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 */
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, 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 */
nlmsg_alloc_ifaddr(uint16_t type,uint16_t flags,struct ifaddrmsg * ifa)83 struct 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 */
nlmsg_alloc_ifinfo(uint16_t type,uint16_t flags,struct ifinfomsg * ifi)93 struct 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 */
nlmsg_alloc_rtmsg(uint16_t type,uint16_t flags,struct rtmsg * rt)103 struct 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 */
netlink_set_kernel_only(struct nl_sock * nl_sk)111 int 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 */
send_netlink_msg(struct nl_msg * msg,struct nl_cb * callbacks)127 void 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
145 cleanup:
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 */
send_ifaddrmsg(uint16_t type,uint16_t flags,struct ifaddrmsg * ifa,struct nl_cb * callbacks)157 void 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 */
netlink_sendrecv(struct nl_msg * msg)173 int 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