[client] Passthrough all non-NetBird chains to prevent them from dropping NetBird traffic (#4899)

client/firewall/nftables/router_linux.go

@@ -27,7 +27,11 @@ import (
 )
 
 const (
-	tableNat               = "nat"
+	tableNat      = "nat"
+	tableMangle   = "mangle"
+	tableRaw      = "raw"
+	tableSecurity = "security"
+
 	chainNameNatPrerouting = "PREROUTING"
 	chainNameRoutingFw     = "netbird-rt-fwd"
 	chainNameRoutingNat    = "netbird-rt-postrouting"
@@ -91,7 +95,7 @@ func newRouter(workTable *nftables.Table, wgIface iFaceMapper, mtu uint16) (*rou
 	var err error
 	r.filterTable, err = r.loadFilterTable()
 	if err != nil {
-		log.Warnf("failed to load filter table, skipping accept rules: %v", err)
+		log.Debugf("ip filter table not found: %v", err)
 	}
 
 	return r, nil
@@ -183,6 +187,33 @@ func (r *router) loadFilterTable() (*nftables.Table, error) {
 	return nil, errFilterTableNotFound
 }
 
+func hookName(hook *nftables.ChainHook) string {
+	if hook == nil {
+		return "unknown"
+	}
+	switch *hook {
+	case *nftables.ChainHookForward:
+		return chainNameForward
+	case *nftables.ChainHookInput:
+		return chainNameInput
+	default:
+		return fmt.Sprintf("hook(%d)", *hook)
+	}
+}
+
+func familyName(family nftables.TableFamily) string {
+	switch family {
+	case nftables.TableFamilyIPv4:
+		return "ip"
+	case nftables.TableFamilyIPv6:
+		return "ip6"
+	case nftables.TableFamilyINet:
+		return "inet"
+	default:
+		return fmt.Sprintf("family(%d)", family)
+	}
+}
+
 func (r *router) createContainers() error {
 	r.chains[chainNameRoutingFw] = r.conn.AddChain(&nftables.Chain{
 		Name:  chainNameRoutingFw,
@@ -930,8 +961,21 @@ func (r *router) RemoveAllLegacyRouteRules() error {
 // In case the FORWARD policy is set to "drop", we add an established/related rule to allow return traffic for the inbound rule.
 // This method also adds INPUT chain rules to allow traffic to the local interface.
 func (r *router) acceptForwardRules() error {
+	var merr *multierror.Error
+
+	if err := r.acceptFilterTableRules(); err != nil {
+		merr = multierror.Append(merr, err)
+	}
+
+	if err := r.acceptExternalChainsRules(); err != nil {
+		merr = multierror.Append(merr, fmt.Errorf("add accept rules to external chains: %w", err))
+	}
+
+	return nberrors.FormatErrorOrNil(merr)
+}
+
+func (r *router) acceptFilterTableRules() error {
 	if r.filterTable == nil {
-		log.Debugf("table 'filter' not found for forward rules, skipping accept rules")
 		return nil
 	}
 
@@ -944,11 +988,11 @@ func (r *router) acceptForwardRules() error {
 	// Try iptables first and fallback to nftables if iptables is not available
 	ipt, err := iptables.New()
 	if err != nil {
-		// filter table exists but iptables is not
+		// iptables is not available but the filter table exists
 		log.Warnf("Will use nftables to manipulate the filter table because iptables is not available: %v", err)
 
 		fw = "nftables"
-		return r.acceptFilterRulesNftables()
+		return r.acceptFilterRulesNftables(r.filterTable)
 	}
 
 	return r.acceptFilterRulesIptables(ipt)
@@ -959,7 +1003,7 @@ func (r *router) acceptFilterRulesIptables(ipt *iptables.IPTables) error {
 
 	for _, rule := range r.getAcceptForwardRules() {
 		if err := ipt.Insert("filter", chainNameForward, 1, rule...); err != nil {
-			merr = multierror.Append(err, fmt.Errorf("add iptables forward rule: %v", err))
+			merr = multierror.Append(merr, fmt.Errorf("add iptables forward rule: %v", err))
 		} else {
 			log.Debugf("added iptables forward rule: %v", rule)
 		}
@@ -967,7 +1011,7 @@ func (r *router) acceptFilterRulesIptables(ipt *iptables.IPTables) error {
 
 	inputRule := r.getAcceptInputRule()
 	if err := ipt.Insert("filter", chainNameInput, 1, inputRule...); err != nil {
-		merr = multierror.Append(err, fmt.Errorf("add iptables input rule: %v", err))
+		merr = multierror.Append(merr, fmt.Errorf("add iptables input rule: %v", err))
 	} else {
 		log.Debugf("added iptables input rule: %v", inputRule)
 	}
@@ -987,18 +1031,70 @@ func (r *router) getAcceptInputRule() []string {
 	return []string{"-i", r.wgIface.Name(), "-j", "ACCEPT"}
 }
 
-func (r *router) acceptFilterRulesNftables() error {
+// acceptFilterRulesNftables adds accept rules to the ip filter table using nftables.
+// This is used when iptables is not available.
+func (r *router) acceptFilterRulesNftables(table *nftables.Table) error {
 	intf := ifname(r.wgIface.Name())
 
+	forwardChain := &nftables.Chain{
+		Name:     chainNameForward,
+		Table:    table,
+		Type:     nftables.ChainTypeFilter,
+		Hooknum:  nftables.ChainHookForward,
+		Priority: nftables.ChainPriorityFilter,
+	}
+	r.insertForwardAcceptRules(forwardChain, intf)
+
+	inputChain := &nftables.Chain{
+		Name:     chainNameInput,
+		Table:    table,
+		Type:     nftables.ChainTypeFilter,
+		Hooknum:  nftables.ChainHookInput,
+		Priority: nftables.ChainPriorityFilter,
+	}
+	r.insertInputAcceptRule(inputChain, intf)
+
+	return r.conn.Flush()
+}
+
+// acceptExternalChainsRules adds accept rules to external chains (non-netbird, non-iptables tables).
+// It dynamically finds chains at call time to handle chains that may have been created after startup.
+func (r *router) acceptExternalChainsRules() error {
+	chains := r.findExternalChains()
+	if len(chains) == 0 {
+		return nil
+	}
+
+	intf := ifname(r.wgIface.Name())
+
+	for _, chain := range chains {
+		if chain.Hooknum == nil {
+			log.Debugf("skipping external chain %s/%s: hooknum is nil", chain.Table.Name, chain.Name)
+			continue
+		}
+
+		log.Debugf("adding accept rules to external %s chain: %s %s/%s",
+			hookName(chain.Hooknum), familyName(chain.Table.Family), chain.Table.Name, chain.Name)
+
+		switch *chain.Hooknum {
+		case *nftables.ChainHookForward:
+			r.insertForwardAcceptRules(chain, intf)
+		case *nftables.ChainHookInput:
+			r.insertInputAcceptRule(chain, intf)
+		}
+	}
+
+	if err := r.conn.Flush(); err != nil {
+		return fmt.Errorf("flush external chain rules: %w", err)
+	}
+
+	return nil
+}
+
+func (r *router) insertForwardAcceptRules(chain *nftables.Chain, intf []byte) {
 	iifRule := &nftables.Rule{
-		Table: r.filterTable,
+		Table: chain.Table,
-		Chain: &nftables.Chain{
+		Chain: chain,
-			Name:     chainNameForward,
-			Table:    r.filterTable,
-			Type:     nftables.ChainTypeFilter,
-			Hooknum:  nftables.ChainHookForward,
-			Priority: nftables.ChainPriorityFilter,
-		},
 		Exprs: []expr.Any{
 			&expr.Meta{Key: expr.MetaKeyIIFNAME, Register: 1},
 			&expr.Cmp{
@@ -1021,30 +1117,19 @@ func (r *router) acceptFilterRulesNftables() error {
 			Data:     intf,
 		},
 	}
-
 	oifRule := &nftables.Rule{
-		Table: r.filterTable,
+		Table:    chain.Table,
-		Chain: &nftables.Chain{
+		Chain:    chain,
-			Name:     chainNameForward,
-			Table:    r.filterTable,
-			Type:     nftables.ChainTypeFilter,
-			Hooknum:  nftables.ChainHookForward,
-			Priority: nftables.ChainPriorityFilter,
-		},
 		Exprs:    append(oifExprs, getEstablishedExprs(2)...),
 		UserData: []byte(userDataAcceptForwardRuleOif),
 	}
 	r.conn.InsertRule(oifRule)
+}
 
+func (r *router) insertInputAcceptRule(chain *nftables.Chain, intf []byte) {
 	inputRule := &nftables.Rule{
-		Table: r.filterTable,
+		Table: chain.Table,
-		Chain: &nftables.Chain{
+		Chain: chain,
-			Name:     chainNameInput,
-			Table:    r.filterTable,
-			Type:     nftables.ChainTypeFilter,
-			Hooknum:  nftables.ChainHookInput,
-			Priority: nftables.ChainPriorityFilter,
-		},
 		Exprs: []expr.Any{
 			&expr.Meta{Key: expr.MetaKeyIIFNAME, Register: 1},
 			&expr.Cmp{
@@ -1058,32 +1143,44 @@ func (r *router) acceptFilterRulesNftables() error {
 		UserData: []byte(userDataAcceptInputRule),
 	}
 	r.conn.InsertRule(inputRule)
-
-	return r.conn.Flush()
 }
 
 func (r *router) removeAcceptFilterRules() error {
+	var merr *multierror.Error
+
+	if err := r.removeFilterTableRules(); err != nil {
+		merr = multierror.Append(merr, err)
+	}
+
+	if err := r.removeExternalChainsRules(); err != nil {
+		merr = multierror.Append(merr, fmt.Errorf("remove external chain rules: %w", err))
+	}
+
+	return nberrors.FormatErrorOrNil(merr)
+}
+
+func (r *router) removeFilterTableRules() error {
 	if r.filterTable == nil {
 		return nil
 	}
 
 	ipt, err := iptables.New()
 	if err != nil {
-		log.Warnf("Will use nftables to manipulate the filter table because iptables is not available: %v", err)
+		log.Debugf("iptables not available, using nftables to remove filter rules: %v", err)
-		return r.removeAcceptFilterRulesNftables()
+		return r.removeAcceptRulesFromTable(r.filterTable)
 	}
 
 	return r.removeAcceptFilterRulesIptables(ipt)
 }
 
-func (r *router) removeAcceptFilterRulesNftables() error {
+func (r *router) removeAcceptRulesFromTable(table *nftables.Table) error {
-	chains, err := r.conn.ListChainsOfTableFamily(nftables.TableFamilyIPv4)
+	chains, err := r.conn.ListChainsOfTableFamily(table.Family)
 	if err != nil {
 		return fmt.Errorf("list chains: %v", err)
 	}
 
 	for _, chain := range chains {
-		if chain.Table.Name != r.filterTable.Name {
+		if chain.Table.Name != table.Name {
 			continue
 		}
 
@@ -1091,27 +1188,101 @@ func (r *router) removeAcceptFilterRulesNftables() error {
 			continue
 		}
 
-		rules, err := r.conn.GetRules(r.filterTable, chain)
+		if err := r.removeAcceptRulesFromChain(table, chain); err != nil {
+			return err
+		}
+	}
+
+	return r.conn.Flush()
+}
+
+func (r *router) removeAcceptRulesFromChain(table *nftables.Table, chain *nftables.Chain) error {
+	rules, err := r.conn.GetRules(table, chain)
+	if err != nil {
+		return fmt.Errorf("get rules from %s/%s: %v", table.Name, chain.Name, err)
+	}
+
+	for _, rule := range rules {
+		if bytes.Equal(rule.UserData, []byte(userDataAcceptForwardRuleIif)) ||
+			bytes.Equal(rule.UserData, []byte(userDataAcceptForwardRuleOif)) ||
+			bytes.Equal(rule.UserData, []byte(userDataAcceptInputRule)) {
+			if err := r.conn.DelRule(rule); err != nil {
+				return fmt.Errorf("delete rule from %s/%s: %v", table.Name, chain.Name, err)
+			}
+		}
+	}
+	return nil
+}
+
+// removeExternalChainsRules removes our accept rules from all external chains.
+// This is deterministic - it scans for chains at removal time rather than relying on saved state,
+// ensuring cleanup works even after a crash or if chains changed.
+func (r *router) removeExternalChainsRules() error {
+	chains := r.findExternalChains()
+	if len(chains) == 0 {
+		return nil
+	}
+
+	for _, chain := range chains {
+		if err := r.removeAcceptRulesFromChain(chain.Table, chain); err != nil {
+			log.Warnf("remove rules from external chain %s/%s: %v", chain.Table.Name, chain.Name, err)
+		}
+	}
+
+	return r.conn.Flush()
+}
+
+// findExternalChains scans for chains from non-netbird tables that have FORWARD or INPUT hooks.
+// This is used both at startup (to know where to add rules) and at cleanup (to ensure deterministic removal).
+func (r *router) findExternalChains() []*nftables.Chain {
+	var chains []*nftables.Chain
+
+	families := []nftables.TableFamily{nftables.TableFamilyIPv4, nftables.TableFamilyINet}
+
+	for _, family := range families {
+		allChains, err := r.conn.ListChainsOfTableFamily(family)
 		if err != nil {
-			return fmt.Errorf("get rules: %v", err)
+			log.Debugf("list chains for family %d: %v", family, err)
+			continue
 		}
 
-		for _, rule := range rules {
+		for _, chain := range allChains {
-			if bytes.Equal(rule.UserData, []byte(userDataAcceptForwardRuleIif)) ||
+			if r.isExternalChain(chain) {
-				bytes.Equal(rule.UserData, []byte(userDataAcceptForwardRuleOif)) ||
+				chains = append(chains, chain)
-				bytes.Equal(rule.UserData, []byte(userDataAcceptInputRule)) {
-				if err := r.conn.DelRule(rule); err != nil {
-					return fmt.Errorf("delete rule: %v", err)
-				}
 			}
 		}
 	}
 
-	if err := r.conn.Flush(); err != nil {
+	return chains
-		return fmt.Errorf(flushError, err)
+}
+
+func (r *router) isExternalChain(chain *nftables.Chain) bool {
+	if r.workTable != nil && chain.Table.Name == r.workTable.Name {
+		return false
 	}
 
-	return nil
+	// Skip all iptables-managed tables in the ip family
+	if chain.Table.Family == nftables.TableFamilyIPv4 && isIptablesTable(chain.Table.Name) {
+		return false
+	}
+
+	if chain.Type != nftables.ChainTypeFilter {
+		return false
+	}
+
+	if chain.Hooknum == nil {
+		return false
+	}
+
+	return *chain.Hooknum == *nftables.ChainHookForward || *chain.Hooknum == *nftables.ChainHookInput
+}
+
+func isIptablesTable(name string) bool {
+	switch name {
+	case tableNameFilter, tableNat, tableMangle, tableRaw, tableSecurity:
+		return true
+	}
+	return false
 }
 
 func (r *router) removeAcceptFilterRulesIptables(ipt *iptables.IPTables) error {
@@ -1119,13 +1290,13 @@ func (r *router) removeAcceptFilterRulesIptables(ipt *iptables.IPTables) error {
 
 	for _, rule := range r.getAcceptForwardRules() {
 		if err := ipt.DeleteIfExists("filter", chainNameForward, rule...); err != nil {
-			merr = multierror.Append(err, fmt.Errorf("remove iptables forward rule: %v", err))
+			merr = multierror.Append(merr, fmt.Errorf("remove iptables forward rule: %v", err))
 		}
 	}
 
 	inputRule := r.getAcceptInputRule()
 	if err := ipt.DeleteIfExists("filter", chainNameInput, inputRule...); err != nil {
-		merr = multierror.Append(err, fmt.Errorf("remove iptables input rule: %v", err))
+		merr = multierror.Append(merr, fmt.Errorf("remove iptables input rule: %v", err))
 	}
 
 	return nberrors.FormatErrorOrNil(merr)