netdev - Re: [PATCH net-next v5 2/5] net/smc: Limit backlog connections

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Date:   Tue, 8 Feb 2022 18:13:42 +0100
From:   Karsten Graul <kgraul@...ux.ibm.com>
To:     "D. Wythe" <alibuda@...ux.alibaba.com>
Cc:     kuba@...nel.org, davem@...emloft.net, netdev@...r.kernel.org,
        linux-s390@...r.kernel.org, linux-rdma@...r.kernel.org
Subject: Re: [PATCH net-next v5 2/5] net/smc: Limit backlog connections

On 08/02/2022 13:53, D. Wythe wrote:
> From: "D. Wythe" <alibuda@...ux.alibaba.com>
> 
> Current implementation does not handling backlog semantics, one
> potential risk is that server will be flooded by infinite amount
> connections, even if client was SMC-incapable.

In this patch you count the number of inflight SMC handshakes as pending and
check them against the defined max_backlog. I really like this improvement.

There is another queue in af_smc.c, the smc accept queue and any new client 
socket that completed the handshake process is enqueued there (in smc_accept_enqueue() )
and is waiting to get accepted by the user space application. To apply the correct
semantics here, I think the number of sockets waiting in the smc accept queue 
should also be counted as backlog connections, right? I see no limit for this queue
now. What do you think?