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Sources/libnl-tiny/genl.c

  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) 2003-2008 Thomas Graf <tgraf@suug.ch>
 10  */
 11 
 12 /**
 13  * @defgroup genl Generic Netlink
 14  *
 15  * @par Message Format
 16  * @code
 17  *  <------- NLMSG_ALIGN(hlen) ------> <---- NLMSG_ALIGN(len) --->
 18  * +----------------------------+- - -+- - - - - - - - - - -+- - -+
 19  * |           Header           | Pad |       Payload       | Pad |
 20  * |      struct nlmsghdr       |     |                     |     |
 21  * +----------------------------+- - -+- - - - - - - - - - -+- - -+
 22  * @endcode
 23  * @code
 24  *  <-------- GENL_HDRLEN -------> <--- hdrlen -->
 25  *                                 <------- genlmsg_len(ghdr) ------>
 26  * +------------------------+- - -+---------------+- - -+------------+
 27  * | Generic Netlink Header | Pad | Family Header | Pad | Attributes |
 28  * |    struct genlmsghdr   |     |               |     |            |
 29  * +------------------------+- - -+---------------+- - -+------------+
 30  * genlmsg_data(ghdr)--------------^                     ^
 31  * genlmsg_attrdata(ghdr, hdrlen)-------------------------
 32  * @endcode
 33  *
 34  * @par Example
 35  * @code
 36  * #include <netlink/netlink.h>
 37  * #include <netlink/genl/genl.h>
 38  * #include <netlink/genl/ctrl.h>
 39  *
 40  * struct nl_sock *sock;
 41  * struct nl_msg *msg;
 42  * int family;
 43  *
 44  * // Allocate a new netlink socket
 45  * sock = nl_socket_alloc();
 46  *
 47  * // Connect to generic netlink socket on kernel side
 48  * genl_connect(sock);
 49  *
 50  * // Ask kernel to resolve family name to family id
 51  * family = genl_ctrl_resolve(sock, "generic_netlink_family_name");
 52  *
 53  * // Construct a generic netlink by allocating a new message, fill in
 54  * // the header and append a simple integer attribute.
 55  * msg = nlmsg_alloc();
 56  * genlmsg_put(msg, NL_AUTO_PID, NL_AUTO_SEQ, family, 0, NLM_F_ECHO,
 57  *             CMD_FOO_GET, FOO_VERSION);
 58  * nla_put_u32(msg, ATTR_FOO, 123);
 59  *
 60  * // Send message over netlink socket
 61  * nl_send_auto_complete(sock, msg);
 62  *
 63  * // Free message
 64  * nlmsg_free(msg);
 65  *
 66  * // Prepare socket to receive the answer by specifying the callback
 67  * // function to be called for valid messages.
 68  * nl_socket_modify_cb(sock, NL_CB_VALID, NL_CB_CUSTOM, parse_cb, NULL);
 69  *
 70  * // Wait for the answer and receive it
 71  * nl_recvmsgs_default(sock);
 72  *
 73  * static int parse_cb(struct nl_msg *msg, void *arg)
 74  * {
 75  *     struct nlmsghdr *nlh = nlmsg_hdr(msg);
 76  *     struct nlattr *attrs[ATTR_MAX+1];
 77  *
 78  *     // Validate message and parse attributes
 79  *     genlmsg_parse(nlh, 0, attrs, ATTR_MAX, policy);
 80  *
 81  *     if (attrs[ATTR_FOO]) {
 82  *         uint32_t value = nla_get_u32(attrs[ATTR_FOO]);
 83  *         ...
 84  *     }
 85  *
 86  *     return 0;
 87  * }
 88  * @endcode
 89  * @{
 90  */
 91 
 92 #include <netlink-generic.h>
 93 #include <netlink/netlink.h>
 94 #include <netlink/genl/genl.h>
 95 #include <netlink/utils.h>
 96 
 97 /**
 98  * @name Socket Creating
 99  * @{
100  */
101 
102 int genl_connect(struct nl_sock *sk)
103 {
104         return nl_connect(sk, NETLINK_GENERIC);
105 }
106 
107 /** @} */
108 
109 /**
110  * @name Sending
111  * @{
112  */
113 
114 /**
115  * Send trivial generic netlink message
116  * @arg sk              Netlink socket.
117  * @arg family          Generic netlink family
118  * @arg cmd             Command
119  * @arg version         Version
120  * @arg flags           Additional netlink message flags.
121  *
122  * Fills out a routing netlink request message and sends it out
123  * using nl_send_simple().
124  *
125  * @return 0 on success or a negative error code.
126  */
127 int genl_send_simple(struct nl_sock *sk, int family, int cmd,
128                      int version, int flags)
129 {
130         struct genlmsghdr hdr = {
131                 .cmd = cmd,
132                 .version = version,
133         };
134 
135         return nl_send_simple(sk, family, flags, &hdr, sizeof(hdr));
136 }
137 
138 /** @} */
139 
140 
141 /**
142  * @name Message Parsing
143  * @{
144  */
145 
146 int genlmsg_valid_hdr(struct nlmsghdr *nlh, int hdrlen)
147 {
148         struct genlmsghdr *ghdr;
149 
150         if (!nlmsg_valid_hdr(nlh, GENL_HDRLEN))
151                 return 0;
152 
153         ghdr = nlmsg_data(nlh);
154         if ((unsigned) genlmsg_len(ghdr) < NLMSG_ALIGN(hdrlen))
155                 return 0;
156 
157         return 1;
158 }
159 
160 int genlmsg_validate(struct nlmsghdr *nlh, int hdrlen, int maxtype,
161                    struct nla_policy *policy)
162 {
163         struct genlmsghdr *ghdr;
164 
165         if (!genlmsg_valid_hdr(nlh, hdrlen))
166                 return -NLE_MSG_TOOSHORT;
167 
168         ghdr = nlmsg_data(nlh);
169         return nla_validate(genlmsg_attrdata(ghdr, hdrlen),
170                             genlmsg_attrlen(ghdr, hdrlen), maxtype, policy);
171 }
172 
173 int genlmsg_parse(struct nlmsghdr *nlh, int hdrlen, struct nlattr *tb[],
174                   int maxtype, struct nla_policy *policy)
175 {
176         struct genlmsghdr *ghdr;
177 
178         if (!genlmsg_valid_hdr(nlh, hdrlen))
179                 return -NLE_MSG_TOOSHORT;
180 
181         ghdr = nlmsg_data(nlh);
182         return nla_parse(tb, maxtype, genlmsg_attrdata(ghdr, hdrlen),
183                          genlmsg_attrlen(ghdr, hdrlen), policy);
184 }
185 
186 /**
187  * Get head of message payload
188  * @arg gnlh    genetlink messsage header
189  */
190 void *genlmsg_data(const struct genlmsghdr *gnlh)
191 {
192         return ((unsigned char *) gnlh + GENL_HDRLEN);
193 }
194 
195 /**
196  * Get lenght of message payload
197  * @arg gnlh    genetlink message header
198  */
199 int genlmsg_len(const struct genlmsghdr *gnlh)
200 {
201         struct nlmsghdr *nlh = (struct nlmsghdr *)((unsigned char *)gnlh -
202                                                         NLMSG_HDRLEN);
203         return (nlh->nlmsg_len - GENL_HDRLEN - NLMSG_HDRLEN);
204 }
205 
206 /**
207  * Get head of attribute data
208  * @arg gnlh    generic netlink message header
209  * @arg hdrlen  length of family specific header
210  */
211 struct nlattr *genlmsg_attrdata(const struct genlmsghdr *gnlh, int hdrlen)
212 {
213         return genlmsg_data(gnlh) + NLMSG_ALIGN(hdrlen);
214 }
215 
216 /**
217  * Get length of attribute data
218  * @arg gnlh    generic netlink message header
219  * @arg hdrlen  length of family specific header
220  */
221 int genlmsg_attrlen(const struct genlmsghdr *gnlh, int hdrlen)
222 {
223         return genlmsg_len(gnlh) - NLMSG_ALIGN(hdrlen);
224 }
225 
226 /** @} */
227 
228 /**
229  * @name Message Building
230  * @{
231  */
232 
233 /**
234  * Add generic netlink header to netlink message
235  * @arg msg             netlink message
236  * @arg pid             netlink process id or NL_AUTO_PID
237  * @arg seq             sequence number of message or NL_AUTO_SEQ
238  * @arg family          generic netlink family
239  * @arg hdrlen          length of user specific header
240  * @arg flags           message flags
241  * @arg cmd             generic netlink command
242  * @arg version         protocol version
243  *
244  * Returns pointer to user specific header.
245  */
246 void *genlmsg_put(struct nl_msg *msg, uint32_t pid, uint32_t seq, int family,
247                   int hdrlen, int flags, uint8_t cmd, uint8_t version)
248 {
249         struct nlmsghdr *nlh;
250         struct genlmsghdr hdr = {
251                 .cmd = cmd,
252                 .version = version,
253         };
254 
255         nlh = nlmsg_put(msg, pid, seq, family, GENL_HDRLEN + hdrlen, flags);
256         if (nlh == NULL)
257                 return NULL;
258 
259         memcpy(nlmsg_data(nlh), &hdr, sizeof(hdr));
260         NL_DBG(2, "msg %p: Added generic netlink header cmd=%d version=%d\n",
261                msg, cmd, version);
262 
263         return nlmsg_data(nlh) + GENL_HDRLEN;
264 }
265 
266 /** @} */
267 
268 /** @} */
269 

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