code example for set a ARP entry (error, )

I try to write some code to set an ARP entry.

but the code at ioctl. alert a error: invalid argument.

WHY???


int setMac(char *dev, unsigned long ip, unsigned char *mac)
{
struct sockaddr addr;
struct sockaddr hw_addr;
struct arpreq req;
int sockfd, i;

/* default Mac to zero, in case we return an error */
memset(mac, '\0', 6);

memset(&addr, '\0', sizeof(addr));
addr.sa_family = AF_INET;
memcpy(&addr.sa_data[2], &ip, 4);

memset(&hw_addr, '\0', sizeof(hw_addr));
/*hw_addr.sa_family = ARPHRD_ETHER;*/
memcpy(hw_addr.sa_data, mac, 6);

memset(&req, '\0', sizeof(req));
memcpy(&req.arp_pa, &addr, sizeof(addr));
memcpy(&req.arp_dev[0], dev, sizeof(req.arp_dev));
memcpy(&req.arp_ha, &hw_addr, sizeof(hw_addr));

if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
{
printf("socket\n");
return (-1);
}

/* try to get an ARP mapping (if available)*/
if (ioctl(sockfd, SIOCSARP, (char *) &req) < 0)
{
printf("ioctl error:%s\n", strerror(errno));
close(sockfd);
return (-1);
}

close(sockfd);
return 0;
}

i solve it.

in the code.

req must designated ARP FALG.

req.arp_flags = ATF_PERM;


"Jesse Song" <(E-Mail Removed)> дÈëÏûÏ¢ÐÂÎÅ:dvocri$ps$(E-Mail Removed)...
>I try to write some code to set an ARP entry.
>
> but the code at ioctl. alert a error: invalid argument.
>
> WHY???
>
>
> int setMac(char *dev, unsigned long ip, unsigned char *mac)
> {
> struct sockaddr addr;
> struct sockaddr hw_addr;
> struct arpreq req;
> int sockfd, i;
>
> /* default Mac to zero, in case we return an error */
> memset(mac, '\0', 6);
>
> memset(&addr, '\0', sizeof(addr));
> addr.sa_family = AF_INET;
> memcpy(&addr.sa_data[2], &ip, 4);
>
> memset(&hw_addr, '\0', sizeof(hw_addr));
> /*hw_addr.sa_family = ARPHRD_ETHER;*/
> memcpy(hw_addr.sa_data, mac, 6);
>
> memset(&req, '\0', sizeof(req));
> memcpy(&req.arp_pa, &addr, sizeof(addr));
> memcpy(&req.arp_dev[0], dev, sizeof(req.arp_dev));
> memcpy(&req.arp_ha, &hw_addr, sizeof(hw_addr));
>
> if ((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
> {
> printf("socket\n");
> return (-1);
> }
>
> /* try to get an ARP mapping (if available)*/
> if (ioctl(sockfd, SIOCSARP, (char *) &req) < 0)
> {
> printf("ioctl error:%s\n", strerror(errno));
> close(sockfd);
> return (-1);
> }
>
> close(sockfd);
> return 0;
> }
>