11.1.2 Declaring the Filter

Here is how this filter is declared in the `raddb/config' file:

filters { filter check_clid { exec-path "/usr/libexec/myfilter"; error-log "myfilter.log"; auth { input-format "%C{User-Name} %C{Calling-Station-Id}"; wait-reply yes; }; }; };

Let's analyze this declaration line by line:

1. filters {

   This keyword opens the filters declaration block. The block may contain several declarations.

2. filter check_clid {

   This line starts the declaration of this particular filter and names it `check_clid'.

3. exec-path "/usr/libexec/myfilter";

   This line tells radiusd where to find the executable image of this filter.

4. error-log "myfilter.log";

   The diagnostic output from this filter must be redirected to the file `myfilter.log' in the current logging directory

5. auth {

   This filter will process authentication requests.

6. input-format "%C{User-Name} %C{Calling-Station-Id}";

   Define the input line format for this filter. The %C{} expressions will be replaced by the values of the corresponding attributes from the incoming request (see section 5.14 Macro Substitution).

7. wait-reply yes;

   radiusd will wait for the reply from this filter to decide whether to authenticate the user.