From fb3049a0ebdb153bc45692271eed68353fb8b745 Mon Sep 17 00:00:00 2001
From: Arvid Norberg <arvid@libtorrent.org>
Date: Mon, 28 Jun 2010 01:30:59 +0000
Subject: [PATCH] fixed rare crash when purging the peer list

---
 ChangeLog      |  1 +
 src/policy.cpp | 12 +++++++-----
 2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 7b8782ebe..5858ee2b3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -33,6 +33,7 @@
 	  incoming connection
 	* added more detailed instrumentation of the disk I/O thread
 
+	* fixed rare crash when purging the peer list
 	* fixed race condition around m_abort in session_impl
 	* fixed bug in web_peer_connection which could cause a hang when downloading
 	  from web servers
diff --git a/src/policy.cpp b/src/policy.cpp
index c8c2e6cf7..76d92dbc6 100644
--- a/src/policy.cpp
+++ b/src/policy.cpp
@@ -382,6 +382,7 @@ namespace libtorrent
 		}
 		TORRENT_ASSERT(m_num_connect_candidates < m_peers.size());
 		if (m_round_robin > i - m_peers.begin()) --m_round_robin;
+		if (m_round_robin >= m_peers.size()) m_round_robin = 0;
 
 #if TORRENT_USE_IPV6
 		if ((*i)->is_v6_addr)
@@ -538,7 +539,7 @@ namespace libtorrent
 			external_ip = address_v4(bytes);
 		}
 
-		if (m_round_robin == m_peers.size()) m_round_robin = 0;
+		if (m_round_robin >= m_peers.size()) m_round_robin = 0;
 
 #ifndef TORRENT_DISABLE_DHT
 		bool pinged = false;
@@ -551,7 +552,7 @@ namespace libtorrent
 		for (int iterations = (std::min)(int(m_peers.size()), 300);
 			iterations > 0; --iterations)
 		{
-			if (m_round_robin == int(m_peers.size())) m_round_robin = 0;
+			if (m_round_robin >= int(m_peers.size())) m_round_robin = 0;
 
 			peer& pe = *m_peers[m_round_robin];
 			int current = m_round_robin;
@@ -778,7 +779,6 @@ namespace libtorrent
 				return false;
 			}
 
-			if (m_round_robin > iter - m_peers.begin()) ++m_round_robin;
 #if TORRENT_USE_IPV6
 			bool is_v6 = c.remote().address().is_v6();
 #endif
@@ -804,6 +804,8 @@ namespace libtorrent
 
 			iter = m_peers.insert(iter, p);
 
+			if (m_round_robin >= iter - m_peers.begin()) ++m_round_robin;
+
 			i = *iter;
 #ifndef TORRENT_DISABLE_GEO_IP
 			int as = ses.as_for_ip(c.remote().address());
@@ -962,10 +964,10 @@ namespace libtorrent
 				, p->address(), peer_address_compare());
 		}
 
-		if (m_round_robin > iter - m_peers.begin()) ++m_round_robin;
-
 		iter = m_peers.insert(iter, p);
 
+		if (m_round_robin >= iter - m_peers.begin()) ++m_round_robin;
+
 #ifndef TORRENT_DISABLE_ENCRYPTION
 		if (flags & 0x01) p->pe_support = true;
 #endif