Bug 444236 - snmpwalk spikes cpu if IPv6 disabled on X86_64 RHEL 5.2Beta
Summary: snmpwalk spikes cpu if IPv6 disabled on X86_64 RHEL 5.2Beta
Status: CLOSED DUPLICATE of bug 431977
Alias: None
Product: Red Hat Enterprise Linux 5
Classification: Red Hat
Component: net-snmp
Version: 5.2
Hardware: x86_64
OS: Linux
high
high
Target Milestone: rc
: ---
Assignee: Jan Safranek
QA Contact:
URL:
Whiteboard:
Keywords:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2008-04-25 21:58 UTC by Michael Stahnke
Modified: 2008-04-28 15:35 UTC (History)
1 user (show)

(edit)
Clone Of:
(edit)
Last Closed: 2008-04-28 13:51:29 UTC


Attachments (Terms of Use)
This is a slightly sanitized version of our snmpd.conf (4.98 KB, application/octet-stream)
2008-04-25 21:59 UTC, Michael Stahnke
no flags Details
The output of snmpwalk (not straced anything) (21.06 KB, text/plain)
2008-04-25 21:59 UTC, Michael Stahnke
no flags Details
The output from top showing a cpu is 100% used (1.18 KB, text/plain)
2008-04-25 22:00 UTC, Michael Stahnke
no flags Details
strace running with snmpwalk (292.74 KB, text/plain)
2008-04-25 22:00 UTC, Michael Stahnke
no flags Details
And a bit of /var/log/messages (1.90 KB, text/plain)
2008-04-25 22:01 UTC, Michael Stahnke
no flags Details

Description Michael Stahnke 2008-04-25 21:58:30 UTC
Description of problem:
If you have disabled ipv6 on RHEL 5 x86_64 via the modprobe.conf, running 
snmpwalk -v2c -c community  127.0.0.1 will spike a single CPU.  

Version-Release number of selected component (if applicable):
This is applicable to every release of net-snmp since 5.1 ISOs were released. 
The lastest version I have tried is is in the RHEL 5.2 Beta channel. 
net-snmp-5.3.1-2


How reproducible:
Always

Steps to Reproduce:
1.  Run RHEL 5.1 or newer x86_64
2.  Disable IPv6 via the modprobe.conf
3.  reboot
4.  service snmpd start
5.  snmpwalk -v2c -c community  127.0.0.1
6.  Look at top output, watch a CPU sit at 100%
  
Actual results:
I have included attachments for the commands. 

Expected results:
Not having 100% spike while snmpd is running.  

Additional info:

It appears to be happening on at least these MIBS
.1.3.6.1.2.1.4.34

.1.3.6.1.2.1.4.35


I have included the following:
snmpd.conf 
snmpwalk_output_normal
strace_snmpwalk
var_log_messages_snip
output_from_top

I also tried to rebuild the SRPM disabling Ipv6, but the build fails.  I am not
sure if that is considered a bug though. 


It appears that this bug isn't new.  Google told me it's been happing in Centos
4, and 5 also.  

Here's a link with some information from the CentOS crew. 

http://bugs.centos.org/view.php?id=1350

Comment 1 Michael Stahnke 2008-04-25 21:59:29 UTC
Created attachment 303824 [details]
This is a slightly sanitized version of our snmpd.conf

Comment 2 Michael Stahnke 2008-04-25 21:59:56 UTC
Created attachment 303825 [details]
The output of snmpwalk (not straced anything)

Comment 3 Michael Stahnke 2008-04-25 22:00:27 UTC
Created attachment 303826 [details]
The output from top showing a cpu is 100% used

Comment 4 Michael Stahnke 2008-04-25 22:00:50 UTC
Created attachment 303827 [details]
strace running with snmpwalk

Comment 5 Michael Stahnke 2008-04-25 22:01:06 UTC
Created attachment 303828 [details]
And a bit of /var/log/messages

Comment 6 Brian 2008-04-28 13:00:21 UTC
I see the same bug. Additionally, snmpd must be restarted after a snmpwalk of
the server to get snmpget's or walks working again.

Some people have reported this is a xen kernel issue, but this happens for us on
non-xen kernels.

Comment 7 Jan Safranek 2008-04-28 13:51:29 UTC
It should be already fixed in RHEL 5.2. It has nothing to do with xen and it
happens only with RHEL 5.1 (I've added a buggy patch there).

*** This bug has been marked as a duplicate of 431977 ***

Comment 8 Michael Stahnke 2008-04-28 14:17:21 UTC
This is not fixed in the currently released net-snmp inthe RHEL 5.2 beta channel.  

I have the latest net-snmp installed that is available in RHN. 
net-snmp-5.3.1-22

If there is a fix, could you direct me to the link?  The other bug says proposed
for RHEL 5.3.  I would like a fix before 2009.  


Comment 9 Jan Safranek 2008-04-28 14:49:24 UTC
it was fixed after beta, in net-snmp-5.3.1-23 to be precise. And the bug has
been evaluated as important enough to fix it in 5.2.

You can find test build at http://people.redhat.com/jsafrane/bugs/444236/

Comment 10 Michael Stahnke 2008-04-28 15:35:23 UTC
Thank you very much for a prompt response. Everything working just fine. 


Note You need to log in before you can comment on or make changes to this bug.