diff --git a/clatd_microbenchmark.c b/clatd_microbenchmark.c
new file mode 100644
index 0000000..fed3100
--- /dev/null
+++ b/clatd_microbenchmark.c
@@ -0,0 +1,214 @@
+/*
+ * 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.
+ *
+ * clatd_microbenchmark.c - micro-benchmark for clatd tun send path
+ *
+ * Run with:
+ *
+ * adb push {$ANDROID_PRODUCT_OUT,}/data/nativetest/clatd_microbenchmark/clatd_microbenchmark
+ * adb shell /data/nativetest/clatd_microbenchmark/clatd_microbenchmark
+ *
+ */
+#include <errno.h>
+#include <fcntl.h>
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <time.h>
+#include <unistd.h>
+#include <sys/ioctl.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <sys/uio.h>
+#include <netinet/in.h>
+#include <netinet/ip.h>
+#include <netinet/ip6.h>
+#include <netinet/udp.h>
+#include <arpa/inet.h>
+#include <linux/if.h>
+#include <linux/if_tun.h>
+
+#include "checksum.h"
+#include "tun.h"
+
+#define DEVICENAME "clat4"
+
+#define PORT 51339
+#define PAYLOADSIZE (1280 - sizeof(struct iphdr) - sizeof(struct udphdr))
+#define NUMPACKETS 1000000
+#define SEC_TO_NANOSEC (1000 * 1000 * 1000)
+
+void init_sockaddr_in(struct sockaddr_in *sin, const char *addr) {
+    sin->sin_family = AF_INET;
+    sin->sin_port = 0;
+    sin->sin_addr.s_addr = inet_addr(addr);
+}
+
+void die(const char *str) {
+    perror(str);
+    exit(1);
+}
+
+int setup_tun() {
+    int fd = tun_open();
+    if (fd == -1) die("tun_open");
+
+    char dev[IFNAMSIZ] = DEVICENAME;
+    int ret = tun_alloc(dev, fd);
+    if (ret == -1) die("tun_alloc");
+    struct ifreq ifr = {
+        .ifr_name = DEVICENAME,
+    };
+
+    int s = socket(AF_INET, SOCK_DGRAM, 0);
+    init_sockaddr_in((struct sockaddr_in *) &ifr.ifr_addr, "192.0.0.4");
+    if (ioctl(s, SIOCSIFADDR, &ifr) < 0) die("SIOCSIFADDR");
+    init_sockaddr_in((struct sockaddr_in *) &ifr.ifr_addr, "255.255.255.248");
+    if (ioctl(s, SIOCSIFNETMASK, &ifr) < 0) die("SIOCSIFNETMASK");
+    if (ioctl(s, SIOCGIFFLAGS, &ifr) < 0) die("SIOCGIFFLAGS");
+    ifr.ifr_flags |= (IFF_UP | IFF_RUNNING);
+    if (ioctl(s, SIOCSIFFLAGS, &ifr) < 0) die("SIOCSIFFLAGS");
+    return fd;
+}
+
+int send_packet(int fd, uint8_t payload[], int len, uint32_t payload_checksum) {
+    struct tun_pi tun = { 0, htons(ETH_P_IP) };
+    struct udphdr udp = {
+        .source = htons(1234),
+        .dest = htons(PORT),
+        .len = htons(len + sizeof(udp)),
+        .check = 0,
+    };
+    struct iphdr ip = {
+        .version = 4,
+        .ihl = 5,
+        .tot_len = htons(len + sizeof(ip) + sizeof(udp)),
+        .frag_off = htons(IP_DF),
+        .ttl = 55,
+        .protocol = IPPROTO_UDP,
+        .saddr = htonl(0xc0000006),  // 192.0.0.6
+        .daddr = htonl(0xc0000004),  // 192.0.0.4
+    };
+    clat_packet out = {
+        { &tun, sizeof(tun) },  // tun header
+        { &ip, sizeof(ip) },    // IP header
+        { NULL, 0 },            // Fragment header
+        { &udp, sizeof(udp) },  // Transport header
+        { NULL, 0 },            // ICMP error IP header
+        { NULL, 0 },            // ICMP error fragment header
+        { NULL, 0 },            // ICMP error transport header
+        { payload, len },       // Payload
+    };
+
+    ip.check = ip_checksum(&ip, sizeof(ip));
+
+    uint32_t sum;
+    sum = ipv4_pseudo_header_checksum(&ip, ntohs(udp.len));
+    sum = ip_checksum_add(sum, &udp, sizeof(udp));
+    sum += payload_checksum;
+    udp.check = ip_checksum_finish(sum);
+
+    return send_tun(fd, out, sizeof(out) / sizeof(out[0]));
+}
+
+double timedelta(const struct timespec tv1, const struct timespec tv2) {
+    struct timespec end = tv2;
+    if (end.tv_nsec < tv1.tv_nsec) {
+        end.tv_sec -= 1;
+        end.tv_nsec += SEC_TO_NANOSEC;
+    }
+    double seconds = (end.tv_sec - tv1.tv_sec);
+    seconds += (((double) (end.tv_nsec - tv1.tv_nsec)) / SEC_TO_NANOSEC);
+    return seconds;
+}
+
+void benchmark(const char *name, int fd, int s, int num, int do_read,
+               uint8_t payload[], int len, uint32_t payload_sum) {
+    int i;
+    char buf[4096];
+    struct timespec tv1, tv2;
+    int write_err = 0, read_err = 0;
+    clock_gettime(CLOCK_MONOTONIC, &tv1);
+    for (i = 0; i < num; i++) {
+        if (send_packet(fd, payload, len, payload_sum) == -1) write_err++;
+        if (do_read && recvfrom(s, buf, sizeof(buf), 0, NULL, NULL) == -1) {
+            read_err++;
+            if (errno == ETIMEDOUT) {
+                printf("Timed out after %d packets!\n", i);
+                break;
+            }
+        }
+    }
+    clock_gettime(CLOCK_MONOTONIC, &tv2);
+    double seconds = timedelta(tv1, tv2);
+    int pps = (int) (i / seconds);
+    double mbps = (i * PAYLOADSIZE / 1000000 * 8 / seconds);
+    printf("%s: %d packets in %.2fs (%d pps, %.2f Mbps), ", name, i, seconds, pps, mbps);
+    printf("read err %d (%.2f%%), write err %d (%.2f%%)\n",
+           read_err, (float) read_err / i * 100,
+           write_err, (float) write_err / i * 100);
+}
+
+int open_socket() {
+    int sock = socket(AF_INET, SOCK_DGRAM | SOCK_NONBLOCK, IPPROTO_UDP);
+
+    int on = 1;
+    if (setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) == -1) die("SO_REUSEADDR");
+
+    struct timeval tv = { 1, 0 };
+    if (setsockopt(sock, SOL_SOCKET, SO_RCVTIMEO, &tv, sizeof(tv)) == -1) die("SO_RCVTIMEO");
+
+    struct sockaddr_in addr = {
+        .sin_family = AF_INET,
+        .sin_port = ntohs(PORT),
+        .sin_addr = { INADDR_ANY }
+    };
+    if (bind(sock, (struct sockaddr *) &addr, sizeof(addr)) == -1) die ("bind");
+
+   return sock;
+}
+
+int main() {
+    int fd = setup_tun();
+    int sock = open_socket();
+
+    int i;
+    uint8_t payload[PAYLOADSIZE];
+    for (i = 0; i < (int) sizeof(payload); i++) {
+        payload[i] = (uint8_t) i;
+    }
+    uint32_t payload_sum = ip_checksum_add(0, payload, sizeof(payload));
+
+    // Check things are working.
+    char buf[4096];
+    if (send_packet(fd, payload, sizeof(payload), payload_sum) == -1) die("send_packet");
+    if (recvfrom(sock, buf, sizeof(buf), 0, NULL, NULL) == -1) die("recvfrom");
+
+    benchmark("Blocking", fd, sock, NUMPACKETS, 1, payload, sizeof(payload), payload_sum);
+    close(fd);
+
+    fd = setup_tun();
+    set_nonblocking(fd);
+    benchmark("No read", fd, sock, NUMPACKETS, 0, payload, sizeof(payload), payload_sum);
+    close(fd);
+
+    fd = setup_tun();
+    set_nonblocking(fd);
+    benchmark("Nonblocking", fd, sock, NUMPACKETS, 1, payload, sizeof(payload), payload_sum);
+    close(fd);
+
+    return 0;
+}