ruresol

ruresol is a high-performance, asynchronous bulk DNS resolver written in Rust. It is designed to process massive lists of IP addresses or hostnames from standard input, resolving them concurrently with configurable limits.

Key Features

• High Concurrency: Uses tokio and futures to handle hundreds or thousands of concurrent DNS queries without spawning OS threads for each.
• Robust Input Handling: Safely handles input streams containing invalid UTF-8 sequences (ignoring only the bad lines), comments (#), and empty lines.
• Configurable Timeouts: Fine-grained control over timeouts per attempt and the number of retries (--timeout, --attempts).
• Flexible Output Ordering:
  • Ordered (Default): Preserves the order of input lines in the output, even if later queries finish first.
  • Unordered (-u): Prints results immediately upon completion for faster visual feedback.
• System Integration: Automatically parses /etc/resolv.conf (on Unix) or Registry (on Windows) to use your system's configured upstream nameservers.
• Precise Error Reporting: Distinguishes between NXDOMAIN, Temporary error (ServFail/Timeout), and empty responses (No records found).

Libraries Used

• hickory-resolver: The core DNS logic. Formerly known as trust-dns, it provides a safe, secure, and fully async DNS implementation.
• tokio: The industry-standard asynchronous runtime for Rust, handling the thread pool and I/O scheduling.
• futures: Used specifically for buffer_unordered and buffered combinators, allowing us to govern the flow of thousands of async tasks efficiently.
• clap: Provides the robust command-line argument parsing and help generation.
• async-stream: Enables the creation of asynchronous streams using generator syntax, allowing efficient, non-blocking reading of stdin.

Installation

Ensure you have Rust installed, then build the project in release mode for maximum performance: cargo build --release

The binary will be located at ./target/release/ruresol.

Usage

Reverse Lookup (IP -> Hostname)

Resolves a list of IPs to their PTR records. # Read from file cat ips.txt | ./target/release/ruresol -r

# High concurrency (500 requests at once) cat huge_list_of_ips.txt | ./target/release/ruresol -r -c 500

Forward Lookup (Hostname -> IP)

Resolves hostnames to A (IPv4) and/or AAAA (IPv6) records. # Resolve to IPv4 only echo "google.com" | ./target/release/ruresol -a -4

# Resolve to both IPv4 and IPv6 echo "example.com" | ./target/release/ruresol -a -4 -6

Advanced Configuration

Fast Failures: Set a short timeout (e.g., 1s) and only 1 attempt to speed up scanning of unresponsive hosts. cat ips.txt | ./target/release/ruresol -r -t 1000 --attempts 1

Immediate Output: Use -u to print results as soon as they arrive, rather than waiting to preserve input order. cat ips.txt | ./target/release/ruresol -r -u

Options

Flag	Long	Description	Default
-r	--reverse	Reverse lookup mode (IP -> Hostname).
-a	--address	Address lookup mode (Hostname -> IP).
-4	--ipv4	Query A records.
-6	--ipv6	Query AAAA records.
-c	--concurrency	Number of simultaneous requests.	200
-t	--timeout	Timeout per query attempt (ms).	2000
	--attempts	Number of retries before giving up.	2
-u	--unordered	Output results immediately (unordered).	False