Additional/MP_JOIN subflows that do not pass some initial handshake
tests currently causes fallback to TCP. That is an RFC violation:
we should instead reset the subflow and leave the the msk untouched.
Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/91 Fixes: f296234c98a8 ("mptcp: Add handling of incoming MP_JOIN requests") Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com> Signed-off-by: Paolo Abeni <pabeni@redhat.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>