who-dis is a DNS resolver that we built to better understand DNS, both from a user and name server perspective. Similar to dig, who-dis takes in a domain name and contacts name servers recursively, until it finds the records for the desired domain name, or bottoms out in some other way.
who-dis supports both recursive and non-recursive requests, result caching, and can decode A/AAAA/CNAME records, with extensibility to support more record types.
./who-dis [-trace] [-no-cache] <domain-name>
-
-traceenables a recursive DNS query. By default, who-dis simply queries 8.8.8.8. But with-traceset, who-dis will query a root server, followed by the name server for the top-level domain, and so on. -
-nocachedisables the use of the cache for answering requests. By default who-dis will consult its cache before making a DNS query. The cache maps domain names to an IP address, a TTL, and the timestamp when the record was cached.
Without setting -trace, the response from who-dis mimicks the behavior of dig:
$ ./who-dis -nocache www.brown.edu
nochache = true; trace = false
### Response from 8.8.8.8 ###
;; QUESTION SECTION:
www.brown.edu IN A
;; ANSWER SECTION:
www.brown.edu 2619 IN CNAME www.brown.edu.cdn.cloudflare.net
www.brown.edu.cdn.cloudflare.net 300 IN A 104.18.3.173
www.brown.edu.cdn.cloudflare.net 300 IN A 104.18.2.173
;; AUTHORITY SECTION:
;; ADDITIONAL SECTION:
A recursive query is similar to dig +trace:
$ ./who-dis -trace -nocache www.brown.edu
nochache = true; trace = true
### Response from 199.9.14.201 ###
;; QUESTION SECTION:
www.brown.edu IN A
;; ANSWER SECTION:
;; AUTHORITY SECTION:
edu 172800 IN NS b.edu-servers.net
edu 172800 IN NS h.edu-servers.net
edu 172800 IN NS i.edu-servers.net
edu 172800 IN NS d.edu-servers.net
edu 172800 IN NS k.edu-servers.net
edu 172800 IN NS a.edu-servers.net
edu 172800 IN NS e.edu-servers.net
edu 172800 IN NS f.edu-servers.net
edu 172800 IN NS c.edu-servers.net
edu 172800 IN NS l.edu-servers.net
edu 172800 IN NS g.edu-servers.net
edu 172800 IN NS j.edu-servers.net
edu 172800 IN NS m.edu-servers.net
;; ADDITIONAL SECTION:
m.edu-servers.net 172800 IN A 192.55.83.30
l.edu-servers.net 172800 IN A 192.41.162.30
k.edu-servers.net 172800 IN A 192.52.178.30
j.edu-servers.net 172800 IN A 192.48.79.30
i.edu-servers.net 172800 IN A 192.43.172.30
h.edu-servers.net 172800 IN A 192.54.112.30
g.edu-servers.net 172800 IN A 192.42.93.30
f.edu-servers.net 172800 IN A 192.35.51.30
e.edu-servers.net 172800 IN A 192.12.94.30
d.edu-servers.net 172800 IN A 192.31.80.30
c.edu-servers.net 172800 IN A 192.26.92.30
b.edu-servers.net 172800 IN A 192.33.14.30
a.edu-servers.net 172800 IN A 192.5.6.30
m.edu-servers.net 172800 IN AAAA 2001:501:b1f9::30
### Response from 192.55.83.30 ###
;; QUESTION SECTION:
www.brown.edu IN A
;; ANSWER SECTION:
;; AUTHORITY SECTION:
brown.edu 172800 IN NS ns1.ucsb.edu
brown.edu 172800 IN NS bru-ns1.brown.edu
brown.edu 172800 IN NS bru-ns2.brown.edu
brown.edu 172800 IN NS bru-ns3.brown.edu
;; ADDITIONAL SECTION:
ns1.ucsb.edu 172800 IN A 128.111.1.1
ns1.ucsb.edu 172800 IN AAAA 2607:f378::1
bru-ns1.brown.edu 172800 IN A 128.148.248.11
bru-ns2.brown.edu 172800 IN A 128.148.248.12
bru-ns3.brown.edu 172800 IN A 128.148.2.13
### Response from 128.111.1.1 ###
;; QUESTION SECTION:
www.brown.edu IN A
;; ANSWER SECTION:
www.brown.edu 3600 IN CNAME www.brown.edu.cdn.cloudflare.net
;; AUTHORITY SECTION:
;; ADDITIONAL SECTION:
Performing the query again gives us a cache hit so we don't have to go back to the root server:
$ ./who-dis -trace www.brown.edu
nochache = false; trace = true
### Cached response ###
brown.edu 128.111.1.1
### Response from 128.111.1.1 ###
;; QUESTION SECTION:
www.brown.edu IN A
;; ANSWER SECTION:
www.brown.edu 3600 IN CNAME www.brown.edu.cdn.cloudflare.net
;; AUTHORITY SECTION:
;; ADDITIONAL SECTION: