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

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.

Restructure the mbuf pkthdr to make it fit for upcoming capabilities and
features. The changes in particular are:

o Remove rarely used "header" pointer and replace it with a 64bit protocol/
layer specific union PH_loc for local use. Protocols can flexibly overlay
their own 8 to 64 bit fields to store information while the packet is
worked on.

o Mechanically convert IP reassembly, IGMP/MLD and ATM to use pkthdr.PH_loc
instead of pkthdr.header.

o Extend csum_flags to 64bits to allow for additional future offload
information to be carried (e.g. iSCSI, IPsec offload, and others).

o Move the RSS hash type enumerator from abusing m_flags to its own 8bit
rsstype field. Adjust accessor macros.

o Add cosqos field to store Class of Service / Quality of Service information
with the packet. It is not yet supported in any drivers but allows us to
get on par with Cisco/Juniper in routing applications (plus MPLS QoS) with
a modernized ALTQ.

o Add four 8 bit fields l[2-5]hlen to store the relative header offsets
from the start of the packet. This is important for various offload
capabilities and to relieve the drivers from having to parse the packet
and protocol headers to find out location of checksums and other
information. Header parsing in drivers is a lot of copy-paste and
unhandled corner cases which we want to avoid.

o Add another flexible 64bit union to map various additional persistent
packet information, like ether_vtag, tso_segsz and csum fields.
Depending on the csum_flags settings some fields may have different usage
making it very flexible and adaptable to future capabilities.

o Restructure the CSUM flags to better signify their outbound (down the
stack) and inbound (up the stack) use. The CSUM flags used to be a bit
chaotic and rather poorly documented leading to incorrect use in many
places. Bring clarity into their use through better naming.
Compatibility mappings are provided to preserve the API. The drivers
can be corrected one by one and MFC'd without issue.

o The size of pkthdr stays the same at 48/56bytes (32/64bit architectures).

Sponsored by: The FreeBSD Foundation

Propagate rename of IFF_OACTIVE and IFF_RUNNING to IFF_DRV_OACTIVE and
IFF_DRV_RUNNING, as well as the move from ifnet.if_flags to
ifnet.if_drv_flags. Device drivers are now responsible for
synchronizing access to these flags, as they are in if_drv_flags. This
helps prevent races between the network stack and device driver in
maintaining the interface flags field.

Many __FreeBSD__ and __FreeBSD_version checks maintained and continued;
some less so.

Reviewed by: pjd, bz
MFC after: 7 days

Stop embedding struct ifnet at the top of driver softcs. Instead the
struct ifnet or the layer 2 common structure it was embedded in have
been replaced with a struct ifnet pointer to be filled by a call to the
new function, if_alloc(). The layer 2 common structure is also allocated
via if_alloc() based on the interface type. It is hung off the new
struct ifnet member, if_l2com.

This change removes the size of these structures from the kernel ABI and
will allow us to better manage them as interfaces come and go.

Other changes of note:
- Struct arpcom is no longer referenced in normal interface code.
Instead the Ethernet address is accessed via the IFP2ENADDR() macro.
To enforce this ac_enaddr has been renamed to _ac_enaddr.
- The second argument to ether_ifattach is now always the mac address
from driver private storage rather than sometimes being ac_enaddr.

Reviewed by: sobomax, sam

Start each of the license/copyright comments with /*-, minor shuffle of lines

Eliminate multiple __FBSDID and sys/cdefs.h.

All three of these drivers abused cv_waitq_empty in the same way by spinning
on it in hopes of making sure that the waitq was empty before going on.
This wasn't needed and probably never would have worked as intended. Now
that cv_waitq_empty() and friends are gone, the code in these drivers that
spins on it can go away too. This should unbreak LINT.

Discussed with: kan

Use __FBSDID().
Also some minor style cleanups.

Make open channels persist across ifconfig down and up. All channels
that are not currently closing when the interface is configured down
will be brough up as soon as the interface is configured up.

Send events for VCC state changes, ACR rate changes and interface state
changes.

This is a driver for IDT77252 based ATM interfaces. It has been tested
with a ProATM-155 and an IDT evaluation board and should also work
with a ProATM-25 (it seems to work at least, I cannot really measure
what the card emits). The driver has been tested on i386 and sparc64,
but should work an other archs also. It supports UBR, CBR, ABR and VBR;
AAL0, AAL5 and AALraw. As an additional feature VCI/VPI 0/0 can be
opened for receiving in AALraw mode and receives all cells not claimed
by other open VCs (even cells with invalid GFC, VPI and VCI fields and
OAM cells).

Thanks to Christian Bucari from ProSum for lending two cards and answering
my questions.