Copy stable/9 to releng/9.3 as part of the 9.3-RELEASE cycle.

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

Copy head to stable/9 as part of 9.0-RELEASE release cycle.

Approved by: re (implicit)

Add ``enable/disable tcpmssfixup'', defaulting to enabled.

Suggested by: julian
Hijacked from: ru (ports/net/tcpmssd)

Allow a ``timeout secs'' filter option to let specific packet types
effect the idle timer in different ways.

Submitted by: Stefan Esser <se@freebsd.org>

With adjustments by me to document the option in the man page and to
give the same semantics for outgoing traffic as incoming.

I made the style more consistent in ip.c - this should really have
been done as a separate commit.

Handle the availability of TUNSIFHEAD. If it's there, use it.

For the moment this is just overhead, but it'll be used for INET6
support later.

$Id$ -> $FreeBSD$

The protocol must be in network byte order (OpenBSD only).

``struct tunnel_header'' -> u_int32_t in OpenBSD.
struct tunnel_header is going soon.

Suggested by: Theo

MFMP: Make ppp multilink capable.
See the file README.changes, and re-read the man page.

Add (BSD) copyright headers.

Add id strings to tun.[ch].
Don't try to open ppp.secret if we're never going to use it.

Abstract data read from and written to the tun device,
allowing for a possible header on the front of all packets.
In OpenBSD, there's a structure containing the address
family here.
If we're building under OpenBSD, set up the ``flags'' part
of struct tuninfo (not there under FreeBSD) so that we config
the interface as POINTOPOINT.
Prefix prototypes with ``extern'' in os.c for consistency.

These changes are cosmetic under FreeBSD, but allow ppp to
build & work under OpenBSD (bar the srandomdev() stuff,
the inclusing of <net/if_var.h> and some Makefile symantecs).