Merge pull request 'Fix DNS resolution: NS name bug, glue bypass, FormatRecord duplicate header, result deduplication' (#23) from agent/go-expert-developer/da16f960 into main

Reviewed-on: http://gitea.hansenits.com.au/hits/ExploreDNS/pulls/23

internal/dns/decode.go

@@ -1,7 +1,6 @@
 package dns
 
 import (
-	"fmt"
 	"strings"
 
 	"github.com/miekg/dns"
@@ -234,12 +233,5 @@ func FormatRecord(rr dns.RR) string {
 	if rr == nil {
 		return ""
 	}
-	header := rr.Header()
-	return fmt.Sprintf("%s %d %s %s %s",
-		header.Name,
-		header.Ttl,
-		dns.ClassToString[header.Class],
-		QNameType(header.Rrtype),
-		rr.String(),
-	)
+	return rr.String()
 }

internal/output/stats.go

@@ -196,3 +196,54 @@ func containsString(items []string, target string) bool {
 	}
 	return false
 }
+
+// DeduplicateResults collapses terminal results that represent the same
+// outcome from the same server into a single entry with summed probability.
+// This prevents the same nameserver failure (or answer) from appearing once
+// per delegation path when several parent servers all refer to the same child.
+func DeduplicateResults(results []traverse.TraversalResult) []traverse.TraversalResult {
+	type entry struct {
+		result traverse.TraversalResult
+		prob   float64
+	}
+	keys := make(map[string]*entry)
+	var order []string
+
+	for _, r := range results {
+		if r.Response == nil || r.Referral == nil {
+			continue
+		}
+		key := resultDeduplicationKey(r)
+		if e, ok := keys[key]; ok {
+			e.prob += r.Referral.Prob
+		} else {
+			keys[key] = &entry{result: r, prob: r.Referral.Prob}
+			order = append(order, key)
+		}
+	}
+
+	deduped := make([]traverse.TraversalResult, 0, len(order))
+	for _, key := range order {
+		e := keys[key]
+		refCopy := *e.result.Referral
+		refCopy.Prob = e.prob
+		deduped = append(deduped, traverse.TraversalResult{
+			Referral: &refCopy,
+			Response: e.result.Response,
+		})
+	}
+	return deduped
+}
+
+func resultDeduplicationKey(r traverse.TraversalResult) string {
+	bailiwick := strings.TrimSuffix(r.Referral.Bailiwick, ".")
+	switch r.Response.Type {
+	case traverse.RespAnswer:
+		key, _ := answerKey(r.Response)
+		return "answer:" + bailiwick + ":" + key
+	case traverse.RespNSResolutionFailed:
+		return "ns_error:" + r.Response.ErrorMessage
+	default:
+		return r.Response.Type.String() + ":" + bailiwick + ":" + r.Response.ErrorMessage
+	}
+}

internal/output/text.go

@@ -120,7 +120,8 @@ func (f *textFormatter) writeResults(results []traverse.TraversalResult) error {
 	}
 
 	terminal := terminalResults(results)
-	for _, result := range terminal {
+	deduped := DeduplicateResults(terminal)
+	for _, result := range deduped {
 		prefix := strings.Repeat("  ", result.Referral.Depth+1)
 		line := prefix + f.formatResultLine(result)
 		if _, err := fmt.Fprintln(f.w, line); err != nil {
@@ -196,14 +197,15 @@ func (f *textFormatter) formatResultLine(result traverse.TraversalResult) string
 	prob := formatProbability(result.Referral.Prob)
 	switch result.Response.Type {
 	case traverse.RespAnswer:
-		key, rrs := answerKey(result.Response)
+		key, _ := answerKey(result.Response)
 		if key == "" {
 			return fmt.Sprintf("%s resulted in answer", prob)
 		}
-		if len(rrs) == 1 {
-			return f.colorize(fmt.Sprintf("%s answered with %s", prob, rrs[0]), colorGreen)
+		nsLabel := ""
+		if result.Referral.Bailiwick != "" && result.Referral.Bailiwick != "." {
+			nsLabel = trimDomain(result.Referral.Bailiwick) + " "
 		}
-		return f.colorize(fmt.Sprintf("%s answered with %s", prob, strings.Join(rrs, " / ")), colorGreen)
+		return f.colorize(fmt.Sprintf("%s %sanswered with %s", prob, nsLabel, key), colorGreen)
 	case traverse.RespNODATA:
 		return fmt.Sprintf("%s found no such record", prob)
 	case traverse.RespNXDOMAIN:

internal/traverse/referral.go

@@ -230,7 +230,10 @@ func (r *Referral) Resolve(ctx context.Context, traverser *Traverser, cache *Inf
 		if resp.Type == RespReferral {
 			children := resp.ChildReferrals()
 			for _, child := range children {
-				if visited != nil && visited[child.Name] {
+				// Only skip visited names when they have no addresses; if glue
+				// was included in the referral response we still need to query
+				// that child to get the authoritative answer.
+				if visited != nil && visited[child.Name] && !child.HasAddresses() {
 					continue
 				}
 				if !stack.Push(child) {

internal/traverse/traverser.go

@@ -227,15 +227,19 @@ func (t *Traverser) processReferral(ctx context.Context, ref *Referral, cache *I
 		}
 		t.mu.Unlock()
 
-		ref.Addresses = t.resolveGlueViaSystem(ctx, ref.Name, cache)
+		// Resolve the nameserver's IP address. The NS hostname is stored in
+		// Bailiwick; ref.Name is the domain being queried (not the NS name).
+		nsToResolve := ref.Bailiwick
+		if nsToResolve == "" || nsToResolve == "." {
+			nsToResolve = ref.Name
+		}
+		nsName := strings.TrimSuffix(nsToResolve, ".")
+
+		ref.Addresses = t.resolveGlueViaSystem(ctx, nsToResolve, cache)
 		if len(ref.Addresses) > 0 {
 			ref.State = StateResolved
 		} else {
-			addrs, err := t.ResolveNS(ctx, ref.Name, cache, visitedCopy, t.depth)
-			nsName := strings.TrimSuffix(ref.Bailiwick, ".")
-			if nsName == "" || nsName == "." {
-				nsName = strings.TrimSuffix(ref.Name, ".")
-			}
+			addrs, err := t.ResolveNS(ctx, nsToResolve, cache, visitedCopy, t.depth)
 			if err != nil {
 				return &Response{
 					Referral:     ref,
@@ -375,7 +379,10 @@ func (t *Traverser) ResolveNS(ctx context.Context, nsName string, cache *InfoCac
 		if resp.Type == RespReferral {
 			children := resp.ChildReferrals()
 			for _, child := range children {
-				if visited != nil && visited[child.Name] {
+				// Only skip visited names when they have no addresses; if glue
+				// was included in the referral response we still need to query
+				// that child to get the authoritative answer.
+				if visited != nil && visited[child.Name] && !child.HasAddresses() {
 					continue
 				}
 				if !stack.Push(child) {