Explicit echo ack protobuf with reliable semantics

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 */