netdev - Re: [PATCH net-next v2 3/3] mptcp: cope better with MP

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Date:   Fri, 15 May 2020 11:10:05 -0700 (PDT)
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     Paolo Abeni <pabeni@...hat.com>
cc:     netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>,
        "David S . Miller" <davem@...emloft.net>,
        Christoph Paasch <cpaasch@...le.com>, mptcp@...ts.01.org
Subject: Re: [PATCH net-next v2 3/3] mptcp: cope better with MP_JOIN
 failure


On Fri, 15 May 2020, Paolo Abeni wrote:

> Currently, on MP_JOIN failure we reset the child
> socket, but leave the request socket untouched.
>
> tcp_check_req will deal with it according to the
> 'tcp_abort_on_overflow' sysctl value - by default the
> req socket will stay alive.
>
> The above leads to inconsistent behavior on MP JOIN
> failure, and bad listener overflow accounting.
>
> This patch addresses the issue leveraging the infrastructure
> just introduced to ask the TCP stack to drop the req on
> failure.
>
> The child socket is not freed anymore by subflow_syn_recv_sock(),
> instead it's moved to a dead state and will be disposed by the
> next sock_put done by the TCP stack, so that listener overflow
> accounting is not affected by MP JOIN failure.
>
> Signed-off-by: Paolo Abeni <pabeni@...hat.com>
> Reviewed-by: Christoph Paasch <cpaasch@...le.com>
> ---
> net/mptcp/subflow.c | 15 +++++++++------
> 1 file changed, 9 insertions(+), 6 deletions(-)
>

Reviewed-by: Mat Martineau <mathew.j.martineau@...ux.intel.com>

--
Mat Martineau
Intel