[Pdns-users] PDNS-Recursor Segfaults

Tue May 20 20:31:49 UTC 2014

Imre,

Can you strace the startup with threads=1?

    Bert

On May 20, 2014 10:25 PM, Imre Gergely <gimre at narancs.net> wrote:
>
>
> Hi
>
> I did manage to reproduce this in a VM. Installed a CentOS 6.5, and recursor 3.5.3 from EPEL. Then I did this:
>
> for i in `seq 1 16`; do for j in `seq 1 254`; do ip a a 10.0.$i.$j/16 dev eth0; done; done
>
> Then I started the recursor, everything went just fine, did a bunch of digs, no problems.
>
> Then I added some more IPs:
>
> for i in `seq 17 32`; do for j in `seq 1 254`; do ip a a 10.0.$i.$j/16 dev eth0; done; done
>
> And then init.d/pdns-recursor restart:
>
> May 20 23:18:24 c605 pdns_recursor[21341]: PowerDNS recursor 3.5.3 (C) 2001-2013 PowerDNS.COM BV (Feb 10 2014, 17:26:52, gcc 4.4.7 20120313 (Red Hat 4.4.7-4))
>  starting up
> May 20 23:18:24 c605 pdns_recursor[21341]: PowerDNS comes with ABSOLUTELY NO WARRANTY. This is free software, and you are welcome to redistribute it according to the terms of the GPL version 2.
> May 20 23:18:24 c605 pdns_recursor[21341]: Operating in 32 bits mode
> May 20 23:18:24 c605 pdns_recursor[21341]: Reading random entropy from '/dev/urandom'
> May 20 23:18:24 c605 pdns_recursor[21341]: Only allowing queries from: 127.0.0.0/8, 10.0.0.0/8, 100.64.0.0/10, 169.254.0.0/16, 192.168.0.0/16, 172.16.0.0/12, ::1/128, fe80::/10
> May 20 23:18:24 c605 pdns_recursor[21341]: Will not send queries to: 127.0.0.0/8, 10.0.0.0/8, 100.64.0.0/10, 169.254.0.0/16, 192.168.0.0/16, 172.16.0.0/12, ::1/128, fe80::/10, 0.0.0.0, ::
> May 20 23:18:24 c605 pdns_recursor[21341]: NOT using IPv6 for outgoing queries - set 'query-local-address6=::' to enable
> May 20 23:18:24 c605 pdns_recursor[21341]: Inserting rfc 1918 private space zones
> May 20 23:18:24 c605 pdns_recursor[21341]: Listening for UDP queries on 127.0.0.1:53
> May 20 23:18:24 c605 pdns_recursor[21341]: Enabled TCP data-ready filter for (slight) DoS protection
> May 20 23:18:24 c605 pdns_recursor[21341]: Listening for TCP queries on 127.0.0.1:53
> May 20 23:18:24 c605 pdns_recursor[21341]: Calling daemonize, going to background
> May 20 23:18:24 c605 pdns_recursor[21342]: Set effective group id to 499
> May 20 23:18:24 c605 pdns_recursor[21342]: Set effective user id to 498
> May 20 23:18:24 c605 pdns_recursor[21342]: Launching 2 threads
> May 20 23:18:24 c605 pdns_recursor[21342]: Done priming cache with root hints
> May 20 23:18:24 c605 pdns_recursor[21342]: Enabled 'epoll' multiplexer
> May 20 23:18:24 c605 pdns_recursor[21342]: Done priming cache with root hints
> May 20 23:18:24 c605 pdns_recursor[21342]: Refreshed . records
> May 20 23:18:25 c605 kernel: pdns_recursor[21345]: segfault at ffff01d4 ip 080b1626 sp b6397890 error 4 in pdns_recursor[8048000+112000]
>
> [root at c605 ~]# ip a |grep inet |wc
>    4322   25927  220579
> [root at c605 ~]# /etc/init.d/pdns-recursor start
> Starting pdns-recursor:                                    [  OK  ]  <-- starts OK
> [root at c605 ~]# /etc/init.d/pdns-recursor stop
> Stopping pdns-recursor:                                    [  OK  ]
>
> Adding one more /24:
>
> [root at c605 ~]# for j in `seq 1 254`; do ip a a 10.0.18.$j/16 dev eth0; done
> [root at c605 ~]# /etc/init.d/pdns-recursor start
> Starting pdns-recursor:                                    [  OK  ]
> [root at c605 ~]# ip a |grep inet |wc
>    4576   27451  233679
>
> It says it starts, but it doesn't, just segfaults.
>
> [root at c605 ~]# file /bin/bash
> /bin/bash: ELF 32-bit LSB executable, Intel 80386, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.18, stripped
>
>
> On 05/20/2014 10:58 PM, James Baer wrote:
>>
>> Hi All - I'm experiencing an issue that I am unsure if it is a bug or just something I need to adjust on my systems to account for. 
>>
>> I have 2 servers, both running pdns_recursor (3.5.3) on Centos 6.5, installed from epel repository. The recursor is only listening on localhost on each system. 
>>
>> I am experiencing somewhat random crashes of the recursor with the following error: 
>>
>> kernel: pdns_recursor[21993]: segfault at 200001fc8 ip 0000000000472780 sp 00007f3f9c03f690 error 4 in pdns_recursor[400000+111000] 
>>
>> Both servers have a large number of ip addresses bound to them, in the range of 3-4k. I was able to replicate the segfaults on one of the servers by adding additional ip addresses. When I got to around 4k ip addresses the recursor simply would not even start, just segafulted right away. I was able to get it to start again, by removing some ip addresses, so i know it has something to do with how many addresses I have bound the server. 
>>
>> Any body have an ideas what I can do to correct this problem? I really don't see a reason why the recursor would care how many ip addresses I have on a system. 
>>
>> thank you 
>>
>>
>>
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>>
>
> -- 
>
> Imre Gergely
>
> http://havaz.net
>
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>