## DNS

Tests needed:
 - encode and decode of each kind of RR
    - so far, have: txt, a, ns, mx, soa, cname, aaaa, srv.
    - that leaves: md, mf, mb, mg, mr, null, wks, ptr, hinfo, minfo
    - most of those are obsolete, so finding wild examples will be
      very difficult

 - encode and decode of several variants of packet, both sensible and not
    - misleading section length count - short, long
    - misleading label length - short, long
    - misleading rdata length - short, long
    - misleading txt record string length - short, long
    - looping domain-name (using compressed format)
    - compressed domain-name pointing into hyperspace
    - txt record with rdata filled with a list of empty byte-strings

### Proxy

#### Make CNAME NXDOMAIN refer to the target record, not the CNAME itself

See also RFC 2308 section 2.1 and
http://homepage.ntlworld.com./jonathan.deboynepollard/FGA/dns-response-taxonomy.html

Basically, if the CNAME record is in the response, that's sufficient
indication that the name of the CNAME exists! So NXDOMAIN clearly
doesn't make sense to apply there.

#### Should the cache replace SOAs by serial number?

It probably shouldn't cache SOA records at all. Djbdns doesn't.
("dnscache does not cache SOA records", from http://cr.yp.to/djbdns/dnscache.html)