Re: [Pdns-users] BIND-Zonefiles: @ vs blank

[Brian Candler]

On 08/08/2019 14:09, Michael Loftis wrote:


we have a zonefile which got recently added TXT entries for SPF
and DMARC:

_dmarc          IN      TXT     "v=DMARC1; p=none; rua=mailto:foo
"
                IN      MX      10 mx.domain.tld.
                IN      TXT     "v=spf1 include:spf1.domain.tld ?all"

Since then, requests for the MX record were not answered any more,
adding a @ fixed it.

I'm wondering now why this happens, as in other zonefiles without TXT
records the blank substitution works.


I've always had the understanding that blank meant "reuse last" so by 
adding the _dmarc TXT record ahead of the blank records you 
inadvertently moved them to be _dmarc.ZONE


You are correct.  All three records shown above are for _dmarc.ZONE

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Re: [Pdns-users] BIND-Zonefiles: @ vs blank

[Bjoern Franke]

Hey,

> 
> I've always had the understanding that blank meant "reuse last" so by
> adding the _dmarc TXT record ahead of the blank records you
> inadvertently moved them to be _dmarc.ZONE
> 
> I could certainly be wrong because I haven't looked at the man page for
> bind zone files in the last decade.

Thanks for that hint. As stated in RFC 1035[1] "If an entry for an RR
begins with a blank, then the RR is assumed to be owned by the last
stated owner". When there are only blanks, it's somehow "substitute with
the domain name", so i "bricked" the entry with the dmarc TXT record.
Only an old documentation for Bind on IRIX[2] says "A blank or tab
character in the name field denotes the current domain."

Regards
Bjoern


[1]https://tools.ietf.org/html/rfc1035
[2]http://csweb.cs.wfu.edu/~torgerse/Kokua/SGI/007-2860-008/sgi_html/apa.html#LE86111-PARENT


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Re: [Pdns-users] BIND-Zonefiles: @ vs blank

[Michael Loftis]

On Thu, Aug 8, 2019 at 07:01 Bjoern Franke  wrote:

> Hi,
>
> we have a zonefile which got recently added TXT entries for SPF and DMARC:
>
> _dmarc  IN  TXT "v=DMARC1; p=none; rua=mailto:foo;
> IN  MX  10 mx.domain.tld.
> IN  TXT "v=spf1 include:spf1.domain.tld ?all"
>
> Since then, requests for the MX record were not answered any more,
> adding a @ fixed it.
>
> I'm wondering now why this happens, as in other zonefiles without TXT
> records the blank substitution works.


I've always had the understanding that blank meant "reuse last" so by
adding the _dmarc TXT record ahead of the blank records you inadvertently
moved them to be _dmarc.ZONE

I could certainly be wrong because I haven't looked at the man page for
bind zone files in the last decade.



>
> Kind regards
> Bjoern
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-- 

"Genius might be described as a supreme capacity for getting its possessors
into trouble of all kinds."
-- Samuel Butler
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[Pdns-users] BIND-Zonefiles: @ vs blank

[Bjoern Franke]

Hi,

we have a zonefile which got recently added TXT entries for SPF and DMARC:

_dmarc  IN  TXT "v=DMARC1; p=none; rua=mailto:foo;
IN  MX  10 mx.domain.tld.
IN  TXT "v=spf1 include:spf1.domain.tld ?all"

Since then, requests for the MX record were not answered any more,
adding a @ fixed it.

I'm wondering now why this happens, as in other zonefiles without TXT
records the blank substitution works.

Kind regards
Bjoern
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