I'm facing with a strange behaviour with k3s. I am migrating a crm application that use Asterisk/FreePBX to make calls.
I have a freepbx/asterisk server and a k3s server.
The strange behaviour is the following:
I call a phone number through my application -> asterisk send to my application the agreed port where the communication should be established -> from my application log I can see the port where asterisk start the communication and another port where my application receive the data. Of course the call end in bad state because asterisk send data on port XXXXX and my application listen on YYYYY.
The YYYYY port is a port assigned by k3s to the asterisk/freepbx request. Seems that a snat is applied.
Investigating I saw that k3s iptables there are this two lines:
-A FLANNEL-POSTRTG -s 10.127.93.0/25 ! -d 224.0.0.0/4 -m comment --comment "flanneld masq" -j MASQUERADE --random-fully -A FLANNEL-POSTRTG ! -s 10.127.93.0/25 -d 10.127.93.0/25 -m comment --comment "flanneld masq" -j MASQUERADE --random-fully
I think that in some way k3s make a kind of re-mapping of UDP port.
Is there a way to change this behaviour? I need that if asterisk/freepbx agreed to send data on port XXXXX, the traffic should effectively arrive on the same port and not in YYYYY port.
Thanks for support, if additional informations are needed I'll provide them.
I made a lot of research in order to try to disable ip masquerading on flannel without success