all: sync with master

internal/dnsforward/config.go

@@ -281,6 +281,10 @@ type ServerConfig struct {
 
 	// ServePlainDNS defines if plain DNS is allowed for incoming requests.
 	ServePlainDNS bool
+
+	// PendingRequestsEnabled defines if duplicate requests should be forwarded
+	// to upstreams along with the original one.
+	PendingRequestsEnabled bool
 }
 
 // UpstreamMode is a enumeration of upstream mode representations.  See
@@ -324,6 +328,9 @@ func (s *Server) newProxyConfig() (conf *proxy.Config, err error) {
 		UsePrivateRDNS:            srvConf.UsePrivateRDNS,
 		PrivateSubnets:            s.privateNets,
 		MessageConstructor:        s,
+		PendingRequests: &proxy.PendingRequestsConfig{
+			Enabled: srvConf.PendingRequestsEnabled,
+		},
 	}
 
 	if srvConf.EDNSClientSubnet.UseCustom {

internal/home/config.go

@@ -261,6 +261,16 @@ type dnsConfig struct {
 	// HostsFileEnabled defines whether to use information from the system hosts
 	// file to resolve queries.
 	HostsFileEnabled bool `yaml:"hostsfile_enabled"`
+
+	// PendingRequests configures duplicate requests policy.
+	PendingRequests *pendingRequests `yaml:"pending_requests"`
+}
+
+// pendingRequests is a block with pending requests configuration.
+type pendingRequests struct {
+	// Enabled controls if duplicate requests should be sent to the upstreams
+	// along with the original one.
+	Enabled bool `yaml:"enabled"`
 }
 
 type tlsConfigSettings struct {
@@ -380,6 +390,9 @@ var config = &configuration{
 		UsePrivateRDNS:   true,
 		ServePlainDNS:    true,
 		HostsFileEnabled: true,
+		PendingRequests: &pendingRequests{
+			Enabled: true,
+		},
 	},
 	TLS: tlsConfigSettings{
 		PortHTTPS:       defaultPortHTTPS,

internal/home/dns.go

@@ -272,6 +272,7 @@ func newServerConfig(
 		ServeHTTP3:             dnsConf.ServeHTTP3,
 		UseHTTP3Upstreams:      dnsConf.UseHTTP3Upstreams,
 		ServePlainDNS:          dnsConf.ServePlainDNS,
+		PendingRequestsEnabled: dnsConf.PendingRequests.Enabled,
 	}
 
 	var initialAddresses []netip.Addr

internal/stats/unit.go

@@ -64,7 +64,7 @@ type Entry struct {
 	Domain string
 
 	// UpstreamStats contains the DNS query statistics for both the upstream and
-	// fallback DNS servers.
+	// fallback DNS servers.  Don't modify items in the slice.
 	UpstreamStats []*proxy.UpstreamStatistics
 
 	// Result is the result of processing the request.