netdev - Re: Fw: [Bug 85091] New: neighbour table overflow is not reported and impacts localhost TCP connectivity

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Message-ID: <CAHA+R7N=3GZ9sR9G-W4CZtyR8aihDc0DLbtQFifURyyBgC=-5A@mail.gmail.com>
Date:	Wed, 24 Sep 2014 12:11:36 -0700
From:	Cong Wang <cwang@...pensource.com>
To:	Stephen Hemminger <stephen@...workplumber.org>
Cc:	netdev <netdev@...r.kernel.org>
Subject: Re: Fw: [Bug 85091] New: neighbour table overflow is not reported and
 impacts localhost TCP connectivity

On Wed, Sep 24, 2014 at 9:32 AM, Stephen Hemminger
<stephen@...workplumber.org> wrote:
> Result:
>
> Kernel has to learn the 16k IP/MAC combinations, as soon as gc_thresh3 is hit,
> netperf stalls, no syslog/kernel message indicates the problem.
>
> The only indication are log entries like this:
>
>   "net_ratelimit: 1464 callbacks suppressed"
>
> No other messages are logged.
>

Looks like we have a race condition between we check gc_thresh3
and add the new entry into the table after locking in __neigh_create().
Otherwise the application layer should get EINVAL to stop.
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