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

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Date:	Tue, 29 Jul 2014 10:48:37 -0700
From:	Cong Wang <cwang@...pensource.com>
To:	zhuyj <zyjzyj2000@...il.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>
Subject: Re: ipv4: net namespace does not inherit network configurations

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.
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