Problem resolving service without TXT records

On Fri, May 05, 2006 at 09:34:42PM +0200, Lennart Poettering
wrote:
> On Fri, 05.05.06 15:23, Mihai Ibanescu (misa+avahiredhat.com) wrote:
> 
> > Hello,
> > 
> > I noticed more people reported this on various web
pages, is this
> > known? If I
> 
> "Various web pages"? Where exactly?

The one that I found right away was:

http://eric.extremebo
redom.net/

I seem to remember another one mentioning the same thing.


> > try to resolve (using unicast DNS) a service that
does not have a TXT record,
> > it will fail. It seems to need an empty TXT record
at the very
> > least.
> 
> An SRV record without a matching TXT record is not a
valid DNS-SD
> service, hence Avahi will treat this as an error. If
you don't need
> the TXT record, than set it a single empty string.

Ah, I was able to find that, but it's kind of buried in the
specs.

http://files.dns-sd.org/draft-cheshire-dnsext-dns-sd.txt
 section 6:

   Every DNS-SD service MUST have a TXT record in
   addition to its SRV record, with same name, even if the
service has
   no additional data to store and the TXT record contains
no more than
   a single zero byte.

Not a bug, sorry for wasting your time.

Misa
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On Fri, 05.05.06 15:43, Mihai Ibanescu (misa+avahiredhat.com) wrote:

> > > try to resolve (using unicast DNS) a service
that does not have a TXT record,
> > > it will fail. It seems to need an empty TXT
record at the very
> > > least.
> > 
> > An SRV record without a matching TXT record is not
a valid DNS-SD
> > service, hence Avahi will treat this as an error.
If you don't need
> > the TXT record, than set it a single empty string.
> 
> Ah, I was able to find that, but it's kind of buried
in the specs.
> 
> http://files.dns-sd.org/draft-cheshire-dnsext-dns-sd.txt
 section 6:
> 
>    Every DNS-SD service MUST have a TXT record in
>    addition to its SRV record, with same name, even if
the service has
>    no additional data to store and the TXT record
contains no more than
>    a single zero byte.
> 
> Not a bug, sorry for wasting your time.


There is a bug: Avahi shouldn't return a Timeout error code
when the
TXT record is missing. On mDNS this makes sense, but on
unicast DNS it
doesn't. 

I create a Trac Ticket for this, so that I don't forget it:

  http://avahi.org/ticket/38


Lennart

-- 
Lennart Poettering; lennart [at] poettering [dot] net
ICQ# 11060553; GPG 0x1A015CC4; http://0pointer.net/lenn
art/
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