Add support for IPv6 networks (on Linux clients) (#1459)

* Feat add basic support for IPv6 networks

Newly generated networks automatically generate an IPv6 prefix of size
64 within the ULA address range, devices obtain a randomly generated
address within this prefix.

Currently, this is Linux only and does not yet support all features
(routes currently cause an error).

* Fix firewall configuration for IPv6 networks

* Fix routing configuration for IPv6 networks

* Feat provide info on IPv6 support for specific client to mgmt server

* Feat allow configuration of IPv6 support through API, improve stability

* Feat add IPv6 support to new firewall implementation

* Fix peer list item response not containing IPv6 address

* Fix nftables breaking on IPv6 address change

* Fix build issues for non-linux systems

* Fix intermittent disconnections when IPv6 is enabled

* Fix test issues and make some minor revisions

* Fix some more testing issues

* Fix more CI issues due to IPv6

* Fix more testing issues

* Add inheritance of IPv6 enablement status from groups

* Fix IPv6 events not having associated messages

* Address first review comments regarding IPv6 support

* Fix IPv6 table being created even when IPv6 is disabled

Also improved stability of IPv6 route and firewall handling on client side

* Fix IPv6 routes not being removed

* Fix DNS IPv6 issues, limit IPv6 nameservers to IPv6 peers

* Improve code for IPv6 DNS server selection, add AAAA custom records

* Ensure IPv6 routes can only exist for IPv6 routing peers

* Fix IPv6 network generation randomness

* Fix a bunch of compilation issues and test failures

* Replace method calls that are unavailable in Go 1.21

* Fix nil dereference in cleanUpDefaultForwardRules6

* Fix nil pointer dereference when persisting IPv6 network in sqlite

* Clean up of client-side code changes for IPv6

* Fix nil dereference in rule mangling and compilation issues

* Add a bunch of client-side test cases for IPv6

* Fix IPv6 tests running on unsupported environments

* Fix import cycle in tests

* Add missing method SupportsIPv6() for windows

* Require IPv6 default route for IPv6 tests

* Fix panics in routemanager tests on non-linux

* Fix some more route manager tests concerning IPv6

* Add some final client-side tests

* Add IPv6 tests for management code, small fixes

* Fix linting issues

* Fix small test suite issues

* Fix linter issues and builds on macOS and Windows again

* fix builds for iOS because of IPv6 breakage

iface/tun_kernel_linux.go

@@ -19,6 +19,7 @@ import (
 type tunKernelDevice struct {
 	name         string
 	address      WGAddress
+	address6     *WGAddress
 	wgPort       int
 	key          string
 	mtu          int
@@ -31,13 +32,14 @@ type tunKernelDevice struct {
 	udpMux     *bind.UniversalUDPMuxDefault
 }
 
-func newTunDevice(name string, address WGAddress, wgPort int, key string, mtu int, transportNet transport.Net) wgTunDevice {
+func newTunDevice(name string, address WGAddress, address6 *WGAddress, wgPort int, key string, mtu int, transportNet transport.Net) wgTunDevice {
 	ctx, cancel := context.WithCancel(context.Background())
 	return &tunKernelDevice{
 		ctx:          ctx,
 		ctxCancel:    cancel,
 		name:         name,
 		address:      address,
+		address6:     address6,
 		wgPort:       wgPort,
 		key:          key,
 		mtu:          mtu,
@@ -136,6 +138,11 @@ func (t *tunKernelDevice) UpdateAddr(address WGAddress) error {
 	return t.assignAddr()
 }
 
+func (t *tunKernelDevice) UpdateAddr6(address6 *WGAddress) error {
+	t.address6 = address6
+	return t.assignAddr()
+}
+
 func (t *tunKernelDevice) Close() error {
 	if t.link == nil {
 		return nil
@@ -168,6 +175,10 @@ func (t *tunKernelDevice) WgAddress() WGAddress {
 	return t.address
 }
 
+func (t *tunKernelDevice) WgAddress6() *WGAddress {
+	return t.address6
+}
+
 func (t *tunKernelDevice) DeviceName() string {
 	return t.name
 }
@@ -203,6 +214,19 @@ func (t *tunKernelDevice) assignAddr() error {
 	} else if err != nil {
 		return err
 	}
+
+	// Configure the optional additional IPv6 address if available.
+	if t.address6 != nil {
+		log.Debugf("adding IPv6 address %s to interface: %s", t.address6.String(), t.name)
+		addr6, _ := netlink.ParseAddr(t.address6.String())
+		err = netlink.AddrAdd(link, addr6)
+		if os.IsExist(err) {
+			log.Infof("interface %s already has the address: %s", t.name, t.address.String())
+		} else if err != nil {
+			return err
+		}
+	}
+
 	// On linux, the link must be brought up
 	err = netlink.LinkSetUp(link)
 	return err