ath: Handle errors from copyout() in ath_rate_fetch_node_stats()

MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D43096

(cherry picked from commit 711880597c6c4ac971eb2aba6a2da

ath: Handle errors from copyout() in ath_rate_fetch_node_stats()

MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D43096

(cherry picked from commit 711880597c6c4ac971eb2aba6a2dadb5933d38dd)

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sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

ath: clean up empty lines in .c and .h files

[ath_rate_sample] Obey the maximum frame length even when using static rates.

I wasn't enforcing the maximum packet length when using static rates
so although the driver was enforcing it itself OK,

[ath_rate_sample] Obey the maximum frame length even when using static rates.

I wasn't enforcing the maximum packet length when using static rates
so although the driver was enforcing it itself OK, the statistics were
sometimes going into the wrong bin.

Tested:

* AR9380, STA mode

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[ath_rate_sample] Fix correct status when completing frames with short failures.

My preivous logic was a bit wrong. This caused transmissions that failed due
to a mix of short and long retries to c

[ath_rate_sample] Fix correct status when completing frames with short failures.

My preivous logic was a bit wrong. This caused transmissions that failed due
to a mix of short and long retries to count intermediate rates as OK if the
LONG retry count indicated some retries had made it to this intermediate rate,
but the SHORT retry count was the one that caused the whole transmit to fail.

Now status is passed in again - and this is the status for the whole transmission -
and then update_stats() does some quick math to see if the current transmission
series hit its long retry count or not before updating things as a success
or failure.

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[ath_rate_sample] Limit the tx schedules for A-MPDU ; don't take short retries
into account and remove the requirement that the MCS rate is "higher" if we're
considering a new rate.

Ok, another fun

[ath_rate_sample] Limit the tx schedules for A-MPDU ; don't take short retries
into account and remove the requirement that the MCS rate is "higher" if we're
considering a new rate.

Ok, another fun one.

* In order for reliable non-software retried higher MCS rates, the TX schedules
(inconsistently!) use hard-coded lower rates at the end of the schedule.
Now, hard-coded is a problem because (a) it means that aggregate formation
is limited by the SLOWEST rate, so I never formed large AMDU frames for
3 stream rates, and (b) if the AP disables lower rates as base rates, it
complains about "unknown rix" every frame you transmit at that rate.

So, for now just disable the third and fourth schedule entry for AMPDUs.
Now I'm forming 32k and 64k aggregates for the higher density MCS rates
much more reliably.

It would be much nicer if the rate schedule stuff wasn't fixed but instead
I'd just populate ath_rc_series[] when I fetch the rates. This is all a
holdover of ye olde pre-11n stuff and I really just need to nuke it.

But for now, ye hack.

* The check for "is this MCS rate better" based on MCS itself is just garbage.
It meant things like going MCS0->7 would be fine, and say 0->8->16 is fine,
(as they're equivalent encoding but 1,2,3 spatial streams), BUT it meant
going something like MCS7->11 would fail even though it's likely that
MCS11 would just be better, both for EWMA/BER and throughput.

So for now just use the average tx time. The "right" way for this comparison
would be to compare PHY bitrates rather than MCS / rate indexes, but I'm not
yet there. The bit rates ARE available in the PHY index, but honestly
I have a lot of other cleaning up to here before I think about that.

* Don't include the RTS/CTS retry count (and thus time) into the average tx time
caluation. It just makes temporarily failures make the rate look bad by
QUITE A LOT, as RTS/CTS exchanges are (a) long, and (b) mostly irrelevant
to the actual rate being tried. If we keep hitting RTS/CTS failures then
there's something ELSE wrong on the channel, not our selected rate.

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[ath_rate_sample] Fix logic for determining whether to bump up an MCS rate.

* Fix formatting, cause reasons;
* Put back the "and the chosen rate is within 90% of the current rate" logic;
* Ensure th

[ath_rate_sample] Fix logic for determining whether to bump up an MCS rate.

* Fix formatting, cause reasons;
* Put back the "and the chosen rate is within 90% of the current rate" logic;
* Ensure the best rate and the current rate aren't the same; this ...
* ... fixes the packets_since_switch[] tracking to actually conut how many
frames since the rate switched, so now I know how stable stuff is; and
* Ensure that MCS can go up to a higher MCS at this or any other spatial stream.
My previous quick hack attempt was doing > rather than >= so you had to go
to both a higher root MCS rate (0..7) and spatial stream. Eg, you couldn't
go from MCS0 (1ss) to MCS8 (2ss) this way.

The best rate and switching rate logic still have a bunch more work to do
because they're still quite touchy when it comes to average tx time but at least
now it's choosing higher rates correctly when it wants to try a higher rate.

Tested:

* AR9380, STA mode

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[ath] [ath_rate_sample] le oops, trim out an #if 1 that I didn't fully delete.

Cool, so now I know it's about 3 weeks between starting on freebsd coding
and breaking the build again. Queue dunce cap.

[ath] [ath_rate] Extend ath_rate_sample to better handle 11n rates and aggregates.

My initial rate control code was .. suboptimal. I wanted to at least get MCS
rates sent, but it didn't do anywhere

[ath] [ath_rate] Extend ath_rate_sample to better handle 11n rates and aggregates.

My initial rate control code was .. suboptimal. I wanted to at least get MCS
rates sent, but it didn't do anywhere near enough to handle low signal level links
or remotely keep accurate statistics.

So, 8 years later, here's what I should've done back then.

* Firstly, I wasn't at all tracking packet sizes other than the two buckets
(250 and 1600 bytes.) So, extend it to include 4096, 8192, 16384, 32768 and
65536. I may go add 2048 at some point if I find it's useful.

This is important for a few reasons. First, when forming A-MPDU or AMSDU
aggregates the frame sizes are larger, and thus the TX time calculation
is woefully, increasingly wrong. Secondly, the behaviour of 802.11 channels
isn't some fixed thing, both due to channel conditions and radios themselves.
Notably, there was some observations done a few years ago on 11n chipsets
which noticed longer aggregates showed an increase in failed A-MPDU sub-frame
reception as you got further along in the transmit time. It could be due to
a variety of things - transmitter linearity, channel conditions changing,
frequency/phase drift, etc - but the observation was to potentially form
shorter aggregates to improve BER.

* .. and then modify the ath TX path to report the length of the aggregate sent,
so as the statistics kept would line up with the correct bucket.

* Then on the rate control look-up side - i was also only using the first frame
length for an A-MPDU rate control lookup which isn't good enough here.
So, add a new method that walks the TID software queue for that node to
find out what the likely length of data available is. It isn't ALL of the
data in the queue because we'll only ever send enough data to fit inside the
block-ack window, so limit how many bytes we return to roughly what ath_tx_form_aggr()
would do.

* .. and cache that in the first ath_buf in the aggregate so it and the eventual
AMPDU length can be returned to the rate control code.

* THEN, modify the rate control code to look at them both when deciding which bucket
to attribute the sent frame on. I'm erring on the side of caution and using the
size bucket that the lookup is based on.

Ok, so now the rate lookups and statistics are "more correct". However, MCS rates
are not the same as 11abg rates in that they're not a monotonically incrementing
set of faster rates and you can't assume that just because a given MCS rate fails,
the next higher one wouldn't work better or be a lower average tx time.

So, I had to do a bunch of surgery to the best rate and sample rate math.
This is the bit that's a WIP.

* First, simplify the statistics updates (update_stats()) to do a single pass on
all rates.
* Next, make sure that each rate average tx time is updated based on /its/ failure/success.
Eg if you sent a frame with { MCS15, MCS12, MCS8 } and MCS8 succeeded, MCS15 and MCS
12 would have their average tx time updated for /their/ part of the transmission,
not the whole transmission.
* Next, EWMA wasn't being fully calculated based on the /failures/ in each of the
rate attempts. So, if MCS15, MCS12 failed above but MCS8 didn't, then ensure
that the statistics noted that /all/ subframes failed at those rates, rather than
the eventual set of transmitted/sent frames. This ensures the EWMA /and/ average
TX time are updated correctly.
* When picking a sample rate and initial rate, probe rates aroud the current MCS
but limit it to MCS0..7 /for all spatial streams/, rather than doing crazy things
like hitting MCS7 and then probing MCS8 - MCS8 is basically MCS0 but two spatial
streams. It's a /lot/ slower than MCS7. Also, the reverse is true - if we're at
MCS8 then don't probe MCS7 as part of it, it's not likely to succeed.
* Fix bugs in pick_best_rate() where I was /immediately/ choosing the highest MCS
rate if there weren't any frames yet transmitted. I was defaulting to 25% EWMA and
.. then each comparison would accept the higher rate. Just skip those; sampling
will fill in the details.

So, this seems to work a lot better. It's not perfect; I'm still seeing a lot of
instability around higher MCS rates because there are bursts of loss/retransmissions
that aren't /too/ bad. But i'll keep iterating over this and tidying up my hacks.

Ok, so why this still something I'm poking at? rather than porting minstrel_ht?

ath_rate_sample tries to minimise airtime, not maximise throughput. I have
extended it with an EWMA based on sub-frame success/failures - high MCS rates
that have partially successful receptions still show super short average frame
times, but a /lot/ of retransmits have to happen for that to work.
So for MCS rates I also track this EWMA and ensure that the rates I'm choosing
don't have super crappy packet failures. I don't mind not getting lower
peak throughput versus minstrel_ht; instead I want to see if I can make "minimise
airtime" work well.

Tested:

* AR9380, STA mode
* AR9344, STA mode
* AR9580, STA/AP mode

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[ath] [ath_rate] Add some extra data into the rate control lookup.

Right now (well, since I did this in 2011/2012) the rate control code
makes some super bad choices for 11n aggregates/rates, and it

[ath] [ath_rate] Add some extra data into the rate control lookup.

Right now (well, since I did this in 2011/2012) the rate control code
makes some super bad choices for 11n aggregates/rates, and it tracks
statistics even more questionably.

It's been long enough and I'm now trying to use it again daily, so let's
start by:

* telling the rate control code if it's an aggregate or not;
* being clearer about the TID - yes it can be extracted from the
ath_buf but this way it can be overridden by the caller without
changing the TID itself.

(This is for doing experiments with voice/video QoS at some point..)

* Return an optional field to limit how long the aggregate is in
microseconds. Right now the rate control code supplies a rate table
and the ath aggr form code will look at the rate table and limit
the aggregate size to 4ms at the slowest rate. Yeah, this is pretty
terrible.

* Add some more TODO comments around handling txpower, rate and
handling filtered frames status so if I continue to have spoons for
this I can go poke at it.

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Mark more nodes as CTLFLAG_MPSAFE or CTLFLAG_NEEDGIANT (7 of many)

r357614 added CTLFLAG_NEEDGIANT to make it easier to find nodes that are
still not MPSAFE (or already are but aren’t properly marke

Mark more nodes as CTLFLAG_MPSAFE or CTLFLAG_NEEDGIANT (7 of many)

r357614 added CTLFLAG_NEEDGIANT to make it easier to find nodes that are
still not MPSAFE (or already are but aren’t properly marked).
Use it in preparation for a general review of all nodes.

This is non-functional change that adds annotations to SYSCTL_NODE and
SYSCTL_PROC nodes using one of the soon-to-be-required flags.

Mark all low hanging fruits as MPSAFE.

Reviewed by: markj
Approved by: kib (mentor, blanket)
Differential Revision: https://reviews.freebsd.org/D23626

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[ath] [ath_rate] Fix ANI calibration during non-ACTIVE states; start poking at rate control

These are some fun issues I've found with my upstairs wifi link at such a ridiculous
low signal level (lik

[ath] [ath_rate] Fix ANI calibration during non-ACTIVE states; start poking at rate control

These are some fun issues I've found with my upstairs wifi link at such a ridiculous
low signal level (like, < 5dB.)

* Add per-station tx/rx rssi statistics, in potential preparation to use that
in the RX rate control.

* Call the rate control on each received frame to let it potentially use
it as a hint for what rates to potentially use. It's a no-op right now.

* Do ANI calibration during scan as well. The ath_newstate() call was disabling the
ANI timer and only re-enabling it during transitions to _RUN. This has the
unfortunate side-effect that if ANI deafened the NIC because of interference
and it disassociated, it wouldn't be reset and the scan would never hear beacons.

The ANI configuration is stored at least globally on some HALs and per-channel
on others. Because of this a NIC reset wouldn't help; the ANI parameters would
simply be programmed back in.

Now, I have a feeling I also need to do this during AUTH/ASSOC too and maybe,
if I'm feeling clever, I need to reset the ANI parameters on a given channel
during a transition through INIT or if the VAP is destroyed/re-created.
However for now this gets me out of the immediate weeds with connectivity
upstairs (and thus I /can/ commit); I'll keep chipping away at tidying this
stuff up in subsequent commits.

Tested:

* AR9344 (Wasp), 2G STA mode

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sys/dev: further adoption of SPDX licensing ID tags.

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

sys/dev: further adoption of SPDX licensing ID tags.

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.

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[ath] [ath_hal] (etc, etc) - begin the task of re-modularising the HAL.

In the deep past, when this code compiled as a binary module, ath_hal
built as a module. This allowed custom, smaller HAL mod

[ath] [ath_hal] (etc, etc) - begin the task of re-modularising the HAL.

In the deep past, when this code compiled as a binary module, ath_hal
built as a module. This allowed custom, smaller HAL modules to be built.
This was especially beneficial for small embedded platforms where you
didn't require /everything/ just to run.

However, sometime around the HAL opening fanfare, the HAL landed here
as one big driver+HAL thing, and a lot of the (dirty) infrastructure
(ie, #ifdef AH_SUPPORT_XXX) to build specific subsets of the HAL went away.
This was retained in sys/conf/files as "ath_hal_XXX" but it wasn't
really floated up to the modules themselves.

I'm now in a position where for the reaaaaaly embedded boards (both the
really old and the last couple generation of QCA MIPS boards) having a
cut down HAL module and driver loaded at runtime is /actually/ beneficial.

This reduces the kernel size down by quite a bit. The MIPS modules look
like this:

adrian@gertrude:~/work/freebsd/head-embedded/src % ls -l ../root/mips_ap/boot/kernel.CARAMBOLA2/ath*ko
-r-xr-xr-x 1 adrian adrian 5076 May 23 23:45 ../root/mips_ap/boot/kernel.CARAMBOLA2/ath_dfs.ko
-r-xr-xr-x 1 adrian adrian 100588 May 23 23:45 ../root/mips_ap/boot/kernel.CARAMBOLA2/ath_hal.ko
-r-xr-xr-x 1 adrian adrian 627324 May 23 23:45 ../root/mips_ap/boot/kernel.CARAMBOLA2/ath_hal_ar9300.ko
-r-xr-xr-x 1 adrian adrian 314588 May 23 23:45 ../root/mips_ap/boot/kernel.CARAMBOLA2/ath_main.ko
-r-xr-xr-x 1 adrian adrian 23472 May 23 23:45 ../root/mips_ap/boot/kernel.CARAMBOLA2/ath_rate.ko

And the x86 versions, like this:

root@gertrude:/home/adrian # ls -l /boot/kernel/ath*ko
-r-xr-xr-x 1 root wheel 36632 May 24 18:32 /boot/kernel/ath_dfs.ko
-r-xr-xr-x 1 root wheel 134440 May 24 18:32 /boot/kernel/ath_hal.ko
-r-xr-xr-x 1 root wheel 82320 May 24 18:32 /boot/kernel/ath_hal_ar5210.ko
-r-xr-xr-x 1 root wheel 104976 May 24 18:32 /boot/kernel/ath_hal_ar5211.ko
-r-xr-xr-x 1 root wheel 236144 May 24 18:32 /boot/kernel/ath_hal_ar5212.ko
-r-xr-xr-x 1 root wheel 336104 May 24 18:32 /boot/kernel/ath_hal_ar5416.ko
-r-xr-xr-x 1 root wheel 598336 May 24 18:32 /boot/kernel/ath_hal_ar9300.ko
-r-xr-xr-x 1 root wheel 406144 May 24 18:32 /boot/kernel/ath_main.ko
-r-xr-xr-x 1 root wheel 55352 May 24 18:32 /boot/kernel/ath_rate.ko

.. so you can see, not building the whole HAL can save quite a bit.
For example, if you don't need AR9300 support, you can actually avoid
wasting half a megabyte of RAM. On embedded routers this is quite a
big deal.

The AR9300 HAL can be later further shrunk because, hilariously,
it indeed supports AH_SUPPORT_<xxx> for optionally adding chipset support.
(I'll chase that down later as it's quite a big savings if you're only
building for a single embedded target.)

So:

* Create a very hackish way to load/unload HAL modules
* Create module metadata for each HAL subtype - ah_osdep_arXXXX.c
* Create module metadata for ath_rate and ath_dfs (bluetooth is
currently just built as part of it)
* .. yes, this means we could actually build multiple rate control
modules and pick one at load time, but I'd rather just glue this
into net80211's rate control code. Oh well, baby steps.
* Main driver is now "ath_main"
* Create an "if_ath" module that does what the ye olde one did -
load PCI glue, main driver, HAL and all child modules.
In this way, if you have "if_ath_load=YES" in /boot/modules.conf
it will load everything the old way and stuff should still work.
* For module autoloading purposes, I actually /did/ fix up
the name of the modules in if_ath_pci and if_ath_ahb.

If you want to selectively load things (eg on ye cheape ARM/MIPS platforms
where RAM is at a premium) you should:

* load ath_hal
* load the chip modules in question
* load ath_rate, ath_dfs
* load ath_main
* load if_ath_pci and/or if_ath_ahb depending upon your particular
bus bind type - this is where probe/attach is done.

TODO:

* AR5312 module and associated pieces - yes, we have the SoC side support
now so the wifi support would be good to "round things out";
* Just nuke AH_SUPPORT_AR5416 for now and always bloat the packet
structures; this'll simplify other things.
* Should add a simple refcnt thing to the HAL RF/chip modules so you
can't unload them whilst you're using them.
* Manpage updates, UPDATING if appropriate, etc.

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Replay r286410. Change KPI of how device drivers that provide wireless
connectivity interact with the net80211 stack.

Historical background: originally wireless devices created an interface,
just li

Replay r286410. Change KPI of how device drivers that provide wireless
connectivity interact with the net80211 stack.

Historical background: originally wireless devices created an interface,
just like Ethernet devices do. Name of an interface matched the name of
the driver that created. Later, wlan(4) layer was introduced, and the
wlanX interfaces become the actual interface, leaving original ones as
"a parent interface" of wlanX. Kernelwise, the KPI between net80211 layer
and a driver became a mix of methods that pass a pointer to struct ifnet
as identifier and methods that pass pointer to struct ieee80211com. From
user point of view, the parent interface just hangs on in the ifconfig
list, and user can't do anything useful with it.

Now, the struct ifnet goes away. The struct ieee80211com is the only
KPI between a device driver and net80211. Details:

- The struct ieee80211com is embedded into drivers softc.
- Packets are sent via new ic_transmit method, which is very much like
the previous if_transmit.
- Bringing parent up/down is done via new ic_parent method, which notifies
driver about any changes: number of wlan(4) interfaces, number of them
in promisc or allmulti state.
- Device specific ioctls (if any) are received on new ic_ioctl method.
- Packets/errors accounting are done by the stack. In certain cases, when
driver experiences errors and can not attribute them to any specific
interface, driver updates ic_oerrors or ic_ierrors counters.

Details on interface configuration with new world order:
- A sequence of commands needed to bring up wireless DOESN"T change.
- /etc/rc.conf parameters DON'T change.
- List of devices that can be used to create wlan(4) interfaces is
now provided by net.wlan.devices sysctl.

Most drivers in this change were converted by me, except of wpi(4),
that was done by Andriy Voskoboinyk. Big thanks to Kevin Lo for testing
changes to at least 8 drivers. Thanks to pluknet@, Oliver Hartmann,
Olivier Cochard, gjb@, mmoll@, op@ and lev@, who also participated in
testing.

Reviewed by: adrian
Sponsored by: Netflix
Sponsored by: Nginx, Inc.

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Revert the wifi ifnet changes until things are more baked and tested.

* 286410
* 286413
* 286416

The initial commit broke a variety of debug and features that aren't
in the GENERIC kernels but are

Revert the wifi ifnet changes until things are more baked and tested.

* 286410
* 286413
* 286416

The initial commit broke a variety of debug and features that aren't
in the GENERIC kernels but are enabled in other platforms.

show more ...

Change KPI of how device drivers that provide wireless connectivity interact
with the net80211 stack.

Historical background: originally wireless devices created an interface,
just like Ethernet devi

Change KPI of how device drivers that provide wireless connectivity interact
with the net80211 stack.

Historical background: originally wireless devices created an interface,
just like Ethernet devices do. Name of an interface matched the name of
the driver that created. Later, wlan(4) layer was introduced, and the
wlanX interfaces become the actual interface, leaving original ones as
"a parent interface" of wlanX. Kernelwise, the KPI between net80211 layer
and a driver became a mix of methods that pass a pointer to struct ifnet
as identifier and methods that pass pointer to struct ieee80211com. From
user point of view, the parent interface just hangs on in the ifconfig
list, and user can't do anything useful with it.

Now, the struct ifnet goes away. The struct ieee80211com is the only
KPI between a device driver and net80211. Details:

- The struct ieee80211com is embedded into drivers softc.
- Packets are sent via new ic_transmit method, which is very much like
the previous if_transmit.
- Bringing parent up/down is done via new ic_parent method, which notifies
driver about any changes: number of wlan(4) interfaces, number of them
in promisc or allmulti state.
- Device specific ioctls (if any) are received on new ic_ioctl method.
- Packets/errors accounting are done by the stack. In certain cases, when
driver experiences errors and can not attribute them to any specific
interface, driver updates ic_oerrors or ic_ierrors counters.

Details on interface configuration with new world order:
- A sequence of commands needed to bring up wireless DOESN"T change.
- /etc/rc.conf parameters DON'T change.
- List of devices that can be used to create wlan(4) interfaces is
now provided by net.wlan.devices sysctl.

Most drivers in this change were converted by me, except of wpi(4),
that was done by Andriy Voskoboinyk. Big thanks to Kevin Lo for testing
changes to at least 8 drivers. Thanks to Olivier Cochard, gjb@, mmoll@,
op@ and lev@, who also participated in testing. Details here:

https://wiki.freebsd.org/projects/ifnet/net80211

Still, drivers: ndis, wtap, mwl, ipw, bwn, wi, upgt, uath were not
tested. Changes to mwl, ipw, bwn, wi, upgt are trivial and chances
of problems are low. The wtap wasn't compilable even before this change.
But the ndis driver is complex, and it is likely to be broken with this
commit. Help with testing and debugging it is appreciated.

Differential Revision: D2655, D2740
Sponsored by: Nginx, Inc.
Sponsored by: Netflix

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Use device_printf() instead of if_printf(). No functional changes.

Print out the final_rix if there's a problem.

The r48589 promised to remove implicit inclusion of if_var.h soon. Prepare
to this event, adding if_var.h to files that do need it. Also, include
all includes that now are included due to implicit po

The r48589 promised to remove implicit inclusion of if_var.h soon. Prepare
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.

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I give up - just throw the EWMA update into the normal update_stats()
routine.

There were still corner cases where the EWMA update stats are being
called on a rix which didn't have an intermediary s

I give up - just throw the EWMA update into the normal update_stats()
routine.

There were still corner cases where the EWMA update stats are being
called on a rix which didn't have an intermediary stats update; thus
no packets were counted against it. Sigh.

This should fix the crashes I've been seeing on recent -HEAD.

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Update the EWMA statistics for each intermediary rate as well as the final
rate.

This fixes two things:

* The intermediary rates now also have their EWMA values changed;
* The existing code was usi

Update the EWMA statistics for each intermediary rate as well as the final
rate.

This fixes two things:

* The intermediary rates now also have their EWMA values changed;
* The existing code was using the wrong value for longtries - so the
EWMA stats were only adjusted for the first rate and not subsequent
rates in a MRR setup.

TODO:

* Merge the EWMA updates into update_stats() now..

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I've had some feedback that CCK rates are more reliable than MCS 0
in some very degenerate conditions.

However, until ath_rate_form_aggr() is taught to not form aggregates
if ANY selected rate is no

I've had some feedback that CCK rates are more reliable than MCS 0
in some very degenerate conditions.

However, until ath_rate_form_aggr() is taught to not form aggregates
if ANY selected rate is non-MCS, this can't yet be enabled.

So, just add a comment.

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Improve performance of the Sample rate algorithm on 802.11n networks.

* Don't treat high percentage failures as "sucessive failures" - high
MCS rates are very picky and will quite happily "fade" f

Improve performance of the Sample rate algorithm on 802.11n networks.

* Don't treat high percentage failures as "sucessive failures" - high
MCS rates are very picky and will quite happily "fade" from low
to high failure % and back again within a few seconds. If they really
don't work, the aggregate will just plain fail.

* Only sample MCS rates +/- 3 from the current MCS. Sample will back off
quite quickly, so there's no need to sample _all_ MCS rates between
a high MCS rate and MCS0; there may be a lot of them.

* Modify the smoothing rate to be 75% rather than 95% - it's more adaptive
but it comes with a cost of being slightly less stable at times.
A per-node, hysterisis behaviour would be nicer.

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Improve the sample rate logging.