Hello,

I´ve googled around about tcp timeout in kamailio tcp connections when the tcp connection is broken.

Found this old question and to me it feels like I’m having that same situation as original question https://www.mail-archive.com/sr-users@lists.kamailio.org/msg15020.html

Also found this https://kamailio.org/mailman3/hyperkitty/list/sr-dev@lists.kamailio.org/thread/CPWL2SQDHVFTI2VEJYIYIVCTBHKREBTC/ and it seems to be the same description pretty much that I´m seeing.

When the tcp connection (or tls) is interrupted in the network it takes around 15min for kamailio to reset the outgoing  tcp connection.

I see in the logs that when restarting kamailio process it logs

2025-03-27 12:25:18.697 { "level": "INFO", "module": "core", "file": "core/tcp_main.c", "line": 3282, "function": "tcp_init", "logprefix": "", "message": "Set TCP_USER_TIMEOUT=10000 ms" }

So I think the fix from this https://github.com/kamailio/kamailio/commit/d893f3af1444c8c4c5db6cd53fb577703007c90c is applied.

This is tested with 5.8.5 and I have tested this by setting up with dispatcher tcp connection to external host

Then with iptables drop traffic to that host, waiting kamailio to notice that destination is down, removing the iptables input and it takes around 15min to recover. (also restarting the kamailio helps and resolves the connection)

And this is what kamailio prints during the test:

Apr  4 08:29:15  kamailio[156947]: { "level": "ERROR", "module": "xlog", "file": "xlog.c", "line": 278, "function": "", "logprefix": "", "message": "Destination down: OPTIONS sip:ext-host;transport=tcp (<null>)" }

Apr  4 08:44:43  kamailio[156957]: { "level": "ERROR", "module": "core", "file": "core/tcp_read.c", "line": 267, "function": "tcp_read_data", "logprefix": "", "message": "error reading: Connection timed out (110) ([]:5060 -> []:47492)" }

Apr  4 08:44:43  kamailio[156957]: { "level": "ERROR", "module": "core", "file": "core/tcp_read.c", "line": 1524, "function": "tcp_read_req", "logprefix": "", "message": "error reading - c: 0x7f8625dea9b0 r: 0x7f8625deaad8 (-1)" }

Apr  4 08:45:05  kamailio[156957]: { "level": "ERROR", "module": "xlog", "file": "xlog.c", "line": 278, "function": "", "logprefix": "Source:[ext-host]:5060, Call-id:4d0e1ccd315c817f-156947@int-host, CSeq:10", "message": "Destination up: OPTIONS sip:ext.host;transport=tcp (<null>)" }

Any advice how to lower the timeout to be quicker in such event?

-Pyry