Keith Winstein
291 lines
9.1 KiB
C++
291 lines
9.1 KiB
C++
#include <assert.h>
|
|
#include <iostream>
|
|
|
|
#include "networktransport.hpp"
|
|
|
|
using namespace Network;
|
|
using namespace std;
|
|
|
|
template <class MyState, class RemoteState>
|
|
uint64_t Transport<MyState, RemoteState>::timestamp( void )
|
|
{
|
|
struct timespec tp;
|
|
|
|
if ( clock_gettime( CLOCK_MONOTONIC, &tp ) < 0 ) {
|
|
throw NetworkException( "clock_gettime", errno );
|
|
}
|
|
|
|
uint64_t millis = tp.tv_nsec / 1000000;
|
|
millis += uint64_t( tp.tv_sec ) * 1000000;
|
|
|
|
return millis;
|
|
}
|
|
|
|
template <class MyState, class RemoteState>
|
|
Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState &initial_remote )
|
|
: connection(),
|
|
server( true ),
|
|
current_state( initial_state ),
|
|
sent_states( 1, TimestampedState<MyState>( timestamp(), 0, initial_state ) ),
|
|
assumed_receiver_state( sent_states.begin() ),
|
|
timeout( INITIAL_TIMEOUT ),
|
|
received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) )
|
|
{
|
|
/* server */
|
|
}
|
|
|
|
template <class MyState, class RemoteState>
|
|
Transport<MyState, RemoteState>::Transport( MyState &initial_state, RemoteState &initial_remote,
|
|
const char *key_str, const char *ip, int port )
|
|
: connection( key_str, ip, port ),
|
|
server( false ),
|
|
current_state( initial_state ),
|
|
sent_states( 1, TimestampedState<MyState>( timestamp(), 0, initial_state ) ),
|
|
assumed_receiver_state( sent_states.begin() ),
|
|
timeout( INITIAL_TIMEOUT ),
|
|
received_states( 1, TimestampedState<RemoteState>( timestamp(), 0, initial_remote ) )
|
|
{
|
|
/* client */
|
|
}
|
|
|
|
template <class MyState, class RemoteState>
|
|
void Transport<MyState, RemoteState>::tick( void )
|
|
{
|
|
/* Update assumed receiver state */
|
|
update_assumed_receiver_state();
|
|
|
|
/* Cut out common prefix of all states */
|
|
rationalize_states();
|
|
|
|
/* Determine if a new diff or empty ack needs to be sent */
|
|
if ( timestamp() - sent_states.back().timestamp >= int64_t( SEND_INTERVAL ) ) {
|
|
/* Send diffs or ack */
|
|
send_to_receiver();
|
|
}
|
|
}
|
|
|
|
template <class MyState, class RemoteState>
|
|
void Transport<MyState, RemoteState>::send_to_receiver( void )
|
|
{
|
|
/* We don't want to assume that this sequence of diffs will
|
|
necessarily bring the receiver to the _actual_ current
|
|
state. That requires perfect round-trip stability of the diff
|
|
mechanism -- stronger than we need (and probably too fragile).
|
|
Instead, we produce the full diff, unlimited by MTU, between
|
|
the assumed receiver state and current state, and apply that
|
|
diff to produce a target receiver state. Then we produce a
|
|
sequence of diffs (this time limited by MTU) that bring us to
|
|
that state. */
|
|
|
|
if ( !connection.get_attached() ) {
|
|
return;
|
|
}
|
|
|
|
MyState target_receiver_state( assumed_receiver_state->state );
|
|
target_receiver_state.apply_string( current_state.diff_from( target_receiver_state, -1 ) );
|
|
|
|
if ( assumed_receiver_state->state == target_receiver_state ) {
|
|
/* send empty ack */
|
|
if ( timestamp() - sent_states.back().timestamp < int64_t( ACK_INTERVAL ) ) {
|
|
return;
|
|
}
|
|
|
|
Instruction inst( assumed_receiver_state->num,
|
|
assumed_receiver_state->num,
|
|
received_states.back().num,
|
|
sent_states.front().num,
|
|
"" );
|
|
string s = inst.tostring();
|
|
connection.send( s );
|
|
assumed_receiver_state->timestamp = timestamp();
|
|
|
|
return;
|
|
}
|
|
|
|
int tries = 0;
|
|
while ( !(assumed_receiver_state->state == target_receiver_state) ) {
|
|
if ( tries++ > 1024 ) {
|
|
fprintf( stderr, "BUG: Convergence limit exceeded.\n" );
|
|
exit( 1 );
|
|
}
|
|
|
|
Instruction inst( assumed_receiver_state->num,
|
|
-1,
|
|
received_states.back().num,
|
|
sent_states.front().num,
|
|
current_state.diff_from( assumed_receiver_state->state,
|
|
connection.get_MTU() - HEADER_LEN ) );
|
|
MyState new_state = assumed_receiver_state->state;
|
|
new_state.apply_string( inst.diff );
|
|
|
|
/* Find the right "new_num" for this instruction. */
|
|
/* Has this state previously been sent? */
|
|
/* should replace with hash table if this becomes demanding */
|
|
typename list< TimestampedState<MyState> >::iterator previously_sent = sent_states.begin();
|
|
while ( ( previously_sent != sent_states.end() )
|
|
&& ( !(previously_sent->state == new_state) ) ) {
|
|
previously_sent++;
|
|
}
|
|
|
|
/* Reusing state numbers is only for intermediate states */
|
|
/* If this is the final diff in a sequence, make sure it does get the highest
|
|
state number (even if we've retread to previously-seen ground ) */
|
|
/* This will force the client to update to this state */
|
|
/*
|
|
if ( (previously_sent->num != sent_states.back().num)
|
|
&& (new_state == target_receiver_state) ) {
|
|
previously_sent = sent_states.end();
|
|
}
|
|
*/
|
|
|
|
if ( previously_sent == sent_states.end() ) { /* not previously sent */
|
|
inst.new_num = sent_states.back().num + 1;
|
|
sent_states.push_back( TimestampedState<MyState>( timestamp(), inst.new_num, new_state ) );
|
|
previously_sent = sent_states.end();
|
|
previously_sent--;
|
|
} else {
|
|
inst.new_num = previously_sent->num;
|
|
previously_sent->timestamp = timestamp();
|
|
}
|
|
|
|
/* send instruction */
|
|
/* XXX what about MTU problem? */
|
|
string s = inst.tostring();
|
|
|
|
try {
|
|
fprintf( stderr, "Sent instruction from %d => %d (terminal %d)\r\n", int(inst.old_num), int(inst.new_num), int(sent_states.back().num) );
|
|
connection.send( s );
|
|
} catch ( MTUException m ) {
|
|
continue;
|
|
}
|
|
|
|
/* successfully sent, probably */
|
|
/* ("probably" because the FIRST size-exceeded datagram doesn't get an error) */
|
|
assumed_receiver_state = previously_sent;
|
|
}
|
|
}
|
|
|
|
template <class MyState, class RemoteState>
|
|
void Transport<MyState, RemoteState>::update_assumed_receiver_state( void )
|
|
{
|
|
uint64_t now = timestamp();
|
|
|
|
/* start from what is known and give benefit of the doubt to unacknowledged states
|
|
transmitted recently enough ago */
|
|
assumed_receiver_state = sent_states.begin();
|
|
|
|
for ( typename list< TimestampedState<MyState> >::iterator i = sent_states.begin();
|
|
i != sent_states.end();
|
|
i++ ) {
|
|
assert( now >= i->timestamp );
|
|
|
|
if ( now - i->timestamp < int64_t(timeout) ) {
|
|
assumed_receiver_state = i;
|
|
}
|
|
}
|
|
}
|
|
|
|
template <class MyState, class RemoteState>
|
|
void Transport<MyState, RemoteState>::rationalize_states( void )
|
|
{
|
|
MyState * const known_receiver_state = &sent_states.front().state;
|
|
|
|
current_state.subtract( known_receiver_state );
|
|
|
|
for ( typename list< TimestampedState<MyState> >::reverse_iterator i = sent_states.rbegin();
|
|
i != sent_states.rend();
|
|
i++ ) {
|
|
i->state.subtract( known_receiver_state );
|
|
}
|
|
}
|
|
|
|
template <class MyState, class RemoteState>
|
|
void Transport<MyState, RemoteState>::recv( void )
|
|
{
|
|
string s( connection.recv() );
|
|
Instruction inst( s );
|
|
|
|
process_acknowledgment_through( inst.ack_num );
|
|
// process_throwaway_until( inst.throwaway.num );
|
|
|
|
/* first, make sure we don't already have the new state */
|
|
for ( typename list< TimestampedState<RemoteState> >::iterator i = received_states.begin();
|
|
i != received_states.end();
|
|
i++ ) {
|
|
if ( inst.new_num == i->num ) {
|
|
i->timestamp = timestamp();
|
|
return;
|
|
}
|
|
}
|
|
|
|
/* now, make sure we do have the old state */
|
|
bool found = 0;
|
|
typename list< TimestampedState<RemoteState> >::iterator reference_state = received_states.begin();
|
|
while ( reference_state != received_states.end() ) {
|
|
if ( inst.old_num == reference_state->num ) {
|
|
found = true;
|
|
break;
|
|
}
|
|
reference_state++;
|
|
}
|
|
|
|
if ( !found ) {
|
|
// fprintf( stderr, "Ignoring out-of-order packet. Reference state %d has been discarded or hasn't yet been received.\n", int(inst.old_num) );
|
|
return;
|
|
}
|
|
|
|
/* apply diff to reference state */
|
|
TimestampedState<RemoteState> new_state = *reference_state;
|
|
new_state.timestamp = timestamp();
|
|
new_state.num = inst.new_num;
|
|
new_state.state.apply_string( inst.diff );
|
|
|
|
if ( new_state.num > received_states.back().num ) {
|
|
process_throwaway_until( inst.throwaway_num );
|
|
}
|
|
|
|
/* Insert new state in sorted place */
|
|
for ( typename list< TimestampedState<RemoteState> >::iterator i = received_states.begin();
|
|
i != received_states.end();
|
|
i++ ) {
|
|
if ( i->num > new_state.num ) {
|
|
received_states.insert( i, new_state );
|
|
return;
|
|
}
|
|
}
|
|
received_states.push_back( new_state );
|
|
}
|
|
|
|
template <class MyState, class RemoteState>
|
|
void Transport<MyState, RemoteState>::process_acknowledgment_through( uint64_t ack_num )
|
|
{
|
|
typename list< TimestampedState<MyState> >::iterator i = sent_states.begin();
|
|
while ( i != sent_states.end() ) {
|
|
typename list< TimestampedState<MyState> >::iterator inext = i;
|
|
inext++;
|
|
if ( i->num < ack_num ) {
|
|
sent_states.erase( i );
|
|
}
|
|
i = inext;
|
|
}
|
|
|
|
assert( sent_states.size() > 0 );
|
|
assert( sent_states.front().num == ack_num );
|
|
}
|
|
|
|
template <class MyState, class RemoteState>
|
|
void Transport<MyState, RemoteState>::process_throwaway_until( uint64_t throwaway_num )
|
|
{
|
|
typename list< TimestampedState<MyState> >::iterator i = received_states.begin();
|
|
while ( i != received_states.end() ) {
|
|
typename list< TimestampedState<MyState> >::iterator inext = i;
|
|
inext++;
|
|
if ( i->num < throwaway_num ) {
|
|
sent_states.erase( i );
|
|
}
|
|
i = inext;
|
|
}
|
|
|
|
assert( received_states.size() > 0 );
|
|
}
|