back port DHT fixes from master (#1209)

back port DHT fixes from master

include/libtorrent/kademlia/traversal_algorithm.hpp

@@ -117,10 +117,10 @@ protected:
 	std::vector<observer_ptr> m_results;
 	node_id const m_target;
 	boost::uint16_t m_ref_count;
-	boost::uint16_t m_invoke_count;
-	boost::uint16_t m_branch_factor;
-	boost::uint16_t m_responses;
-	boost::uint16_t m_timeouts;
+	boost::int16_t m_invoke_count;
+	boost::int16_t m_branch_factor;
+	boost::int16_t m_responses;
+	boost::int16_t m_timeouts;
 
 	// the IP addresses of the nodes in m_results
 	std::set<boost::uint32_t> m_peer4_prefixes;

src/kademlia/get_item.cpp

@@ -141,11 +141,7 @@ observer_ptr get_item::new_observer(void* ptr
 
 bool get_item::invoke(observer_ptr o)
 {
-	if (m_done)
-	{
-		m_invoke_count = -1;
-		return false;
-	}
+	if (m_done) return false;
 
 	entry e;
 	e["y"] = "q";

src/kademlia/get_peers.cpp

@@ -134,11 +134,7 @@ char const* get_peers::name() const { return "get_peers"; }
 
 bool get_peers::invoke(observer_ptr o)
 {
-	if (m_done)
-	{
-		m_invoke_count = -1;
-		return false;
-	}
+	if (m_done) return false;
 
 	entry e;
 	e["y"] = "q";

src/kademlia/put_data.cpp

@@ -88,11 +88,7 @@ void put_data::done()
 
 bool put_data::invoke(observer_ptr o)
 {
-	if (m_done)
-	{
-		m_invoke_count = -1;
-		return false;
-	}
+	if (m_done) return false;
 
 	// TODO: what if o is not an isntance of put_data_observer? This need to be
 	// redesigned for better type saftey.

src/kademlia/traversal_algorithm.cpp

@@ -319,6 +319,8 @@ void traversal_algorithm::failed(observer_ptr o, int flags)
 
 	if (m_results.empty()) return;
 
+	bool decrement_branch_factor = false;
+
 	TORRENT_ASSERT(o->flags & observer::flag_queried);
 	if (flags & short_timeout)
 	{
@@ -329,7 +331,10 @@ void traversal_algorithm::failed(observer_ptr o, int flags)
 		// around for some more, but open up the slot
 		// by increasing the branch factor
 		if ((o->flags & observer::flag_short_timeout) == 0)
+		{
+			TORRENT_ASSERT(m_branch_factor < (std::numeric_limits<boost::int16_t>::max)());
 			++m_branch_factor;
+		}
 		o->flags |= observer::flag_short_timeout;
 #ifndef TORRENT_DISABLE_LOGGING
 		if (get_node().observer())
@@ -350,8 +355,7 @@ void traversal_algorithm::failed(observer_ptr o, int flags)
 		o->flags |= observer::flag_failed;
 		// if this flag is set, it means we increased the
 		// branch factor for it, and we should restore it
-		if (o->flags & observer::flag_short_timeout)
-			--m_branch_factor;
+		decrement_branch_factor = (o->flags & observer::flag_short_timeout) != 0;
 
 #ifndef TORRENT_DISABLE_LOGGING
 		if (get_node().observer())
@@ -372,12 +376,18 @@ void traversal_algorithm::failed(observer_ptr o, int flags)
 		--m_invoke_count;
 	}
 
-	if (flags & prevent_request)
+	// this is another reason to decrement the branch factor, to prevent another
+	// request from filling this slot. Only ever decrement once per response though
+	decrement_branch_factor |= (flags & prevent_request);
+
+	if (decrement_branch_factor)
 	{
+		TORRENT_ASSERT(m_branch_factor > 0);
 		--m_branch_factor;
 		if (m_branch_factor <= 0) m_branch_factor = 1;
 	}
-	bool is_done = add_requests();
+
+	bool const is_done = add_requests();
 	if (is_done) done();
 }
 
@@ -499,7 +509,7 @@ bool traversal_algorithm::add_requests()
 		o->flags |= observer::flag_queried;
 		if (invoke(*i))
 		{
-			TORRENT_ASSERT(m_invoke_count < (std::numeric_limits<boost::uint16_t>::max)());
+			TORRENT_ASSERT(m_invoke_count < (std::numeric_limits<boost::int16_t>::max)());
 			++m_invoke_count;
 			++outstanding;
 		}