wip

5 files changed, 64 insertions, 29 deletions

diff --git a/lib/connections/service.go b/lib/connections/service.go
index f832c5685..4786eec54 100644
--- a/lib/connections/service.go
+++ b/lib/connections/service.go
@@ -68,7 +68,6 @@ var (
 const (
 	perDeviceWarningIntv          = 15 * time.Minute
 	tlsHandshakeTimeout           = 10 * time.Second
-	minConnectionReplaceAge       = 10 * time.Second
 	minConnectionLoopSleep        = 5 * time.Second
 	stdConnectionLoopSleep        = time.Minute
 	worstDialerPriority           = math.MaxInt32
@@ -318,17 +317,17 @@ func (s *service) connectionCheckEarly(remoteID protocol.DeviceID, c internalCon
 		return errNetworkNotAllowed
 	}
 
-	// Lower priority is better, just like nice etc.
-	if ct, ok := s.model.Connection(remoteID); ok {
-		if ct.Priority() > c.priority || time.Since(ct.Statistics().StartedAt) > minConnectionReplaceAge {
-			l.Debugf("Switching connections %s (existing: %s new: %s)", remoteID, ct, c)
-		} else if cfg.MultipleConnections <= s.connectionsForDevice(cfg.DeviceID) {
-			// We should not already be connected to the other party. TODO: This
-			// could use some better handling. If the old connection is dead but
-			// hasn't timed out yet we may want to drop *that* connection and keep
-			// this one. But in case we are two devices connecting to each other
-			// in parallel we don't want to do that or we end up with no
-			// connections still established...
+	if existing := s.connectionsForDevice(cfg.DeviceID); existing > 0 {
+		// Check if the new connection is better than an existing one. Lower
+		// priority is better, just like `nice` etc.
+		if ct, ok := s.model.Connection(remoteID); ok {
+			if ct.Priority() > c.priority {
+				l.Debugf("Switching connections %s (existing: %s new: %s)", remoteID, ct, c)
+				return nil
+			}
+		}
+		if existing >= cfg.MultipleConnections {
+			// We're not allowed to accept any more connections to this device.
 			return errDeviceAlreadyConnected
 		}
 	}
diff --git a/lib/connections/structs.go b/lib/connections/structs.go
index 2040fcb08..10feadaa3 100644
--- a/lib/connections/structs.go
+++ b/lib/connections/structs.go
@@ -93,21 +93,28 @@ func (t connType) Transport() string {
 
 func newInternalConn(tc tlsConn, connType connType, isLocal bool, priority int) internalConn {
 	now := time.Now()
-	buf := binary.BigEndian.AppendUint64(nil, uint64(now.UnixNano()))
-	hash := sha256.Sum224([]byte(fmt.Sprintf("%v-%v-%v", tc.LocalAddr(), connType.Transport(), tc.RemoteAddr())))
-	buf = append(buf, hash[:]...)
-	connectionID := base32.HexEncoding.WithPadding(base32.NoPadding).EncodeToString(buf)
-
 	return internalConn{
 		tlsConn:       tc,
 		connType:      connType,
 		isLocal:       isLocal,
 		priority:      priority,
 		establishedAt: now.Truncate(time.Second),
-		connectionID:  connectionID,
+		connectionID:  newConnectionID(tc, connType, now),
 	}
 }
 
+// newConnection generates a connection ID. The connection ID is designed to
+// be 1) unique for each connection (even those reusing the same socket
+// address on both sides), 2) sortable so that the connection with the
+// lowest ID will be the primary one. This also coincides with being the
+// oldest connection.
+func newConnectionID(tc tlsConn, connType connType, now time.Time) string {
+	buf := binary.BigEndian.AppendUint64(nil, uint64(now.UnixNano()))
+	hash := sha256.Sum224([]byte(fmt.Sprintf("%v-%v-%v", tc.LocalAddr(), connType.Transport(), tc.RemoteAddr())))
+	buf = append(buf, hash[:]...)
+	return base32.HexEncoding.WithPadding(base32.NoPadding).EncodeToString(buf)
+}
+
 func (c internalConn) Close() error {
 	// *tls.Conn.Close() does more than it says on the tin. Specifically, it
 	// sends a TLS alert message, which might block forever if the
diff --git a/lib/model/model.go b/lib/model/model.go
index 967a9f629..7d15f9130 100644
--- a/lib/model/model.go
+++ b/lib/model/model.go
@@ -163,6 +163,7 @@ type model struct {
 	pmut                sync.RWMutex
 	conns               map[string]protocol.Connection // connection ID -> connection
 	deviceConns         map[protocol.DeviceID][]string // device -> connection IDs (invariant: if the key exists, the value is len >= 1, with the primary connection at the start of the slice)
+	promotedConn        map[protocol.DeviceID]string   // device -> last promoted connection ID
 	connRequestLimiters map[protocol.DeviceID]*util.Semaphore
 	closed              map[string]chan struct{} // connection ID -> closed channel
 	helloMessages       map[protocol.DeviceID]protocol.Hello
@@ -248,6 +249,7 @@ func NewModel(cfg config.Wrapper, id protocol.DeviceID, clientName, clientVersio
 		pmut:                sync.NewRWMutex(),
 		conns:               make(map[string]protocol.Connection),
 		deviceConns:         make(map[protocol.DeviceID][]string),
+		promotedConn:        make(map[protocol.DeviceID]string),
 		connRequestLimiters: make(map[protocol.DeviceID]*util.Semaphore),
 		closed:              make(map[string]chan struct{}),
 		helloMessages:       make(map[protocol.DeviceID]protocol.Hello),
@@ -1912,6 +1914,7 @@ func (m *model) Closed(conn protocol.Connection, err error) {
 	if len(remainingConns) == 0 {
 		// All device connections closed
 		delete(m.deviceConns, deviceID)
+		delete(m.promotedConn, deviceID)
 		delete(m.connRequestLimiters, deviceID)
 		delete(m.helloMessages, deviceID)
 		delete(m.remoteFolderStates, deviceID)
@@ -2433,10 +2436,33 @@ func (m *model) promoteConnections() {
 	defer m.pmut.Unlock()
 
 	for deviceID, connIDs := range m.deviceConns {
+		// Figure out the best current connection priority for this device.
+		bestPriority := m.conns[connIDs[0]].Priority()
+		for _, connID := range connIDs[1:] {
+			priority := m.conns[connID].Priority()
+			if priority < bestPriority {
+				bestPriority = priority
+			}
+		}
+
+		// Close connections with a worse connection priority than best.
+		closing := make(map[string]bool)
+		for _, connID := range connIDs {
+			if m.conns[connID].Priority() > bestPriority {
+				l.Infoln("Closing connection", connID, "to", deviceID.Short(), "because it has a worse connection priority than the best connection")
+				go m.conns[connID].Close(errReplacingConnection)
+				closing[connID] = true
+			}
+		}
+
 		cm, passwords := m.generateClusterConfigFRLocked(deviceID)
-		if idxh, ok := m.indexHandlers[deviceID]; !ok || idxh.conn.ConnectionID() != connIDs[0] {
-			// Primary device lacks an index handler. We should promote the
-			// primary connection to be the index handling one.
+		if !closing[connIDs[0]] && m.promotedConn[deviceID] != connIDs[0] {
+			// The last promoted connection is not the current primary; we
+			// should promote the primary connection to be the index
+			// handling one. We do this by sending a ClusterConfig on it,
+			// which will cause the other side to start sending us index
+			// messages there. (On our side, we manage index handlers based
+			// on where we get ClusterConfigs from the peer.)
 			l.Infoln("Promoting connection", connIDs[0], "to", deviceID.Short())
 			conn := m.conns[connIDs[0]]
 			if conn.Statistics().StartedAt.IsZero() {
@@ -2444,11 +2470,15 @@ func (m *model) promoteConnections() {
 				conn.Start()
 			}
 			conn.ClusterConfig(cm)
+			m.promotedConn[deviceID] = connIDs[0]
 		}
 
-		// Make sure any new connections also get started, and a
+		// Make sure any other new connections also get started, and a
 		// secondary-marked ClusterConfig.
 		for _, connID := range connIDs[1:] {
+			if closing[connID] {
+				continue
+			}
 			conn := m.conns[connID]
 			if conn.Statistics().StartedAt.IsZero() {
 				conn.SetFolderPasswords(passwords)
diff --git a/test/h1/config.xml b/test/h1/config.xml
index 8dce0e261..7e2f87944 100644
--- a/test/h1/config.xml
+++ b/test/h1/config.xml
@@ -1,5 +1,5 @@
 <configuration version="37">
-    <folder id="default" label="" path="s1?files=10000&amp;sizeavg=25000000" type="sendreceive" rescanIntervalS="3600" fsWatcherEnabled="false" fsWatcherDelayS="10" ignorePerms="false" autoNormalize="true">
+    <folder id="default" label="" path="s1" type="sendreceive" rescanIntervalS="3600" fsWatcherEnabled="false" fsWatcherDelayS="10" ignorePerms="false" autoNormalize="true">
         <filesystemType>fake</filesystemType>
         <device id="I6KAH76-66SLLLB-5PFXSOA-UFJCDZC-YAOMLEK-CP2GB32-BV5RQST-3PSROAU" introducedBy="">
             <encryptionPassword></encryptionPassword>
@@ -123,9 +123,9 @@
         <connectionLimitEnough>0</connectionLimitEnough>
         <connectionLimitMax>0</connectionLimitMax>
         <insecureAllowOldTLSVersions>false</insecureAllowOldTLSVersions>
-        <connectionPriorityTcpLan>20</connectionPriorityTcpLan>
+        <connectionPriorityTcpLan>10</connectionPriorityTcpLan>
         <connectionPriorityQuicLan>20</connectionPriorityQuicLan>
-        <connectionPriorityTcpWan>40</connectionPriorityTcpWan>
+        <connectionPriorityTcpWan>30</connectionPriorityTcpWan>
         <connectionPriorityQuicWan>40</connectionPriorityQuicWan>
         <connectionPriorityRelay>50</connectionPriorityRelay>
         <connectionPriorityUpgradeThreshold>0</connectionPriorityUpgradeThreshold>
diff --git a/test/h2/config.xml b/test/h2/config.xml
index 704dafbd2..a56c6335e 100644
--- a/test/h2/config.xml
+++ b/test/h2/config.xml
@@ -44,8 +44,7 @@
         </xattrFilter>
     </folder>
     <device id="I6KAH76-66SLLLB-5PFXSOA-UFJCDZC-YAOMLEK-CP2GB32-BV5RQST-3PSROAU" name="s1" compression="metadata" introducer="false" skipIntroductionRemovals="false" introducedBy="">
-        <address>tcp://127.0.0.1:22001</address>
-        <address>quic://127.0.0.1:22001</address>
+        <address>dynamic</address>
         <paused>false</paused>
         <autoAcceptFolders>false</autoAcceptFolders>
         <maxSendKbps>0</maxSendKbps>
@@ -121,9 +120,9 @@
         <connectionLimitEnough>0</connectionLimitEnough>
         <connectionLimitMax>0</connectionLimitMax>
         <insecureAllowOldTLSVersions>false</insecureAllowOldTLSVersions>
-        <connectionPriorityTcpLan>20</connectionPriorityTcpLan>
+        <connectionPriorityTcpLan>10</connectionPriorityTcpLan>
         <connectionPriorityQuicLan>20</connectionPriorityQuicLan>
-        <connectionPriorityTcpWan>40</connectionPriorityTcpWan>
+        <connectionPriorityTcpWan>30</connectionPriorityTcpWan>
         <connectionPriorityQuicWan>40</connectionPriorityQuicWan>
         <connectionPriorityRelay>50</connectionPriorityRelay>
         <connectionPriorityUpgradeThreshold>0</connectionPriorityUpgradeThreshold>