B2B_ENTITIES module

Admin Guide

Overview

The B2BUA implementation in OpenSIPS is separated in two layers:

a lower one(coded in this module)- which implements the basic functions of a UAS and UAC
a upper one - which represents the logic engine of B2BUA, responsible of actually implementing the B2BUA services using the functions offered by the low level.

This module stores records corresponding to the dialogs in which the B2BUA is involved. It exports an API to be called from other modules which offers functions for creating a new dialog record, for sending requests or replies in one dialog and will also notify the upper level module when a request or reply is received inside one stored dialog.

The records are separated in two types: b2b server entities and b2b client entities depending on the mode they are created. An entity created for a received initial message will be a server entity, while a entity that will send an initial request(create a new dialog) will be a b2b client entity. The name corresponds to the behavior in the first transaction - if UAS - server entity and if UAC - client entity.

This module does not implement a B2BUA alone, but needs a B2B logic implementing module.

The module is able to respond to authentication challanges if the uac_auth module is loaded first. The list of credentials for b2b authentication is also provided by the uac_auth module.

Dependencies

OpenSIPS Modules

tm
a db module
uac_auth (mandatory if authentication is required)

External Libraries or Applications

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

none

Exported Parameters

server_hsize (int)

The size of the hash table that stores the b2b server entities. It is the 2 logarithmic value of the real size.

Default value is “9” (512 records).

...
modparam("b2b_entities", "server_hsize", 10)
...

client_hsize (int)

The size of the hash table that stores the b2b client entities. It is the 2 logarithmic value of the real size.

Default value is “9” (512 records).

...
modparam("b2b_entities", "client_hsize", 10)
...

script_req_route (str)

The name of the b2b script route that will be called when B2B requests are received.

...
modparam("b2b_entities", "script_req_route", "b2b_request")
...

script_reply_route (str)

The name of the b2b script route that will be called when B2B replies are received.

...
modparam("b2b_entities", "script_reply_route", "b2b_reply")
...

db_url (str)

Database URL. It is not compulsory, if not set data is not stored in database.

...
modparam("b2b_entities", "db_url", "mysql://opensips:opensipsrw@127.0.0.1/opensips")
...

cachedb_url (str)

URL of a NoSQL database to be used. Only Redis is supported at the moment.

...
modparam("b2b_entities", "cachedb_url", "redis://localhost:6379/")
...

cachedb_key_prefix (string)

Prefix to use for every key set in the NoSQL database.

Default value is “b2be$“.

...
modparam("b2b_entities", "cachedb_key_prefix", "b2b")
...

update_period (int)

The time interval at which to update the info in database.

Default value is “100”.

...
modparam("b2b_entities", "update_period", 60)
...

b2b_key_prefix (string)

The string to use when generating the key ( it is inserted in the SIP messages as callid or to tag. It is useful to set this prefix if you use more instances of opensips B2BUA cascaded in the same architecture. Sometimes opensips B2BUA looks at the callid or totag to see if it has the format it uses to determine if the request was sent by it.

Default value is “B2B”.

...
modparam("b2b_entities", "b2b_key_prefix", "B2B1")
...

db_mode (int)

The B2B modules have support for the 3 type of database storage

NO DB STORAGE - set this parameter to 0
WRITE THROUGH (synchronous write in database) - set this parameter to 1
WRITE BACK (update in db from time to time) - set this parameter to 2

Default value is “2” (WRITE BACK).

...
modparam("b2b_entities", "db_mode", 1)
...

db_table (str)

The name of the table that will be used for storing B2B entities

Default value is “b2b_entities”

...
modparam("b2b_entities", "db_table", "some table name")
...

cluster_id (int)

The ID of the cluster this instance belongs to. Setting this parameter enables clustering support for the OpenSIPS B2BUA by replicating the B2B entities (B2B dialogs) between instances. This also ensures restart persistency through the clusterer module’s data “sync” mechanism.

This OpenSIPS cluster exposes the “b2be-entities-repl” capability in order to mark nodes as eligible for becoming data donors during an arbitrary sync request. Consequently, the cluster must have at least one node marked with the “seed” value as the clusterer.flags column/property in order to be fully functional. Consult the clusterer - Capabilities chapter for more details.

Default value is “0” (clustering disabled)

...
modparam("b2b_entities", "cluster_id", 10)
...

passthru_prack (int)

This parameter allows to control, whether a PRACK should be generated locally (=0) or if we request it to be end-to-end (=1).

Default value is “0” (generate PRACK locally)

...
modparam("b2b_entities", "passthru_prack", 1)
...

advertised_contact (str)

Contact to use in generated messages for UA session started with the mi ua session client start MI function.

...
modparam("b2b_entities", "advertised_contact", "opensips@10.10.10.10:5060")
...

ua_default_timeout (str)

Default timeout, in seconds, for UA session started with the ua session server init function or the mi ua session client start MI function. After this interval a BYE will be sent and the session will be deleted.

If not set the default is 43200 (12 hours).

...
modparam("b2b_entities", "ua_default_timeout", 7200)
...

Exported Functions

ua_session_server_init([key], [flags])

This function initializes a new UA session by processing an initial INVITE. Further requests/replies received belonging to this session will only be handled via the E UA SESSION event.

Parameters:

key (var, optional) - Variable to return the b2b entity key of the new UA session.
flags (string, optional) - configures options for this UA session via the following flags:
- t[nn] - maximum duration of this session in seconds. After this timeout a BYE will be sent and the session will be deleted. If this is not set, the default timeout, configured with ua default timeout will be used. Example: t3600
- a - report the receving of ACK requests via the E UA SESSION event.
- r - report the receving of replies via the E UA SESSION event.
- d - disable the automatic sending of ACK upon receving a 200 OK reply for INVITE (in case of UAC session) or re-INVITE.
- h - provide the headers of the SIP request/reply in the E UA SESSION event.
- b - provide the body of the SIP request/reply in the E UA SESSION event.
- n - do not trigger the E UA SESSION event (with event_type NEW) for initial INVITES handled with this function.

This function can be used from REQUEST_ROUTE.

...
if(is_method("INVITE") && !has_totag()) {
   ua_session_server_init($var(b2b_key), "arhb");

   ua_session_reply($var(b2b_key), "INVITE", 200, "OK", $var(my_sdp));

   exit;
}
...

ua_session_update(key, method, [body], [extra_headers], [content_type])

Sends a sequential request for a UA session started with the ua session server init function or the mi ua session client start MI function.

Parameters:

key (string) - b2b entity key of the UA session.
method (string) - name of the SIP method for this request.
body (string, optional) - body to include in the SIP message.
extra_headers (string, optional) - extra headers to include in the SIP message.
content_type (string, optional) - Content-Type header. If the parameter is missing and a body is provided, “Content-Type: application/sdp” will be used.

This function can be used from REQUEST_ROUTE, EVENT_ROUTE.

...
ua_session_update($var(b2b_key), "OPTIONS");
...

ua_session_reply(key, method, code, [reason], [body], [extra_headers], [content_type])

Sends a reply for a UA session started with the ua session server init function or the mi ua session client start MI function.

Parameters:

key (string) - b2b entity key of the UA session.
method (string) - name of the SIP method that is replied to.
code (int) - reply code.
reason (string, optional) - reply reason string.
body (string, optional) - body to include in the SIP message.
extra_headers (string, optional) - extra headers to include in the SIP message.
content_type (string, optional) - Content-Type header. If the parameter is missing and a body is provided, “Content-Type: application/sdp” will be used.

This function can be used from REQUEST_ROUTE, EVENT_ROUTE.

...
ua_session_reply($var(b2b_key), "INVITE", 180, "Ringing");
...

ua_session_terminate(key, [extra_headers])

Terminate a UA session started with the ua session server init function or the mi ua session client start MI function.

Parameters:

key (string) - b2b entity key of the UA session.
extra_headers (string, optional) - extra headers to include in the SIP message

This function can be used from REQUEST_ROUTE, EVENT_ROUTE.

...
ua_session_terminate($var(b2b_key));
...

Exported MI Functions

b2be_list

This command can be used to list the internals of the b2b entities.

Name: b2be_list

Parameters: none

MI FIFO Command Format:

  opensips-cli -x mi b2be_list

ua_session_client_start

This command starts a new UAC session by sending an initial INVITE. Further requests/replies received belonging to this session will only be handled via the E UA SESSION event.

Name: ua_session_client_start

Parameters:

ruri - Request URI
to - To URI; can also be specified as: display_name,uri in order to set a Display Name, eg. Alice,sip:alice@opensips.org.
from - From URI; can also be specified as: display_name,uri in order to set a Display Name, eg. Alice,sip:alice@opensips.org
proxy (optional) - URI of the outbound proxy to send the INVITE to
body (optional) - message body
content_type (optional) - Content Type header to use. If missing and a body is provided, “Content-Type: application/sdp” will be used.
extra_headers (optional) - extra headers
flags (optional) - flags with the same meaning as for the flags paramater of ua session server init.
socket (optional) - OpenSIPS sending socket

opensips-cli Command Format:

opensips-cli -x mi ua_session_client_start ruri=sip:bob@opensips.org \
to=sip:bob@opensips.org from=sip:alice@opensips.org flags=arhb

ua_session_update

Sends a sequential request for a UA session started with the ua session server init function or the mi ua session client start MI function.

Name: ua_session_update

Parameters:

key - b2b entity key of the UA session.
method - name of the SIP method for this request.
body (optional) - body to include in the SIP message.
extra_headers (optional) - extra headers to include in the SIP message.
content_type (string) - Content-Type header. If the parameter is missing and a body is provided, “Content-Type: application/sdp” will be used.

opensips-cli Command Format:

opensips-cli -x mi ua_session_update key=B2B.436.1925389.1649338095 method=OPTIONS

ua_session_reply

Sends a reply for a UA session started with the ua session server init function or the mi ua session client start MI function.

Name: ua_session_reply

Parameters:

key - b2b entity key of the UA session.
method - name of the SIP method that is replied to.
code - reply code
reason - reply reason string
body (optional) - body to include in the SIP message
extra_headers (optional) - extra headers to include in the SIP message
content_type (optional) - Content-Type header. If the parameter is missing and a body is provided, “Content-Type: application/sdp” will be used.

opensips-cli Command Format:

opensips-cli -x mi ua_session_reply key=B2B.436.1925389.1649338095 method=OPTIONS code=200 reason=OK

ua_session_terminate

Terminate a UA session started with the ua session server init function or the mi ua session client start MI function.

Name: ua_session_terminate

Parameters:

key - b2b entity key of the UA session.
extra_headers (optional) - extra headers to include in the SIP message

opensips-cli Command Format:

opensips-cli -x mi ua_session_terminate key=B2B.436.1925389.1649338095

ua_session_list

List information about UA sessions started with ua session server init function or the mi ua session client start MI function.

Name: ua_session_list

Parameters:

key (optional) - b2b entity key of the UA session to list. If missing, all sessions will be listed.

MI FIFO Command Format:

  opensips-cli -x mi ua_session_list

Exported Events

E_UA_SESSION

This event is triggered for requests/replies belonging to an ongoing UA session started with the ua session server init function or the mi ua session client start MI function.

Note that replies will not be reported at all unless the r flag was set when initiating the UA session. Also ACK requests are only reported if the a flag was set.

Parameters:

key - b2b entity key of the UA session.
entity_type - indicates whether this is a UAS or UAc entity.
event_type - the type of event:
- NEW - for initial INVITE requests, handled with the ua session server init function.
- EARLY - for 1xx provisional responses
- ANSWERED - for 2xx successful responses
- REJECTED - for 3xx-6xx failure responses
- UPDATED - for any sequential requests, including ACK but excluding BYE/CANCEL
- TERMINATED - for BYE or CANCEL requests
status - the reply status code if the message is a SIP reply
reason - the reply reason if the message is a SIP reply
method - the SIP method name
body - SIP message body
headers - full list of all SIP headers in the message.

Developer Guide

The module provides an API that can be used from other OpenSIPS modules. The API offers the functions for creating and handing dialogs. A dialog can be created on a receipt initial message, and this will correspond to a b2b server entity, or initiated by the server and in this case a client entity will be created in b2b_entities module.

b2b_load_api(b2b_api_t* api)

This function binds the b2b_entities modules and fills the structure the exported functions that will be described in detail.

...
typedef struct b2b_api {
  b2b_server_new_t          server_new;
  b2b_client_new_t          client_new;

  b2b_send_request_t        send_request;
  b2b_send_reply_t          send_reply;

  b2b_entity_delete_t       entity_delete;

  b2b_restore_linfo_t       restore_logic_info;
  b2b_update_b2bl_param_t   update_b2bl_param;
}b2b_api_t;
...

server_new

Field type:

...
typedef str* (*b2b_server_new_t) (struct sip_msg* , str* local_contact,
    b2b_notify_t , str *mod_name, str* logic_key, struct b2b_tracer *tracer,
    void *param, b2b_param_free_cb free_param);
...

This function asks the b2b_entities modules to create a new server entity record. The internal processing actually extracts the dialog information from the message and constructs a record that will be stored in a hash table. The second parameters is a pointer to a function that the b2b_entities module will call when a event will come for that dialog (a request or reply). The third parameter is a pointer to a value that will be stored and given as a parameter when the notify function will be called(it has to be allocated in shared memory).

The return value is an identifier for the record that will be mentioned when calling other functions that represent actions in the dialog(send request, send reply).

The notify function has the following prototype:

...
typedef int (*b2b_notify_t)(struct sip_msg* msg, str* id, int type, void* param);
...

This function is called when a request or reply is received for a dialog handled by b2b_entities. The first parameter is the message, the second is the identifier for the dialog, the third is a flag that says which is the type of the message(it has two possible values - B2B_REQUEST and B2B_REPLY). The last parameter is the parameter by the upper module when the entity was created.

client_new

Field type:

...
typedef str* (*b2b_client_new_t) (client_info_t* , b2b_notify_t b2b_cback,
        b2b_add_dlginfo_t add_dlginfo_f, str *mod_name, str *logic_key,
        struct b2b_tracer *tracer, void *param, b2b_param_free_cb free_param);
...

This function asks the b2b_entities modules to create a new client entity record and also create a new dialog by sending an initial message. The parameters are all the values needed for the initial request to which the notify function and parameter are added. The b2b_cback parameter is a pointer to the callback that must be called when an event happens(receiving a reply or request) in the dialog created with this function. The add_dlginfo_f parameter is also a function pointer to a callback that will be called when a final success response will be received for the created dialog. The callback will receive as parameter the complete dialog information for the record. It should be stored and used when calling send_request or send_reply functions.

The return value is an identifier for the record that will be mentioned when calling other functions that represent actions in the dialog(send request, send reply).

send_request

Field type:

...
typedef int (*b2b_send_request_t)(enum b2b_entity_type ,str* b2b_key, str* method,
    str* extra_headers, str* body, b2b_dlginfo_t*);
...

This function asks the b2b_entities modules to send a request inside a b2b dialog identified by b2b_key. The first parameter is the entity type and can have two values: B2B_SERVER and B2B_CLIENT. The second is the identifier returned by the create function(server_new or client_new) and the next are the informations needed for the new request: method, extra_headers, body. The last parameter contains the dialog information - callid, to tag, from tag. These are needed to make a perfect match to of b2b_entities record for which a new request must be sent.

The return value is 0 for success and a negative value for error.

send_reply

Field type:

...
typedef int (*b2b_send_reply_t)(enum b2b_entity_type et, str* b2b_key, int code, str* text,
    str* body, str* extra_headers, b2b_dlginfo_t* dlginfo);
...

This function asks the b2b_entities modules to send a reply inside a b2b dialog identified by b2b_key. The first parameter is the entity type and can have two values: B2B_SERVER and B2B_CLIENT. The second is the identifier returned by the create function(server_new or client_new) and the next are the informations needed for the new reply: code, text, body, extra_headers. The last parameter contains the dialog information used for matching the right record.

The return value is 0 for success and a negative value for error.

entity_delete

Field type:

...
typedef void (*b2b_entity_delete_t)(enum b2b_entity_type et, str* b2b_key,
   b2b_dlginfo_t* dlginfo);
...

This function must be called by the upper level function to delete the records in b2b_entities. The records are not cleaned up by the b2b_entities module and the upper level module must take care to delete them.

restore_logic_info

Field type:

...
typedef int (*b2b_restore_linfo_t)(enum b2b_entity_type type, str* key,
    b2b_notify_t cback, void *param, b2b_param_free_cb free_param);
...

This function is used at startup when loading the data from the database to restore the pointer to the callback function.

update_b2bl_param

Field type:

...
typedef int (*b2b_update_b2bl_param_t)(enum b2b_entity_type type, str* key,
    str* param, int replicate);
...

This function can be used to change the logic param stored for an entity ( useful in case an entity is moved between logic records).

Contributors

By Commit Statistics

Top contributors by DevScore⁽¹⁾, authored commits⁽²⁾ and lines added/removed⁽³⁾

#	Name	DevScore	Commits	Lines++	Lines—
1.	Anca Vamanu	189	94	7072	2093
2.	Vlad Patrascu (@rvlad-patrascu)	136	62	5751	1455
3.	Razvan Crainea (@razvancrainea)	92	72	945	671
4.	Bogdan-Andrei Iancu (@bogdan-iancu)	61	51	583	270
5.	Ovidiu Sas (@ovidiusas)	58	42	1047	408
6.	Liviu Chircu (@liviuchircu)	23	17	157	188
7.	Stefan Darius (@dariusstefan)	19	5	1154	207
8.	Carsten Bock	7	4	105	79
9.	Vlad Paiu (@vladpaiu)	6	4	78	51
10.	Maksym Sobolyev (@sobomax)	6	4	29	22

All remaining contributors: Nick Altmann (@nikbyte), Giedrius, Stanislaw Pitucha, Peter Lemenkov (@lemenkov), Ionut Ionita (@ionutrazvanionita), @DMOsipov, Walter Doekes (@wdoekes), Stéphane Alnet (@shimaore), Ryan Bullock (@rrb3942), Henk Hesselink, Ibrahim Shahzad.

(1) DevScore = author_commits + author_lines_added / (project_lines_added / project_commits) + author_lines_deleted / (project_lines_deleted / project_commits)

(2) including any documentation-related commits, excluding merge commits

(3) ignoring whitespace edits, renamed files and auto-generated files

By Commit Activity

#	Name	Commit Activity
1.	Stefan Darius (@dariusstefan)	Jun 2026 - Jul 2026
2.	Razvan Crainea (@razvancrainea)	Dec 2010 - Jun 2026
3.	Bogdan-Andrei Iancu (@bogdan-iancu)	Aug 2009 - Dec 2025
4.	Ovidiu Sas (@ovidiusas)	Nov 2010 - Nov 2025
5.	Ibrahim Shahzad	Jul 2025 - Jul 2025
6.	Liviu Chircu (@liviuchircu)	Mar 2014 - Sep 2024
7.	Maksym Sobolyev (@sobomax)	Jan 2021 - Nov 2023
8.	Vlad Patrascu (@rvlad-patrascu)	May 2017 - Jun 2023
9.	Giedrius	Apr 2023 - May 2023
10.	Carsten Bock	Mar 2022 - Apr 2022

All remaining contributors: Nick Altmann (@nikbyte), Peter Lemenkov (@lemenkov), @DMOsipov, Ionut Ionita (@ionutrazvanionita), Walter Doekes (@wdoekes), Vlad Paiu (@vladpaiu), Ryan Bullock (@rrb3942), Stéphane Alnet (@shimaore), Anca Vamanu, Henk Hesselink, Stanislaw Pitucha.

(1) including any documentation-related commits, excluding merge commits

Documentation

Contributors

Last edited by: Razvan Crainea (@razvancrainea), Liviu Chircu (@liviuchircu), Vlad Patrascu (@rvlad-patrascu), Carsten Bock, Peter Lemenkov (@lemenkov), Bogdan-Andrei Iancu (@bogdan-iancu), Vlad Paiu (@vladpaiu), Ovidiu Sas (@ovidiusas), Anca Vamanu.

License

All documentation files (i.e. .md extension) are licensed under the Creative Common License 4.0