Phillip/449 iterative cache extra queries regression

src/zdns/lookup.go

@@ -437,6 +437,80 @@ func (r *Resolver) cachedRetryingLookup(ctx context.Context, q Question, nameSer
 			return r, isCached, StatusBlacklist, 0, nil
 		}
 	}
+	if !requestIteration {
+		// We're performing our own iteration, let's try checking the cache for the next authority
+		// For example, if we query yahoo.com and google.com, we don't need to go to the root servers for the gTLD
+		// servers twice, they'll be identical
+		name := strings.ToLower(q.Name)
+		layer = strings.ToLower(layer)
+		// get the next authority to query
+		authName, err := nextAuthority(name, layer)
+		if err != nil {
+			r.verboseLog(depth+2, err)
+			return SingleQueryResult{}, isCached, StatusAuthFail, 0, errors.Wrap(err, "could not get next authority with name: "+name+" and layer: "+layer)
+		}
+		if name != layer && authName != layer {
+			// we have a valid authority to check the cache for
+			var result SingleQueryResult
+			result.Answers = make([]interface{}, 0)
+			result.Additional = make([]interface{}, 0)
+			result.Authorities = make([]interface{}, 0)
+			if authName == "" {
+				r.verboseLog(depth+2, "Can't parse name to authority properly. name: ", name, ", layer: ", layer)
+				return SingleQueryResult{}, isCached, StatusAuthFail, 0, nil
+			}
+			r.verboseLog(depth+2, "Cache auth check for ", authName)
+			var qAuth Question
+			qAuth.Name = authName
+			qAuth.Type = dns.TypeNS
+			qAuth.Class = dns.ClassINET
+			cachedResult, ok = r.cache.GetCachedResult(qAuth, nil, depth+2)
+			if ok {
+				isCached = true
+				// we have a cache hit on the NS record for the authorities. Let's construct a response with the NS
+				// record. However, the caller is going to expect an answer as if they'd queried the root server, so we
+				// need to populate the authority and additionals, and remove the NS answers since the caller didn't
+				// perform an NS lookup.
+				for _, ans := range cachedResult.Answers {
+					ns, ansOk := ans.(Answer)
+					if !ansOk {
+						continue
+					}
+					if ns.Type == "NS" {
+						result.Authorities = append(result.Authorities, ns)
+					}
+				}
+				// populate the additionals from the cache
+				// starting with A records
+				for _, ans := range cachedResult.Answers {
+					var qAdd Question
+					qAdd.Name = strings.TrimSuffix(ans.(Answer).Answer, ".")
+					qAdd.Type = dns.TypeA
+					qAdd.Class = dns.ClassINET
+					cachedResult, ok = r.cache.GetCachedResult(qAdd, nil, depth+2)
+					if ok {
+						result.Additional = append(result.Additional, cachedResult.Answers...)
+					}
+				}
+				// now AAAA records
+				for _, ans := range cachedResult.Answers {
+					var qAdd Question
+					qAdd.Name = strings.TrimSuffix(ans.(Answer).Answer, ".")
+					qAdd.Type = dns.TypeAAAA
+					qAdd.Class = dns.ClassINET
+					cachedResult, ok = r.cache.GetCachedResult(qAdd, nil, depth+2)
+					if ok {
+						result.Additional = append(result.Additional, cachedResult.Answers...)
+					}
+				}
+				// only want to return if we actually have additionals and authorities from the cache for the caller
+				if len(result.Additional) > 0 && len(result.Authorities) > 0 {
+					return result, isCached, StatusNoError, 0, nil
+				}
+				// unsuccessful in retrieving from the cache, we'll continue to the wire
+			}
+		}
+	}
 
 	// Alright, we're not sure what to do, go to the wire.
 	result, status, try, err := r.retryingLookup(ctx, q, nameServer, requestIteration)

src/zdns/util.go

@@ -19,6 +19,8 @@ import (
 	"net"
 	"strings"
 
+	"github.com/pkg/errors"
+
 	log "github.com/sirupsen/logrus"
 
 	"github.com/zmap/dns"
@@ -108,6 +110,39 @@ func checkGlueHelper(server, ansType string, result SingleQueryResult) (SingleQu
 	return SingleQueryResult{}, StatusError
 }
 
+// nextAuthority returns the next authority to query based on the current name and layer
+// Example: nextAuthority("www.google.com", ".") -> "com"
+func nextAuthority(name, layer string) (string, error) {
+	// We are our own authority for PTRs
+	// (This is dealt with elsewhere)
+	if strings.HasSuffix(name, "in-addr.arpa") && layer == "." {
+		return "in-addr.arpa", nil
+	}
+
+	idx := strings.LastIndex(name, ".")
+	if idx < 0 || (idx+1) >= len(name) {
+		return name, nil
+	}
+	if layer == "." {
+		return name[idx+1:], nil
+	}
+
+	if !strings.HasSuffix(name, layer) {
+		return "", errors.New("Server did not provide appropriate resolvers to continue recursion")
+	}
+
+	// Limit the search space to the prefix of the string that isn't layer
+	idx = strings.LastIndex(name, layer) - 1
+	if idx < 0 || (idx+1) >= len(name) {
+		// Out of bounds. We are our own authority
+		return name, nil
+	}
+	// Find the next step in the layer
+	idx = strings.LastIndex(name[0:idx], ".")
+	next := name[idx+1:]
+	return next, nil
+}
+
 func makeVerbosePrefix(depth int) string {
 	return fmt.Sprintf("DEPTH %02d", depth) + ":" + strings.Repeat("  ", 2*depth)
 }