Maintained by: NLnet Labs

Trying to fetch SRV data with libunbound / libldns

Rick van Rein
Thu May 12 15:51:36 CEST 2016


Hello,

I'm trying to use libunbound (and possibly libldns) to pull out SRV
records.  I am not certain how to proceed, based on the documentation
that I could found in the form of man pages, tutorials and doxygen.

Am I correct that libunbound returns RDATA unmodified, and is basically
concerned with the security chain but not the RDATA contents?  And so,
that I have to turn to another tool?

I therefore looked at LDNS, but that does not seem to help either.  I
don't mind following the RFC (though in the case of SRV it is not
explicit on the wire format) to pull out data, but I would be surprised
if I was to make assumptions about the structure of hosts, especially
because it may point back into a DNS packet.  Is this really how it is
done though?  Then, should I assume the data[i]/len[i] to be pointers
into the frame, and compute offsets manually?

I can hardly believe that this hasn't been tried before :) but as I
said, I can't find the documentation that answers this with clarity.  So
any help is welcome, including pointers to documentation that I've
overlooked!

Thanks,
 -Rick