sys: Remove ancient SCCS tags.

Remove ancient SCCS tags from the tree, automated scripting, with two
minor fixup to keep things compiling. All the common forms in the tree
were removed with a perl script.

Sponsored by: Netflix

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

Remove /^\s*\*+\s*\$FreeBSD\$.*$\n/

tcp: rearrange enum and remove unused variable

Rearrange the enum tt_which such that TT_REXMIT is 0. This allows
an extension of the BBLog event RTO in a backwards compatible way.
Remove tcptimers, which was only used in trpt, a utility removed
from the source tree recently.

Reviewed by: glebius@, guest-ccui@
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D38547

tcp: use single locked callout per tcpcb for the TCP timers

Use only one callout structure per tcpcb that is responsible for handling
all five TCP timeouts. Use locked version of callout, of course. The
callout function tcp_timer_enter() chooses soonest timer and executes it
with lock held. Unless the timer reports that the tcpcb has been freed,
the callout is rescheduled for next soonest timer, if there is any.

With single callout per tcpcb on connection teardown we should be able
to fully stop the callout and immediately free it, avoiding use of
callout_async_drain(). There is one gotcha here: callout_stop() can
actually touch our memory when a rare race condition happens. See
comment above tcp_timer_stop(). Synchronous stop of the callout makes
tcp_discardcb() the single entry point for tcpcb destructor, merging the
tcp_freecb() to the end of the function.

While here, also remove lots of lingering checks in the beginning of
TCP timer functions. With a locked callout they are unnecessary.

While here, clean unused parts of timer KPI for the pluggable TCP stacks.

While here, remove TCPDEBUG from tcp_timer.c, as this allows for more
simplification of TCP timers. The TCPDEBUG is scheduled for removal.

Move the DTrace probes in timers to the beginning of a function, where
a tcpcb is always existing.

Discussed with: rrs, tuexen, rscheff (the TCP part of the diff)
Reviewed by: hselasky, kib, mav (the callout part)
Differential revision: https://reviews.freebsd.org/D37321

tcp: remove tcp_timer_suspend()

It was a temporary code added together with RACK to fight against
TCP timer races.

tcp: embed inpcb into tcpcb

For the TCP protocol inpcb storage specify allocation size that would
provide space to most of the data a TCP connection needs, embedding
into struct tcpcb several structures, that previously were allocated
separately.

The most import one is the inpcb itself. With embedding we can provide
strong guarantee that with a valid TCP inpcb the tcpcb is always valid
and vice versa. Also we reduce number of allocs/frees per connection.
The embedded inpcb is placed in the beginning of the struct tcpcb,
since in_pcballoc() requires that. However, later we may want to move
it around for cache line efficiency, and this can be done with a little
effort. The new intotcpcb() macro is ready for such move.

The congestion algorithm data, the TCP timers and osd(9) data are
also embedded into tcpcb, and temprorary struct tcpcb_mem goes away.
There was no extra allocation here, but we went through extra pointer
every time we accessed this data.

One interesting side effect is that now TCP data is allocated from
SMR-protected zone. Potentially this allows the TCP stacks or other
TCP related modules to utilize that for their own synchronization.

Large part of the change was done with sed script:

s/tp->ccv->/tp->t_ccv./g
s/tp->ccv/\&tp->t_ccv/g
s/tp->cc_algo/tp->t_cc/g
s/tp->t_timers->tt_/tp->tt_/g
s/CCV\(ccv, osd\)/\&CCV(ccv, t_osd)/g

Dependency side effect is that code that needs to know struct tcpcb
should also know struct inpcb, that added several <netinet/in_pcb.h>.

Differential revision: https://reviews.freebsd.org/D37127

tcp: remove tcptw, the compressed timewait state structure

The memory savings the tcptw brought back in 2003 (see 340c35de6a2) no
longer justify the complexity required to maintain it. For longer
explanation please check out the email [1].

Surpisingly through almost 20 years the TCP stack functionality of
handling the TIME_WAIT state with a normal tcpcb did not bitrot. The
existing tcp_input() properly handles a tcpcb in TCPS_TIME_WAIT state,
which is confirmed by the packetdrill tcp-testsuite [2].

This change just removes tcptw and leaves INP_TIMEWAIT. The flag will
be removed in a separate commit. This makes it easier to review and
possibly debug the changes.

[1] https://lists.freebsd.org/archives/freebsd-net/2022-January/001206.html
[2] https://github.com/freebsd-net/tcp-testsuite

Differential revision: https://reviews.freebsd.org/D36398

tcp_timers: provide tcp_timer_drop() and tcp_timer_close()

Two functions to call tcp_drop() and tcp_close() from a callout context.
Garbage collect tcp_inpinfo_lock_del(), it has a single use now.

Differential revision: https://reviews.freebsd.org/D36397

Tcp progress timeout

Rack has had the ability to timeout connections that just sit idle automatically. This
feature of course is off by default and requires the user set it on (though the socket option
has been missing in tcp_usrreq.c). Lets get the progress timeout fully supported in
the base stack as well as rack.

Reviewed by: tuexen
Sponsored by: Netflix Inc
Differential Revision: https://reviews.freebsd.org/D36716

tcp: virtualise net.inet.tcp.msl sysctl.

VNET teardown waits 2*MSL (60 seconds by default) before expiring
tcp PCBs. These PCBs holds references to nexthops, which, in turn,
reference ifnets. This chain results in VNET interfaces being destroyed
and moved to default VNET only after 60 seconds.
Allow tcp_msl to be set in jail by virtualising net.inet.tcp.msl sysctl,
permitting more predictable VNET tests outcomes.

MFC after: 1 week
Reviewed by: glebius
Differential Revision: https://reviews.freebsd.org/D33270

Add tcp_freecb() - single place to free tcpcb.

Until this change there were two places where we would free tcpcb -
tcp_discardcb() in case if all timers are drained and tcp_timer_discard()
otherwise. They were pretty much copy-n-paste, except that in the
default case we would run tcp_hc_update(). Merge this into single
function tcp_freecb() and move new short version of tcp_timer_discard()
to tcp_timer.c and make it static.

Reviewed by: rrs, hselasky
Differential revision: https://reviews.freebsd.org/D32965

kern: net: remove TCP_LINGERTIME

TCP_LINGERTIME can be traced back to BSD 4.4 Lite and perhaps beyond, in
exactly the same form that it appears here modulo slightly different
context. It used to be the case that there was a single pr_usrreq
method with requests dispatched to it; these exact two lines appeared in
tcp_usrreq's PRU_ATTACH handling.

The only purpose of this that I can find is to cause surprising behavior
on accepted connections. Newly-created sockets will never hit these
paths as one cannot set SO_LINGER prior to socket(2). If SO_LINGER is
set on a listening socket and inherited, one would expect the timeout to
be inherited rather than changed arbitrarily like this -- noting that
SO_LINGER is nonsense on a listening socket beyond inheritance, since
they cannot be 'connected' by definition.

Neither Illumos nor Linux reset the timer like this based on testing and
inspection of Illumos, and testing of Linux.

Reviewed by: rscheff, tuexen
Differential Revision: https://reviews.freebsd.org/D28265

Reduce default TCP delayed ACK timeout to 40ms.

Reviewed by: kbowling, tuexen
Approved by: tuexen (mentor)
MFC after: 2 weeks
Sponsored by: NetApp, Inc.
Differential Revision: https://reviews.freebsd.org/D23281

White space cleanup -- remove trailing tab's or spaces
from any line.

Sponsored by: Netflix Inc.

vnet: virtualise more network stack sysctls.

Virtualise tcp_always_keepalive, TCP and UDP log_in_vain. All three are
set in the netoptions startup script, which we would love to run for VNETs
as well [1].

While virtualising the log_in_vain sysctls seems pointles at first for as
long as the kernel message buffer is not virtualised, it at least allows
an administrator to debug the base system or an individual jail if needed
without turning the logging on for all jails running on a system.

PR: 243193 [1]
MFC after: 2 weeks

Add sysctl variable net.inet.tcp.rexmit_initial for setting RTO.Initial
used by TCP.

Reviewed by: rrs@, 0mp@
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D19355

Reduce the TCP initial retransmission timeout from 3 seconds to
1 second as allowed by RFC 6298.

Reviewed by: kbowling@, Richard Scheffenegger
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D18941

Use exponential backoff for retransmitting SYN segments as specified
in the TCP RFCs.

Reviewed by: rrs@, Richard Scheffenegger
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D18974

epoch(9): allow preemptible epochs to compose

- Add tracker argument to preemptible epochs
- Inline epoch read path in kernel and tied modules
- Change in_epoch to take an epoch as argument
- Simplify tfb_tcp_do_segment to not take a ti_locked argument,
there's no longer any benefit to dropping the pcbinfo lock
and trying to do so just adds an error prone branchfest to
these functions
- Remove cases of same function recursion on the epoch as
recursing is no longer free.
- Remove the the TAILQ_ENTRY and epoch_section from struct
thread as the tracker field is now stack or heap allocated
as appropriate.

Tested by: pho and Limelight Networks
Reviewed by: kbowling at llnw dot com
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D16066

This commit brings in a new refactored TCP stack called Rack.
Rack includes the following features:
- A different SACK processing scheme (the old sack structures are not used).
- RACK (Recent acknowledgment) where counting dup-acks is no longer done
instead time is used to knwo when to retransmit. (see the I-D)
- TLP (Tail Loss Probe) where we will probe for tail-losses to attempt
to try not to take a retransmit time-out. (see the I-D)
- Burst mitigation using TCPHTPS
- PRR (partial rate reduction) see the RFC.

Once built into your kernel, you can select this stack by either
socket option with the name of the stack is "rack" or by setting
the global sysctl so the default is rack.

Note that any connection that does not support SACK will be kicked
back to the "default" base FreeBSD stack (currently known as "default").

To build this into your kernel you will need to enable in your
kernel:
makeoptions WITH_EXTRA_TCP_STACKS=1
options TCPHPTS

Sponsored by: Netflix Inc.
Differential Revision: https://reviews.freebsd.org/D15525

Export tcp_always_keepalive for use by the Chelsio TOM module.

This used to work by accident with ld.bfd even though always_keepalive
was marked as static. LLD honors static more correctly, so export this
variable properly (including moving it into the tcp_* namespace).

Reviewed by: bz, emaste
MFC after: 2 weeks
Sponsored by: Chelsio Communications
Differential Revision: https://reviews.freebsd.org/D14129

sys: further adoption of SPDX licensing ID tags.

Mainly focus on files that use BSD 3-Clause license.

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.

Special thanks to Wind River for providing access to "The Duke of
Highlander" tool: an older (2014) run over FreeBSD tree was useful as a
starting point.

Declare pmtud_blackhole global variables in tcp_timer.h, so that
alternative TCP stacks can legally use them.

Hide struct inpcb, struct tcpcb from the userland.

This is a painful change, but it is needed. On the one hand, we avoid
modifying them, and this slows down some ideas, on the other hand we still
eventually modify them and tools like netstat(1) never work on next version of
FreeBSD. We maintain a ton of spares in them, and we already got some ifdef
hell at the end of tcpcb.

Details:
- Hide struct inpcb, struct tcpcb under _KERNEL || _WANT_FOO.
- Make struct xinpcb, struct xtcpcb pure API structures, not including
kernel structures inpcb and tcpcb inside. Export into these structures
the fields from inpcb and tcpcb that are known to be used, and put there
a ton of spare space.
- Make kernel and userland utilities compilable after these changes.
- Bump __FreeBSD_version.

Reviewed by: rrs, gnn
Differential Revision: D10018

Renumber copyright clause 4

Renumber cluase 4 to 3, per what everybody else did when BSD granted
them permission to remove clause 3. My insistance on keeping the same
numbering for legal reasons is too pedantic, so give up on that point.

Submitted by: Jan Schaumann <jschauma@stevens.edu>
Pull Request: https://github.com/freebsd/freebsd/pull/96

Don't zero out srtt after excess retransmits

If the TCP stack has retransmitted more than 1/4 of the total
number of retransmits before a connection drop, it decides that
its current RTT estimate is hopelessly out of date and decides
to recalculate it from scratch starting with the next ACK.

Unfortunately, it implements this by zeroing out the current RTT
estimate. Drop this hack entirely, as it makes it significantly more
difficult to debug connection issues. Instead check for excessive
retransmits at the point where srtt is updated from an ACK being
received. If we've exceeded 1/4 of the maximum retransmits,
discard the previous srtt estimate and replace it with the latest
rtt measurement.

Differential Revision: https://reviews.freebsd.org/D9519
Reviewed by: gnn
Sponsored by: Dell EMC Isilon

This cleans up the timer code in TCP and also makes it so we do not
take the INFO lock *unless* we are really going to delete the TCB.

Differential Revision: D7136

This cleans up the timers code in TCP to start using the new
async_drain functionality. This as been tested in NF as well as
by Verisign. Still to do in here is to remove all the old flags. They
are currently left being maintained but probably are no longer needed.

Sponsored by: Netflix Inc.
Differential Revision: http://reviews.freebsd.org/D5924

Persist timers TCPTV_PERSMIN and TCPTV_PERSMAX are hardcoded with 5 seconds and
60 seconds, respectively. Turn them into sysctls that can be tuned live. The
default values of 5 seconds and 60 seconds have been retained.

Submitted by: Jason Wolfe (j at nitrology dot com)
Reviewed by: gnn, rrs, hiren, bz
MFC after: 1 week
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D5024

Put r284245 back in place: If at first this fix was seen as a temporary
workaround for a callout(9) issue, it turns out it is instead the right
way to use callout in mpsafe mode without using callout_drain().

r284245 commit message:

Fix a callout race condition introduced in TCP timers callouts with r281599.
In TCP timer context, it is not enough to check callout_stop() return value
to decide if a callout is still running or not, previous callout_reset()
return values have also to be checked.

Differential Revision: https://reviews.freebsd.org/D2763

Revert r284245: "Fix a callout race condition introduced in TCP
timers callouts with r281599."

r281599 fixed a TCP timer race condition, but due a callout(9) bug
it also introduced another race condition workaround-ed with r284245.
The callout(9) bug being fixed with r286880, we can now revert the
workaround (r284245).

Differential Revision: https://reviews.freebsd.org/D2079 (Initial change)
Differential Revision: https://reviews.freebsd.org/D2763 (Workaround)
Differential Revision: https://reviews.freebsd.org/D3078 (Fix)
Sponsored by: Verisign, Inc.
MFC after: 2 weeks

Remove unused TCPTV_SRTTDFLT. We initialize srtt with TCPTV_SRTTBASE when we
don't have any rtt estimate.

Differential Revision: D3334
Sponsored by: Limelight Networks

Fix a callout race condition introduced in TCP timers callouts with r281599.
In TCP timer context, it is not enough to check callout_stop() return value
to decide if a callout is still running or not, previous callout_reset()
return values have also to be checked.

Differential Revision: https://reviews.freebsd.org/D2763
Reviewed by: hiren
Approved by: hiren
MFC after: 1 day
Sponsored by: Verisign, Inc.

Fix an old and well-documented use-after-free race condition in
TCP timers:
- Add a reference from tcpcb to its inpcb
- Defer tcpcb deletion until TCP timers have finished

Differential Revision: https://reviews.freebsd.org/D2079
Submitted by: jch, Marc De La Gueronniere <mdelagueronniere@verisign.com>
Reviewed by: imp, rrs, adrian, jhb, bz
Approved by: jhb
Sponsored by: Verisign, Inc.

Fix a race condition in TCP timewait between tcp_tw_2msl_reuse() and
tcp_tw_2msl_scan(). This race condition drives unplanned timewait
timeout cancellation. Also simplify implementation by holding inpcb
reference and removing tcptw reference counting.

Differential Revision: https://reviews.freebsd.org/D826
Submitted by: Marc De la Gueronniere <mdelagueronniere@verisign.com>
Submitted by: jch
Reviewed By: jhb (mentor), adrian, rwatson
Sponsored by: Verisign, Inc.
MFC after: 2 weeks
X-MFC-With: r264321

Currently, the TCP slow timer can starve TCP input processing while it
walks the list of connections in TIME_WAIT closing expired connections
due to contention on the global TCP pcbinfo lock.

To remediate, introduce a new global lock to protect the list of
connections in TIME_WAIT. Only acquire the TCP pcbinfo lock when
closing an expired connection. This limits the window of time when
TCP input processing is stopped to the amount of time needed to close
a single connection.

Submitted by: Julien Charbon <jcharbon@verisign.com>
Reviewed by: rwatson, rrs, adrian
MFC after: 2 months

Add DELACK to list of timers.

MFC after: 1 week

Define the delayed ACK timeout value directly as hz/10 instead of
obfuscating it by going through PR_FASTHZ. No functional change.

MFC after: 2 weeks

For retransmits of SYN|ACK from the syncache use the slightly more
aggressive special tcp_syn_backoff[] retransmit schedule instead of
the normal tcp_backoff[] schedule for established connections.

MFC after: 2 weeks

Add new socket options: TCP_KEEPINIT, TCP_KEEPIDLE, TCP_KEEPINTVL and
TCP_KEEPCNT, that allow to control initial timeout, idle time, idle
re-send interval and idle send count on a per-socket basis.

Reviewed by: andre, bz, lstewart

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

Remove the TCP inflight bandwidth limiter as announced in r211315
to give way for the pluggable congestion control framework. It is
the task of the congestion control algorithm to set the congestion
window and amount of inflight data without external interference.

In 'struct tcpcb' the variables previously used by the inflight
limiter are renamed to spares to keep the ABI intact and to have
some more space for future extensions.

In 'struct tcp_info' the variable 'tcpi_snd_bwnd' is not removed to
preserve the ABI. It is always set to 0.

In siftr.c in 'struct pkt_node' the variable 'snd_bwnd' is not removed
to preserve the ABI. It is always set to 0.

These unused variable in the various structures may be reused in the
future or garbage collected before the next release or at some other
point when an ABI change happens anyway for other reasons.

No MFC is planned. The inflight bandwidth limiter stays disabled by
default in the other branches but remains available.

Add the ability to see TCP timers via netstat -x. This can be a useful
feature when you have a seemingly stuck socket and want to figure
out why it has not been closed yet.

No plans to MFC this, as it changes the netstat sysctl ABI.

Reviewed by: andre, rwatson, Eric Van Gyzen

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

Two changes:

- Reintegrate the ANSI C function declaration change
from tcp_timer.c rev 1.92

- Reorganize the tcpcb structure so that it has a single
pointer to the "tcp_timer" structure which contains all
of the tcp timer callouts. This change means that when
the single tcp timer change is reintegrated, tcpcb will
not change in size, and therefore the ABI between
netstat and the kernel will not change.

Neither of these changes should have any functional
impact.

Reviewed by: bmah, rrs
Approved by: re (bmah)

Back out tcp_timer.c:1.93 and associated changes that reimplemented the many
TCP timers as a single timer, but retain the API changes necessary to
reintroduce this change. This will back out the source of at least two
reported problems: lock leaks in certain timer edge cases, and TCP timers
continuing to fire after a connection has closed (a bug previously fixed and
then reintroduced with the timer rewrite).

In a follow-up commit, some minor restylings and comment changes performed
after the TCP timer rewrite will be reapplied, and a further change to allow
the TCP timer rewrite to be added back without disturbing the ABI. The new
design is believed to be a good thing, but the outstanding issues are
leading to significant stability/correctness problems that are holding
up 7.0.

This patch was generated by silby, but is being committed by proxy due to
poor network connectivity for silby this week.

Approved by: re (kensmith)
Submitted by: silby
Tested by: rwatson, kris
Problems reported by: peter, kris, others

Change TCPTV_MIN to be independent of HZ. While it was documented to
be in ticks "for algorithm stability" when originally committed, it turns
out that it has a significant impact in timing out connections. When we
changed HZ from 100 to 1000, this had a big effect on reducing the time
before dropping connections.

To demonstrate, boot with kern.hz=100. ssh to a box on local ethernet
and establish a reliable round-trip-time (ie: type a few commands).
Then unplug the ethernet and press a key. Time how long it takes to
drop the connection.

The old behavior (with hz=100) caused the connection to typically drop
between 90 and 110 seconds of getting no response.

Now boot with kern.hz=1000 (default). The same test causes the ssh session
to drop after just 9-10 seconds. This is a big deal on a wifi connection.

With kern.hz=1000, change sysctl net.inet.tcp.rexmit_min from 3 to 30.
Note how it behaves the same as when HZ was 100. Also, note that when
booting with hz=100, net.inet.tcp.rexmit_min *used* to be 30.

This commit changes TCPTV_MIN to be scaled with hz. rexmit_min should
always be about 30. If you set hz to Really Slow(TM), there is a safety
feature to prevent a value of 0 being used.

This may be revised in the future, but for the time being, it restores the
old, pre-hz=1000 behavior, which is significantly less annoying.

As a workaround, to avoid rebooting or rebuilding a kernel, you can run
"sysctl net.inet.tcp.rexmit_min=30" and add "net.inet.tcp.rexmit_min=30"
to /etc/sysctl.conf. This is safe to run from 6.0 onwards.

Approved by: re (rwatson)
Reviewed by: andre, silby

Remove now unused stuff forgotten in the previous commit.

Move TIME_WAIT related functions and timer handling from files
other than repo copied tcp_subr.c into tcp_timewait.c#1.284:

tcp_input.c#1.350 tcp_timewait() -> tcp_twcheck()

tcp_timer.c#1.92 tcp_timer_2msl_reset() -> tcp_tw_2msl_reset()
tcp_timer.c#1.92 tcp_timer_2msl_stop() -> tcp_tw_2msl_stop()
tcp_timer.c#1.92 tcp_timer_2msl_tw() -> tcp_tw_2msl_scan()

This is a mechanical move with appropriate renames and making
them static if used only locally.

The tcp_tw_2msl_scan() cleanup function is still run from the
tcp_slowtimo() in tcp_timer.c.

Make "struct tcp_timer" visible only to the kernel, and unbreak world.

Change the TCP timer system from using the callout system five times
directly to a merged model where only one callout, the next to fire,
is registered.

Instead of callout_reset(9) and callout_stop(9) the new function
tcp_timer_activate() is used which then internally manages the callout.

The single new callout is a mutex callout on inpcb simplifying the
locking a bit.

tcp_timer() is the called function which handles all race conditions
in one place and then dispatches the individual timer functions.

Reviewed by: rwatson (earlier version)

Reap FIN_WAIT_2 connections marked SOCANTRCVMORE faster. This mitigate
potential issues where the peer does not close, potentially leaving
thousands of connections in FIN_WAIT_2. This is controlled by a new sysctl
fast_finwait2_recycle, which is disabled by default.

Reviewed by: gnn, silby.

if min is greater than max, prefer max over min... I managed to get a
retransmit timer that was going to take 19 days to trigger...

Reviewed by: silby

Back when we had T/TCP support, we used to apply different
timeouts for TCP and T/TCP connections in the TIME_WAIT
state, and we had two separate timed wait queues for them.
Now that is has gone, the timeout is always 2*MSL again,
and there is no reason to keep two queues (the first was
unused anyway!).

Also, reimplement the remaining queue using a TAILQ (it
was technically impossible before, with two queues).

Fixes an edge case bug in timewait handling where ticks rolling over causing
the timewait expiry to be exactly 0 corrupts the timewait queues (and that entry).
Reviewed by: silby

Have TCP Inflight disable itself if the RTT is below a certain
threshold. Inflight doesn't make sense on a LAN as it has
trouble figuring out the maximal bandwidth because of the coarse
tick granularity.

The sysctl net.inet.tcp.inflight.rttthresh specifies the threshold
in milliseconds below which inflight will disengage. It defaults
to 10ms.

Tested by: Joao Barros <joao.barros-at-gmail.com>,
Rich Murphey <rich-at-whiteoaklabs.com>
Sponsored by: TCP/IP Optimization Fundraise 2005

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

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 advertising clause from University of California Regent's
license, per letter dated July 22, 1999 and email from Peter Wemm,
Alan Cox and Robert Watson.

Approved by: core, peter, alc, rwatson

Remove a panic(); if the zone allocator can't provide more timewait
structures, reuse the oldest one. Also move the expiry timer from
a per-structure callout to the tcp slow timer.

Sponsored by: DARPA, NAI Labs

Add a TCP TIMEWAIT state which uses less space than a fullblown TCP
control block. Allow the socket and tcpcb structures to be freed
earlier than inpcb. Update code to understand an inp w/o a socket.

Reviewed by: hsu, silby, jayanth
Sponsored by: DARPA, NAI Labs

make the strings for tcptimers, tanames and prurequests const to silence
warnings.

Introduce two new sysctl's:

net.inet.tcp.rexmit_min (default 3 ticks equiv)

This sysctl is the retransmit timer RTO minimum,
specified in milliseconds. This value is
designed for algorithmic stability only.

net.inet.tcp.rexmit_slop (default 200ms)

This sysctl is the retransmit timer RTO slop
which is added to every retransmit timeout and
is designed to handle protocol stack overheads
and delayed ack issues.

Note that the *original* code applied a 1-second
RTO minimum but never applied real slop to the RTO
calculation, so any RTO calculation over one second
would have no slop and thus not account for
protocol stack overheads (TCP timestamps are not
a measure of protocol turnaround!). Essentially,
the original code made the RTO calculation almost
completely irrelevant.

Please note that the 200ms slop is debateable.
This commit is not meant to be a line in the sand,
and if the community winds up deciding that increasing
it is the correct solution then it's easy to do.
Note that larger values will destroy performance
on lossy networks while smaller values may result in
a greater number of unnecessary retransmits.

I don't know how the minimum retransmit timeout managed to get set to
one second but it badly breaks throughput on networks with minor packet
loss.

Complaints by: at least two people tracked down to this.
MFC after: 3 days

Remove __P.

Change #ifdef KERNEL to #ifdef _KERNEL in the public headers. "KERNEL"
is an application space macro and the applications are supposed to be free
to use it as they please (but cannot). This is consistant with the other
BSD's who made this change quite some time ago. More commits to come.

Change the delayed ack time from 200ms to 100ms.

This results in closer behavior to earlier versions, where the fixed
200ms timer actually resulted in a delay anywhere from 1..200ms, with
the average delay being 100ms.

Pointed out by: dg

Remove conversion macros that were used during development.

Restructure TCP timeout handling:

- eliminate the fast/slow timeout lists for TCP and instead use a
callout entry for each timer.
- increase the TCP timer granularity to HZ
- implement "bad retransmit" recovery, as presented in
"On Estimating End-to-End Network Path Properties", by Allman and Paxson.

Submitted by: jlemon, wollmann

$Id$ -> $FreeBSD$

Some staticized variables were still declared to be extern.

Back out part 1 of the MCFH that changed $Id$ to $FreeBSD$. We are not
ready for it yet.

Make the long-awaited change from $Id$ to $FreeBSD$

This will make a number of things easier in the future, as well as (finally!)
avoiding the Id-smashing problem which has plagued developers for so long.

Boy, I'm glad we're not using sup anymore. This update would have been
insane otherwise.

Make the misnamed tcp initial keepalive timer value (which is really the
time, in seconds, that state for non-established TCP sessions stays about)
a sysctl modifyable variable.

[part 1 of two commits, I just realized I can't play with the indices as
I was typing this commit message.]

Better selection of initial retransmit timeout when no cached
RTT information is available.

Submitted by: kbracey@art.acorn.co.uk (Kevin Bracey)
(slightly modified by me)

Fix a bunch of spelling errors in the comment fields of
a bunch of system include files.

New style sysctl & staticize alot of stuff.

Get rid of some unneeded #ifdef TTCP lines. Also, get rid of some
bogus commons declared in header files.

Merge in T/TCP TCP header file changes.

Made idempotent.

Submitted by: Paul

Added $Id$

The big 4.4BSD Lite to FreeBSD 2.0.0 (Development) patch.

Reviewed by: Rodney W. Grimes
Submitted by: John Dyson and David Greenman

BSD 4.4 Lite Kernel Sources