1 /*
2 * lib/genl/genl.c Generic Netlink
3 *
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation version 2.1
7 * of the License.
8 *
9 * Copyright (c) 2003-2012 Thomas Graf <tgraf@suug.ch>
10 */
11
12 /**
13 * @defgroup genl Generic Netlink Library (libnl-genl)
14 *
15 * @{
16 */
17
18 #include <netlink-private/genl.h>
19 #include <netlink/netlink.h>
20 #include <netlink/genl/genl.h>
21 #include <netlink/utils.h>
22
23 /**
24 * @name Generic Netlink Socket
25 * @{
26 */
27
28 /**
29 * Connect a Generic Netlink socket
30 * @arg sk Unconnected Netlink socket
31 *
32 * This function expects a struct nl_socket object previously allocated via
33 * nl_socket_alloc(). It calls nl_connect() to create the local socket file
34 * descriptor and binds the socket to the \c NETLINK_GENERIC Netlink protocol.
35 *
36 * Using this function is equivalent to:
37 * @code
38 * nl_connect(sk, NETLINK_GENERIC);
39 * @endcode
40 *
41 * @see nl_connect()
42 *
43 * @return 0 on success or a negative error code.
44 */
genl_connect(struct nl_sock * sk)45 int genl_connect(struct nl_sock *sk)
46 {
47 return nl_connect(sk, NETLINK_GENERIC);
48 }
49
50 /** @} */
51
52 /**
53 * @name Sending Data
54 * @{
55 */
56
57 /**
58 * Send a Generic Netlink message consisting only of a header
59 * @arg sk Generic Netlink socket
60 * @arg family Numeric family identifier
61 * @arg cmd Numeric command identifier
62 * @arg version Interface version
63 * @arg flags Additional Netlink message flags (optional)
64 *
65 * This function is a shortcut for sending a Generic Netlink message without
66 * any message payload. The message will only consist of the Netlink and
67 * Generic Netlink headers. The header is constructed based on the specified
68 * parameters and passed on to nl_send_simple() to send it on the specified
69 * socket.
70 *
71 * @par Example:
72 * @code
73 * #include <netlink/genl/genl.h>
74 * #include <linux/genetlink.h>
75 *
76 * err = genl_send_simple(sk, GENL_ID_CTRL, CTRL_CMD_GETFAMILY, CTRL_VERSION,
77 * NLM_F_DUMP);
78 * @endcode
79 *
80 * @see nl_send_simple()
81 *
82 * @return 0 on success or a negative error code.
83 */
genl_send_simple(struct nl_sock * sk,int family,int cmd,int version,int flags)84 int genl_send_simple(struct nl_sock *sk, int family, int cmd,
85 int version, int flags)
86 {
87 struct genlmsghdr hdr = {
88 .cmd = cmd,
89 .version = version,
90 };
91
92 return nl_send_simple(sk, family, flags, &hdr, sizeof(hdr));
93 }
94
95 /** @} */
96
97 /**
98 * @name Message Parsing
99 * @{
100 */
101
102 /**
103 * Validate Generic Netlink message headers
104 * @arg nlh Pointer to Netlink message header
105 * @arg hdrlen Length of user header
106 *
107 * Verifies the integrity of the Netlink and Generic Netlink headers by
108 * enforcing the following requirements:
109 * - Valid Netlink message header (nlmsg_valid_hdr())
110 * - Presence of a complete Generic Netlink header
111 * - At least \c hdrlen bytes of payload included after the generic
112 * netlink header.
113 *
114 * @return A positive integer (true) if the headers are valid or
115 * 0 (false) if not.
116 */
genlmsg_valid_hdr(struct nlmsghdr * nlh,int hdrlen)117 int genlmsg_valid_hdr(struct nlmsghdr *nlh, int hdrlen)
118 {
119 struct genlmsghdr *ghdr;
120
121 if (!nlmsg_valid_hdr(nlh, GENL_HDRLEN))
122 return 0;
123
124 ghdr = nlmsg_data(nlh);
125 if (genlmsg_len(ghdr) < NLMSG_ALIGN(hdrlen))
126 return 0;
127
128 return 1;
129 }
130
131 /**
132 * Validate Generic Netlink message including attributes
133 * @arg nlh Pointer to Netlink message header
134 * @arg hdrlen Length of user header
135 * @arg maxtype Maximum attribtue id expected
136 * @arg policy Attribute validation policy
137 *
138 * Verifies the validity of the Netlink and Generic Netlink headers using
139 * genlmsg_valid_hdr() and calls nla_validate() on the message payload to
140 * verify the integrity of eventual attributes.
141 *
142 * @note You may call genlmsg_parse() directly to perform validation and
143 * parsing in a single step.
144 *
145 * @see genlmsg_valid_hdr()
146 * @see nla_validate()
147 * @see genlmsg_parse()
148 *
149 * @return 0 on success or a negative error code.
150 */
genlmsg_validate(struct nlmsghdr * nlh,int hdrlen,int maxtype,struct nla_policy * policy)151 int genlmsg_validate(struct nlmsghdr *nlh, int hdrlen, int maxtype,
152 struct nla_policy *policy)
153 {
154 struct genlmsghdr *ghdr;
155
156 if (!genlmsg_valid_hdr(nlh, hdrlen))
157 return -NLE_MSG_TOOSHORT;
158
159 ghdr = nlmsg_data(nlh);
160 return nla_validate(genlmsg_attrdata(ghdr, hdrlen),
161 genlmsg_attrlen(ghdr, hdrlen), maxtype, policy);
162 }
163
164 /**
165 * Parse Generic Netlink message including attributes
166 * @arg nlh Pointer to Netlink message header
167 * @arg hdrlen Length of user header
168 * @arg tb Array to store parsed attributes
169 * @arg maxtype Maximum attribute id expected
170 * @arg policy Attribute validation policy
171 *
172 * Verifies the validity of the Netlink and Generic Netlink headers using
173 * genlmsg_valid_hdr() and calls nla_parse() on the message payload to
174 * parse eventual attributes.
175 *
176 * @par Example:
177 * @code
178 * struct nlattr *attrs[MY_TYPE_MAX+1];
179 *
180 * if ((err = genlsmg_parse(nlmsg_nlh(msg), sizeof(struct my_hdr), attrs,
181 * MY_TYPE_MAX, attr_policy)) < 0)
182 * // ERROR
183 * @endcode
184 *
185 * @see genlmsg_valid_hdr()
186 * @see genlmsg_validate()
187 * @see nla_parse()
188 *
189 * @return 0 on success or a negative error code.
190 */
genlmsg_parse(struct nlmsghdr * nlh,int hdrlen,struct nlattr * tb[],int maxtype,struct nla_policy * policy)191 int genlmsg_parse(struct nlmsghdr *nlh, int hdrlen, struct nlattr *tb[],
192 int maxtype, struct nla_policy *policy)
193 {
194 struct genlmsghdr *ghdr;
195
196 if (!genlmsg_valid_hdr(nlh, hdrlen))
197 return -NLE_MSG_TOOSHORT;
198
199 ghdr = nlmsg_data(nlh);
200 return nla_parse(tb, maxtype, genlmsg_attrdata(ghdr, hdrlen),
201 genlmsg_attrlen(ghdr, hdrlen), policy);
202 }
203
204 /**
205 * Return pointer to Generic Netlink header
206 * @arg nlh Netlink message header
207 *
208 * @return Pointer to Generic Netlink message header
209 */
genlmsg_hdr(struct nlmsghdr * nlh)210 struct genlmsghdr *genlmsg_hdr(struct nlmsghdr *nlh)
211 {
212 return nlmsg_data(nlh);
213 }
214
215 /**
216 * Return length of message payload including user header
217 * @arg gnlh Generic Netlink message header
218 *
219 * @see genlmsg_data()
220 *
221 * @return Length of user payload including an eventual user header in
222 * number of bytes.
223 */
genlmsg_len(const struct genlmsghdr * gnlh)224 int genlmsg_len(const struct genlmsghdr *gnlh)
225 {
226 const struct nlmsghdr *nlh;
227
228 nlh = (const struct nlmsghdr *)((const unsigned char *) gnlh - NLMSG_HDRLEN);
229 return (nlh->nlmsg_len - GENL_HDRLEN - NLMSG_HDRLEN);
230 }
231
232
233 /**
234 * Return pointer to user header
235 * @arg gnlh Generic Netlink message header
236 *
237 * Calculates the pointer to the user header based on the pointer to
238 * the Generic Netlink message header.
239 *
240 * @return Pointer to the user header
241 */
genlmsg_user_hdr(const struct genlmsghdr * gnlh)242 void *genlmsg_user_hdr(const struct genlmsghdr *gnlh)
243 {
244 return genlmsg_data(gnlh);
245 }
246
247 /**
248 * Return pointer to user data
249 * @arg gnlh Generic netlink message header
250 * @arg hdrlen Length of user header
251 *
252 * Calculates the pointer to the user data based on the pointer to
253 * the Generic Netlink message header.
254 *
255 * @see genlmsg_user_datalen()
256 *
257 * @return Pointer to the user data
258 */
genlmsg_user_data(const struct genlmsghdr * gnlh,const int hdrlen)259 void *genlmsg_user_data(const struct genlmsghdr *gnlh, const int hdrlen)
260 {
261 return genlmsg_user_hdr(gnlh) + NLMSG_ALIGN(hdrlen);
262 }
263
264 /**
265 * Return length of user data
266 * @arg gnlh Generic Netlink message header
267 * @arg hdrlen Length of user header
268 *
269 * @see genlmsg_user_data()
270 *
271 * @return Length of user data in bytes
272 */
genlmsg_user_datalen(const struct genlmsghdr * gnlh,const int hdrlen)273 int genlmsg_user_datalen(const struct genlmsghdr *gnlh, const int hdrlen)
274 {
275 return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen);
276 }
277
278 /**
279 * Return pointer to message attributes
280 * @arg gnlh Generic Netlink message header
281 * @arg hdrlen Length of user header
282 *
283 * @see genlmsg_attrlen()
284 *
285 * @return Pointer to the start of the message's attributes section.
286 */
genlmsg_attrdata(const struct genlmsghdr * gnlh,int hdrlen)287 struct nlattr *genlmsg_attrdata(const struct genlmsghdr *gnlh, int hdrlen)
288 {
289 return genlmsg_user_data(gnlh, hdrlen);
290 }
291
292 /**
293 * Return length of message attributes
294 * @arg gnlh Generic Netlink message header
295 * @arg hdrlen Length of user header
296 *
297 * @see genlmsg_attrdata()
298 *
299 * @return Length of the message section containing attributes in number
300 * of bytes.
301 */
genlmsg_attrlen(const struct genlmsghdr * gnlh,int hdrlen)302 int genlmsg_attrlen(const struct genlmsghdr *gnlh, int hdrlen)
303 {
304 return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen);
305 }
306
307 /** @} */
308
309 /**
310 * @name Message Construction
311 * @{
312 */
313
314 /**
315 * Add Generic Netlink headers to Netlink message
316 * @arg msg Netlink message object
317 * @arg port Netlink port or NL_AUTO_PORT
318 * @arg seq Sequence number of message or NL_AUTO_SEQ
319 * @arg family Numeric family identifier
320 * @arg hdrlen Length of user header
321 * @arg flags Additional Netlink message flags (optional)
322 * @arg cmd Numeric command identifier
323 * @arg version Interface version
324 *
325 * Calls nlmsg_put() on the specified message object to reserve space for
326 * the Netlink header, the Generic Netlink header, and a user header of
327 * specified length. Fills out the header fields with the specified
328 * parameters.
329 *
330 * @par Example:
331 * @code
332 * struct nl_msg *msg;
333 * struct my_hdr *user_hdr;
334 *
335 * if (!(msg = nlmsg_alloc()))
336 * // ERROR
337 *
338 * user_hdr = genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, family_id,
339 * sizeof(struct my_hdr), 0, MY_CMD_FOO, 0);
340 * if (!user_hdr)
341 * // ERROR
342 * @endcode
343 *
344 * @see nlmsg_put()
345 *
346 * Returns Pointer to user header or NULL if an error occurred.
347 */
genlmsg_put(struct nl_msg * msg,uint32_t port,uint32_t seq,int family,int hdrlen,int flags,uint8_t cmd,uint8_t version)348 void *genlmsg_put(struct nl_msg *msg, uint32_t port, uint32_t seq, int family,
349 int hdrlen, int flags, uint8_t cmd, uint8_t version)
350 {
351 struct nlmsghdr *nlh;
352 struct genlmsghdr hdr = {
353 .cmd = cmd,
354 .version = version,
355 };
356
357 nlh = nlmsg_put(msg, port, seq, family, GENL_HDRLEN + hdrlen, flags);
358 if (nlh == NULL)
359 return NULL;
360
361 memcpy(nlmsg_data(nlh), &hdr, sizeof(hdr));
362 NL_DBG(2, "msg %p: Added generic netlink header cmd=%d version=%d\n",
363 msg, cmd, version);
364
365 return nlmsg_data(nlh) + GENL_HDRLEN;
366 }
367
368 /** @} */
369
370 /**
371 * @name Deprecated
372 * @{
373 */
374
375 /**
376 * Return pointer to message payload
377 * @arg gnlh Generic Netlink message header
378 *
379 * @deprecated This function has been deprecated due to inability to specify
380 * the length of the user header. Use genlmsg_user_hdr()
381 * respectively genlmsg_user_data().
382 *
383 * @return Pointer to payload section
384 */
genlmsg_data(const struct genlmsghdr * gnlh)385 void *genlmsg_data(const struct genlmsghdr *gnlh)
386 {
387 return ((unsigned char *) gnlh + GENL_HDRLEN);
388 }
389
390 /** @} */
391 /** @} */
392