Commit Graph

96 Commits

Author SHA1 Message Date
Luciano Coelho 33ffd952c2 mac80211: split ieee80211_vif_change_channel in two
ieee80211_vif_change_channel() locks chanctx_mtx.  When implementing
channel reservation for CS, we will need to call the function to
change channel when the lock is already held, so split the part that
requires the lock out and leave the locking in the original function.

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2014-04-09 10:55:50 +02:00
Michal Kazior 4e141dad26 mac80211: protect AP VLAN list with local->mtx
It was impossible to change chanctx of master AP
for AP VLANs because the copy function requires
RTNL which can't be simply taken in mac80211 code
due to possible deadlocks.

This is required for future chanctx reservation
that re-bind vifs to new chanctx. This requires
safe AP VLAN iteration without RTNL.

Now VLANs can be iterated while holding either
RTNL or local->mtx because the list is modified
while holding both of these locks.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2014-04-09 10:55:49 +02:00
Luciano Coelho 73de86a389 cfg80211/mac80211: move interface counting for combination check to mac80211
Move the counting part of the interface combination check from
cfg80211 to mac80211.

This is needed to simplify locking when the driver has to perform a
combination check by itself (eg. with channel-switch).

Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2014-04-09 10:55:43 +02:00
Monam Agarwal 0c2bef4621 mac80211: use RCU_INIT_POINTER
rcu_assign_pointer() ensures that the initialization of a structure is
carried out before storing a pointer to that structure. However, in the
case that NULL is assigned there's no structure to initialize so using
RCU_INIT_POINTER instead is safe and more efficient.

Signed-off-by: Monam Agarwal <monamagarwal123@gmail.com>
[squash eight tiny patches, rewrite commit log]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2014-04-09 10:55:30 +02:00
Michal Kazior 9b4816f543 mac80211: fix radar_enabled propagation
If chandef had non-HT width it was possible for
radar_enabled update to not be propagated properly
through drv_config(). This happened because
ieee80211_hw_conf_chan() would never see different
local->hw.conf.chandef and local->_oper_chandef.

This wasn't a problem with HT chandefs because
_oper_chandef width is reset to non-HT in
ieee80211_free_chanctx() making
ieee80211_hw_conf_chan() to kick in.

This problem led (at least) ath10k to not start
CAC if prior CAC was cancelled and both CACs were
requested for identical non-HT chandefs.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2014-04-09 10:48:36 +02:00
Ido Yariv 7b8a9cdd1f mac80211: Disable SMPS for the monitor interface
All antennas should be operational when monitoring to maximize
reception.

Signed-off-by: Ido Yariv <idox.yariv@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2014-04-09 10:47:58 +02:00
David S. Miller 85dcce7a73 Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net
Conflicts:
	drivers/net/usb/r8152.c
	drivers/net/xen-netback/netback.c

Both the r8152 and netback conflicts were simple overlapping
changes.

Signed-off-by: David S. Miller <davem@davemloft.net>
2014-03-14 22:31:55 -04:00
Eliad Peller 1c37a72c1b mac80211: consider virtual mon when calculating min_def
When calculating the current max bw required for
a channel context, we didn't consider the virtual
monitor interface, resulting in its channel context
being narrower than configured.

This broke monitor mode with iwlmvm, which uses the
minimal width.

Reported-by: Ido Yariv <idox.yariv@intel.com>
Signed-off-by: Eliad Peller <eliadx.peller@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2014-03-03 13:48:13 +01:00
Michal Kazior cc901de1bc mac80211: fix sdata->radar_required locking
radar_required setting wasn't protected by
local->mtx in some places. This should prevent
from scanning/radar detection/roc colliding.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2014-02-04 21:58:10 +01:00
Johannes Berg 34a3740d6b mac80211: fix iflist_mtx/mtx locking in radar detection
The scan code creates an iflist_mtx -> mtx locking dependency,
and a few other places, notably radar detection, were creating
the opposite dependency, causing lockdep to complain. As scan
and radar detection are mutually exclusive, the deadlock can't
really happen in practice, but it's still bad form.

A similar issue exists in the monitor mode code, but this is
only used by channel-context drivers right now and those have
to have hardware scan, so that also can't happen.

Still, fix these issues by making some of the channel context
code require the mtx to be held rather than acquiring it, thus
allowing the monitor/radar callers to keep the iflist_mtx->mtx
lock ordering.

While at it, also fix access to the local->scanning variable
in the radar code, and document that radar_detect_enabled is
now properly protected by the mtx.

All this would now introduce an ABBA deadlock between the DFS
work cancelling and local->mtx, so change the locking there a
bit to not need to use cancel_delayed_work_sync() but be able
to just use cancel_delayed_work(). The work is also safely
stopped/removed when the interface is stopped, so no extra
changes are needed.

Reported-by: Kalle Valo <kvalo@qca.qualcomm.com>
Tested-by: Simon Wunderlich <sw@simonwunderlich.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-12-19 13:33:33 +01:00
Johannes Berg 367bbd10ee mac80211: make ieee80211_recalc_radar_chanctx static
The function is only used in one file, so move it up a
bit to avoid forward declarations and make it static.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-12-18 10:33:06 +01:00
Eliad Peller 21f659bf1f mac80211: add min required channel definition field
Add a new field to ieee80211_chanctx_conf to indicate
the min required channel configuration.

Tuning to a narrower channel might help reducing
the noise level and saving some power.

The min required channel definition is the max of
all min required channel definitions of the interfaces
bound to this channel context.

In AP mode, use 20MHz when there are no connected station.
When a new station is added/removed, calculate the new max
bandwidth supported by any of the stations (e.g. 80MHz when
80MHz and 40MHz stations are connected).

In other cases, simply use bss_conf.chandef as the
min required chandef.

Notify drivers about changes to this field by calling
drv_change_chanctx with a new CHANGE_MIN_WIDTH notification.

Signed-off-by: Eliad Peller <eliad@wizery.com>
Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-11-25 20:52:05 +01:00
Luciano Coelho 33787fc4be mac80211: move csa_chandef to sdata
There is no reason why we should have only one channel switch
announcement at a time for a single phy.  When support for channel
switch with multiple contexts and multiple vifs per context is
implemented, we will need the chandef data for each vif.  Move the
csa_chandef structure to sdata to prepare for this.

Reviewed-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Luciano Coelho <luciano.coelho@intel.com>
[Fixed compilation with mesh]
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-11-25 20:51:58 +01:00
Arik Nemtsov 7578d57520 mac80211: implement STA CSA for drivers using channel contexts
Limit the current implementation to a single channel context used by
a single vif, thereby avoiding multi-vif/channel complexities.

Reuse the main function from AP CSA code, but move a portion out in
order to fit the STA scenario.

Add a new mac80211 HW flag so we don't break devices that don't support
channel switch with channel-contexts. The new behavior will be opt-in.

Signed-off-by: Arik Nemtsov <arik@wizery.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-10-02 18:18:23 +02:00
Simon Wunderlich 73da7d5bab mac80211: add channel switch command and beacon callbacks
The count field in CSA must be decremented with each beacon
transmitted. This patch implements the functionality for drivers
using ieee80211_beacon_get(). Other drivers must call back manually
after reaching count == 0.

This patch also contains the handling and finish worker for the channel
switch command, and mac80211/chanctx code to allow to change a channel
definition of an active channel context.

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Mathias Kretschmer <mathias.kretschmer@fokus.fraunhofer.de>
[small cleanups, catch identical chandef]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-08-01 18:30:33 +02:00
Johannes Berg a42c74ee60 Merge remote-tracking branch 'wireless-next/master' into mac80211-next 2013-04-22 15:31:43 +02:00
Simon Wunderlich e47468518b mac80211: fix recalc_radar hwconf sync problem
local->hw.conf maybe not be synced when recalcing whether radar is
enabled, sometimes leaving radar enabled even if it's not neccesary
anymore.

Fix this by:
 * setting radar_enabled when creating the chanctx
 * turning radar_enabled off before destroying the last channel context

Reported-by: Zefir Kurtisi <zefir.kurtisi@neratec.com>
Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-04-10 20:24:16 +02:00
John W. Linville 655d8e2328 Merge branch 'for-john' of git://git.kernel.org/pub/scm/linux/kernel/git/jberg/mac80211-next
Conflicts:
	drivers/net/wireless/ath/carl9170/debug.c
	drivers/net/wireless/ath/carl9170/main.c
	net/mac80211/ieee80211_i.h
2013-04-10 14:09:54 -04:00
Karl Beldan 675a0b049a mac80211: Use a cfg80211_chan_def in ieee80211_hw_conf_chan
Drivers that don't use chanctxes cannot perform VHT association because
they still use a "backward compatibility" pair of {ieee80211_channel,
nl80211_channel_type} in ieee80211_conf and ieee80211_local.

Signed-off-by: Karl Beldan <karl.beldan@rivierawaves.com>
[fix kernel-doc]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-03-25 19:19:35 +01:00
Johannes Berg 382a103b2b mac80211: fix idle handling sequence
Corey Richardson reported that my idle handling cleanup
(commit fd0f979a1b, "mac80211: simplify idle handling")
broke ath9k_htc. The reason appears to be that it wants
to go out of idle before switching channels. To fix it,
reimplement that sequence.

Reported-by: Corey Richardson <corey@octayn.net>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-03-25 16:50:18 +01:00
Johannes Berg 2c9b735982 mac80211: add ieee80211_vif_change_bandwidth
For HT and VHT the current bandwidth can change,
add the function ieee80211_vif_change_bandwidth()
to take care of this. It returns a failure if the
new bandwidth isn't compatible with the existing
channel context, the caller has to handle that.
When it happens, also inform the driver that the
bandwidth changed for this virtual interface (no
drivers would actually care today though.)

Changing to/from HT/VHT isn't allowed though.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-02-15 09:41:36 +01:00
Johannes Berg 18942d3be0 mac80211: fix ieee80211_change_chandef name
This should be called ieee80211_change_chanctx() since
it changes the channel context, not a chandef.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-02-15 09:41:34 +01:00
Johannes Berg 5bbe754d9e mac80211: don't call bss_info_changed on p2p-device/monitor
Since the idle decision rework, mac80211 started calling
bss_info_changed() for the driver's monitor interface,
which causes a crash for iwlwifi, but drivers generally
don't expect this to happen. Therefore, avoid it.

While at it, also prevent calling it in such cases and
only print a warning. For the P2P Device interface the
idle will no longer be called (no channel context), so
also prevent that and warn on it.

Reported-by: Chaitanya <chaitanya.mgit@gmail.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-02-15 09:41:11 +01:00
Simon Wunderlich 164eb02d07 mac80211: add radar detection command/event
Add command to trigger radar detection in the driver/FW.
Once radar detection is started it should continuously
monitor for radars as long as the channel active.
If radar is detected usermode notified with 'radar
detected' event.

Scanning and remain on channel functionality must be disabled
while doing radar detection/scanning, and vice versa.

Based on original patch by Victor Goldenshtein <victorg@ti.com>

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-02-15 09:41:04 +01:00
Johannes Berg fd0f979a1b mac80211: simplify idle handling
Now that we have channel contexts, idle is (pretty
much) equivalent to not having a channel context.
Change the code to use this relation so that there
no longer is a need for a lot of idle recalculate
calls everywhere.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-02-11 18:45:01 +01:00
Johannes Berg 1f4ac5a63f mac80211: explicitly copy channels to VLANs where needed
Currently the code assigns channel contexts to VLANs
(for use by the TX/RX code) when the AP master gets
its channel context assigned. This works fine, but
in the upcoming radar detection work the VLANs don't
require a channel context (during radar detection)
and assigning one to them anyway causes issues with
locking and also inconsistencies -- a VLAN interface
that is added before radar detection would get the
channel context, while one added during it wouldn't.

Fix these issues moving the channel context copying
to a new explicit operation that will not be used
in the radar detection code.

Acked-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-02-11 18:44:57 +01:00
Johannes Berg 8a61af65c6 mac80211: fix channel context iteration
During suspend/resume channel contexts might be
iterated even if they haven't been re-added to
the driver, keep track of this and skip them in
iteration. Also use the new status for sanity
checks.

Also clarify the fact that during HW restart all
contexts are iterated over (thanks Eliad.)

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-01-03 13:01:35 +01:00
Johannes Berg 4d76d21bd7 mac80211: assign VLAN channel contexts
Make AP_VLAN type interfaces track the AP master channel
context so they have one assigned for the various lookups.
Don't give them their own refcount etc. since they're just
slaves to the AP master.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2013-01-03 12:59:58 +01:00
Johannes Berg 4bf88530be mac80211: convert to channel definition struct
Convert mac80211 (and where necessary, some drivers a
little bit) to the new channel definition struct.

This will allow extending mac80211 for VHT, which is
currently restricted to channel contexts since there
are no drivers using that which makes it easier. As
I also don't care about VHT for drivers not using the
channel context API, I won't convert the previous API
to VHT support.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2012-11-26 12:42:59 +01:00
Johannes Berg 1ea6f9c0d4 mac80211: handle TX power per virtual interface
Even before channel contexts/multi-channel, having a
single global TX power limit was already problematic,
in particular if two managed interfaces connected to
two APs with different power constraints. The channel
context introduction completely broke this though and
in fact I had disabled TX power configuration there
for drivers using channel contexts.

Change everything to track TX power per interface so
that different user settings and different channel
maxima are treated correctly. Also continue tracking
the global TX power though for compatibility with
applications that attempt to configure the wiphy's
TX power globally.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2012-10-30 09:11:34 +01:00
Johannes Berg 3448c00583 mac80211: add channel context iterator
Drivers may need to iterate the active channel
contexts, export an iterator function to allow
that. To make it possible, use RCU-safe list
functions.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2012-10-17 11:02:10 +02:00
Johannes Berg 04ecd2578e mac80211: track needed RX chains for channel contexts
On each channel that the device is operating on, it
may need to listen using one or more chains depending
on the SMPS settings of the interfaces using it. The
previous channel context changes completely removed
this ability (before, it was available as the SMPS
mode).

Add per-context tracking of the required static and
dynamic RX chains and notify the driver on changes.
To achieve this, track the chains and SMPS mode used
on each virtual interface and update the channel
context whenever this changes.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2012-10-17 11:02:09 +02:00
Johannes Berg 55de908ab2 mac80211: use channel contexts
Instead of operating on a single channel only,
use the new channel context infrastructure in
all mac80211 code.

This enables drivers that want to use the new
channel context infrastructure to use multiple
channels, while nothing should change for all
the other drivers that don't support it.

Right now this disables both TX power settings
and spatial multiplexing powersave. Both need
to be re-enabled on a channel context basis.

Additionally, when channel contexts are used
drop the connection when channel switch is
received rather than trying to handle it. This
will have to be improved later.

[With fixes from Eliad and Emmanuel incorporated]
Signed-off-by: Eliad Peller <eliad@wizery.com>
Signed-off-by: Emmanuel Grumbach <emmanuel.grumbach@intel.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2012-10-17 11:02:09 +02:00
Michal Kazior e89a96f5cc mac80211: reuse channels for channel contexts
Reuse channels with compatible channel types. Some
channel types are compatible and can be used
concurrently.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2012-10-16 20:22:44 +02:00
Michal Kazior 35f2fce9a4 mac80211: use channel context notifications
Channel context pointer will be accessible on
both assign and unassign events.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2012-10-16 20:22:43 +02:00
Michal Kazior d01a1e6586 mac80211: introduce channel context skeleton code
Channel context are the foundation for multi-channel
operation. They are are immutable and are re-created
(or re-used if other interfaces are bound to a certain
channel and a compatible channel type) on channel
switching.

This is an initial implementation and more features
will come in separate patches.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
[some changes including RCU protection]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2012-10-16 20:22:41 +02:00
Michal Kazior 23a85b45cf mac80211: refactor set_channel_type
Split functionality for further reuse.

Will prevent code duplication when channel context
channel_type merging is introduced.

Signed-off-by: Michal Kazior <michal.kazior@tieto.com>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
2012-09-06 17:55:00 +02:00
Thomas Pedersen be0f42377f mac80211: allow channel change while mesh is down
Allow channel change on a mesh interface if the interface is up and no
mesh is started.

Signed-off-by: Thomas Pedersen <thomas@cozybit.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2012-06-05 15:21:47 -04:00
Johannes Berg 64f68e5d15 mac80211: remove channel type argument from rate_update
The channel type argument to the rate_update()
callback isn't really the correct way to give
the rate control algorithm about the desired
RX bandwidth of the peer.

Remove this argument, and instead update the
STA capabilities with 20/40 appropriately. The
SMPS update done by this callback works in the
same way, so this makes the callback cleaner.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2012-04-10 14:54:08 -04:00
Paul Stewart 3117bbdb78 mac80211: Don't let regulatory make us deaf
When regulatory information changes our HT behavior (e.g,
when we get a country code from the AP we have just associated
with), we should use this information to change the power with
which we transmit, and what channels we transmit.  Sometimes
the channel parameters we derive from regulatory information
contradicts the parameters we used in association.  For example,
we could have associated specifying HT40, but the regulatory
rules we apply may forbid HT40 operation.

In the situation above, we should reconfigure ourselves to
transmit in HT20 only, however it makes no sense for us to
disable receive in HT40, since if we associated with these
parameters, the AP has every reason to expect we can and
will receive packets this way.  The code in mac80211 does
not have the capability of sending the appropriate action
frames to signal a change in HT behaviour so the AP has
no clue we can no longer receive frames encoded this way.
In some broken AP implementations, this can leave us
effectively deaf if the AP never retries in lower HT rates.

This change breaks up the channel_type parameter in the
ieee80211_enable_ht function into a separate receive and
transmit part.  It honors the channel flags set by regulatory
in order to configure the rate control algorithm, but uses
the capability flags to configure the channel on the radio,
since these were used in association to set the AP's transmit
rate.

Signed-off-by: Paul Stewart <pstew@chromium.org>
Cc: Sam Leffler <sleffler@chromium.org>
Cc: Johannes Berg <johannes@sipsolutions.net>
Reviewed-by: Luis R Rodriguez <mcgrof@frijolero.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2012-03-13 14:55:53 -04:00
Johannes Berg e9980e6d20 mac80211: refactor __ieee80211_get_channel_mode
Use a switch statement instead of a list of if
statements. Also include AP_VLAN in the list
and skip them since the AP interface will also
be looked at.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2012-01-24 14:08:39 -05:00
Felix Fietkau 9db372fdd5 mac80211: fix channel type recalculation with HT and non-HT interfaces
When running an AP interface along with the cooked monitor interface created
by hostapd, adding an interface and deleting it again triggers a channel type
recalculation during which the (non-HT) monitor interface takes precedence
over the HT AP interface, thus causing the channel type to be set to non-HT.
Fix this by ensuring that a more wide channel type will not be overwritten
by a less wide channel type.

Signed-off-by: Felix Fietkau <nbd@openwrt.org>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2011-03-14 14:46:58 -04:00
Johannes Berg 46a5ebaf02 cfg80211/mac80211: use lockdep_assert_held
Instead of using a WARN_ON(!mutex_is_locked())
use lockdep_assert_held() which compiles away
completely when lockdep isn't enabled, and
also is a more accurate assertion since it
checks that the current thread is holding the
mutex.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2010-09-16 15:46:00 -04:00
Johannes Berg 368a07d26a mac80211: make a function static
sparse correctly complains that
__ieee80211_get_channel_mode is not static.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2010-05-28 13:41:27 -04:00
Johannes Berg 0aaffa9b96 mac80211: improve HT channel handling
Currently, when one interface switches HT mode,
all others will follow along. This is clearly
undesirable, since the new one might switch to
no-HT while another one is operating in HT.

Address this issue by keeping track of the HT
mode per interface, and allowing only changes
that are compatible, i.e. switching into HT40+
is not possible when another interface is in
HT40-, in that case the second one needs to
fall back to HT20.

Also, to allow drivers to know what's going on,
store the per-interface HT mode (channel type)
in the virtual interface's bss_conf.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2010-05-07 14:55:51 -04:00
Johannes Berg f444de05d2 cfg80211/mac80211: better channel handling
Currently (all tested with hwsim) you can do stupid
things like setting up an AP on a certain channel,
then adding another virtual interface and making
that associate on another channel -- this will make
the beaconing to move channel but obviously without
the necessary IEs data update.

In order to improve this situation, first make the
configuration APIs (cfg80211 and nl80211) aware of
multi-channel operation -- we'll eventually need
that in the future anyway. There's one userland API
change and one API addition. The API change is that
now SET_WIPHY must be called with virtual interface
index rather than only wiphy index in order to take
effect for that interface -- luckily all current
users (hostapd) do that. For monitor interfaces, the
old setting is preserved, but monitors are always
slaved to other devices anyway so no guarantees.

The second userland API change is the introduction
of a per virtual interface SET_CHANNEL command, that
hostapd should use going forward to make it easier
to understand what's going on (it can automatically
detect a kernel with this command).

Other than mac80211, no existing cfg80211 drivers
are affected by this change because they only allow
a single virtual interface.

mac80211, however, now needs to be aware that the
channel settings are per interface now, and needs
to disallow (for now) real multi-channel operation,
which is another important part of this patch.

One of the immediate benefits is that you can now
start hostapd to operate on a hardware that already
has a connection on another virtual interface, as
long as you specify the same channel.

Note that two things are left unhandled (this is an
improvement -- not a complete fix):

 * different HT/no-HT modes

   currently you could start an HT AP and then
   connect to a non-HT network on the same channel
   which would configure the hardware for no HT;
   that can be fixed fairly easily

 * CSA

   An AP we're connected to on a virtual interface
   might indicate switching channels, and in that
   case we would follow it, regardless of how many
   other interfaces are operating; this requires
   more effort to fix but is pretty rare after all

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
2010-05-07 14:55:50 -04:00