fix(update): do not update if public IP is part of multiple IPs found in records

internal/update/helpers.go

@@ -32,14 +32,22 @@ func (s *Service) logInfoNoLookupUpdate(hostname, ipKind string, lastIP, ip neti
 		ipKind, hostname, lastIP, ipKind, ip))
 }
 
-func (s *Service) logDebugLookupSkip(hostname, ipKind string, recordIP, ip netip.Addr) {
+func (s *Service) logDebugLookupSkip(hostname, ipKind string, recordIPs []netip.Addr, ip netip.Addr) {
 	s.logger.Debug(fmt.Sprintf("%s address of %s is %s and your %s address"+
-		" is %s, skipping update", ipKind, hostname, recordIP, ipKind, ip))
+		" is %s, skipping update", ipKind, hostname, ipsToString(recordIPs), ipKind, ip))
 }
 
-func (s *Service) logInfoLookupUpdate(hostname, ipKind string, recordIP, ip netip.Addr) {
-	s.logger.Info(fmt.Sprintf("%s address of %s is %s and your %s address  is %s",
-		ipKind, hostname, recordIP, ipKind, ip))
+func (s *Service) logInfoLookupUpdate(hostname, ipKind string, recordIPs []netip.Addr, ip netip.Addr) {
+	s.logger.Info(fmt.Sprintf("%s address of %s is %s and your %s address is %s",
+		ipKind, hostname, ipsToString(recordIPs), ipKind, ip))
+}
+
+func ipsToString(ips []netip.Addr) string {
+	ipStrings := make([]string, len(ips))
+	for i, ip := range ips {
+		ipStrings[i] = ip.String()
+	}
+	return strings.Join(ipStrings, ", ")
 }
 
 type joinedErrors struct { //nolint:errname

internal/update/service.go

@@ -52,7 +52,7 @@ func NewService(db Database, updater UpdaterInterface, ipGetter PublicIPFetcher,
 }
 
 func (s *Service) lookupIPsResilient(ctx context.Context, hostname string, tries int) (
-	ipv4 netip.Addr, ipv6 netip.Addr, err error,
+	ipv4, ipv6 []netip.Addr, err error,
 ) {
 	for range tries {
 		ipv4, ipv6, err = s.lookupIPs(ctx, hostname)
@@ -60,34 +60,29 @@ func (s *Service) lookupIPsResilient(ctx context.Context, hostname string, tries
 			return ipv4, ipv6, nil
 		}
 	}
-	return netip.Addr{}, netip.Addr{}, err
+	return nil, nil, err
 }
 
 func (s *Service) lookupIPs(ctx context.Context, hostname string) (
-	ipv4 netip.Addr, ipv6 netip.Addr, err error,
+	ipv4, ipv6 []netip.Addr, err error,
 ) {
 	netIPs, err := s.resolver.LookupIP(ctx, "ip", hostname)
 	if err != nil {
-		return netip.Addr{}, netip.Addr{}, err
+		return nil, nil, err
 	}
-	ips := make([]netip.Addr, len(netIPs))
-	for i, netIP := range netIPs {
+
+	ipv4 = make([]netip.Addr, 0, len(netIPs))
+	ipv6 = make([]netip.Addr, 0, len(netIPs))
+	for _, netIP := range netIPs {
 		switch {
 		case netIP == nil:
 		case netIP.To4() != nil:
-			ips[i] = netip.AddrFrom4([4]byte(netIP.To4()))
+			ipv4 = append(ipv4, netip.AddrFrom4([4]byte(netIP.To4())))
 		default: // IPv6
-			ips[i] = netip.AddrFrom16([16]byte(netIP.To16()))
+			ipv6 = append(ipv6, netip.AddrFrom16([16]byte(netIP.To16())))
 		}
 	}
 
-	for _, ip := range ips {
-		if ip.Is6() {
-			ipv6 = ip
-		} else {
-			ipv4 = ip
-		}
-	}
 	return ipv4, ipv6, nil
 }
 
@@ -204,7 +199,7 @@ func (s *Service) shouldUpdateRecordWithLookup(ctx context.Context, hostname str
 	ipVersion ipversion.IPVersion, publicIP netip.Addr,
 ) (update bool) {
 	const tries = 5
-	recordIPv4, recordIPv6, err := s.lookupIPsResilient(ctx, hostname, tries)
+	recordIPv4s, recordIPv6s, err := s.lookupIPsResilient(ctx, hostname, tries)
 	if err != nil {
 		ctxErr := ctx.Err()
 		if ctxErr != nil {
@@ -216,18 +211,27 @@ func (s *Service) shouldUpdateRecordWithLookup(ctx context.Context, hostname str
 	}
 
 	ipKind := ipVersionToIPKind(ipVersion)
-	recordIP := recordIPv4
+	recordIPs := recordIPv4s
 	if publicIP.Is6() {
-		recordIP = recordIPv6
+		recordIPs = recordIPv6s
 	}
-	recordIP = getIPMatchingVersion(recordIP, recordIPv4, recordIPv6, ipVersion)
+	recordIPs = getIPsMatchingVersion(recordIPs, recordIPv4s, recordIPv6s, ipVersion)
 
-	if publicIP.IsValid() && publicIP.Compare(recordIP) != 0 {
+	if publicIP.IsValid() && !ipsContainsIP(recordIPs, publicIP) {
 		// Note if the recordIP is not valid (not found), we want to update.
-		s.logInfoLookupUpdate(hostname, ipKind, recordIP, publicIP)
+		s.logInfoLookupUpdate(hostname, ipKind, recordIPs, publicIP)
 		return true
 	}
-	s.logDebugLookupSkip(hostname, ipKind, recordIP, publicIP)
+	s.logDebugLookupSkip(hostname, ipKind, recordIPs, publicIP)
+	return false
+}
+
+func ipsContainsIP(ips []netip.Addr, ip netip.Addr) bool {
+	for _, ip2 := range ips {
+		if ip.Compare(ip2) == 0 {
+			return true
+		}
+	}
 	return false
 }
 
@@ -239,8 +243,22 @@ func getIPMatchingVersion(ip, ipv4, ipv6 netip.Addr, ipVersion ipversion.IPVersi
 		return ipv4
 	case ipversion.IP6:
 		return ipv6
+	default:
+		panic(fmt.Sprintf("invalid IP version %s", ipVersion))
+	}
+}
+
+func getIPsMatchingVersion(ip, ipv4, ipv6 []netip.Addr, ipVersion ipversion.IPVersion) []netip.Addr {
+	switch ipVersion {
+	case ipversion.IP4or6:
+		return ip
+	case ipversion.IP4:
+		return ipv4
+	case ipversion.IP6:
+		return ipv6
+	default:
+		panic(fmt.Sprintf("invalid IP version %s", ipVersion))
 	}
-	return netip.Addr{}
 }
 
 func setInitialUpToDateStatus(db Database, id uint, updateIP netip.Addr, now time.Time) error {