[Users] OpenSER as a Load Balancer for Asterisk and RE-INVITEs

[Edoardo Serra]

Hi all,
	I have an OpenSER acting as a registrar server and as a load balancer 
(with dispatcher module) for a cluster of PSTN Gateways based on Asterisk.

When an inbound call is coming from the PSTN, Asterisks dial 
SIP/user at openser and the call is properly forwarded to the correct user 
in OpenSER location table

But, if the user wants, for example, to put the call On-Hold, its user 
agent sends a RE-INVITE to OpenSER.
My problem is that OpenSER (correctly) dispatch the call to a random 
Asterisk GW, and, if it's not the GW which is handling the call, On-Hold 
does not work and another call is originated.

Tnx in advance for help

Edoardo

My openser.cfg follows

# $Id: ser.cfg,v 1.21.4.1 2003/11/10 15:35:15 andrei Exp $
# ----------- global configuration parameters ------------------------

check_via=yes    # (cmd. line: -v)
dns=no          # (cmd. line: -r)
rev_dns=no      # (cmd. line: -R)
fifo="/tmp/ser_fifo"

#uid=nobody
#gid=nobody

# ------------------ module loading ----------------------------------
loadmodule "/usr/lib/openser/modules/sl.so"
loadmodule "/usr/lib/openser/modules/tm.so"
loadmodule "/usr/lib/openser/modules/rr.so"
loadmodule "/usr/lib/openser/modules/maxfwd.so"
loadmodule "/usr/lib/openser/modules/usrloc.so"
loadmodule "/usr/lib/openser/modules/registrar.so"
loadmodule "/usr/lib/openser/modules/nathelper.so"
loadmodule "/usr/lib/openser/modules/textops.so"
loadmodule "/usr/lib/openser/modules/exec.so"
loadmodule "/usr/lib/openser/modules/uri.so"
loadmodule "/usr/lib/openser/modules/uri_db.so"
loadmodule "/usr/lib/openser/modules/dispatcher.so"
loadmodule "/usr/lib/openser/modules/mysql.so"
loadmodule "/usr/lib/openser/modules/auth.so"
loadmodule "/usr/lib/openser/modules/auth_db.so"

modparam("usrloc", "db_mode", 2)
modparam("usrloc", "db_url", "mysql://user:pass@192.168.252.5/openser")
modparam("usrloc", "timer_interval", 120)
modparam("auth_db", "calculate_ha1", 0)
modparam("auth_db", "db_url", "mysql://user:pass@192.168.252.5/db")
modparam("uri_db", "db_url", "mysql://user:pass@192.168.252.5/openser")
modparam("rr", "enable_full_lr", 1)
modparam("registrar", "nat_flag", 6)
modparam("registrar", "max_expires", 3600)
modparam("registrar", "min_expires", 60)
modparam("registrar", "append_branches", 0)
modparam("registrar", "desc_time_order", 1)
modparam("nathelper", "natping_interval", 20) # Ping interval 20 s
modparam("nathelper", "ping_nated_only", 1)   # Ping only clients behind NAT
modparam("dispatcher", "force_dst", 1)

# -------------------------  request routing logic -------------------
# main routing logic

route{
         if (!mf_process_maxfwd_header("10")) {
                 sl_send_reply("483","Too Many Hops");
                 exit;
         };
         if ( msg:len > max_len ) {
                 sl_send_reply("513", "Message too big");
                 exit;
         };

         if ( (method=="OPTIONS") || (method=="SUBSCRIBE") || 
(method=="NOTIFY") ) {
                 sl_send_reply("405", "Method Not Allowed");
                 exit;
         }

         if (!method=="REGISTER") {
                 record_route();
         };


         if ((src_ip==ip.of.asterisk.1) || (src_ip==ip.of.asterisk.1)) {
                 if (!lookup("location")) {
                         sl_send_reply("486", "Busy here");
                         exit;
                 };
                 if (!t_relay()) {
                         sl_reply_error();
                 };
                 exit;
         };

         if (nat_uac_test("3")) {
                 if ((method=="REGISTER") || (method=="INVITE") || 
(method=="OPTIONS")) {
                         fix_nated_contact();
                         force_rport();
                         setflag(6);    # Mark as NATed
                 }
         }

         if (method=="REGISTER") {
                 if (!proxy_authorize("exorsa", "openser_view")) {
                         proxy_challenge("exorsa", "0");
                         exit;
                 }
                 if (!check_to()) {
                         sl_send_reply("403", "Digest username and URI 
username do NOT match! Stay away!");
                         exit;
                 }

                 save("location");

                 exit;
         };


	if (method=="INVITE") {
		if (!proxy_authorize("exorsa", "openser_view")) {
			proxy_challenge("exorsa", "0");
			exit;
		}

		if (!check_from()) {
			sl_send_reply("403", "Digest username and URI username do NOT match! 
Stay away!");
			exit;
		}
	}

         # loose-route processing
         if (loose_route()) {
                 # mark routing logic in request
                 append_hf("P-hint: rr-enforced\r\n");
                 route(1);
                 exit;
         };

         if (!uri==myself) {
                 # mark routing logic in request
                 append_hf("P-hint: outbound\r\n");
                 route(1);
                 exit;
         };

         append_hf("P-hint: usrloc applied\r\n");
         route(1);
}

route[1]
{
         # !! Nathelper
         if (uri=~"[@:](192\.168\.|10\.|172\.(1[6-9]|2[0-9]|3[0-1])\.)" 
&& !search("^Route:")){
             sl_send_reply("479", "We don't forward to private IP 
addresses");
             exit;
         };

         # NAT processing of replies; apply to all transactions (for 
example,
         # re-INVITEs from public to private UA are hard to identify as
         # NATed at the moment of request processing); look at replies
         t_on_reply("1");

	if ((src_ip!=ip.of.asterisk.1) && (src_ip!=ip.of.asterisk.2)) {
	        ds_select_dst("1", "0");
         }

         if (!t_relay()) {
                 sl_reply_error();
         };
}

# !! Nathelper
onreply_route[1] {
     # NATed transaction ?
     if (isflagset(6) && status =~ "(183)|2[0-9][0-9]") {
         fix_nated_contact();
     # otherwise, is it a transaction behind a NAT and we did not
     # know at time of request processing ? (RFC1918 contacts)
     } else if (nat_uac_test("1")) {
         fix_nated_contact();
     };
}