hostapd: fix IEEE 802.11r (fast roaming) defaults

Use ft_psk_generate_local=1 by default, as it makes everything else fairly
trivial. All of the r0kh/r1kh and key management stuff goes away and hostapd
fairly much does it all	for us.

We do need to provide nas_identifier, which can	be derived from	the BSSID,
and we need to generate	a mobility_domain, for which we	default	to the first
four chars of the md5sum of the	SSID.

The complex manual setup should also still work, but the defaults also
now work easily out of the box. Verified by manually running hostapd
(with the autogenerated config) and watching the debug output:

wlan2: STA ac:37:43:a0:a6:ae WPA: FT authentication already completed - do not start 4-way handshake

 This was previous submitted to LEDE in
 https://github.com/lede-project/source/pull/1382

[dwmw2: Rewrote commit message]
Signed-off-by: Gospod Nassa <devianca@gmail.com>
Signed-off-by: David Woodhouse <dwmw2@infradead.org>

package/network/services/hostapd/files/hostapd.sh

@@ -422,32 +422,38 @@ hostapd_set_bss_options() {
 		set_default ieee80211r 0
 
 		if [ "$ieee80211r" -gt "0" ]; then
-			json_get_vars mobility_domain r0_key_lifetime r1_key_holder \
-				reassociation_deadline pmk_r1_push ft_psk_generate_local ft_over_ds
-			json_get_values r0kh r0kh
-			json_get_values r1kh r1kh
+			json_get_vars mobility_domain ft_psk_generate_local ft_over_ds reassociation_deadline
 			
-			set_default mobility_domain "4f57"
-			set_default r0_key_lifetime 10000
-			set_default reassociation_deadline 1000
-			set_default pmk_r1_push 0
-			set_default ft_psk_generate_local 0
+			set_default mobility_domain "$(echo "$ssid" | md5sum | head -c 4)"
+			set_default ft_psk_generate_local 1
 			set_default ft_over_ds 1
+			set_default reassociation_deadline 1000
 
 			append bss_conf "mobility_domain=$mobility_domain" "$N"
-			append bss_conf "r0_key_lifetime=$r0_key_lifetime" "$N"
-			[ -n "$r1_key_holder" ] && append bss_conf "r1_key_holder=$r1_key_holder" "$N"
-			append bss_conf "reassociation_deadline=$reassociation_deadline" "$N"
-			append bss_conf "pmk_r1_push=$pmk_r1_push" "$N"
 			append bss_conf "ft_psk_generate_local=$ft_psk_generate_local" "$N"
 			append bss_conf "ft_over_ds=$ft_over_ds" "$N"
-
-			for kh in $r0kh; do
-				append bss_conf "r0kh=${kh//,/ }" "$N"
-			done
-			for kh in $r1kh; do
-				append bss_conf "r1kh=${kh//,/ }" "$N"
-			done
+			append bss_conf "reassociation_deadline=$reassociation_deadline" "$N"
+			[ -n "$nasid" ] || append bss_conf "nas_identifier=${macaddr//\:}" "$N"
+
+			if [ "$ft_psk_generate_local" -eq "0" ]; then
+				json_get_vars r0_key_lifetime r1_key_holder pmk_r1_push
+				json_get_values r0kh r0kh
+				json_get_values r1kh r1kh
+
+				set_default r0_key_lifetime 10000
+				set_default pmk_r1_push 0
+
+				[ -n "$r1_key_holder" ] && append bss_conf "r1_key_holder=$r1_key_holder" "$N"
+				append bss_conf "r0_key_lifetime=$r0_key_lifetime" "$N"
+				append bss_conf "pmk_r1_push=$pmk_r1_push" "$N"
+
+				for kh in $r0kh; do
+					append bss_conf "r0kh=${kh//,/ }" "$N"
+				done
+				for kh in $r1kh; do
+					append bss_conf "r1kh=${kh//,/ }" "$N"
+				done
+			fi
 		fi
 
 		append bss_conf "wpa_disable_eapol_key_retries=$wpa_disable_eapol_key_retries" "$N"