Re: ipv4: net namespace does not inherit network configurations

From: zhuyj
Date: Mon Oct 13 2014 - 04:20:53 EST

Hi, Miller && Cong

Can we merge this patch into kernel mainline? since the independence
between ipv4 and ipv6 is inconsistent even in the latest linux kernel(3.17-rc7),
that is, the net namespace is independent in ipv6 while it is not in ipv4.

Thanks a lot.
Zhu Yanjun

On 07/30/2014 01:48 AM, Cong Wang wrote:
On Tue, Jul 29, 2014 at 2:29 AM, zhuyj <zyjzyj2000@xxxxxxxxx> wrote:

I did a test on kernel3.16 rc6:

root@qemu1:~# echo 1 > /proc/sys/net/ipv6/conf/all/forwarding
root@qemu1:~# echo 1 > /proc/sys/net/ipv4/conf/all/forwarding
root@qemu1:~# ip netns list
root@qemu1:~# ip netns add fib1
root@qemu1:~# ip netns exec fib1 bash
root@qemu1:~# cat /proc/sys/net/ipv6/conf/all/forwarding
root@qemu1:~# cat /proc/sys/net/ipv4/conf/all/forwarding

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

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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