netdev - Re: [PATCH v2 net-next 5/9] mptcp: subflow: add mptcp_subflow_init_cookie

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Message-ID: <alpine.OSX.2.23.453.2007311538230.30834@nataliet-mobl.amr.corp.intel.com>
Date:   Fri, 31 Jul 2020 15:38:47 -0700 (PDT)
From:   Mat Martineau <mathew.j.martineau@...ux.intel.com>
To:     Florian Westphal <fw@...len.de>
cc:     netdev@...r.kernel.org, edumazet@...gle.com,
        matthieu.baerts@...sares.net, pabeni@...hat.com
Subject: Re: [PATCH v2 net-next 5/9] mptcp: subflow: add mptcp_subflow_init_cookie_req
 helper

On Thu, 30 Jul 2020, Florian Westphal wrote:

> Will be used to initialize the mptcp request socket when a MP_CAPABLE
> request was handled in syncookie mode, i.e. when a TCP ACK containing a
> MP_CAPABLE option is a valid syncookie value.
>
> Normally (non-cookie case), MPTCP will generate a unique 32 bit connection
> ID and stores it in the MPTCP token storage to be able to retrieve the
> mptcp socket for subflow joining.
>
> In syncookie case, we do not want to store any state, so just generate the
> unique ID and use it in the reply.
>
> This means there is a small window where another connection could generate
> the same token.
>
> When Cookie ACK comes back, we check that the token has not been registered
> in the mean time.  If it was, the connection needs to fall back to TCP.
>
> Changes in v2:
> - use req->syncookie instead of passing 'want_cookie' arg to ->init_req()
>   (Eric Dumazet)
>
> Signed-off-by: Florian Westphal <fw@...len.de>
> ---
> include/net/mptcp.h  | 10 +++++++++
> net/mptcp/protocol.h |  1 +
> net/mptcp/subflow.c  | 50 +++++++++++++++++++++++++++++++++++++++++++-
> net/mptcp/token.c    | 26 +++++++++++++++++++++++
> 4 files changed, 86 insertions(+), 1 deletion(-)

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

--
Mat Martineau
Intel