mptcp: fallback to TCP after SYN+MPC drops

Some middleboxes might be nasty with MPTCP, and decide to drop packets
with MPTCP options, instead of just dropping the MPTCP options (or
letting them pass...).

In this case, it sounds better to fallback to "plain" TCP, and try
again.

Closes: https://github.com/multipath-tcp/mptcp_net-next/issues/477
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
5 files changed