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

int mac_aton(char *addr, unsigned char *ptr){
int i, v[6];
if((i = sscanf(addr, "%x:%x:%x:%x:%x:%x", &v[0], &v[1], &v[2], &v[3],
&v[4], &v[5])) !=6){
fprintf(stderr, "arp: invalid Ethernet address '%s'\n", addr);
return(1);
        } /* End of If*/
for(i = 0; i < 6; i++){
ptr[i] = v[i];
        } /* End of For */
return(0);
}

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

if(argc < 3 || argc > 4){
fprintf(stderr, "usage: %s <ip_addr> <hw_addr> [temp|pub|perm|trail]\n",
argv[0]);
fprintf(stderr, "default: temp.\n");
exit(-1);
        } /* End of If */

int s, flags;
char *host = argv[1];

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

bzero((caddr_t)&req, sizeof(req)); /* caddr_t is not really needed. */

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);
        } /* End of If */
bcopy((char *)hp->h_addr, (char *)&sin->sin_addr, sizeof(sin->sin_addr));
        } /* End of If */

if(mac_aton(argv[2], req.arp_ha.sa_data)){ /* If address is valid... */
return(-1);
}

argc -=2;
argv +=2;

flags = ATF_PERM | ATF_COM;

while(argc-- > 0){
if(!(strncmp(argv[0], "temp", 4))){
flags &= ~ATF_PERM;
        } else if(!(strncmp(argv[0], "pub", 3))){
flags |= ATF_PUBL;
        } else if(!(strncmp(argv[0], "trail", 5))){
flags |= ATF_USETRAILERS;
        } else if(!(strncmp(argv[0], "dontpub", 7))){ /* Not working yet */
flags |= ATF_DONTPUB;
        } else if(!(strncmp(argv[0], "perm", 4))){
flags = ATF_PERM;
        } else {
flags &= ~ATF_PERM;
        } /* End of Else*/
argv++;
        }/* End of While */

req.arp_flags = flags; /* Finally, asign the flags to the structure */
strcpy(req.arp_dev, "eth0"); /* Asign the device.  */

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

if(ioctl(s, SIOCSARP, (caddr_t)&req) <0){ /* caddr_t not really needed. */
perror(host);
exit(-1);
        } /* End of If */

printf("ARP cache entry successfully added.\n");
close(s);
return(0);
}