tcp_hostcache: remove unnecessary socketvar.h

sys: Remove $FreeBSD$: one-line .c pattern

Remove /^[\s*]*__FBSDID\("\$FreeBSD\$"\);?\s*\n/

tcp(4): Fix a typo in a sysctl description

- s/entires/entries/

MFC after: 3 days

tcp_hostcache: use SMR for lookups, mutex(9) for updates.

In certain cases, e.g. a SYN-flood from a limited set of hosts,
the TCP hostcache becomes the main contention point. To solve
that, this change introduces lockless lookups on the hostcache.

The cache remains a hash, however buckets are now CK_SLIST. For
updates a bucket mutex is obtained, for read an SMR section is
entered.

Reviewed by: markj, rscheff
Differential revision: https://reviews.freebsd.org/D29729

Fix off-by-one error in KASSERT from 02f26e98c7f4.

tcp_hostcache: make THC_LOCK/UNLOCK macros to work with hash head pointer.
Not a functional change.

tcp_hostcache: style(9)

Reviewed by: rscheff

tcp_hostcache: remove extraneous check.
All paths leading here already checked this setting.

Reviewed by: rscheff

tcp_hostcache: implement tcp_hc_updatemtu() via tcp_hc_update.
Locking changes are planned here, and without this change too
much copy-and-paste would be between these two functions.

Reviewed by: rscheff

tcp: Use jenkins_hash32() in hostcache

As other parts of the base tcp stack (eg.
tcp fastopen) already use jenkins_hash32,
and the properties appear reasonably good,
switching to use that.

Reviewed By: tuexen, #transport, ae
MFC after: 2 weeks
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29515

tcp_hostcache.c: remove unneeded includes.

Reviewed by: rscheff

tcp_hostcache: add bool argument for tcp_hc_lookup() to tell are we
looking to only read from the result, or to update it as well.
For now doesn't affect locking, but allows to push stats and expire
update into single place.

Reviewed by: rscheff

tcp_hostcache: hide rmx_hits/rmx_updates under ifdef.

They have little value unless you do some profiling investigations,
but they are performance bottleneck.

Reviewed by: rscheff

Remove tcp_hostcache.h. Everything is private.

Reviewed by: rscheff

fix typo in 38ea2bd0698e

Use sbuf_drain unconditionally

After making sbuf_drain safe for external use,
there is no need to protect the call.

MFC after: 2 weeks
Reviewed By: tuexen, #transport
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29545

tcp: Shouldn't drain empty sbuf

MFC after: 2 weeks
Reviewed By: tuexen, #transport
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29524

tcp: Add hash histogram output and validate bucket length accounting

Provide a histogram output to check, if the hashsize or
bucketlimit could be optimized. Also add some basic sanity
checks around the accounting of the hash utilization.

MFC after: 2 weeks
Reviewed By: tuexen, #transport
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29506

tcp: For hostcache performance, use atomics instead of counters

As accessing the tcp hostcache happens frequently on some
classes of servers, it was recommended to use atomic_add/subtract
rather than (per-CPU distributed) counters, which have to be
summed up at high cost to cache efficiency.

PR: 254333
MFC after: 2 weeks
Sponsored by: NetApp, Inc.
Reviewed By: #transport, tuexen, jtl
Differential Revision: https://reviews.freebsd.org/D29522

tcp: Make hostcache.cache_count MPSAFE by using a counter_u64_t

Addressing the underlying root cause for cache_count to
show unexpectedly high values, by protecting all arithmetic on
that global variable by using counter(9).

PR: 254333
Reviewed By: tuexen, #transport
MFC after: 2 weeks
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29510

tcp: drain tcp_hostcache_list in between per-bucket locks

Explicitly drain the sbuf after completing each hash bucket
to minimize the work performed while holding the hash
bucket lock.

PR: 254333
MFC after: 2 weeks
Reviewed By: tuexen, jhb, #transport
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29483

tcp: reduce memory footprint when listing tcp hostcache

In tcp_hostcache_list, the sbuf used would need a large (~2MB)
blocking allocation of memory (M_WAITOK), when listing a
full hostcache. This may stall the requestor for an indeterminate
time.

A further optimization is to return the expected userspace
buffersize right away, rather than preparing the output of
each current entry of the hostcase, provided by: @tuexen.

This makes use of the ready-made functions of sbuf to work
with sysctl, and repeatedly drain the much smaller buffer.

PR: 254333
MFC after: 2 weeks
Reviewed By: #transport, tuexen
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D29471

Mark more nodes as CTLFLAG_MPSAFE or CTLFLAG_NEEDGIANT (17 of many)

r357614 added CTLFLAG_NEEDGIANT to make it easier to find nodes that are
still not MPSAFE (or already are but aren’t properly marked).
Use it in preparation for a general review of all nodes.

This is non-functional change that adds annotations to SYSCTL_NODE and
SYSCTL_PROC nodes using one of the soon-to-be-required flags.

Mark all obvious cases as MPSAFE. All entries that haven't been marked
as MPSAFE before are by default marked as NEEDGIANT

Approved by: kib (mentor, blanket)
Commented by: kib, gallatin, melifaro
Differential Revision: https://reviews.freebsd.org/D23718

Don't use uninitialised stack memory if the sysctl variable
net.inet.tcp.hostcache.enable is set to 0.
The bug resulted in using possibly a too small MSS value or wrong
initial retransmission timer settings. Possibly the value used
for ssthresh was also wrong.

Submitted by: Richard Scheffenegger
Reviewed by: Cheng Cui, rgrimes@, tuexen@
MFC after: 1 week
Differential Revision: https://reviews.freebsd.org/D23687

Use the new VNET_DEFINE_STATIC macro when we are defining static VNET
variables.

Reviewed by: bz
Sponsored by: DARPA, AFRL
Differential Revision: https://reviews.freebsd.org/D16147

sys: general adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 2-Clause license, however the tool I
was using misidentified many licenses so this was mostly a manual - error
prone - task.

The Software Package Data Exchange (SPDX) group provides a specification
to make it easier for automated tools to detect and summarize well known
opensource licenses. We are gradually adopting the specification, noting
that the tags are considered only advisory and do not, in any way,
superceed or replace the license texts.

No functional change intended.

Use inet_ntoa_r() instead of inet_ntoa() throughout the kernel

inet_ntoa() cannot be used safely in a multithreaded environment
because it uses a static local buffer. Instead, use inet_ntoa_r()
with a buffer on the caller's stack.

Suggested by: glebius, emaste
Reviewed by: gnn
MFC after: 2 weeks
Sponsored by: Dell EMC
Differential Revision: https://reviews.freebsd.org/D9625

sysctl net.inet.tcp.hostcache.list in a jail can see connections from other
jails and the host. This commit fixes it.

PR: 200361
Submitted by: bz (original version), hiren (minor corrections)
Reported by: Marcus Reid <marcus at blazingdot dot com>
Reviewed by: bz, gnn
Tested by: Lohith Bellad <lohithbsd at gmail dot com>
MFC after: 1 week
Sponsored by: Limelight Networks (minor corrections)

Remove "long" variables from the TCP stack (not including the modular
congestion control framework).

Reviewed by: gnn, lstewart (partial)
Sponsored by: Juniper Networks, Netflix
Differential Revision: (multiple)
Tested by: Limelight, Netflix

This adds a sysctl which allows you to disable the TCP hostcache. This is handy
during testing of network related changes where cached entries may pollute your
results, or during known congestion events where you don't want to unfairly
penalize hosts.

Prior to r232346 this would have meant you would break any connection with a sub
1500 MTU, as the hostcache was authoritative. All entries as they stand today
should simply be used to pre populate values for efficiency.

Submitted by: Jason Wolfe (j at nitrology dot com)
Reviewed by: rwatson, sbruno, rrs , bz (earlier version)
MFC after: 2 weeks
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D6198

Clean up unused bandwidth entry in the TCP hostcache.

Submitted by: Jason Wolfe (j at nitrology dot com)
Reviewed by: rrs, hiren
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D4154

CALLOUT_MPSAFE has lost its meaning since r141428, i.e., for more than ten
years for head. However, it is continuously misused as the mpsafe argument
for callout_init(9). Deprecate the flag and clean up callout_init() calls
to make them more consistent.

Differential Revision: https://reviews.freebsd.org/D2613
Reviewed by: jhb
MFC after: 2 weeks

Add a new sysctl net.inet.tcp.hostcache.purgenow=1 to expire and purge all
entries in hostcache immediately.

In collaboration with: bz, rwatson
MFC after: 1 week
Relnotes: yes
Sponsored by: Limelight Networks

Go back to using sbuf_new() with a preallocated large buffer, to avoid
triggering an sbuf auto-drain copyout while holding a lock.

Pointed out by: jhb
Pointy hat: ian

Use sbuf_new_for_sysctl() instead of plain sbuf_new() to ensure sysctl
string returned to userland is nulterminated.

PR: 195668

Use an sbuf to generate the output of the net.inet.tcp.hostcache.list
sysctl to avoid a possible buffer overflow if the cache grows while the
text is being generated.

PR: 172675
MFC after: 2 weeks

Remove SYSCTL_VNET_* macros, and simply put CTLFLAG_VNET where needed.

Sponsored by: Nginx, Inc.

Add scope zone id to the in_endpoints and hc_metrics structures.

A non-global IPv6 address can be used in more than one zone of the same
scope. This zone index is used to identify to which zone a non-global
address belongs.

Also we can have many foreign hosts with equal non-global addresses,
but from different zones. So, they can have different metrics in the
host cache.

Obtained from: Yandex LLC
Sponsored by: Yandex LLC

The r48589 promised to remove implicit inclusion of if_var.h soon. Prepare
to this event, adding if_var.h to files that do need it. Also, include
all includes that now are included due to implicit pollution via if_var.h

Sponsored by: Netflix
Sponsored by: Nginx, Inc.

- Update cachelimit after hashsize and bucketlimit were set.

Reported by: az
Reviewed by: melifaro
Approved by: kib (mentor)
MFC after: 1 week

Fix RTTVAR scale in net.inet.tcp.hostcache.list sysctl.

Reviewed by: andre
MFC after: 3 days

Mark all SYSCTL_NODEs static that have no corresponding SYSCTL_DECLs.

The SYSCTL_NODE macro defines a list that stores all child-elements of
that node. If there's no SYSCTL_DECL macro anywhere else, there's no
reason why it shouldn't be static.

sysctl(9) cleanup checkpoint: amd64 GENERIC builds cleanly.

Commit the net* piece.

After some off-list discussion, revert a number of changes to the
DPCPU_DEFINE and VNET_DEFINE macros, as these cause problems for various
people working on the affected files. A better long-term solution is
still being considered. This reversal may give some modules empty
set_pcpu or set_vnet sections, but these are harmless.

Changes reverted:

------------------------------------------------------------------------
r215318 | dim | 2010-11-14 21:40:55 +0100 (Sun, 14 Nov 2010) | 4 lines

Instead of unconditionally emitting .globl's for the __start_set_xxx and
__stop_set_xxx symbols, only emit them when the set_vnet or set_pcpu
sections are actually defined.

------------------------------------------------------------------------
r215317 | dim | 2010-11-14 21:38:11 +0100 (Sun, 14 Nov 2010) | 3 lines

Apply the STATIC_VNET_DEFINE and STATIC_DPCPU_DEFINE macros throughout
the tree.

------------------------------------------------------------------------
r215316 | dim | 2010-11-14 21:23:02 +0100 (Sun, 14 Nov 2010) | 2 lines

Add macros to define static instances of VNET_DEFINE and DPCPU_DEFINE.

Apply the STATIC_VNET_DEFINE and STATIC_DPCPU_DEFINE macros throughout
the tree.

A new jail(8) with a configuration file, to replace the work currently done
by /etc/rc.d/jail.

MFC r207369:
MFP4: @176978-176982, 176984, 176990-176994, 177441

"Whitspace" churn after the VIMAGE/VNET whirls.

Remove the need for some "init" functions within the network
stack, like pim6_init(), icmp_init() or significantly shorten
others like ip6_init() and nd6_init(), using static initialization
again where possible and formerly missed.

Move (most) variables back to the place they used to be before the
container structs and VIMAGE_GLOABLS (before r185088) and try to
reduce the diff to stable/7 and earlier as good as possible,
to help out-of-tree consumers to update from 6.x or 7.x to 8 or 9.

This also removes some header file pollution for putatively
static global variables.

Revert VIMAGE specific changes in ipfilter::ip_auth.c, that are
no longer needed.

Reviewed by: jhb
Discussed with: rwatson
Sponsored by: The FreeBSD Foundation
Sponsored by: CK Software GmbH

MFP4: @176978-176982, 176984, 176990-176994, 177441

"Whitspace" churn after the VIMAGE/VNET whirls.

Remove the need for some "init" functions within the network
stack, like pim6_init(), icmp_init() or significantly shorten
others like ip6_init() and nd6_init(), using static initialization
again where possible and formerly missed.

Move (most) variables back to the place they used to be before the
container structs and VIMAGE_GLOABLS (before r185088) and try to
reduce the diff to stable/7 and earlier as good as possible,
to help out-of-tree consumers to update from 6.x or 7.x to 8 or 9.

This also removes some header file pollution for putatively
static global variables.

Revert VIMAGE specific changes in ipfilter::ip_auth.c, that are
no longer needed.

Reviewed by: jhb
Discussed with: rwatson
Sponsored by: The FreeBSD Foundation
Sponsored by: CK Software GmbH
MFC after: 6 days

MFC r203724:

Properly free resources when destroying the TCP hostcache while
tearing down a network stack (in the VIMAGE jail+vnet case).

For that break out the logic from tcp_hc_purge() into an internal
function we can call from both, the sysctl handler and the
tcp_hc_destroy().

Reviewed by: silby, lstewart

Properly free resources when destroying the TCP hostcache while
tearing down a network stack (in the VIMAGE jail+vnet case).

For that break out the logic from tcp_hc_purge() into an internal
function we can call from both, the sysctl handler and the
tcp_hc_destroy().

Sponsored by: ISPsystem
Reviewed by: silby, lstewart
MFC After: 8 days

Merge the remainder of kern_vimage.c and vimage.h into vnet.c and
vnet.h, we now use jails (rather than vimages) as the abstraction
for virtualization management, and what remained was specific to
virtual network stacks. Minor cleanups are done in the process,
and comments updated to reflect these changes.

Reviewed by: bz
Approved by: re (vimage blanket)

Remove unused VNET_SET() and related macros; only VNET_GET() is
ever actually used. Rename VNET_GET() to VNET() to shorten
variable references.

Discussed with: bz, julian
Reviewed by: bz
Approved by: re (kensmith, kib)

Build on Jeff Roberson's linker-set based dynamic per-CPU allocator
(DPCPU), as suggested by Peter Wemm, and implement a new per-virtual
network stack memory allocator. Modify vnet to use the allocator
instead of monolithic global container structures (vinet, ...). This
change solves many binary compatibility problems associated with
VIMAGE, and restores ELF symbols for virtualized global variables.

Each virtualized global variable exists as a "reference copy", and also
once per virtual network stack. Virtualized global variables are
tagged at compile-time, placing the in a special linker set, which is
loaded into a contiguous region of kernel memory. Virtualized global
variables in the base kernel are linked as normal, but those in modules
are copied and relocated to a reserved portion of the kernel's vnet
region with the help of a the kernel linker.

Virtualized global variables exist in per-vnet memory set up when the
network stack instance is created, and are initialized statically from
the reference copy. Run-time access occurs via an accessor macro, which
converts from the current vnet and requested symbol to a per-vnet
address. When "options VIMAGE" is not compiled into the kernel, normal
global ELF symbols will be used instead and indirection is avoided.

This change restores static initialization for network stack global
variables, restores support for non-global symbols and types, eliminates
the need for many subsystem constructors, eliminates large per-subsystem
structures that caused many binary compatibility issues both for
monitoring applications (netstat) and kernel modules, removes the
per-function INIT_VNET_*() macros throughout the stack, eliminates the
need for vnet_symmap ksym(2) munging, and eliminates duplicate
definitions of virtualized globals under VIMAGE_GLOBALS.

Bump __FreeBSD_version and update UPDATING.

Portions submitted by: bz
Reviewed by: bz, zec
Discussed with: gnn, jamie, jeff, jhb, julian, sam
Suggested by: peter
Approved by: re (kensmith)

After cleaning up rt_tables from vnet.h and cleaning up opt_route.h
a lot of files no longer need route.h either. Garbage collect them.
While here remove now unneeded vnet.h #includes as well.

Introduce an infrastructure for dismantling vnet instances.

Vnet modules and protocol domains may now register destructor
functions to clean up and release per-module state. The destructor
mechanisms can be triggered by invoking "vimage -d", or a future
equivalent command which will be provided via the new jail framework.

While this patch introduces numerous placeholder destructor functions,
many of those are currently incomplete, thus leaking memory or (even
worse) failing to stop all running timers. Many of such issues are
already known and will be incrementaly fixed over the next weeks in
smaller incremental commits.

Apart from introducing new fields in structs ifnet, domain, protosw
and vnet_net, which requires the kernel and modules to be rebuilt, this
change should have no impact on nooptions VIMAGE builds, since vnet
destructors can only be called in VIMAGE kernels. Moreover,
destructor functions should be in general compiled in only in
options VIMAGE builds, except for kernel modules which can be safely
kldunloaded at run time.

Bump __FreeBSD_version to 800097.
Reviewed by: bz, julian
Approved by: rwatson, kib (re), julian (mentor)

A NOP change: style / whitespace cleanup of the noise that slipped
into r191816.

Spotted by: bz
Approved by: julian (mentor) (an earlier version of the diff)

Change the curvnet variable from a global const struct vnet *,
previously always pointing to the default vnet context, to a
dynamically changing thread-local one. The currvnet context
should be set on entry to networking code via CURVNET_SET() macros,
and reverted to previous state via CURVNET_RESTORE(). Recursions
on curvnet are permitted, though strongly discuouraged.

This change should have no functional impact on nooptions VIMAGE
kernel builds, where CURVNET_* macros expand to whitespace.

The curthread->td_vnet (aka curvnet) variable's purpose is to be an
indicator of the vnet context in which the current network-related
operation takes place, in case we cannot deduce the current vnet
context from any other source, such as by looking at mbuf's
m->m_pkthdr.rcvif->if_vnet, sockets's so->so_vnet etc. Moreover, so
far curvnet has turned out to be an invaluable consistency checking
aid: it helps to catch cases when sockets, ifnets or any other
vnet-aware structures may have leaked from one vnet to another.

The exact placement of the CURVNET_SET() / CURVNET_RESTORE() macros
was a result of an empirical iterative process, whith an aim to
reduce recursions on CURVNET_SET() to a minimum, while still reducing
the scope of CURVNET_SET() to networking only operations - the
alternative would be calling CURVNET_SET() on each system call entry.
In general, curvnet has to be set in three typicall cases: when
processing socket-related requests from userspace or from within the
kernel; when processing inbound traffic flowing from device drivers
to upper layers of the networking stack, and when executing
timer-driven networking functions.

This change also introduces a DDB subcommand to show the list of all
vnet instances.

Approved by: julian (mentor)

Update stats in struct tcpstat using two new macros, TCPSTAT_ADD() and
TCPSTAT_INC(), rather than directly manipulating the fields across the
kernel. This will make it easier to change the implementation of
these statistics, such as using per-CPU versions of the data structures.

MFC after: 3 days

Use inc_flags instead of the inc_isipv6 alias which so far
had been the only flag with random usage patterns.
Switch inc_flags to be used as a real bit field by using
INC_ISIPV6 with bitops to check for the 'isipv6' condition.

While here fix a place or two where in case of v4 inc_flags
were not properly initialized before.[1]

Found by: rwatson during review [1]
Discussed with: rwatson
Reviewed by: rwatson
MFC after: 4 weeks

Rather than using hidden includes (with cicular dependencies),
directly include only the header files needed. This reduces the
unneeded spamming of various headers into lots of files.

For now, this leaves us with very few modules including vnet.h
and thus needing to depend on opt_route.h.

Reviewed by: brooks, gnn, des, zec, imp
Sponsored by: The FreeBSD Foundation

Unhide declarations of network stack virtualization structs from
underneath #ifdef VIMAGE blocks.

This change introduces some churn in #include ordering and nesting
throughout the network stack and drivers but is not expected to cause
any additional issues.

In the next step this will allow us to instantiate the virtualization
container structures and switch from using global variables to their
"containerized" counterparts.

Reviewed by: bz, julian
Approved by: julian (mentor)
Obtained from: //depot/projects/vimage-commit2/...
X-MFC after: never
Sponsored by: NLnet Foundation, The FreeBSD Foundation

Change the initialization methodology for global variables scheduled
for virtualization.

Instead of initializing the affected global variables at instatiation,
assign initial values to them in initializer functions. As a rule,
initialization at instatiation for such variables should never be
introduced again from now on. Furthermore, enclose all instantiations
of such global variables in #ifdef VIMAGE_GLOBALS blocks.

Essentialy, this change should have zero functional impact. In the next
phase of merging network stack virtualization infrastructure from
p4/vimage branch, the new initialization methology will allow us to
switch between using global variables and their counterparts residing in
virtualization containers with minimum code churn, and in the long run
allow us to intialize multiple instances of such container structures.

Discussed at: devsummit Strassburg
Reviewed by: bz, julian
Approved by: julian (mentor)
Obtained from: //depot/projects/vimage-commit2/...
X-MFC after: never
Sponsored by: NLnet Foundation, The FreeBSD Foundation

- Import the HEAD csup code which is the basis for the cvsmode work.

Step 1.5 of importing the network stack virtualization infrastructure
from the vimage project, as per plan established at devsummit 08/08:
http://wiki.freebsd.org/Image/Notes200808DevSummit

Introduce INIT_VNET_*() initializer macros, VNET_FOREACH() iterator
macros, and CURVNET_SET() context setting macros, all currently
resolving to NOPs.

Prepare for virtualization of selected SYSCTL objects by introducing a
family of SYSCTL_V_*() macros, currently resolving to their global
counterparts, i.e. SYSCTL_V_INT() == SYSCTL_INT().

Move selected #defines from sys/sys/vimage.h to newly introduced header
files specific to virtualized subsystems (sys/net/vnet.h,
sys/netinet/vinet.h etc.).

All the changes are verified to have zero functional impact at this
point in time by doing MD5 comparision between pre- and post-change
object files(*).

(*) netipsec/keysock.c did not validate depending on compile time options.

Implemented by: julian, bz, brooks, zec
Reviewed by: julian, bz, brooks, kris, rwatson, ...
Approved by: julian (mentor)
Obtained from: //depot/projects/vimage-commit2/...
X-MFC after: never
Sponsored by: NLnet Foundation, The FreeBSD Foundation

Wrap an 81 column SYSCTL_NODE decleration.

Obtained from: //depot/projects/vimage-commit2/...

Fix typo in comment.

Fix some of the formatting fixes.. It's amazing how some thing stand out
in a commit message.

A bunch of formatting fixes brough to light by, or created by the Vimage commit
a few days ago.

Commit step 1 of the vimage project, (network stack)
virtualization work done by Marko Zec (zec@).

This is the first in a series of commits over the course
of the next few weeks.

Mark all uses of global variables to be virtualized
with a V_ prefix.
Use macros to map them back to their global names for
now, so this is a NOP change only.

We hope to have caught at least 85-90% of what is needed
so we do not invalidate a lot of outstanding patches again.

Obtained from: //depot/projects/vimage-commit2/...
Reviewed by: brooks, des, ed, mav, julian,
jamie, kris, rwatson, zec, ...
(various people I forgot, different versions)
md5 (with a bit of help)
Sponsored by: NLnet Foundation, The FreeBSD Foundation
X-MFC after: never
V_Commit_Message_Reviewed_By: more people than the patch

Add FBSDID to all files in netinet so that people can more
easily include file version information in bug reports.

Approved by: re (kensmith)

Replace a constant with an already defined symbolic name for it.

Tested with: md5(1)

Add a sysctl for the purge run interval so that it can
be tuned along with the rest of hostcache parameters.
The new sysctl name is `net.inet.tcp.hostcache.prune'.

In tcp_hc_insert() we may have the case where we have hit the global
cache size limit but this bucket row is empty. Normally we want to
recycle the oldest entry in the bucket row. If there isn't any the
TAILQ_REMOVE leads to a panic by trying to remove a non-existing
element. Fix this by just returning NULL and failing the insert.
This is not a problem as the TCP hostache is only advisory.

Submitted by: jhb

Normalize spelling and grammar in TCP hostcache comments.

Match up SYSCTL declarations in style.

MFp4: 92972, 98913 + one more change

In ip6_sprintf no longer use and return one of eight static buffers
for printing/logging ipv6 addresses.
The caller now has to hand in a sufficiently large buffer as first
argument.

/* -> /*- for license, minor formatting changes

Minor grammer fix in comment.

Remove RFC1644 T/TCP support from the TCP side of the network stack.

A complete rationale and discussion is given in this message
and the resulting discussion:

http://docs.freebsd.org/cgi/mid.cgi?4177C8AD.6060706

Note that this commit removes only the functional part of T/TCP
from the tcp_* related functions in the kernel. Other features
introduced with RFC1644 are left intact (socket layer changes,
sendmsg(2) on connection oriented protocols) and are meant to
be reused by a simpler and less intrusive reimplemention of the
previous T/TCP functionality.

Discussed on: -arch

White space cleanup for netinet before branch:

- Trailing tab/space cleanup
- Remove spurious spaces between or before tabs

This change avoids touching files that Andre likely has in his working
set for PFIL hooks changes for IPFW/DUMMYNET.

Approved by: re (scottl)
Submitted by: Xin LI <delphij@frontfree.net>

Remove the UMA_ZONE_NOFREE flag to all uma_zcreate() calls in the IP and
TCP code. This flag would have prevented giving back excessive free slabs
to the global pool after a transient peak usage.

Correct the displayed bandwidth calculation for a readout via sysctl. The
saved value does not have to be scaled with HZ; it is already in bytes per
second. Only the multiply by eight remains to show bits per second (bps).

Fix a potential race when purging expired hostcache entries.

Spotted by: luigi

Swap destination and source arguments of two bcopy() calls.

Before committing the initial tcp_hostcache I changed them from memcpy()
to conform with FreeBSD style without realizing the difference in argument
definition.

This fixes hostcache operation for IPv6 (in general and explicitly IPv6
path mtu discovery) and T/TCP (RFC1644).

Submitted by: Taku YAMAMOTO <taku@cent.saitama-u.ac.jp>
Approved by: re (rwatson)

Fix an optimization where I made an ifdef'd out section to broad.

When the hostcache bucket limit is reached the last bucket wasn't
removed from the bucket row but inserted a few lines later at the
bucket row head again. This leads to infinite loop when the same
bucket row is accessed the next time for a lookup/insert or purge
action.

Tested by: imp, Matt Smith
Approved by: re (rwatson)

Introduce tcp_hostcache and remove the tcp specific metrics from
the routing table. Move all usage and references in the tcp stack
from the routing table metrics to the tcp hostcache.

It caches measured parameters of past tcp sessions to provide better
initial start values for following connections from or to the same
source or destination. Depending on the network parameters to/from
the remote host this can lead to significant speedups for new tcp
connections after the first one because they inherit and shortcut
the learning curve.

tcp_hostcache is designed for multiple concurrent access in SMP
environments with high contention and is hash indexed by remote
ip address.

It removes significant locking requirements from the tcp stack with
regard to the routing table.

Reviewed by: sam (mentor), bms
Reviewed by: -net, -current, core@kame.net (IPv6 parts)
Approved by: re (scottl)