[client] Mark netbird data plane traffic to identify interface traffic correctly (#3623)

client/firewall/iptables/router_linux.go

@@ -41,6 +41,8 @@ const (
 	jumpManglePre  = "jump-mangle-pre"
 	jumpNatPre     = "jump-nat-pre"
 	jumpNatPost    = "jump-nat-post"
+	markManglePre  = "mark-mangle-pre"
+	markManglePost = "mark-mangle-post"
 	matchSet       = "--match-set"
 
 	dnatSuffix = "_dnat"
@@ -115,6 +117,10 @@ func (r *router) init(stateManager *statemanager.Manager) error {
 		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
@@ -348,12 +354,16 @@ func (r *router) Reset() error {
 	if err := r.cleanUpDefaultForwardRules(); err != nil {
 		merr = multierror.Append(merr, err)
 	}
-	r.rules = make(map[string][]string)
 
 	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)
@@ -423,6 +433,57 @@ func (r *router) createContainers() error {
 	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{
@@ -464,7 +525,7 @@ func (r *router) insertEstablishedRule(chain string) error {
 }
 
 func (r *router) addJumpRules() error {
-	// Jump to NAT chain
+	// 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)

client/firewall/iptables/router_linux_test.go

@@ -46,7 +46,9 @@ func TestIptablesManager_RestoreOrCreateContainers(t *testing.T) {
 	// 5. jump rule to PRE nat chain
 	// 6. static outbound masquerade rule
 	// 7. static return masquerade rule
-	require.Len(t, manager.rules, 7, "should have created rules map")
+	// 8. mangle prerouting mark rule
+	// 9. mangle postrouting mark rule
+	require.Len(t, manager.rules, 9, "should have created rules map")
 
 	exists, err := manager.iptablesClient.Exists(tableNat, chainPOSTROUTING, "-j", chainRTNAT)
 	require.NoError(t, err, "should be able to query the iptables %s table and %s chain", tableNat, chainPOSTROUTING)

client/firewall/nftables/acl_linux.go

@@ -27,7 +27,8 @@ const (
 	// filter chains contains the rules that jump to the rules chains
 	chainNameInputFilter       = "netbird-acl-input-filter"
 	chainNameForwardFilter     = "netbird-acl-forward-filter"
-	chainNamePrerouting    = "netbird-rt-prerouting"
+	chainNameManglePrerouting  = "netbird-mangle-prerouting"
+	chainNameManglePostrouting = "netbird-mangle-postrouting"
 
 	allowNetbirdInputRuleID = "allow Netbird incoming traffic"
 )
@@ -462,13 +463,15 @@ func (m *AclManager) createDefaultChains() (err error) {
 // go through the input filter as well. This will enable e.g. Docker services to keep working by accessing the
 // netbird peer IP.
 func (m *AclManager) allowRedirectedTraffic(chainFwFilter *nftables.Chain) error {
-	m.chainPrerouting = m.rConn.AddChain(&nftables.Chain{
+	// Chain is created by route manager
-		Name:     chainNamePrerouting,
+	// TODO: move creation to a common place
+	m.chainPrerouting = &nftables.Chain{
+		Name:     chainNameManglePrerouting,
 		Table:    m.workTable,
 		Type:     nftables.ChainTypeFilter,
 		Hooknum:  nftables.ChainHookPrerouting,
 		Priority: nftables.ChainPriorityMangle,
-	})
+	}
 
 	m.addFwmarkToForward(chainFwFilter)
 

client/firewall/nftables/router_linux.go

@@ -100,6 +100,10 @@ func (r *router) init(workTable *nftables.Table) error {
 		return fmt.Errorf("create containers: %w", err)
 	}
 
+	if err := r.setupDataPlaneMark(); err != nil {
+		log.Errorf("failed to set up data plane mark: %v", err)
+	}
+
 	return nil
 }
 
@@ -196,15 +200,21 @@ func (r *router) createContainers() error {
 		Type:     nftables.ChainTypeNAT,
 	})
 
-	// Chain is created by acl manager
+	r.chains[chainNameManglePostrouting] = r.conn.AddChain(&nftables.Chain{
-	// TODO: move creation to a common place
+		Name:     chainNameManglePostrouting,
-	r.chains[chainNamePrerouting] = &nftables.Chain{
+		Table:    r.workTable,
-		Name:     chainNamePrerouting,
+		Hooknum:  nftables.ChainHookPostrouting,
+		Priority: nftables.ChainPriorityMangle,
+		Type:     nftables.ChainTypeFilter,
+	})
+
+	r.chains[chainNameManglePrerouting] = r.conn.AddChain(&nftables.Chain{
+		Name:     chainNameManglePrerouting,
 		Table:    r.workTable,
 		Hooknum:  nftables.ChainHookPrerouting,
 		Priority: nftables.ChainPriorityMangle,
 		Type:     nftables.ChainTypeFilter,
-	}
+	})
 
 	// Add the single NAT rule that matches on mark
 	if err := r.addPostroutingRules(); err != nil {
@@ -220,7 +230,83 @@ func (r *router) createContainers() error {
 	}
 
 	if err := r.conn.Flush(); err != nil {
-		return fmt.Errorf("nftables: unable to initialize table: %v", err)
+		return fmt.Errorf("initialize tables: %v", err)
+	}
+
+	return nil
+}
+
+// setupDataPlaneMark configures the fwmark for the data plane
+func (r *router) setupDataPlaneMark() error {
+	if r.chains[chainNameManglePrerouting] == nil || r.chains[chainNameManglePostrouting] == nil {
+		return errors.New("no mangle chains found")
+	}
+
+	ctNew := getCtNewExprs()
+	preExprs := []expr.Any{
+		&expr.Meta{
+			Key:      expr.MetaKeyIIFNAME,
+			Register: 1,
+		},
+		&expr.Cmp{
+			Op:       expr.CmpOpEq,
+			Register: 1,
+			Data:     ifname(r.wgIface.Name()),
+		},
+	}
+	preExprs = append(preExprs, ctNew...)
+	preExprs = append(preExprs,
+		&expr.Immediate{
+			Register: 1,
+			Data:     binaryutil.NativeEndian.PutUint32(nbnet.DataPlaneMarkIn),
+		},
+		&expr.Ct{
+			Key:            expr.CtKeyMARK,
+			Register:       1,
+			SourceRegister: true,
+		},
+	)
+
+	preNftRule := &nftables.Rule{
+		Table: r.workTable,
+		Chain: r.chains[chainNameManglePrerouting],
+		Exprs: preExprs,
+	}
+	r.conn.AddRule(preNftRule)
+
+	postExprs := []expr.Any{
+		&expr.Meta{
+			Key:      expr.MetaKeyOIFNAME,
+			Register: 1,
+		},
+		&expr.Cmp{
+			Op:       expr.CmpOpEq,
+			Register: 1,
+			Data:     ifname(r.wgIface.Name()),
+		},
+	}
+	postExprs = append(postExprs, ctNew...)
+	postExprs = append(postExprs,
+		&expr.Immediate{
+			Register: 1,
+			Data:     binaryutil.NativeEndian.PutUint32(nbnet.DataPlaneMarkOut),
+		},
+		&expr.Ct{
+			Key:            expr.CtKeyMARK,
+			Register:       1,
+			SourceRegister: true,
+		},
+	)
+
+	postNftRule := &nftables.Rule{
+		Table: r.workTable,
+		Chain: r.chains[chainNameManglePostrouting],
+		Exprs: postExprs,
+	}
+	r.conn.AddRule(postNftRule)
+
+	if err := r.conn.Flush(); err != nil {
+		return fmt.Errorf("flush: %w", err)
 	}
 
 	return nil
@@ -516,26 +602,10 @@ func (r *router) addNatRule(pair firewall.RouterPair) error {
 		op = expr.CmpOpNeq
 	}
 
-	exprs := []expr.Any{
 	// We only care about NEW connections to mark them and later identify them in the postrouting chain for masquerading.
 	// Masquerading will take care of the conntrack state, which means we won't need to mark established connections.
-		&expr.Ct{
+	exprs := getCtNewExprs()
-			Key:      expr.CtKeySTATE,
+	exprs = append(exprs,
-			Register: 1,
-		},
-		&expr.Bitwise{
-			SourceRegister: 1,
-			DestRegister:   1,
-			Len:            4,
-			Mask:           binaryutil.NativeEndian.PutUint32(expr.CtStateBitNEW),
-			Xor:            binaryutil.NativeEndian.PutUint32(0),
-		},
-		&expr.Cmp{
-			Op:       expr.CmpOpNeq,
-			Register: 1,
-			Data:     []byte{0, 0, 0, 0},
-		},
-
 		// interface matching
 		&expr.Meta{
 			Key:      expr.MetaKeyIIFNAME,
@@ -546,7 +616,7 @@ func (r *router) addNatRule(pair firewall.RouterPair) error {
 			Register: 1,
 			Data:     ifname(r.wgIface.Name()),
 		},
-	}
+	)
 
 	exprs = append(exprs, sourceExp...)
 	exprs = append(exprs, destExp...)
@@ -578,7 +648,7 @@ func (r *router) addNatRule(pair firewall.RouterPair) error {
 
 	r.rules[ruleKey] = r.conn.AddRule(&nftables.Rule{
 		Table:    r.workTable,
-		Chain:    r.chains[chainNamePrerouting],
+		Chain:    r.chains[chainNameManglePrerouting],
 		Exprs:    exprs,
 		UserData: []byte(ruleKey),
 	})
@@ -1324,3 +1394,24 @@ func applyPort(port *firewall.Port, isSource bool) []expr.Any {
 
 	return exprs
 }
+
+func getCtNewExprs() []expr.Any {
+	return []expr.Any{
+		&expr.Ct{
+			Key:      expr.CtKeySTATE,
+			Register: 1,
+		},
+		&expr.Bitwise{
+			SourceRegister: 1,
+			DestRegister:   1,
+			Len:            4,
+			Mask:           binaryutil.NativeEndian.PutUint32(expr.CtStateBitNEW),
+			Xor:            binaryutil.NativeEndian.PutUint32(0),
+		},
+		&expr.Cmp{
+			Op:       expr.CmpOpNeq,
+			Register: 1,
+			Data:     []byte{0, 0, 0, 0},
+		},
+	}
+}

client/firewall/nftables/router_linux_test.go

@@ -100,7 +100,7 @@ func TestNftablesManager_AddNatRule(t *testing.T) {
 				natRuleKey := firewall.GenKey(firewall.PreroutingFormat, testCase.InputPair)
 				found := 0
 				for _, chain := range rtr.chains {
-					if chain.Name == chainNamePrerouting {
+					if chain.Name == chainNameManglePrerouting {
 						rules, err := nftablesTestingClient.GetRules(chain.Table, chain)
 						require.NoError(t, err, "should list rules for %s table and %s chain", chain.Table.Name, chain.Name)
 						for _, rule := range rules {
@@ -141,7 +141,7 @@ func TestNftablesManager_RemoveNatRule(t *testing.T) {
 			// Verify the rule was added
 			natRuleKey := firewall.GenKey(firewall.PreroutingFormat, testCase.InputPair)
 			found := false
-			rules, err := rtr.conn.GetRules(rtr.workTable, rtr.chains[chainNamePrerouting])
+			rules, err := rtr.conn.GetRules(rtr.workTable, rtr.chains[chainNameManglePrerouting])
 			require.NoError(t, err, "should list rules")
 			for _, rule := range rules {
 				if len(rule.UserData) > 0 && string(rule.UserData) == natRuleKey {
@@ -157,7 +157,7 @@ func TestNftablesManager_RemoveNatRule(t *testing.T) {
 
 			// Verify the rule was removed
 			found = false
-			rules, err = rtr.conn.GetRules(rtr.workTable, rtr.chains[chainNamePrerouting])
+			rules, err = rtr.conn.GetRules(rtr.workTable, rtr.chains[chainNameManglePrerouting])
 			require.NoError(t, err, "should list rules after removal")
 			for _, rule := range rules {
 				if len(rule.UserData) > 0 && string(rule.UserData) == natRuleKey {

client/iface/configurer/usp.go

@@ -357,7 +357,7 @@ func toWgUserspaceString(wgCfg wgtypes.Config) string {
 
 func getFwmark() int {
 	if nbnet.AdvancedRouting() {
-		return nbnet.NetbirdFwmark
+		return nbnet.ControlPlaneMark
 	}
 	return 0
 }

client/internal/netflow/conntrack/conntrack.go

@@ -14,6 +14,7 @@ import (
 	"github.com/ti-mo/netfilter"
 
 	nftypes "github.com/netbirdio/netbird/client/internal/netflow/types"
+	nbnet "github.com/netbirdio/netbird/util/net"
 )
 
 const defaultChannelSize = 100
@@ -176,7 +177,7 @@ func (c *ConnTrack) handleEvent(event nfct.Event) {
 	srcIP := flow.TupleOrig.IP.SourceAddress
 	dstIP := flow.TupleOrig.IP.DestinationAddress
 
-	if !c.relevantFlow(srcIP, dstIP) {
+	if !c.relevantFlow(flow.Mark, srcIP, dstIP) {
 		return
 	}
 
@@ -193,7 +194,7 @@ func (c *ConnTrack) handleEvent(event nfct.Event) {
 	}
 
 	flowID := c.getFlowID(flow.ID)
-	direction := c.inferDirection(srcIP, dstIP)
+	direction := c.inferDirection(flow.Mark, srcIP, dstIP)
 
 	eventType := nftypes.TypeStart
 	eventStr := "New"
@@ -224,15 +225,14 @@ func (c *ConnTrack) handleEvent(event nfct.Event) {
 }
 
 // relevantFlow checks if the flow is related to the specified interface
-func (c *ConnTrack) relevantFlow(srcIP, dstIP netip.Addr) bool {
+func (c *ConnTrack) relevantFlow(mark uint32, srcIP, dstIP netip.Addr) bool {
-	// TODO: filter traffic by interface
+	if nbnet.IsDataPlaneMark(mark) {
-
+		return true
-	wgnet := c.iface.Address().Network
-	if !wgnet.Contains(srcIP.AsSlice()) && !wgnet.Contains(dstIP.AsSlice()) {
-		return false
 	}
 
-	return true
+	// fallback if mark rules are not in place
+	wgnet := c.iface.Address().Network
+	return wgnet.Contains(srcIP.AsSlice()) || wgnet.Contains(dstIP.AsSlice())
 }
 
 // mapRxPackets maps packet counts to RX based on flow direction
@@ -282,7 +282,15 @@ func (c *ConnTrack) getFlowID(conntrackID uint32) uuid.UUID {
 	return uuid.NewSHA1(c.instanceID, buf[:])
 }
 
-func (c *ConnTrack) inferDirection(srcIP, dstIP netip.Addr) nftypes.Direction {
+func (c *ConnTrack) inferDirection(mark uint32, srcIP, dstIP netip.Addr) nftypes.Direction {
+	switch mark {
+	case nbnet.DataPlaneMarkIn:
+		return nftypes.Ingress
+	case nbnet.DataPlaneMarkOut:
+		return nftypes.Egress
+	}
+
+	// fallback if marks are not set
 	wgaddr := c.iface.Address().IP
 	wgnetwork := c.iface.Address().Network
 	src, dst := srcIP.AsSlice(), dstIP.AsSlice()
@@ -298,8 +306,6 @@ func (c *ConnTrack) inferDirection(srcIP, dstIP netip.Addr) nftypes.Direction {
 	case wgnetwork.Contains(dst):
 		// resource network -> netbird network
 		return nftypes.Egress
-
-		// TODO: handle site2site traffic
 	}
 
 	return nftypes.DirectionUnknown

client/internal/netflow/types/types.go

@@ -10,6 +10,8 @@ import (
 	"github.com/netbirdio/netbird/client/iface/wgaddr"
 )
 
+const ZoneID = 0x1BD0
+
 type Protocol uint8
 
 const (

client/internal/routemanager/systemops/systemops_linux.go

@@ -57,8 +57,8 @@ func getSetupRules() []ruleParams {
 	return []ruleParams{
 		{100, -1, syscall.RT_TABLE_MAIN, netlink.FAMILY_V4, false, 0, "rule with suppress prefixlen v4"},
 		{100, -1, syscall.RT_TABLE_MAIN, netlink.FAMILY_V6, false, 0, "rule with suppress prefixlen v6"},
-		{110, nbnet.NetbirdFwmark, NetbirdVPNTableID, netlink.FAMILY_V4, true, -1, "rule v4 netbird"},
+		{110, nbnet.ControlPlaneMark, NetbirdVPNTableID, netlink.FAMILY_V4, true, -1, "rule v4 netbird"},
-		{110, nbnet.NetbirdFwmark, NetbirdVPNTableID, netlink.FAMILY_V6, true, -1, "rule v6 netbird"},
+		{110, nbnet.ControlPlaneMark, NetbirdVPNTableID, netlink.FAMILY_V6, true, -1, "rule v6 netbird"},
 	}
 }
 

util/net/env_linux.go

@@ -88,9 +88,21 @@ func CheckFwmarkSupport() bool {
 		log.Warnf("failed to dial with fwmark: %v", err)
 		return false
 	}
+
+	defer func() {
 		if err := conn.Close(); err != nil {
 			log.Warnf("failed to close connection: %v", err)
+		}
+	}()
 
+	if err := conn.SetWriteDeadline(time.Now().Add(time.Millisecond * 100)); err != nil {
+		log.Warnf("failed to set write deadline: %v", err)
+		return false
+	}
+
+	if _, err := conn.Write([]byte("")); err != nil {
+		log.Warnf("failed to write to fwmark connection: %v", err)
+		return false
 	}
 
 	return true

util/net/net.go

@@ -8,14 +8,40 @@ import (
 )
 
 const (
-	// NetbirdFwmark is the fwmark value used by Netbird via wireguard
+	// ControlPlaneMark is the fwmark value used to mark packets that should not be routed through the NetBird interface to
-	NetbirdFwmark = 0x1BD00
+	// avoid routing loops.
+	// This includes all control plane traffic (mgmt, signal, flows), relay, ICE/stun/turn and everything that is emitted by the wireguard socket.
+	// It doesn't collide with the other marks, as the others are used for data plane traffic only.
+	ControlPlaneMark = 0x1BD00
 
-	PreroutingFwmarkRedirected       = 0x1BD01
+	// Data plane marks (0x1BD10 - 0x1BDFF)
-	PreroutingFwmarkMasquerade       = 0x1BD11
+
-	PreroutingFwmarkMasqueradeReturn = 0x1BD12
+	// DataPlaneMarkLower is the lowest value for the data plane range
+	DataPlaneMarkLower = 0x1BD10
+	// DataPlaneMarkUpper is the highest value for the data plane range
+	DataPlaneMarkUpper = 0x1BDFF
+
+	// DataPlaneMarkIn is the mark for inbound data plane traffic.
+	DataPlaneMarkIn = 0x1BD10
+
+	// DataPlaneMarkOut is the mark for outbound data plane traffic.
+	DataPlaneMarkOut = 0x1BD11
+
+	// PreroutingFwmarkRedirected is applied to packets that are were redirected (input -> forward, e.g. by Docker or Podman) for special handling.
+	PreroutingFwmarkRedirected = 0x1BD20
+
+	// PreroutingFwmarkMasquerade is applied to packets that arrive from the NetBird interface and should be masqueraded.
+	PreroutingFwmarkMasquerade = 0x1BD21
+
+	// PreroutingFwmarkMasqueradeReturn is applied to packets that will leave through the NetBird interface and should be masqueraded.
+	PreroutingFwmarkMasqueradeReturn = 0x1BD22
 )
 
+// IsDataPlaneMark determines if a fwmark is in the data plane range (0x1BD10-0x1BDFF)
+func IsDataPlaneMark(fwmark uint32) bool {
+	return fwmark >= DataPlaneMarkLower && fwmark <= DataPlaneMarkUpper
+}
+
 // ConnectionID provides a globally unique identifier for network connections.
 // It's used to track connections throughout their lifecycle so the close hook can correlate with the dial hook.
 type ConnectionID string

util/net/net_linux.go

@@ -51,5 +51,5 @@ func setRawSocketMark(conn syscall.RawConn) error {
 }
 
 func setSocketOptInt(fd int) error {
-	return syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_MARK, NetbirdFwmark)
+	return syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_MARK, ControlPlaneMark)
 }