libwg-go: use gopath

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

app/tools/libwg-go/src/git.zx2c4.com/wireguard-go/tun/api-android.go

@@ -0,0 +1,31 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+package tun
+
+import (
+	"git.zx2c4.com/wireguard-go/rwcancel"
+	"os"
+)
+
+func CreateTUNFromFD(tun_fd int) (TUNDevice, string, error) {
+	tun := &nativeTun{
+		fd:     os.NewFile(uintptr(tun_fd), "/dev/tun"),
+		events: make(chan TUNEvent, 5),
+		errors: make(chan error, 5),
+		nopi:   true,
+	}
+	var err error
+	tun.fdCancel, err = rwcancel.NewRWCancel(tun_fd)
+	if err != nil {
+		return nil, "", err
+	}
+	name, err := tun.Name()
+	if err != nil {
+		tun.fdCancel.Cancel()
+		return nil, "", err
+	}
+	return tun, name, nil
+}