Dynamic Routing Module

Bogdan-Andrei Iancu

   www.opensips-solutions.com

Edited by

Bogdan-Andrei Iancu

Edited by

Anca-Maria Vamanu

   Copyright © 2005-2008 Voice Sistem SRL

   Copyright © 2009-2012 www.opensips-solutions.com
   Revision History
   Revision $Revision$ $Date: 2012-03-22 20:43:49 +0200
                              (Thu, 22 Mar 2012) $
     __________________________________________________________

   Table of Contents

   1. Admin Guide

        1.1. Overview

              1.1.1. Introduction
              1.1.2. Features
              1.1.3. Performance
              1.1.4. Dynamic Routing Concepts
              1.1.5. Routing Rule Processing
              1.1.6. Probing and Disabling destinations

        1.2. Dependencies

              1.2.1. OpenSIPS Modules
              1.2.2. External Libraries or Applications

        1.3. Exported Parameters

              1.3.1. db_url(str)
              1.3.2. drd_table(str)
              1.3.3. drr_table(str)
              1.3.4. drg_table(str)
              1.3.5. drc_table(str)
              1.3.6. ruri_avp (str)
              1.3.7. gw_id_avp (str)
              1.3.8. gw_attrs_avp (str)
              1.3.9. gw_priprefix_avp (str)
              1.3.10. rule_id_avp (str)
              1.3.11. rule_attrs_avp (str)
              1.3.12. rule_prefix_avp (str)
              1.3.13. carrier_id_avp (str)
              1.3.14. carrier_attrs_avp (str)
              1.3.15. define_blacklist (str)
              1.3.16. default_group (int)
              1.3.17. force_dns (int)
              1.3.18. probing_interval (integer)
              1.3.19. probing_method (string)
              1.3.20. probing_from (string)
              1.3.21. probing_reply_codes (string)
              1.3.22. use_domain (int)
              1.3.23. drg_user_col (str)
              1.3.24. drg_domain_col (str)
              1.3.25. drg_grpid_col (str)

        1.4. Exported Functions

              1.4.1. do_routing([[[groupID],flags],gw_whitelist])
              1.4.2. route_to_carrier(carrier_id)
              1.4.3. route_to_gw(gw_id)
              1.4.4. use_next_gw()/next_routing()
              1.4.5. goes_to_gw([[type],flags])
              1.4.6. is_from_gw( [type, [flag]])
              1.4.7. dr_is_gw(src_pv, [type, [flag]])
              1.4.8. dr_disable()

        1.5. Exported MI Functions

              1.5.1. dr_reload
              1.5.2. dr_gw_status
              1.5.3. dr_carrier_status

        1.6. Installation

   2. Developer Guide

   List of Examples

   1.1. Set db_url parameter
   1.2. Set drd_table parameter
   1.3. Set drr_table parameter
   1.4. Set drg_table parameter
   1.5. Set drc_table parameter
   1.6. Set ruri_avp parameter
   1.7. Set gw_id_avp parameter
   1.8. Set gw_attrs_avp parameter
   1.9. Set gw_priprefix_avp parameter
   1.10. Set rule_id_avp parameter
   1.11. Set rule_attrs_avp parameter
   1.12. Set rule_prefix_avp parameter
   1.13. Set carrier_id_avp parameter
   1.14. Set carrier_attrs_avp parameter
   1.15. Set define_blacklist parameter
   1.16. Set default_group parameter
   1.17. Set force_dns parameter
   1.18. Set probing_interval parameter
   1.19. Set probing_method parameter
   1.20. Set probing_from parameter
   1.21. Set probing_reply_codes parameter
   1.22. Set use_domain parameter
   1.23. Set drg_user_col parameter
   1.24. Set drg_domain_col parameter
   1.25. Set drg_grpid_col parameter
   1.26. do_routing usage
   1.27. route_to_carrier usage
   1.28. route_to_gw usage
   1.29. use_next_gw usage
   1.30. goes_to_gw usage
   1.31. is_from_gw usage
   1.32. dr_is_gw usage
   1.33. dr_disable() usage
   1.34. dr_gw_status usage
   1.35. dr_carrier_status usage

Chapter 1. Admin Guide

1.1. Overview

1.1.1. Introduction

   Dynamic Routing is a module for selecting (based on multiple
   criteria) the best gateway/destination to be used for
   delivering a certain call. Least Cost Routing (LCR) is a
   special case of dynamic routing - when the rules are ordered
   based on costs. Dynamic Routing comes with many features
   regarding routing rule selection:
     * prefix based
     * caller/group based
     * time based
     * priority based

   , processing :
     * stripping and prefixing
     * default rules
     * inbound and outbound processing
     * script route triggering

   and failure handling:
     * serial forking
     * weight based GW selection
     * random GW selection
     * GW probing for crashes

1.1.2. Features

   The dynamic routing implementation for OpenSIPS is designed
   with the following properties:
     * routing info (destinations, carriers, rules, groups) are
       stored in a database and loaded into memory at start up
       time; reload at runtime via an Management Interface
       command.
     * weigth-based or random selection of the destinations (from
       a rule or from a carrier), failure detection of gateways
       (with switching to next available gateway).
     * able to handle large volume of routing info (10M of rules)
       with minimal speed/time and memory consumption penalties
     * script integration - Pseudo variables support in functions;
       scripting route triggering when rules are matched
     * bidirectional behavior - inbound and outbound processing
       (strip and prefixing when sending and receiving from a
       destination/GW)
     * blacklisting - the module allows definition of backlists
       based on the destination IPs. This blacklists are to be
       used to prevent malicious forwarding to GWs (based on DNS
       lookups) when the script logic does none-GE forwarding
       (like foreign domains).

1.1.3. Performance

   There were several tests performed regarding the performance of
   the module when dealing with a large number of routing rules.

   The tests were performed with a set of 383000 rules and to
   values were measured:
     * time to load from DB
     * used shared memory

   The time to load was varying between 4 seconds and 8 seconds,
   depending of the caching of the DB client - the first load was
   the slowest (as the DB query hits the disk drive); the
   following are faster as data is already cached in the DB
   client. So technically speaking, the time to load (without the
   time to query which is DB type dependent) is ~4 seconds

   After loading the data into shared memory ~ 96M of memory were
   used exclusively for the DR data.

1.1.4. Dynamic Routing Concepts

   DR engine uses several concepts in order to define how the
   routing should be done (describing all the dependecies between
   destinations and routing rules).

1.1.4.1. Destination/Gateways

   These are the end SIP entities where actually the traffic needs
   to be sent after routing. They are stored in a table called
   “dr_gateways”. Gateway addresses are stored in a separate table
   because of need to access them independent of Dynamic Routing
   processing (e.g., adding/ removing gateway PRI prefix
   before/after performing other operation -- receiving/relaying
   to gateway).

   In DR, a gateway is defined by:
     * id (string)
     * SIP address (SIP URI)
     * type (number to allow to group GW based on purpose, like
       inbound, outbound, etc)
     * strip value (number of digits) from dialled number
     * prefix (string) to be added to dialled number
     * attributes (not used by DR engine, but only pushed to
       script level when routing to this GW)
     * probing mode (how the GW should be probed at SIP level -
       see the probing chapter)

   The Gateways are to be used from the routing rule or from the
   carrier definition. They are all the time referred by their ID.

1.1.4.2. Carriers

   The carrier concept is used if you need to group gateways in
   order to have a better control on how the GWs will be used by
   DR rules; like in what order the GWs will be used.

   Basically, a carrier is a set of gateways which have its own
   sorting algorithm and its own attribute string. They are by
   default defined in the “dr_carriers” table.

   In DR, a carrier is defined by:
     * id (string)
     * list of gateways with/without weights (string)
       (Ex:“gw1=10,gw4=10” or “gw1,gw2”
     * flags : 0x1 - use weight for sorting the list and not
       definition order; 0x2 - use only the first gateway from the
       carrier (depending on the sorting); 0x4 - disable the usage
       of this carrier
     * attributes (not used by DR engine, but only pushed to
       script level when routing to this carrier)

   The Carriers are to be used only from the routing rule
   definition. They are all the time referred by their ID.

1.1.4.3. Routing Rules

   These are the actual rule which control the routing - like
   based on different criterias (prefix, time, priority, etc) they
   will decide to which gateways the call will be sent.

   Default name for the table storing rule definitions is
   “dr_rules”.

   In DR, a carrier is defined by:
     * group (list of numbers) - rules can be grouped (a rule may
       belong to multiple groups in the same time ) and you can
       use only a certian group at a point; like having a
       “premium” or “standard” or “interstate” or “intrastate”
       groups of rules to be used in different cases
     * prefix (string with digits only) - prefix to be used for
       matching this rule (longest prefix matching)
     * time validity (time recurrence string) - when this rule is
       valid from time point of view (see RFC 2445)
     * priority (number) - prority off the rule - higher value,
       higher priority (see rule section alg)
     * script route ID (string) - if defined, then execute the
       route with the specified ID when this rule is matched.
       That's it, a route which can be used to perform custom
       operations on message. NOTE that no modification is
       performed at signaling level and you must NOT do any
       signalling operations in that script route
     * list of GWs/carriers (string) - a comma separated list of
       gateways or carriers (defined by IDs) to be used for this
       rule; the carrier IDs are prefixed with “#” sign. For each
       ID (GW or carrier) you may specify a weight. For how this
       list will be interpreted (as order) see the rule selection
       section. Example of list: “gw1,gw4,#cr3” or
       “gw1=10,gw4=10,#cr3=80”
     * attributes (not used by DR engine, but only pushed to
       script level when this rule matched and been used)

   More on time recurrence:
     * A date-time expression that defines the time recurrence to
       match for current rule. Time recurrences are based closely
       on the specification of recurring intervals of time in the
       Internet Calendaring and Scheduling Core Object
       Specification (calendar COS), RFC 2445. The set of
       attributes used in routing rule specification is subset of
       time recurrence attributes.
     * The value stored in database has the format of:
       <dtstart>|<duration>|<freq>|<until>|<interval>|<byday>|<bym
       onthday>|<byyearday>|<byweekno>|<bymonth>
     * When an attribute is not specified, the corresponding place
       must be left empty, whenever another attribute that follows
       in the list has to be specified.

1.1.5. Routing Rule Processing

   The module can be used to find out which is the best gateway to
   use for new calls terminated to PSTN. The algorithm to select
   the rule is as follows:
     * the module discovers the routing group of the originating
       user. This step is skipped if a routing group is passed
       from the script as parameter.
     * once the group is known, in the subset of the rules for
       this group the module looks for the one that matches the
       destination based on "prefix" column. The set of rules with
       the longest prefix is chosen. If no digit from the prefix
       matches, the default rules are used (rules with no prefix)
     * within the set of rules is applied the time criteria, and
       the rule which has the highest priority and matches the
       time criteria is selected to drive the routing.
     * Once found the rule, it may contain a route ID to execute.
       If a certain flag is set, then the processing is stopped
       after executing the route block.
     * The rule must contain a chain of gateways and carriers. The
       module will execute serial forking for each address in
       chain (in which order the destinations will be tried,
       depends on the defintion order or depends on the weights
       (weights selection must be enabled). The next address in
       chain is used only if the previously has failed.
     * With the right gateway address found, the prefix (PRI) of
       the gateway is added to the request URI and then the
       request is forwarded.

   If no rule is found to match the selection criteria an default
   action must be taken (e.g., error response sent back). If the
   gateway in the chain has no prefix the request is forwarded
   without adding any prefix to the request URI.

1.1.6. Probing and Disabling destinations

   The module has the capability to monitor the status of the
   destinations by doing SIP probing (sending SIP requests like
   OPTIONS).

   For each destination, you can configure what kind of probing
   should be done (probe_mode column):
     * (0) - no probing at all;
     * (1) - probing only when the destination is in disabled mode
       (disabling via MI command will competely stop the probing
       also). The destination will be automatically re-enabled
       when the probing will succeed next time;
     * (2) - probing all the time. If disabled, the destination
       will be automatically re-enabled when the probing will
       succeed next time;

   A destination can become disabled in two ways:
     * script detection - by calling from script the dr_disable()
       function after trying the destination. In this case, if
       probing mode for the destination is (1) or (2), the
       destination will be automatically re-enabled when the
       probing will succeed.
     * MI command - by calling the dr_gw_status MI command for
       disabling (on demand) the destination. If so, the probing
       and re-enabling of this destination will be completly
       disabled until you re-enable it again via MI command - this
       is designed to allow controlled and complete disabling of
       some destination during maintenance.

1.2. Dependencies

1.2.1. OpenSIPS Modules

   The following modules must be loaded before this module:
     * a database module.

     * tm module.

1.2.2. External Libraries or Applications

     * none.

1.3. Exported Parameters

1.3.1. db_url(str)

   The database url.

   Default value is “NULL”.

   Example 1.1. Set db_url parameter
...
modparam("drouting", "db_url",
        "mysql://opensips:opensipsrw@localhost/opensips")
...

1.3.2. drd_table(str)

   The name of the db table storing gateway addresses.

   Default value is “dr_gateways”.

   Example 1.2. Set drd_table parameter
...
modparam("drouting", "drd_table", "dr_gateways")
...

1.3.3. drr_table(str)

   The name of the db table storing routing rules.

   Default value is “dr_rules”.

   Example 1.3. Set drr_table parameter
...
modparam("drouting", "drr_table", "rules")
...

1.3.4. drg_table(str)

   The name of the db table storing groups.

   Default value is “dr_groups”.

   Example 1.4. Set drg_table parameter
...
modparam("drouting", "drg_table", "groups")
...

1.3.5. drc_table(str)

   The name of the db table storing definitions of the carriers
   that will be used directly by the routing rules.

   Default value is “dr_gw_lists”.

   Example 1.5. Set drc_table parameter
...
modparam("drouting", "drc_table", "my_dr_carriers")
...

1.3.6. ruri_avp (str)

   The name of the avp for storing Request URIs to be later used
   (alternative destiantions for the current one).

   Default value is “$avp(0xad346b2f)”.

   Example 1.6. Set ruri_avp parameter
...
modparam("drouting", "ruri_avp", '$avp(dr_ruri)')
modparam("drouting", "ruri_avp", '$avp(33)')
...

1.3.7. gw_id_avp (str)

   The name of the avp for storing the id of the current selected
   gateway/destination - once a new destination is selected (via
   the use_next_gw() function), the AVP will be updated with the
   ID of the new selected gateway/destination.

   Default value is “$avp(0xad346b30)”.

   Example 1.7. Set gw_id_avp parameter
...
modparam("drouting", "gw_id_avp", '$avp(gw_id)')
modparam("drouting", "gw_id_avp", '$avp(334)')
...

1.3.8. gw_attrs_avp (str)

   The name of the avp for storing the attributes of the current
   selected destination/gateway - once a new destination is
   selected (via the use_next_gw() function), the AVP will be
   updated with the attrs of the new used destination.

   Default value is “NULL”.

   Example 1.8. Set gw_attrs_avp parameter
...
modparam("drouting", "gw_attrs_avp", '$avp(gw_attrs)')
modparam("drouting", "gw_attrs_avp", '$avp(67)')
...

1.3.9. gw_priprefix_avp (str)

   The name of the avp for storing the PRI prefix of the current
   selected destination/gateway - once a new destination is
   selected (via the use_next_gw() function), the AVP will be
   updated with the PRI prefix of the new used destination.

   Default value is “NULL”.

   Example 1.9. Set gw_priprefix_avp parameter
...
modparam("drouting", "gw_priprefix_avp", '$avp(gw_priprefix)')
...

1.3.10. rule_id_avp (str)

   The name of the avp for storing the id of the current matched
   routing rule (see dr_rules table).

   Default value is “NULL”.

   Example 1.10. Set rule_id_avp parameter
...
modparam("drouting", "rule_id_avp", '$avp(rule_id)')
modparam("drouting", "rule_id_avp", '$avp(335)')
...

1.3.11. rule_attrs_avp (str)

   The name of the avp for storing the attributes of the current
   matched routing rule (see dr_rules table).

   Default value is “NULL”.

   Example 1.11. Set rule_attrs_avp parameter
...
modparam("drouting", "rule_attrs_avp", '$avp(rule_attrs)')
modparam("drouting", "rule_attrs_avp", '$avp(66)')
...

1.3.12. rule_prefix_avp (str)

   The actual prefix that matched the routing rule (the part from
   RURI username that matched the routing rule).

   Default value is “NULL”.

   Example 1.12. Set rule_prefix_avp parameter
...
modparam("drouting", "rule_prefix_avp", '$avp(dr_prefix)')
...

1.3.13. carrier_id_avp (str)

   AVP to be populate with the ID string for the carrier the
   current GW belongs to.

   Default value is “NULL”.

   Example 1.13. Set carrier_id_avp parameter
...
modparam("drouting", "carrier_id_avp", '$avp(carrier_id)')
...

1.3.14. carrier_attrs_avp (str)

   AVP to be populate with the attributes string for the carrier
   the current GW belongs to.

   Default value is “NULL”.

   Example 1.14. Set carrier_attrs_avp parameter
...
modparam("drouting", "carrier_attrs_avp", '$avp(carrier_attrs)')
...

1.3.15. define_blacklist (str)

   Defines a backlist based on a list of GW types - the list will
   contain the IPs (no port, all protocols) of the GWs with the
   specified types.

   Multiple instances of this param are allowed.

   Default value is “NULL”.

   Example 1.15. Set define_blacklist parameter
...
modparam("drouting", "define_blacklist", 'bl_name= 3,5,25,23')
modparam("drouting", "define_blacklist", 'list= 4,2')
...

1.3.16. default_group (int)

   Group to be used if the caller (FROM user) is not found in the
   GROUP table.

   Default value is “NONE”.

   Example 1.16. Set default_group parameter
...
modparam("drouting", "default_group", 4)
...

1.3.17. force_dns (int)

   Force DNS resolving of GW/destination names (if not IPs) during
   startup. If not enabled, the GW name will be blindly used
   during routing.

   Default value is “1 (enabled)”.

   Example 1.17. Set force_dns parameter
...
modparam("drouting", "force_dns", 0)
...

1.3.18. probing_interval (integer)

   How often (in seconds) the probing of a destination should be
   done. If set to 0, the probing will be disabled as
   functionality (for all destinations)

   Default value is “30”.

   Example 1.18. Set probing_interval parameter
...
modparam("drouting", "probing_interval", 60)
...

1.3.19. probing_method (string)

   The SIP method to be used for the probing requests.

   Default value is “"OPTIONS"”.

   Example 1.19. Set probing_method parameter
...
modparam("drouting", "probing_method", "INFO")
...

1.3.20. probing_from (string)

   The FROM SIP URI to be advertised in the SIP probing requests.

   Default value is “"sip:prober@localhost"”.

   Example 1.20. Set probing_from parameter
...
modparam("drouting", "probing_from", "sip:pinger@192.168.2.10")
...

1.3.21. probing_reply_codes (string)

   A comma separted list of SIP reply codes. The codes defined
   here will be considered as valid reply codes for probing
   messages, apart for 200.

   Default value is “NULL”.

   Example 1.21. Set probing_reply_codes parameter
...
modparam("drouting", "probing_reply_codes", "501, 403")
...

1.3.22. use_domain (int)

   Flag to configure whether to use domain match when querying
   database for user's routing group.

   Default value is “1”.

   Example 1.22. Set use_domain parameter
...
modparam("drouting", "use_domain", 0)
...

1.3.23. drg_user_col (str)

   The name of the column in group db table where the username is
   stored.

   Default value is “username”.

   Example 1.23. Set drg_user_col parameter
...
modparam("drouting", "drg_user_col", "user")
...

1.3.24. drg_domain_col (str)

   The name of the column in group db table where the domain is
   stored.

   Default value is “domain”.

   Example 1.24. Set drg_domain_col parameter
...
modparam("drouting", "drg_domain_col", "host")
...

1.3.25. drg_grpid_col (str)

   The name of the column in group db table where the group id is
   stored.

   Default value is “groupid”.

   Example 1.25. Set drg_grpid_col parameter
...
modparam("drouting", "drg_grpid_col", "grpid")
...

1.4. Exported Functions

1.4.1.  do_routing([[[groupID],flags],gw_whitelist])

   Function to trigger routing of the message according to the
   rules in the database table and the configured parameters.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE and
   LOCAL_ROUTE.

   The function can take two optional parameters:
     * groupID - the routing group the caller belongs to - this
       may be a static numerical value or an AVP specification
       (value must be numerical type, string types are ignored!).
       If none specified, the function will automatically try to
       query the dr_group table to get this information;
     * flags - Controlls the behavior of the function. Possible
       flags are:
          + W - Instead of using the destination (from the rule
            definition) in the given order, sort them based on
            their weight.
          + F - Enable rule fallback; normally the engine is using
            a single rule for routing a call; by setting this
            flag, the enging will fallback and use rules with less
            priority or shorter prefix when all the destination
            from the current rules failed.
          + L - Do strict lenght matching over the prefix -
            actually DR engine will do full number maching and not
            prefix matching anymore.
          + C - Only check if the dialed number matches any
            routing rule, without loading / applying any routing
            info (no GW is set, the RURI is not altered)
     * gw_whitelist - a comma separated white list of gateways.
       This will force routing over this list of carriers or
       gateways (a subset of what found in the prefix rules).

   Example 1.26. do_routing usage
...
# all groups, sort on order
do_routing();
...
# group id 0, sort on order
do_routing("0");
...
# group id from $avp(10), sort on order
do_routing("$avp(10)");
...
# all groups, sort on weights
do_routing("","W");
...
# group id 2, sort on order, fallback rule
do_routing("2","F");
...

1.4.2.  route_to_carrier(carrier_id)

   Function to trigger the direct routing to a given carrier. In
   this case the routing is not done prefix based, but carrier
   based (call will be sent to the GWs of that carrier, based on
   carrier policy)

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE and
   LOCAL_ROUTE..

   Function takes a single mandatory parameter, the ID of the
   carrier to be used (variables are accepted).

   Example 1.27. route_to_carrier usage
...
if ( route_to_carrier("my_top_carrier") ) {
        t_on_failure("next_gw");
        t_relay();
        exit;
}
...

1.4.3.  route_to_gw(gw_id)

   Function to trigger the direct routing to a given gateway.
   Attributes and per-gw preocessing will be available.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE and
   LOCAL_ROUTE.

   Function takes a single mandatory parameter, the ID of the
   gateway to be used (variables are accepted).

   Example 1.28. route_to_gw usage
...
if ( route_to_gw("gw_europe") ) {
        t_relay();
        exit;
}
...

1.4.4.  use_next_gw()/next_routing()

   The function takes the next available destination (set by
   do_routing, as alternative destinations) and push it into RURI.
   Note that the function just sets the RURI (nothing more).

   If a new RURI is set, the used destination is removed from the
   pending set of alternative destinations.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE and
   LOCAL_ROUTE.

   The function returns true only if a new RURI was set. False is
   returned is no other alternative destinations are found or in
   case of internal processing error.

   Example 1.29. use_next_gw usage
...
if (use_next_gw()) {
        t_relay();
        exit;
}
...

1.4.5.  goes_to_gw([[type],flags])

   Function returns true if the destination of the current request
   (destination URI or Request URI) points (as IP) to one of the
   gateways. There no DNS lookups done if the domain part of the
   URI is not an IP.

   This function does not change anything in the message.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE,
   BRANCH_ROUTE and LOCAL_ROUTE.

   The function can take two optional parameters:
     * type (optional) - GW/destination type to be checked; a
       negative value (ex: -1) means match any group;
     * flags (optional) - what operations should be performed when
       a GW matches:
          + 's' (Strip) - apply to the username of RURI the strip
            defined by the GW
          + 'p' (Prefix) - apply to the username of RURI the
            prefix defined by the GW
          + 'a' (Attributes) - return the attributes string
            defined by the GW into gw_attrs_avp AVP
          + 'i' (Gateway ID) - return the gateway id into
            gw_id_avp AVP
          + 'n' (Ignore port) - ignores port number during
            matching

   Example 1.30. goes_to_gw usage
...
if (goes_to_gw("1")) {
        sl_send_reply("403","Forbidden");
        exit;
}
...

1.4.6.  is_from_gw( [type, [flag]])

   The function checks if the sender of the message is a gateway
   from a certain group.

   This function can be used from REQUEST_ROUTE, FAILURE_ROUTE and
   ONREPLY_ROUTE.

   The function can take two optional parameters:
     * type (optional) - GW/destination type to be checked; a
       negative value (ex: -1) means match any group;
     * flags (optional) - what operations should be performed when
       a GW matches:
          + 's' (Strip) - apply to the username of RURI the strip
            defined by the GW
          + 'p' (Prefix) - apply to the username of RURI the
            prefix defined by the GW
          + 'a' (Attributes) - return the attributes string
            defined by the GW into gw_attrs_avp AVP
          + 'i' (Gateway ID) - return the gateway id into
            gw_id_avp AVP
          + 'n' (Ignore port) - ignores port number during
            matching

   Example 1.31. is_from_gw usage
...
if (is_from_gw("3","1") {
}
...

1.4.7.  dr_is_gw(src_pv, [type, [flag]])

   The function checks if the ip address in pvar src_pv is a
   gateway from a certain group.

   This function can be used from REQUEST_ROUTE, ONREPLY_ROUTE,
   FAILURE_ROUTE, BRANCH_ROUTE, LOCAL_ROUTE, STARTUP_ROUTE,
   TIMER_ROUTE and EVENT_ROUTE.

   Meaning of the parameters is as follows:
     * src_pv (mandatory) - pvar containing SIP URI. May be a
       script var or avp.
     * type (optional) - GW/destination type to be checked; a
       negative value (ex: -1) means match any group;
     * flags (optional) - what operations should be performed when
       a GW matches:
          + 's' (Strip) - apply to the username of RURI the strip
            defined by the GW
          + 'p' (Prefix) - apply to the username of RURI the
            prefix defined by the GW
          + 'a' (Attributes) - return the attributes string
            defined by the GW into gw_attrs_avp pvar
          + 'i' (Gateway ID) - return the gateway id into
            gw_id_avp pvar
          + 'n' (Ignore port) - ignores port number

   Example 1.32. dr_is_gw usage
...
if (dr_is_gw("$avp(uac)","3") {
}
...

1.4.8.  dr_disable()

   Marks as disabled the last destination that was used for the
   current call. The disabling done via this function will prevent
   the destination to be used for usage from now on. The probing
   mechanism can re-enable this peer (see the probing section in
   the begining)

   This function can be used from REQUEST_ROUTE and FAILURE_ROUTE.

   Example 1.33. dr_disable() usage
...
if (t_check_status("(408)|(5[0-9][0-9])")) {
        dr_disable();

}

...

1.5. Exported MI Functions

1.5.1.  dr_reload

   Command to reload routing rules from database.

   It takes no parameter.

   MI FIFO Command Format:
                :dr_reload:fifo_reply
                _empty_line_

1.5.2. dr_gw_status

   Gets or sets the status (enabled or disabled) of a gateway. The
   function may take from 0 to 2 parameters. If none, it will list
   all gateways along with their status. If one parameter is
   provided, that must be the id of a gateway and the function
   will return the status of that gateway. If 2 parameters are
   provided, first must be the ID of the ID of a GW and the second
   must be the new status to be forced for that GW (0 - disable, 1
   - enable).

   MI FIFO Command Format:
                :dr_gw_status:_reply_fifo_file_
                GW_id
                status (optional)
                _empty_line_

   Example 1.34. dr_gw_status usage
$ ./opensipsctl fifo dr_gw_status 2
Enabled:: no
$ ./opensipsctl fifo dr_gw_status 2 1
$ ./opensipsctl fifo dr_gw_status 2
Enabled:: yes

1.5.3. dr_carrier_status

   Gets or sets the status (enabled or disabled) of a carrier. The
   function may take from 0 to 2 parameters. If none, it will list
   all carriers along with their status. If one parameter is
   provided, that must be the id of a carrier and the function
   will return the status of that carrier. If 2 parameters are
   provided, first must be the ID of the ID of a carrier and the
   second must be the new status to be forced for that carrier (0
   - disable, 1 - enable).

   MI FIFO Command Format:
                :dr_carrier_status:_reply_fifo_file_
                carrier_id
                status (optional)
                _empty_line_

   Example 1.35. dr_carrier_status usage
$ ./opensipsctl fifo dr_carrier_status CR1
Enabled:: no
$ ./opensipsctl fifo dr_carrier_status CR1 1
$ ./opensipsctl fifo dr_carrier_status CR1
Enabled:: yes

1.6. Installation

   The module requires 4 table in OpenSIPS database: dr_groups,
   dr_gateways, dr_carriers, dr_rules. The SQL syntax to create
   them can be found in drouting-create.sql script in the database
   directories in the opensips/scripts folder. You can also find
   the complete database documentation on the project webpage,
   http://www.opensips.org/html/docs/db/db-schema-devel.html.

Chapter 2. Developer Guide

   The module provides no function to be used by other OpenSIPS
   modules.
