Explicit echo ack protobuf with reliable semantics

src/frontend/mosh-server.cc

@@ -251,12 +251,16 @@ void serve( int host_fd, Terminal::Complete &terminal, ServerConnection &network
 	break;
       }
 
+      uint64_t now = Network::timestamp();
+
       if ( pollfds[ 0 ].revents & POLLIN ) {
 	/* packet received from the network */
 	network.recv();
 	
 	/* is new user input available for the terminal? */
 	if ( network.get_remote_state_num() != last_remote_num ) {
+	  last_remote_num = network.get_remote_state_num();
+
 	  string terminal_to_host;
 	  
 	  Network::UserStream us;
@@ -277,6 +281,9 @@ void serve( int host_fd, Terminal::Complete &terminal, ServerConnection &network
 	    }
 	  }
 
+	  /* 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() ) {
 	    network.set_current_state( terminal );
@@ -381,7 +388,7 @@ void serve( int host_fd, Terminal::Complete &terminal, ServerConnection &network
 
       /* update utmp if has been more than 10 seconds since heard from client */
       if ( connected_utmp ) {
-	if ( network.get_latest_remote_state().timestamp < Network::timestamp() - 10000 ) {
+	if ( network.get_latest_remote_state().timestamp < now - 10000 ) {
 	  utempter_remove_added_record();
 
 	  char tmp[ 64 ];
@@ -392,6 +399,7 @@ void serve( int host_fd, Terminal::Complete &terminal, ServerConnection &network
 	}
       }
 
+      terminal.set_echo_ack( now );
       network.tick();
     } catch ( Network::NetworkException e ) {
       fprintf( stderr, "%s: %s\n", e.function.c_str(), strerror( e.the_errno ) );

src/frontend/stmclient.cc

@@ -182,7 +182,7 @@ bool STMClient::process_network_input( void )
 
   overlays.get_prediction_engine().set_local_frame_acked( network->get_sent_state_acked() );
   overlays.get_prediction_engine().set_send_interval( network->send_interval() );
-  overlays.get_prediction_engine().set_local_frame_late_acked( network->get_sent_state_late_acked() );
+  overlays.get_prediction_engine().set_local_frame_late_acked( network->get_latest_remote_state().state.get_echo_ack() );
 
   return true;
 }

src/network/networktransport.cc

@@ -33,7 +33,6 @@ Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState
     sender( &connection, initial_state ),
     received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) ),
     last_receiver_state( initial_remote ),
-    sent_state_late_acked( 0 ),
     fragments(),
     verbose( false )
 {
@@ -47,7 +46,6 @@ Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState
     sender( &connection, initial_state ),
     received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) ),
     last_receiver_state( initial_remote ),
-    sent_state_late_acked( 0 ),
     fragments(),
     verbose( false )
 {
@@ -68,9 +66,6 @@ void Transport<MyState, RemoteState>::recv( void )
     }
 
     sender.process_acknowledgment_through( inst.ack_num() );
-    if ( inst.late_ack_num() > sent_state_late_acked ) {
-      sent_state_late_acked = inst.late_ack_num();
-    }
 
     /* first, make sure we don't already have the new state */
     for ( typename list< TimestampedState<RemoteState> >::iterator i = received_states.begin();

src/network/networktransport.h

@@ -47,7 +47,6 @@ namespace Network {
     /* simple receiver */
     list< TimestampedState<RemoteState> > received_states;
     RemoteState last_receiver_state; /* the state we were in when user last queried state */
-    uint64_t sent_state_late_acked;
     FragmentAssembly fragments;
     bool verbose;
 
@@ -97,7 +96,6 @@ namespace Network {
 
     uint64_t get_sent_state_acked( void ) const { return sender.get_sent_state_acked(); }
     uint64_t get_sent_state_last( void ) const { return sender.get_sent_state_last(); }
-    uint64_t get_sent_state_late_acked( void ) const { return sent_state_late_acked; }
 
     unsigned int send_interval( void ) const { return sender.send_interval(); }
 

src/network/transportfragment.cc

@@ -142,7 +142,6 @@ vector<Fragment> Fragmenter::make_fragments( Instruction &inst, int MTU )
        || (inst.new_num() != last_instruction.new_num())
        || (inst.ack_num() != last_instruction.ack_num())
        || (inst.throwaway_num() != last_instruction.throwaway_num())
-       || (inst.late_ack_num() != last_instruction.late_ack_num())
        || (inst.protocol_version() != last_instruction.protocol_version())
        || (last_MTU != MTU) ) {
     next_instruction_id++;

src/network/transportsender.cc

@@ -43,8 +43,6 @@ TransportSender<MyState>::TransportSender( Connection *s_connection, MyState &in
     shutdown_tries( 0 ),
     ack_num( 0 ),
     pending_data_ack( false ),
-    ack_timestamp( 0 ),
-    ack_history(),
     SEND_MINDELAY( 15 ),
     last_heard( 0 )
 {
@@ -260,14 +258,11 @@ void TransportSender<MyState>::send_in_fragments( string diff, uint64_t new_num
 {
   Instruction inst;
 
-  uint64_t now = timestamp();
-
   inst.set_protocol_version( MOSH_PROTOCOL_VERSION );
   inst.set_old_num( assumed_receiver_state->num );
   inst.set_new_num( new_num );
   inst.set_ack_num( ack_num );
   inst.set_throwaway_num( sent_states.front().num );
-  inst.set_late_ack_num( get_late_ack( now ) );
   inst.set_diff( diff );
 
   if ( new_num == uint64_t(-1) ) {
@@ -280,12 +275,11 @@ void TransportSender<MyState>::send_in_fragments( string diff, uint64_t new_num
     connection->send( i->tostring() );
 
     if ( verbose ) {
-      fprintf( stderr, "[%u] Sent [%d=>%d] id %d, frag %d ack=%d, late_ack=%d, throwaway=%d, len=%d, frame rate=%.2f, timeout=%d, srtt=%.1f age=%llu\n",
+      fprintf( stderr, "[%u] Sent [%d=>%d] id %d, frag %d ack=%d, throwaway=%d, len=%d, frame rate=%.2f, timeout=%d, srtt=%.1f\n",
 	       (unsigned int)(timestamp() % 100000), (int)inst.old_num(), (int)inst.new_num(), (int)i->id, (int)i->fragment_num,
-	       (int)inst.ack_num(), (int)inst.late_ack_num(), (int)inst.throwaway_num(), (int)i->contents.size(),
+	       (int)inst.ack_num(), (int)inst.throwaway_num(), (int)i->contents.size(),
 	       1000.0 / (double)send_interval(),
-	       (int)connection->timeout(), connection->get_SRTT(),
-	       (long long)(now - ack_timestamp) );
+	       (int)connection->timeout(), connection->get_SRTT() );
     }
 
   }
@@ -318,23 +312,4 @@ template <class MyState>
 void TransportSender<MyState>::set_ack_num( uint64_t s_ack_num )
 {
   ack_num = s_ack_num;
-  ack_timestamp = timestamp();
-  ack_history.push_back( make_pair( ack_num, ack_timestamp ) );
-}
-
-/* The "late" ack is for the input state that has had enough time on the host to have been echoed */
-template <class MyState>
-uint64_t TransportSender<MyState>::get_late_ack( uint64_t now )
-{
-  uint64_t newest_echo_ack = 0;
-
-  for ( BOOST_AUTO( i, ack_history.begin() ); i != ack_history.end(); i++ ) {
-    if ( i->second < now - ECHO_TIMEOUT ) {
-      newest_echo_ack = i->first;
-    }
-  }
-
-  ack_history.remove_if( (&_1)->*&pair<uint64_t, uint64_t>::first < newest_echo_ack );
-
-  return newest_echo_ack;
 }

src/network/transportsender.h

@@ -43,7 +43,6 @@ namespace Network {
     static const int ACK_INTERVAL = 3000; /* ms between empty acks */
     static const int ACK_DELAY = 100; /* ms before delayed ack */
     static const int SHUTDOWN_RETRIES = 3; /* number of shutdown packets to send before giving up */
-    static const int ECHO_TIMEOUT = 50; /* for late ack */
     static const int ACTIVE_RETRY_TIMEOUT = 10000; /* attempt to resend at frame rate */
 
     /* helper methods for tick() */
@@ -82,10 +81,6 @@ namespace Network {
     /* information about receiver state */
     uint64_t ack_num;
     bool pending_data_ack;
-    uint64_t ack_timestamp;
-
-    list< pair<uint64_t, uint64_t> > ack_history;
-    uint64_t get_late_ack( uint64_t now ); /* calculate delayed "echo" acknowledgment */
 
     unsigned int SEND_MINDELAY; /* ms to collect all input */
 

src/protobufs/hostinput.proto

@@ -19,7 +19,12 @@ message ResizeMessage {
   optional int32 height = 6;
 }
 
+message EchoAck {
+  optional uint64 echo_ack_num = 8;
+}
+
 extend Instruction {
   optional HostBytes hostbytes = 2;
   optional ResizeMessage resize = 3;
+  optional EchoAck echoack = 7;
 }

src/protobufs/transportinstruction.proto

@@ -9,7 +9,6 @@ message Instruction {
   optional uint64 new_num = 3;
   optional uint64 ack_num = 4;
   optional uint64 throwaway_num = 5;
-  optional uint64 late_ack_num = 7;
 
   optional bytes diff = 6;
 }

src/statesync/completeterminal.cc

@@ -16,6 +16,9 @@
     along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
 
+#include <boost/typeof/typeof.hpp>
+#include <boost/lambda/lambda.hpp>
+
 #include "completeterminal.h"
 
 #include "hostinput.pb.h"
@@ -24,6 +27,7 @@ using namespace std;
 using namespace Parser;
 using namespace Terminal;
 using namespace HostBuffers;
+using namespace boost::lambda;
 
 string Complete::act( const string &str )
 {
@@ -52,10 +56,16 @@ string Complete::act( const Action *act )
 }
 
 /* interface for Network::Transport */
-string Complete::diff_from( const Complete &existing )
+string Complete::diff_from( const Complete &existing ) const
 {
   HostBuffers::HostMessage output;
 
+  if ( existing.get_echo_ack() != get_echo_ack() ) {
+    assert( get_echo_ack() >= existing.get_echo_ack() );
+    Instruction *new_echo = output.add_instruction();
+    new_echo->MutableExtension( echoack )->set_echo_ack_num( get_echo_ack() );
+  }
+
   if ( !(existing.get_fb() == get_fb()) ) {
     if ( (existing.get_fb().ds.get_width() != terminal.get_fb().ds.get_width())
 	 || (existing.get_fb().ds.get_height() != terminal.get_fb().ds.get_height()) ) {
@@ -82,6 +92,10 @@ void Complete::apply_string( string diff )
     } else if ( input.instruction( i ).HasExtension( resize ) ) {
       act( new Resize( input.instruction( i ).GetExtension( resize ).width(),
 		       input.instruction( i ).GetExtension( resize ).height() ) );
+    } else if ( input.instruction( i ).HasExtension( echoack ) ) {
+      uint64_t inst_echo_ack_num = input.instruction( i ).GetExtension( echoack ).echo_ack_num();
+      assert( inst_echo_ack_num >= echo_ack );
+      echo_ack = inst_echo_ack_num;
     }
   }
 }
@@ -89,5 +103,25 @@ void Complete::apply_string( string diff )
 bool Complete::operator==( Complete const &x ) const
 {
   //  assert( parser == x.parser ); /* parser state is irrelevant for us */
-  return terminal == x.terminal;
+  return (terminal == x.terminal) && (echo_ack == x.echo_ack);
+}
+
+void Complete::set_echo_ack( uint64_t now )
+{
+  uint64_t newest_echo_ack = 0;
+
+  for ( BOOST_AUTO( i, input_history.begin() ); i != input_history.end(); i++ ) {
+    if ( i->second < now - ECHO_TIMEOUT ) {
+      newest_echo_ack = i->first;
+    }
+  }
+
+  input_history.remove_if( (&_1)->*&pair<uint64_t, uint64_t>::first < newest_echo_ack );
+
+  echo_ack = newest_echo_ack;
+}
+
+void Complete::register_input_frame( uint64_t n, uint64_t now )
+{
+  input_history.push_back( make_pair( n, now ) );
 }

src/statesync/completeterminal.h

@@ -19,6 +19,9 @@
 #ifndef COMPLETE_TERMINAL_HPP
 #define COMPLETE_TERMINAL_HPP
 
+#include <list>
+#include <stdint.h>
+
 #include "parser.h"
 #include "terminal.h"
 
@@ -30,8 +33,14 @@ namespace Terminal {
     Parser::UTF8Parser parser;
     Terminal::Emulator terminal;
 
+    std::list< std::pair<uint64_t, uint64_t> > input_history;
+    uint64_t echo_ack;
+
+    static const int ECHO_TIMEOUT = 50; /* for late ack */
+
   public:
-    Complete( size_t width, size_t height ) : parser(), terminal( width, height ) {}
+    Complete( size_t width, size_t height ) : parser(), terminal( width, height ),
+					      input_history(), echo_ack( 0 ) {}
     
     std::string act( const std::string &str );
     std::string act( const Parser::Action *act );
@@ -39,9 +48,13 @@ namespace Terminal {
     const Framebuffer & get_fb( void ) const { return terminal.get_fb(); }
     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 );
+    void register_input_frame( uint64_t n, uint64_t now );
+
     /* interface for Network::Transport */
     void subtract( const Complete * ) {}
-    std::string diff_from( const Complete &existing );
+    std::string diff_from( const Complete &existing ) const;
     void apply_string( std::string diff );
     bool operator==( const Complete &x ) const;
   };

src/statesync/user.cc

@@ -37,9 +37,9 @@ void UserStream::subtract( const UserStream *prefix )
   }
 }
 
-string UserStream::diff_from( const UserStream &existing )
+string UserStream::diff_from( const UserStream &existing ) const
 {
-  deque<UserEvent>::iterator my_it = actions.begin();
+  deque<UserEvent>::const_iterator my_it = actions.begin();
 
   for ( deque<UserEvent>::const_iterator i = existing.actions.begin();
 	i != existing.actions.end();

src/statesync/user.h

@@ -73,7 +73,7 @@ namespace Network {
     
     /* interface for Network::Transport */
     void subtract( const UserStream *prefix );
-    string diff_from( const UserStream &existing );
+    string diff_from( const UserStream &existing ) const;
     void apply_string( string diff );
     bool operator==( const UserStream &x ) const { return actions == x.actions; }
   };