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Subject: Re: [PATCH RFC/RFT net-next 00/17] net: Convert neighbor tables to
 per-namespace
To:     Cong Wang <xiyou.wangcong@gmail.com>
Cc:     Linux Kernel Network Developers <netdev@vger.kernel.org>,
        nikita.leshchenko@oracle.com,
        Roopa Prabhu <roopa@cumulusnetworks.com>,
        Stephen Hemminger <stephen@networkplumber.org>,
        Ido Schimmel <idosch@mellanox.com>,
        Jiri Pirko <jiri@mellanox.com>,
        Saeed Mahameed <saeedm@mellanox.com>, alex.aring@gmail.com,
        linux-wpan@vger.kernel.org,
        NetFilter <netfilter-devel@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
References: <20180717120651.15748-1-dsahern@kernel.org>
 <CAM_iQpW4g2v6xk49Gz+WBasKaO9VUk3Q-umX7iBRK-mAhn21Fw@mail.gmail.com>
From:   David Ahern <dsahern@gmail.com>
Message-ID: <1a3f59a9-0ba5-c83f-16a6-f9550a84f693@gmail.com>
Date:   Tue, 17 Jul 2018 11:43:16 -0600
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On 7/17/18 11:40 AM, Cong Wang wrote:
> On Tue, Jul 17, 2018 at 5:11 AM <dsahern@kernel.org> wrote:
>>
>> From: David Ahern <dsahern@gmail.com>
>>
>> Nikita Leshenko reported that neighbor entries in one namespace can
>> evict neighbor entries in another. The problem is that the neighbor
>> tables have entries across all namespaces without separate accounting
>> and with global limits on when to scan for entries to evict.
> 
> It is nothing new, people including me already noticed this before.
> 
> 
>>
>> Resolve by making the neighbor tables for ipv4, ipv6 and decnet per
>> namespace and making the accounting and threshold limits per namespace.
> 
> 
> The last discussion about this a long time ago concluded that neigh
> table entries are controllable by remote, so after moving it to per netns,
> it would be easier to DOS the host.
> 

There are still limits on the total number of entries and with
per-namespace limits an admin has better control.