package/libnl-tiny/src/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 (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 /** @} */