2 This file is part of GNUnet.
3 (C) 2010 Christian Grothoff (and other contributing authors)
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13 General Public License for more details.
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22 * @file src/transport/gnunet-nat-server-windows.c
23 * @brief Windows tool to help bypass NATs using ICMP method
24 * This code will work under W32 only
25 * @author Christian Grothoff
27 * This program will send ONE ICMP message every 500 ms RAW sockets
28 * to a DUMMY IP address and also listens for ICMP replies. Since
29 * it uses RAW sockets, it must be run as an administrative user.
30 * In order to keep the security risk of the resulting binary
31 * minimal, the program ONLY opens the two RAW sockets with administrative
32 * privileges, then drops them and only then starts to process
33 * command line arguments. The code also does not link against
34 * any shared libraries (except libc) and is strictly minimal
35 * (except for checking for errors). The following list of people
36 * have reviewed this code and considered it safe since the last
37 * modification (if you reviewed it, please have your name added
47 #include <sys/types.h>
48 #include <sys/socket.h>
49 #include <arpa/inet.h>
50 #include <sys/select.h>
51 #include <netinet/ip.h>
52 #include <netinet/ip_icmp.h>
53 #include <netinet/in.h>
56 #include <sys/types.h>
67 typedef unsigned int uid_t;
68 typedef SOCKET Socket;
69 typedef unsigned short ushort;
71 #define IPDEFTTL 64 /* default ttl, from RFC 1340 */
72 #define ICMP_TIME_EXCEEDED 11 /* Time Exceeded */
73 #define IP_HDRINCL 3 /* int; Header is included with data. */
79 * Must match IP given in the client.
81 #define DUMMY_IP "192.0.2.86"
86 * How often do we send our ICMP messages to receive replies?
88 #define ICMP_SEND_FREQUENCY_MS 500
96 uint16_t flags_frag_offset;
121 static Socket icmpsock;
123 static Socket rawsock;
125 static struct in_addr dummy;
128 calc_checksum(const uint16_t *data,
135 for (i=0;i<bytes/2;i++)
137 sum = (sum & 0xffff) + (sum >> 16);
138 sum = htons(0xffff - sum);
144 * @param af address family
145 * @param cp the address to print
146 * @param buf where to write the address result
148 static int inet_pton (int af, char *cp, void *buf)
153 ssize = sizeof(struct in_addr);
154 fprintf (stderr, "in_addr size %d", ssize);
155 fprintf (stderr, "buf size %d", sizeof(buf));
156 ret = WSAStringToAddress (cp, af, NULL, (LPSOCKADDR)buf, &ssize);
160 fprintf(stderr, "Error %d handling address %s", WSAGetLastError(), cp);
170 make_echo (const struct in_addr *src_ip,
171 struct icmp_packet *echo)
173 memset(echo, 0, sizeof(struct icmp_packet));
174 echo->type = ICMP_ECHO;
178 echo->checksum = htons(calc_checksum((uint16_t*)echo, sizeof (struct icmp_packet)));
183 * Send an ICMP message to the dummy IP.
185 * @param my_ip source address (our ip address)
188 send_icmp_echo (const struct in_addr *my_ip)
190 struct icmp_packet icmp_echo;
191 struct sockaddr_in dst;
194 struct ip_packet ip_pkt;
195 struct icmp_packet icmp_pkt;
196 char packet[sizeof (ip_pkt) + sizeof (icmp_pkt)];
199 memset(&ip_pkt, 0, sizeof(ip_pkt));
200 ip_pkt.vers_ihl = 0x45;
202 ip_pkt.pkt_len = sizeof (packet);
204 ip_pkt.flags_frag_offset = 0;
205 ip_pkt.ttl = IPDEFTTL;
206 ip_pkt.proto = IPPROTO_ICMP;
208 ip_pkt.src_ip = my_ip->s_addr;
209 ip_pkt.dst_ip = dummy.s_addr;
210 ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
211 memcpy (packet, &ip_pkt, sizeof (ip_pkt));
212 off += sizeof (ip_pkt);
213 make_echo (my_ip, &icmp_echo);
214 memcpy (&packet[off], &icmp_echo, sizeof (icmp_echo));
215 off += sizeof (icmp_echo);
217 memset (&dst, 0, sizeof (dst));
218 dst.sin_family = AF_INET;
219 dst.sin_addr = dummy;
220 err = sendto(rawsock,
222 (struct sockaddr*)&dst,
228 "sendto failed: %s\n", strerror(errno));
234 "Error: partial send of ICMP message\n");
240 process_icmp_response ()
245 struct ip_packet ip_pkt;
246 struct icmp_packet icmp_pkt;
247 struct udp_packet udp_pkt;
252 have = read (icmpsock, buf, sizeof (buf));
256 "Error reading raw socket: %s\n",
262 if (have == sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2 + sizeof(uint32_t))
266 else if (have != sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2)
270 "Received ICMP message of unexpected size: %u bytes\n",
271 (unsigned int) have);
276 memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
277 off += sizeof (ip_pkt);
278 memcpy (&icmp_pkt, &buf[off], sizeof (icmp_pkt));
279 off += sizeof (icmp_pkt);
280 if ( ((ip_pkt.proto != IPPROTO_ICMP) && (ip_pkt.proto != IPPROTO_UDP)) ||
281 (icmp_pkt.type != ICMP_TIME_EXCEEDED) ||
282 (icmp_pkt.code != 0) )
284 /* maybe we got an actual reply back... */
291 memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
292 off += sizeof (ip_pkt);
295 if (ip_pkt.proto == IPPROTO_UDP)
302 memcpy(&port, &buf[sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2], sizeof(uint32_t));
305 DWORD ssize = sizeof(buf);
306 WSAAddressToString((LPSOCKADDR)&sip, sizeof(sip), NULL, buf, &ssize);
307 fprintf (stdout, "%s:%d\n", buf, port);
314 sizeof (buf)), port);
319 memcpy(&udp_pkt, &buf[off], sizeof(udp_pkt));
321 DWORD ssize = sizeof(buf);
322 WSAAddressToString((LPSOCKADDR)&sip, sizeof(sip), NULL, buf, &ssize);
323 fprintf (stdout, "%s:%d\n", buf, ntohs((int)udp_pkt.length));
330 sizeof (buf)), ntohl(udp_pkt.length));
336 DWORD ssize = sizeof(buf);
337 WSAAddressToString((LPSOCKADDR)&sip, sizeof(sip), NULL, buf, &ssize);
338 fprintf (stdout, "%s\n", buf);
357 ret = socket (AF_INET, SOCK_RAW, IPPROTO_ICMP);
361 "Error opening RAW socket: %s\n",
366 if (ret == INVALID_SOCKET)
368 fprintf (stderr, "Invalid socket %d!\n", ret);
372 if (ret >= FD_SETSIZE)
375 "Socket number too large (%d > %u)\n",
377 (unsigned int) FD_SETSIZE);
392 ret = socket (AF_INET, SOCK_RAW, IPPROTO_RAW);
396 "Error opening RAW socket: %s\n",
400 if (setsockopt(ret, SOL_SOCKET, SO_BROADCAST,
401 (char *)&one, sizeof(one)) == -1)
403 "setsockopt failed: %s\n",
405 if (setsockopt(ret, IPPROTO_IP, IP_HDRINCL,
406 (char *)&one, sizeof(one)) == -1)
408 "setsockopt failed: %s\n",
415 main (int argc, char *const *argv)
417 struct sockaddr_storage external;
421 struct sockaddr_storage saddr;
428 if (WSAStartup (MAKEWORD (2, 1), &wsaData) != 0)
430 fprintf (stderr, "Failed to find Winsock 2.1 or better.\n");
435 if (-1 == (icmpsock = make_icmp_socket()))
437 if (-1 == (rawsock = make_raw_socket()))
444 if (0 != setresuid (uid, uid, uid))
446 "Failed to setresuid: %s\n",
452 "This program must be started with our (internal NAT) IP as the only argument.\n");
456 if (1 != inet_pton (AF_INET, argv[1], &saddr))
459 "Error parsing IPv4 address: %s, error %s\n",
460 argv[1], strerror (errno));
464 if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy)) abort ();
468 FD_SET (icmpsock, &rs);
470 tv.tv_usec = ICMP_SEND_FREQUENCY_MS * 1000;
471 select (icmpsock + 1, &rs, NULL, NULL, &tv);
472 if (FD_ISSET (icmpsock, &rs))
473 process_icmp_response ();
474 send_icmp_echo (&external);
478 closesocket(icmpsock);
479 closesocket(rawsock);
486 /* end of gnunet-nat-server-windows.c */