Update contrib/mobile for the latest iOS build

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