12897 FIX check_icmp: Failed to resolve multiple addresses

In Checkmk versions 2.0.0i1 to 2.0.0p5 the active check "check_icmp"
(a.k.a. <i>PING</i> service) failed when configured for a host
with multiple IP addresses.

Change-Id: I6c6656f075b3375d9ab4b495604ac8c8789f2970

.werks/12897

@@ -0,0 +1,14 @@
+Title: check_icmp: Failed to resolve multiple addresses
+Class: fix
+Compatible: compat
+Component: checks
+Date: 1622116447
+Edition: cre
+Knowledge: doc
+Level: 1
+State: unknown
+Version: 2.1.0i1
+
+In Checkmk versions 2.0.0i1 to 2.0.0p5 the active check "check_icmp"
+(a.k.a. <i>PING</i> service) failed when configured for a host
+with multiple IP addresses.

checks/check_icmp

@@ -59,7 +59,11 @@ def check_icmp_arguments(params):
     else:  # custom
         args.append(target[1])
 
-    return args
+    # Unfortunately, we must return a single string here.
+    # Otherwise shell quoting will be applied to every element
+    # of the list, which will interfere with macro replacements like
+    # "$HOST_ADDRESSES_4$" -> "1.2.3.4 5.6.7.8"
+    return ' '.join(args)
 
 
 def check_icmp_description(params):

tests/unit/checks/test_check_icmp.py

@@ -11,7 +11,7 @@
 
 
 @pytest.mark.parametrize("params,expected_args",
-                         [({}, ["-w", "200.00,80%", "-c", "500.00,100%", "$HOSTADDRESS$"])])
+                         [({}, "-w 200.00,80% -c 500.00,100% $HOSTADDRESS$")])
 def test_check_icmp_argument_parsing(params, expected_args):
     """Tests if all required arguments are present."""
     active_check = ActiveCheck("check_icmp")