10.1.2 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 Macro Substitution).

7. wait-reply yes;

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