merged DHT feature from libtorrent_aio

docs/manual.rst

@@ -1407,6 +1407,7 @@ struct has the following members::
 		int max_torrents;
 		bool restrict_routing_ips;
 		bool restrict_search_ips;
+		bool extended_routing_table;
 	};
 
 ``max_peers_reply`` is the maximum number of peers the node will send in
@@ -1439,6 +1440,10 @@ distance.
 with IPs with very close CIDR distance. This also defaults to true and helps
 mitigate certain attacks on the DHT.
 
+``extended_routing_table`` makes the first buckets in the DHT routing
+table fit 128, 64, 32 and 16 nodes respectively, as opposed to the
+standard size of 8. All other buckets have size 8 still.
+
 The ``dht_settings`` struct used to contain a ``service_port`` member to control
 which port the DHT would listen on and send messages from. This field is deprecated
 and ignored. libtorrent always tries to open the UDP socket on the same port

include/libtorrent/kademlia/routing_table.hpp

@@ -129,12 +129,12 @@ public:
 	void find_node(node_id const& id, std::vector<node_entry>& l
 		, int options, int count = 0);
 	
-	int bucket_size(int 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::iterator i = m_buckets.begin();
+		table_t::const_iterator i = m_buckets.begin();
 		std::advance(i, bucket);
 		return (int)i->live_nodes.size();
 	}
@@ -162,6 +162,8 @@ public:
 
 	void touch_bucket(node_id const& target);
 
+	int bucket_limit(int bucket) const;
+
 private:
 
 	typedef std::list<routing_table_node> table_t;

include/libtorrent/session_settings.hpp

@@ -950,6 +950,7 @@ namespace libtorrent
 			, max_torrent_search_reply(20)
 			, restrict_routing_ips(true)
 			, restrict_search_ips(true)
+			, extended_routing_table(true)
 		{}
 		
 		// the maximum number of peers to send in a
@@ -991,6 +992,11 @@ namespace libtorrent
 		// applies the same IP restrictions on nodes
 		// received during a DHT search (traversal algorithm)
 		bool restrict_search_ips;
+
+		// if this is set, the first few buckets in the routing
+		// table are enlarged, to make room for more nodes in order
+		// to lower the look-up times
+		bool extended_routing_table;
 	};
 #endif
 

src/kademlia/routing_table.cpp

@@ -67,6 +67,16 @@ routing_table::routing_table(node_id const& id, int bucket_size
 {
 }
 
+int routing_table::bucket_limit(int bucket) const
+{
+	if (!m_settings.extended_routing_table) return m_bucket_size;
+
+	int size_exceptions[] = {16, 8, 4, 2};
+	if (bucket < sizeof(size_exceptions)/sizeof(size_exceptions[0]))
+		return m_bucket_size * size_exceptions[bucket];
+	return m_bucket_size;
+}
+
 void routing_table::status(session_status& s) const
 {
 	boost::tie(s.dht_nodes, s.dht_node_cache) = size();
@@ -131,19 +141,20 @@ void routing_table::print_state(std::ostream& os) const
 		os << "-";
 	os << "\n";
 
-	for (int k = 0; k < m_bucket_size; ++k)
+	int max_size = bucket_limit(0);
+	for (int k = 0; k < max_size; ++k)
 	{
 		for (table_t::const_iterator i = m_buckets.begin(), end(m_buckets.end());
 			i != end; ++i)
 		{
-			os << (int(i->live_nodes.size()) > (m_bucket_size - 1 - k) ? "|" : " ");
+			os << (int(i->live_nodes.size()) > (max_size - 1 - k) ? "|" : " ");
 		}
 		os << "\n";
 	}
 	for (int i = 0; i < 160; ++i) os << "+";
 	os << "\n";
 
-	for (int k = 0; k < m_bucket_size; ++k)
+	for (int k = 0; k < max_size; ++k)
 	{
 		for (table_t::const_iterator i = m_buckets.begin(), end(m_buckets.end());
 			i != end; ++i)
@@ -403,6 +414,8 @@ bool routing_table::add_node(node_entry e)
 	table_t::iterator i = find_bucket(e.id);
 	bucket_t& b = i->live_nodes;
 	bucket_t& rb = i->replacements;
+	int bucket_index = std::distance(m_buckets.begin(), i);
+	int bucket_size_limit = bucket_limit(bucket_index);
 
 	bucket_t::iterator j;
 
@@ -473,9 +486,9 @@ bool routing_table::add_node(node_entry e)
 	}
 
 	// if there's room in the main bucket, just insert it
-	if (int(b.size()) < m_bucket_size)
+	if (int(b.size()) < bucket_size_limit)
 	{
-		if (b.empty()) b.reserve(m_bucket_size);
+		if (b.empty()) b.reserve(bucket_size_limit);
 		b.push_back(e);
 		m_ips.insert(e.addr.to_v4().to_bytes());
 //		TORRENT_LOG(table) << "inserting node: " << e.id << " " << e.addr;
@@ -603,7 +616,7 @@ bool routing_table::add_node(node_entry e)
 
 	// move any node whose (160 - distane_exp(m_id, id)) >= (i - m_buckets.begin())
 	// to the new bucket
-	int bucket_index = std::distance(m_buckets.begin(), i);
+	int new_bucket_size = bucket_limit(bucket_index + 1);
 	for (bucket_t::iterator j = b.begin(); j != b.end();)
 	{
 		if (distance_exp(m_id, j->id) >= 159 - bucket_index)
@@ -623,7 +636,7 @@ bool routing_table::add_node(node_entry e)
 	{
 		if (distance_exp(m_id, j->id) >= 159 - bucket_index)
 		{
-			if (int(b.size()) >= m_bucket_size)
+			if (int(b.size()) >= bucket_size_limit)
 			{
 				++j;
 				continue;
@@ -633,7 +646,7 @@ bool routing_table::add_node(node_entry e)
 		else
 		{
 			// this entry belongs in the new bucket
-			if (int(new_bucket.size()) < m_bucket_size)
+			if (int(new_bucket.size()) < new_bucket_size)
 				new_bucket.push_back(*j);
 			else
 				new_replacement_bucket.push_back(*j);
@@ -645,7 +658,7 @@ bool routing_table::add_node(node_entry e)
 	// now insert the new node in the appropriate bucket
 	if (distance_exp(m_id, e.id) >= 159 - bucket_index)
 	{
-		if (int(b.size()) < m_bucket_size)
+		if (int(b.size()) < bucket_size_limit)
 		{
 			b.push_back(e);
 			added = true;
@@ -658,7 +671,7 @@ bool routing_table::add_node(node_entry e)
 	}
 	else
 	{
-		if (int(new_bucket.size()) < m_bucket_size)
+		if (int(new_bucket.size()) < new_bucket_size)
 		{
 			new_bucket.push_back(e);
 			added = true;

src/session_impl.cpp

@@ -472,7 +472,12 @@ namespace aux {
 		TORRENT_SETTING(integer, service_port)
 #endif
 		TORRENT_SETTING(integer, max_fail_count)
+		TORRENT_SETTING(integer, max_torrents)
+		TORRENT_SETTING(integer, max_dht_items)
 		TORRENT_SETTING(integer, max_torrent_search_reply)
+		TORRENT_SETTING(boolean, restrict_routing_ips)
+		TORRENT_SETTING(boolean, restrict_search_ips)
+		TORRENT_SETTING(boolean, extended_routing_table)
 	};
 #undef TORRENT_SETTING
 #endif