selftests/bpf: Adding a namespace reset for tc_redirect

This patch delete ns_src/ns_dst/ns_redir namespaces before recreating
them, making the test more robust.

Signed-off-by: Yucong Sun <sunyucong@gmail.com>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/20211025223345.2136168-5-fallentree@fb.com

tools/testing/selftests/bpf/prog_tests/tc_redirect.c

@@ -176,6 +176,18 @@ static int netns_setup_namespaces(const char *verb)
 	return 0;
 }
 
+static void netns_setup_namespaces_nofail(const char *verb)
+{
+	const char * const *ns = namespaces;
+	char cmd[128];
+
+	while (*ns) {
+		snprintf(cmd, sizeof(cmd), "ip netns %s %s > /dev/null 2>&1", verb, *ns);
+		system(cmd);
+		ns++;
+	}
+}
+
 struct netns_setup_result {
 	int ifindex_veth_src_fwd;
 	int ifindex_veth_dst_fwd;
@@ -762,6 +774,8 @@ static void test_tc_redirect_peer_l3(struct netns_setup_result *setup_result)
 
 static void *test_tc_redirect_run_tests(void *arg)
 {
+	netns_setup_namespaces_nofail("delete");
+
 	RUN_TEST(tc_redirect_peer);
 	RUN_TEST(tc_redirect_peer_l3);
 	RUN_TEST(tc_redirect_neigh);