141 lines
4.1 KiB
C
141 lines
4.1 KiB
C
/* arp/simple_request.c */
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#include "arp.h"
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int main(int argc, char **argv)
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{
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/* ARGUMENT PARSING
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- network interface to use
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- target IP address
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*/
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if (argc < 3) {
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printf("[FAIL] Too few arguments\n"
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"Usage: %s <interface> <target IP address>\n", argv[0]);
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exit(EXIT_FAILURE);
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}
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char *if_name = argv[1];
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char *target_ip_string = argv[2];
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struct in_addr target_ip;
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if (!inet_pton(AF_INET, target_ip_string, &target_ip)) {
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perror("[FAIL] inet_pton() (badly formatted IP address)");
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exit(EXIT_FAILURE);
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}
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printf("ARP request for IP address %s on interface %s\n",
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target_ip_string, if_name);
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/* ====================================================================== */
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/* RAW SOCKET CREATION */
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/* We open the raw socket */
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/* AF_PACKET: This is a raw Ethernet packet (Linux only, requires root)
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SOCK_DGRAM: The link-layer header is constructed automatically
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(to build it ourselves, we could have used SOCK_RAW)
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ETH_P_ALL: We want to listen to every EtherType (here, we could
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also have chosen ETH_P_ARP) */
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int sockfd = socket(AF_PACKET, SOCK_DGRAM, htons(ETH_P_ARP));
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if (sockfd < 0) {
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perror("[FAIL] socket()");
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exit(EXIT_FAILURE);
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}
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#ifdef DEBUG
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printf("[OK] Raw Ethernet socket started successfully\n");
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#endif
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/* ====================================================================== */
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/* INFORMATION ON THE LOCAL COMPUTER:
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- index number of the network interface
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- local IP address
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- local MAC address
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*/
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/* Since this is very low-level, we can't use the usual interface
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name (e.g. "eth0"), so we need to get the index number of the
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ethernet interface. */
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//char *if_name = "wlp3s0"; /* Change this if needed */
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struct ifreq ifrindex;
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size_t if_name_len = strlen(if_name);
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if (if_name_len < sizeof(ifrindex.ifr_name)) {
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memcpy(ifrindex.ifr_name, if_name, if_name_len);
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ifrindex.ifr_name[if_name_len] = 0;
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}
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else {
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printf("[FAIL] Error: interface name is too long\n");
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}
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/* We use ioctl() with SIOCGIFINDEX */
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if (ioctl(sockfd, SIOCGIFINDEX, &ifrindex) == -1) {
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perror("[FAIL] ioctl()");
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exit(EXIT_FAILURE);
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}
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int ifindex = ifrindex.ifr_ifindex;
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#ifdef DEBUG
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printf("[OK] Index number of the Ethernet interface %s: %d\n", if_name, ifindex);
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#endif
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/* We get our IP address using ioctl() and SIOCGIFADDR */
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struct ifreq ifraddr;
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if (if_name_len < sizeof(ifraddr.ifr_name)) {
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memcpy(ifraddr.ifr_name, if_name, if_name_len);
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ifraddr.ifr_name[if_name_len] = 0;
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}
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else {
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printf("[FAIL] Error: interface name is too long\n");
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}
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if (ioctl(sockfd, SIOCGIFADDR, &ifraddr) == -1) {
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perror("[FAIL] ioctl()");
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exit(EXIT_FAILURE);
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}
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struct sockaddr_in *ipaddr = (struct sockaddr_in *) &ifraddr.ifr_addr;
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char local_ip_string[16];
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if (!inet_ntop(AF_INET, &ipaddr->sin_addr, local_ip_string, sizeof(local_ip_string))) {
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perror("[FAIL] inet_ntop()");
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exit(EXIT_FAILURE);
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}
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#ifdef DEBUG
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printf("[OK] Local IP address: %s\n", local_ip_string);
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#endif
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/* We get the MAC address using ioctl() (again) with SIOCGIFHWADDR */
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struct ifreq ifrhwaddr;
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if (if_name_len < sizeof(ifrhwaddr.ifr_name)) {
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memcpy(ifrhwaddr.ifr_name, if_name, if_name_len);
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ifrhwaddr.ifr_name[if_name_len] = 0;
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}
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else {
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printf("[FAIL] Error: interface name is too long\n");
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}
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if (ioctl(sockfd, SIOCGIFHWADDR, &ifrhwaddr) == -1) {
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perror("[FAIL] ioctl()");
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exit(EXIT_FAILURE);
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}
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unsigned char *macaddr = (unsigned char *) &ifrhwaddr.ifr_hwaddr.sa_data;
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#ifdef DEBUG
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printf("[OK] Local MAC address: %02x:%02x:%02x:%02x:%02x:%02x\n",
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macaddr[0], macaddr[1], macaddr[2], macaddr[3], macaddr[4], macaddr[5]);
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#endif
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/* ====================================================================== */
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send_arp_request(sockfd, ifindex, ipaddr, macaddr, target_ip);
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/* ====================================================================== */
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/* We listens to the answer */
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struct ether_arp *result = malloc(sizeof(struct ether_arp));
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listen_arp_frame(sockfd, result);
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exit(EXIT_SUCCESS);
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}
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