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reduce UDP clock bias by rounding clock and adjusting for RTT

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zzz
2010-11-26 14:57:16 +00:00
parent e1e6db2b3c
commit 78a588af0e
2 changed files with 23 additions and 5 deletions
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2
router/java/src/net/i2p/router/transport/udp/PacketBuilder.java
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@@ -1084,7 +1084,7 @@ class PacketBuilder {
// header
data[off] = flagByte;
off++;
long now = _context.clock().now() / 1000;
long now = (_context.clock().now() + 500) / 1000;
DataHelper.toLong(data, off, 4, now);
// todo: add support for rekeying and extended options
return packet;

26
router/java/src/net/i2p/router/transport/udp/PeerState.java
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@@ -63,8 +63,13 @@ class PeerState {
private boolean _rekeyBeganLocally;
/** when were the current cipher and MAC keys established/rekeyed? */
private long _keyEstablishedTime;
/** how far off is the remote peer from our clock, in milliseconds? */
/**
* How far off is the remote peer from our clock, in milliseconds?
* A positive number means our clock is ahead of theirs.
*/
private long _clockSkew;
/** what is the current receive second, for congestion control? */
private long _currentReceiveSecond;
/** when did we last send them a packet? */
@@ -346,8 +351,13 @@ class PeerState {
public boolean getRekeyBeganLocally() { return _rekeyBeganLocally; }
/** when were the current cipher and MAC keys established/rekeyed? */
public long getKeyEstablishedTime() { return _keyEstablishedTime; }
/** how far off is the remote peer from our clock, in milliseconds? */
/**
* How far off is the remote peer from our clock, in milliseconds?
* A positive number means our clock is ahead of theirs.
*/
public long getClockSkew() { return _clockSkew ; }
/** what is the current receive second, for congestion control? */
public long getCurrentReceiveSecond() { return _currentReceiveSecond; }
/** when did we last send them a packet? */
@@ -444,10 +454,17 @@ class PeerState {
public void setRekeyBeganLocally(boolean local) { _rekeyBeganLocally = local; }
/** when were the current cipher and MAC keys established/rekeyed? */
public void setKeyEstablishedTime(long when) { _keyEstablishedTime = when; }
/** how far off is the remote peer from our clock, in milliseconds? */
/**
* Update the moving-average clock skew based on the current difference.
* The raw skew will be adjusted for RTT/2 here.
* @param skew milliseconds, NOT adjusted for RTT.
* A positive number means our clock is ahead of theirs.
*/
public void adjustClockSkew(long skew) {
_clockSkew = (long) (0.9*(float)_clockSkew + 0.1*(float)skew);
_clockSkew = (long) (0.9*(float)_clockSkew + 0.1*(float)(skew - (_rtt / 2)));
}
/** what is the current receive second, for congestion control? */
public void setCurrentReceiveSecond(long sec) { _currentReceiveSecond = sec; }
/** when did we last send them a packet? */
@@ -679,6 +696,7 @@ class PeerState {
*
*/
public List<Long> getCurrentFullACKs() {
// no such element exception seen here
ArrayList<Long> rv = new ArrayList(_currentACKs);
// include some for retransmission
rv.addAll(_currentACKsResend);