linux-kernel - RE: [RFC PATCH 00/30] Kernel NET policy

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Message-ID: <37D7C6CF3E00A74B8858931C1DB2F07712C19A4A@SHSMSX103.ccr.corp.intel.com>
Date:	Tue, 19 Jul 2016 01:49:41 +0000
From:	"Liang, Kan" <kan.liang@...el.com>
To:	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	Andi Kleen <andi@...stfloor.org>
CC:	Florian Westphal <fw@...len.de>,
	"davem@...emloft.net" <davem@...emloft.net>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"intel-wired-lan@...ts.osuosl.org" <intel-wired-lan@...ts.osuosl.org>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"mingo@...hat.com" <mingo@...hat.com>,
	"peterz@...radead.org" <peterz@...radead.org>,
	"kuznet@....inr.ac.ru" <kuznet@....inr.ac.ru>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"yoshfuji@...ux-ipv6.org" <yoshfuji@...ux-ipv6.org>,
	"kaber@...sh.net" <kaber@...sh.net>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"keescook@...omium.org" <keescook@...omium.org>,
	"viro@...iv.linux.org.uk" <viro@...iv.linux.org.uk>,
	"gorcunov@...nvz.org" <gorcunov@...nvz.org>,
	"john.stultz@...aro.org" <john.stultz@...aro.org>,
	"aduyck@...antis.com" <aduyck@...antis.com>,
	"ben@...adent.org.uk" <ben@...adent.org.uk>,
	"decot@...glers.com" <decot@...glers.com>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>
Subject: RE: [RFC PATCH 00/30] Kernel NET policy



> 
> > Also of course it would be fundamentally less efficient than kernel
> > code doing that, just because of the additional context switches
> > needed.
> 
> Synchronizing or configuring any kind of queues already requires rtnl_mutex.
> I didn't test it but acquiring rtnl mutex in inet_recvmsg is unlikely to fly
> performance wise and

Yes, rtnl will bring some overheads. But the configuration is one time thing for
application or socket. It only happens on receiving first packet.
Unless the application/socket only transmit few packets, the overhead
could be ignored. If they only transmit few packets, why they care about
performance?

> might even be very dangerous under DoS attacks (like
> I see in 24/30).
> 
Patch 29/30 tries to prevent such case.

Thanks,
Kan