UAC_REDIRECT Module

UAC REDIRECT - User Agent Client redirection - module enhance Kamailio with the functionality of being able to handle (interpret, filter, log and follow) redirect responses ( 3xx replies class).

UAC REDIRECT module offer stateful processing, gathering the contacts from all 3xx branches of a call.

The module provide a powerful mechanism for selecting and filtering the contacts to be used for the new redirect:

number based - limits like the number of total contacts to be used or the maximum number of contacts per branch to be selected.
Regular Expression based - combinations of deny and accept filters allow a strict control of the contacts to be used for redirection.

When selecting from a 3xx branch the contacts to be used, the contacts will be ordered and prioritized based on the “q” value.

1.2. Accounting

UAC REDIRECT module allows to log all the redirection (to be later used for CDR aggregation). This functionality may be dynamically enabled for each redirection situation.

The logging will be done via the accounting module functions (all are supported). The information to be logged will be the same as the normal logged information directly via ACC module, but with following differences:

reason phrase - which will be dynamically set by the redirection function;
outgoing URI - which will be the redirect URI.

For each redirect contact, a separate record will be logged. For example, if a call is redirected to three new contacts, the module will log three additional records corresponding to each redirect URI.

1.3. Dependencies

1.3.1. Kamailio Modules

The following modules must be loaded before this module:

TM - Transaction Module, for accessing replies.
ACC - Accounting Module, but only if the logging feature is used.

1.3.2. External Libraries or Applications

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

None

1.4. Exported Parameters

1.4.1. `default_filter` (string)

The default behavior in filtering contacts. It may be “accept” or “deny”.

The default value is “accept”.

Example 1.1. Set default_filter module parameter

...
modparam("uac_redirect","default_filter","deny")
...

1.4.2. `deny_filter` (string)

The regular expression for default deny filtering. It make sens to be defined on only if the default_filter parameter is set to “accept”. All contacts matching the deny_filter will be rejected; the rest of them will be accepted for redirection.

The parameter may be defined only one - multiple definition will overwrite the previous definitions. If more regular expression need to be defined, use the set_deny_filter() scripting function.

This parameter is optional, it's default value being NULL.

Example 1.2. Set deny_filter module parameter

...
modparam("uac_redirect","deny_filter",".*@siphub\.net")
...

1.4.3. `accept_filter` (string)

The regular expression for default accept filtering. It make sens to be defined on only if the default_filter parameter is set to “deny”. All contacts matching the accept_filter will be accepted; the rest of them will be rejected for redirection.

The parameter may be defined only one - multiple definition will overwrite the previous definitions. If more regular expression need to be defined, use the set_accept_filter() scripting function.

This parameter is optional, it's default value being NULL.

Example 1.3. Set accept_filter module parameter

...
modparam("uac_redirect","accept_filter",".*@siphub\.net")
...

1.4.4. `acc_function` (string)

Specifies the accounting function to be used. Just be defining this parameter, the accounting support will not be enabled. Accounting may only be enabled via two parameters set_accept_filter() scripting function.

Its values my be:

acc_log_request
acc_db_request
acc_rad_request
acc_diam_request

The default value is “acc_log_request”.

Example 1.4. Set acc_function parameter

...
modparam("uac_redirect","acc_function","acc_db_request")
...

1.4.5. `acc_db_table` (string)

Specifies the accounting table to be used if DB accounting was chosen (acc_function was set to “acc_db_request”). Just be defining this parameter, the accounting support will not be enabled. Accounting may only be enabled via two parameters set_accept_filter() scripting function.

The default value is “acc”.

Example 1.5. Set acc_db_table parameter

...
modparam("uac_redirect","acc_db_table","acc_redirect")
...

1.5. Exported Functions

1.5.1. `set_deny_filter(filter,flags)`

Sets additional deny filters. Maximum 6 may be combined. This additional filter will apply only to the current message - it will not have a global effect.

Default or previous added deny filter may be reset depending of the flag parameter value:

reset_all - reset both default and previous added deny filters;
reset_default - reset only the default deny filter;
reset_added - reset only the previous added deny filters;
empty - no reset, just add the filter.

This function can be used from FAILURE_ROUTE.

Example 1.6. set_deny_filter usage

...
set_deny_filter(".*@domain2.net","reset_all");
set_deny_filter(".*@domain1.net","");
...

1.5.2. `set_accept_filter(filter,flags)`

Sets additional accept filters. Maximum 6 may be combined. This additional filter will apply only to the current message - it will not have a global effect.

Default or previous added deny filter may be reset depending of the flag parameter value:

reset_all - reset both default and previous added accept filters;
reset_default - reset only the default accept filter;
reset_added - reset only the previous added accept filters;
empty - no reset, just add the filter.

This function can be used from FAILURE_ROUTE.

Example 1.7. set_accept_filter usage

...
set_accept_filter(".*@domain2.net","reset_added");
set_accept_filter(".*@domain1.net","");
...

1.5.3. `get_redirects(max)`

The function may be called only from failure routes. It will extract the contacts from all 3xx branches and append them as new branches. Note that the function will not forward the new branches, this must be done explicitly from script.

How many contacts (in total and per branch) are selected depends of the max parameter values. Its syntax is:

max = max_total [":" max_branch]
max_total = number of total contacts to be selected
max_branch = number of contacts per branch to be selected

Both “max_total” and “max_branch” are positive integer. To specify unlimited values, use 0 value or "*" character.

NOTE that during the selection process, each set of contacts from a specific branch are ordered based on “q” value.

This function will produce no accounting records.

This function can be used from FAILURE_ROUTE.

Example 1.8. get_redirects usage

...
# max 2 contacts per branch, but no overall limit
get_redirects("*:2");
...
# no limits per branch, but not more than 6 overall contacts
get_redirects("6:*");
...
# no restrictions
get_redirects("*");
...

1.5.4. `get_redirects(max,reason)`

The function has same functionality as get_redirects(max) function, but it will produce accounting records.

The accounting records will be mark by the reason phrase.

If this function appears in the script, at startup, the module will import the accounting function. Otherwise not.

This function can be used from FAILURE_ROUTE.

Example 1.9. get_redirects usage

...
get_redirects("4:1","Redirected");
...

1.6. Script Example

Example 1.10. Redirection script example

loadmodule "modules/sl/sl.so"
loadmodule "modules/usrloc/usrloc.so"
loadmodule "modules/registrar/registrar.so"
loadmodule "modules/tm/tm.so"
loadmodule "modules/acc/acc.so"
loadmodule "modules/uac_redirect/uac_redirect.so"

modparam("usrloc", "db_mode",   0)

route{
	if (uri==myself) {

		if (method=="REGISTER") {
			save("location");
			exit;
		};

		if (!lookup("location")) {
			sl_send_reply("404", "Not Found");
			exit;
		};
		# do redirect with accounting
		t_on_failure("2");
	} else {
		# just do redirect
		t_on_failure("1");
	}

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

failure_route[1] {
	get_redirects("3:1");
	t_relay();
}

failure_route[2] {
	get_redirects("6:2","redirect");
	t_relay();
}

UAC_REDIRECT Module

Bogdan-Andrei Iancu

Edited by

Bogdan-Andrei Iancu

Chapter 1. Admin Guide

1.1. Overview

1.2. Accounting

1.3. Dependencies

1.3.1. Kamailio Modules

1.3.2. External Libraries or Applications

1.4. Exported Parameters

1.4.1. default_filter (string)

1.4.2. deny_filter (string)

1.4.3. accept_filter (string)

1.4.4. acc_function (string)

1.4.5. acc_db_table (string)

1.5. Exported Functions

1.5.1. set_deny_filter(filter,flags)

1.5.2. set_accept_filter(filter,flags)

1.5.3. get_redirects(max)

1.5.4. get_redirects(max,reason)

1.6. Script Example

1.4.1. `default_filter` (string)

1.4.2. `deny_filter` (string)

1.4.3. `accept_filter` (string)

1.4.4. `acc_function` (string)

1.4.5. `acc_db_table` (string)

1.5.1. `set_deny_filter(filter,flags)`

1.5.2. `set_accept_filter(filter,flags)`

1.5.3. `get_redirects(max)`

1.5.4. `get_redirects(max,reason)`