Keith Winstein
314 lines
9.0 KiB
C++
314 lines
9.0 KiB
C++
#include <assert.h>
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#include <iostream>
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#include "networktransport.hpp"
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using namespace Network;
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using namespace std;
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template <class MyState, class RemoteState>
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Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState &initial_remote )
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: connection(),
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server( true ),
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current_state( initial_state ),
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sent_states( 1, TimestampedState<MyState>( timestamp(), 0, initial_state ) ),
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assumed_receiver_state( sent_states.begin() ),
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received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) ),
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last_receiver_state( initial_remote ),
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fragments()
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{
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/* server */
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}
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template <class MyState, class RemoteState>
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Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState &initial_remote,
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const char *key_str, const char *ip, int port )
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: connection( key_str, ip, port ),
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server( false ),
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current_state( initial_state ),
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sent_states( 1, TimestampedState<MyState>( timestamp(), 0, initial_state ) ),
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assumed_receiver_state( sent_states.begin() ),
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received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) ),
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last_receiver_state( initial_remote ),
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fragments()
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{
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/* client */
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}
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/* Returns the number of ms to wait until next (possible) event */
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template <class MyState, class RemoteState>
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int Transport<MyState, RemoteState>::tick( void )
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{
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/* Determine if a new diff or empty ack needs to be sent */
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if ( timestamp() - sent_states.back().timestamp >= int64_t( SEND_INTERVAL ) ) {
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/* Update assumed receiver state */
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update_assumed_receiver_state();
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/* Cut out common prefix of all states */
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rationalize_states();
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/* Send diffs or ack */
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send_to_receiver();
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return SEND_INTERVAL;
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}
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int64_t wait = sent_states.back().timestamp + SEND_INTERVAL - timestamp();
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if ( wait < 0 ) {
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wait = 0;
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}
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return wait;
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}
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template <class MyState, class RemoteState>
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void Transport<MyState, RemoteState>::send_to_receiver( void )
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{
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if ( !connection.get_attached() ) {
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return;
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}
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if ( (assumed_receiver_state->num == sent_states.back().num)
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&& (sent_states.back().state == current_state) ) {
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/* send empty ack */
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if ( (!connection.pending_timestamp())
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&& (timestamp() - sent_states.back().timestamp < int64_t( ACK_INTERVAL )) ) {
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return;
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}
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/* XXX should increment number each time */
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Instruction inst( assumed_receiver_state->num,
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assumed_receiver_state->num,
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received_states.back().num,
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sent_states.front().num,
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0, true,
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"" );
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string s = inst.tostring();
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connection.send( s, false );
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assumed_receiver_state->timestamp = timestamp();
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return;
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}
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string diff = current_state.diff_from( assumed_receiver_state->state );
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uint64_t new_num;
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if ( current_state == sent_states.back().state ) { /* previously sent */
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new_num = sent_states.back().num;
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} else { /* new state */
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new_num = sent_states.back().num + 1;
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}
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bool done = false;
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int MTU_tries = 0;
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while ( !done ) {
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MTU_tries++;
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if ( MTU_tries > 20 ) {
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fprintf( stderr, "Error, could not send fragments after 20 tries (MTU = %d).\n",
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connection.get_MTU() );
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}
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try {
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send_in_fragments( diff, new_num );
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done = true;
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} catch ( MTUException m ) {
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fprintf( stderr, "Caught Path MTU exception, MTU now = %d\n", connection.get_MTU() );
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done = false;
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}
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if ( new_num == sent_states.back().num ) {
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sent_states.back().timestamp = timestamp();
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} else {
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sent_states.push_back( TimestampedState<MyState>( timestamp(), new_num, current_state ) );
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}
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new_num++;
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}
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/* successfully sent, probably */
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/* ("probably" because the FIRST size-exceeded datagram doesn't get an error) */
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assumed_receiver_state = sent_states.end();
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assumed_receiver_state--;
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}
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template <class MyState, class RemoteState>
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void Transport<MyState, RemoteState>::update_assumed_receiver_state( void )
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{
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uint64_t now = timestamp();
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/* start from what is known and give benefit of the doubt to unacknowledged states
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transmitted recently enough ago */
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assumed_receiver_state = sent_states.begin();
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for ( typename list< TimestampedState<MyState> >::iterator i = sent_states.begin();
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i != sent_states.end();
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i++ ) {
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assert( now >= i->timestamp );
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if ( int(now - i->timestamp) < connection.timeout() ) {
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assumed_receiver_state = i;
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} else {
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return;
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}
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}
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}
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template <class MyState, class RemoteState>
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void Transport<MyState, RemoteState>::rationalize_states( void )
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{
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MyState * const known_receiver_state = &sent_states.front().state;
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current_state.subtract( known_receiver_state );
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for ( typename list< TimestampedState<MyState> >::reverse_iterator i = sent_states.rbegin();
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i != sent_states.rend();
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i++ ) {
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i->state.subtract( known_receiver_state );
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}
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}
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template <class MyState, class RemoteState>
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void Transport<MyState, RemoteState>::recv( void )
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{
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string s( connection.recv() );
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Instruction frag( s );
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if ( fragments.add_fragment( frag ) ) { /* complete packet */
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Instruction inst = fragments.get_assembly();
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process_acknowledgment_through( inst.ack_num );
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/* first, make sure we don't already have the new state */
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for ( typename list< TimestampedState<RemoteState> >::iterator i = received_states.begin();
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i != received_states.end();
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i++ ) {
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if ( inst.new_num == i->num ) {
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i->timestamp = timestamp();
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return;
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}
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}
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/* now, make sure we do have the old state */
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bool found = 0;
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typename list< TimestampedState<RemoteState> >::iterator reference_state = received_states.begin();
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while ( reference_state != received_states.end() ) {
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if ( inst.old_num == reference_state->num ) {
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found = true;
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break;
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}
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reference_state++;
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}
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if ( !found ) {
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// fprintf( stderr, "Ignoring out-of-order packet. Reference state %d has been discarded or hasn't yet been received.\n", int(inst.old_num) );
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return;
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}
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/* apply diff to reference state */
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TimestampedState<RemoteState> new_state = *reference_state;
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new_state.timestamp = timestamp();
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new_state.num = inst.new_num;
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new_state.state.apply_string( inst.diff );
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process_throwaway_until( inst.throwaway_num );
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/* Insert new state in sorted place */
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for ( typename list< TimestampedState<RemoteState> >::iterator i = received_states.begin();
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i != received_states.end();
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i++ ) {
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if ( i->num > new_state.num ) {
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received_states.insert( i, new_state );
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return;
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}
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}
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received_states.push_back( new_state );
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}
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}
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template <class MyState, class RemoteState>
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void Transport<MyState, RemoteState>::process_acknowledgment_through( uint64_t ack_num )
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{
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typename list< TimestampedState<MyState> >::iterator i = sent_states.begin();
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while ( i != sent_states.end() ) {
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typename list< TimestampedState<MyState> >::iterator inext = i;
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inext++;
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if ( i->num < ack_num ) {
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sent_states.erase( i );
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}
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i = inext;
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}
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assert( sent_states.size() > 0 );
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assert( sent_states.front().num == ack_num );
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}
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template <class MyState, class RemoteState>
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void Transport<MyState, RemoteState>::process_throwaway_until( uint64_t throwaway_num )
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{
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typename list< TimestampedState<RemoteState> >::iterator i = received_states.begin();
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while ( i != received_states.end() ) {
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typename list< TimestampedState<RemoteState> >::iterator inext = i;
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inext++;
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if ( i->num < throwaway_num ) {
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received_states.erase( i );
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}
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i = inext;
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}
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assert( received_states.size() > 0 );
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}
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template <class MyState, class RemoteState>
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string Transport<MyState, RemoteState>::get_remote_diff( void )
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{
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/* find diff between last receiver state and current remote state, then rationalize states */
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string ret( received_states.back().state.diff_from( last_receiver_state ) );
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MyState * const oldest_receiver_state = &received_states.front().state;
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for ( typename list< TimestampedState<RemoteState> >::reverse_iterator i = received_states.rbegin();
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i != received_states.rend();
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i++ ) {
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i->state.subtract( oldest_receiver_state );
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}
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last_receiver_state = received_states.back().state;
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return ret;
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}
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template <class MyState, class RemoteState>
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void Transport<MyState, RemoteState>::send_in_fragments( string diff, uint64_t new_num )
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{
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uint16_t fragment_num = 0;
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while ( !diff.empty() ) {
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string this_fragment;
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assert( fragment_num <= 32767 );
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bool final = false;
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if ( int( diff.size() + HEADER_LEN ) > connection.get_MTU() ) {
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this_fragment = string( diff.begin(), diff.begin() + connection.get_MTU() - HEADER_LEN );
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diff = string( diff.begin() + connection.get_MTU() - HEADER_LEN, diff.end() );
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} else {
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this_fragment = diff;
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diff.clear();
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final = true;
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}
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Instruction inst( assumed_receiver_state->num,
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new_num,
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received_states.back().num,
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sent_states.front().num,
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fragment_num++, final,
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this_fragment );
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string s = inst.tostring();
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connection.send( s );
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}
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}
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