linux/net/mac80211/scan.c
Helmut Schaa df13cce53a mac80211: Improve software scan timing
The current software scan implemenation in mac80211 returns to the operating
channel after each scanned channel. However, in some situations (e.g. no
traffic) it would be nicer to scan a few channels in a row to speed up
the scan itself.

Hence, after scanning a channel, check if we have queued up any tx frames and
return to the operating channel in that case.

Unfortunately we don't know if the AP has buffered any frames for us. Hence,
scan only as many channels in a row as the pm_qos latency and the negotiated
listen interval allows us to.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2010-03-09 15:03:07 -05:00

765 lines
20 KiB
C

/*
* Scanning implementation
*
* Copyright 2003, Jouni Malinen <jkmaline@cc.hut.fi>
* Copyright 2004, Instant802 Networks, Inc.
* Copyright 2005, Devicescape Software, Inc.
* Copyright 2006-2007 Jiri Benc <jbenc@suse.cz>
* Copyright 2007, Michael Wu <flamingice@sourmilk.net>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
#include <linux/if_arp.h>
#include <linux/rtnetlink.h>
#include <linux/pm_qos_params.h>
#include <net/sch_generic.h>
#include <net/mac80211.h>
#include "ieee80211_i.h"
#include "driver-ops.h"
#include "mesh.h"
#define IEEE80211_PROBE_DELAY (HZ / 33)
#define IEEE80211_CHANNEL_TIME (HZ / 33)
#define IEEE80211_PASSIVE_CHANNEL_TIME (HZ / 8)
struct ieee80211_bss *
ieee80211_rx_bss_get(struct ieee80211_local *local, u8 *bssid, int freq,
u8 *ssid, u8 ssid_len)
{
struct cfg80211_bss *cbss;
cbss = cfg80211_get_bss(local->hw.wiphy,
ieee80211_get_channel(local->hw.wiphy, freq),
bssid, ssid, ssid_len, 0, 0);
if (!cbss)
return NULL;
return (void *)cbss->priv;
}
static void ieee80211_rx_bss_free(struct cfg80211_bss *cbss)
{
struct ieee80211_bss *bss = (void *)cbss->priv;
kfree(bss_mesh_id(bss));
kfree(bss_mesh_cfg(bss));
}
void ieee80211_rx_bss_put(struct ieee80211_local *local,
struct ieee80211_bss *bss)
{
if (!bss)
return;
cfg80211_put_bss(container_of((void *)bss, struct cfg80211_bss, priv));
}
static bool is_uapsd_supported(struct ieee802_11_elems *elems)
{
u8 qos_info;
if (elems->wmm_info && elems->wmm_info_len == 7
&& elems->wmm_info[5] == 1)
qos_info = elems->wmm_info[6];
else if (elems->wmm_param && elems->wmm_param_len == 24
&& elems->wmm_param[5] == 1)
qos_info = elems->wmm_param[6];
else
/* no valid wmm information or parameter element found */
return false;
return qos_info & IEEE80211_WMM_IE_AP_QOSINFO_UAPSD;
}
struct ieee80211_bss *
ieee80211_bss_info_update(struct ieee80211_local *local,
struct ieee80211_rx_status *rx_status,
struct ieee80211_mgmt *mgmt,
size_t len,
struct ieee802_11_elems *elems,
struct ieee80211_channel *channel,
bool beacon)
{
struct cfg80211_bss *cbss;
struct ieee80211_bss *bss;
int clen;
s32 signal = 0;
if (local->hw.flags & IEEE80211_HW_SIGNAL_DBM)
signal = rx_status->signal * 100;
else if (local->hw.flags & IEEE80211_HW_SIGNAL_UNSPEC)
signal = (rx_status->signal * 100) / local->hw.max_signal;
cbss = cfg80211_inform_bss_frame(local->hw.wiphy, channel,
mgmt, len, signal, GFP_ATOMIC);
if (!cbss)
return NULL;
cbss->free_priv = ieee80211_rx_bss_free;
bss = (void *)cbss->priv;
/* save the ERP value so that it is available at association time */
if (elems->erp_info && elems->erp_info_len >= 1) {
bss->erp_value = elems->erp_info[0];
bss->has_erp_value = 1;
}
if (elems->tim) {
struct ieee80211_tim_ie *tim_ie =
(struct ieee80211_tim_ie *)elems->tim;
bss->dtim_period = tim_ie->dtim_period;
}
bss->supp_rates_len = 0;
if (elems->supp_rates) {
clen = IEEE80211_MAX_SUPP_RATES - bss->supp_rates_len;
if (clen > elems->supp_rates_len)
clen = elems->supp_rates_len;
memcpy(&bss->supp_rates[bss->supp_rates_len], elems->supp_rates,
clen);
bss->supp_rates_len += clen;
}
if (elems->ext_supp_rates) {
clen = IEEE80211_MAX_SUPP_RATES - bss->supp_rates_len;
if (clen > elems->ext_supp_rates_len)
clen = elems->ext_supp_rates_len;
memcpy(&bss->supp_rates[bss->supp_rates_len],
elems->ext_supp_rates, clen);
bss->supp_rates_len += clen;
}
bss->wmm_used = elems->wmm_param || elems->wmm_info;
bss->uapsd_supported = is_uapsd_supported(elems);
if (!beacon)
bss->last_probe_resp = jiffies;
return bss;
}
ieee80211_rx_result
ieee80211_scan_rx(struct ieee80211_sub_if_data *sdata, struct sk_buff *skb)
{
struct ieee80211_rx_status *rx_status = IEEE80211_SKB_RXCB(skb);
struct ieee80211_mgmt *mgmt;
struct ieee80211_bss *bss;
u8 *elements;
struct ieee80211_channel *channel;
size_t baselen;
int freq;
__le16 fc;
bool presp, beacon = false;
struct ieee802_11_elems elems;
if (skb->len < 2)
return RX_DROP_UNUSABLE;
mgmt = (struct ieee80211_mgmt *) skb->data;
fc = mgmt->frame_control;
if (ieee80211_is_ctl(fc))
return RX_CONTINUE;
if (skb->len < 24)
return RX_DROP_MONITOR;
presp = ieee80211_is_probe_resp(fc);
if (presp) {
/* ignore ProbeResp to foreign address */
if (memcmp(mgmt->da, sdata->vif.addr, ETH_ALEN))
return RX_DROP_MONITOR;
presp = true;
elements = mgmt->u.probe_resp.variable;
baselen = offsetof(struct ieee80211_mgmt, u.probe_resp.variable);
} else {
beacon = ieee80211_is_beacon(fc);
baselen = offsetof(struct ieee80211_mgmt, u.beacon.variable);
elements = mgmt->u.beacon.variable;
}
if (!presp && !beacon)
return RX_CONTINUE;
if (baselen > skb->len)
return RX_DROP_MONITOR;
ieee802_11_parse_elems(elements, skb->len - baselen, &elems);
if (elems.ds_params && elems.ds_params_len == 1)
freq = ieee80211_channel_to_frequency(elems.ds_params[0]);
else
freq = rx_status->freq;
channel = ieee80211_get_channel(sdata->local->hw.wiphy, freq);
if (!channel || channel->flags & IEEE80211_CHAN_DISABLED)
return RX_DROP_MONITOR;
bss = ieee80211_bss_info_update(sdata->local, rx_status,
mgmt, skb->len, &elems,
channel, beacon);
if (bss)
ieee80211_rx_bss_put(sdata->local, bss);
dev_kfree_skb(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;
}
void ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted)
{
struct ieee80211_local *local = hw_to_local(hw);
bool was_hw_scan;
mutex_lock(&local->scan_mtx);
/*
* It's ok to abort a not-yet-running scan (that
* we have one at all will be verified by checking
* local->scan_req next), but not to complete it
* successfully.
*/
if (WARN_ON(!local->scanning && !aborted))
aborted = true;
if (WARN_ON(!local->scan_req)) {
mutex_unlock(&local->scan_mtx);
return;
}
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;
local->scanning = 0;
local->scan_channel = NULL;
/* we only have to protect scan_req and hw/sw scan */
mutex_unlock(&local->scan_mtx);
ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
if (was_hw_scan)
goto done;
ieee80211_configure_filter(local);
drv_sw_scan_complete(local);
ieee80211_offchannel_return(local, true);
done:
ieee80211_recalc_idle(local);
ieee80211_mlme_notify_scan_completed(local);
ieee80211_ibss_notify_scan_completed(local);
ieee80211_mesh_notify_scan_completed(local);
ieee80211_queue_work(&local->hw, &local->work_work);
}
EXPORT_SYMBOL(ieee80211_scan_completed);
static int ieee80211_start_sw_scan(struct ieee80211_local *local)
{
/*
* Hardware/driver doesn't support hw_scan, so use software
* scanning instead. First send a nullfunc frame with power save
* bit on so that AP will buffer the frames for us while we are not
* listening, then send probe requests to each channel and wait for
* the responses. After all channels are scanned, tune back to the
* original channel and send a nullfunc frame with power save bit
* off to trigger the AP to send us all the buffered frames.
*
* Note that while local->sw_scanning is true everything else but
* nullfunc frames and probe requests will be dropped in
* ieee80211_tx_h_check_assoc().
*/
drv_sw_scan_start(local);
ieee80211_offchannel_stop_beaconing(local);
local->leave_oper_channel_time = 0;
local->next_scan_state = SCAN_DECISION;
local->scan_channel_idx = 0;
drv_flush(local, false);
ieee80211_configure_filter(local);
ieee80211_queue_delayed_work(&local->hw,
&local->scan_work,
IEEE80211_CHANNEL_TIME);
return 0;
}
static int __ieee80211_start_scan(struct ieee80211_sub_if_data *sdata,
struct cfg80211_scan_request *req)
{
struct ieee80211_local *local = sdata->local;
int rc;
if (local->scan_req)
return -EBUSY;
if (!list_empty(&local->work_list)) {
/* wait for the work to finish/time out */
local->scan_req = req;
local->scan_sdata = sdata;
return 0;
}
if (local->ops->hw_scan) {
u8 *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;
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;
/*
* After allocating local->hw_scan_req, we must
* go through until ieee80211_prep_hw_scan(), so
* anything that might be changed here and leave
* this function early must not go after this
* allocation.
*/
}
local->scan_req = req;
local->scan_sdata = sdata;
if (local->ops->hw_scan)
__set_bit(SCAN_HW_SCANNING, &local->scanning);
else
__set_bit(SCAN_SW_SCANNING, &local->scanning);
/*
* Kicking off the scan need not be protected,
* only the scan variable stuff, since now
* local->scan_req is assigned and other callers
* will abort their scan attempts.
*
* This avoids too many locking dependencies
* so that the scan completed calls have more
* locking freedom.
*/
ieee80211_recalc_idle(local);
mutex_unlock(&local->scan_mtx);
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) {
kfree(local->hw_scan_req);
local->hw_scan_req = NULL;
local->scanning = 0;
ieee80211_recalc_idle(local);
local->scan_req = NULL;
local->scan_sdata = NULL;
}
return rc;
}
static unsigned long
ieee80211_scan_get_channel_time(struct ieee80211_channel *chan)
{
/*
* TODO: channel switching also consumes quite some time,
* add that delay as well to get a better estimation
*/
if (chan->flags & IEEE80211_CHAN_PASSIVE_SCAN)
return IEEE80211_PASSIVE_CHANNEL_TIME;
return IEEE80211_PROBE_DELAY + IEEE80211_CHANNEL_TIME;
}
static int ieee80211_scan_state_decision(struct ieee80211_local *local,
unsigned long *next_delay)
{
bool associated = false;
bool tx_empty = true;
bool bad_latency;
bool listen_int_exceeded;
unsigned long min_beacon_int = 0;
struct ieee80211_sub_if_data *sdata;
struct ieee80211_channel *next_chan;
/* if no more bands/channels left, complete scan and advance to the idle state */
if (local->scan_channel_idx >= local->scan_req->n_channels) {
ieee80211_scan_completed(&local->hw, false);
return 1;
}
/*
* check if at least one STA interface is associated,
* check if at least one STA interface has pending tx frames
* and grab the lowest used beacon interval
*/
mutex_lock(&local->iflist_mtx);
list_for_each_entry(sdata, &local->interfaces, list) {
if (!ieee80211_sdata_running(sdata))
continue;
if (sdata->vif.type == NL80211_IFTYPE_STATION) {
if (sdata->u.mgd.associated) {
associated = true;
if (sdata->vif.bss_conf.beacon_int <
min_beacon_int || min_beacon_int == 0)
min_beacon_int =
sdata->vif.bss_conf.beacon_int;
if (!qdisc_all_tx_empty(sdata->dev)) {
tx_empty = false;
break;
}
}
}
}
mutex_unlock(&local->iflist_mtx);
if (local->scan_channel) {
/*
* we're currently scanning a different channel, let's
* see if we can scan another channel without interfering
* with the current traffic situation.
*
* Since we don't know if the AP has pending frames for us
* we can only check for our tx queues and use the current
* pm_qos requirements for rx. Hence, if no tx traffic occurs
* at all we will scan as many channels in a row as the pm_qos
* latency allows us to. Additionally we also check for the
* currently negotiated listen interval to prevent losing
* frames unnecessarily.
*
* Otherwise switch back to the operating channel.
*/
next_chan = local->scan_req->channels[local->scan_channel_idx];
bad_latency = time_after(jiffies +
ieee80211_scan_get_channel_time(next_chan),
local->leave_oper_channel_time +
usecs_to_jiffies(pm_qos_requirement(PM_QOS_NETWORK_LATENCY)));
listen_int_exceeded = time_after(jiffies +
ieee80211_scan_get_channel_time(next_chan),
local->leave_oper_channel_time +
usecs_to_jiffies(min_beacon_int * 1024) *
local->hw.conf.listen_interval);
if (associated && ( !tx_empty || bad_latency ||
listen_int_exceeded))
local->next_scan_state = SCAN_ENTER_OPER_CHANNEL;
else
local->next_scan_state = SCAN_SET_CHANNEL;
} else {
/*
* we're on the operating channel currently, let's
* leave that channel now to scan another one
*/
local->next_scan_state = SCAN_LEAVE_OPER_CHANNEL;
}
*next_delay = 0;
return 0;
}
static void ieee80211_scan_state_leave_oper_channel(struct ieee80211_local *local,
unsigned long *next_delay)
{
ieee80211_offchannel_stop_station(local);
__set_bit(SCAN_OFF_CHANNEL, &local->scanning);
/*
* What if the nullfunc frames didn't arrive?
*/
drv_flush(local, false);
if (local->ops->flush)
*next_delay = 0;
else
*next_delay = HZ / 10;
/* remember when we left the operating channel */
local->leave_oper_channel_time = jiffies;
/* advance to the next channel to be scanned */
local->next_scan_state = SCAN_SET_CHANNEL;
}
static void ieee80211_scan_state_enter_oper_channel(struct ieee80211_local *local,
unsigned long *next_delay)
{
/* switch back to the operating channel */
local->scan_channel = NULL;
ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
/*
* Only re-enable station mode interface now; beaconing will be
* re-enabled once the full scan has been completed.
*/
ieee80211_offchannel_return(local, false);
__clear_bit(SCAN_OFF_CHANNEL, &local->scanning);
*next_delay = HZ / 5;
local->next_scan_state = SCAN_DECISION;
}
static void ieee80211_scan_state_set_channel(struct ieee80211_local *local,
unsigned long *next_delay)
{
int skip;
struct ieee80211_channel *chan;
skip = 0;
chan = local->scan_req->channels[local->scan_channel_idx];
local->scan_channel = chan;
if (ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL))
skip = 1;
/* advance state machine to next channel/band */
local->scan_channel_idx++;
if (skip) {
/* if we skip this channel return to the decision state */
local->next_scan_state = SCAN_DECISION;
return;
}
/*
* Probe delay is used to update the NAV, cf. 11.1.3.2.2
* (which unfortunately doesn't say _why_ step a) is done,
* but it waits for the probe delay or until a frame is
* received - and the received frame would update the NAV).
* For now, we do not support waiting until a frame is
* received.
*
* In any case, it is not necessary for a passive scan.
*/
if (chan->flags & IEEE80211_CHAN_PASSIVE_SCAN ||
!local->scan_req->n_ssids) {
*next_delay = IEEE80211_PASSIVE_CHANNEL_TIME;
local->next_scan_state = SCAN_DECISION;
return;
}
/* active scan, send probes */
*next_delay = IEEE80211_PROBE_DELAY;
local->next_scan_state = SCAN_SEND_PROBE;
}
static void ieee80211_scan_state_send_probe(struct ieee80211_local *local,
unsigned long *next_delay)
{
int i;
struct ieee80211_sub_if_data *sdata = local->scan_sdata;
for (i = 0; i < local->scan_req->n_ssids; i++)
ieee80211_send_probe_req(
sdata, NULL,
local->scan_req->ssids[i].ssid,
local->scan_req->ssids[i].ssid_len,
local->scan_req->ie, local->scan_req->ie_len);
/*
* After sending probe requests, wait for probe responses
* on the channel.
*/
*next_delay = IEEE80211_CHANNEL_TIME;
local->next_scan_state = SCAN_DECISION;
}
void ieee80211_scan_work(struct work_struct *work)
{
struct ieee80211_local *local =
container_of(work, struct ieee80211_local, scan_work.work);
struct ieee80211_sub_if_data *sdata = local->scan_sdata;
unsigned long next_delay = 0;
mutex_lock(&local->scan_mtx);
if (!sdata || !local->scan_req) {
mutex_unlock(&local->scan_mtx);
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;
local->scan_req = NULL;
local->scan_sdata = NULL;
rc = __ieee80211_start_scan(sdata, req);
mutex_unlock(&local->scan_mtx);
if (rc)
ieee80211_scan_completed(&local->hw, true);
return;
}
mutex_unlock(&local->scan_mtx);
/*
* Avoid re-scheduling when the sdata is going away.
*/
if (!ieee80211_sdata_running(sdata)) {
ieee80211_scan_completed(&local->hw, true);
return;
}
/*
* as long as no delay is required advance immediately
* without scheduling a new work
*/
do {
switch (local->next_scan_state) {
case SCAN_DECISION:
if (ieee80211_scan_state_decision(local, &next_delay))
return;
break;
case SCAN_SET_CHANNEL:
ieee80211_scan_state_set_channel(local, &next_delay);
break;
case SCAN_SEND_PROBE:
ieee80211_scan_state_send_probe(local, &next_delay);
break;
case SCAN_LEAVE_OPER_CHANNEL:
ieee80211_scan_state_leave_oper_channel(local, &next_delay);
break;
case SCAN_ENTER_OPER_CHANNEL:
ieee80211_scan_state_enter_oper_channel(local, &next_delay);
break;
}
} while (next_delay == 0);
ieee80211_queue_delayed_work(&local->hw, &local->scan_work, next_delay);
}
int ieee80211_request_scan(struct ieee80211_sub_if_data *sdata,
struct cfg80211_scan_request *req)
{
int res;
mutex_lock(&sdata->local->scan_mtx);
res = __ieee80211_start_scan(sdata, req);
mutex_unlock(&sdata->local->scan_mtx);
return res;
}
int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata,
const u8 *ssid, u8 ssid_len)
{
struct ieee80211_local *local = sdata->local;
int ret = -EBUSY;
mutex_lock(&local->scan_mtx);
/* busy scanning */
if (local->scan_req)
goto unlock;
memcpy(local->int_scan_req->ssids[0].ssid, ssid, IEEE80211_MAX_SSID_LEN);
local->int_scan_req->ssids[0].ssid_len = ssid_len;
ret = __ieee80211_start_scan(sdata, sdata->local->int_scan_req);
unlock:
mutex_unlock(&local->scan_mtx);
return ret;
}
void ieee80211_scan_cancel(struct ieee80211_local *local)
{
bool abortscan;
cancel_delayed_work_sync(&local->scan_work);
/*
* Only call this function when a scan can't be
* queued -- mostly at suspend under RTNL.
*/
mutex_lock(&local->scan_mtx);
abortscan = test_bit(SCAN_SW_SCANNING, &local->scanning) ||
(!local->scanning && local->scan_req);
mutex_unlock(&local->scan_mtx);
if (abortscan)
ieee80211_scan_completed(&local->hw, true);
}