hostapd: configure inter-AP communication interface for 802.11r

In setups using VLAN bridge filtering, hostapd may need to communicate using
a VLAN interface on top of the bridge, instead of using the bridge directly

Signed-off-by: Felix Fietkau <nbd@nbd.name>

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

@@ -805,6 +805,7 @@ hostapd_set_bss_options() {
 				;;
 			esac
 
+			[ -n "$network_ifname" ] && append bss_conf "ft_iface=$network_ifname" "$N"
 			append bss_conf "mobility_domain=$mobility_domain" "$N"
 			append bss_conf "ft_psk_generate_local=$ft_psk_generate_local" "$N"
 			append bss_conf "ft_over_ds=$ft_over_ds" "$N"

package/network/services/hostapd/patches/730-ft_iface.patch

@@ -0,0 +1,38 @@
+--- a/hostapd/config_file.c
++++ b/hostapd/config_file.c
+@@ -3031,6 +3031,8 @@ static int hostapd_config_fill(struct ho
+ 		wpa_printf(MSG_INFO,
+ 			   "Line %d: Obsolete peerkey parameter ignored", line);
+ #ifdef CONFIG_IEEE80211R_AP
++	} else if (os_strcmp(buf, "ft_iface") == 0) {
++		os_strlcpy(bss->ft_iface, pos, sizeof(bss->ft_iface));
+ 	} else if (os_strcmp(buf, "mobility_domain") == 0) {
+ 		if (os_strlen(pos) != 2 * MOBILITY_DOMAIN_ID_LEN ||
+ 		    hexstr2bin(pos, bss->mobility_domain,
+--- a/src/ap/ap_config.h
++++ b/src/ap/ap_config.h
+@@ -277,6 +277,7 @@ struct airtime_sta_weight {
+ struct hostapd_bss_config {
+ 	char iface[IFNAMSIZ + 1];
+ 	char bridge[IFNAMSIZ + 1];
++	char ft_iface[IFNAMSIZ + 1];
+ 	char vlan_bridge[IFNAMSIZ + 1];
+ 	char wds_bridge[IFNAMSIZ + 1];
+
+--- a/src/ap/wpa_auth_glue.c
++++ b/src/ap/wpa_auth_glue.c
+@@ -1565,8 +1565,12 @@ int hostapd_setup_wpa(struct hostapd_dat
+ 	    wpa_key_mgmt_ft(hapd->conf->wpa_key_mgmt)) {
+ 		const char *ft_iface;
+
+-		ft_iface = hapd->conf->bridge[0] ? hapd->conf->bridge :
+-			   hapd->conf->iface;
++		if (hapd->conf->ft_iface[0])
++			ft_iface = hapd->conf->ft_iface;
++		else if (hapd->conf->bridge[0])
++			ft_iface = hapd->conf->bridge;
++		else
++			ft_iface = hapd->conf->iface;
+ 		hapd->l2 = l2_packet_init(ft_iface, NULL, ETH_P_RRB,
+ 					  hostapd_rrb_receive, hapd, 1);
+ 		if (!hapd->l2) {