SEND_LOCK;
   t = libnet_build_arp(
           ARPHRD_ETHER,            /* hardware addr */
           ETHERTYPE_IP,            /* protocol addr */
           MEDIA_ADDR_LEN,          /* hardware addr size */
           IP_ADDR_LEN,             /* protocol addr size */
           type,                    /* operation type */
           smac,                    /* sender hardware addr */
           (u_char *)&(sip->addr),  /* sender protocol addr */
           tmac,                    /* target hardware addr */
           (u_char *)&(tip->addr),  /* target protocol addr */
           NULL,                    /* payload */
           0,                       /* payload size */
           GBL_IFACE->lnet,          /* libnet handle */
           0);                      /* pblock id */
//check return value, no problems here
c = libnet_write(l);
if (c == -1)
//BADLY EXIT
/* clear the pblock */
libnet_clear_packet(GBL_IFACE->lnet);
SEND_UNLOCK;