ZeroTierOne/node/Topology.cpp

/*
 * ZeroTier One - Network Virtualization Everywhere
 * Copyright (C) 2011-2015  ZeroTier, Inc.
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 *
 * --
 *
 * ZeroTier may be used and distributed under the terms of the GPLv3, which
 * are available at: http://www.gnu.org/licenses/gpl-3.0.html
 *
 * If you would like to embed ZeroTier into a commercial application or
 * redistribute it in a modified binary form, please contact ZeroTier Networks
 * LLC. Start here: http://www.zerotier.com/
 */

#include "Constants.hpp"
#include "Topology.hpp"
#include "RuntimeEnvironment.hpp"
#include "Node.hpp"
#include "Network.hpp"
#include "NetworkConfig.hpp"
#include "Buffer.hpp"

namespace ZeroTier {

// Old root servers
//#define ZT_DEFAULT_WORLD_LENGTH 494
//static const unsigned char ZT_DEFAULT_WORLD[ZT_DEFAULT_WORLD_LENGTH] = {0x01,0x00,0x00,0x00,0x00,0x08,0xea,0xc9,0x0a,0x00,0x00,0x01,0x4f,0xdf,0xbf,0xfc,0xbb,0x6c,0x7e,0x15,0x67,0x85,0x1b,0xb4,0x65,0x04,0x01,0xaf,0x56,0xbf,0xe7,0x63,0x9d,0x77,0xef,0xa4,0x1e,0x61,0x53,0x88,0xcb,0x8d,0x78,0xe5,0x47,0x38,0x98,0x5a,0x6c,0x8a,0xdd,0xe6,0x9c,0x65,0xdf,0x1a,0x80,0x63,0xce,0x2e,0x4d,0x48,0x24,0x3d,0x68,0x87,0x96,0x13,0x89,0xba,0x25,0x6f,0xc9,0xb0,0x9f,0x20,0xc5,0x4c,0x51,0x7b,0x30,0xb7,0x5f,0xba,0xca,0xa4,0xc5,0x48,0xa3,0x15,0xab,0x2f,0x1d,0x64,0xe8,0x04,0x42,0xb3,0x1c,0x51,0x8b,0x2a,0x04,0x01,0xf8,0xe1,0x81,0xaf,0x60,0x2f,0x70,0x3e,0xcd,0x0b,0x21,0x38,0x19,0x62,0x02,0xbd,0x0e,0x33,0x1d,0x0a,0x7b,0xf1,0xec,0xad,0xef,0x54,0xb3,0x7b,0x17,0x84,0xaa,0xda,0x0a,0x85,0x5d,0x0b,0x1c,0x05,0x83,0xb9,0x0e,0x3e,0xe3,0xb4,0xd1,0x8b,0x5b,0x64,0xf7,0xcf,0xe1,0xff,0x5d,0xc2,0x2a,0xcf,0x60,0x7b,0x09,0xb4,0xa3,0x86,0x3c,0x5a,0x7e,0x31,0xa0,0xc7,0xb4,0x86,0xe3,0x41,0x33,0x04,0x7e,0x19,0x87,0x6a,0xba,0x00,0x2a,0x6e,0x2b,0x23,0x18,0x93,0x0f,0x60,0xeb,0x09,0x7f,0x70,0xd0,0xf4,0xb0,0x28,0xb2,0xcd,0x6d,0x3d,0x0c,0x63,0xc0,0x14,0xb9,0x03,0x9f,0xf3,0x53,0x90,0xe4,0x11,0x81,0xf2,0x16,0xfb,0x2e,0x6f,0xa8,0xd9,0x5c,0x1e,0xe9,0x66,0x71,0x56,0x41,0x19,0x05,0xc3,0xdc,0xcf,0xea,0x78,0xd8,0xc6,0xdf,0xaf,0xba,0x68,0x81,0x70,0xb3,0xfa,0x00,0x01,0x04,0xc6,0xc7,0x61,0xdc,0x27,0x09,0x88,0x41,0x40,0x8a,0x2e,0x00,0xbb,0x1d,0x31,0xf2,0xc3,0x23,0xe2,0x64,0xe9,0xe6,0x41,0x72,0xc1,0xa7,0x4f,0x77,0x89,0x95,0x55,0xed,0x10,0x75,0x1c,0xd5,0x6e,0x86,0x40,0x5c,0xde,0x11,0x8d,0x02,0xdf,0xfe,0x55,0x5d,0x46,0x2c,0xcf,0x6a,0x85,0xb5,0x63,0x1c,0x12,0x35,0x0c,0x8d,0x5d,0xc4,0x09,0xba,0x10,0xb9,0x02,0x5d,0x0f,0x44,0x5c,0xf4,0x49,0xd9,0x2b,0x1c,0x00,0x01,0x04,0x6b,0xbf,0x2e,0xd2,0x27,0x09,0x8a,0xcf,0x05,0x9f,0xe3,0x00,0x48,0x2f,0x6e,0xe5,0xdf,0xe9,0x02,0x31,0x9b,0x41,0x9d,0xe5,0xbd,0xc7,0x65,0x20,0x9c,0x0e,0xcd,0xa3,0x8c,0x4d,0x6e,0x4f,0xcf,0x0d,0x33,0x65,0x83,0x98,0xb4,0x52,0x7d,0xcd,0x22,0xf9,0x31,0x12,0xfb,0x9b,0xef,0xd0,0x2f,0xd7,0x8b,0xf7,0x26,0x1b,0x33,0x3f,0xc1,0x05,0xd1,0x92,0xa6,0x23,0xca,0x9e,0x50,0xfc,0x60,0xb3,0x74,0xa5,0x00,0x01,0x04,0xa2,0xf3,0x4d,0x6f,0x27,0x09,0x9d,0x21,0x90,0x39,0xf3,0x00,0x01,0xf0,0x92,0x2a,0x98,0xe3,0xb3,0x4e,0xbc,0xbf,0xf3,0x33,0x26,0x9d,0xc2,0x65,0xd7,0xa0,0x20,0xaa,0xb6,0x9d,0x72,0xbe,0x4d,0x4a,0xcc,0x9c,0x8c,0x92,0x94,0x78,0x57,0x71,0x25,0x6c,0xd1,0xd9,0x42,0xa9,0x0d,0x1b,0xd1,0xd2,0xdc,0xa3,0xea,0x84,0xef,0x7d,0x85,0xaf,0xe6,0x61,0x1f,0xb4,0x3f,0xf0,0xb7,0x41,0x26,0xd9,0x0a,0x6e,0x00,0x01,0x04,0x80,0xc7,0xc5,0xd9,0x27,0x09};

#define ZT_DEFAULT_WORLD_LENGTH 582
static const unsigned char ZT_DEFAULT_WORLD[ZT_DEFAULT_WORLD_LENGTH] = {0x01,0x00,0x00,0x00,0x00,0x08,0xea,0xc9,0x0a,0x00,0x00,0x01,0x50,0xa6,0x54,0xe4,0x8e,0x72,0xb0,0x3b,0xbe,0x73,0xda,0xbd,0xfb,0x85,0x77,0x9f,0xc9,0x2e,0x17,0xc8,0x11,0x6e,0xda,0x61,0x80,0xd1,0x41,0xcb,0x7c,0x2d,0x2b,0xa4,0x34,0x75,0x19,0x64,0x20,0x80,0x0a,0x22,0x32,0xf2,0x01,0x6c,0xfe,0x79,0xa6,0x7d,0xec,0x10,0x7e,0x03,0xf3,0xa2,0xa0,0x19,0xc8,0x7c,0xfd,0x6c,0x56,0x52,0xa8,0xfb,0xdc,0xfb,0x93,0x81,0x3e,0xe4,0xe9,0x51,0xc1,0xe1,0x39,0x50,0xcd,0x17,0x82,0x9d,0x74,0xf1,0xa9,0x5b,0x03,0x14,0x2c,0xa7,0xc0,0x7f,0x21,0x8b,0xad,0xdd,0xa5,0x04,0x26,0x35,0xa6,0xab,0xc1,0x49,0x64,0x2c,0xda,0x65,0x52,0x77,0xf3,0xf0,0x70,0x00,0xcd,0xc3,0xff,0x3b,0x19,0x77,0x4c,0xab,0xb6,0x35,0xbb,0x77,0xcf,0x54,0xe5,0x6d,0x01,0x9d,0x43,0x92,0x0a,0x6d,0x00,0x23,0x8e,0x0a,0x3d,0xba,0x36,0xc3,0xa1,0xa4,0xad,0x13,0x8f,0x46,0xff,0xcc,0x8f,0x9e,0xc2,0x3c,0x06,0xf8,0x3b,0xf3,0xa2,0x5f,0x71,0xcc,0x07,0x35,0x7f,0x02,0xd6,0xdd,0xca,0x6a,0xb5,0x00,0x4e,0x76,0x12,0x07,0xd8,0xb4,0x20,0x0b,0xe4,0x4f,0x47,0x8e,0x3d,0xa1,0x48,0xc1,0x60,0x99,0x11,0x0e,0xe7,0x1b,0x64,0x58,0x6d,0xda,0x11,0x8e,0x40,0x22,0xab,0x63,0x68,0x2c,0xe1,0x37,0xda,0x8b,0xa8,0x17,0xfc,0x7f,0x73,0xaa,0x31,0x63,0xf2,0xe3,0x33,0x93,0x3e,0x29,0x94,0xc4,0x6b,0x4f,0x41,0x19,0x30,0x7b,0xe8,0x85,0x5a,0x72,0x00,0x0a,0x04,0xbc,0xa6,0x5e,0xb1,0x27,0x09,0x06,0x2a,0x03,0xb0,0xc0,0x00,0x02,0x00,0xd0,0x00,0x00,0x00,0x00,0x00,0x7d,0x00,0x01,0x27,0x09,0x04,0x9f,0xcb,0x61,0xab,0x27,0x09,0x06,0x26,0x04,0xa8,0x80,0x08,0x00,0x00,0xa1,0x00,0x00,0x00,0x00,0x00,0x54,0x60,0x01,0x27,0x09,0x04,0xa9,0x39,0x8f,0x68,0x27,0x09,0x06,0x26,0x07,0xf0,0xd0,0x1d,0x01,0x00,0x57,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x02,0x27,0x09,0x04,0x68,0xee,0xb6,0x53,0x27,0x09,0x06,0x20,0x01,0x19,0xf0,0xac,0x00,0x08,0x09,0x54,0x00,0x00,0xff,0xfe,0x15,0xf3,0xf4,0x27,0x09,0x04,0x80,0xc7,0xb6,0x09,0x27,0x09,0x06,0x24,0x00,0x61,0x80,0x00,0x00,0x00,0xd0,0x00,0x00,0x00,0x00,0x00,0x1b,0x10,0x01,0x27,0x09,0x16,0xeb,0xbd,0x6c,0x5d,0x00,0x47,0xd3,0x9b,0xca,0x9d,0x0a,0x5c,0xf7,0x01,0x48,0xe3,0x9f,0x6c,0x45,0x19,0x9e,0x17,0xe0,0xe3,0x2e,0x4e,0x46,0xca,0xc0,0x1a,0xe5,0xbc,0xb2,0x12,0x24,0x13,0x7b,0x09,0x7f,0x40,0xbd,0xd9,0x82,0xa9,0x21,0xc3,0xaa,0xbd,0xcb,0x9a,0xda,0x8b,0x4f,0x2b,0xb0,0x59,0x37,0x53,0xbf,0xdb,0x21,0xcf,0x12,0xea,0xc2,0x8c,0x8d,0x90,0x42,0x00,0x0a,0x04,0x2d,0x21,0x04,0x43,0x27,0x09,0x06,0x26,0x00,0x3c,0x00,0x00,0x00,0x00,0x00,0xf0,0x3c,0x91,0xff,0xfe,0x67,0xb7,0x04,0x27,0x09,0x04,0x8b,0xa2,0x9d,0xf3,0x27,0x09,0x06,0x2a,0x01,0x7e,0x01,0x00,0x00,0x00,0x00,0xf0,0x3c,0x91,0xff,0xfe,0x67,0x3f,0xfd,0x27,0x09,0x04,0x2d,0x20,0xf6,0xb3,0x27,0x09,0x06,0x20,0x01,0x19,0xf0,0x58,0x00,0x8b,0xf8,0x54,0x00,0x00,0xff,0xfe,0x15,0xb3,0x9a,0x27,0x09,0x04,0x2d,0x20,0xf8,0x57,0x27,0x09,0x06,0x20,0x01,0x19,0xf0,0x70,0x00,0x9b,0xc9,0x54,0x00,0x00,0xff,0xfe,0x15,0xc4,0xf5,0x27,0x09,0x04,0x9f,0xcb,0x02,0x9a,0x27,0x09,0x06,0x26,0x04,0xa8,0x80,0x0c,0xad,0x00,0xd0,0x00,0x00,0x00,0x00,0x00,0x26,0x70,0x01,0x27,0x09};

Topology::Topology(const RuntimeEnvironment *renv) :
	RR(renv),
	_amRoot(false)
{
	std::string alls(RR->node->dataStoreGet("peers.save"));
	const uint8_t *all = reinterpret_cast<const uint8_t *>(alls.data());
	RR->node->dataStoreDelete("peers.save");

	unsigned int ptr = 0;
	while ((ptr + 4) < alls.size()) {
		try {
			const unsigned int reclen = ( // each Peer serialized record is prefixed by a record length
					((((unsigned int)all[ptr]) & 0xff) << 24) |
					((((unsigned int)all[ptr + 1]) & 0xff) << 16) |
					((((unsigned int)all[ptr + 2]) & 0xff) << 8) |
					(((unsigned int)all[ptr + 3]) & 0xff)
				);
			unsigned int pos = 0;
			SharedPtr<Peer> p(Peer::deserializeNew(RR->identity,Buffer<ZT_PEER_SUGGESTED_SERIALIZATION_BUFFER_SIZE>(all + ptr,reclen + 4),pos));
			ptr += pos;
			if (!p)
				break; // stop if invalid records
			if (p->address() != RR->identity.address())
				_peers[p->address()] = p;
		} catch ( ... ) {
			break; // stop if invalid records
		}
	}

	clean(RR->node->now());

	std::string dsWorld(RR->node->dataStoreGet("world"));
	World cachedWorld;
	try {
		Buffer<ZT_WORLD_MAX_SERIALIZED_LENGTH> dswtmp(dsWorld.data(),dsWorld.length());
		cachedWorld.deserialize(dswtmp,0);
	} catch ( ... ) {
		cachedWorld = World(); // clear if cached world is invalid
	}
	World defaultWorld;
	{
		Buffer<ZT_DEFAULT_WORLD_LENGTH> wtmp(ZT_DEFAULT_WORLD,ZT_DEFAULT_WORLD_LENGTH);
		defaultWorld.deserialize(wtmp,0); // throws on error, which would indicate a bad static variable up top
	}
	if (cachedWorld.shouldBeReplacedBy(defaultWorld,false)) {
		_setWorld(defaultWorld);
		if (dsWorld.length() > 0)
			RR->node->dataStoreDelete("world");
	} else _setWorld(cachedWorld);
}

Topology::~Topology()
{
	Buffer<ZT_PEER_SUGGESTED_SERIALIZATION_BUFFER_SIZE> pbuf;
	std::string all;

	Address *a = (Address *)0;
	SharedPtr<Peer> *p = (SharedPtr<Peer> *)0;
	Hashtable< Address,SharedPtr<Peer> >::Iterator i(_peers);
	while (i.next(a,p)) {
		if (std::find(_rootAddresses.begin(),_rootAddresses.end(),*a) == _rootAddresses.end()) {
			pbuf.clear();
			try {
				(*p)->serialize(pbuf);
				try {
					all.append((const char *)pbuf.data(),pbuf.size());
				} catch ( ... ) {
					return; // out of memory? just skip
				}
			} catch ( ... ) {} // peer too big? shouldn't happen, but it so skip
		}
	}

	RR->node->dataStorePut("peers.save",all,true);
}

SharedPtr<Peer> Topology::addPeer(const SharedPtr<Peer> &peer)
{
	if (peer->address() == RR->identity.address()) {
		TRACE("BUG: addPeer() caught and ignored attempt to add peer for self");
		throw std::logic_error("cannot add peer for self");
	}

	SharedPtr<Peer> np;
	{
		Mutex::Lock _l(_lock);
		SharedPtr<Peer> &hp = _peers[peer->address()];
		if (!hp)
			hp = peer;
		np = hp;
	}
	np->use(RR->node->now());
	saveIdentity(np->identity());

	return np;
}

SharedPtr<Peer> Topology::getPeer(const Address &zta)
{
	if (zta == RR->identity.address()) {
		TRACE("BUG: ignored attempt to getPeer() for self, returned NULL");
		return SharedPtr<Peer>();
	}

	Mutex::Lock _l(_lock);

	SharedPtr<Peer> &ap = _peers[zta];

	if (ap) {
		ap->use(RR->node->now());
		return ap;
	}

	Identity id(_getIdentity(zta));
	if (id) {
		try {
			ap = SharedPtr<Peer>(new Peer(RR->identity,id));
			ap->use(RR->node->now());
			return ap;
		} catch ( ... ) {} // invalid identity?
	}

	// If we get here it means we read an invalid cache identity or had some other error
	_peers.erase(zta);
	return SharedPtr<Peer>();
}

Identity Topology::getIdentity(const Address &zta)
{
	{
		Mutex::Lock _l(_lock);
		SharedPtr<Peer> &ap = _peers[zta];
		if (ap)
			return ap->identity();
	}
	return _getIdentity(zta);
}

void Topology::saveIdentity(const Identity &id)
{
	if (id) {
		char p[128];
		Utils::snprintf(p,sizeof(p),"iddb.d/%.10llx",(unsigned long long)id.address().toInt());
		RR->node->dataStorePut(p,id.toString(false),false);
	}
}

SharedPtr<Peer> Topology::getBestRoot(const Address *avoid,unsigned int avoidCount,bool strictAvoid)
{
	const uint64_t now = RR->node->now();
	Mutex::Lock _l(_lock);

	if (_amRoot) {
		/* If I am a root server, the "best" root server is the one whose address
		 * is numerically greater than mine (with wrap at top of list). This
		 * causes packets searching for a route to pretty much literally
		 * circumnavigate the globe rather than bouncing between just two. */

		if (_rootAddresses.size() > 1) { // gotta be one other than me for this to work
			for(unsigned long p=0;p<_rootAddresses.size();++p) {
				if (_rootAddresses[p] == RR->identity.address()) {
					for(unsigned long q=1;q<_rootAddresses.size();++q) {
						SharedPtr<Peer> *nextsn = _peers.get(_rootAddresses[(p + q) % _rootAddresses.size()]);
						if ((nextsn)&&((*nextsn)->hasActiveDirectPath(now))) {
							(*nextsn)->use(now);
							return *nextsn;
						}
					}
					break;
				}
			}
		}

	} else {
		/* If I am not a root server, the best root server is the active one with
		 * the lowest latency. */

		unsigned int bestLatencyOverall = ~((unsigned int)0);
		unsigned int bestLatencyNotAvoid = ~((unsigned int)0);
		const SharedPtr<Peer> *bestOverall = (const SharedPtr<Peer> *)0;
		const SharedPtr<Peer> *bestNotAvoid = (const SharedPtr<Peer> *)0;

		for(std::vector< SharedPtr<Peer> >::const_iterator r(_rootPeers.begin());r!=_rootPeers.end();++r) {
			if ((*r)->hasActiveDirectPath(now)) {
				bool avoiding = false;
				for(unsigned int i=0;i<avoidCount;++i) {
					if (avoid[i] == (*r)->address()) {
						avoiding = true;
						break;
					}
				}
				unsigned int l = (*r)->latency();
				if (!l) l = ~l; // zero latency indicates no measurment, so make this 'max'
				if (l <= bestLatencyOverall) {
					bestLatencyOverall = l;
					bestOverall = &(*r);
				}
				if ((!avoiding)&&(l <= bestLatencyNotAvoid)) {
					bestLatencyNotAvoid = l;
					bestNotAvoid = &(*r);
				}
			}
		}

		if (bestNotAvoid) {
			(*bestNotAvoid)->use(now);
			return *bestNotAvoid;
		} else if ((!strictAvoid)&&(bestOverall)) {
			(*bestOverall)->use(now);
			return *bestOverall;
		}

		/*
		unsigned int l,bestLatency = 65536;
		uint64_t lds,ldr;

		// First look for a best root by comparing latencies, but exclude
		// root servers that have not responded to direct messages in order to
		// try to exclude any that are dead or unreachable.
		for(std::vector< SharedPtr<Peer> >::const_iterator sn(_rootPeers.begin());sn!=_rootPeers.end();) {
			// Skip explicitly avoided relays
			for(unsigned int i=0;i<avoidCount;++i) {
				if (avoid[i] == (*sn)->address())
					goto keep_searching_for_roots;
			}

			// Skip possibly comatose or unreachable relays
			lds = (*sn)->lastDirectSend();
			ldr = (*sn)->lastDirectReceive();
			if ((lds)&&(lds > ldr)&&((lds - ldr) > ZT_PEER_RELAY_CONVERSATION_LATENCY_THRESHOLD))
				goto keep_searching_for_roots;

			if ((*sn)->hasActiveDirectPath(now)) {
				l = (*sn)->latency();
				if (bestRoot) {
					if ((l)&&(l < bestLatency)) {
						bestLatency = l;
						bestRoot = *sn;
					}
				} else {
					if (l)
						bestLatency = l;
					bestRoot = *sn;
				}
			}

keep_searching_for_roots:
			++sn;
		}

		if (bestRoot) {
			bestRoot->use(now);
			return bestRoot;
		} else if (strictAvoid)
			return SharedPtr<Peer>();

		// If we have nothing from above, just pick one without avoidance criteria.
		for(std::vector< SharedPtr<Peer> >::const_iterator sn=_rootPeers.begin();sn!=_rootPeers.end();++sn) {
			if ((*sn)->hasActiveDirectPath(now)) {
				unsigned int l = (*sn)->latency();
				if (bestRoot) {
					if ((l)&&(l < bestLatency)) {
						bestLatency = l;
						bestRoot = *sn;
					}
				} else {
					if (l)
						bestLatency = l;
					bestRoot = *sn;
				}
			}
		}
		*/
	}
	return SharedPtr<Peer>();
}

bool Topology::isUpstream(const Identity &id) const
{
	if (isRoot(id))
		return true;
	std::vector< SharedPtr<Network> > nws(RR->node->allNetworks());
	for(std::vector< SharedPtr<Network> >::const_iterator nw(nws.begin());nw!=nws.end();++nw) {
		SharedPtr<NetworkConfig> nc((*nw)->config2());
		if (nc) {
			for(std::vector< std::pair<Address,InetAddress> >::const_iterator r(nc->relays().begin());r!=nc->relays().end();++r) {
				if (r->first == id.address())
					return true;
			}
		}
	}
	return false;
}

bool Topology::worldUpdateIfValid(const World &newWorld)
{
	Mutex::Lock _l(_lock);
	if (_world.shouldBeReplacedBy(newWorld,true)) {
		_setWorld(newWorld);
		try {
			Buffer<ZT_WORLD_MAX_SERIALIZED_LENGTH> dswtmp;
			newWorld.serialize(dswtmp,false);
			RR->node->dataStorePut("world",dswtmp.data(),dswtmp.size(),false);
		} catch ( ... ) {
			RR->node->dataStoreDelete("world");
		}
		return true;
	}
	return false;
}

void Topology::clean(uint64_t now)
{
	Mutex::Lock _l(_lock);
	Hashtable< Address,SharedPtr<Peer> >::Iterator i(_peers);
	Address *a = (Address *)0;
	SharedPtr<Peer> *p = (SharedPtr<Peer> *)0;
	while (i.next(a,p)) {
		if (((now - (*p)->lastUsed()) >= ZT_PEER_IN_MEMORY_EXPIRATION)&&(std::find(_rootAddresses.begin(),_rootAddresses.end(),*a) == _rootAddresses.end())) {
			_peers.erase(*a);
		} else {
			(*p)->clean(RR,now);
		}
	}
}

unsigned long Topology::countAlive() const
{
	const uint64_t now = RR->node->now();
	unsigned long cnt = 0;
	Mutex::Lock _l(_lock);
	Hashtable< Address,SharedPtr<Peer> >::Iterator i(const_cast<Topology *>(this)->_peers);
	Address *a = (Address *)0;
	SharedPtr<Peer> *p = (SharedPtr<Peer> *)0;
	while (i.next(a,p)) {
		if ((*p)->alive(now))
			++cnt;
	}
	return cnt;
}

Identity Topology::_getIdentity(const Address &zta)
{
	char p[128];
	Utils::snprintf(p,sizeof(p),"iddb.d/%.10llx",(unsigned long long)zta.toInt());
	std::string ids(RR->node->dataStoreGet(p));
	if (ids.length() > 0) {
		try {
			return Identity(ids);
		} catch ( ... ) {} // ignore invalid IDs
	}
	return Identity();
}

void Topology::_setWorld(const World &newWorld)
{
	// assumed _lock is locked (or in constructor)
	_world = newWorld;
	_amRoot = false;
	_rootAddresses.clear();
	_rootPeers.clear();
	for(std::vector<World::Root>::const_iterator r(_world.roots().begin());r!=_world.roots().end();++r) {
		_rootAddresses.push_back(r->identity.address());
		if (r->identity.address() == RR->identity.address()) {
			_amRoot = true;
		} else {
			SharedPtr<Peer> *rp = _peers.get(r->identity.address());
			if (rp) {
				_rootPeers.push_back(*rp);
			} else {
				SharedPtr<Peer> newrp(new Peer(RR->identity,r->identity));
				_peers.set(r->identity.address(),newrp);
				_rootPeers.push_back(newrp);
			}
		}
	}
}

} // namespace ZeroTier