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Hello,<br>
<br>
<br>
<div class="moz-cite-prefix">On 12/03/15 17:51, canuck15 wrote:<br>
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cite="mid:BLU436-SMTP667FC434527F976E194E96DA060@phx.gbl"
type="cite">
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I am reading the documentation for the ipops module
dns_int_match_ip() function and it states the following:<br>
<br>
"<span style="color: rgb(0, 0, 0); font-family: Helvetica, Arial;
font-size: 12px; font-style: normal; font-variant: normal;
font-weight: normal; letter-spacing: normal; line-height:
normal; orphans: auto; text-align: justify; text-indent: 0px;
text-transform: none; white-space: normal; widows: 1;
word-spacing: 0px; -webkit-text-stroke-width: 0px; display:
inline !important; float: none; background-color: rgb(255, 255,
255);">Returns TRUE if ipaddr is associated by DNS to hostname.
FALSE otherwise. It uses internal DNS resolver. At this moment,
the function might not check all the IP addresses as returned by
dns_sys_match_ip(), because the internal resolver targets to
discover the first address to be used for relaying SIP traffic.
Thus is better to use dns_sys_match_ip() if the host you want to
check has many IP addresses, in different address famililies
(IPv4/6)."<br>
<br>
I am not sure what that statement means. I will be using this
for IP authentication where the records it is checking against
are in a mysql database and may or may not be be using the DNS
name instead of the IP. Many of those DNS names could return
several IP addresses and the incoming call could be on any one
of those IP addresses. So when I do a check of a hostname
against an IP address I want all returned A or srv IP's to be
checked against the IP. Not just the first IP returned when
checked. I do not believe dns_sys_match() will be fast enough
on a busy server so I would prefer to using dns_int_match_ip().
<br>
<br>
If anyone can clarify what that statement means regarding
"internal resolver targets to discover the first address" and
whether that would affect my use it would be greatly
appreciated.<br>
<br>
On a related note, is there any way to check the contents of the
dns resolver cache? I looked through kamctl and kamcmd but
didn't find anything. I tried "kamctl address show" but that
didn't return anything. <br>
</span></blockquote>
the internal DNS resolver is optimized for sending out SIP requests
and uses an embedded cache. It can result that some DNS responses
are cached and kept in memory for a while. Also, there are
parameters in core of kamailio to tune what kind of dns requests to
do (NAPTR, SRV, ...). Based on those, not all options to discover
the ip of a hostname for sip forwarding are tried. E.g., it can try
only SRV for UDP/IPv6 if that is the highest configured priority and
has a result for forwarding the SIP packet.<br>
<br>
In other words, internal DNS doesn't try to discover all the IP
addresses associated with a hostname, only those relevant for sip
and can stop at first valid response, not following other dns query
options that could be eventually done.<br>
<br>
Cheers,<br>
Daniel<br>
<pre class="moz-signature" cols="72">--
Daniel-Constantin Mierla
<a class="moz-txt-link-freetext" href="http://twitter.com/#!/miconda">http://twitter.com/#!/miconda</a> - <a class="moz-txt-link-freetext" href="http://www.linkedin.com/in/miconda">http://www.linkedin.com/in/miconda</a>
Kamailio World Conference, May 27-29, 2015
Berlin, Germany - <a class="moz-txt-link-freetext" href="http://www.kamailioworld.com">http://www.kamailioworld.com</a></pre>
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