buffer overflow in arp (RHBZ #164695)

Steps to Reproduce:
1. arp -s 172.16.1.3 00:80:c8:04:05:06 -D eth0

arp.c

@@ -243,7 +243,7 @@ static int arp_getdevhw(char *ifname, struct sockaddr *sa, struct hwtype *hw)
     struct ifreq ifr;
     struct hwtype *xhw;
 
-    strcpy(ifr.ifr_name, ifname);
+    strncpy(ifr.ifr_name, ifname, IFNAMSIZ);
     if (ioctl(sockfd, SIOCGIFHWADDR, &ifr) < 0) {
 	fprintf(stderr, _("arp: cant get HW-Address for `%s': %s.\n"), ifname, strerror(errno));
 	return (-1);