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From: Eric Dumazet <eric.dumazet@gmail.com>
To: Subash Abhinov Kasiviswanathan <subashab@codeaurora.org>
Cc: netdev@vger.kernel.org, Stephen Hemminger <stephen@networkplumber.org>
Subject: Re: [PATCH net-next v2] net: Add sysctl to toggle early demux for tcp and udp
Date: Thu, 09 Mar 2017 20:25:36 -0800	[thread overview]
Message-ID: <1489119936.28631.28.camel@edumazet-glaptop3.roam.corp.google.com> (raw)
In-Reply-To: <1489116660-4244-1-git-send-email-subashab@codeaurora.org>

On Thu, 2017-03-09 at 20:31 -0700, Subash Abhinov Kasiviswanathan wrote:
> Certain system process significant unconnected UDP workload.
> It would be preferrable to disable UDP early demux for those systems
> and enable it for TCP only.

> +void tcp_v4_early_demux_configure(int enable)
> +{
> +	if (enable)
> +		tcp_protocol.early_demux = tcp_v4_early_demux;
> +	else
> +		tcp_protocol.early_demux = NULL;
> +}
> +
> +void udp_v4_early_demux_configure(int enable)
> +{
> +	if (enable)
> +		udp_protocol.early_demux = udp_v4_early_demux;
> +	else
> +		udp_protocol.early_demux = NULL;
> +}
> +


Well, then you need to make sure ipprot->early_demux is read once in the
callers, like ip_rcv_finish(), otherwise compiler could read it twice
and we could deref a NULL pointer.

ipprot = rcu_dereference(inet_protos[protocol]);
if (ipprot && ipprot->early_demux) {
    ipprot->early_demux(skb);   // crash

  parent reply	other threads:[~2017-03-10  4:25 UTC|newest]

Thread overview: 15+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-03-10  3:31 [PATCH net-next v2] net: Add sysctl to toggle early demux for tcp and udp Subash Abhinov Kasiviswanathan
2017-03-10  3:42 ` Tom Herbert
2017-03-10  5:26   ` Subash Abhinov Kasiviswanathan
2017-03-10 16:33     ` Tom Herbert
2017-03-11  0:22       ` Eric Dumazet
2017-03-11  0:49         ` Tom Herbert
2017-03-18 17:32           ` Subash Abhinov Kasiviswanathan
2017-03-18 17:44             ` Tom Herbert
2017-03-19  2:07               ` Subash Abhinov Kasiviswanathan
2017-03-19 19:18                 ` Eric Dumazet
2017-03-21 22:49                 ` Tom Herbert
2017-03-10  4:25 ` Eric Dumazet [this message]
2017-03-10  7:34   ` Subash Abhinov Kasiviswanathan
2017-03-10 12:42 ` kbuild test robot
2017-03-10 12:44 ` kbuild test robot

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