# &adminguide;

## Overview

The module implements the Diversion extensions as per RFC 5806. 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.

Note that RFC 5806 has historic status.

## Dependencies

### &kamailio; Modules

None.

### External Libraries or Applications

The following libraries or applications must be installed before running &kamailio; with this module loaded:

- None.

## 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).

#### `suffix` usage

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

## Functions

### `add_diversion(reason [, uri])`

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). If 'uri' parameter is missing, 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

- uri - The URI to be set in Diversion header

The parameters can contain pseudo-variables.

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

#### `add_diversion` usage

    ...
    add_diversion("user-busy");
    add_diversion("user-busy", "$ru");
    ...

## 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