Long TXT record

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Long TXT record

Gabriele Nencioni
Hi,
I know that this topic is already discussed on the ml (and I have just
read the related posts), but I have a doubt about my pdns version.


So... I have a PowerDNS Authoritative Server version 2.9.22 configured
with a mysql backend version 5.1.61 where the records structure table is
the following:

Table: records
Create Table: CREATE TABLE `records` (
   `id` int(11) NOT NULL AUTO_INCREMENT,
   `domain_id` int(11) NOT NULL,
   `name` varchar(255) NOT NULL,
   `type` varchar(6) NOT NULL,
   `content` varchar(255) NOT NULL,
   `ttl` int(11) NOT NULL,
   `prio` int(11) DEFAULT NULL,
   `change_date` int(11) DEFAULT NULL,
   PRIMARY KEY (`id`),
   KEY `nametype_index` (`name`,`type`),
   KEY `domain_id` (`domain_id`)
) ENGINE=InnoDB AUTO_INCREMENT=37680801 DEFAULT CHARSET=utf8
1 row in set (0.00 sec)


My question is:
is it possible perform an alter table to change the column field in a
varchar(64000) in order to insert a TXT record longer than 255 bytes?
If so, can pdns serve the long TXT records (after tha operation)?
If so, how will pdns serve the long records, splitting them?

I saw that it is already so with the latest pdns version, but I don't
know if it is possible with the 2.9.22 version.

Thanks in advance
Regards,

--
Gabriele Nencioni
System Administrator
eml [hidden email]

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Re: Long TXT record

Craig Whitmore
> My question is:
> is it possible perform an alter table to change the column field in a
> varchar(64000) in order to insert a TXT record longer than 255 bytes?
> If so, can pdns serve the long TXT records (after tha operation)?
> If so, how will pdns serve the long records, splitting them?

You cannot have a single TXT record longer than 255 characters..

http://www.faqs.org/rfcs/rfc1035.html Section 2.3.4

And if you want longer records then see..

http://tools.ietf.org/html/rfc4408#section-3.1.3

Do you want to create invalid DNS packets?


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Re: Long TXT record

Pieter Lexis-2
In reply to this post by Gabriele Nencioni
Hi Gabriele,

On 08/05/2015 08:58 AM, Gabriele Nencioni wrote:
> My question is:
> is it possible perform an alter table to change the column field in a
> varchar(64000) in order to insert a TXT record longer than 255 bytes?
> If so, can pdns serve the long TXT records (after tha operation)?
> If so, how will pdns serve the long records, splitting them?
>
> I saw that it is already so with the latest pdns version, but I don't
> know if it is possible with the 2.9.22 version.

It is not possible in the 2.9 series to have TXT records (or content)
longer than 255 characters. You can always create multiple TXT records
for the same name. If you to an alter table, add the larger txt record
and request it, you'll get a broken packet.

Also, please consider upgrading to PowerDNS 3.X as the 2.9 series is
absolutely end of life [1].

Best regards,

Pieter Lexis

1 - https://doc.powerdns.com/md/end-of-life/

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Re: Long TXT record

Gabriele Nencioni
In reply to this post by Craig Whitmore
Hi,
thanks for your reply

On 08/05/2015 10:47 AM, Craig Whitmore wrote:

>> My question is:
>> is it possible perform an alter table to change the column field in a
>> varchar(64000) in order to insert a TXT record longer than 255 bytes?
>> If so, can pdns serve the long TXT records (after tha operation)?
>> If so, how will pdns serve the long records, splitting them?
>
> You cannot have a single TXT record longer than 255 characters..
>
> http://www.faqs.org/rfcs/rfc1035.html Section 2.3.4
>
> And if you want longer records then see..
>
> http://tools.ietf.org/html/rfc4408#section-3.1.3
>
> Do you want to create invalid DNS packets?
Obviously not!

Probably I badly explained myself.

I know that the size limit is 255 chars, and given that there is the way
to create a multiple string in a single dns record;

then my question was: does pdns 2.9.22 support the multiple string once
the the content field size has been changed from varchar(255) to
varchar(64000)?


Regards,
--
Gabriele Nencioni
System Administrator
eml [hidden email]

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