1 files changed, 110 insertions, 0 deletions

diff --git a/tests/accept_filter_probe.py b/tests/accept_filter_probe.py
new file mode 100644
index 0000000..22f585a
--- /dev/null
+++ b/tests/accept_filter_probe.py
@@ -0,0 +1,110 @@
+"""What a deferred accept does to connections that never send anything.
+
+Those connections never reach opentracker, so its own client timeout cannot
+clean them up: whatever bound exists is the kernel's. This measures it, and
+then asks the question that follows from it -- whether enough of them keep
+the tracker from answering anybody else.
+
+    make opentracker
+    python3 tests/accept_filter_probe.py
+
+On FreeBSD the filter does nothing unless accf_data is loaded, so run it both
+ways to see whether the numbers differ:
+
+    kldload accf_data
+"""
+
+import os
+import socket
+import signal
+import subprocess
+import sys
+import tempfile
+import time
+import urllib.error
+import urllib.request
+
+TRACKER = os.environ.get("OPENTRACKER", "./opentracker")
+IDLE = int(os.environ.get("IDLE", "300"))
+PATIENCE = float(os.environ.get("PATIENCE", "90"))
+HASH = "".join("%%%02x" % b for b in range(1, 21))
+
+
+def start(port):
+    directory = tempfile.mkdtemp(prefix="ot-accf-")
+    with open(os.path.join(directory, "conf"), "w") as handle:
+        handle.write("listen.tcp 127.0.0.1:%d\nlisten.udp 127.0.0.1:%d\n" % (port, port))
+    log = open(os.path.join(directory, "log"), "w+b")
+    tracker = subprocess.Popen([TRACKER, "-f", os.path.join(directory, "conf")], stdout=log, stderr=log)
+    for _ in range(300):
+        try:
+            socket.create_connection(("127.0.0.1", port), timeout=0.2).close()
+            return tracker, log
+        except OSError:
+            time.sleep(0.02)
+    tracker.kill()
+    raise SystemExit("tracker never listened on %d" % port)
+
+
+def announce(port, timeout=5):
+    """One ordinary request, so we can see whether the tracker still serves."""
+    started = time.time()
+    try:
+        urllib.request.urlopen(
+            "http://127.0.0.1:%d/announce?info_hash=%s&peer_id=-OT0001-probe0000001&port=6881&left=0" % (port, HASH),
+            timeout=timeout,
+        ).read()
+        return time.time() - started, None
+    except Exception as problem:  # noqa: BLE001 - reported, not swallowed
+        return time.time() - started, problem
+
+
+def main():
+    port = int(os.environ.get("PORT", "28000"))
+    tracker, log = start(port)
+    try:
+        print("  how long a connection that says nothing is held")
+        quiet = socket.create_connection(("127.0.0.1", port), timeout=5)
+        quiet.settimeout(PATIENCE)
+        started = time.time()
+        try:
+            held = "dropped after %.1f s" % (time.time() - started) if quiet.recv(1) == b"" else "sent us something"
+        except socket.timeout:
+            held = "still open after %.0f s" % PATIENCE
+        except OSError as problem:
+            held = "ended after %.1f s: %s" % (time.time() - started, problem)
+        quiet.close()
+        print("    %s" % held)
+
+        print("  and whether %d of them keep anybody else out" % IDLE)
+        before, problem = announce(port)
+        print("    a request before: %.0f ms%s" % (before * 1000, "" if problem is None else " (%s)" % problem))
+
+        idlers = []
+        for _ in range(IDLE):
+            try:
+                idlers.append(socket.create_connection(("127.0.0.1", port), timeout=2))
+            except OSError as problem:
+                print("    could only open %d of them: %s" % (len(idlers), problem))
+                break
+        print("    holding %d connections that have sent nothing" % len(idlers))
+
+        during, problem = announce(port, timeout=10)
+        print("    a request during: %.0f ms%s" % (during * 1000, "" if problem is None else "  REFUSED: %s" % problem))
+
+        for idler in idlers:
+            idler.close()
+        after, problem = announce(port)
+        print("    a request after:  %.0f ms%s" % (after * 1000, "" if problem is None else " (%s)" % problem))
+    finally:
+        tracker.send_signal(signal.SIGINT)
+        try:
+            tracker.wait(timeout=10)
+        except subprocess.TimeoutExpired:
+            tracker.kill()
+            tracker.wait()
+        log.close()
+
+
+if __name__ == "__main__":
+    main()