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