Commit Graph

90 Commits

Author SHA1 Message Date
Richard Scheffenegger
3767427354 TCP Cubic: improve reaction to (and rollback from) RTO
1. fix compliancy issue of CUBIC RTO handling according to RFC8312 section 4.7
2. add CUBIC CC_RTO_ERR handling

Submitted by:	chengc_netapp.com
Reviewed by:	rrs, tuexen, rscheff
MFC after:	2 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D26808
2020-10-24 16:11:46 +00:00
Richard Scheffenegger
39a12f0178 tcp: move cwnd and ssthresh updates into cc modules
This will pave the way of setting ssthresh differently in TCP CUBIC, according
to RFC8312 section 4.7.

No functional change, only code movement.

Submitted by:	chengc_netapp.com
Reviewed by:	rrs, tuexen, rscheff
MFC after:	2 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D26807
2020-10-24 16:09:18 +00:00
Richard Scheffenegger
1567c937e2 TCP newreno: improve after_idle ssthresh
Adjust ssthresh in after_idle to the maximum of
the prior ssthresh, or 3/4 of the prior cwnd. See
RFC2861 section 2 for an in depth explanation for
the rationale around this.

As newreno is the default "fall-through" reaction,
most tcp variants will benefit from this.

Reviewed by:	tuexen
MFC after:	2 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D22438
2020-09-25 10:23:14 +00:00
Richard Scheffenegger
e74e64a191 cc_mod: remove unused CCF_DELACK definition
During the DCTCP improvements, use of CCF_DELACK was
removed. This change is just to rename the unused flag
bit to prevent use of it, without also re-implementing
the tcp_input and tcp_output interfaces.

No functional change.

Reviewed by:	chengc_netapp.com, tuexen
MFC after:	2 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D26181
2020-09-10 00:46:38 +00:00
Mateusz Guzik
662c13053f net: clean up empty lines in .c and .h files 2020-09-01 21:19:14 +00:00
Richard Scheffenegger
ad7a0eb189 TCP Cubic: recalculate cwnd for every ACK.
Since cubic calculates cwnd based on absolute
time, retaining RFC3465 (ABC) once-per-window updates
can lead to dramatic changes of cwnd in the convex
region. Updating cwnd for each incoming ack minimizes
this delta, preventing unintentional line-rate bursts.

Reviewed by:	chengc_netapp.com, tuexen (mentor)
MFC after:	2 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D26060
2020-08-18 19:34:31 +00:00
Richard Scheffenegger
a459638fc4 TCP Cubic: Have Fast Convergence Heuristic work for ECN, and align concave region
The Cubic concave region was not aligned nicely for the very first exit from
slow start, where a 50% cwnd reduction is done instead of the normal 30%.

This addresses an issue, where a short line-rate burst could result from that
sudden jump of cwnd.

In addition, the Fast Convergence Heuristic has been expanded to work also
with ECN induced congestion response.

Submitted by:	chengc_netapp.com
Reported by:	chengc_netapp.com
Reviewed by:	tuexen (mentor), rgrimes (mentor)
Approved by:	tuexen (mentor), rgrimes (mentor)
MFC after:	3 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D25976
2020-08-13 16:45:55 +00:00
Richard Scheffenegger
2bb6dfabbe TCP Cubic: After leaving slowstart fix unintended cwnd jump.
Initializing K to zero in D23655 introduced a miscalculation,
where cwnd would suddenly jump to cwnd_max instead of gradually
increasing, after leaving slow-start.

Properly calculating K instead of resetting it to zero resolves
this issue. Also making sure, that cwnd is recalculated at the
earliest opportunity once slow-start is over.

Reported by:	chengc_netapp.com
Reviewed by:	chengc_netapp.com, tuexen (mentor), rgrimes (mentor)
Approved by:	tuexen (mentor), rgrimes (mentor)
MFC after:	3 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D25746
2020-08-13 16:38:51 +00:00
Richard Scheffenegger
cce999b38f Fix style and comment around concave/convex regions in TCP cubic.
In cubic, the concave region is when snd_cwnd starts growing slower
towards max_cwnd (cwnd at the time of the congestion event), and
the convex region is when snd_cwnd starts to grow faster and
eventually appearing like slow-start like growth.

PR:		238478
Reviewed by:	tuexen (mentor), rgrimes (mentor)
Approved by:	tuexen (mentor), rgrimes (mentor)
MFC after:	2 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D24657
2020-07-21 16:21:52 +00:00
Richard Scheffenegger
66ba9aafcf Add MODULE_VERSION to TCP loadable congestion control modules.
Without versioning information, using preexisting loader /
linker code is not easily possible when another module may
have dependencies on pre-loaded modules, and also doesn't
allow the automatic loading of dependent modules.

No functional change of the actual modules.

Reviewed by:	tuexen (mentor), rgrimes (mentor)
Approved by:	tuexen (mentor), rgrimes (mentor)
MFC after:	2 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D25744
2020-07-20 23:47:27 +00:00
Richard Scheffenegger
6e26dd0dbe TCP: fix cubic RTO reaction.
Proper TCP Cubic operation requires the knowledge
of the maximum congestion window prior to the
last congestion event.

This restores and improves a bugfix previously added
by jtl@ but subsequently removed due to a revert.

Reported by:	chengc_netapp.com
Reviewed by:	chengc_netapp.com, tuexen (mentor)
Approved by:	tuexen (mentor), rgrimes (mentor)
MFC after:	2 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D25133
2020-06-24 13:52:53 +00:00
Richard Scheffenegger
2fda0a6f3a Prevent TCP Cubic to abruptly increase cwnd after app-limited
Cubic calculates the new cwnd based on absolute time
elapsed since the start of an epoch. A cubic epoch is
started on congestion events, or once the congestion
avoidance phase is started, after slow-start has
completed.

When a sender is application limited for an extended
amount of time and subsequently a larger volume of data
becomes ready for sending, Cubic recalculates cwnd
with a lingering cubic epoch. This recalculation
of the cwnd can induce a massive increase in cwnd,
causing a burst of data to be sent at line rate by
the sender.

This adds a flag to reset the cubic epoch once a
session transitions from app-limited to cwnd-limited
to prevent the above effect.

Reviewed by:	chengc_netapp.com, tuexen (mentor)
Approved by:	tuexen (mentor), rgrimes (mentor)
MFC after:	3 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D25065
2020-06-10 07:32:02 +00:00
Richard Scheffenegger
6907bbae18 Prevent TCP Cubic to abruptly increase cwnd after slow-start
Introducing flags to track the initial Wmax dragging and exit
from slow-start in TCP Cubic. This prevents sudden jumps in the
caluclated cwnd by cubic, especially when the flow is application
limited during slow start (cwnd can not grow as fast as expected).
The downside is that cubic may remain slightly longer in the
concave region before starting the convex region beyond Wmax again.

Reviewed by:	chengc_netapp.com, tuexen (mentor)
Approved by:	tuexen (mentor), rgrimes (mentor, blanket)
MFC after:	3 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D23655
2020-06-09 21:07:58 +00:00
Richard Scheffenegger
e68cde59c3 DCTCP: update alpha only once after loss recovery.
In mixed ECN marking and loss scenarios it was found, that
the alpha value of DCTCP is updated two times. The second
update happens with freshly initialized counters indicating
to ECN loss. Overall this leads to alpha not adjusting as
quickly as expected to ECN markings, and therefore lead to
excessive loss.

Reported by:	Cheng Cui
Reviewed by:	chengc_netapp.com, rrs, tuexen (mentor)
Approved by:	tuexen (mentor)
MFC after:	2 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D24817
2020-05-21 21:42:49 +00:00
Richard Scheffenegger
14558b9953 Introduce a lower bound of 2 MSS to TCP Cubic.
Running TCP Cubic together with ECN could end up reducing cwnd down to 1 byte, if the
receiver continously sets the ECE flag, resulting in very poor transmission speeds.

In line with RFC6582 App. B, a lower bound of 2 MSS is introduced, as well as a typecast
to prevent any potential integer overflows during intermediate calculation steps of the
adjusted cwnd.

Reported by:	Cheng Cui
Reviewed by:	tuexen (mentor)
Approved by:	tuexen (mentor)
MFC after:	2 weeks
Sponsored by:	NetApp, Inc.
Differential Revision:	https://reviews.freebsd.org/D23353
2020-04-30 11:11:28 +00:00
Pawel Biernacki
7029da5c36 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
2020-02-26 14:26:36 +00:00
Randall Stewart
481be5de9d White space cleanup -- remove trailing tab's or spaces
from any line.

Sponsored by:	Netflix Inc.
2020-02-12 13:31:36 +00:00
Michael Tuexen
9cc711c9ff Sending CWR after an RTO is according to RFC 3168 generally required
and not only for the DCTCP congestion control.

Submitted by:		Richard Scheffenegger
Reviewed by:		rgrimes, tuexen@, Cheng Cui
MFC after:		1 week
Differential Revision:	https://reviews.freebsd.org/D23119
2020-01-25 13:45:10 +00:00
Michael Tuexen
e11c9783e1 Fix delayed ACK generation for DCTCP.
Submitted by:		Richard Scheffenegger
Reviewed by:		chengc@netapp.com, rgrimes@, tuexen@
Differential Revision:	https://reviews.freebsd.org/D22644
2019-12-31 16:15:47 +00:00
Michael Tuexen
7d87664a04 Add curly braces missed in https://svnweb.freebsd.org/changeset/base/354773
Sponsored by:		Netflix, Inc.
CID:			1407649
2019-12-31 12:29:01 +00:00
Edward Tomasz Napierala
adc56f5a38 Make use of the stats(3) framework in the TCP stack.
This makes it possible to retrieve per-connection statistical
information such as the receive window size, RTT, or goodput,
using a newly added TCP_STATS getsockopt(3) option, and extract
them using the stats_voistat_fetch(3) API.

See the net/tcprtt port for an example consumer of this API.

Compared to the existing TCP_INFO system, the main differences
are that this mechanism is easy to extend without breaking ABI,
and provides statistical information instead of raw "snapshots"
of values at a given point in time.  stats(3) is more generic
and can be used in both userland and the kernel.

Reviewed by:	thj
Tested by:	thj
Obtained from:	Netflix
Relnotes:	yes
Sponsored by:	Klara Inc, Netflix
Differential Revision:	https://reviews.freebsd.org/D20655
2019-12-02 20:58:04 +00:00
Michael Tuexen
3cf38784e2 Move all ECN related flags from the flags to the flags2 field.
This allows adding more ECN related flags in the future.
No functional change intended.

Submitted by:		Richard Scheffenegger
Reviewed by:		rrs@, tuexen@
Differential Revision:	https://reviews.freebsd.org/D22497
2019-12-01 21:01:33 +00:00
Michael Tuexen
c968c769af Add boundary and overflow checks to the formulas used in the TCP CUBIC
congestion control module.

Submitted by:		Richard Scheffenegger
Reviewed by:		rgrimes@
Differential Revision:	https://reviews.freebsd.org/D19118
2019-11-16 12:00:22 +00:00
Michael Tuexen
b0c1a13e4e Improve TCP CUBIC specific after idle reaction.
The adjustments are inspired by the Linux stack, which has had a
functionally equivalent implementation for more than a decade now.

Submitted by:		Richard Scheffenegger
Reviewed by:		Cheng Cui
Differential Revision:	https://reviews.freebsd.org/D18982
2019-11-16 11:57:12 +00:00
Michael Tuexen
35cd141b4b Implement a tCP CUBIC-specific after idle reaction.
This patch addresses a very common case of frequent application stalls,
where TCP runs idle and looses the state of the network.

Submitted by:		Richard Scheffenegger
Reviewed by:		Cheng Cui
Differential Revision:	https://reviews.freebsd.org/D18954
2019-11-16 11:37:26 +00:00
Michael Tuexen
453e633384 Revert https://svnweb.freebsd.org/changeset/base/354708
I used the wrong Differential Revision, so back it out and do it right
in a follow-up commit.
2019-11-16 11:10:09 +00:00
Michael Tuexen
730cbbc10d For idle TCP sessions using the CUBIC congestio control, reset ssthresh
to the higher of the previous ssthresh or 3/4 of the prior cwnd.

Submitted by:		Richard Scheffenegger
Reviewed by:		Cheng Cui
Differential Revision:	https://reviews.freebsd.org/D18982
2019-11-14 16:28:02 +00:00
Michael Tuexen
bb63f59b22 When performing after_idle() or post_recovery(), don't disable the
DCTCP specific methods. Also fallthrough NewReno for non ECN capable
TCP connections and improve the integer arithmetic.

Obtained from:		Richard Scheffenegger
MFC after:		1 week
Differential Revision:	https://reviews.freebsd.org/D20550
2019-07-29 09:19:48 +00:00
Michael Tuexen
333ba164d6 * Improve input validation of sysctl parameters for DCTPC.
* Initialize the alpha parameter to a conservative value (like Linux)
* Improve handling of arithmetic.
* Improve man-page

Obtained from:		Richard Scheffenegger
MFC after:		1 week
Differential Revision:	https://reviews.freebsd.org/D20549
2019-07-29 08:50:35 +00:00
Michael Tuexen
5cc11a89db Prevent cwnd to collapse down to 1 MSS after exiting recovery.
This is descrined in RFC 6582, which updates RFC 3782.

Submitted by:		Richard Scheffenegger
Reviewed by:		lstewart@
MFC after:		1 week
Differential Revision:	https://reviews.freebsd.org/D17614
2019-05-09 07:11:08 +00:00
Michael Tuexen
aa36fbd6fa Ensure that when using the TCP CDG congestion control and setting the
sysctl variable net.inet.tcp.cc.cdg.smoothing_factor to 0, the smoothing
is disabled. Without this patch, a division by zero orrurs.

PR:			193762
Reviewed by:		lstewart@, rrs@
MFC after:		3 days
Sponsored by:		Netflix, Inc.
Differential Revision:	https://reviews.freebsd.org/D19071
2019-02-08 20:42:49 +00:00
Michael Tuexen
7dc90a1de0 Fix a bug in the restart window computation of TCP New Reno
When implementing support for IW10, an update in the computation
of the restart window used after an idle phase was missed. To
minimize code duplication, implement the logic in tcp_compute_initwnd()
and call it. This fixes a bug in NewReno, which was not aware of
IW10.

Submitted by:		Richard Scheffenegger
Reviewed by:		tuexen@
MFC after:		1 week
Differential Revision:	https://reviews.freebsd.org/D18940
2019-01-25 13:57:09 +00:00
Hiren Panchasara
51e712f865 Revert r331567 CC Cubic: fix underflow for cubic_cwnd()
This change is causing TCP connections using cubic to hang. Need to dig more to
find exact cause and fix it.

Reported by:	tj at mrsk dot me, Matt Garber (via twitter)
Discussed with:	sbruno (previously), allanjude, cperciva
MFC after:	3 days
2018-12-15 17:01:16 +00:00
Brooks Davis
855acb84ca Fix bugs in plugable CC algorithm and siftr sysctls.
Use the sysctl_handle_int() handler to write out the old value and read
the new value into a temporary variable. Use the temporary variable
for any checks of values rather than using the CAST_PTR_INT() macro on
req->newptr. The prior usage read directly from userspace memory if the
sysctl() was called correctly. This is unsafe and doesn't work at all on
some architectures (at least i386.)

In some cases, the code could also be tricked into reading from kernel
memory and leaking limited information about the contents or crashing
the system. This was true for CDG, newreno, and siftr on all platforms
and true for i386 in all cases. The impact of this bug is largest in
VIMAGE jails which have been configured to allow writing to these
sysctls.

Per discussion with the security officer, we will not be issuing an
advisory for this issue as root access and a non-default config are
required to be impacted.

Reviewed by:	markj, bz
Discussed with:	gordon (security officer)
MFC after:	3 days
Security:	kernel information leak, local DoS (both require root)
Differential Revision:	https://reviews.freebsd.org/D18443
2018-12-15 15:06:22 +00:00
Michael Tuexen
c8b53ced95 Limit option_len for the TCP_CCALGOOPT.
Limiting the length to 2048 bytes seems to be acceptable, since
the values used right now are using 8 bytes.

Reviewed by:		glebius, bz, rrs
MFC after:		3 days
Sponsored by:		Netflix, Inc.
Differential Revision:	https://reviews.freebsd.org/D18366
2018-11-30 10:50:07 +00:00
Andrew Turner
5f901c92a8 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
2018-07-24 16:35:52 +00:00
Matt Macy
2269988749 NULL out cc_data in pluggable TCP {cc}_cb_destroy
When ABE was added (rS331214) to NewReno and leak fixed (rS333699) , it now has
a destructor (newreno_cb_destroy) for per connection state. Other congestion
controls may allocate and free cc_data on entry and exit, but the field is
never explicitly NULLed if moving back to NewReno which only internally
allocates stateful data (no entry contstructor) resulting in a situation where
newreno_cb_destory might be called on a junk pointer.

 -    NULL out cc_data in the framework after calling {cc}_cb_destroy
 -    free(9) checks for NULL so there is no need to perform not NULL checks
     before calling free.
 -    Improve a comment about NewReno in tcp_ccalgounload

This is the result of a debugging session from Jason Wolfe, Jason Eggleston,
and mmacy@ and very helpful insight from lstewart@.

Submitted by: Kevin Bowling
Reviewed by: lstewart
Sponsored by: Limelight Networks
Differential Revision: https://reviews.freebsd.org/D16282
2018-07-22 05:37:58 +00:00
Lawrence Stewart
9891578a40 Plug a memory leak and potential NULL-pointer dereference introduced in r331214.
Each TCP connection that uses the system default cc_newreno(4) congestion
control algorithm module leaks a "struct newreno" (8 bytes of memory) at
connection initialisation time. The NULL-pointer dereference is only germane
when using the ABE feature, which is disabled by default.

While at it:

- Defer the allocation of memory until it is actually needed given that ABE is
  optional and disabled by default.

- Document the ENOMEM errno in getsockopt(2)/setsockopt(2).

- Document ENOMEM and ENOBUFS in tcp(4) as being synonymous given that they are
  used interchangeably throughout the code.

- Fix a few other nits also accidentally omitted from the original patch.

Reported by:	Harsh Jain on freebsd-net@
Tested by:	tjh@
Differential Revision:	https://reviews.freebsd.org/D15358
2018-05-17 02:46:27 +00:00
Sean Bruno
68ff29affa cc_cubic:
- Update cubic parameters to draft-ietf-tcpm-cubic-04

Submitted by:	Matt Macy <mmacy@mattmacy.io>
Reviewed by:	lstewart
Differential Revision:	https://reviews.freebsd.org/D10556
2018-05-03 15:01:27 +00:00
Sean Bruno
e2041bfa7c CC Cubic: fix underflow for cubic_cwnd()
Singed calculations in cubic_cwnd() can result in negative cwnd
value which is then cast to an unsigned value. Values less than
1 mss are generally bad for other parts of the code, also fixed.

Submitted by:	Jason Eggleston <jason@eggnet.com>
Sponsored by:	Limelight Networks
Differential Revision:	https://reviews.freebsd.org/D14141
2018-03-26 19:53:36 +00:00
Lawrence Stewart
370efe5ac8 Add support for the experimental Internet-Draft "TCP Alternative Backoff with
ECN (ABE)" proposal to the New Reno congestion control algorithm module.
ABE reduces the amount of congestion window reduction in response to
ECN-signalled congestion relative to the loss-inferred congestion response.

More details about ABE can be found in the Internet-Draft:
https://tools.ietf.org/html/draft-ietf-tcpm-alternativebackoff-ecn

The implementation introduces four new sysctls:

- net.inet.tcp.cc.abe defaults to 0 (disabled) and can be set to non-zero to
  enable ABE for ECN-enabled TCP connections.

- net.inet.tcp.cc.newreno.beta and net.inet.tcp.cc.newreno.beta_ecn set the
  multiplicative window decrease factor, specified as a percentage, applied to
  the congestion window in response to a loss-based or ECN-based congestion
  signal respectively. They default to the values specified in the draft i.e.
  beta=50 and beta_ecn=80.

- net.inet.tcp.cc.abe_frlossreduce defaults to 0 (disabled) and can be set to
  non-zero to enable the use of standard beta (50% by default) when repairing
  loss during an ECN-signalled congestion recovery episode. It enables a more
  conservative congestion response and is provided for the purposes of
  experimentation as a result of some discussion at IETF 100 in Singapore.

The values of beta and beta_ecn can also be set per-connection by way of the
TCP_CCALGOOPT TCP-level socket option and the new CC_NEWRENO_BETA or
CC_NEWRENO_BETA_ECN CC algo sub-options.

Submitted by:	Tom Jones <tj@enoti.me>
Tested by:	Tom Jones <tj@enoti.me>, Grenville Armitage <garmitage@swin.edu.au>
Relnotes:	Yes
Differential Revision:	https://reviews.freebsd.org/D11616
2018-03-19 16:37:47 +00:00
Pedro F. Giffuni
fe267a5590 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.
2017-11-27 15:23:17 +00:00
Ed Maste
1edbb54fe9 cc_cubic: restore braces around if-condition block
r307901 was reverted in r321480, restoring an incorrect block
delimitation bug present in the original cc_cubic commit. Restore
only the bugfix (brace addition) from r307901.

CID:		1090182
Approved by:	sbruno
2017-07-26 21:23:09 +00:00
Sean Bruno
43053c125a Revert r307901 - Inform CC modules about loss events.
This was discussed between various transport@ members and it was
requested to be reverted and discussed.

Submitted by:	Kevin Bowling <kevin.bowling@kev009.com>
Reported by:	lawrence
Reviewed by:	hiren
Sponsored by:	Limelight Networks
2017-07-25 15:08:52 +00:00
Sean Bruno
5d53981a18 Revert r308180 - Set slow start threshold more accurrately on loss ...
This was discussed between various transport@ members and it was
requested to be reverted and discussed.

Submitted by:	kevin
Reported by:	lawerence
Reviewed by:	hiren
2017-07-25 15:03:05 +00:00
Conrad Meyer
1d64db52f3 Fix a variety of cosmetic typos and misspellings
No functional change.

PR:		216096, 216097, 216098, 216101, 216102, 216106, 216109, 216110
Reported by:	Bulat <bltsrc at mail.ru>
Sponsored by:	Dell EMC Isilon
2017-01-15 18:00:45 +00:00
Hiren Panchasara
e04310d59b Set slow start threshold more accurately on loss to be flightsize/2 instead of
cwnd/2 as recommended by RFC5681. (spotted by mmacy at nextbsd dot org)

Restore pre-r307901 behavior of aligning ssthresh/cwnd on mss boundary. (spotted
by slawa at zxy dot spb dot ru)

Tested by:	    dim, Slawa <slawa at zxy dot spb dot ru>
MFC after:	    1 month
X-MFC with:	    r307901
Sponsored by:	    Limelight Networks
Differential Revision:	https://reviews.freebsd.org/D8349
2016-11-01 21:08:37 +00:00
Hiren Panchasara
4e7f755377 FreeBSD tcp stack used to inform respective congestion control module about the
loss event but not use or obay the recommendations i.e. values set by it in some
cases.

Here is an attempt to solve that confusion by following relevant RFCs/drafts.
Stack only sets congestion window/slow start threshold values when there is no
CC module availalbe to take that action. All CC modules are inspected and
updated when needed to take appropriate action on loss.

tcp_stacks/fastpath module has been updated to adapt these changes.

Note: Probably, the most significant change would be to not bring congestion
window down to 1MSS on a loss signaled by 3-duplicate acks and letting
respective CC decide that value.

In collaboration with:	Matt Macy <mmacy at nextbsd dot org>
Discussed on:		transport@ mailing list
Reviewed by:		jtl
MFC after:		1 month
Sponsored by:		Limelight Networks
Differential Revision:	https://reviews.freebsd.org/D8225
2016-10-25 05:45:47 +00:00
Hiren Panchasara
dd13b7d387 Undo r307899. It needs a bit more work and proper commit log. 2016-10-25 05:07:51 +00:00
Hiren Panchasara
95d8236011 In Collaboration with: Matt Macy <mmacy at nextbsd dot com>
Reviewed by:		    jtl
Sponsored by:		    Limelight Networks
Differential Revision:	    https://reviews.freebsd.org/D8225
2016-10-25 05:03:33 +00:00