DFS: Sanitize channel availability checks

Fixes corner case of holes in channel list and simplifies availability
checks.

Signed-hostap: Michal Kazior <michal.kazior@tieto.com>

diff --git a/src/ap/dfs.c b/src/ap/dfs.c
index 6a16306c5c825d4fb507df3a31ef78e89fb50866..736f2344d26b555b717ded11c5735315f220942c 100644 (file)
--- a/src/ap/dfs.c
+++ b/src/ap/dfs.c
@@ -94,6 +94,31 @@ static int dfs_is_chan_allowed(struct hostapd_channel_data *chan, int n_chans)
 }
 
 
+static int dfs_chan_range_available(struct hostapd_hw_modes *mode,
+                                   int first_chan_idx, int num_chans)
+{
+       struct hostapd_channel_data *first_chan, *chan;
+       int i;
+
+       if (first_chan_idx + num_chans >= mode->num_channels)
+               return 0;
+
+       first_chan = &mode->channels[first_chan_idx];
+
+       for (i = 0; i < num_chans; i++) {
+               chan = &mode->channels[first_chan_idx + i];
+
+               if (first_chan->freq + i * 20 != chan->freq)
+                       return 0;
+
+               if (!dfs_channel_available(chan))
+                       return 0;
+       }
+
+       return 1;
+}
+
+
 /*
  * The function assumes HT40+ operation.
  * Make sure to adjust the following variables after calling this:
@@ -106,8 +131,8 @@ static int dfs_find_channel(struct hostapd_data *hapd,
                            int idx)
 {
        struct hostapd_hw_modes *mode;
-       struct hostapd_channel_data *chan, *next_chan;
-       int i, j, channel_idx = 0, n_chans;
+       struct hostapd_channel_data *chan;
+       int i, channel_idx = 0, n_chans;
 
        mode = hapd->iface->current_mode;
        n_chans = dfs_get_used_n_chans(hapd);
@@ -116,24 +141,15 @@ static int dfs_find_channel(struct hostapd_data *hapd,
        for (i = 0; i < mode->num_channels; i++) {
                chan = &mode->channels[i];
 
-               /* Skip not available channels */
-               if (!dfs_channel_available(chan))
+               /* Skip HT40/VHT incompatible channels */
+               if (hapd->iconf->ieee80211n &&
+                   hapd->iconf->secondary_channel &&
+                   !dfs_is_chan_allowed(chan, n_chans))
                        continue;
 
-               /* Skip HT40/VHT uncompatible channels */
-               if (hapd->iconf->ieee80211n &&
-                   hapd->iconf->secondary_channel) {
-                       if (!dfs_is_chan_allowed(chan, n_chans))
-                               continue;
-
-                       for (j = 1; j < n_chans; j++) {
-                               next_chan = &mode->channels[i + j];
-                               if (!dfs_channel_available(next_chan))
-                                       break;
-                       }
-                       if (j != n_chans)
-                               continue;
-               }
+               /* Skip incompatible chandefs */
+               if (!dfs_chan_range_available(mode, i, n_chans))
+                       continue;
 
                if (ret_chan && idx == channel_idx) {
                        wpa_printf(MSG_DEBUG, "Selected ch. #%d", chan->chan);