/*
 * Copyright (c)2013-2021 ZeroTier, Inc.
 *
 * Use of this software is governed by the Business Source License included
 * in the LICENSE.TXT file in the project's root directory.
 *
 * Change Date: 2026-01-01
 *
 * On the date above, in accordance with the Business Source License, use
 * of this software will be governed by version 2.0 of the Apache License.
 */
/****/

#ifndef ZT_PEER_HPP
#define ZT_PEER_HPP

#include "Constants.hpp"
#include "Context.hpp"
#include "Node.hpp"
#include "Path.hpp"
#include "Address.hpp"
#include "Utils.hpp"
#include "Identity.hpp"
#include "InetAddress.hpp"
#include "SharedPtr.hpp"
#include "Mutex.hpp"
#include "Endpoint.hpp"
#include "Locator.hpp"
#include "Protocol.hpp"
#include "AES.hpp"
#include "SymmetricKey.hpp"
#include "Containers.hpp"

#define ZT_PEER_MARSHAL_SIZE_MAX ( \
  1 + \
  ZT_ADDRESS_LENGTH + \
  ZT_SYMMETRIC_KEY_SIZE + \
  ZT_IDENTITY_MARSHAL_SIZE_MAX + \
  1 + ZT_LOCATOR_MARSHAL_SIZE_MAX + \
  (2 * 4) + \
  2 )

#define ZT_PEER_DEDUP_BUFFER_SIZE 1024
#define ZT_PEER_DEDUP_BUFFER_MASK 1023U
#define ZT_PEER_EPHEMERAL_KEY_BUFFER_SIZE 3
#define ZT_PEER_EPHEMERAL_KEY_COUNT_MAX (ZT_PEER_EPHEMERAL_KEY_BUFFER_SIZE + 1)

namespace ZeroTier {

class Topology;

/**
 * Peer on P2P Network (virtual layer 1)
 */
class Peer
{
	friend class SharedPtr< Peer >;
	friend class Topology;

public:
	/**
	 * Create an uninitialized peer
	 *
	 * New peers must be initialized via either init() or unmarshal() prior to
	 * use or null pointer dereference may occur.
	 */
	Peer();

	~Peer();

	/**
	 * Initialize peer with an identity
	 *
	 * @param peerIdentity The peer's identity
	 * @return True if initialization was succcesful
	 */
	bool init(const Context &ctx, const CallContext &cc, const Identity &peerIdentity);

	/**
	 * @return This peer's ZT address (short for identity().address())
	 */
	ZT_INLINE Address address() const noexcept
	{ return m_id.address(); }

	/**
	 * @return This peer's identity
	 */
	ZT_INLINE const Identity &identity() const noexcept
	{ return m_id; }

	/**
	 * @return Current locator or NULL if no locator is known
	 */
	ZT_INLINE const SharedPtr< const Locator > locator() const noexcept
	{
		RWMutex::RLock l(m_lock);
		return m_locator;
	}

	/**
	 * Set or update peer locator
	 *
	 * This checks the locator's timestamp against the current locator and
	 * replace it if newer.
	 *
	 * @param loc Locator update
	 * @param verify If true, verify locator's signature and structure
	 * @return New locator or previous if it was not replaced.
	 */
	ZT_INLINE SharedPtr< const Locator > setLocator(const SharedPtr< const Locator > &loc, const bool verify) noexcept
	{
		RWMutex::Lock l(m_lock);
		if ((loc) && ((!m_locator) || (m_locator->revision() < loc->revision()))) {
			if ((!verify) || loc->verify(m_id))
				m_locator = loc;
		}
		return m_locator;
	}

	/**
	 * Log receipt of an authenticated packet
	 *
	 * This is called by the decode pipe when a packet is proven to be authentic
	 * and appears to be valid.
	 *
	 * @param path Path over which packet was received
	 * @param hops ZeroTier (not IP) hops
	 * @param packetId Packet ID
	 * @param verb Packet verb
	 * @param inReVerb In-reply verb for OK or ERROR verbs
	 */
	void received(
		const Context &ctx,
		const CallContext &cc,
		const SharedPtr< Path > &path,
		unsigned int hops,
		uint64_t packetId,
		unsigned int payloadLength,
		Protocol::Verb verb,
		Protocol::Verb inReVerb);

	/**
	 * Log sent data
	 *
	 * @param bytes Number of bytes written
	 */
	ZT_INLINE void sent(const CallContext &cc, const unsigned int bytes) noexcept
	{
		m_lastSend.store(cc.ticks, std::memory_order_relaxed);
		m_outMeter.log(cc.ticks, bytes);
	}

	/**
	 * Called when traffic destined for a different peer is sent to this one
	 *
	 * @param bytes Number of bytes relayed
	 */
	ZT_INLINE void relayed(const CallContext &cc, const unsigned int bytes) noexcept
	{ m_relayedMeter.log(cc.ticks, bytes); }

	/**
	 * Get the current best direct path or NULL if none
	 *
	 * @return Current best path or NULL if there is no direct path
	 */
	ZT_INLINE SharedPtr< Path > path(const CallContext &cc) noexcept
	{ return SharedPtr< Path >(reinterpret_cast<Path *>(m_bestPath.load(std::memory_order_acquire))); }

	/**
	 * Send data to this peer over a specific path only
	 *
	 * @param data Data to send
	 * @param len Length in bytes
	 * @param via Path over which to send data (may or may not be an already-learned path for this peer)
	 */
	ZT_INLINE void send(const Context &ctx, const CallContext &cc, const void *data, unsigned int len, const SharedPtr< Path > &via) noexcept
	{
		via->send(ctx, cc, data, len);
		sent(cc, len);
	}

	/**
	 * Send data to this peer over the best available path
	 *
	 * If there is a working direct path it will be used. Otherwise the data will be
	 * sent via a root server.
	 *
	 * @param data Data to send
	 * @param len Length in bytes
	 */
	void send(const Context &ctx, const CallContext &cc, const void *data, unsigned int len) noexcept;

	/**
	 * Do ping, probes, re-keying, and keepalive with this peer, as needed.
	 */
	void pulse(const Context &ctx, const CallContext &cc);

	/**
	 * Attempt to contact this peer at a given endpoint.
	 *
	 * The attempt doesn't happen immediately. It's added to a queue for the
	 * next invocation of pulse().
	 *
	 * @param ep Endpoint to attempt to contact
	 * @param tries Number of times to try (default: 1)
	 */
	void contact(const Context &ctx, const CallContext &cc, const Endpoint &ep, int tries = 1);

	/**
	 * Reset paths within a given IP scope and address family
	 *
	 * Resetting a path involves sending an ECHO to it and then deactivating
	 * it until or unless it responds. This is done when we detect a change
	 * to our external IP or another system change that might invalidate
	 * many or all current paths.
	 *
	 * @param scope IP scope
	 * @param inetAddressFamily Family e.g. AF_INET
	 */
	void resetWithinScope(const Context &ctx, const CallContext &cc, InetAddress::IpScope scope, int inetAddressFamily);

	/**
	 * @return Time of last receive of anything, whether direct or relayed
	 */
	ZT_INLINE int64_t lastReceive() const noexcept
	{ return m_lastReceive.load(std::memory_order_relaxed); }

	/**
	 * @return Average latency of all direct paths or -1 if no direct paths or unknown
	 */
	ZT_INLINE int latency() const noexcept
	{
		RWMutex::RLock l(m_lock);
		int ltot = 0;
		int lcnt = 0;
		for (unsigned int i = 0; i < m_alivePathCount; ++i) {
			int lat = m_paths[i]->latency();
			if (lat > 0) {
				ltot += lat;
				++lcnt;
			}
		}
		return (ltot > 0) ? (lcnt / ltot) : -1;
	}

	/**
	 * @return Cipher suite that should be used to communicate with this peer
	 */
	ZT_INLINE uint8_t cipher() const noexcept
	{
		//if (m_vProto >= 11)
		//	return ZT_PROTO_CIPHER_SUITE__AES_GMAC_SIV;
		return ZT_PROTO_CIPHER_POLY1305_SALSA2012;
	}

	/**
	 * @return The permanent shared key for this peer computed by simple identity agreement
	 */
	ZT_INLINE SymmetricKey &identityKey() noexcept
	{ return m_identityKey; }

	/**
	 * @return AES instance for HELLO dictionary / encrypted section encryption/decryption
	 */
	ZT_INLINE const AES &identityHelloDictionaryEncryptionCipher() const noexcept
	{ return m_helloCipher; }

	/**
	 * @return Key for HMAC on HELLOs
	 */
	ZT_INLINE const uint8_t *identityHelloHmacKey() const noexcept
	{ return m_helloMacKey; }

	/**
	 * @return Raw identity key bytes
	 */
	ZT_INLINE const uint8_t *rawIdentityKey() const noexcept
	{ return m_identityKey.key(); }

	/**
	 * @return Current best key: either the latest ephemeral or the identity key
	 */
	ZT_INLINE SymmetricKey &key() noexcept
	{ return *reinterpret_cast<SymmetricKey *>(m_key.load(std::memory_order_relaxed)); }

	/**
	 * Get keys other than a key we have already tried.
	 *
	 * This is used when a packet arrives that doesn't decrypt with the preferred
	 * key. It fills notYetTried[] with other keys that haven't been tried yet,
	 * which can include the identity key and any older session keys.
	 *
	 * @param alreadyTried Key we've already tried or NULL if none
	 * @param notYetTried All keys known (long lived or session) other than alreadyTried
	 * @return Number of pointers written to notYetTried[]
	 */
	ZT_INLINE int getOtherKeys(const SymmetricKey *const alreadyTried, SymmetricKey *notYetTried[ZT_PEER_EPHEMERAL_KEY_COUNT_MAX]) noexcept
	{
		RWMutex::RLock l(m_lock);
		int cnt = 0;
		if (alreadyTried != &m_identityKey)
			notYetTried[cnt++] = &m_identityKey;
		for (unsigned int k=0;k<ZT_PEER_EPHEMERAL_KEY_BUFFER_SIZE;++k) {
			SymmetricKey *const kk = &m_ephemeralSessions[k].key;
			if (m_ephemeralSessions[k].established && (alreadyTried != kk))
				notYetTried[cnt++] = kk;
		}
		return cnt;
	}

	/**
	 * Set a flag ordering a key renegotiation ASAP.
	 *
	 * This can be called if there's any hint of an issue with the current key.
	 * It's also called if any of the secondary possible keys returned by
	 * getOtherKeys() decrypt a valid packet, indicating a desynchronization
	 * in which key should be used.
	 */
	ZT_INLINE void setKeyRenegotiationNeeded() noexcept
	{
		RWMutex::Lock l(m_lock);
		m_keyRenegotiationNeeded = true;
	}

	/**
	 * Set the currently known remote version of this peer's client
	 *
	 * @param vproto Protocol version
	 * @param vmaj Major version
	 * @param vmin Minor version
	 * @param vrev Revision
	 */
	ZT_INLINE void setRemoteVersion(unsigned int vproto, unsigned int vmaj, unsigned int vmin, unsigned int vrev) noexcept
	{
		RWMutex::Lock l(m_lock);
		m_vProto = (uint16_t)vproto;
		m_vMajor = (uint16_t)vmaj;
		m_vMinor = (uint16_t)vmin;
		m_vRevision = (uint16_t)vrev;
	}

	/**
	 * Get the remote version of this peer.
	 *
	 * If false is returned, the value of the value-result variables is
	 * undefined.
	 *
	 * @param vProto Set to protocol version
	 * @param vMajor Set to major version
	 * @param vMinor Set to minor version
	 * @param vRevision Set to revision
	 * @return True if remote version is known
	 */
	ZT_INLINE bool remoteVersion(uint16_t &vProto, uint16_t &vMajor, uint16_t &vMinor, uint16_t &vRevision)
	{
		RWMutex::RLock l(m_lock);
		return (((vProto = m_vProto)|(vMajor = m_vMajor)|(vMinor = m_vMinor)|(vRevision = m_vRevision)) != 0);
	}

	/**
	 * @return True if there is at least one alive direct path
	 */
	ZT_INLINE bool directlyConnected() const noexcept
	{
		RWMutex::RLock l(m_lock);
		return m_alivePathCount > 0;
	}

	/**
	 * Get all paths
	 *
	 * @param paths Vector of paths with the first path being the current preferred path
	 */
	ZT_INLINE void getAllPaths(Vector< SharedPtr< Path > > &paths) const
	{
		RWMutex::RLock l(m_lock);
		paths.assign(m_paths, m_paths + m_alivePathCount);
	}

	/**
	 * Save the latest version of this peer to the data store
	 */
	void save(const Context &ctx, const CallContext &cc) const;

	static constexpr int marshalSizeMax() noexcept
	{ return ZT_PEER_MARSHAL_SIZE_MAX; }

	int marshal(const Context &ctx, uint8_t data[ZT_PEER_MARSHAL_SIZE_MAX]) const noexcept;
	int unmarshal(const Context &ctx, int64_t ticks, const uint8_t *restrict data, int len) noexcept;

	/**
	 * Rate limit gate for inbound WHOIS requests
	 */
	ZT_INLINE bool rateGateInboundWhoisRequest(CallContext &cc) noexcept
	{
		if ((cc.ticks - m_lastWhoisRequestReceived.load(std::memory_order_relaxed)) >= ZT_PEER_WHOIS_RATE_LIMIT) {
			m_lastWhoisRequestReceived.store(cc.ticks, std::memory_order_relaxed);
			return true;
		}
		return false;
	}

	/**
	 * Rate limit gate for inbound ECHO requests
	 */
	ZT_INLINE bool rateGateEchoRequest(CallContext &cc) noexcept
	{
		if ((cc.ticks - m_lastEchoRequestReceived.load(std::memory_order_relaxed)) >= ZT_PEER_GENERAL_RATE_LIMIT) {
			m_lastEchoRequestReceived.store(cc.ticks, std::memory_order_relaxed);
			return true;
		}
		return false;
	}

	/**
	 * Rate limit gate for inbound probes
	 */
	ZT_INLINE bool rateGateProbeRequest(CallContext &cc) noexcept
	{
		if ((cc.ticks - m_lastProbeReceived.load(std::memory_order_relaxed)) > ZT_PEER_PROBE_RESPONSE_RATE_LIMIT) {
			m_lastProbeReceived.store(cc.ticks, std::memory_order_relaxed);
			return true;
		}
		return false;
	}

	/**
	 * Packet deduplication filter for incoming packets
	 * 
	 * This flags a packet ID and returns true if the same packet ID was already
	 * flagged. This is done in an atomic operation if supported.
	 * 
	 * @param packetId Packet ID to check/flag
	 * @return True if this is a duplicate
	 */
	ZT_INLINE bool deduplicateIncomingPacket(const uint64_t packetId) noexcept
	{ return m_dedup[Utils::hash32((uint32_t)packetId) & ZT_PEER_DEDUP_BUFFER_MASK].exchange(packetId, std::memory_order_relaxed) == packetId; }

private:
	struct p_EphemeralPublic
	{
		uint8_t type;
		uint8_t c25519Public[ZT_C25519_ECDH_PUBLIC_KEY_SIZE];
		uint8_t p384Public[ZT_ECC384_PUBLIC_KEY_SIZE];
	};

	static_assert(sizeof(p_EphemeralPublic) == (1 + ZT_C25519_ECDH_PUBLIC_KEY_SIZE + ZT_ECC384_PUBLIC_KEY_SIZE), "p_EphemeralPublic has extra padding");

	struct p_EphemeralPrivate
	{
		ZT_INLINE p_EphemeralPrivate() noexcept: creationTime(-1)
		{}

		ZT_INLINE ~p_EphemeralPrivate()
		{ Utils::burn(this, sizeof(p_EphemeralPublic)); }

		int64_t creationTime;
		uint64_t sha384OfPublic[6];
		p_EphemeralPublic pub;
		uint8_t c25519Private[ZT_C25519_ECDH_PRIVATE_KEY_SIZE];
		uint8_t p384Private[ZT_ECC384_PRIVATE_KEY_SIZE];
	};

	struct p_EphemeralSession
	{
		ZT_INLINE p_EphemeralSession() noexcept: established(false)
		{}

		uint64_t sha384OfPeerPublic[6];
		SymmetricKey key;
		bool established;
	};

	void m_prioritizePaths(const CallContext &cc);
	unsigned int m_sendProbe(const Context &ctx, const CallContext &cc, int64_t localSocket, const InetAddress &atAddress, const uint16_t *ports, unsigned int numPorts);
	void m_deriveSecondaryIdentityKeys() noexcept;
	unsigned int m_hello(const Context &ctx, const CallContext &cc, int64_t localSocket, const InetAddress &atAddress, bool forceNewKey);

		// Guards all fields except those otherwise indicated (and atomics of course).
	RWMutex m_lock;

	// Long lived key resulting from agreement with this peer's identity.
	SymmetricKey m_identityKey;

	// Cipher for encrypting or decrypting the encrypted section of HELLO packets.
	AES m_helloCipher;

	// Key for HELLO HMAC-SHA384
	uint8_t m_helloMacKey[ZT_SYMMETRIC_KEY_SIZE];

	// Keys we have generated and sent.
	p_EphemeralPrivate m_ephemeralKeysSent[ZT_PEER_EPHEMERAL_KEY_BUFFER_SIZE];

	// Sessions created when OK(HELLO) is received.
	p_EphemeralSession m_ephemeralSessions[ZT_PEER_EPHEMERAL_KEY_BUFFER_SIZE];

	// Pointer to active key (SymmetricKey).
	std::atomic< uintptr_t > m_key;

	// Flag indicating that we should rekey at next pulse().
	bool m_keyRenegotiationNeeded;

	// This peer's public identity.
	Identity m_id;

	// This peer's most recent (by revision) locator, or NULL if none on file.
	SharedPtr< const Locator > m_locator;

	// The last time something was received or sent.
	std::atomic< int64_t > m_lastReceive;
	std::atomic< int64_t > m_lastSend;

	// The last time we sent a full HELLO to this peer.
	int64_t m_lastSentHello; // only checked while locked

	// The last time a WHOIS request was received from this peer (anti-DOS / anti-flood).
	std::atomic< int64_t > m_lastWhoisRequestReceived;

	// The last time an ECHO request was received from this peer (anti-DOS / anti-flood).
	std::atomic< int64_t > m_lastEchoRequestReceived;

	// The last time we got a probe from this peer.
	std::atomic< int64_t > m_lastProbeReceived;

	// Deduplication buffer.
	std::atomic< uint64_t > m_dedup[ZT_PEER_DEDUP_BUFFER_SIZE];

	// Meters measuring actual bandwidth in, out, and relayed via this peer (mostly if this is a root).
	Meter<> m_inMeter;
	Meter<> m_outMeter;
	Meter<> m_relayedMeter;

	// Direct paths sorted in descending order of preference.
	SharedPtr< Path > m_paths[ZT_MAX_PEER_NETWORK_PATHS];

	// Size of m_paths[] in non-NULL paths (max: MAX_PEER_NETWORK_PATHS).
	unsigned int m_alivePathCount;

	// Current best path (pointer to Path).
	std::atomic<uintptr_t> m_bestPath;

	// For SharedPtr<>
	std::atomic< int > __refCount;

	struct p_TryQueueItem
	{
		ZT_INLINE p_TryQueueItem() :
			target(),
			iteration(0)
		{}

		ZT_INLINE p_TryQueueItem(const Endpoint &t, int iter) :
			target(t),
			iteration(iter)
		{}

		Endpoint target;
		int iteration;
	};

	// Queue of endpoints to try.
	List< p_TryQueueItem > m_tryQueue;

	// Time each endpoint was last tried, for rate limiting.
	Map< Endpoint, int64_t > m_lastTried;

	// Version of remote peer, if known.
	uint16_t m_vProto;
	uint16_t m_vMajor;
	uint16_t m_vMinor;
	uint16_t m_vRevision;
};

} // namespace ZeroTier

#endif