netbird/client/firewall/iptables/router_linux.go

//go:build !android

package iptables

import (
	"fmt"
	"net/netip"
	"strconv"
	"strings"

	"github.com/coreos/go-iptables/iptables"
	"github.com/hashicorp/go-multierror"
	ipset "github.com/lrh3321/ipset-go"
	log "github.com/sirupsen/logrus"

	nberrors "github.com/netbirdio/netbird/client/errors"
	firewall "github.com/netbirdio/netbird/client/firewall/manager"
	nbid "github.com/netbirdio/netbird/client/internal/acl/id"
	"github.com/netbirdio/netbird/client/internal/routemanager/ipfwdstate"
	"github.com/netbirdio/netbird/client/internal/routemanager/refcounter"
	"github.com/netbirdio/netbird/client/internal/statemanager"
	nbnet "github.com/netbirdio/netbird/client/net"
)

// constants needed to manage and create iptable rules
const (
	tableFilter = "filter"
	tableNat    = "nat"
	tableMangle = "mangle"

	chainPOSTROUTING        = "POSTROUTING"
	chainPREROUTING         = "PREROUTING"
	chainFORWARD            = "FORWARD"
	chainRTNAT              = "NETBIRD-RT-NAT"
	chainRTFWDIN            = "NETBIRD-RT-FWD-IN"
	chainRTFWDOUT           = "NETBIRD-RT-FWD-OUT"
	chainRTPRE              = "NETBIRD-RT-PRE"
	chainRTRDR              = "NETBIRD-RT-RDR"
	chainNATOutput          = "NETBIRD-NAT-OUTPUT"
	chainRTMSSCLAMP         = "NETBIRD-RT-MSSCLAMP"
	routingFinalForwardJump = "ACCEPT"
	routingFinalNatJump     = "MASQUERADE"

	jumpManglePre  = "jump-mangle-pre"
	jumpNatPre     = "jump-nat-pre"
	jumpNatPost    = "jump-nat-post"
	jumpNatOutput  = "jump-nat-output"
	jumpMSSClamp   = "jump-mss-clamp"
	markManglePre  = "mark-mangle-pre"
	markManglePost = "mark-mangle-post"
	matchSet       = "--match-set"

	dnatSuffix = "_dnat"
	snatSuffix = "_snat"
	fwdSuffix  = "_fwd"

	// ipv4TCPHeaderSize is the minimum IPv4 (20) + TCP (20) header size for MSS calculation.
	ipv4TCPHeaderSize = 40
	// ipv6TCPHeaderSize is the minimum IPv6 (40) + TCP (20) header size for MSS calculation.
	ipv6TCPHeaderSize = 60
)

type ruleInfo struct {
	chain string
	table string
	rule  []string
}

type routeFilteringRuleParams struct {
	Source      firewall.Network
	Destination firewall.Network
	Proto       firewall.Protocol
	SPort       *firewall.Port
	DPort       *firewall.Port
	Direction   firewall.RuleDirection
	Action      firewall.Action
}

type routeRules map[string][]string

// the ipset library currently does not support comments, so we use the name only (string)
type ipsetCounter = refcounter.Counter[string, []netip.Prefix, struct{}]

type router struct {
	iptablesClient   *iptables.IPTables
	rules            routeRules
	ipsetCounter     *ipsetCounter
	wgIface          iFaceMapper
	legacyManagement bool
	mtu              uint16
	v6               bool

	stateManager *statemanager.Manager
	ipFwdState   *ipfwdstate.IPForwardingState
}

func newRouter(iptablesClient *iptables.IPTables, wgIface iFaceMapper, mtu uint16) (*router, error) {
	r := &router{
		iptablesClient: iptablesClient,
		rules:          make(map[string][]string),
		wgIface:        wgIface,
		mtu:            mtu,
		v6:             iptablesClient.Proto() == iptables.ProtocolIPv6,
		ipFwdState:     ipfwdstate.NewIPForwardingState(),
	}

	r.ipsetCounter = refcounter.New(
		func(name string, sources []netip.Prefix) (struct{}, error) {
			return struct{}{}, r.createIpSet(name, sources)
		},
		func(name string, _ struct{}) error {
			return r.deleteIpSet(name)
		},
	)

	return r, nil
}

func (r *router) init(stateManager *statemanager.Manager) error {
	r.stateManager = stateManager

	if err := r.cleanUpDefaultForwardRules(); err != nil {
		log.Errorf("failed to clean up rules from FORWARD chain: %s", err)
	}

	if err := r.createContainers(); err != nil {
		return fmt.Errorf("create containers: %w", err)
	}

	if err := r.setupDataPlaneMark(); err != nil {
		log.Errorf("failed to set up data plane mark: %v", err)
	}

	r.updateState()

	return nil
}

func (r *router) AddRouteFiltering(
	id []byte,
	sources []netip.Prefix,
	destination firewall.Network,
	proto firewall.Protocol,
	sPort *firewall.Port,
	dPort *firewall.Port,
	action firewall.Action,
) (firewall.Rule, error) {
	ruleKey := nbid.GenerateRouteRuleKey(sources, destination, proto, sPort, dPort, action)
	if _, ok := r.rules[string(ruleKey)]; ok {
		return ruleKey, nil
	}

	var source firewall.Network
	if len(sources) > 1 {
		source.Set = firewall.NewPrefixSet(sources)
	} else if len(sources) > 0 {
		source.Prefix = sources[0]
	}

	params := routeFilteringRuleParams{
		Source:      source,
		Destination: destination,
		Proto:       proto,
		SPort:       sPort,
		DPort:       dPort,
		Action:      action,
	}

	rule, err := r.genRouteRuleSpec(params, sources)
	if err != nil {
		return nil, fmt.Errorf("generate route rule spec: %w", err)
	}

	// Insert DROP rules at the beginning, append ACCEPT rules at the end
	if action == firewall.ActionDrop {
		// after the established rule
		err = r.iptablesClient.Insert(tableFilter, chainRTFWDIN, 2, rule...)
	} else {
		err = r.iptablesClient.Append(tableFilter, chainRTFWDIN, rule...)
	}

	if err != nil {
		return nil, fmt.Errorf("add route rule: %v", err)
	}

	r.rules[string(ruleKey)] = rule

	r.updateState()

	return ruleKey, nil
}

func (r *router) hasRule(id string) bool {
	_, ok := r.rules[id]
	return ok
}

func (r *router) DeleteRouteRule(rule firewall.Rule) error {
	ruleKey := rule.ID()

	if rule, exists := r.rules[ruleKey]; exists {
		if err := r.iptablesClient.Delete(tableFilter, chainRTFWDIN, rule...); err != nil {
			return fmt.Errorf("delete route rule: %v", err)
		}
		delete(r.rules, ruleKey)

		if err := r.decrementSetCounter(rule); err != nil {
			return fmt.Errorf("decrement ipset counter: %w", err)
		}
	} else {
		log.Debugf("route rule %s not found", ruleKey)
	}

	r.updateState()

	return nil
}

func (r *router) decrementSetCounter(rule []string) error {
	sets := r.findSets(rule)
	var merr *multierror.Error
	for _, setName := range sets {
		if _, err := r.ipsetCounter.Decrement(setName); err != nil {
			merr = multierror.Append(merr, fmt.Errorf("decrement counter: %w", err))
		}
	}

	return nberrors.FormatErrorOrNil(merr)
}

func (r *router) findSets(rule []string) []string {
	var sets []string
	for i, arg := range rule {
		if arg == "-m" && i+3 < len(rule) && rule[i+1] == "set" && rule[i+2] == matchSet {
			sets = append(sets, rule[i+3])
		}
	}
	return sets
}

func (r *router) createIpSet(setName string, sources []netip.Prefix) error {
	if err := r.createIPSet(setName); err != nil {
		return fmt.Errorf("create set %s: %w", setName, err)
	}

	for _, prefix := range sources {
		if err := r.addPrefixToIPSet(setName, prefix); err != nil {
			return fmt.Errorf("add element to set %s: %w", setName, err)
		}
	}

	return nil
}

func (r *router) deleteIpSet(setName string) error {
	if err := r.destroyIPSet(setName); err != nil {
		return fmt.Errorf("destroy set %s: %w", setName, err)
	}

	log.Debugf("Deleted unused ipset %s", setName)
	return nil
}

// AddNatRule inserts an iptables rule pair into the nat chain
func (r *router) AddNatRule(pair firewall.RouterPair) error {
	if r.legacyManagement {
		log.Warnf("This peer is connected to a NetBird Management service with an older version. Allowing all traffic for %s", pair.Destination)
		if err := r.addLegacyRouteRule(pair); err != nil {
			return fmt.Errorf("add legacy routing rule: %w", err)
		}
	}

	if !pair.Masquerade {
		return nil
	}

	if err := r.addNatRule(pair); err != nil {
		return fmt.Errorf("add nat rule: %w", err)
	}

	if err := r.addNatRule(firewall.GetInversePair(pair)); err != nil {
		return fmt.Errorf("add inverse nat rule: %w", err)
	}

	r.updateState()

	return nil
}

// RemoveNatRule removes an iptables rule pair from forwarding and nat chains
func (r *router) RemoveNatRule(pair firewall.RouterPair) error {
	if pair.Masquerade {
		if err := r.removeNatRule(pair); err != nil {
			return fmt.Errorf("remove nat rule: %w", err)
		}

		if err := r.removeNatRule(firewall.GetInversePair(pair)); err != nil {
			return fmt.Errorf("remove inverse nat rule: %w", err)
		}
	}

	if err := r.removeLegacyRouteRule(pair); err != nil {
		return fmt.Errorf("remove legacy routing rule: %w", err)
	}

	r.updateState()

	return nil
}

// addLegacyRouteRule adds a legacy routing rule for mgmt servers pre route acls
func (r *router) addLegacyRouteRule(pair firewall.RouterPair) error {
	ruleKey := firewall.GenKey(firewall.ForwardingFormat, pair)

	if err := r.removeLegacyRouteRule(pair); err != nil {
		return err
	}

	rule := []string{"-s", pair.Source.String(), "-d", pair.Destination.String(), "-j", routingFinalForwardJump}
	if err := r.iptablesClient.Append(tableFilter, chainRTFWDIN, rule...); err != nil {
		return fmt.Errorf("add legacy forwarding rule %s -> %s: %v", pair.Source, pair.Destination, err)
	}

	r.rules[ruleKey] = rule

	return nil
}

func (r *router) removeLegacyRouteRule(pair firewall.RouterPair) error {
	ruleKey := firewall.GenKey(firewall.ForwardingFormat, pair)

	if rule, exists := r.rules[ruleKey]; exists {
		if err := r.iptablesClient.DeleteIfExists(tableFilter, chainRTFWDIN, rule...); err != nil {
			return fmt.Errorf("remove legacy forwarding rule %s -> %s: %v", pair.Source, pair.Destination, err)
		}
		delete(r.rules, ruleKey)

		if err := r.decrementSetCounter(rule); err != nil {
			return fmt.Errorf("decrement ipset counter: %w", err)
		}
	}

	return nil
}

// GetLegacyManagement returns the current legacy management mode
func (r *router) GetLegacyManagement() bool {
	return r.legacyManagement
}

// SetLegacyManagement sets the route manager to use legacy management mode
func (r *router) SetLegacyManagement(isLegacy bool) {
	r.legacyManagement = isLegacy
}

// RemoveAllLegacyRouteRules removes all legacy routing rules for mgmt servers pre route acls
func (r *router) RemoveAllLegacyRouteRules() error {
	var merr *multierror.Error
	for k, rule := range r.rules {
		if !strings.HasPrefix(k, firewall.ForwardingFormatPrefix) {
			continue
		}
		if err := r.iptablesClient.DeleteIfExists(tableFilter, chainRTFWDIN, rule...); err != nil {
			merr = multierror.Append(merr, fmt.Errorf("remove legacy forwarding rule: %v", err))
		} else {
			delete(r.rules, k)
		}
	}

	r.updateState()

	return nberrors.FormatErrorOrNil(merr)
}

func (r *router) Reset() error {
	var merr *multierror.Error
	if err := r.cleanUpDefaultForwardRules(); err != nil {
		merr = multierror.Append(merr, err)
	}

	if err := r.ipsetCounter.Flush(); err != nil {
		merr = multierror.Append(merr, err)
	}

	if err := r.cleanupDataPlaneMark(); err != nil {
		merr = multierror.Append(merr, err)
	}

	r.rules = make(map[string][]string)
	r.updateState()

	return nberrors.FormatErrorOrNil(merr)
}

func (r *router) cleanUpDefaultForwardRules() error {
	if err := r.cleanJumpRules(); err != nil {
		return fmt.Errorf("clean jump rules: %w", err)
	}

	log.Debug("flushing routing related tables")

	// Remove jump rules from built-in chains before deleting custom chains,
	// otherwise the chain deletion fails with "device or resource busy".
	jumpRule := []string{"-j", chainNATOutput}
	if err := r.iptablesClient.Delete(tableNat, "OUTPUT", jumpRule...); err != nil {
		log.Debugf("clean OUTPUT jump rule: %v", err)
	}

	for _, chainInfo := range []struct {
		chain string
		table string
	}{
		{chainRTFWDIN, tableFilter},
		{chainRTFWDOUT, tableFilter},
		{chainRTPRE, tableMangle},
		{chainRTNAT, tableNat},
		{chainRTRDR, tableNat},
		{chainNATOutput, tableNat},
		{chainRTMSSCLAMP, tableMangle},
	} {
		ok, err := r.iptablesClient.ChainExists(chainInfo.table, chainInfo.chain)
		if err != nil {
			return fmt.Errorf("check chain %s in table %s: %w", chainInfo.chain, chainInfo.table, err)
		} else if ok {
			if err = r.iptablesClient.ClearAndDeleteChain(chainInfo.table, chainInfo.chain); err != nil {
				return fmt.Errorf("clear and delete chain %s in table %s: %w", chainInfo.chain, chainInfo.table, err)
			}
		}
	}

	return nil
}

func (r *router) createContainers() error {
	for _, chainInfo := range []struct {
		chain string
		table string
	}{
		{chainRTFWDIN, tableFilter},
		{chainRTFWDOUT, tableFilter},
		{chainRTPRE, tableMangle},
		{chainRTNAT, tableNat},
		{chainRTRDR, tableNat},
		{chainRTMSSCLAMP, tableMangle},
	} {
		// Fallback: clear chains that survived an unclean shutdown.
		if ok, _ := r.iptablesClient.ChainExists(chainInfo.table, chainInfo.chain); ok {
			if err := r.iptablesClient.ClearAndDeleteChain(chainInfo.table, chainInfo.chain); err != nil {
				log.Warnf("clear stale chain %s in %s: %v", chainInfo.chain, chainInfo.table, err)
			}
		}
		if err := r.iptablesClient.NewChain(chainInfo.table, chainInfo.chain); err != nil {
			return fmt.Errorf("create chain %s in table %s: %w", chainInfo.chain, chainInfo.table, err)
		}
	}

	if err := r.insertEstablishedRule(chainRTFWDIN); err != nil {
		return fmt.Errorf("insert established rule: %w", err)
	}

	if err := r.insertEstablishedRule(chainRTFWDOUT); err != nil {
		return fmt.Errorf("insert established rule: %w", err)
	}

	if err := r.addPostroutingRules(); err != nil {
		return fmt.Errorf("add static nat rules: %w", err)
	}

	if err := r.addJumpRules(); err != nil {
		return fmt.Errorf("add jump rules: %w", err)
	}

	if err := r.addMSSClampingRules(); err != nil {
		log.Errorf("failed to add MSS clamping rules: %s", err)
	}

	return nil
}

// setupDataPlaneMark configures the fwmark for the data plane
func (r *router) setupDataPlaneMark() error {
	var merr *multierror.Error
	preRule := []string{
		"-i", r.wgIface.Name(),
		"-m", "conntrack", "--ctstate", "NEW",
		"-j", "CONNMARK", "--set-mark", fmt.Sprintf("%#x", nbnet.DataPlaneMarkIn),
	}

	if err := r.iptablesClient.AppendUnique(tableMangle, chainPREROUTING, preRule...); err != nil {
		merr = multierror.Append(merr, fmt.Errorf("add mangle prerouting rule: %w", err))
	} else {
		r.rules[markManglePre] = preRule
	}

	postRule := []string{
		"-o", r.wgIface.Name(),
		"-m", "conntrack", "--ctstate", "NEW",
		"-j", "CONNMARK", "--set-mark", fmt.Sprintf("%#x", nbnet.DataPlaneMarkOut),
	}

	if err := r.iptablesClient.AppendUnique(tableMangle, chainPOSTROUTING, postRule...); err != nil {
		merr = multierror.Append(merr, fmt.Errorf("add mangle postrouting rule: %w", err))
	} else {
		r.rules[markManglePost] = postRule
	}

	return nberrors.FormatErrorOrNil(merr)
}

func (r *router) cleanupDataPlaneMark() error {
	var merr *multierror.Error
	if preRule, exists := r.rules[markManglePre]; exists {
		if err := r.iptablesClient.DeleteIfExists(tableMangle, chainPREROUTING, preRule...); err != nil {
			merr = multierror.Append(merr, fmt.Errorf("remove mangle prerouting rule: %w", err))
		} else {
			delete(r.rules, markManglePre)
		}
	}

	if postRule, exists := r.rules[markManglePost]; exists {
		if err := r.iptablesClient.DeleteIfExists(tableMangle, chainPOSTROUTING, postRule...); err != nil {
			merr = multierror.Append(merr, fmt.Errorf("remove mangle postrouting rule: %w", err))
		} else {
			delete(r.rules, markManglePost)
		}
	}

	return nberrors.FormatErrorOrNil(merr)
}

func (r *router) addPostroutingRules() error {
	// First rule for outbound masquerade
	rule1 := []string{
		"-m", "mark", "--mark", fmt.Sprintf("%#x", nbnet.PreroutingFwmarkMasquerade),
		"!", "-o", "lo",
		"-j", routingFinalNatJump,
	}
	if err := r.iptablesClient.Append(tableNat, chainRTNAT, rule1...); err != nil {
		return fmt.Errorf("add outbound masquerade rule: %v", err)
	}
	r.rules["static-nat-outbound"] = rule1

	// Second rule for return traffic masquerade
	rule2 := []string{
		"-m", "mark", "--mark", fmt.Sprintf("%#x", nbnet.PreroutingFwmarkMasqueradeReturn),
		"-o", r.wgIface.Name(),
		"-j", routingFinalNatJump,
	}
	if err := r.iptablesClient.Append(tableNat, chainRTNAT, rule2...); err != nil {
		return fmt.Errorf("add return masquerade rule: %v", err)
	}
	r.rules["static-nat-return"] = rule2

	return nil
}

// addMSSClampingRules adds MSS clamping rules to prevent fragmentation for forwarded traffic.
func (r *router) addMSSClampingRules() error {
	overhead := uint16(ipv4TCPHeaderSize)
	if r.v6 {
		overhead = ipv6TCPHeaderSize
	}
	mss := r.mtu - overhead

	// Add jump rule from FORWARD chain in mangle table to our custom chain
	jumpRule := []string{
		"-j", chainRTMSSCLAMP,
	}
	if err := r.iptablesClient.Insert(tableMangle, chainFORWARD, 1, jumpRule...); err != nil {
		return fmt.Errorf("add jump to MSS clamp chain: %w", err)
	}
	r.rules[jumpMSSClamp] = jumpRule

	ruleOut := []string{
		"-o", r.wgIface.Name(),
		"-p", "tcp",
		"--tcp-flags", "SYN,RST", "SYN",
		"-j", "TCPMSS",
		"--set-mss", fmt.Sprintf("%d", mss),
	}
	if err := r.iptablesClient.Append(tableMangle, chainRTMSSCLAMP, ruleOut...); err != nil {
		return fmt.Errorf("add outbound MSS clamp rule: %w", err)
	}
	r.rules["mss-clamp-out"] = ruleOut

	return nil
}

func (r *router) insertEstablishedRule(chain string) error {
	establishedRule := getConntrackEstablished()

	err := r.iptablesClient.Insert(tableFilter, chain, 1, establishedRule...)
	if err != nil {
		return fmt.Errorf("failed to insert established rule: %v", err)
	}

	ruleKey := "established-" + chain
	r.rules[ruleKey] = establishedRule

	return nil
}

func (r *router) addJumpRules() error {
	// Jump to nat chain
	natRule := []string{"-j", chainRTNAT}
	if err := r.iptablesClient.Insert(tableNat, chainPOSTROUTING, 1, natRule...); err != nil {
		return fmt.Errorf("add nat postrouting jump rule: %v", err)
	}
	r.rules[jumpNatPost] = natRule

	// Jump to mangle prerouting chain
	preRule := []string{"-j", chainRTPRE}
	if err := r.iptablesClient.Insert(tableMangle, chainPREROUTING, 1, preRule...); err != nil {
		return fmt.Errorf("add mangle prerouting jump rule: %v", err)
	}
	r.rules[jumpManglePre] = preRule

	// Jump to nat prerouting chain
	rdrRule := []string{"-j", chainRTRDR}
	if err := r.iptablesClient.Insert(tableNat, chainPREROUTING, 1, rdrRule...); err != nil {
		return fmt.Errorf("add nat prerouting jump rule: %v", err)
	}
	r.rules[jumpNatPre] = rdrRule

	return nil
}

func (r *router) cleanJumpRules() error {
	for _, ruleKey := range []string{jumpNatPost, jumpManglePre, jumpNatPre, jumpMSSClamp} {
		if rule, exists := r.rules[ruleKey]; exists {
			var table, chain string
			switch ruleKey {
			case jumpNatPost:
				table = tableNat
				chain = chainPOSTROUTING
			case jumpManglePre:
				table = tableMangle
				chain = chainPREROUTING
			case jumpNatPre:
				table = tableNat
				chain = chainPREROUTING
			case jumpMSSClamp:
				table = tableMangle
				chain = chainFORWARD
			default:
				return fmt.Errorf("unknown jump rule: %s", ruleKey)
			}

			if err := r.iptablesClient.DeleteIfExists(table, chain, rule...); err != nil {
				return fmt.Errorf("delete rule from chain %s in table %s, err: %v", chain, table, err)
			}
			delete(r.rules, ruleKey)
		}
	}
	return nil
}

func (r *router) addNatRule(pair firewall.RouterPair) error {
	ruleKey := firewall.GenKey(firewall.NatFormat, pair)

	if rule, exists := r.rules[ruleKey]; exists {
		if err := r.iptablesClient.DeleteIfExists(tableMangle, chainRTPRE, rule...); err != nil {
			return fmt.Errorf("error while removing existing marking rule for %s: %v", pair.Destination, err)
		}
		delete(r.rules, ruleKey)
	}

	markValue := nbnet.PreroutingFwmarkMasquerade
	if pair.Inverse {
		markValue = nbnet.PreroutingFwmarkMasqueradeReturn
	}

	rule := []string{"-i", r.wgIface.Name()}
	if pair.Inverse {
		rule = []string{"!", "-i", r.wgIface.Name()}
	}

	rule = append(rule,
		"-m", "conntrack",
		"--ctstate", "NEW",
	)
	sourceExp, err := r.applyNetwork("-s", pair.Source, nil)
	if err != nil {
		return fmt.Errorf("apply network -s: %w", err)
	}
	destExp, err := r.applyNetwork("-d", pair.Destination, nil)
	if err != nil {
		return fmt.Errorf("apply network -d: %w", err)
	}

	rule = append(rule, sourceExp...)
	rule = append(rule, destExp...)
	rule = append(rule,
		"-j", "MARK", "--set-mark", fmt.Sprintf("%#x", markValue),
	)

	// Ensure nat rules come first, so the mark can be overwritten.
	// Currently overwritten by the dst-type LOCAL rules for redirected traffic.
	if err := r.iptablesClient.Insert(tableMangle, chainRTPRE, 1, rule...); err != nil {
		// TODO: rollback ipset counter
		return fmt.Errorf("error while adding marking rule for %s: %v", pair.Destination, err)
	}

	r.rules[ruleKey] = rule

	r.updateState()
	return nil
}

func (r *router) removeNatRule(pair firewall.RouterPair) error {
	ruleKey := firewall.GenKey(firewall.NatFormat, pair)

	if rule, exists := r.rules[ruleKey]; exists {
		if err := r.iptablesClient.DeleteIfExists(tableMangle, chainRTPRE, rule...); err != nil {
			return fmt.Errorf("error while removing marking rule for %s: %v", pair.Destination, err)
		}
		delete(r.rules, ruleKey)

		if err := r.decrementSetCounter(rule); err != nil {
			return fmt.Errorf("decrement ipset counter: %w", err)
		}
	} else {
		log.Debugf("marking rule %s not found", ruleKey)
	}

	r.updateState()
	return nil
}

func (r *router) updateState() {
	if r.stateManager == nil {
		return
	}

	var currentState *ShutdownState
	if existing := r.stateManager.GetState(currentState); existing != nil {
		if existingState, ok := existing.(*ShutdownState); ok {
			currentState = existingState
		}
	}
	if currentState == nil {
		currentState = &ShutdownState{}
	}

	currentState.Lock()
	defer currentState.Unlock()

	if r.v6 {
		currentState.RouteRules6 = r.rules
		currentState.RouteIPsetCounter6 = r.ipsetCounter
	} else {
		currentState.RouteRules = r.rules
		currentState.RouteIPsetCounter = r.ipsetCounter
	}

	if err := r.stateManager.UpdateState(currentState); err != nil {
		log.Errorf("failed to update state: %v", err)
	}
}

func (r *router) AddDNATRule(rule firewall.ForwardRule) (firewall.Rule, error) {
	if err := r.ipFwdState.RequestForwarding(); err != nil {
		return nil, err
	}

	ruleKey := rule.ID()
	if _, exists := r.rules[ruleKey+dnatSuffix]; exists {
		return rule, nil
	}

	toDestination := rule.TranslatedAddress.String()
	switch {
	case len(rule.TranslatedPort.Values) == 0:
		// no translated port, use original port
	case len(rule.TranslatedPort.Values) == 1:
		toDestination += fmt.Sprintf(":%d", rule.TranslatedPort.Values[0])
	case rule.TranslatedPort.IsRange && len(rule.TranslatedPort.Values) == 2:
		// need the "/originalport" suffix to avoid dnat port randomization
		toDestination += fmt.Sprintf(":%d-%d/%d", rule.TranslatedPort.Values[0], rule.TranslatedPort.Values[1], rule.DestinationPort.Values[0])
	default:
		return nil, fmt.Errorf("invalid translated port: %v", rule.TranslatedPort)
	}

	proto := strings.ToLower(string(rule.Protocol))

	rules := make(map[string]ruleInfo, 3)

	// DNAT rule
	dnatRule := []string{
		"!", "-i", r.wgIface.Name(),
		"-p", proto,
		"-j", "DNAT",
		"--to-destination", toDestination,
	}
	dnatRule = append(dnatRule, applyPort("--dport", &rule.DestinationPort)...)
	rules[ruleKey+dnatSuffix] = ruleInfo{
		table: tableNat,
		chain: chainRTRDR,
		rule:  dnatRule,
	}

	// SNAT rule
	snatRule := []string{
		"-o", r.wgIface.Name(),
		"-p", proto,
		"-d", rule.TranslatedAddress.String(),
		"-j", "MASQUERADE",
	}
	snatRule = append(snatRule, applyPort("--dport", &rule.TranslatedPort)...)
	rules[ruleKey+snatSuffix] = ruleInfo{
		table: tableNat,
		chain: chainRTNAT,
		rule:  snatRule,
	}

	// Forward filtering rule, if fwd policy is DROP
	forwardRule := []string{
		"-o", r.wgIface.Name(),
		"-p", proto,
		"-d", rule.TranslatedAddress.String(),
		"-j", "ACCEPT",
	}
	forwardRule = append(forwardRule, applyPort("--dport", &rule.TranslatedPort)...)
	rules[ruleKey+fwdSuffix] = ruleInfo{
		table: tableFilter,
		chain: chainRTFWDOUT,
		rule:  forwardRule,
	}

	for key, ruleInfo := range rules {
		if err := r.iptablesClient.Append(ruleInfo.table, ruleInfo.chain, ruleInfo.rule...); err != nil {
			if rollbackErr := r.rollbackRules(rules); rollbackErr != nil {
				log.Errorf("rollback failed: %v", rollbackErr)
			}
			return nil, fmt.Errorf("add rule %s: %w", key, err)
		}
		r.rules[key] = ruleInfo.rule
	}

	r.updateState()
	return rule, nil
}

func (r *router) rollbackRules(rules map[string]ruleInfo) error {
	var merr *multierror.Error
	for key, ruleInfo := range rules {
		if err := r.iptablesClient.DeleteIfExists(ruleInfo.table, ruleInfo.chain, ruleInfo.rule...); err != nil {
			merr = multierror.Append(merr, fmt.Errorf("rollback rule %s: %w", key, err))
			// On rollback error, add to rules map for next cleanup
			r.rules[key] = ruleInfo.rule
		}
	}
	if merr != nil {
		r.updateState()
	}
	return nberrors.FormatErrorOrNil(merr)
}

func (r *router) DeleteDNATRule(rule firewall.Rule) error {
	if err := r.ipFwdState.ReleaseForwarding(); err != nil {
		log.Errorf("%v", err)
	}

	ruleKey := rule.ID()

	var merr *multierror.Error
	if dnatRule, exists := r.rules[ruleKey+dnatSuffix]; exists {
		if err := r.iptablesClient.Delete(tableNat, chainRTRDR, dnatRule...); err != nil {
			merr = multierror.Append(merr, fmt.Errorf("delete DNAT rule: %w", err))
		}
		delete(r.rules, ruleKey+dnatSuffix)
	}

	if snatRule, exists := r.rules[ruleKey+snatSuffix]; exists {
		if err := r.iptablesClient.Delete(tableNat, chainRTNAT, snatRule...); err != nil {
			merr = multierror.Append(merr, fmt.Errorf("delete SNAT rule: %w", err))
		}
		delete(r.rules, ruleKey+snatSuffix)
	}

	if fwdRule, exists := r.rules[ruleKey+fwdSuffix]; exists {
		if err := r.iptablesClient.Delete(tableFilter, chainRTFWDOUT, fwdRule...); err != nil {
			merr = multierror.Append(merr, fmt.Errorf("delete forward rule: %w", err))
		}
		delete(r.rules, ruleKey+fwdSuffix)
	}

	r.updateState()
	return nberrors.FormatErrorOrNil(merr)
}

func (r *router) genRouteRuleSpec(params routeFilteringRuleParams, sources []netip.Prefix) ([]string, error) {
	var rule []string

	sourceExp, err := r.applyNetwork("-s", params.Source, sources)
	if err != nil {
		return nil, fmt.Errorf("apply network -s: %w", err)

	}
	destExp, err := r.applyNetwork("-d", params.Destination, nil)
	if err != nil {
		return nil, fmt.Errorf("apply network -d: %w", err)
	}

	rule = append(rule, sourceExp...)
	rule = append(rule, destExp...)

	if params.Proto != firewall.ProtocolALL {
		rule = append(rule, "-p", strings.ToLower(protoForFamily(params.Proto, r.v6)))
		rule = append(rule, applyPort("--sport", params.SPort)...)
		rule = append(rule, applyPort("--dport", params.DPort)...)
	}

	rule = append(rule, "-j", actionToStr(params.Action))

	return rule, nil
}

func (r *router) applyNetwork(flag string, network firewall.Network, prefixes []netip.Prefix) ([]string, error) {
	direction := "src"
	if flag == "-d" {
		direction = "dst"
	}

	if network.IsSet() {
		name := r.ipsetName(network.Set.HashedName())
		if _, err := r.ipsetCounter.Increment(name, prefixes); err != nil {
			return nil, fmt.Errorf("create or get ipset: %w", err)
		}

		return []string{"-m", "set", matchSet, name, direction}, nil
	}
	if network.IsPrefix() {
		return []string{flag, network.Prefix.String()}, nil
	}

	// nolint:nilnil
	return nil, nil
}

func (r *router) UpdateSet(set firewall.Set, prefixes []netip.Prefix) error {
	name := r.ipsetName(set.HashedName())
	var merr *multierror.Error
	for _, prefix := range prefixes {
		if err := r.addPrefixToIPSet(name, prefix); err != nil {
			merr = multierror.Append(merr, fmt.Errorf("add prefix to ipset: %w", err))
		}
	}
	if merr == nil {
		log.Debugf("updated set %s with prefixes %v", name, prefixes)
	}

	return nberrors.FormatErrorOrNil(merr)
}

// AddInboundDNAT adds an inbound DNAT rule redirecting traffic from NetBird peers to local services.
func (r *router) AddInboundDNAT(localAddr netip.Addr, protocol firewall.Protocol, originalPort, translatedPort uint16) error {
	ruleID := fmt.Sprintf("inbound-dnat-%s-%s-%d-%d", localAddr.String(), protocol, originalPort, translatedPort)

	if _, exists := r.rules[ruleID]; exists {
		return nil
	}

	dnatRule := []string{
		"-i", r.wgIface.Name(),
		"-p", strings.ToLower(protoForFamily(protocol, r.v6)),
		"--dport", strconv.Itoa(int(originalPort)),
		"-d", localAddr.String(),
		"-m", "addrtype", "--dst-type", "LOCAL",
		"-j", "DNAT",
		"--to-destination", ":" + strconv.Itoa(int(translatedPort)),
	}

	ruleInfo := ruleInfo{
		table: tableNat,
		chain: chainRTRDR,
		rule:  dnatRule,
	}

	if err := r.iptablesClient.Append(ruleInfo.table, ruleInfo.chain, ruleInfo.rule...); err != nil {
		return fmt.Errorf("add inbound DNAT rule: %w", err)
	}
	r.rules[ruleID] = ruleInfo.rule

	r.updateState()
	return nil
}

// RemoveInboundDNAT removes an inbound DNAT rule.
func (r *router) RemoveInboundDNAT(localAddr netip.Addr, protocol firewall.Protocol, originalPort, translatedPort uint16) error {
	ruleID := fmt.Sprintf("inbound-dnat-%s-%s-%d-%d", localAddr.String(), protocol, originalPort, translatedPort)

	if dnatRule, exists := r.rules[ruleID]; exists {
		if err := r.iptablesClient.Delete(tableNat, chainRTRDR, dnatRule...); err != nil {
			return fmt.Errorf("delete inbound DNAT rule: %w", err)
		}
		delete(r.rules, ruleID)
	}

	r.updateState()
	return nil
}

// ensureNATOutputChain lazily creates the OUTPUT NAT chain and jump rule on first use.
func (r *router) ensureNATOutputChain() error {
	if _, exists := r.rules[jumpNatOutput]; exists {
		return nil
	}

	chainExists, err := r.iptablesClient.ChainExists(tableNat, chainNATOutput)
	if err != nil {
		return fmt.Errorf("check chain %s: %w", chainNATOutput, err)
	}
	if !chainExists {
		if err := r.iptablesClient.NewChain(tableNat, chainNATOutput); err != nil {
			return fmt.Errorf("create chain %s: %w", chainNATOutput, err)
		}
	}

	jumpRule := []string{"-j", chainNATOutput}
	if err := r.iptablesClient.Insert(tableNat, "OUTPUT", 1, jumpRule...); err != nil {
		if !chainExists {
			if delErr := r.iptablesClient.ClearAndDeleteChain(tableNat, chainNATOutput); delErr != nil {
				log.Warnf("failed to rollback chain %s: %v", chainNATOutput, delErr)
			}
		}
		return fmt.Errorf("add OUTPUT jump rule: %w", err)
	}
	r.rules[jumpNatOutput] = jumpRule

	r.updateState()
	return nil
}

// AddOutputDNAT adds an OUTPUT chain DNAT rule for locally-generated traffic.
func (r *router) AddOutputDNAT(localAddr netip.Addr, protocol firewall.Protocol, originalPort, translatedPort uint16) error {
	ruleID := fmt.Sprintf("output-dnat-%s-%s-%d-%d", localAddr.String(), protocol, originalPort, translatedPort)

	if _, exists := r.rules[ruleID]; exists {
		return nil
	}

	if err := r.ensureNATOutputChain(); err != nil {
		return err
	}

	dnatRule := []string{
		"-p", strings.ToLower(string(protocol)),
		"--dport", strconv.Itoa(int(originalPort)),
		"-d", localAddr.String(),
		"-j", "DNAT",
		"--to-destination", ":" + strconv.Itoa(int(translatedPort)),
	}

	if err := r.iptablesClient.Append(tableNat, chainNATOutput, dnatRule...); err != nil {
		return fmt.Errorf("add output DNAT rule: %w", err)
	}
	r.rules[ruleID] = dnatRule

	r.updateState()
	return nil
}

// RemoveOutputDNAT removes an OUTPUT chain DNAT rule.
func (r *router) RemoveOutputDNAT(localAddr netip.Addr, protocol firewall.Protocol, originalPort, translatedPort uint16) error {
	ruleID := fmt.Sprintf("output-dnat-%s-%s-%d-%d", localAddr.String(), protocol, originalPort, translatedPort)

	if dnatRule, exists := r.rules[ruleID]; exists {
		if err := r.iptablesClient.Delete(tableNat, chainNATOutput, dnatRule...); err != nil {
			return fmt.Errorf("delete output DNAT rule: %w", err)
		}
		delete(r.rules, ruleID)
	}

	r.updateState()
	return nil
}

func applyPort(flag string, port *firewall.Port) []string {
	if port == nil {
		return nil
	}

	if port.IsRange && len(port.Values) == 2 {
		return []string{flag, fmt.Sprintf("%d:%d", port.Values[0], port.Values[1])}
	}

	if len(port.Values) > 1 {
		portList := make([]string, len(port.Values))
		for i, p := range port.Values {
			portList[i] = strconv.Itoa(int(p))
		}
		return []string{"-m", "multiport", flag, strings.Join(portList, ",")}
	}

	return []string{flag, strconv.Itoa(int(port.Values[0]))}
}

// ipsetName returns the ipset name, suffixed with "-v6" for the v6 router
// to avoid collisions since ipsets are global in the kernel.
func (r *router) ipsetName(name string) string {
	if r.v6 {
		return name + "-v6"
	}
	return name
}

func (r *router) createIPSet(name string) error {
	opts := ipset.CreateOptions{
		Replace: true,
	}
	if r.v6 {
		opts.Family = ipset.FamilyIPV6
	}

	if err := ipset.Create(name, ipset.TypeHashNet, opts); err != nil {
		return fmt.Errorf("create ipset %s: %w", name, err)
	}

	log.Debugf("created ipset %s with type hash:net", name)
	return nil
}

func (r *router) addPrefixToIPSet(name string, prefix netip.Prefix) error {
	addr := prefix.Addr()
	ip := addr.AsSlice()

	entry := &ipset.Entry{
		IP:      ip,
		CIDR:    uint8(prefix.Bits()),
		Replace: true,
	}

	if err := ipset.Add(name, entry); err != nil {
		return fmt.Errorf("add prefix to ipset %s: %w", name, err)
	}

	return nil
}

func (r *router) destroyIPSet(name string) error {
	return ipset.Destroy(name)
}