Resolvalid

Resolvalid is a Go tool that will generate or validate a list of DNS servers, providing you with a file containing only valid DNS servers.

Installation

To install Resolvalid, use the go install command:

go install github.com/mmarting/resolvalid@latest

Usage

Use -h to display the help for the tool:

resolvalid -h

Resolvalid requires an output (-o) file name as the only mandatory parameter. The tool admits the following options:

Options

-o, --output:       Output file for valid DNS servers (required).
-f, --file:         File containing the list of DNS servers (optional).
-u, --url:          URL containing the file of DNS servers (optional, default: https://public-dns.info/nameservers.txt).
-td, --test-domain: Domain used to test DNS servers (optional, default: randomly chosen from predefined domains).
-t, --threads:      Number of concurrent threads (optional, default: 20).
-to, --timeout:     Timeout for DNS queries (optional, default: 2s).
-s, --silent:       Suppress output to the screen (optional).
-h, --help:         Display help information.

Examples

Use a local file with DNS Servers and output valid ones to a file:

resolvalid -f dns_servers.txt -o valid_servers.txt

Use a URL hosting a list of DNS Servers and output valid ones to a file with custom timeout:

resolvalid -u https://example.com/dns_list.txt -o valid_servers.txt -to 5s

Suppress screen output, use custom test domain and use 50 threads:

resolvalid -f dns_servers.txt -o valid_servers.txt -td mytestdomain.com -t 50 -s

Notes

This tool was created as a project for learning Go, so don't expect a highly optimized code. At the same time, I was trying to reduce the time my recon automation tool was taking to validate my DNS servers list, which I've achieved with this tool.

Thanks

• vortexau: For inspiring me to write this tool after a few years of using their tool to validate my DNS server lists: dnsvalidator

• miek: For creating the Go DNS library I'm using in this tool: dns

Author

Martín Martín

LinkedIn

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License

resolvalid is distributed under GPL v3 License.