Listen queue overflow

[Lawrence K. Chen, P.Eng.]

On 2013-11-18 17:57, Lawrence K. Chen, P.Eng. wrote:
> On 2013-11-14 17:04, Mark Andrews wrote:
>> In message 
>> <FD9B2CB2B33E394FAE3B7466954760571D666C24 at DFWX10HMPTC01.AMER.DELL.CO
>> M>, Vinny_Abello at Dell.com writes:
>>> Hi Everyone,
>>> 
>>> I recently had a recursive server running BIND 9.9.4 on FreeBSD 9.2
>>> appear to wedge and stop responding to clients. I had a flurry of these
>>> errors on the console:
>>> 
>>> sonewconn: pcb 0xfffffe007211d930: Listen queue overflow: 16 already in
>>> queue awaiting acceptance
>>> 

>> 
>> You can tune tcp-listen-queue in named.conf.  The current default is 10.
>> 
>>> Thanks!
>>> 
>>> -Vinny
>>> 
> 
> My logs have been filling up with
> 
> sonewconn: pcb 0xfffffe02bb7187a8: Listen queue overflow: 10 already in
> queue awaiting acceptance
> 
> Which seems to have started since upgrading to FreeBSD 9.2 (though there
> have been other changes, but on the email front...so looking at BIND hadn't
> crossed my mind at all until I spotted this thread), though its only on one
> server, so I had been hunting around trying to figure out where its been
> coming from.
> 

So, digging around further....16 is QLEN, and the message is shown when QLEN 
is > 3 * QLIM / 2.  So, QLEN = 16 for QLIM = 10 is right.

So, I need to find something with QLIM = 6 in my case?  Hmm, my proxy server. 
  Which seemed to be the only thing busy at the same time as when these 
messages appear in my logs.

Meanwhile...I had this happen today...

sonewconn: pcb 0xfffffe00a7367930: Listen queue overflow: 5 already in queue 
awaiting acceptance

Which does correspond with QLIM=3, where tcp-listen-queue's minimum and 
default was 3...until 9.9 where it's minimum and default became 10.

-- 
Who: Lawrence K. Chen, P.Eng. - W0LKC - Sr. Unix Systems Administrator
For: Enterprise Server Technologies (EST) -- & SafeZone Ally