linux-kernel - Re: [PATCH RFC/RFT net-next 00/17] net: Convert neighbor tables to per-namespace

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Message-ID: <1a3f59a9-0ba5-c83f-16a6-f9550a84f693@gmail.com>
Date:   Tue, 17 Jul 2018 11:43:16 -0600
From:   David Ahern <dsahern@...il.com>
To:     Cong Wang <xiyou.wangcong@...il.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        nikita.leshchenko@...cle.com,
        Roopa Prabhu <roopa@...ulusnetworks.com>,
        Stephen Hemminger <stephen@...workplumber.org>,
        Ido Schimmel <idosch@...lanox.com>,
        Jiri Pirko <jiri@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>, alex.aring@...il.com,
        linux-wpan@...r.kernel.org,
        NetFilter <netfilter-devel@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RFC/RFT net-next 00/17] net: Convert neighbor tables to
 per-namespace

On 7/17/18 11:40 AM, Cong Wang wrote:
> On Tue, Jul 17, 2018 at 5:11 AM <dsahern@...nel.org> wrote:
>>
>> From: David Ahern <dsahern@...il.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.