mptcp: add subflow_v(4,6)_send_synack()
The send_synack() needs to be overridden for MPTCP to support TFO for
two reasons:
- There is not be enough space in the TCP options if the TFO cookie has
to be added in the SYN+ACK with other options: MSS (4), SACK OK (2),
Timestamps (10), Window Scale (3+1), TFO (10+2), MP_CAPABLE (12).
MPTCPv1 specs -- RFC 8684, section B.1 [1] -- suggest to drop the TCP
timestamps option in this case.
- The data received in the SYN has to be handled: the SKB can be
dequeued from the subflow sk and transferred to the MPTCP sk. Counters
need to be updated accordingly and the application can be notified at
the end because some bytes have been received.
[1] https://www.rfc-editor.org/rfc/rfc8684.html#section-b.1
Co-developed-by: Paolo Abeni <pabeni@redhat.com>
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
Co-developed-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Dmytro Shytyi <dmytro@shytyi.net>
Signed-off-by: Matthieu Baerts <matthieu.baerts@tessares.net>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
4 files changed
