SV: using variable

[Lars Jacobsen]

As i se it:

substring( option agent.circuit-id, 2,2)= "10"
means consider CID as text string and match from second character and two character ahead

substring( option agent.circuit-id, 2,2)= 10
means consider CID as integer and match from second byte and two bytes ahead

/Lars

-----Oprindelig meddelelse-----
Fra: dhcp-users-bounce at isc.org [mailto:dhcp-users-bounce at isc.org] På vegne af Pierre LEONARD
Sendt: 22. marts 2006 12:33
Til: dhcp-users at isc.org
Emne: Re: using variable

Simon Hobson a e'crit:
>Pierre LEONARD wrote:
>
>  
>
>>you understood my problem but there is another problem:
>>
>>/*class "vlan1-clients" { match if <insert conditions here> } ;
>>
>>*/it's not possible to use my variable instead of "<insert conditions
>>here>" and i don't why
>>i can just use it like following:
>>
>>/*set test = "value";
>>if test = "value" {<treatement>;}
>>*/
>>and the treatment cannot be a block subnet, shared-network, pool, class...
>>so i'm blocked
>>
>>
>>
>>_my complete code:_
>>
>>#checking vlan
>>if (binary-to-ascii (10, 16, "", substring( option agent.circuit-id, 2,
>>2))= "10" {
>>log(info , "checking vlan");
>>
>>#checking switch
>>if binary-to-ascii(16, 8, ":", substring( option agent.remote-id, 2, 6))
>>= "<mac address>") {
>>log( info, "checking switch mac address");
>>set test = "ok";
>>}
>>}
>>
>>#*********************************************class
>>definitions**************************************************
>>class "port20" {
>>match if binary-to-ascii (10, 8, "/", suffix( option agent.circuit-id,
>>2)) = "0/19";
>># match if test = "ok"; #launch but don't function
>>}
>>
>>class "port21" {
>>match if binary-to-ascii (10, 8, "/", suffix (option agent.circuit-id,
>>2)) = "0/20";
>># match if test = "ok"; #launch but don't function
>>}
>>    
>>
>
>OK, I can't help with the way you want to do it as I've never gone 
>into that detail with the server. But how about :
>
>class "s1p20" {
>   match if (substring( option agent.remote-id, 2, 6) = aa:bb:cc:dd:ee:ff)
>        and (suffix( option agent.circuit-id, 2) = 00:16) ;
>   log (info, "Switch 1, Port 0/20 matched" ) ;
>}
>
>Someone please correct me if I'm wrong, but I think you can specify a 
>hex string like that instead of using binary-to-ascii. Hence, a 
>decrease in size of the config, and a decrease in the processing 
>required to evaluate all the possible classes - note that the server 
>must evaluate every class definition since (in the general case) any 
>client may be a member of more than one class.
>
>Since this sort of thing should be machine generated anyway for 
>anything more than a trivial setup, it should be no problem using hex 
>like that.
>
>Simon
>
>
>
>  
>
i tried your proposition and all it's good but there is still a problem 
with the offset of the substring function
in each tutorial that i found in order to get the vlan we use the 
followinf syntaxe :

/substring( option agent.circuit-id, 2,2)= "10";
/
if we read the man we can explain this syntaxe like this : " 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" but it's not very logical because in this case substring 
return 2 bytes and begin at the the third byte (offset = 2).

unfortunately the structure of circuit-id is :

-----------------------------------------------------------------------------------------------------------------------------------------------------------
|suboption type (1) | length (1) | circuit-id type (1) | length (1) | 
vlan (2) | module (1) | port (1)|
-----------------------------------------------------------------------------------------------------------------------------------------------------------

in order to respect this structure the correct syntaxe of substring 
function to get the vlan had to be :

/substring (option agent circuit-id, 4, 2)= "10"; /but that does not 
function...

who could explain me why ?????