VNET_DRING_REG_EXT_MSG_SIZE
msgsize = VNET_DRING_REG_EXT_MSG_SIZE(ldcp->rx_data_ncookies);
VNET_DRING_REG_EXT_MSG_SIZE(ldcp->tx_data_ncookies);
VNET_DRING_REG_EXT_MSG_SIZE(dp->data_ncookies);
VNET_DRING_REG_EXT_MSG_SIZE(lp->dringp->data_ncookies);
mp = kmem_zalloc(VNET_DRING_REG_EXT_MSG_SIZE(dp->data_ncookies),
VNET_DRING_REG_EXT_MSG_SIZE(VNET_DATA_AREA_COOKIES)