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
10 #include <linux/netfilter/nf_conntrack_tcp.h>
11
main(void)12 int main(void)
13 {
14 struct mnl_socket *nl;
15 struct nlmsghdr *nlh;
16 struct nfgenmsg *nfh;
17 char buf[MNL_SOCKET_BUFFER_SIZE];
18 unsigned int seq, portid;
19 struct nf_conntrack *ct;
20 int ret;
21
22 nl = mnl_socket_open(NETLINK_NETFILTER);
23 if (nl == NULL) {
24 perror("mnl_socket_open");
25 exit(EXIT_FAILURE);
26 }
27
28 if (mnl_socket_bind(nl, 0, MNL_SOCKET_AUTOPID) < 0) {
29 perror("mnl_socket_bind");
30 exit(EXIT_FAILURE);
31 }
32 portid = mnl_socket_get_portid(nl);
33
34 nlh = mnl_nlmsg_put_header(buf);
35 nlh->nlmsg_type = (NFNL_SUBSYS_CTNETLINK << 8) | IPCTNL_MSG_CT_NEW;
36 nlh->nlmsg_flags = NLM_F_REQUEST|NLM_F_CREATE|NLM_F_EXCL|NLM_F_ACK;
37 nlh->nlmsg_seq = seq = time(NULL);
38
39 nfh = mnl_nlmsg_put_extra_header(nlh, sizeof(struct nfgenmsg));
40 nfh->nfgen_family = AF_INET;
41 nfh->version = NFNETLINK_V0;
42 nfh->res_id = 0;
43
44 ct = nfct_new();
45 if (ct == NULL) {
46 perror("nfct_new");
47 return 0;
48 }
49
50 nfct_set_attr_u8(ct, ATTR_L3PROTO, AF_INET);
51 nfct_set_attr_u32(ct, ATTR_IPV4_SRC, inet_addr("1.1.1.1"));
52 nfct_set_attr_u32(ct, ATTR_IPV4_DST, inet_addr("2.2.2.2"));
53
54 nfct_set_attr_u8(ct, ATTR_L4PROTO, IPPROTO_TCP);
55 nfct_set_attr_u16(ct, ATTR_PORT_SRC, htons(20));
56 nfct_set_attr_u16(ct, ATTR_PORT_DST, htons(10));
57
58 nfct_setobjopt(ct, NFCT_SOPT_SETUP_REPLY);
59
60 nfct_set_attr_u8(ct, ATTR_TCP_STATE, TCP_CONNTRACK_SYN_SENT);
61 nfct_set_attr_u32(ct, ATTR_TIMEOUT, 100);
62
63 nfct_nlmsg_build(nlh, ct);
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 (ret > 0) {
73 ret = mnl_cb_run(buf, ret, seq, portid, NULL, NULL);
74 if (ret <= MNL_CB_STOP)
75 break;
76 ret = mnl_socket_recvfrom(nl, buf, sizeof(buf));
77 }
78 if (ret == -1) {
79 perror("mnl_socket_recvfrom");
80 exit(EXIT_FAILURE);
81 }
82
83 mnl_socket_close(nl);
84
85 return 0;
86 }
87