Title: eth_set_rec_conf ()
eth_set_rec_conf() sends a message requesting the ethernet task to change the receiving capabilities for an ethernet port. For example, if an ethernet file descriptor is being configured to receive broadcasts, eth_set_rec_conf() will send a message to the ethernet task requesting that broadcast packets for the port be accepted.
Note that eth_set_rec_conf() is called by eth_ioctl() for a NWIOSETHOPT (NetWork IO Set ETHernet OPTions) request. Since only root can open and configure the device file /dev/eth, only root can configure an ethernet file descriptor and, therefore, only root is able to place the ethernet card in promiscuous mode.