[PATCH v9 mptcp-next 0/6] mptcp: address stall under memory pressure

[Paolo Abeni <pabeni@redhat.com>]

This an attempt to fix the data transfer stall reported by Geliang and
Gang more carefully enforcing memory constraints at the MPTCP level.

This iteration introduces has no significant change over the previous
one; the already merged patches has been dropped, and the remaining ones
rebases on top. The main delta is the commit message for patch 4, here
completely reworderd, as its content become obsoleted in the past
reworks.

Note that `multi_chunk_sendfile` and `multiproc*` test cases in
mptcp_data *may* require longer timeout than default[1].

Patch 1 is actually a fix for a pre-existing issues targeting net,
included here just for my convenience.

Patch 2 and 3 make the admission check much more strict for incoming
packets exceeding the memory limits, with some exception for fallback
sockets.
Patch 4 implements OoO queue pruning for MPTCP.
Finally patch 5 and 6 improve the MPTCP-level retransmission schema to
make recovery from memory pressure/after MPTCP-level drop significantly
faster.

[1] In my testing on v8 and v9 mptcp_data survived a few hundred
iterations with the default timeout. Some independent testing would be
appreciated.
---
v8 -> v9:
  - dropped already merged old patches 1-3
  - reworded commit message in patch 4

Paolo Abeni (6):
  mptcp: allow subflow rcv wnd to shrink
  mptcp: explicitly drop over memory limits
  mptcp: enforce hard limit on backlog flushing
  mptcp: implemented OoO queue pruning
  mptcp: move the retrans loop to a separate helper
  mptcp: let the retrans scheduler do its job.

 net/mptcp/mib.c      |   3 +
 net/mptcp/mib.h      |   3 +
 net/mptcp/options.c  |  35 +++++-
 net/mptcp/protocol.c | 247 +++++++++++++++++++++++++++++++------------
 4 files changed, 218 insertions(+), 70 deletions(-)

-- 
2.54.0