Fix timing of echo acks

src/frontend/mosh-server.cc

@@ -245,13 +245,15 @@ void serve( int host_fd, Terminal::Complete &terminal, ServerConnection &network
 
   while ( 1 ) {
     try {
-      int active_fds = poll( pollfds, 3, network.wait_time() );
+      uint64_t now = Network::timestamp();
+
+      int active_fds = poll( pollfds, 3, min( network.wait_time(), terminal.wait_time( now ) ) );
       if ( active_fds < 0 ) {
 	perror( "poll" );
 	break;
       }
 
-      uint64_t now = Network::timestamp();
+      now = Network::timestamp();
 
       if ( pollfds[ 0 ].revents & POLLIN ) {
 	/* packet received from the network */
@@ -281,8 +283,10 @@ void serve( int host_fd, Terminal::Complete &terminal, ServerConnection &network
 	    }
 	  }
 
+	  if ( !us.empty() ) {
 	    /* register input frame number for future echo ack */
 	    terminal.register_input_frame( last_remote_num, now );
+	  }
 
 	  /* update client with new state of terminal */
 	  if ( !network.shutdown_in_progress() ) {
@@ -399,7 +403,13 @@ void serve( int host_fd, Terminal::Complete &terminal, ServerConnection &network
 	}
       }
 
-      terminal.set_echo_ack( now );
+      if ( terminal.set_echo_ack( now ) ) {
+	/* update client with new echo ack */
+	if ( !network.shutdown_in_progress() ) {
+	  network.set_current_state( terminal );
+	}
+      }
+
       network.tick();
     } catch ( Network::NetworkException e ) {
       fprintf( stderr, "%s: %s\n", e.function.c_str(), strerror( e.the_errno ) );

src/network/transportsender.cc

@@ -104,7 +104,11 @@ int TransportSender<MyState>::wait_time( void )
 {
   calculate_timers();
 
-  uint64_t next_wakeup = min( next_ack_time, next_send_time );
+  uint64_t next_wakeup = next_ack_time;
+  if ( next_send_time < next_wakeup ) {
+    next_wakeup = next_send_time;
+  }
+
   uint64_t now = timestamp();
 
   if ( !connection->get_attached() ) {

src/statesync/completeterminal.cc

@@ -106,8 +106,9 @@ bool Complete::operator==( Complete const &x ) const
   return (terminal == x.terminal) && (echo_ack == x.echo_ack);
 }
 
-void Complete::set_echo_ack( uint64_t now )
+bool Complete::set_echo_ack( uint64_t now )
 {
+  bool ret = false;
   uint64_t newest_echo_ack = 0;
 
   for ( BOOST_AUTO( i, input_history.begin() ); i != input_history.end(); i++ ) {
@@ -118,10 +119,33 @@ void Complete::set_echo_ack( uint64_t now )
 
   input_history.remove_if( (&_1)->*&pair<uint64_t, uint64_t>::first < newest_echo_ack );
 
+  if ( echo_ack != newest_echo_ack ) {
+    ret = true;
+  }
+
   echo_ack = newest_echo_ack;
+
+  return ret;
 }
 
 void Complete::register_input_frame( uint64_t n, uint64_t now )
 {
   input_history.push_back( make_pair( n, now ) );
 }
+
+int Complete::wait_time( uint64_t now ) const
+{
+  if ( input_history.size() < 2 ) {
+    return INT_MAX;
+  }
+
+  BOOST_AUTO( it, input_history.begin() );
+  it++;
+
+  uint64_t next_echo_ack_time = it->second + ECHO_TIMEOUT;
+  if ( next_echo_ack_time <= now ) {
+    return 0;
+  } else {
+    return next_echo_ack_time - now;
+  }
+}

src/statesync/completeterminal.h

@@ -49,8 +49,9 @@ namespace Terminal {
     bool parser_grounded( void ) const { return parser.is_grounded(); }
 
     uint64_t get_echo_ack( void ) const { return echo_ack; }
-    void set_echo_ack( uint64_t now );
+    bool set_echo_ack( uint64_t now );
     void register_input_frame( uint64_t n, uint64_t now );
+    int wait_time( uint64_t now ) const;
 
     /* interface for Network::Transport */
     void subtract( const Complete * ) {}

src/statesync/user.h

@@ -68,7 +68,8 @@ namespace Network {
     void push_back( Parser::UserByte s_userbyte ) { actions.push_back( UserEvent( s_userbyte ) ); }
     void push_back( Parser::Resize s_resize ) { actions.push_back( UserEvent( s_resize ) ); }
     
-    size_t size( void ) { return actions.size(); }
+    bool empty( void ) const { return actions.empty(); }
+    size_t size( void ) const { return actions.size(); }
     const Parser::Action *get_action( unsigned int i );
     
     /* interface for Network::Transport */