use random peer IDs in anonymous mode

ChangeLog

@@ -1,6 +1,7 @@
 	* fix uTP edge case where udp socket buffer fills up
 	* fix nagle implementation in uTP
 
+	* use random peer IDs in anonymous mode
 	* fix move_storage bugs
 	* fix unnecessary dependency on boost.date_time when building boost.asio as separate compilation
 	* always use SO_REUSEADDR and deprecate the flag to turn it on

include/libtorrent/session_settings.hpp

@@ -757,10 +757,11 @@ namespace libtorrent
 		// we have none of the files and go straight to download
 		bool no_recheck_incomplete_resume;
 
-		// when this is true, libtorrent will take actions to make sure any
+		// when this is true, libtorrent will take actions to make sure no
 		// privacy sensitive information is leaked out from the client. This
 		// mode is assumed to be combined with using a proxy for all your
 		// traffic. With this option, your true IP address will not be exposed
+		// nor anything that can tie your connection to your true IP
 		bool anonymous_mode;
 
 		// the number of milliseconds between internal ticks. Should be no

src/bt_peer_connection.cpp

@@ -755,8 +755,18 @@ namespace libtorrent
 		ptr += 20;
 
 		// peer id
-		memcpy(ptr, &m_ses.get_peer_id()[0], 20);
-//		ptr += 20;
+		if (m_ses.m_settings.anonymous_mode)
+		{
+			// in anonymous mode, every peer connection
+			// has a unique peer-id
+			for (int i = 0; i < 20; ++i)
+				*ptr++ = rand();
+		}
+		else
+		{
+			memcpy(ptr, &m_ses.get_peer_id()[0], 20);
+//			ptr += 20;
+		}
 
 #ifdef TORRENT_VERBOSE_LOGGING
 		peer_log("==> HANDSHAKE [ ih: %s ]", to_hex(ih.to_string()).c_str());