/*
 * ZeroTier One - Global Peer to Peer Ethernet
 * Copyright (C) 2012-2013  ZeroTier Networks LLC
 *
 * 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 "RuntimeEnvironment.hpp"
#include "Topology.hpp"
#include "PacketDecoder.hpp"
#include "Switch.hpp"
#include "Peer.hpp"

namespace ZeroTier {

bool PacketDecoder::tryDecode(const RuntimeEnvironment *_r)
	throw(std::out_of_range,std::runtime_error)
{
	Address source(source());

	if ((!encrypted())&&(verb() == Packet::VERB_HELLO)) {
		// Unencrypted HELLOs are handled here since they are used to
		// populate our identity cache in the first place. Thus we might get
		// a HELLO for someone for whom we don't have a Peer record.
		TRACE("HELLO from %s(%s)",source.toString().c_str(),fromAddr.toString().c_str());
		_doHELLO(localPort,fromAddr,packet);
		return true;
	}

	SharedPtr<Peer> peer = _r->topology->getPeer(source);
	if (peer) {
		uint64_t now = Utils::now();
		unsigned int latency = 0;

		if (!packet.hmacVerify(peer->macKey())) {
			TRACE("dropped packet from %s(%s), HMAC authentication failed (size: %u)",source.toString().c_str(),fromAddr.toString().c_str(),packet.size());
			return true;
		}

		if (packet.encrypted()) {
			packet.decrypt(peer->cryptKey());
		} else {
			// Unencrypted is tolerated in case we want to run this on
			// devices where squeezing out cycles matters. HMAC is
			// what's really important.
			TRACE("ODD: %s from %s(%s) wasn't encrypted",Packet::verbString(packet.verb()),source.toString().c_str(),fromAddr.toString().c_str());
		}

		if (!packet.uncompress()) {
			TRACE("dropped packet from %s(%s), compressed data invalid",source.toString().c_str(),fromAddr.toString().c_str());
			return true;
		}

		switch(packet.verb()) {
			case Packet::VERB_NOP:
				TRACE("NOP from %s(%s)",source.toString().c_str(),fromAddr.toString().c_str());
				break;
			case Packet::VERB_HELLO:
				// HELLO is normally handled up top, but this is legal. Pointless, but legal.
				_doHELLO(localPort,fromAddr,packet);
				break;
			case Packet::VERB_ERROR:
				try {
#ifdef ZT_TRACE
					Packet::Verb inReVerb = (Packet::Verb)packet[ZT_PROTO_VERB_ERROR_IDX_IN_RE_VERB];
					Packet::ErrorCode errorCode = (Packet::ErrorCode)packet[ZT_PROTO_VERB_ERROR_IDX_ERROR_CODE];
					TRACE("ERROR %s from %s(%s) in-re %s",Packet::errorString(errorCode),source.toString().c_str(),fromAddr.toString().c_str(),Packet::verbString(inReVerb));
#endif
					// TODO:
					// The fact is that the protocol works fine without error handling.
					// The only error that really needs to be handled here is duplicate
					// identity collision, which if it comes from a supernode should cause
					// us to restart and regenerate a new identity.
				} catch (std::exception &ex) {
					TRACE("dropped ERROR from %s(%s): unexpected exception: %s",source.toString().c_str(),fromAddr.toString().c_str(),ex.what());
				} catch ( ... ) {
					TRACE("dropped ERROR from %s(%s): unexpected exception: (unknown)",source.toString().c_str(),fromAddr.toString().c_str());
				}
				break;
			case Packet::VERB_OK:
				try {
					Packet::Verb inReVerb = (Packet::Verb)packet[ZT_PROTO_VERB_OK_IDX_IN_RE_VERB];
					switch(inReVerb) {
						case Packet::VERB_HELLO:
							// OK from HELLO permits computation of latency.
							latency = std::min((unsigned int)(now - packet.at<uint64_t>(ZT_PROTO_VERB_HELLO__OK__IDX_TIMESTAMP)),(unsigned int)0xffff);
							TRACE("%s(%s): OK(HELLO), latency: %u",source.toString().c_str(),fromAddr.toString().c_str(),latency);
							break;
						case Packet::VERB_WHOIS:
							// Right now we only query supernodes for WHOIS and only accept
							// OK back from them. If we query other nodes, we'll have to
							// do something to prevent WHOIS cache poisoning such as
							// using the packet ID field in the OK packet to match with the
							// original query. Technically we should be doing this anyway.
							TRACE("%s(%s): OK(%s)",source.toString().c_str(),fromAddr.toString().c_str(),Packet::verbString(inReVerb));
							if (_r->topology->isSupernode(source))
								_r->topology->addPeer(SharedPtr<Peer>(new Peer(_r->identity,Identity(packet,ZT_PROTO_VERB_WHOIS__OK__IDX_IDENTITY))),&Switch::_CBaddPeerFromWhois,this);
							break;
						default:
							TRACE("%s(%s): OK(%s)",source.toString().c_str(),fromAddr.toString().c_str(),Packet::verbString(inReVerb));
							break;
					}
				} catch (std::exception &ex) {
					TRACE("dropped OK from %s(%s): unexpected exception: %s",source.toString().c_str(),fromAddr.toString().c_str(),ex.what());
				} catch ( ... ) {
					TRACE("dropped OK from %s(%s): unexpected exception: (unknown)",source.toString().c_str(),fromAddr.toString().c_str());
				}
				break;
			case Packet::VERB_WHOIS:
				if (packet.payloadLength() == ZT_ADDRESS_LENGTH) {
					SharedPtr<Peer> p(_r->topology->getPeer(Address(packet.payload())));
					if (p) {
						Packet outp(source,_r->identity.address(),Packet::VERB_OK);
						outp.append((unsigned char)Packet::VERB_WHOIS);
						outp.append(packet.packetId());
						p->identity().serialize(outp,false);
						outp.encrypt(peer->cryptKey());
						outp.hmacSet(peer->macKey());
						_r->demarc->send(localPort,fromAddr,outp.data(),outp.size(),-1);
						TRACE("sent WHOIS response to %s for %s",source.toString().c_str(),Address(packet.payload()).toString().c_str());
					} else {
						Packet outp(source,_r->identity.address(),Packet::VERB_ERROR);
						outp.append((unsigned char)Packet::VERB_WHOIS);
						outp.append(packet.packetId());
						outp.append((unsigned char)Packet::ERROR_NOT_FOUND);
						outp.append(packet.payload(),ZT_ADDRESS_LENGTH);
						outp.encrypt(peer->cryptKey());
						outp.hmacSet(peer->macKey());
						_r->demarc->send(localPort,fromAddr,outp.data(),outp.size(),-1);
						TRACE("sent WHOIS ERROR to %s for %s (not found)",source.toString().c_str(),Address(packet.payload()).toString().c_str());
					}
				} else {
					TRACE("dropped WHOIS from %s(%s): missing or invalid address",source.toString().c_str(),fromAddr.toString().c_str());
				}
				break;
			case Packet::VERB_RENDEZVOUS:
				try {
					Address with(packet.field(ZT_PROTO_VERB_RENDEZVOUS_IDX_ZTADDRESS,ZT_ADDRESS_LENGTH));
					RendezvousQueueEntry qe;
					if (_r->topology->getPeer(with)) {
						unsigned int port = packet.at<uint16_t>(ZT_PROTO_VERB_RENDEZVOUS_IDX_PORT);
						unsigned int addrlen = packet[ZT_PROTO_VERB_RENDEZVOUS_IDX_ADDRLEN];
						if ((port > 0)&&((addrlen == 4)||(addrlen == 16))) {
							qe.inaddr.set(packet.field(ZT_PROTO_VERB_RENDEZVOUS_IDX_ADDRESS,addrlen),addrlen,port);
							qe.fireAtTime = now + ZT_RENDEZVOUS_NAT_T_DELAY; // then send real packet in a few ms
							qe.localPort = _r->demarc->pick(qe.inaddr);
							TRACE("RENDEZVOUS from %s says %s might be at %s, starting NAT-t",source.toString().c_str(),with.toString().c_str(),qe.inaddr.toString().c_str());
							_r->demarc->send(qe.localPort,qe.inaddr,"\0",1,ZT_FIREWALL_OPENER_HOPS); // start with firewall opener
							{
								Mutex::Lock _l(_rendezvousQueue_m);
								_rendezvousQueue[with] = qe;
							}
						} else {
							TRACE("dropped corrupt RENDEZVOUS from %s(%s) (bad address or port)",source.toString().c_str(),fromAddr.toString().c_str());
						}
					} else {
						TRACE("ignored RENDEZVOUS from %s(%s) to meet unknown peer %s",source.toString().c_str(),fromAddr.toString().c_str(),with.toString().c_str());
					}
				} catch (std::exception &ex) {
					TRACE("dropped RENDEZVOUS from %s(%s): %s",source.toString().c_str(),fromAddr.toString().c_str(),ex.what());
				} catch ( ... ) {
					TRACE("dropped RENDEZVOUS from %s(%s): unexpected exception",source.toString().c_str(),fromAddr.toString().c_str());
				}
				break;
			case Packet::VERB_FRAME:
				try {
					SharedPtr<Network> network(_r->nc->network(packet.at<uint64_t>(ZT_PROTO_VERB_FRAME_IDX_NETWORK_ID)));
					if (network) {
						if (network->isAllowed(source)) {
							unsigned int etherType = packet.at<uint16_t>(ZT_PROTO_VERB_FRAME_IDX_ETHERTYPE);
							if ((etherType != ZT_ETHERTYPE_ARP)&&(etherType != ZT_ETHERTYPE_IPV4)&&(etherType != ZT_ETHERTYPE_IPV6)) {
								TRACE("dropped FRAME from %s: unsupported ethertype",source.toString().c_str());
							} else if (packet.size() > ZT_PROTO_VERB_FRAME_IDX_PAYLOAD) {
								network->tap().put(source.toMAC(),network->tap().mac(),etherType,packet.data() + ZT_PROTO_VERB_FRAME_IDX_PAYLOAD,packet.size() - ZT_PROTO_VERB_FRAME_IDX_PAYLOAD);
							}
						} else {
							TRACE("dropped FRAME from %s(%s): not a member of closed network %llu",source.toString().c_str(),fromAddr.toString().c_str(),network->id());
						}
					} else {
						TRACE("dropped FRAME from %s(%s): network %llu unknown",source.toString().c_str(),fromAddr.toString().c_str(),packet.at<uint64_t>(ZT_PROTO_VERB_FRAME_IDX_NETWORK_ID));
					}
				} catch (std::exception &ex) {
					TRACE("dropped FRAME from %s(%s): unexpected exception: %s",source.toString().c_str(),fromAddr.toString().c_str(),ex.what());
				} catch ( ... ) {
					TRACE("dropped FRAME from %s(%s): unexpected exception: (unknown)",source.toString().c_str(),fromAddr.toString().c_str());
				}
				break;
			case Packet::VERB_MULTICAST_LIKE:
				try {
					unsigned int ptr = ZT_PACKET_IDX_PAYLOAD;
					unsigned int numAccepted = 0;

					// Iterate through 18-byte network,MAC,ADI tuples:
					while ((ptr + 18) <= packet.size()) {
						uint64_t nwid = packet.at<uint64_t>(ptr); ptr += 8;
						SharedPtr<Network> network(_r->nc->network(nwid));
						if (network) {
							if (network->isAllowed(source)) {
								MAC mac(packet.field(ptr,6)); ptr += 6;
								uint32_t adi = packet.at<uint32_t>(ptr); ptr += 4;
								TRACE("peer %s likes multicast group %s:%.8lx on network %llu",source.toString().c_str(),mac.toString().c_str(),(unsigned long)adi,nwid);
								_multicaster.likesMulticastGroup(nwid,MulticastGroup(mac,adi),source,now);
								++numAccepted;
							} else {
								TRACE("ignored MULTICAST_LIKE from %s(%s): not a member of closed network %llu",source.toString().c_str(),fromAddr.toString().c_str(),nwid);
							}
						} else {
							TRACE("ignored MULTICAST_LIKE from %s(%s): network %llu unknown or we are not a member",source.toString().c_str(),fromAddr.toString().c_str(),nwid);
						}
					}

					Packet outp(source,_r->identity.address(),Packet::VERB_OK);
					outp.append((unsigned char)Packet::VERB_MULTICAST_LIKE);
					outp.append(packet.packetId());
					outp.append((uint16_t)numAccepted);
					outp.encrypt(peer->cryptKey());
					outp.hmacSet(peer->macKey());
					_r->demarc->send(localPort,fromAddr,outp.data(),outp.size(),-1);
				} catch (std::exception &ex) {
					TRACE("dropped MULTICAST_LIKE from %s(%s): unexpected exception: %s",source.toString().c_str(),fromAddr.toString().c_str(),ex.what());
				} catch ( ... ) {
					TRACE("dropped MULTICAST_LIKE from %s(%s): unexpected exception: (unknown)",source.toString().c_str(),fromAddr.toString().c_str());
				}
				break;
			case Packet::VERB_MULTICAST_FRAME:
				try {
					SharedPtr<Network> network(_r->nc->network(packet.at<uint64_t>(ZT_PROTO_VERB_MULTICAST_FRAME_IDX_NETWORK_ID)));
					if (network) {
						if (network->isAllowed(source)) {
							if (packet.size() > ZT_PROTO_VERB_MULTICAST_FRAME_IDX_PAYLOAD) {
								Address originalSubmitterAddress(packet.field(ZT_PROTO_VERB_MULTICAST_FRAME_IDX_SUBMITTER_ADDRESS,ZT_ADDRESS_LENGTH));
								MAC fromMac(packet.field(ZT_PROTO_VERB_MULTICAST_FRAME_IDX_SOURCE_MAC,6));
								MulticastGroup mg(MAC(packet.field(ZT_PROTO_VERB_MULTICAST_FRAME_IDX_DESTINATION_MAC,6)),packet.at<uint32_t>(ZT_PROTO_VERB_MULTICAST_FRAME_IDX_ADI));
								unsigned int hops = packet[ZT_PROTO_VERB_MULTICAST_FRAME_IDX_HOP_COUNT];
								unsigned int etherType = packet.at<uint16_t>(ZT_PROTO_VERB_MULTICAST_FRAME_IDX_ETHERTYPE);
								unsigned int datalen = packet.at<uint16_t>(ZT_PROTO_VERB_MULTICAST_FRAME_IDX_PAYLOAD_LENGTH);
								unsigned int signaturelen = packet.at<uint16_t>(ZT_PROTO_VERB_MULTICAST_FRAME_IDX_SIGNATURE_LENGTH);
								unsigned char *dataAndSignature = packet.field(ZT_PROTO_VERB_MULTICAST_FRAME_IDX_PAYLOAD,datalen + signaturelen);

								bool isDuplicate = _multicaster.checkAndUpdateMulticastHistory(fromMac,mg,payload,payloadLen,network->id(),now);

								if (originalSubmitterAddress == _r->identity.address()) {
									// Technically should not happen, since the original submitter is
									// excluded from consideration as a propagation recipient.
									TRACE("dropped boomerang MULTICAST_FRAME received from %s(%s)",source.toString().c_str(),fromAddr.toString().c_str());
								} else if ((!isDuplicate)||(_r->topology.isSupernode(_r->identity.address()))) {
									// If I am a supernode, I will repeatedly propagate duplicates. That's
									// because supernodes are used to bridge sparse multicast groups. Non-
									// supernodes will ignore duplicates completely.
									SharedPtr<Peer> originalSubmitter(_r->topology->getPeer(originalSubmitterAddress));
									if (!originalSubmitter) {
										TRACE("requesting WHOIS on original multicast frame submitter %s",originalSubmitterAddress.toString().c_str());
										_requestWhois(originalSubmitterAddress,packet.packetId());
										return false;
									} else if (Multicaster::verifyMulticastPacket(originalSubmitter->identity(),fromMac,mg,etherType,data,datalen,dataAndSignature + datalen,signaturelen)) {
										if (!isDuplicate)
											network->tap().put(fromMac,mg.mac(),etherType,payload,payloadLen);
										_propagateMulticast(network,originalSubmitterAddress,source,packet.field(ZT_PROTO_VERB_MULTICAST_FRAME_IDX_BLOOM,ZT_PROTO_VERB_MULTICAST_FRAME_BLOOM_FILTER_SIZE),mg,hops+1,fromMac,etherType,payload,payloadLen);
									} else {
										LOG("rejected MULTICAST_FRAME from %s(%s) due to failed signature check (claims original sender %s)",source.toString().c_str(),fromAddr.toString().c_str(),originalSubmitterAddress.toString().c_str());
									}
								} else {
									TRACE("dropped redundant MULTICAST_FRAME from %s(%s)",source.toString().c_str(),fromAddr.toString().c_str());
								}
							} else {
								TRACE("dropped MULTICAST_FRAME from %s(%s): invalid short packet",source.toString().c_str(),fromAddr.toString().c_str());
							}
						} else {
							TRACE("dropped MULTICAST_FRAME from %s(%s): not a member of closed network %llu",source.toString().c_str(),fromAddr.toString().c_str(),network->id());
						}
					} else {
						TRACE("dropped MULTICAST_FRAME from %s(%s): network %llu unknown or we are not a member",source.toString().c_str(),fromAddr.toString().c_str(),packet.at<uint64_t>(ZT_PROTO_VERB_MULTICAST_FRAME_IDX_NETWORK_ID));
					}
				} catch (std::exception &ex) {
					TRACE("dropped MULTICAST_FRAME from %s(%s): unexpected exception: %s",source.toString().c_str(),fromAddr.toString().c_str(),ex.what());
				} catch ( ... ) {
					TRACE("dropped MULTICAST_FRAME from %s(%s): unexpected exception: (unknown)",source.toString().c_str(),fromAddr.toString().c_str());
				}
				break;
			default:
				// This might be something from a new or old version of the protocol.
				// Technically it passed HMAC so the packet is still valid, but we
				// ignore it.
				TRACE("ignored unrecognized verb %.2x from %s(%s)",(unsigned int)packet.verb(),source.toString().c_str(),fromAddr.toString().c_str());
				break;
		}

		// Update peer timestamps and learn new links. This must only ever
		// be called on an authenticated and technically valid packet, since
		// we only learn paths to peers over the WAN by hearing directly
		// from them over those paths. (Or by having them authoritatively
		// and statically defined, like with supernodes, but that's done
		// elsewhere.)
		peer->onReceive(_r,localPort,fromAddr,latency,packet.hops(),packet.verb(),now);
	} else {
		_requestWhois(source,packet.packetId());
		return false;
	}

	return true;
}

void PacketDecoder::_doHELLO(Demarc::Port localPort,const InetAddress &fromAddr)
{
	Address source(source());

	try {
		unsigned int protoVersion = packet[ZT_PROTO_VERB_HELLO_IDX_PROTOCOL_VERSION];
		unsigned int vMajor = packet[ZT_PROTO_VERB_HELLO_IDX_MAJOR_VERSION];
		unsigned int vMinor = packet[ZT_PROTO_VERB_HELLO_IDX_MINOR_VERSION];
		unsigned int vRevision = packet.at<uint16_t>(ZT_PROTO_VERB_HELLO_IDX_REVISION);
		uint64_t timestamp = packet.at<uint64_t>(ZT_PROTO_VERB_HELLO_IDX_TIMESTAMP);
		Identity id(packet,ZT_PROTO_VERB_HELLO_IDX_IDENTITY);

		SharedPtr<Peer> candidate(new Peer(_r->identity,id));
		candidate->setPathAddress(fromAddr,false);

		// Initial sniff test
		if (protoVersion != ZT_PROTO_VERSION) {
			TRACE("rejected HELLO from %s(%s): invalid protocol version",source.toString().c_str(),fromAddr.toString().c_str());
			Packet outp(source,_r->identity.address(),Packet::VERB_ERROR);
			outp.append((unsigned char)Packet::VERB_HELLO);
			outp.append(packet.packetId());
			outp.append((unsigned char)Packet::ERROR_BAD_PROTOCOL_VERSION);
			outp.encrypt(candidate->cryptKey());
			outp.hmacSet(candidate->macKey());
			_r->demarc->send(localPort,fromAddr,outp.data(),outp.size(),-1);
			return;
		}
		if (id.address().isReserved()) {
			TRACE("rejected HELLO from %s(%s): identity has reserved address",source.toString().c_str(),fromAddr.toString().c_str());
			Packet outp(source,_r->identity.address(),Packet::VERB_ERROR);
			outp.append((unsigned char)Packet::VERB_HELLO);
			outp.append(packet.packetId());
			outp.append((unsigned char)Packet::ERROR_IDENTITY_INVALID);
			outp.encrypt(candidate->cryptKey());
			outp.hmacSet(candidate->macKey());
			_r->demarc->send(localPort,fromAddr,outp.data(),outp.size(),-1);
			return;
		}
		if (id.address() != source) {
			TRACE("rejected HELLO from %s(%s): identity is not for sender of packet (HELLO is a self-announcement)",source.toString().c_str(),fromAddr.toString().c_str());
			Packet outp(source,_r->identity.address(),Packet::VERB_ERROR);
			outp.append((unsigned char)Packet::VERB_HELLO);
			outp.append(packet.packetId());
			outp.append((unsigned char)Packet::ERROR_INVALID_REQUEST);
			outp.encrypt(candidate->cryptKey());
			outp.hmacSet(candidate->macKey());
			_r->demarc->send(localPort,fromAddr,outp.data(),outp.size(),-1);
			return;
		}

		// Is this a HELLO for a peer we already know? If so just update its
		// packet receive stats and send an OK.
		SharedPtr<Peer> existingPeer(_r->topology->getPeer(id.address()));
		if ((existingPeer)&&(existingPeer->identity() == id)) {
			existingPeer->onReceive(_r,localPort,fromAddr,0,packet.hops(),Packet::VERB_HELLO,Utils::now());

			Packet outp(source,_r->identity.address(),Packet::VERB_OK);
			outp.append((unsigned char)Packet::VERB_HELLO);
			outp.append(packet.packetId());
			outp.append(timestamp);
			outp.encrypt(existingPeer->cryptKey());
			outp.hmacSet(existingPeer->macKey());
			_r->demarc->send(localPort,fromAddr,outp.data(),outp.size(),-1);
			return;
		}

		// Otherwise we call addPeer() and set up a callback to handle the verdict
		_CBaddPeerFromHello_Data *arg = new _CBaddPeerFromHello_Data;
		arg->parent = this;
		arg->source = source;
		arg->fromAddr = fromAddr;
		arg->localPort = localPort;
		arg->vMajor = vMajor;
		arg->vMinor = vMinor;
		arg->vRevision = vRevision;
		arg->helloPacketId = packet.packetId();
		arg->helloTimestamp = timestamp;
		_r->topology->addPeer(candidate,&Switch::_CBaddPeerFromHello,arg);
	} catch (std::exception &ex) {
		TRACE("dropped HELLO from %s(%s): %s",source.toString().c_str(),fromAddr.toString().c_str(),ex.what());
	} catch ( ... ) {
		TRACE("dropped HELLO from %s(%s): unexpected exception",source.toString().c_str(),fromAddr.toString().c_str());
	}
}

} // namespace ZeroTier