how to measure the RSSI strength signal between peers using wifi direct?

there is no feature to measure the RSSI between peers in Wifi-direct, so how to get RSSI between them. actually i go under API for WIFI to see how they measure WIFI RSSI So i see that they send Command as parameter to native method, but i can't catch this command!!! in this method wifi_send_command in wifi.c from this link. as i know Android is under linux, the iwconfig is linux command to get the wireless information interface, if i used it can i get the Wifi direct information ? or it is just return the access points network information? anyone have any idea about this ?