feat(aws-provider): create flag to support sub-domains match parent

The current implementation of external-dns from sig-external-dns does
not support domain filtering (--domain-filter) for sub-domains on Route53,
such as test.sub-domain.domain.com. The function MatchParent was recently
removed from the base code, but it is still necessary for this purpose.
An example of a use case for this support is having a cluster per hosted
zone with a hundred ingress related to that zone with different variants of
sub-domains. With the matchParent function and zone-match-parent flag,
external-dns will now support an extended automatic match for sub-domains.

endpoint/domain_filter.go

@@ -199,3 +199,24 @@ func (df *DomainFilter) UnmarshalJSON(b []byte) error {
 	*df = NewRegexDomainFilter(include, exclude)
 	return nil
 }
+
+func (df DomainFilter) MatchParent(domain string) bool {
+	if matchFilter(df.exclude, domain, false) {
+		return false
+	}
+	if len(df.Filters) == 0 {
+		return true
+	}
+
+	strippedDomain := strings.ToLower(strings.TrimSuffix(domain, "."))
+	for _, filter := range df.Filters {
+		if filter == "" || strings.HasPrefix(filter, ".") {
+			// We don't check parents if the filter is prefixed with "."
+			continue
+		}
+		if strings.HasSuffix(filter, "."+strippedDomain) {
+			return true
+		}
+	}
+	return false
+}

endpoint/domain_filter_test.go

@@ -668,3 +668,104 @@ func deserialize[T any](t *testing.T, serialized map[string]T) DomainFilter {
 
 	return deserialized
 }
+
+func TestDomainFilterMatchParent(t *testing.T) {
+	parentMatchTests := []domainFilterTest{
+		{
+			[]string{"a.example.com."},
+			[]string{},
+			[]string{"example.com"},
+			true,
+			map[string][]string{
+				"include": {"a.example.com"},
+			},
+		},
+		{
+			[]string{" a.example.com "},
+			[]string{},
+			[]string{"example.com"},
+			true,
+			map[string][]string{
+				"include": {"a.example.com"},
+			},
+		},
+		{
+			[]string{""},
+			[]string{},
+			[]string{"example.com"},
+			true,
+			map[string][]string{},
+		},
+		{
+			[]string{".a.example.com."},
+			[]string{},
+			[]string{"example.com"},
+			false,
+			map[string][]string{
+				"include": {".a.example.com"},
+			},
+		},
+		{
+			[]string{"a.example.com.", "b.example.com"},
+			[]string{},
+			[]string{"example.com"},
+			true,
+			map[string][]string{
+				"include": {"a.example.com", "b.example.com"},
+			},
+		},
+		{
+			[]string{"a.example.com"},
+			[]string{},
+			[]string{"b.example.com"},
+			false,
+			map[string][]string{
+				"include": {"a.example.com"},
+			},
+		},
+		{
+			[]string{"example.com"},
+			[]string{},
+			[]string{"example.com"},
+			false,
+			map[string][]string{
+				"include": {"example.com"},
+			},
+		},
+		{
+			[]string{"example.com"},
+			[]string{},
+			[]string{"anexample.com"},
+			false,
+			map[string][]string{
+				"include": {"example.com"},
+			},
+		},
+		{
+			[]string{""},
+			[]string{},
+			[]string{""},
+			true,
+			map[string][]string{},
+		},
+	}
+	for i, tt := range parentMatchTests {
+		t.Run(fmt.Sprintf("%d", i), func(t *testing.T) {
+			domainFilter := NewDomainFilterWithExclusions(tt.domainFilter, tt.exclusions)
+
+			assertSerializes(t, domainFilter, tt.expectedSerialization)
+			deserialized := deserialize(t, map[string][]string{
+				"include": tt.domainFilter,
+				"exclude": tt.exclusions,
+			})
+
+			for _, domain := range tt.domains {
+				assert.Equal(t, tt.expected, domainFilter.MatchParent(domain), "%v", domain)
+				assert.Equal(t, tt.expected, domainFilter.MatchParent(domain+"."), "%v", domain+".")
+
+				assert.Equal(t, tt.expected, deserialized.MatchParent(domain), "deserialized %v", domain)
+				assert.Equal(t, tt.expected, deserialized.MatchParent(domain+"."), "deserialized %v", domain+".")
+			}
+		})
+	}
+}

pkg/apis/externaldns/types.go

@@ -92,6 +92,7 @@ type Config struct {
 	AWSPreferCNAME                     bool
 	AWSZoneCacheDuration               time.Duration
 	AWSSDServiceCleanup                bool
+	AWSZoneMatchParent                 bool
 	AWSDynamoDBRegion                  string
 	AWSDynamoDBTable                   string
 	AzureConfigFile                    string
@@ -257,6 +258,7 @@ var defaultConfig = &Config{
 	AlibabaCloudConfigFile:      "/etc/kubernetes/alibaba-cloud.json",
 	AWSZoneType:                 "",
 	AWSZoneTagFilter:            []string{},
+	AWSZoneMatchParent:          false,
 	AWSAssumeRole:               "",
 	AWSAssumeRoleExternalID:     "",
 	AWSBatchChangeSize:          1000,
@@ -488,6 +490,7 @@ func (cfg *Config) ParseFlags(args []string) error {
 	app.Flag("aws-api-retries", "When using the AWS API, set the maximum number of retries before giving up.").Default(strconv.Itoa(defaultConfig.AWSAPIRetries)).IntVar(&cfg.AWSAPIRetries)
 	app.Flag("aws-prefer-cname", "When using the AWS provider, prefer using CNAME instead of ALIAS (default: disabled)").BoolVar(&cfg.AWSPreferCNAME)
 	app.Flag("aws-zones-cache-duration", "When using the AWS provider, set the zones list cache TTL (0s to disable).").Default(defaultConfig.AWSZoneCacheDuration.String()).DurationVar(&cfg.AWSZoneCacheDuration)
+	app.Flag("aws-zone-match-parent", "Expand limit possible target by sub-domains (default: disabled)").BoolVar(&cfg.AWSZoneMatchParent)
 	app.Flag("aws-sd-service-cleanup", "When using the AWS CloudMap provider, delete empty Services without endpoints (default: disabled)").BoolVar(&cfg.AWSSDServiceCleanup)
 	app.Flag("azure-config-file", "When using the Azure provider, specify the Azure configuration file (required when --provider=azure)").Default(defaultConfig.AzureConfigFile).StringVar(&cfg.AzureConfigFile)
 	app.Flag("azure-resource-group", "When using the Azure provider, override the Azure resource group to use (required when --provider=azure-private-dns)").Default(defaultConfig.AzureResourceGroup).StringVar(&cfg.AzureResourceGroup)

provider/aws/aws.go

@@ -239,8 +239,10 @@ type AWSProvider struct {
 	zoneTypeFilter provider.ZoneTypeFilter
 	// filter hosted zones by tags
 	zoneTagFilter provider.ZoneTagFilter
-	preferCNAME   bool
+	// extend filter for sub-domains in the zone (e.g. first.us-east-1.example.com)
-	zonesCache    *zonesListCache
+	zoneMatchParent bool
+	preferCNAME     bool
+	zonesCache      *zonesListCache
 	// queue for collecting changes to submit them in the next iteration, but after all other changes
 	failedChangesQueue map[string]Route53Changes
 }
@@ -251,6 +253,7 @@ type AWSConfig struct {
 	ZoneIDFilter         provider.ZoneIDFilter
 	ZoneTypeFilter       provider.ZoneTypeFilter
 	ZoneTagFilter        provider.ZoneTagFilter
+	ZoneMatchParent      bool
 	BatchChangeSize      int
 	BatchChangeInterval  time.Duration
 	EvaluateTargetHealth bool
@@ -267,6 +270,7 @@ func NewAWSProvider(awsConfig AWSConfig, client Route53API) (*AWSProvider, error
 		zoneIDFilter:         awsConfig.ZoneIDFilter,
 		zoneTypeFilter:       awsConfig.ZoneTypeFilter,
 		zoneTagFilter:        awsConfig.ZoneTagFilter,
+		zoneMatchParent:      awsConfig.ZoneMatchParent,
 		batchChangeSize:      awsConfig.BatchChangeSize,
 		batchChangeInterval:  awsConfig.BatchChangeInterval,
 		evaluateTargetHealth: awsConfig.EvaluateTargetHealth,
@@ -301,7 +305,12 @@ func (p *AWSProvider) Zones(ctx context.Context) (map[string]*route53.HostedZone
 			}
 
 			if !p.domainFilter.Match(aws.StringValue(zone.Name)) {
-				continue
+				if !p.zoneMatchParent {
+					continue
+				}
+				if !p.domainFilter.MatchParent(aws.StringValue(zone.Name)) {
+					continue
+				}
 			}
 
 			// Only fetch tags if a tag filter was specified