mac80211: handle power constraint/country IE better
Currently, mac80211 uses the power constraint IE, and reduces
the regulatory max TX power by it. This can cause issues if
the AP is advertising a large power constraint value matching
a high TX power in its country IE, for example in this case:
...
Country: US Environment: Indoor/Outdoor
...
Channels [157 - 157] @ 30 dBm
...
Power constraint: 13 dB
...
What happened here is that our local regulatory TX power is
15 dBm, and gets reduced by 13 dB so we end up with only
2 dBm effective TX power, which is way too low.
Instead, handle the country IE/power constraint IE combined
and restrict our TX power to the max of the regulatory power
and the maximum power advertised by the AP, in this case
17 dBm (= 30 dBm - 13 dB).
Also print a message when this happens to let the user know
and help us debug issues with it.
Reported-by: Carl A. Cook <CACook@quantum-equities.com>
Tested-by: Carl A. Cook <CACook@quantum-equities.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 0ca3413..45a9fa6 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -779,18 +779,71 @@
}
static void ieee80211_handle_pwr_constr(struct ieee80211_sub_if_data *sdata,
- u16 capab_info, u8 *pwr_constr_elem)
+ struct ieee80211_channel *channel,
+ const u8 *country_ie, u8 country_ie_len,
+ const u8 *pwr_constr_elem)
{
- struct ieee80211_conf *conf = &sdata->local->hw.conf;
+ struct ieee80211_country_ie_triplet *triplet;
+ int chan = ieee80211_frequency_to_channel(channel->center_freq);
+ int i, chan_pwr, chan_increment, new_ap_level;
+ bool have_chan_pwr = false;
- if (!(capab_info & WLAN_CAPABILITY_SPECTRUM_MGMT))
+ /* Invalid IE */
+ if (country_ie_len % 2 || country_ie_len < IEEE80211_COUNTRY_IE_MIN_LEN)
return;
- if ((*pwr_constr_elem <= conf->channel->max_reg_power) &&
- (*pwr_constr_elem != sdata->local->power_constr_level)) {
- sdata->local->power_constr_level = *pwr_constr_elem;
- ieee80211_hw_config(sdata->local, 0);
+ triplet = (void *)(country_ie + 3);
+ country_ie_len -= 3;
+
+ switch (channel->band) {
+ default:
+ WARN_ON_ONCE(1);
+ /* fall through */
+ case IEEE80211_BAND_2GHZ:
+ case IEEE80211_BAND_60GHZ:
+ chan_increment = 1;
+ break;
+ case IEEE80211_BAND_5GHZ:
+ chan_increment = 4;
+ break;
}
+
+ /* find channel */
+ while (country_ie_len >= 3) {
+ u8 first_channel = triplet->chans.first_channel;
+
+ if (first_channel >= IEEE80211_COUNTRY_EXTENSION_ID)
+ goto next;
+
+ for (i = 0; i < triplet->chans.num_channels; i++) {
+ if (first_channel + i * chan_increment == chan) {
+ have_chan_pwr = true;
+ chan_pwr = triplet->chans.max_power;
+ break;
+ }
+ }
+ if (have_chan_pwr)
+ break;
+
+ next:
+ triplet++;
+ country_ie_len -= 3;
+ }
+
+ if (!have_chan_pwr)
+ return;
+
+ new_ap_level = max_t(int, 0, chan_pwr - *pwr_constr_elem);
+
+ if (sdata->local->ap_power_level == new_ap_level)
+ return;
+
+ sdata_info(sdata,
+ "Limiting TX power to %d (%d - %d) dBm as advertised by %pM\n",
+ new_ap_level, chan_pwr, *pwr_constr_elem,
+ sdata->u.mgd.bssid);
+ sdata->local->ap_power_level = new_ap_level;
+ ieee80211_hw_config(sdata->local, 0);
}
void ieee80211_enable_dyn_ps(struct ieee80211_vif *vif)
@@ -1394,7 +1447,7 @@
memset(&ifmgd->ht_capa, 0, sizeof(ifmgd->ht_capa));
memset(&ifmgd->ht_capa_mask, 0, sizeof(ifmgd->ht_capa_mask));
- local->power_constr_level = 0;
+ local->ap_power_level = 0;
del_timer_sync(&local->dynamic_ps_timer);
cancel_work_sync(&local->dynamic_ps_enable_work);
@@ -2499,14 +2552,13 @@
bssid, true);
}
- /* Note: country IE parsing is done for us by cfg80211 */
- if (elems.country_elem) {
- /* TODO: IBSS also needs this */
- if (elems.pwr_constr_elem)
- ieee80211_handle_pwr_constr(sdata,
- le16_to_cpu(mgmt->u.probe_resp.capab_info),
- elems.pwr_constr_elem);
- }
+ if (elems.country_elem && elems.pwr_constr_elem &&
+ mgmt->u.probe_resp.capab_info &
+ cpu_to_le16(WLAN_CAPABILITY_SPECTRUM_MGMT))
+ ieee80211_handle_pwr_constr(sdata, local->oper_channel,
+ elems.country_elem,
+ elems.country_elem_len,
+ elems.pwr_constr_elem);
ieee80211_bss_info_change_notify(sdata, changed);
}