From 3092b7ca44603da608d924e20f8982253c8bafb1 Mon Sep 17 00:00:00 2001
From: arvidn <arvid@libtorrent.org>
Date: Wed, 5 Feb 2020 18:01:38 +0100
Subject: [PATCH] fix binding TCP and UDP sockets to the same port, when
 specifying port 0

---
 ChangeLog                   |  1 +
 simulation/libsimulator     |  2 +-
 simulation/test_session.cpp | 46 +++++++++++++++++++++++++++++++++++++
 src/session_impl.cpp        |  2 ++
 4 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/ChangeLog b/ChangeLog
index 8f7bcc7f4..d5712bb21 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,6 @@
 1.2.4 release
 
+	* fix binding TCP and UDP sockets to the same port, when specifying port 0
 	* fix announce_to_all_trackers and announce_to_all_tiers behavior
 	* fix suggest_read_cache setting
 	* back-off tracker hostname looksups resulting in NXDOMAIN
diff --git a/simulation/libsimulator b/simulation/libsimulator
index ba65f2fc2..3e4a9fc7a 160000
--- a/simulation/libsimulator
+++ b/simulation/libsimulator
@@ -1 +1 @@
-Subproject commit ba65f2fc25cb0cf6ab141102952b9c5c54f02c41
+Subproject commit 3e4a9fc7a5971104154d11a361139043029435c5
diff --git a/simulation/test_session.cpp b/simulation/test_session.cpp
index fa7dfda21..d53c47b74 100644
--- a/simulation/test_session.cpp
+++ b/simulation/test_session.cpp
@@ -41,6 +41,7 @@ POSSIBILITY OF SUCH DAMAGE.
 #include "simulator/utils.hpp" // for timer
 #include "settings.hpp"
 #include "create_torrent.hpp"
+#include "setup_transfer.hpp" // for addr()
 
 using namespace lt;
 
@@ -175,3 +176,48 @@ TORRENT_TEST(add_extension_while_transfer)
 	TEST_CHECK(p->m_files_checked);
 }
 #endif // TORRENT_DISABLE_EXTENSIONS
+
+// make sure TCP and UDP listen sockets use the same port
+TORRENT_TEST(tie_listen_ports)
+{
+	using namespace libtorrent;
+
+	sim::default_config network_cfg;
+	sim::simulation sim{network_cfg};
+	sim::asio::io_service ios { sim, addr("50.0.0.1")};
+
+	lt::session_proxy zombie;
+
+	// create session
+	auto pack = settings();
+	pack.set_str(settings_pack::listen_interfaces, "0.0.0.0:0");
+	pack.set_int(settings_pack::alert_mask, alert::error_notification
+		| alert::status_notification
+		| alert::torrent_log_notification);
+
+	auto ses = std::make_shared<lt::session>(pack, ios);
+
+	std::vector<int> listen_ports;
+
+	// only monitor alerts for session 0 (the downloader)
+	print_alerts(*ses, [&](lt::session&, lt::alert const* a){
+		if (auto const* la = alert_cast<listen_succeeded_alert>(a))
+		{
+			listen_ports.push_back(la->port);
+		}
+	});
+
+	sim::timer t(sim, lt::seconds(30), [&](boost::system::error_code const&)
+	{
+	// TEST
+		zombie = ses->abort();
+		ses.reset();
+
+		TEST_CHECK(listen_ports.size() > 0);
+		int const port = listen_ports.front();
+		for (int const p : listen_ports)
+			TEST_EQUAL(p, port);
+	});
+
+	sim.run();
+}
diff --git a/src/session_impl.cpp b/src/session_impl.cpp
index 35ed6dffa..0891fdb76 100644
--- a/src/session_impl.cpp
+++ b/src/session_impl.cpp
@@ -1549,6 +1549,8 @@ namespace aux {
 			TORRENT_ASSERT(ret->local_endpoint.port() == bind_ep.port()
 				|| bind_ep.port() == 0);
 
+			if (bind_ep.port() == 0) bind_ep = ret->local_endpoint;
+
 			ret->sock->listen(m_settings.get_int(settings_pack::listen_queue_size), ec);
 			last_op = operation_t::sock_listen;