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