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

bring the NGM_IPFW_COOKIE back into ng_ipfw.h, libnetgraph expects
to find it there. Unfortunately this reintroduces the dependency
on ip_fw_pfil.c

bring in several cleanups tested in ipfw3-head branch, namely:

r201011
- move most of ng_ipfw.h into ip_fw_private.h, as this code is
ipfw-specific. This removes a dependency on ng_ipfw.h from some files.

- move many equivalent definitions of direction (IN, OUT) for
reinjected packets into ip_fw_private.h

- document the structure of the packet tags used for dummynet
and netgraph;

r201049
- merge some common code to attach/detach hooks into
a single function.

r201055
- remove some duplicated code in ip_fw_pfil. The input
and output processing uses almost exactly the same code so
there is no need to use two separate hooks.
ip_fw_pfil.o goes from 2096 to 1382 bytes of .text

r201057 (see the svn log for full details)
- macros to make the conversion of ip_len and ip_off
between host and network format more explicit

r201113 (the remaining parts)
- readability fixes -- put braces around some large for() blocks,
localize variables so the compiler does not think they are uninitialized,
do not insist on precise allocation size if we have more than we need.

r201119
- when doing a lookup, keys must be in big endian format because
this is what the radix code expects (this fixes a bug in the
recently-introduced 'lookup' option)

No ABI changes in this commit.

MFC after: 1 week

merge code from ipfw3-head to reduce contention on the ipfw lock
and remove all O(N) sequences from kernel critical sections in ipfw.

In detail:

1. introduce a IPFW_UH_LOCK to arbitrate requests from
the upper half of the kernel. Some things, such as 'ipfw show',
can be done holding this lock in read mode, whereas insert and
delete require IPFW_UH_WLOCK.

2. introduce a mapping structure to keep rules together. This replaces
the 'next' chain currently used in ipfw rules. At the moment
the map is a simple array (sorted by rule number and then rule_id),
so we can find a rule quickly instead of having to scan the list.
This reduces many expensive lookups from O(N) to O(log N).

3. when an expensive operation (such as insert or delete) is done
by userland, we grab IPFW_UH_WLOCK, create a new copy of the map
without blocking the bottom half of the kernel, then acquire
IPFW_WLOCK and quickly update pointers to the map and related info.
After dropping IPFW_LOCK we can then continue the cleanup protected
by IPFW_UH_LOCK. So userland still costs O(N) but the kernel side
is only blocked for O(1).

4. do not pass pointers to rules through dummynet, netgraph, divert etc,
but rather pass a <slot, chain_id, rulenum, rule_id> tuple.
We validate the slot index (in the array of #2) with chain_id,
and if successful do a O(1) dereference; otherwise, we can find
the rule in O(log N) through <rulenum, rule_id>

All the above does not change the userland/kernel ABI, though there
are some disgusting casts between pointers and uint32_t

Operation costs now are as follows:

Function Old Now Planned
-------------------------------------------------------------------
+ skipto X, non cached O(N) O(log N)
+ skipto X, cached O(1) O(1)
XXX dynamic rule lookup O(1) O(log N) O(1)
+ skipto tablearg O(N) O(1)
+ reinject, non cached O(N) O(log N)
+ reinject, cached O(1) O(1)
+ kernel blocked during setsockopt() O(N) O(1)
-------------------------------------------------------------------

The only (very small) regression is on dynamic rule lookup and this will
be fixed in a day or two, without changing the userland/kernel ABI

Supported by: Valeria Paoli
MFC after: 1 month

Close long existed race with net.inet.ip.fw.one_pass = 0:
If packet leaves ipfw to other kernel subsystem (dummynet, netgraph, etc)
it carries pointer to matching ipfw rule. If this packet then reinjected back
to ipfw, ruleset processing starts from that rule. If rule was deleted
meanwhile, due to existed race condition panic was possible (as well as
other odd effects like parsing rules in 'reap list').

P.S. this commit changes ABI so userland ipfw related binaries should be
recompiled.

MFC after: 1 month
Tested by: Mikolaj Golub

Remove unused now field.

Add a ng_ipfw node, implementing a quick and simple interface between
ipfw(4) and netgraph(4) facilities.

Reviewed by: andre, brooks, julian