[client] Improve route acl (#2705)

- Update nftables library to v0.2.0
- Mark traffic that was originally destined for local and applies the input rules in the forward chain if said traffic was redirected (e.g. by Docker)
- Add nft rules to internal map only if flush was successful
- Improve error message if handle is 0 (= not found or hasn't been refreshed)
- Add debug logging when route rules are added
- Replace nftables userdata (rule ID) with a rule hash

client/firewall/iptables/acl_linux.go

@@ -11,6 +11,7 @@ import (
 	log "github.com/sirupsen/logrus"
 
 	firewall "github.com/netbirdio/netbird/client/firewall/manager"
+	nbnet "github.com/netbirdio/netbird/util/net"
 )
 
 const (
@@ -21,13 +22,19 @@ const (
 	chainNameOutputRules = "NETBIRD-ACL-OUTPUT"
 )
 
+type entry struct {
+	spec     []string
+	position int
+}
+
 type aclManager struct {
 	iptablesClient     *iptables.IPTables
 	wgIface            iFaceMapper
 	routingFwChainName string
 
-	entries    map[string][][]string
-	ipsetStore *ipsetStore
+	entries         map[string][][]string
+	optionalEntries map[string][]entry
+	ipsetStore      *ipsetStore
 }
 
 func newAclManager(iptablesClient *iptables.IPTables, wgIface iFaceMapper, routingFwChainName string) (*aclManager, error) {
@@ -36,8 +43,9 @@ func newAclManager(iptablesClient *iptables.IPTables, wgIface iFaceMapper, routi
 		wgIface:            wgIface,
 		routingFwChainName: routingFwChainName,
 
-		entries:    make(map[string][][]string),
-		ipsetStore: newIpsetStore(),
+		entries:         make(map[string][][]string),
+		optionalEntries: make(map[string][]entry),
+		ipsetStore:      newIpsetStore(),
 	}
 
 	err := ipset.Init()
@@ -46,6 +54,7 @@ func newAclManager(iptablesClient *iptables.IPTables, wgIface iFaceMapper, routi
 	}
 
 	m.seedInitialEntries()
+	m.seedInitialOptionalEntries()
 
 	err = m.cleanChains()
 	if err != nil {
@@ -232,6 +241,19 @@ func (m *aclManager) cleanChains() error {
 		}
 	}
 
+	ok, err = m.iptablesClient.ChainExists("mangle", "PREROUTING")
+	if err != nil {
+		return fmt.Errorf("list chains: %w", err)
+	}
+	if ok {
+		for _, rule := range m.entries["PREROUTING"] {
+			err := m.iptablesClient.DeleteIfExists("mangle", "PREROUTING", rule...)
+			if err != nil {
+				log.Errorf("failed to delete rule: %v, %s", rule, err)
+			}
+		}
+	}
+
 	for _, ipsetName := range m.ipsetStore.ipsetNames() {
 		if err := ipset.Flush(ipsetName); err != nil {
 			log.Errorf("flush ipset %q during reset: %v", ipsetName, err)
@@ -267,6 +289,17 @@ func (m *aclManager) createDefaultChains() error {
 		}
 	}
 
+	for chainName, entries := range m.optionalEntries {
+		for _, entry := range entries {
+			if err := m.iptablesClient.InsertUnique(tableName, chainName, entry.position, entry.spec...); err != nil {
+				log.Errorf("failed to insert optional entry %v: %v", entry.spec, err)
+				continue
+			}
+			m.entries[chainName] = append(m.entries[chainName], entry.spec)
+		}
+	}
+	clear(m.optionalEntries)
+
 	return nil
 }
 
@@ -295,6 +328,22 @@ func (m *aclManager) seedInitialEntries() {
 	m.appendToEntries("FORWARD", append([]string{"-o", m.wgIface.Name()}, established...))
 }
 
+func (m *aclManager) seedInitialOptionalEntries() {
+	m.optionalEntries["FORWARD"] = []entry{
+		{
+			spec:     []string{"-m", "mark", "--mark", fmt.Sprintf("%#x", nbnet.PreroutingFwmark), "-j", chainNameInputRules},
+			position: 2,
+		},
+	}
+
+	m.optionalEntries["PREROUTING"] = []entry{
+		{
+			spec:     []string{"-t", "mangle", "-i", m.wgIface.Name(), "-m", "addrtype", "--dst-type", "LOCAL", "-j", "MARK", "--set-mark", fmt.Sprintf("%#x", nbnet.PreroutingFwmark)},
+			position: 1,
+		},
+	}
+}
+
 func (m *aclManager) appendToEntries(chainName string, spec []string) {
 	m.entries[chainName] = append(m.entries[chainName], spec)
 }

client/firewall/iptables/manager_linux.go

@@ -78,7 +78,7 @@ func (m *Manager) AddPeerFiltering(
 }
 
 func (m *Manager) AddRouteFiltering(
-	sources [] netip.Prefix,
+	sources []netip.Prefix,
 	destination netip.Prefix,
 	proto firewall.Protocol,
 	sPort *firewall.Port,

client/firewall/iptables/router_linux.go

@@ -305,10 +305,7 @@ func (r *router) cleanUpDefaultForwardRules() error {
 
 	log.Debug("flushing routing related tables")
 	for _, chain := range []string{chainRTFWD, chainRTNAT} {
-		table := tableFilter
-		if chain == chainRTNAT {
-			table = tableNat
-		}
+		table := r.getTableForChain(chain)
 
 		ok, err := r.iptablesClient.ChainExists(table, chain)
 		if err != nil {
@@ -329,15 +326,19 @@ func (r *router) cleanUpDefaultForwardRules() error {
 func (r *router) createContainers() error {
 	for _, chain := range []string{chainRTFWD, chainRTNAT} {
 		if err := r.createAndSetupChain(chain); err != nil {
-			return fmt.Errorf("create chain %s: %v", chain, err)
+			return fmt.Errorf("create chain %s: %w", chain, err)
 		}
 	}
 
 	if err := r.insertEstablishedRule(chainRTFWD); err != nil {
-		return fmt.Errorf("insert established rule: %v", err)
+		return fmt.Errorf("insert established rule: %w", err)
 	}
 
-	return r.addJumpRules()
+	if err := r.addJumpRules(); err != nil {
+		return fmt.Errorf("add jump rules: %w", err)
+	}
+
+	return nil
 }
 
 func (r *router) createAndSetupChain(chain string) error {