#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

#include <libmnl/libmnl.h>
#include <linux/genetlink.h>

static void parse_genl_mc_grps(struct nlattr *nested)
{
	struct nlattr *pos;
	int len;

	mnl_attr_for_each_nested(pos, nested, len) {
		struct nlattr *tb[CTRL_ATTR_MCAST_GRP_MAX+1];

		mnl_attr_parse_nested(pos, tb, CTRL_ATTR_MCAST_GRP_MAX);
		if (tb[CTRL_ATTR_MCAST_GRP_ID]) {
			printf("id-0x%x ",
				mnl_attr_get_u32(tb[CTRL_ATTR_MCAST_GRP_ID]));
		}
		if (tb[CTRL_ATTR_MCAST_GRP_NAME]) {
			printf("name: %s ",
				mnl_attr_get_str(tb[CTRL_ATTR_MCAST_GRP_NAME]));
		}
		printf("\n");
	}
}

static void parse_genl_family_ops(struct nlattr *nested)
{
	struct nlattr *pos;
	int len;

	mnl_attr_for_each_nested(pos, nested, len) {
		struct nlattr *tb[CTRL_ATTR_OP_MAX+1];

		mnl_attr_parse_nested(pos, tb, CTRL_ATTR_OP_MAX);
		if (tb[CTRL_ATTR_OP_ID]) {
			printf("id-0x%x ",
				mnl_attr_get_u32(tb[CTRL_ATTR_OP_ID]));
		}
		if (tb[CTRL_ATTR_OP_MAX]) {
			printf("flags ");
		}
		printf("\n");
	}
}

static int data_cb(const struct nlmsghdr *nlh, void *data)
{
	struct nlattr *tb[CTRL_ATTR_MAX+1];
	struct genlmsghdr *genl = mnl_nlmsg_get_data(nlh);

	/* this does not come from the kernel. */
	if (nlh->nlmsg_pid != 0)
		return MNL_CB_OK;

	mnl_attr_parse_at_offset(nlh, sizeof(*genl), tb, CTRL_ATTR_MAX);
	if (tb[CTRL_ATTR_FAMILY_NAME]) {
		printf("name=%s\t",
			mnl_attr_get_str(tb[CTRL_ATTR_FAMILY_NAME]));
	}
	if (tb[CTRL_ATTR_FAMILY_ID]) {
		printf("id=%u\t",
			mnl_attr_get_u16(tb[CTRL_ATTR_FAMILY_ID]));
	}
	if (tb[CTRL_ATTR_VERSION]) {
		printf("version=%u\t",
			mnl_attr_get_u32(tb[CTRL_ATTR_VERSION]));
	}
	if (tb[CTRL_ATTR_HDRSIZE]) {
		printf("hdrsize=%u\t",
			mnl_attr_get_u32(tb[CTRL_ATTR_HDRSIZE]));
	}
	if (tb[CTRL_ATTR_MAXATTR]) {
		printf("maxattr=%u\t",
			mnl_attr_get_u32(tb[CTRL_ATTR_MAXATTR]));
	}
	if (tb[CTRL_ATTR_OPS]) {
		printf("\nops:\n");
		parse_genl_family_ops(tb[CTRL_ATTR_OPS]);
	}
	if (tb[CTRL_ATTR_MCAST_GROUPS]) {
		printf("\ngrps:\n");
		parse_genl_mc_grps(tb[CTRL_ATTR_MCAST_GROUPS]);
	}
	return MNL_CB_OK;
}

int main(int argc, char *argv[])
{
	struct mnl_socket *nl;
	char buf[getpagesize()];
	struct nlmsghdr *nlh;
	struct genlmsghdr *genl;
	int ret;
	unsigned int seq;

	if (argc != 2) {
		printf("%s [family name]\n", argv[0]);
		exit(EXIT_FAILURE);
	}

	nlh = mnl_nlmsg_put_header(buf);
	nlh->nlmsg_type	= GENL_ID_CTRL;
	nlh->nlmsg_flags = NLM_F_REQUEST | NLM_F_ACK;
	nlh->nlmsg_seq = seq = time(NULL);

	genl = mnl_nlmsg_put_extra_header(nlh, sizeof(struct genlmsghdr));
	genl->cmd = CTRL_CMD_GETFAMILY;
	genl->version = 1;

	mnl_attr_put_u32(nlh, CTRL_ATTR_FAMILY_ID, GENL_ID_CTRL);
	mnl_attr_put_str_null(nlh, CTRL_ATTR_FAMILY_NAME, argv[1]);

	nl = mnl_socket_open(NETLINK_GENERIC);
	if (nl == NULL) {
		perror("mnl_socket_open");
		exit(EXIT_FAILURE);
	}

	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
		perror("mnl_socket_bind");
		exit(EXIT_FAILURE);
	}

	if (mnl_socket_sendto(nl, nlh, mnl_nlmsg_get_len(nlh)) < 0) {
		perror("mnl_socket_send");
		exit(EXIT_FAILURE);
	}

	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
	while (ret > 0) {
		ret = mnl_cb_run(buf, ret, seq, data_cb, NULL);
		if (ret <= 0)
			break;
		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
	}
	if (ret == -1) {
		perror("error");
		exit(EXIT_FAILURE);
	}

	mnl_socket_close(nl);

	return 0;
}