netdev - Re: [PATCH v2] netns: correctly use per-netns ipv4 sysctl_tcp

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Message-ID: <CAF1ivSbYF=wYaPR3XQOZZ_KcvAVYdnU0=deDaCYMLTnhoJ3OZw@mail.gmail.com>
Date:	Thu, 12 Jul 2012 19:17:18 +0800
From:	Lin Ming <mlin@...pku.edu.cn>
To:	Huang Qiang <h.huangqiang@...wei.com>
Cc:	David Miller <davem@...emloft.net>, glommer@...allels.com,
	netdev@...r.kernel.org, containers@...ts.linux-foundation.org,
	yangzhenzhang@...wei.com
Subject: Re: [PATCH v2] netns: correctly use per-netns ipv4 sysctl_tcp_mem

On Thu, Jul 12, 2012 at 5:33 PM, Huang Qiang <h.huangqiang@...wei.com> wrote:
> From: Yang Zhenzhang <yangzhenzhang@...wei.com>
>
> Now, kernel allows each net namespace to independently set up its levels
> for tcp memory pressure thresholds.
>
> But it seems there is a bug, as using the following steps:
>
> [root@...t socket]# lxc-start -n test -f config /bin/bash
> [root@...-test socket]# ip route add default via 192.168.58.2
> [root@...-test socket]# echo 0 0 0 > /proc/sys/net/ipv4/tcp_mem
> [root@...-test socket]# scp root@....168.58.174:/home/tcp_mem_test .
>
> and it still can transport the "tcp_mem_test" file which we hope it
> would not.
>
> It's because inet_init() (net/ipv4/af_inet.c)initialize the tcp_prot.sysctl_mem:
> tcp_prot.sysctl_mem = init_net.ipv4.sysctl_tcp_mem;
>
> So when the protocal is TCP, sk->sk_prot->sysctl_mem(following code)

s/protocal/protocol/

> always use the ipv4 sysctl_tcp_mem of init_net namespace rather than
> it's own net namespace.
> This patch simply set "prot" equal to net->ipv4.sysctl_tcp_mem when
> the protocol type is TCP.
>
> Signed-off-by: Yang Zhenzhang <yangzhenzhang@...wei.com>
> Signed-off-by: Huang Qiang <h.huangqiang@...wei.com>
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