Add core traversal engine with iterative resolution from root servers:
- referral.go: Referral struct with name, type, bailiwick, addresses, state
- cache.go: Chained InfoCache with parent inheritance for NS and glue records
- stack.go: LIFO stack with configurable max depth enforcement
- response.go: Response classifier (referral, answer, CNAME follow, NODATA,
NXDOMAIN, SERVFAIL) with child referral generation and probability splitting
- traverser.go: Traverser orchestrates full traversal from root to leaf,
following all referral branches, handling CNAME chains, and respecting
max depth limits
Add IterativeQuery/IterativeQueryWithExchange to dns package (RD=false queries).
57 new tests covering all acceptance criteria: traversal from root to leaf,
comprehensive branch following, max depth enforcement, probability distribution,
chained cache behavior, CNAME following, NXDOMAIN/SERVFAIL handling, context
cancellation, and concurrent access.
Co-authored-by: multica-agent <github@multica.ai>
Add Resolver interface, BasicResolver, and CachingResolver to internal/dns.
CachingResolver wraps any Resolver with an in-memory cache keyed by
(server IP, name, type, class). Cache entries respect DNS TTL from
responses, falling back to a configurable default TTL. Thread-safe
using sync.RWMutex. Includes Len, Clear, and PurgeExpired methods
for cache management.
Closes HAN-379 (Phase 2.2).
Co-authored-by: multica-agent <github@multica.ai>
Add RootServer struct and DiscoverRoots function that queries the local
resolver for NS records of the root zone, resolves each root name to
A/AAAA addresses, and returns a list of RootServer structs.
Supports:
- Default: discovers a single root server from local resolver
- --root-server override to target a specific root server
- --all-root-servers to discover all 13 root servers
- --root-aaaa flag to include IPv6 addresses
Includes unit tests for all helper functions and integration tests
that skip gracefully when no resolver is available.
Co-authored-by: multica-agent <github@multica.ai>
