[RFC PATCH 0/3] mptcp: fix MP_JOIN failure handling

[Paolo Abeni <pabeni@redhat.com>]

Currently if we hit an MP_JOIN failure on the third ack, the child socket is
closed with reset, but the request socket is not deleted, causing weird
behaviors.

The main problem is that MPTCP's MP_JOIN code needs to plug it's own
'valid 3rd ack' checks and the current TCP callbacks do not allow that.

This series tries to address the above shortcoming introducing a new MPTCP
specific bit in a 'struct sock' hole, and leveraging that to allow
tcp_check_req releasing the request socket when needed.

The above allows cleaning-up a bit current MPTCP hooking in tcp_check_req().

An alternative solution, possibly cleaner but more invasive, would be
changing the 'bool *own_req' syn_recv_sock() argument into 'int *req_status'
and let MPTCP set it to 'REQ_DROP'.

Paolo Abeni (3):
  mptcp: add new sock flag to deal with join subflows
  inet_connection_sock: factor out destroy helper.
  mptcp: cope better with MP_JOIN failure

 include/linux/tcp.h                |  1 +
 include/net/inet_connection_sock.h |  8 ++++++++
 include/net/mptcp.h                | 17 ++++++++++-------
 net/ipv4/inet_connection_sock.c    |  6 +-----
 net/ipv4/tcp_minisocks.c           |  2 +-
 net/mptcp/protocol.c               |  7 -------
 net/mptcp/subflow.c                | 17 +++++++++++------
 7 files changed, 32 insertions(+), 26 deletions(-)

-- 
2.21.3