NAME

       rlm_expr - FreeRADIUS Module

DESCRIPTION

       The  rlm_expr module allows the server to perform limited mathematical calculations.  This
       module is not called directly in any section, it is invoked through the dynamic  expansion
       of strings.

       For example, some NAS boxes send a NAS-Port attribute which is a 32-bit number composed of
       port, card, and interface, all in different bytes.  To see  these  attributes  split  into
       pieces, you can have an entry in the 'users' file like:

       DEFAULT
           Vendor-Interface = `%{expr: %{NAS-Port} / (256 * 256)}`,
           Vendor-Card = `%{expr: (%{NAS-Port} / 256) %% 256}`,
           Vendor-Port = `%{expr: %{NAS-Port} %% 256}`

       where the attributes Vendor-Interface, Vendor-Card, and Vendor-Port are attributes created
       by either you or a vendor-supplied dictionary.

       The methematical operators supported by the expression module are:

       +      addition

       -      subtraction

       /      division

       %%     modulo remainder

       *      multiplication

       &      boolean AND

       |      boolean OR

       ()     grouping of sub-expressions

       NOTE: The modulo remainder operator is '%%',  and  not  '%'.   This  is  due  to  the  '%'
       character being used as a special character for dynamic translation.

       NOTE:  These  operators  do NOT have precedence.  The parsing of the input string, and the
       calculation of the answer, is done strictly left to right.   If  you  wish  to  order  the
       expressions, you MUST group them into sub-expression, as shown in the previous example.

       All of the calculations are performed as unsigned 32-bit integers.

CONFIGURATION

       modules {
         ...
         expr {
         }
         ...
       }
        ...
       instantiate {
         ...
         expr
         ...
       }

SECTIONS

       instantiate

FILES

       /etc/raddb/radiusd.conf

SEE ALSO

       radiusd(8), radiusd.conf(5)

AUTHOR

       Chris Parker, cparker@segv.org

                                         5 February 2004                              rlm_expr(5)