1. Maxfwd Module

Bogdan Iancu

   FhG FOKUS

   Copyright © 2003 FhG FOKUS
     __________________________________________________________________

   1.1. Overview
   1.2. Functions

        1.2.1. maxfwd_process(max_value)
        1.2.2. maxfwd_at_least(min_value)

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. Functions

1.2.1.  maxfwd_process(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". An OK
   code is returned by the function.

   If a Max-Forward header is already present, its value will be
   decremented. If after this operation its value will be positive
   non-zero, an OK code will be returned. Otherwise (for a zero value) an
   error code will be returned. Note that an error code will be also
   returned if the SIP message couldn't be parsed or if the Max-Forward
   header's body invalid (non numerical string or negative numerical
   value).

   Meaning of the parameters is as follows:
     * max_value - Value to be added if there is no Max-Forwards header
       field in the message.

   Example 1. maxfwd_process usage
# initial sanity checks -- messages with
# max_forwards==0, or excessively long requests
if (!maxfwd_process(10)) {
    sl_send_reply(483, "Too many hops");
    drop;
};

1.2.2.  maxfwd_at_least(min_value)

   Test is there is enough hops in Max-forward header, i.e. we know how
   many hops is required to reach target. Returns true if Max-Forward
   header is present in the received request and the value is greater than
   "min_value".

   Meaning of the parameters is as follows:
     * min_value - Min. number of required hops

   Example 2. maxfwd_at_least usage
if (!maxfwd_at_least(3)) {
    sl_send_reply(483, "Too many hops");
    drop;
};