5 #include <sys/socket.h>
7 #include <netinet/in.h>
13 #include <linux/if_tun.h>
21 #if __has_include(<sys/random.h>)
22 #include <sys/random.h>
24 int getrandom(void* buf, size_t len, unsigned int flags) {
25 FILE* f = fopen("/dev/urandom", "r");
26 int res = fread(buf, len, 1, f);
32 #define PACKET_READ_OFFS (20-16)
33 #define PACKET_READ_SIZE (1500 - PACKET_READ_OFFS)
35 static int tun_alloc(char *dev, const char* local_ip, const char* remote_ip, int queues, int *fds)
44 memset(&ifr, 0, sizeof(ifr));
46 /* Flags: IFF_TUN - TUN device (no Ethernet headers)
47 * IFF_TAP - TAP device
49 * IFF_NO_PI - Do not provide packet information
51 ifr.ifr_flags = IFF_TUN | IFF_NO_PI | IFF_MULTI_QUEUE;
52 strncpy(ifr.ifr_name, dev, IFNAMSIZ);
54 for (i = 0; i < queues; i++) {
55 if((fd = open("/dev/net/tun", O_RDWR)) < 0)
57 err = ioctl(fd, TUNSETIFF, (void *) &ifr);
65 sprintf(buf, "ip link set %s mtu %d", dev, PACKET_READ_SIZE);
69 sprintf(buf, "ip addr add %s/32 dev %s", local_ip, dev);
73 sprintf(buf, "ip link set %s up", dev);
77 sprintf(buf, "ip route add %s/32 dev %s", remote_ip, dev);
83 for (--i; i >= 0; i--)
88 static int check_ip_header(const unsigned char* buf, ssize_t buf_len, uint8_t expected_type) {
94 if ((buf[0] & 0xf0) != (4 << 4)) {
99 uint8_t num_words = buf[0] & 0xf;
100 int header_size = num_words * 4;
101 if (header_size < 20) {
102 fprintf(stderr, "Invalid IPv4 IHL size (%d)\n", header_size);
106 if ((((uint16_t)buf[2]) << 8 | buf[3]) != buf_len) {
107 //fprintf(stderr, "Packet len %u != %ld\n", ((uint16_t)buf[2]) << 8 | buf[3], buf_len);
111 if (buf[9] != expected_type) {
112 fprintf(stderr, "Packet type %u, not %u\n", buf[9], expected_type);
119 #define UDP_PORTS 4242
120 static int check_udp_header(const unsigned char* buf, ssize_t buf_len) {
124 if (((((uint16_t)buf[0]) << 8) | (buf[1])) != UDP_PORTS) {
127 if (((((uint16_t)buf[2]) << 8) | (buf[3])) != UDP_PORTS) {
133 void print_packet(const unsigned char* buf, ssize_t buf_len) {
134 for (ssize_t i = 0; i < buf_len; ) {
135 for (int j = 0; i < buf_len && j < 20; i++, j++)
136 fprintf(stderr, "%02x", buf[i]);
137 fprintf(stderr, "\n");
141 static uint32_t data_checksum(const unsigned char* buf, size_t len) {
147 sum += (*buf++) << 8;
148 if (sum & 0x80000000)
149 sum = (sum & 0xFFFF) + (sum >> 16);
159 static uint16_t finalize_data_checksum(uint32_t sum) {
161 sum = (sum & 0xFFFF) + (sum >> 16);
163 return (uint16_t)(~sum);
166 static uint16_t tcp_checksum(const unsigned char* buff, size_t len, in_addr_t src_addr, in_addr_t dest_addr)
168 uint16_t *ip_src = (uint16_t*)&src_addr, *ip_dst = (uint16_t*)&dest_addr;
169 uint32_t sum = data_checksum(buff, len);
175 sum += htons(IPPROTO_TCP);
178 return finalize_data_checksum(sum);
181 static std::atomic<uint32_t> highest_recvd_seq(0), cur_seq(0);
182 static std::atomic<uint16_t> local_port(0);
183 static uint16_t remote_port;
184 static bool are_server;
186 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) {
187 buf[0 ] = local_port >> 8; // src port
188 buf[1 ] = local_port; // src port
189 buf[2 ] = remote_port >> 8; // dst port
190 buf[3 ] = remote_port; // dst port
192 uint32_t seq = cur_seq.fetch_add((syn || synack) ? 1 : len, std::memory_order_acq_rel);
193 buf[4 ] = seq >> (8 * 3); // SEQ
194 buf[5 ] = seq >> (8 * 2); // SEQ
195 buf[6 ] = seq >> (8 * 1); // SEQ
196 buf[7 ] = seq >> (8 * 0); // SEQ
198 uint32_t their_seq = highest_recvd_seq.load(std::memory_order_relaxed);
199 buf[8 ] = their_seq >> (8 * 3); // ACK
200 buf[9 ] = their_seq >> (8 * 2); // ACK
201 buf[10] = their_seq >> (8 * 1); // ACK
202 buf[11] = their_seq >> (8 * 0); // ACK
204 bool longpkt = syn || synack;
205 buf[12] = (longpkt ? 6 : 5) << 4; // data offset
207 buf[13] = 1 << 1; // SYN
209 buf[13] = (1 << 1) | (1 << 4); // SYN + ACK
211 buf[13] = 1 << 4; // ACK
213 buf[13] = 3 << 3; // PSH + ACK
214 buf[14] = 0xff; // Window Size
215 buf[15] = 0xff; // Window Size
217 buf[16] = 0x00; // Checksum
218 buf[17] = 0x00; // Checksum
219 buf[18] = 0x00; // URG Pointer
220 buf[19] = 0x00; // URG Pointer
223 buf[20] = 0x01; // NOP
224 buf[21] = 0x03; // Window Scale
225 buf[22] = 0x03; // Window Scale Option Length
226 buf[23] = 0x0e; // 1GB Window Size (0xffff << 0x0e)
229 uint16_t checksum = tcp_checksum(buf, len + 20 + (longpkt ? 4 : 0), src_addr, dest_addr);
230 buf[16] = checksum; // Checksum
231 buf[17] = checksum >> 8; // Checksum
234 // len is data length, not including headers!
235 static void build_ip_header(unsigned char* buf, uint16_t len, uint8_t proto, const in_addr_t& src_addr, const in_addr_t& dest_addr) {
236 buf[0 ] = (4 << 4) | 5; // IPv4 + IHL of 5 (20 bytes)
237 buf[1 ] = 0; // DSCP 0 + ECN 0
238 buf[2 ] = (len + 20) >> 8; // Length
239 buf[3 ] = (len + 20); // Length
240 memset(buf + 4, 0, 4); // Identification and Fragment 0s
241 buf[6 ] = 1 << 6; // DF bit
242 buf[8 ] = 255; // TTL
243 buf[9 ] = proto; // Protocol Number
244 buf[10] = 0; // Checksum
245 buf[11] = 0; // Checksum
247 memcpy(buf + 12, &src_addr, 4);
248 memcpy(buf + 16, &dest_addr, 4);
250 uint16_t checksum = finalize_data_checksum(data_checksum(buf, 20));
252 buf[11] = checksum >> 8;
255 // length is data length, not including headers
256 static void build_udp_header(unsigned char* buf, uint16_t len) {
257 buf[0] = UDP_PORTS >> 8;
258 buf[1] = UDP_PORTS & 0xff;
259 buf[2] = UDP_PORTS >> 8;
260 buf[3] = UDP_PORTS & 0xff;
261 buf[4] = (len + 8) >> 8;
264 // Checksum 0 for now
270 const signed char p_util_hexdigit[256] =
271 { -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
272 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
273 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
274 0,1,2,3,4,5,6,7,8,9,-1,-1,-1,-1,-1,-1,
275 -1,0xa,0xb,0xc,0xd,0xe,0xf,-1,-1,-1,-1,-1,-1,-1,-1,-1,
276 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
277 -1,0xa,0xb,0xc,0xd,0xe,0xf,-1,-1,-1,-1,-1,-1,-1,-1,-1,
278 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
279 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
280 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
281 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
282 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
283 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
284 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
285 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,
286 -1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1,-1, };
288 uint32_t hex_to_num(const unsigned char* buf) {
289 const unsigned char* pbegin = buf;
290 while (p_util_hexdigit[*buf] != -1)
294 unsigned char* p1 = (unsigned char*)&res;
295 unsigned char* pend = p1 + 4;
296 while (buf >= pbegin && p1 < pend) {
297 *p1 = p_util_hexdigit[*buf--];
299 *p1 |= ((unsigned char)p_util_hexdigit[*buf--] << 4);
307 #define TUN_IF_COUNT 4
309 static int fd[TUN_IF_COUNT];
310 static struct sockaddr_in dest;
311 static in_addr_t src, tun_src, tun_dest;
312 static uint64_t tcp_init_magic;
314 #define PENDING_MESSAGES_BUFF_SIZE (0x3000)
315 #define PACKET_READ_OFFS (20-16)
316 #define PACKET_READ_SIZE (1500 - PACKET_READ_OFFS)
317 #define THREAD_POLL_SLEEP_MICS 50
318 struct MessageQueue {
319 std::tuple<sockaddr_in, std::array<unsigned char, PACKET_READ_SIZE + PACKET_READ_OFFS>, ssize_t> messagesPendingRingBuff[PENDING_MESSAGES_BUFF_SIZE];
320 std::atomic<uint16_t> nextPendingMessage, nextUndefinedMessage;
321 MessageQueue() : nextPendingMessage(0), nextUndefinedMessage(0) {}
322 MessageQueue(MessageQueue&& q) =delete;
323 MessageQueue(MessageQueue& q) =delete;
326 static MessageQueue tcp_to_tun_queue;
327 static std::chrono::steady_clock::time_point last_ack_recv;
329 static void tcp_to_tun() {
330 unsigned char buf[1500];
331 struct sockaddr_in pkt_src;
332 memset(&pkt_src, 0, sizeof(pkt_src));
335 socklen_t hostsz = sizeof(pkt_src);
336 ssize_t nread = recvfrom(fdr, buf, sizeof(buf), 0, (struct sockaddr*)&pkt_src, &hostsz);
338 fprintf (stderr, "Failed to read tcp raw sock\n");
342 if (tcp_to_tun_queue.nextPendingMessage == (tcp_to_tun_queue.nextUndefinedMessage + 1) % PENDING_MESSAGES_BUFF_SIZE)
345 auto& new_msg = tcp_to_tun_queue.messagesPendingRingBuff[tcp_to_tun_queue.nextUndefinedMessage];
346 std::get<0>(new_msg) = pkt_src;
347 memcpy(std::get<1>(new_msg).data(), buf, nread);
348 std::get<2>(new_msg) = nread;
350 tcp_to_tun_queue.nextUndefinedMessage = (tcp_to_tun_queue.nextUndefinedMessage + 1) % PENDING_MESSAGES_BUFF_SIZE;
354 static void tcp_to_tun_queue_process() {
356 while (tcp_to_tun_queue.nextUndefinedMessage == tcp_to_tun_queue.nextPendingMessage) {
357 std::this_thread::sleep_for(std::chrono::microseconds(THREAD_POLL_SLEEP_MICS));
360 auto& msg = tcp_to_tun_queue.messagesPendingRingBuff[tcp_to_tun_queue.nextPendingMessage];
362 const sockaddr_in& pkt_src = std::get<0>(msg);
363 unsigned char* buf = std::get<1>(msg).data();
364 ssize_t nread = std::get<2>(msg);
366 int header_size = check_ip_header(buf, nread, 0x06); // Only support TCP
370 if (nread - header_size < 20) {
371 fprintf(stderr, "Short TCP packet\n");
375 unsigned char* tcp_buf = buf + header_size;
377 if (((tcp_buf[2] << 8) | tcp_buf[3]) != local_port) continue;
379 bool syn = tcp_buf[13] & (1 << 1);
380 bool ack = tcp_buf[13] & (1 << 4);
382 if (are_server && syn && !ack) {
383 // We're a server and just got a client
384 if (tcp_buf[4 ] != uint8_t(tcp_init_magic >> (7 * 8)) ||
385 tcp_buf[5 ] != uint8_t(tcp_init_magic >> (6 * 8)) ||
386 tcp_buf[6 ] != uint8_t(tcp_init_magic >> (5 * 8)) ||
387 tcp_buf[7 ] != uint8_t(tcp_init_magic >> (4 * 8)) ||
388 tcp_buf[8 ] != uint8_t(tcp_init_magic >> (3 * 8)) ||
389 tcp_buf[9 ] != uint8_t(tcp_init_magic >> (2 * 8)) ||
390 tcp_buf[10] != uint8_t(tcp_init_magic >> (1 * 8)) ||
391 tcp_buf[11] != uint8_t(tcp_init_magic >> (0 * 8)))
394 fprintf(stderr, "Got SYN, sending SYNACK\n");
395 remote_port = (tcp_buf[0] << 8) | tcp_buf[1];
399 if (((tcp_buf[0] << 8) | tcp_buf[1]) != remote_port) continue;
400 if (pkt_src.sin_addr.s_addr != dest.sin_addr.s_addr) continue;
402 uint8_t num_words = (tcp_buf[12] & 0xf0) >> 4;
403 int tcp_header_size = num_words * 4;
404 if (tcp_header_size < 20) {
405 fprintf(stderr, "Invalid TCP header size (%d)\n", tcp_header_size);
409 highest_recvd_seq = ((((uint32_t)tcp_buf[4]) << (8 * 3)) |
410 (((uint32_t)tcp_buf[5]) << (8 * 2)) |
411 (((uint32_t)tcp_buf[6]) << (8 * 1)) |
412 (((uint32_t)tcp_buf[7]) << (8 * 0))) +
413 (syn ? 1 : nread - header_size - tcp_header_size);
416 last_ack_recv = std::chrono::steady_clock::now();
418 if (are_server && syn && !ack) {
419 build_tcp_header(tcp_buf, 0, 0, 1, src, dest.sin_addr.s_addr);
421 ssize_t res = sendto(fdr, tcp_buf, 20 + 4, 0, (struct sockaddr*)&dest, sizeof(dest));
424 fprintf(stderr, "Failed to send SYNACK with err %d (%s)\n", err, strerror(err));
427 tcp_buf += tcp_header_size - 20 - 8; // IPv4 header is 20 bytes + UDP header is 8 bytes
429 // Replace TCP with IPv4 header
430 build_udp_header(tcp_buf + 20, nread - tcp_header_size - header_size);
431 build_ip_header(tcp_buf, nread - tcp_header_size - header_size + 8, 0x11, tun_dest, tun_src); // UDP
433 write(fd[0], tcp_buf, nread - tcp_header_size - header_size + 20 + 8);
435 } while ((tcp_to_tun_queue.nextPendingMessage = (tcp_to_tun_queue.nextPendingMessage + 1) % PENDING_MESSAGES_BUFF_SIZE) || true);
438 static std::atomic_int tun_if_thread(0), tun_if_process_thread(0);
439 static std::atomic_bool pause_tun_read_reinit_tcp(false);
440 static MessageQueue tun_to_tcp_queue[TUN_IF_COUNT];
442 static void tun_to_tcp() {
443 unsigned char buf[PACKET_READ_SIZE];
445 int thread = tun_if_thread.fetch_add(1);
446 MessageQueue& queue = tun_to_tcp_queue[thread];
449 ssize_t nread = read(fd[thread], buf, sizeof(buf));
450 if (pause_tun_read_reinit_tcp)
454 fprintf (stderr, "Failed to read tun if\n");
458 if (queue.nextPendingMessage == (queue.nextUndefinedMessage + 1) % PENDING_MESSAGES_BUFF_SIZE)
461 auto& new_msg = queue.messagesPendingRingBuff[queue.nextUndefinedMessage];
462 memcpy(std::get<1>(new_msg).data() + PACKET_READ_OFFS, buf, nread);
463 std::get<2>(new_msg) = nread;
465 queue.nextUndefinedMessage = (queue.nextUndefinedMessage + 1) % PENDING_MESSAGES_BUFF_SIZE;
469 static void tun_to_tcp_queue_process() {
470 int thread = tun_if_process_thread.fetch_add(1);
471 MessageQueue& queue = tun_to_tcp_queue[thread];
474 while (queue.nextUndefinedMessage == queue.nextPendingMessage) {
475 std::this_thread::sleep_for(std::chrono::microseconds(THREAD_POLL_SLEEP_MICS));
477 if (pause_tun_read_reinit_tcp)
480 auto& msg = queue.messagesPendingRingBuff[queue.nextPendingMessage];
482 unsigned char* buf = std::get<1>(msg).data();
483 ssize_t nread = std::get<2>(msg);
485 int header_size = check_ip_header(buf + PACKET_READ_OFFS, nread, 0x11); // Only support UDP
489 if (header_size + 8 > nread) {
490 fprintf(stderr, "Short UDP packet\n");
494 if (check_udp_header(buf + PACKET_READ_OFFS + header_size, nread - header_size) != 8) {
495 fprintf(stderr, "Bad UDP header\n");
499 unsigned char* tcp_start = buf + PACKET_READ_OFFS + header_size + 8 - 20;
500 build_tcp_header(tcp_start, nread - header_size - 8, 0, 0, src, dest.sin_addr.s_addr);
502 ssize_t res = sendto(fdr, tcp_start, nread + 20 - 8 - header_size, 0, (struct sockaddr*)&dest, sizeof(dest));
505 fprintf(stderr, "Failed to send with err %d (%s)\n", err, strerror(err));
508 } while ((queue.nextPendingMessage = (queue.nextPendingMessage + 1) % PENDING_MESSAGES_BUFF_SIZE) || true);
513 // Send SYN and SYN/ACK
517 if (local_port) // Doing a re-init
518 pause_tun_read_reinit_tcp = true;
520 uint16_t local_port_tmp = 0;
521 while (local_port_tmp < 1024)
522 assert(getrandom(&local_port_tmp, sizeof(local_port_tmp), 0) == sizeof(local_port_tmp));
524 local_port = local_port_tmp;
527 uint32_t starting_ack = 0, starting_seq = 0;
528 memcpy(&starting_ack, &tcp_init_magic, 4);
529 memcpy(&starting_seq, ((const unsigned char*)&tcp_init_magic) + 4, 4);
530 highest_recvd_seq = starting_ack;
531 cur_seq = starting_seq;
533 if (!pause_tun_read_reinit_tcp) { // Not doing a re-init
534 std::thread t(&tcp_to_tun);
535 std::thread t2(&tcp_to_tun_queue_process);
540 unsigned char buf[1500];
542 build_tcp_header(buf, 0, 1, 0, src, dest.sin_addr.s_addr);
543 ssize_t res = sendto(fdr, buf, 20 + 4, 0, (struct sockaddr*)&dest, sizeof(dest));
546 fprintf(stderr, "Failed to send initial SYN with err %d (%s)\n", err, strerror(err));
552 for (i = 0; i < 1000 && highest_recvd_seq == starting_ack; i++)
553 std::this_thread::sleep_for(std::chrono::milliseconds(10));
554 if (i == 1000) // Will come back in 10 seconds
558 fprintf(stderr, "Got SYNACK, sending ACK and starting tun listen\n");
560 build_tcp_header(buf, 0, 0, 0, src, dest.sin_addr.s_addr);
561 ssize_t res = sendto(fdr, buf, 20, 0, (struct sockaddr*)&dest, sizeof(dest));
564 fprintf(stderr, "Failed to send initial ACK with err %d (%s)\n", err, strerror(err));
569 if (pause_tun_read_reinit_tcp) {
570 pause_tun_read_reinit_tcp = false;
572 for (int i = 0; i < TUN_IF_COUNT; i++) {
573 std::thread t3(&tun_to_tcp);
574 std::thread t4(&tun_to_tcp_queue_process);
583 int main(int argc, char* argv[]) {
584 assert(argc > 1 && "Need tun name");
585 assert(argc > 2 && "Need tun remote host");
586 assert(argc > 3 && "Need tun local host");
587 assert(argc > 4 && "Need server port");
588 assert(argc > 5 && "Need shared secret");
589 assert(argc > 6 && "Need mode (client or server)");
590 assert(argc > 7 && "Need src host");
591 if (std::string(argv[6]) == std::string("client"))
592 assert(argc > 8 && "Need dest host");
594 assert(std::string(argv[6]) == std::string("client") || std::string(argv[6]) == std::string("server"));
595 are_server = (std::string(argv[6]) == std::string("server"));
598 // Parse args into variables
601 char tun_name[IFNAMSIZ];
603 memset(tun_name, 0, sizeof(tun_name));
604 strcpy(tun_name, argv[1]);
606 tun_dest = inet_addr(argv[2]);
607 tun_src = inet_addr(argv[3]);
610 local_port = atoi(argv[4]);
613 // Get local port in do_init() so that we pick a new one on reload
614 remote_port = atoi(argv[4]);
617 tcp_init_magic = atoll(argv[5]);
619 src = inet_addr(argv[7]);
621 memset(&dest, 0, sizeof(dest));
623 dest.sin_family = AF_INET;
624 dest.sin_addr.s_addr = inet_addr(argv[8]);
628 // Create tun and bind to sockets...
631 if (tun_alloc(tun_name, argv[3], argv[2], TUN_IF_COUNT, fd) != 0) {
632 fprintf(stderr, "Failed to alloc tun if\n");
636 fdr = socket(AF_INET, SOCK_RAW, IPPROTO_TCP);
638 fprintf(stderr, "Failed to get raw socket\n");
647 std::this_thread::sleep_for(std::chrono::seconds(15));
648 if (!are_server && last_ack_recv < std::chrono::steady_clock::now() - std::chrono::seconds(15)) {