TXT record data length limit is too short

Bug #1595265 reported by Paul Glass on 2016-06-22
18
This bug affects 3 people
Affects Status Importance Assigned to Milestone
Designate
Low
Unassigned

Bug Description

A similar bug is reported here as "fixed" https://bugs.launchpad.net/designate/+bug/1474012. The limit on TXT data is now 255 bytes, which is too short for certain use cases. Designate should support creation of TXT records with data much longer than 255 bytes.

Kiall Mac Innes (kiall) wrote :
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Some notes on this:

 <mugsie> #topic bug triage
 * openstack has changed topic for #openstack-meeting-alt to: "bug triage (Meeting topic: Designate)"
 <timsim> https://bugs.launchpad.net/designate/+bug/1595265
 <openstack> Launchpad bug 1595265 in Designate "TXT record data length limit is too short" [Undecided,New]
 <Kiall> I think we already have a bug for that
 <mugsie> its closed
 <Kiall> No, a diff one
 <Kiall> 1 sec
 <mugsie> oh
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 <Kiall> https://bugs.launchpad.net/designate/+bug/1474012 is closed alright
 <openstack> Launchpad bug 1474012 in Designate "Incorrect length limit for TXT record data" [Medium,Fix committed] - Assigned to Federico Ceratto (federico-ceratto)
 <mugsie> I think this is more of a feature req ?
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 <federico3> since quite a while
 <Kiall> So - I think it's a rather large change to make it work with longer than 255 chars
 <mugsie> yeah
 <timsim> Kiall: We don't use a varchar(255) col for it
 <Kiall> Technically, we support only single part TXT recrods, where each part is at most 255 charas
 <mugsie> as it will change who it is stored, and how we conncatinate it in mdns
 <Kiall> anything more needs to be split in the DNS wire format response... but.. where do we split?
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 <Kiall> i.e. TXT is defined as an array of strings, each up to 255 chars long.
 <Kiall> we don't have it modeled as an array
 <timsim> So we'd have to split it every 255 into multiple records?
 <timsim> oh i see
 <mugsie> I dont think we can target this to a particular relase anyway
 <Kiall> Not multiple records, just in the TXT's rdata
 <mugsie> we can mark it as low ?
 <mugsie> and if someone has cycles, propose a spec to show how we can fix it?
 <Kiall> i.e. foo.com. IN TXT "255 chars" "255 chars" "255 chars"
 <timsim> pglass what was the thing that made us run into this?
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 <pglass> uhh, it's not big enough for spf records or something
 <Kiall> <sidenote>Use SPF inclides</sidenote>
 <Kiall> includes*
 <Kiall> We *may* be able to hard split on 255, or split on word boundaries, or something.. but I've no clue how valid that is
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 <mugsie> Kiall: can you dump ^ into the bug?
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 <mugsie> and say we will want a spec for any fix
 <Kiall> <sidenode> SPF includes look like this.... _spf.google.com. 295 IN TXT "v=spf1 include:_netblocks.google.com include:_netblocks2.google.com include:_netblocks3.google.com ~all"</sidenote>
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Tim Simmons (timsim) on 2016-06-29
Changed in designate:
status: New → Triaged
importance: Undecided → Low
Dmitry Galkin (galkindmitrii) wrote :
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Hi All,

I've wrote a patch to address this issue and it allows to create TXT records that are longer than 255 chars. But there is a question below that, perhaps, somebody can answer.

[root@aio1-utility-container-10fda1d7 ~]# openstack recordset show 50bb30dd-5c84-42fc-b2e7-fc37a198ccfd aeb5681d-edca-4f30-8aec-47c3f35adbc0
+-------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| Field | Value |
+-------------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+
| action | NONE |
| created_at | 2017-12-15T10:17:13.000000 |
| description | test |
| id | aeb5681d-edca-4f30-8aec-47c3f35adbc0 |
| name | test7.openstack.tech. |
| project_id | b8a1e1371d22406cb89afd936cb20d0e |
| records | bbbbbbbbbbbb...

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Graham Hayes (grahamhayes) wrote :

The problem is that for long txt records, it is actually a list of strings, each under 255.

We would need to split the string then send that to eventlet's DNS sub system

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