int main()

in bpf/xdp_router_ipv4_user.c [641:750]
97 lines of code
20 McCabe index (conditional complexity)

int main(int ac, char **argv)
{
	struct bpf_prog_load_attr prog_load_attr = {
		.prog_type	= BPF_PROG_TYPE_XDP,
	};
	struct bpf_prog_info info = {};
	__u32 info_len = sizeof(info);
	const char *optstr = "SF";
	struct bpf_object *obj;
	char filename[256];
	char **ifname_list;
	int prog_fd, opt;
	int err, i = 1;

	snprintf(filename, sizeof(filename), "%s_kern.o", argv[0]);
	prog_load_attr.file = filename;

	total_ifindex = ac - 1;
	ifname_list = (argv + 1);

	while ((opt = getopt(ac, argv, optstr)) != -1) {
		switch (opt) {
		case 'S':
			flags |= XDP_FLAGS_SKB_MODE;
			total_ifindex--;
			ifname_list++;
			break;
		case 'F':
			flags &= ~XDP_FLAGS_UPDATE_IF_NOEXIST;
			total_ifindex--;
			ifname_list++;
			break;
		default:
			usage(basename(argv[0]));
			return 1;
		}
	}

	if (!(flags & XDP_FLAGS_SKB_MODE))
		flags |= XDP_FLAGS_DRV_MODE;

	if (optind == ac) {
		usage(basename(argv[0]));
		return 1;
	}

	if (bpf_prog_load_xattr(&prog_load_attr, &obj, &prog_fd))
		return 1;

	printf("\n******************loading bpf file*********************\n");
	if (!prog_fd) {
		printf("bpf_prog_load_xattr: %s\n", strerror(errno));
		return 1;
	}

	lpm_map_fd = bpf_object__find_map_fd_by_name(obj, "lpm_map");
	rxcnt_map_fd = bpf_object__find_map_fd_by_name(obj, "rxcnt");
	arp_table_map_fd = bpf_object__find_map_fd_by_name(obj, "arp_table");
	exact_match_map_fd = bpf_object__find_map_fd_by_name(obj,
							     "exact_match");
	tx_port_map_fd = bpf_object__find_map_fd_by_name(obj, "tx_port");
	if (lpm_map_fd < 0 || rxcnt_map_fd < 0 || arp_table_map_fd < 0 ||
	    exact_match_map_fd < 0 || tx_port_map_fd < 0) {
		printf("bpf_object__find_map_fd_by_name failed\n");
		return 1;
	}

	ifindex_list = (int *)calloc(total_ifindex, sizeof(int *));
	for (i = 0; i < total_ifindex; i++) {
		ifindex_list[i] = if_nametoindex(ifname_list[i]);
		if (!ifindex_list[i]) {
			printf("Couldn't translate interface name: %s",
			       strerror(errno));
			return 1;
		}
	}
	prog_id_list = (__u32 *)calloc(total_ifindex, sizeof(__u32 *));
	for (i = 0; i < total_ifindex; i++) {
		if (bpf_set_link_xdp_fd(ifindex_list[i], prog_fd, flags) < 0) {
			printf("link set xdp fd failed\n");
			int recovery_index = i;

			for (i = 0; i < recovery_index; i++)
				bpf_set_link_xdp_fd(ifindex_list[i], -1, flags);

			return 1;
		}
		err = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
		if (err) {
			printf("can't get prog info - %s\n", strerror(errno));
			return err;
		}
		prog_id_list[i] = info.id;
		memset(&info, 0, sizeof(info));
		printf("Attached to %d\n", ifindex_list[i]);
	}
	signal(SIGINT, int_exit);
	signal(SIGTERM, int_exit);

	printf("\n*******************ROUTE TABLE*************************\n");
	get_route_table(AF_INET);
	printf("\n*******************ARP TABLE***************************\n");
	get_arp_table(AF_INET);
	if (monitor_route() < 0) {
		printf("Error in receiving route update");
		return 1;
	}

	return 0;
}