feat: implement DNS server fingerprinting (HAN-384) (#10)

internal/output/runner.go

@@ -3,7 +3,9 @@ package output
 import (
 	"context"
 	"fmt"
+	"net"
 
+	"github.com/hits/ExploreDNS/internal/fingerprint"
 	"github.com/hits/ExploreDNS/internal/traverse"
 )
 
@@ -25,6 +27,13 @@ func RunTraversal(ctx context.Context, traverser *traverse.Traverser, cfg *Confi
 		return results, err
 	}
 
+	// Fingerprint servers when both ShowVersions and ShowServers are enabled.
+	// Gating on ShowServers avoids unnecessary network calls when versions
+	// would not be displayed anyway.
+	if cfg.ShowVersions && cfg.ShowServers {
+		cfg.Fingerprints = fingerprint.New().FingerprintAll(ctx, collectUniqueServerIPs(results))
+	}
+
 	if err := formatter.WriteSummary(results); err != nil {
 		return results, err
 	}
@@ -34,3 +43,20 @@ func RunTraversal(ctx context.Context, traverser *traverse.Traverser, cfg *Confi
 
 	return results, nil
 }
+
+// collectUniqueServerIPs returns the set of unique server IPs seen in results.
+func collectUniqueServerIPs(results []traverse.TraversalResult) []net.IP {
+	seen := make(map[string]bool)
+	var ips []net.IP
+	for _, r := range results {
+		if r.Response == nil || r.Response.Server == nil {
+			continue
+		}
+		key := r.Response.Server.String()
+		if !seen[key] {
+			seen[key] = true
+			ips = append(ips, r.Response.Server)
+		}
+	}
+	return ips
+}