added abuse protection to DHT. nodes that hammer will be ignored

include/libtorrent/kademlia/dht_tracker.hpp

@@ -128,6 +128,19 @@ namespace libtorrent { namespace dht
 		// used to resolve hostnames for nodes
 		udp::resolver m_host_resolver;
 
+		// used to ignore abusive dht nodes
+		struct node_ban_entry
+		{
+			node_ban_entry(): count(0) {}
+			udp::endpoint src;
+			ptime limit;
+			int count;
+		};
+
+		enum { num_ban_nodes = 20 };
+
+		node_ban_entry m_ban_nodes[num_ban_nodes];
+
 		// reference counter for intrusive_ptr
 		mutable boost::detail::atomic_count m_refs;
 

include/libtorrent/time.hpp

@@ -99,6 +99,7 @@ namespace libtorrent
 		time_duration operator/(int rhs) const { return time_duration(diff / rhs); }
 		explicit time_duration(boost::int64_t d) : diff(d) {}
 		time_duration& operator-=(time_duration const& c) { diff -= c.diff; return *this; }
+		time_duration operator+(time_duration const& c) { return time_duration(diff + c.diff); }
 		boost::int64_t diff;
 	};
 

src/kademlia/dht_tracker.cpp

@@ -405,6 +405,54 @@ namespace libtorrent { namespace dht
 
 		if (error) return;
 
+		node_ban_entry* match = 0;
+		node_ban_entry* min = m_ban_nodes;
+		ptime now = time_now();
+		for (node_ban_entry* i = m_ban_nodes; i < m_ban_nodes + num_ban_nodes; ++i)
+		{
+			if (i->src == m_remote_endpoint[current_buffer])
+			{
+				match = i;
+				break;
+			}
+			if (i->count < min->count) min = i;
+		}
+
+		if (match)
+		{
+			++match->count;
+			if (match->count >= 20)
+			{
+				if (now < match->limit)
+				{
+#ifdef TORRENT_DHT_VERBOSE_LOGGING
+					if (match->count == 20)
+					{
+						TORRENT_LOG(dht_tracker) << time_now_string() << " BANNING PEER [ ip: "
+							<< m_remote_endpoint[current_buffer] << " | "
+							"time: " << total_seconds((now - match->limit) + seconds(5))
+							<< " | count: " << match->count << " ]";
+					}
+#endif
+					// we've received 20 messages in less than 5 seconds from
+					// this node. Ignore it until it's silent for 5 minutes
+					match->limit = now + minutes(5);
+					return;
+				}
+
+				// we got 50 messages from this peer, but it was in
+				// more than 5 seconds. Reset the counter and the timer
+				match->count = 0;
+				match->limit = now + seconds(5);
+			}
+		}
+		else
+		{
+			min->count = 1;
+			min->limit = now + seconds(5);
+			min->src = m_remote_endpoint[current_buffer];
+		}
+
 #ifdef TORRENT_DHT_VERBOSE_LOGGING
 		++m_total_message_input;
 		m_total_in_bytes += bytes_transferred;