linux-toradex.git/Documentation/networking/mptcp-sysctl.rst, branch v6.15

mptcp: sysctl: add available_path_managers

2025-03-20T09:14:49+00:00

Similarly to net.mptcp.available_schedulers, this patch adds a new one
net.mptcp.available_path_managers to list the available path managers.

Signed-off-by: Geliang Tang 
Reviewed-by: Matthieu Baerts (NGI0) 
Signed-off-by: Matthieu Baerts (NGI0) 
Reviewed-by: Simon Horman 
Link: https://patch.msgid.link/20250313-net-next-mptcp-pm-ops-intro-v1-11-f4e4a88efc50@kernel.org
Signed-off-by: Paolo Abeni

mptcp: sysctl: set path manager by name

2025-03-20T09:14:48+00:00

Similar to net.mptcp.scheduler, a new net.mptcp.path_manager sysctl knob
is added to determine which path manager will be used by each newly
created MPTCP socket by setting the name of it.

Dealing with an explicit name is easier than with a number, especially
when more PMs will be introduced.

This sysctl knob makes the old one "pm_type" deprecated.

Signed-off-by: Geliang Tang 
Reviewed-by: Matthieu Baerts (NGI0) 
Signed-off-by: Matthieu Baerts (NGI0) 
Reviewed-by: Simon Horman 
Link: https://patch.msgid.link/20250313-net-next-mptcp-pm-ops-intro-v1-8-f4e4a88efc50@kernel.org
Signed-off-by: Paolo Abeni

doc: mptcp: sysctl: blackhole_timeout is per-netns

2025-01-30T13:02:19+00:00

All other sysctl entries mention it, and it is a per-namespace sysctl.

So mention it as well.

Fixes: 27069e7cb3d1 ("mptcp: disable active MPTCP in case of blackhole")
Reviewed-by: Mat Martineau 
Signed-off-by: Matthieu Baerts (NGI0) 
Signed-off-by: Paolo Abeni

mptcp: sysctl: add syn_retrans_before_tcp_fallback

2025-01-19T01:32:01+00:00

The number of SYN + MPC retransmissions before falling back to TCP was
fixed to 2. This is certainly a good default value, but having a fixed
number can be a problem in some environments.

The current behaviour means that if all packets are dropped, there will
be:

- The initial SYN + MPC

- 2 retransmissions with MPC

- The next ones will be without MPTCP.

So typically ~3 seconds before falling back to TCP. In some networks
where some temporally blackholes are unfortunately frequent, or when a
client tries to initiate connections while the network is not ready yet,
this can cause new connections not to have MPTCP connections.

In such environments, it is now possible to increase the number of SYN
retransmissions with MPTCP options to make sure MPTCP is used.

Interesting values are:

- 0: the first retransmission will be done without MPTCP options: quite
     aggressive, but also a higher risk of detecting false-positive
     MPTCP blackholes.

- >= 128: all SYN retransmissions will keep the MPTCP options: back to
          the < 6.12 behaviour.

The default behaviour is not changed here.

Reviewed-by: Mat Martineau 
Signed-off-by: Matthieu Baerts (NGI0) 
Link: https://patch.msgid.link/20250117-net-next-mptcp-syn_retrans_before_tcp_fallback-v1-1-ab4b187099b0@kernel.org
Signed-off-by: Jakub Kicinski

mptcp: disable active MPTCP in case of blackhole

2024-09-11T22:57:50+00:00

An MPTCP firewall blackhole can be detected if the following SYN
retransmission after a fallback to "plain" TCP is accepted.

In case of blackhole, a similar technique to the one in place with TFO
is now used: MPTCP can be disabled for a certain period of time, 1h by
default. This time period will grow exponentially when more blackhole
issues get detected right after MPTCP is re-enabled and will reset to
the initial value when the blackhole issue goes away.

The blackhole period can be modified thanks to a new sysctl knob:
blackhole_timeout. Two new MIB counters help understanding what's
happening:

- 'Blackhole', incremented when a blackhole is detected.
- 'MPCapableSYNTXDisabled', incremented when an MPTCP connection
  directly falls back to TCP during the blackhole period.

Because the technique is inspired by the one used by TFO, an important
part of the new code is similar to what can find in tcp_fastopen.c, with
some adaptations to the MPTCP case.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/57
Signed-off-by: Matthieu Baerts (NGI0) 
Link: https://patch.msgid.link/20240909-net-next-mptcp-fallback-x-mpc-v1-3-da7ebb4cd2a3@kernel.org
Signed-off-by: Jakub Kicinski

doc: mptcp: alphabetical order

2024-06-01T22:18:01+00:00

Similar to what is done in other 'sysctl' pages: it looks clearer from a
readability perspective.

This might cause troubles in the short/mid-term with the backports, but
by not putting new entries at the end, this can help to reduce conflicts
in case of backports in the long term. We don't change the information
here too often, so it looks OK to do that.

Reviewed-by: Mat Martineau 
Signed-off-by: Matthieu Baerts (NGI0) 
Link: https://lore.kernel.org/r/20240530-upstream-net-20240520-mptcp-doc-v3-2-e94cdd9f2673@kernel.org
Signed-off-by: Jakub Kicinski

doc: mptcp: add missing 'available_schedulers' entry

2024-06-01T22:18:01+00:00

This sysctl knob has been added recently, but the documentation has not
been updated.

This knob is used to show the available schedulers choices that are
registered, similar to 'net.ipv4.tcp_available_congestion_control'.

Fixes: 73c900aa3660 ("mptcp: add net.mptcp.available_schedulers")
Reviewed-by: Mat Martineau 
Signed-off-by: Matthieu Baerts (NGI0) 
Link: https://lore.kernel.org/r/20240530-upstream-net-20240520-mptcp-doc-v3-1-e94cdd9f2673@kernel.org
Signed-off-by: Jakub Kicinski

mptcp: add a new sysctl for make after break timeout

2023-10-25T19:23:33+00:00

The MPTCP protocol allows sockets with no alive subflows to stay
in ESTABLISHED status for and user-defined timeout, to allow for
later subflows creation.

Currently such timeout is constant - TCP_TIMEWAIT_LEN. Let the
user-space configure them via a newly added sysctl, to better cope
with busy servers and simplify (make them faster) the relevant
pktdrill tests.

Note that the new know does not apply to orphaned MPTCP socket
waiting for the data_fin handshake completion: they always wait
TCP_TIMEWAIT_LEN.

Reviewed-by: Mat Martineau 
Signed-off-by: Paolo Abeni 
Signed-off-by: Mat Martineau 
Link: https://lore.kernel.org/r/20231023-send-net-next-20231023-2-v1-1-9dc60939d371@kernel.org
Signed-off-by: Jakub Kicinski

mptcp: add a new sysctl scheduler

2023-08-23T00:31:18+00:00

This patch adds a new sysctl, named scheduler, to support for selection
of different schedulers. Export mptcp_get_scheduler helper to get this
sysctl.

Acked-by: Paolo Abeni 
Reviewed-by: Mat Martineau 
Signed-off-by: Geliang Tang 
Signed-off-by: Mat Martineau 
Link: https://lore.kernel.org/r/20230821-upstream-net-next-20230818-v1-4-0c860fb256a8@kernel.org
Signed-off-by: Jakub Kicinski

Documentation: mptcp: fix pm_type formatting

2022-09-13T08:18:44+00:00

When looking at the rendered HTML version, we can see 'pm_type' is not
displayed with a bold font:

  https://docs.kernel.org/5.19/networking/mptcp-sysctl.html

The empty line under 'pm_type' is then removed to have the same style as
the others.

Fixes: 6bb63ccc25d4 ("mptcp: Add a per-namespace sysctl to set the default path manager type")
Signed-off-by: Matthieu Baerts 
Link: https://lore.kernel.org/r/20220906180404.1255873-2-matthieu.baerts@tessares.net
Signed-off-by: Paolo Abeni