DIVERSION module

Admin Guide

Overview

The module implements the Diversion extensions as per draft-levy-sip-diversion-08. The diversion extensions are useful in various scenarios involving call forwarding. Typically one needs to communicate the original recipient of the call to the PSTN gateway and this is what the diversion extensions can be used for.

Dependencies

OpenSIPS Modules

None.

External Libraries or Applications

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

None.

Exported Parameters

suffix (string)

The suffix to be appended to the end of the header field. You can use the parameter to specify additional parameters to be added to the header field, see the example.

Default value is "" (empty string).

modparam("diversion", "suffix", ";privacy=full")

Exported Functions

add_diversion(reason)

The function adds a new diversion header field before any other existing Diversion header field in the message (the newly added Diversion header field will become the topmost Diversion header field). The inbound (without any modifications done by the proxy server) Request-URI will be used as the Diversion URI.

Meaning of the parameters is as follows:

reason - The reason string to be added as the reason parameter

This function can be used from REQUEST_ROUTE, FAILURE_ROUTE.

...
add_diversion("user-busy");
...

Diversion Example

The following example shows a Diversion header field added to INVITE message. The original INVITE received by the user agent of sip:bob@sip.org is:

INVITE sip:bob@sip.org SIP/2.0
Via: SIP/2.0/UDP 1.2.3.4:5060
From: "mark" <sip:mark@sip.org>;tag=ldgheoihege
To: "Bob" <sip:bob@sip.org>
Call-ID: adgasdkgjhkjha@1.2.3.4
CSeq: 3 INVITE
Contact: <sip:mark@1.2.3.4>
Content-Length: 0

The INVITE message is diverted by the user agent of sip:bob@sip.org because the user was talking to someone else and the new destination is sip:alice@sip.org :

INVITE sip:alice@sip.org SIP/2.0
Via: SIP/2.0/UDP 5.6.7.8:5060
Via: SIP/2.0/UDP 1.2.3.4:5060
From: "mark" <sip:mark@sip.org>;tag=ldgheoihege
To: "Bob" <sip:bob@sip.org>
Call-ID: adgasdkgjhkjha@1.2.3.4
CSeq: 3 INVITE
Diversion: <sip:bob@sip.org>;reason=user-busy
Contact: <sip:mark@1.2.3.4>
Content-Length: 0

Developer Guide

According to the specification new Diversion header field should be inserted as the topmost Diversion header field in the message, that means before any other existing Diversion header field in the message. In addition to that, add_diversion function can be called several times and each time it should insert the new Diversion header field as the topmost one.

In order to implement this, add_diversion function creates the anchor in data_lump lists as a static variable to ensure that the next call of the function will use the same anchor and would insert new Diversion headers before the one created in the previous execution. To my knowledge this is the only way of inserting the diversion header field before any other created in previous runs of the function.

The anchor kept this way is only valid for a single message and we have to invalidate it when another message is being processed. For this reason, the function also stores the id of the message in another static variable and compares the value of that variable with the id of the SIP message being processed. If they differ then the anchor will be invalidated and the function creates a new one.

The following code snippet shows the code that invalidates the anchor, new anchor will be created when the anchor variable is set to 0.

static inline int add_diversion_helper(struct sip_msg* msg, str* s)
{
    static struct lump* anchor = 0;
    static int msg_id = 0;

    if (msg_id != msg->id) {
        msg_id = msg->id;
        anchor = 0;
    }
...
}

Contributors

By Commit Statistics

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

#	Name	DevScore	Commits	Lines++	Lines—
1.	Daniel-Constantin Mierla (@miconda)	15	13	29	21
2.	Bogdan-Andrei Iancu (@bogdan-iancu)	15	12	103	75
3.	Jan Janak (@janakj)	10	4	529	14
4.	Stefan Darius (@dariusstefan)	7	4	213	37
5.	Henning Westerholt (@henningw)	5	3	3	27
6.	Konstantin Bokarius	3	1	3	5
7.	Razvan Crainea (@razvancrainea)	3	1	2	2
8.	Edson Gellert Schubert	3	1	0	92
9.	Andreas Heise	2	1	1	0

(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)	Jun 2026 - Jun 2026
3.	Bogdan-Andrei Iancu (@bogdan-iancu)	Jul 2005 - Aug 2009
4.	Henning Westerholt (@henningw)	Apr 2007 - May 2008
5.	Daniel-Constantin Mierla (@miconda)	Oct 2005 - Mar 2008
6.	Konstantin Bokarius	Mar 2008 - Mar 2008
7.	Edson Gellert Schubert	Feb 2008 - Feb 2008
8.	Andreas Heise	Oct 2007 - Oct 2007
9.	Jan Janak (@janakj)	Nov 2004 - Dec 2004

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

Documentation

Contributors

Last edited by: Razvan Crainea (@razvancrainea), Bogdan-Andrei Iancu (@bogdan-iancu), Daniel-Constantin Mierla (@miconda), Konstantin Bokarius, Edson Gellert Schubert, Jan Janak (@janakj).

License

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