I've dealt with the same issue, and as far as I understand, the problem is with Freeswitch not supporting branching and IIRC not recognizing that the via branch has changed. Adding a sleep function as indicated in that link is a blocking process, so if you have this serial forking occur frequently it could cause kamailio to have issues. There is a non-blocking async_sleep function that I didn't have success with, but that was probably a misunderstanding of how it worked on my part. With that said, you might try adding another sip_profile to your freeswitch server (on a different port) and see if sending the serially forked call to the other sip_profile addresses it. Otherwise, I'd recommend adding another freeswich instance (even if it's on the same server) rather than calling sleep();
Regards, Kaufman
________________________________ From: Alex A via sr-users Sent: Wednesday, March 19, 2025 4:58 PM To: sr-users@lists.kamailio.org Cc: Alex A Subject: [SR-Users] How to place a delay between cancelling branch and retrying next one on timer expiry?
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Hi All,
I have an interesting use-case where I need to place a delay between cancelling branch and retrying next one.
Background: Running Kamailio 5.6.x
Kamailio routes requests via a freeswitch B2BUA server on select call flows (where B2BUA functionality is required). Call flow examples: PSTN --> Kamailio --> Freeswitch --> appserver1 PSTN --> Kamailio --> Freeswitch --> appserver2
On attempt failures, a branch retry is required from appserver1 to appserver2; however freeswitch B2BUA remains the same Since Freeswitch does not quite follow the RFC 3261 timer K specifications (should be 0 seconds for reliable transports, but FS keeps transactions for T4 (set to 2 seconds)); I have implemented an artificial delay in failure route before retrying (as per recommendation described here: https://freeswitch-users.freeswitch.narkive.com/TsSye66D/482-request-merged-... )
Script config: onreply_route[MANAGE_REPLY] { xlog("L_INFO", "reply $T_reply_code received"); if (t_check_status( "1[1-9][0-9]")) { t_reset_fr(); } else { t_set_fr(120000); } }
route(NATDETECT); #!ifdef WITH_RTPENGINE route(RTPMANAGE); #!endif }
route[RELAY] {
if (is_method("INVITE|BYE|SUBSCRIBE|UPDATE")) { if(!t_is_set("branch_route")) t_on_branch("MANAGE_BRANCH"); }
if (is_method("INVITE|SUBSCRIBE|UPDATE")) { if(!t_is_set("onreply_route")) t_on_reply("MANAGE_REPLY"); }
if(is_method("INVITE|BYE|UPDATE|CANCEL|ACK")) { setflag(FLT_DLGINFO); }
if (!t_relay()) { sl_reply_error(); }
exit; }
route[TOCARRIER] { process bunch of things, attach custom headers, generate request URI
t_on_failure("MANAGE_FAILURE_CARRIER"); route(RELAY); }
failure_route[MANAGE_FAILURE_CARRIER] { xlog("L_INFO", "reply $T_reply_code received"); if ($avp(inbound_attempt)<=1){ if ($dlg_var(b2bua)=="true"){ usleep(1900000); } route("TOCARRIER");
}
Call Flows:
The above fix works well when an explicit error reply is received back.
error reply SIP exchange: SBC --> INVITE(branch0) ---> Freeswitch SBC <-- 503 <-- Freeswitch failure_route executed (sleep runs here) SBC --> INVITE(branch1) ---> Freeswitch call continues as expected.
however does not work when NO reply is received at all and the timer expires. Current timer expiry SIP exchange: SBC --> INVITE(branch0) ---> Freeswitch SBC <-- 100/180 <-- Freeswitch SBC (timer expires) failure_route executed (sleep runs here) SBC --> INVITE(branch1) ---> Freeswitch SBC <-- 482 Merged <-- Freeswitch SBC --> CANCEL(branch0) ---> Freeswitch
I am looking to CANCEL branch0 before the sleep delay runs
Based on source code, t_cancel_branches("this") can only be executed in reply_route; however the chellenge is that reply_route never sees the "faked 408" on timer expiry(although the failure route does see $T_reply_code 408).
Any suggestions on how to handle this would be greatly appreciated.
TIA