<p></p>
<h3>Description</h3>
<p>I notice a test failure when validating Kamailio 5.4.x, and after looking at the SIP traces, Kamailio is does not forwarding the first ACK.<br>
However, it does it after receiving a 200 OK re-transmission .</p>
<pre><code>        192.0.2.12:5062               192.0.2.24:5060             
       ──────────┬─────────          ──────────┬───────── 
                 │                             │                    
                 │                             │                                
                 │                             │       200 coco (SDP
                 │                             │ <<<────────────────           
          200 coco (SDP)                       │                    
<───────────────────────────────────────────── │             
 ACK                                           │                    
─────────────────────────────────────────────> │                    
 ACK                                           │                    
───────────────────────────────────────────>>> │                    
                 │                             │       200 coco (SDP
                 │                             │ <<<────────────────
          200 coco (SDP)                       │                    
<───────────────────────────────────────────── │                            
                 │                             │                    
 ACK                                           │                    
─────────────────────────────────────────────> │                                    
                 │                             │             ACK    
                 │                             │ ──────────────────>
</code></pre>
<h3>Troubleshooting</h3>
<p>I did proceed by isolation and ended up concluding that this commit was triggering this behavior.<br>
Simply, reverting this commit is fixing the problem.</p>
<pre><code>commit 28049aafc8dd06c160ce5e7b8d5e4fc728441b0c
Author: Semen Darienko <semen.darienko@wildix.com>
Date:   Sun May 3 12:26:45 2020 +0200

    core: dns - use all NAPTR records
    
    - enable using of all NAPTR records instead of the first one ordered by
    priority
    - GH #2290
</code></pre>
<p>I did not look at the code modification and/or anything config specific yet, I will try to find some time to debug.</p>

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