2 files changed, 59 insertions, 6 deletions

diff --git a/tests/integration/harness.py b/tests/integration/harness.py
index 122c36d..b98ce83 100644
--- a/tests/integration/harness.py
+++ b/tests/integration/harness.py
@@ -49,12 +49,26 @@ def bdecode(data):
     return value(0)[1]
 
 
-def free_port():
-    probe = socket.socket()
-    probe.bind(("127.0.0.1", 0))
-    port = probe.getsockname()[1]
-    probe.close()
-    return port
+def free_port(attempts=50):
+    """A port free for both protocols, because the tracker binds both.
+
+    Asking the kernel for a free tcp port says nothing about the udp port of
+    the same number, and anything on the machine holding that one makes the
+    tracker exit at once with "Address already in use".
+    """
+    for _ in range(attempts):
+        tcp = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+        udp = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        try:
+            tcp.bind(("127.0.0.1", 0))
+            udp.bind(("127.0.0.1", tcp.getsockname()[1]))
+            return tcp.getsockname()[1]
+        except OSError:
+            continue
+        finally:
+            tcp.close()
+            udp.close()
+    raise AssertionError("no port free for both tcp and udp after %d tries" % attempts)
 
 
 class Tracker:
diff --git a/tests/integration/test_expiry.py b/tests/integration/test_expiry.py
new file mode 100644
index 0000000..5a21e57
--- /dev/null
+++ b/tests/integration/test_expiry.py
@@ -0,0 +1,39 @@
+"""What the expiry sweep finds, and what it must not find.
+
+A plain request is answered and the connection closed by http_close, not by
+the sweep. If that path left the descriptor's slot behind, the sweep would
+walk into it once the client timeout had passed and free a cookie that is
+already gone; the sanitizer build reports that and teardown turns it into a
+failure.
+
+Both halves share one tracker and one wait, because the wait is the whole
+cost of the test.
+
+The two numbers below mirror OT_CLIENT_TIMEOUT and
+OT_CLIENT_TIMEOUT_CHECKINTERVAL in FEATURES_integration.
+"""
+
+import socket
+import time
+import unittest
+
+from harness import TrackerTestCase
+
+CLIENT_TIMEOUT = 5
+CHECK_INTERVAL = 1
+
+
+class ExpirySweep(TrackerTestCase):
+    def test_the_sweep_takes_the_idle_and_leaves_the_answered(self):
+        idle = socket.create_connection(("127.0.0.1", self.tracker.port), timeout=5)
+        try:
+            self.assertEqual(self.tracker.announce(self.hash_for("expiry-sweep"))[b"complete"], 1)
+
+            time.sleep(CLIENT_TIMEOUT + 3 * CHECK_INTERVAL)
+
+            self.assertEqual(self.tracker.torrent_count(), 1, "the tracker stopped serving while sweeping")
+
+            idle.settimeout(5)
+            self.assertEqual(idle.recv(64), b"", "a connection that never sent a request was not swept")
+        finally:
+            idle.close()