netdev - Re: [PATCH net-next] ipv4: enable route flushing in network namespaces

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Date:   Mon, 24 Jun 2019 21:59:21 +0200
From:   Christian Brauner <christian@...uner.io>
To:     David Ahern <dsahern@...il.com>, davem@...emloft.net,
        kuznet@....inr.ac.ru, yoshfuji@...ux-ipv6.org,
        netdev@...r.kernel.org
CC:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next] ipv4: enable route flushing in network namespaces

On June 24, 2019 9:49:33 PM GMT+02:00, David Ahern <dsahern@...il.com> wrote:
>On 6/24/19 7:29 AM, Christian Brauner wrote:
>> Tools such as vpnc try to flush routes when run inside network
>> namespaces by writing 1 into /proc/sys/net/ipv4/route/flush. This
>> currently does not work because flush is not enabled in non-initial
>> network namespaces.
>> Since routes are per network namespace it is safe to enable
>> /proc/sys/net/ipv4/route/flush in there.
>> 
>> Link: https://github.com/lxc/lxd/issues/4257
>> Signed-off-by: Christian Brauner <christian.brauner@...ntu.com>
>> ---
>>  net/ipv4/route.c | 12 ++++++++----
>>  1 file changed, 8 insertions(+), 4 deletions(-)
>> 
>
>why not teach vpnc to use rtnetlink and then add a flush option to
>RTM_DELROUTE?

I think that if you can do it unprivileged through netlink
you should also allow it through sysctls.
Even the original commit references it
to make it possible to enable the sysctls
1-by-1 as needed.