linux-kernel - Re: [PATCH net v4] Fix race for duplicate reqsk on identical SYN

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Date: Mon, 24 Jun 2024 15:56:57 +0200
From: Eric Dumazet <edumazet@...gle.com>
To: luoxuanqiang <luoxuanqiang@...inos.cn>
Cc: kuniyu@...zon.com, kuba@...nel.org, davem@...emloft.net, pabeni@...hat.com, 
	dccp@...r.kernel.org, dsahern@...nel.org, fw@...len.de, 
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org, 
	alexandre.ferrieux@...nge.com
Subject: Re: [PATCH net v4] Fix race for duplicate reqsk on identical SYN

On Fri, Jun 21, 2024 at 3:39 AM luoxuanqiang <luoxuanqiang@...inos.cn> wrote:
>
> When bonding is configured in BOND_MODE_BROADCAST mode, if two identical
> SYN packets are received at the same time and processed on different CPUs,
> it can potentially create the same sk (sock) but two different reqsk
> (request_sock) in tcp_conn_request().
>
> These two different reqsk will respond with two SYNACK packets, and since
> the generation of the seq (ISN) incorporates a timestamp, the final two
> SYNACK packets will have different seq values.
>
> The consequence is that when the Client receives and replies with an ACK
> to the earlier SYNACK packet, we will reset(RST) it.
>
> ========================================================================
>

Reviewed-by: Eric Dumazet <edumazet@...gle.com>