Table of Contents
List of Examples
max_limit parametermaxfwd_process usageis_maxfwd_lt usageTable of Contents
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.
The following modules must be loaded before this module:
No dependencies on other Kamailio modules.
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”.
Note: This check is done when calling the maxfwd_process() function.
The range of values stretches from 1 to 256, which is the maximum MAX-FORWARDS value allowed by RFC 3261. Its value can be changed at runtime.
Default value is “256”.
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). The parameter can be a variable.
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. maxfwd_process usage
...
# initial sanity checks -- messages with
# max_forwards==0, or excessively long requests
if (!maxfwd_process("10") && $retcode==-1) {
sl_send_reply("483","Too Many Hops");
exit;
};
...
Checks if the Max-Forward header value is less then the “max_value” parameter value. It considers also the value of the new inserted header (if locally added). The parameter can be a variable.
Retuning codes:
1 (true) - header was found or set and its value is stricly less than “max_value”.
-1 (false) - the header was found or set and its value is greater or equal to “max_value”.
-2 (false) - header was not found or not set.
-3 (false) - error during processing.
The return code may be extensivly tested via script variable “retcode” (or “$?”).
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;
};
...