• Home
  • Line#
  • Scopes#
  • Navigate#
  • Raw
  • Download
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