/**
* @file src/transport/gnunet-nat-client-udp.c
- * @brief Test for NAT traversal using ICMP method.
+ * @brief Tool to help bypass NATs using ICMP method; must run as root (SUID will do)
+ * This code will work under GNU/Linux only.
* @author Christian Grothoff
+ *
+ * This program will send ONE ICMP message using RAW sockets
+ * to the IP address specified as the second argument. The ICMP
+ * message will have as it's payload a UDP packet. Since
+ * it uses RAW sockets, it must be installed SUID or run as 'root'.
+ * In order to keep the security risk of the resulting SUID binary
+ * minimal, the program ONLY opens the RAW socket with root
+ * privileges, then drops them and only then starts to process
+ * command line arguments. The code also does not link against
+ * any shared libraries (except libc) and is strictly minimal
+ * (except for checking for errors). The following list of people
+ * have reviewed this code and considered it safe since the last
+ * modification (if you reviewed it, please have your name added
+ * to the list):
+ *
+ * - Christian Grothoff
*/
+#define _GNU_SOURCE
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <errno.h>
#include <stdlib.h>
#include <stdint.h>
+#include <netinet/ip.h>
+#include <netinet/ip_icmp.h>
#include <netinet/in.h>
-#include <time.h>
/**
- * How often do we send our UDP messages to keep ports open (and to
- * try to connect, of course). Use small value since we are the
- * initiator and should hence be rather aggressive.
+ * Must match IP given in the server.
*/
-#define UDP_SEND_FREQUENCY_MS 5
+#define DUMMY_IP "1.2.3.4"
+#define HAVE_PORT 1
/**
* Port we always try to use.
*/
-#define NAT_TRAV_PORT 22223
+#define NAT_TRAV_PORT 22225
-/**
- * Number of UDP ports to keep open at the same time (typically >= 256).
- * Should be less than FD_SETSIZE.
- */
-#define NUM_UDP_PORTS 1000
+struct ip_packet
+{
+ uint8_t vers_ihl;
+ uint8_t tos;
+ uint16_t pkt_len;
+ uint16_t id;
+ uint16_t flags_frag_offset;
+ uint8_t ttl;
+ uint8_t proto;
+ uint16_t checksum;
+ uint32_t src_ip;
+ uint32_t dst_ip;
+};
-/**
- * How often do we retry to open and bind a UDP socket before giving up?
- */
-#define MAX_BIND_TRIES 10
+struct icmp_packet
+{
+ uint8_t type;
+ uint8_t code;
+ uint16_t checksum;
+ uint32_t reserved;
-/**
- * How often do we try at most? We expect to need (for the worst kind
- * of NAT) on average 64512 / 512 = 126 attempts to have the right
- * destination port and we then need to also (in the worst case) have
- * the right source port (so 126 * 64512 = 8128512 packets on
- * average!). That's obviously a bit much, so we give up earlier. The
- * given value corresponds to about 1 minute of runtime (for a send
- * frequency of one packet per ms).
- *
- * NOW: if the *server* would listen for Linux-generated ICMP
- * "Destination unreachables" we *might* increase our chances since
- * maybe the firewall has some older/other UDP rules (this was
- * the case during testing for me), but obviously that would mean
- * more SUID'ed code. Yuck.
- */
-#define MAX_TRIES 62500
+};
-#define LOW_PORT 32768
+struct icmp_echo_packet
+{
+ uint8_t type;
+ uint8_t code;
+ uint16_t checksum;
+ uint32_t reserved;
+ uint32_t data;
+};
+
+struct udp_packet
+{
+ uint16_t src_port;
+
+ uint16_t dst_port;
+
+ uint32_t length;
+};
+
+
+static int rawsock;
+
+static struct in_addr dummy;
+
+static struct in_addr target;
+
+#if HAVE_PORT
+ static uint32_t port;
+#endif
-/**
- * create a random port number that is not totally
- * unlikely to be chosen by the nat box.
- */
static uint16_t
-make_port ()
+calc_checksum(const uint16_t *data,
+ unsigned int bytes)
{
- return LOW_PORT + ( (unsigned int)rand ()) % (64 * 1024 - LOW_PORT);
-}
+ uint32_t sum;
+ unsigned int i;
+ sum = 0;
+ for (i=0;i<bytes/2;i++)
+ sum += data[i];
+ sum = (sum & 0xffff) + (sum >> 16);
+ sum = htons(0xffff - sum);
+ return sum;
+}
/**
- * create a fresh udp socket bound to a random local port,
- * or, if the argument is zero, to the NAT_TRAV_PORT.
+ * Send an ICMP message to the target.
*
- * @param i counter
- * @return -1 on error
+ * @param my_ip source address
+ * @param other target address
*/
-static int
-make_udp_socket (int i)
+static void
+send_icmp (const struct in_addr *my_ip,
+ const struct in_addr *other)
{
- int ret;
- int tries;
- struct sockaddr_in src;
+ struct ip_packet ip_pkt;
+ struct icmp_packet icmp_pkt;
+ struct udp_packet udp_pkt;
+
+ struct sockaddr_in dst;
+ char packet[sizeof(ip_pkt) * 2 + sizeof(icmp_pkt) * 2 + sizeof(char)];
+
+#if ORIGINAL
+#if HAVE_PORT
+ char packet[sizeof (struct ip_packet)*2 + sizeof (struct icmp_packet) + sizeof(struct icmp_echo_packet)];
+#else
+ char packet[sizeof (struct ip_packet)*2 + sizeof (struct icmp_packet)*2];
+#endif
+#endif
+ size_t off;
+ int err;
+
+ /* ip header: send to (known) ip address */
+#if ORIGINAL
+ off = 0;
+ memset(&ip_pkt, 0, sizeof(ip_pkt));
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = sizeof (packet); /* huh? */
+ ip_pkt.id = 1;
+ ip_pkt.flags_frag_offset = 0;
+ ip_pkt.ttl = IPDEFTTL;
+ ip_pkt.proto = IPPROTO_ICMP;
+ ip_pkt.checksum = 0;
+ ip_pkt.src_ip = my_ip->s_addr;
+ ip_pkt.dst_ip = other->s_addr;
+ ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (struct ip_packet)));
+ memcpy (packet, &ip_pkt, sizeof (struct ip_packet));
+ off += sizeof (ip_pkt);
+ /* icmp reply: time exceeded */
+ icmp_pkt = (struct icmp_packet*) &packet[off];
+ memset(icmp_pkt, 0, sizeof(struct icmp_packet));
+ icmp_pkt->type = ICMP_TIME_EXCEEDED;
+ icmp_pkt->code = 0;
+ icmp_pkt->reserved = 0;
+ icmp_pkt->checksum = 0;
+
+ off += sizeof (struct icmp_packet);
+#endif
+
+ off = 0;
+ memset(&ip_pkt, 0, sizeof(ip_pkt));
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = htons(sizeof (packet));
+ ip_pkt.id = htons(256);
+ ip_pkt.flags_frag_offset = 0;
+ ip_pkt.ttl = 128;
+ ip_pkt.proto = IPPROTO_ICMP;
+ ip_pkt.checksum = 0;
+ ip_pkt.src_ip = my_ip->s_addr;
+ ip_pkt.dst_ip = other->s_addr;
+ ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
+ memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
+ off += sizeof(ip_pkt);
+
+ /* ip header of the presumably 'lost' udp packet */
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+#if HAVE_PORT
+ ip_pkt.pkt_len = (sizeof (struct ip_packet) + sizeof (struct icmp_echo_packet));
+#else
+ ip_pkt.pkt_len = (sizeof (struct ip_packet) + sizeof (struct icmp_packet));
+#endif
+
+ icmp_pkt.type = 11; // TTL exceeded
+ icmp_pkt.code = 0;
+ icmp_pkt.checksum = 0;
+ icmp_pkt.reserved = 0;
+ memcpy(&packet[off], &icmp_pkt, sizeof(icmp_pkt));
+ off += sizeof(icmp_pkt);
+
+
+ // build inner IP header
+ memset(&ip_pkt, 0, sizeof(ip_pkt));
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = htons(sizeof (ip_pkt) + sizeof(udp_pkt));
+ ip_pkt.id = htons(0);
+ ip_pkt.flags_frag_offset = 0;
+ ip_pkt.ttl = 128;
+ ip_pkt.proto = IPPROTO_UDP;
+ ip_pkt.checksum = 0;
+ ip_pkt.src_ip = other->s_addr;
+ ip_pkt.dst_ip = dummy.s_addr;
+ ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
+ memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
+ off += sizeof(ip_pkt);
+
+ // build UDP header
+ udp_pkt.src_port = htons(NAT_TRAV_PORT); /* FIXME: does this port matter? */
+ udp_pkt.dst_port = htons(NAT_TRAV_PORT);
+ uint32_t newval = inet_addr("1.2.3.4");
+ memcpy(&udp_pkt.length, &newval, sizeof(uint32_t));
+ memcpy(&packet[off], &udp_pkt, sizeof(udp_pkt));
+ off += sizeof(udp_pkt);
- for (tries=0;tries<MAX_BIND_TRIES;tries++)
+
+
+ // set ICMP checksum
+ icmp_pkt.checksum = htons(calc_checksum((uint16_t*)&packet[sizeof(ip_pkt)],
+ sizeof (icmp_pkt) + sizeof(ip_pkt) + sizeof(udp_pkt)));
+ memcpy (&packet[sizeof(ip_pkt)], &icmp_pkt, sizeof (icmp_pkt));
+
+ /* End of new code */
+#if ORIGINAL
+ ip_pkt.id = 1;
+ ip_pkt.flags_frag_offset = 0;
+ ip_pkt.ttl = 1; /* real TTL would be 1 on a time exceeded packet */
+ ip_pkt.proto = IPPROTO_ICMP;
+ ip_pkt.src_ip = other->s_addr;
+ ip_pkt.dst_ip = dummy.s_addr;
+ ip_pkt.checksum = 0;
+ ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (struct ip_packet)));
+ memcpy (&packet[off], &ip_pkt, sizeof (struct ip_packet));
+ off += sizeof (struct ip_packet);
+
+
+#if HAVE_PORT
+ icmp_pkt->checksum = htons(calc_checksum((uint16_t*)icmp_pkt,
+ sizeof (struct icmp_packet) + sizeof(struct ip_packet) + sizeof(struct icmp_echo_packet)));
+
+#else
+ icmp_pkt->checksum = htons(calc_checksum((uint16_t*)icmp_pkt,
+ sizeof (struct icmp_packet)*2 + sizeof(struct ip_packet)));
+
+#endif
+
+
+#endif
+
+ memset (&dst, 0, sizeof (dst));
+ dst.sin_family = AF_INET;
+ dst.sin_addr = *other;
+ err = sendto(rawsock,
+ packet,
+ off, 0,
+ (struct sockaddr*)&dst,
+ sizeof(dst)); /* or sizeof 'struct sockaddr'? */
+ if (err < 0)
{
- ret = socket (AF_INET, SOCK_DGRAM, IPPROTO_UDP);
- if (-1 == ret)
- {
- fprintf (stderr,
- "Error opening udp socket: %s\n",
- strerror (errno));
- return -1;
- }
- if (ret >= FD_SETSIZE)
- {
- fprintf (stderr,
- "Socket number too large (%d > %u)\n",
- ret,
- (unsigned int) FD_SETSIZE);
- close (ret);
- return -1;
- }
- memset (&src, 0, sizeof (src));
- src.sin_family = AF_INET;
- if (i == 0)
- src.sin_port = htons (NAT_TRAV_PORT);
- else
- src.sin_port = htons (make_port ());
- if (0 != bind (ret, (struct sockaddr*) &src, sizeof (src)))
- {
- close (ret);
- continue;
- }
- return ret;
+ fprintf(stderr,
+ "sendto failed: %s\n", strerror(errno));
+ }
+ else if (err != off)
+ {
+ fprintf(stderr,
+ "Error: partial send of ICMP message\n");
}
- fprintf (stderr,
- "Error binding udp socket: %s\n",
- strerror (errno));
- return -1;
}
+static int
+make_raw_socket ()
+{
+ const int one = 1;
+ int ret;
+
+ ret = socket (AF_INET, SOCK_RAW, IPPROTO_RAW);
+ if (-1 == ret)
+ {
+ fprintf (stderr,
+ "Error opening RAW socket: %s\n",
+ strerror (errno));
+ return -1;
+ }
+ if (setsockopt(ret, SOL_SOCKET, SO_BROADCAST,
+ (char *)&one, sizeof(one)) == -1)
+ fprintf(stderr,
+ "setsockopt failed: %s\n",
+ strerror (errno));
+ if (setsockopt(ret, IPPROTO_IP, IP_HDRINCL,
+ (char *)&one, sizeof(one)) == -1)
+ fprintf(stderr,
+ "setsockopt failed: %s\n",
+ strerror (errno));
+ return ret;
+}
int
main (int argc, char *const *argv)
{
- int udpsocks[NUM_UDP_PORTS];
- char command[512];
struct in_addr external;
- struct in_addr target;
- int ret;
- unsigned int pos;
- int i;
- int max;
- struct sockaddr_in dst;
- struct sockaddr_in src;
- int first_round = 1;
- char dummybuf[65536];
- unsigned int tries;
- struct timeval tv;
- socklen_t slen;
- fd_set rs;
-
+ uid_t uid;
+
+ if (-1 == (rawsock = make_raw_socket()))
+ return 1;
+ uid = getuid ();
+ if (0 != setresuid (uid, uid, uid))
+ fprintf (stderr,
+ "Failed to setresuid: %s\n",
+ strerror (errno));
+#if HAVE_PORT
+ if (argc != 4)
+ {
+ fprintf (stderr,
+ "This program must be started with our IP, the targets external IP, and our port as arguments.\n");
+ return 1;
+ }
+ port = atoi(argv[3]);
+#else
if (argc != 3)
{
fprintf (stderr,
- "This program must be started with our IP and the targets external IP as arguments.\n");
+ "This program must be started with our IP and the targets external IP as arguments.\n");
return 1;
}
+#endif
if ( (1 != inet_pton (AF_INET, argv[1], &external)) ||
(1 != inet_pton (AF_INET, argv[2], &target)) )
{
strerror (errno));
return 1;
}
- snprintf (command,
- sizeof (command),
- "gnunet-nat-client %s %s",
- argv[1],
- argv[2]);
- if (0 != (ret = system (command)))
- {
- if (ret == -1)
- fprintf (stderr,
- "Error running `%s': %s\n",
- command,
- strerror (errno));
- return 1;
- }
- fprintf (stderr,
- "Trying to connect to `%s'\n",
- argv[2]);
- srand (time(NULL));
- for (i=0;i<NUM_UDP_PORTS;i++)
- udpsocks[i] = make_udp_socket (i);
- memset (&dst, 0, sizeof (dst));
- dst.sin_family = AF_INET;
- dst.sin_addr = target;
- pos = 0;
- tries = 0;
- while (MAX_TRIES > tries++)
- {
- FD_ZERO (&rs);
- for (i=0;i<NUM_UDP_PORTS;i++)
- {
- if (udpsocks[i] != -1)
- FD_SET (udpsocks[i], &rs);
- if (udpsocks[i] > max)
- max = udpsocks[i];
- }
- tv.tv_sec = 0;
- tv.tv_usec = UDP_SEND_FREQUENCY_MS * 1000;
- select (max + 1, &rs, NULL, NULL, &tv);
- for (i=0;i<NUM_UDP_PORTS;i++)
- {
- if (udpsocks[i] == -1)
- continue;
- if (! FD_ISSET (udpsocks[i], &rs))
- continue;
- slen = sizeof (src);
- recvfrom (udpsocks[i],
- dummybuf, sizeof (dummybuf), 0,
- (struct sockaddr*) &src,
- &slen);
- if (slen != sizeof (src))
- {
- fprintf (stderr,
- "Unexpected size of address.\n");
- continue;
- }
- if (0 != memcmp (&src.sin_addr,
- &target,
- sizeof (external)))
- {
- fprintf (stderr,
- "Unexpected sender IP\n");
- continue;
- }
- /* discovered port! */
- fprintf (stdout,
- "%s:%u\n",
- argv[2],
- ntohs (src.sin_port));
- dst.sin_port = src.sin_port;
- if (-1 == sendto (udpsocks[i],
- NULL, 0, 0,
- (struct sockaddr*) &dst, sizeof (dst)))
- {
- fprintf (stderr,
- "sendto failed: %s\n",
- strerror (errno));
- return 2; /* oops */
- }
- /* success! */
- fprintf (stderr,
- "Succeeded after %u packets.\n",
- tries);
- return 0;
- }
- if (udpsocks[pos] == -1)
- {
- udpsocks[pos] = make_udp_socket (pos);
- continue;
- }
- if ( (0 == ((unsigned int)rand() % NUM_UDP_PORTS)) ||
- (1 == first_round) )
- dst.sin_port = htons (NAT_TRAV_PORT);
- else
- dst.sin_port = htons (make_port ());
- fprintf (stderr,
- "Sending UDP packet to `%s:%u'\n",
- argv[2],
- ntohs (dst.sin_port));
- first_round = 0;
- if (-1 == sendto (udpsocks[pos],
- NULL, 0, 0,
- (struct sockaddr*) &dst, sizeof (dst)))
- {
- fprintf (stderr,
- "sendto failed: %s\n",
- strerror (errno));
- close (udpsocks[pos]);
- udpsocks[pos] = make_udp_socket (pos);
- }
- pos = (pos+1) % NUM_UDP_PORTS;
- }
- fprintf (stderr,
- "Giving up after %u tries.\n",
- tries);
- return 3;
+ if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy)) abort ();
+ send_icmp (&external,
+ &target);
+ close (rawsock);
+ return 0;
}
-/* end of client-test.c */
+/* end of gnunet-nat-client-udp.c */
#define DUMMY_IP "1.2.3.4"
#define HAVE_PORT 1
+#define NAT_TRAV_PORT 22225
+
struct ip_packet
{
uint8_t vers_ihl;
uint32_t data;
};
-
+struct udp_packet
+{
+ uint16_t src_port;
+
+ uint16_t dst_port;
+
+ uint32_t length;
+};
+
static int rawsock;
static struct in_addr dummy;
}
#endif
+/**
+ * Send an ICMP message to the target.
+ *
+ * @param my_ip source address
+ * @param other target address
+ */
+static void
+send_icmp_udp (const struct in_addr *my_ip,
+ const struct in_addr *other)
+{
+ struct ip_packet ip_pkt;
+ struct icmp_packet icmp_pkt;
+ struct udp_packet udp_pkt;
+
+ struct sockaddr_in dst;
+ char packet[sizeof(ip_pkt) * 2 + sizeof(icmp_pkt) * 2 + sizeof(uint32_t)];
+
+ size_t off;
+ int err;
+
+ /* ip header: send to (known) ip address */
+ off = 0;
+ memset(&ip_pkt, 0, sizeof(ip_pkt));
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = htons(sizeof (packet));
+ ip_pkt.id = htons(256);
+ ip_pkt.flags_frag_offset = 0;
+ ip_pkt.ttl = 128;
+ ip_pkt.proto = IPPROTO_ICMP;
+ ip_pkt.checksum = 0;
+ ip_pkt.src_ip = my_ip->s_addr;
+ ip_pkt.dst_ip = other->s_addr;
+ ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
+ memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
+ off += sizeof(ip_pkt);
+
+ /* ip header of the presumably 'lost' udp packet */
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = (sizeof (struct ip_packet) + sizeof (struct icmp_echo_packet));
+
+ icmp_pkt.type = 11; /* TTL exceeded */
+ icmp_pkt.code = 0;
+ icmp_pkt.checksum = 0;
+ icmp_pkt.reserved = 0;
+ memcpy(&packet[off], &icmp_pkt, sizeof(icmp_pkt));
+ off += sizeof(icmp_pkt);
+
+ /* build inner IP header */
+ memset(&ip_pkt, 0, sizeof(ip_pkt));
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = htons(sizeof (ip_pkt) + sizeof(udp_pkt));
+ ip_pkt.id = htons(0);
+ ip_pkt.flags_frag_offset = 0;
+ ip_pkt.ttl = 128;
+ ip_pkt.proto = IPPROTO_UDP;
+ ip_pkt.checksum = 0;
+ ip_pkt.src_ip = other->s_addr;
+ ip_pkt.dst_ip = dummy.s_addr;
+ ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
+ memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
+ off += sizeof(ip_pkt);
+
+ /* build UDP header */
+ udp_pkt.src_port = htons(NAT_TRAV_PORT); /* FIXME: does this port matter? */
+ udp_pkt.dst_port = htons(NAT_TRAV_PORT);
+
+ memset(&udp_pkt.length, 0, sizeof(uint32_t));
+#if HAVE_PORT
+ udp_pkt.length = htonl(port);
+#endif
+ memcpy(&packet[off], &udp_pkt, sizeof(udp_pkt));
+ off += sizeof(udp_pkt);
+
+ /* set ICMP checksum */
+ icmp_pkt.checksum = htons(calc_checksum((uint16_t*)&packet[sizeof(ip_pkt)],
+ sizeof (icmp_pkt) + sizeof(ip_pkt) + sizeof(udp_pkt)));
+ memcpy (&packet[sizeof(ip_pkt)], &icmp_pkt, sizeof (icmp_pkt));
+
+
+ memset (&dst, 0, sizeof (dst));
+ dst.sin_family = AF_INET;
+ dst.sin_addr = *other;
+ err = sendto(rawsock,
+ packet,
+ off, 0,
+ (struct sockaddr*)&dst,
+ sizeof(dst));
+
+ if (err < 0)
+ {
+ fprintf(stderr,
+ "sendto failed: %s\n", strerror(errno));
+ }
+ else if (err != off)
+ {
+ fprintf(stderr,
+ "Error: partial send of ICMP message\n");
+ }
+}
+
/**
* Send an ICMP message to the target.
if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy)) abort ();
send_icmp (&external,
&target);
+ send_icmp_udp (&external,
+ &target);
close (rawsock);
return 0;
}
/**
* @file src/transport/gnunet-nat-server-udp.c
- * @brief Test for NAT traversal using ICMP method.
+ * @brief This program will send ONE UDP message every 500 ms
+ * to a DUMMY IP address and also listens for ICMP replies.
+ *
* @author Christian Grothoff
*/
#include <sys/types.h>
#include <time.h>
+#define DUMMY_IP "1.2.3.4"
/**
- * How often do we send our UDP messages to keep ports open (and to
- * try to connect, of course). Assuming the NAT closes UDP ports
- * after 60s, we need at least about 100ms here for 512 ports;
- * however, we should open the ports quickly (and we don't yet
- * differentiate between the first round and later rounds), so we pick
- * a much lower value here for now.
+ * How often do we send our UDP message to keep ports open (and to
+ * try to connect, of course).
*/
-#define UDP_SEND_FREQUENCY_MS 50
+#define UDP_SEND_FREQUENCY_MS 500
/**
* Port we always try to use.
#define NAT_TRAV_PORT 22225
/**
- * Number of UDP ports to keep open at the same time (typically >= 256).
- * Should be less than FD_SETSIZE.
+ * Number of UDP ports to send to
*/
-#define NUM_UDP_PORTS 1000
+#define NUM_UDP_PORTS 1
/**
* How often do we retry to open and bind a UDP socket before giving up?
*/
#define MAX_BIND_TRIES 10
-/**
- * How long do we try at most? We expect the other side to give
- * up after about one minute for now.
- */
-#define MAX_DURATION 60000
-
#define LOW_PORT 32768
-/**
- * create a random port number that is not totally
- * unlikely to be chosen by the nat box.
- */
-static uint16_t
-make_port ()
+static struct in_addr dummy;
+
+static int icmpsock;
+
+struct icmp_packet
{
- return LOW_PORT + ( (unsigned int)rand ()) % (64 * 1024 - LOW_PORT - 2);
-}
+ uint8_t type;
+ uint8_t code;
+ uint16_t checksum;
+ uint32_t reserved;
+};
+
+struct udp_packet
+{
+ uint16_t src_port;
+
+ uint16_t dst_port;
+
+ uint32_t length;
+};
+
+struct ip_packet
+{
+ uint8_t vers_ihl;
+ uint8_t tos;
+ uint16_t pkt_len;
+ uint16_t id;
+ uint16_t flags_frag_offset;
+ uint8_t ttl;
+ uint8_t proto;
+ uint16_t checksum;
+ uint32_t src_ip;
+ uint32_t dst_ip;
+};
+
+#if DUMMY
+static uint16_t
+calc_checksum(const uint16_t *data,
+ unsigned int bytes)
+{
+ uint32_t sum;
+ unsigned int i;
+
+ sum = 0;
+ for (i=0;i<bytes/2;i++)
+ sum += data[i];
+ sum = (sum & 0xffff) + (sum >> 16);
+ sum = htons(0xffff - sum);
+ return sum;
+}
+#endif
/**
- * create a fresh udp socket bound to a random local port,
- * or, if the argument is zero, to the NAT_TRAV_PORT.
+ * create a fresh udp socket bound to the NAT_TRAV_PORT.
*
- * @param i counter
* @return -1 on error
*/
static int
-make_udp_socket (int i)
+make_udp_socket ()
{
int ret;
int tries;
struct sockaddr_in src;
- for (tries=0;tries<MAX_BIND_TRIES;tries++)
+ for (tries=0; tries<MAX_BIND_TRIES; tries++)
{
ret = socket (AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (-1 == ret)
}
memset (&src, 0, sizeof (src));
src.sin_family = AF_INET;
- if (i == 0)
- src.sin_port = htons (NAT_TRAV_PORT);
- else
- src.sin_port = htons (make_port ());
+ src.sin_port = htons (NAT_TRAV_PORT);
+
if (0 != bind (ret, (struct sockaddr*) &src, sizeof (src)))
{
close (ret);
return -1;
}
+#define LOW_PORT 32768
+
+/**
+ * create a random port number that is not totally
+ * unlikely to be chosen by the nat box.
+ */
+static uint16_t
+make_port ()
+{
+ return LOW_PORT + ( (unsigned int)rand ()) % (64 * 1024 - LOW_PORT - 2);
+}
+
+static int
+make_icmp_socket ()
+{
+ int ret;
+
+ ret = socket (AF_INET, SOCK_RAW, IPPROTO_ICMP);
+ if (-1 == ret)
+ {
+ fprintf (stderr,
+ "Error opening RAW socket: %s\n",
+ strerror (errno));
+ return -1;
+ }
+ if (ret >= FD_SETSIZE)
+ {
+ fprintf (stderr,
+ "Socket number too large (%d > %u)\n",
+ ret,
+ (unsigned int) FD_SETSIZE);
+ close (ret);
+ return -1;
+ }
+ return ret;
+}
+
+#if DUMMY
+/**
+ * Send a UDP message to the dummy IP.
+ *
+ * @param my_ip source address (our ip address)
+ */
+static void
+send_dummy_udp (const struct in_addr *my_ip)
+{
+ struct sockaddr_in dst;
+ size_t off;
+ int err;
+ struct ip_packet ip_pkt;
+ struct ip_packet udp_pkt;
+ char packet[sizeof (ip_pkt) + sizeof (udp_pkt)];
+
+
+ // build inner IP header
+ memset(&ip_pkt, 0, sizeof(ip_pkt));
+ ip_pkt.vers_ihl = 0x45;
+ ip_pkt.tos = 0;
+ ip_pkt.pkt_len = htons(sizeof (ip_pkt) + sizeof(udp_pkt));
+ ip_pkt.id = htons(0);
+ ip_pkt.flags_frag_offset = 0;
+ ip_pkt.ttl = 128;
+ ip_pkt.proto = IPPROTO_UDP;
+ ip_pkt.checksum = 0;
+ ip_pkt.src_ip = my_ip->s_addr;
+ ip_pkt.dst_ip = inet_addr(dummy.s_addr);
+ ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
+ memcpy(&packet[off], &ip_pkt, sizeof(ip_pkt));
+ off += sizeof(ip_pkt);
+
+ // build UDP header
+ udp_pkt.src_port = NAT_TRAV_PORT;
+ udp_pkt.dst_port = htons(NAT_TRAV_PORT);
+
+ uint32_t newval = inet_addr("1.2.3.4");
+ memcpy(&udp_pkt.length, &newval, sizeof(uint32_t));
+
+ off += sizeof(udp_pkt);
+
+ err = sendto(rawsock,
+ ip_pkt, off, 0,
+ (struct sockaddr*)&dst,
+ sizeof(dst));
+ if (err < 0)
+ {
+#if VERBOSE
+ fprintf(stderr,
+ "sendto failed: %s\n", strerror(errno));
+#endif
+ }
+ else if (err != off)
+ {
+ fprintf(stderr,
+ "Error: partial send of UDP message\n");
+ }
+}
+#endif
+
+static void
+process_icmp_response()
+{
+ char buf[65536];
+ ssize_t have;
+ struct in_addr sip;
+ struct ip_packet ip_pkt;
+ struct icmp_packet icmp_pkt;
+ size_t off;
+ int have_port;
+ //uint32_t port;
+
+ have = read (icmpsock, buf, sizeof (buf));
+ if (have == -1)
+ {
+ fprintf (stderr,
+ "Error reading raw socket: %s\n",
+ strerror (errno));
+ return;
+ }
+
+ off = 0;
+ memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
+ off += sizeof (ip_pkt);
+ memcpy (&icmp_pkt, &buf[off], sizeof (icmp_pkt));
+ off += sizeof (icmp_pkt);
+ if ( (ip_pkt.proto != IPPROTO_ICMP) ||
+ (icmp_pkt.type != 11) ||
+ (icmp_pkt.code != 0) )
+ {
+ /* maybe we got an actual reply back... */
+ return;
+ }
+
+ memcpy(&sip,
+ &ip_pkt.src_ip,
+ sizeof (sip));
+
+ fprintf (stderr,
+ "Received ICMP message of size: %u bytes from %s\n",
+ (unsigned int) have,
+ inet_ntop (AF_INET,
+ &sip,
+ buf,
+ sizeof (buf)));
+
+ have_port = 0;
+ if (have == sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2 + sizeof(uint32_t))
+ {
+ have_port = 1;
+ }
+ else if (have != sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2)
+ {
+#if VERBOSE
+ fprintf (stderr,
+ "Received ICMP message of unexpected size: %u bytes\n",
+ (unsigned int) have);
+#endif
+ return;
+ }
+}
int
main (int argc, char *const *argv)
{
int udpsocks[NUM_UDP_PORTS];
- char command[512];
struct in_addr external;
- struct in_addr target;
- int ret;
unsigned int pos;
int i;
- int max;
struct sockaddr_in dst;
- struct sockaddr_in src;
int first_round = 1;
- char dummybuf[65536];
unsigned int tries;
struct timeval tv;
- socklen_t slen;
fd_set rs;
time_t stime;
- if (argc != 3)
+ if (argc != 2)
{
fprintf (stderr,
- "This program must be started with our IP and the targets external IP as arguments.\n");
+ "This program must be started with our (internal) IP as the single argument.\n");
return 1;
}
- if ( (1 != inet_pton (AF_INET, argv[1], &external)) ||
- (1 != inet_pton (AF_INET, argv[2], &target)) )
+ if ( (1 != inet_pton (AF_INET, argv[1], &external)))
{
fprintf (stderr,
"Error parsing IPv4 address: %s\n",
strerror (errno));
return 1;
}
+
+ if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy)) abort ();
+
fprintf (stderr,
"Trying to connect to %s\n",
- argv[2]);
+ DUMMY_IP);
srand (stime = time(NULL));
for (i=0;i<NUM_UDP_PORTS;i++)
udpsocks[i] = make_udp_socket (i);
+
+ if (-1 == (icmpsock = make_icmp_socket()))
+ return 1;
+
memset (&dst, 0, sizeof (dst));
dst.sin_family = AF_INET;
- dst.sin_addr = target;
+ dst.sin_addr = dummy;
pos = 0;
tries = 0;
- while (stime + MAX_DURATION >= time (NULL))
+
+ while (1)
{
tries++;
+
FD_ZERO (&rs);
- for (i=0;i<NUM_UDP_PORTS;i++)
- {
- if (udpsocks[i] != -1)
- FD_SET (udpsocks[i], &rs);
- if (udpsocks[i] > max)
- max = udpsocks[i];
- }
+ FD_SET (icmpsock, &rs);
tv.tv_sec = 0;
tv.tv_usec = UDP_SEND_FREQUENCY_MS * 1000;
- select (max + 1, &rs, NULL, NULL, &tv);
- for (i=0;i<NUM_UDP_PORTS;i++)
- {
- if (udpsocks[i] == -1)
- continue;
- if (! FD_ISSET (udpsocks[i], &rs))
- continue;
- slen = sizeof (src);
- recvfrom (udpsocks[i],
- dummybuf, sizeof (dummybuf), 0,
- (struct sockaddr*) &src,
- &slen);
- if (slen != sizeof (src))
- {
- fprintf (stderr,
- "Unexpected size of address.\n");
- continue;
- }
- if (0 != memcmp (&src.sin_addr,
- &target,
- sizeof (external)))
- {
- fprintf (stderr,
- "Unexpected sender IP\n");
- continue;
- }
- /* discovered port! */
- fprintf (stdout,
- "%s:%u\n",
- argv[2],
- ntohs (src.sin_port));
- dst.sin_port = src.sin_port;
- if (-1 == sendto (udpsocks[i],
- NULL, 0, 0,
- (struct sockaddr*) &dst, sizeof (dst)))
- {
- fprintf (stderr,
- "sendto failed: %s\n",
- strerror (errno));
- return 2; /* oops */
- }
- /* success! */
- fprintf (stderr,
- "Succeeded after %u packets.\n",
- tries);
- return 0;
- }
+ select (icmpsock + 1, &rs, NULL, NULL, &tv);
+ if (FD_ISSET (icmpsock, &rs))
+ process_icmp_response ();
+
if (udpsocks[pos] == -1)
{
udpsocks[pos] = make_udp_socket (pos);
dst.sin_port = htons (NAT_TRAV_PORT);
else
dst.sin_port = htons (make_port ());
+#if VERBOSE
fprintf (stderr,
"Sending UDP packet to `%s:%u'\n",
- argv[2],
+ DUMMY_IP,
ntohs (dst.sin_port));
+
+#endif
first_round = 0;
if (-1 == sendto (udpsocks[pos],
NULL, 0, 0,
return 3;
}
-/* end of server-test.c */
+/* end of gnunet-nat-server-udp.c */
projects / oweals / gnunet.git / commitdiff