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Diversion Module
Jan Janak
FhG FOKUS
Edited by
Jan Janak
Copyright 2004 FhG FOKUS
_________________________________________________________
Table of Contents
1. User's Guide
1.1. Overview
1.2. Dependencies
1.2.1. OpenSER Modules
1.2.2. External Libraries or Applications
1.3. Exported Parameters
1.3.1. suffix (string)
1.4. Exported Functions
1.4.1. add_diversion(reason)
1.4.2. Diversion Example
2. Developer's Guide
3. Frequently Asked Questions
List of Examples
1-1. suffix usage
1-2. add_diversion usage
_________________________________________________________
Chapter 1. User's Guide
1.1. 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.
Warning
The draft-levy-sip-diversion-08 is expired!! See IETF I-D
tracker.
_________________________________________________________
1.2. Dependencies
1.2.1. OpenSER Modules
None.
_________________________________________________________
1.2.2. External Libraries or Applications
The following libraries or applications must be installed
before running OpenSER with this module loaded:
* None.
_________________________________________________________
1.3. Exported Parameters
1.3.1. 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).
Example 1-1. suffix usage
modparam("diversion", "suffix", ";privacy=full")
_________________________________________________________
1.4. Exported Functions
1.4.1. 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.
Example 1-2. add_diversion usage
...
add_diversion("user-busy");
...
_________________________________________________________
1.4.2. 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
_________________________________________________________
Chapter 2. Developer's 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;
}
...
}
_________________________________________________________
Chapter 3. Frequently Asked Questions
3.1. Where can I find more about OpenSER?
3.2. Where can I post a question about this module?
3.3. How can I report a bug?
3.1. Where can I find more about OpenSER?
Take a look at http://openser.org/.
3.2. Where can I post a question about this module?
First at all check if your question was already answered on
one of our mailing lists:
* User Mailing List -
http://openser.org/cgi-bin/mailman/listinfo/users
* Developer Mailing List -
http://openser.org/cgi-bin/mailman/listinfo/devel
E-mails regarding any stable OpenSER release should be sent to
<users@openser.org> and e-mails regarding development versions
should be sent to <devel@openser.org>.
If you want to keep the mail private, send it to
<team@openser.org>.
3.3. How can I report a bug?
Please follow the guidelines provided at:
http://sourceforge.net/tracker/?group_id=139143.
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