Revert "Merge branch 'main' into feature/remote-debug"

This reverts commit 6d6333058c, reversing
changes made to 446aded1f7.

util/net/conn.go

@@ -0,0 +1,31 @@
+//go:build !ios
+
+package net
+
+import (
+	"net"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// Conn wraps a net.Conn to override the Close method
+type Conn struct {
+	net.Conn
+	ID ConnectionID
+}
+
+// Close overrides the net.Conn Close method to execute all registered hooks after closing the connection
+func (c *Conn) Close() error {
+	err := c.Conn.Close()
+
+	dialerCloseHooksMutex.RLock()
+	defer dialerCloseHooksMutex.RUnlock()
+
+	for _, hook := range dialerCloseHooks {
+		if err := hook(c.ID, &c.Conn); err != nil {
+			log.Errorf("Error executing dialer close hook: %v", err)
+		}
+	}
+
+	return err
+}

util/net/dial.go

@@ -0,0 +1,58 @@
+//go:build !ios
+
+package net
+
+import (
+	"fmt"
+	"net"
+
+	log "github.com/sirupsen/logrus"
+)
+
+func DialUDP(network string, laddr, raddr *net.UDPAddr) (*net.UDPConn, error) {
+	if CustomRoutingDisabled() {
+		return net.DialUDP(network, laddr, raddr)
+	}
+
+	dialer := NewDialer()
+	dialer.LocalAddr = laddr
+
+	conn, err := dialer.Dial(network, raddr.String())
+	if err != nil {
+		return nil, fmt.Errorf("dialing UDP %s: %w", raddr.String(), err)
+	}
+
+	udpConn, ok := conn.(*Conn).Conn.(*net.UDPConn)
+	if !ok {
+		if err := conn.Close(); err != nil {
+			log.Errorf("Failed to close connection: %v", err)
+		}
+		return nil, fmt.Errorf("expected UDP connection, got different type: %T", conn)
+	}
+
+	return udpConn, nil
+}
+
+func DialTCP(network string, laddr, raddr *net.TCPAddr) (*net.TCPConn, error) {
+	if CustomRoutingDisabled() {
+		return net.DialTCP(network, laddr, raddr)
+	}
+
+	dialer := NewDialer()
+	dialer.LocalAddr = laddr
+
+	conn, err := dialer.Dial(network, raddr.String())
+	if err != nil {
+		return nil, fmt.Errorf("dialing TCP %s: %w", raddr.String(), err)
+	}
+
+	tcpConn, ok := conn.(*Conn).Conn.(*net.TCPConn)
+	if !ok {
+		if err := conn.Close(); err != nil {
+			log.Errorf("Failed to close connection: %v", err)
+		}
+		return nil, fmt.Errorf("expected TCP connection, got different type: %T", conn)
+	}
+
+	return tcpConn, nil
+}

util/net/dial_ios.go

@@ -0,0 +1,13 @@
+package net
+
+import (
+	"net"
+)
+
+func DialUDP(network string, laddr, raddr *net.UDPAddr) (*net.UDPConn, error) {
+	return net.DialUDP(network, laddr, raddr)
+}
+
+func DialTCP(network string, laddr, raddr *net.TCPAddr) (*net.TCPConn, error) {
+	return net.DialTCP(network, laddr, raddr)
+}

util/net/dialer.go

@@ -0,0 +1,21 @@
+package net
+
+import (
+	"net"
+)
+
+// Dialer extends the standard net.Dialer with the ability to execute hooks before
+// and after connections. This can be used to bypass the VPN for connections using this dialer.
+type Dialer struct {
+	*net.Dialer
+}
+
+// NewDialer returns a customized net.Dialer with overridden Control method
+func NewDialer() *Dialer {
+	dialer := &Dialer{
+		Dialer: &net.Dialer{},
+	}
+	dialer.init()
+
+	return dialer
+}

util/net/dialer_dial.go

@@ -0,0 +1,107 @@
+//go:build !ios
+
+package net
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"sync"
+
+	"github.com/hashicorp/go-multierror"
+	log "github.com/sirupsen/logrus"
+)
+
+type DialerDialHookFunc func(ctx context.Context, connID ConnectionID, resolvedAddresses []net.IPAddr) error
+type DialerCloseHookFunc func(connID ConnectionID, conn *net.Conn) error
+
+var (
+	dialerDialHooksMutex  sync.RWMutex
+	dialerDialHooks       []DialerDialHookFunc
+	dialerCloseHooksMutex sync.RWMutex
+	dialerCloseHooks      []DialerCloseHookFunc
+)
+
+// AddDialerHook allows adding a new hook to be executed before dialing.
+func AddDialerHook(hook DialerDialHookFunc) {
+	dialerDialHooksMutex.Lock()
+	defer dialerDialHooksMutex.Unlock()
+	dialerDialHooks = append(dialerDialHooks, hook)
+}
+
+// AddDialerCloseHook allows adding a new hook to be executed on connection close.
+func AddDialerCloseHook(hook DialerCloseHookFunc) {
+	dialerCloseHooksMutex.Lock()
+	defer dialerCloseHooksMutex.Unlock()
+	dialerCloseHooks = append(dialerCloseHooks, hook)
+}
+
+// RemoveDialerHooks removes all dialer hooks.
+func RemoveDialerHooks() {
+	dialerDialHooksMutex.Lock()
+	defer dialerDialHooksMutex.Unlock()
+	dialerDialHooks = nil
+
+	dialerCloseHooksMutex.Lock()
+	defer dialerCloseHooksMutex.Unlock()
+	dialerCloseHooks = nil
+}
+
+// DialContext wraps the net.Dialer's DialContext method to use the custom connection
+func (d *Dialer) DialContext(ctx context.Context, network, address string) (net.Conn, error) {
+	log.Debugf("Dialing %s %s", network, address)
+
+	if CustomRoutingDisabled() {
+		return d.Dialer.DialContext(ctx, network, address)
+	}
+
+	var resolver *net.Resolver
+	if d.Resolver != nil {
+		resolver = d.Resolver
+	}
+
+	connID := GenerateConnID()
+	if dialerDialHooks != nil {
+		if err := callDialerHooks(ctx, connID, address, resolver); err != nil {
+			log.Errorf("Failed to call dialer hooks: %v", err)
+		}
+	}
+
+	conn, err := d.Dialer.DialContext(ctx, network, address)
+	if err != nil {
+		return nil, fmt.Errorf("d.Dialer.DialContext: %w", err)
+	}
+
+	// Wrap the connection in Conn to handle Close with hooks
+	return &Conn{Conn: conn, ID: connID}, nil
+}
+
+// Dial wraps the net.Dialer's Dial method to use the custom connection
+func (d *Dialer) Dial(network, address string) (net.Conn, error) {
+	return d.DialContext(context.Background(), network, address)
+}
+
+func callDialerHooks(ctx context.Context, connID ConnectionID, address string, resolver *net.Resolver) error {
+	host, _, err := net.SplitHostPort(address)
+	if err != nil {
+		return fmt.Errorf("split host and port: %w", err)
+	}
+	ips, err := resolver.LookupIPAddr(ctx, host)
+	if err != nil {
+		return fmt.Errorf("failed to resolve address %s: %w", address, err)
+	}
+
+	log.Debugf("Dialer resolved IPs for %s: %v", address, ips)
+
+	var result *multierror.Error
+
+	dialerDialHooksMutex.RLock()
+	defer dialerDialHooksMutex.RUnlock()
+	for _, hook := range dialerDialHooks {
+		if err := hook(ctx, connID, ips); err != nil {
+			result = multierror.Append(result, fmt.Errorf("executing dial hook: %w", err))
+		}
+	}
+
+	return result.ErrorOrNil()
+}

util/net/dialer_init_android.go

@@ -0,0 +1,5 @@
+package net
+
+func (d *Dialer) init() {
+	d.Dialer.Control = ControlProtectSocket
+}

util/net/dialer_init_linux.go

@@ -0,0 +1,12 @@
+//go:build !android
+
+package net
+
+import "syscall"
+
+// init configures the net.Dialer Control function to set the fwmark on the socket
+func (d *Dialer) init() {
+	d.Dialer.Control = func(_, _ string, c syscall.RawConn) error {
+		return setRawSocketMark(c)
+	}
+}

util/net/dialer_init_nonlinux.go

@@ -0,0 +1,7 @@
+//go:build !linux
+
+package net
+
+func (d *Dialer) init() {
+	// implemented on Linux and Android only
+}

util/net/env.go

@@ -0,0 +1,34 @@
+package net
+
+import (
+	"os"
+	"strconv"
+
+	log "github.com/sirupsen/logrus"
+
+	"github.com/netbirdio/netbird/client/iface/netstack"
+)
+
+const (
+	envDisableCustomRouting = "NB_DISABLE_CUSTOM_ROUTING"
+)
+
+// CustomRoutingDisabled returns true if custom routing is disabled.
+// This will fall back to the operation mode before the exit node functionality was implemented.
+// In particular exclusion routes won't be set up and all dialers and listeners will use net.Dial and net.Listen, respectively.
+func CustomRoutingDisabled() bool {
+	if netstack.IsEnabled() {
+		return true
+	}
+
+	var customRoutingDisabled bool
+	if val := os.Getenv(envDisableCustomRouting); val != "" {
+		var err error
+		customRoutingDisabled, err = strconv.ParseBool(val)
+		if err != nil {
+			log.Warnf("failed to parse %s: %v", envDisableCustomRouting, err)
+		}
+	}
+
+	return customRoutingDisabled
+}

util/net/env_generic.go

@@ -0,0 +1,12 @@
+//go:build !linux || android
+
+package net
+
+func Init() {
+	// nothing to do on non-linux
+}
+
+func AdvancedRouting() bool {
+	// non-linux currently doesn't support advanced routing
+	return false
+}

util/net/env_linux.go

@@ -0,0 +1,131 @@
+//go:build linux && !android
+
+package net
+
+import (
+	"errors"
+	"os"
+	"strconv"
+	"syscall"
+	"time"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/vishvananda/netlink"
+
+	"github.com/netbirdio/netbird/client/iface/netstack"
+)
+
+const (
+	// these have the same effect, skip socket env supported for backward compatibility
+	envSkipSocketMark   = "NB_SKIP_SOCKET_MARK"
+	envUseLegacyRouting = "NB_USE_LEGACY_ROUTING"
+)
+
+var advancedRoutingSupported bool
+
+func Init() {
+	advancedRoutingSupported = checkAdvancedRoutingSupport()
+}
+
+func AdvancedRouting() bool {
+	return advancedRoutingSupported
+}
+
+func checkAdvancedRoutingSupport() bool {
+	var err error
+
+	var legacyRouting bool
+	if val := os.Getenv(envUseLegacyRouting); val != "" {
+		legacyRouting, err = strconv.ParseBool(val)
+		if err != nil {
+			log.Warnf("failed to parse %s: %v", envUseLegacyRouting, err)
+		}
+	}
+
+	var skipSocketMark bool
+	if val := os.Getenv(envSkipSocketMark); val != "" {
+		skipSocketMark, err = strconv.ParseBool(val)
+		if err != nil {
+			log.Warnf("failed to parse %s: %v", envSkipSocketMark, err)
+		}
+	}
+
+	// requested to disable advanced routing
+	if legacyRouting || skipSocketMark ||
+		// envCustomRoutingDisabled disables the custom dialers.
+		// There is no point in using advanced routing without those, as they set up fwmarks on the sockets.
+		CustomRoutingDisabled() ||
+		// netstack mode doesn't need routing at all
+		netstack.IsEnabled() {
+
+		log.Info("advanced routing has been requested to be disabled")
+		return false
+	}
+
+	if !CheckFwmarkSupport() || !CheckRuleOperationsSupport() {
+		log.Warn("system doesn't support required routing features, falling back to legacy routing")
+		return false
+	}
+
+	log.Info("system supports advanced routing")
+
+	return true
+}
+
+func CheckFwmarkSupport() bool {
+	// temporarily enable advanced routing to check fwmarks are supported
+	old := advancedRoutingSupported
+	advancedRoutingSupported = true
+	defer func() {
+		advancedRoutingSupported = old
+	}()
+
+	dialer := NewDialer()
+	dialer.Timeout = 100 * time.Millisecond
+
+	conn, err := dialer.Dial("udp", "127.0.0.1:9")
+	if err != nil {
+		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
+}
+
+func CheckRuleOperationsSupport() bool {
+	rule := netlink.NewRule()
+	// low precedence, semi-random
+	rule.Priority = 32321
+	rule.Table = syscall.RT_TABLE_MAIN
+	rule.Family = netlink.FAMILY_V4
+
+	if err := netlink.RuleAdd(rule); err != nil {
+		if errors.Is(err, syscall.EOPNOTSUPP) {
+			log.Warn("IP rule operations are not supported")
+			return false
+		}
+		log.Warnf("failed to test rule support: %v", err)
+		return false
+	}
+
+	if err := netlink.RuleDel(rule); err != nil {
+		log.Warnf("failed to delete test rule: %v", err)
+	}
+	return true
+}

util/net/listen.go

@@ -0,0 +1,37 @@
+//go:build !ios
+
+package net
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"sync"
+
+	"github.com/pion/transport/v3"
+	log "github.com/sirupsen/logrus"
+)
+
+// ListenUDP listens on the network address and returns a transport.UDPConn
+// which includes support for write and close hooks.
+func ListenUDP(network string, laddr *net.UDPAddr) (transport.UDPConn, error) {
+	if CustomRoutingDisabled() {
+		return net.ListenUDP(network, laddr)
+	}
+
+	conn, err := NewListener().ListenPacket(context.Background(), network, laddr.String())
+	if err != nil {
+		return nil, fmt.Errorf("listen UDP: %w", err)
+	}
+
+	packetConn := conn.(*PacketConn)
+	udpConn, ok := packetConn.PacketConn.(*net.UDPConn)
+	if !ok {
+		if err := packetConn.Close(); err != nil {
+			log.Errorf("Failed to close connection: %v", err)
+		}
+		return nil, fmt.Errorf("expected UDPConn, got different type: %T", udpConn)
+	}
+
+	return &UDPConn{UDPConn: udpConn, ID: packetConn.ID, seenAddrs: &sync.Map{}}, nil
+}

util/net/listen_ios.go

@@ -0,0 +1,11 @@
+//go:build ios
+
+package net
+
+import (
+	"net"
+)
+
+func ListenUDP(network string, laddr *net.UDPAddr) (*net.UDPConn, error) {
+	return net.ListenUDP(network, laddr)
+}

util/net/listener.go

@@ -0,0 +1,21 @@
+package net
+
+import (
+	"net"
+)
+
+// ListenerConfig extends the standard net.ListenConfig with the ability to execute hooks before
+// responding via the socket and after closing. This can be used to bypass the VPN for listeners.
+type ListenerConfig struct {
+	*net.ListenConfig
+}
+
+// NewListener creates a new ListenerConfig instance.
+func NewListener() *ListenerConfig {
+	listener := &ListenerConfig{
+		ListenConfig: &net.ListenConfig{},
+	}
+	listener.init()
+
+	return listener
+}

util/net/listener_init_android.go

@@ -0,0 +1,6 @@
+package net
+
+// init configures the net.ListenerConfig Control function to set the fwmark on the socket
+func (l *ListenerConfig) init() {
+	l.ListenConfig.Control = ControlProtectSocket
+}

util/net/listener_init_linux.go

@@ -0,0 +1,14 @@
+//go:build !android
+
+package net
+
+import (
+	"syscall"
+)
+
+// init configures the net.ListenerConfig Control function to set the fwmark on the socket
+func (l *ListenerConfig) init() {
+	l.ListenConfig.Control = func(_, _ string, c syscall.RawConn) error {
+		return setRawSocketMark(c)
+	}
+}

util/net/listener_init_nonlinux.go

@@ -0,0 +1,7 @@
+//go:build !linux
+
+package net
+
+func (l *ListenerConfig) init() {
+	// implemented on Linux and Android only
+}

util/net/listener_listen.go

@@ -0,0 +1,205 @@
+//go:build !ios
+
+package net
+
+import (
+	"context"
+	"fmt"
+	"net"
+	"net/netip"
+	"sync"
+
+	log "github.com/sirupsen/logrus"
+)
+
+// ListenerWriteHookFunc defines the function signature for write hooks for PacketConn.
+type ListenerWriteHookFunc func(connID ConnectionID, ip *net.IPAddr, data []byte) error
+
+// ListenerCloseHookFunc defines the function signature for close hooks for PacketConn.
+type ListenerCloseHookFunc func(connID ConnectionID, conn net.PacketConn) error
+
+// ListenerAddressRemoveHookFunc defines the function signature for hooks called when addresses are removed.
+type ListenerAddressRemoveHookFunc func(connID ConnectionID, prefix netip.Prefix) error
+
+var (
+	listenerWriteHooksMutex         sync.RWMutex
+	listenerWriteHooks              []ListenerWriteHookFunc
+	listenerCloseHooksMutex         sync.RWMutex
+	listenerCloseHooks              []ListenerCloseHookFunc
+	listenerAddressRemoveHooksMutex sync.RWMutex
+	listenerAddressRemoveHooks      []ListenerAddressRemoveHookFunc
+)
+
+// AddListenerWriteHook allows adding a new write hook to be executed before a UDP packet is sent.
+func AddListenerWriteHook(hook ListenerWriteHookFunc) {
+	listenerWriteHooksMutex.Lock()
+	defer listenerWriteHooksMutex.Unlock()
+	listenerWriteHooks = append(listenerWriteHooks, hook)
+}
+
+// AddListenerCloseHook allows adding a new hook to be executed upon closing a UDP connection.
+func AddListenerCloseHook(hook ListenerCloseHookFunc) {
+	listenerCloseHooksMutex.Lock()
+	defer listenerCloseHooksMutex.Unlock()
+	listenerCloseHooks = append(listenerCloseHooks, hook)
+}
+
+// AddListenerAddressRemoveHook allows adding a new hook to be executed when an address is removed.
+func AddListenerAddressRemoveHook(hook ListenerAddressRemoveHookFunc) {
+	listenerAddressRemoveHooksMutex.Lock()
+	defer listenerAddressRemoveHooksMutex.Unlock()
+	listenerAddressRemoveHooks = append(listenerAddressRemoveHooks, hook)
+}
+
+// RemoveListenerHooks removes all listener hooks.
+func RemoveListenerHooks() {
+	listenerWriteHooksMutex.Lock()
+	defer listenerWriteHooksMutex.Unlock()
+	listenerWriteHooks = nil
+
+	listenerCloseHooksMutex.Lock()
+	defer listenerCloseHooksMutex.Unlock()
+	listenerCloseHooks = nil
+
+	listenerAddressRemoveHooksMutex.Lock()
+	defer listenerAddressRemoveHooksMutex.Unlock()
+	listenerAddressRemoveHooks = nil
+}
+
+// ListenPacket listens on the network address and returns a PacketConn
+// which includes support for write hooks.
+func (l *ListenerConfig) ListenPacket(ctx context.Context, network, address string) (net.PacketConn, error) {
+	if CustomRoutingDisabled() {
+		return l.ListenConfig.ListenPacket(ctx, network, address)
+	}
+
+	pc, err := l.ListenConfig.ListenPacket(ctx, network, address)
+	if err != nil {
+		return nil, fmt.Errorf("listen packet: %w", err)
+	}
+	connID := GenerateConnID()
+
+	return &PacketConn{PacketConn: pc, ID: connID, seenAddrs: &sync.Map{}}, nil
+}
+
+// PacketConn wraps net.PacketConn to override its WriteTo and Close methods to include hook functionality.
+type PacketConn struct {
+	net.PacketConn
+	ID        ConnectionID
+	seenAddrs *sync.Map
+}
+
+// WriteTo writes a packet with payload b to addr, executing registered write hooks beforehand.
+func (c *PacketConn) WriteTo(b []byte, addr net.Addr) (n int, err error) {
+	callWriteHooks(c.ID, c.seenAddrs, b, addr)
+	return c.PacketConn.WriteTo(b, addr)
+}
+
+// Close overrides the net.PacketConn Close method to execute all registered hooks before closing the connection.
+func (c *PacketConn) Close() error {
+	c.seenAddrs = &sync.Map{}
+	return closeConn(c.ID, c.PacketConn)
+}
+
+// UDPConn wraps net.UDPConn to override its WriteTo and Close methods to include hook functionality.
+type UDPConn struct {
+	*net.UDPConn
+	ID        ConnectionID
+	seenAddrs *sync.Map
+}
+
+// WriteTo writes a packet with payload b to addr, executing registered write hooks beforehand.
+func (c *UDPConn) WriteTo(b []byte, addr net.Addr) (n int, err error) {
+	callWriteHooks(c.ID, c.seenAddrs, b, addr)
+	return c.UDPConn.WriteTo(b, addr)
+}
+
+// Close overrides the net.UDPConn Close method to execute all registered hooks before closing the connection.
+func (c *UDPConn) Close() error {
+	c.seenAddrs = &sync.Map{}
+	return closeConn(c.ID, c.UDPConn)
+}
+
+// RemoveAddress removes an address from the seen cache and triggers removal hooks.
+func (c *PacketConn) RemoveAddress(addr string) {
+	if _, exists := c.seenAddrs.LoadAndDelete(addr); !exists {
+		return
+	}
+
+	ipStr, _, err := net.SplitHostPort(addr)
+	if err != nil {
+		log.Errorf("Error splitting IP address and port: %v", err)
+		return
+	}
+
+	ipAddr, err := netip.ParseAddr(ipStr)
+	if err != nil {
+		log.Errorf("Error parsing IP address %s: %v", ipStr, err)
+		return
+	}
+
+	prefix := netip.PrefixFrom(ipAddr, ipAddr.BitLen())
+
+	listenerAddressRemoveHooksMutex.RLock()
+	defer listenerAddressRemoveHooksMutex.RUnlock()
+
+	for _, hook := range listenerAddressRemoveHooks {
+		if err := hook(c.ID, prefix); err != nil {
+			log.Errorf("Error executing listener address remove hook: %v", err)
+		}
+	}
+}
+
+
+// WrapPacketConn wraps an existing net.PacketConn with nbnet functionality
+func WrapPacketConn(conn net.PacketConn) *PacketConn {
+	return &PacketConn{
+		PacketConn: conn,
+		ID:         GenerateConnID(),
+		seenAddrs:  &sync.Map{},
+	}
+}
+
+func callWriteHooks(id ConnectionID, seenAddrs *sync.Map, b []byte, addr net.Addr) {
+	// Lookup the address in the seenAddrs map to avoid calling the hooks for every write
+	if _, loaded := seenAddrs.LoadOrStore(addr.String(), true); !loaded {
+		ipStr, _, splitErr := net.SplitHostPort(addr.String())
+		if splitErr != nil {
+			log.Errorf("Error splitting IP address and port: %v", splitErr)
+			return
+		}
+
+		ip, err := net.ResolveIPAddr("ip", ipStr)
+		if err != nil {
+			log.Errorf("Error resolving IP address: %v", err)
+			return
+		}
+		log.Debugf("Listener resolved IP for %s: %s", addr, ip)
+
+		func() {
+			listenerWriteHooksMutex.RLock()
+			defer listenerWriteHooksMutex.RUnlock()
+
+			for _, hook := range listenerWriteHooks {
+				if err := hook(id, ip, b); err != nil {
+					log.Errorf("Error executing listener write hook: %v", err)
+				}
+			}
+		}()
+	}
+}
+
+func closeConn(id ConnectionID, conn net.PacketConn) error {
+	err := conn.Close()
+
+	listenerCloseHooksMutex.RLock()
+	defer listenerCloseHooksMutex.RUnlock()
+
+	for _, hook := range listenerCloseHooks {
+		if err := hook(id, conn); err != nil {
+			log.Errorf("Error executing listener close hook: %v", err)
+		}
+	}
+
+	return err
+}

util/net/listener_listen_ios.go

@@ -0,0 +1,10 @@
+package net
+
+import (
+	"net"
+)
+
+// WrapPacketConn on iOS just returns the original connection since iOS handles its own networking
+func WrapPacketConn(conn *net.UDPConn) *net.UDPConn {
+	return conn
+}

util/net/net.go

@@ -0,0 +1,83 @@
+package net
+
+import (
+	"fmt"
+	"math/big"
+	"net"
+	"net/netip"
+
+	"github.com/google/uuid"
+)
+
+const (
+	// ControlPlaneMark is the fwmark value used to mark packets that should not be routed through the NetBird interface to
+	// 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
+
+	// Data plane marks (0x1BD10 - 0x1BDFF)
+
+	// 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
+
+type AddHookFunc func(connID ConnectionID, IP net.IP) error
+type RemoveHookFunc func(connID ConnectionID) error
+
+// GenerateConnID generates a unique identifier for each connection.
+func GenerateConnID() ConnectionID {
+	return ConnectionID(uuid.NewString())
+}
+
+func GetLastIPFromNetwork(network netip.Prefix, fromEnd int) (netip.Addr, error) {
+	var endIP net.IP
+	addr := network.Addr().AsSlice()
+	mask := net.CIDRMask(network.Bits(), len(addr)*8)
+
+	for i := 0; i < len(addr); i++ {
+		endIP = append(endIP, addr[i]|^mask[i])
+	}
+
+	// convert to big.Int
+	endInt := big.NewInt(0)
+	endInt.SetBytes(endIP)
+
+	// subtract fromEnd from the last ip
+	fromEndBig := big.NewInt(int64(fromEnd))
+	resultInt := big.NewInt(0)
+	resultInt.Sub(endInt, fromEndBig)
+
+	ip, ok := netip.AddrFromSlice(resultInt.Bytes())
+	if !ok {
+		return netip.Addr{}, fmt.Errorf("invalid IP address from network %s", network)
+	}
+
+	return ip.Unmap(), nil
+}

util/net/net_linux.go

@@ -0,0 +1,55 @@
+//go:build !android
+
+package net
+
+import (
+	"fmt"
+	"syscall"
+)
+
+// SetSocketMark sets the SO_MARK option on the given socket connection
+func SetSocketMark(conn syscall.Conn) error {
+	if !AdvancedRouting() {
+		return nil
+	}
+
+	sysconn, err := conn.SyscallConn()
+	if err != nil {
+		return fmt.Errorf("get raw conn: %w", err)
+	}
+
+	return setRawSocketMark(sysconn)
+}
+
+// SetSocketOpt sets the SO_MARK option on the given file descriptor
+func SetSocketOpt(fd int) error {
+	if !AdvancedRouting() {
+		return nil
+	}
+
+	return setSocketOptInt(fd)
+}
+
+func setRawSocketMark(conn syscall.RawConn) error {
+	var setErr error
+
+	err := conn.Control(func(fd uintptr) {
+		if !AdvancedRouting() {
+			return
+		}
+		setErr = setSocketOptInt(int(fd))
+	})
+	if err != nil {
+		return fmt.Errorf("control: %w", err)
+	}
+
+	if setErr != nil {
+		return fmt.Errorf("set SO_MARK: %w", setErr)
+	}
+
+	return nil
+}
+
+func setSocketOptInt(fd int) error {
+	return syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_MARK, ControlPlaneMark)
+}

util/net/net_test.go

@@ -0,0 +1,94 @@
+package net
+
+import (
+	"net/netip"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+func TestGetLastIPFromNetwork(t *testing.T) {
+	tests := []struct {
+		name      string
+		network   string
+		fromEnd   int
+		expected  string
+		expectErr bool
+	}{
+		{
+			name:     "IPv4 /24 network - last IP (fromEnd=0)",
+			network:  "192.168.1.0/24",
+			fromEnd:  0,
+			expected: "192.168.1.255",
+		},
+		{
+			name:     "IPv4 /24 network - fromEnd=1",
+			network:  "192.168.1.0/24",
+			fromEnd:  1,
+			expected: "192.168.1.254",
+		},
+		{
+			name:     "IPv4 /24 network - fromEnd=5",
+			network:  "192.168.1.0/24",
+			fromEnd:  5,
+			expected: "192.168.1.250",
+		},
+		{
+			name:     "IPv4 /16 network - last IP",
+			network:  "10.0.0.0/16",
+			fromEnd:  0,
+			expected: "10.0.255.255",
+		},
+		{
+			name:     "IPv4 /16 network - fromEnd=256",
+			network:  "10.0.0.0/16",
+			fromEnd:  256,
+			expected: "10.0.254.255",
+		},
+		{
+			name:     "IPv4 /32 network - single host",
+			network:  "192.168.1.100/32",
+			fromEnd:  0,
+			expected: "192.168.1.100",
+		},
+		{
+			name:     "IPv6 /64 network - last IP",
+			network:  "2001:db8::/64",
+			fromEnd:  0,
+			expected: "2001:db8::ffff:ffff:ffff:ffff",
+		},
+		{
+			name:     "IPv6 /64 network - fromEnd=1",
+			network:  "2001:db8::/64",
+			fromEnd:  1,
+			expected: "2001:db8::ffff:ffff:ffff:fffe",
+		},
+		{
+			name:     "IPv6 /128 network - single host",
+			network:  "2001:db8::1/128",
+			fromEnd:  0,
+			expected: "2001:db8::1",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			network, err := netip.ParsePrefix(tt.network)
+			require.NoError(t, err, "Failed to parse network prefix")
+
+			result, err := GetLastIPFromNetwork(network, tt.fromEnd)
+
+			if tt.expectErr {
+				assert.Error(t, err)
+				return
+			}
+			require.NoError(t, err)
+
+			expectedIP, err := netip.ParseAddr(tt.expected)
+			require.NoError(t, err, "Failed to parse expected IP")
+
+			assert.Equal(t, expectedIP, result, "IP mismatch for network %s with fromEnd=%d", tt.network, tt.fromEnd)
+		})
+	}
+}

util/net/protectsocket_android.go

@@ -0,0 +1,42 @@
+package net
+
+import (
+	"fmt"
+	"sync"
+	"syscall"
+)
+
+var (
+	androidProtectSocketLock sync.Mutex
+	androidProtectSocket     func(fd int32) bool
+)
+
+func SetAndroidProtectSocketFn(fn func(fd int32) bool) {
+	androidProtectSocketLock.Lock()
+	androidProtectSocket = fn
+	androidProtectSocketLock.Unlock()
+}
+
+// ControlProtectSocket is a Control function that sets the fwmark on the socket
+func ControlProtectSocket(_, _ string, c syscall.RawConn) error {
+	var aErr error
+	err := c.Control(func(fd uintptr) {
+		androidProtectSocketLock.Lock()
+		defer androidProtectSocketLock.Unlock()
+
+		if androidProtectSocket == nil {
+			aErr = fmt.Errorf("socket protection function not set")
+			return
+		}
+
+		if !androidProtectSocket(int32(fd)) {
+			aErr = fmt.Errorf("failed to protect socket via Android")
+		}
+	})
+
+	if err != nil {
+		return err
+	}
+
+	return aErr
+}