ipv4: net namespace does not inherit network configurations

[zhuyj]

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Hi,all

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
0
root@qemu1:~# 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.

Based on this patch [ipv6: fix bad free of addrconf_init_net], I made
a new patch to fix this problem on ipv4.

Any reply is appreciated.

Zhu Yanjun