netdev - [BUG?] arp_cache: neighbor table overflow... and DoS

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Message-ID: <CAA85sZtKBAdUqmJS2xPA3AbZfA7+jqQRxKKjY9GCckfG-LgRtw@mail.gmail.com>
Date:   Wed, 17 Apr 2019 10:42:45 +0200
From:   Ian Kumlien <ian.kumlien@...il.com>
To:     Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: [BUG?] arp_cache: neighbor table overflow... and DoS

Hi,

I'm part of a team running a small:ish cloud - we have an issue atm
where neutron thinks that some hosts exists
and should be linked. This results in a arp flood - which on it's own
is not a problem.

As soon as we get "neighbour: arp_cache: neighbor table overflow!" the
machine stops responding to connections..
Even if this feels like a bit of a special case, it also feels *very* wrong ;)

It's like the "I can't find" queries add to the cache without adding a
entry - arp -a - n |wc -l is only 149 f.ex.

Anyone with ideas or clues?