linux/Documentation/networking/mptcp-sysctl.rst
Paolo Abeni ff5a0b421c mptcp: faster active backup recovery
The msk can use backup subflows to transmit in-sequence data
only if there are no other active subflow. On active backup
scenario, the MPTCP connection can do forward progress only
due to MPTCP retransmissions - rtx can pick backup subflows.

This patch introduces a new flag flow MPTCP subflows: if the
underlying TCP connection made no progresses for long time,
and there are other less problematic subflows available, the
given subflow become stale.

Stale subflows are not considered active: if all non backup
subflows become stale, the MPTCP scheduler can pick backup
subflows for plain transmissions.

Stale subflows can return in active state, as soon as any reply
from the peer is observed.

Active backup scenarios can now leverage the available b/w
with no restrinction.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/207
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2021-08-14 11:37:25 +01:00

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.. SPDX-License-Identifier: GPL-2.0
=====================
MPTCP Sysfs variables
=====================
/proc/sys/net/mptcp/* Variables
===============================
enabled - BOOLEAN
Control whether MPTCP sockets can be created.
MPTCP sockets can be created if the value is 1. This is a
per-namespace sysctl.
Default: 1 (enabled)
add_addr_timeout - INTEGER (seconds)
Set the timeout after which an ADD_ADDR control message will be
resent to an MPTCP peer that has not acknowledged a previous
ADD_ADDR message.
The default value matches TCP_RTO_MAX. This is a per-namespace
sysctl.
Default: 120
checksum_enabled - BOOLEAN
Control whether DSS checksum can be enabled.
DSS checksum can be enabled if the value is nonzero. This is a
per-namespace sysctl.
Default: 0
allow_join_initial_addr_port - BOOLEAN
Allow peers to send join requests to the IP address and port number used
by the initial subflow if the value is 1. This controls a flag that is
sent to the peer at connection time, and whether such join requests are
accepted or denied.
Joins to addresses advertised with ADD_ADDR are not affected by this
value.
This is a per-namespace sysctl.
Default: 1
stale_loss_cnt - INTEGER
The number of MPTCP-level retransmission intervals with no traffic and
pending outstanding data on a given subflow required to declare it stale.
The packet scheduler ignores stale subflows.
A low stale_loss_cnt value allows for fast active-backup switch-over,
an high value maximize links utilization on edge scenarios e.g. lossy
link with high BER or peer pausing the data processing.
This is a per-namespace sysctl.
Default: 4