Validate HT40 channel pair validity based on IEEE 802.11n Annex J

diff --git a/hostapd/hw_features.c b/hostapd/hw_features.c
index 6cf0437..7d41803 100644 (file)
--- a/hostapd/hw_features.c
+++ b/hostapd/hw_features.c
@@ -170,6 +170,73 @@ static int hostapd_prepare_rates(struct hostapd_data *hapd,
 }
 
 
+#ifdef CONFIG_IEEE80211N
+static int ieee80211n_allowed_ht40_channel_pair(struct hostapd_iface *iface)
+{
+       int sec_chan, ok, j, first;
+       int allowed[] = { 36, 44, 52, 60, 100, 108, 116, 124, 132, 149, 157,
+                         184, 192 };
+       size_t k;
+
+       if (!iface->conf->secondary_channel)
+               return 1; /* HT40 not used */
+
+       sec_chan = iface->conf->channel + iface->conf->secondary_channel * 4;
+       wpa_printf(MSG_DEBUG, "HT40: control channel: %d  "
+                  "secondary channel: %d",
+                  iface->conf->channel, sec_chan);
+
+       /* Verify that HT40 secondary channel is an allowed 20 MHz
+        * channel */
+       ok = 0;
+       for (j = 0; j < iface->current_mode->num_channels; j++) {
+               struct hostapd_channel_data *chan =
+                       &iface->current_mode->channels[j];
+               if (!(chan->flag & HOSTAPD_CHAN_DISABLED) &&
+                   chan->chan == sec_chan) {
+                       ok = 1;
+                       break;
+               }
+       }
+       if (!ok) {
+               wpa_printf(MSG_ERROR, "HT40 secondary channel %d not allowed",
+                          sec_chan);
+               return 0;
+       }
+
+       /*
+        * Verify that HT40 primary,secondary channel pair is allowed per
+        * IEEE 802.11n Annex J. This is only needed for 5 GHz band since
+        * 2.4 GHz rules allow all cases where the secondary channel fits into
+        * the list of allowed channels (already checked above).
+        */
+       if (iface->current_mode->mode != HOSTAPD_MODE_IEEE80211A)
+               return 1;
+
+       if (iface->conf->secondary_channel > 0)
+               first = iface->conf->channel;
+       else
+               first = sec_chan;
+
+       ok = 0;
+       for (k = 0; k < sizeof(allowed) / sizeof(allowed[0]); k++) {
+               if (first == allowed[k]) {
+                       ok = 1;
+                       break;
+               }
+       }
+       if (!ok) {
+               wpa_printf(MSG_ERROR, "HT40 channel pair (%d, %d) not allowed",
+                          iface->conf->channel,
+                          iface->conf->secondary_channel);
+               return 0;
+       }
+
+       return 1;
+}
+#endif /* CONFIG_IEEE80211N */
+
+
 /**
  * hostapd_select_hw_mode - Select the hardware mode
  * @iface: Pointer to interface data.
@@ -233,6 +300,11 @@ int hostapd_select_hw_mode(struct hostapd_iface *iface)
                return -1;
        }
 
+#ifdef CONFIG_IEEE80211N
+       if (!ieee80211n_allowed_ht40_channel_pair(iface))
+               return -1;
+#endif /* CONFIG_IEEE80211N */
+
        if (hostapd_prepare_rates(iface->bss[0], iface->current_mode)) {
                wpa_printf(MSG_ERROR, "Failed to prepare rates table.");
                hostapd_logger(iface->bss[0], NULL, HOSTAPD_MODULE_IEEE80211,