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<p>Indeed, at this stage there is no dialog established and there
can be many To-tags in 1xx provisional responses (eg, a parallel
forking scenario) -- the to-tag of the dialog has to be taken from
200ok.</p>
<p>This parameter is probably to have a shortcut of doing:</p>
<p>failure_route[REMAP503] {</p>
<p> if(t_check_status("503")) {</p>
<p> t_reply("500", "Server error");<br>
exit;</p>
<p>}</p>
<p>Being like the server application is generating the 500 (so using
own tag), instead of forwarding the 503. Not a bug, but if anyone
is willing to add an option to allow re-using the to-tag from
received reply, I am fine with it.</p>
<p>Anyhow, even if this would be fixed, I am wondering how yate is
going to work in parallel/serial forking scenarios where different
to-tags flow for a while and the final failure response can have
any to-tag, including a new one (e.g., from a device not sending
any 1xx or again from kamailio (e.g., when last target doesn't
reply at all)).</p>
<p>Cheers,<br>
Daniel<br>
</p>
<div class="moz-cite-prefix">On 23.07.20 06:08, M S wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAFZQphzM=C--zqrSSHfGvJSusWZaytM80Yosbuhhc6sBesvrZg@mail.gmail.com">
<meta http-equiv="content-type" content="text/html; charset=UTF-8">
<div>
<div dir="auto">The SIP code 503 is tricky in the sense that i
can indicate either server maintenance or server overload. In
both cases it can send Retry-After header and any subsequent
requests from same source are ignored for the duration of
Retry-After interval. [1].</div>
</div>
<div dir="auto"><br>
</div>
<div dir="auto">Additionally RFC3261 and RFC3263 define that
transport failures (generally due to fatal ICMP errors in UDP
and connection failures in TCP) should be treated as 503
response. [2].</div>
<div dir="auto"><br>
</div>
<div dir="auto">So in all above cases, it is most likely that
dialog does not establishes at all and 503 response is treated
similar to stateless response. Therefore, a to-tag can be
added/replaced before sending it to UAC.</div>
<div dir="auto"><br>
</div>
<div dir="auto">Theoretically, kamailio should check and use
to-tag from 503 response when converting it to 500 response and
only create new to-tag if it is absent.</div>
<div dir="auto"><br>
</div>
<div dir="auto">References:</div>
<div dir="auto"><br>
</div>
<div dir="auto">
<div>[1] <a
href="https://tools.ietf.org/html/rfc3261#section-21.5.4"
moz-do-not-send="true">https://tools.ietf.org/html/rfc3261#section-21.5.4</a></div>
<div dir="auto"><br>
</div>
<div>[2] <a
href="https://tools.ietf.org/html/draft-hilt-sip-correction-503-01#section-4"
moz-do-not-send="true">https://tools.ietf.org/html/draft-hilt-sip-correction-503-01#section-4</a></div>
<br>
</div>
<div dir="auto"><br>
</div>
<div dir="auto">Hope this helps.</div>
<div dir="auto"><br>
</div>
<div dir="auto"><br>
</div>
<div><br>
<div class="gmail_quote">
<div dir="ltr" class="gmail_attr">On Wed, 22 Jul 2020 at
21:08, Henning Westerholt <<a
href="mailto:hw@skalatan.de" moz-do-not-send="true">hw@skalatan.de</a>>
wrote:<br>
</div>
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
<div link="blue" vlink="purple" lang="DE">
<div class="m_-5300728039720019352WordSection1">
<p class="MsoNormal"><span>Hello,</span></p>
<p class="MsoNormal"><span> </span></p>
<p class="MsoNormal"><span lang="EN-GB">Apparently, this
is the way the code works:</span></p>
<p class="MsoNormal"><span lang="EN-GB"> </span></p>
<p class="MsoNormal"><span lang="EN-GB">t_reply.c:</span></p>
<p class="MsoNormal"><span lang="EN-GB">
if (relayed_code==503 && tm_remap_503_500){</span></p>
<p class="MsoNormal"><span lang="EN-GB">
/* replace a final 503 with a 500:</span></p>
<p class="MsoNormal"><span lang="EN-GB">
* generate a "FAKE" reply and a
new to_tag (for easier</span></p>
<p class="MsoNormal"><span lang="EN-GB">
* debugging)*/</span></p>
<p class="MsoNormal"><span lang="EN-GB"> </span></p>
<p class="MsoNormal"><span lang="EN-GB">Lets see if
maybe others can comment as well. Otherwise you
could just open an issue on our tracker, it is
probably not that hard to change this.</span></p>
<p class="MsoNormal"><span lang="EN-GB"> </span></p>
<p class="MsoNormal"><span lang="EN-GB">Cheers,</span></p>
<p class="MsoNormal"><span lang="EN-GB"> </span></p>
<p class="MsoNormal"><span lang="EN-GB">Henning</span></p>
<div>
<p class="MsoNormal"><span lang="EN-GB"> </span></p>
<p class="MsoNormal"><span lang="EN-GB">-- </span></p>
<p class="MsoNormal"><span lang="EN-GB">Henning
Westerholt –
</span><span><a href="https://skalatan.de/blog/"
target="_blank" moz-do-not-send="true"><span
style="color:#0563c1" lang="EN-GB">https://skalatan.de/blog/</span></a></span><span
lang="EN-GB"></span></p>
<p class="MsoNormal"><span lang="EN-GB">Kamailio
services –
</span><span><a href="https://gilawa.com/"
target="_blank" moz-do-not-send="true"><span
style="color:#0563c1" lang="EN-GB">https://gilawa.com</span></a></span><span>
<span lang="EN-GB"></span></span></p>
</div>
<p class="MsoNormal"><span lang="EN-GB"> </span></p>
<div>
<div style="border:none;border-top:solid #e1e1e1
1.0pt;padding:3.0pt 0cm 0cm 0cm">
<p class="MsoNormal" style="margin-left:35.4pt"><b>From:</b>
sr-users <<a
href="mailto:sr-users-bounces@lists.kamailio.org"
target="_blank" moz-do-not-send="true">sr-users-bounces@lists.kamailio.org</a>>
<b>On Behalf Of </b>Gerry | Rigatta<br>
<b>Sent:</b> Wednesday, July 22, 2020 8:58 PM<br>
<b>To:</b> Kamailio (SER) - Users Mailing List
<<a href="mailto:sr-users@lists.kamailio.org"
target="_blank" moz-do-not-send="true">sr-users@lists.kamailio.org</a>><br>
<b>Subject:</b> [SR-Users] bug ? remap_503_500
breaks dialogs</p>
</div>
</div>
<p class="MsoNormal" style="margin-left:35.4pt"> </p>
<p class="MsoNormal" style="margin-left:35.4pt">Hi,</p>
<div>
<p class="MsoNormal" style="margin-left:35.4pt"> </p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt">I am
using Kamailio 5.2. </p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt"> </p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt">Apparently
the remapping of 503 to 500 codes in the tm module
does also change the to-tag. This behaviour breaks
dialogs with yate and therefore calls hang and the
503 remains unacknowledged. After disabling the 503
to 500 remapping with modparam("tm",
"remap_503_500", 0) all works fine again.</p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt"> </p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt">Changing
the to-tag in a dialog seems to contradict RFC3261,
or do I see this wrongly?</p>
</div>
<div>
<h2 style="margin-left:35.4pt"><a
name="m_-5300728039720019352_section-12"
moz-do-not-send="true"></a><a
href="https://tools.ietf.org/html/rfc3261#section-12"
target="_blank" moz-do-not-send="true"><span><span
style="font-family:"Arial",sans-serif">12</span></span><span></span></a><span></span><span
style="font-family:"Arial",sans-serif">
Dialogs</span></h2>
<h2 style="margin-left:35.4pt"><span
style="font-family:"Arial",sans-serif">A
dialog is identified at each UA with a dialog ID,
which consists of a Call-ID value, a local tag and
a remote tag…"</span></h2>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt"> </p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt">Thanks
for looking into this.</p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt"> </p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt">Gerry</p>
</div>
<div>
<p class="MsoNormal" style="margin-left:35.4pt"> </p>
</div>
</div>
</div>
_______________________________________________<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>
</div>
<br>
<fieldset class="mimeAttachmentHeader"></fieldset>
<pre class="moz-quote-pre" wrap="">_______________________________________________
Kamailio (SER) - Users Mailing List
<a class="moz-txt-link-abbreviated" href="mailto:sr-users@lists.kamailio.org">sr-users@lists.kamailio.org</a>
<a class="moz-txt-link-freetext" href="https://lists.kamailio.org/cgi-bin/mailman/listinfo/sr-users">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">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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