## DNS

Make RData and RRType the same thing so it becomes impossible to make
a mistake.

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)

### Zero-timeout RRs in subqueries

Currently they make it appear that there are no available answers!

E.g. this IN A query for maps.bpl.org. Note the zero-timeout A records
that come back from dns-lproof2.

    1348086228 DNS: '#s(udp-address "127.0.0.1" 41127) asks '#s(udp-listener 5555) 44280
    1348086228    : (list (question (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in #f))
    1348086228 dns-vm PID 114447 ((packet-relay #s(active-request #s(udp-address 127.0.0.1 41127) 44280))) started
    1348086228 DNS: (question (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in #f)
    1348086228 dns-vm PID 114448 ((question-handler #s(question #(struct:domain (maps bpl org) (maps bpl org)) a in #f))) started
    1348086228 dns-vm PID 114449 ((network-query #s(question #(struct:domain (maps bpl org) (maps bpl org)) a in #f))) started
    1348086228 DNS: (question (domain '(#"dns-lproof1" #"bpl" #"org") '(#"dns-lproof1" #"bpl" #"org")) 'a 'in (ns-subq (question (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in #f)))
    1348086228 dns-vm PID 114450 ((question-handler #s(question #(struct:domain (dns-lproof1 bpl org) (dns-lproof1 bpl org)) a in #s((ns-subq subquestion 1) #s(question #(struct:domain (maps bpl org) (maps bpl org)) a in #f))))) started
    1348086228 DNS: (answered-question (question (domain '(#"dns-lproof1" #"bpl" #"org") '(#"dns-lproof1" #"bpl" #"org")) 'a 'in (ns-subq (question (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in #f))) (complete-answer (set (rr (domain '(#"dns-lproof1" #"bpl" #"org") '(#"dns-lproof1" #"bpl" #"org")) 'a 'in 9484 '#(192 80 65 2))) (set) (set)))
    1348086228 dns-vm PID 114450 ((question-handler #s(question #(struct:domain (dns-lproof1 bpl org) (dns-lproof1 bpl org)) a in #s((ns-subq subquestion 1) #s(question #(struct:domain (maps bpl org) (maps bpl org)) a in #f))))) garbage-collected
    1348086228 DNS: '(request network-query/allocate-query-id441781 allocate-query-id)
    1348086228 DNS: '(reply network-query/allocate-query-id441781 11080)
    1348086228 DNS: '#s(udp-handle dns-client) asks '#s(udp-address "192.80.65.2" 53) 11080
    1348086228    : (list (question (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in #f))
    1348086228 DNS: '#s(set-timer (#s(udp-handle dns-client) 11080) 3000 relative)
    1348086231 DNS: '#s(timer-expired (#s(udp-handle dns-client) 11080) 1348086231475.239)
    1348086231 DNS: (question (domain '(#"dns-lproof2" #"bpl" #"org") '(#"dns-lproof2" #"bpl" #"org")) 'a 'in (ns-subq (question (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in #f)))
    1348086231 DNS: '(release-query-id 11080)
    1348086231 dns-vm PID 114451 ((question-handler #s(question #(struct:domain (dns-lproof2 bpl org) (dns-lproof2 bpl org)) a in #s((ns-subq subquestion 1) #s(question #(struct:domain (maps bpl org) (maps bpl org)) a in #f))))) started
    1348086231 DNS: (answered-question (question (domain '(#"dns-lproof2" #"bpl" #"org") '(#"dns-lproof2" #"bpl" #"org")) 'a 'in (ns-subq (question (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in #f))) (complete-answer (set (rr (domain '(#"dns-lproof2" #"bpl" #"org") '(#"dns-lproof2" #"bpl" #"org")) 'a 'in 9481 '#(216 236 248 2))) (set) (set)))
    1348086231 dns-vm PID 114451 ((question-handler #s(question #(struct:domain (dns-lproof2 bpl org) (dns-lproof2 bpl org)) a in #s((ns-subq subquestion 1) #s(question #(struct:domain (maps bpl org) (maps bpl org)) a in #f))))) garbage-collected
    1348086231 DNS: '(request network-query/allocate-query-id441790 allocate-query-id)
    1348086231 DNS: '(reply network-query/allocate-query-id441790 8847)
    1348086231 DNS: '#s(udp-handle dns-client) asks '#s(udp-address "216.236.248.2" 53) 8847
    1348086231    : (list (question (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in #f))
    1348086231 DNS: '#s(set-timer (#s(udp-handle dns-client) 8847) 3000 relative)
    1348086231 DNS: '#s(udp-address "216.236.248.2" 53) answers '#s(udp-handle dns-client)

    1348086231    : (dns-message 8847 'response 'query 'authoritative 'not-truncated 'no-recursion-desired 'no-recursion-available 'no-error (list (question (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in #f)) (list (rr (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in 0 '#(216 236 252 42)) (rr (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in 0 '#(192 80 65 42))) '() '())
    1348086231 DNS: (network-reply 'referral441777 (complete-answer (set (rr (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in 0 '#(192 80 65 42)) (rr (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in 0 '#(216 236 252 42))) (set) (set)))
    1348086231 DNS: '(release-query-id 8847)
    1348086231 dns-vm PID 114449 ((network-query #s(question #(struct:domain (maps bpl org) (maps bpl org)) a in #f))) garbage-collected
    1348086231 DNS: (answered-question (question (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in #f) (complete-answer (set) (set) (set)))
    1348086231 DNS: (set-timer (list 'check-dns-expiry (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org"))) 0 'relative)
    1348086231 dns-vm PID 114448 ((question-handler #s(question #(struct:domain (maps bpl org) (maps bpl org)) a in #f))) garbage-collected
    1348086231 DNS: '#s(udp-listener 5555) answers '#s(udp-address "127.0.0.1" 41127)
    1348086231    : (dns-message 44280 'response 'query 'non-authoritative 'not-truncated 'recursion-desired 'recursion-available 'no-error (list (question (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org")) 'a 'in #f)) '() '() '())
    1348086231 dns-vm PID 114447 ((packet-relay #s(active-request #s(udp-address 127.0.0.1 41127) 44280))) garbage-collected
    1348086231 DNS: (timer-expired (list 'check-dns-expiry (domain '(#"maps" #"bpl" #"org") '(#"maps" #"bpl" #"org"))) 1348086231532.27)