fix: split long TXT records into 255-character chunks

internal/stackitprovider/helper.go

@@ -71,8 +71,14 @@ func modifyChange(change *endpoint.Endpoint) {
 func getStackitRecordSetPayload(change *endpoint.Endpoint) stackitdnsclient.CreateRecordSetPayload {
 	records := make([]stackitdnsclient.RecordPayload, len(change.Targets))
 	for i := range change.Targets {
+		content := change.Targets[i]
+
+		if change.RecordType == txtRecord {
+			content = formatTXTContent(content)
+		}
+
 		records[i] = stackitdnsclient.RecordPayload{
-			Content: change.Targets[i],
+			Content: content,
 		}
 	}
 
@@ -88,8 +94,14 @@ func getStackitRecordSetPayload(change *endpoint.Endpoint) stackitdnsclient.Crea
 func getStackitPartialUpdateRecordSetPayload(change *endpoint.Endpoint) stackitdnsclient.PartialUpdateRecordSetPayload {
 	records := make([]stackitdnsclient.RecordPayload, len(change.Targets))
 	for i := range change.Targets {
+		content := change.Targets[i]
+
+		if change.RecordType == txtRecord {
+			content = formatTXTContent(content)
+		}
+
 		records[i] = stackitdnsclient.RecordPayload{
-			Content: change.Targets[i],
+			Content: content,
 		}
 	}
 
@@ -126,3 +138,32 @@ func safeTTLToInt32(ttl endpoint.TTL) *int32 {
 
 	return &v
 }
+
+// formatTXTContent splits long TXT records into 255-character chunks separated by spaces.
+func formatTXTContent(content string) string {
+	cleanContent := strings.Trim(content, `"`)
+
+	if len(cleanContent) <= 255 {
+		return content
+	}
+
+	var chunks []string
+	for i := 0; i < len(cleanContent); i += 255 {
+		end := i + 255
+		if end > len(cleanContent) {
+			end = len(cleanContent)
+		}
+		chunks = append(chunks, `"`+cleanContent[i:end]+`"`)
+	}
+
+	return strings.Join(chunks, " ")
+}
+
+// unformatTXTContent reverses the DNS chunking and quoting process.
+func unformatTXTContent(content string) string {
+	if strings.Contains(content, `" "`) {
+		return strings.ReplaceAll(content, `" "`, ``)
+	}
+
+	return content
+}

internal/stackitprovider/helper_test.go

@@ -2,6 +2,7 @@ package stackitprovider
 
 import (
 	"reflect"
+	"strings"
 	"testing"
 
 	stackitdnsclient "github.com/stackitcloud/stackit-sdk-go/services/dns/v1api"
@@ -214,3 +215,100 @@ func TestGetStackitRRSetRecordPatch(t *testing.T) {
 		t.Errorf("getStackitRRSetRecordPatch() = %v, want %v", got, expected)
 	}
 }
+
+func TestFormatTXTContent(t *testing.T) {
+	t.Parallel()
+
+	// Generate strings of exact lengths for testing
+	string255 := strings.Repeat("a", 255)
+	string256 := strings.Repeat("a", 256)
+	string511 := strings.Repeat("a", 511)
+
+	tests := []struct {
+		name    string
+		content string
+		want    string
+	}{
+		{
+			name:    "Short string without quotes",
+			content: "hello world",
+			want:    "hello world",
+		},
+		{
+			name:    "Short string with existing quotes",
+			content: `"hello world"`,
+			want:    `"hello world"`,
+		},
+		{
+			name:    "Exactly 255 characters unquoted",
+			content: string255,
+			want:    string255,
+		},
+		{
+			name:    "Exactly 255 characters quoted",
+			content: `"` + string255 + `"`,
+			want:    `"` + string255 + `"`,
+		},
+		{
+			name:    "256 characters (requires 2 chunks)",
+			content: string256,
+			want:    `"` + string255 + `" "a"`,
+		},
+		{
+			name:    "511 characters (requires 3 chunks)",
+			content: string511,
+			want:    `"` + string255 + `" "` + string255 + `" "a"`,
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			if got := formatTXTContent(tt.content); got != tt.want {
+				t.Errorf("formatTXTContent() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}
+
+func TestUnformatTXTContent(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name    string
+		content string
+		want    string
+	}{
+		{
+			name:    "Unquoted short string",
+			content: "hello world",
+			want:    "hello world",
+		},
+		{
+			name:    "Single chunk quoted string",
+			content: `"hello world"`,
+			want:    `"hello world"`,
+		},
+		{
+			name:    "Two chunk string",
+			content: `"hello" "world"`,
+			want:    `"helloworld"`,
+		},
+		{
+			name:    "Three chunk string",
+			content: `"chunk1" "chunk2" "chunk3"`,
+			want:    `"chunk1chunk2chunk3"`,
+		},
+	}
+
+	for _, tt := range tests {
+		tt := tt
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			if got := unformatTXTContent(tt.content); got != tt.want {
+				t.Errorf("unformatTXTContent() = %v, want %v", got, tt.want)
+			}
+		})
+	}
+}

internal/stackitprovider/records.go

@@ -8,6 +8,8 @@ import (
 	"sigs.k8s.io/external-dns/provider"
 )
 
+const txtRecord = "TXT"
+
 // Records returns resource records.
 func (d *StackitDNSProvider) Records(ctx context.Context) ([]*endpoint.Endpoint, error) {
 	zones, err := d.zoneFetcherClient.zones(ctx)
@@ -114,7 +116,12 @@ func endpointsFromRecords(name, recordType string, ttl endpoint.TTL, records []s
 	for i := range records {
 		rec := &records[i]
 
-		endpoints = append(endpoints, endpoint.NewEndpointWithTTL(name, recordType, ttl, rec.Content))
+		content := rec.Content
+		if recordType == txtRecord {
+			content = unformatTXTContent(content)
+		}
+
+		endpoints = append(endpoints, endpoint.NewEndpointWithTTL(name, recordType, ttl, content))
 	}
 
 	return endpoints