[Kea-users] segfault with libmysqlclient / libmariadbclient

[Thomas Markwalder]

Hello Jean:

We had this reported by another user recently and have tracked down
the issue. We are working it under http://kea.isc.org/ticket/5354.

There is a admin work around that might make life easier for you.
MySQL defines a variable, "wait_timeout" which determines how long
a client connection may remain idle before the server drops it.
The default global value for this is 28800 seconds. 

Kea does not explicitly set this value so it adheres to the global value.
If this value on your system is smaller than the idle times Kea experiences
the current code will fall over with a segfault.

You can work around this by making the global value bigger.  The other
user's system had it set to 60 seconds, so Kea fell over pretty regularly.

You can check the value with mysql:

mysql> show variables like "wait_timeout";
+---------------+-------+
| Variable_name | Value |
+---------------+-------+
| wait_timeout  | 60    |
+---------------+-------+
1 row in set (0.00 sec)

If you log in as mysql root user you can set it globally through
mysql as well:

mysql> set wait_timeout = 86400;

This may not be appropriate for your system if you have lots of MySQL
clients.  We
could also provide a patch for you test with if this work around isn't
suitable. 

Regards,

Thomas Markwalder
ISC Software Engineering


On 4/11/17 4:06 PM, Fohr Jean noel wrote:
>
> Hi all
>
>
> I'm facing unexplained kea-dhcp4 crashes due to segfaults:
>
>
> On Centos 7 using EPEL kea-1.1 package 
> kea-dhcp4[8539]: segfault at 451 ip 00007f30486ada1c sp
> 00007ffecca26360 error 4 in libmysqlclient.so.18.0.0[7f304868b000+2de000]
>
>
> Or on debian 8 using unstable kea-1.1 packages:
>
> kea-dhcp4[17079]: segfault at 451 ip 00007fc29c9fdccc sp
> 00007ffe774b3db0 error 4 in
> libmariadbclient.so.18.0.0[7fc29c9d2000+37c000]
>
>
> I haven' been able to find any clue on what triggers this: i'm using
> remote mysql 5.7 server for leases and host reservations​
>
>
> Any help would be apreciated!
>
>
> Thanks,
>
>
> Jean-Noël Fohr
> CHU de Clermont-Ferrand
> Equipe Réseaux/Télécoms - reseau-telecom at chu-clermontferrand.fr
>
> Tél: 04 73 75 20 26
> Mail: jnfohr at chu-clermontferrand.fr
>
>
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