[PATCH mptcp-next v1 0/9] 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.

Patch 1/9 moves the bound check before entering the TCP socket.
Patch 2, 3 and 4 are cleanups/refactors finalized to safely re-using TCP
helpers on MPTCP skbs.
Patch 5 makes TCP pruning related helpers available to MPTCP and patch 6
makes use of them. Patch 7 addresses an edge scenario that could still
lead to transfer stall under memory pressure.
Finally patch 8 and 9 improve the MPTCP-level retransmission schema to
make recovery from memory pressure significanly faster.

Note that the diffstat is biases by the quite large patch 4/9, which
contains mechanical transformation of existing code; "real" changes are
noticiable smaller.

Tested successfully vs the test cases proposed by Geliang and Gang.
---
RFC -> v1:
 - dropped old patch 4 & 5
 - addressed AI reported comments
 - added retrans refactor.

Paolo Abeni (9):
  mptcp: move checks vs rcvbuf size earlier in the RX path
  mptcp: drop the mptcp_ooo_try_coalesce() helper
  mptcp: remove CB offset field
  mptcp: sync mptcp skb cb layout with tcp one
  tcp: expose the tcp_collapse_ofo_queue() helper to mptcp usage, too
  mptcp: implemented OoO queue pruning
  mptcp: track prune recovery status
  mptcp: move the retrans loop to a separate helper
  mptcp: let the retrans scheduler do its job.

 include/net/tcp.h    |   8 ++
 net/ipv4/tcp_input.c |  55 +++++---
 net/mptcp/fastopen.c |   1 -
 net/mptcp/mib.c      |   3 +
 net/mptcp/mib.h      |   3 +
 net/mptcp/options.c  |  55 +++++++-
 net/mptcp/protocol.c | 328 ++++++++++++++++++++++++++++---------------
 net/mptcp/protocol.h |  11 +-
 net/mptcp/subflow.c  |   2 +
 9 files changed, 323 insertions(+), 143 deletions(-)

-- 
2.53.0