/**
* @file src/transport/gnunet-nat-client.c
* @brief Tool to help bypass NATs using ICMP method; must run as root (SUID will do)
- * This code will work under GNU/Linux only.
+ * This code will work under GNU/Linux only.
* @author Christian Grothoff
*
* This program will send ONE ICMP message using RAW sockets
*
* - 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/types.h>
#include <stdint.h>
#include <netinet/ip.h>
#include <netinet/ip_icmp.h>
-#include <netinet/in.h>
+#include <netinet/in.h>
/**
* Must match IP given in the server.
/**
* 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;
uint16_t checksum;
- uint32_t reserved;
+ uint32_t unused;
+
+ /* followed by original payload */
};
-struct icmp_echo_packet
+struct icmp_echo_header
{
uint8_t type;
uint16_t checksum;
uint32_t reserved;
-
- uint32_t data;
};
/**
* 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;
};
/**
* Target "dummy" address of the packet we pretend to respond to.
*/
static struct in_addr dummy;
-
+
/**
* Our "source" port.
*/
* @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 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;
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;
-
+ char packet[sizeof(struct ip_header) * 2 +
+ sizeof(struct icmp_ttl_exceeded_header) +
+ sizeof(struct udp_header)];
+ struct ip_header ip_pkt;
+ struct icmp_ttl_exceeded_header icmp_pkt;
+ struct udp_header 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.pkt_len = htons (sizeof (packet));
ip_pkt.id = htons(256);
ip_pkt.flags_frag_offset = 0;
ip_pkt.ttl = 128;
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_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);
- /* 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.type = ICMP_TIME_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);
+ icmp_pkt.unused = 0;
+ memcpy(&packet[off],
+ &icmp_pkt,
+ sizeof(struct icmp_ttl_exceeded_header));
+ off += sizeof(struct icmp_ttl_exceeded_header);
- /* build inner IP header */
- memset(&ip_pkt, 0, sizeof(ip_pkt));
+ /* ip header of the presumably 'lost' udp packet */
ip_pkt.vers_ihl = 0x45;
ip_pkt.tos = 0;
- ip_pkt.pkt_len = htons(sizeof (ip_pkt) + sizeof(udp_pkt));
+ ip_pkt.pkt_len = htons(sizeof (struct ip_header) +
+ sizeof (struct udp_header));
ip_pkt.id = htons(0);
ip_pkt.flags_frag_offset = 0;
ip_pkt.ttl = 128;
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);
+ 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);
/* build UDP header */
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 = htons (port);
- memcpy(&packet[off], &udp_pkt, sizeof(udp_pkt));
- off += sizeof(udp_pkt);
+ udp_pkt.crc = 0;
+ memcpy(&packet[off],
+ &udp_pkt,
+ sizeof(struct udp_header));
+ off += sizeof(struct udp_header);
/* 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));
-
+ icmp_pkt.checksum = htons(calc_checksum((uint16_t*)&packet[sizeof(struct ip_header)],
+ sizeof (struct icmp_ttl_exceeded_header) +
+ sizeof (struct ip_header) +
+ sizeof (struct udp_header)));
+ memcpy (&packet[sizeof(struct ip_header)],
+ &icmp_pkt,
+ sizeof (struct icmp_ttl_exceeded_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 = *other;
err = sendto(rawsock,
packet,
- off, 0,
+ sizeof (packet), 0,
(struct sockaddr*)&dst,
sizeof(dst));
-
if (err < 0)
{
fprintf(stderr,
"sendto failed: %s\n", strerror(errno));
}
- else if (err != off)
+ else if (sizeof (packet) != (size_t) err)
{
fprintf(stderr,
"Error: partial send of ICMP message\n");
send_icmp (const struct in_addr *my_ip,
const struct in_addr *other)
{
- struct ip_packet ip_pkt;
- struct icmp_packet icmp_pkt;
- struct icmp_echo_packet icmp_echo;
+ struct ip_header ip_pkt;
+ struct icmp_ttl_exceeded_header icmp_ttl;
+ struct icmp_echo_header icmp_echo;
struct sockaddr_in dst;
- char packet[sizeof (struct ip_packet)*2 + sizeof (struct icmp_packet) + sizeof(struct icmp_echo_packet)];
-
+ char packet[sizeof (struct ip_header) * 2 +
+ sizeof (struct icmp_ttl_exceeded_header) +
+ sizeof (struct icmp_echo_header)];
size_t off;
int err;
off = 0;
ip_pkt.vers_ihl = 0x45;
ip_pkt.tos = 0;
- ip_pkt.pkt_len = sizeof (packet); /* huh? */
- 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 = other->s_addr;
- ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (struct ip_packet)));
- memcpy (&packet[off], &ip_pkt, sizeof (struct ip_packet));
+ 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 (ip_pkt);
/* icmp reply: time exceeded */
- icmp_pkt.type = ICMP_TIME_EXCEEDED;
- icmp_pkt.code = 0;
- icmp_pkt.reserved = 0;
- icmp_pkt.checksum = 0;
+ icmp_ttl.type = ICMP_TIME_EXCEEDED;
+ icmp_ttl.code = 0;
+ icmp_ttl.checksum = 0;
+ icmp_ttl.unused = 0;
memcpy (&packet[off],
- &icmp_pkt,
- sizeof (struct icmp_packet));
- off += sizeof (struct icmp_packet);
+ &icmp_ttl,
+ sizeof (struct icmp_ttl_exceeded_header));
+ off += sizeof (struct icmp_ttl_exceeded_header);
/* 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.pkt_len = htons (sizeof (struct ip_header) + sizeof (struct icmp_echo_header));
+ ip_pkt.id = htons (256);
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);
+ 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.reserved = htonl (port);
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.checksum = htons(calc_checksum((uint16_t*) &icmp_echo,
+ sizeof (struct icmp_echo_header)));
+ memcpy (&packet[off],
&icmp_echo,
- sizeof(struct icmp_echo_packet));
+ sizeof(struct icmp_echo_header));
/* no go back to calculate ICMP packet checksum */
- off = sizeof (ip_pkt);
- icmp_pkt.checksum = htons(calc_checksum((uint16_t*) &packet[off],
- sizeof (struct icmp_packet) + sizeof(struct ip_packet) + sizeof(struct icmp_echo_packet)));
+ off = sizeof (struct ip_header);
+ icmp_ttl.checksum = htons(calc_checksum((uint16_t*) &packet[off],
+ sizeof (struct icmp_ttl_exceeded_header) +
+ sizeof (struct ip_header) +
+ sizeof (struct icmp_echo_header)));
memcpy (&packet[off],
- &icmp_pkt,
- sizeof (struct icmp_packet));
+ &icmp_ttl,
+ sizeof (struct icmp_ttl_exceeded_header));
/* prepare for transmission */
memset (&dst, 0, sizeof (dst));
dst.sin_len = sizeof (struct sockaddr_in);
#endif
dst.sin_addr = *other;
- err = sendto(rawsock,
- packet,
- sizeof (packet), 0,
- (struct sockaddr*)&dst,
- sizeof(struct sockaddr_in));
- if (err < 0)
+ err = sendto(rawsock,
+ packet,
+ sizeof (packet), 0,
+ (struct sockaddr*)&dst,
+ sizeof(dst));
+ if (err < 0)
{
fprintf(stderr,
"sendto failed: %s\n", strerror(errno));
}
- else if (err != sizeof (packet))
+ else if (sizeof (packet) != (size_t) err)
{
fprintf(stderr,
"Error: partial send of ICMP message\n");
"Error opening RAW socket: %s\n",
strerror (errno));
return -1;
- }
- if (setsockopt(ret, SOL_SOCKET, SO_BROADCAST,
- (char *)&one, sizeof(one)) == -1)
+ }
+ if (0 != 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 (0 != setsockopt(ret, IPPROTO_IP, IP_HDRINCL,
+ (char *)&one, sizeof(one)))
{
fprintf(stderr,
"setsockopt failed: %s\n",
uid_t uid;
unsigned int p;
- if (argc != 4)
+ if (4 != argc)
{
fprintf (stderr,
"This program must be started with our IP, the targets external IP, and our port as arguments.\n");
return 1;
}
if ( (1 != sscanf (argv[3], "%u", &p) ) ||
- (p == 0) ||
- (p > 0xFFFF) )
+ (0 == p) ||
+ (0xFFFF < p) )
{
fprintf (stderr,
"Error parsing port value `%s'\n",
return 1;
}
port = (uint16_t) p;
- 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");
return 2;
}
if (-1 == (rawsock = make_raw_socket()))
- return 2;
+ return 2;
uid = getuid ();
if (0 != setresuid (uid, uid, uid))
{
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