send write token if peer is alraedy stored

include/libtorrent/kademlia/dht_storage.hpp

@@ -125,7 +125,7 @@ namespace dht
 		// for this info_hash.
 		//
 		virtual bool get_peers(sha1_hash const& info_hash, udp protocol
-			, bool noseed, bool scrape
+			, bool noseed, bool scrape, address const& requester
 			, entry& peers) const = 0;
 
 		// This function is named announce_peer for consistency with the

include/libtorrent/kademlia/node.hpp

@@ -220,7 +220,7 @@ private:
 	void send_single_refresh(udp::endpoint const& ep, int bucket
 		, node_id const& id = node_id());
 	bool lookup_peers(sha1_hash const& info_hash, entry& reply
-		, bool noseed, bool scrape) const;
+		, bool noseed, bool scrape, address const& requester) const;
 
 	libtorrent::dht_settings const& m_settings;
 

src/kademlia/dht_storage.cpp

@@ -186,7 +186,7 @@ namespace
 		}
 
 		bool get_peers(sha1_hash const& info_hash, udp const protocol
-			, bool const noseed, bool const scrape
+			, bool const noseed, bool const scrape, address const& requester
 			, entry& peers) const override
 		{
 			auto const i = m_map.find(info_hash);
@@ -256,7 +256,19 @@ namespace
 					++m;
 				}
 			}
-			return int(i->second.peers.size()) >= m_settings.max_peers;
+
+			if (int(i->second.peers.size()) < m_settings.max_peers)
+				return false;
+
+			// we're at the max peers stored for this torrent
+			// only send a write token if the requester is already in the set
+			// only check for a match on IP because the peer may be announcing
+			// a different port than the one it is using to send DHT messages
+			peer_entry requester_entry;
+			requester_entry.addr.address(requester);
+			auto requester_iter = i->second.peers.lower_bound(requester_entry);
+			return requester_iter == i->second.peers.end()
+				|| requester_iter->addr.address() != requester;
 		}
 
 		void announce_peer(sha1_hash const& info_hash

src/kademlia/node.cpp

@@ -751,12 +751,12 @@ void node::status(session_status& s)
 #endif
 
 bool node::lookup_peers(sha1_hash const& info_hash, entry& reply
-	, bool noseed, bool scrape) const
+	, bool noseed, bool scrape, address const& requester) const
 {
 	if (m_observer)
 		m_observer->get_peers(info_hash);
 
-	return m_storage.get_peers(info_hash, protocol(), noseed, scrape, reply);
+	return m_storage.get_peers(info_hash, protocol(), noseed, scrape, requester, reply);
 }
 
 entry write_nodes_entry(std::vector<node_entry> const& nodes)
@@ -858,7 +858,10 @@ void node::incoming_request(msg const& m, entry& e)
 		bool scrape = false;
 		if (msg_keys[1] && msg_keys[1].int_value() != 0) noseed = true;
 		if (msg_keys[2] && msg_keys[2].int_value() != 0) scrape = true;
-		bool full = lookup_peers(info_hash, reply, noseed, scrape);
+		// If our storage is full we want to withhold the write token so that
+		// announces will spill over to our neighbors. This widens the
+		// perimeter of nodes which store peers for this torrent
+		bool full = lookup_peers(info_hash, reply, noseed, scrape, m.addr.address());
 		if (!full) reply["token"] = generate_token(m.addr, info_hash);
 
 #ifndef TORRENT_DISABLE_LOGGING

test/test_dht_storage.cpp

@@ -100,7 +100,7 @@ TORRENT_TEST(announce_peer)
 	std::unique_ptr<dht_storage_interface> s(create_default_dht_storage(sett));
 
 	entry peers;
-	s->get_peers(n1, udp::v4(), false, false, peers);
+	s->get_peers(n1, udp::v4(), false, false, address(), peers);
 
 	TEST_CHECK(peers["n"].string().empty())
 	TEST_CHECK(peers["values"].list().empty());
@@ -112,7 +112,7 @@ TORRENT_TEST(announce_peer)
 
 	s->announce_peer(n1, p1, "torrent_name", false);
 	peers = entry();
-	s->get_peers(n1, udp::v4(), false, false, peers);
+	s->get_peers(n1, udp::v4(), false, false, address(), peers);
 	TEST_EQUAL(peers["n"].string(), "torrent_name")
 	TEST_EQUAL(peers["values"].list().size(), 1)
 
@@ -120,7 +120,7 @@ TORRENT_TEST(announce_peer)
 	s->announce_peer(n2, p3, "torrent_name1", false);
 	s->announce_peer(n3, p4, "torrent_name2", false);
 	peers = entry();
-	s->get_peers(n3, udp::v4(), false, false, peers);
+	s->get_peers(n3, udp::v4(), false, false, address(), peers);
 	TEST_CHECK(!peers.find_key("values"));
 }
 
@@ -142,11 +142,11 @@ TORRENT_TEST(dual_stack)
 	s->announce_peer(n1, p5, "torrent_name", false);
 
 	entry peers4;
-	s->get_peers(n1, udp::v4(), false, false, peers4);
+	s->get_peers(n1, udp::v4(), false, false, address(), peers4);
 	TEST_EQUAL(peers4["values"].list().size(), 3);
 
 	entry peers6;
-	s->get_peers(n1, udp::v6(), false, false, peers6);
+	s->get_peers(n1, udp::v6(), false, false, address(), peers6);
 	TEST_EQUAL(peers6["values"].list().size(), 2);
 }