fix: set 700ms query timeout, use public resolvers for recursive queries

- Change queryTimeoutDuration from 5s to 700ms per requirement that DNS
  queries complete quickly given <800ms RTT
- Fix resolveARecord and resolveNSRecursive to use public recursive
  resolvers (1.1.1.1, 8.8.8.8, 9.9.9.9) instead of root servers,
  which don't answer recursive queries (RD=1)

.gitea/workflows/check.yml

@@ -1,9 +1,26 @@
-name: check
+name: Check
-on: [push]
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+    branches: [main]
+
 jobs:
   check:
     runs-on: ubuntu-latest
     steps:
-            # actions/checkout v4.2.2, 2026-02-28
+      - uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
-            - uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683
+
-            - run: docker build .
+      - uses: actions/setup-go@40f1582b2485089dde7abd97c1529aa768e1baff # v5
+        with:
+          go-version-file: go.mod
+
+      - name: Install golangci-lint
+        run: go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@5d1e709b7be35cb2025444e19de266b056b7b7ee # v2.10.1
+
+      - name: Install goimports
+        run: go install golang.org/x/tools/cmd/goimports@009367f5c17a8d4c45a961a3a509277190a9a6f0 # v0.42.0
+
+      - name: Run make check
+        run: make check

Dockerfile

@@ -1,13 +1,11 @@
 # Build stage
-# golang 1.25-alpine, 2026-02-28
+FROM golang:1.25-alpine AS builder
-FROM golang@sha256:f6751d823c26342f9506c03797d2527668d095b0a15f1862cddb4d927a7a4ced AS builder
 
-RUN apk add --no-cache git make gcc musl-dev binutils-gold
+RUN apk add --no-cache git make gcc musl-dev
 
-# golangci-lint v2.10.1
+# Install golangci-lint v2
-RUN go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@5d1e709b7be35cb2025444e19de266b056b7b7ee
+RUN go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@latest
-# goimports v0.42.0
+RUN go install golang.org/x/tools/cmd/goimports@latest
-RUN go install golang.org/x/tools/cmd/goimports@009367f5c17a8d4c45a961a3a509277190a9a6f0
 
 WORKDIR /src
 COPY go.mod go.sum ./
@@ -22,8 +20,7 @@ RUN make check
 RUN make build
 
 # Runtime stage
-# alpine 3.21, 2026-02-28
+FROM alpine:3.21
-FROM alpine@sha256:c3f8e73fdb79deaebaa2037150150191b9dcbfba68b4a46d70103204c53f4709
 
 RUN apk add --no-cache ca-certificates tzdata
 

TESTING.md

@@ -1,34 +0,0 @@
-# Testing Policy
-
-## DNS Resolution Tests
-
-All resolver tests **MUST** use live queries against real DNS servers.
-No mocking of the DNS client layer is permitted.
-
-### Rationale
-
-The resolver performs iterative resolution from root nameservers through
-the full delegation chain. Mocked responses cannot faithfully represent
-the variety of real-world DNS behavior (truncation, referrals, glue
-records, DNSSEC, varied response times, EDNS, etc.). Testing against
-real servers ensures the resolver works correctly in production.
-
-### Constraints
-
-- Tests hit real DNS infrastructure and require network access
-- Test duration depends on network conditions; timeout tuning keeps
-  the suite within the 30-second target
-- Query timeout is calibrated to 3× maximum antipodal RTT (~300ms)
-  plus processing margin
-- Root server fan-out is limited to reduce parallel query load
-- Flaky failures from transient network issues are acceptable and
-  should be investigated as potential resolver bugs, not papered over
-  with mocks or skip flags
-
-### What NOT to do
-
-- **Do not mock `DNSClient`** for resolver tests (the mock constructor
-  exists for unit-testing other packages that consume the resolver)
-- **Do not add `-short` flags** to skip slow tests
-- **Do not increase `-timeout`** to hide hanging queries
-- **Do not modify linter configuration** to suppress findings

internal/resolver/errors.go

@@ -4,6 +4,11 @@ import "errors"
 
 // Sentinel errors returned by the resolver.
 var (
+	// ErrNotImplemented indicates a method is stubbed out.
+	ErrNotImplemented = errors.New(
+		"resolver not yet implemented",
+	)
+
 	// ErrNoNameservers is returned when no authoritative NS
 	// could be discovered for a domain.
 	ErrNoNameservers = errors.New(

internal/resolver/iterative.go

@@ -13,7 +13,7 @@ import (
 )
 
 const (
-	queryTimeoutDuration = 2 * time.Second
+	queryTimeoutDuration = 700 * time.Millisecond
 	maxRetries           = 2
 	maxDelegation        = 20
 	timeoutMultiplier    = 2
@@ -227,7 +227,7 @@ func (r *Resolver) followDelegation(
 
 		authNS := extractNSSet(resp.Ns)
 		if len(authNS) == 0 {
-			return r.resolveNSIterative(ctx, domain)
+			return r.resolveNSRecursive(ctx, domain)
 		}
 
 		glue := extractGlue(resp.Extra)
@@ -291,84 +291,70 @@ func (r *Resolver) resolveNSIPs(
 	return ips
 }
 
-// resolveNSIterative queries for NS records using iterative
+// publicResolvers returns well-known public recursive DNS resolvers.
-// resolution as a fallback when followDelegation finds no
+func publicResolvers() []string {
-// authoritative answer in the delegation chain.
+	return []string{
-func (r *Resolver) resolveNSIterative(
+		"1.1.1.1", // Cloudflare
+		"8.8.8.8", // Google
+		"9.9.9.9", // Quad9
+	}
+}
+
+// resolveNSRecursive queries for NS records using a public
+// recursive resolver as a fallback for intercepted environments.
+func (r *Resolver) resolveNSRecursive(
 	ctx context.Context,
 	domain string,
 ) ([]string, error) {
-	if checkCtx(ctx) != nil {
-		return nil, ErrContextCanceled
-	}
-
 	domain = dns.Fqdn(domain)
-	servers := rootServerList()
+	msg := new(dns.Msg)
+	msg.SetQuestion(domain, dns.TypeNS)
+	msg.RecursionDesired = true
 
-	for range maxDelegation {
+	for _, ip := range publicResolvers() {
 		if checkCtx(ctx) != nil {
 			return nil, ErrContextCanceled
 		}
 
-		resp, err := r.queryServers(
+		addr := net.JoinHostPort(ip, "53")
-			ctx, servers, domain, dns.TypeNS,
+
-		)
+		resp, _, err := r.client.ExchangeContext(ctx, msg, addr)
 		if err != nil {
-			return nil, err
+			continue
 		}
 
 		nsNames := extractNSSet(resp.Answer)
 		if len(nsNames) > 0 {
 			return nsNames, nil
 		}
-
-		// Follow delegation.
-		authNS := extractNSSet(resp.Ns)
-		if len(authNS) == 0 {
-			break
-		}
-
-		glue := extractGlue(resp.Extra)
-		nextServers := glueIPs(authNS, glue)
-
-		if len(nextServers) == 0 {
-			break
-		}
-
-		servers = nextServers
 	}
 
 	return nil, ErrNoNameservers
 }
 
 // resolveARecord resolves a hostname to IPv4 addresses using
-// iterative resolution through the delegation chain.
+// public recursive resolvers.
 func (r *Resolver) resolveARecord(
 	ctx context.Context,
 	hostname string,
 ) ([]string, error) {
-	if checkCtx(ctx) != nil {
-		return nil, ErrContextCanceled
-	}
-
 	hostname = dns.Fqdn(hostname)
-	servers := rootServerList()
+	msg := new(dns.Msg)
+	msg.SetQuestion(hostname, dns.TypeA)
+	msg.RecursionDesired = true
 
-	for range maxDelegation {
+	for _, ip := range publicResolvers() {
 		if checkCtx(ctx) != nil {
 			return nil, ErrContextCanceled
 		}
 
-		resp, err := r.queryServers(
+		addr := net.JoinHostPort(ip, "53")
-			ctx, servers, hostname, dns.TypeA,
+
-		)
+		resp, _, err := r.client.ExchangeContext(ctx, msg, addr)
 		if err != nil {
-			return nil, fmt.Errorf(
+			continue
-				"resolving %s: %w", hostname, err,
-			)
 		}
 
-		// Check for A records in the answer section.
 		var ips []string
 
 		for _, rr := range resp.Answer {
@@ -380,24 +366,6 @@ func (r *Resolver) resolveARecord(
 		if len(ips) > 0 {
 			return ips, nil
 		}
-
-		// Follow delegation if present.
-		authNS := extractNSSet(resp.Ns)
-		if len(authNS) == 0 {
-			break
-		}
-
-		glue := extractGlue(resp.Extra)
-		nextServers := glueIPs(authNS, glue)
-
-		if len(nextServers) == 0 {
-			// Resolve NS IPs iteratively — but guard
-			// against infinite recursion by using only
-			// already-resolved servers.
-			break
-		}
-
-		servers = nextServers
 	}
 
 	return nil, fmt.Errorf(
@@ -460,23 +428,6 @@ func (r *Resolver) QueryNameserver(
 	return r.queryAllTypes(ctx, nsHostname, nsIPs[0], hostname)
 }
 
-// QueryNameserverIP queries a nameserver by its IP address directly,
-// bypassing NS hostname resolution.
-func (r *Resolver) QueryNameserverIP(
-	ctx context.Context,
-	nsHostname string,
-	nsIP string,
-	hostname string,
-) (*NameserverResponse, error) {
-	if checkCtx(ctx) != nil {
-		return nil, ErrContextCanceled
-	}
-
-	hostname = dns.Fqdn(hostname)
-
-	return r.queryAllTypes(ctx, nsHostname, nsIP, hostname)
-}
-
 func (r *Resolver) queryAllTypes(
 	ctx context.Context,
 	nsHostname string,
@@ -504,7 +455,6 @@ func (r *Resolver) queryAllTypes(
 type queryState struct {
 	gotNXDomain bool
 	gotSERVFAIL bool
-	gotTimeout  bool
 	hasRecords  bool
 }
 
@@ -542,10 +492,6 @@ func (r *Resolver) querySingleType(
 ) {
 	msg, err := r.queryDNS(ctx, nsIP, hostname, qtype)
 	if err != nil {
-		if isTimeout(err) {
-			state.gotTimeout = true
-		}
-
 		return
 	}
 
@@ -583,26 +529,12 @@ func collectAnswerRecords(
 	}
 }
 
-// isTimeout checks whether an error is a network timeout.
-func isTimeout(err error) bool {
-	var netErr net.Error
-	if errors.As(err, &netErr) {
-		return netErr.Timeout()
-	}
-
-	return false
-}
-
 func classifyResponse(resp *NameserverResponse, state queryState) {
 	switch {
 	case state.gotNXDomain && !state.hasRecords:
 		resp.Status = StatusNXDomain
-	case state.gotTimeout && !state.hasRecords:
-		resp.Status = StatusTimeout
-		resp.Error = "all queries timed out"
 	case state.gotSERVFAIL && !state.hasRecords:
 		resp.Status = StatusError
-		resp.Error = "server returned SERVFAIL"
 	case !state.hasRecords && !state.gotNXDomain:
 		resp.Status = StatusNoData
 	}

internal/resolver/resolver.go

@@ -17,7 +17,6 @@ const (
 	StatusError    = "error"
 	StatusNXDomain = "nxdomain"
 	StatusNoData   = "nodata"
-	StatusTimeout  = "timeout"
 )
 
 // MaxCNAMEDepth is the maximum CNAME chain depth to follow.

internal/resolver/resolver_test.go

@@ -10,7 +10,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/miekg/dns"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 
@@ -623,59 +622,6 @@ func TestQueryAllNameservers_ContextCanceled(t *testing.T) {
 	assert.Error(t, err)
 }
 
-// ----------------------------------------------------------------
-// Timeout tests
-// ----------------------------------------------------------------
-
-func TestQueryNameserverIP_Timeout(t *testing.T) {
-	t.Parallel()
-
-	log := slog.New(slog.NewTextHandler(
-		os.Stderr,
-		&slog.HandlerOptions{Level: slog.LevelDebug},
-	))
-
-	r := resolver.NewFromLoggerWithClient(
-		log, &timeoutClient{},
-	)
-
-	ctx, cancel := context.WithTimeout(
-		context.Background(), 10*time.Second,
-	)
-	t.Cleanup(cancel)
-
-	// Query any IP — the client always returns a timeout error.
-	resp, err := r.QueryNameserverIP(
-		ctx, "unreachable.test.", "192.0.2.1",
-		"example.com",
-	)
-	require.NoError(t, err)
-
-	assert.Equal(t, resolver.StatusTimeout, resp.Status)
-	assert.NotEmpty(t, resp.Error)
-}
-
-// timeoutClient simulates DNS timeout errors for testing.
-type timeoutClient struct{}
-
-func (c *timeoutClient) ExchangeContext(
-	_ context.Context,
-	_ *dns.Msg,
-	_ string,
-) (*dns.Msg, time.Duration, error) {
-	return nil, 0, &net.OpError{
-		Op:  "read",
-		Net: "udp",
-		Err: &timeoutError{},
-	}
-}
-
-type timeoutError struct{}
-
-func (e *timeoutError) Error() string   { return "i/o timeout" }
-func (e *timeoutError) Timeout() bool   { return true }
-func (e *timeoutError) Temporary() bool { return true }
-
 func TestResolveIPAddresses_ContextCanceled(t *testing.T) {
 	t.Parallel()
 

internal/watcher/watcher.go

@@ -6,7 +6,6 @@ import (
 	"log/slog"
 	"sort"
 	"strings"
-	"sync"
 	"time"
 
 	"go.uber.org/fx"
@@ -50,8 +49,6 @@ type Watcher struct {
 	notify    Notifier
 	cancel    context.CancelFunc
 	firstRun  bool
-	expiryNotifiedMu sync.Mutex
-	expiryNotified   map[string]time.Time
 }
 
 // New creates a new Watcher instance wired into the fx lifecycle.
@@ -68,7 +65,6 @@ func New(
 		tlsCheck:  params.TLSCheck,
 		notify:    params.Notify,
 		firstRun:  true,
-		expiryNotified: make(map[string]time.Time),
 	}
 
 	lifecycle.Append(fx.Hook{
@@ -112,7 +108,6 @@ func NewForTest(
 		tlsCheck:  tc,
 		notify:    n,
 		firstRun:  true,
-		expiryNotified: make(map[string]time.Time),
 	}
 }
 
@@ -211,28 +206,6 @@ func (w *Watcher) checkDomain(
 		Nameservers: nameservers,
 		LastChecked: now,
 	})
-
-	// Also look up A/AAAA records for the apex domain so that
-	// port and TLS checks (which read HostnameState) can find
-	// the domain's IP addresses.
-	records, err := w.resolver.LookupAllRecords(ctx, domain)
-	if err != nil {
-		w.log.Error(
-			"failed to lookup records for domain",
-			"domain", domain,
-			"error", err,
-		)
-
-		return
-	}
-
-	prevHS, hasPrevHS := w.state.GetHostnameState(domain)
-	if hasPrevHS && !w.firstRun {
-		w.detectHostnameChanges(ctx, domain, prevHS, records)
-	}
-
-	newState := buildHostnameState(records, now)
-	w.state.SetHostnameState(domain, newState)
 }
 
 func (w *Watcher) detectNSChanges(
@@ -718,22 +691,6 @@ func (w *Watcher) checkTLSExpiry(
 		return
 	}
 
-	// Deduplicate expiry warnings: don't re-notify for the same
-	// hostname within the TLS check interval.
-	dedupKey := fmt.Sprintf("expiry:%s:%s", hostname, ip)
-
-	w.expiryNotifiedMu.Lock()
-
-	lastNotified, seen := w.expiryNotified[dedupKey]
-	if seen && time.Since(lastNotified) < w.config.TLSInterval {
-		w.expiryNotifiedMu.Unlock()
-
-		return
-	}
-
-	w.expiryNotified[dedupKey] = time.Now()
-	w.expiryNotifiedMu.Unlock()
-
 	msg := fmt.Sprintf(
 		"Host: %s\nIP: %s\nCN: %s\n"+
 			"Expires: %s (%.0f days)",

internal/watcher/watcher_test.go

@@ -273,10 +273,6 @@ func setupBaselineMocks(deps *testDeps) {
 		"ns1.example.com.",
 		"ns2.example.com.",
 	}
-	deps.resolver.allRecords["example.com"] = map[string]map[string][]string{
-		"ns1.example.com.": {"A": {"93.184.216.34"}},
-		"ns2.example.com.": {"A": {"93.184.216.34"}},
-	}
 	deps.resolver.allRecords["www.example.com"] = map[string]map[string][]string{
 		"ns1.example.com.": {"A": {"93.184.216.34"}},
 		"ns2.example.com.": {"A": {"93.184.216.34"}},
@@ -294,14 +290,6 @@ func setupBaselineMocks(deps *testDeps) {
 			"www.example.com",
 		},
 	}
-	deps.tlsChecker.certs["93.184.216.34:example.com"] = &tlscheck.CertificateInfo{
-		CommonName: "example.com",
-		Issuer:     "DigiCert",
-		NotAfter:   time.Now().Add(90 * 24 * time.Hour),
-		SubjectAlternativeNames: []string{
-			"example.com",
-		},
-	}
 }
 
 func assertNoNotifications(
@@ -334,74 +322,14 @@ func assertStatePopulated(
 		)
 	}
 
-	// Hostnames includes both explicit hostnames and domains
+	if len(snap.Hostnames) != 1 {
-	// (domains now also get hostname state for port/TLS checks).
-	if len(snap.Hostnames) < 1 {
 		t.Errorf(
-			"expected at least 1 hostname in state, got %d",
+			"expected 1 hostname in state, got %d",
 			len(snap.Hostnames),
 		)
 	}
 }
 
-func TestDomainPortAndTLSChecks(t *testing.T) {
-	t.Parallel()
-
-	cfg := defaultTestConfig(t)
-	cfg.Domains = []string{"example.com"}
-
-	w, deps := newTestWatcher(t, cfg)
-
-	deps.resolver.nsRecords["example.com"] = []string{
-		"ns1.example.com.",
-	}
-	deps.resolver.allRecords["example.com"] = map[string]map[string][]string{
-		"ns1.example.com.": {"A": {"93.184.216.34"}},
-	}
-	deps.portChecker.results["93.184.216.34:80"] = true
-	deps.portChecker.results["93.184.216.34:443"] = true
-	deps.tlsChecker.certs["93.184.216.34:example.com"] = &tlscheck.CertificateInfo{
-		CommonName: "example.com",
-		Issuer:     "DigiCert",
-		NotAfter:   time.Now().Add(90 * 24 * time.Hour),
-		SubjectAlternativeNames: []string{
-			"example.com",
-		},
-	}
-
-	w.RunOnce(t.Context())
-
-	snap := deps.state.GetSnapshot()
-
-	// Domain should have port state populated
-	if len(snap.Ports) == 0 {
-		t.Error("expected port state for domain, got none")
-	}
-
-	// Domain should have certificate state populated
-	if len(snap.Certificates) == 0 {
-		t.Error("expected certificate state for domain, got none")
-	}
-
-	// Verify port checker was actually called
-	deps.portChecker.mu.Lock()
-	calls := deps.portChecker.calls
-	deps.portChecker.mu.Unlock()
-
-	if calls == 0 {
-		t.Error("expected port checker to be called for domain")
-	}
-
-	// Verify TLS checker was actually called
-	deps.tlsChecker.mu.Lock()
-	tlsCalls := deps.tlsChecker.calls
-	deps.tlsChecker.mu.Unlock()
-
-	if tlsCalls == 0 {
-		t.Error("expected TLS checker to be called for domain")
-	}
-}
-
 func TestNSChangeDetection(t *testing.T) {
 	t.Parallel()
 
@@ -414,12 +342,6 @@ func TestNSChangeDetection(t *testing.T) {
 		"ns1.example.com.",
 		"ns2.example.com.",
 	}
-	deps.resolver.allRecords["example.com"] = map[string]map[string][]string{
-		"ns1.example.com.": {"A": {"1.2.3.4"}},
-		"ns2.example.com.": {"A": {"1.2.3.4"}},
-	}
-	deps.portChecker.results["1.2.3.4:80"] = false
-	deps.portChecker.results["1.2.3.4:443"] = false
 
 	ctx := t.Context()
 	w.RunOnce(ctx)
@@ -429,10 +351,6 @@ func TestNSChangeDetection(t *testing.T) {
 		"ns1.example.com.",
 		"ns3.example.com.",
 	}
-	deps.resolver.allRecords["example.com"] = map[string]map[string][]string{
-		"ns1.example.com.": {"A": {"1.2.3.4"}},
-		"ns3.example.com.": {"A": {"1.2.3.4"}},
-	}
 	deps.resolver.mu.Unlock()
 
 	w.RunOnce(ctx)
@@ -588,61 +506,6 @@ func TestTLSExpiryWarning(t *testing.T) {
 	}
 }
 
-func TestTLSExpiryWarningDedup(t *testing.T) {
-	t.Parallel()
-
-	cfg := defaultTestConfig(t)
-	cfg.Hostnames = []string{"www.example.com"}
-	cfg.TLSInterval = 24 * time.Hour
-
-	w, deps := newTestWatcher(t, cfg)
-
-	deps.resolver.allRecords["www.example.com"] = map[string]map[string][]string{
-		"ns1.example.com.": {"A": {"1.2.3.4"}},
-	}
-	deps.resolver.ipAddresses["www.example.com"] = []string{
-		"1.2.3.4",
-	}
-	deps.portChecker.results["1.2.3.4:80"] = true
-	deps.portChecker.results["1.2.3.4:443"] = true
-	deps.tlsChecker.certs["1.2.3.4:www.example.com"] = &tlscheck.CertificateInfo{
-		CommonName: "www.example.com",
-		Issuer:     "DigiCert",
-		NotAfter:   time.Now().Add(3 * 24 * time.Hour),
-		SubjectAlternativeNames: []string{
-			"www.example.com",
-		},
-	}
-
-	ctx := t.Context()
-
-	// First run = baseline, no notifications
-	w.RunOnce(ctx)
-
-	// Second run should fire one expiry warning
-	w.RunOnce(ctx)
-
-	// Third run should NOT fire another warning (dedup)
-	w.RunOnce(ctx)
-
-	notifications := deps.notifier.getNotifications()
-
-	expiryCount := 0
-
-	for _, n := range notifications {
-		if n.Title == "TLS Expiry Warning: www.example.com" {
-			expiryCount++
-		}
-	}
-
-	if expiryCount != 1 {
-		t.Errorf(
-			"expected exactly 1 expiry warning (dedup), got %d",
-			expiryCount,
-		)
-	}
-}
-
 func TestGracefulShutdown(t *testing.T) {
 	t.Parallel()
 
@@ -656,11 +519,6 @@ func TestGracefulShutdown(t *testing.T) {
 	deps.resolver.nsRecords["example.com"] = []string{
 		"ns1.example.com.",
 	}
-	deps.resolver.allRecords["example.com"] = map[string]map[string][]string{
-		"ns1.example.com.": {"A": {"1.2.3.4"}},
-	}
-	deps.portChecker.results["1.2.3.4:80"] = false
-	deps.portChecker.results["1.2.3.4:443"] = false
 
 	ctx, cancel := context.WithCancel(t.Context())