Getting Started

Install via Composer: composer require daverandom/libdns
Primary entry points are Resolver (for queries) and MessageBuilder/MessageParser (for constructing/parsing DNS messages)
Start with Resolver::resolve($domain, DNS::TYPE_A) to perform a simple A record lookup synchronously
Check the README for basic examples—focus on the Resolver class and its resolve() method, which handles query construction and transport (UDP/TCP/TLS) automatically
For async or non-blocking usage (e.g., with ReactPHP), use the Async\Resolver adapter (if bundled) or integrate manually via ReactPHP’s event loop

Implementation Patterns

Caching Layer Integration: Wrap the Resolver with PSR-16 or PSR-6 cache adapters to reduce DNS load and latency—especially important for CLI tools or services making repeated lookups for the same domain
Custom DNS Transport: Override default transports by injecting a custom TransportInterface implementation (e.g., for testing with a mock server, or enforcing DoH/DoT endpoints)
Domain Validation & Filtering: Use parsed Record objects to programmatically inspect TTLs, priorities (MX), or security-relevant records (e.g., verify DMARC via _dmarc TXT records)
Build-Time DNS Checks: Integrate in CI pipelines to preflight domain configurations (e.g., confirm SPF, DKIM, and DMARC records exist before deployment)
Custom Record Types: Extend with MessageBuilder to craft and send arbitrary queries (e.g., TYPE=65 for HTTPS records) without relying on external tools like dig

No built-in resolution of CNAME chains: The resolver does not automatically follow CNAME or DNAME records—you must manually handle redirection by inspecting the response and re-resolving
UDP packet size limits: Avoid large UDP responses (>512 bytes) without enabling EDNS0—configure Resolver with EdnsOptions or force TCP fallback if needed
Testing pitfalls: Mock DNS responses using Parser on raw binary (e.g., via @covers fixtures), not by mocking Resolver directly—actual DNS parsing is nontrivial and often misestimated
Time-sensitive record caches: The library is not a caching resolver—TTLs in responses are returned but not enforced. Implement your own TTL tracking or re-resolve logic
IPv6 support: While the library supports AAAA records, ensure your environment (especially CLI) can bind to IPv6 sockets if resolver defaults are used; explicitly configure Transport to prefer IPv4 if needed