linux-kernel - Re: ipv4: net namespace does not inherit network configurations

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Message-ID: <53D9A2F0.4040808@gmail.com>
Date:	Thu, 31 Jul 2014 09:59:12 +0800
From:	zhuyj <zyjzyj2000@...il.com>
To:	Cong Wang <cwang@...pensource.com>
CC:	"David S. Miller" <davem@...emloft.net>,
	Hong Zhiguo <honkiko@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	netdev <netdev@...r.kernel.org>,
	"Tao, Yue" <Yue.Tao@...driver.com>,
	Alexandre Dietsch <alexandre.dietsch@...driver.com>,
	zhuyj <zyjzyj2000@...il.com>
Subject: Re: ipv4: net namespace does not inherit network configurations

On 07/30/2014 01:48 AM, Cong Wang wrote:
> On Tue, Jul 29, 2014 at 2:29 AM, zhuyj <zyjzyj2000@...il.com> wrote:
>> Hi,all
>>
>> I did a test on kernel3.16 rc6:
>>
>> root@...u1:~# echo 1 > /proc/sys/net/ipv6/conf/all/forwarding
>> root@...u1:~# echo 1 > /proc/sys/net/ipv4/conf/all/forwarding
>> root@...u1:~# ip netns list
>> root@...u1:~# ip netns add fib1
>> root@...u1:~# ip netns exec fib1 bash
>> root@...u1:~# cat /proc/sys/net/ipv6/conf/all/forwarding
>> 0
>> root@...u1:~# cat /proc/sys/net/ipv4/conf/all/forwarding
>> 1
>>
>> The behavior of ipv4 and ipv6 is very inconsistent. I checked
>> the kernel source code. I found that from this patch
>> [ipv6: fix bad free of addrconf_init_net], the above difference
>> appeared.
>>
>> Since a net namespace is independent to another. That is, there
>> is no any relationship between the net namespaces. So the behavior
>> of ipv4 is not correct.
>>
> Well, they are already independent, not shared, just that the initial
> value is duplicated from init_net for IPv4.
>
> This change might break existing applications which rely on this
> behavior, but given IPv6 change is almost the same, I think it's ok.
>
> BTW, you need to submit a patch as normal, instead of as an attachment.
>
OK. Thanks a lot.

Zhu Yanjun
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