#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <netdb.h>
#include <netinet/in.h>
#include <net/if.h>
#include <errno.h>
#include <sys/ioctl.h>
#include <sys/socket.h>
#include <net/if_arp.h>

char *mac_ntoa(unsigned char *ptr){
static char address[30];

sprintf(address, "%02X:%02X:%02X:%02X:%02X:%02X",
ptr[0], ptr[1], ptr[2], ptr[3], ptr[4], ptr[5]);

return(address);
} /* End of mac_ntoa */

void mac_aton(char *buffer, char *pointer){
int i;
char c, val;
for(i = 0; i < 6; i++){
if(!(c = tolower(*pointer++))){
fprintf(stderr, "Invalid MAC Address.\n");
exit(-1);
        }/* End of If*/
if(isdigit(c)){
val = c - '0';
        }/* End of If*/
else if(c >= 'a' && c <= 'f'){
val = c - 'a' + 10;
        }/* End of Else If*/
else{
fprintf(stderr, "Invalid MAC Address.\n");
exit(-1);
        }/* End of Else */
if(isdigit(c)){
val = c - '0';
        } /* End of If*/
else if(c >= 'a' && c <= 'f'){
val = c - 'a' + 10;
        } /* End of Else If*/
else{
fprintf(stderr, "Invalid MAC Address.\n");
exit(-1);
        } /*End of Else*/
*buffer++ |= val; /* Store into buffer */
if(*pointer == ':'){
pointer++;
        } /* End of If */
} /* End of For */
} /* End of mac_aton */


int main(int argc, char* argv[]){
int s;

struct arpreq req;
struct hostent *hp;
struct sockaddr_in *sin;

char *host = argv[1];

bzero((caddr_t)&req, sizeof(req));
sin = (struct sockaddr_in *)&req.arp_pa;
sin->sin_family = AF_INET;
sin->sin_addr.s_addr = inet_addr(host);
if(sin->sin_addr.s_addr ==-1){
if(!(hp = gethostbyname(host))){
fprintf(stderr, "arp: %s ", host);
herror((char *)NULL);
return(-1);
}
bcopy((char *)hp->h_addr, (char *)&sin->sin_addr, 
sizeof(sin->sin_addr));
}
strcpy(req.arp_dev, "eth0");
mac_aton(req.arp_ha.sa_data, argv[2]);

argc -=2;
argv +=2;

req.arp_flags = ATF_PERM;

while(argc-- > 0){
if(!(strncmp(argv[0], "temp", 4))){
req.arp_flags &= ~ATF_PERM;
    } else if (!(strncmp(argv[0], "pub", 3))){
req.arp_flags |= ATF_PUBL;
    } else if (!(strncmp(argv[0], "trail", 5))){
req.arp_flags |= ATF_USETRAILERS;
}
argv++;
}/* End of While */

if((s = socket(AF_INET, SOCK_DGRAM, 0)) < 0){
perror("socket() failed.");
exit(-1);
}

if(ioctl(s, SIOCSARP, (caddr_t)&req) <0){
perror(host);
exit(-1);
}
printf("added.\n");
close(s);
return(0);
}

root@host:~# ./a.out 192.168.0.2 AA:BB:CC:DD:EE:FF temp
192.168.0.2: Invalid argument