[Pdns-users] Multipart TXT records
Julian Mehnle
julian at mehnle.net
Mon Mar 1 19:25:57 UTC 2010
Leen Besselink wrote:
> You can also see that here:
>
> http://doc.powerdns.com/changelog.html
>
> I'm unsure about what it does mean though.
>
> My first thought would be that it's code to split large TXT-records
> over different TXT-records.
>
> Or just that multi TXT-records didn't work at all, a bug, as mentioned
> in the log.
I think pre-2.9.21, multi-"part" TXT records didn't work at all.
Actually, RFC 1035 defines a TXT RR to be composed of "One or more
<character-string>s" (not "parts", and a <character-string> as:
"a single length octet followed by that number of characters.
<character-string> is treated as binary information, and can be up
to 256 characters in length (including the length octet)".
Thus the rationale for having more than one (character) strings in a
single TXT RR is to build a TXT RR that is longer than 255 characters.
The way TXT RRs work in the PowerDNS authoritative server is that each of
a TXT RR's strings must be enclosed in double quotes, even if the TXT RR
consists of only a single string.
E.g.:
"foo bar quux" (single string)
"foo " "bar " "quux" (three strings)
Those values still need to be quoted when specified in an SQL command.
E.g.:
INSERT INTO dns_records (name, rrtype, content) VALUES (
'txt.example.com', 'TXT', '"foo bar quux")
INSERT INTO dns_records (name, rrtype, content) VALUES (
'txt.example.com', 'TXT', '"foo " "bar " "quux"')
-Julian
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