Merge branch 'master' of github.com:DNSCrypt/dnscrypt-proxy

* 'master' of github.com:DNSCrypt/dnscrypt-proxy:
  Make return value explicit
  Repair stale respones for DoH
  Define a constant for the TTL of stale responses
  Update plugin_cache.go (#1900)

Author: jedisct1

dnscrypt-proxy/plugin_cache.go

@@ -10,6 +10,8 @@ import (
 	"github.com/miekg/dns"
 )
 
+const StaleResponseTtl = 30 * time.Second
+
 type CachedResponse struct {
 	expiration time.Time
 	msg        dns.Msg
@@ -68,29 +70,35 @@ func (plugin *PluginCache) Reload() error {
 
 func (plugin *PluginCache) Eval(pluginsState *PluginsState, msg *dns.Msg) error {
 	cacheKey := computeCacheKey(pluginsState, msg)
+
 	cachedResponses.RLock()
-	defer cachedResponses.RUnlock()
 	if cachedResponses.cache == nil {
+		cachedResponses.RUnlock()
 		return nil
 	}
 	cachedAny, ok := cachedResponses.cache.Get(cacheKey)
 	if !ok {
+		cachedResponses.RUnlock()
 		return nil
 	}
 	cached := cachedAny.(CachedResponse)
-
+	expiration := cached.expiration
 	synth := cached.msg.Copy()
+	cachedResponses.RUnlock()
+
 	synth.Id = msg.Id
 	synth.Response = true
 	synth.Compress = true
 	synth.Question = msg.Question
 
-	if time.Now().After(cached.expiration) {
+	if time.Now().After(expiration) {
+		expiration2 := time.Now().Add(StaleResponseTtl)
+		updateTTL(synth, expiration2)
 		pluginsState.sessionData["stale"] = synth
 		return nil
 	}
 
-	updateTTL(synth, cached.expiration)
+	updateTTL(synth, expiration)
 
 	pluginsState.synthResponse = synth
 	pluginsState.action = PluginsActionSynth

dnscrypt-proxy/proxy.go

@@ -572,9 +572,10 @@ func (proxy *Proxy) clientsCountDec() {
 	}
 }
 
-func (proxy *Proxy) processIncomingQuery(clientProto string, serverProto string, query []byte, clientAddr *net.Addr, clientPc net.Conn, start time.Time, onlyCached bool) (response []byte) {
+func (proxy *Proxy) processIncomingQuery(clientProto string, serverProto string, query []byte, clientAddr *net.Addr, clientPc net.Conn, start time.Time, onlyCached bool) []byte {
+	var response []byte = nil
 	if len(query) < MinDNSPacketSize {
-		return
+		return response
 	}
 	pluginsState := NewPluginsState(proxy, clientProto, clientAddr, serverProto, start)
 	serverName := "-"
@@ -586,25 +587,25 @@ func (proxy *Proxy) processIncomingQuery(clientProto string, serverProto string,
 	}
 	query, _ = pluginsState.ApplyQueryPlugins(&proxy.pluginsGlobals, query, needsEDNS0Padding)
 	if len(query) < MinDNSPacketSize || len(query) > MaxDNSPacketSize {
-		return
+		return response
 	}
 	if pluginsState.action == PluginsActionDrop {
 		pluginsState.returnCode = PluginsReturnCodeDrop
 		pluginsState.ApplyLoggingPlugins(&proxy.pluginsGlobals)
-		return
+		return response
 	}
 	var err error
 	if pluginsState.synthResponse != nil {
 		response, err = pluginsState.synthResponse.PackBuffer(response)
 		if err != nil {
 			pluginsState.returnCode = PluginsReturnCodeParseError
 			pluginsState.ApplyLoggingPlugins(&proxy.pluginsGlobals)
-			return
+			return response
 		}
 	}
 	if onlyCached {
 		if len(response) == 0 {
-			return
+			return response
 		}
 		serverInfo = nil
 	}
@@ -621,7 +622,7 @@ func (proxy *Proxy) processIncomingQuery(clientProto string, serverProto string,
 			if err != nil {
 				pluginsState.returnCode = PluginsReturnCodeParseError
 				pluginsState.ApplyLoggingPlugins(&proxy.pluginsGlobals)
-				return
+				return response
 			}
 			serverInfo.noticeBegin(proxy)
 			if serverProto == "udp" {
@@ -639,7 +640,7 @@ func (proxy *Proxy) processIncomingQuery(clientProto string, serverProto string,
 					if err != nil {
 						pluginsState.returnCode = PluginsReturnCodeParseError
 						pluginsState.ApplyLoggingPlugins(&proxy.pluginsGlobals)
-						return
+						return response
 					}
 					response, err = proxy.exchangeWithTCPServer(serverInfo, sharedKey, encryptedQuery, clientNonce)
 				}
@@ -660,25 +661,26 @@ func (proxy *Proxy) processIncomingQuery(clientProto string, serverProto string,
 				}
 				pluginsState.ApplyLoggingPlugins(&proxy.pluginsGlobals)
 				serverInfo.noticeFailure(proxy)
-				return
+				return response
 			}
 		} else if serverInfo.Proto == stamps.StampProtoTypeDoH {
 			tid := TransactionID(query)
 			SetTransactionID(query, 0)
 			serverInfo.noticeBegin(proxy)
 			serverResponse, _, tls, _, err := proxy.xTransport.DoHQuery(serverInfo.useGet, serverInfo.URL, query, proxy.timeout)
 			SetTransactionID(query, tid)
-			if err == nil || tls == nil || !tls.HandshakeComplete {
-				response = nil
-			} else if stale, ok := pluginsState.sessionData["stale"]; ok {
-				dlog.Debug("Serving stale response")
-				response, err = (stale.(*dns.Msg)).Pack()
+
+			if err != nil || tls == nil || !tls.HandshakeComplete {
+				if stale, ok := pluginsState.sessionData["stale"]; ok {
+					dlog.Debug("Serving stale response")
+					response, err = (stale.(*dns.Msg)).Pack()
+				}
 			}
 			if err != nil {
 				pluginsState.returnCode = PluginsReturnCodeNetworkError
 				pluginsState.ApplyLoggingPlugins(&proxy.pluginsGlobals)
 				serverInfo.noticeFailure(proxy)
-				return
+				return response
 			}
 			if response == nil {
 				response = serverResponse
@@ -689,7 +691,7 @@ func (proxy *Proxy) processIncomingQuery(clientProto string, serverProto string,
 		} else if serverInfo.Proto == stamps.StampProtoTypeODoHTarget {
 			tid := TransactionID(query)
 			if len(serverInfo.odohTargetConfigs) == 0 {
-				return
+				return response
 			}
 			target := serverInfo.odohTargetConfigs[rand.Intn(len(serverInfo.odohTargetConfigs))]
 			odohQuery, err := target.encryptQuery(query)
@@ -736,7 +738,7 @@ func (proxy *Proxy) processIncomingQuery(clientProto string, serverProto string,
 				pluginsState.returnCode = PluginsReturnCodeNetworkError
 				pluginsState.ApplyLoggingPlugins(&proxy.pluginsGlobals)
 				serverInfo.noticeFailure(proxy)
-				return
+				return response
 			}
 		} else {
 			dlog.Fatal("Unsupported protocol")
@@ -745,26 +747,26 @@ func (proxy *Proxy) processIncomingQuery(clientProto string, serverProto string,
 			pluginsState.returnCode = PluginsReturnCodeParseError
 			pluginsState.ApplyLoggingPlugins(&proxy.pluginsGlobals)
 			serverInfo.noticeFailure(proxy)
-			return
+			return response
 		}
 		response, err = pluginsState.ApplyResponsePlugins(&proxy.pluginsGlobals, response, ttl)
 		if err != nil {
 			pluginsState.returnCode = PluginsReturnCodeParseError
 			pluginsState.ApplyLoggingPlugins(&proxy.pluginsGlobals)
 			serverInfo.noticeFailure(proxy)
-			return
+			return response
 		}
 		if pluginsState.action == PluginsActionDrop {
 			pluginsState.returnCode = PluginsReturnCodeDrop
 			pluginsState.ApplyLoggingPlugins(&proxy.pluginsGlobals)
-			return
+			return response
 		}
 		if pluginsState.synthResponse != nil {
 			response, err = pluginsState.synthResponse.PackBuffer(response)
 			if err != nil {
 				pluginsState.returnCode = PluginsReturnCodeParseError
 				pluginsState.ApplyLoggingPlugins(&proxy.pluginsGlobals)
-				return
+				return response
 			}
 		}
 		if rcode := Rcode(response); rcode == dns.RcodeServerFailure { // SERVFAIL
@@ -788,15 +790,15 @@ func (proxy *Proxy) processIncomingQuery(clientProto string, serverProto string,
 		if serverInfo != nil {
 			serverInfo.noticeFailure(proxy)
 		}
-		return
+		return response
 	}
 	if clientProto == "udp" {
 		if len(response) > pluginsState.maxUnencryptedUDPSafePayloadSize {
 			response, err = TruncatedResponse(response)
 			if err != nil {
 				pluginsState.returnCode = PluginsReturnCodeParseError
 				pluginsState.ApplyLoggingPlugins(&proxy.pluginsGlobals)
-				return
+				return response
 			}
 		}
 		clientPc.(net.PacketConn).WriteTo(response, *clientAddr)
@@ -813,7 +815,7 @@ func (proxy *Proxy) processIncomingQuery(clientProto string, serverProto string,
 			if serverInfo != nil {
 				serverInfo.noticeFailure(proxy)
 			}
-			return
+			return response
 		}
 		if clientPc != nil {
 			clientPc.Write(response)