---- a/hostapd/config_file.c
-+++ b/hostapd/config_file.c
-@@ -2648,6 +2648,10 @@ static int hostapd_config_fill(struct ho
- line);
- return 1;
- }
-+ } else if (os_strcmp(buf, "dynamic_ht40") == 0) {
-+ conf->dynamic_ht40 = atoi(pos);
-+ if (conf->dynamic_ht40 == 1)
-+ conf->dynamic_ht40 = 1500;
- } else if (os_strcmp(buf, "require_ht") == 0) {
- conf->require_ht = atoi(pos);
- } else if (os_strcmp(buf, "obss_interval") == 0) {
---- a/src/ap/ap_config.h
-+++ b/src/ap/ap_config.h
-@@ -580,6 +580,7 @@ struct hostapd_config {
- int ieee80211n;
- int secondary_channel;
- int require_ht;
-+ int dynamic_ht40;
- int obss_interval;
- u32 vht_capab;
- int ieee80211ac;
---- a/src/ap/hostapd.c
-+++ b/src/ap/hostapd.c
-@@ -22,6 +22,7 @@
- #include "beacon.h"
- #include "iapp.h"
- #include "ieee802_1x.h"
-+#include "ieee802_11.h"
- #include "ieee802_11_auth.h"
- #include "vlan_init.h"
- #include "wpa_auth.h"
-@@ -328,6 +329,7 @@ static void hostapd_cleanup(struct hosta
- static void hostapd_cleanup_iface_partial(struct hostapd_iface *iface)
- {
- wpa_printf(MSG_DEBUG, "%s(%p)", __func__, iface);
-+ hostapd_deinit_ht(iface);
- hostapd_free_hw_features(iface->hw_features, iface->num_hw_features);
- iface->hw_features = NULL;
- os_free(iface->current_rates);
---- a/src/ap/hostapd.h
-+++ b/src/ap/hostapd.h
-@@ -330,6 +330,9 @@ struct hostapd_iface {
- /* Overlapping BSS information */
- int olbc_ht;
-
-+ int force_20mhz;
-+ struct os_time last_20mhz_trigger;
-+
- u16 ht_op_mode;
-
- /* surveying helpers */
---- a/src/ap/ieee802_11.c
-+++ b/src/ap/ieee802_11.c
-@@ -1556,6 +1556,9 @@ static void handle_beacon(struct hostapd
- sizeof(mgmt->u.beacon)), &elems,
- 0);
-
-+ if (!elems.ht_capabilities)
-+ hostapd_trigger_20mhz(hapd->iface);
-+
- ap_list_process_beacon(hapd->iface, mgmt, &elems, fi);
- }
-
---- a/src/ap/ieee802_11.h
-+++ b/src/ap/ieee802_11.h
-@@ -83,4 +83,17 @@ int hostapd_update_time_adv(struct hosta
- void hostapd_client_poll_ok(struct hostapd_data *hapd, const u8 *addr);
- u8 * hostapd_eid_bss_max_idle_period(struct hostapd_data *hapd, u8 *eid);
-
-+#ifdef CONFIG_IEEE80211N
-+void hostapd_trigger_20mhz(struct hostapd_iface *iface);
-+void hostapd_deinit_ht(struct hostapd_iface *iface);
-+
-+#else
-+static inline void hostapd_deinit_ht(struct hostapd_iface *iface)
-+{
-+}
-+static inline void hostapd_trigger_20mhz(struct hostapd_iface *iface)
-+{
-+}
-+#endif /* CONFIG_IEEE80211N */
-+
- #endif /* IEEE802_11_H */
---- a/src/ap/ieee802_11_ht.c
-+++ b/src/ap/ieee802_11_ht.c
-@@ -13,9 +13,11 @@
- #include "common/ieee802_11_defs.h"
- #include "hostapd.h"
- #include "ap_config.h"
-+#include "ap_drv_ops.h"
- #include "sta_info.h"
- #include "beacon.h"
- #include "ieee802_11.h"
-+#include "utils/eloop.h"
-
-
- u8 * hostapd_eid_ht_capabilities(struct hostapd_data *hapd, u8 *eid)
-@@ -92,6 +94,9 @@ u8 * hostapd_eid_ht_operation(struct hos
-
- oper->primary_chan = hapd->iconf->channel;
- oper->operation_mode = host_to_le16(hapd->iface->ht_op_mode);
-+ if (hapd->iface->force_20mhz)
-+ goto skip;
-+
- if (hapd->iconf->secondary_channel == 1)
- oper->ht_param |= HT_INFO_HT_PARAM_SECONDARY_CHNL_ABOVE |
- HT_INFO_HT_PARAM_STA_CHNL_WIDTH;
-@@ -99,6 +104,7 @@ u8 * hostapd_eid_ht_operation(struct hos
- oper->ht_param |= HT_INFO_HT_PARAM_SECONDARY_CHNL_BELOW |
- HT_INFO_HT_PARAM_STA_CHNL_WIDTH;
-
-+skip:
- pos += sizeof(*oper);
-
- return pos;
-@@ -288,3 +294,84 @@ void hostapd_get_ht_capab(struct hostapd
-
- neg_ht_cap->ht_capabilities_info = host_to_le16(cap);
- }
-+
-+static void hostapd_set_force_20mhz(struct hostapd_iface *iface);
-+
-+static void hostapd_restore_40mhz(void *eloop_data, void *user_ctx)
-+{
-+ struct hostapd_iface *iface = eloop_data;
-+ struct os_time time;
-+ int timeout;
-+
-+ if (!iface->last_20mhz_trigger.sec)
-+ return;
-+
-+ os_get_time(&time);
-+ timeout = iface->last_20mhz_trigger.sec + iface->conf->dynamic_ht40 -
-+ time.sec;
-+
-+ if (timeout > 0) {
-+ eloop_register_timeout(timeout, 0, hostapd_restore_40mhz,
-+ iface, NULL);
-+ return;
-+ }
-+
-+ iface->last_20mhz_trigger.sec = 0;
-+ iface->last_20mhz_trigger.usec = 0;
-+
-+ iface->force_20mhz = 0;
-+ hostapd_set_force_20mhz(iface);
-+}
-+
-+static void hostapd_set_force_20mhz(struct hostapd_iface *iface)
-+{
-+ int secondary_channel;
-+ int i;
-+
-+ ieee802_11_set_beacons(iface);
-+
-+ for (i = 0; i < iface->num_bss; i++) {
-+ struct hostapd_data *hapd = iface->bss[i];
-+
-+ if (iface->force_20mhz)
-+ secondary_channel = 0;
-+ else
-+ secondary_channel = hapd->iconf->secondary_channel;
-+
-+ if (hostapd_set_freq(hapd, hapd->iconf->hw_mode, iface->freq,
-+ hapd->iconf->channel,
-+ hapd->iconf->ieee80211n,
-+ hapd->iconf->ieee80211ac,
-+ secondary_channel,
-+ hapd->iconf->vht_oper_chwidth,
-+ hapd->iconf->vht_oper_centr_freq_seg0_idx,
-+ hapd->iconf->vht_oper_centr_freq_seg1_idx)) {
-+ wpa_printf(MSG_ERROR, "Could not set channel for "
-+ "kernel driver");
-+ }
-+ }
-+}
-+
-+void hostapd_deinit_ht(struct hostapd_iface *iface)
-+{
-+ eloop_cancel_timeout(hostapd_restore_40mhz, iface, NULL);
-+}
-+
-+void hostapd_trigger_20mhz(struct hostapd_iface *iface)
-+{
-+ if (!iface->conf->dynamic_ht40)
-+ return;
-+
-+ if (!iface->force_20mhz) {
-+ iface->force_20mhz = 1;
-+ hostapd_set_force_20mhz(iface);
-+ }
-+
-+ if (!iface->last_20mhz_trigger.sec) {
-+ eloop_cancel_timeout(hostapd_restore_40mhz, iface, NULL);
-+ eloop_register_timeout(iface->conf->dynamic_ht40, 0,
-+ hostapd_restore_40mhz, iface, NULL);
-+ }
-+
-+ os_get_time(&iface->last_20mhz_trigger);
-+}