6 #include <sys/socket.h>
8 #include <netinet/in.h>
10 #include <arpa/inet.h>
13 #include <linux/if_tun.h>
20 #if __has_include(<sys/random.h>)
21 #include <sys/random.h>
23 int getrandom(void* buf, size_t len, unsigned int flags) {
24 FILE* f = fopen("/dev/urandom", "r");
25 int res = fread(buf, len, 1, f);
32 static int tun_alloc(char *dev, int queues, int *fds)
40 memset(&ifr, 0, sizeof(ifr));
42 /* Flags: IFF_TUN - TUN device (no Ethernet headers)
43 * IFF_TAP - TAP device
45 * IFF_NO_PI - Do not provide packet information
47 ifr.ifr_flags = IFF_TUN | IFF_NO_PI | IFF_MULTI_QUEUE;
48 strncpy(ifr.ifr_name, dev, IFNAMSIZ);
50 for (i = 0; i < queues; i++) {
51 if((fd = open("/dev/net/tun", O_RDWR)) < 0)
53 err = ioctl(fd, TUNSETIFF, (void *) &ifr);
62 for (--i; i >= 0; i--)
67 static int check_ip_header(const unsigned char* buf, ssize_t buf_len, uint8_t expected_type) {
73 if ((buf[0] & 0xf0) != (4 << 4)) {
78 uint8_t num_words = buf[0] & 0xf;
79 int header_size = num_words * 4;
80 if (header_size < 20) {
81 fprintf(stderr, "Invalid IPv4 IHL size (%d)\n", header_size);
85 if ((((uint16_t)buf[2]) << 8 | buf[3]) != buf_len) {
86 //fprintf(stderr, "Packet len %u != %ld\n", ((uint16_t)buf[2]) << 8 | buf[3], buf_len);
90 if (buf[9] != expected_type) {
91 fprintf(stderr, "Packet type %u, not %u\n", buf[9], expected_type);
98 void print_packet(const unsigned char* buf, ssize_t buf_len) {
99 for (ssize_t i = 0; i < buf_len; ) {
100 for (int j = 0; i < buf_len && j < 20; i++, j++)
101 fprintf(stderr, "%02x", buf[i]);
102 fprintf(stderr, "\n");
106 static uint32_t data_checksum(const unsigned char* buf, size_t len) {
112 sum += (*buf++) << 8;
113 if (sum & 0x80000000)
114 sum = (sum & 0xFFFF) + (sum >> 16);
124 static uint16_t finalize_data_checksum(uint32_t sum) {
126 sum = (sum & 0xFFFF) + (sum >> 16);
128 return (uint16_t)(~sum);
131 static uint16_t tcp_checksum(const unsigned char* buff, size_t len, in_addr_t src_addr, in_addr_t dest_addr)
133 uint16_t *ip_src = (uint16_t*)&src_addr, *ip_dst = (uint16_t*)&dest_addr;
134 uint32_t sum = data_checksum(buff, len);
140 sum += htons(IPPROTO_TCP);
143 return finalize_data_checksum(sum);
146 static std::atomic<uint32_t> highest_recvd_seq(0), cur_seq(0);
147 static std::atomic<uint16_t> local_port(0);
148 static uint16_t remote_port;
149 static bool are_server;
151 static void build_tcp_header(unsigned char* buf, uint32_t len, int syn, int synack, in_addr_t src_addr, in_addr_t dest_addr) {
152 buf[0 ] = local_port >> 8; // src port
153 buf[1 ] = local_port; // src port
154 buf[2 ] = remote_port >> 8; // dst port
155 buf[3 ] = remote_port; // dst port
157 uint32_t seq = cur_seq.fetch_add((syn || synack) ? 1 : len, std::memory_order_acq_rel);
158 buf[4 ] = seq >> (8 * 3); // SEQ
159 buf[5 ] = seq >> (8 * 2); // SEQ
160 buf[6 ] = seq >> (8 * 1); // SEQ
161 buf[7 ] = seq >> (8 * 0); // SEQ
163 uint32_t their_seq = highest_recvd_seq.load(std::memory_order_relaxed);
164 buf[8 ] = their_seq >> (8 * 3); // ACK
165 buf[9 ] = their_seq >> (8 * 2); // ACK
166 buf[10] = their_seq >> (8 * 1); // ACK
167 buf[11] = their_seq >> (8 * 0); // ACK
169 bool longpkt = syn || synack;
170 buf[12] = (longpkt ? 6 : 5) << 4; // data offset
172 buf[13] = 1 << 1; // SYN
174 buf[13] = (1 << 1) | (1 << 4); // SYN + ACK
176 buf[13] = 1 << 4; // ACK
178 buf[13] = 3 << 3; // PSH + ACK
179 buf[14] = 0xff; // Window Size
180 buf[15] = 0xff; // Window Size
182 buf[16] = 0x00; // Checksum
183 buf[17] = 0x00; // Checksum
184 buf[18] = 0x00; // URG Pointer
185 buf[19] = 0x00; // URG Pointer
188 buf[20] = 0x01; // NOP
189 buf[21] = 0x03; // Window Scale
190 buf[22] = 0x03; // Window Scale Option Length
191 buf[23] = 0x0e; // 1GB Window Size (0xffff << 0x0e)
194 uint16_t checksum = tcp_checksum(buf, len + 20 + (longpkt ? 4 : 0), src_addr, dest_addr);
195 buf[16] = checksum; // Checksum
196 buf[17] = checksum >> 8; // Checksum
199 static void build_ip_header(unsigned char* buf, uint32_t len, uint8_t proto, const in_addr_t& src_addr, const in_addr_t& dest_addr) {
200 buf[0 ] = (4 << 4) | 5; // IPv4 + IHL of 5 (20 bytes)
201 buf[1 ] = 0; // DSCP 0 + ECN 0
202 buf[2 ] = (len + 20) >> 8; // Length
203 buf[3 ] = (len + 20); // Length
204 memset(buf + 4, 0, 4); // Identification and Fragment 0s
205 buf[6 ] = 1 << 6; // DF bit
206 buf[8 ] = 255; // TTL
207 buf[9 ] = proto; // Protocol Number
208 buf[10] = 0; // Checksum
209 buf[11] = 0; // Checksum
211 memcpy(buf + 12, &src_addr, 4);
212 memcpy(buf + 16, &dest_addr, 4);
214 uint16_t checksum = finalize_data_checksum(data_checksum(buf, 20));
216 buf[11] = checksum >> 8;
220 const signed char p_util_hexdigit[256] =
221 { -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
222 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
223 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
224 0,1,2,3,4,5,6,7,8,9,-1,-1,-1,-1,-1,-1,
225 -1,0xa,0xb,0xc,0xd,0xe,0xf,-1,-1,-1,-1,-1,-1,-1,-1,-1,
226 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
227 -1,0xa,0xb,0xc,0xd,0xe,0xf,-1,-1,-1,-1,-1,-1,-1,-1,-1,
228 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
229 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
230 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
231 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
232 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
233 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
234 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
235 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
236 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, };
238 uint32_t hex_to_num(const char* buf) {
239 const char* pbegin = buf;
240 while (p_util_hexdigit[*buf] != -1)
244 unsigned char* p1 = (unsigned char*)&res;
245 unsigned char* pend = p1 + 4;
246 while (buf >= pbegin && p1 < pend) {
247 *p1 = p_util_hexdigit[*buf--];
249 *p1 |= ((unsigned char)p_util_hexdigit[*buf--] << 4);
257 #define TUN_IF_COUNT 4
259 static int fd[TUN_IF_COUNT];
260 static struct sockaddr_in dest;
261 static in_addr_t src, tun_src, tun_dest, ipip_src, ipip_dest;
262 static const uint64_t tcp_init_magic = 0x1badcafedeadbeefULL;
264 #define PENDING_MESSAGES_BUFF_SIZE (0x3000)
265 #define PACKET_READ_SIZE 1500
266 #define THREAD_POLL_SLEEP_MICS 50
267 struct MessageQueue {
268 std::tuple<sockaddr_in, std::array<unsigned char, PACKET_READ_SIZE>, ssize_t> messagesPendingRingBuff[PENDING_MESSAGES_BUFF_SIZE];
269 std::atomic<uint16_t> nextPendingMessage, nextUndefinedMessage;
270 MessageQueue() : nextPendingMessage(0), nextUndefinedMessage(0) {}
271 MessageQueue(MessageQueue&& q) =delete;
272 MessageQueue(MessageQueue& q) =delete;
275 static MessageQueue tcp_to_tun_queue;
276 static std::chrono::steady_clock::time_point last_ack_recv;
278 static void tcp_to_tun() {
279 unsigned char buf[1500];
280 struct sockaddr_in pkt_src;
281 memset(&pkt_src, 0, sizeof(pkt_src));
284 socklen_t hostsz = sizeof(pkt_src);
285 ssize_t nread = recvfrom(fdr, buf, sizeof(buf), 0, (struct sockaddr*)&pkt_src, &hostsz);
287 fprintf (stderr, "Failed to read tcp raw sock\n");
291 if (tcp_to_tun_queue.nextPendingMessage == (tcp_to_tun_queue.nextUndefinedMessage + 1) % PENDING_MESSAGES_BUFF_SIZE)
294 auto& new_msg = tcp_to_tun_queue.messagesPendingRingBuff[tcp_to_tun_queue.nextUndefinedMessage];
295 std::get<0>(new_msg) = pkt_src;
296 memcpy(std::get<1>(new_msg).data(), buf, nread);
297 std::get<2>(new_msg) = nread;
299 tcp_to_tun_queue.nextUndefinedMessage = (tcp_to_tun_queue.nextUndefinedMessage + 1) % PENDING_MESSAGES_BUFF_SIZE;
303 static void tcp_to_tun_queue_process() {
305 while (tcp_to_tun_queue.nextUndefinedMessage == tcp_to_tun_queue.nextPendingMessage) {
306 std::this_thread::sleep_for(std::chrono::microseconds(THREAD_POLL_SLEEP_MICS));
309 auto& msg = tcp_to_tun_queue.messagesPendingRingBuff[tcp_to_tun_queue.nextPendingMessage];
311 const sockaddr_in& pkt_src = std::get<0>(msg);
312 unsigned char* buf = std::get<1>(msg).data();
313 ssize_t nread = std::get<2>(msg);
315 int header_size = check_ip_header(buf, nread, 0x06); // Only support TCP
319 if (nread - header_size < 20) {
320 fprintf(stderr, "Short TCP packet\n");
324 unsigned char* tcp_buf = buf + header_size;
326 if (((tcp_buf[2] << 8) | tcp_buf[3]) != local_port) continue;
328 bool syn = tcp_buf[13] & (1 << 1);
329 bool ack = tcp_buf[13] & (1 << 4);
331 if (are_server && syn && !ack) {
332 // We're a server and just got a client
333 if (tcp_buf[4 ] != uint8_t(tcp_init_magic >> (7 * 8)) ||
334 tcp_buf[5 ] != uint8_t(tcp_init_magic >> (6 * 8)) ||
335 tcp_buf[6 ] != uint8_t(tcp_init_magic >> (5 * 8)) ||
336 tcp_buf[7 ] != uint8_t(tcp_init_magic >> (4 * 8)) ||
337 tcp_buf[8 ] != uint8_t(tcp_init_magic >> (3 * 8)) ||
338 tcp_buf[9 ] != uint8_t(tcp_init_magic >> (2 * 8)) ||
339 tcp_buf[10] != uint8_t(tcp_init_magic >> (1 * 8)) ||
340 tcp_buf[11] != uint8_t(tcp_init_magic >> (0 * 8)))
343 fprintf(stderr, "Got SYN, sending SYNACK\n");
344 remote_port = (tcp_buf[0] << 8) | tcp_buf[1];
348 if (((tcp_buf[0] << 8) | tcp_buf[1]) != remote_port) continue;
349 if (pkt_src.sin_addr.s_addr != dest.sin_addr.s_addr) continue;
351 uint8_t num_words = (tcp_buf[12] & 0xf0) >> 4;
352 int tcp_header_size = num_words * 4;
353 if (tcp_header_size < 20) {
354 fprintf(stderr, "Invalid TCP header size (%d)\n", tcp_header_size);
358 highest_recvd_seq = ((((uint32_t)tcp_buf[4]) << (8 * 3)) |
359 (((uint32_t)tcp_buf[5]) << (8 * 2)) |
360 (((uint32_t)tcp_buf[6]) << (8 * 1)) |
361 (((uint32_t)tcp_buf[7]) << (8 * 0))) +
362 (syn ? 1 : nread - header_size - tcp_header_size);
365 last_ack_recv = std::chrono::steady_clock::now();
367 if (are_server && syn && !ack) {
368 build_tcp_header(tcp_buf, 0, 0, 1, src, dest.sin_addr.s_addr);
370 ssize_t res = sendto(fdr, tcp_buf, 20 + 4, 0, (struct sockaddr*)&dest, sizeof(dest));
373 fprintf(stderr, "Failed to send SYNACK with err %d (%s)\n", err, strerror(err));
376 tcp_buf += tcp_header_size - 20;
378 // Replace TCP with IPv4 header
379 //build_ip_header(tcp_buf, nread - tcp_header_size - header_size, 0x01, ipip_dest, ipip_src); // ICMP
380 build_ip_header(tcp_buf, nread - tcp_header_size - header_size, 0x11, ipip_dest, ipip_src); // UDP
382 build_ip_header(tcp_buf - 20, nread - tcp_header_size - header_size + 20, 0x04, tun_dest, tun_src);
384 write(fd[0], tcp_buf - 20, nread - tcp_header_size - header_size + 40);
386 } while ((tcp_to_tun_queue.nextPendingMessage = (tcp_to_tun_queue.nextPendingMessage + 1) % PENDING_MESSAGES_BUFF_SIZE) || true);
389 static std::atomic_int tun_if_thread(0), tun_if_process_thread(0);
390 static std::atomic_bool pause_tun_read_reinit_tcp(false);
391 static MessageQueue tun_to_tcp_queue[TUN_IF_COUNT];
393 static void tun_to_tcp() {
394 unsigned char buf[PACKET_READ_SIZE];
396 int thread = tun_if_thread.fetch_add(1);
397 MessageQueue& queue = tun_to_tcp_queue[thread];
400 ssize_t nread = read(fd[thread], buf, sizeof(buf));
401 if (pause_tun_read_reinit_tcp)
405 fprintf (stderr, "Failed to read tun if\n");
409 if (queue.nextPendingMessage == (queue.nextUndefinedMessage + 1) % PENDING_MESSAGES_BUFF_SIZE)
412 auto& new_msg = queue.messagesPendingRingBuff[queue.nextUndefinedMessage];
413 memcpy(std::get<1>(new_msg).data(), buf, nread);
414 std::get<2>(new_msg) = nread;
416 queue.nextUndefinedMessage = (queue.nextUndefinedMessage + 1) % PENDING_MESSAGES_BUFF_SIZE;
420 static void tun_to_tcp_queue_process() {
421 int thread = tun_if_process_thread.fetch_add(1);
422 MessageQueue& queue = tun_to_tcp_queue[thread];
425 while (queue.nextUndefinedMessage == queue.nextPendingMessage) {
426 std::this_thread::sleep_for(std::chrono::microseconds(THREAD_POLL_SLEEP_MICS));
428 if (pause_tun_read_reinit_tcp)
431 auto& msg = queue.messagesPendingRingBuff[queue.nextPendingMessage];
433 unsigned char* buf = std::get<1>(msg).data();
434 ssize_t nread = std::get<2>(msg);
436 int header_size = check_ip_header(buf, nread, 0x04); // Only support IPIP
440 int internal_header_size = check_ip_header(buf + header_size, nread - header_size, 0x11); // Only support UDP
441 //int internal_header_size = check_ip_header(buf + header_size, nread - header_size, 0x01); // Only support ICMP
442 if (internal_header_size < 0)
445 if (internal_header_size + header_size + 8 > nread) {
446 fprintf(stderr, "Short UDP-in-IPIP packet\n");
450 size_t tcp_start_offset = header_size + internal_header_size - 20;
451 build_tcp_header(buf + tcp_start_offset, nread - tcp_start_offset - 20, 0, 0, src, dest.sin_addr.s_addr);
453 ssize_t res = sendto(fdr, buf + tcp_start_offset, nread - tcp_start_offset, 0, (struct sockaddr*)&dest, sizeof(dest));
456 fprintf(stderr, "Failed to send with err %d (%s)\n", err, strerror(err));
459 } while ((queue.nextPendingMessage = (queue.nextPendingMessage + 1) % PENDING_MESSAGES_BUFF_SIZE) || true);
464 // Send SYN and SYN/ACK
468 if (local_port) // Doing a re-init
469 pause_tun_read_reinit_tcp = true;
471 uint16_t local_port_tmp = 0;
472 while (local_port_tmp < 1024)
473 assert(getrandom(&local_port_tmp, sizeof(local_port_tmp), 0) == sizeof(local_port_tmp));
475 local_port = local_port_tmp;
478 uint32_t starting_ack = 0, starting_seq = 0;
479 memcpy(&starting_ack, &tcp_init_magic, 4);
480 memcpy(&starting_seq, ((const unsigned char*)&tcp_init_magic) + 4, 4);
481 highest_recvd_seq = starting_ack;
482 cur_seq = starting_seq;
484 if (!pause_tun_read_reinit_tcp) { // Not doing a re-init
485 std::thread t(&tcp_to_tun);
486 std::thread t2(&tcp_to_tun_queue_process);
491 unsigned char buf[1500];
493 build_tcp_header(buf, 0, 1, 0, src, dest.sin_addr.s_addr);
494 ssize_t res = sendto(fdr, buf, 20 + 4, 0, (struct sockaddr*)&dest, sizeof(dest));
497 fprintf(stderr, "Failed to send initial SYN with err %d (%s)\n", err, strerror(err));
503 for (i = 0; i < 1000 && highest_recvd_seq == starting_ack; i++)
504 std::this_thread::sleep_for(std::chrono::milliseconds(10));
505 if (i == 1000) // Will come back in 10 seconds
509 fprintf(stderr, "Got SYNACK, sending ACK and starting tun listen\n");
511 build_tcp_header(buf, 0, 0, 0, src, dest.sin_addr.s_addr);
512 ssize_t res = sendto(fdr, buf, 20, 0, (struct sockaddr*)&dest, sizeof(dest));
515 fprintf(stderr, "Failed to send initial ACK with err %d (%s)\n", err, strerror(err));
520 if (pause_tun_read_reinit_tcp) {
521 pause_tun_read_reinit_tcp = false;
523 for (int i = 0; i < TUN_IF_COUNT; i++) {
524 std::thread t3(&tun_to_tcp);
525 std::thread t4(&tun_to_tcp_queue_process);
534 int main(int argc, char* argv[]) {
535 assert(argc > 1 && "Need tun name");
536 assert(argc > 2 && "Need tun remote host");
537 assert(argc > 3 && "Need tun local host");
538 assert(argc > 4 && "Need ipip remote host");
539 assert(argc > 5 && "Need ipip local host");
540 assert(argc > 6 && "Need server port");
541 assert(argc > 7 && "Need mode (client or server)");
542 assert(argc > 8 && "Need src host");
543 if (std::string(argv[7]) == std::string("client"))
544 assert(argc > 9 && "Need dest host");
546 assert(std::string(argv[7]) == std::string("client") || std::string(argv[7]) == std::string("server"));
547 are_server = (std::string(argv[7]) == std::string("server"));
550 // Parse args into variables
553 char tun_name[IFNAMSIZ];
555 memset(tun_name, 0, sizeof(tun_name));
556 strcpy(tun_name, argv[1]);
558 tun_dest = inet_addr(argv[2]);
559 tun_src = inet_addr(argv[3]);
561 ipip_dest = inet_addr(argv[4]);
562 ipip_src = inet_addr(argv[5]);
565 local_port = atoi(argv[6]);
568 // Get local port in do_init() so that we pick a new one on reload
569 remote_port = atoi(argv[6]);
572 src = inet_addr(argv[8]);
574 memset(&dest, 0, sizeof(dest));
576 dest.sin_family = AF_INET;
577 dest.sin_addr.s_addr = inet_addr(argv[9]);
581 // Create tun and bind to sockets...
584 if (tun_alloc(tun_name, TUN_IF_COUNT, fd) < 0) {
585 fprintf(stderr, "Failed to alloc tun if\n");
589 fdr = socket(AF_INET, SOCK_RAW, IPPROTO_TCP);
591 fprintf(stderr, "Failed to get raw socket\n");
600 std::this_thread::sleep_for(std::chrono::seconds(15));
601 if (!are_server && last_ack_recv < std::chrono::steady_clock::now() - std::chrono::seconds(15)) {