* - Nathan Evans
*/
#define _GNU_SOURCE
+#if HAVE_CONFIG_H
+/* Just needed for HAVE_SOCKADDR_IN_SIN_LEN test macro! */
+#include "gnunet_config.h"
+#endif
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#define NAT_TRAV_PORT 22225
+/**
+ * IPv4 header.
+ */
struct ip_packet
{
+
+ /**
+ * Version (4 bits) + Internet header length (4 bits)
+ */
uint8_t vers_ihl;
+
+ /**
+ * Type of service
+ */
uint8_t tos;
+
+ /**
+ * Total length
+ */
uint16_t pkt_len;
+
+ /**
+ * Identification
+ */
uint16_t id;
+
+ /**
+ * Flags (3 bits) + Fragment offset (13 bits)
+ */
uint16_t flags_frag_offset;
+
+ /**
+ * Time to live
+ */
uint8_t ttl;
+
+ /**
+ * Protocol
+ */
uint8_t proto;
+
+ /**
+ * Header checksum
+ */
uint16_t checksum;
+
+ /**
+ * Source address
+ */
uint32_t src_ip;
+
+ /**
+ * Destination address
+ */
uint32_t dst_ip;
};
+/**
+ * Format of ICMP packet.
+ */
struct icmp_packet
{
uint8_t type;
+
uint8_t code;
+
uint16_t checksum;
- uint32_t reserved;
+ uint32_t reserved;
};
struct icmp_echo_packet
{
uint8_t type;
+
uint8_t code;
+
uint16_t checksum;
+
uint32_t reserved;
+
uint32_t data;
};
+/**
+ * Beginning of UDP packet.
+ */
struct udp_packet
{
uint16_t src_port;
uint32_t length;
};
+/**
+ * Socket we use to send our fake ICMP replies.
+ */
static int rawsock;
+/**
+ * Target "dummy" address of the packet we pretend to respond to.
+ */
static struct in_addr dummy;
-static uint32_t port;
+/**
+ * Our "source" port.
+ */
+static uint16_t port;
+
+/**
+ * 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,
unsigned int bytes)
}
-static void
-make_echo (const struct in_addr *src_ip,
- struct icmp_echo_packet *echo, uint32_t num)
-{
- memset(echo, 0, sizeof(struct icmp_echo_packet));
- echo->type = ICMP_ECHO;
- echo->code = 0;
- echo->reserved = 0;
- echo->checksum = 0;
- echo->data = htons(num);
- echo->checksum = htons(calc_checksum((uint16_t*)echo,
- sizeof (struct icmp_echo_packet)));
-}
-
-
/**
* Send an ICMP message to the target.
*
off += sizeof(ip_pkt);
/* build UDP header */
- udp_pkt.src_port = htons(NAT_TRAV_PORT); /* FIXME: does this port matter? */
+ udp_pkt.src_port = htons(NAT_TRAV_PORT);
udp_pkt.dst_port = htons(NAT_TRAV_PORT);
memset(&udp_pkt.length, 0, sizeof(uint32_t));
- udp_pkt.length = htonl(port);
+ udp_pkt.length = htons (port);
memcpy(&packet[off], &udp_pkt, sizeof(udp_pkt));
off += sizeof(udp_pkt);
const struct in_addr *other)
{
struct ip_packet ip_pkt;
- struct icmp_packet *icmp_pkt;
+ struct icmp_packet icmp_pkt;
struct icmp_echo_packet icmp_echo;
struct sockaddr_in dst;
char packet[sizeof (struct ip_packet)*2 + sizeof (struct icmp_packet) + sizeof(struct icmp_echo_packet)];
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 = sizeof (packet); /* huh? */
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 (ip_pkt);
+ /* icmp reply: time exceeded */
+ icmp_pkt.type = ICMP_TIME_EXCEEDED;
+ icmp_pkt.code = 0;
+ icmp_pkt.reserved = 0;
+ icmp_pkt.checksum = 0;
+ memcpy (&packet[off],
+ &icmp_pkt,
+ sizeof (struct icmp_packet));
off += sizeof (struct icmp_packet);
/* 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));
-
ip_pkt.id = 1;
ip_pkt.flags_frag_offset = 0;
ip_pkt.ttl = 1; /* real TTL would be 1 on a time exceeded packet */
memcpy (&packet[off], &ip_pkt, sizeof (struct ip_packet));
off += sizeof (struct ip_packet);
- make_echo (other, &icmp_echo, port);
- memcpy (&packet[off], &icmp_echo, sizeof(struct icmp_echo_packet));
- off += sizeof (struct icmp_echo_packet);
-
- icmp_pkt->checksum = htons(calc_checksum((uint16_t*)icmp_pkt,
- sizeof (struct icmp_packet) + sizeof(struct ip_packet) + sizeof(struct icmp_echo_packet)));
-
+ icmp_echo.type = ICMP_ECHO;
+ icmp_echo.code = 0;
+ icmp_echo.reserved = 0;
+ icmp_echo.checksum = 0;
+ icmp_echo.data = htons(port);
+ icmp_echo.checksum = htons(calc_checksum((uint16_t*) &icmp_echo,
+ sizeof (struct icmp_echo_packet)));
+ memcpy (&packet[off],
+ &icmp_echo,
+ sizeof(struct icmp_echo_packet));
+
+ /* no go back to calculate ICMP packet checksum */
+ off = sizeof (ip_pkt);
+ icmp_pkt.checksum = htons(calc_checksum(&packet[off],
+ sizeof (struct icmp_packet) + sizeof(struct ip_packet) + sizeof(struct icmp_echo_packet)));
+ memcpy (&packet[off],
+ &icmp_pkt,
+ sizeof (struct icmp_packet));
+
+ /* prepare for transmission */
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 = *other;
err = sendto(rawsock,
packet,
off, 0,
(struct sockaddr*)&dst,
- sizeof(dst)); /* or sizeof 'struct sockaddr'? */
+ sizeof(struct sockaddr_in));
if (err < 0)
{
fprintf(stderr,
}
+/**
+ * Create an ICMP raw socket for writing.
+ *
+ * @return -1 on error
+ */
static int
make_raw_socket ()
{
}
if (setsockopt(ret, SOL_SOCKET, SO_BROADCAST,
(char *)&one, sizeof(one)) == -1)
- fprintf(stderr,
- "setsockopt failed: %s\n",
- strerror (errno));
+ {
+ fprintf(stderr,
+ "setsockopt failed: %s\n",
+ strerror (errno));
+ close (ret);
+ return -1;
+ }
if (setsockopt(ret, IPPROTO_IP, IP_HDRINCL,
(char *)&one, sizeof(one)) == -1)
- fprintf(stderr,
- "setsockopt failed: %s\n",
- strerror (errno));
+ {
+ fprintf(stderr,
+ "setsockopt failed: %s\n",
+ strerror (errno));
+ close (ret);
+ return -1;
+ }
return ret;
}
struct in_addr external;
struct in_addr target;
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));
+ unsigned int p;
if (argc != 4)
{
"This program must be started with our IP, the targets external IP, and our port as arguments.\n");
return 1;
}
- port = atoi(argv[3]);
-
if ( (1 != inet_pton (AF_INET, argv[1], &external)) ||
(1 != inet_pton (AF_INET, argv[2], &target)) )
{
strerror (errno));
return 1;
}
- if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy)) abort ();
+ if ( (1 != sscanf (argv[3], "%u", &p) ) ||
+ (p == 0) ||
+ (p > 0xFFFF) )
+ {
+ fprintf (stderr,
+ "Error parsing port value `%s'\n",
+ argv[3]);
+ return 1;
+ }
+ port = (uint16_t) p;
+ if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy))
+ {
+ fprintf (stderr,
+ "Internal error converting dummy IP to binary.\n");
+ return 2;
+ }
+ if (-1 == (rawsock = make_raw_socket()))
+ return 2;
+ uid = getuid ();
+ if (0 != setresuid (uid, uid, uid))
+ {
+ fprintf (stderr,
+ "Failed to setresuid: %s\n",
+ strerror (errno));
+ /* not critical, continue anyway */
+ }
send_icmp (&external,
&target);
send_icmp_udp (&external,
- &target);
+ &target);
close (rawsock);
return 0;
}
projects / oweals / gnunet.git / commitdiff