* to the list):
*
* - Nathan Evans
+ * - Christian Grothoff
*/
#define _GNU_SOURCE
*/
#define VERBOSE 0
-
-typedef unsigned int uid_t;
-typedef SOCKET Socket;
-typedef unsigned short ushort;
-#define IPDEFTTL 64
-#define ICMP_ECHO 8
-#define ICMP_TIME_EXCEEDED 11 /* Time Exceeded
-
/**
* Must match IP given in the client.
*/
#define DUMMY_IP "192.0.2.86"
+/**
+ * Default Port
+ */
+#define NAT_TRAV_PORT 22225
+
+/**
+ * TTL to use for our outgoing messages.
+ */
+#define IPDEFTTL 64
+
+#define ICMP_ECHO 8
+
+#define ICMP_TIME_EXCEEDED 11
+
/**
* 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)
*/
- u_char vers_ihl;
+ uint8_t vers_ihl;
/**
* Type of service
*/
- u_char tos;
+ uint8_t tos;
/**
* Total length
*/
- u_short pkt_len;
+ uint16_t pkt_len;
/**
* Identification
*/
- u_short id;
+ uint16_t id;
/**
* Flags (3 bits) + Fragment offset (13 bits)
*/
- u_short flags_frag_offset;
+ uint16_t flags_frag_offset;
/**
* Time to live
*/
- u_char ttl;
+ uint8_t ttl;
/**
- * Protocol
+ * Protocol
*/
- u_char proto;
+ uint8_t proto;
/**
* Header checksum
*/
- u_short checksum;
+ uint16_t checksum;
/**
* Source address
*/
- u_long src_ip;
+ uint32_t src_ip;
/**
- * Destination address
+ * Destination address
*/
- u_long dst_ip;
+ 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;
+
+ uint8_t code;
+
+ uint16_t checksum;
+
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 Socket icmpsock;
+/**
+ * Socket we use to receive "fake" ICMP replies.
+ */
+static SOCKET icmpsock;
+
+/**
+ * Socket we use to send our ICMP requests.
+ */
+static SOCKET rawsock;
-static Socket rawsock;
+/**
+ * Socket we use to send our UDP requests.
+ */
+static SOCKET udpsock;
+/**
+ * Target "dummy" address.
+ */
static struct in_addr dummy;
+
/**
* CRC-16 for IP/ICMP headers.
+ *
+ * @param data what to calculate the CRC over
+ * @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;
}
+
/**
* Convert IPv4 address from text to binary form.
*
* @param af address family
* @param cp the address to print
* @param buf where to write the address result
+ * @return 1 on success
*/
-static int
-inet_pton (int af,
- const char *cp,
+static int
+inet_pton (int af,
+ const char *cp,
struct in_addr *buf)
{
buf->s_addr = inet_addr(cp);
if (buf->s_addr == INADDR_NONE)
{
- fprintf(stderr,
- "Error %d handling address %s",
- WSAGetLastError(),
+ fprintf(stderr,
+ "Error %d handling address %s",
+ WSAGetLastError(),
cp);
return 0;
}
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.pkt_len = htons (sizeof (packet));
ip_pkt.id = htons (256);
ip_pkt.flags_frag_offset = 0;
ip_pkt.ttl = IPDEFTTL;
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.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;
dst.sin_addr = dummy;
- err = sendto(rawsock,
+ err = sendto(rawsock,
packet, off, 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)
+ {
+ 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;
+ dst.sin_addr = dummy;
+ dst.sin_port = htons (NAT_TRAV_PORT);
+ err = sendto(udpsock,
+ NULL, 0, 0,
+ (struct sockaddr*)&dst,
+ sizeof(dst));
+ 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");
}
+/**
+ * We've received an ICMP response. Process it.
+ */
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;
- 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;
- int have_udp;
- uint32_t port;
+ uint16_t port;
+ DWORD ssize;
have = read (icmpsock, buf, sizeof (buf));
if (have == -1)
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) )
- {
- /* maybe we got an actual reply back... */
- return;
- }
- memcpy(&sip,
- &ip_pkt.src_ip,
- sizeof (sip));
- memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
- off += sizeof (ip_pkt);
- have_udp = (ip_pkt.proto == IPPROTO_UDP);
-
- if (have_port)
+ 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) )
{
- memcpy(&port,
- &buf[sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2],
- sizeof(uint32_t));
- port = ntohs(port);
- DWORD ssize = sizeof(buf);
- WSAAddressToString((LPSOCKADDR)&sip,
- sizeof(sip),
- NULL,
- buf,
- &ssize);
- fprintf (stdout,
- "%s:%d\n",
- buf,
- port);
+ /* different type than what we want */
+ return;
}
- else if (have_udp)
+ /* skip 2nd IP header */
+ memcpy (&ip_pkt,
+ &buf[off],
+ sizeof (struct ip_header));
+ off += sizeof (struct ip_header);
+
+ switch (ip_pkt.proto)
{
- memcpy(&udp_pkt,
- &buf[off],
- sizeof(udp_pkt));
- DWORD ssize = sizeof(buf);
- WSAAddressToString((LPSOCKADDR)&sip,
- sizeof(sip),
- NULL,
- buf,
- &ssize);
- fprintf (stdout,
- "%s:%d\n",
- buf,
- ntohs((int)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;
}
+
+ ssize = sizeof(buf);
+ WSAAddressToString((LPSOCKADDR)&source_ip,
+ sizeof(source_ip),
+ NULL,
+ buf,
+ &ssize);
+ if (port == 0)
+ fprintf (stdout,
+ "%s\n",
+ buf);
else
- {
- DWORD ssize = sizeof(buf);
- WSAAddressToString((LPSOCKADDR)&sip,
- sizeof(sip),
- NULL,
- buf,
- &ssize);
- fprintf (stdout,
- "%s\n",
- buf);
- }
+ fprintf (stdout,
+ "%s:%u\n",
+ buf,
+ (unsigned int) port);
fflush (stdout);
}
-static Socket
+/**
+ * Create an ICMP raw socket for reading.
+ *
+ * @return INVALID_SOCKET on error
+ */
+static SOCKET
make_icmp_socket ()
{
- Socket ret;
+ SOCKET ret;
ret = socket (AF_INET, SOCK_RAW, IPPROTO_ICMP);
if (INVALID_SOCKET == ret)
fprintf (stderr,
"Error opening RAW socket: %s\n",
strerror (errno));
- return -1;
- }
+ return INVALID_SOCKET;
+ }
return ret;
}
-static Socket
+/**
+ * Create an ICMP raw socket for writing.
+ *
+ * @return INVALID_SOCKET on error
+ */
+static SOCKET
make_raw_socket ()
{
DWORD bOptVal = TRUE;
return INVALID_SOCKET;
}
- if (setsockopt(rawsock,
- SOL_SOCKET,
- SO_BROADCAST,
- (char*)&bOptVal, bOptLen) != 0)
+ if (0 != setsockopt(rawsock,
+ SOL_SOCKET,
+ SO_BROADCAST,
+ (char*)&bOptVal, bOptLen))
{
- fprintf(stderr,
+ fprintf(stderr,
"Error setting SO_BROADCAST to ON: %s\n",
strerror (errno));
closesocket(rawsock);
return INVALID_SOCKET;
}
- if (setsockopt(rawsock,
- IPPROTO_IP,
- IP_HDRINCL,
- (char*)&bOptVal, bOptLen) != 0)
+ if (0 != setsockopt(rawsock,
+ IPPROTO_IP,
+ IP_HDRINCL,
+ (char*)&bOptVal, bOptLen))
{
- fprintf(stderr,
+ fprintf(stderr,
"Error setting IP_HDRINCL to ON: %s\n",
strerror (errno));
closesocket(rawsock);
}
+/**
+ * Create a UDP socket for writing.
+ *
+ * @param my_ip source address (our ip address)
+ * @return INVALID_SOCKET on error
+ */
+static SOCKET
+make_udp_socket (const struct in_addr *my_ip)
+{
+ SOCKET ret;
+ struct sockaddr_in addr;
+
+ ret = socket (AF_INET, SOCK_DGRAM, 0);
+ if (INVALID_SOCKET == ret)
+ {
+ fprintf (stderr,
+ "Error opening UDP socket: %s\n",
+ strerror (errno));
+ return INVALID_SOCKET;
+ }
+ memset (&addr, 0, sizeof (addr));
+ addr.sin_family = AF_INET;
+ addr.sin_addr = *my_ip;
+ addr.sin_port = htons (NAT_TRAV_PORT);
+ if (0 != bind (ret,
+ (struct sockaddr *)&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;
WSADATA wsaData;
+ unsigned int alt;
- if (argc != 2)
+ alt = 0;
+ if (2 != argc)
{
fprintf (stderr,
"This program must be started with our (internal NAT) IP as the only argument.\n");
argv[1], 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");
fprintf (stderr, "Failed to find Winsock 2.1 or better.\n");
return 2;
}
- if (-1 == (icmpsock = make_icmp_socket()))
+ if (INVALID_SOCKET == (icmpsock = make_icmp_socket()))
{
- return 3;
+ return 3;
+ }
+ if (INVALID_SOCKET == (make_raw_socket()))
+ {
+ closesocket (icmpsock);
+ return 3;
}
- if (-1 == (make_raw_socket()))
+ if (INVALID_SOCKET == (udpsock = make_udp_socket(&external)))
{
closesocket (icmpsock);
- return 3;
+ closesocket (rawsock);
+ return 3;
}
while (1)
{
FD_ZERO (&rs);
FD_SET (icmpsock, &rs);
tv.tv_sec = 0;
- tv.tv_usec = ICMP_SEND_FREQUENCY_MS * 1000;
- if (0 != select (icmpsock + 1, &rs, NULL, NULL, &tv))
+ tv.tv_usec = ICMP_SEND_FREQUENCY_MS * 1000;
+ if (-1 == select (icmpsock + 1, &rs, NULL, NULL, &tv))
{
if (errno == EINTR)
continue;
}
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) */
closesocket(icmpsock);
closesocket(rawsock);
+ closesocket(udpsock);
WSACleanup ();
- return 4; /* select failed! */
+ return 4;
}
projects / oweals / gnunet.git / blobdiff