How to compile c-ares on Windows with Visual Studio?

Check the INSTALL.md file for build instructions; typically, use CMake or provided Visual Studio project files. The README links to detailed setup, but you may need to configure paths and dependencies manually.

c-ares vs getaddrinfo: which is better for async DNS?

c-ares excels in asynchronous, non-blocking queries and parallel resolution, while getaddrinfo is often blocking and system-dependent. Use c-ares for performance-critical apps; getaddrinfo is simpler for basic sync lookups.

Does c-ares support DNS over TLS?

The README doesn't list DNS over TLS (DoT) support in its RFCs; it focuses on traditional DNS protocols. For encrypted DNS, you might need to implement it externally or use a different library.

Is c-ares thread-safe for multi-threaded applications?

Yes, c-ares is designed for asynchronous operation and can be used in multi-threaded contexts, but proper initialization and callback handling are required; refer to the API documentation for thread-safety guidelines.

How to handle DNS query failures with c-ares callbacks?

Use the async callback functions provided by c-ares to check status codes and error messages; the library includes detailed error reporting, but you need to implement retry logic and fallbacks in your application code.

Can c-ares be used in embedded Linux systems with limited resources?

Yes, c-ares is cross-platform and efficient, but for extremely memory-constrained systems, profile its usage; alternatives like lightweight resolvers might be better if async features aren't needed.

c-ares — C Library for Async DNS Resolution

What is c-ares?

c-ares is a C library for asynchronous DNS resolution, designed to perform non-blocking and parallel DNS queries. It abstracts the intricacies of the DNS protocol, providing a modern, secure alternative to system resolvers. The library focuses on cross-platform compatibility and adherence to the latest DNS RFCs.

Target Audience

Developers building network applications in C or other languages that require efficient, non-blocking DNS resolution, such as embedded systems, servers, and high-performance clients.

Value Proposition

c-ares offers a more secure and reliable DNS resolver than many system-provided alternatives, with a strong emphasis on asynchronous operations, extensive RFC support, and rigorous security practices through continuous fuzzing and testing.

A C library for asynchronous DNS requests

Use Cases

Best For

Implementing non-blocking DNS lookups in network servers
Building cross-platform applications requiring consistent DNS resolution
Enhancing security in DNS parsing and query handling
Developing embedded systems with limited threading capabilities
Performing parallel DNS queries for high-performance clients
Replacing system DNS resolvers with a more robust library

Not Ideal For

Projects requiring only simple, synchronous DNS lookups without async benefits
Applications that need to implement a full DNS server with authoritative or recursive capabilities
Developers working in high-level languages like Python or JavaScript where built-in async DNS APIs are sufficient
Ultra-constrained embedded systems where a minimal, non-library resolver is preferred due to memory limits

Pros & Cons

Pros

Asynchronous Query Handling

Enables non-blocking and parallel DNS queries, preventing application stalls, as emphasized in the README for applications needing multiple queries without blocking.

Cross-Platform Portability

Runs on Linux, FreeBSD, macOS, Windows, Android, iOS, and more, ensuring consistent DNS resolution across diverse operating systems.

Security-Focused Design

Implements safe parsers and data builders, validated through extensive automated testing and constant fuzzing via OSS Fuzz, reducing common C library vulnerabilities.

Modern Standards Compliance

Supports key DNS RFCs including EDNS0, IPv6 (AAAA), SRV, DANE, SVCB/HTTPS, and DNS Cookies, keeping up with the latest protocol features.

System-Agnostic Resolver

Aims to be a better DNS resolver than system-provided ones, as stated in the README, offering improved reliability and performance regardless of platform.

Cons

C Language Barrier

Requires C knowledge or language bindings for integration, which can be a hurdle for projects in non-C languages, adding complexity to setup.

Limited to Stub Resolution

Only functions as a DNS stub resolver, lacking features for full DNS server operations like authoritative serving or caching recursion, as admitted in its design.

No Built-in DoH Support

While it supports modern RFCs, DNS over HTTPS (DoH) is not mentioned in the features, limiting use in privacy-focused applications without additional implementation.

Integration Overhead

Adding a C library to projects, especially in non-C environments, involves build system adjustments and potential binding issues, increasing initial setup effort.

Frequently Asked Questions

What is c-ares?

Target Audience

Developers building network applications in C or other languages that require efficient, non-blocking DNS resolution, such as embedded systems, servers, and high-performance clients.

Value Proposition

Use Cases

Best For

Implementing non-blocking DNS lookups in network servers
Building cross-platform applications requiring consistent DNS resolution
Enhancing security in DNS parsing and query handling
Developing embedded systems with limited threading capabilities
Performing parallel DNS queries for high-performance clients
Replacing system DNS resolvers with a more robust library

Not Ideal For

Projects requiring only simple, synchronous DNS lookups without async benefits
Applications that need to implement a full DNS server with authoritative or recursive capabilities
Developers working in high-level languages like Python or JavaScript where built-in async DNS APIs are sufficient
Ultra-constrained embedded systems where a minimal, non-library resolver is preferred due to memory limits

Pros & Cons

Pros

Asynchronous Query Handling

Enables non-blocking and parallel DNS queries, preventing application stalls, as emphasized in the README for applications needing multiple queries without blocking.

Cross-Platform Portability

Runs on Linux, FreeBSD, macOS, Windows, Android, iOS, and more, ensuring consistent DNS resolution across diverse operating systems.

Security-Focused Design

Implements safe parsers and data builders, validated through extensive automated testing and constant fuzzing via OSS Fuzz, reducing common C library vulnerabilities.

Modern Standards Compliance

Supports key DNS RFCs including EDNS0, IPv6 (AAAA), SRV, DANE, SVCB/HTTPS, and DNS Cookies, keeping up with the latest protocol features.

System-Agnostic Resolver

Aims to be a better DNS resolver than system-provided ones, as stated in the README, offering improved reliability and performance regardless of platform.

Cons

C Language Barrier

Requires C knowledge or language bindings for integration, which can be a hurdle for projects in non-C languages, adding complexity to setup.

Limited to Stub Resolution

Only functions as a DNS stub resolver, lacking features for full DNS server operations like authoritative serving or caching recursion, as admitted in its design.

No Built-in DoH Support

While it supports modern RFCs, DNS over HTTPS (DoH) is not mentioned in the features, limiting use in privacy-focused applications without additional implementation.

Integration Overhead

Adding a C library to projects, especially in non-C environments, involves build system adjustments and potential binding issues, increasing initial setup effort.

Frequently Asked Questions

c-ares

What is c-ares?

Overview

Use Cases

Best For

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions

Related Projects

Found a gem we're missing?

c-ares

What is c-ares?

Overview

Use Cases

Best For

Not Ideal For

Pros & Cons

Pros

Cons

Frequently Asked Questions

Related Projects

Found a gem we're missing?