This code implements a scaled-back DNS resolver client. The user inputs a domain name and the DNS resolver client will return the IP address currently associated with that domain name. Information is also cached to speed up further lookups
###usage
lookup < domain-name > performs a DNS lookup on the given domain name.
trace < on/off > turns on lookup tracing. This allows the user to understand the route the program took through the DNS hierarchy to reach the returned IP address.
server IP changes the DNS server to start future searches from.
dump prints the cache.
quit quits the process.
###usage examples
lookup < domain-name > []
Here we perform a DNS lookup on the google.com, facebook.com and github.com.
For the first query, we get the answer google.com A 300 172.217.3.206, which tells us that the query was to google.com, that this is an answer, that the time-to-live is 300 and finally that the IP address is 172.217.3.206.
trace < on/off >
Here we perform a DNS lookup on google.com with tracing on. Our client first queries the l-root server at IP address 199.7.83.42. The l-root server responds with a list of com nameservers. We select the first com nameserver and query it for the IP of google.com, as we queried the l-root server. The com nameserver will respond with a list of nameservers for which we will query and so on until we reach the server responsible for google.com, which has IP address 172.217.3.206.
The full output of this command can be found in the appendix below.
dump
Here we first perfom a DNS lookup on google.com again and receive an IP address. We then perform a dump command which will print out all the cached information. This information is a lot of the same information that was printed when we called perform thed lookup with tracing on.
The full output of this command can be found in the appendix below.
tracing for lookup google.com:
DNSLOOKUP> lookup google.com
Query ID 62410 google.com A --> 199.7.83.42
Response ID: 62410 Authoritative = false
Answers (0)
Nameservers (13)
com 172800 NS a.gtld-servers.net
com 172800 NS b.gtld-servers.net
com 172800 NS c.gtld-servers.net
com 172800 NS d.gtld-servers.net
com 172800 NS e.gtld-servers.net
com 172800 NS f.gtld-servers.net
com 172800 NS g.gtld-servers.net
com 172800 NS h.gtld-servers.net
com 172800 NS i.gtld-servers.net
com 172800 NS j.gtld-servers.net
com 172800 NS k.gtld-servers.net
com 172800 NS l.gtld-servers.net
com 172800 NS m.gtld-servers.net
Additional Information (14)
a.gtld-servers.net 172800 A 192.5.6.30
b.gtld-servers.net 172800 A 192.33.14.30
c.gtld-servers.net 172800 A 192.26.92.30
d.gtld-servers.net 172800 A 192.31.80.30
e.gtld-servers.net 172800 A 192.12.94.30
f.gtld-servers.net 172800 A 192.35.51.30
g.gtld-servers.net 172800 A 192.42.93.30
h.gtld-servers.net 172800 A 192.54.112.30
i.gtld-servers.net 172800 A 192.43.172.30
j.gtld-servers.net 172800 A 192.48.79.30
k.gtld-servers.net 172800 A 192.52.178.30
l.gtld-servers.net 172800 A 192.41.162.30
m.gtld-servers.net 172800 A 192.55.83.30
a.gtld-servers.net 172800 AAAA 2001:503:a83e:0:0:0:2:30
Query ID 54875 google.com A --> 192.5.6.30
Response ID: 54875 Authoritative = false
Answers (0)
Nameservers (4)
google.com 172800 NS ns2.google.com
google.com 172800 NS ns1.google.com
google.com 172800 NS ns3.google.com
google.com 172800 NS ns4.google.com
Additional Information (4)
ns2.google.com 172800 A 216.239.34.10
ns1.google.com 172800 A 216.239.32.10
ns3.google.com 172800 A 216.239.36.10
ns4.google.com 172800 A 216.239.38.10
Query ID 25738 google.com A --> 216.239.34.10
Response ID: 25738 Authoritative = true
Answers (1)
google.com 300 A 216.58.193.78
Nameservers (0)
Additional Information (0)
google.com A 300 216.58.193.78
dump for google.com:
DNSLOOKUP> dump
a.gtld-servers.net A 171659 192.5.6.30
a.gtld-servers.net AAAA 171659 2001:503:a83e:0:0:0:2:30
b.gtld-servers.net A 171659 192.33.14.30
c.gtld-servers.net A 171659 192.26.92.30
com NS 171659 f.gtld-servers.net
com NS 171659 k.gtld-servers.net
com NS 171659 a.gtld-servers.net
com NS 171659 b.gtld-servers.net
com NS 171659 d.gtld-servers.net
com NS 171659 j.gtld-servers.net
com NS 171659 h.gtld-servers.net
com NS 171659 e.gtld-servers.net
com NS 171659 l.gtld-servers.net
com NS 171659 c.gtld-servers.net
com NS 171659 m.gtld-servers.net
com NS 171659 g.gtld-servers.net
com NS 171659 i.gtld-servers.net
d.gtld-servers.net A 171659 192.31.80.30
e.gtld-servers.net A 171659 192.12.94.30
f.gtld-servers.net A 171659 192.35.51.30
g.gtld-servers.net A 171659 192.42.93.30
google.com NS 171659 ns3.google.com
google.com NS 171659 ns1.google.com
google.com NS 171659 ns4.google.com
google.com NS 171659 ns2.google.com
h.gtld-servers.net A 171659 192.54.112.30
i.gtld-servers.net A 171659 192.43.172.30
j.gtld-servers.net A 171659 192.48.79.30
k.gtld-servers.net A 171659 192.52.178.30
l.gtld-servers.net A 171659 192.41.162.30
m.gtld-servers.net A 171659 192.55.83.30
ns1.google.com A 171659 216.239.32.10
ns2.google.com A 171659 216.239.34.10
ns3.google.com A 171659 216.239.36.10
ns4.google.com A 171659 216.239.38.10