Re: [PATCH 1/1] commit c6825c0976fa7893692e0e43b09740b419b23c09 upstream.

[Ani Sinha <ani@arista.com>]

On Thu, Oct 29, 2015 at 6:21 PM, Neal P. Murphy
<neal.p.murphy@alum.wpi.edu> wrote:
> On Thu, 29 Oct 2015 17:01:24 -0700
> Ani Sinha <ani@arista.com> wrote:
>
>> On Wed, Oct 28, 2015 at 11:40 PM, Neal P. Murphy
>> <neal.p.murphy@alum.wpi.edu> wrote:
>> > On Wed, 28 Oct 2015 02:36:50 -0400
>> > "Neal P. Murphy" <neal.p.murphy@alum.wpi.edu> wrote:
>> >
>> >> On Mon, 26 Oct 2015 21:06:33 +0100
>> >> Pablo Neira Ayuso <pablo@netfilter.org> wrote:
>> >>
>> >> > Hi,
>> >> >
>> >> > On Mon, Oct 26, 2015 at 11:55:39AM -0700, Ani Sinha wrote:
>> >> > > netfilter: nf_conntrack: fix RCU race in nf_conntrack_find_get
>> >> >
>> >> > Please, no need to Cc everyone here. Please, submit your Netfilter
>> >> > patches to netfilter-devel@vger.kernel.org.
>> >> >
>> >> > Moreover, it would be great if the subject includes something
>> >> > descriptive on what you need, for this I'd suggest:
>> >> >
>> >> > [PATCH -stable 3.4,backport] netfilter: nf_conntrack: fix RCU race in nf_conntrack_find_get
>> >> >
>> >> > I'm including Neal P. Murphy, he said he would help testing these
>> >> > backports, getting a Tested-by: tag usually speeds up things too.
>> >>
>> >
>> > I've probably done about as much seat-of-the-pants testing as I can. All opening/closing the same destination IP/port.
>> >
>> > Host: Debian Jessie, 8-core Vishera 8350 at 4.4 GHz, 16GiB RAM at (I think) 2100MHz.
>> >
>> > Traffic generator 1: 6-CPU KVM running 64-bit Smoothwall Express 3.1 (linux 3.4.109 without these patches), with 8GiB RAM and 9GiB swap. Packets sent across PURPLE (to bypass NAT and firewall).
>> >
>> > Traffic generator 2: 32-bit KVM running Smoothwall Express 3.1 (linux 3.4.110 with these patches), 3GiB RAM and minimal swap.
>> >
>> > In the first set of tests, generator 1's traffic passed through Generator 2 as a NATting firewall, to the host's web server. In the second set of tests, generator 2's traffic went through NAT to the host's web server.
>> >
>> > The load tests:
>> >   - 2500 processes using 2500 addresses and random src ports
>> >   - 2500 processes using 2500 addresses and the same src port
>> >   - 2500 processes using the same src address and port
>> >
>> > I also tested using stock NF timeouts and using 1 second timeouts.
>> >
>> > Bandwidth used got as high as 16Mb/s for some tests.
>> >
>> > Conntracks got up to 200 000 or so or bounced between 1 and 2, depending on the test and the timeouts.
>> >
>> > I did not reproduce the problem these patches solve. But more importantly, I saw no problems at all. Each time I terminated a test, RAM usage returned to about that of post-boot; so there were no apparent memory leaks. No kernel messages and no netfilter messages appeared during the tests.
>> >
>> > If I have time, I suppose I could run another set of tests: 2500 source processes using 2500 addresses times 200 ports to connect to 2500 addresses times 200 ports on a destination system. Each process opens 200 sockets, then closes them. And repeats ad infinitum. But I might have to be clever since I can't run 500 000 processes; but I could run 20 VMs; that would get it down to about 12 000 processes per VM. And I might have to figure out how to allow allow processes on the destination system to open hundreds or thousands of sockets.
>>
>> Should I resend the patch with a Tested-by: tag?
>
> ... Oh, wait. Not yet. The dawn just broke over ol' Marblehead here. I only tested TCP; I need to hammer UDP, too.
>
> Can I set the timeouts to zero? Or is one as low as I can go?

I don't see any assertion or check against 0 sec timeouts. You can
try. Your conntrack entries will be constantly flushing.

>
> N