*
* - Christian Grothoff
* - Nathan Evans
+ * - Benjamin Kuperman (22 Aug 2010)
*/
#if HAVE_CONFIG_H
/* Just needed for HAVE_SOCKADDR_IN_SIN_LEN test macro! */
#else
#define _GNU_SOURCE
#endif
-#include <sys/types.h>
+#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <sys/select.h>
#include <time.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
-#include <netinet/in.h>
+#include <netinet/in.h>
/**
* Should we print some debug output?
*/
#define DUMMY_IP "192.0.2.86"
+/**
+ * Port for UDP
+ */
+#define NAT_TRAV_PORT 22225
+
/**
* How often do we send our ICMP messages to receive replies?
*/
/**
* IPv4 header.
*/
-struct ip_packet
+struct ip_header
{
/**
- * Version (4 bits) + Internet header length (4 bits)
+ * Version (4 bits) + Internet header length (4 bits)
*/
uint8_t vers_ihl;
uint8_t ttl;
/**
- * Protocol
+ * Protocol
*/
uint8_t proto;
-
+
/**
* Header checksum
*/
uint32_t src_ip;
/**
- * Destination address
+ * Destination address
*/
uint32_t dst_ip;
};
/**
* Format of ICMP packet.
*/
-struct icmp_packet
+struct icmp_ttl_exceeded_header
+{
+ uint8_t type;
+
+ uint8_t code;
+
+ uint16_t checksum;
+
+ uint32_t unused;
+
+ /* followed by original payload */
+};
+
+struct icmp_echo_header
{
uint8_t type;
uint32_t reserved;
};
+
/**
* Beginning of UDP packet.
*/
-struct udp_packet
+struct udp_header
{
uint16_t src_port;
uint16_t dst_port;
- uint32_t length;
+ uint16_t length;
+
+ uint16_t crc;
};
/**
*/
static int rawsock;
+/**
+ * Socket we use to send our UDP requests.
+ */
+static int udpsock;
+
/**
* Target "dummy" address.
*/
* @param bytes number of bytes in data (must be multiple of 2)
* @return the CRC 16.
*/
-static uint16_t
-calc_checksum(const uint16_t *data,
+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];
+ for (i=0;i<bytes/2;i++)
+ sum += data[i];
sum = (sum & 0xffff) + (sum >> 16);
sum = htons(0xffff - sum);
return sum;
static void
send_icmp_echo (const struct in_addr *my_ip)
{
- struct icmp_packet icmp_echo;
+ char packet[sizeof (struct ip_header) + sizeof (struct icmp_echo_header)];
+ struct icmp_echo_header icmp_echo;
+ struct ip_header ip_pkt;
struct sockaddr_in dst;
size_t off;
int err;
- struct ip_packet ip_pkt;
- struct icmp_packet icmp_pkt;
- char packet[sizeof (ip_pkt) + sizeof (icmp_pkt)];
off = 0;
- memset(&ip_pkt, 0, sizeof(ip_pkt));
ip_pkt.vers_ihl = 0x45;
ip_pkt.tos = 0;
- ip_pkt.pkt_len = sizeof (packet);
- ip_pkt.id = 1;
+ ip_pkt.pkt_len = htons (sizeof (packet));
+ ip_pkt.id = htons (256);
ip_pkt.flags_frag_offset = 0;
ip_pkt.ttl = IPDEFTTL;
ip_pkt.proto = IPPROTO_ICMP;
- ip_pkt.checksum = 0;
+ ip_pkt.checksum = 0;
ip_pkt.src_ip = my_ip->s_addr;
ip_pkt.dst_ip = dummy.s_addr;
- ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
- memcpy (packet, &ip_pkt, sizeof (ip_pkt));
- off += sizeof (ip_pkt);
+ ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt,
+ sizeof (struct ip_header)));
+ memcpy (&packet[off],
+ &ip_pkt,
+ sizeof (struct ip_header));
+ off += sizeof (struct ip_header);
icmp_echo.type = ICMP_ECHO;
icmp_echo.code = 0;
- icmp_echo.reserved = 0;
icmp_echo.checksum = 0;
- icmp_echo.checksum = htons(calc_checksum((uint16_t*)&icmp_echo,
- sizeof (struct icmp_packet)));
- memcpy (&packet[off], &icmp_echo, sizeof (icmp_echo));
- off += sizeof (icmp_echo);
-
+ icmp_echo.reserved = 0;
+ icmp_echo.checksum = htons(calc_checksum((uint16_t*)&icmp_echo,
+ sizeof (struct icmp_echo_header)));
+ memcpy (&packet[off],
+ &icmp_echo,
+ sizeof (struct icmp_echo_header));
+ off += sizeof (struct icmp_echo_header);
+
+ memset (&dst, 0, sizeof (dst));
+ dst.sin_family = AF_INET;
+#if HAVE_SOCKADDR_IN_SIN_LEN
+ dst.sin_len = sizeof (struct sockaddr_in);
+#endif
+ dst.sin_addr = dummy;
+ err = sendto(rawsock,
+ packet, off, 0,
+ (struct sockaddr*)&dst,
+ sizeof(dst));
+ if (err < 0)
+ {
+#if VERBOSE
+ fprintf(stderr,
+ "sendto failed: %s\n", strerror(errno));
+#endif
+ }
+ else if (sizeof (packet) != err)
+ {
+ fprintf(stderr,
+ "Error: partial send of ICMP message\n");
+ }
+}
+
+
+/**
+ * Send a UDP message to the dummy IP.
+ */
+static void
+send_udp ()
+{
+ struct sockaddr_in dst;
+ ssize_t err;
+
memset (&dst, 0, sizeof (dst));
dst.sin_family = AF_INET;
#if HAVE_SOCKADDR_IN_SIN_LEN
dst.sin_len = sizeof (struct sockaddr_in);
#endif
dst.sin_addr = dummy;
- err = sendto(rawsock,
- packet, off, 0,
- (struct sockaddr*)&dst,
+ dst.sin_port = htons (NAT_TRAV_PORT);
+ err = sendto(udpsock,
+ NULL, 0, 0,
+ (struct sockaddr*)&dst,
sizeof(dst));
- if (err < 0)
+ if (err < 0)
{
#if VERBOSE
fprintf(stderr,
"sendto failed: %s\n", strerror(errno));
#endif
}
- else if (err != off)
+ else if (0 != err)
{
fprintf(stderr,
"Error: partial send of ICMP message\n");
{
char buf[65536];
ssize_t have;
- struct in_addr sip;
- struct ip_packet ip_pkt;
- struct icmp_packet icmp_pkt;
- struct udp_packet udp_pkt;
+ struct in_addr source_ip;
+ struct ip_header ip_pkt;
+ struct icmp_ttl_exceeded_header icmp_ttl;
+ struct icmp_echo_header icmp_echo;
+ struct udp_header udp_pkt;
size_t off;
- int have_port;
- uint32_t port;
-
+ uint16_t port;
+
have = read (icmpsock, buf, sizeof (buf));
- if (have == -1)
+ if (-1 == have)
{
fprintf (stderr,
"Error reading raw socket: %s\n",
strerror (errno));
- return;
+ return;
}
- have_port = 0;
#if VERBOSE
fprintf (stderr,
"Received message of %u bytes\n",
(unsigned int) have);
#endif
- 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 (have < (ssize_t) (sizeof (struct ip_header) + sizeof (struct icmp_ttl_exceeded_header) + sizeof (struct ip_header)))
{
-#if VERBOSE
- fprintf (stderr,
- "Received ICMP message of unexpected size: %u bytes\n",
- (unsigned int) have);
-#endif
+ /* malformed */
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) && (ip_pkt.proto != IPPROTO_UDP)) ||
- (icmp_pkt.type != ICMP_TIME_EXCEEDED) ||
- (icmp_pkt.code != 0) )
+ memcpy (&ip_pkt,
+ &buf[off],
+ sizeof (struct ip_header));
+ off += sizeof (struct ip_header);
+ memcpy(&source_ip,
+ &ip_pkt.src_ip,
+ sizeof (source_ip));
+ memcpy (&icmp_ttl,
+ &buf[off],
+ sizeof (struct icmp_ttl_exceeded_header));
+ off += sizeof (struct icmp_ttl_exceeded_header);
+ if ( (ICMP_TIME_EXCEEDED != icmp_ttl.type) ||
+ (0 != icmp_ttl.code) )
{
- /* maybe we got an actual reply back... */
- return;
+ /* different type than what we want */
+ return;
}
- memcpy(&sip,
- &ip_pkt.src_ip,
- sizeof (sip));
- memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
- off += sizeof (ip_pkt);
+ /* skip 2nd IP header */
+ memcpy (&ip_pkt,
+ &buf[off],
+ sizeof (struct ip_header));
+ off += sizeof (struct ip_header);
- if (have_port)
+ switch (ip_pkt.proto)
{
- memcpy(&port,
- &buf[sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2],
- sizeof(uint32_t));
- port = ntohs(port);
- fprintf (stdout,
- "%s:%d\n",
- inet_ntop (AF_INET,
- &sip,
- buf,
- sizeof (buf)),
- port);
- }
- else if (ip_pkt.proto == IPPROTO_UDP)
- {
- memcpy(&udp_pkt,
- &buf[off],
- sizeof(udp_pkt));
- fprintf (stdout,
- "%s:%d\n",
- inet_ntop (AF_INET,
- &sip,
- buf,
- sizeof (buf)),
- ntohs((uint16_t) udp_pkt.length));
+ case IPPROTO_ICMP:
+ if (have != (sizeof (struct ip_header) * 2 +
+ sizeof (struct icmp_ttl_exceeded_header) +
+ sizeof (struct icmp_echo_header)) )
+ {
+ /* malformed */
+ return;
+ }
+ /* grab ICMP ECHO content */
+ memcpy (&icmp_echo,
+ &buf[off],
+ sizeof (struct icmp_echo_header));
+ port = (uint16_t) ntohl (icmp_echo.reserved);
+ break;
+ case IPPROTO_UDP:
+ if (have != (sizeof (struct ip_header) * 2 +
+ sizeof (struct icmp_ttl_exceeded_header) +
+ sizeof (struct udp_header)) )
+ {
+ /* malformed */
+ return;
+ }
+ /* grab UDP content */
+ memcpy (&udp_pkt,
+ &buf[off],
+ sizeof (struct udp_header));
+ port = ntohs (udp_pkt.length);
+ break;
+ default:
+ /* different type than what we want */
+ return;
}
+
+ if (port == 0)
+ fprintf (stdout,
+ "%s\n",
+ inet_ntop (AF_INET,
+ &source_ip,
+ buf,
+ sizeof (buf)));
else
- {
- fprintf (stdout,
- "%s\n",
- inet_ntop (AF_INET,
- &sip,
- buf,
- sizeof (buf)));
- }
+ fprintf (stdout,
+ "%s:%u\n",
+ inet_ntop (AF_INET,
+ &source_ip,
+ buf,
+ sizeof (buf)),
+ (unsigned int) port);
fflush (stdout);
}
"Error opening RAW socket: %s\n",
strerror (errno));
return -1;
- }
- if (ret >= FD_SETSIZE)
+ }
+ if (ret >= FD_SETSIZE)
{
fprintf (stderr,
"Socket number too large (%d > %u)\n",
"Error opening RAW socket: %s\n",
strerror (errno));
return -1;
- }
- if (setsockopt(ret,
- SOL_SOCKET,
- SO_BROADCAST,
- (char *)&one,
- sizeof(one)) == -1)
+ }
+ if (-1 == setsockopt(ret,
+ SOL_SOCKET,
+ SO_BROADCAST,
+ (char *)&one, sizeof(one)))
{
fprintf(stderr,
"setsockopt failed: %s\n",
close (ret);
return -1;
}
- if (setsockopt(ret,
- IPPROTO_IP,
- IP_HDRINCL,
- (char *)&one, sizeof(one)) == -1)
+ if (-1 == setsockopt(ret,
+ IPPROTO_IP,
+ IP_HDRINCL,
+ (char *)&one, sizeof(one)))
{
fprintf(stderr,
"setsockopt failed: %s\n",
}
+/**
+ * Create a UDP socket for writinging.
+ *
+ * @param my_ip source address (our ip address)
+ * @return -1 on error
+ */
+static int
+make_udp_socket (const struct in_addr *my_ip)
+{
+ int ret;
+ struct sockaddr_in addr;
+
+ ret = socket (AF_INET, SOCK_DGRAM, 0);
+ if (-1 == ret)
+ {
+ fprintf (stderr,
+ "Error opening UDP socket: %s\n",
+ strerror (errno));
+ return -1;
+ }
+ memset (&addr,
+ 0,
+ sizeof (addr));
+ addr.sin_family = AF_INET;
+#if HAVE_SOCKADDR_IN_SIN_LEN
+ addr.sin_len = sizeof (struct sockaddr_in);
+#endif
+ addr.sin_addr = *my_ip;
+ addr.sin_port = htons (NAT_TRAV_PORT);
+
+ if (0 != bind (ret,
+ &addr,
+ sizeof(addr)))
+ {
+ fprintf (stderr,
+ "Error binding UDP socket to port %u: %s\n",
+ NAT_TRAV_PORT,
+ strerror (errno));
+ /* likely problematic, but not certain, try to continue */
+ }
+ return ret;
+}
+
+
int
-main (int argc,
+main (int argc,
char *const *argv)
{
struct in_addr external;
fd_set rs;
struct timeval tv;
uid_t uid;
+ unsigned int alt;
- if (argc != 2)
+ if (2 != argc)
{
fprintf (stderr,
"This program must be started with our (internal NAT) IP as the only argument.\n");
strerror (errno));
return 1;
}
- if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy))
+ if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy))
{
fprintf (stderr,
"Internal error converting dummy IP to binary.\n");
}
if (-1 == (icmpsock = make_icmp_socket()))
{
- return 3;
+ return 3;
}
if (-1 == (rawsock = make_raw_socket()))
{
close (icmpsock);
- return 3;
+ return 3;
}
uid = getuid ();
if (0 != setresuid (uid, uid, uid))
{
fprintf (stderr,
"Failed to setresuid: %s\n",
- strerror (errno));
+ strerror (errno));
/* not critical, continue anyway */
}
+ if (-1 == (udpsock = make_udp_socket(&external)))
+ {
+ close (icmpsock);
+ close (rawsock);
+ return 3;
+ }
+ alt = 0;
while (1)
{
FD_ZERO (&rs);
FD_SET (icmpsock, &rs);
tv.tv_sec = 0;
- tv.tv_usec = ICMP_SEND_FREQUENCY_MS * 1000;
+ tv.tv_usec = ICMP_SEND_FREQUENCY_MS * 1000;
if (-1 == select (icmpsock + 1, &rs, NULL, NULL, &tv))
{
if (errno == EINTR)
}
if (FD_ISSET (icmpsock, &rs))
process_icmp_response ();
- send_icmp_echo (&external);
- }
+ if (0 == (++alt % 2))
+ send_icmp_echo (&external);
+ else
+ send_udp ();
+ }
/* select failed (internal error or OS out of resources) */
close (icmpsock);
close (rawsock);
+ close (udpsock);
return 4;
}
projects / oweals / gnunet.git / blobdiff