1.3.1. OpenSER Modules

The following modules must be loaded before this module:

• dialog - dialog module and its decencies. (tm)

• sl - stateless module.

1.3.2. External Libraries or Applications

The following libraries or applications must be installed before running OpenSER with this module loaded:

• None.

1.4.1. enable_stats (integer)

If the statistics support should be enabled or not. Via statistic variables, the module provide information about the dialog processing. Set it to zero to disable or to non-zero to enable it.

Default value is "1" (enabled).

...
modparam("sst", "enable_stats", 0)
...

1.4.2. min_se (integer)

The value is used to set the proxies MIN-SE value and is used in the 422 reply as the proxies MIN-SE: header value if the sstCheckMin() flag is set to true and the check fails.

If not set and sstCheckMin() is called with the send-reply flag set to true, the default 1800 seconds will be used as the compare and the MIN-SE: header value if the 422 reply is sent.

Default value is "1800" seconds.

...
modparam("sst", "min_se", 2400)
...

1.4.3. timeout_avp (string)

This parameter MUST be set to the same value as the dialog parameter of the same name. If this parameter is NOT set, the sst module will not do anything!

This is how the sst module knows which avp in the dialog module to change with the new expire value.

Default value is "NULL!" it is not set by default.

...
modparam("dialog", "timeout_avp", "$avp(i:10)")
# Set the sst modules timeout_avp to be the same value
modparam("sst", "timeout_avp", "$avp(i:10)")
...

1.4.4. reject_to_small (integer)

In the initial INVITE if the UAC has requested a Session-Expire: and it's value is smaller then our local policies Min-SE (see min_se above), then the PROXY has the right to reject the call by replying to the message with a 422 Session Timer Too Small and state our local Min-SE: value. The INVITE is NOT forwarded on through the PROXY.

This flag if true will tell the SST module to reject the INVITE with a 422 response. If false, the INVITE is forwarded through the PROXY with out any modifications.

Default value is "1" (true/on).

...
modparam("sst", "reject_to_small", 0)
...

1.4.5. sst_flag (integer)

Keeping with OpenSER, the module will not do anything to any message unless instructed to do so via the openser.cfg script. You must set the sst_flag value in the setflag() call of the INVITE you want the sst module to process. But before you can do that, you need to tell the sst module which flag value you are assigning to sst.

In most cases when ever you set the dialog flag you will want to set the sst flag. If the dialog flag is not set and the sst flag is set, it will not have any effect.

This parameter must be set of the module will not load.

Default value is "Not set!".

...
modparam("dialog", "dlg_flag", 5)
modparam("sst", "sst_flag", 6)
...
route {
  ...
  if (method=="INVITE") {
    setflag(5); # set the dialog flag
    setflag(6); # Set the sst flag
  }
  ...
}

1.5.1. sstCheckMin(send_reply_flag)

Check the current Session-Expires / MIN-SE values against the sst_min_se parameter value. If the Session-Expires or MIN_SE header value is less then modules minimum value, this function will return true.

If the fuction is called with the send_reply_flag set to true (1) and the requested Session-Expires / MIN-SE values are too small, a 422 reply will be sent for you. The 422 will carry a MIN-SE: header with the sst min_se parameter value set.

Meaning of the parameters is as follows:

• min_allowed - The value to compare the MIN_SE header value to.

...
modparam("dialog", "timeout_avp", "$avp(i:4242)")
modparam("dialog", "dlg_flag", 5)
...
modparam("sst", "sst_flag", 6)
modparam("sst", "timeout_avp", "$avp(i:4242)")
modparam("sst", "min_se", 2400) # Must be >= 90
...

route {
  if (method=="INVITE") {
	if (sstCheckMin("1")) {
		xlog("L_ERR", "422 Session Timer Too Small reply sent.\n");
		exit;
	}
	# track the session timers via the dialog module
	setflag(5);
	setflag(6);
  }
}

... or ...

route {
  if (method=="INVITE") {
	if (sstCheckMin("0")) {
		xlog("L_ERR", "Session Timer Too Small, dropping request\n");
		exit;
	}
	# track the session timers via the dialog module
	setflag(5);
	setflag(6);
  }
}
...

1.6.1. expired_sst

Number of dialogs which got expired session timer.