From 72c9b2b13530807a689746d148a254fe73b3115f Mon Sep 17 00:00:00 2001
From: Guus Sliepen <guus@tinc-vpn.org>
Date: Sun, 7 Apr 2024 15:44:00 +0200
Subject: [PATCH] Handle multicast being blocked in the test suite

If multicast is supported in principle, but multicast packets are blocked
by the firewall, then the multicast test will time out and reports an
error. Detect this case and don't fail.
---
 test/integration/device_multicast.py | 30 ++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/test/integration/device_multicast.py b/test/integration/device_multicast.py
index 1a0d55a9..1b46c42c 100755
--- a/test/integration/device_multicast.py
+++ b/test/integration/device_multicast.py
@@ -2,7 +2,9 @@
 
 """Test multicast device."""
 
+import enum
 import os
+import select
 import socket
 import struct
 import time
@@ -16,7 +18,13 @@ MCAST_ADDR = "224.15.98.12"
 PORT = 38245
 
 
-def multicast_works() -> bool:
+class MulticastSupport(enum.Enum):
+    NO = 0
+    BLOCKED = 1
+    YES = 2
+
+
+def multicast_works() -> MulticastSupport:
     """Check if multicast is supported and works."""
 
     msg = b"foobar"
@@ -31,9 +39,17 @@ def multicast_works() -> bool:
             with socket.socket(socket.AF_INET, socket.SOCK_DGRAM) as client:
                 client.sendto(msg, (MCAST_ADDR, PORT))
 
-            return msg == server.recv(16)
+            try:
+                select.select([server], [], [], 1)
+                if msg == server.recv(16, socket.MSG_DONTWAIT):
+                    return MulticastSupport.YES
+            except OSError:
+                pass
+
+            return MulticastSupport.BLOCKED
     except OSError:
-        return False
+        log.info("no")
+        return MulticastSupport.NO
 
 
 def test_no_mcast_support(foo: Tinc) -> None:
@@ -82,9 +98,15 @@ def test_device_multicast(ctx: Test) -> None:
     foo.cmd("set", "Device", f"{MCAST_ADDR} {PORT}")
     foo.cmd("set", "LogLevel", "10")
 
-    if multicast_works():
+    multicast_support = multicast_works()
+    if multicast_support == MulticastSupport.YES:
+        log.info("multicast supported")
         test_rx_tx(foo)
+    elif multicast_support == MulticastSupport.BLOCKED:
+        log.info("multicast blocked")
+        pass
     else:
+        log.info("multicast not supported")
         test_no_mcast_support(foo)
 
 
-- 
2.20.1