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<p>For the records, I added a modparam to corex module which allows
adding A/AAAA records in the internal dns cache at startup. It
could be useful in this case as alternative for /etc/hostname
entries, but also at least for some testing scenarios to avoid
updating records on dns server, which may take time to propagate.</p>
<p> * <a
href="https://www.kamailio.org/docs/modules/devel/modules/corex.html#corex.p.dns_cache">https://www.kamailio.org/docs/modules/devel/modules/corex.html#corex.p.dns_cache</a></p>
<p>During runtime, there are rpc commands to add/remove records in
the dns cache.</p>
<p>Cheers,<br>
Daniel<br>
</p>
<div class="moz-cite-prefix">On 20.05.20 20:56, Daniel-Constantin
Mierla wrote:<br>
</div>
<blockquote type="cite"
cite="mid:8d4b76a6-190d-deaa-8ff5-8945d7afb5ee@gmail.com">
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<p>Hello,</p>
<p>having use_dns_cache=no is not that bad if you have a local dns
cache application pointed by /etc/resolv.conf, provided that you
do not need srv based load balancing.<br>
</p>
<p>Not being the developer of dns resolving part in kamailio and
the dns cache, I investigated a bit and practically the
/etc/hosts is the pre-dns way of associating domains to ip
addresses, without ttl and other attributes specific to dns
records. That seems the reason the libc dns related functions do
not use it implicitly, thus also not reflected inside kamailio
dns caching.</p>
<p>Now, you can add records to kamailio dns cache via rpc
commands, which can be done also from config using
jsonrpc_exec() from jsonrpcs module (e.g., using
event_route[htable:mod-init] before sip traffic is handled). The
command should be liked:</p>
<p>kamctl rpc dns.add_a domain ttl ipaddr flags</p>
<p>The flags can be 1 to add it as a bad record (blacklisted
domain) or 2 to add it as permanent record (do not expire). You
can use dns.add_aaaa for ipv6.<br>
</p>
<p>Actually I am now thinking to add the possibility to add to dns
cache via modparam of ipops module, to make it easier overall.</p>
<p>Cheers,<br>
Daniel<br>
</p>
<div class="moz-cite-prefix">On 20.05.20 19:35, George
Diamantopoulos wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAPcKEYMmrLxoLvS1_hw_kKXFA7JGt5ohEk9_Pf5z5it94e0Mxg@mail.gmail.com">
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charset=UTF-8">
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<div>Hello all,</div>
<div><br>
</div>
<div>Thank you for your enlightening answers. I ended up
creating DNS entries anyway, so it's all good now.
use_dns_cache=no sounded a little scary :-).<br>
</div>
<div><br>
</div>
<div>BR.</div>
<div>George<br>
</div>
<br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Tue, 19 May 2020 at
19:44, Daniel-Constantin Mierla <<a
href="mailto:miconda@gmail.com" moz-do-not-send="true">miconda@gmail.com</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0px 0px 0px
0.8ex;border-left:1px solid
rgb(204,204,204);padding-left:1ex">A quick follow up as I
found quite interesting that nowadays *BSDs allow<br>
specifying order of lookup in resolv.conf to include the
hosts file, but<br>
that doesn't seem to be in Linux:<br>
<br>
* <a
href="https://man.openbsd.org/resolv.conf.5#lookup"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://man.openbsd.org/resolv.conf.5#lookup</a><br>
<br>
Cheers,<br>
Daniel<br>
<br>
<br>
On 19.05.20 17:48, Daniel-Constantin Mierla wrote:<br>
> Hello,<br>
><br>
> worth to clarify that Kamailio doesn't implement a
dns resolver from<br>
> scratch, it still uses the functions from libc. It
only does caching and<br>
> try to use cashing records first.<br>
><br>
> By default, the following dns functions are used
internally when the<br>
> cache doesn't have the record already -- they are set
in the dns_func<br>
> structure:<br>
><br>
> struct dns_func_t dns_func = {<br>
> res_init,<br>
> res_search,<br>
> gethostbyname,<br>
> #ifdef HAVE_GETHOSTBYNAME2<br>
> gethostbyname2<br>
> #else<br>
> NULL<br>
> #endif<br>
> };<br>
><br>
> So practically by leveraging res_init()/res_search()
is relying on<br>
> /etc/resolv.conf to do DNS queries, which is not
using the /etc/hosts<br>
> (iirc). For more see:<br>
><br>
> * <a href="https://linux.die.net/man/3/res_search"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://linux.die.net/man/3/res_search</a><br>
><br>
> Cheers,<br>
> Daniel<br>
><br>
> On 19.05.20 17:23, Alex Balashov wrote:<br>
>> You are correct that Kamailio does not use the
libc resolver /<br>
>> libresolv, but rather its own resolver, which
ignores /etc/hosts.<br>
>><br>
>> -- Alex<br>
>><br>
>> On 5/19/20 10:42 AM, George Diamantopoulos wrote:<br>
>>> Hello all,<br>
>>><br>
>>> I've come across this today when trying to
setup DMQ replication:<br>
>>><br>
>>> root@sbcpub0-stage-lhe0-cn1:/root# systemctl
restart kamailio<br>
>>> root@sbcpub0-stage-lhe0-cn1:/root# kamcmd
dmq.list_nodes<br>
>>> {<br>
>>> host: 172.30.154.189<br>
>>> port: 5090<br>
>>> resolved_ip: 172.30.154.189<br>
>>> status: active<br>
>>> last_notification: 0<br>
>>> local: 1<br>
>>> }<br>
>>> root@sbcpub0-stage-lhe0-cn1:/root# getent
hosts<br>
>>> <a href="http://dmq-ng.services.domain.com"
rel="noreferrer" target="_blank" moz-do-not-send="true">dmq-ng.services.domain.com</a>
<<a href="http://dmq-ng.services.domain.com"
rel="noreferrer" target="_blank" moz-do-not-send="true">http://dmq-ng.services.domain.com</a>><br>
>>> 172.30.154.189 <a
href="http://dmq-ng.services.domain.com"
rel="noreferrer" target="_blank" moz-do-not-send="true">dmq-ng.services.domain.com</a><br>
>>> <<a
href="http://dmq-ng.services.domain.com"
rel="noreferrer" target="_blank" moz-do-not-send="true">http://dmq-ng.services.domain.com</a>><br>
>>> 172.17.130.13 <a
href="http://dmq-ng.services.domain.com"
rel="noreferrer" target="_blank" moz-do-not-send="true">dmq-ng.services.domain.com</a><br>
>>> <<a
href="http://dmq-ng.services.domain.com"
rel="noreferrer" target="_blank" moz-do-not-send="true">http://dmq-ng.services.domain.com</a>><br>
>>><br>
>>> root@sbcpub0-stage-lhe0-cn1:/root# grep
dmq-ng /etc/kamailio/*<br>
>>>
/etc/kamailio/kamailio-module-params.cfg:modparam("dmq",<br>
>>> "notification_address", "sip:<a
href="http://dmq-ng.services.domain.com:5090"
rel="noreferrer" target="_blank" moz-do-not-send="true">dmq-ng.services.domain.com:5090</a><br>
>>> <<a
href="http://dmq-ng.services.domain.com:5090"
rel="noreferrer" target="_blank" moz-do-not-send="true">http://dmq-ng.services.domain.com:5090</a>>")<br>
>>><br>
>>> In another case, where the resolving IPs for
the DMQ service hostname<br>
>>> were listed as A records in DNS, this worked
as expected.<br>
>>> In this case, the second host of the DMQ
group is not listed in<br>
>>> dmq.list_nodes, despite its being set in
/etc/hosts, as shown by the<br>
>>> getent command.<br>
>>><br>
>>> Doesn't kamailio use nss for hostname
resolution? Am I missing<br>
>>> something else? Thanks!<br>
>>><br>
>>> BR,<br>
>>> George<br>
>>><br>
>>><br>
>>>
_______________________________________________<br>
>>> Kamailio (SER) - Users Mailing List<br>
>>> <a href="mailto:sr-users@lists.kamailio.org"
target="_blank" moz-do-not-send="true">sr-users@lists.kamailio.org</a><br>
>>> <a
href="https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users</a><br>
>>><br>
>> -- <br>
>> Alex Balashov | Principal | Evariste Systems LLC<br>
>><br>
>> Tel: +1-706-510-6800 / +1-800-250-5920
(toll-free)<br>
>> Web: <a href="http://www.evaristesys.com/"
rel="noreferrer" target="_blank" moz-do-not-send="true">http://www.evaristesys.com/</a>,
<a href="http://www.csrpswitch.com/" rel="noreferrer"
target="_blank" moz-do-not-send="true">http://www.csrpswitch.com/</a><br>
>><br>
>> _______________________________________________<br>
>> Kamailio (SER) - Users Mailing List<br>
>> <a href="mailto:sr-users@lists.kamailio.org"
target="_blank" moz-do-not-send="true">sr-users@lists.kamailio.org</a><br>
>> <a
href="https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users</a><br>
> -- <br>
> Daniel-Constantin Mierla -- <a
href="http://www.asipto.com" rel="noreferrer"
target="_blank" moz-do-not-send="true">www.asipto.com</a><br>
> <a href="http://www.twitter.com/miconda"
rel="noreferrer" target="_blank" moz-do-not-send="true">www.twitter.com/miconda</a>
-- <a href="http://www.linkedin.com/in/miconda"
rel="noreferrer" target="_blank" moz-do-not-send="true">www.linkedin.com/in/miconda</a><br>
> Funding: <a href="https://www.paypal.me/dcmierla"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://www.paypal.me/dcmierla</a><br>
><br>
-- <br>
Daniel-Constantin Mierla -- <a
href="http://www.asipto.com" rel="noreferrer"
target="_blank" moz-do-not-send="true">www.asipto.com</a><br>
<a href="http://www.twitter.com/miconda" rel="noreferrer"
target="_blank" moz-do-not-send="true">www.twitter.com/miconda</a>
-- <a href="http://www.linkedin.com/in/miconda"
rel="noreferrer" target="_blank" moz-do-not-send="true">www.linkedin.com/in/miconda</a><br>
Funding: <a href="https://www.paypal.me/dcmierla"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://www.paypal.me/dcmierla</a><br>
<br>
<br>
_______________________________________________<br>
Kamailio (SER) - Users Mailing List<br>
<a href="mailto:sr-users@lists.kamailio.org"
target="_blank" moz-do-not-send="true">sr-users@lists.kamailio.org</a><br>
<a
href="https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users</a><br>
</blockquote>
</div>
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<br>
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<pre class="moz-quote-pre" wrap="">_______________________________________________
Kamailio (SER) - Users Mailing List
<a class="moz-txt-link-abbreviated" href="mailto:sr-users@lists.kamailio.org" moz-do-not-send="true">sr-users@lists.kamailio.org</a>
<a class="moz-txt-link-freetext" href="https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users" moz-do-not-send="true">https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users</a>
</pre>
</blockquote>
<pre class="moz-signature" cols="72">--
Daniel-Constantin Mierla -- <a class="moz-txt-link-abbreviated" href="http://www.asipto.com" moz-do-not-send="true">www.asipto.com</a>
<a class="moz-txt-link-abbreviated" href="http://www.twitter.com/miconda" moz-do-not-send="true">www.twitter.com/miconda</a> -- <a class="moz-txt-link-abbreviated" href="http://www.linkedin.com/in/miconda" moz-do-not-send="true">www.linkedin.com/in/miconda</a>
Funding: <a class="moz-txt-link-freetext" href="https://www.paypal.me/dcmierla" moz-do-not-send="true">https://www.paypal.me/dcmierla</a></pre>
</blockquote>
<pre class="moz-signature" cols="72">--
Daniel-Constantin Mierla -- <a class="moz-txt-link-abbreviated" href="http://www.asipto.com">www.asipto.com</a>
<a class="moz-txt-link-abbreviated" href="http://www.twitter.com/miconda">www.twitter.com/miconda</a> -- <a class="moz-txt-link-abbreviated" href="http://www.linkedin.com/in/miconda">www.linkedin.com/in/miconda</a>
Funding: <a class="moz-txt-link-freetext" href="https://www.paypal.me/dcmierla">https://www.paypal.me/dcmierla</a></pre>
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