From df8a57efb7d51069b9a40eae80a9c8c7ccb300aa Mon Sep 17 00:00:00 2001
From: Steven Siloti <ssiloti@gmail.com>
Date: Sun, 10 Sep 2017 01:25:04 -0700
Subject: [PATCH] select which DHT port to report based on the connection's
 local endpoint (#2316)

---
 include/libtorrent/aux_/session_impl.hpp      |  9 +--------
 include/libtorrent/aux_/session_interface.hpp |  2 +-
 src/bt_peer_connection.cpp                    |  2 +-
 src/session_impl.cpp                          | 16 ++++++++++++++++
 4 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/include/libtorrent/aux_/session_impl.hpp b/include/libtorrent/aux_/session_impl.hpp
index 5f52f794e..b04a13f89 100644
--- a/include/libtorrent/aux_/session_impl.hpp
+++ b/include/libtorrent/aux_/session_impl.hpp
@@ -600,14 +600,7 @@ namespace aux {
 
 #ifndef TORRENT_DISABLE_DHT
 			bool is_dht_running() const { return (m_dht.get() != nullptr); }
-			int external_udp_port() const override
-			{
-				for (auto const& s : m_listen_sockets)
-				{
-					if (s->udp_sock) return s->udp_external_port;
-				}
-				return -1;
-			}
+			int external_udp_port(address const& local_address) const override;
 #endif
 
 #if TORRENT_USE_I2P
diff --git a/include/libtorrent/aux_/session_interface.hpp b/include/libtorrent/aux_/session_interface.hpp
index 8755f529b..52533ec2e 100644
--- a/include/libtorrent/aux_/session_interface.hpp
+++ b/include/libtorrent/aux_/session_interface.hpp
@@ -300,7 +300,7 @@ namespace libtorrent { namespace aux {
 		virtual bool announce_dht() const = 0;
 		virtual void add_dht_node(udp::endpoint const& n) = 0;
 		virtual bool has_dht() const = 0;
-		virtual int external_udp_port() const = 0;
+		virtual int external_udp_port(address const& local_address) const = 0;
 		virtual dht::dht_tracker* dht() = 0;
 		virtual void prioritize_dht(std::weak_ptr<torrent> t) = 0;
 #endif
diff --git a/src/bt_peer_connection.cpp b/src/bt_peer_connection.cpp
index 5d8e3d202..cdeedcd90 100644
--- a/src/bt_peer_connection.cpp
+++ b/src/bt_peer_connection.cpp
@@ -333,7 +333,7 @@ namespace {
 #ifndef TORRENT_DISABLE_DHT
 		if (m_supports_dht_port && m_ses.has_dht())
 		{
-			int const port = m_ses.external_udp_port();
+			int const port = m_ses.external_udp_port(local_endpoint().address());
 			if (port >= 0) write_dht_port(port);
 		}
 #endif
diff --git a/src/session_impl.cpp b/src/session_impl.cpp
index b1b73a9e6..7e53626d6 100644
--- a/src/session_impl.cpp
+++ b/src/session_impl.cpp
@@ -2151,6 +2151,22 @@ namespace {
 #endif
 	}
 
+#ifndef TORRENT_DISABLE_DHT
+	int session_impl::external_udp_port(address const& local_address) const
+	{
+		auto ls = std::find_if(m_listen_sockets.begin(), m_listen_sockets.end()
+			, [&](std::shared_ptr<listen_socket_t> const& e)
+		{
+			return e->local_endpoint.address() == local_address;
+		});
+
+		if (ls != m_listen_sockets.end())
+			return (*ls)->udp_external_port;
+		else
+			return -1;
+	}
+#endif
+
 #if TORRENT_USE_I2P
 
 	proxy_settings session_impl::i2p_proxy() const