MFC r312787:

Currently the fragment info is placed at the top of the linked list
under a shared read lock. This patch attempts to upgrade the lock to
an exclusive write lock. If the exclusive write lock fails to be
obtained, the current fragment is not placed at the head of the list.

This portion of the patch was inspired by NetBSD ip_frag.c r1.4 (which
effectively removed the section of code that performed the reordering).

The patch to sys/contrib/ipfilter/netinet/ip_compat.h adds the
MUTEX_TRY_UPGRADE macro to support the patch to ip_frag.c.

The patch to contrib/ipfilter/lib/rwlock_emul.c supports this patch
by emulating the mutex in userspace when exercised by ipftest(1).

Inspired by: NetBSD ip_frag.c r1.4

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

Revert r288682

I meant to do this on ^/user/ngie/more-tests

Pointyhat to: ngie (use svn info next time...)

Update ipfilter 4.1.28 --> 5.1.2.

Approved by: glebius (mentor)
BSD Licensed by: Darren Reed <darrenr@reed.wattle.id.au> (author)

Merge IPFilter 4.1.23 back to HEAD
See src/contrib/ipfilter/HISTORY for details of changes since 4.1.13

* Someone imported a lot of files with the wrong CVS tag, so lots of files need
that fixed in them....
* Keep unnecessary files out of the non-vendor part of this CVS repository.

This commit was generated by cvs2svn to compensate for changes in r145510,
which included commits to RCS files with non-trunk default branches.

import ipfilter 4.1.8 into the vendor branch