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Commit 04b7b2ff authored by Johannes Berg's avatar Johannes Berg
Browse files

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: default avatarCarl A. Cook <CACook@quantum-equities.com>
Tested-by: default avatarCarl A. Cook <CACook@quantum-equities.com>
Signed-off-by: default avatarJohannes Berg <johannes.berg@intel.com>
parent 3a6a0d8e

net/mac80211/ieee80211_i.h

+1 −1
Original line number Diff line number Diff line
@@ -1059,7 +1059,7 @@ struct ieee80211_local { 
	bool disable_dynamic_ps;



	int user_power_level; /* in dBm */

	int power_constr_level; /* in dBm */

	int ap_power_level; /* in dBm */



	enum ieee80211_smps_mode smps_mode;

net/mac80211/main.c

+3 −5
Original line number Diff line number Diff line
@@ -150,13 +150,11 @@ int ieee80211_hw_config(struct ieee80211_local *local, u32 changed) 


	if (test_bit(SCAN_SW_SCANNING, &local->scanning) ||

	    test_bit(SCAN_ONCHANNEL_SCANNING, &local->scanning) ||

	    test_bit(SCAN_HW_SCANNING, &local->scanning))

	    test_bit(SCAN_HW_SCANNING, &local->scanning) ||

	    !local->ap_power_level)

		power = chan->max_power;

	else

		power = local->power_constr_level ?

			min(chan->max_power,

				(chan->max_reg_power  - local->power_constr_level)) :

			chan->max_power;

		power = min(chan->max_power, local->ap_power_level);



	if (local->user_power_level >= 0)

		power = min(power, local->user_power_level);

net/mac80211/mlme.c

+68 −16
Original line number Diff line number Diff line
@@ -779,18 +779,71 @@ void ieee80211_sta_process_chanswitch(struct ieee80211_sub_if_data *sdata, 
}



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 @@ static void ieee80211_set_disassoc(struct ieee80211_sub_if_data *sdata, 
	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 @@ static void ieee80211_rx_mgmt_beacon(struct ieee80211_sub_if_data *sdata, 
						  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),

	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);

}