libnl  3.5.0
nf-ct-events.c
1 /* SPDX-License-Identifier: LGPL-2.1-only */
2 /*
3  * src/nf-ct-events.c Listen on Conntrack Events
4  *
5  * This library is free software; you can redistribute it and/or
6  * modify it under the terms of the GNU Lesser General Public
7  * License as published by the Free Software Foundation version 2.1
8  * of the License.
9  *
10  * Copyright (c) 2018 Avast software
11  */
12 
13 #include <netlink/cli/utils.h>
14 #include <netlink/cli/ct.h>
15 
16 #include <linux/netlink.h>
17 #include <linux/netfilter/nfnetlink.h>
18 #include <linux/netfilter/nfnetlink_conntrack.h>
19 
21 {
22  int ce_refcnt;
23  struct nl_object_ops * ce_ops;
24  struct nl_cache * ce_cache;
25  struct nl_list_head ce_list;
26  int ce_msgtype;
27  int ce_flags;
28  uint64_t ce_mask;
29 };
30 
31 static void nf_conntrack_parse_callback(struct nl_object *obj, void *opaque)
32 {
33  struct nl_dump_params params = {
34  .dp_fd = stdout,
35  .dp_type = NL_DUMP_DETAILS,
36  };
37 
38  nl_object_dump(obj, &params);
39 }
40 
41 static int nf_conntrack_event_callback(struct nl_msg *msg, void *opaque)
42 {
43  int err;
44  struct nlmsghdr *hdr = nlmsg_hdr(msg);
45 
46  enum cntl_msg_types type = (enum cntl_msg_types) NFNL_MSG_TYPE(hdr->nlmsg_type);
47 
48  int flags = hdr->nlmsg_flags;
49 
50  if (type == IPCTNL_MSG_CT_DELETE) {
51  printf("DELETE ");
52  } else if (type == IPCTNL_MSG_CT_NEW) {
53  if (flags & (NLM_F_CREATE|NLM_F_EXCL)) {
54  printf("NEW ");
55  } else {
56  printf("UPDATE ");
57  }
58  } else {
59  printf("UNKNOWN ");
60  }
61 
62  if ((err = nl_msg_parse(msg, &nf_conntrack_parse_callback, opaque)) < 0) {
63  nl_cli_fatal(err, "nl_msg_parse: %s", nl_geterror(err));
64  }
65  /* Continue with next event */
66  return NL_OK;
67 }
68 
69 int main(int argc, char *argv[])
70 {
71  struct nl_sock *socket;
72  int err;
73 
74  socket = nl_cli_alloc_socket();
75  if (socket == NULL) {
76  nl_cli_fatal(ENOBUFS, "Unable to allocate netlink socket");
77  }
78 
79  /*
80  * Disable sequence number checking.
81  * This is required to allow messages to be processed which were not requested by
82  * a preceding request message, e.g. netlink events.
83  */
85 
86  /* subscribe conntrack events */
87  nl_join_groups(socket, NF_NETLINK_CONNTRACK_NEW |
88  NF_NETLINK_CONNTRACK_UPDATE |
89  NF_NETLINK_CONNTRACK_DESTROY |
90  NF_NETLINK_CONNTRACK_EXP_NEW |
91  NF_NETLINK_CONNTRACK_EXP_UPDATE |
92  NF_NETLINK_CONNTRACK_EXP_DESTROY);
93 
94  nl_cli_connect(socket, NETLINK_NETFILTER);
95 
96  nl_socket_modify_cb(socket, NL_CB_VALID, NL_CB_CUSTOM, &nf_conntrack_event_callback, 0);
97 
98  while (1) {
99 
100  errno = 0;
101  if ((err = nl_recvmsgs_default(socket)) < 0) {
102  switch (errno) {
103  case ENOBUFS:
104  // just print warning
105  fprintf(stderr, "Lost events because of ENOBUFS\n");
106  break;
107  case EAGAIN:
108  case EINTR:
109  // continue reading
110  break;
111  default:
112  nl_cli_fatal(err, "Failed to receive: %s", nl_geterror(err));
113  }
114  }
115  }
116 }
FILE * dp_fd
File descriptor the dumping output should go to.
Definition: types.h:83
Customized handler specified by the user.
Definition: handlers.h:83
Dump all attributes but no statistics.
Definition: types.h:23
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:771
void nl_object_dump(struct nl_object *obj, struct nl_dump_params *params)
Dump this object according to the specified parameters.
Definition: object.c:289
void nl_socket_disable_seq_check(struct nl_sock *sk)
Disable sequence number checking.
Definition: socket.c:283
struct nlmsghdr * nlmsg_hdr(struct nl_msg *n)
Return actual netlink message.
Definition: msg.c:543
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:1094
Message is valid.
Definition: handlers.h:95
void nl_cli_fatal(int err, const char *fmt,...)
Print error message and quit application.
Definition: utils.c:78
Proceed with wathever would come next.
Definition: handlers.h:64
Dumping parameters.
Definition: types.h:33
void nl_join_groups(struct nl_sock *sk, int groups)
Join multicast groups (deprecated)
Definition: socket.c:533