1. CPL Module

Bogdan-Andrei Iancu

   FhG FOKUS

   Copyright © 2003 FhG FOKUS
     __________________________________________________________________

   1.1. Overview
   1.2. Dependencies

        1.2.1. SER Modules
        1.2.2. External Libraries or Applications

   1.3. Parameters

        1.3.1. cpl_db (string)
        1.3.2. cpl_table (string)
        1.3.3. cpl_dtd_file (string)
        1.3.4. log_dir (string)
        1.3.5. proxy_recurse (int)
        1.3.6. proxy_route (int)
        1.3.7. nat_flag (int)
        1.3.8. lookup_domain (int)

   1.4. Functions

        1.4.1. cpl_run_script(type,mode)
        1.4.2. cpl_process_register()

1.1. Overview

   cpl-c modules implements a CPL (Call Processing Language) interpreter.
   Support for uploading/downloading/removing scripts via SIP REGISTER
   method is implemented.

1.2. Dependencies

1.2.1. SER Modules

   The following modules must be loaded before this module:
     * tm.  Transaction Manager, used for proxying/forking requests.
     * sl.  StateLess module - used for sending stateless reply when
       responding to REGISTER request or for sending back error responses.
     * usrloc.  User location module - used for implementing
       lookup("registration") (adding into location set of the users'
       contact)

1.2.2. External Libraries or Applications

   The following libraries or applications must be installed before
   running SER with this module loaded:
     * libxml2.  This library contains an engine for XML parsing, DTD
       validation and DOM manipulation.

1.3. Parameters

1.3.1. cpl_db (string)

   A SQL URL have to be given to the module for knowing where the database
   containing the table with CPL scripts is locates. If required a user
   name and password can be specified for allowing the module to connect
   to the database server.

Warning

   This parameter is mandatory.

   Example 1. Set cpl_db parameter
...
modparam("cpl_c","cpl_db","mysql://user:passwd@host/database")
...

1.3.2. cpl_table (string)

   Indicates the name of the table that store the CPL scripts. This table
   must be locate into the database specified by "cpl_db" parameter. For
   more about the format of the CPL table please see
   modules/cpl-c/init.mysql.

Warning

   This parameter is mandatory.

   Example 2. Set cpl_table parameter
...
modparam("cpl_c","cpl_table","cpltable")
...

1.3.3. cpl_dtd_file (string)

   Points to the DTD file describing the CPL grammar. The file name may
   include also the path to the file. This path can be absolute or
   relative (be careful the path will be relative to the starting
   directory of SER).

Warning

   This parameter is mandatory.

   Example 3. Set cpl_dtd_file parameter
...
modparam("cpl_c","cpl_dtd_file","/etc/ser/cpl-06.dtd")
...

1.3.4. log_dir (string)

   Points to a directory where should be created all the log file
   generated by the LOG CPL node. A log file per user will be created (on
   demand) having the name username.log.

Note

   If this parameter is absent, the logging will be disabled without
   generating error on execution.

   Example 4. Set log_dir parameter
...
modparam("cpl_c","log_dir","/var/log/ser/cpl")
...

1.3.5. proxy_recurse (int)

   Tells for how many time is allow to have recurse for PROXY CPL node If
   it has value 2, when doing proxy, only twice the proxy action will be
   re-triggered by a redirect response; the third time, the proxy
   execution will end by going on REDIRECTION branch. The recurse feature
   can be disable by setting this parameter to 0

   Default value of this parameter is 0.

   Example 5. Set proxy_recurse parameter
...
modparam("cpl_c","proxy_recurse",2)
...

1.3.6. proxy_route (int)

   Before doing proxy (forward), a script route can be executed. All
   modifications made by that route will be reflected only for the current
   branch.

   Default value of this parameter is 0 (none).

   Example 6. Set proxy_route parameter
...
modparam("cpl_c","proxy_route",1)
...

1.3.7. nat_flag (int)

   Sets the flag used for marking calls via NAT. Used by lookup tag when
   retrieving a contact behind a NAT (this flag will be set).

   Default value of this parameter is 6.

   Example 7. Set nat_flag parameter
...
modparam("cpl_c","nat_flag",4)
...

1.3.8. lookup_domain (int)

   Tells if the lookup tag should use or not the domain part when doing
   user location search. Set it to a non zero value to force also domain
   matching.

   Default value of this parameter is 0.

   Example 8. Set lookup_domain parameter
...
modparam("cpl_c","lookup_domain",1)
...

1.4. Functions

1.4.1.  cpl_run_script(type,mode)

   Starts the execution of the CPL script. The user name is fetched from
   new_uri or requested uri or from To header -in this order- (for
   incoming execution) or from FROM header (for outgoing execution).
   Regarding the stateful/stateless message processing, the function is
   very flexible, being able to run in different modes (see below
   the"mode" parameter). Normally this function will end script execution.
   There is no guaranty that the CPL script interpretation ended when ser
   script ended also (for the same INVITE ;-)) - this can happen when the
   CPL script does a PROXY and the script interpretation pause after
   proxying and it will be resume when some reply is received (this can
   happen in a different process of SER). If the function returns to
   script, the SIP server should continue with the normal behavior as if
   no script existed. When some error is returned, the function itself
   haven't sent any SIP error reply (this can be done from script).

   Meaning of the parameters is as follows:
     * type - which part of the script should be run; set it to "incoming"
       for having the incoming part of script executed (when an INVITE is
       received) or to "outgoing" for running the outgoing part of script
       (when a user is generating an INVITE - call).
     * mode - sets the interpreter mode as stateless/stateful behavior.
       The following modes are accepted:
          + IS_STATELESS - the current INVITE has no transaction created
            yet. All replies (redirection or deny) will be done is a
            stateless way. The execution will switch to stateful only when
            proxy is done. So, if the function returns, will be in
            stateless mode.
          + IS_STATEFUL - the current INVITE has already a transaction
            associated. All signaling operations (replies or proxy) will
            be done in stateful way.So, if the function returns, will be
            in stateful mode.
          + FORCE_STATEFUL - the current INVITE has no transaction created
            yet. All signaling operations will be done is a stateful way
            (on signaling, the transaction will be created from within the
            interpreter). So, if the function returns, will be in
            stateless mode.

Note
       is_stateful is very difficult to manage from the routing script
       (script processing can continue in stateful mode); is_stateless is
       the fastest and consumes less resources (transaction is created
       only if proxying is done), but there is only a minimal protection
       against retransmissions (since replies are send statelessly);
       force_stateful is a good compromise - all signaling is done
       stateful (retransmission protection) and in the same time, if
       returning to script, it will be in stateless mode (easy to continue
       the routing script execution)

   Example 9. cpl_run_script usage
...
cpl_run_script("incoming","force_stateful");
...

1.4.2.  cpl_process_register()

   This function MUST be called only for REGISTER requests. It checks if
   the current REGISTER request is related or not with CPL script
   upload/download/ remove. If it is, all the needed operation will be
   done. For checking if the REGISTER is CPL related, the function looks
   fist to "Content-Type" header. If it exists and has a the mime type set
   to "application/cpl+xml" means this is a CPL script upload/remove
   operation. The distinction between to case is made by looking at
   "Content-Disposition" header; id its value is "script;action=store",
   means it's an upload; if it's "script;action=remove", means it's a
   remove operation; other values are considered to be errors. If no
   "Content-Type" header is present, the function looks to "Accept" header
   and if it contains the "*" or "application/cpl-xml" the request it will
   be consider one for downloading CPL scripts. The functions returns to
   script only if the REGISTER is not related to CPL. In other case, the
   function will send by itself the necessary replies (stateless - using
   sl), including for errors.