diff --git a/ap/app/clatd/tun.c b/ap/app/clatd/tun.c
new file mode 100755
index 0000000..7e62e44
--- /dev/null
+++ b/ap/app/clatd/tun.c
@@ -0,0 +1,90 @@
+/*
+ * Copyright 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * tun.c - tun device functions
+ */
+#include <fcntl.h>
+#include <string.h>
+#include <unistd.h>
+#include <arpa/inet.h>
+//#include <linux/if.h>
+#include <net/if.h>
+#include <linux/if_tun.h>
+#include <sys/ioctl.h>
+#include <sys/uio.h>
+
+#include "clatd.h"
+
+/* function: tun_open
+ * tries to open the tunnel device
+ */
+int tun_open() {
+  int fd;
+
+  fd = open("/dev/tun", O_RDWR);
+  if(fd < 0) {
+    fd = open("/dev/net/tun", O_RDWR);
+  }
+
+  return fd;
+}
+
+/* function: tun_alloc
+ * creates a tun interface and names it
+ * dev - the name for the new tun device
+ */
+int tun_alloc(char *dev, int fd) {
+  struct ifreq ifr;
+  int err;
+
+  memset(&ifr, 0, sizeof(ifr));
+
+  ifr.ifr_flags = IFF_TUN;
+  if( *dev ) {
+    strncpy(ifr.ifr_name, dev, IFNAMSIZ);
+    ifr.ifr_name[IFNAMSIZ-1] = '\0';
+  }
+
+  if( (err = ioctl(fd, TUNSETIFF, (void *) &ifr)) < 0 ){
+    close(fd);
+    return err;
+  }
+  strcpy(dev, ifr.ifr_name);
+  return 0;
+}
+
+/* function: set_nonblocking
+ * sets a filedescriptor to non-blocking mode
+ * fd - the filedescriptor
+ * returns: 0 on success, -1 on failure
+ */
+int set_nonblocking(int fd) {
+  int flags = fcntl(fd, F_GETFL);
+  if (flags == -1) {
+    return flags;
+  }
+  return fcntl(fd, F_SETFL, flags | O_NONBLOCK);
+}
+
+/* function: send_tun
+ * sends a clat_packet to a tun interface
+ * fd      - the tun filedescriptor
+ * out     - the packet to send
+ * iov_len - the number of entries in the clat_packet
+ * returns: number of bytes read on success, -1 on failure
+ */
+int send_tun(int fd, clat_packet out, int iov_len) {
+  return writev(fd, out, iov_len);
+}