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/route_linux.go

@@ -26,7 +26,8 @@ const (
 
 // some presets for building nftable rules
 var (
-	zeroXor = binaryutil.NativeEndian.PutUint32(0)
+	zeroXor  = binaryutil.NativeEndian.PutUint32(0)
+	zeroXor6 = []byte{0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0, 0x0}
 
 	exprCounterAccept = []expr.Any{
 		&expr.Counter{},
@@ -39,48 +40,69 @@ var (
 )
 
 type router struct {
-	ctx         context.Context
-	stop        context.CancelFunc
-	conn        *nftables.Conn
-	workTable   *nftables.Table
-	filterTable *nftables.Table
-	chains      map[string]*nftables.Chain
+	ctx          context.Context
+	stop         context.CancelFunc
+	conn         *nftables.Conn
+	workTable    *nftables.Table
+	workTable6   *nftables.Table
+	filterTable  *nftables.Table
+	filterTable6 *nftables.Table
+	chains       map[string]*nftables.Chain
+	chains6      map[string]*nftables.Chain
 	// rules is useful to avoid duplicates and to get missing attributes that we don't have when adding new rules
-	rules                    map[string]*nftables.Rule
-	isDefaultFwdRulesEnabled bool
+	rules                     map[string]*nftables.Rule
+	rules6                    map[string]*nftables.Rule
+	isDefaultFwdRulesEnabled  bool
+	isDefaultFwdRulesEnabled6 bool
 }
 
-func newRouter(parentCtx context.Context, workTable *nftables.Table) (*router, error) {
+func newRouter(parentCtx context.Context, workTable *nftables.Table, workTable6 *nftables.Table) (*router, error) {
 	ctx, cancel := context.WithCancel(parentCtx)
 
 	r := &router{
-		ctx:       ctx,
-		stop:      cancel,
-		conn:      &nftables.Conn{},
-		workTable: workTable,
-		chains:    make(map[string]*nftables.Chain),
-		rules:     make(map[string]*nftables.Rule),
+		ctx:        ctx,
+		stop:       cancel,
+		conn:       &nftables.Conn{},
+		workTable:  workTable,
+		workTable6: workTable6,
+		chains:     make(map[string]*nftables.Chain),
+		chains6:    make(map[string]*nftables.Chain),
+		rules:      make(map[string]*nftables.Rule),
+		rules6:     make(map[string]*nftables.Rule),
 	}
 
 	var err error
-	r.filterTable, err = r.loadFilterTable()
+	r.filterTable, r.filterTable6, err = r.loadFilterTables()
 	if err != nil {
 		if errors.Is(err, errFilterTableNotFound) {
-			log.Warnf("table 'filter' not found for forward rules")
+			log.Warnf("table 'filter' not found for forward rules for one of the supported address families-")
 		} else {
 			return nil, err
 		}
 	}
 
-	err = r.cleanUpDefaultForwardRules()
+	err = r.cleanUpDefaultForwardRules(false)
 	if err != nil {
 		log.Errorf("failed to clean up rules from FORWARD chain: %s", err)
 	}
 
-	err = r.createContainers()
+	err = r.cleanUpDefaultForwardRules(true)
+	if err != nil {
+		log.Errorf("failed to clean up rules from IPv6 FORWARD chain: %s", err)
+	}
+
+	err = r.createContainers(false)
 	if err != nil {
 		log.Errorf("failed to create containers for route: %s", err)
 	}
+
+	if r.workTable6 != nil {
+		err = r.createContainers(true)
+		if err != nil {
+			log.Errorf("failed to create v6 containers for route: %s", err)
+		}
+	}
+
 	return r, err
 }
 
@@ -90,43 +112,99 @@ func (r *router) RouteingFwChainName() string {
 
 // ResetForwardRules cleans existing nftables default forward rules from the system
 func (r *router) ResetForwardRules() {
-	err := r.cleanUpDefaultForwardRules()
+	err := r.cleanUpDefaultForwardRules(false)
+	if err != nil {
+		log.Errorf("failed to reset forward rules: %s", err)
+	}
+	err = r.cleanUpDefaultForwardRules(true)
 	if err != nil {
 		log.Errorf("failed to reset forward rules: %s", err)
 	}
 }
 
-func (r *router) loadFilterTable() (*nftables.Table, error) {
+func (r *router) RestoreAfterV6Reset(newWorktable6 *nftables.Table) error {
+	r.workTable6 = newWorktable6
+	if newWorktable6 != nil {
+
+		err := r.cleanUpDefaultForwardRules(true)
+		if err != nil {
+			log.Errorf("failed to clean up rules from IPv6 FORWARD chain: %s", err)
+		}
+
+		err = r.createContainers(true)
+		if err != nil {
+			return err
+		}
+
+		for name, rule := range r.rules6 {
+			rule = &nftables.Rule{
+				Table:    r.workTable6,
+				Chain:    r.chains6[rule.Chain.Name],
+				Exprs:    rule.Exprs,
+				UserData: rule.UserData,
+			}
+			r.rules6[name] = r.conn.AddRule(rule)
+		}
+	}
+	return r.conn.Flush()
+}
+
+func (r *router) loadFilterTables() (*nftables.Table, *nftables.Table, error) {
 	tables, err := r.conn.ListTablesOfFamily(nftables.TableFamilyIPv4)
 	if err != nil {
-		return nil, fmt.Errorf("nftables: unable to list tables: %v", err)
+		return nil, nil, fmt.Errorf("nftables: unable to list tables: %v", err)
 	}
 
+	var table4 *nftables.Table = nil
 	for _, table := range tables {
 		if table.Name == "filter" {
-			return table, nil
+			table4 = table
+			break
 		}
 	}
 
-	return nil, errFilterTableNotFound
+	var table6 *nftables.Table = nil
+	tables, err = r.conn.ListTablesOfFamily(nftables.TableFamilyIPv6)
+	if err != nil {
+		return nil, nil, fmt.Errorf("nftables: unable to list tables: %v", err)
+	}
+	for _, table := range tables {
+		if table.Name == "filter" {
+			table6 = table
+			break
+		}
+	}
+
+	err = nil
+	if table4 == nil || table6 == nil {
+		err = errFilterTableNotFound
+	}
+
+	return table4, table6, err
 }
 
-func (r *router) createContainers() error {
+func (r *router) createContainers(forV6 bool) error {
+	workTable := r.workTable
+	chainStorage := r.chains
+	if forV6 {
+		workTable = r.workTable6
+		chainStorage = r.chains6
+	}
 
-	r.chains[chainNameRouteingFw] = r.conn.AddChain(&nftables.Chain{
+	chainStorage[chainNameRouteingFw] = r.conn.AddChain(&nftables.Chain{
 		Name:  chainNameRouteingFw,
-		Table: r.workTable,
+		Table: workTable,
 	})
 
-	r.chains[chainNameRoutingNat] = r.conn.AddChain(&nftables.Chain{
+	chainStorage[chainNameRoutingNat] = r.conn.AddChain(&nftables.Chain{
 		Name:     chainNameRoutingNat,
-		Table:    r.workTable,
+		Table:    workTable,
 		Hooknum:  nftables.ChainHookPostrouting,
 		Priority: nftables.ChainPriorityNATSource - 1,
 		Type:     nftables.ChainTypeNAT,
 	})
 
-	err := r.refreshRulesMap()
+	err := r.refreshRulesMap(forV6)
 	if err != nil {
 		log.Errorf("failed to clean up rules from FORWARD chain: %s", err)
 	}
@@ -140,7 +218,13 @@ func (r *router) createContainers() error {
 
 // InsertRoutingRules inserts a nftable rule pair to the forwarding chain and if enabled, to the nat chain
 func (r *router) InsertRoutingRules(pair manager.RouterPair) error {
-	err := r.refreshRulesMap()
+	parsedIp, _, _ := net.ParseCIDR(pair.Source)
+
+	if parsedIp.To4() == nil && r.workTable6 == nil {
+		return fmt.Errorf("nftables: attempted to add IPv6 routing rule even though IPv6 is not enabled for this host")
+	}
+
+	err := r.refreshRulesMap(parsedIp.To4() == nil)
 	if err != nil {
 		return err
 	}
@@ -165,7 +249,11 @@ func (r *router) InsertRoutingRules(pair manager.RouterPair) error {
 		}
 	}
 
-	if r.filterTable != nil && !r.isDefaultFwdRulesEnabled {
+	filterTable := r.filterTable
+	if parsedIp.To4() == nil {
+		filterTable = r.filterTable6
+	}
+	if filterTable != nil && !r.isDefaultFwdRulesEnabled {
 		log.Debugf("add default accept forward rule")
 		r.acceptForwardRule(pair.Source)
 	}
@@ -191,7 +279,13 @@ func (r *router) insertRoutingRule(format, chainName string, pair manager.Router
 
 	ruleKey := manager.GenKey(format, pair.ID)
 
-	_, exists := r.rules[ruleKey]
+	parsedIp, _, _ := net.ParseCIDR(pair.Source)
+	rules := r.rules
+	if parsedIp.To4() == nil {
+		rules = r.rules6
+	}
+
+	_, exists := rules[ruleKey]
 	if exists {
 		err := r.removeRoutingRule(format, pair)
 		if err != nil {
@@ -199,18 +293,35 @@ func (r *router) insertRoutingRule(format, chainName string, pair manager.Router
 		}
 	}
 
-	r.rules[ruleKey] = r.conn.InsertRule(&nftables.Rule{
-		Table:    r.workTable,
-		Chain:    r.chains[chainName],
+	table, chain := r.workTable, r.chains[chainName]
+	if parsedIp.To4() == nil {
+		table, chain = r.workTable6, r.chains6[chainName]
+	}
+
+	newRule := r.conn.InsertRule(&nftables.Rule{
+		Table:    table,
+		Chain:    chain,
 		Exprs:    expression,
 		UserData: []byte(ruleKey),
 	})
+
+	if parsedIp.To4() == nil {
+		r.rules[ruleKey] = newRule
+	} else {
+		r.rules6[ruleKey] = newRule
+	}
 	return nil
 }
 
 func (r *router) acceptForwardRule(sourceNetwork string) {
 	src := generateCIDRMatcherExpressions(true, sourceNetwork)
 	dst := generateCIDRMatcherExpressions(false, "0.0.0.0/0")
+	table := r.filterTable
+	parsedIp, _, _ := net.ParseCIDR(sourceNetwork)
+	if parsedIp.To4() == nil {
+		dst = generateCIDRMatcherExpressions(false, "::/0")
+		table = r.filterTable6
+	}
 
 	var exprs []expr.Any
 	exprs = append(src, append(dst, &expr.Verdict{ // nolint:gocritic
@@ -218,10 +329,10 @@ func (r *router) acceptForwardRule(sourceNetwork string) {
 	})...)
 
 	rule := &nftables.Rule{
-		Table: r.filterTable,
+		Table: table,
 		Chain: &nftables.Chain{
 			Name:     "FORWARD",
-			Table:    r.filterTable,
+			Table:    table,
 			Type:     nftables.ChainTypeFilter,
 			Hooknum:  nftables.ChainHookForward,
 			Priority: nftables.ChainPriorityFilter,
@@ -233,6 +344,9 @@ func (r *router) acceptForwardRule(sourceNetwork string) {
 	r.conn.AddRule(rule)
 
 	src = generateCIDRMatcherExpressions(true, "0.0.0.0/0")
+	if parsedIp.To4() == nil {
+		src = generateCIDRMatcherExpressions(true, "::/0")
+	}
 	dst = generateCIDRMatcherExpressions(false, sourceNetwork)
 
 	exprs = append(src, append(dst, &expr.Verdict{ //nolint:gocritic
@@ -240,10 +354,10 @@ func (r *router) acceptForwardRule(sourceNetwork string) {
 	})...)
 
 	rule = &nftables.Rule{
-		Table: r.filterTable,
+		Table: table,
 		Chain: &nftables.Chain{
 			Name:     "FORWARD",
-			Table:    r.filterTable,
+			Table:    table,
 			Type:     nftables.ChainTypeFilter,
 			Hooknum:  nftables.ChainHookForward,
 			Priority: nftables.ChainPriorityFilter,
@@ -252,12 +366,21 @@ func (r *router) acceptForwardRule(sourceNetwork string) {
 		UserData: []byte(userDataAcceptForwardRuleDst),
 	}
 	r.conn.AddRule(rule)
-	r.isDefaultFwdRulesEnabled = true
+	if parsedIp.To4() == nil {
+		r.isDefaultFwdRulesEnabled6 = true
+	} else {
+		r.isDefaultFwdRulesEnabled = true
+	}
 }
 
 // RemoveRoutingRules removes a nftable rule pair from forwarding and nat chains
 func (r *router) RemoveRoutingRules(pair manager.RouterPair) error {
-	err := r.refreshRulesMap()
+	parsedIp, _, _ := net.ParseCIDR(pair.Source)
+	if parsedIp.To4() == nil && r.workTable6 == nil {
+		return fmt.Errorf("nftables: attempted to remove IPv6 routing rule even though IPv6 is not enabled for this host")
+	}
+
+	err := r.refreshRulesMap(parsedIp.To4() == nil)
 	if err != nil {
 		return err
 	}
@@ -282,8 +405,12 @@ func (r *router) RemoveRoutingRules(pair manager.RouterPair) error {
 		return err
 	}
 
-	if len(r.rules) == 0 {
-		err := r.cleanUpDefaultForwardRules()
+	rulesList := r.rules
+	if parsedIp.To4() == nil {
+		rulesList = r.rules6
+	}
+	if len(rulesList) == 0 {
+		err := r.cleanUpDefaultForwardRules(parsedIp.To4() == nil)
 		if err != nil {
 			log.Errorf("failed to clean up rules from FORWARD chain: %s", err)
 		}
@@ -301,7 +428,13 @@ func (r *router) RemoveRoutingRules(pair manager.RouterPair) error {
 func (r *router) removeRoutingRule(format string, pair manager.RouterPair) error {
 	ruleKey := manager.GenKey(format, pair.ID)
 
-	rule, found := r.rules[ruleKey]
+	parsedIp, _, _ := net.ParseCIDR(pair.Source)
+	rules := r.rules
+	if parsedIp.To4() == nil {
+		rules = r.rules6
+	}
+
+	rule, found := rules[ruleKey]
 	if found {
 		ruleType := "forwarding"
 		if rule.Chain.Type == nftables.ChainTypeNAT {
@@ -315,49 +448,68 @@ func (r *router) removeRoutingRule(format string, pair manager.RouterPair) error
 
 		log.Debugf("nftables: removing %s rule for %s", ruleType, pair.Destination)
 
-		delete(r.rules, ruleKey)
+		delete(rules, ruleKey)
 	}
 	return nil
 }
 
 // refreshRulesMap refreshes the rule map with the latest rules. this is useful to avoid
 // duplicates and to get missing attributes that we don't have when adding new rules
-func (r *router) refreshRulesMap() error {
-	for _, chain := range r.chains {
+func (r *router) refreshRulesMap(forV6 bool) error {
+	chainList := r.chains
+	if forV6 {
+		chainList = r.chains6
+	}
+	for _, chain := range chainList {
 		rules, err := r.conn.GetRules(chain.Table, chain)
 		if err != nil {
 			return fmt.Errorf("nftables: unable to list rules: %v", err)
 		}
 		for _, rule := range rules {
 			if len(rule.UserData) > 0 {
-				r.rules[string(rule.UserData)] = rule
+				if forV6 {
+					r.rules6[string(rule.UserData)] = rule
+				} else {
+					r.rules[string(rule.UserData)] = rule
+				}
 			}
 		}
 	}
 	return nil
 }
 
-func (r *router) cleanUpDefaultForwardRules() error {
-	if r.filterTable == nil {
-		r.isDefaultFwdRulesEnabled = false
+func (r *router) cleanUpDefaultForwardRules(forV6 bool) error {
+	tableFamily := nftables.TableFamilyIPv4
+	filterTable := r.filterTable
+	if forV6 {
+		tableFamily = nftables.TableFamilyIPv6
+		filterTable = r.filterTable6
+	}
+
+	if filterTable == nil {
+		if forV6 {
+			r.isDefaultFwdRulesEnabled6 = false
+		} else {
+			r.isDefaultFwdRulesEnabled = false
+		}
 		return nil
 	}
 
-	chains, err := r.conn.ListChainsOfTableFamily(nftables.TableFamilyIPv4)
+	chains, err := r.conn.ListChainsOfTableFamily(tableFamily)
 	if err != nil {
 		return err
 	}
 
 	var rules []*nftables.Rule
 	for _, chain := range chains {
-		if chain.Table.Name != r.filterTable.Name {
+		if chain.Table.Name != filterTable.Name {
 			continue
 		}
 		if chain.Name != "FORWARD" {
 			continue
 		}
 
-		rules, err = r.conn.GetRules(r.filterTable, chain)
+		rules, err = r.conn.GetRules(filterTable, chain)
 		if err != nil {
 			return err
 		}
@@ -371,7 +523,12 @@ func (r *router) cleanUpDefaultForwardRules() error {
 			}
 		}
 	}
-	r.isDefaultFwdRulesEnabled = false
+
+	if forV6 {
+		r.isDefaultFwdRulesEnabled6 = false
+	} else {
+		r.isDefaultFwdRulesEnabled = false
+	}
 	return r.conn.Flush()
 }
 
@@ -387,6 +544,18 @@ func generateCIDRMatcherExpressions(source bool, cidr string) []expr.Any {
 	} else {
 		offSet = 16 // dst offset
 	}
+	addrLen := uint32(4)
+	zeroXor := zeroXor
+
+	if ip.To4() == nil {
+		if source {
+			offSet = 8 // src offset
+		} else {
+			offSet = 24 // dst offset
+		}
+		addrLen = 16
+		zeroXor = zeroXor6
+	}
 
 	return []expr.Any{
 		// fetch src add
@@ -394,13 +563,13 @@ func generateCIDRMatcherExpressions(source bool, cidr string) []expr.Any {
 			DestRegister: 1,
 			Base:         expr.PayloadBaseNetworkHeader,
 			Offset:       offSet,
-			Len:          4,
+			Len:          addrLen,
 		},
 		// net mask
 		&expr.Bitwise{
 			DestRegister:   1,
 			SourceRegister: 1,
-			Len:            4,
+			Len:            addrLen,
 			Mask:           network.Mask,
 			Xor:            zeroXor,
 		},