c/arp/arp.c

   1 #define _DEFAULT_SOURCE 1
   2 #define _POSIX_C_SOURCE 200809L
   3 #define _XOPEN_SOURCE 700
   4
   5 #include <stdio.h>
   6 #include <endian.h>
   7 #include <unistd.h>
   8 #include <stdint.h>
   9 #include <arpa/inet.h>
  10 #include <sys/ioctl.h>
  11 #include <string.h>
  12 #include <net/if_arp.h>
  13
  14 uint64_t arp_ip2mac(const char *dev, const char *ip) {
  15   int ret;
  16   struct arpreq arpreq;
  17   int iArpFD;
  18
  19   struct sockaddr_in *sin = (struct sockaddr_in *) &arpreq.arp_pa;
  20   uint64_t mac = 0;
  21
  22   memset(&arpreq, 0, sizeof(struct arpreq));
  23
  24   strcpy(arpreq.arp_dev, dev);
  25   //sprintf(arpreq.arp_dev, "eth-pub.%d", vlan);
  26
  27   iArpFD = socket(AF_INET, SOCK_DGRAM, 0);
  28   if (iArpFD == -1)
  29   {
  30     printf("Cannot open packet socket");
  31     return 0;
  32   }
  33
  34   struct timeval tv = {
  35     .tv_sec = 0,
  36     .tv_usec = 200000
  37   };
  38   setsockopt(iArpFD, SOL_SOCKET, SO_RCVTIMEO,&tv,sizeof(struct timeval));
  39
  40   sin->sin_family = AF_INET;
  41   sin->sin_addr.s_addr = inet_addr(ip);
  42   sin->sin_port = htons(4242);
  43
  44   sendto(iArpFD, "PING", 4, MSG_NOSIGNAL,
  45                (struct sockaddr*) sin, sizeof(struct sockaddr_in));
  46
  47
  48   char blah[5];
  49   if(recvfrom(iArpFD, blah, sizeof(blah), 0,
  50     (struct sockaddr *) sin, (socklen_t * restrict) sizeof(struct sockaddr)) < 0)
  51   {
  52     //printf("UDP ping timeout\n");
  53   }
  54
  55   ret = ioctl(iArpFD, SIOCGARP, &arpreq);
  56   close(iArpFD);
  57
  58   if(ret < 0) {
  59     printf("RET: %d FAMILY: %d\n", ret, arpreq.arp_ha.sa_family);
  60     perror("SIOCGARP");
  61     return 0;
  62   }
  63
  64   memcpy(&mac, &arpreq.arp_ha.sa_data[0], 6);
  65   mac = be64toh(mac<<16);
  66
  67   return mac;
  68 }
  69
  70 int main() {
  71   char *dev = "eth0";
  72   char *ip = "10.10.161.3";
  73   uint64_t mac = arp_ip2mac(dev, ip);
  74
  75   printf("DEV %s IP %s MAC: %.12lX %s\n", dev, ip, mac, mac?"OK":"FAIL");
  76 }
  77