netdev - Re: [PATCH net-next] net: ipv4: allocate ipv4_devconf memory for init

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Date:   Sun, 16 Dec 2018 11:06:39 -0800
From:   Cong Wang <xiyou.wangcong@...il.com>
To:     Tonghao Zhang <xiangxia.m.yue@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH net-next] net: ipv4: allocate ipv4_devconf memory for init_net

On Sun, Dec 16, 2018 at 8:24 AM <xiangxia.m.yue@...il.com> wrote:
>
> From: Tonghao Zhang <xiangxia.m.yue@...il.com>
>
> The devconf setting on the init_net will affect other
> namespace when them created. For example:
>
> $ cat /proc/sys/net/ipv4/conf/all/rp_filter
> 0
> $ echo 2 > /proc/sys/net/ipv4/conf/all/rp_filter
> $ cat /proc/sys/net/ipv4/conf/all/rp_filter
> 2
>
> $ ip netns add ns100
> $ ip netns exec ns100 bash
> $ cat /proc/sys/net/ipv4/conf/all/rp_filter
> 2
>
> The value of rp_filter in the ns100, should be 0 as
> default, but it is 2 same as _init_net_.

This has been a known issue for a long time. There
were several attempts to fix this.

The concern here is whether it breaks existing applications'
expectation with the change like yours. There was a proposal
introduces a new /proc file to control this behavior, I forget
why it is not accepted either. Please check netdev archives.

Thanks.