Copy stable/10@r272459 to releng/10.1 as part of
the 10.1-RELEASE process.

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

Copy head (r256279) to stable/10 as part of the 10.0-RELEASE cycle.

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

Make ppp WARNS=5 clean

Re-implement LQM, this time according to the rfc.

PR: 11293
MFC after: 4 weeks

Cosmetic: Make struct mbuf more like kernel mbufs.

$Id$ -> $FreeBSD$

o Alter the mbuf type as it's processed by different layers.
o Show more information about missing MP fragments in ``show mp''.
o Do away with mbuf_Log(). It was showing mbuf stats twice on
receipt of LCP/CCP/IPCP packets.... ???!!?
o Pre-allocate a bit extra when creating LQR packets to avoid having
to allocate another mbuf in mbuf_Prepend().

Oops - hook the sync push diagnostics correctly.

Allow ``host:port/udp'' devices and support ``host:port/tcp'' as
being the same as the previous (still supported) ``host:port''
syntax for tcp socket devices.

A udp device uses synchronous ppp rather than async, and avoids
the double-retransmit overhead that comes with ppp over tcp (it's
usually a bad idea to transport IP over a reliable transport that
itself is using an unreliable transport). PPP over UDP provides
througput of ** 1.5Mb per second ** with all compression disabled,
maxing out a PPro/200 when running ppp twice, back-to-back.

This proves that PPPoE is plausable in userland....

This change adds a few more handler functions to struct device and
allows derivations of struct device (which may contain their own
data etc) to pass themselves through the unix domain socket for MP.
** At last **, struct physical has lost all the tty crud !

iov2physical() is now smart enough to restore the correct stack of
layers so that MP servers will work again.

The version number has bumped as our MP link transfer contents have
changed (they now may contain a `struct device').

Don't extract the protocol twice in MP mode (resulting in protocol
rejects for every MP packet). This was broken with my original
layering changes.

Add ``Physical'' and ``Sync'' log levels for logging the relevent
raw packets and add protocol-tracking LogDEBUG stuff in various
LayerPush & LayerPull functions.

Assign our physical device name for incoming tcp connections by
calling getpeername().

Assign our physical device name for incoming udp connections from
the address retrieved by the first recvfrom().

o Redesign the layering mechanism and make the aliasing code part of
the layering.

We now ``stack'' layers as soon as we open the device (when we figure
out what we're dealing with). A static set of `dispatch' routines are
also declared for dealing with incoming packets after they've been
`pulled' up through the stacked layers.

Physical devices are now assigned handlers based on the device type
when they're opened. For the moment there are three device types;
ttys, execs and tcps.

o Increment version number to 2.2
o Make an entry in [uw]tmp for non-tty -direct invocations (after
pap/chap authentication).
o Make throughput counters quad_t's
o Account for the absolute number of mbuf malloc()s and free()s in
``show mem''.
o ``show modem'' becomes ``show physical''.