libnl  3.7.0
nf-ct-events.c
1 /* SPDX-License-Identifier: LGPL-2.1-only */
2 /*
3  * Copyright (c) 2018 Avast software
4  */
5 
6 #include <netlink/cli/utils.h>
7 #include <netlink/cli/ct.h>
8 
9 #include <linux/netlink.h>
10 #include <linux/netfilter/nfnetlink.h>
11 #include <linux/netfilter/nfnetlink_conntrack.h>
12 
14 {
15  int ce_refcnt;
16  struct nl_object_ops * ce_ops;
17  struct nl_cache * ce_cache;
18  struct nl_list_head ce_list;
19  int ce_msgtype;
20  int ce_flags;
21  uint64_t ce_mask;
22 };
23 
24 static void nf_conntrack_parse_callback(struct nl_object *obj, void *opaque)
25 {
26  struct nl_dump_params params = {
27  .dp_fd = stdout,
28  .dp_type = NL_DUMP_DETAILS,
29  };
30 
31  nl_object_dump(obj, &params);
32 }
33 
34 static int nf_conntrack_event_callback(struct nl_msg *msg, void *opaque)
35 {
36  int err;
37  struct nlmsghdr *hdr = nlmsg_hdr(msg);
38 
39  enum cntl_msg_types type = (enum cntl_msg_types) NFNL_MSG_TYPE(hdr->nlmsg_type);
40 
41  int flags = hdr->nlmsg_flags;
42 
43  if (type == IPCTNL_MSG_CT_DELETE) {
44  printf("DELETE ");
45  } else if (type == IPCTNL_MSG_CT_NEW) {
46  if (flags & (NLM_F_CREATE|NLM_F_EXCL)) {
47  printf("NEW ");
48  } else {
49  printf("UPDATE ");
50  }
51  } else {
52  printf("UNKNOWN ");
53  }
54 
55  if ((err = nl_msg_parse(msg, &nf_conntrack_parse_callback, opaque)) < 0) {
56  nl_cli_fatal(err, "nl_msg_parse: %s", nl_geterror(err));
57  }
58  /* Continue with next event */
59  return NL_OK;
60 }
61 
62 int main(int argc, char *argv[])
63 {
64  struct nl_sock *socket;
65  int err;
66 
67  socket = nl_cli_alloc_socket();
68  if (socket == NULL) {
69  nl_cli_fatal(ENOBUFS, "Unable to allocate netlink socket");
70  }
71 
72  /*
73  * Disable sequence number checking.
74  * This is required to allow messages to be processed which were not requested by
75  * a preceding request message, e.g. netlink events.
76  */
78 
79  /* subscribe conntrack events */
80  nl_join_groups(socket, NF_NETLINK_CONNTRACK_NEW |
81  NF_NETLINK_CONNTRACK_UPDATE |
82  NF_NETLINK_CONNTRACK_DESTROY |
83  NF_NETLINK_CONNTRACK_EXP_NEW |
84  NF_NETLINK_CONNTRACK_EXP_UPDATE |
85  NF_NETLINK_CONNTRACK_EXP_DESTROY);
86 
87  nl_cli_connect(socket, NETLINK_NETFILTER);
88 
89  nl_socket_modify_cb(socket, NL_CB_VALID, NL_CB_CUSTOM, &nf_conntrack_event_callback, 0);
90 
91  while (1) {
92 
93  errno = 0;
94  if ((err = nl_recvmsgs_default(socket)) < 0) {
95  switch (errno) {
96  case ENOBUFS:
97  // just print warning
98  fprintf(stderr, "Lost events because of ENOBUFS\n");
99  break;
100  case EAGAIN:
101  case EINTR:
102  // continue reading
103  break;
104  default:
105  nl_cli_fatal(err, "Failed to receive: %s", nl_geterror(err));
106  }
107  }
108  }
109 }
@ NL_OK
Proceed with whatever would come next.
Definition: handlers.h:58
@ NL_CB_VALID
Message is valid.
Definition: handlers.h:89
@ NL_CB_CUSTOM
Customized handler specified by the user.
Definition: handlers.h:77
void nl_cli_fatal(int err, const char *fmt,...)
Print error message and quit application.
Definition: utils.c:71
struct nlmsghdr * nlmsg_hdr(struct nl_msg *n)
Return actual netlink message.
Definition: msg.c:536
void nl_object_dump(struct nl_object *obj, struct nl_dump_params *params)
Dump this object according to the specified parameters.
Definition: object.c:287
int nl_recvmsgs_default(struct nl_sock *sk)
Receive a set of message from a netlink socket using handlers in nl_sock.
Definition: nl.c:1087
void nl_join_groups(struct nl_sock *sk, int groups)
Join multicast groups (deprecated)
Definition: socket.c:527
void nl_socket_disable_seq_check(struct nl_sock *sk)
Disable sequence number checking.
Definition: socket.c:277
int nl_socket_modify_cb(struct nl_sock *sk, enum nl_cb_type type, enum nl_cb_kind kind, nl_recvmsg_msg_cb_t func, void *arg)
Modify the callback handler associated with the socket.
Definition: socket.c:765
@ NL_DUMP_DETAILS
Dump all attributes but no statistics.
Definition: types.h:17
Dumping parameters.
Definition: types.h:28
FILE * dp_fd
File descriptor the dumping output should go to.
Definition: types.h:77