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

client/firewall/nftables/manager_linux.go

@@ -36,17 +36,25 @@ func Create(context context.Context, wgIface iFaceMapper) (*Manager, error) {
 		wgIface: wgIface,
 	}
 
-	workTable, err := m.createWorkTable()
+	workTable, err := m.createWorkTable(nftables.TableFamilyIPv4)
 	if err != nil {
 		return nil, err
 	}
 
-	m.router, err = newRouter(context, workTable)
+	var workTable6 *nftables.Table
+	if wgIface.Address6() != nil {
+		workTable6, err = m.createWorkTable(nftables.TableFamilyIPv6)
+		if err != nil {
+			return nil, err
+		}
+	}
+
+	m.router, err = newRouter(context, workTable, workTable6)
 	if err != nil {
 		return nil, err
 	}
 
-	m.aclManager, err = newAclManager(workTable, wgIface, m.router.RouteingFwChainName())
+	m.aclManager, err = newAclManager(workTable, workTable6, wgIface, m.router.RouteingFwChainName())
 	if err != nil {
 		return nil, err
 	}
@@ -54,6 +62,54 @@ func Create(context context.Context, wgIface iFaceMapper) (*Manager, error) {
 	return m, nil
 }
 
+// Resets the IPv6 Firewall Table to adapt to changes in IP addresses
+func (m *Manager) ResetV6Firewall() error {
+
+	// First, prepare reset by deleting all currently active rules.
+	workTable6, err := m.aclManager.PrepareV6Reset()
+	if err != nil {
+		return err
+	}
+
+	// Depending on whether we now have an IPv6 address, we now either have to create/empty an IPv6 table, or delete it.
+	if m.wgIface.Address6() != nil {
+		if workTable6 != nil {
+			m.rConn.FlushTable(workTable6)
+		} else {
+			workTable6, err = m.createWorkTable(nftables.TableFamilyIPv6)
+			if err != nil {
+				return err
+			}
+		}
+	} else {
+		m.rConn.DelTable(workTable6)
+		workTable6 = nil
+	}
+	err = m.rConn.Flush()
+	if err != nil {
+		return err
+	}
+
+	// Restore routing rules.
+	err = m.router.RestoreAfterV6Reset(workTable6)
+	if err != nil {
+		return err
+	}
+
+	// Restore basic firewall chains (needs to happen after routes because chains from router must exist).
+	// Does not restore rules (will be done later during the update, when UpdateFiltering will be called at some point)
+	err = m.aclManager.ReinitAfterV6Reset(workTable6)
+	if err != nil {
+		return err
+	}
+
+	return m.rConn.Flush()
+}
+
+func (m *Manager) V6Active() bool {
+	return m.aclManager.v6Active
+}
+
 // AddFiltering rule to the firewall
 //
 // If comment argument is empty firewall manager should set
@@ -72,7 +128,7 @@ func (m *Manager) AddFiltering(
 	defer m.mutex.Unlock()
 
 	rawIP := ip.To4()
-	if rawIP == nil {
+	if rawIP == nil && m.wgIface.Address6() == nil {
 		return nil, fmt.Errorf("unsupported IP version: %s", ip.String())
 	}
 
@@ -114,6 +170,8 @@ func (m *Manager) AllowNetbird() error {
 	m.mutex.Lock()
 	defer m.mutex.Unlock()
 
+	// Note for devs: When adding IPv6 support to uspfilter, the implementation of createDefaultAllowRules()
+	// must be adjusted to include IPv6 rules.
 	err := m.aclManager.createDefaultAllowRules()
 	if err != nil {
 		return fmt.Errorf("failed to create default allow rules: %v", err)
@@ -211,8 +269,8 @@ func (m *Manager) Flush() error {
 	return m.aclManager.Flush()
 }
 
-func (m *Manager) createWorkTable() (*nftables.Table, error) {
-	tables, err := m.rConn.ListTablesOfFamily(nftables.TableFamilyIPv4)
+func (m *Manager) createWorkTable(tableFamily nftables.TableFamily) (*nftables.Table, error) {
+	tables, err := m.rConn.ListTablesOfFamily(tableFamily)
 	if err != nil {
 		return nil, fmt.Errorf("list of tables: %w", err)
 	}
@@ -223,7 +281,7 @@ func (m *Manager) createWorkTable() (*nftables.Table, error) {
 		}
 	}
 
-	table := m.rConn.AddTable(&nftables.Table{Name: tableName, Family: nftables.TableFamilyIPv4})
+	table := m.rConn.AddTable(&nftables.Table{Name: tableName, Family: tableFamily})
 	err = m.rConn.Flush()
 	return table, err
 }