samples/bpf: tc_bench01_redirect add option for listing

Add option for listing tc ingress filters, as I constantly forget
the exact tc command for viewing it.

Cmdline option --list with optional_argument.  Listing uses ingress ifname
if argument not specified for --list=dev.  Notice, getopts is annoying, and
need an equal-sign "=" for assigning an optional_argument.

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>

kernel/samples/bpf/tc_bench01_redirect_user.c

@@ -34,6 +34,8 @@ static const struct option long_options[] = {
 	{"ifindex-egress", required_argument,	NULL, 'x' },
 	/* Allow specifying tc cmd via argument */
 	{"tc-cmd",	required_argument,	NULL, 't' },
+	/* HINT assign: optional_arguments with '=' */
+	{"list",	optional_argument,	NULL, 'l' },
 	{0, 0, NULL,  0 }
 };
 
@@ -106,6 +108,26 @@ static int tc_ingress_attach_bpf(const char* dev, const char* bpf_obj)
 	return ret;
 }
 
+static int tc_list_ingress_filter(const char* dev)
+{
+	char cmd[CMD_MAX];
+	int ret = 0;
+
+	memset(&cmd, 0, CMD_MAX);
+	snprintf(cmd, CMD_MAX,
+		 "%s filter show dev %s ingress",
+		 tc_cmd, dev);
+	if (verbose) printf(" - Run: %s\n", cmd);
+	ret = system(cmd);
+	if (ret) {
+		fprintf(stderr,
+			"ERR(%d): tc cannot list filters\n Cmdline:%s\n",
+			ret, cmd);
+		exit(EXIT_FAILURE);
+	}
+	return ret;
+}
+
 static char ingress_ifname[IF_NAMESIZE];
 static char egress_ifname[IF_NAMESIZE];
 static char buf_ifname[IF_NAMESIZE] = "(unknown-dev)";
@@ -131,6 +153,7 @@ bool validate_ifname(const char* input_ifname, char *output_ifname)
 
 int main(int argc, char **argv)
 {
+	bool list_ingress_tc_filter = false;
 	int longindex = 0, opt, fd = -1;
 	int egress_ifindex = -1;
 	int ingress_ifindex = 0;
@@ -141,6 +164,8 @@ int main(int argc, char **argv)
 	char bpf_obj[256];
 	snprintf(bpf_obj, sizeof(bpf_obj), "%s_kern.o", argv[0]);
 
+	memset(ingress_ifname, 0, IF_NAMESIZE); /* Can be used uninitialized */
+
 	/* Parse commands line args */
 	while ((opt = getopt_long(argc, argv, "h",
 				  long_options, &longindex)) != -1) {
@@ -173,6 +198,20 @@ int main(int argc, char **argv)
 				return EXIT_FAILURE;
 			}
 			break;
+		case 'l':
+			if (optarg &&
+			    !validate_ifname(optarg,(char *)&ingress_ifname)) {
+				fprintf(stderr,
+					"ERR: input --list=ifname invalid\n");
+				return EXIT_FAILURE;
+			}
+			if (strlen(ingress_ifname) == 0) {
+				fprintf(stderr,
+					"ERR: need input --list=ifname\n");
+				return EXIT_FAILURE;
+			}
+			list_ingress_tc_filter = true;
+			break;
 		case 't':
 			len = strlen(optarg);
 			if (len >= CMD_MAX_TC) {
@@ -197,6 +236,13 @@ int main(int argc, char **argv)
 		}
 	}
 
+	if (list_ingress_tc_filter) {
+		if (verbose)
+			printf("TC list ingress filters on device %s\n",
+			       ingress_ifname);
+		tc_list_ingress_filter(ingress_ifname);
+	}
+
 	fd = bpf_obj_get(mapfile);
 	if (fd < 0) {
 		fprintf(stderr, "ERROR: cannot open bpf_obj_get(%s): %s(%d)\n",