libnl  3.5.0
genl.c
1 /* SPDX-License-Identifier: LGPL-2.1-only */
2 /*
3  * lib/genl/genl.c Generic Netlink
4  *
5  * This library is free software; you can redistribute it and/or
6  * modify it under the terms of the GNU Lesser General Public
7  * License as published by the Free Software Foundation version 2.1
8  * of the License.
9  *
10  * Copyright (c) 2003-2012 Thomas Graf <tgraf@suug.ch>
11  */
12 
13 /**
14  * @defgroup genl Generic Netlink Library (libnl-genl)
15  *
16  * @{
17  */
18 
19 #include <netlink-private/genl.h>
20 #include <netlink/netlink.h>
21 #include <netlink/genl/genl.h>
22 #include <netlink/utils.h>
23 
24 /**
25  * @name Generic Netlink Socket
26  * @{
27  */
28 
29 /**
30  * Connect a Generic Netlink socket
31  * @arg sk Unconnected Netlink socket
32  *
33  * This function expects a struct nl_socket object previously allocated via
34  * nl_socket_alloc(). It calls nl_connect() to create the local socket file
35  * descriptor and binds the socket to the \c NETLINK_GENERIC Netlink protocol.
36  *
37  * Using this function is equivalent to:
38  * @code
39  * nl_connect(sk, NETLINK_GENERIC);
40  * @endcode
41  *
42  * @see nl_connect()
43  *
44  * @return 0 on success or a negative error code.
45  */
46 int genl_connect(struct nl_sock *sk)
47 {
48  return nl_connect(sk, NETLINK_GENERIC);
49 }
50 
51 /** @} */
52 
53 /**
54  * @name Sending Data
55  * @{
56  */
57 
58 /**
59  * Send a Generic Netlink message consisting only of a header
60  * @arg sk Generic Netlink socket
61  * @arg family Numeric family identifier
62  * @arg cmd Numeric command identifier
63  * @arg version Interface version
64  * @arg flags Additional Netlink message flags (optional)
65  *
66  * This function is a shortcut for sending a Generic Netlink message without
67  * any message payload. The message will only consist of the Netlink and
68  * Generic Netlink headers. The header is constructed based on the specified
69  * parameters and passed on to nl_send_simple() to send it on the specified
70  * socket.
71  *
72  * @par Example:
73  * @code
74  * #include <netlink/genl/genl.h>
75  * #include <linux/genetlink.h>
76  *
77  * err = genl_send_simple(sk, GENL_ID_CTRL, CTRL_CMD_GETFAMILY, CTRL_VERSION,
78  * NLM_F_DUMP);
79  * @endcode
80  *
81  * @see nl_send_simple()
82  *
83  * @return 0 on success or a negative error code. Due to a bug, this function
84  * returns the number of bytes sent. Treat any non-negative number as success.
85  */
86 int genl_send_simple(struct nl_sock *sk, int family, int cmd,
87  int version, int flags)
88 {
89  struct genlmsghdr hdr = {
90  .cmd = cmd,
91  .version = version,
92  };
93 
94  return nl_send_simple(sk, family, flags, &hdr, sizeof(hdr));
95 }
96 
97 /** @} */
98 
99 /**
100  * @name Message Parsing
101  * @{
102  */
103 
104 /**
105  * Validate Generic Netlink message headers
106  * @arg nlh Pointer to Netlink message header
107  * @arg hdrlen Length of user header
108  *
109  * Verifies the integrity of the Netlink and Generic Netlink headers by
110  * enforcing the following requirements:
111  * - Valid Netlink message header (nlmsg_valid_hdr())
112  * - Presence of a complete Generic Netlink header
113  * - At least \c hdrlen bytes of payload included after the generic
114  * netlink header.
115  *
116  * @return A positive integer (true) if the headers are valid or
117  * 0 (false) if not.
118  */
119 int genlmsg_valid_hdr(struct nlmsghdr *nlh, int hdrlen)
120 {
121  struct genlmsghdr *ghdr;
122 
123  if (!nlmsg_valid_hdr(nlh, GENL_HDRLEN))
124  return 0;
125 
126  ghdr = nlmsg_data(nlh);
127  if (genlmsg_len(ghdr) < NLMSG_ALIGN(hdrlen))
128  return 0;
129 
130  return 1;
131 }
132 
133 /**
134  * Validate Generic Netlink message including attributes
135  * @arg nlh Pointer to Netlink message header
136  * @arg hdrlen Length of user header
137  * @arg maxtype Maximum attribtue id expected
138  * @arg policy Attribute validation policy
139  *
140  * Verifies the validity of the Netlink and Generic Netlink headers using
141  * genlmsg_valid_hdr() and calls nla_validate() on the message payload to
142  * verify the integrity of eventual attributes.
143  *
144  * @note You may call genlmsg_parse() directly to perform validation and
145  * parsing in a single step.
146  *
147  * @see genlmsg_valid_hdr()
148  * @see nla_validate()
149  * @see genlmsg_parse()
150  *
151  * @return 0 on success or a negative error code.
152  */
153 int genlmsg_validate(struct nlmsghdr *nlh, int hdrlen, int maxtype,
154  const struct nla_policy *policy)
155 {
156  struct genlmsghdr *ghdr;
157 
158  if (!genlmsg_valid_hdr(nlh, hdrlen))
159  return -NLE_MSG_TOOSHORT;
160 
161  ghdr = nlmsg_data(nlh);
162  return nla_validate(genlmsg_attrdata(ghdr, hdrlen),
163  genlmsg_attrlen(ghdr, hdrlen), maxtype, policy);
164 }
165 
166 /**
167  * Parse Generic Netlink message including attributes
168  * @arg nlh Pointer to Netlink message header
169  * @arg hdrlen Length of user header
170  * @arg tb Array to store parsed attributes
171  * @arg maxtype Maximum attribute id expected
172  * @arg policy Attribute validation policy
173  *
174  * Verifies the validity of the Netlink and Generic Netlink headers using
175  * genlmsg_valid_hdr() and calls nla_parse() on the message payload to
176  * parse eventual attributes.
177  *
178  * @par Example:
179  * @code
180  * struct nlattr *attrs[MY_TYPE_MAX+1];
181  *
182  * if ((err = genlmsg_parse(nlmsg_hdr(msg), sizeof(struct my_hdr), attrs,
183  * MY_TYPE_MAX, attr_policy)) < 0)
184  * // ERROR
185  * @endcode
186  *
187  * @see genlmsg_valid_hdr()
188  * @see genlmsg_validate()
189  * @see nla_parse()
190  *
191  * @return 0 on success or a negative error code.
192  */
193 int genlmsg_parse(struct nlmsghdr *nlh, int hdrlen, struct nlattr *tb[],
194  int maxtype, const struct nla_policy *policy)
195 {
196  struct genlmsghdr *ghdr;
197 
198  if (!genlmsg_valid_hdr(nlh, hdrlen))
199  return -NLE_MSG_TOOSHORT;
200 
201  ghdr = nlmsg_data(nlh);
202  return nla_parse(tb, maxtype, genlmsg_attrdata(ghdr, hdrlen),
203  genlmsg_attrlen(ghdr, hdrlen), policy);
204 }
205 
206 /**
207  * Return pointer to Generic Netlink header
208  * @arg nlh Netlink message header
209  *
210  * @return Pointer to Generic Netlink message header
211  */
212 struct genlmsghdr *genlmsg_hdr(struct nlmsghdr *nlh)
213 {
214  return nlmsg_data(nlh);
215 }
216 
217 /**
218  * Return length of message payload including user header
219  * @arg gnlh Generic Netlink message header
220  *
221  * @see genlmsg_data()
222  *
223  * @return Length of user payload including an eventual user header in
224  * number of bytes.
225  */
226 int genlmsg_len(const struct genlmsghdr *gnlh)
227 {
228  const struct nlmsghdr *nlh;
229 
230  nlh = (const struct nlmsghdr *)((const unsigned char *) gnlh - NLMSG_HDRLEN);
231  return (nlh->nlmsg_len - GENL_HDRLEN - NLMSG_HDRLEN);
232 }
233 
234 
235 /**
236  * Return pointer to user header
237  * @arg gnlh Generic Netlink message header
238  *
239  * Calculates the pointer to the user header based on the pointer to
240  * the Generic Netlink message header.
241  *
242  * @return Pointer to the user header
243  */
244 void *genlmsg_user_hdr(const struct genlmsghdr *gnlh)
245 {
246  return genlmsg_data(gnlh);
247 }
248 
249 /**
250  * Return pointer to user data
251  * @arg gnlh Generic netlink message header
252  * @arg hdrlen Length of user header
253  *
254  * Calculates the pointer to the user data based on the pointer to
255  * the Generic Netlink message header.
256  *
257  * @see genlmsg_user_datalen()
258  *
259  * @return Pointer to the user data
260  */
261 void *genlmsg_user_data(const struct genlmsghdr *gnlh, const int hdrlen)
262 {
263  return (char *) genlmsg_user_hdr(gnlh) + NLMSG_ALIGN(hdrlen);
264 }
265 
266 /**
267  * Return length of user data
268  * @arg gnlh Generic Netlink message header
269  * @arg hdrlen Length of user header
270  *
271  * @see genlmsg_user_data()
272  *
273  * @return Length of user data in bytes
274  */
275 int genlmsg_user_datalen(const struct genlmsghdr *gnlh, const int hdrlen)
276 {
277  return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen);
278 }
279 
280 /**
281  * Return pointer to message attributes
282  * @arg gnlh Generic Netlink message header
283  * @arg hdrlen Length of user header
284  *
285  * @see genlmsg_attrlen()
286  *
287  * @return Pointer to the start of the message's attributes section.
288  */
289 struct nlattr *genlmsg_attrdata(const struct genlmsghdr *gnlh, int hdrlen)
290 {
291  return genlmsg_user_data(gnlh, hdrlen);
292 }
293 
294 /**
295  * Return length of message attributes
296  * @arg gnlh Generic Netlink message header
297  * @arg hdrlen Length of user header
298  *
299  * @see genlmsg_attrdata()
300  *
301  * @return Length of the message section containing attributes in number
302  * of bytes.
303  */
304 int genlmsg_attrlen(const struct genlmsghdr *gnlh, int hdrlen)
305 {
306  return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen);
307 }
308 
309 /** @} */
310 
311 /**
312  * @name Message Construction
313  * @{
314  */
315 
316 /**
317  * Add Generic Netlink headers to Netlink message
318  * @arg msg Netlink message object
319  * @arg port Netlink port or NL_AUTO_PORT
320  * @arg seq Sequence number of message or NL_AUTO_SEQ
321  * @arg family Numeric family identifier
322  * @arg hdrlen Length of user header
323  * @arg flags Additional Netlink message flags (optional)
324  * @arg cmd Numeric command identifier
325  * @arg version Interface version
326  *
327  * Calls nlmsg_put() on the specified message object to reserve space for
328  * the Netlink header, the Generic Netlink header, and a user header of
329  * specified length. Fills out the header fields with the specified
330  * parameters.
331  *
332  * @par Example:
333  * @code
334  * struct nl_msg *msg;
335  * struct my_hdr *user_hdr;
336  *
337  * if (!(msg = nlmsg_alloc()))
338  * // ERROR
339  *
340  * user_hdr = genlmsg_put(msg, NL_AUTO_PORT, NL_AUTO_SEQ, family_id,
341  * sizeof(struct my_hdr), 0, MY_CMD_FOO, 0);
342  * if (!user_hdr)
343  * // ERROR
344  * @endcode
345  *
346  * @see nlmsg_put()
347  *
348  * Returns Pointer to user header or NULL if an error occurred.
349  */
350 void *genlmsg_put(struct nl_msg *msg, uint32_t port, uint32_t seq, int family,
351  int hdrlen, int flags, uint8_t cmd, uint8_t version)
352 {
353  struct nlmsghdr *nlh;
354  struct genlmsghdr hdr = {
355  .cmd = cmd,
356  .version = version,
357  };
358 
359  nlh = nlmsg_put(msg, port, seq, family, GENL_HDRLEN + hdrlen, flags);
360  if (nlh == NULL)
361  return NULL;
362 
363  memcpy(nlmsg_data(nlh), &hdr, sizeof(hdr));
364  NL_DBG(2, "msg %p: Added generic netlink header cmd=%d version=%d\n",
365  msg, cmd, version);
366 
367  return (char *) nlmsg_data(nlh) + GENL_HDRLEN;
368 }
369 
370 /** @} */
371 
372 /**
373  * @name Deprecated
374  * @{
375  */
376 
377 /**
378  * Return pointer to message payload
379  * @arg gnlh Generic Netlink message header
380  *
381  * @deprecated This function has been deprecated due to inability to specify
382  * the length of the user header. Use genlmsg_user_hdr()
383  * respectively genlmsg_user_data().
384  *
385  * @return Pointer to payload section
386  */
387 void *genlmsg_data(const struct genlmsghdr *gnlh)
388 {
389  return ((unsigned char *) gnlh + GENL_HDRLEN);
390 }
391 
392 /** @} */
393 /** @} */
int nla_parse(struct nlattr *tb[], int maxtype, struct nlattr *head, int len, const struct nla_policy *policy)
Create attribute index based on a stream of attributes.
Definition: attr.c:243
void * genlmsg_user_hdr(const struct genlmsghdr *gnlh)
Return pointer to user header.
Definition: genl.c:244
void * nlmsg_data(const struct nlmsghdr *nlh)
Return pointer to message payload.
Definition: msg.c:107
int genlmsg_parse(struct nlmsghdr *nlh, int hdrlen, struct nlattr *tb[], int maxtype, const struct nla_policy *policy)
Parse Generic Netlink message including attributes.
Definition: genl.c:193
Attribute validation policy.
Definition: attr.h:69
int genl_connect(struct nl_sock *sk)
Connect a Generic Netlink socket.
Definition: genl.c:46
int genlmsg_validate(struct nlmsghdr *nlh, int hdrlen, int maxtype, const struct nla_policy *policy)
Validate Generic Netlink message including attributes.
Definition: genl.c:153
void * genlmsg_put(struct nl_msg *msg, uint32_t port, uint32_t seq, int family, int hdrlen, int flags, uint8_t cmd, uint8_t version)
Add Generic Netlink headers to Netlink message.
Definition: genl.c:350
int genlmsg_user_datalen(const struct genlmsghdr *gnlh, const int hdrlen)
Return length of user data.
Definition: genl.c:275
int genl_send_simple(struct nl_sock *sk, int family, int cmd, int version, int flags)
Send a Generic Netlink message consisting only of a header.
Definition: genl.c:86
int nl_connect(struct nl_sock *sk, int protocol)
Create file descriptor and bind socket.
Definition: nl.c:104
struct nlmsghdr * nlmsg_put(struct nl_msg *n, uint32_t pid, uint32_t seq, int type, int payload, int flags)
Add a netlink message header to a netlink message.
Definition: msg.c:510
struct nlattr * genlmsg_attrdata(const struct genlmsghdr *gnlh, int hdrlen)
Return pointer to message attributes.
Definition: genl.c:289
struct genlmsghdr * genlmsg_hdr(struct nlmsghdr *nlh)
Return pointer to Generic Netlink header.
Definition: genl.c:212
int genlmsg_attrlen(const struct genlmsghdr *gnlh, int hdrlen)
Return length of message attributes.
Definition: genl.c:304
void * genlmsg_data(const struct genlmsghdr *gnlh)
Return pointer to message payload.
Definition: genl.c:387
int nl_send_simple(struct nl_sock *sk, int type, int flags, void *buf, size_t size)
Construct and transmit a Netlink message.
Definition: nl.c:581
int genlmsg_len(const struct genlmsghdr *gnlh)
Return length of message payload including user header.
Definition: genl.c:226
int genlmsg_valid_hdr(struct nlmsghdr *nlh, int hdrlen)
Validate Generic Netlink message headers.
Definition: genl.c:119
int nla_validate(const struct nlattr *head, int len, int maxtype, const struct nla_policy *policy)
Validate a stream of attributes.
Definition: attr.c:295
void * genlmsg_user_data(const struct genlmsghdr *gnlh, const int hdrlen)
Return pointer to user data.
Definition: genl.c:261