2010-08-28 16:38:01

by Jouni Malinen

Subject: [PATCH] mac80211: Add DS Parameter Set into Probe Request on 2.4 GHz

IEEE Std 802.11k-2008 added DS Parameter Set information element into
Probe Request frames as an optional information on 2.4 GHz band (and
mandatory, if radio measurements are enabled). This allows APs to
filter out Probe Request frames that may be received from neighboring
overlapping channels and by doing so, reduce the number of unnecessary
frames in the air. Make mac80211 add this IE into Probe Request frames
whenever the channel is known (i.e., whenever hwscan is not used).

Signed-off-by: Jouni Malinen <[email protected]>

---
net/mac80211/ieee80211_i.h | 3 ++-
net/mac80211/scan.c | 3 ++-
net/mac80211/util.c | 16 ++++++++++++++--
3 files changed, 18 insertions(+), 4 deletions(-)

(note: this is on top of the previous Probe Request SuppRates masking
patch)

--- uml.orig/net/mac80211/ieee80211_i.h 2010-08-28 19:30:30.000000000 +0300
+++ uml/net/mac80211/ieee80211_i.h 2010-08-28 19:34:22.000000000 +0300
@@ -1229,7 +1229,8 @@ void ieee80211_send_auth(struct ieee8021
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,
- enum ieee80211_band band, u32 rate_mask);
+ enum ieee80211_band band, u32 rate_mask,
+ u8 channel);
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);
--- uml.orig/net/mac80211/scan.c 2010-08-28 19:30:30.000000000 +0300
+++ uml/net/mac80211/scan.c 2010-08-28 19:34:22.000000000 +0300
@@ -243,7 +243,8 @@ static bool ieee80211_prep_hw_scan(struc
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, (u32) -1);
+ req->ie, req->ie_len, band, (u32) -1,
+ 0);
local->hw_scan_req->ie_len = ielen;

return true;
--- uml.orig/net/mac80211/util.c 2010-08-28 19:30:30.000000000 +0300
+++ uml/net/mac80211/util.c 2010-08-28 19:34:22.000000000 +0300
@@ -904,7 +904,8 @@ void ieee80211_send_auth(struct ieee8021

int ieee80211_build_preq_ies(struct ieee80211_local *local, u8 *buffer,
const u8 *ie, size_t ie_len,
- enum ieee80211_band band, u32 rate_mask)
+ enum ieee80211_band band, u32 rate_mask,
+ u8 channel)
{
struct ieee80211_supported_band *sband;
u8 *pos;
@@ -956,6 +957,12 @@ int ieee80211_build_preq_ies(struct ieee
pos += ext_rates_len;
}

+ if (channel && sband->band == IEEE80211_BAND_2GHZ) {
+ *pos++ = WLAN_EID_DS_PARAMS;
+ *pos++ = 1;
+ *pos++ = channel;
+ }
+
/* insert custom IEs that go before HT */
if (ie && ie_len) {
static const u8 before_ht[] = {
@@ -1022,6 +1029,7 @@ void ieee80211_send_probe_req(struct iee
struct ieee80211_mgmt *mgmt;
size_t buf_len;
u8 *buf;
+ u8 chan;

/* FIXME: come up with a proper value */
buf = kmalloc(200 + ie_len, GFP_KERNEL);
@@ -1031,10 +1039,14 @@ void ieee80211_send_probe_req(struct iee
return;
}

+ chan = ieee80211_frequency_to_channel(
+ local->hw.conf.channel->center_freq);
+
buf_len = ieee80211_build_preq_ies(local, buf, ie, ie_len,
local->hw.conf.channel->band,
sdata->rc_rateidx_mask
- [local->hw.conf.channel->band]);
+ [local->hw.conf.channel->band],
+ chan);

skb = ieee80211_probereq_get(&local->hw, &sdata->vif,
ssid, ssid_len,

--
Jouni Malinen PGP id EFC895FA

2010-08-30 07:47:10

by Johannes Berg

Subject: Re: [PATCH] mac80211: Add DS Parameter Set into Probe Request on 2.4 GHz

On Sat, 2010-08-28 at 19:37 +0300, Jouni Malinen wrote:
> IEEE Std 802.11k-2008 added DS Parameter Set information element into
> Probe Request frames as an optional information on 2.4 GHz band (and
> mandatory, if radio measurements are enabled). This allows APs to
> filter out Probe Request frames that may be received from neighboring
> overlapping channels and by doing so, reduce the number of unnecessary
> frames in the air. Make mac80211 add this IE into Probe Request frames
> whenever the channel is known (i.e., whenever hwscan is not used).

Nice.

Acked-by: Johannes Berg <[email protected]>

johannes