lib/connections, lib/model: Track last connection duration (ref #7223) (#7242)

This adds a statistic to track the last connection duration per device.
It isn't used for much in this PR, but it's available for #7223 to use
in deciding how to order device connection attempts (deprioritizing
devices that just dropped our connection the last time).

lib/connections/quic_dial.go

@@ -87,7 +87,7 @@ func (d *quicDialer) Dial(ctx context.Context, _ protocol.DeviceID, uri *url.URL
 		return internalConn{}, errors.Wrap(err, "open stream")
 	}
 
-	return internalConn{&quicTlsConn{session, stream, createdConn}, connTypeQUICClient, quicPriority}, nil
+	return newInternalConn(&quicTlsConn{session, stream, createdConn}, connTypeQUICClient, quicPriority), nil
 }
 
 type quicDialerFactory struct {

lib/connections/quic_listen.go

@@ -150,7 +150,7 @@ func (t *quicListener) serve(ctx context.Context) error {
 			continue
 		}
 
-		t.conns <- internalConn{&quicTlsConn{session, stream, nil}, connTypeQUICServer, quicPriority}
+		t.conns <- newInternalConn(&quicTlsConn{session, stream, nil}, connTypeQUICServer, quicPriority)
 	}
 }
 

lib/connections/relay_dial.go

@@ -63,7 +63,7 @@ func (d *relayDialer) Dial(ctx context.Context, id protocol.DeviceID, uri *url.U
 		return internalConn{}, err
 	}
 
-	return internalConn{tc, connTypeRelayClient, relayPriority}, nil
+	return newInternalConn(tc, connTypeRelayClient, relayPriority), nil
 }
 
 type relayDialerFactory struct{}

lib/connections/relay_listen.go

@@ -105,7 +105,7 @@ func (t *relayListener) serve(ctx context.Context) error {
 				continue
 			}
 
-			t.conns <- internalConn{tc, connTypeRelayServer, relayPriority}
+			t.conns <- newInternalConn(tc, connTypeRelayServer, relayPriority)
 
 		// Poor mans notifier that informs the connection service that the
 		// relay URI has changed. This can only happen when we connect to a

lib/connections/structs.go

@@ -35,8 +35,9 @@ type tlsConn interface {
 // came from (type, priority).
 type internalConn struct {
 	tlsConn
-	connType connType
-	priority int
+	connType      connType
+	priority      int
+	establishedAt time.Time
 }
 
 type connType int
@@ -82,6 +83,15 @@ func (t connType) Transport() string {
 	}
 }
 
+func newInternalConn(tc tlsConn, connType connType, priority int) internalConn {
+	return internalConn{
+		tlsConn:       tc,
+		connType:      connType,
+		priority:      priority,
+		establishedAt: time.Now(),
+	}
+}
+
 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
@@ -119,6 +129,10 @@ func (c internalConn) Transport() string {
 	return transport + "6"
 }
 
+func (c internalConn) EstablishedAt() time.Time {
+	return c.establishedAt
+}
+
 func (c internalConn) String() string {
 	return fmt.Sprintf("%s-%s/%s/%s", c.LocalAddr(), c.RemoteAddr(), c.Type(), c.Crypto())
 }

lib/connections/tcp_dial.go

@@ -57,7 +57,7 @@ func (d *tcpDialer) Dial(ctx context.Context, _ protocol.DeviceID, uri *url.URL)
 		return internalConn{}, err
 	}
 
-	return internalConn{tc, connTypeTCPClient, tcpPriority}, nil
+	return newInternalConn(tc, connTypeTCPClient, tcpPriority), nil
 }
 
 type tcpDialerFactory struct{}

lib/connections/tcp_listen.go

@@ -137,7 +137,7 @@ func (t *tcpListener) serve(ctx context.Context) error {
 			continue
 		}
 
-		t.conns <- internalConn{tc, connTypeTCPServer, tcpPriority}
+		t.conns <- newInternalConn(tc, connTypeTCPServer, tcpPriority)
 	}
 }