From 4e0a4db9b4a7786367c8b3c03e054643f86db8da Mon Sep 17 00:00:00 2001
From: Arvid Norberg <arvid.norberg@gmail.com>
Date: Sun, 12 Jun 2016 20:36:05 -0400
Subject: [PATCH] fixed inverted priority of incoming piece suggestions (#809)

---
 ChangeLog                    |  1 +
 src/peer_connection.cpp      |  8 +++--
 test/test_fast_extension.cpp | 62 +++++++++++++++++++++++++++++++++++-
 3 files changed, 68 insertions(+), 3 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 14a6db264..5bed298dd 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,6 @@
 1.1.1 release
 
+	* fixed inverted priority of incoming piece suggestions
 	* optimize allow-fast logic
 	* fix issue where FAST extension messages were not used during handshake
 	* fixed crash on invalid input in http_parser
diff --git a/src/peer_connection.cpp b/src/peer_connection.cpp
index ffb399a7c..e77bd43d1 100644
--- a/src/peer_connection.cpp
+++ b/src/peer_connection.cpp
@@ -1580,10 +1580,14 @@ namespace libtorrent
 				return;
 		}
 
+		// the piece picker will prioritize the pieces from the beginning to end.
+		// the later the suggestion is received, the higher priority we should
+		// ascribe to it, so we need to insert suggestions at the front of the
+		// queue.
 		if (int(m_suggested_pieces.size()) > m_settings.get_int(settings_pack::max_suggest_pieces))
-			m_suggested_pieces.erase(m_suggested_pieces.begin());
+			m_suggested_pieces.resize(m_settings.get_int(settings_pack::max_suggest_pieces) - 1);
 
-		m_suggested_pieces.push_back(index);
+		m_suggested_pieces.insert(m_suggested_pieces.begin(), index);
 
 #ifndef TORRENT_DISABLE_LOGGING
 		peer_log(peer_log_alert::info, "SUGGEST_PIECE", "piece: %d added to set: %d"
diff --git a/test/test_fast_extension.cpp b/test/test_fast_extension.cpp
index bd99207dd..61e8ceeb2 100644
--- a/test/test_fast_extension.cpp
+++ b/test/test_fast_extension.cpp
@@ -626,7 +626,7 @@ TORRENT_TEST(reject_suggest)
 
 		using namespace libtorrent::detail;
 		char* ptr = recv_buffer + 1;
-		int piece = read_int32(ptr);
+		int const piece = read_int32(ptr);
 
 		std::vector<int>::iterator i = std::find(suggested.begin()
 			, suggested.end(), piece);
@@ -660,6 +660,66 @@ TORRENT_TEST(reject_suggest)
 	print_session_log(*ses);
 }
 
+TORRENT_TEST(suggest_order)
+{
+	std::cerr << "\n === test suggest ===\n" << std::endl;
+
+	sha1_hash ih;
+	boost::shared_ptr<lt::session> ses;
+	io_service ios;
+	tcp::socket s(ios);
+	setup_peer(s, ih, ses);
+
+	char recv_buffer[1000];
+	do_handshake(s, ih, recv_buffer);
+	print_session_log(*ses);
+	send_have_all(s);
+	print_session_log(*ses);
+
+	std::vector<int> suggested;
+	suggested.push_back(0);
+	suggested.push_back(1);
+	suggested.push_back(2);
+	suggested.push_back(3);
+
+	std::for_each(suggested.begin(), suggested.end()
+		, boost::bind(&send_suggest_piece, boost::ref(s), _1));
+	print_session_log(*ses);
+
+	send_unchoke(s);
+	print_session_log(*ses);
+
+	int fail_counter = 100;
+	while (!suggested.empty() && fail_counter > 0)
+	{
+		print_session_log(*ses);
+		int len = read_message(s, recv_buffer, sizeof(recv_buffer));
+		if (len == -1) break;
+		print_message(recv_buffer, len);
+		int msg = recv_buffer[0];
+		fail_counter--;
+
+		// we're just interested in requests
+		if (msg != 0x6) continue;
+
+		using namespace libtorrent::detail;
+		char* ptr = recv_buffer + 1;
+		int const piece = read_int32(ptr);
+
+		// make sure we receive the requests inverse order of sending the suggest
+		// messages. The last suggest should be the highest priority
+		int const expected_piece = suggested.back();
+		suggested.pop_back();
+		TEST_EQUAL(piece, expected_piece);
+	}
+	print_session_log(*ses);
+	TEST_CHECK(fail_counter > 0);
+
+	s.close();
+	test_sleep(500);
+	print_session_log(*ses);
+}
+
 TORRENT_TEST(multiple_bitfields)
 {
 	std::cerr << "\n === test multiple bitfields ===\n" << std::endl;