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 */
76 * Must match IP given in the client.
78 #define DUMMY_IP "192.0.2.86"
83 * How often do we send our ICMP messages to receive replies?
85 #define ICMP_SEND_FREQUENCY_MS 500
93 uint16_t flags_frag_offset;
100 u_char vers_ihl; // Version (4 bits) + Internet header length (4 bits)
101 u_char tos; // Type of service
102 u_short pkt_len; // Total length
103 u_short id; // Identification
104 u_short flags_frag_offset; // Flags (3 bits) + Fragment offset (13 bits)
105 u_char ttl; // Time to live
106 u_char proto; // Protocol
107 u_short checksum; // Header checksum
108 u_long src_ip; // Source address
109 u_long dst_ip; // Destination address
129 static Socket icmpsock;
131 static Socket rawsock;
133 static struct in_addr dummy;
136 calc_checksum(const uint16_t *data,
143 for (i=0;i<bytes/2;i++)
145 sum = (sum & 0xffff) + (sum >> 16);
146 sum = htons(0xffff - sum);
152 * @param af address family
153 * @param cp the address to print
154 * @param buf where to write the address result
156 static int inet_pton (int af, char *cp, struct in_addr *buf)
158 //ret = WSAStringToAddress (cp, af, NULL, (LPSOCKADDR)buf, &ssize);
159 buf->s_addr = inet_addr(cp);
160 if (buf->s_addr == INADDR_NONE)
162 fprintf(stderr, "Error %d handling address %s", WSAGetLastError(), cp);
171 make_echo (const struct in_addr *src_ip,
172 struct icmp_packet *echo)
174 memset(echo, 0, sizeof(struct icmp_packet));
175 echo->type = ICMP_ECHO;
179 echo->checksum = htons(calc_checksum((uint16_t*)echo, sizeof (struct icmp_packet)));
184 * Send an ICMP message to the dummy IP.
186 * @param my_ip source address (our ip address)
189 send_icmp_echo (const struct in_addr *my_ip)
191 struct icmp_packet icmp_echo;
192 struct sockaddr_in dst;
195 struct ip_packet ip_pkt;
196 struct icmp_packet icmp_pkt;
197 char packet[sizeof (ip_pkt) + sizeof (icmp_pkt)];
200 memset(&ip_pkt, 0, sizeof(ip_pkt));
201 ip_pkt.vers_ihl = 0x45;
203 ip_pkt.pkt_len = sizeof (packet);
204 ip_pkt.id = htons (256);
205 ip_pkt.flags_frag_offset = 0;
206 ip_pkt.ttl = IPDEFTTL;
207 ip_pkt.proto = IPPROTO_ICMP;
209 ip_pkt.src_ip = my_ip->s_addr;
210 ip_pkt.dst_ip = dummy.s_addr;
211 ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
212 memcpy (packet, &ip_pkt, sizeof (ip_pkt));
213 off += sizeof (ip_pkt);
215 make_echo (my_ip, &icmp_echo);
216 memcpy (&packet[off], &icmp_echo, sizeof (icmp_echo));
217 off += sizeof (icmp_echo);
219 memset (&dst, 0, sizeof (dst));
220 dst.sin_family = AF_INET;
221 dst.sin_addr = dummy;
222 err = sendto(rawsock,
224 (struct sockaddr*)&dst,
230 "sendto failed: %s\n", strerror(errno));
236 "Error: partial send of ICMP message\n");
242 process_icmp_response ()
247 struct ip_packet ip_pkt;
248 struct icmp_packet icmp_pkt;
249 struct udp_packet udp_pkt;
254 have = read (icmpsock, buf, sizeof (buf));
258 "Error reading raw socket: %s\n",
265 "Received message of %u bytes\n",
266 (unsigned int) have);
268 if (have == sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2 + sizeof(uint32_t))
272 else if (have != sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2)
276 "Received ICMP message of unexpected size: %u bytes\n",
277 (unsigned int) have);
282 memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
283 off += sizeof (ip_pkt);
284 memcpy (&icmp_pkt, &buf[off], sizeof (icmp_pkt));
285 off += sizeof (icmp_pkt);
286 if ( ((ip_pkt.proto != IPPROTO_ICMP) && (ip_pkt.proto != IPPROTO_UDP)) ||
287 (icmp_pkt.type != ICMP_TIME_EXCEEDED) ||
288 (icmp_pkt.code != 0) )
290 /* maybe we got an actual reply back... */
297 memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
298 off += sizeof (ip_pkt);
301 if (ip_pkt.proto == IPPROTO_UDP)
308 memcpy(&port, &buf[sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2], sizeof(uint32_t));
311 DWORD ssize = sizeof(buf);
312 WSAAddressToString((LPSOCKADDR)&sip, sizeof(sip), NULL, buf, &ssize);
313 fprintf (stdout, "%s:%d\n", buf, port);
320 sizeof (buf)), port);
325 memcpy(&udp_pkt, &buf[off], sizeof(udp_pkt));
327 DWORD ssize = sizeof(buf);
328 WSAAddressToString((LPSOCKADDR)&sip, sizeof(sip), NULL, buf, &ssize);
329 fprintf (stdout, "%s:%d\n", buf, ntohs((int)udp_pkt.length));
336 sizeof (buf)), ntohl(udp_pkt.length));
342 DWORD ssize = sizeof(buf);
343 WSAAddressToString((LPSOCKADDR)&sip, sizeof(sip), NULL, buf, &ssize);
344 fprintf (stdout, "%s\n", buf);
363 ret = socket (AF_INET, SOCK_RAW, IPPROTO_ICMP);
367 "Error opening RAW socket: %s\n",
371 if (ret == INVALID_SOCKET)
373 fprintf (stderr, "Invalid socket %d!\n", ret);
385 DWORD bOptVal = TRUE;
386 int bOptLen = sizeof(bOptVal);
388 rawsock = socket (AF_INET, SOCK_RAW, IPPROTO_ICMP);
392 "Error opening RAW socket: %s\n",
396 if (setsockopt(rawsock, SOL_SOCKET, SO_BROADCAST, (char*)&bOptVal, bOptLen) == 0)
398 fprintf(stderr, "Set SO_BROADCAST: ON\n");
402 fprintf(stderr, "Error setting SO_BROADCAST: ON\n");
404 if (setsockopt(rawsock, IPPROTO_IP, IP_HDRINCL, (char*)&bOptVal, bOptLen) == 0)
406 fprintf(stderr, "Set IP_HDRINCL: ON\n");
410 fprintf(stderr, "Error setting IP_HDRINCL: ON\n");
417 main (int argc, char *const *argv)
419 struct in_addr external;
429 if (WSAStartup (MAKEWORD (2, 2), &wsaData) != 0)
431 fprintf (stderr, "Failed to find Winsock 2.1 or better.\n");
436 if (-1 == (icmpsock = make_icmp_socket()))
438 if (-1 == (make_raw_socket()))
445 if (0 != setresuid (uid, uid, uid))
447 "Failed to setresuid: %s\n",
453 "This program must be started with our (internal NAT) IP as the only argument.\n");
457 if (1 != inet_pton (AF_INET, argv[1], &external))
460 "Error parsing IPv4 address: %s, error %s\n",
461 argv[1], strerror (errno));
465 if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy)) abort ();
469 FD_SET (icmpsock, &rs);
471 tv.tv_usec = ICMP_SEND_FREQUENCY_MS * 1000;
472 select (icmpsock + 1, &rs, NULL, NULL, &tv);
473 if (FD_ISSET (icmpsock, &rs))
474 process_icmp_response ();
475 send_icmp_echo (&external);
479 closesocket(icmpsock);
480 closesocket(rawsock);
487 /* end of gnunet-nat-server-windows.c */