This challenge corresponds to the 22nd part of the Coding Challenges series by John Crickett https://codingchallenges.fyi/challenges/challenge-dns-resolver.
dns_query.ts: This file contains the code for querying a server for a DNS record.dns_message.ts: This file contains the code for creating a DNS query message.utils.ts: This file contains the utility functions for converting a DNS message to a valid byte string.types.ts: All the interfaces and types used in the project are defined in this file.enums.ts: All the enums used in the project are defined in this file.parser.ts: The DNS message parser corresponding to the messages sent by server.dns_resolver.ts: The main class implementation for DNS resolution.dns_resolver.index.ts: The command line version of the DNS resolution.
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Created types and interface for DnsMessage and DnsQuery.
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Added enums for Type and Classes.
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Added utils to convert DNS message to a valid byte string. This included handling the header, domain strings, ip addresses and the question section. Here the major roadblock was handling Buffer and performing operations on it. I handled it by converting the buffer into a hex string.
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Wrote a simple UDP based client to create a DNS query for a domain and print out the response from the server.
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Added DNS Message Parser. The major challenge here was to handle the compression of domain labels. This was done by maintaining a map of the domain labels and their corresponding offsets.
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Added automated tests for parser and RR data parsing.
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Updated DNS Message class to take in partial headers.
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Revamped code and added DNS Resolver class to handle automated testing.
You can use the ts-node tool to run the DNS resolver as follows:
npx ts-node dns_resolver.index.ts <domain>
# Example
npx ts-node dns_resolver.index.ts google.comTo run the tests for the DNS resolution tool, go to the root directory of this repository and run the following command:
npm test src/22/