Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

net80211: fix LOR/deadlock in ieee80211_ff_node_cleanup().

Add new lock for stageq (part of ieee80211_superg structure) and
ni_tx_superg (part of ieee80211_node structure);
drop com_lock protection where it is used to protect them.

While here, drop duplicate OPACKETS counter incrementation.

ni_tx_ampdu is not protected with it (however, it is also used without
locking in other places; probably, it requires some other solution
to be thread-safe).

Tested with RTL8188CUS (AP) and RTL8188EU (STA).

NOTE: Since this change breaks KBI, all wireless drivers need to be
recompiled.

Reviewed by: adrian
Approved by: re (gjb)
Differential Revision: https://reviews.freebsd.org/D6958

[net80211] Initial A-MSDU support for testing / evaluation

A-MSDU is another 11n aggregation mechanism where multiple ethernet
frames get LLC encapsulated (so they have a length field), padded,
and put in a single MPDU (802.11 MAC frame.) This means it gets sent
out as a single frame, with a single seqno, it's acked as one frame, etc.

It turns out that, hah, atheros fast frames is almost but not quite
like this, so I'm reusing all of the current superg/fast-frames stuff
in order to actually transmit A-MSDU. Yes, this means that A-MSDU
frames are also only aggregated two at a time, so it's not necessarily
a huge win, but it's better than nothing.

This doesn't do anything by default - the driver needs to say it does
A-MSDU as well as set the AMSDU software TX capability so this code path
gets exercised.

For now, the only driver that enables this is urtwn. I'll enable it
for rsu at some point soon.
Tested:

* Add an amsdu encap path to aggregate two frames, same as the
fast-frames path.

* Always do the superg init/teardown and node init/teardown stuff,
regardless of whether the nodes are doing fast-frames (the ATH
capability stuff.) That way we can reuse it for amsdu.

* Don't do AMSDU for multicast/broadcast and EAPOL frames.

* If we're doing A-MPDU, then don't bother doing FF/A-MSDU.
We can likely do both together, but I don't want to change
behaviour.

* Teach the fast frames approx txtime logic to support the 11n
rates. But, since we don't currently have a full "current rate"
support, assume it's HT20, long-gi, etc. That way we overshoot
on the TX time estimation, so we're always inside the requirements.
(And we only aggregate two frames for now, so we're not really
going to exceed that.)

* Drop the maximum FF age default down to 2ms, otherwise we end up
with some very annoyingly large latencies.

TODO:

* We only aggregate two ethernet frames, so I'm not checking the max
A-MSDU size. But when it comes time to support >2 frames, we should
obey that.

Tested:

* urtwn(4)

Atheros SuperG bug fixes, as part of hunting down kern/174283.

The stageqdepth (global, over all staging queues) was being kept
incorrectly. It was being incremented whenever things were added,
but only decremented during a flush. During active fast frames activity
it wasn't being decremented, resulting in it always having a non-zero
value during normal fast-frames operation.

It was only used when checking if the aging queue should be checked;
we may as well just defer to each of those staging queue counters (which
look correct, thankfully.)

Whilst I'm here, add locking assertions in the staging queue add/remove
functions. The current crash shows that the staging queue has one frame,
but only has a tail pointer set (the head pointer being set to NULL.)
I'd like to grab a few more crashes where these locking assertions are
in place so I can narrow down the issue between "somehow locking is
messed up and things are racy" and "the stage queue head/tail pointer
manipulation logic is subtly wrong."

Tested:

* AR5416 STA, AR5413 AP; with FastFrames enabled in the AR5416 HAL.

PR: kern/174283

Don't panic if the stageq here is empty; just fall through with NULL
pointers and leave the stage queue flush routine to just do nothing
(since both head and tail here will be NULL.)

This should quieten the "stageq empty" panic where the stageq itself
is empty, but it won't fix the second KASSERT() here "staging queue empty"
as that's likely a different underlying problem.

PR: kern/174283

make superg/fast-frames state dynamically-allocated (and indirect off
the com structure instead of embedded); this reduces the overhead when
not configured and reduces visibility of the contents

Hoist 802.11 encapsulation up into net80211:
o call ieee80211_encap in ieee80211_start so frames passed down to drivers
are already encapsulated
o remove ieee80211_encap calls in drivers
o fixup wi so it recreates the 802.3 head it requires from the 802.11
header contents
o move fast-frame aggregation from ath to net80211 (conditional on
IEEE80211_SUPPORT_SUPERG):
- aggregation is now done in ieee80211_start; it is enabled when the
packets/sec exceeds ieee80211_ffppsmin (net.wlan.ffppsmin) and frames
are held on a staging queue according to ieee80211_ffagemax
(net.wlan.ffagemax) to wait for a frame to combine with
- drivers must call back to age/flush the staging queue (ath does this
on tx done, at swba, and on rx according to the state of the tx queues
and/or the contents of the staging queue)
- remove fast-frame-related data structures from ath
- add ieee80211_ff_node_init and ieee80211_ff_node_cleanup to handle
per-node fast-frames state (we reuse 11n tx ampdu state)
o change ieee80211_encap calling convention to include an explicit vap
so frames coming through a WDS vap are recognized w/o setting M_WDS

With these changes any device able to tx/rx 3Kbyte+ frames can use fast-frames.

Reviewed by: thompsa, rpaulo, avatar, imp, sephe

o move tdma+superg protocol defs out of public view
o add #ifdef _KERNEL to superg+tdma include files so they can be used
by user code to get the protocol defs

Fix enough bits so that fast frames work again:
o include ath ie in beacon frames
o fix probe response check for including ath ie
o add ieee80211_add_athcap shorthand for ap-side ie additions

split Atheros SuperG support out into it's own file that's included only
with a new IEEE80211_SUPPORT_SUPERG option