summaryrefslogtreecommitdiffstats
path: root/lib/genl/genl.c
blob: 055be919e1d35d71b0ce69f1880b2b1cfb5ec89b (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
/*
 * lib/genl/genl.c		Generic Netlink
 *
 *	This library is free software; you can redistribute it and/or
 *	modify it under the terms of the GNU Lesser General Public
 *	License as published by the Free Software Foundation version 2.1
 *	of the License.
 *
 * Copyright (c) 2003-2008 Thomas Graf <tgraf@suug.ch>
 */

/**
 * @defgroup genl Generic Netlink
 *
 * @par Message Format
 * @code
 *  <------- NLMSG_ALIGN(hlen) ------> <---- NLMSG_ALIGN(len) --->
 * +----------------------------+- - -+- - - - - - - - - - -+- - -+
 * |           Header           | Pad |       Payload       | Pad |
 * |      struct nlmsghdr       |     |                     |     |
 * +----------------------------+- - -+- - - - - - - - - - -+- - -+
 * @endcode
 * @code
 *  <-------- GENL_HDRLEN -------> <--- hdrlen -->
 *                                 <------- genlmsg_len(ghdr) ------>
 * +------------------------+- - -+---------------+- - -+------------+
 * | Generic Netlink Header | Pad | Family Header | Pad | Attributes |
 * |    struct genlmsghdr   |     |               |     |            |
 * +------------------------+- - -+---------------+- - -+------------+
 * genlmsg_data(ghdr)--------------^                     ^
 * genlmsg_attrdata(ghdr, hdrlen)-------------------------
 * @endcode
 *
 * @par Example
 * @code
 * #include <netlink/netlink.h>
 * #include <netlink/genl/genl.h>
 * #include <netlink/genl/ctrl.h>
 *
 * struct nl_sock *sock;
 * struct nl_msg *msg;
 * int family;
 *
 * // Allocate a new netlink socket
 * sock = nl_socket_alloc();
 *
 * // Connect to generic netlink socket on kernel side
 * genl_connect(sock);
 *
 * // Ask kernel to resolve family name to family id
 * family = genl_ctrl_resolve(sock, "generic_netlink_family_name");
 *
 * // Construct a generic netlink by allocating a new message, fill in
 * // the header and append a simple integer attribute.
 * msg = nlmsg_alloc();
 * genlmsg_put(msg, NL_AUTO_PID, NL_AUTO_SEQ, family, 0, NLM_F_ECHO,
 *             CMD_FOO_GET, FOO_VERSION);
 * nla_put_u32(msg, ATTR_FOO, 123);
 *
 * // Send message over netlink socket
 * nl_send_auto_complete(sock, msg);
 *
 * // Free message
 * nlmsg_free(msg);
 *
 * // Prepare socket to receive the answer by specifying the callback
 * // function to be called for valid messages.
 * nl_socket_modify_cb(sock, NL_CB_VALID, NL_CB_CUSTOM, parse_cb, NULL);
 *
 * // Wait for the answer and receive it
 * nl_recvmsgs_default(sock);
 *
 * static int parse_cb(struct nl_msg *msg, void *arg)
 * {
 *     struct nlmsghdr *nlh = nlmsg_hdr(msg);
 *     struct nlattr *attrs[ATTR_MAX+1];
 *
 *     // Validate message and parse attributes
 *     genlmsg_parse(nlh, 0, attrs, ATTR_MAX, policy);
 *
 *     if (attrs[ATTR_FOO]) {
 *         uint32_t value = nla_get_u32(attrs[ATTR_FOO]);
 *         ...
 *     }
 *
 *     return 0;
 * }
 * @endcode
 * @{
 */

#include <netlink-generic.h>
#include <netlink/netlink.h>
#include <netlink/genl/genl.h>
#include <netlink/utils.h>

/**
 * @name Socket Creating
 * @{
 */

int genl_connect(struct nl_sock *sk)
{
	return nl_connect(sk, NETLINK_GENERIC);
}

/** @} */

/**
 * @name Sending
 * @{
 */

/**
 * Send trivial generic netlink message
 * @arg sk		Netlink socket.
 * @arg family		Generic netlink family
 * @arg cmd		Command
 * @arg version		Version
 * @arg flags		Additional netlink message flags.
 *
 * Fills out a routing netlink request message and sends it out
 * using nl_send_simple().
 *
 * @return 0 on success or a negative error code.
 */
int genl_send_simple(struct nl_sock *sk, int family, int cmd,
		     int version, int flags)
{
	struct genlmsghdr hdr = {
		.cmd = cmd,
		.version = version,
	};

	return nl_send_simple(sk, family, flags, &hdr, sizeof(hdr));
}

/** @} */


/**
 * @name Message Parsing
 * @{
 */

int genlmsg_valid_hdr(struct nlmsghdr *nlh, int hdrlen)
{
	struct genlmsghdr *ghdr;

	if (!nlmsg_valid_hdr(nlh, GENL_HDRLEN))
		return 0;

	ghdr = nlmsg_data(nlh);
	if (genlmsg_len(ghdr) < NLMSG_ALIGN(hdrlen))
		return 0;

	return 1;
}

int genlmsg_validate(struct nlmsghdr *nlh, int hdrlen, int maxtype,
		   struct nla_policy *policy)
{
	struct genlmsghdr *ghdr;

	if (!genlmsg_valid_hdr(nlh, hdrlen))
		return -NLE_MSG_TOOSHORT;

	ghdr = nlmsg_data(nlh);
	return nla_validate(genlmsg_attrdata(ghdr, hdrlen),
			    genlmsg_attrlen(ghdr, hdrlen), maxtype, policy);
}

int genlmsg_parse(struct nlmsghdr *nlh, int hdrlen, struct nlattr *tb[],
		  int maxtype, struct nla_policy *policy)
{
	struct genlmsghdr *ghdr;

	if (!genlmsg_valid_hdr(nlh, hdrlen))
		return -NLE_MSG_TOOSHORT;

	ghdr = nlmsg_data(nlh);
	return nla_parse(tb, maxtype, genlmsg_attrdata(ghdr, hdrlen),
			 genlmsg_attrlen(ghdr, hdrlen), policy);
}

/**
 * Get head of message payload
 * @arg gnlh	genetlink messsage header
 */
void *genlmsg_data(const struct genlmsghdr *gnlh)
{
	return ((unsigned char *) gnlh + GENL_HDRLEN);
}

/**
 * Get lenght of message payload
 * @arg gnlh	genetlink message header
 */
int genlmsg_len(const struct genlmsghdr *gnlh)
{
	struct nlmsghdr *nlh = (struct nlmsghdr *)((unsigned char *)gnlh -
							NLMSG_HDRLEN);
	return (nlh->nlmsg_len - GENL_HDRLEN - NLMSG_HDRLEN);
}

/**
 * Get head of attribute data
 * @arg gnlh	generic netlink message header
 * @arg hdrlen	length of family specific header
 */
struct nlattr *genlmsg_attrdata(const struct genlmsghdr *gnlh, int hdrlen)
{
	return genlmsg_data(gnlh) + NLMSG_ALIGN(hdrlen);
}

/**
 * Get length of attribute data
 * @arg gnlh	generic netlink message header
 * @arg hdrlen	length of family specific header
 */
int genlmsg_attrlen(const struct genlmsghdr *gnlh, int hdrlen)
{
	return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen);
}

/** @} */

/**
 * @name Message Building
 * @{
 */

/**
 * Add generic netlink header to netlink message
 * @arg msg		netlink message
 * @arg pid		netlink process id or NL_AUTO_PID
 * @arg seq		sequence number of message or NL_AUTO_SEQ
 * @arg family		generic netlink family
 * @arg hdrlen		length of user specific header
 * @arg flags		message flags
 * @arg cmd		generic netlink command
 * @arg version		protocol version
 *
 * Returns pointer to user specific header.
 */
void *genlmsg_put(struct nl_msg *msg, uint32_t pid, uint32_t seq, int family,
		  int hdrlen, int flags, uint8_t cmd, uint8_t version)
{
	struct nlmsghdr *nlh;
	struct genlmsghdr hdr = {
		.cmd = cmd,
		.version = version,
	};

	nlh = nlmsg_put(msg, pid, seq, family, GENL_HDRLEN + hdrlen, flags);
	if (nlh == NULL)
		return NULL;

	memcpy(nlmsg_data(nlh), &hdr, sizeof(hdr));
	NL_DBG(2, "msg %p: Added generic netlink header cmd=%d version=%d\n",
	       msg, cmd, version);

	return nlmsg_data(nlh) + GENL_HDRLEN;
}

/** @} */

/** @} */