[dns-operations] wrapsrv -- DNS SRV record command line wrapper

Robert Edmonds edmonds at isc.org
Thu Jul 2 19:25:04 UTC 2009

Michael Graff wrote:
> The real problem comes in when "just try the first address" applications
> meet "SRV wrapper."  That's where the real annoyances lie IMHO.  Random
> failures, random different performance... but you get that anyway I suppose.

hm, good point.  this part of RFC 2782:

            For each element in the new list

                query the DNS for address records for the Target or
                use any such records found in the Additional Data
                section of the earlier SRV response.

                for each address record found, try to connect to the
               (protocol, address, service).

wrapsrv leaves up to the invoked command.  since that's going to
generate extra DNS queries anyway, it might be nice to have wrapsrv do
the A/AAAA lookup and pass a numeric address to the command.

> I don't know, I think the application supporting more than one address
> returned for an A or AAAA query is one step closer to the current
> century.  Having them magically get an ordered list of A or AAAA records
> seems like an overall win to me.

an ordered list is part of the way there, but i don't see any good way
to introduce non-equal weights into the existing getaddrinfo(3)

Robert Edmonds
edmonds at isc.org

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