1/*
2 * Copyright 2012 Daniel Drown <dan-android@drown.org>
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 * http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 *
16 * netlink_callbacks.c - generic callbacks for netlink responses
17 */
18#include <netinet/in.h>
19#include <net/if.h>
20
21#include <linux/rtnetlink.h>
22#include <netlink/handlers.h>
23#include <netlink/msg.h>
24
25/* function: ack_handler
26 * generic netlink callback for ack messages
27 * msg  - netlink message
28 * data - pointer to an int, stores the success code
29 */
30static int ack_handler(__attribute__((unused)) struct nl_msg *msg, void *data) {
31  int *retval = data;
32  *retval = 0;
33  return NL_OK;
34}
35
36/* function: error_handler
37 * generic netlink callback for error messages
38 * nla  - error source
39 * err  - netlink error message
40 * arg  - pointer to an int, stores the error code
41 */
42static int error_handler(__attribute__((unused)) struct sockaddr_nl *nla,
43                         struct nlmsgerr *err, void *arg) {
44  int *retval = arg;
45  if(err->error < 0) {
46    *retval = err->error;
47  } else {
48    *retval = 0; // NLMSG_ERROR used as reply type on no error
49  }
50  return NL_OK;
51}
52
53/* function: alloc_ack_callbacks
54 * allocates a set of netlink callbacks.  returns NULL on failure.  callbacks will modify retval with <0 meaning failure
55 * retval - shared state between caller and callback functions
56 */
57struct nl_cb *alloc_ack_callbacks(int *retval) {
58  struct nl_cb *callbacks;
59
60  callbacks = nl_cb_alloc(NL_CB_DEFAULT);
61  if(!callbacks) {
62    return NULL;
63  }
64  nl_cb_set(callbacks, NL_CB_ACK, NL_CB_CUSTOM, ack_handler, retval);
65  nl_cb_err(callbacks, NL_CB_CUSTOM, error_handler, retval);
66  return callbacks;
67}
68