2 This file is part of GNUnet.
3 (C) 2010 Christian Grothoff (and other contributing authors)
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12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 General Public License for more details.
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17 Free Software Foundation, Inc., 59 Temple Place - Suite 330,
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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
48 #include <sys/types.h>
57 typedef unsigned int uid_t;
58 typedef SOCKET Socket;
59 typedef unsigned short ushort;
62 #define ICMP_TIME_EXCEEDED 11 /* Time Exceeded
65 * Must match IP given in the client.
67 #define DUMMY_IP "192.0.2.86"
72 * How often do we send our ICMP messages to receive replies?
74 #define ICMP_SEND_FREQUENCY_MS 500
82 uint16_t flags_frag_offset;
89 u_char vers_ihl; // Version (4 bits) + Internet header length (4 bits)
90 u_char tos; // Type of service
91 u_short pkt_len; // Total length
92 u_short id; // Identification
93 u_short flags_frag_offset; // Flags (3 bits) + Fragment offset (13 bits)
94 u_char ttl; // Time to live
95 u_char proto; // Protocol
96 u_short checksum; // Header checksum
97 u_long src_ip; // Source address
98 u_long dst_ip; // Destination address
118 static Socket icmpsock;
120 static Socket rawsock;
122 static struct in_addr dummy;
125 calc_checksum(const uint16_t *data,
132 for (i=0;i<bytes/2;i++)
134 sum = (sum & 0xffff) + (sum >> 16);
135 sum = htons(0xffff - sum);
140 * @param af address family
141 * @param cp the address to print
142 * @param buf where to write the address result
144 static int inet_pton (int af, char *cp, struct in_addr *buf)
146 //ret = WSAStringToAddress (cp, af, NULL, (LPSOCKADDR)buf, &ssize);
147 buf->s_addr = inet_addr(cp);
148 if (buf->s_addr == INADDR_NONE)
150 fprintf(stderr, "Error %d handling address %s", WSAGetLastError(), cp);
158 make_echo (const struct in_addr *src_ip,
159 struct icmp_packet *echo)
161 memset(echo, 0, sizeof(struct icmp_packet));
162 echo->type = ICMP_ECHO;
166 echo->checksum = htons(calc_checksum((uint16_t*)echo, sizeof (struct icmp_packet)));
171 * Send an ICMP message to the dummy IP.
173 * @param my_ip source address (our ip address)
176 send_icmp_echo (const struct in_addr *my_ip)
178 struct icmp_packet icmp_echo;
179 struct sockaddr_in dst;
182 struct ip_packet ip_pkt;
183 struct icmp_packet icmp_pkt;
184 char packet[sizeof (ip_pkt) + sizeof (icmp_pkt)];
187 memset(&ip_pkt, 0, sizeof(ip_pkt));
188 ip_pkt.vers_ihl = 0x45;
190 ip_pkt.pkt_len = sizeof (packet);
191 ip_pkt.id = htons (256);
192 ip_pkt.flags_frag_offset = 0;
193 ip_pkt.ttl = IPDEFTTL;
194 ip_pkt.proto = IPPROTO_ICMP;
196 ip_pkt.src_ip = my_ip->s_addr;
197 ip_pkt.dst_ip = dummy.s_addr;
198 ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
199 memcpy (packet, &ip_pkt, sizeof (ip_pkt));
200 off += sizeof (ip_pkt);
202 make_echo (my_ip, &icmp_echo);
203 memcpy (&packet[off], &icmp_echo, sizeof (icmp_echo));
204 off += sizeof (icmp_echo);
206 memset (&dst, 0, sizeof (dst));
207 dst.sin_family = AF_INET;
208 dst.sin_addr = dummy;
209 err = sendto(rawsock,
211 (struct sockaddr*)&dst,
217 "sendto failed: %s\n", strerror(errno));
223 "Error: partial send of ICMP message\n");
229 process_icmp_response ()
234 struct ip_packet ip_pkt;
235 struct icmp_packet icmp_pkt;
236 struct udp_packet udp_pkt;
241 have = read (icmpsock, buf, sizeof (buf));
245 "Error reading raw socket: %s\n",
252 "Received message of %u bytes\n",
253 (unsigned int) have);
255 if (have == sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2 + sizeof(uint32_t))
259 else if (have != sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2)
263 "Received ICMP message of unexpected size: %u bytes\n",
264 (unsigned int) have);
269 memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
270 off += sizeof (ip_pkt);
271 memcpy (&icmp_pkt, &buf[off], sizeof (icmp_pkt));
272 off += sizeof (icmp_pkt);
273 if ( ((ip_pkt.proto != IPPROTO_ICMP) && (ip_pkt.proto != IPPROTO_UDP)) ||
274 (icmp_pkt.type != ICMP_TIME_EXCEEDED) ||
275 (icmp_pkt.code != 0) )
277 /* maybe we got an actual reply back... */
284 memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
285 off += sizeof (ip_pkt);
288 if (ip_pkt.proto == IPPROTO_UDP)
295 memcpy(&port, &buf[sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2], sizeof(uint32_t));
297 DWORD ssize = sizeof(buf);
298 WSAAddressToString((LPSOCKADDR)&sip, sizeof(sip), NULL, buf, &ssize);
299 fprintf (stdout, "%s:%d\n", buf, port);
304 memcpy(&udp_pkt, &buf[off], sizeof(udp_pkt));
305 DWORD ssize = sizeof(buf);
306 WSAAddressToString((LPSOCKADDR)&sip, sizeof(sip), NULL, buf, &ssize);
307 fprintf (stdout, "%s:%d\n", buf, ntohs((int)udp_pkt.length));
311 DWORD ssize = sizeof(buf);
312 WSAAddressToString((LPSOCKADDR)&sip, sizeof(sip), NULL, buf, &ssize);
313 fprintf (stdout, "%s\n", buf);
324 ret = socket (AF_INET, SOCK_RAW, IPPROTO_ICMP);
328 "Error opening RAW socket: %s\n",
332 if (ret == INVALID_SOCKET)
334 fprintf (stderr, "Invalid socket %d!\n", ret);
344 DWORD bOptVal = TRUE;
345 int bOptLen = sizeof(bOptVal);
347 rawsock = socket (AF_INET, SOCK_RAW, IPPROTO_ICMP);
351 "Error opening RAW socket: %s\n",
356 if (setsockopt(rawsock, SOL_SOCKET, SO_BROADCAST, (char*)&bOptVal, bOptLen) != 0)
357 fprintf(stderr, "Error setting SO_BROADCAST: ON\n");
359 if (setsockopt(rawsock, IPPROTO_IP, IP_HDRINCL, (char*)&bOptVal, bOptLen) != 0)
360 fprintf(stderr, "Error setting IP_HDRINCL: ON\n");
366 main (int argc, char *const *argv)
368 struct in_addr external;
374 if (WSAStartup (MAKEWORD (2, 1), &wsaData) != 0)
376 fprintf (stderr, "Failed to find Winsock 2.1 or better.\n");
380 if (-1 == (icmpsock = make_icmp_socket()))
382 if (-1 == (make_raw_socket()))
391 "This program must be started with our (internal NAT) IP as the only argument.\n");
395 if (1 != inet_pton (AF_INET, argv[1], &external))
398 "Error parsing IPv4 address: %s, error %s\n",
399 argv[1], strerror (errno));
403 if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy)) abort ();
407 FD_SET (icmpsock, &rs);
409 tv.tv_usec = ICMP_SEND_FREQUENCY_MS * 1000;
410 select (icmpsock + 1, &rs, NULL, NULL, &tv);
411 if (FD_ISSET (icmpsock, &rs))
412 process_icmp_response ();
413 send_icmp_echo (&external);
416 closesocket(icmpsock);
417 closesocket(rawsock);
423 /* end of gnunet-nat-server-windows.c */