Allow disabling custom routing (#1840)

util/net/dialer_generic.go

@@ -49,6 +49,10 @@ func RemoveDialerHooks() {
 
 // 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) {
+	if CustomRoutingDisabled() {
+		return d.Dialer.DialContext(ctx, network, address)
+	}
+
 	var resolver *net.Resolver
 	if d.Resolver != nil {
 		resolver = d.Resolver
@@ -123,6 +127,10 @@ func callDialerHooks(ctx context.Context, connID ConnectionID, address string, r
 }
 
 func DialUDP(network string, laddr, raddr *net.UDPAddr) (*net.UDPConn, error) {
+	if CustomRoutingDisabled() {
+		return net.DialUDP(network, laddr, raddr)
+	}
+
 	dialer := NewDialer()
 	dialer.LocalAddr = laddr
 
@@ -143,6 +151,10 @@ func DialUDP(network string, laddr, raddr *net.UDPAddr) (*net.UDPConn, error) {
 }
 
 func DialTCP(network string, laddr, raddr *net.TCPAddr) (*net.TCPConn, error) {
+	if CustomRoutingDisabled() {
+		return net.DialTCP(network, laddr, raddr)
+	}
+
 	dialer := NewDialer()
 	dialer.LocalAddr = laddr
 

util/net/listener_generic.go

@@ -8,6 +8,7 @@ import (
 	"net"
 	"sync"
 
+	"github.com/pion/transport/v3"
 	log "github.com/sirupsen/logrus"
 )
 
@@ -52,6 +53,10 @@ func RemoveListenerHooks() {
 // 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)
@@ -144,7 +149,11 @@ func closeConn(id ConnectionID, conn net.PacketConn) error {
 
 // 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) (*UDPConn, error) {
+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)

util/net/net.go

@@ -1,10 +1,16 @@
 package net
 
-import "github.com/google/uuid"
+import (
+	"os"
+
+	"github.com/google/uuid"
+)
 
 const (
 	// NetbirdFwmark is the fwmark value used by Netbird via wireguard
 	NetbirdFwmark = 0x1BD00
+
+	envDisableCustomRouting = "NB_DISABLE_CUSTOM_ROUTING"
 )
 
 // ConnectionID provides a globally unique identifier for network connections.
@@ -15,3 +21,7 @@ type ConnectionID string
 func GenerateConnID() ConnectionID {
 	return ConnectionID(uuid.NewString())
 }
+
+func CustomRoutingDisabled() bool {
+	return os.Getenv(envDisableCustomRouting) == "true"
+}

util/net/net_linux.go

@@ -21,7 +21,7 @@ func SetRawSocketMark(conn syscall.RawConn) error {
 	var setErr error
 
 	err := conn.Control(func(fd uintptr) {
-		setErr = syscall.SetsockoptInt(int(fd), syscall.SOL_SOCKET, syscall.SO_MARK, NetbirdFwmark)
+		setErr = SetSocketOpt(int(fd))
 	})
 	if err != nil {
 		return fmt.Errorf("control: %w", err)
@@ -33,3 +33,11 @@ func SetRawSocketMark(conn syscall.RawConn) error {
 
 	return nil
 }
+
+func SetSocketOpt(fd int) error {
+	if CustomRoutingDisabled() {
+		return nil
+	}
+
+	return syscall.SetsockoptInt(fd, syscall.SOL_SOCKET, syscall.SO_MARK, NetbirdFwmark)
+}