Roadmap

Done

• RFC 2131 / 2132 wire codec — Parse + BuildReply (OFFER / ACK / NAK).
• Decision core — the stateless Decide state machine, build-tag-free.
• Linux UDP/67 server — SO_BINDTODEVICE bind, receive loop, broadcast reply.
• Cross-platform surface — non-Linux build stub + socket-free StubServer.
• Optional metrics — the Metrics hook + a Prometheus adapter in prom.
• 100% coverage — error branches included, socket paths via syscall seams (no root), across the six 64-bit Go targets.

Deliberately out of scope (for now)

• Unicast replies. The server always broadcasts. The spec allows a unicast reply to chaddr when the client's BROADCAST flag is clear; that is a candidate addition once there is a concrete client that needs it.
• Lease persistence / an address pool. The library is stateless by design — you own the address plan through Source. Dynamic allocation from a pool, with conflict detection and a lease database, is a layer that belongs above this one.
• DHCPv6. This is a DHCPv4 server. IPv6 leasing (RFC 8415) is a separate protocol and out of scope for this module.
• Relay / giaddr handling. The current target is a single directly-attached segment; relayed requests are parsed but not specially routed.

Design guarantees that will not change

• Pure Go, zero cgo in the core.
• No third-party dependency in the core module — only the opt-in prom sub-package imports Prometheus.
• The decision core stays portable and socket-free, so it is testable everywhere.