Add default firewall rule to allow netbird traffic (#1056)

Add a default firewall rule to allow netbird traffic to be handled 
by the access control managers.

Userspace manager behavior:
- When running on Windows, a default rule is add on Windows firewall
- For Linux, we are using one of the Kernel managers to add a single rule
- This PR doesn't handle macOS

Kernel manager behavior:
- For NFtables, if there is a filter table, an INPUT rule is added
- Iptables follows the previous flow if running on kernel mode. If running 
on userspace mode, it adds a single rule for INPUT and OUTPUT chains

A new checkerFW package has been introduced to consolidate checks across
route and access control managers.
It supports a new environment variable to skip nftables and allow iptables tests

.gitignore

@@ -19,3 +19,4 @@ client/.distfiles/
 infrastructure_files/setup.env
 infrastructure_files/setup-*.env
 .vscode
+.DS_Store

client/firewall/firewall.go

@@ -40,6 +40,9 @@ const (
 // It declares methods which handle actions required by the
 // Netbird client for ACL and routing functionality
 type Manager interface {
+	// AllowNetbird allows netbird interface traffic
+	AllowNetbird() error
+
 	// AddFiltering rule to the firewall
 	//
 	// If comment argument is empty firewall manager should set

client/firewall/iptables/manager_linux.go

@@ -44,6 +44,7 @@ type Manager struct {
 type iFaceMapper interface {
 	Name() string
 	Address() iface.WGAddress
+	IsUserspaceBind() bool
 }
 
 type ruleset struct {
@@ -52,7 +53,7 @@ type ruleset struct {
 }
 
 // Create iptables firewall manager
-func Create(wgIface iFaceMapper) (*Manager, error) {
+func Create(wgIface iFaceMapper, ipv6Supported bool) (*Manager, error) {
 	m := &Manager{
 		wgIface: wgIface,
 		inputDefaultRuleSpecs: []string{
@@ -62,26 +63,26 @@ func Create(wgIface iFaceMapper) (*Manager, error) {
 		rulesets: make(map[string]ruleset),
 	}
 
-	if err := ipset.Init(); err != nil {
+	err := ipset.Init()
+	if err != nil {
 		return nil, fmt.Errorf("init ipset: %w", err)
 	}
 
 	// init clients for booth ipv4 and ipv6
-	ipv4Client, err := iptables.NewWithProtocol(iptables.ProtocolIPv4)
+	m.ipv4Client, err = iptables.NewWithProtocol(iptables.ProtocolIPv4)
 	if err != nil {
 		return nil, fmt.Errorf("iptables is not installed in the system or not supported")
 	}
-	if isIptablesClientAvailable(ipv4Client) {
-		m.ipv4Client = ipv4Client
+
+	if ipv6Supported {
+		m.ipv6Client, err = iptables.NewWithProtocol(iptables.ProtocolIPv6)
+		if err != nil {
+			log.Warnf("ip6tables is not installed in the system or not supported: %v. Access rules for this protocol won't be applied.", err)
+		}
 	}
 
-	ipv6Client, err := iptables.NewWithProtocol(iptables.ProtocolIPv6)
-	if err != nil {
-		log.Errorf("ip6tables is not installed in the system or not supported: %v", err)
-	} else {
-		if isIptablesClientAvailable(ipv6Client) {
-			m.ipv6Client = ipv6Client
-		}
+	if m.ipv4Client == nil && m.ipv6Client == nil {
+		return nil, fmt.Errorf("iptables is not installed in the system or not enough permissions to use it")
 	}
 
 	if err := m.Reset(); err != nil {
@@ -90,11 +91,6 @@ func Create(wgIface iFaceMapper) (*Manager, error) {
 	return m, nil
 }
 
-func isIptablesClientAvailable(client *iptables.IPTables) bool {
-	_, err := client.ListChains("filter")
-	return err == nil
-}
-
 // AddFiltering rule to the firewall
 //
 // If comment is empty rule ID is used as comment
@@ -276,6 +272,38 @@ func (m *Manager) Reset() error {
 	return nil
 }
 
+// AllowNetbird allows netbird interface traffic
+func (m *Manager) AllowNetbird() error {
+	if m.wgIface.IsUserspaceBind() {
+		_, err := m.AddFiltering(
+			net.ParseIP("0.0.0.0"),
+			"all",
+			nil,
+			nil,
+			fw.RuleDirectionIN,
+			fw.ActionAccept,
+			"",
+			"allow netbird interface traffic",
+		)
+		if err != nil {
+			return fmt.Errorf("failed to allow netbird interface traffic: %w", err)
+		}
+		_, err = m.AddFiltering(
+			net.ParseIP("0.0.0.0"),
+			"all",
+			nil,
+			nil,
+			fw.RuleDirectionOUT,
+			fw.ActionAccept,
+			"",
+			"allow netbird interface traffic",
+		)
+		return err
+	}
+
+	return nil
+}
+
 // Flush doesn't need to be implemented for this manager
 func (m *Manager) Flush() error { return nil }
 
@@ -406,7 +434,7 @@ func (m *Manager) client(ip net.IP) (*iptables.IPTables, error) {
 			return nil, fmt.Errorf("failed to create default drop all in netbird input chain: %w", err)
 		}
 
-		if err := client.AppendUnique("filter", "INPUT", m.inputDefaultRuleSpecs...); err != nil {
+		if err := client.Insert("filter", "INPUT", 1, m.inputDefaultRuleSpecs...); err != nil {
 			return nil, fmt.Errorf("failed to create input chain jump rule: %w", err)
 		}
 

client/firewall/iptables/manager_linux_test.go

@@ -33,6 +33,8 @@ func (i *iFaceMock) Address() iface.WGAddress {
 	panic("AddressFunc is not set")
 }
 
+func (i *iFaceMock) IsUserspaceBind() bool { return false }
+
 func TestIptablesManager(t *testing.T) {
 	ipv4Client, err := iptables.NewWithProtocol(iptables.ProtocolIPv4)
 	require.NoError(t, err)
@@ -53,7 +55,7 @@ func TestIptablesManager(t *testing.T) {
 	}
 
 	// just check on the local interface
-	manager, err := Create(mock)
+	manager, err := Create(mock, true)
 	require.NoError(t, err)
 
 	time.Sleep(time.Second)
@@ -141,7 +143,7 @@ func TestIptablesManagerIPSet(t *testing.T) {
 	}
 
 	// just check on the local interface
-	manager, err := Create(mock)
+	manager, err := Create(mock, true)
 	require.NoError(t, err)
 
 	time.Sleep(time.Second)
@@ -229,7 +231,7 @@ func TestIptablesCreatePerformance(t *testing.T) {
 	for _, testMax := range []int{10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000} {
 		t.Run(fmt.Sprintf("Testing %d rules", testMax), func(t *testing.T) {
 			// just check on the local interface
-			manager, err := Create(mock)
+			manager, err := Create(mock, true)
 			require.NoError(t, err)
 			time.Sleep(time.Second)
 

client/firewall/nftables/manager_linux.go

@@ -29,6 +29,8 @@ const (
 
 	// FilterOutputChainName is the name of the chain that is used for filtering outgoing packets
 	FilterOutputChainName = "netbird-acl-output-filter"
+
+	AllowNetbirdInputRuleID = "allow Netbird incoming traffic"
 )
 
 var anyIP = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
@@ -379,7 +381,7 @@ func (m *Manager) chain(
 		if c != nil {
 			return c, nil
 		}
-		return m.createChainIfNotExists(tf, name, hook, priority, cType)
+		return m.createChainIfNotExists(tf, FilterTableName, name, hook, priority, cType)
 	}
 
 	if ip.To4() != nil {
@@ -399,13 +401,20 @@ func (m *Manager) chain(
 }
 
 // table returns the table for the given family of the IP address
-func (m *Manager) table(family nftables.TableFamily) (*nftables.Table, error) {
+func (m *Manager) table(
+	family nftables.TableFamily, tableName string,
+) (*nftables.Table, error) {
+	// we cache access to Netbird ACL table only
+	if tableName != FilterTableName {
+		return m.createTableIfNotExists(nftables.TableFamilyIPv4, tableName)
+	}
+
 	if family == nftables.TableFamilyIPv4 {
 		if m.tableIPv4 != nil {
 			return m.tableIPv4, nil
 		}
 
-		table, err := m.createTableIfNotExists(nftables.TableFamilyIPv4)
+		table, err := m.createTableIfNotExists(nftables.TableFamilyIPv4, tableName)
 		if err != nil {
 			return nil, err
 		}
@@ -417,7 +426,7 @@ func (m *Manager) table(family nftables.TableFamily) (*nftables.Table, error) {
 		return m.tableIPv6, nil
 	}
 
-	table, err := m.createTableIfNotExists(nftables.TableFamilyIPv6)
+	table, err := m.createTableIfNotExists(nftables.TableFamilyIPv6, tableName)
 	if err != nil {
 		return nil, err
 	}
@@ -425,19 +434,21 @@ func (m *Manager) table(family nftables.TableFamily) (*nftables.Table, error) {
 	return m.tableIPv6, nil
 }
 
-func (m *Manager) createTableIfNotExists(family nftables.TableFamily) (*nftables.Table, error) {
+func (m *Manager) createTableIfNotExists(
+	family nftables.TableFamily, tableName string,
+) (*nftables.Table, error) {
 	tables, err := m.rConn.ListTablesOfFamily(family)
 	if err != nil {
 		return nil, fmt.Errorf("list of tables: %w", err)
 	}
 
 	for _, t := range tables {
-		if t.Name == FilterTableName {
+		if t.Name == tableName {
 			return t, nil
 		}
 	}
 
-	table := m.rConn.AddTable(&nftables.Table{Name: FilterTableName, Family: nftables.TableFamilyIPv4})
+	table := m.rConn.AddTable(&nftables.Table{Name: tableName, Family: nftables.TableFamilyIPv4})
 	if err := m.rConn.Flush(); err != nil {
 		return nil, err
 	}
@@ -446,12 +457,13 @@ func (m *Manager) createTableIfNotExists(family nftables.TableFamily) (*nftables
 
 func (m *Manager) createChainIfNotExists(
 	family nftables.TableFamily,
+	tableName string,
 	name string,
 	hooknum nftables.ChainHook,
 	priority nftables.ChainPriority,
 	chainType nftables.ChainType,
 ) (*nftables.Chain, error) {
-	table, err := m.table(family)
+	table, err := m.table(family, tableName)
 	if err != nil {
 		return nil, err
 	}
@@ -638,6 +650,22 @@ func (m *Manager) Reset() error {
 		return fmt.Errorf("list of chains: %w", err)
 	}
 	for _, c := range chains {
+		// delete Netbird allow input traffic rule if it exists
+		if c.Table.Name == "filter" && c.Name == "INPUT" {
+			rules, err := m.rConn.GetRules(c.Table, c)
+			if err != nil {
+				log.Errorf("get rules for chain %q: %v", c.Name, err)
+				continue
+			}
+			for _, r := range rules {
+				if bytes.Equal(r.UserData, []byte(AllowNetbirdInputRuleID)) {
+					if err := m.rConn.DelRule(r); err != nil {
+						log.Errorf("delete rule: %v", err)
+					}
+				}
+			}
+		}
+
 		if c.Name == FilterInputChainName || c.Name == FilterOutputChainName {
 			m.rConn.DelChain(c)
 		}
@@ -702,6 +730,53 @@ func (m *Manager) Flush() error {
 	return nil
 }
 
+// AllowNetbird allows netbird interface traffic
+func (m *Manager) AllowNetbird() error {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+
+	tf := nftables.TableFamilyIPv4
+	if m.wgIface.Address().IP.To4() == nil {
+		tf = nftables.TableFamilyIPv6
+	}
+
+	chains, err := m.rConn.ListChainsOfTableFamily(tf)
+	if err != nil {
+		return fmt.Errorf("list of chains: %w", err)
+	}
+
+	var chain *nftables.Chain
+	for _, c := range chains {
+		if c.Table.Name == "filter" && c.Name == "INPUT" {
+			chain = c
+			break
+		}
+	}
+
+	if chain == nil {
+		log.Debugf("chain INPUT not found. Skiping add allow netbird rule")
+		return nil
+	}
+
+	rules, err := m.rConn.GetRules(chain.Table, chain)
+	if err != nil {
+		return fmt.Errorf("failed to get rules for the INPUT chain: %v", err)
+	}
+
+	if rule := m.detectAllowNetbirdRule(rules); rule != nil {
+		log.Debugf("allow netbird rule already exists: %v", rule)
+		return nil
+	}
+
+	m.applyAllowNetbirdRules(chain)
+
+	err = m.rConn.Flush()
+	if err != nil {
+		return fmt.Errorf("failed to flush allow input netbird rules: %v", err)
+	}
+	return nil
+}
+
 func (m *Manager) flushWithBackoff() (err error) {
 	backoff := 4
 	backoffTime := 1000 * time.Millisecond
@@ -745,6 +820,44 @@ func (m *Manager) refreshRuleHandles(table *nftables.Table, chain *nftables.Chai
 	return nil
 }
 
+func (m *Manager) applyAllowNetbirdRules(chain *nftables.Chain) {
+	rule := &nftables.Rule{
+		Table: chain.Table,
+		Chain: chain,
+		Exprs: []expr.Any{
+			&expr.Meta{Key: expr.MetaKeyIIFNAME, Register: 1},
+			&expr.Cmp{
+				Op:       expr.CmpOpEq,
+				Register: 1,
+				Data:     ifname(m.wgIface.Name()),
+			},
+			&expr.Verdict{
+				Kind: expr.VerdictAccept,
+			},
+		},
+		UserData: []byte(AllowNetbirdInputRuleID),
+	}
+	_ = m.rConn.InsertRule(rule)
+}
+
+func (m *Manager) detectAllowNetbirdRule(existedRules []*nftables.Rule) *nftables.Rule {
+	ifName := ifname(m.wgIface.Name())
+	for _, rule := range existedRules {
+		if rule.Table.Name == "filter" && rule.Chain.Name == "INPUT" {
+			if len(rule.Exprs) < 4 {
+				if e, ok := rule.Exprs[0].(*expr.Meta); !ok || e.Key != expr.MetaKeyIIFNAME {
+					continue
+				}
+				if e, ok := rule.Exprs[1].(*expr.Cmp); !ok || e.Op != expr.CmpOpEq || !bytes.Equal(e.Data, ifName) {
+					continue
+				}
+				return rule
+			}
+		}
+	}
+	return nil
+}
+
 func encodePort(port fw.Port) []byte {
 	bs := make([]byte, 2)
 	binary.BigEndian.PutUint16(bs, uint16(port.Values[0]))

client/firewall/uspfilter/allow_netbird.go

@@ -0,0 +1,19 @@
+//go:build !windows && !linux
+
+package uspfilter
+
+// Reset firewall to the default state
+func (m *Manager) Reset() error {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+
+	m.outgoingRules = make(map[string]RuleSet)
+	m.incomingRules = make(map[string]RuleSet)
+
+	return nil
+}
+
+// AllowNetbird allows netbird interface traffic
+func (m *Manager) AllowNetbird() error {
+	return nil
+}

client/firewall/uspfilter/allow_netbird_linux.go

@@ -0,0 +1,21 @@
+package uspfilter
+
+// AllowNetbird allows netbird interface traffic
+func (m *Manager) AllowNetbird() error {
+	return nil
+}
+
+// Reset firewall to the default state
+func (m *Manager) Reset() error {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+
+	m.outgoingRules = make(map[string]RuleSet)
+	m.incomingRules = make(map[string]RuleSet)
+
+	if m.resetHook != nil {
+		return m.resetHook()
+	}
+
+	return nil
+}

client/firewall/uspfilter/allow_netbird_windows.go

@@ -0,0 +1,91 @@
+package uspfilter
+
+import (
+	"errors"
+	"fmt"
+	"os/exec"
+	"strings"
+	"syscall"
+)
+
+type action string
+
+const (
+	addRule    action = "add"
+	deleteRule action = "delete"
+
+	firewallRuleName     = "Netbird"
+	noRulesMatchCriteria = "No rules match the specified criteria"
+)
+
+// Reset firewall to the default state
+func (m *Manager) Reset() error {
+	m.mutex.Lock()
+	defer m.mutex.Unlock()
+
+	m.outgoingRules = make(map[string]RuleSet)
+	m.incomingRules = make(map[string]RuleSet)
+
+	if err := manageFirewallRule(firewallRuleName, deleteRule); err != nil {
+		return fmt.Errorf("couldn't remove windows firewall: %w", err)
+	}
+
+	return nil
+}
+
+// AllowNetbird allows netbird interface traffic
+func (m *Manager) AllowNetbird() error {
+	return manageFirewallRule(firewallRuleName,
+		addRule,
+		"dir=in",
+		"enable=yes",
+		"action=allow",
+		"profile=any",
+		"localip="+m.wgIface.Address().IP.String(),
+	)
+}
+
+func manageFirewallRule(ruleName string, action action, args ...string) error {
+	active, err := isFirewallRuleActive(ruleName)
+	if err != nil {
+		return err
+	}
+
+	if (action == addRule && !active) || (action == deleteRule && active) {
+		baseArgs := []string{"advfirewall", "firewall", string(action), "rule", "name=" + ruleName}
+		args := append(baseArgs, args...)
+
+		cmd := exec.Command("netsh", args...)
+		cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
+		return cmd.Run()
+	}
+
+	return nil
+}
+
+func isFirewallRuleActive(ruleName string) (bool, error) {
+	args := []string{"advfirewall", "firewall", "show", "rule", "name=" + ruleName}
+
+	cmd := exec.Command("netsh", args...)
+	cmd.SysProcAttr = &syscall.SysProcAttr{HideWindow: true}
+	output, err := cmd.Output()
+	if err != nil {
+		var exitError *exec.ExitError
+		if errors.As(err, &exitError) {
+			// if the firewall rule is not active, we expect last exit code to be 1
+			exitStatus := exitError.Sys().(syscall.WaitStatus).ExitStatus()
+			if exitStatus == 1 {
+				if strings.Contains(string(output), noRulesMatchCriteria) {
+					return false, nil
+				}
+			}
+		}
+		return false, err
+	}
+
+	if strings.Contains(string(output), noRulesMatchCriteria) {
+		return false, nil
+	}
+
+	return true, nil
+}

client/firewall/uspfilter/uspfilter.go

@@ -19,6 +19,7 @@ const layerTypeAll = 0
 // IFaceMapper defines subset methods of interface required for manager
 type IFaceMapper interface {
 	SetFilter(iface.PacketFilter) error
+	Address() iface.WGAddress
 }
 
 // RuleSet is a set of rules grouped by a string key
@@ -30,6 +31,8 @@ type Manager struct {
 	incomingRules map[string]RuleSet
 	wgNetwork     *net.IPNet
 	decoders      sync.Pool
+	wgIface       IFaceMapper
+	resetHook func() error
 
 	mutex sync.RWMutex
 }
@@ -65,6 +68,7 @@ func Create(iface IFaceMapper) (*Manager, error) {
 		},
 		outgoingRules: make(map[string]RuleSet),
 		incomingRules: make(map[string]RuleSet),
+		wgIface:       iface,
 	}
 
 	if err := iface.SetFilter(m); err != nil {
@@ -171,17 +175,6 @@ func (m *Manager) DeleteRule(rule fw.Rule) error {
 	return nil
 }
 
-// Reset firewall to the default state
-func (m *Manager) Reset() error {
-	m.mutex.Lock()
-	defer m.mutex.Unlock()
-
-	m.outgoingRules = make(map[string]RuleSet)
-	m.incomingRules = make(map[string]RuleSet)
-
-	return nil
-}
-
 // Flush doesn't need to be implemented for this manager
 func (m *Manager) Flush() error { return nil }
 
@@ -375,3 +368,8 @@ func (m *Manager) RemovePacketHook(hookID string) error {
 	}
 	return fmt.Errorf("hook with given id not found")
 }
+
+// SetResetHook which will be executed in the end of Reset method
+func (m *Manager) SetResetHook(hook func() error) {
+	m.resetHook = hook
+}

client/firewall/uspfilter/uspfilter_test.go

@@ -16,6 +16,7 @@ import (
 
 type IFaceMock struct {
 	SetFilterFunc func(iface.PacketFilter) error
+	AddressFunc   func() iface.WGAddress
 }
 
 func (i *IFaceMock) SetFilter(iface iface.PacketFilter) error {
@@ -25,6 +26,13 @@ func (i *IFaceMock) SetFilter(iface iface.PacketFilter) error {
 	return i.SetFilterFunc(iface)
 }
 
+func (i *IFaceMock) Address() iface.WGAddress {
+	if i.AddressFunc == nil {
+		return iface.WGAddress{}
+	}
+	return i.AddressFunc()
+}
+
 func TestManagerCreate(t *testing.T) {
 	ifaceMock := &IFaceMock{
 		SetFilterFunc: func(iface.PacketFilter) error { return nil },

client/internal/acl/manager_create.go

@@ -6,6 +6,8 @@ import (
 	"fmt"
 	"runtime"
 
+	log "github.com/sirupsen/logrus"
+
 	"github.com/netbirdio/netbird/client/firewall/uspfilter"
 )
 
@@ -17,6 +19,9 @@ func Create(iface IFaceMapper) (manager *DefaultManager, err error) {
 		if err != nil {
 			return nil, err
 		}
+		if err := fm.AllowNetbird(); err != nil {
+			log.Errorf("failed to allow netbird interface traffic: %v", err)
+		}
 		return newDefaultManager(fm), nil
 	}
 	return nil, fmt.Errorf("not implemented for this OS: %s", runtime.GOOS)

client/internal/acl/manager_create_linux.go

@@ -7,26 +7,68 @@ import (
 	"github.com/netbirdio/netbird/client/firewall/iptables"
 	"github.com/netbirdio/netbird/client/firewall/nftables"
 	"github.com/netbirdio/netbird/client/firewall/uspfilter"
+	"github.com/netbirdio/netbird/client/internal/checkfw"
 )
 
 // Create creates a firewall manager instance for the Linux
-func Create(iface IFaceMapper) (manager *DefaultManager, err error) {
+func Create(iface IFaceMapper) (*DefaultManager, error) {
+	// on the linux system we try to user nftables or iptables
+	// in any case, because we need to allow netbird interface traffic
+	// so we use AllowNetbird traffic from these firewall managers
+	// for the userspace packet filtering firewall
 	var fm firewall.Manager
+	var err error
+
+	checkResult := checkfw.Check()
+	switch checkResult {
+	case checkfw.IPTABLES, checkfw.IPTABLESWITHV6:
+		log.Debug("creating an iptables firewall manager for access control")
+		ipv6Supported := checkResult == checkfw.IPTABLESWITHV6
+		if fm, err = iptables.Create(iface, ipv6Supported); err != nil {
+			log.Infof("failed to create iptables manager for access control: %s", err)
+		}
+	case checkfw.NFTABLES:
+		log.Debug("creating an nftables firewall manager for access control")
+		if fm, err = nftables.Create(iface); err != nil {
+			log.Debugf("failed to create nftables manager for access control: %s", err)
+		}
+	}
+
+	var resetHookForUserspace func() error
+	if fm != nil && err == nil {
+		// err shadowing is used here, to ignore this error
+		if err := fm.AllowNetbird(); err != nil {
+			log.Errorf("failed to allow netbird interface traffic: %v", err)
+		}
+		resetHookForUserspace = fm.Reset
+	}
+
 	if iface.IsUserspaceBind() {
 		// use userspace packet filtering firewall
-		if fm, err = uspfilter.Create(iface); err != nil {
+		usfm, err := uspfilter.Create(iface)
+		if err != nil {
 			log.Debugf("failed to create userspace filtering firewall: %s", err)
 			return nil, err
 		}
-	} else {
-		if fm, err = nftables.Create(iface); err != nil {
-			log.Debugf("failed to create nftables manager: %s", err)
-			// fallback to iptables
-			if fm, err = iptables.Create(iface); err != nil {
-				log.Errorf("failed to create iptables manager: %s", err)
-				return nil, err
-			}
+
+		// set kernel space firewall Reset as hook for userspace firewall
+		// manager Reset method, to clean up
+		if resetHookForUserspace != nil {
+			usfm.SetResetHook(resetHookForUserspace)
 		}
+
+		// to be consistent for any future extensions.
+		// ignore this error
+		if err := usfm.AllowNetbird(); err != nil {
+			log.Errorf("failed to allow netbird interface traffic: %v", err)
+		}
+		fm = usfm
+	}
+
+	if fm == nil || err != nil {
+		log.Errorf("failed to create firewall manager: %s", err)
+		// no firewall manager found or initialized correctly
+		return nil, err
 	}
 
 	return newDefaultManager(fm), nil

client/internal/acl/manager_test.go

@@ -1,11 +1,13 @@
 package acl
 
 import (
+	"net"
 	"testing"
 
 	"github.com/golang/mock/gomock"
 
 	"github.com/netbirdio/netbird/client/internal/acl/mocks"
+	"github.com/netbirdio/netbird/iface"
 	mgmProto "github.com/netbirdio/netbird/management/proto"
 )
 
@@ -32,13 +34,22 @@ func TestDefaultManager(t *testing.T) {
 	ctrl := gomock.NewController(t)
 	defer ctrl.Finish()
 
-	iface := mocks.NewMockIFaceMapper(ctrl)
-	iface.EXPECT().IsUserspaceBind().Return(true)
-	// iface.EXPECT().Name().Return("lo")
-	iface.EXPECT().SetFilter(gomock.Any())
+	ifaceMock := mocks.NewMockIFaceMapper(ctrl)
+	ifaceMock.EXPECT().IsUserspaceBind().Return(true)
+	ifaceMock.EXPECT().SetFilter(gomock.Any())
+	ip, network, err := net.ParseCIDR("172.0.0.1/32")
+	if err != nil {
+		t.Fatalf("failed to parse IP address: %v", err)
+	}
+
+	ifaceMock.EXPECT().Name().Return("lo").AnyTimes()
+	ifaceMock.EXPECT().Address().Return(iface.WGAddress{
+		IP:      ip,
+		Network: network,
+	}).AnyTimes()
 
 	// we receive one rule from the management so for testing purposes ignore it
-	acl, err := Create(iface)
+	acl, err := Create(ifaceMock)
 	if err != nil {
 		t.Errorf("create ACL manager: %v", err)
 		return
@@ -311,13 +322,22 @@ func TestDefaultManagerEnableSSHRules(t *testing.T) {
 	ctrl := gomock.NewController(t)
 	defer ctrl.Finish()
 
-	iface := mocks.NewMockIFaceMapper(ctrl)
-	iface.EXPECT().IsUserspaceBind().Return(true)
-	// iface.EXPECT().Name().Return("lo")
-	iface.EXPECT().SetFilter(gomock.Any())
+	ifaceMock := mocks.NewMockIFaceMapper(ctrl)
+	ifaceMock.EXPECT().IsUserspaceBind().Return(true)
+	ifaceMock.EXPECT().SetFilter(gomock.Any())
+	ip, network, err := net.ParseCIDR("172.0.0.1/32")
+	if err != nil {
+		t.Fatalf("failed to parse IP address: %v", err)
+	}
+
+	ifaceMock.EXPECT().Name().Return("lo").AnyTimes()
+	ifaceMock.EXPECT().Address().Return(iface.WGAddress{
+		IP:      ip,
+		Network: network,
+	}).AnyTimes()
 
 	// we receive one rule from the management so for testing purposes ignore it
-	acl, err := Create(iface)
+	acl, err := Create(ifaceMock)
 	if err != nil {
 		t.Errorf("create ACL manager: %v", err)
 		return

client/internal/checkfw/check.go

@@ -0,0 +1,3 @@
+//go:build !linux
+
+package checkfw

client/internal/checkfw/check_linux.go

@@ -0,0 +1,56 @@
+//go:build !android
+
+package checkfw
+
+import (
+	"os"
+
+	"github.com/coreos/go-iptables/iptables"
+	"github.com/google/nftables"
+)
+
+const (
+	// UNKNOWN is the default value for the firewall type for unknown firewall type
+	UNKNOWN FWType = iota
+	// IPTABLES is the value for the iptables firewall type
+	IPTABLES
+	// IPTABLESWITHV6 is the value for the iptables firewall type with ipv6
+	IPTABLESWITHV6
+	// NFTABLES is the value for the nftables firewall type
+	NFTABLES
+)
+
+// SKIP_NFTABLES_ENV is the environment variable to skip nftables check
+const SKIP_NFTABLES_ENV = "NB_SKIP_NFTABLES_CHECK"
+
+// FWType is the type for the firewall type
+type FWType int
+
+// Check returns the firewall type based on common lib checks. It returns UNKNOWN if no firewall is found.
+func Check() FWType {
+	nf := nftables.Conn{}
+	if _, err := nf.ListChains(); err == nil && os.Getenv(SKIP_NFTABLES_ENV) != "true" {
+		return NFTABLES
+	}
+
+	ip, err := iptables.NewWithProtocol(iptables.ProtocolIPv4)
+	if err == nil {
+		if isIptablesClientAvailable(ip) {
+			ipSupport := IPTABLES
+			ipv6, ip6Err := iptables.NewWithProtocol(iptables.ProtocolIPv6)
+			if ip6Err == nil {
+				if isIptablesClientAvailable(ipv6) {
+					ipSupport = IPTABLESWITHV6
+				}
+			}
+			return ipSupport
+		}
+	}
+
+	return UNKNOWN
+}
+
+func isIptablesClientAvailable(client *iptables.IPTables) bool {
+	_, err := client.ListChains("filter")
+	return err == nil
+}

client/internal/routemanager/firewall_linux.go

@@ -7,6 +7,8 @@ import (
 	"fmt"
 
 	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/client/internal/checkfw"
 )
 
 const (
@@ -26,20 +28,20 @@ func genKey(format string, input string) string {
 	return fmt.Sprintf(format, input)
 }
 
-// NewFirewall if supported, returns an iptables manager, otherwise returns a nftables manager
-func NewFirewall(parentCTX context.Context) (firewallManager, error) {
-	manager, err := newNFTablesManager(parentCTX)
-	if err == nil {
-		log.Debugf("nftables firewall manager will be used")
-		return manager, nil
+// newFirewall if supported, returns an iptables manager, otherwise returns a nftables manager
+func newFirewall(parentCTX context.Context) (firewallManager, error) {
+	checkResult := checkfw.Check()
+	switch checkResult {
+	case checkfw.IPTABLES, checkfw.IPTABLESWITHV6:
+		log.Debug("creating an iptables firewall manager for route rules")
+		ipv6Supported := checkResult == checkfw.IPTABLESWITHV6
+		return newIptablesManager(parentCTX, ipv6Supported)
+	case checkfw.NFTABLES:
+		log.Info("creating an nftables firewall manager for route rules")
+		return newNFTablesManager(parentCTX), nil
 	}
-	fMgr, err := newIptablesManager(parentCTX)
-	if err != nil {
-		log.Debugf("failed to initialize iptables for root mgr: %s", err)
-		return nil, err
-	}
-	log.Debugf("iptables firewall manager will be used")
-	return fMgr, nil
+
+	return nil, fmt.Errorf("couldn't initialize nftables or iptables clients. Using a dummy firewall manager for route rules")
 }
 
 func getInPair(pair routerPair) routerPair {

client/internal/routemanager/firewall_nonlinux.go

@@ -6,9 +6,10 @@ package routemanager
 import (
 	"context"
 	"fmt"
+	"runtime"
 )
 
-// NewFirewall returns a nil manager
-func NewFirewall(context.Context) (firewallManager, error) {
-	return nil, fmt.Errorf("firewall not supported on this OS")
+// newFirewall returns a nil manager
+func newFirewall(context.Context) (firewallManager, error) {
+	return nil, fmt.Errorf("firewall not supported on %s", runtime.GOOS)
 }

client/internal/routemanager/iptables_linux.go

@@ -49,29 +49,28 @@ type iptablesManager struct {
 	mux        sync.Mutex
 }
 
-func newIptablesManager(parentCtx context.Context) (*iptablesManager, error) {
+func newIptablesManager(parentCtx context.Context, ipv6Supported bool) (*iptablesManager, error) {
 	ipv4Client, err := iptables.NewWithProtocol(iptables.ProtocolIPv4)
 	if err != nil {
-		return nil, err
-	} else if !isIptablesClientAvailable(ipv4Client) {
-		return nil, fmt.Errorf("iptables is missing for ipv4")
-	}
-	ipv6Client, err := iptables.NewWithProtocol(iptables.ProtocolIPv6)
-	if err != nil {
-		log.Debugf("failed to initialize iptables for ipv6: %s", err)
-	} else if !isIptablesClientAvailable(ipv6Client) {
-		log.Infof("iptables is missing for ipv6")
-		ipv6Client = nil
+		return nil, fmt.Errorf("failed to initialize iptables for ipv4: %s", err)
 	}
 
 	ctx, cancel := context.WithCancel(parentCtx)
-	return &iptablesManager{
+	manager := &iptablesManager{
 		ctx:        ctx,
 		stop:       cancel,
 		ipv4Client: ipv4Client,
-		ipv6Client: ipv6Client,
 		rules:      make(map[string]map[string][]string),
-	}, nil
+	}
+
+	if ipv6Supported {
+		manager.ipv6Client, err = iptables.NewWithProtocol(iptables.ProtocolIPv6)
+		if err != nil {
+			log.Warnf("failed to initialize iptables for ipv6: %s. Routes for this protocol won't be applied.", err)
+		}
+	}
+
+	return manager, nil
 }
 
 // CleanRoutingRules cleans existing iptables resources that we created by the agent
@@ -486,8 +485,3 @@ func getIptablesRuleType(table string) string {
 	}
 	return ruleType
 }
-
-func isIptablesClientAvailable(client *iptables.IPTables) bool {
-	_, err := client.ListChains("filter")
-	return err == nil
-}

client/internal/routemanager/iptables_linux_test.go

@@ -16,11 +16,12 @@ func TestIptablesManager_RestoreOrCreateContainers(t *testing.T) {
 		t.SkipNow()
 	}
 
-	manager, _ := newIptablesManager(context.TODO())
+	manager, err := newIptablesManager(context.TODO(), true)
+	require.NoError(t, err, "should return a valid iptables manager")
 
 	defer manager.CleanRoutingRules()
 
-	err := manager.RestoreOrCreateContainers()
+	err = manager.RestoreOrCreateContainers()
 	require.NoError(t, err, "shouldn't return error")
 
 	require.Len(t, manager.rules, 2, "should have created maps for ipv4 and ipv6")

client/internal/routemanager/manager.go

@@ -36,7 +36,7 @@ type DefaultManager struct {
 
 // NewManager returns a new route manager
 func NewManager(ctx context.Context, pubKey string, wgInterface *iface.WGIface, statusRecorder *peer.Status, initialRoutes []*route.Route) *DefaultManager {
-	serverRouter, err := newServerRouter(ctx, wgInterface)
+	srvRouter, err := newServerRouter(ctx, wgInterface)
 	if err != nil {
 		log.Errorf("server router is not supported: %s", err)
 	}
@@ -46,7 +46,7 @@ func NewManager(ctx context.Context, pubKey string, wgInterface *iface.WGIface,
 		ctx:            mCTX,
 		stop:           cancel,
 		clientNetworks: make(map[string]*clientNetwork),
-		serverRouter:   serverRouter,
+		serverRouter:   srvRouter,
 		statusRecorder: statusRecorder,
 		wgInterface:    wgInterface,
 		pubKey:         pubKey,

client/internal/routemanager/manager_test.go

@@ -3,11 +3,12 @@ package routemanager
 import (
 	"context"
 	"fmt"
-	"github.com/pion/transport/v2/stdnet"
 	"net/netip"
 	"runtime"
 	"testing"
 
+	"github.com/pion/transport/v2/stdnet"
+
 	"github.com/stretchr/testify/require"
 
 	"github.com/netbirdio/netbird/client/internal/peer"
@@ -30,6 +31,7 @@ func TestManagerUpdateRoutes(t *testing.T) {
 		inputInitRoutes               []*route.Route
 		inputRoutes                   []*route.Route
 		inputSerial                   uint64
+		removeSrvRouter               bool
 		serverRoutesExpected          int
 		clientNetworkWatchersExpected int
 	}{
@@ -117,6 +119,35 @@ func TestManagerUpdateRoutes(t *testing.T) {
 			serverRoutesExpected:          1,
 			clientNetworkWatchersExpected: 1,
 		},
+		{
+			name: "Should Create 1 Route For Client and Skip Server Route On Empty Server Router",
+			inputRoutes: []*route.Route{
+				{
+					ID:          "a",
+					NetID:       "routeA",
+					Peer:        localPeerKey,
+					Network:     netip.MustParsePrefix("100.64.30.250/30"),
+					NetworkType: route.IPv4Network,
+					Metric:      9999,
+					Masquerade:  false,
+					Enabled:     true,
+				},
+				{
+					ID:          "b",
+					NetID:       "routeB",
+					Peer:        remotePeerKey1,
+					Network:     netip.MustParsePrefix("8.8.9.9/32"),
+					NetworkType: route.IPv4Network,
+					Metric:      9999,
+					Masquerade:  false,
+					Enabled:     true,
+				},
+			},
+			inputSerial:                   1,
+			removeSrvRouter:               true,
+			serverRoutesExpected:          0,
+			clientNetworkWatchersExpected: 1,
+		},
 		{
 			name: "Should Create 1 HA Route and 1 Standalone",
 			inputRoutes: []*route.Route{
@@ -385,6 +416,10 @@ func TestManagerUpdateRoutes(t *testing.T) {
 			routeManager := NewManager(ctx, localPeerKey, wgInterface, statusRecorder, nil)
 			defer routeManager.Stop()
 
+			if testCase.removeSrvRouter {
+				routeManager.serverRouter = nil
+			}
+
 			if len(testCase.inputInitRoutes) > 0 {
 				err = routeManager.UpdateRoutes(testCase.inputSerial, testCase.inputRoutes)
 				require.NoError(t, err, "should update routes with init routes")
@@ -395,7 +430,7 @@ func TestManagerUpdateRoutes(t *testing.T) {
 
 			require.Len(t, routeManager.clientNetworks, testCase.clientNetworkWatchersExpected, "client networks size should match")
 
-			if runtime.GOOS == "linux" {
+			if runtime.GOOS == "linux" && routeManager.serverRouter != nil {
 				sr := routeManager.serverRouter.(*defaultServerRouter)
 				require.Len(t, sr.routes, testCase.serverRoutesExpected, "server networks size should match")
 			}

client/internal/routemanager/nftables_linux.go

@@ -86,10 +86,10 @@ type nftablesManager struct {
 	mux                 sync.Mutex
 }
 
-func newNFTablesManager(parentCtx context.Context) (*nftablesManager, error) {
+func newNFTablesManager(parentCtx context.Context) *nftablesManager {
 	ctx, cancel := context.WithCancel(parentCtx)
 
-	mgr := &nftablesManager{
+	return &nftablesManager{
 		ctx:                 ctx,
 		stop:                cancel,
 		conn:                &nftables.Conn{},
@@ -97,18 +97,6 @@ func newNFTablesManager(parentCtx context.Context) (*nftablesManager, error) {
 		rules:               make(map[string]*nftables.Rule),
 		defaultForwardRules: make([]*nftables.Rule, 2),
 	}
-
-	err := mgr.isSupported()
-	if err != nil {
-		return nil, err
-	}
-
-	err = mgr.readFilterTable()
-	if err != nil {
-		return nil, err
-	}
-
-	return mgr, nil
 }
 
 // CleanRoutingRules cleans existing nftables rules from the system
@@ -147,6 +135,10 @@ func (n *nftablesManager) RestoreOrCreateContainers() error {
 	}
 
 	for _, table := range tables {
+		if table.Name == "filter" {
+			n.filterTable = table
+			continue
+		}
 		if table.Name == nftablesTable {
 			if table.Family == nftables.TableFamilyIPv4 {
 				n.tableIPv4 = table
@@ -259,21 +251,6 @@ func (n *nftablesManager) refreshRulesMap() error {
 	return nil
 }
 
-func (n *nftablesManager) readFilterTable() error {
-	tables, err := n.conn.ListTables()
-	if err != nil {
-		return err
-	}
-
-	for _, t := range tables {
-		if t.Name == "filter" {
-			n.filterTable = t
-			return nil
-		}
-	}
-	return nil
-}
-
 func (n *nftablesManager) eraseDefaultForwardRule() error {
 	if n.defaultForwardRules[0] == nil {
 		return nil
@@ -544,14 +521,6 @@ func (n *nftablesManager) removeRoutingRule(format string, pair routerPair) erro
 	return nil
 }
 
-func (n *nftablesManager) isSupported() error {
-	_, err := n.conn.ListChains()
-	if err != nil {
-		return fmt.Errorf("nftables is not supported: %s", err)
-	}
-	return nil
-}
-
 // getPayloadDirectives get expression directives based on ip version and direction
 func getPayloadDirectives(direction string, isIPv4 bool, isIPv6 bool) (uint32, uint32, []byte) {
 	switch {

client/internal/routemanager/nftables_linux_test.go

@@ -10,20 +10,23 @@ import (
 	"github.com/google/nftables/expr"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
+
+	"github.com/netbirdio/netbird/client/internal/checkfw"
 )
 
 func TestNftablesManager_RestoreOrCreateContainers(t *testing.T) {
 
-	manager, err := newNFTablesManager(context.TODO())
-	if err != nil {
-		t.Fatalf("failed to create nftables manager: %s", err)
+	if checkfw.Check() != checkfw.NFTABLES {
+		t.Skip("nftables not supported on this OS")
 	}
 
+	manager := newNFTablesManager(context.TODO())
+
 	nftablesTestingClient := &nftables.Conn{}
 
 	defer manager.CleanRoutingRules()
 
-	err = manager.RestoreOrCreateContainers()
+	err := manager.RestoreOrCreateContainers()
 	require.NoError(t, err, "shouldn't return error")
 
 	require.Len(t, manager.chains, 2, "should have created chains for ipv4 and ipv6")
@@ -126,19 +129,19 @@ func TestNftablesManager_RestoreOrCreateContainers(t *testing.T) {
 }
 
 func TestNftablesManager_InsertRoutingRules(t *testing.T) {
+	if checkfw.Check() != checkfw.NFTABLES {
+		t.Skip("nftables not supported on this OS")
+	}
 
 	for _, testCase := range insertRuleTestCases {
 		t.Run(testCase.name, func(t *testing.T) {
-			manager, err := newNFTablesManager(context.TODO())
-			if err != nil {
-				t.Fatalf("failed to create nftables manager: %s", err)
-			}
+			manager := newNFTablesManager(context.TODO())
 
 			nftablesTestingClient := &nftables.Conn{}
 
 			defer manager.CleanRoutingRules()
 
-			err = manager.RestoreOrCreateContainers()
+			err := manager.RestoreOrCreateContainers()
 			require.NoError(t, err, "shouldn't return error")
 
 			err = manager.InsertRoutingRules(testCase.inputPair)
@@ -226,19 +229,19 @@ func TestNftablesManager_InsertRoutingRules(t *testing.T) {
 }
 
 func TestNftablesManager_RemoveRoutingRules(t *testing.T) {
+	if checkfw.Check() != checkfw.NFTABLES {
+		t.Skip("nftables not supported on this OS")
+	}
 
 	for _, testCase := range removeRuleTestCases {
 		t.Run(testCase.name, func(t *testing.T) {
-			manager, err := newNFTablesManager(context.TODO())
-			if err != nil {
-				t.Fatalf("failed to create nftables manager: %s", err)
-			}
+			manager := newNFTablesManager(context.TODO())
 
 			nftablesTestingClient := &nftables.Conn{}
 
 			defer manager.CleanRoutingRules()
 
-			err = manager.RestoreOrCreateContainers()
+			err := manager.RestoreOrCreateContainers()
 			require.NoError(t, err, "shouldn't return error")
 
 			table := manager.tableIPv4

client/internal/routemanager/server_nonandroid.go

@@ -22,7 +22,7 @@ type defaultServerRouter struct {
 }
 
 func newServerRouter(ctx context.Context, wgInterface *iface.WGIface) (serverRouter, error) {
-	firewall, err := NewFirewall(ctx)
+	firewall, err := newFirewall(ctx)
 	if err != nil {
 		return nil, err
 	}