Programming Assignment DNS Resolver
Problem Overview
The goal of this assignment is to implement a DNS resolver.
The DNS resolver takes a hostname as an input and issues a series of iterative
queries to obtain the IP address (A record) for the hostname.
For example,
C:\>myresolver cse.unl.edu
cse.unl.edu A = 129.93.165.2
Your resolver must also be able to follow aliases (CNAME records) to obtain the IP
address of the hostname.
A sample output is,
C:\>myresolver www.cse.unl.edu
www.cse.unl.edu A = CNAME to cse.unl.edu
cse.unl.edu A = 129.93.165.2
If a hostname does not exist or does not have an A record, your resolver should
indicate that.
For example,
C:\>grads.cse.unl.edu
grads.cse.unl.edu A = does not exist
Normally there are several redundant servers for each DNS zone. If one server is
down or has other problems, you should try a different server. Only if none of the servers
are responsive can you report a DNS error.
There are a large number of DNS resource record types. Your code is required to
support queries for A records. In order to do this, your resolver will also need to
understand the following DNS resource record types.
CNAME records. When resolving CNAME records, your code must continue to
follow the CNAME chain until it either finds an IP address at the end of the
chain or proves that the CNAME chain is misconfigured (that is, the chain of
CNAMEs leads to a hostname that does not exist or the chain leads to a loop).
SOA records. SOA records are sent to indicate a requested name does not exist.
NS records. NS records identify servers to ask and your code must start from a
DNS root server and follow a chain of NS records until you find the NS server
docsity.com
