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 accept filter code is not specific to the FreeBSD IPv4 network stack,
so it really should not be under "optional inet". The fact that uipc_accf.c
lives under kern/ lends some weight to making it a "standard" file.

Moving kern/uipc_accf.c from "optional inet" to "standard" eliminates the
need for #ifdef INET in kern/uipc_socket.c.

Also, this meant the net.inet.accf.unloadable sysctl needed to move, as
net.inet does not exist without networking compiled in (as it lives in
netinet/in_proto.c.) The new sysctl has been named net.accf.unloadable.

In order to support existing accept filter sysctls, the net.inet.accf node
has been added netinet/in_proto.c.

Submitted by: Steve Kiernan <stevek@juniper.net>
Obtained from: Juniper Networks, Inc.

(S)LIST_HEAD_INITIALIZER takes a (S)LIST_HEAD as an argument.
Fix some wrong usages.
Note: this does not affect generated binaries as this argument is not used.

PR: 137213
Submitted by: Eygene Ryabinkin (initial version)
MFC after: 1 month

Retire the MALLOC and FREE macros. They are an abomination unto style(9).

MFC after: 3 months

o setsockopt(2) cannot remove accept filter. [1]
o getsockopt(SO_ACCEPTFILTER) always returns success on listen socket
even we didn't install accept filter on the socket.
o Fix these bugs and add regression tests for them.

Submitted by: Igor Sysoev [1]
Reviewed by: alfred
MFC after: 2 weeks

Move the logic implementing retrieval of the SO_ACCEPTFILTER socket option
from uipc_socket.c to uipc_accf.c in do_getopt_accept_filter(), so that it
now matches do_setopt_accept_filter(). Slightly reformulate the logic to
match the optimistic allocation of storage for the argument in advance,
and slightly expand the coverage of the socket lock.

Part two of post-SMPng cleanup of accept filter registration: perform all
allocation up front before grabbing the socket mutex and doing the
registration work. The result is a lot cleaner.

First step in simplifying accept filter socket option logic in the
post-SMPng world order. Centralize handling of the socket option
clear case in do_setopt_accept_filter().

Re-style do_setopt_accept_filter() to match uipc_accf.c style, and fix
one other style nit in the file.

MFC after: 3 days

Move do_setopt_accept_filter() from uipc_socket.c to uipc_accf.c, where
the rest of the accept filter code currently lives.

MFC after: 3 days

Minor style tweaks: line wrap comments and lines more consistently.

MFC after: 3 days

/* -> /*- for copyright notices, minor format tweaks as necessary

Add a global mutex, accept_filter_mtx, to protect the global list of
accept filters and prevent read-modify-write races.

Add some missing <sys/module.h> includes which are masked by the
one on death-row in <sys/kernel.h>

Use __FBSDID().

Back out M_* changes, per decision of the TRB.

Approved by: trb

Remove M_TRYWAIT/M_WAITOK/M_WAIT. Callers should use 0.
Merge M_NOWAIT/M_DONTWAIT into a single flag M_NOWAIT.

Revert the last bits of my bogus move of NMBCLUSTERS
to <sys/param.h>

Move the definition of NMBCLUSTERS from src/sys/kern/uipc_mbuf.c
to <sys/param.h>, so it's available to src/sys/netinet/ip_input.c,
and remove the now unneeded includes of "opt_param.h".

MFC after: 1 week

Remove unneeded #include <sys/proc.h> lines.

Accept filter maintainance

Update copyrights.

Introduce a new sysctl node:
net.inet.accf

Although acceptfilters need refcounting to be properly (safely) unloaded
as a temporary hack allow them to be unloaded if the sysctl
net.inet.accf.unloadable is set, this is really for developers who want
to work on thier own filters.

A near complete re-write of the accf_http filter:
1) Parse check if the request is HTTP/1.0 or HTTP/1.1 if not dump
to the application.
Because of the performance implications of this there is a sysctl
'net.inet.accf.http.parsehttpversion' that when set to non-zero
parses the HTTP version.
The default is to parse the version.
2) Check if a socket has filled and dump to the listener
3) optimize the way that mbuf boundries are handled using some voodoo
4) even though you'd expect accept filters to only be used on TCP
connections that don't use m_nextpkt I've fixed the accept filter
for socket connections that use this.

This rewrite of accf_http should allow someone to use them and maintain
full HTTP compliance as long as net.inet.accf.http.parsehttpversion is
set.

disallow unload until we do proper refcounting

return of the accept filter part II

accept filters are now loadable as well as able to be compiled into
the kernel.

two accept filters are provided, one that returns sockets when data
arrives the other when an http request is completed (doesn't work
with 0.9 requests)

Reviewed by: jmg