1/*
2 * Copyright 2012 Daniel Drown
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_msg.c - send an ifaddrmsg/ifinfomsg/rtmsg via netlink
17 */
18
19#include <netinet/in.h>
20#include <linux/netlink.h>
21#include <linux/rtnetlink.h>
22#include <string.h>
23#include <errno.h>
24
25#include <netlink-local.h>
26#include <netlink-types.h>
27#include <netlink/socket.h>
28#include <netlink/netlink.h>
29#include <netlink/msg.h>
30
31#include "netlink_msg.h"
32#include "netlink_callbacks.h"
33
34/* function: family_size
35 * returns the size of the address structure for the given family, or 0 on error
36 * family - AF_INET or AF_INET6
37 */
38size_t inet_family_size(int family) {
39  if(family == AF_INET) {
40    return sizeof(struct in_addr);
41  } else if(family == AF_INET6) {
42    return sizeof(struct in6_addr);
43  } else {
44    return 0;
45  }
46}
47
48/* function: nlmsg_alloc_generic
49 * allocates a netlink message with the given struct inside of it. returns NULL on failure
50 * type           - netlink message type
51 * flags          - netlink message flags
52 * payload_struct - pointer to a struct to add to netlink message
53 * payload_len    - bytelength of structure
54 */
55struct nl_msg *nlmsg_alloc_generic(uint16_t type, uint16_t flags, void *payload_struct, size_t payload_len) {
56  struct nl_msg *msg;
57
58  msg = nlmsg_alloc();
59  if(!msg) {
60    return NULL;
61  }
62
63  if ((sizeof(struct nl_msg) + payload_len) > msg->nm_size) {
64    nlmsg_free(msg);
65    return NULL;
66  }
67
68  msg->nm_nlh->nlmsg_len = NLMSG_LENGTH(payload_len);
69  msg->nm_nlh->nlmsg_flags = flags;
70  msg->nm_nlh->nlmsg_type = type;
71
72  memcpy(nlmsg_data(msg->nm_nlh), payload_struct, payload_len);
73
74  return msg;
75}
76
77/* function: nlmsg_alloc_ifaddr
78 * allocates a netlink message with a struct ifaddrmsg inside of it. returns NULL on failure
79 * type  - netlink message type
80 * flags - netlink message flags
81 * ifa   - ifaddrmsg to copy into the new netlink message
82 */
83struct nl_msg *nlmsg_alloc_ifaddr(uint16_t type, uint16_t flags, struct ifaddrmsg *ifa) {
84  return nlmsg_alloc_generic(type, flags, ifa, sizeof(*ifa));
85}
86
87/* function: nlmsg_alloc_ifinfo
88 * allocates a netlink message with a struct ifinfomsg inside of it. returns NULL on failure
89 * type  - netlink message type
90 * flags - netlink message flags
91 * ifi   - ifinfomsg to copy into the new netlink message
92 */
93struct nl_msg *nlmsg_alloc_ifinfo(uint16_t type, uint16_t flags, struct ifinfomsg *ifi) {
94  return nlmsg_alloc_generic(type, flags, ifi, sizeof(*ifi));
95}
96
97/* function: nlmsg_alloc_rtmsg
98 * allocates a netlink message with a struct rtmsg inside of it. returns NULL on failure
99 * type  - netlink message type
100 * flags - netlink message flags
101 * rt    - rtmsg to copy into the new netlink message
102 */
103struct nl_msg *nlmsg_alloc_rtmsg(uint16_t type, uint16_t flags, struct rtmsg *rt) {
104  return nlmsg_alloc_generic(type, flags, rt, sizeof(*rt));
105}
106
107/* function: netlink_set_kernel_only
108 * sets a socket to receive messages only from the kernel
109 * sock - socket to connect
110 */
111int netlink_set_kernel_only(struct nl_sock *nl_sk) {
112  struct sockaddr_nl addr = { AF_NETLINK, 0, 0, 0 };
113
114  if (!nl_sk) {
115    return -EFAULT;
116  }
117
118  int sockfd = nl_socket_get_fd(nl_sk);
119  return connect(sockfd, (struct sockaddr *) &addr, sizeof(addr));
120}
121
122/* function: send_netlink_msg
123 * sends a netlink message, reads a response, and hands the response(s) to the callbacks
124 * msg       - netlink message to send
125 * callbacks - callbacks to use on responses
126 */
127void send_netlink_msg(struct nl_msg *msg, struct nl_cb *callbacks) {
128  struct nl_sock *nl_sk;
129
130  nl_sk = nl_socket_alloc();
131  if(!nl_sk)
132    goto cleanup;
133
134  if(nl_connect(nl_sk, NETLINK_ROUTE) != 0)
135    goto cleanup;
136
137  if(nl_send_auto_complete(nl_sk, msg) < 0)
138    goto cleanup;
139
140  if(netlink_set_kernel_only(nl_sk) < 0)
141    goto cleanup;
142
143  nl_recvmsgs(nl_sk, callbacks);
144
145cleanup:
146  if(nl_sk)
147    nl_socket_free(nl_sk);
148}
149
150/* function: send_ifaddrmsg
151 * sends a netlink/ifaddrmsg message and hands the responses to the callbacks
152 * type      - netlink message type
153 * flags     - netlink message flags
154 * ifa       - ifaddrmsg to send
155 * callbacks - callbacks to use with the responses
156 */
157void send_ifaddrmsg(uint16_t type, uint16_t flags, struct ifaddrmsg *ifa, struct nl_cb *callbacks) {
158  struct nl_msg *msg = NULL;
159
160  msg = nlmsg_alloc_ifaddr(type, flags, ifa);
161  if(!msg)
162    return;
163
164  send_netlink_msg(msg, callbacks);
165
166  nlmsg_free(msg);
167}
168
169/* function: netlink_sendrecv
170 * send a nl_msg and return an int status - only supports OK/ERROR responses
171 * msg - msg to send
172 */
173int netlink_sendrecv(struct nl_msg *msg) {
174  struct nl_cb *callbacks = NULL;
175  int retval = -EIO;
176
177  callbacks = alloc_ack_callbacks(&retval);
178  if(!callbacks) {
179    return -ENOMEM;
180  }
181
182  send_netlink_msg(msg, callbacks);
183
184  nl_cb_put(callbacks);
185
186  return retval;
187}
188