Unexpected behavior with pick-first-value

Wed Apr 27 15:04:57 UTC 2016

Hi Glenn, thanks for your answer.
Yes, "if" evaluation it's discarded.

I now understood why the behavior of pick-first-value, I was 
interpreting a match functionality for the purposes of comparing and 
passes to the next, etc, now I see that it is not. Thanks for the 
lighting :).

Cheers, Bernardo.

------ Original Message ------
From: "Glenn Satchell" <glenn.satchell at uniq.com.au>
To: "Users of ISC DHCP" <dhcp-users at lists.isc.org>
Sent: 27/04/2016 11:39:28
Subject: Re: Unexpected behavior with pick-first-value

>ok, thinking more about it, that syntax won't work.
>
>However, what's happenning in your case is that the option
>dhcp-client-identifier is non-null so gets chosen but that string 
>doesn't
>match the sub-class string. What it doesn't do is match any of the 
>three,
>and thinking about it I can't see how you might do that without a gian
>'if' statement.
>
>It looks like you have read the dhcp-eval man page.
>
>regards,
>-glenn
>
>On Thu, April 28, 2016 12:22 am, Bernardo wrote:
>>  Hi Glenn, thanks for your answer.
>>
>>  I tried with your proposal and gives me error:
>>
>>  class "test" { match (option dhcp-client-identifier or hardware or
>>                                                              ^
>>  Configuration file errors encountered -- exiting
>>
>>  The "^" it's points to hardware. Remember that I use the version 
>>3.1.1.
>>
>>  Anyway, even though English is not my native language, I understand 
>>that
>>  pick-first-value would have to return the match as the manual says 
>>"Each
>>  expression is evaluated, starting with the first in
>>  the list, until an expression is found that does not evaluate to a 
>>null
>>  value.".
>>
>>  Cheers, Bernardo.
>>
>>  ------ Original Message ------
>>  From: "Glenn Satchell" <glenn.satchell at uniq.com.au>
>>  To: "Users of ISC DHCP" <dhcp-users at lists.isc.org>
>>  Sent: 27/04/2016 11:07:21
>>  Subject: Re: Unexpected behavior with pick-first-value
>>
>>>Hi Bernado
>>>
>>>pick-first-value is working as specified. The thing to be matched
>>>against
>>>is the first non-null value in the list. Therefore in your first case
>>>where you have:
>>>
>>>match pick-first-value (option dhcp-client-identifier, hardware,
>>>suffix(option dhcp-client-identifier, 7));
>>>
>>>the thing to be matched against is option dhcp-client-identifier.
>>>
>>>If you want to match against any of the three you need to use match 
>>>...
>>>or
>>>... or ..., for example:
>>>
>>>match (option dhcp-client-identifier or hardware or suffix(option
>>>dhcp-client-identifier, 7));
>>>
>>>regards,
>>>-glenn
>>>
>>>On Wed, April 27, 2016 11:59 pm, Bernardo wrote:
>>>>   Hi,
>>>>
>>>>   I running a DHCP Server version V3.1.1 and I have the following
>>>>   situation in which I expect that pick-first-value works in a 
>>>>certain
>>>>way
>>>>   and do not get it.
>>>>
>>>>   I have this information from DHCP for the device:
>>>>
>>>>   Client-identifier: ff:10:08:19:d9:00:03:00:01:bc:c8:10:08:19:d9
>>>>   Hardware: 1:bc:c8:10:8:19:d9
>>>>
>>>>   To obtain this information I use the following logs:
>>>>
>>>>   log (info, concat ("Lease request from hardware ",
>>>>binary-to-ascii(16,
>>>>   8, ":", substring(hardware, 0, 7)), " in subnet xx"));
>>>>   log (info, concat ("Lease request from identifier ",
>>>>binary-to-ascii(16,
>>>>   8, ":", option dhcp-client-identifier), " in subnet xx"));
>>>>   log (info, concat ("Lease request from suffix identifier ",
>>>>   binary-to-ascii(16, 8, ":", suffix(option dhcp-client-identifier,
>>>>7)), "
>>>>   in subnet xx"));
>>>>
>>>>   And the results is:
>>>>
>>>>   Apr 27 06:27:01 dev dhcpd: Lease request from hardware
>>>>   1:bc:c8:10:8:19:d9 in subnet xx
>>>>   Apr 27 06:27:01 dev dhcpd: Lease request from identifier
>>>>   ff:10:8:19:d9:0:3:0:1:bc:c8:10:8:19:d9 in subnet xx
>>>>   Apr 27 06:27:01 dev dhcpd: Lease request from suffix identifier
>>>>   1:bc:c8:10:8:19:d9 in subnet xx
>>>>
>>>>   I use these very simple instructions to create a class and 
>>>>subclass:
>>>>
>>>>   class "test" { match pick-first-value (option 
>>>>dhcp-client-identifier,
>>>>   hardware, suffix(option dhcp-client-identifier, 7)); }
>>>>   subclass "test" 1:bc:c8:10:08:19:d9 {}
>>>>
>>>>   So, here the problem, I expect that if Client-identifier does not
>>>>match
>>>>   try with the hardware data and then with suffix data, right, but 
>>>>this
>>>>   does not happen.
>>>>
>>>>   I change the match for this pick-first-value (hardware, option
>>>>   dhcp-client-identifier) and then the device it's classified under 
>>>>the
>>>>   test class.
>>>>   I change the match for this pick-first-value (option
>>>>   dhcp-client-identifier, suffix(option dhcp-client-identifier, 7),
>>>>   hardware) and then the device it's not classified.
>>>>   I change the match for this pick-first-value (suffix(option
>>>>   dhcp-client-identifier, 7), option dhcp-client-identifier, 
>>>>hardware)
>>>>and
>>>>   then the device it's classified under the test class.
>>>>
>>>>   So, apparently pick-first-value classifies only when the first 
>>>>data
>>>>   matches the declared value in a subclass.
>>>>
>>>>   I'm missing something ? It is this the behavior expected ? I copy
>>>>below
>>>>   what the manual says regarding pick-first-value:
>>>>
>>>>   pick-first-value (data-expr1 [ ... exprn ] )
>>>>
>>>>   The pick-first-value function takes any number of data expressions 
>>>>as
>>>>   its arguments. Each expression is evaluated, starting with the 
>>>>first
>>>>in
>>>>   the list, until an expression is found that does not evaluate to a
>>>>null
>>>>   value. That expression is returned, and none of the subsequent
>>>>   expressions are evaluated. If all expressions evaluate to a null
>>>>value,
>>>>   the null value is returned.
>>>>
>>>>   P.S.: I have solved my problem with the last example of a match, 
>>>>but
>>>>I
>>>>   wonder if I'm doing something wrong with my analysis.
>>>>
>>>>   Greetings, Bernardo.
>>>>
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>>>>
>>>
>>>
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