Stream the delegation check's queries too

Every DNS query the name server checks send is now reported from
exchangeHostPort as a dig command line with a short answer (addresses,
referral, DS, NXDOMAIN) and its round-trip time; the serials check's SOA
queries keep their own events with the server's result. The delegation
check streams with ?stream=1 like /serials, and the Name servers tab
shows its queries as they happen, keeps its result and follows a running
check when you come back.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/nscheck/nscheck.go

@@ -20,8 +20,10 @@ import (
 	"net"
 	"net/netip"
 	"sort"
+	"strconv"
 	"strings"
 	"sync"
+	"sync/atomic"
 	"syscall"
 	"time"
 
@@ -93,24 +95,118 @@ type Checker struct {
 	// IsLocal reports whether an address belongs to this host (default:
 	// its interface addresses and loopback).
 	IsLocal func(netip.Addr) bool
-	// Watch, if set, is told about each query Serials sends and its
-	// outcome as it happens (the web UI shows them while it waits). It is
-	// called from several goroutines at once.
+	// Watch, if set, is told about each DNS query the checks send and
+	// its outcome as it happens (the web UI shows them while it waits).
+	// It is called from several goroutines at once.
 	Watch func(Event)
 }
 
-// Event is a query Serials starts or finishes (Checker.Watch).
+// Event is a query a check starts or finishes (Checker.Watch).
 type Event struct {
 	// Kind is "start" or "end" (of query ID).
 	Kind string `json:"kind"`
-	ID   int    `json:"id"`
+	ID   int64  `json:"id"`
 	// Query describes what is asked, as a dig command line.
 	Query string `json:"query,omitempty"`
-	// End: the server's result (SOA queries), or the addresses found or
-	// the error (address lookups).
-	Result    *Result  `json:"result,omitempty"`
-	Addresses []string `json:"addresses,omitempty"`
-	Error     string   `json:"error,omitempty"`
+	// End: Answer sums up the answer ("192.0.2.1, 2001:db8::1",
+	// "NXDOMAIN", "referral to a.nic.lol., …"), or Error says why there
+	// is none. Serials' SOA queries give the server's Result instead.
+	Answer string  `json:"answer,omitempty"`
+	Error  string  `json:"error,omitempty"`
+	RTTMs  int64   `json:"rtt_ms,omitempty"`
+	Result *Result `json:"result,omitempty"`
+}
+
+// eventIDs numbers events; 0 is left for the caller's own steps.
+var eventIDs atomic.Int64
+
+func (c *Checker) startEvent(query string) int64 {
+	if c.Watch == nil {
+		return 0
+	}
+	id := eventIDs.Add(1)
+	c.Watch(Event{Kind: "start", ID: id, Query: query})
+	return id
+}
+
+func (c *Checker) endEvent(e Event) {
+	if c.Watch != nil {
+		e.Kind = "end"
+		c.Watch(e)
+	}
+}
+
+// quietKey in a context stops exchangeHostPort from reporting the query:
+// the caller reports it with more to say (Serials' SOA queries).
+type quietKey struct{}
+
+// digQuery is the dig command line for m sent to hostport.
+func digQuery(m *dns.Msg, hostport string, key *Key) string {
+	host, port, err := net.SplitHostPort(hostport)
+	if err != nil {
+		host, port = hostport, ""
+	}
+	if len(m.Question) == 0 {
+		return "dig @" + host
+	}
+	q := m.Question[0]
+	s := digLine(host, port, q.Name, dns.TypeToString[q.Qtype], !m.RecursionDesired, key)
+	if o := m.IsEdns0(); o != nil && o.Do() {
+		s += " +dnssec"
+	}
+	return s
+}
+
+// sumAnswer sums up a DNS answer in a few words.
+func sumAnswer(resp *dns.Msg) string {
+	if resp.Rcode != dns.RcodeSuccess {
+		return dns.RcodeToString[resp.Rcode]
+	}
+	var vals []string
+	for _, rr := range resp.Answer {
+		switch v := rr.(type) {
+		case *dns.A:
+			vals = append(vals, v.A.String())
+		case *dns.AAAA:
+			vals = append(vals, v.AAAA.String())
+		case *dns.NS:
+			vals = append(vals, v.Ns)
+		case *dns.SOA:
+			vals = append(vals, "serial "+strconv.FormatUint(uint64(v.Serial), 10))
+		case *dns.DS:
+			vals = append(vals, "DS "+strconv.Itoa(int(v.KeyTag)))
+		case *dns.RRSIG:
+		default:
+			vals = append(vals, dns.TypeToString[rr.Header().Rrtype])
+		}
+	}
+	if len(vals) == 0 {
+		var ns []string
+		for _, rr := range resp.Ns {
+			switch v := rr.(type) {
+			case *dns.NS:
+				ns = append(ns, v.Ns)
+			case *dns.SOA:
+				return "no such record"
+			}
+		}
+		if len(ns) > 0 {
+			return "referral to " + shorten(ns)
+		}
+		return "empty answer"
+	}
+	s := shorten(vals)
+	if !resp.Authoritative && !resp.RecursionAvailable {
+		s += " (not authoritative)"
+	}
+	return s
+}
+
+func shorten(vals []string) string {
+	if len(vals) > 3 {
+		return strings.Join(vals[:3], ", ") + " and " + strconv.Itoa(len(vals)-3) + " more"
+	}
+	return strings.Join(vals, ", ")
 }
 
 // digLine is a dig command line for a query (no TSIG secret).
@@ -196,16 +292,25 @@ func (c *Checker) exchange(ctx context.Context, m *dns.Msg, addr string, key *Ke
 	return c.exchangeHostPort(ctx, m, net.JoinHostPort(addr, c.port()), key)
 }
 
-func (c *Checker) exchangeHostPort(ctx context.Context, m *dns.Msg, hostport string, key *Key) (*dns.Msg, time.Duration, error) {
+func (c *Checker) exchangeHostPort(ctx context.Context, m *dns.Msg, hostport string, key *Key) (resp *dns.Msg, rtt time.Duration, err error) {
+	if c.Watch != nil && ctx.Value(quietKey{}) == nil {
+		id := c.startEvent(digQuery(m, hostport, key))
+		defer func() {
+			e := Event{ID: id, RTTMs: rtt.Milliseconds()}
+			if err != nil {
+				e.Error = err.Error()
+			} else {
+				e.Answer = sumAnswer(resp)
+			}
+			c.endEvent(e)
+		}()
+	}
 	cl := &dns.Client{Timeout: c.timeout()}
 	if key != nil {
 		name := dns.Fqdn(key.Name)
 		cl.TsigSecret = map[string]string{name: key.Secret}
 		m.SetTsig(name, dns.Fqdn(key.Algorithm), 300, time.Now().Unix())
 	}
-	var resp *dns.Msg
-	var rtt time.Duration
-	var err error
 	for try := 0; try < 2; try++ {
 		resp, rtt, err = cl.ExchangeContext(ctx, m, hostport)
 		if err == nil || ctx.Err() != nil {
@@ -262,7 +367,7 @@ func (c *Checker) soa(ctx context.Context, zone string, key *Key, ref *uint32, r
 	if port == "" {
 		port = c.port()
 	}
-	resp, rtt, err := c.exchangeHostPort(ctx, m, net.JoinHostPort(r.Address, port), key)
+	resp, rtt, err := c.exchangeHostPort(context.WithValue(ctx, quietKey{}, true), m, net.JoinHostPort(r.Address, port), key)
 	if err != nil {
 		var ne net.Error
 		switch {
@@ -322,42 +427,19 @@ func (c *Checker) Serials(ctx context.Context, zone string, ref *uint32, targets
 		out = append(out, r)
 		mu.Unlock()
 	}
-	var ids int
-	start := func(query string) int {
-		if c.Watch == nil {
-			return 0
-		}
-		mu.Lock()
-		ids++
-		id := ids
-		mu.Unlock()
-		c.Watch(Event{Kind: "start", ID: id, Query: query})
-		return id
-	}
-	end := func(e Event) {
-		if c.Watch != nil {
-			e.Kind = "end"
-			c.Watch(e)
-		}
-	}
 	seen := map[string]bool{}
 	for _, t := range targets {
 		addrs := t.Addresses
 		if addrs == nil && t.Name != "" {
-			res, _ := c.resolver()
-			id := start(digLine(res, "", t.Name, "A, AAAA", false, nil))
 			found, err := c.lookup(ctx, t.Name)
 			if err != nil || len(found) == 0 {
 				msg := "no A or AAAA record"
 				if err != nil {
 					msg = "looking up its address: " + err.Error()
 				}
-				r := Result{Name: t.Name, Source: t.Source, Status: "no_address", Error: msg}
-				end(Event{ID: id, Error: msg, Result: &r})
-				add(r)
+				add(Result{Name: t.Name, Source: t.Source, Status: "no_address", Error: msg})
 				continue
 			}
-			end(Event{ID: id, Addresses: found})
 			addrs = found
 		}
 		for _, a := range addrs {
@@ -381,11 +463,13 @@ func (c *Checker) Serials(ctx context.Context, zone string, ref *uint32, targets
 			if port == "" {
 				port = c.port()
 			}
-			id := start(digLine(r.Address, port, zone, "SOA", true, t.Key))
+			// Reported here rather than by exchange: the end carries the
+			// server's status.
+			id := c.startEvent(digLine(r.Address, port, zone, "SOA", true, t.Key))
 			go func(r Result, key *Key) {
 				defer wg.Done()
 				c.soa(ctx, zone, key, ref, &r)
-				end(Event{ID: id, Result: &r})
+				c.endEvent(Event{ID: id, Result: &r, RTTMs: r.RTTMs})
 				add(r)
 			}(r, t.Key)
 		}

internal/nscheck/nscheck_test.go

@@ -6,6 +6,7 @@ import (
 	"net/netip"
 	"strconv"
 	"strings"
+	"sync"
 	"testing"
 	"time"
 
@@ -307,3 +308,64 @@ func TestDelegationDS(t *testing.T) {
 		}
 	}
 }
+
+// TestWatch: with Watch set, every query is reported as it starts and
+// ends, as a dig command line with a summary of the answer.
+func TestWatch(t *testing.T) {
+	port, res := internet(t, func(q dns.Question) *dns.Msg {
+		m := new(dns.Msg)
+		if q.Qtype == dns.TypeNS && q.Name == "adbraun.lol." {
+			m.Ns = []dns.RR{rr("adbraun.lol. 3600 IN NS ns1.adbraun.lol.")}
+			m.Extra = []dns.RR{rr("ns1.adbraun.lol. 3600 IN A 127.0.0.12")}
+		}
+		return m
+	})
+	var mu sync.Mutex
+	var events []Event
+	c := checker(port, res)
+	c.Watch = func(e Event) {
+		mu.Lock()
+		events = append(events, e)
+		mu.Unlock()
+	}
+	ref := uint32(7)
+	c.Delegation(context.Background(), "adbraun.lol.", []string{"ns1.adbraun.lol."}, map[string][]string{"ns1.adbraun.lol.": {"127.0.0.12"}}, &ref, nil)
+	open := map[int64]string{}
+	var queries, answers []string
+	for _, e := range events {
+		switch e.Kind {
+		case "start":
+			if !strings.HasPrefix(e.Query, "dig @") {
+				t.Errorf("query %q", e.Query)
+			}
+			open[e.ID] = e.Query
+			queries = append(queries, e.Query)
+		case "end":
+			q, ok := open[e.ID]
+			if !ok {
+				t.Errorf("end without start: %+v", e)
+			}
+			delete(open, e.ID)
+			a := e.Answer + e.Error
+			if e.Result != nil {
+				a = e.Result.Status
+			}
+			answers = append(answers, q+" => "+a)
+		}
+	}
+	if len(open) != 0 {
+		t.Errorf("never ended: %v", open)
+	}
+	all := strings.Join(answers, "\n")
+	for _, want := range []string{
+		" adbraun.lol. NS +norec => referral to ns1.adbraun.lol.",        // asking a parent server
+		"@127.0.0.12 -p " + port + " adbraun.lol. SOA +norec => in_sync", // asking the delegated server
+	} {
+		if !strings.Contains(all, want) {
+			t.Errorf("no %q in\n%s", want, all)
+		}
+	}
+	if len(queries) < 4 {
+		t.Errorf("only %d queries:\n%s", len(queries), all)
+	}
+}