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mac80211: split hardware scan by band
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There's currently a very odd bug in mac80211 -- a
hardware scan that is done while the hardware is
really operating on 2.4 GHz will include CCK rates
in the probe request frame, even on 5 GHz (if the
driver uses the mac80211 IEs). Vice versa, if the
hardware is operating on 5 GHz the 2.4 GHz probe
requests will not include CCK rates even though
they should.

Fix this by splitting up cfg80211 scan requests by
band -- recalculating the IEs every time -- and
requesting only per-band scans from the driver.

Apparently this bug hasn't been a problem yet, but
it is imaginable that some older access points get
confused if confronted with such behaviour.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
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Johannes Berg authored and John W. Linville committed Oct 30, 2009
1 parent b59f04c commit 4d36ec5
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Showing 3 changed files with 80 additions and 32 deletions.
8 changes: 4 additions & 4 deletions net/mac80211/ieee80211_i.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -667,10 +667,9 @@ struct ieee80211_local {
unsigned long scanning;
struct cfg80211_ssid scan_ssid;
struct cfg80211_scan_request *int_scan_req;
struct cfg80211_scan_request *scan_req;
struct cfg80211_scan_request *scan_req, *hw_scan_req;
struct ieee80211_channel *scan_channel;
const u8 *orig_ies;
int orig_ies_len;
enum ieee80211_band hw_scan_band;
int scan_channel_idx;
int scan_ies_len;

Expand Down Expand Up @@ -1050,7 +1049,8 @@ void ieee80211_send_auth(struct ieee80211_sub_if_data *sdata,
u8 *extra, size_t extra_len, const u8 *bssid,
const u8 *key, u8 key_len, u8 key_idx);
int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
const u8 *ie, size_t ie_len);
const u8 *ie, size_t ie_len,
enum ieee80211_band band);
void ieee80211_send_probe_req(struct ieee80211_sub_if_data *sdata, u8 *dst,
const u8 *ssid, size_t ssid_len,
const u8 *ie, size_t ie_len);
Expand Down
96 changes: 71 additions & 25 deletions net/mac80211/scan.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -187,6 +187,39 @@ ieee80211_scan_rx(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
return RX_QUEUED;
}

/* return false if no more work */
static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
{
struct cfg80211_scan_request *req = local->scan_req;
enum ieee80211_band band;
int i, ielen, n_chans;

do {
if (local->hw_scan_band == IEEE80211_NUM_BANDS)
return false;

band = local->hw_scan_band;
n_chans = 0;
for (i = 0; i < req->n_channels; i++) {
if (req->channels[i]->band == band) {
local->hw_scan_req->channels[n_chans] =
req->channels[i];
n_chans++;
}
}

local->hw_scan_band++;
} while (!n_chans);

local->hw_scan_req->n_channels = n_chans;

ielen = ieee80211_build_preq_ies(local, (u8 *)local->hw_scan_req->ie,
req->ie, req->ie_len, band);
local->hw_scan_req->ie_len = ielen;

return true;
}

/*
* inform AP that we will go to sleep so that it will buffer the frames
* while we scan
Expand Down Expand Up @@ -247,13 +280,6 @@ static void ieee80211_scan_ps_disable(struct ieee80211_sub_if_data *sdata)
}
}

static void ieee80211_restore_scan_ies(struct ieee80211_local *local)
{
kfree(local->scan_req->ie);
local->scan_req->ie = local->orig_ies;
local->scan_req->ie_len = local->orig_ies_len;
}

void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
{
struct ieee80211_local *local = hw_to_local(hw);
Expand All @@ -272,15 +298,22 @@ void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
return;
}

if (test_bit(SCAN_HW_SCANNING, &local->scanning))
ieee80211_restore_scan_ies(local);
was_hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) {
ieee80211_queue_delayed_work(&local->hw,
&local->scan_work, 0);
mutex_unlock(&local->scan_mtx);
return;
}

kfree(local->hw_scan_req);
local->hw_scan_req = NULL;

if (local->scan_req != local->int_scan_req)
cfg80211_scan_done(local->scan_req, aborted);
local->scan_req = NULL;
local->scan_sdata = NULL;

was_hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
local->scanning = 0;
local->scan_channel = NULL;

Expand Down Expand Up @@ -392,19 +425,23 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,

if (local->ops->hw_scan) {
u8 *ies;
int ielen;

ies = kmalloc(2 + IEEE80211_MAX_SSID_LEN +
local->scan_ies_len + req->ie_len, GFP_KERNEL);
if (!ies)
local->hw_scan_req = kmalloc(
sizeof(*local->hw_scan_req) +
req->n_channels * sizeof(req->channels[0]) +
2 + IEEE80211_MAX_SSID_LEN + local->scan_ies_len +
req->ie_len, GFP_KERNEL);
if (!local->hw_scan_req)
return -ENOMEM;

ielen = ieee80211_build_preq_ies(local, ies,
req->ie, req->ie_len);
local->orig_ies = req->ie;
local->orig_ies_len = req->ie_len;
req->ie = ies;
req->ie_len = ielen;
local->hw_scan_req->ssids = req->ssids;
local->hw_scan_req->n_ssids = req->n_ssids;
ies = (u8 *)local->hw_scan_req +
sizeof(*local->hw_scan_req) +
req->n_channels * sizeof(req->channels[0]);
local->hw_scan_req->ie = ies;

local->hw_scan_band = 0;
}

local->scan_req = req;
Expand Down Expand Up @@ -436,16 +473,17 @@ static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
ieee80211_recalc_idle(local);
mutex_unlock(&local->scan_mtx);

if (local->ops->hw_scan)
rc = drv_hw_scan(local, local->scan_req);
else
if (local->ops->hw_scan) {
WARN_ON(!ieee80211_prep_hw_scan(local));
rc = drv_hw_scan(local, local->hw_scan_req);
} else
rc = ieee80211_start_sw_scan(local);

mutex_lock(&local->scan_mtx);

if (rc) {
if (local->ops->hw_scan)
ieee80211_restore_scan_ies(local);
kfree(local->hw_scan_req);
local->hw_scan_req = NULL;
local->scanning = 0;

ieee80211_recalc_idle(local);
Expand Down Expand Up @@ -654,6 +692,14 @@ void ieee80211_scan_work(struct work_struct *work)
return;
}

if (local->hw_scan_req) {
int rc = drv_hw_scan(local, local->hw_scan_req);
mutex_unlock(&local->scan_mtx);
if (rc)
ieee80211_scan_completed(&local->hw, true);
return;
}

if (local->scan_req && !local->scanning) {
struct cfg80211_scan_request *req = local->scan_req;
int rc;
Expand Down
8 changes: 5 additions & 3 deletions net/mac80211/util.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -872,13 +872,14 @@ void ieee80211_send_auth(struct ieee80211_sub_if_data *sdata,
}

int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
const u8 *ie, size_t ie_len)
const u8 *ie, size_t ie_len,
enum ieee80211_band band)
{
struct ieee80211_supported_band *sband;
u8 *pos, *supp_rates_len, *esupp_rates_len = NULL;
int i;

sband = local->hw.wiphy->bands[local->hw.conf.channel->band];
sband = local->hw.wiphy->bands[band];

pos = buffer;

Expand Down Expand Up @@ -966,7 +967,8 @@ void ieee80211_send_probe_req(struct ieee80211_sub_if_data *sdata, u8 *dst,
memcpy(pos, ssid, ssid_len);
pos += ssid_len;

skb_put(skb, ieee80211_build_preq_ies(local, pos, ie, ie_len));
skb_put(skb, ieee80211_build_preq_ies(local, pos, ie, ie_len,
local->hw.conf.channel->band));

ieee80211_tx_skb(sdata, skb, 0);
}
Expand Down

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