Upgrade dnsjava to cope with Azure CNAME lists

[anjackson]

We have a problem with the latest H3 release - it is unable to resolve the domain coronavirus.data.gov.uk.

Poking via the scripting console, using code cribbed from FetchDNS, we run:

//Groovy
import org.xbill.DNS.DClass;
import org.xbill.DNS.Lookup;
import org.xbill.DNS.Record;
import org.xbill.DNS.Type;
import org.xbill.DNS.Name;

lookupName = "coronavirus.data.gov.uk.";
look = new Lookup(lookupName, Type.A, DClass.IN);
look.getDefaultCache(DClass.IN).clearCache();
look.setCache(null);
rrecordSet = look.run();
rawOut.println(rrecordSet);
rawOut.println(look.getErrorString());
rawOut.println(look.getAliases());

gives

null
CNAME loop
[coronavirus.data.gov.uk., covid19stat.azureedge.net., covid19stat.afd.azureedge.net., afd.t-0001.t-msedge.net., t-0001.t-msedge.net.]

i.e. a null result due to a CNAME loop. Inspecting dnsjava Lookup @ v.2.0.3, we can see that after 6 CNAME steps it assumes it's a CNAME loop.

A command-line lookup shows:

# dig @1.1.1.1 coronavirus.data.gov.uk

; <<>> DiG 9.11.4-P2-RedHat-9.11.4-16.P2.el7_8.3 <<>> @1.1.1.1 coronavirus.data.gov.uk
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 63111
;; flags: qr rd ra; QUERY: 1, ANSWER: 7, AUTHORITY: 0, ADDITIONAL: 1

;; OPT PSEUDOSECTION:
; EDNS: version: 0, flags:; udp: 1232
;; QUESTION SECTION:
;coronavirus.data.gov.uk.       IN      A

;; ANSWER SECTION:
coronavirus.data.gov.uk. 244    IN      CNAME   covid19stat.azureedge.net.
covid19stat.azureedge.net. 1744 IN      CNAME   covid19stat.afd.azureedge.net.
covid19stat.afd.azureedge.net. 244 IN   CNAME   afd.t-0001.t-msedge.net.
afd.t-0001.t-msedge.net. 184    IN      CNAME   t-0001.t-msedge.net.
t-0001.t-msedge.net.    4       IN      CNAME   Edge-Prod-MAN30r3.ctrl.t-0001.t-msedge.net.
Edge-Prod-MAN30r3.ctrl.t-0001.t-msedge.net. 184 IN CNAME standard.t-0001.t-msedge.net.
standard.t-0001.t-msedge.net. 184 IN    A       13.107.246.10

;; Query time: 4 msec
;; SERVER: 1.1.1.1#53(1.1.1.1)
;; WHEN: Thu Jul 30 20:38:43 BST 2020
;; MSG SIZE  rcvd: 268

i.e. the CNAME path is seven steps long.

As of dnsjava v.2.1.9 the maximum number of iterations has been upped to 10. Therefore upgrading javadns to a more recent version should solve this problem. The most recent version is dnsjava v.3.2.2.

[anjackson]

As a workaround, I think we can set FetchDNS.setAcceptNonDnsResolves(true); which should fall back on host DNS resolution when dnsjava fails.