[Dnsmasq-discuss] dhcp-option and vendor class

[Ben]

Simon Kelley wrote:
> Ben wrote:
>> Simon Kelley wrote:
>>> Ben wrote:
>>>> This works:
>>>>
>>>>  dhcp-vendorclass=apc,APC
>>>>  dhcp-option=apc,43,01:04:31:41:50:43:02:01:01
>>>>
>>>> but this doesn't:
>>>>
>>>>  dhcp-option=vendor:APC,43,01:04:31:41:50:43:02:01:01
>>>>
>>>> What am I missing here?  Shouldn't the "vendor:APC" syntax work?
>>>
>>> It does work: it does the encapsulation for you, so you need
>>>
>>> dhcp-option=vendor:APC,01,31:41:50:43
>>> dhcp-option=vendor:APC,02,01:01
>>>
>>> depending on what those options are, you may what to use a more 
>>> natural representation than hex bytes.
>>>
>>>
>>> Your second example is taking the already-encapsulated options, 
>>> treating them as a single option and encapsulating them again, which 
>>> confuses things somewhat.
>>>>
>>>
>>> Cheers,
>>>
>>> Simon.
>>>
>>>
>>>
>> Simon,
>>
>> Thanks for the reply but i am afraid i still don't get it.
>>
>> I pulled that string straight from the APC manual without knowing 
>> what it means. 
>> http://www.apcmedia.com/salestools/ASTE-6Z5QEW_R0_EN.pdf page 61/62.
>>
>> How would i go about representing it in a more natural way?
>>
>> Ben
>>
>
>
> Apolgies, I assumed too much in my first reply.
>
> dhcp options are represented like this:
>
> <option number> <length of data> <bytes of data>
>
> packed together, with an 0xff option number to mark the end. The 
> option numbers are defined by IETF. Encapulated options is the IETF 
> option number 43, and the data part contains a complete set of options 
> "nested" inside it, but of course with the options numbers privately 
> defined by the vendor.
>
> So your
>
> dhcp-option=apc,43,01:04:31:41:50:43:02:01:01
>
> will generate the byte-string (43 is 2b hex)
>
> 2b:09:01:04:31:41:50:43:02:01:01
>
> and the encapsulated options in the data part are
>
> 01 (length 4) 31:41:50:43
> 02 (length 1) 01
>
> Looking at the documentation, the APC is expecting the string "1APC" 
> as encapsulated option 1 and a flag which enables use of BOOTP or DHCP 
> as encapsulated option 2
>
> so we can represnt these as
>
> dhcp-option=vendor:APC,1,"1APC"
> dhcp-option=vendor:APC,2,1b
>
> The "b" after the one tells dnsmasq that the integer "1" is to be 
> represented as a single byte. (It knows this stuff for IETF options, 
> but not for privately defined ones)
>
> dnsmasq will send these options only if the client send a vendor class 
> which matches "APC" and will gather them together withing an 
> encapsulating option 43 - just what you want.
>
> HTH
>
> Simon.
>
Simon,

Thanks again for the huge help. After sleeping on it it makes more sense.

I will put that in place and test it out.

Ben