Merge svn+ssh://svn.freebsd.org/base/head@207793

Final update to current version of head in preparation for reintegration.

Switch to our preferred 2-clause BSD license.

Approved by: kmacy

IFH@204581

- make printf conditional
- fix witness warnings by making configuration lock a mutex

Merge from head at r201628.

# This hasn't been tested, and there are at least three bad commits
# that need to be backed out before the branch will be stable again.

Add media ioctl support and link notifications so that devd will attempt
to run dhclient on a netfront (xn) device that is setup for DHCP in
/etc/rc.conf.

PR: kern/136251 (fixed differently than th

Add media ioctl support and link notifications so that devd will attempt
to run dhclient on a netfront (xn) device that is setup for DHCP in
/etc/rc.conf.

PR: kern/136251 (fixed differently than the submitted patch)

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Remove commented out reference to if_watchdog and an assignment of zero to
if_timer.

Reviewed by: scottl

Merge from head

Merge from head up to r188941 (last revision before the USB stack switch)

- MFC

update backend_changed to reflect .m prototype

- Merge from HEAD

Fix compilation when compiled w/out WITNESS.

Submitted by: Edwin Shao <poleris@gmail.com>

Delete useless #ifdef; make it more obvious if setting TSO fails.

Clear IFF_DRV_OACTIVE if at least one TX xen/mbuf ring slot has been freed.

Enforce that there are actually enough xenbus TX ring descriptors available
before attempting to queue the packet.

Comment tidyup; comment where the next explicit check should
appear.

Ensure that there are enough TX mbuf ring slots available before beginning
to dequeue a packet.

The tx path was trying to ensure that enough Xenbus TX ring slots existed but
it didn't check to see w

Ensure that there are enough TX mbuf ring slots available before beginning
to dequeue a packet.

The tx path was trying to ensure that enough Xenbus TX ring slots existed but
it didn't check to see whether the mbuf TX ring slots were also available.
They get freed in xn_txeof() which occurs after transmission, rather than earlier
on in the process. (The same happens under Linux too.)

Due to whatever reason (CPU use, scheduling, memory constraints, whatever) the
mbuf TX ring may not have enough slots free and would allocate slot 0. This is
used as the freelist head pointer to represent "free" mbuf TX ring slots; setting
this to an actual mbuf value rather than an id crashes the code.

This commit introduces some basic code to track the TX mbuf ring use and then
(hopefully!) ensures that enough slots are free in said TX mbuf ring before it
enters the actual work loop.

A few notes:

* Similar logic needs to be introduced to check there are enough actual slots
available in the xenbuf TX ring. There's some logic which is invoked earlier
but it doesn't hard-check against the number of available ring slots.
Its trivial to do; I'll do it in a subsequent commit.

* As I've now commented in the source, it is likely possible to deadlock the
driver under certain conditions where the rings aren't receiving any changes
(which I should enumerate) and thus Xen doesn't send any further software
interrupts. I need to make sure that the timer(s) are running right and
the queues are periodically kicked.

PR: 134926

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Do the invariant check before the mbuf is dereferenced.

Flesh out some inline documentation which hopefully reflect the intended
reality of these functions.

Add in some INVARIANT checks in the TX mbuf descriptor "freelist" management code.

Slot 0 must always remain "free" and be a pointer to the first free entry in the
mbuf descriptor list. It is thus a

Add in some INVARIANT checks in the TX mbuf descriptor "freelist" management code.

Slot 0 must always remain "free" and be a pointer to the first free entry in the
mbuf descriptor list. It is thus an error to have code allocate or push slot 0
back into the list.

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Merge from HEAD

The merge in r189699 reverted part of the work done in a previous commit
(r188036.)

Re-revert that change so the Xen networking functions again.

Update the projects tree to a newer FreeBSD current.