From ac914d44157d6a44cd981108354aba20f8209739 Mon Sep 17 00:00:00 2001
From: Alden Torres <aldenml@gmail.com>
Date: Fri, 1 Sep 2017 13:28:27 -0400
Subject: [PATCH] avoid port mapping of local addresses (#2296)

---
 src/broadcast_socket.cpp |  7 +++++++
 src/session_impl.cpp     | 10 +++++++++-
 2 files changed, 16 insertions(+), 1 deletion(-)

diff --git a/src/broadcast_socket.cpp b/src/broadcast_socket.cpp
index fbc816493..41449e65e 100644
--- a/src/broadcast_socket.cpp
+++ b/src/broadcast_socket.cpp
@@ -69,10 +69,17 @@ namespace libtorrent {
 #if TORRENT_USE_IPV6
 			if (a.is_v6())
 			{
+				// NOTE: site local is deprecated but by
+				// https://www.ietf.org/rfc/rfc3879.txt:
+				// routers SHOULD be configured to prevent
+				// routing of this prefix by default.
+
 				address_v6 const a6 = a.to_v6();
 				return a6.is_loopback()
 					|| a6.is_link_local()
+					|| a6.is_site_local()
 					|| a6.is_multicast_link_local()
+					|| a6.is_multicast_site_local()
 					//  fc00::/7, unique local address
 					|| (a6.to_bytes()[0] & 0xfe) == 0xfc;
 			}
diff --git a/src/session_impl.cpp b/src/session_impl.cpp
index 2611d81d7..0c037bcdd 100644
--- a/src/session_impl.cpp
+++ b/src/session_impl.cpp
@@ -2172,12 +2172,20 @@ namespace {
 			if (map_handle != -1) m.delete_mapping(map_handle);
 			map_handle = -1;
 
+#if TORRENT_USE_IPV6
+			address const addr = ep.address();
+			// with IPv4 the interface might be behind NAT so we can't skip them
+			// based on the scope of the local address
+			if (addr.is_v6() && is_local(addr))
+				return;
+#endif
+
 			// only update this mapping if we actually have a socket listening
 			if (ep != EndpointType())
 				map_handle = m.add_mapping(protocol, ep.port(), ep);
 		}
 
-		tcp::endpoint to_tcp(udp::endpoint const ep)
+		tcp::endpoint to_tcp(udp::endpoint const& ep)
 		{
 			return tcp::endpoint(ep.address(), ep.port());
 		}