selftests/net: add variable NS_LIST for lib.sh

Add a global variable NS_LIST to store all the namespaces that setup_ns
created, so the caller could call cleanup_all_ns() instead of remember
all the netns names when using cleanup_ns().
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Link: https://lore.kernel.org/r/20231213060856.4030084-2-liuhangbin@gmail.comSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/lib.sh

@@ -6,6 +6,8 @@
 
 # Kselftest framework requirement - SKIP code is 4.
 ksft_skip=4
+# namespace list created by setup_ns
+NS_LIST=""
 
 ##############################################################################
 # Helpers
@@ -56,6 +58,11 @@ cleanup_ns()
 	return $ret
 }
 
+cleanup_all_ns()
+{
+	cleanup_ns $NS_LIST
+}
+
 # setup netns with given names as prefix. e.g
 # setup_ns local remote
 setup_ns()
@@ -82,4 +89,5 @@ setup_ns()
 		ip -n "$ns" link set lo up
 		ns_list="$ns_list $ns"
 	done
+	NS_LIST="$NS_LIST $ns_list"
 }