The SPDX folks have obsoleted the BSD-2-Clause-FreeBSD identifier. Catch
up to that fact and revert to their recommended match of BSD-2-Clause.
Discussed with: pfg
MFC After: 3 days
Sponsored by: Netflix
Summary:
In preparation of making if_t completely opaque outside of the netstack,
explicitly include the header. <net/if_var.h> will stop including the
header in the future.
Sponsored by: Juniper Networks, Inc.
Reviewed by: glebius, melifaro
Differential Revision: https://reviews.freebsd.org/D38200
Going through the Frame (Sub)types the "QOS Data" being called "QOS"
scheme leads to a naming conflict for QOS_CFPOLL and QOS_CFACKPOLL
(if added). Rename QOS* to QOS_DATA* to avoid the conflict and
to also better match the standards name.
No functional changes intended.
Sponsored by: The FreeBSD Foundation
MFC after: 5 days
Reviewed by: hselasky
Differential Revision: https://reviews.freebsd.org/D36409
Replace a malloc() by IEEE80211_MALLOC().
For malloc flags even in the local ieee80211_freebsd.c there was a mix
of both versions M_ and IEEE80211_M_.
Consistently use the IEEE80211_M_ malloc options everywhere.
If the field is changed for malloc, it'll also be changed for the
other accessor functions taking a "how" field to avoid any confusion.
Sponsored by: The FreeBSD Foundation
MFC after: 1 week
Reviewed by: adrian
Differential Revision: https://reviews.freebsd.org/D36249
Summary: This returns whether the given 802.11 frame has the protected bit set.
Test Plan:
* tested in AP/STA mode
* STA mode - local athp/ath10k driver
* AP mode - in tree ath driver
Subscribers: imp, melifaro, glebius
Reviewed by: bz
Approved by: bz
Differential Revision: https://reviews.freebsd.org/D36183
Introduce (*iv_update_bss)() with a default implementation to allow
drivers to overload/intercept the time when we swap iv_bss.
This helps firmware based drivers to synchronize state with firmware.
Otherwise, for some state changes, we begin with one ni (and in
LinuxKPI lsta) and try to finish with another ni (and a new lsta
in different state) and may no longer have access to the previous state.
This also saves us from constantly checking for ni changes complicating
code.
No functional changes intended.
Sponsored by: The FreeBSD Foundation
MFC after: 3 days
X-MFC: move (*iv_update_bss) to spare area
No longer accept plaintext A-MSDU frames that start with an RFC1042
header with EtherType EAPOL. This is done by only accepting EAPOL
packets that are included in non-aggregated 802.11 frames.
Note that before this patch, FreeBSD also only accepted EAPOL frames
that are sent in a non-aggregated 802.11 frame due to bugs in
processing EAPOL packets inside A-MSDUs. In other words,
compatibility with legitimate devices remains the same.
This relates to section 6.5 in the 2021 Usenix "FragAttacks" (Fragment
and Forge: Breaking Wi-Fi Through Frame Aggregation and Fragmentation)
paper.
Submitted by: Mathy Vanhoef (Mathy.Vanhoef kuleuven.be)
Security: CVE-2020-26144
PR: 256120
MFC after: 7 days
Differential Revision: https://reviews.freebsd.org/D30665
Mitigate A-MSDU injection attacks by detecting if the destination address
of a subframe equals an RFC1042 (i.e., LLC/SNAP) header, and if so
dropping the complete A-MSDU frame. This mitigates known attacks,
although new (unknown) aggregation-based attacks may remain possible.
This defense works because in A-MSDU aggregation injection attacks, a
normal encrypted Wi-Fi frame is turned into an A-MSDU frame. This means
the first 6 bytes of the first A-MSDU subframe correspond to an RFC1042
header. In other words, the destination MAC address of the first A-MSDU
subframe contains the start of an RFC1042 header during an aggregation
attack. We can detect this and thereby prevent this specific attack.
This relates to section 7.2 in the 2021 Usenix "FragAttacks" (Fragment
and Forge: Breaking Wi-Fi Through Frame Aggregation and Fragmentation)
paper.
Submitted by: Mathy Vanhoef (Mathy.Vanhoef kuleuven.be)
Security: CVE-2020-24588
PR: 256119
Differential Revision: https://reviews.freebsd.org/D30664
ieee80211_defrag() accepts fragmented 802.11 frames in a protected Wi-Fi
network even when some of the fragments are not encrypted.
Track whether the fragments are encrypted or not and only accept
successive ones if they match the state of the first fragment.
This relates to section 6.3 in the 2021 Usenix "FragAttacks" (Fragment
and Forge: Breaking Wi-Fi Through Frame Aggregation and Fragmentation)
paper.
Submitted by: Mathy Vanhoef (Mathy.Vanhoef kuleuven.be)
Security: CVE-2020-26147
PR: 256118
Differential Revision: https://reviews.freebsd.org/D30663
- Perform ifp mismatch checks (to determine if a send tag is allocated
for a different ifp than the one the packet is being output on), in
ip_output() and ip6_output(). This avoids sending packets with send
tags to ifnet drivers that don't support send tags.
Since we are now checking for ifp mismatches before invoking
if_output, we can now try to allocate a new tag before invoking
if_output sending the original packet on the new tag if allocation
succeeds.
To avoid code duplication for the fragment and unfragmented cases,
add ip_output_send() and ip6_output_send() as wrappers around
if_output and nd6_output_ifp, respectively. All of the logic for
setting send tags and dealing with send tag-related errors is done
in these wrapper functions.
For pseudo interfaces that wrap other network interfaces (vlan and
lagg), wrapper send tags are now allocated so that ip*_output see
the wrapper ifp as the ifp in the send tag. The if_transmit
routines rewrite the send tags after performing an ifp mismatch
check. If an ifp mismatch is detected, the transmit routines fail
with EAGAIN.
- To provide clearer life cycle management of send tags, especially
in the presence of vlan and lagg wrapper tags, add a reference count
to send tags managed via m_snd_tag_ref() and m_snd_tag_rele().
Provide a helper function (m_snd_tag_init()) for use by drivers
supporting send tags. m_snd_tag_init() takes care of the if_ref
on the ifp meaning that code alloating send tags via if_snd_tag_alloc
no longer has to manage that manually. Similarly, m_snd_tag_rele
drops the refcount on the ifp after invoking if_snd_tag_free when
the last reference to a send tag is dropped.
This also closes use after free races if there are pending packets in
driver tx rings after the socket is closed (e.g. from tcpdrop).
In order for m_free to work reliably, add a new CSUM_SND_TAG flag in
csum_flags to indicate 'snd_tag' is set (rather than 'rcvif').
Drivers now also check this flag instead of checking snd_tag against
NULL. This avoids false positive matches when a forwarded packet
has a non-NULL rcvif that was treated as a send tag.
- cxgbe was relying on snd_tag_free being called when the inp was
detached so that it could kick the firmware to flush any pending
work on the flow. This is because the driver doesn't require ACK
messages from the firmware for every request, but instead does a
kind of manual interrupt coalescing by only setting a flag to
request a completion on a subset of requests. If all of the
in-flight requests don't have the flag when the tag is detached from
the inp, the flow might never return the credits. The current
snd_tag_free command issues a flush command to force the credits to
return. However, the credit return is what also frees the mbufs,
and since those mbufs now hold references on the tag, this meant
that snd_tag_free would never be called.
To fix, explicitly drop the mbuf's reference on the snd tag when the
mbuf is queued in the firmware work queue. This means that once the
inp's reference on the tag goes away and all in-flight mbufs have
been queued to the firmware, tag's refcount will drop to zero and
snd_tag_free will kick in and send the flush request. Note that we
need to avoid doing this in the middle of ethofld_tx(), so the
driver grabs a temporary reference on the tag around that loop to
defer the free to the end of the function in case it sends the last
mbuf to the queue after the inp has dropped its reference on the
tag.
- mlx5 preallocates send tags and was using the ifp pointer even when
the send tag wasn't in use. Explicitly use the ifp from other data
structures instead.
- Sprinkle some assertions in various places to assert that received
packets don't have a send tag, and that other places that overwrite
rcvif (e.g. 802.11 transmit) don't clobber a send tag pointer.
Reviewed by: gallatin, hselasky, rgrimes, ae
Sponsored by: Netflix
Differential Revision: https://reviews.freebsd.org/D20117
Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.
The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.
No functional change intended.
When doing AMSDU offload, the driver (for now!) presents 802.11 frames with
the same sequence number and crypto sequence number / IV values up to the stack.
But, this will trip afoul over the sequence number detection.
So drivers now have a way to signify that a frame is part of an offloaded
AMSDU group, so we can just ensure that we pass those frames up to the
stack.
The logic will be a bit messy - the TL;DR will be that if it's part of
the previously seen sequence number then it belongs in the same burst.
But if we get a repeat of the same sequence number (eg we sent an ACK
but the receiver didn't hear it) then we shouldn't be passing those frames
up. So, we can't just say "all subframes go up", we need to track
whether we've seen the end of a burst of frames for the given sequence
number or not, so we know whether to actually pass them up or not.
The first part of doing all of this is to ensure the ieee80211_rx_stats
struct is available in the RX sequence number check path and the
RX ampdu reorder path. So, start by passing the pointer into these
functions to avoid doing another lookup.
The actual support will come in a subsequent commit once I know the
functionality actually works!
* teach the crypto modules about receive offload - although I have
to do some further reviewing in places where we /can't/ have an RX key
* teach the RX data path about receive offload encryption - check the flag,
handle NULL key, do decap and checking as appropriate.
Tested:
* iwn(4), STA mode
* ath(4), STA and AP mode
* ath10k port, STA mode (hardware encryption)
Reviewed by: avos
Differential Revision: https://reviews.freebsd.org/D8533
Hide subtype mask/shift (which is used for index calculation
in ieee80211_mgt_subtype_name[] array) in function call.
Tested with RTL8188CUS, STA mode.
Reviewed by: adrian
Differential Revision: https://reviews.freebsd.org/D5369
- Add definitions for Timing Advertisement and Control Wrapper frames.
- Refresh ieee80211_mgt_subtype_name and ieee80211_ctl_subtype_name
arrays.
- Count Timing Advertisement frames as discarded management frames in all
modes.
Approved by: adrian (mentor)
Differential Revision: https://reviews.freebsd.org/D5331
Move error handling into ieee80211_parent_xmitpkt() instead of spreading it
between functions.
Submitted by: <s3erios@gmail.com>
Differential Revision: https://reviews.freebsd.org/D3772
Smart NICs with firmware (eg wpi, iwn, the new atheros parts, the intel 7260
series, etc) support doing a lot of things in firmware. This includes but
isn't limited to things like scanning, sending probe requests and receiving
probe responses. However, net80211 doesn't know about any of this - it still
drives the whole scan/probe infrastructure itself.
In order to move towards suppoting smart NICs, the receive path needs to
know about the channel/details for each received packet. In at least
the iwn and 7260 firmware (and I believe wpi, but I haven't tried it yet)
it will do the scanning, power-save and off-channel buffering for you -
all you need to do is handle receiving beacons and probe responses on
channels that aren't what you're currently on. However the whole receive
path is peppered with ic->ic_curchan and manual scan/powersave handling.
The beacon parsing code also checks ic->ic_curchan to determine if the
received beacon is on the correct channel or not.[1]
So:
* add freq/ieee values to ieee80211_rx_stats;
* change ieee80211_parse_beacon() to accept the 'current' channel
as an argument;
* modify the iv_input() and iv_recv_mgmt() methods to include the rx_stats;
* add a new method - ieee80211_lookup_channel_rxstats() - that looks up
a channel based on the contents of ieee80211_rx_stats;
* if it exists, use it in the mgmt path to switch the current channel
(which still defaults to ic->ic_curchan) over to something determined
by rx_stats.
This is enough to kick-start scan offload support in the Intel 7260
driver that Rui/I are working on. It also is a good start for scan
offload support for a handful of existing NICs (wpi, iwn, some USB
parts) and it'll very likely dramatically improve stability/performance
there. It's not the whole thing - notably, we don't need to do powersave,
we should not scan all channels, and we should leave probe request sending
to the firmware and not do it ourselves. But, this allows for continued
development on the above features whilst actually having a somewhat
working NIC.
TODO:
* Finish tidying up how the net80211 input path works.
Right now ieee80211_input / ieee80211_input_all act as the top-level
that everything feeds into; it should change so the MIMO input routines
are those and the legacy routines are phased out.
* The band selection should be done by the driver, not by the net80211
layer.
* ieee80211_lookup_channel_rxstats() only determines 11b or 11g channels
for now - this is enough for scanning, but not 100% true in all cases.
If we ever need to handle off-channel scan support for things like
static-40MHz or static-80MHz, or turbo-G, or half/quarter rates,
then we should extend this.
[1] This is a side effect of frequency-hopping and CCK modes - you
can receive beacons when you think you're on a different channel.
In particular, CCK (which is used by the low 11b rates, eg beacons!)
is decodable from adjacent channels - just at a low SNR.
FH is a side effect of having the hardware/firmware do the frequency
hopping - it may pick up beacons transmitted from other FH networks
that are in a different phase of hopping frequencies.
ieee80211_pwrsave() can fail due to queue overflow, check its return code
and increment oerrors counter when it fails. Also handle more error cases
and update oerrors counter when we don't send mbuf due to some errors.
Return ENETDOWN when parent interface isn't ready. Update obytes and omcasts
counters in corresponding places.
PR: 184626
Differential Revision: https://reviews.freebsd.org/D2621
Reviewed by: adrian
MFC after: 1 week
frames to 0
From IEEE Std. 802.11-2012, 8.3.2.1 "Data frame format", p. 415 (513):
"The Sequence Control field for QoS (+)Null frames is ignored by the receiver
upon reception."
At this moment, any <mode>_input() function interprets them as regular QoS data
frames with TID = 0. As a result, stations, that use another TX sequence for
QoS Null frames (e.g. wpi(4), where (QoS) Null frames are generated by the
firmware), may experience significant packet loss with any other NIC in hostap
mode.
Tested:
* wpi(4) (author)
* iwn(4) - Intel 5100, STA mode (me)
PR: kern/200128
Submitted by: Andriy Voskoboinyk <s3erios@gmail.com>
The origin of WEP comes from IEEE Std 802.11-1997 where it defines
whether the frame body of MAC frame has been encrypted using WEP
algorithm or not.
IEEE Std. 802.11-2007 changes WEP to Protected Frame, indicates
whether the frame is protected by a cryptographic encapsulation
algorithm.
Reviewed by: adrian, rpaulo
to this event, adding if_var.h to files that do need it. Also, include
all includes that now are included due to implicit pollution via if_var.h
Sponsored by: Netflix
Sponsored by: Nginx, Inc.
upper layer(s).
This eliminates the if_snd queue from net80211. Yay!
This unfortunately has a few side effects:
* It breaks ALTQ to net80211 for now - sorry everyone, but fixing
parallelism and eliminating the if_snd queue is more important
than supporting this broken traffic scheduling model. :-)
* There's no VAP and IC flush methods just yet - I think I'll add
some NULL methods for now just as placeholders.
* It reduces throughput a little because now net80211 will drop packets
rather than buffer them if the driver doesn't do its own buffering.
This will be addressed in the future as I implement per-node software
queues.
Tested:
* ath(4) and iwn(4) in STA operation
This patchset implements a new TX lock, covering both the per-VAP (and
thus per-node) TX locking and the serialisation through to the underlying
physical device.
This implements the hard requirement that frames to the underlying physical
device are scheduled to the underlying device in the same order that they
are processed at the VAP layer. This includes adding extra encapsulation
state (such as sequence numbers and CCMP IV numbers.) Any order mismatch
here will result in dropped packets at the receiver.
There are multiple transmit contexts from the upper protocol layers as well
as the "raw" interface via the management and BPF transmit paths.
All of these need to be correctly serialised or bad behaviour will result
under load.
The specifics:
* add a new TX IC lock - it will eventually just be used for serialisation
to the underlying physical device but for now it's used for both the
VAP encapsulation/serialisation and the physical device dispatch.
This lock is specifically non-recursive.
* Methodize the parent transmit, vap transmit and ic_raw_xmit function
pointers; use lock assertions in the parent/vap transmit routines.
* Add a lock assertion in ieee80211_encap() - the TX lock must be held
here to guarantee sensible behaviour.
* Refactor out the packet sending code from ieee80211_start() - now
ieee80211_start() is just a loop over the ifnet queue and it dispatches
each VAP packet send through ieee80211_start_pkt().
Yes, I will likely rename ieee80211_start_pkt() to something that
better reflects its status as a VAP packet transmit path. More on
that later.
* Add locking around the management and BAR TX sending - to ensure that
encapsulation and TX are done hand-in-hand.
* Add locking in the mesh code - again, to ensure that encapsulation
and mesh transmit are done hand-in-hand.
* Add locking around the power save queue and ageq handling, when
dispatching to the parent interface.
* Add locking around the WDS handoff.
* Add a note in the mesh dispatch code that the TX path needs to be
re-thought-out - right now it's doing a direct parent device transmit
rather than going via the vap layer. It may "work", but it's likely
incorrect (as it bypasses any possible per-node power save and
aggregation handling.)
Why not a per-VAP or per-node lock?
Because in order to ensure per-VAP ordering, we'd have to hold the
VAP lock across parent->if_transmit(). There are a few problems
with this:
* There's some state being setup during each driver transmit - specifically,
the encryption encap / CCMP IV setup. That should eventually be dragged
back into the encapsulation phase but for now it lives in the driver TX path.
This should be locked.
* Two drivers (ath, iwn) re-use the node->ni_txseqs array in order to
allocate sequence numbers when doing transmit aggregation. This should
also be locked.
* Drivers may have multiple frames queued already - so when one calls
if_transmit(), it may end up dispatching multiple frames for different
VAPs/nodes, each needing a different lock when handling that particular
end destination.
So to be "correct" locking-wise, we'd end up needing to grab a VAP or
node lock inside the driver TX path when setting up crypto / AMPDU sequence
numbers, and we may already _have_ a TX lock held - mostly for the same
destination vap/node, but sometimes it'll be for others. That could lead
to LORs and thus deadlocks.
So for now, I'm sticking with an IC TX lock. It has the advantage of
papering over the above and it also has the added advantage that I can
assert that it's being held when doing a parent device transmit.
I'll look at splitting the locks out a bit more later on.
General outstanding net80211 TX path issues / TODO:
* Look into separating out the VAP serialisation and the IC handoff.
It's going to be tricky as parent->if_transmit() doesn't give me the
opportunity to split queuing from driver dispatch. See above.
* Work with monthadar to fix up the mesh transmit path so it doesn't go via
the parent interface when retransmitting frames.
* Push the encryption handling back into the driver, if it's at all
architectually sane to do so. I know it's possible - it's what mac80211
in Linux does.
* Make ieee80211_raw_xmit() queue a frame into VAP or parent queue rather
than doing a short-cut direct into the driver. There are QoS issues
here - you do want your management frames to be encapsulated and pushed
onto the stack sooner than the (large, bursty) amount of data frames
that are queued. But there has to be a saner way to do this.
* Fragments are still broken - drivers need to be upgraded to an if_transmit()
implementation and then fragmentation handling needs to be properly fixed.
Tested:
* STA - AR5416, AR9280, Intel 5300 abgn wifi
* Hostap - AR5416, AR9160, AR9280
* Mesh - some testing by monthadar@, more to come.
handling.
The current sequence number code does a few things incorrectly:
* It didn't try eliminating duplications from HT nodes. I guess it's assumed
that out of order / retransmission handling would be handled by the AMPDU RX
routines. If a HT node isn't doing AMPDU RX, then retransmissions need to
be eliminated. Since most of my debugging is based on this (as AMPDU TX
software packet aggregation isn't yet handled), handle this corner case.
* When a sequence number of 4095 was received, any subsequent sequence number
is going to be (by definition) less than 4095. So if the following sequence
number (0) doesn't initially occur and the retransmit is received, it's
incorrectly eliminated by the IEEE80211_FC1_RETRY && SEQ_LEQ() check.
Try to handle this better.
This almost completely eliminates out of order TCP statistics showing up during
iperf testing for the 11a, 11g and non-aggregate 11n AMPDU RX case. The only
other packet loss conditions leading to this are due to baseband resets or
heavy interference.
clean up parts of the *_recv_mgmt() functions.
- make sure appropriate counters are bumped and debug messages are printed
- order the unhandled subtypes by value and add a few missing ones
- fix some whitespace nits
- remove duplicate code in adhoc_recv_mgmt()
- remove a useless comment, probably left in while c&p
long-term work before they can be serviced. Packets are tagged and
assigned an age (in seconds) at the point they are added to the
queue. If a packet is not retrieved before it's age expires it is
reclaimed. Tagging can take two forms: a reference to an ieee80211_node
(as happens in the tx path) or an opaque token in cases where there
is no reference or the node structure is not stable (i.e. it's going
to be destroyed).
o add ic_stageq to replace the per-node wds staging queue used for
dynamic wds
o add ieee80211_mac_hash for building ageq tokens; this computes a
32-bit hash from an 802.11 mac address (copied from the bridge)
o while here fix a stray ';' noticed in IEEE80211_PSQ_INIT
Reviewed by: rpaulo
Approved by: re (kensmith)
o add a new facility for components to register send+recv handlers
o ieee80211_send_action and ieee80211_recv_action now use the registered
handlers to dispatch operations
o rev ieee80211_send_action api to enable passing arbitrary data
o rev ieee80211_recv_action api to pass the 802.11 frame header as it may
be difficult to locate
o update existing IEEE80211_ACTION_CAT_BA and IEEE80211_ACTION_CAT_HT handling
o update mwl for api rev
Reviewed by: rpaulo
Approved by: re (kensmith)
o do not attach DLT_IEEE802_11_RADIO unless both tx and rx headers are
present; this is assumed in the capture code paths
o verify the above with asserts in ieee80211_radiotap_{rx,tx}
o add missing checks for active taps before calling ieee80211_radiotap_rx
o replace DLT_IEEE802_11 support in net80211 with DLT_IEEE802_11_RADIO
and remove explicit bpf support from wireless drivers; drivers now
use ieee80211_radiotap_attach to setup shared data structures that
hold the radiotap header for each packet tx/rx
o remove rx timestamp from the rx path; it was used only by the tdma support
for debugging and was mostly useless due to it being 32-bits and mostly
unavailable
o track DLT_IEEE80211_RADIO bpf attachments and maintain per-vap and
per-com state when there are active taps
o track the number of monitor mode vaps
o use bpf tap and monitor mode vap state to decide when to collect radiotap
state and dispatch frames; drivers no longer explicitly directly check
bpf state or use bpf calls to tap frames
o handle radiotap state updates on channel change in net80211; drivers
should not do this (unless they bypass net80211 which is almost always
a mistake)
o update various drivers to be more consistent/correct in handling radiotap
o update ral to include TSF in radiotap'd frames
o add promisc mode callback to wi
Reviewed by: cbzimmer, rpaulo, thompsa
to be encapsulated before dispatching to the driver
o eliminate M_WDS now that we call ieee80211_encap directly and can supply
the wds vap to indicate a 4-address frame should be created
capabilities reported by the ap. These need to be cross-checked
against the local configuration in the vap. Previously we were
only checking the ap capabilities which meant that if an ap reported
it was ff-capable but we were not setup to use them we'd try to do
ff aggregation and drop the frame.
There are a number of problems to be fixed here but applying this
fix immediately as the problem causes all traffic to stop (and has
not workaround).
Reported by: Ashish Shukla
For receive:
o explicitly tag rx frames w/ M_AMPDU instead of passing frames through
the reorder processing according to the node having HT and the frame
being QoS data
o relax ieee80211_ampdu_reorder asserts to allow any frame to be passed
in, unsuitable frames are returned to the caller for normal processing;
this permits drivers that cannot inspect the PLCP to mark all data
frames as potential ampdu candidates with only a small penalty
o add M_AMPDU_MPDU to identify frames resubmitted from the reorder q
For transmit:
o tag aggregation candidates with M_AMPDU_MPDU
o fix the QoS ack policy set in ampdu subframes; we only support immediate
BA streams which should be marked for "normal ack" to get implicit block
ack behaviour; interestingly certain vendor parts BA'd frames with the
11e BA ack policy set
o do not assign a sequence # to aggregation candidates; this must be done
when frames are submitted for transmit (NB: this can/will be handled
better when aggregation is pulled up to net80211)
Note this includes changes to all drivers and moves some device firmware
loading to use firmware(9) and a separate module (e.g. ral). Also there
no longer are separate wlan_scan* modules; this functionality is now
bundled into the wlan module.
Supported by: Hobnob and Marvell
Reviewed by: many
Obtained from: Atheros (some bits)
