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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>
This commit is contained in:
Johannes Berg 2012-09-05 13:41:37 +02:00
parent 3a6a0d8ee8
commit 04b7b2ff50
3 changed files with 72 additions and 22 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
net/mac80211/ieee80211_i.h
View File

@ -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;

8
net/mac80211/main.c
View File

@ -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);

84
net/mac80211/mlme.c
View File

@ -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),
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);
}