernetes versions from GitHub branches
+func fetchKubernetesVersions(minVersion string) ([]string, error) {
+	var versions []string
+	page := 1
+	for {
+		url := fmt.Sprintf(branchesAPIURL, page)
+		branchNames, err := fetchBranchNames(url)
+		if err != nil {
+			return nil, err
+		}
+		if len(branchNames) == 0 {
+			break
+		}
+		for _, branch := range branchNames {
+			if strings.HasPrefix(branch, "release-1.") {
+				version := strings.TrimPrefix(branch, "release-")
+				if compareVersions(version, minVersion) >= 0 {
+					versions = append(versions, version)
+				}
+			}
+		}
+		page++
+	}
+	if len(versions) == 0 {
+		return nil, errors.New("no Kubernetes versions found")
+	}
+	// Remove duplicates and sort
+	versionSet := make(map[string]struct{})
+	for _, v := range versions {
+		versionSet[v] = struct{}{}
+	}
+	versions = nil
+	for v := range versionSet {
+		versions = append(versions, v)
+	}
+	sort.Slice(versions, func(i, j int) bool {
+		return compareVersions(versions[i], versions[j]) < 0
+	})
+	return versions, nil
+}
+
+// Fetch branch names from GitHub API
+func fetchBranchNames(url string) ([]string, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return nil, fmt.Errorf("HTTP GET error: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return nil, fmt.Errorf("non-200 HTTP status: %d", resp.StatusCode)
+	}
+
+	var branches []struct {
+		Name string `json:"name"`
+	}
+	if err := json.NewDecoder(resp.Body).Decode(&branches); err != nil {
+		return nil, fmt.Errorf("decoding JSON error: %w", err)
+	}
+
+	var branchNames []string
+	for _, branch := range branches {
+		branchNames = append(branchNames, branch.Name)
+	}
+	return branchNames, nil
+}
+
+func fetchCoreDNSVersions(versions []string) (map[string]string, error) {
+	versionMap := make(map[string]string)
+	re := regexp.MustCompile(`CoreDNSVersion\s*=\s*"([^"]+)"`)
+
+	for _, k8sVersion := range versions {
+		branch := "release-" + k8sVersion
+		url := fmt.Sprintf(constantsURLTemplate, branch)
+		coreDNSVersion, err := extractCoreDNSVersion(url, re)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "Warning: Failed for Kubernetes %s: %v\n", k8sVersion, err)
+			continue
+		}
+		versionMap[k8sVersion] = coreDNSVersion
+	}
+
+	if len(versionMap) == 0 {
+		return nil, errors.New("no CoreDNS versions found")
+	}
+
+	return versionMap, nil
+}
+
+func extractCoreDNSVersion(url string, re *regexp.Regexp) (string, error) {
+	resp, err := http.Get(url)
+	if err != nil {
+		return "", fmt.Errorf("HTTP GET error: %w", err)
+	}
+	defer resp.Body.Close()
+
+	if resp.StatusCode != http.StatusOK {
+		return "", fmt.Errorf("non-200 HTTP status: %d", resp.StatusCode)
+	}
+
+	bodyBytes, err := io.ReadAll(resp.Body)
+	if err != nil {
+		return "", fmt.Errorf("reading body error: %w", err)
+	}
+
+	matches := re.FindStringSubmatch(string(bodyBytes))
+	if len(matches) != 2 {
+		return "", errors.New("CoreDNSVersion not found")
+	}
+
+	return matches[1], nil
+}
+
+func generateGoFile(versionMap map[string]string, outputPath string) error {
+	data := prepareTemplateData(versionMap)
+
+	tmpl, err := template.New("versionMapping").Parse(goTemplate)
+	if err != nil {
+		return fmt.Errorf("parsing template error: %w", err)
+	}
+
+	var buf bytes.Buffer
+	if err := tmpl.Execute(&buf, data); err != nil {
+		return fmt.Errorf("executing template error: %w", err)
+	}
+
+	formattedSrc, err := format.Source(buf.Bytes())
+	if err != nil {
+		return fmt.Errorf("formatting source code error: %w", err)
+	}
+
+	if err := os.MkdirAll(path.Dir(outputPath), os.ModePerm); err != nil {
+		return fmt.Errorf("creating directories error: %w", err)
+	}
+
+	if err := os.WriteFile(outputPath, formattedSrc, 0644); err != nil {
+		return fmt.Errorf("writing file error: %w", err)
+	}
+
+	return nil
+}
+
+func prepareTemplateData(versionMap map[string]string) map[string]interface{} {
+	type Const struct {
+		Name    string
+		Version string
+	}
+
+	var k8sConstants []Const
+	var coreDNSConstants []Const
+	type versionMapEntry struct {
+		KubernetesVersion string
+		KubernetesConst   string
+		CoreDNSConst      string
+	}
+	var versionMapList []versionMapEntry
+
+	// Maps for deduplication
+	k8sConstMap := make(map[string]string)
+	coreDNSConstMap := make(map[string]string)
+
+	// Collect unique CoreDNS versions
+	uniqueCoreDNSVersions := make(map[string]bool)
+	for _, coreDNSVersion := range versionMap {
+		uniqueCoreDNSVersions[coreDNSVersion] = true
+	}
+
+	// Generate constants for Kubernetes versions
+	for k8sVersion := range versionMap {
+		constName := versionToConst("Kubernetes", k8sVersion)
+		k8sConstMap[k8sVersion] = constName
+	}
+
+	// Generate constants for CoreDNS versions
+	for coreDNSVersion := range uniqueCoreDNSVersions {
+		constName := versionToConst("CoreDNS", coreDNSVersion)
+		coreDNSConstMap[coreDNSVersion] = constName
+	}
+
+	// Prepare constants slices
+	for k8sVersion, constName := range k8sConstMap {
+		k8sConstants = append(k8sConstants, Const{Name: constName, Version: k8sVersion})
+	}
+	for coreDNSVersion, constName := range coreDNSConstMap {
+		coreDNSConstants = append(coreDNSConstants, Const{Name: constName, Version: coreDNSVersion})
+	}
+
+	// Sort constants
+	sort.Slice(k8sConstants, func(i, j int) bool {
+		return compareVersions(k8sConstants[i].Version, k8sConstants[j].Version) < 0
+	})
+	sort.Slice(coreDNSConstants, func(i, j int) bool {
+		return compareVersions(coreDNSConstants[i].Version, coreDNSConstants[j].Version) < 0
+	})
+
+	// Map Kubernetes constants to CoreDNS constants
+	for k8sVersion, coreDNSVersion := range versionMap {
+		versionMapList = append(versionMapList, versionMapEntry{
+			KubernetesVersion: k8sVersion,
+			KubernetesConst:   k8sConstMap[k8sVersion],
+			CoreDNSConst:      coreDNSConstMap[coreDNSVersion],
+		})
+	}
+
+	// Sort version map
+	sort.Slice(versionMapList, func(i, j int) bool {
+		return compareVersions(versionMapList[i].KubernetesVersion, versionMapList[j].KubernetesVersion) < 0
+	})
+
+	data := map[string]interface{}{
+		"KubernetesConstants": k8sConstants,
+		"CoreDNSConstants":    coreDNSConstants,
+		"VersionMap":          versionMapList,
+	}
+
+	return data
+}
+
+func versionToConst(prefix, version string) string {
+	// Remove 'v' prefix if present
+	version = strings.TrimPrefix(version, "v")
+	// Replace dots with underscores
+	version = strings.ReplaceAll(version, ".", "_")
+	// Prepend the prefix and 'V'
+	return prefix + "_V" + version
+}
+
+// compareVersions compares version strings numerically
+func compareVersions(a, b string) int {
+	aParts := strings.Split(a, ".")
+	bParts := strings.Split(b, ".")
+	maxParts := len(aParts)
+	if len(bParts) > maxParts {
+		maxParts = len(bParts)
+	}
+	for i := 0; i < maxParts; i++ {
+		var aPart, bPart int
+		if i < len(aParts) {
+			fmt.Sscanf(aParts[i], "%d", &aPart)
+		}
+		if i < len(bParts) {
+			fmt.Sscanf(bParts[i], "%d", &bPart)
+		}
+		if aPart != bPart {
+			if aPart < bPart {
+				return -1
+			}
+			return 1
+		}
+	}
+	return 0
+}

hack/tools/coredns-versions/main.go

@@ -55,3 +55,8 @@ api.sync.%: ; $(info $(M) syncing external API: $(PROVIDER_MODULE_$*)/$(PROVIDER
 	  $(PROVIDER_API_DIR)
 	find $(PROVIDER_API_DIR) -type d -exec chmod 0755 {} \;
 	find $(PROVIDER_API_DIR) -type f -exec chmod 0644 {} \;
+
+.PHONY: coredns.sync
+coredns.sync: ## Syncs the Kubernetes version to CoreDNS version mapping used in the cluster upgrade
+coredns.sync: ; $(info $(M) syncing CoreDNS version mapping)
+	go run hack/tools/coredns-versions/main.go