Document passive_scan option for wpa_supplicant.conf

This should save the next person to need this behavior some time.

Signed-off-by: Ben Greear <greearb@candelatech.com>

wpa_supplicant/wpa_supplicant.conf

@@ -118,6 +118,25 @@ eapol_version=1
 # networks are found, a new IBSS or AP mode network is created.
 ap_scan=1
 
+# Whether to force passive scan for network connection
+#
+# By default, scans will send out Probe Request frames on channels that allow
+# active scanning. This advertise the local station to the world. Normally this
+# is fine, but users may wish to do passive scanning where the radio should only
+# listen quietly for Beacon frames and not send any Probe Request frames. Actual
+# functionality may be driver dependent.
+#
+# This parameter can be used to force only passive scanning to be used
+# for network connection cases. It should be noted that this will slow
+# down scan operations and reduce likelihood of finding the AP. In
+# addition, some use cases will override this due to functional
+# requirements, e.g., for finding an AP that uses hidden SSID
+# (scan_ssid=1) or P2P device discovery.
+#
+# 0:  Do normal scans (allow active scans) (default)
+# 1:  Do passive scans.
+#passive_scan=0
+
 # MPM residency
 # By default, wpa_supplicant implements the mesh peering manager (MPM) for an
 # open mesh. However, if the driver can implement the MPM, you may set this to