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benjojo/icmp4.c

Created Oct 11, 2015
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How to trigger SNMP counter bug
/* Copyright (C) 2011-2015 P.D. Buchan (pdbuchan@yahoo.com)
This program is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
// Send an IPv4 ICMP packet via raw socket.
// Stack fills out layer 2 (data link) information (MAC addresses) for us.
// Values set for echo request packet, includes some ICMP data.
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h> // close()
#include <string.h> // strcpy, memset(), and memcpy()
#include <netdb.h> // struct addrinfo
#include <sys/types.h> // needed for socket(), uint8_t, uint16_t, uint32_t
#include <sys/socket.h> // needed for socket()
#include <netinet/in.h> // IPPROTO_RAW, IPPROTO_IP, IPPROTO_ICMP, INET_ADDRSTRLEN
#include <netinet/ip.h> // struct ip and IP_MAXPACKET (which is 65535)
#include <netinet/ip_icmp.h> // struct icmp, ICMP_ECHO
#include <arpa/inet.h> // inet_pton() and inet_ntop()
#include <sys/ioctl.h> // macro ioctl is defined
#include <bits/ioctls.h> // defines values for argument "request" of ioctl.
#include <net/if.h> // struct ifreq
#include <errno.h> // errno, perror()
// Define some constants.
#define IP4_HDRLEN 21 // IPv4 header length
#define ICMP_HDRLEN 8 // ICMP header length for echo request, excludes data
// Function prototypes
uint16_t checksum (uint16_t *, int);
char *allocate_strmem (int);
uint8_t *allocate_ustrmem (int);
int *allocate_intmem (int);
int
main (int argc, char **argv)
{
int status, datalen, sd, *ip_flags;
const int on = 1;
char *interface, *target, *src_ip, *dst_ip;
struct ip iphdr;
struct icmp icmphdr;
uint8_t *data, *packet;
struct addrinfo hints, *res;
struct sockaddr_in *ipv4, sin;
struct ifreq ifr;
void *tmp;
// Allocate memory for various arrays.
data = allocate_ustrmem (IP_MAXPACKET);
packet = allocate_ustrmem (IP_MAXPACKET);
interface = allocate_strmem (40);
target = allocate_strmem (40);
src_ip = allocate_strmem (INET_ADDRSTRLEN);
dst_ip = allocate_strmem (INET_ADDRSTRLEN);
ip_flags = allocate_intmem (4);
// Interface to send packet through.
strcpy (interface, "eth0");
// Submit request for a socket descriptor to look up interface.
if ((sd = socket (AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0) {
perror ("socket() failed to get socket descriptor for using ioctl() ");
exit (EXIT_FAILURE);
}
// Use ioctl() to look up interface index which we will use to
// bind socket descriptor sd to specified interface with setsockopt() since
// none of the other arguments of sendto() specify which interface to use.
memset (&ifr, 0, sizeof (ifr));
snprintf (ifr.ifr_name, sizeof (ifr.ifr_name), "%s", interface);
if (ioctl (sd, SIOCGIFINDEX, &ifr) < 0) {
perror ("ioctl() failed to find interface ");
return (EXIT_FAILURE);
}
close (sd);
printf ("Index for interface %s is %i\n", interface, ifr.ifr_ifindex);
// Source IPv4 address: you need to fill this out
strcpy (src_ip, "192.168.1.132");
// Destination URL or IPv4 address: you need to fill this out
strcpy (target, "www.google.com");
// Fill out hints for getaddrinfo().
memset (&hints, 0, sizeof (struct addrinfo));
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = hints.ai_flags | AI_CANONNAME;
// Resolve target using getaddrinfo().
if ((status = getaddrinfo (target, NULL, &hints, &res)) != 0) {
fprintf (stderr, "getaddrinfo() failed: %s\n", gai_strerror (status));
exit (EXIT_FAILURE);
}
ipv4 = (struct sockaddr_in *) res->ai_addr;
tmp = &(ipv4->sin_addr);
if (inet_ntop (AF_INET, tmp, dst_ip, INET_ADDRSTRLEN) == NULL) {
status = errno;
fprintf (stderr, "inet_ntop() failed.\nError message: %s", strerror (status));
exit (EXIT_FAILURE);
}
freeaddrinfo (res);
// ICMP data
datalen = 4;
data[0] = 'T';
data[1] = 'e';
data[2] = 's';
data[3] = 't';
// IPv4 header
// IPv4 header length (4 bits): Number of 32-bit words in header = 5
iphdr.ip_hl = /* IP4_HDRLEN / sizeof (uint32_t); */ 0x46;
// Internet Protocol version (4 bits): IPv4
iphdr.ip_v = 4;
// Type of service (8 bits)
iphdr.ip_tos = 0;
// Total length of datagram (16 bits): IP header + ICMP header + ICMP data
iphdr.ip_len = htons (IP4_HDRLEN + ICMP_HDRLEN + datalen);
// ID sequence number (16 bits): unused, since single datagram
iphdr.ip_id = htons (0);
// Flags, and Fragmentation offset (3, 13 bits): 0 since single datagram
// Zero (1 bit)
ip_flags[0] = 0;
// Do not fragment flag (1 bit)
ip_flags[1] = 0;
// More fragments following flag (1 bit)
ip_flags[2] = 0;
// Fragmentation offset (13 bits)
ip_flags[3] = 0;
iphdr.ip_off = htons ((ip_flags[0] << 15)
+ (ip_flags[1] << 14)
+ (ip_flags[2] << 13)
+ ip_flags[3]);
// Time-to-Live (8 bits): default to maximum value
iphdr.ip_ttl = 255;
// Transport layer protocol (8 bits): 1 for ICMP
iphdr.ip_p = IPPROTO_ICMP;
// Source IPv4 address (32 bits)
if ((status = inet_pton (AF_INET, src_ip, &(iphdr.ip_src))) != 1) {
fprintf (stderr, "inet_pton() failed.\nError message: %s", strerror (status));
exit (EXIT_FAILURE);
}
// Destination IPv4 address (32 bits)
if ((status = inet_pton (AF_INET, dst_ip, &(iphdr.ip_dst))) != 1) {
fprintf (stderr, "inet_pton() failed.\nError message: %s", strerror (status));
exit (EXIT_FAILURE);
}
// IPv4 header checksum (16 bits): set to 0 when calculating checksum
iphdr.ip_sum = 0;
iphdr.ip_sum = checksum ((uint16_t *) &iphdr, IP4_HDRLEN);
// ICMP header
// Message Type (8 bits): echo request
icmphdr.icmp_type = ICMP_ECHO;
// Message Code (8 bits): echo request
icmphdr.icmp_code = 0;
// Identifier (16 bits): usually pid of sending process - pick a number
icmphdr.icmp_id = htons (1000);
// Sequence Number (16 bits): starts at 0
icmphdr.icmp_seq = htons (0);
// ICMP header checksum (16 bits): set to 0 when calculating checksum
icmphdr.icmp_cksum = 0;
// Prepare packet.
// First part is an IPv4 header.
memcpy (packet, &iphdr, IP4_HDRLEN);
// Next part of packet is upper layer protocol header.
memcpy ((packet + IP4_HDRLEN), &icmphdr, ICMP_HDRLEN);
// Finally, add the ICMP data.
memcpy (packet + IP4_HDRLEN + ICMP_HDRLEN, data, datalen);
// Calculate ICMP header checksum
icmphdr.icmp_cksum = checksum ((uint16_t *) (packet + IP4_HDRLEN), ICMP_HDRLEN + datalen);
memcpy ((packet + IP4_HDRLEN), &icmphdr, ICMP_HDRLEN);
// The kernel is going to prepare layer 2 information (ethernet frame header) for us.
// For that, we need to specify a destination for the kernel in order for it
// to decide where to send the raw datagram. We fill in a struct in_addr with
// the desired destination IP address, and pass this structure to the sendto() function.
memset (&sin, 0, sizeof (struct sockaddr_in));
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = iphdr.ip_dst.s_addr;
// Submit request for a raw socket descriptor.
if ((sd = socket (AF_INET, SOCK_RAW, IPPROTO_RAW)) < 0) {
perror ("socket() failed ");
exit (EXIT_FAILURE);
}
// Set flag so socket expects us to provide IPv4 header.
if (setsockopt (sd, IPPROTO_IP, IP_HDRINCL, &on, sizeof (on)) < 0) {
perror ("setsockopt() failed to set IP_HDRINCL ");
exit (EXIT_FAILURE);
}
// Bind socket to interface index.
if (setsockopt (sd, SOL_SOCKET, SO_BINDTODEVICE, &ifr, sizeof (ifr)) < 0) {
perror ("setsockopt() failed to bind to interface ");
exit (EXIT_FAILURE);
}
// Send packet.
if (sendto (sd, packet, IP4_HDRLEN + ICMP_HDRLEN + datalen, 0, (struct sockaddr *) &sin, sizeof (struct sockaddr)) < 0) {
perror ("sendto() failed ");
exit (EXIT_FAILURE);
}
// Close socket descriptor.
close (sd);
// Free allocated memory.
free (data);
free (packet);
free (interface);
free (target);
free (src_ip);
free (dst_ip);
free (ip_flags);
return (EXIT_SUCCESS);
}
// Computing the internet checksum (RFC 1071).
// Note that the internet checksum does not preclude collisions.
uint16_t
checksum (uint16_t *addr, int len)
{
int count = len;
register uint32_t sum = 0;
uint16_t answer = 0;
// Sum up 2-byte values until none or only one byte left.
while (count > 1) {
sum += *(addr++);
count -= 2;
}
// Add left-over byte, if any.
if (count > 0) {
sum += *(uint8_t *) addr;
}
// Fold 32-bit sum into 16 bits; we lose information by doing this,
// increasing the chances of a collision.
// sum = (lower 16 bits) + (upper 16 bits shifted right 16 bits)
while (sum >> 16) {
sum = (sum & 0xffff) + (sum >> 16);
}
// Checksum is one's compliment of sum.
answer = ~sum;
return (answer);
}
// Allocate memory for an array of chars.
char *
allocate_strmem (int len)
{
void *tmp;
if (len <= 0) {
fprintf (stderr, "ERROR: Cannot allocate memory because len = %i in allocate_strmem().\n", len);
exit (EXIT_FAILURE);
}
tmp = (char *) malloc (len * sizeof (char));
if (tmp != NULL) {
memset (tmp, 0, len * sizeof (char));
return (tmp);
} else {
fprintf (stderr, "ERROR: Cannot allocate memory for array allocate_strmem().\n");
exit (EXIT_FAILURE);
}
}
// Allocate memory for an array of unsigned chars.
uint8_t *
allocate_ustrmem (int len)
{
void *tmp;
if (len <= 0) {
fprintf (stderr, "ERROR: Cannot allocate memory because len = %i in allocate_ustrmem().\n", len);
exit (EXIT_FAILURE);
}
tmp = (uint8_t *) malloc (len * sizeof (uint8_t));
if (tmp != NULL) {
memset (tmp, 0, len * sizeof (uint8_t));
return (tmp);
} else {
fprintf (stderr, "ERROR: Cannot allocate memory for array allocate_ustrmem().\n");
exit (EXIT_FAILURE);
}
}
// Allocate memory for an array of ints.
int *
allocate_intmem (int len)
{
void *tmp;
if (len <= 0) {
fprintf (stderr, "ERROR: Cannot allocate memory because len = %i in allocate_intmem().\n", len);
exit (EXIT_FAILURE);
}
tmp = (int *) malloc (len * sizeof (int));
if (tmp != NULL) {
memset (tmp, 0, len * sizeof (int));
return (tmp);
} else {
fprintf (stderr, "ERROR: Cannot allocate memory for array allocate_intmem().\n");
exit (EXIT_FAILURE);
}
}
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