19 May
2020
19 May
'20
7:42 p.m.
A quick follow up as I found quite interesting that nowadays *BSDs allow
specifying order of lookup in resolv.conf to include the hosts file, but
that doesn't seem to be in Linux:
* https://man.openbsd.org/resolv.conf.5#lookup
Cheers,
Daniel
On 19.05.20 17:48, Daniel-Constantin Mierla wrote:
Hello,
worth to clarify that Kamailio doesn't implement a dns resolver from
scratch, it still uses the functions from libc. It only does caching and
try to use cashing records first.
By default, the following dns functions are used internally when the
cache doesn't have the record already -- they are set in the dns_func
structure:
struct dns_func_t dns_func = {
res_init,
res_search,
gethostbyname,
#ifdef HAVE_GETHOSTBYNAME2
gethostbyname2
#else
NULL
#endif
};
So practically by leveraging res_init()/res_search() is relying on
/etc/resolv.conf to do DNS queries, which is not using the /etc/hosts
(iirc). For more see:
* https://linux.die.net/man/3/res_search
Cheers,
Daniel
On 19.05.20 17:23, Alex Balashov wrote:
--
Daniel-Constantin Mierla -- www.asipto.com
www.twitter.com/miconda -- www.linkedin.com/in/miconda
Funding: https://www.paypal.me/dcmierla
You are correct that Kamailio does not use the
libc resolver /
libresolv, but rather its own resolver, which ignores /etc/hosts.
-- Alex
On 5/19/20 10:42 AM, George Diamantopoulos wrote:
--
Daniel-Constantin Mierla -- www.asipto.com
www.twitter.com/miconda -- www.linkedin.com/in/miconda
Funding: https://www.paypal.me/dcmierla
Hello all,
I've come across this today when trying to setup DMQ replication:
root@sbcpub0-stage-lhe0-cn1:/root# systemctl restart kamailio
root@sbcpub0-stage-lhe0-cn1:/root# kamcmd dmq.list_nodes
{
host: 172.30.154.189
port: 5090
resolved_ip: 172.30.154.189
status: active
last_notification: 0
local: 1
}
root@sbcpub0-stage-lhe0-cn1:/root# getent hosts
dmq-ng.services.domain.com <http://dmq-ng.services.domain.com>
172.30.154.189 dmq-ng.services.domain.com
<http://dmq-ng.services.domain.com>
172.17.130.13 dmq-ng.services.domain.com
<http://dmq-ng.services.domain.com>
root@sbcpub0-stage-lhe0-cn1:/root# grep dmq-ng /etc/kamailio/*
/etc/kamailio/kamailio-module-params.cfg:modparam("dmq",
"notification_address", "sip:dmq-ng.services.domain.com:5090
<http://dmq-ng.services.domain.com:5090>")
In another case, where the resolving IPs for the DMQ service hostname
were listed as A records in DNS, this worked as expected.
In this case, the second host of the DMQ group is not listed in
dmq.list_nodes, despite its being set in /etc/hosts, as shown by the
getent command.
Doesn't kamailio use nss for hostname resolution? Am I missing
something else? Thanks!
BR,
George
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--
Alex Balashov | Principal | Evariste Systems LLC
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