Re: [PATCH mptcp-next v3 2/8] mptcp: add start_seq in the msk

[Paolo Abeni <pabeni@redhat.com>]

On Tue, 2021-09-14 at 17:19 +0800, Geliang Tang wrote:
> This patch added a new member named start_seq to the msk to keep track of
> the beginning of the last fully-acked data segment. This would be updated
> in __mptcp_clean_una.
> 
> Signed-off-by: Geliang Tang <geliangtang@gmail.com>
> ---
>  net/mptcp/protocol.c | 3 +++
>  net/mptcp/protocol.h | 1 +
>  2 files changed, 4 insertions(+)
> 
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index 71a5427609a9..e804ca0ac9e1 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -1071,6 +1071,7 @@ static void __mptcp_clean_una(struct sock *sk)
>  			WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
>  		}
>  
> +		msk->start_seq = dfrag->data_seq;
>  		dfrag_clear(sk, dfrag);
>  		cleaned = true;
>  	}
> @@ -2891,6 +2892,7 @@ struct sock *mptcp_sk_clone(const struct sock *sk,
>  	msk->wnd_end = msk->snd_nxt + req->rsk_rcv_wnd;
>  	msk->setsockopt_seq = mptcp_sk(sk)->setsockopt_seq;
>  	msk->last_retrans_seq = subflow_req->idsn - 1;
> +	msk->start_seq = 0;

I think 'start_seq' should be initialized to 'subflow_req->idsn - 1'.

The field name itself is a bit unclear to me. Something like
'last_fully_acked_dss_start_seq' would be more expressive, but it would
not be a better name at all ;) Any suggestion for a good alternative
name more than welcome! (otherwise we could add some more verbose
comment nearby the field definition)

/P