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<tt>Hi Artem,<br>
<br>
On the "real-behavior" - OpenSIPS generates and sends an OPTIONS
request (a NAT ping) via the stale connection to A. You say :<br>
<br>
1) the TCP write operation in OpenSIPSÂ blocks ? (you mentioned
the tcp_send_timeout)<br>
<br>
2) the retransmission you mentioned, are at TCP level or SIP level
? If at TCP level, these are done by the TCP/IP stack in the
Operating System, they are not done by OpenSIPS.<br>
<br>
The received BYE is not sent out as the outgoing connection (to A)
is locked by the process trying to send the OPTIONS to A (assuming
that the write operation blocks).<br>
<br>
Best regards,<br>
</tt>
<pre class="moz-signature" cols="72">Bogdan-Andrei Iancu
OpenSIPS Founder and Developer
<a class="moz-txt-link-freetext" href="https://www.opensips-solutions.com">https://www.opensips-solutions.com</a>
OpenSIPS Summit 2019
<a class="moz-txt-link-freetext" href="https://www.opensips.org/events/Summit-2019Amsterdam/">https://www.opensips.org/events/Summit-2019Amsterdam/</a>
</pre>
<div class="moz-cite-prefix">On 03/25/2019 04:40 PM, Artem Chalkov
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:1015401553524846@sas1-19a94364928d.qloud-c.yandex.net">
<div xmlns="http://www.w3.org/1999/xhtml">Hi all.</div>
<div xmlns="http://www.w3.org/1999/xhtml">
<div>Today i encountered some strange behavior in TCP handling.
Case:</div>
<div>A - caller, proto=tcp, behind NAT</div>
<div>B - callee, proto=udp, not behind NAT</div>
<div>Nathelper is active, so A is pinged by OPTIONS from
opensips.</div>
<div>A registering and then calling to B, B answers, A sends ACK
for 200 and in some moment after that - disappears from
network (for example - unplug network cable).</div>
<div>After that B send BYE request.</div>
<div>Â </div>
<div>Parameters of proto_tcp:</div>
<div>
<div>modparam("proto_tcp", "tcp_port", 5060)</div>
<div>modparam("proto_tcp", "tcp_send_timeout", 5000)</div>
<div>modparam("proto_tcp", "tcp_async", 1)</div>
<div>modparam("proto_tcp", "tcp_crlf_pingpong", 0)</div>
<div>Â </div>
</div>
<div>Â </div>
<div>Expected behavior:</div>
<div>1. if TCP session is still active: opensips will try to
send BYE to A via TCP and close TCP-connection after 5000ms
(tcp_send_timeout interval), send 477 Send Failed to himself
and 408 to B, as result of BYE transaction.</div>
<div>2. if TCP session is no active (after some TCP-FIN):
opensips will try to re-establish TCP session, and if it will
be not successfull - send 477 Send Failed to himself and 408
to B, as result of BYE transaction.</div>
<div>Â </div>
<div>Real behavior:</div>
<div>TCP session is active (there was no TCP-FIN), next
OPTIONS-ping from opensips is not answered by A (because he
disappeared from network) on TCP-level (no TCP-ACK for request
with options), opensips starts to send TCP-retransminnions of
last OPTIONS request (and continue to send this
retransmissions in a next few minutes), not trying to send BYE
request at all, not trying to close TCP session. After
fr_timeout number of  seconds opensips sends 408 to B as
result of BYE transaction and not sends 477 to himself.</div>
<div>Â </div>
<div>There is screenshot of my example:</div>
<div><a rel="noopener noreferrer"
href="https://imgur.com/HNxwxPo" moz-do-not-send="true">https://imgur.com/HNxwxPo</a></div>
<div>Â </div>
<div>So - it looks like opensips totally ignore tcp_send_timeout
value and it leads to some misbehavior in handling TCP
requests. Am i right or i missed something?</div>
</div>
<div xmlns="http://www.w3.org/1999/xhtml">Â </div>
<div xmlns="http://www.w3.org/1999/xhtml">Â </div>
<br>
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<br>
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</pre>
</blockquote>
<br>
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