Perform an initial benchmark to use servers with the lowest latency

(initially according to the certificate rtt)

dnscrypt-proxy/certs.go

@@ -21,9 +21,9 @@ type CertInfo struct {
 	CryptoConstruction CryptoConstruction
 }
 
-func FetchCurrentCert(proxy *Proxy, proto string, pk ed25519.PublicKey, serverAddress string, providerName string) (CertInfo, error) {
+func FetchCurrentCert(proxy *Proxy, proto string, pk ed25519.PublicKey, serverAddress string, providerName string) (CertInfo, int, error) {
 	if len(pk) != ed25519.PublicKeySize {
-		return CertInfo{}, errors.New("Invalid public key length")
+		return CertInfo{}, 0, errors.New("Invalid public key length")
 	}
 	if !strings.HasSuffix(providerName, ".") {
 		providerName = providerName + "."
@@ -31,9 +31,9 @@ func FetchCurrentCert(proxy *Proxy, proto string, pk ed25519.PublicKey, serverAd
 	query := new(dns.Msg)
 	query.SetQuestion(providerName, dns.TypeTXT)
 	client := dns.Client{Net: proto, UDPSize: uint16(MaxDNSUDPPacketSize)}
-	in, _, err := client.Exchange(query, serverAddress)
+	in, rtt, err := client.Exchange(query, serverAddress)
 	if err != nil {
-		return CertInfo{}, err
+		return CertInfo{}, 0, err
 	}
 	now := uint32(time.Now().Unix())
 	certInfo := CertInfo{CryptoConstruction: UndefinedConstruction}
@@ -108,12 +108,12 @@ func FetchCurrentCert(proxy *Proxy, proto string, pk ed25519.PublicKey, serverAd
 		certInfo.CryptoConstruction = cryptoConstruction
 		copy(certInfo.ServerPk[:], serverPk[:])
 		copy(certInfo.MagicQuery[:], binCert[104:112])
-		dlog.Noticef("[%v] Valid cert (crypto version %d) found", providerName, cryptoConstruction)
+		dlog.Noticef("[%v] Valid cert (crypto version %d) found - rtt: %dms", providerName, cryptoConstruction, rtt.Nanoseconds()/1000000)
 	}
 	if certInfo.CryptoConstruction == UndefinedConstruction {
-		return certInfo, errors.New("No useable certificate found")
+		return certInfo, 0, errors.New("No useable certificate found")
 	}
-	return certInfo, nil
+	return certInfo, int(rtt.Nanoseconds() / 1000000), nil
 }
 
 func isDigit(b byte) bool { return b >= '0' && b <= '9' }

dnscrypt-proxy/serversInfo.go

@@ -53,6 +53,7 @@ type ServerInfo struct {
 	TCPAddr            *net.TCPAddr
 	lastActionTS       time.Time
 	rtt                ewma.MovingAverage
+	initialRtt         int
 }
 
 type ServersInfo struct {
@@ -106,6 +107,21 @@ func (serversInfo *ServersInfo) refresh(proxy *Proxy) (int, error) {
 			liveServers++
 		}
 	}
+	serversInfo.Lock()
+	inner := serversInfo.inner
+	innerLen := len(inner)
+	for i := 0; i < innerLen; i++ {
+		for j := i + 1; j < innerLen; j++ {
+			if inner[j].initialRtt < inner[i].initialRtt {
+				inner[j], inner[i] = inner[i], inner[j]
+			}
+		}
+	}
+	serversInfo.inner = inner
+	if innerLen > 1 {
+		dlog.Noticef("Server with the lowest initial latency: %s (rtt: %dms)", inner[0].Name, inner[0].initialRtt)
+	}
+	serversInfo.Unlock()
 	return liveServers, err
 }
 
@@ -140,7 +156,7 @@ func (serversInfo *ServersInfo) fetchServerInfo(proxy *Proxy, name string, stamp
 	if err != nil || len(serverPk) != ed25519.PublicKeySize {
 		dlog.Fatalf("Unsupported public key: [%v]", serverPk)
 	}
-	certInfo, err := FetchCurrentCert(proxy, proxy.mainProto, serverPk, stamp.serverAddrStr, stamp.providerName)
+	certInfo, rtt, err := FetchCurrentCert(proxy, proxy.mainProto, serverPk, stamp.serverAddrStr, stamp.providerName)
 	if err != nil {
 		return ServerInfo{}, err
 	}
@@ -161,6 +177,7 @@ func (serversInfo *ServersInfo) fetchServerInfo(proxy *Proxy, name string, stamp
 		Timeout:            proxy.timeout,
 		UDPAddr:            remoteUDPAddr,
 		TCPAddr:            remoteTCPAddr,
+		initialRtt:         rtt,
 	}
 	return serverInfo, nil
 }