Update contrib/mobile for the latest iOS build

src/tun/options.go

@@ -6,6 +6,8 @@ func (m *TunAdapter) _applyOption(opt SetupOption) {
 		m.config.name = v
 	case InterfaceMTU:
 		m.config.mtu = v
+	case FileDescriptor:
+		m.config.fd = int32(v)
 	}
 }
 
@@ -15,6 +17,8 @@ type SetupOption interface {
 
 type InterfaceName string
 type InterfaceMTU uint64
+type FileDescriptor int32
 
-func (a InterfaceName) isSetupOption() {}
-func (a InterfaceMTU) isSetupOption()  {}
+func (a InterfaceName) isSetupOption()  {}
+func (a InterfaceMTU) isSetupOption()   {}
+func (a FileDescriptor) isSetupOption() {}

src/tun/tun.go

@@ -37,6 +37,7 @@ type TunAdapter struct {
 	isOpen    bool
 	isEnabled bool // Used by the writer to drop sessionTraffic if not enabled
 	config    struct {
+		fd   int32
 		name InterfaceName
 		mtu  InterfaceMTU
 	}
@@ -119,7 +120,13 @@ func (tun *TunAdapter) _start() error {
 	if tun.rwc.MaxMTU() < mtu {
 		mtu = tun.rwc.MaxMTU()
 	}
-	if err := tun.setup(string(tun.config.name), addr, mtu); err != nil {
+	var err error
+	if tun.config.fd > 0 {
+		err = tun.setupFD(tun.config.fd, addr, mtu)
+	} else {
+		err = tun.setup(string(tun.config.name), addr, mtu)
+	}
+	if err != nil {
 		return err
 	}
 	if tun.MTU() != mtu {

src/tun/tun_darwin.go

@@ -1,5 +1,5 @@
-//go:build !mobile
-// +build !mobile
+//go:build darwin || ios
+// +build darwin ios
 
 package tun
 
@@ -7,6 +7,7 @@ package tun
 
 import (
 	"encoding/binary"
+	"os"
 	"strconv"
 	"strings"
 	"unsafe"
@@ -34,6 +35,31 @@ func (tun *TunAdapter) setup(ifname string, addr string, mtu uint64) error {
 	return tun.setupAddress(addr)
 }
 
+// Configures the "utun" adapter from an existing file descriptor.
+func (tun *TunAdapter) setupFD(fd int32, addr string, mtu uint64) error {
+	dfd, err := unix.Dup(int(fd))
+	if err != nil {
+		return err
+	}
+	err = unix.SetNonblock(dfd, true)
+	if err != nil {
+		unix.Close(dfd)
+		return err
+	}
+	iface, err := wgtun.CreateTUNFromFile(os.NewFile(uintptr(dfd), "/dev/tun"), 0)
+	if err != nil {
+		unix.Close(dfd)
+		return err
+	}
+	tun.iface = iface
+	if m, err := iface.MTU(); err == nil {
+		tun.mtu = getSupportedMTU(uint64(m))
+	} else {
+		tun.mtu = 0
+	}
+	return nil // tun.setupAddress(addr)
+}
+
 const (
 	darwin_SIOCAIFADDR_IN6       = 2155899162 // netinet6/in6_var.h
 	darwin_IN6_IFF_NODAD         = 0x0020     // netinet6/in6_var.h