hostapd: Fix to downgrade bandwidth in radar detection

Upon radar detection we used to search channels with the same bandwidth.
This way we might not find any other channels. If there are no channels
available with that bandwidth the AP service will be stopped. To avoid
this problem, also search a suitable channel by downgrading the
bandwidth. This scenario is applicable during CAC as well.

Signed-off-by: Seevalamuthu Mariappan <seevalam@codeaurora.org>

diff --git a/src/ap/dfs.c b/src/ap/dfs.c
index 554231e189f15e240e21a07c43aebf2bb0872d1b..d0b448e2958fcd4dc894d27f27ac01211bb2e982 100644 (file)
--- a/src/ap/dfs.c
+++ b/src/ap/dfs.c
@@ -851,6 +851,41 @@ int hostapd_dfs_pre_cac_expired(struct hostapd_iface *iface, int freq,
 }
 
 
+static struct hostapd_channel_data *
+dfs_downgrade_bandwidth(struct hostapd_iface *iface, int *secondary_channel,
+                       u8 *oper_centr_freq_seg0_idx,
+                       u8 *oper_centr_freq_seg1_idx, int *skip_radar)
+{
+       struct hostapd_channel_data *channel;
+
+       for (;;) {
+               channel = dfs_get_valid_channel(iface, secondary_channel,
+                                               oper_centr_freq_seg0_idx,
+                                               oper_centr_freq_seg1_idx,
+                                               *skip_radar);
+               if (channel) {
+                       wpa_printf(MSG_DEBUG, "DFS: Selected channel: %d",
+                                  channel->chan);
+                       return channel;
+               }
+
+               if (*skip_radar) {
+                       *skip_radar = 0;
+               } else {
+                       if (iface->conf->vht_oper_chwidth == CHANWIDTH_USE_HT)
+                               break;
+                       *skip_radar = 1;
+                       iface->conf->vht_oper_chwidth--;
+               }
+       }
+
+       wpa_printf(MSG_INFO,
+                  "%s: no DFS channels left, waiting for NOP to finish",
+                  __func__);
+       return NULL;
+}
+
+
 static int hostapd_dfs_start_channel_switch_cac(struct hostapd_iface *iface)
 {
        struct hostapd_channel_data *channel;
@@ -868,8 +903,14 @@ static int hostapd_dfs_start_channel_switch_cac(struct hostapd_iface *iface)
                                        skip_radar);
 
        if (!channel) {
-               wpa_printf(MSG_ERROR, "No valid channel available");
-               return err;
+               channel = dfs_downgrade_bandwidth(iface, &secondary_channel,
+                                                 &oper_centr_freq_seg0_idx,
+                                                 &oper_centr_freq_seg1_idx,
+                                                 &skip_radar);
+               if (!channel) {
+                       wpa_printf(MSG_ERROR, "No valid channel available");
+                       return err;
+               }
        }
 
        wpa_printf(MSG_DEBUG, "DFS will switch to a new channel %d",
@@ -898,11 +939,13 @@ static int hostapd_dfs_start_channel_switch(struct hostapd_iface *iface)
        int secondary_channel;
        u8 oper_centr_freq_seg0_idx;
        u8 oper_centr_freq_seg1_idx;
+       u8 new_vht_oper_chwidth;
        int skip_radar = 1;
        struct csa_settings csa_settings;
        unsigned int i;
        int err = 1;
        struct hostapd_hw_modes *cmode = iface->current_mode;
+       u8 current_vht_oper_chwidth = iface->conf->vht_oper_chwidth;
 
        wpa_printf(MSG_DEBUG, "%s called (CAC active: %s, CSA active: %s)",
                   __func__, iface->cac_started ? "yes" : "no",
@@ -936,28 +979,25 @@ static int hostapd_dfs_start_channel_switch(struct hostapd_iface *iface)
                 * requires to perform a CAC first.
                 */
                skip_radar = 0;
-               channel = dfs_get_valid_channel(iface, &secondary_channel,
-                                               &oper_centr_freq_seg0_idx,
-                                               &oper_centr_freq_seg1_idx,
-                                               skip_radar);
-               if (!channel) {
-                       wpa_printf(MSG_INFO,
-                                  "%s: no DFS channels left, waiting for NOP to finish",
-                                  __func__);
+               channel = dfs_downgrade_bandwidth(iface, &secondary_channel,
+                                                 &oper_centr_freq_seg0_idx,
+                                                 &oper_centr_freq_seg1_idx,
+                                                 &skip_radar);
+               if (!channel)
                        return err;
+               if (!skip_radar) {
+                       iface->freq = channel->freq;
+                       iface->conf->channel = channel->chan;
+                       iface->conf->secondary_channel = secondary_channel;
+                       hostapd_set_oper_centr_freq_seg0_idx(
+                               iface->conf, oper_centr_freq_seg0_idx);
+                       hostapd_set_oper_centr_freq_seg1_idx(
+                               iface->conf, oper_centr_freq_seg1_idx);
+
+                       hostapd_disable_iface(iface);
+                       hostapd_enable_iface(iface);
+                       return 0;
                }
-
-               iface->freq = channel->freq;
-               iface->conf->channel = channel->chan;
-               iface->conf->secondary_channel = secondary_channel;
-               hostapd_set_oper_centr_freq_seg0_idx(iface->conf,
-                                                    oper_centr_freq_seg0_idx);
-               hostapd_set_oper_centr_freq_seg1_idx(iface->conf,
-                                                    oper_centr_freq_seg1_idx);
-
-               hostapd_disable_iface(iface);
-               hostapd_enable_iface(iface);
-               return 0;
        }
 
        wpa_printf(MSG_DEBUG, "DFS will switch to a new channel %d",
@@ -966,6 +1006,9 @@ static int hostapd_dfs_start_channel_switch(struct hostapd_iface *iface)
                "freq=%d chan=%d sec_chan=%d", channel->freq,
                channel->chan, secondary_channel);
 
+       new_vht_oper_chwidth = iface->conf->vht_oper_chwidth;
+       iface->conf->vht_oper_chwidth = current_vht_oper_chwidth;
+
        /* Setup CSA request */
        os_memset(&csa_settings, 0, sizeof(csa_settings));
        csa_settings.cs_count = 5;
@@ -980,7 +1023,7 @@ static int hostapd_dfs_start_channel_switch(struct hostapd_iface *iface)
                                      iface->conf->ieee80211ac,
                                      iface->conf->ieee80211ax,
                                      secondary_channel,
-                                     hostapd_get_oper_chwidth(iface->conf),
+                                     new_vht_oper_chwidth,
                                      oper_centr_freq_seg0_idx,
                                      oper_centr_freq_seg1_idx,
                                      cmode->vht_capab,
@@ -1004,6 +1047,7 @@ static int hostapd_dfs_start_channel_switch(struct hostapd_iface *iface)
                iface->freq = channel->freq;
                iface->conf->channel = channel->chan;
                iface->conf->secondary_channel = secondary_channel;
+               iface->conf->vht_oper_chwidth = new_vht_oper_chwidth;
                hostapd_set_oper_centr_freq_seg0_idx(iface->conf,
                                                     oper_centr_freq_seg0_idx);
                hostapd_set_oper_centr_freq_seg1_idx(iface->conf,