LinuxKPI: Constantly use _LINUXKPI_ prefix in include guards

MFC after: 1 week
Reviewed by: bz, emaste, hselasky, manu
Differential Revision: https://reviews.freebsd.org/D33562

LinuxKPI/OFED: (re)move inetdevice.h implementation

The two functions in linux/inetdevice.h are highly FreeBSD/ifnet
specific. This is a result of struct net_device being mapped to
struct ifnet.

The only known consumer of these functions are two files in the
ofed/infiniband code.

As a first step of cleaning up copy linux/inetdevice.h to
rdma/ib_addr_freebsd.h. (It stayed a separate file to preserve
copyright and license of the original file; otherwise it could be
merged into ib_addr.h where more EPOCH/vnet/.. are already used).

Slightly rename the function to not conflict with LinuxKPI
in the future.

Remove the three last, now unneeded includes of inetdevice.h and
zap linux/inetdevice.h to an empty header file with only the forward
include to netdevice.h remaining.

Sponsored-by: The FreeBSD Foundation
MFC-after: 2 weeks
Reviewed-by: hselasky, kib
X-D-R: D29366 (extracted as further cleanup)
Differential Revision: https://reviews.freebsd.org/D29434

Mechanical cleanup of epoch(9) usage in network stack.

- Remove macros that covertly create epoch_tracker on thread stack. Such
macros a quite unsafe, e.g. will produce a buggy code if same macro is
used in embedded scopes. Explicitly declare epoch_tracker always.

- Unmask interface list IFNET_RLOCK_NOSLEEP(), interface address list
IF_ADDR_RLOCK() and interface AF specific data IF_AFDATA_RLOCK() read
locking macros to what they actually are - the net_epoch.
Keeping them as is is very misleading. They all are named FOO_RLOCK(),
while they no longer have lock semantics. Now they allow recursion and
what's more important they now no longer guarantee protection against
their companion WLOCK macros.
Note: INP_HASH_RLOCK() has same problems, but not touched by this commit.

This is non functional mechanical change. The only functionally changed
functions are ni6_addrs() and ni6_store_addrs(), where we no longer enter
epoch recursively.

Discussed with: jtl, gallatin

ibcore: ip6_dev_find() needs to know the scope ID.

Else the wrong network device can be returned for link-local addresses.

Submitted by: hselasky@
Approved by: hselasky (mentor)
MFC after: 1 week
Sponsored by: Mellanox Technologies

UDP: further performance improvements on tx

Cumulative throughput while running 64
netperf -H $DUT -t UDP_STREAM -- -m 1
on a 2x8x2 SKL went from 1.1Mpps to 2.5Mpps

Single stream throughput increases from 910kpps to 1.18Mpps

Baseline:
https://people.freebsd.org/~mmacy/2018.05.11/udpsender2.svg

- Protect read access to global ifnet list with epoch
https://people.freebsd.org/~mmacy/2018.05.11/udpsender3.svg

- Protect short lived ifaddr references with epoch
https://people.freebsd.org/~mmacy/2018.05.11/udpsender4.svg

- Convert if_afdata read lock path to epoch
https://people.freebsd.org/~mmacy/2018.05.11/udpsender5.svg

A fix for the inpcbhash contention is pending sufficient time
on a canary at LLNW.

Reviewed by: gallatin
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D15409

Only search the scope ID in ip6_find_dev() for IPv6 addresses which
have a scope ID. Change size of the searched scope ID to the full
16-bits. There can typically be more than 255 interfaces.

Suggested by: ae @
MFC after: 1 week
Sponsored by: Mellanox Technologies

Resolve IPv6 scope ID issues when using ip6_find_dev() in the LinuxKPI.

Workaround problem that ifa_ifwithaddr() also matches the scope ID of
the IPv6 address when searching for a maching IPv6 address. For now
simply try all valid scope IDs until a match is found.

MFC after: 1 week
Sponsored by: Mellanox Technologies

Add helper function similar to ip_dev_find() to the LinuxKPI to lookup
a network device by its IPv6 address in the given VNET.

MFC after: 1 week
Sponsored by: Mellanox Technologies

Add basic support for VIMAGE to the LinuxKPI and ibcore.

Support is implemented by mapping Linux's "struct net" into FreeBSD's
"struct vnet". Currently only vnet0 is supported by ibcore.

MFC after: 1 week
Sponsored by: Mellanox Technologies

Finish process of moving the LinuxKPI module into the default kernel build.

- Move all files related to the LinuxKPI into sys/compat/linuxkpi and
its subfolders.
- Update sys/conf/files and some Makefiles to use new file locations.
- Added description of COMPAT_LINUXKPI to sys/conf/NOTES which in turn
adds the LinuxKPI to all LINT builds.
- The LinuxKPI can be added to the kernel by setting the
COMPAT_LINUXKPI option. The OFED kernel option no longer builds the
LinuxKPI into the kernel. This was done to keep the build rules for
the LinuxKPI in sys/conf/files simple.
- Extend the LinuxKPI module to include support for USB by moving the
Linux USB compat from usb.ko to linuxkpi.ko.
- Bump the FreeBSD_version.
- A universe kernel build has been done.

Reviewed by: np @ (cxgb and cxgbe related changes only)
Sponsored by: Mellanox Technologies