RFC 8684 says:
If the token is unknown or the host wants to refuse subflow establishment
(for example, due to a limit on the number of subflows it will permit),
the receiver will send back a reset (RST) signal, analogous to an unknown
port in TCP, containing an MP_TCPRST option (Section 3.6) with an
"MPTCP specific error" reason code.
mptcp-next doesn't support MP_TCPRST yet, this can be added in another
change.
Signed-off-by: Florian Westphal <fw@strlen.de>
Reviewed-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>