[Operators] On indirection in SRV record targets

Matthew Wild mwild1 at gmail.com
Sat Sep 19 09:24:27 CDT 2009

According to RFC 2782, SRV record targets are *not* allowed to be
"alias" records, this includes CNAMEs and PTRs for example. I just
made a change (not yet checked in) to Prosody which (unintentionally)
would render domains configured in such a way unreachable. I restarted
my server with the new code for testing to find a handful of my
contacts can no longer accessible.

I (reluctantly) plan to add a workaround to Prosody which can be
enabled per the admin's discretion. Whether I make it default or not
is undecided yet :)

I'd just like to spread the knowledge about this issue. As an excerise
I ran a quick script over the list of services at
http://xmpp.org/services/ .

   jabber.co.nz: Target 'jabber.yeahnah.co.nz.' uses a CNAME for a target!
   jabber.loudas.com: Target 'jabber.yeahnah.co.nz.' uses a CNAME for a target!
   jabber.yeahnah.co.nz: Target 'jabber.yeahnah.co.nz.' uses a CNAME
for a target!
   jabber.fourecks.de: Target 'v6.jabber.i-pobox.net.' has no A record!
   sternenschweif.de: Target 'v6.jabber.i-pobox.net.' has no A record!
   jabber-me.de: Target '' has no A record!

...so we're not doing too badly, the non-CNAME errors are because
v6.jabber.i-pobox.net has only an AAAA (IPv6) record, and
jabber-me.de's DNS servers seem completely unreachable.

I think perhaps we should also add this to our checklist for new services.


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