syncache errors

[Mike Tancsa]

At 11:33 AM 8/29/2010, Andre Oppermann wrote:
>On 29.08.2010 16:09, Mike Tancsa wrote:
>>After upgrading to a recent STABLE, I have been seeing the 
>>following sporadic errors
>>
>>Aug 28 04:15:15 smarthost2 kernel: TCP: [xx.yy.165.120]:53617 to 
>>[xx.yy.164.50]:25; syncache_socket:
>>Socket create failed due to limits or memory shortage
>>
>>this is with
>>FreeBSD 8.1-STABLE #7: Wed Aug 25 15:32:05 EDT 2010
>>and the previous kernel was from July 20th.
>>
>>The odd thing is that the error is triggered from a RELENG_6 host 
>>only it would seem. I noticed
>>there are a number of syncache and tcp updates to RELENG_8, is it 
>>possible this is related ? I dont
>>have any specific tweaks in /etc/sysctl.conf
>>
>>other than
>>net.inet.tcp.log_in_vain: 1
>>net.inet.udp.log_in_vain: 1
>
>The log_in_vain sysctl would cause the logging of syncache errors
>as well (net.inet.tcp.log_debug).  This was a POLA violation and
>I've separated them on August 27 on 8-stable.  So if you update
>you won't see them anymore.  That doesn't change the fact that
>the socket create failed though.
>
>If it only happens from a RELENG_6 box it probably is a problem
>with port re-usage by RELENG_6.  The difficulty is that sonewconn()
>fails and doesn't return an error code.  Hence it may be one of
>listen queue limits reached, memory shortage or a problem with
>inserting the inpcb into the hash lists.

Actually, I think I might have found the issue.  I was focusing on 
the "memory" part not the limits.  The 'RELENG_6 only' is just a 
fluke as thats a box that sends a lot of email to this particular 
server.  It turns out, sendmail was rate limiting the server
sm-mta[25923]: deferring connections on daemon IPv4: 8 per second
and somehow syncache is aware/logs this now where as it did not before ?

         ---Mike




>--
>Andre

--------------------------------------------------------------------
Mike Tancsa,                                      tel +1 519 651 3400
Sentex Communications,                            mike at sentex.net
Providing Internet since 1994                    www.sentex.net
Cambridge, Ontario Canada                         www.sentex.net/mike