1#include <stdio.h>
2#include <stdlib.h>
3#include <unistd.h>
4#include <time.h>
5#include <arpa/inet.h>
6
7#include <libmnl/libmnl.h>
8#include <libnetfilter_conntrack/libnetfilter_conntrack.h>
9
10static int data_cb(const struct nlmsghdr *nlh, void *data)
11{
12	struct nf_expect *exp;
13	uint32_t type = NFCT_T_UNKNOWN;
14	char buf[4096];
15
16	exp = nfexp_new();
17	if (exp == NULL)
18		return MNL_CB_OK;
19
20	if (nfexp_nlmsg_parse(nlh, exp) < 0) {
21		perror("failed to parse message from kernel");
22		return MNL_CB_ERROR;
23	}
24
25	nfexp_snprintf(buf, sizeof(buf), exp, type, NFCT_O_DEFAULT, 0);
26	printf("%s\n", buf);
27
28	nfexp_destroy(exp);
29
30	return MNL_CB_OK;
31}
32
33int main(void)
34{
35	struct mnl_socket *nl;
36	char buf[MNL_SOCKET_BUFFER_SIZE];
37	struct nlmsghdr *nlh;
38	struct nfgenmsg *nfh;
39	uint32_t seq, portid;
40	int ret;
41
42	nl = mnl_socket_open(NETLINK_NETFILTER);
43	if (nl == NULL) {
44		perror("mnl_socket_open");
45		exit(EXIT_FAILURE);
46	}
47
48	if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
49		perror("mnl_socket_bind");
50		exit(EXIT_FAILURE);
51	}
52
53	portid = mnl_socket_get_portid(nl);
54
55	nlh = mnl_nlmsg_put_header(buf);
56	nlh->nlmsg_type = (NFNL_SUBSYS_CTNETLINK_EXP << 8) | IPCTNL_MSG_EXP_GET;
57	nlh->nlmsg_flags = NLM_F_REQUEST|NLM_F_DUMP|NLM_F_ACK;
58	nlh->nlmsg_seq = seq = time(NULL);
59
60	nfh = mnl_nlmsg_put_extra_header(nlh, sizeof(struct nfgenmsg));
61	nfh->nfgen_family = AF_INET;
62	nfh->version = NFNETLINK_V0;
63	nfh->res_id = 0;
64
65	ret = mnl_socket_sendto(nl, nlh, nlh->nlmsg_len);
66	if (ret == -1) {
67		perror("mnl_socket_recvfrom");
68		exit(EXIT_FAILURE);
69	}
70
71	ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
72	while (1) {
73		ret = mnl_cb_run(buf, ret, seq, portid, data_cb, NULL);
74		if (ret <= MNL_CB_STOP)
75			break;
76
77		ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
78	}
79	if (ret == -1) {
80		perror("mnl_socket_recvfrom");
81		exit(EXIT_FAILURE);
82	}
83
84	mnl_socket_close(nl);
85
86	return 0;
87}
88