/*
 * ZeroTier One - Network Virtualization Everywhere
 * Copyright (C) 2011-2017  ZeroTier, Inc.  https://www.zerotier.com/
 *
 * 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/>.
 *
 * --
 *
 * You can be released from the requirements of the license by purchasing
 * a commercial license. Buying such a license is mandatory as soon as you
 * develop commercial closed-source software that incorporates or links
 * directly against ZeroTier software without disclosing the source code
 * of your own application.
 */

#include "../version.h"

#include "Constants.hpp"
#include "Peer.hpp"
#include "Node.hpp"
#include "Switch.hpp"
#include "Network.hpp"
#include "SelfAwareness.hpp"
#include "Packet.hpp"
#include "Trace.hpp"
#include "InetAddress.hpp"

namespace ZeroTier {

Peer::Peer(const RuntimeEnvironment *renv,const Identity &myIdentity,const Identity &peerIdentity) :
	RR(renv),
	_lastReceive(0),
	_lastNontrivialReceive(0),
	_lastTriedMemorizedPath(0),
	_lastDirectPathPushSent(0),
	_lastDirectPathPushReceive(0),
	_lastCredentialRequestSent(0),
	_lastWhoisRequestReceived(0),
	_lastEchoRequestReceived(0),
	_lastComRequestReceived(0),
	_lastComRequestSent(0),
	_lastCredentialsReceived(0),
	_lastTrustEstablishedPacketReceived(0),
	_lastSentFullHello(0),
	_vProto(0),
	_vMajor(0),
	_vMinor(0),
	_vRevision(0),
	_id(peerIdentity),
	_directPathPushCutoffCount(0),
	_credentialsCutoffCount(0)
{
	if (!myIdentity.agree(peerIdentity,_key,ZT_PEER_SECRET_KEY_LENGTH))
		throw ZT_EXCEPTION_INVALID_ARGUMENT;
}

void Peer::received(
	void *tPtr,
	const SharedPtr<Path> &path,
	const unsigned int hops,
	const uint64_t packetId,
	const Packet::Verb verb,
	const uint64_t inRePacketId,
	const Packet::Verb inReVerb,
	const bool trustEstablished,
	const uint64_t networkId)
{
	const int64_t now = RR->node->now();

	_lastReceive = now;
	switch (verb) {
		case Packet::VERB_FRAME:
		case Packet::VERB_EXT_FRAME:
		case Packet::VERB_NETWORK_CONFIG_REQUEST:
		case Packet::VERB_NETWORK_CONFIG:
		case Packet::VERB_MULTICAST_FRAME:
			_lastNontrivialReceive = now;
			break;
		default: break;
	}

	if (trustEstablished) {
		_lastTrustEstablishedPacketReceived = now;
		path->trustedPacketReceived(now);
	}

	if (_vProto >= 9)
		path->updateLinkQuality((unsigned int)(packetId & 7));

	if (hops == 0) {
		// If this is a direct packet (no hops), update existing paths or learn new ones

		bool havePath = false;
		{
			Mutex::Lock _l(_paths_m);
			for(unsigned int i=0;i<ZT_MAX_PEER_NETWORK_PATHS;++i) {
				if (_paths[i].p) {
					if (_paths[i].p == path) {
						_paths[i].lr = now;
						havePath = true;
						break;
					}
				} else break;
			}
		}

		bool attemptToContact = false;
		if ((!havePath)&&(RR->node->shouldUsePathForZeroTierTraffic(tPtr,_id.address(),path->localSocket(),path->address()))) {
			Mutex::Lock _l(_paths_m);

			// Paths are redunant if they duplicate an alive path to the same IP or
			// with the same local socket and address family.
			bool redundant = false;
			for(unsigned int i=0;i<ZT_MAX_PEER_NETWORK_PATHS;++i) {
				if (_paths[i].p) {
					if ( (_paths[i].p->alive(now)) && ( ((_paths[i].p->localSocket() == path->localSocket())&&(_paths[i].p->address().ss_family == path->address().ss_family)) || (_paths[i].p->address().ipsEqual2(path->address())) ) )  {
						redundant = true;
						break;
					}
				} else break;
			}

			if (!redundant) {
				unsigned int replacePath = ZT_MAX_PEER_NETWORK_PATHS;
				int replacePathQuality = 0;
				for(unsigned int i=0;i<ZT_MAX_PEER_NETWORK_PATHS;++i) {
					if (_paths[i].p) {
						const int q = _paths[i].p->quality(now);
						if (q > replacePathQuality) {
							replacePathQuality = q;
							replacePath = i;
						}
					} else {
						replacePath = i;
						break;
					}
				}

				if (replacePath != ZT_MAX_PEER_NETWORK_PATHS) {
					if (verb == Packet::VERB_OK) {
						RR->t->peerLearnedNewPath(tPtr,networkId,*this,path,packetId);
						_paths[replacePath].lr = now;
						_paths[replacePath].p = path;
						_paths[replacePath].priority = 1;
					} else {
						attemptToContact = true;
					}
				}
			}
		}

		if (attemptToContact) {
			attemptToContactAt(tPtr,path->localSocket(),path->address(),now,true,path->nextOutgoingCounter());
			path->sent(now);
			RR->t->peerConfirmingUnknownPath(tPtr,networkId,*this,path,packetId,verb);
		}
	}

	// If we have a trust relationship periodically push a message enumerating
	// all known external addresses for ourselves. We now do this even if we
	// have a current path since we'll want to use new ones too.
	if (this->trustEstablished(now)) {
		if ((now - _lastDirectPathPushSent) >= ZT_DIRECT_PATH_PUSH_INTERVAL) {
			_lastDirectPathPushSent = now;

			std::vector<InetAddress> pathsToPush;

			std::vector<InetAddress> dps(RR->node->directPaths());
			for(std::vector<InetAddress>::const_iterator i(dps.begin());i!=dps.end();++i)
				pathsToPush.push_back(*i);

			// Do symmetric NAT prediction if we are communicating indirectly.
			if (hops > 0) {
				std::vector<InetAddress> sym(RR->sa->getSymmetricNatPredictions());
				for(unsigned long i=0,added=0;i<sym.size();++i) {
					InetAddress tmp(sym[(unsigned long)RR->node->prng() % sym.size()]);
					if (std::find(pathsToPush.begin(),pathsToPush.end(),tmp) == pathsToPush.end()) {
						pathsToPush.push_back(tmp);
						if (++added >= ZT_PUSH_DIRECT_PATHS_MAX_PER_SCOPE_AND_FAMILY)
							break;
					}
				}
			}

			if (pathsToPush.size() > 0) {
				std::vector<InetAddress>::const_iterator p(pathsToPush.begin());
				while (p != pathsToPush.end()) {
					Packet outp(_id.address(),RR->identity.address(),Packet::VERB_PUSH_DIRECT_PATHS);
					outp.addSize(2); // leave room for count

					unsigned int count = 0;
					while ((p != pathsToPush.end())&&((outp.size() + 24) < 1200)) {
						uint8_t addressType = 4;
						switch(p->ss_family) {
							case AF_INET:
								break;
							case AF_INET6:
								addressType = 6;
								break;
							default: // we currently only push IP addresses
								++p;
								continue;
						}

						outp.append((uint8_t)0); // no flags
						outp.append((uint16_t)0); // no extensions
						outp.append(addressType);
						outp.append((uint8_t)((addressType == 4) ? 6 : 18));
						outp.append(p->rawIpData(),((addressType == 4) ? 4 : 16));
						outp.append((uint16_t)p->port());

						++count;
						++p;
					}

					if (count) {
						outp.setAt(ZT_PACKET_IDX_PAYLOAD,(uint16_t)count);
						outp.armor(_key,true,path->nextOutgoingCounter());
						path->send(RR,tPtr,outp.data(),outp.size(),now);
					}
				}
			}
		}
	}
}

SharedPtr<Path> Peer::getBestPath(int64_t now,bool includeExpired) const
{
	Mutex::Lock _l(_paths_m);

	unsigned int bestPath = ZT_MAX_PEER_NETWORK_PATHS;
	long bestPathQuality = 2147483647;
	for(unsigned int i=0;i<ZT_MAX_PEER_NETWORK_PATHS;++i) {
		if (_paths[i].p) {
			if ((includeExpired)||((now - _paths[i].lr) < ZT_PEER_PATH_EXPIRATION)) {
				const long q = _paths[i].p->quality(now) / _paths[i].priority;
				if (q <= bestPathQuality) {
					bestPathQuality = q;
					bestPath = i;
				}
			}
		} else break;
	}

	if (bestPath != ZT_MAX_PEER_NETWORK_PATHS)
		return _paths[bestPath].p;
	return SharedPtr<Path>();
}

void Peer::introduce(void *const tPtr,const int64_t now,const SharedPtr<Peer> &other) const
{
	unsigned int myBestV4ByScope[ZT_INETADDRESS_MAX_SCOPE+1];
	unsigned int myBestV6ByScope[ZT_INETADDRESS_MAX_SCOPE+1];
	long myBestV4QualityByScope[ZT_INETADDRESS_MAX_SCOPE+1];
	long myBestV6QualityByScope[ZT_INETADDRESS_MAX_SCOPE+1];
	unsigned int theirBestV4ByScope[ZT_INETADDRESS_MAX_SCOPE+1];
	unsigned int theirBestV6ByScope[ZT_INETADDRESS_MAX_SCOPE+1];
	long theirBestV4QualityByScope[ZT_INETADDRESS_MAX_SCOPE+1];
	long theirBestV6QualityByScope[ZT_INETADDRESS_MAX_SCOPE+1];
	for(int i=0;i<=ZT_INETADDRESS_MAX_SCOPE;++i) {
		myBestV4ByScope[i] = ZT_MAX_PEER_NETWORK_PATHS;
		myBestV6ByScope[i] = ZT_MAX_PEER_NETWORK_PATHS;
		myBestV4QualityByScope[i] = 2147483647;
		myBestV6QualityByScope[i] = 2147483647;
		theirBestV4ByScope[i] = ZT_MAX_PEER_NETWORK_PATHS;
		theirBestV6ByScope[i] = ZT_MAX_PEER_NETWORK_PATHS;
		theirBestV4QualityByScope[i] = 2147483647;
		theirBestV6QualityByScope[i] = 2147483647;
	}

	Mutex::Lock _l1(_paths_m);

	for(unsigned int i=0;i<ZT_MAX_PEER_NETWORK_PATHS;++i) {
		if (_paths[i].p) {
			const long q = _paths[i].p->quality(now) / _paths[i].priority;
			const unsigned int s = (unsigned int)_paths[i].p->ipScope();
			switch(_paths[i].p->address().ss_family) {
				case AF_INET:
					if (q <= myBestV4QualityByScope[s]) {
						myBestV4QualityByScope[s] = q;
						myBestV4ByScope[s] = i;
					}
					break;
				case AF_INET6:
					if (q <= myBestV6QualityByScope[s]) {
						myBestV6QualityByScope[s] = q;
						myBestV6ByScope[s] = i;
					}
					break;
			}
		} else break;
	}

	Mutex::Lock _l2(other->_paths_m);

	for(unsigned int i=0;i<ZT_MAX_PEER_NETWORK_PATHS;++i) {
		if (other->_paths[i].p) {
			const long q = other->_paths[i].p->quality(now) / other->_paths[i].priority;
			const unsigned int s = (unsigned int)other->_paths[i].p->ipScope();
			switch(other->_paths[i].p->address().ss_family) {
				case AF_INET:
					if (q <= theirBestV4QualityByScope[s]) {
						theirBestV4QualityByScope[s] = q;
						theirBestV4ByScope[s] = i;
					}
					break;
				case AF_INET6:
					if (q <= theirBestV6QualityByScope[s]) {
						theirBestV6QualityByScope[s] = q;
						theirBestV6ByScope[s] = i;
					}
					break;
			}
		} else break;
	}

	unsigned int mine = ZT_MAX_PEER_NETWORK_PATHS;
	unsigned int theirs = ZT_MAX_PEER_NETWORK_PATHS;

	for(int s=ZT_INETADDRESS_MAX_SCOPE;s>=0;--s) {
		if ((myBestV6ByScope[s] != ZT_MAX_PEER_NETWORK_PATHS)&&(theirBestV6ByScope[s] != ZT_MAX_PEER_NETWORK_PATHS)) {
			mine = myBestV6ByScope[s];
			theirs = theirBestV6ByScope[s];
			break;
		}
		if ((myBestV4ByScope[s] != ZT_MAX_PEER_NETWORK_PATHS)&&(theirBestV4ByScope[s] != ZT_MAX_PEER_NETWORK_PATHS)) {
			mine = myBestV4ByScope[s];
			theirs = theirBestV4ByScope[s];
			break;
		}
	}

	if (mine != ZT_MAX_PEER_NETWORK_PATHS) {
		unsigned int alt = (unsigned int)RR->node->prng() & 1; // randomize which hint we send first for black magickal NAT-t reasons
		const unsigned int completed = alt + 2;
		while (alt != completed) {
			if ((alt & 1) == 0) {
				Packet outp(_id.address(),RR->identity.address(),Packet::VERB_RENDEZVOUS);
				outp.append((uint8_t)0);
				other->_id.address().appendTo(outp);
				outp.append((uint16_t)other->_paths[theirs].p->address().port());
				if (other->_paths[theirs].p->address().ss_family == AF_INET6) {
					outp.append((uint8_t)16);
					outp.append(other->_paths[theirs].p->address().rawIpData(),16);
				} else {
					outp.append((uint8_t)4);
					outp.append(other->_paths[theirs].p->address().rawIpData(),4);
				}
				outp.armor(_key,true,_paths[mine].p->nextOutgoingCounter());
				_paths[mine].p->send(RR,tPtr,outp.data(),outp.size(),now);
			} else {
				Packet outp(other->_id.address(),RR->identity.address(),Packet::VERB_RENDEZVOUS);
				outp.append((uint8_t)0);
				_id.address().appendTo(outp);
				outp.append((uint16_t)_paths[mine].p->address().port());
				if (_paths[mine].p->address().ss_family == AF_INET6) {
					outp.append((uint8_t)16);
					outp.append(_paths[mine].p->address().rawIpData(),16);
				} else {
					outp.append((uint8_t)4);
					outp.append(_paths[mine].p->address().rawIpData(),4);
				}
				outp.armor(other->_key,true,other->_paths[theirs].p->nextOutgoingCounter());
				other->_paths[theirs].p->send(RR,tPtr,outp.data(),outp.size(),now);
			}
			++alt;
		}
	}
}

void Peer::sendHELLO(void *tPtr,const int64_t localSocket,const InetAddress &atAddress,int64_t now,unsigned int counter)
{
	Packet outp(_id.address(),RR->identity.address(),Packet::VERB_HELLO);

	outp.append((unsigned char)ZT_PROTO_VERSION);
	outp.append((unsigned char)ZEROTIER_ONE_VERSION_MAJOR);
	outp.append((unsigned char)ZEROTIER_ONE_VERSION_MINOR);
	outp.append((uint16_t)ZEROTIER_ONE_VERSION_REVISION);
	outp.append(now);
	RR->identity.serialize(outp,false);
	atAddress.serialize(outp);

	outp.append((uint64_t)RR->topology->planetWorldId());
	outp.append((uint64_t)RR->topology->planetWorldTimestamp());

	const unsigned int startCryptedPortionAt = outp.size();

	std::vector<World> moons(RR->topology->moons());
	std::vector<uint64_t> moonsWanted(RR->topology->moonsWanted());
	outp.append((uint16_t)(moons.size() + moonsWanted.size()));
	for(std::vector<World>::const_iterator m(moons.begin());m!=moons.end();++m) {
		outp.append((uint8_t)m->type());
		outp.append((uint64_t)m->id());
		outp.append((uint64_t)m->timestamp());
	}
	for(std::vector<uint64_t>::const_iterator m(moonsWanted.begin());m!=moonsWanted.end();++m) {
		outp.append((uint8_t)World::TYPE_MOON);
		outp.append(*m);
		outp.append((uint64_t)0);
	}

	outp.cryptField(_key,startCryptedPortionAt,outp.size() - startCryptedPortionAt);

	RR->node->expectReplyTo(outp.packetId());

	if (atAddress) {
		outp.armor(_key,false,counter); // false == don't encrypt full payload, but add MAC
		RR->node->putPacket(tPtr,localSocket,atAddress,outp.data(),outp.size());
	} else {
		RR->sw->send(tPtr,outp,false); // false == don't encrypt full payload, but add MAC
	}
}

void Peer::attemptToContactAt(void *tPtr,const int64_t localSocket,const InetAddress &atAddress,int64_t now,bool sendFullHello,unsigned int counter)
{
	if ( (!sendFullHello) && (_vProto >= 5) && (!((_vMajor == 1)&&(_vMinor == 1)&&(_vRevision == 0))) ) {
		Packet outp(_id.address(),RR->identity.address(),Packet::VERB_ECHO);
		RR->node->expectReplyTo(outp.packetId());
		outp.armor(_key,true,counter);
		RR->node->putPacket(tPtr,localSocket,atAddress,outp.data(),outp.size());
	} else {
		sendHELLO(tPtr,localSocket,atAddress,now,counter);
	}
}

void Peer::tryMemorizedPath(void *tPtr,int64_t now)
{
	if ((now - _lastTriedMemorizedPath) >= ZT_TRY_MEMORIZED_PATH_INTERVAL) {
		_lastTriedMemorizedPath = now;
		InetAddress mp;
		if (RR->node->externalPathLookup(tPtr,_id.address(),-1,mp))
			attemptToContactAt(tPtr,-1,mp,now,true,0);
	}
}

unsigned int Peer::doPingAndKeepalive(void *tPtr,int64_t now)
{
	unsigned int sent = 0;

	Mutex::Lock _l(_paths_m);

	const bool sendFullHello = ((now - _lastSentFullHello) >= ZT_PEER_PING_PERIOD);
	_lastSentFullHello = now;

	// Right now we only keep pinging links that have the maximum priority. The
	// priority is used to track cluster redirections, meaning that when a cluster
	// redirects us its redirect target links override all other links and we
	// let those old links expire.
	long maxPriority = 0;
	for(unsigned int i=0;i<ZT_MAX_PEER_NETWORK_PATHS;++i) {
		if (_paths[i].p)
			maxPriority = std::max(_paths[i].priority,maxPriority);
		else break;
	}

	unsigned int j = 0;
	for(unsigned int i=0;i<ZT_MAX_PEER_NETWORK_PATHS;++i) {
		if (_paths[i].p) {
			// Clean expired and reduced priority paths
			if ( ((now - _paths[i].lr) < ZT_PEER_PATH_EXPIRATION) && (_paths[i].priority == maxPriority) ) {
				if ((sendFullHello)||(_paths[i].p->needsHeartbeat(now))) {
					attemptToContactAt(tPtr,_paths[i].p->localSocket(),_paths[i].p->address(),now,sendFullHello,_paths[i].p->nextOutgoingCounter());
					_paths[i].p->sent(now);
					sent |= (_paths[i].p->address().ss_family == AF_INET) ? 0x1 : 0x2;
				}
				if (i != j)
					_paths[j] = _paths[i];
				++j;
			}
		} else break;
	}
	while(j < ZT_MAX_PEER_NETWORK_PATHS) {
		_paths[j].lr = 0;
		_paths[j].p.zero();
		_paths[j].priority = 1;
		++j;
	}

	return sent;
}

void Peer::clusterRedirect(void *tPtr,const SharedPtr<Path> &originatingPath,const InetAddress &remoteAddress,const int64_t now)
{
	SharedPtr<Path> np(RR->topology->getPath(originatingPath->localSocket(),remoteAddress));
	RR->t->peerRedirected(tPtr,0,*this,np);

	attemptToContactAt(tPtr,originatingPath->localSocket(),remoteAddress,now,true,np->nextOutgoingCounter());

	{
		Mutex::Lock _l(_paths_m);

		// New priority is higher than the priority of the originating path (if known)
		long newPriority = 1;
		for(unsigned int i=0;i<ZT_MAX_PEER_NETWORK_PATHS;++i) {
			if (_paths[i].p) {
				if (_paths[i].p == originatingPath) {
					newPriority = _paths[i].priority;
					break;
				}
			} else break;
		}
		newPriority += 2;

		// Erase any paths with lower priority than this one or that are duplicate
		// IPs and add this path.
		unsigned int j = 0;
		for(unsigned int i=0;i<ZT_MAX_PEER_NETWORK_PATHS;++i) {
			if (_paths[i].p) {
				if ((_paths[i].priority >= newPriority)&&(!_paths[i].p->address().ipsEqual2(remoteAddress))) {
					if (i != j)
						_paths[j] = _paths[i];
					++j;
				}
			}
		}
		if (j < ZT_MAX_PEER_NETWORK_PATHS) {
			_paths[j].lr = now;
			_paths[j].p = np;
			_paths[j].priority = newPriority;
			++j;
			while (j < ZT_MAX_PEER_NETWORK_PATHS) {
				_paths[j].lr = 0;
				_paths[j].p.zero();
				_paths[j].priority = 1;
				++j;
			}
		}
	}
}

void Peer::resetWithinScope(void *tPtr,InetAddress::IpScope scope,int inetAddressFamily,int64_t now)
{
	Mutex::Lock _l(_paths_m);
	for(unsigned int i=0;i<ZT_MAX_PEER_NETWORK_PATHS;++i) {
		if (_paths[i].p) {
			if ((_paths[i].p->address().ss_family == inetAddressFamily)&&(_paths[i].p->ipScope() == scope)) {
				attemptToContactAt(tPtr,_paths[i].p->localSocket(),_paths[i].p->address(),now,false,_paths[i].p->nextOutgoingCounter());
				_paths[i].p->sent(now);
				_paths[i].lr = 0; // path will not be used unless it speaks again
			}
		} else break;
	}
}

} // namespace ZeroTier