second commit

src/main/kotlin/TunDevice.kt

@@ -17,8 +17,8 @@ class TunDevice(
         output = FileOutputStream(fd)
     }
 
-    private fun openTun(name: String): java.io.FileDescriptor {
-        val fd = java.io.FileDescriptor()
+    private fun openTun(name: String): FileDescriptor {
+        val fd = FileDescriptor()
 
         val tun = RandomAccessFile("/dev/net/tun", "rw")
         val field = tun.javaClass.getDeclaredField("fd")

src/main/tun.c

@@ -0,0 +1,22 @@
+#include <fcntl.h>
+#include <linux/if_tun.h>
+#include <linux/if.h>
+#include <sys/ioctl.h>
+#include <string.h>
+#include <unistd.h>
+
+int create_tun(char *dev) {
+    struct ifreq ifr;
+    int fd = open("/dev/net/tun", O_RDWR);
+
+    memset(&ifr, 0, sizeof(ifr));
+
+    ifr.ifr_flags = IFF_TUN | IFF_NO_PI;
+    strcpy(ifr.ifr_name, dev);
+
+    ioctl(fd, TUNSETIFF, &ifr);
+
+    return fd;
+}
+
+// gcc -shared -o libtun.so -fPIC src/main/tun.c