[SR-Users] Tweaking TCP settings

[Dovid Bender]

Hi,

First off please forgive my lack of knowledge on how TCP works.

We are using Kamailio 5.0.7 and we have an issue where clients are
connecting via TCP and their NAT devices are closing up. Because of this we
want to send TCP keep alives every so often.

1) When restarting Kamailio it's sends a RST. Is this Kamailio sending it
out or is it linux sending it when the application is killed? The issue we
have is if say we need to do a restart 2-3 times (yes we should normally do
that) then we end up with 3x registrations in the db (since when using db
mode if the connection goes away it won't remove the reg from the db (as
per -
https://kamailio.org/docs/modules/5.0.x/modules/usrloc.html#usrloc.p.handle_lost_tcp
)

2) I haven testing with the following settings.
a. tcp_crlf_ping=yes
b. tcp_keepcnt = 3
c. tcp_keepidle = 5

With the above I see the TCP keep alives coming in every 75 seconds. If I
tcp_keepintvl = 10 then I see TCP keep alives going out from Kamailio to
the phone. As per
https://www.kamailio.org/wiki/cookbooks/5.0.x/core#tcp_keepintvl it says
"Time interval between keepalive probes, when the previous probe failed".
Looking at my captures Kamilio sends out the TCP keep alive and gets it
back. Is Kamailio not seeing it? With the above it seems to be working the
way I want it but I want to make sure that I am doing it right.

3) For the devs on here how hard would it be to implement handle_lost_tcp
for DB-Only?

TIA and a happy new year to all.

Regards,

Dovid
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