Re: [PATCH] ipv4: Namespaceify tcp_max_orphans knob

From: 严海双 <redacted>
Date: Sat, 9 Sep 2017 13:09:57 +0800

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On 2017年9月9日, at 下午12:35, Cong Wang [off-list ref] wrote:

On Fri, Sep 8, 2017 at 6:25 PM, 严海双 [off-list ref] wrote:

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On 2017年9月9日, at 上午6:13, Cong Wang [off-list ref] wrote:

On Wed, Sep 6, 2017 at 8:10 PM, Haishuang Yan
[off-list ref] wrote:

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Different namespace application might require different maximal number
of TCP sockets independently of the host.

So after your patch we could have N * net->ipv4.sysctl_tcp_max_orphans
in a whole system, right? This just makes OOM easier to trigger.

From my understanding, before the patch, we had N * net->ipv4.sysctl_tcp_max_orphans,
and after the patch, we could have ns1.sysctl_tcp_max_orphans + ns2.sysctl_tcp_max_orphans
+ ns3.sysctl_tcp_max_orphans, is that right? Thanks for your reviewing.

Nope, by N I mean the number of containers. Before your patch, the limit
is global, after your patch it is per container.

Yeah, for example, if there is N containers, before the patch, I mean the limit is:

	N * net->ipv4.sysctl_tcp_max_orphans

After the patch, the limit is:

	ns1. net->ipv4.sysctl_tcp_max_orphans + ns2. net->ipv4.sysctl_tcp_max_orphans + …

Not true.

Please remove "N" from your equation of the current situation.

"sysctl_tcp_max_orphans" applies to entire system, it is a global limit,
comparing one limit against all orphans in the system, there is no N.