[client] Add IPv6 reverse DNS and host configurator support

client/internal/dns.go

@@ -12,52 +12,83 @@ import (
 	nbdns "github.com/netbirdio/netbird/dns"
 )
 
-func createPTRRecord(aRecord nbdns.SimpleRecord, prefix netip.Prefix) (nbdns.SimpleRecord, bool) {
-	ip, err := netip.ParseAddr(aRecord.RData)
+func createPTRRecord(record nbdns.SimpleRecord, prefix netip.Prefix) (nbdns.SimpleRecord, bool) {
+	ip, err := netip.ParseAddr(record.RData)
 	if err != nil {
-		log.Warnf("failed to parse IP address %s: %v", aRecord.RData, err)
+		log.Warnf("failed to parse IP address %s: %v", record.RData, err)
 		return nbdns.SimpleRecord{}, false
 	}
 
+	ip = ip.Unmap()
 	if !prefix.Contains(ip) {
 		return nbdns.SimpleRecord{}, false
 	}
 
-	ipOctets := strings.Split(ip.String(), ".")
-	slices.Reverse(ipOctets)
-	rdnsName := dns.Fqdn(strings.Join(ipOctets, ".") + ".in-addr.arpa")
+	var rdnsName string
+	if ip.Is4() {
+		octets := strings.Split(ip.String(), ".")
+		slices.Reverse(octets)
+		rdnsName = dns.Fqdn(strings.Join(octets, ".") + ".in-addr.arpa")
+	} else {
+		// Expand to full 32 nibbles in reverse order (LSB first) per RFC 3596.
+		raw := ip.As16()
+		nibbles := make([]string, 32)
+		for i := 0; i < 16; i++ {
+			nibbles[31-i*2] = fmt.Sprintf("%x", raw[i]>>4)
+			nibbles[31-i*2-1] = fmt.Sprintf("%x", raw[i]&0x0f)
+		}
+		rdnsName = dns.Fqdn(strings.Join(nibbles, ".") + ".ip6.arpa")
+	}
 
 	return nbdns.SimpleRecord{
 		Name:  rdnsName,
 		Type:  int(dns.TypePTR),
-		Class: aRecord.Class,
-		TTL:   aRecord.TTL,
-		RData: dns.Fqdn(aRecord.Name),
+		Class: record.Class,
+		TTL:   record.TTL,
+		RData: dns.Fqdn(record.Name),
 	}, true
 }
 
-// generateReverseZoneName creates the reverse DNS zone name for a given network
+// generateReverseZoneName creates the reverse DNS zone name for a given network.
+// For IPv4 it produces an in-addr.arpa name, for IPv6 an ip6.arpa name.
 func generateReverseZoneName(network netip.Prefix) (string, error) {
-	networkIP := network.Masked().Addr()
+	networkIP := network.Masked().Addr().Unmap()
+	bits := network.Bits()
+
+	if networkIP.Is4() {
+		// Round up to nearest byte.
+		octetsToUse := (bits + 7) / 8
+
+		octets := strings.Split(networkIP.String(), ".")
+		if octetsToUse > len(octets) {
+			return "", fmt.Errorf("invalid network mask size for reverse DNS: %d", bits)
+		}
+
+		reverseOctets := make([]string, octetsToUse)
+		for i := 0; i < octetsToUse; i++ {
+			reverseOctets[octetsToUse-1-i] = octets[i]
+		}
 
-	if !networkIP.Is4() {
-		return "", fmt.Errorf("reverse DNS is only supported for IPv4 networks, got: %s", networkIP)
+		return dns.Fqdn(strings.Join(reverseOctets, ".") + ".in-addr.arpa"), nil
 	}
 
-	// round up to nearest byte
-	octetsToUse := (network.Bits() + 7) / 8
+	// IPv6: round up to nearest nibble (4-bit boundary).
+	nibblesToUse := (bits + 3) / 4
 
-	octets := strings.Split(networkIP.String(), ".")
-	if octetsToUse > len(octets) {
-		return "", fmt.Errorf("invalid network mask size for reverse DNS: %d", network.Bits())
+	raw := networkIP.As16()
+	allNibbles := make([]string, 32)
+	for i := 0; i < 16; i++ {
+		allNibbles[i*2] = fmt.Sprintf("%x", raw[i]>>4)
+		allNibbles[i*2+1] = fmt.Sprintf("%x", raw[i]&0x0f)
 	}
 
-	reverseOctets := make([]string, octetsToUse)
-	for i := 0; i < octetsToUse; i++ {
-		reverseOctets[octetsToUse-1-i] = octets[i]
+	// Take the first nibblesToUse nibbles (network portion), reverse them.
+	used := make([]string, nibblesToUse)
+	for i := 0; i < nibblesToUse; i++ {
+		used[nibblesToUse-1-i] = allNibbles[i]
 	}
 
-	return dns.Fqdn(strings.Join(reverseOctets, ".") + ".in-addr.arpa"), nil
+	return dns.Fqdn(strings.Join(used, ".") + ".ip6.arpa"), nil
 }
 
 // zoneExists checks if a zone with the given name already exists in the configuration
@@ -71,7 +102,7 @@ func zoneExists(config *nbdns.Config, zoneName string) bool {
 	return false
 }
 
-// collectPTRRecords gathers all PTR records for the given network from A records
+// collectPTRRecords gathers all PTR records for the given network from A and AAAA records.
 func collectPTRRecords(config *nbdns.Config, prefix netip.Prefix) []nbdns.SimpleRecord {
 	var records []nbdns.SimpleRecord
 
@@ -80,7 +111,7 @@ func collectPTRRecords(config *nbdns.Config, prefix netip.Prefix) []nbdns.Simple
 			continue
 		}
 		for _, record := range zone.Records {
-			if record.Type != int(dns.TypeA) {
+			if record.Type != int(dns.TypeA) && record.Type != int(dns.TypeAAAA) {
 				continue
 			}
 

client/internal/dns/host_darwin.go

@@ -298,6 +298,7 @@ func (s *systemConfigurator) getSystemDNSSettings() (SystemDNSSettings, error) {
 			if ip, err := netip.ParseAddr(address); err == nil && !ip.IsUnspecified() {
 				ip = ip.Unmap()
 				serverAddresses = append(serverAddresses, ip)
+				// Prefer the first IPv4 server as ServerIP since our DNS listener is IPv4.
 				if !dnsSettings.ServerIP.IsValid() && ip.Is4() {
 					dnsSettings.ServerIP = ip
 				}

client/internal/dns/network_manager_unix.go

@@ -110,8 +110,15 @@ func (n *networkManagerDbusConfigurator) applyDNSConfig(config HostDNSConfig, st
 
 	connSettings.cleanDeprecatedSettings()
 
-	convDNSIP := binary.LittleEndian.Uint32(config.ServerIP.AsSlice())
-	connSettings[networkManagerDbusIPv4Key][networkManagerDbusDNSKey] = dbus.MakeVariant([]uint32{convDNSIP})
+	ipKey := networkManagerDbusIPv4Key
+	if config.ServerIP.Is6() {
+		ipKey = networkManagerDbusIPv6Key
+		raw := config.ServerIP.As16()
+		connSettings[ipKey][networkManagerDbusDNSKey] = dbus.MakeVariant([][]byte{raw[:]})
+	} else {
+		convDNSIP := binary.LittleEndian.Uint32(config.ServerIP.AsSlice())
+		connSettings[ipKey][networkManagerDbusDNSKey] = dbus.MakeVariant([]uint32{convDNSIP})
+	}
 	var (
 		searchDomains []string
 		matchDomains  []string
@@ -146,8 +153,8 @@ func (n *networkManagerDbusConfigurator) applyDNSConfig(config HostDNSConfig, st
 		n.routingAll = false
 	}
 
-	connSettings[networkManagerDbusIPv4Key][networkManagerDbusDNSPriorityKey] = dbus.MakeVariant(priority)
-	connSettings[networkManagerDbusIPv4Key][networkManagerDbusDNSSearchKey] = dbus.MakeVariant(newDomainList)
+	connSettings[ipKey][networkManagerDbusDNSPriorityKey] = dbus.MakeVariant(priority)
+	connSettings[ipKey][networkManagerDbusDNSSearchKey] = dbus.MakeVariant(newDomainList)
 
 	state := &ShutdownState{
 		ManagerType: networkManager,

client/internal/dns/systemd_linux.go

@@ -90,8 +90,12 @@ func (s *systemdDbusConfigurator) supportCustomPort() bool {
 }
 
 func (s *systemdDbusConfigurator) applyDNSConfig(config HostDNSConfig, stateManager *statemanager.Manager) error {
+	family := int32(unix.AF_INET)
+	if config.ServerIP.Is6() {
+		family = unix.AF_INET6
+	}
 	defaultLinkInput := systemdDbusDNSInput{
-		Family:  unix.AF_INET,
+		Family:  family,
 		Address: config.ServerIP.AsSlice(),
 	}
 	if err := s.callLinkMethod(systemdDbusSetDNSMethodSuffix, []systemdDbusDNSInput{defaultLinkInput}); err != nil {

client/internal/dns/upstream_ios.go

@@ -21,6 +21,8 @@ type upstreamResolverIOS struct {
 	*upstreamResolverBase
 	lIP           netip.Addr
 	lNet          netip.Prefix
+	lIPv6         netip.Addr
+	lNetV6        netip.Prefix
 	interfaceName string
 }
 
@@ -37,6 +39,8 @@ func newUpstreamResolver(
 		upstreamResolverBase: upstreamResolverBase,
 		lIP:                  wgIface.Address().IP,
 		lNet:                 wgIface.Address().Network,
+		lIPv6:                wgIface.Address().IPv6,
+		lNetV6:               wgIface.Address().IPv6Net,
 		interfaceName:        wgIface.Name(),
 	}
 	ios.upstreamClient = ios
@@ -66,12 +70,23 @@ func (u *upstreamResolverIOS) exchange(ctx context.Context, upstream string, r *
 		upstreamIP = upstreamIP.Unmap()
 	}
 	needsPrivate := u.lNet.Contains(upstreamIP) ||
+		u.lNetV6.Contains(upstreamIP) ||
 		(u.routeMatch != nil && u.routeMatch(upstreamIP))
 	if needsPrivate {
-		log.Debugf("using private client to query %s via upstream %s", r.Question[0].Name, upstream)
-		client, err = GetClientPrivate(u.lIP, u.interfaceName, timeout)
-		if err != nil {
-			return nil, 0, fmt.Errorf("create private client: %s", err)
+		var bindIP netip.Addr
+		switch {
+		case upstreamIP.Is6() && u.lIPv6.IsValid():
+			bindIP = u.lIPv6
+		case upstreamIP.Is4() && u.lIP.IsValid():
+			bindIP = u.lIP
+		}
+
+		if bindIP.IsValid() {
+			log.Debugf("using private client to query %s via upstream %s", r.Question[0].Name, upstream)
+			client, err = GetClientPrivate(bindIP, u.interfaceName, timeout)
+			if err != nil {
+				return nil, 0, fmt.Errorf("create private client: %s", err)
+			}
 		}
 	}
 
@@ -88,16 +103,18 @@ func GetClientPrivate(ip netip.Addr, interfaceName string, dialTimeout time.Dura
 		return nil, err
 	}
 
+	proto, opt := unix.IPPROTO_IP, unix.IP_BOUND_IF
+	if ip.Is6() {
+		proto, opt = unix.IPPROTO_IPV6, unix.IPV6_BOUND_IF
+	}
+
 	dialer := &net.Dialer{
-		LocalAddr: &net.UDPAddr{
-			IP:   ip.AsSlice(),
-			Port: 0, // Let the OS pick a free port
-		},
+		LocalAddr: net.UDPAddrFromAddrPort(netip.AddrPortFrom(ip, 0)),
 		Timeout: dialTimeout,
 		Control: func(network, address string, c syscall.RawConn) error {
 			var operr error
 			fn := func(s uintptr) {
-				operr = unix.SetsockoptInt(int(s), unix.IPPROTO_IP, unix.IP_BOUND_IF, index)
+				operr = unix.SetsockoptInt(int(s), proto, opt, index)
 			}
 
 			if err := c.Control(fn); err != nil {

client/internal/dns_test.go

@@ -0,0 +1,138 @@
+package internal
+
+import (
+	"net/netip"
+	"testing"
+
+	"github.com/miekg/dns"
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+
+	nbdns "github.com/netbirdio/netbird/dns"
+)
+
+func TestCreatePTRRecord_IPv4(t *testing.T) {
+	record := nbdns.SimpleRecord{
+		Name:  "peer1.netbird.cloud.",
+		Type:  int(dns.TypeA),
+		Class: nbdns.DefaultClass,
+		TTL:   300,
+		RData: "100.64.0.5",
+	}
+	prefix := netip.MustParsePrefix("100.64.0.0/16")
+
+	ptr, ok := createPTRRecord(record, prefix)
+	require.True(t, ok)
+	assert.Equal(t, "5.0.64.100.in-addr.arpa.", ptr.Name)
+	assert.Equal(t, int(dns.TypePTR), ptr.Type)
+	assert.Equal(t, "peer1.netbird.cloud.", ptr.RData)
+}
+
+func TestCreatePTRRecord_IPv6(t *testing.T) {
+	record := nbdns.SimpleRecord{
+		Name:  "peer1.netbird.cloud.",
+		Type:  int(dns.TypeAAAA),
+		Class: nbdns.DefaultClass,
+		TTL:   300,
+		RData: "fd00:1234:5678::1",
+	}
+	prefix := netip.MustParsePrefix("fd00:1234:5678::/48")
+
+	ptr, ok := createPTRRecord(record, prefix)
+	require.True(t, ok)
+	assert.Equal(t, "1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.0.8.7.6.5.4.3.2.1.0.0.d.f.ip6.arpa.", ptr.Name)
+	assert.Equal(t, int(dns.TypePTR), ptr.Type)
+	assert.Equal(t, "peer1.netbird.cloud.", ptr.RData)
+}
+
+func TestCreatePTRRecord_OutOfRange(t *testing.T) {
+	record := nbdns.SimpleRecord{
+		Name:  "peer1.netbird.cloud.",
+		Type:  int(dns.TypeA),
+		RData: "10.0.0.1",
+	}
+	prefix := netip.MustParsePrefix("100.64.0.0/16")
+
+	_, ok := createPTRRecord(record, prefix)
+	assert.False(t, ok)
+}
+
+func TestGenerateReverseZoneName_IPv4(t *testing.T) {
+	tests := []struct {
+		prefix   string
+		expected string
+	}{
+		{"100.64.0.0/16", "64.100.in-addr.arpa."},
+		{"10.0.0.0/8", "10.in-addr.arpa."},
+		{"192.168.1.0/24", "1.168.192.in-addr.arpa."},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.prefix, func(t *testing.T) {
+			zone, err := generateReverseZoneName(netip.MustParsePrefix(tt.prefix))
+			require.NoError(t, err)
+			assert.Equal(t, tt.expected, zone)
+		})
+	}
+}
+
+func TestGenerateReverseZoneName_IPv6(t *testing.T) {
+	tests := []struct {
+		prefix   string
+		expected string
+	}{
+		{"fd00:1234:5678::/48", "8.7.6.5.4.3.2.1.0.0.d.f.ip6.arpa."},
+		{"fd00::/16", "0.0.d.f.ip6.arpa."},
+		{"fd12:3456:789a:bcde::/64", "e.d.c.b.a.9.8.7.6.5.4.3.2.1.d.f.ip6.arpa."},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.prefix, func(t *testing.T) {
+			zone, err := generateReverseZoneName(netip.MustParsePrefix(tt.prefix))
+			require.NoError(t, err)
+			assert.Equal(t, tt.expected, zone)
+		})
+	}
+}
+
+func TestCollectPTRRecords_BothFamilies(t *testing.T) {
+	config := &nbdns.Config{
+		CustomZones: []nbdns.CustomZone{
+			{
+				Domain: "netbird.cloud.",
+				Records: []nbdns.SimpleRecord{
+					{Name: "peer1.netbird.cloud.", Type: int(dns.TypeA), RData: "100.64.0.1"},
+					{Name: "peer1.netbird.cloud.", Type: int(dns.TypeAAAA), RData: "fd00::1"},
+					{Name: "peer2.netbird.cloud.", Type: int(dns.TypeA), RData: "100.64.0.2"},
+				},
+			},
+		},
+	}
+
+	v4Records := collectPTRRecords(config, netip.MustParsePrefix("100.64.0.0/16"))
+	assert.Len(t, v4Records, 2, "should collect 2 A record PTRs for the v4 prefix")
+
+	v6Records := collectPTRRecords(config, netip.MustParsePrefix("fd00::/64"))
+	assert.Len(t, v6Records, 1, "should collect 1 AAAA record PTR for the v6 prefix")
+}
+
+func TestAddReverseZone_IPv6(t *testing.T) {
+	config := &nbdns.Config{
+		CustomZones: []nbdns.CustomZone{
+			{
+				Domain: "netbird.cloud.",
+				Records: []nbdns.SimpleRecord{
+					{Name: "peer1.netbird.cloud.", Type: int(dns.TypeAAAA), RData: "fd00:1234:5678::1"},
+				},
+			},
+		},
+	}
+
+	addReverseZone(config, netip.MustParsePrefix("fd00:1234:5678::/48"))
+
+	require.Len(t, config.CustomZones, 2)
+	reverseZone := config.CustomZones[1]
+	assert.Equal(t, "8.7.6.5.4.3.2.1.0.0.d.f.ip6.arpa.", reverseZone.Domain)
+	assert.Len(t, reverseZone.Records, 1)
+	assert.Equal(t, int(dns.TypePTR), reverseZone.Records[0].Type)
+}