regexp or substring match

[Glenn Satchell]

On 07/21/10 05:17, Tony Hunter wrote:
> On Tue, Jul 20, 2010 at 02:58:46PM -0400, Adam Moffett wrote:
>> Could I put a client in a class based on his ethernet MAC address like so?:
>>
>> class "A1" {
>>        match if hardware ethernet=a:0:3e:d4:60:73;
>>      }
>>
>> If I can do that, is there a way to match only the first 3 bytes of
>> the MAC address, so that I'm assigning a certain ethernet vendor
>> code to a class?
>>
>> Like something along these lines:
>> class "A1" {
>>        match if hardware ethernet=a:0:3e:*;
>>      }
>
> We've used something very similar to match vendor specific hardware:
> class "joohong" {
> 	match if binary-to-ascii(16,8,":",substring(option dhcp-client-identifier,0,4)) = "1:0:50:d4" ;
> }
>

No need to convert to an ascii string first as you can compare as a 
binary hex list, eg:

class "A1" {
         match if substring(hardware, 0, 3) = a:0:3e;
}

With today's cpu speeds this optimisation probably makes little 
difference for any size of network, but you'll know you're doing your 
part :)

See the dhcp-eval man page for the list of functions available and the 
definition of strings, eg:

      substring (data-expr, offset, length)

        The substring operator evaluates the data  expression  and
        returns  the  substring  of  the result of that evaluation
        that starts offset bytes from  the  beginning,  continuing
        for  length  bytes.

      colon-separated hexadecimal list

        A list of hexadecimal octet values, separated  by  colons,
        may be specified as a data expression.

      string

        A string, enclosed in quotes, may be specified as  a  data
        expression,  and  returns  the  text  between  the quotes,
        encoded in  ASCII.

HTH

regards,
-glenn