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Tighten up dead path detection. Should now auto-detect dead paths in less than 10 seconds at a very small cost in ECHO requests (or HELLOs for older peers). GitHib issue #272

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This commit is contained in:
Adam Ierymenko 2016-01-06 10:00:03 -08:00
parent 4d94ae77b4
commit 05b2c0743f
3 changed files with 65 additions and 11 deletions
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31
node/Peer.cpp
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@ -168,7 +168,10 @@ void Peer::received(
} else {
uint64_t slotLRmin = 0xffffffffffffffffULL;
for(unsigned int p=0;p<ZT_MAX_PEER_NETWORK_PATHS;++p) {
if (_paths[p].lastReceived() <= slotLRmin) {
if (!_paths[p].active(now)) {
slot = &(_paths[p]);
break;
} else if (_paths[p].lastReceived() <= slotLRmin) {
slotLRmin = _paths[p].lastReceived();
slot = &(_paths[p]);
}
@ -249,11 +252,12 @@ bool Peer::doPingAndKeepalive(uint64_t now,int inetAddressFamily)
//TRACE("PING %s(%s) after %llums/%llums send/receive inactivity",_id.address().toString().c_str(),p->address().toString().c_str(),now - p->lastSend(),now - p->lastReceived());
sendHELLO(p->localAddress(),p->address(),now);
p->sent(now);
} else if (((now - p->lastSend()) >= ZT_NAT_KEEPALIVE_DELAY)&&(!p->reliable())) {
p->pinged(now);
} else if (((now - std::max(p->lastSend(),p->lastKeepalive())) >= ZT_NAT_KEEPALIVE_DELAY)&&(!p->reliable())) {
//TRACE("NAT keepalive %s(%s) after %llums/%llums send/receive inactivity",_id.address().toString().c_str(),p->address().toString().c_str(),now - p->lastSend(),now - p->lastReceived());
_natKeepaliveBuf += (uint32_t)((now * 0x9e3779b1) >> 1); // tumble this around to send constantly varying (meaningless) payloads
RR->node->putPacket(p->localAddress(),p->address(),&_natKeepaliveBuf,sizeof(_natKeepaliveBuf));
p->sent(now);
p->sentKeepalive(now);
} else {
//TRACE("no PING or NAT keepalive: addr==%s reliable==%d %llums/%llums send/receive inactivity",p->address().toString().c_str(),(int)p->reliable(),now - p->lastSend(),now - p->lastReceived());
}
@ -339,6 +343,8 @@ bool Peer::resetWithinScope(InetAddress::IpScope scope,uint64_t now)
unsigned int y = 0;
while (x < np) {
if (_paths[x].address().ipScope() == scope) {
// Resetting a path means sending a HELLO and then forgetting it. If we
// get OK(HELLO) then it will be re-learned.
sendHELLO(_paths[x].localAddress(),_paths[x].address(),now);
} else {
_paths[y++] = _paths[x];
@ -491,7 +497,22 @@ bool Peer::_checkPath(Path &p,const uint64_t now)
if (!p.active(now))
return false;
if ( (p.lastSend() > p.lastReceived()) && ((p.lastSend() - p.lastReceived()) >= ZT_PEER_DEAD_PATH_DETECTION_NO_ANSWER_TIMEOUT) ) {
/* Dead path detection: if we have sent something to this peer and have not
* yet received a reply, double check this path. The majority of outbound
* packets including Ethernet frames do generate some kind of reply either
* immediately or at some point in the near future. This will occasionally
* (every NO_ANSWER_TIMEOUT ms) check paths unnecessarily if traffic that
* does not generate a response is being sent such as multicast announcements
* or frames belonging to unidirectional UDP protocols, but the cost is very
* tiny and the benefit in reliability is very large. This takes care of many
* failure modes including crap NATs that forget links and spurious changes
* to physical network topology that cannot be otherwise detected.
*
* Each time we do this we increment a probation counter in the path. This
* counter is reset on any packet receive over this path. If it reaches the
* MAX_PROBATION threshold the path is considred dead. */
if ( (p.lastSend() > p.lastReceived()) && ((p.lastSend() - p.lastReceived()) >= ZT_PEER_DEAD_PATH_DETECTION_NO_ANSWER_TIMEOUT) && ((now - p.lastPing()) >= ZT_PEER_DEAD_PATH_DETECTION_NO_ANSWER_TIMEOUT) ) {
TRACE("%s(%s) has not answered, checking if dead (probation: %u)",_id.address().toString().c_str(),p.address().toString().c_str(),p.probation());
if ( (_vProto >= 5) && ( !((_vMajor == 1)&&(_vMinor == 1)&&(_vRevision == 0)) ) ) {
@ -499,9 +520,11 @@ bool Peer::_checkPath(Path &p,const uint64_t now)
Packet outp(_id.address(),RR->identity.address(),Packet::VERB_ECHO);
outp.armor(_key,true);
p.send(RR,outp.data(),outp.size(),now);
p.pinged(now);
} else {
sendHELLO(p.localAddress(),p.address(),now);
p.sent(now);
p.pinged(now);
}
p.increaseProbation();