Re: dns_hash_put(): unlinked item errors

> > On Jun 10, 2025, at 4:00 PM, JR Richardson via sr-users <[email protected]> wrote:
> >
> > Hey Folks,
> >
> > Running kamailio 5.8.4, haven't needed or used DNS functions
> > previously but recently completed clearip integration, which requires
> > sip request to use URL instead of IP and resolve where to send
> > request. Within hours of adding URL lookups I started getting dns_hash
> > unlinked errors. I correlated the log errors to when the URL changed
> > IP. I assume the caching is working because kamailio sends to the same
> > IP for a few minutes, then switches IP, sends to new IP for a few
> > minutes, then switches IP again and this activity continues.
> >
> > Here are some log errors:
> >
> > switch IP
> > Jun 10 14:14:17 siprouter1-pve186 /usr/local/sbin/kamailio[8111]:
> > WARNING: <core> [core/dns_cache.c:170]: dns_hash_put(): unlinked item
> > 0x7fa0f9b9fcc0
> > Jun 10 14:14:19 siprouter1-pve186 /usr/local/sbin/kamailio[8122]:
> > WARNING: <core> [core/dns_cache.c:185]: dns_hash_put_shm_unsafe():
> > unlinked item 0x7fa0f9b9fcc0
> >
> > switch IP
> > Jun 10 14:15:00 siprouter1-pve186 /usr/local/sbin/kamailio[8111]:
> > WARNING: <core> [core/dns_cache.c:170]: dns_hash_put(): unlinked item
> > 0x7fa0f9b9ee00
> > Jun 10 14:15:03 siprouter1-pve186 /usr/local/sbin/kamailio[8122]:
> > WARNING: <core> [core/dns_cache.c:185]: dns_hash_put_shm_unsafe():
> > unlinked item 0x7fa0f9b9ee00
> >
> > switch IP
> > Jun 10 14:15:33 siprouter1-pve186 /usr/local/sbin/kamailio[8110]:
> > WARNING: <core> [core/dns_cache.c:170]: dns_hash_put(): unlinked item
> > 0x7fa0f9b8e640
> > Jun 10 14:15:33 siprouter1-pve186 /usr/local/sbin/kamailio[8122]:
> > WARNING: <core> [core/dns_cache.c:185]: dns_hash_put_shm_unsafe():
> > unlinked item 0x7fa0f9b8e640
> >
> > switch IP
> > Jun 10 14:20:37 siprouter1-pve186 /usr/local/sbin/kamailio[8109]:
> > WARNING: <core> [core/dns_cache.c:170]: dns_hash_put(): unlinked item
> > 0x7fa0f9b3eb60
> >
> > switch IP
> > Jun 10 14:21:12 siprouter1-pve186 /usr/local/sbin/kamailio[8117]:
> > WARNING: <core> [core/dns_cache.c:170]: dns_hash_put(): unlinked item
> > 0x7fa0f9b830f0
> > Jun 10 14:21:23 siprouter1-pve186 /usr/local/sbin/kamailio[8122]:
> > WARNING: <core> [core/dns_cache.c:185]: dns_hash_put_shm_unsafe():
> > unlinked item 0x7fa0f9b830f0
> >
> > Here are my DNS config parameters, nothing I've changed made any
> > difference. And as far as I can tell I'm not dropping any clearip
> > queries.
> > dns=no
> > rev_dns=no
> > use_dns_failover=on
> > dns_try_ipv6=no
> >
> > I did find a patch update for this error back from 2023 and the patch
> > is in my /src/core/dns_cache.c as expected but still getting errors.
> >
> > Any guidance in clearing this error?
> >
> > Thanks.
> > JR
>
>
> Not an answer to your question, but to use failover, use_dns_cache (I believe) needs to be on.
>
> https://github.com/kamailio/kamailio/blob/master/doc/tutorials/dns.txt
>
> Fred Posner

Hi Fred,

I read through the DNS docs and believe I have a good understanding,
dns_cache is on my default so you don't have to explicitly define it
in the config. After further diagnosis I found the dns errors
"dns_hash_put(): unlinked item" happen at the same time the DNS query
goes out (around 4min30sec to 5min intervals) but the errors in the
log don't happen on every DNS query, they only appear when the URL IP
changes.

This is what I'm seeing, matching timestamps to DNS queries and SIP
Invites to clearip.
DNS query clearip.com IP#1 no error
DNS query clearip.com IP#1 no error
DNS query clearip.com IP#2 error
DNS query clearip.com IP#1 error
DNS query clearip.com IP#1 no error
DNS query clearip.com IP#2 error
DNS query clearip.com IP#2 no error
DNS query clearip.com IP#2 no error
DNS query clearip.com IP#1 error

Because I'm not seeing any performance or SIP processing issues, I now
believe the log entry is a false positive and can be disregarded, I
mean it is a warning, but there is no ill effect as far as I can tell,
just a lot of log messages, maybe this message should be downgraded to
informational?
WARNING: <core> [core/dns_cache.c:170]: dns_hash_put(): unlinked item ......
WARNING: <core> [core/dns_cache.c:185]: dns_hash_put_shm_unsafe():
unlinked item ...... *****(why is this one "shm_unsafe")

Thanks.

JR
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