Subject: Re: [PATCH] tcp: ensure non-empty connection request queue

From: Rick Jones <[email-masked]>
Date: Wed, 4 May 2016 10:24:24 -0700

On 05/03/2016 05:25 PM, Eric Dumazet wrote:
> On Tue, 2016-05-03 at 23:54 +0200, Peter Wu wrote:
>> When applications use listen() with a backlog of 0, the kernel would
>> set the maximum connection request queue to zero. This causes false
>> reports of SYN flooding (if tcp_syncookies is enabled) or packet drops
>> otherwise.
>>

> Well, I believe I already gave my opinion on this.
>
> listen backlog is not a hint. This is a limit.
>
> It is the limit of outstanding children in accept queue.
>
> If backlog is 0, no child can be put in the accept queue.
>
> It is therefore Working As Intented.

Dropping the connection attempt makes sense, but is entering/claiming 
synflood really indicated in the case of a zero-length accept queue?

rick