2 This file is part of GNUnet.
3 (C) 2010 Christian Grothoff (and other contributing authors)
5 GNUnet is free software; you can redistribute it and/or modify
6 it under the terms of the GNU General Public License as published
7 by the Free Software Foundation; either version 3, or (at your
8 option) any later version.
10 GNUnet is distributed in the hope that it will be useful, but
11 WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 General Public License for more details.
15 You should have received a copy of the GNU General Public License
16 along with GNUnet; see the file COPYING. If not, write to the
17 Free Software Foundation, Inc., 59 Temple Place - Suite 330,
18 Boston, MA 02111-1307, USA.
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>
58 * Should we print some debug output?
66 #define ICMP_TIME_EXCEEDED 11 /* Time Exceeded
69 * Must match IP given in the client.
71 #define DUMMY_IP "192.0.2.86"
74 * How often do we send our ICMP messages to receive replies?
76 #define ICMP_SEND_FREQUENCY_MS 500
85 * Version (4 bits) + Internet header length (4 bits)
105 * Flags (3 bits) + Fragment offset (13 bits)
107 u_short flags_frag_offset;
130 * Destination address
136 * Format of ICMP packet.
147 * Beginning of UDP packet.
158 static SOCKET icmpsock;
160 static SOCKET rawsock;
162 static struct in_addr dummy;
165 * CRC-16 for IP/ICMP headers.
168 calc_checksum(const uint16_t *data,
175 for (i=0;i<bytes/2;i++)
177 sum = (sum & 0xffff) + (sum >> 16);
178 sum = htons(0xffff - sum);
183 * Convert IPv4 address from text to binary form.
185 * @param af address family
186 * @param cp the address to print
187 * @param buf where to write the address result
194 buf->s_addr = inet_addr(cp);
195 if (buf->s_addr == INADDR_NONE)
198 "Error %d handling address %s",
208 * Send an ICMP message to the dummy IP.
210 * @param my_ip source address (our ip address)
213 send_icmp_echo (const struct in_addr *my_ip)
215 struct icmp_packet icmp_echo;
216 struct sockaddr_in dst;
219 struct ip_packet ip_pkt;
220 struct icmp_packet icmp_pkt;
221 char packet[sizeof (ip_pkt) + sizeof (icmp_pkt)];
224 memset(&ip_pkt, 0, sizeof(ip_pkt));
225 ip_pkt.vers_ihl = 0x45;
227 ip_pkt.pkt_len = sizeof (packet);
228 ip_pkt.id = htons (256);
229 ip_pkt.flags_frag_offset = 0;
230 ip_pkt.ttl = IPDEFTTL;
231 ip_pkt.proto = IPPROTO_ICMP;
233 ip_pkt.src_ip = my_ip->s_addr;
234 ip_pkt.dst_ip = dummy.s_addr;
235 ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
236 memcpy (packet, &ip_pkt, sizeof (ip_pkt));
237 off += sizeof (ip_pkt);
239 icmp_echo.type = ICMP_ECHO;
241 icmp_echo.reserved = 0;
242 icmp_echo.checksum = 0;
243 icmp_echo.checksum = htons(calc_checksum((uint16_t*) &icmp_echo,
244 sizeof (struct icmp_packet)));
245 memcpy (&packet[off], &icmp_echo, sizeof (icmp_echo));
246 off += sizeof (icmp_echo);
248 memset (&dst, 0, sizeof (dst));
249 dst.sin_family = AF_INET;
250 dst.sin_addr = dummy;
251 err = sendto(rawsock,
253 (struct sockaddr*)&dst,
259 "sendto failed: %s\n", strerror(errno));
265 "Error: partial send of ICMP message\n");
271 process_icmp_response ()
276 struct ip_packet ip_pkt;
277 struct icmp_packet icmp_pkt;
278 struct udp_packet udp_pkt;
284 have = read (icmpsock, buf, sizeof (buf));
288 "Error reading raw socket: %s\n",
295 "Received message of %u bytes\n",
296 (unsigned int) have);
298 if (have == sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2 + sizeof(uint32_t))
302 else if (have != sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2)
306 "Received ICMP message of unexpected size: %u bytes\n",
307 (unsigned int) have);
312 memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
313 off += sizeof (ip_pkt);
314 memcpy (&icmp_pkt, &buf[off], sizeof (icmp_pkt));
315 off += sizeof (icmp_pkt);
316 if ( ((ip_pkt.proto != IPPROTO_ICMP) && (ip_pkt.proto != IPPROTO_UDP)) ||
317 (icmp_pkt.type != ICMP_TIME_EXCEEDED) ||
318 (icmp_pkt.code != 0) )
320 /* maybe we got an actual reply back... */
326 memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
327 off += sizeof (ip_pkt);
328 have_udp = (ip_pkt.proto == IPPROTO_UDP);
333 &buf[sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2],
336 DWORD ssize = sizeof(buf);
337 WSAAddressToString((LPSOCKADDR)&sip,
352 DWORD ssize = sizeof(buf);
353 WSAAddressToString((LPSOCKADDR)&sip,
361 ntohs((int)udp_pkt.length));
365 DWORD ssize = sizeof(buf);
366 WSAAddressToString((LPSOCKADDR)&sip,
384 ret = socket (AF_INET, SOCK_RAW, IPPROTO_ICMP);
385 if (INVALID_SOCKET == ret)
388 "Error opening RAW socket: %s\n",
399 DWORD bOptVal = TRUE;
400 int bOptLen = sizeof(bOptVal);
402 rawsock = socket (AF_INET, SOCK_RAW, IPPROTO_ICMP);
403 if (INVALID_SOCKET == rawsock)
406 "Error opening RAW socket: %s\n",
408 return INVALID_SOCKET;
411 if (setsockopt(rawsock,
414 (char*)&bOptVal, bOptLen) != 0)
417 "Error setting SO_BROADCAST to ON: %s\n",
419 closesocket(rawsock);
420 return INVALID_SOCKET;
422 if (setsockopt(rawsock,
425 (char*)&bOptVal, bOptLen) != 0)
428 "Error setting IP_HDRINCL to ON: %s\n",
430 closesocket(rawsock);
431 return INVALID_SOCKET;
441 struct in_addr external;
449 "This program must be started with our (internal NAT) IP as the only argument.\n");
452 if (1 != inet_pton (AF_INET, argv[1], &external))
455 "Error parsing IPv4 address: %s, error %s\n",
456 argv[1], strerror (errno));
459 if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy))
462 "Internal error converting dummy IP to binary.\n");
465 if (WSAStartup (MAKEWORD (2, 1), &wsaData) != 0)
467 fprintf (stderr, "Failed to find Winsock 2.1 or better.\n");
470 if (-1 == (icmpsock = make_icmp_socket()))
474 if (-1 == (make_raw_socket()))
476 closesocket (icmpsock);
482 FD_SET (icmpsock, &rs);
484 tv.tv_usec = ICMP_SEND_FREQUENCY_MS * 1000;
485 if (0 != select (icmpsock + 1, &rs, NULL, NULL, &tv))
490 "select failed: %s\n",
494 if (FD_ISSET (icmpsock, &rs))
495 process_icmp_response ();
496 send_icmp_echo (&external);
498 closesocket(icmpsock);
499 closesocket(rawsock);
501 return 4; /* select failed! */
505 /* end of gnunet-nat-server-windows.c */