feat(dns): add wildcard record resolution
Implements wildcard DNS resolution with most-specific suffix matching for dns.resolve, dns.resolve.txt, and dns.resolve.all paths. Co-Authored-By: Virgil <virgil@lethean.io>
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Virgil
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dcf8601296
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3 changed files with 253 additions and 0 deletions
3
go.mod
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3
go.mod
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module dappco.re/go/dns
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go 1.22
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186
service.go
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186
service.go
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package dns
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import (
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"fmt"
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"slices"
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"strings"
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"sync"
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)
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type NameRecords struct {
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A []string `json:"a"`
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AAAA []string `json:"aaaa"`
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TXT []string `json:"txt"`
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NS []string `json:"ns"`
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}
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type ResolveAllResult struct {
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A []string `json:"a"`
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AAAA []string `json:"aaaa"`
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TXT []string `json:"txt"`
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NS []string `json:"ns"`
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}
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type Service struct {
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mu sync.RWMutex
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records map[string]NameRecords
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}
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type ServiceOptions struct {
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Records map[string]NameRecords
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}
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func NewService(options ServiceOptions) *Service {
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cached := make(map[string]NameRecords, len(options.Records))
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for name, record := range options.Records {
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cached[normalizeName(name)] = record
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}
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return &Service{
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records: cached,
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}
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}
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func (service *Service) SetRecord(name string, record NameRecords) {
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service.mu.Lock()
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defer service.mu.Unlock()
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service.records[normalizeName(name)] = record
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}
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func (service *Service) RemoveRecord(name string) {
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service.mu.Lock()
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defer service.mu.Unlock()
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delete(service.records, normalizeName(name))
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}
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func (service *Service) Resolve(name string) (ResolveAllResult, bool) {
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record, ok := service.findRecord(name)
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if !ok {
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return ResolveAllResult{}, false
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}
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return resolveResult(record), true
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}
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func (service *Service) ResolveTXT(name string) ([]string, bool) {
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record, ok := service.findRecord(name)
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if !ok {
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return nil, false
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}
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return append([]string(nil), record.TXT...), true
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}
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func (service *Service) ResolveAll(name string) (ResolveAllResult, bool) {
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record, ok := service.findRecord(name)
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if !ok {
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return ResolveAllResult{}, false
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}
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return resolveResult(record), true
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}
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func (service *Service) Health() map[string]any {
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service.mu.RLock()
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defer service.mu.RUnlock()
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return map[string]any{
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"status": "ready",
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"names_cached": len(service.records),
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"tree_root": "stubbed",
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}
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}
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func (service *Service) findRecord(name string) (NameRecords, bool) {
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service.mu.RLock()
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defer service.mu.RUnlock()
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normalized := normalizeName(name)
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if record, ok := service.records[normalized]; ok {
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return record, true
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}
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match, ok := findWildcardMatch(normalized, service.records)
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return match, ok
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}
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func resolveResult(record NameRecords) ResolveAllResult {
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return ResolveAllResult{
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A: append([]string(nil), record.A...),
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AAAA: append([]string(nil), record.AAAA...),
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TXT: append([]string(nil), record.TXT...),
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NS: append([]string(nil), record.NS...),
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}
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}
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func findWildcardMatch(name string, records map[string]NameRecords) (NameRecords, bool) {
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bestMatch := ""
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for candidate := range records {
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if !strings.HasPrefix(candidate, "*.") {
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continue
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}
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suffix := strings.TrimPrefix(candidate, "*.")
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if wildcardMatches(suffix, name) {
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if betterWildcardMatch(candidate, bestMatch) {
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bestMatch = candidate
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}
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}
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}
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if bestMatch == "" {
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return NameRecords{}, false
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}
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return records[bestMatch], true
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}
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func wildcardMatches(suffix, name string) bool {
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parts := strings.Split(suffix, ".")
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if len(parts) == 0 || len(name) <= len(suffix)+1 {
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return false
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}
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if !strings.HasSuffix(name, "."+suffix) {
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return false
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}
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return strings.Count(name[:len(name)-len(suffix)], ".") >= 1
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}
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func betterWildcardMatch(candidate, current string) bool {
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if current == "" {
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return true
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}
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remainingCandidate := strings.TrimPrefix(candidate, "*.")
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remainingCurrent := strings.TrimPrefix(current, "*.")
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if len(remainingCandidate) > len(remainingCurrent) {
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return true
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}
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if len(remainingCandidate) == len(remainingCurrent) {
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return candidate < current
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}
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return false
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}
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func normalizeName(name string) string {
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trimmed := strings.TrimSpace(strings.ToLower(name))
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if trimmed == "" {
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return ""
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}
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if strings.HasSuffix(trimmed, ".") {
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trimmed = strings.TrimSuffix(trimmed, ".")
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}
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return trimmed
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}
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func (service *Service) String() string {
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return fmt.Sprintf("dns.Service{records=%d}", len(service.records))
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}
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func MergeRecords(values ...[]string) []string {
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unique := []string{}
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seen := map[string]bool{}
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for _, batch := range values {
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for _, value := range batch {
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if seen[value] {
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continue
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}
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seen[value] = true
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unique = append(unique, value)
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}
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}
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slices.Sort(unique)
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return unique
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}
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64
service_test.go
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64
service_test.go
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@ -0,0 +1,64 @@
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package dns
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import "testing"
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func TestServiceResolveUsesExactNameBeforeWildcard(t *testing.T) {
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service := NewService(ServiceOptions{
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Records: map[string]NameRecords{
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"*.charon.lthn": {
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A: []string{"10.69.69.165"},
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},
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"gateway.charon.lthn": {
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A: []string{"10.10.10.10"},
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},
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},
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})
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result, ok := service.Resolve("gateway.charon.lthn")
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if !ok {
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t.Fatal("expected exact record to resolve")
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}
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if len(result.A) != 1 || result.A[0] != "10.10.10.10" {
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t.Fatalf("unexpected resolve result: %#v", result.A)
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}
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}
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func TestServiceResolveUsesMostSpecificWildcard(t *testing.T) {
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service := NewService(ServiceOptions{
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Records: map[string]NameRecords{
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"*.lthn": {
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A: []string{"10.0.0.1"},
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},
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"*.charon.lthn": {
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A: []string{"10.0.0.2"},
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},
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},
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})
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result, ok := service.Resolve("gateway.charon.lthn")
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if !ok {
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t.Fatal("expected wildcard record to resolve")
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}
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if len(result.A) != 1 || result.A[0] != "10.0.0.2" {
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t.Fatalf("unexpected wildcard match: %#v", result.A)
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}
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}
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func TestServiceResolveTXTUsesWildcard(t *testing.T) {
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service := NewService(ServiceOptions{
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Records: map[string]NameRecords{
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"*.gateway.charon.lthn": {
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TXT: []string{"v=lthn1 type=gateway"},
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},
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},
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})
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result, ok := service.ResolveTXT("node1.gateway.charon.lthn.")
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if !ok {
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t.Fatal("expected wildcard TXT record")
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}
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if len(result) != 1 || result[0] != "v=lthn1 type=gateway" {
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t.Fatalf("unexpected TXT record: %#v", result)
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}
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}
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