NOTE: HEADS UP read the note below if your kernel config is not including GENERIC!!
This patch does a bit of cleanup on TCP congestion control modules. There were some rather
interesting surprises that one could get i.e. where you use a socket option to change
from one CC (say cc_cubic) to another CC (say cc_vegas) and you could in theory get
a memory failure and end up on cc_newreno. This is not what one would expect. The
new code fixes this by requiring a cc_data_sz() function so we can malloc with M_WAITOK
and pass in to the init function preallocated memory. The CC init is expected in this
case *not* to fail but if it does and a module does break the
"no fail with memory given" contract we do fall back to the CC that was in place at the time.
This also fixes up a set of common newreno utilities that can be shared amongst other
CC modules instead of the other CC modules reaching into newreno and executing
what they think is a "common and understood" function. Lets put these functions in
cc.c and that way we have a common place that is easily findable by future developers or
bug fixers. This also allows newreno to evolve and grow support for its features i.e. ABE
and HYSTART++ without having to dance through hoops for other CC modules, instead
both newreno and the other modules just call into the common functions if they desire
that behavior or roll there own if that makes more sense.
Note: This commit changes the kernel configuration!! If you are not using GENERIC in
some form you must add a CC module option (one of CC_NEWRENO, CC_VEGAS, CC_CUBIC,
CC_CDG, CC_CHD, CC_DCTCP, CC_HTCP, CC_HD). You can have more than one defined
as well if you desire. Note that if you create a kernel configuration that does not
define a congestion control module and includes INET or INET6 the kernel compile will
break. Also you need to define a default, generic adds 'options CC_DEFAULT=\"newreno\"
but you can specify any string that represents the name of the CC module (same names
that show up in the CC module list under net.inet.tcp.cc). If you fail to add the
options CC_DEFAULT in your kernel configuration the kernel build will also break.
Reviewed by: Michael Tuexen
Sponsored by: Netflix Inc.
RELNOTES:YES
Differential Revision: https://reviews.freebsd.org/D32693
TCP Hystart draft version -03:
https://datatracker.ietf.org/doc/html/draft-ietf-tcpm-hystartplusplus
Is a new version of hystart that allows one to carefully exit slow start if the RTT
spikes too much. The newer version has a slower-slow-start so to speak that then
kicks in for five round trips. To see if you exited too early, if not into congestion avoidance.
This commit will add that feature to our newreno CC and add the needed bits in rack to
be able to enable it.
Reviewed by: tuexen
Sponsored by: Netflix Inc.
Differential Revision: https://reviews.freebsd.org/D32373
This fixes several breakages (panics) since the tcp_lro code was
committed that have been reported. Quite a few new features are
now in rack (prefecting of DGP -- Dynamic Goodput Pacing among the
largest). There is also support for ack-war prevention. Documents
comming soon on rack..
Sponsored by: Netflix
Reviewed by: rscheff, mtuexen
Differential Revision: https://reviews.freebsd.org/D30036
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
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
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
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
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
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
tso_segsz pkthdr field during RX processing, and use the information in TCP for
more correct accounting and as a congestion control input. This is only a start,
and an audit of other uses for the data is left as future work.
Reviewed by: gallatin, rrs
Sponsored by: Netflix, Inc.
Differential Revision: https://reviews.freebsd.org/D7564
