premiere-libtorrent/include/libtorrent/kademlia/routing_table.hpp

/*

Copyright (c) 2006-2016, Arvid Norberg
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    * Redistributions in binary form must reproduce the above copyright
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      contributors may be used to endorse or promote products derived
      from this software without specific prior written permission.

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*/

#ifndef ROUTING_TABLE_HPP
#define ROUTING_TABLE_HPP

#include "libtorrent/aux_/disable_warnings_push.hpp"

#include <vector>
#include <set>

#include <boost/cstdint.hpp>
#include <boost/utility.hpp>
#include <boost/tuple/tuple.hpp>
#include <boost/array.hpp>
#include <boost/noncopyable.hpp>
#include <boost/unordered_set.hpp>

#include "libtorrent/aux_/disable_warnings_pop.hpp"

#include <libtorrent/kademlia/node_id.hpp>
#include <libtorrent/kademlia/node_entry.hpp>
#include <libtorrent/session_settings.hpp>
#include <libtorrent/assert.hpp>
#include <libtorrent/time.hpp>

namespace libtorrent
{
#ifndef TORRENT_NO_DEPRECATE
	struct session_status;
#endif
	struct dht_routing_bucket;
}

namespace libtorrent { namespace dht
{
struct dht_logger;

typedef std::vector<node_entry> bucket_t;

struct routing_table_node
{
	bucket_t replacements;
	bucket_t live_nodes;
};

// differences in the implementation from the description in
// the paper:
//
// * Nodes are not marked as being stale, they keep a counter
// 	that tells how many times in a row they have failed. When
// 	a new node is to be inserted, the node that has failed
// 	the most times is replaced. If none of the nodes in the
// 	bucket has failed, then it is put in the replacement
// 	cache (just like in the paper).

namespace impl
{
	template <typename F>
	inline void forwarder(void* userdata, node_entry const& node)
	{
		F* f = reinterpret_cast<F*>(userdata);
		(*f)(node);
	}
}

class TORRENT_EXTRA_EXPORT routing_table : boost::noncopyable
{
public:
	// TODO: 3 to improve memory locality and scanning performance, turn the
	// routing table into a single vector with boundaries for the nodes instead.
	// Perhaps replacement nodes should be in a separate vector.
	typedef std::vector<routing_table_node> table_t;

	routing_table(node_id const& id, int bucket_size
		, dht_settings const& settings
		, dht_logger* log);

#ifndef TORRENT_NO_DEPRECATE
	void status(session_status& s) const;
#endif

	void status(std::vector<dht_routing_bucket>& s) const;

	void node_failed(node_id const& id, udp::endpoint const& ep);

	// adds an endpoint that will never be added to
	// the routing table
	void add_router_node(udp::endpoint router);

	// iterates over the router nodes added
	typedef std::set<udp::endpoint>::const_iterator router_iterator;
	router_iterator router_begin() const { return m_router_nodes.begin(); }
	router_iterator router_end() const { return m_router_nodes.end(); }

	enum add_node_status_t {
		failed_to_add = 0,
		node_added,
		need_bucket_split
	};
	add_node_status_t add_node_impl(node_entry e);

	bool add_node(node_entry e);

	// this function is called every time the node sees
	// a sign of a node being alive. This node will either
	// be inserted in the k-buckets or be moved to the top
	// of its bucket.
	bool node_seen(node_id const& id, udp::endpoint ep, int rtt);

	// this may add a node to the routing table and mark it as
	// not pinged. If the bucket the node falls into is full,
	// the node will be ignored.
	void heard_about(node_id const& id, udp::endpoint const& ep);

	// change our node ID. This can be expensive since nodes must be moved around
	// and potentially dropped
	void update_node_id(node_id id);

	node_entry const* next_refresh();

	enum
	{
		// nodes that have not been pinged are considered failed by this flag
		include_failed = 1
	};

	// fills the vector with the count nodes from our buckets that
	// are nearest to the given id.
	void find_node(node_id const& id, std::vector<node_entry>& l
		, int options, int count = 0);
	void remove_node(node_entry* n
		, table_t::iterator bucket) ;

	int bucket_size(int bucket) const
	{
		int num_buckets = m_buckets.size();
		if (num_buckets == 0) return 0;
		if (bucket >= num_buckets) bucket = num_buckets - 1;
		table_t::const_iterator i = m_buckets.begin();
		std::advance(i, bucket);
		return int(i->live_nodes.size());
	}

	template <typename F>
	void for_each_node(F f)
	{
		for_each_node(&impl::forwarder<F>, &impl::forwarder<F>, reinterpret_cast<void*>(&f));
	}

	void for_each_node(void (*)(void*, node_entry const&)
		, void (*)(void*, node_entry const&), void* userdata) const;

	int bucket_size() const { return m_bucket_size; }

	// returns the number of nodes in the main buckets, number of nodes in the
	// replacement buckets and the number of nodes in the main buckets that have
	// been pinged and confirmed up
	boost::tuple<int, int, int> size() const;

	boost::int64_t num_global_nodes() const;

	// the number of bits down we have full buckets
	// i.e. essentially the number of full buckets
	// we have
	int depth() const;

	int num_active_buckets() const { return m_buckets.size(); }

	void replacement_cache(bucket_t& nodes) const;

#if defined TORRENT_DEBUG
	// used for debug and monitoring purposes. This will print out
	// the state of the routing table to the given stream
	void print_state(std::ostream& os) const;
#endif

	int bucket_limit(int bucket) const;

#if TORRENT_USE_INVARIANT_CHECKS
	void check_invariant() const;
#endif

	bool is_full(int bucket) const;

private:

#ifndef TORRENT_DISABLE_LOGGING
	dht_logger* m_log;
#endif

	table_t::iterator find_bucket(node_id const& id);

	void split_bucket();

	// return a pointer the node_entry with the given endpoint
	// or 0 if we don't have such a node. Both the address and the
	// port has to match
	node_entry* find_node(udp::endpoint const& ep
		, routing_table::table_t::iterator* bucket);

	dht_settings const& m_settings;

	// (k-bucket, replacement cache) pairs
	// the first entry is the bucket the furthest
	// away from our own ID. Each time the bucket
	// closest to us (m_buckets.back()) has more than
	// bucket size nodes in it, another bucket is
	// added to the end and it's split up between them
	table_t m_buckets;

	node_id m_id; // our own node id

	// the last seen depth (i.e. levels in the routing table)
	// it's mutable because it's updated by depth(), which is const
	mutable int m_depth;

	// the last time we refreshed our own bucket
	// refreshed every 15 minutes
	mutable time_point m_last_self_refresh;

	// this is a set of all the endpoints that have
	// been identified as router nodes. They will
	// be used in searches, but they will never
	// be added to the routing table.
	std::set<udp::endpoint> m_router_nodes;

	// these are all the IPs that are in the routing
	// table. It's used to only allow a single entry
	// per IP in the whole table. Currently only for
	// IPv4
	boost::unordered_multiset<address_v4::bytes_type> m_ips;

	// constant called k in paper
	int m_bucket_size;
};

} } // namespace libtorrent::dht

#endif // ROUTING_TABLE_HPP