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maxfwd Module
Bogdan-Andrei Iancu
voice-system.ro
Edited by
Bogdan-Andrei Iancu
Copyright 2003 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. max_limit (integer)
1.4. Exported Functions
1.4.1. mf_process_maxfwd_header(max_value)
1.4.2. is_maxfwd_lt(max_value)
2. Developer's Guide
3. Frequently Asked Questions
List of Examples
1-1. Set max_limit parameter
1-2. mx_process_maxfwd_header usage
1-3. is_maxfwd_lt usage
_________________________________________________________
Chapter 1. User's Guide
1.1. Overview
The module implements all the operations regarding MaX-Forward
header field, like adding it (if not present) or decrementing
and checking the value of the existent one.
_________________________________________________________
1.2. Dependencies
1.2.1. OpenSER Modules
The following modules must be loaded before this module:
* No dependencies on other OpenSER modules.
_________________________________________________________
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. max_limit (integer)
Set an upper limit for the max-forward value in the outgoing
requests. If the header is present, the decremented value is
not allowed to exceed this max_limits - if it does, the header
value will by decreased to "max_limit".
The range of values stretches from 1 to 256, which is the
maximum MAX-FORWARDS value allowed by RFC 3261.
Default value is "256".
Example 1-1. Set max_limit parameter
...
modparam("maxfwd", "max_limit", 32)
...
_________________________________________________________
1.4. Exported Functions
1.4.1. mf_process_maxfwd_header(max_value)
If no Max-Forward header is present in the received request, a
header will be added having the original value equal with
"max_value". If a Max-Forward header is already present, its
value will be decremented (if not 0).
Retuning codes:
* 2 (true) - header was not found and a new header was
succesfully added.
* 1 (true) - header was found and its value was successfully
decremented (had a non-0 value).
* -1 (false) - the header was found and its value is 0
(cannot be decremented).
* -2 (false) - error during processing.
The return code may be extensivly tested via script variable
"retcode" (or "$?").
Meaning of the parameters is as follows:
* max_value - Value to be added if there is no Max-Forwards
header field in the message.
This function can be used from REQUEST_ROUTE.
Example 1-2. mx_process_maxfwd_header usage
...
# initial sanity checks -- messages with
# max_forwards==0, or excessively long requests
if (!mf_process_maxfwd_header("10") && retcode==-1) {
sl_send_reply("483","Too Many Hops");
exit;
};
...
_________________________________________________________
1.4.2. is_maxfwd_lt(max_value)
Checks if the Max-Forward header value is less then the
"max_value" parameter value. It considers also the value of
the new inserted header (if locally added).
Retuning codes:
* 1 (true) - header was found or set and its value is
stricly less than "max_value".
* -1 (false) - the header was found or set and its value is
greater or equal to "max_value".
* -2 (false) - header was not found or not set.
* -3 (false) - error during processing.
The return code may be extensivly tested via script variable
"retcode" (or "$?").
Meaning of the parameters is as follows:
* max_value - value to check the Max-Forward.value against
(as less than).
Example 1-3. is_maxfwd_lt usage
...
# next hope is a gateway, so make no sens to
# forward if MF is 0 (after decrement)
if ( is_maxfwd_lt("1") ) {
sl_send_reply("483","Too Many Hops");
exit;
};
...
_________________________________________________________
Chapter 2. Developer's Guide
The module does not provide any API to use in other OpenSER
modules.
_________________________________________________________
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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