*/
#define VERBOSE 0
+/**
+ * Must match IP given in the client.
+ */
+#define DUMMY_IP "192.0.2.86"
+
/**
* TTL to use for our outgoing messages.
*/
#define ICMP_TIME_EXCEEDED 11 /* Time Exceeded */
-/**
- * Must match IP given in the client.
- */
-#define DUMMY_IP "192.0.2.86"
-
/**
* How often do we send our ICMP messages to receive replies?
*/
struct udp_packet udp_pkt;
size_t off;
int have_port;
- int have_udp;
uint32_t port;
have = read (icmpsock, buf, sizeof (buf));
sizeof (sip));
memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
off += sizeof (ip_pkt);
- have_udp = (ip_pkt.proto == IPPROTO_UDP);
if (have_port)
{
buf,
port);
}
- else if (have_udp)
+ else if (ip_pkt.proto == IPPROTO_UDP)
{
memcpy(&udp_pkt,
&buf[off],
fprintf (stdout,
"%s:%d\n",
buf,
- ntohs((int)udp_pkt.length));
+ ntohs((uint16_t)udp_pkt.length));
}
else
{
/**
* Create an ICMP raw socket for reading.
+ *
+ * @return INVALID_SOCKET on error
*/
static SOCKET
make_icmp_socket ()
fprintf (stderr,
"Error opening RAW socket: %s\n",
strerror (errno));
- return -1;
+ return INVALID_SOCKET;
}
return ret;
}
/**
* Create an ICMP raw socket for writing.
+ *
+ * @return INVALID_SOCKET on error
*/
static SOCKET
make_raw_socket ()
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;
}
- if (-1 == (make_raw_socket()))
+ if (INVALID_SOCKET == (make_raw_socket()))
{
closesocket (icmpsock);
return 3;
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))
+ if (-1 == select (icmpsock + 1, &rs, NULL, NULL, &tv))
{
if (errno == EINTR)
continue;
#include <netinet/ip_icmp.h>
#include <netinet/in.h>
+/**
+ * Should we print some debug output?
+ */
+#define VERBOSE 0
+
/**
* Must match IP given in the client.
*/
#define DUMMY_IP "192.0.2.86"
-#define VERBOSE 0
-
/**
* How often do we send our ICMP messages to receive replies?
*/
#define ICMP_SEND_FREQUENCY_MS 500
+/**
+ * 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;
};
struct icmp_packet
{
uint8_t type;
+
uint8_t code;
+
uint16_t checksum;
+
uint32_t reserved;
};
uint32_t length;
};
+/**
+ * Socket we use to receive "fake" ICMP replies.
+ */
static int icmpsock;
+/**
+ * Socket we use to send our ICMP requests.
+ */
static int rawsock;
+/**
+ * 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,
unsigned int bytes)
}
-static void
-make_echo (const struct in_addr *src_ip,
- struct icmp_packet *echo)
-{
- memset(echo, 0, sizeof(struct icmp_packet));
- echo->type = ICMP_ECHO;
- echo->code = 0;
- echo->reserved = 0;
- echo->checksum = 0;
- echo->checksum = htons(calc_checksum((uint16_t*)echo, sizeof (struct icmp_packet)));
-}
-
-
/**
* Send an ICMP message to the dummy IP.
*
ip_pkt.checksum = htons(calc_checksum((uint16_t*)&ip_pkt, sizeof (ip_pkt)));
memcpy (packet, &ip_pkt, sizeof (ip_pkt));
off += sizeof (ip_pkt);
+
+ 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)));
+
make_echo (my_ip, &icmp_echo);
+
memcpy (&packet[off], &icmp_echo, sizeof (icmp_echo));
off += sizeof (icmp_echo);
}
+/**
+ * We've received an ICMP response. Process it.
+ */
static void
process_icmp_response ()
{
struct udp_packet udp_pkt;
size_t off;
int have_port;
- int have_udp;
uint32_t port;
have = read (icmpsock, buf, sizeof (buf));
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;
memcpy(&sip,
&ip_pkt.src_ip,
sizeof (sip));
-
memcpy (&ip_pkt, &buf[off], sizeof (ip_pkt));
off += sizeof (ip_pkt);
- have_udp = 0;
- if (ip_pkt.proto == IPPROTO_UDP)
- {
- have_udp = 1;
- }
-
if (have_port)
{
- memcpy(&port, &buf[sizeof (struct ip_packet) *2 + sizeof (struct icmp_packet) * 2], sizeof(uint32_t));
+ 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);
+ "%s:%d\n",
+ inet_ntop (AF_INET,
+ &sip,
+ buf,
+ sizeof (buf)),
+ port);
}
- else if (have_udp)
+ else if (ip_pkt.proto == IPPROTO_UDP)
{
- memcpy(&udp_pkt, &buf[off], sizeof(udp_pkt));
+ memcpy(&udp_pkt,
+ &buf[off],
+ sizeof(udp_pkt));
fprintf (stdout,
"%s:%d\n",
inet_ntop (AF_INET,
&sip,
buf,
- sizeof (buf)), ntohl(udp_pkt.length));
+ sizeof (buf)),
+ ntohs((uint16_t) udp_pkt.length));
}
else
{
fprintf (stdout,
- "%s\n",
- inet_ntop (AF_INET,
- &sip,
- buf,
- sizeof (buf)));
+ "%s\n",
+ inet_ntop (AF_INET,
+ &sip,
+ buf,
+ sizeof (buf)));
}
fflush (stdout);
}
+/**
+ * Create an ICMP raw socket for reading.
+ *
+ * @return -1 on error
+ */
static int
make_icmp_socket ()
{
}
+/**
+ * Create an ICMP raw socket for writing.
+ *
+ * @return -1 on error
+ */
static int
make_raw_socket ()
{
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,
+ if (setsockopt(ret,
+ SOL_SOCKET,
+ SO_BROADCAST,
+ (char *)&one,
+ sizeof(one)) == -1)
+ {
+ 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;
}
int
-main (int argc, char *const *argv)
+main (int argc,
+ char *const *argv)
{
struct in_addr external;
fd_set rs;
struct timeval tv;
uid_t uid;
- if (-1 == (icmpsock = make_icmp_socket()))
- return 1;
- if (-1 == (rawsock = make_raw_socket()))
- {
- close (icmpsock);
- return 1;
- }
- uid = getuid ();
- if (0 != setresuid (uid, uid, uid))
- fprintf (stderr,
- "Failed to setresuid: %s\n",
- strerror (errno));
if (argc != 2)
{
fprintf (stderr,
strerror (errno));
return 1;
}
- if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy)) abort ();
+ if (1 != inet_pton (AF_INET, DUMMY_IP, &dummy))
+ {
+ fprintf (stderr,
+ "Internal error converting dummy IP to binary.\n");
+ return 2;
+ }
+ if (-1 == (icmpsock = make_icmp_socket()))
+ {
+ return 3;
+ }
+ if (-1 == (rawsock = make_raw_socket()))
+ {
+ close (icmpsock);
+ return 3;
+ }
+ uid = getuid ();
+ if (0 != setresuid (uid, uid, uid))
+ {
+ fprintf (stderr,
+ "Failed to setresuid: %s\n",
+ strerror (errno));
+ /* not critical, continue anyway */
+ }
while (1)
{
FD_ZERO (&rs);
FD_SET (icmpsock, &rs);
tv.tv_sec = 0;
tv.tv_usec = ICMP_SEND_FREQUENCY_MS * 1000;
- select (icmpsock + 1, &rs, NULL, NULL, &tv);
+ if (-1 == select (icmpsock + 1, &rs, NULL, NULL, &tv))
+ {
+ if (errno == EINTR)
+ continue;
+ fprintf (stderr,
+ "select failed: %s\n",
+ strerror (errno));
+ break;
+ }
if (FD_ISSET (icmpsock, &rs))
process_icmp_response ();
send_icmp_echo (&external);
}
- return 0;
+ /* select failed (internal error or OS out of resources) */
+ close (icmpsock);
+ close (rawsock);
+ return 4;
}
projects / oweals / gnunet.git / commitdiff