[MPTCP] Re: [PATCH mptcp-next v4 08/12] mptcp: Use full MPTCP-level disconnect state machine

[MPTCP] Re: [PATCH mptcp-next v4 08/12] mptcp: Use full MPTCP-level disconnect state machine

[Mat Martineau]

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On Thu, 23 Jul 2020, Mat Martineau wrote:

> RFC 8684 appendix D describes the connection state machine for
> MPTCP. This patch implements the DATA_FIN / DATA_ACK exchanges and
> MPTCP-level socket state changes described in that appendix, rather than
> simply sending DATA_FIN along with TCP FIN when disconnecting subflows.
>
> DATA_FIN is now sent and acknowledged before shutting down the
> subflows. Received DATA_FIN information (if not part of a data packet)
> is written to the MPTCP socket when the incoming DSS option is parsed by
> the subflow, and the MPTCP worker is scheduled to process the
> flag. DATA_FIN received as part of a full DSS mapping will be handled
> when the mapping is processed.
>
> The DATA_FIN is acknowledged by the worker if the reader is caught
> up. If there is still data to be moved to the MPTCP-level queue, ack_seq
> will be incremented to account for the DATA_FIN when it reaches the end
> of the stream and a DATA_ACK will be sent to the peer.
>
> In this RFC patch, DATA_FIN is sent when calling shutdown(fd, SHUT_WR)
> on the MPTCP socket. mptcp_close() has not yet been updated to wait for
> the peer to DATA_ACK before forcing all the subflows to be closed and
> cleaned up. The handshake is working with both peers using test programs
> with shutdown() and delays, but is not yet working consistently with the
> self tests. It also doesn't currently detect if fallback has happened,
> so there are extra acks sent on fallback connections.
>

Oops, this last paragraph was a holdover from the RFCv1 patch on this 
list. I deleted it before sending to netdev.

--
Mat Martineau
Intel