include/net/genetlink.h

   1 /* SPDX-License-Identifier: GPL-2.0 */
   2 #ifndef __NET_GENERIC_NETLINK_H
   3 #define __NET_GENERIC_NETLINK_H
   4
   5 #include <linux/genetlink.h>
   6 #include <net/netlink.h>
   7 #include <net/net_namespace.h>
   8
   9 #define GENLMSG_DEFAULT_SIZE (NLMSG_DEFAULT_SIZE - GENL_HDRLEN)
  10
  11 /**
  12  * struct genl_multicast_group - generic netlink multicast group
  13  * @name: name of the multicast group, names are per-family
  14  */
  15 struct genl_multicast_group {
  16         char                    name[GENL_NAMSIZ];
  17 };
  18
  19 struct genl_ops;
  20 struct genl_info;
  21
  22 /**
  23  * struct genl_family - generic netlink family
  24  * @id: protocol family identifier (private)
  25  * @hdrsize: length of user specific header in bytes
  26  * @name: name of family
  27  * @version: protocol version
  28  * @maxattr: maximum number of attributes supported
  29  * @netnsok: set to true if the family can handle network
  30  *      namespaces and should be presented in all of them
  31  * @parallel_ops: operations can be called in parallel and aren't
  32  *      synchronized by the core genetlink code
  33  * @pre_doit: called before an operation's doit callback, it may
  34  *      do additional, common, filtering and return an error
  35  * @post_doit: called after an operation's doit callback, it may
  36  *      undo operations done by pre_doit, for example release locks
  37  * @mcast_bind: a socket bound to the given multicast group (which
  38  *      is given as the offset into the groups array)
  39  * @mcast_unbind: a socket was unbound from the given multicast group.
  40  *      Note that unbind() will not be called symmetrically if the
  41  *      generic netlink family is removed while there are still open
  42  *      sockets.
  43  * @attrbuf: buffer to store parsed attributes (private)
  44  * @mcgrps: multicast groups used by this family
  45  * @n_mcgrps: number of multicast groups
  46  * @mcgrp_offset: starting number of multicast group IDs in this family
  47  *      (private)
  48  * @ops: the operations supported by this family
  49  * @n_ops: number of operations supported by this family
  50  */
  51 struct genl_family {
  52         int                     id;             /* private */
  53         unsigned int            hdrsize;
  54         char                    name[GENL_NAMSIZ];
  55         unsigned int            version;
  56         unsigned int            maxattr;
  57         bool                    netnsok;
  58         bool                    parallel_ops;
  59         int                     (*pre_doit)(const struct genl_ops *ops,
  60                                             struct sk_buff *skb,
  61                                             struct genl_info *info);
  62         void                    (*post_doit)(const struct genl_ops *ops,
  63                                              struct sk_buff *skb,
  64                                              struct genl_info *info);
  65         int                     (*mcast_bind)(struct net *net, int group);
  66         void                    (*mcast_unbind)(struct net *net, int group);
  67         struct nlattr **        attrbuf;        /* private */
  68         const struct genl_ops * ops;
  69         const struct genl_multicast_group *mcgrps;
  70         unsigned int            n_ops;
  71         unsigned int            n_mcgrps;
  72         unsigned int            mcgrp_offset;   /* private */
  73         struct module           *module;
  74 };
  75
  76 struct nlattr **genl_family_attrbuf(const struct genl_family *family);
  77
  78 /**
  79  * struct genl_info - receiving information
  80  * @snd_seq: sending sequence number
  81  * @snd_portid: netlink portid of sender
  82  * @nlhdr: netlink message header
  83  * @genlhdr: generic netlink message header
  84  * @userhdr: user specific header
  85  * @attrs: netlink attributes
  86  * @_net: network namespace
  87  * @user_ptr: user pointers
  88  * @extack: extended ACK report struct
  89  */
  90 struct genl_info {
  91         u32                     snd_seq;
  92         u32                     snd_portid;
  93         struct nlmsghdr *       nlhdr;
  94         struct genlmsghdr *     genlhdr;
  95         void *                  userhdr;
  96         struct nlattr **        attrs;
  97         possible_net_t          _net;
  98         void *                  user_ptr[2];
  99         struct netlink_ext_ack *extack;
 100 };
 101
 102 static inline struct net *genl_info_net(struct genl_info *info)
 103 {
 104         return read_pnet(&info->_net);
 105 }
 106
 107 static inline void genl_info_net_set(struct genl_info *info, struct net *net)
 108 {
 109         write_pnet(&info->_net, net);
 110 }
 111
 112 #define GENL_SET_ERR_MSG(info, msg) NL_SET_ERR_MSG((info)->extack, msg)
 113
 114 static inline int genl_err_attr(struct genl_info *info, int err,
 115                                 struct nlattr *attr)
 116 {
 117         info->extack->bad_attr = attr;
 118
 119         return err;
 120 }
 121
 122 /**
 123  * struct genl_ops - generic netlink operations
 124  * @cmd: command identifier
 125  * @internal_flags: flags used by the family
 126  * @flags: flags
 127  * @policy: attribute validation policy
 128  * @doit: standard command callback
 129  * @start: start callback for dumps
 130  * @dumpit: callback for dumpers
 131  * @done: completion callback for dumps
 132  */
 133 struct genl_ops {
 134         const struct nla_policy *policy;
 135         int                    (*doit)(struct sk_buff *skb,
 136                                        struct genl_info *info);
 137         int                    (*start)(struct netlink_callback *cb);
 138         int                    (*dumpit)(struct sk_buff *skb,
 139                                          struct netlink_callback *cb);
 140         int                    (*done)(struct netlink_callback *cb);
 141         u8                      cmd;
 142         u8                      internal_flags;
 143         u8                      flags;
 144 };
 145
 146 int genl_register_family(struct genl_family *family);
 147 int genl_unregister_family(const struct genl_family *family);
 148 void genl_notify(const struct genl_family *family, struct sk_buff *skb,
 149                  struct genl_info *info, u32 group, gfp_t flags);
 150
 151 void *genlmsg_put(struct sk_buff *skb, u32 portid, u32 seq,
 152                   const struct genl_family *family, int flags, u8 cmd);
 153
 154 /**
 155  * genlmsg_nlhdr - Obtain netlink header from user specified header
 156  * @user_hdr: user header as returned from genlmsg_put()
 157  *
 158  * Returns pointer to netlink header.
 159  */
 160 static inline struct nlmsghdr *genlmsg_nlhdr(void *user_hdr)
 161 {
 162         return (struct nlmsghdr *)((char *)user_hdr -
 163                                    GENL_HDRLEN -
 164                                    NLMSG_HDRLEN);
 165 }
 166
 167 /**
 168  * genlmsg_parse - parse attributes of a genetlink message
 169  * @nlh: netlink message header
 170  * @family: genetlink message family
 171  * @tb: destination array with maxtype+1 elements
 172  * @maxtype: maximum attribute type to be expected
 173  * @policy: validation policy
 174  * @extack: extended ACK report struct
 175  */
 176 static inline int genlmsg_parse(const struct nlmsghdr *nlh,
 177                                 const struct genl_family *family,
 178                                 struct nlattr *tb[], int maxtype,
 179                                 const struct nla_policy *policy,
 180                                 struct netlink_ext_ack *extack)
 181 {
 182         return nlmsg_parse(nlh, family->hdrsize + GENL_HDRLEN, tb, maxtype,
 183                            policy, extack);
 184 }
 185
 186 /**
 187  * genl_dump_check_consistent - check if sequence is consistent and advertise if not
 188  * @cb: netlink callback structure that stores the sequence number
 189  * @user_hdr: user header as returned from genlmsg_put()
 190  *
 191  * Cf. nl_dump_check_consistent(), this just provides a wrapper to make it
 192  * simpler to use with generic netlink.
 193  */
 194 static inline void genl_dump_check_consistent(struct netlink_callback *cb,
 195                                               void *user_hdr)
 196 {
 197         nl_dump_check_consistent(cb, genlmsg_nlhdr(user_hdr));
 198 }
 199
 200 /**
 201  * genlmsg_put_reply - Add generic netlink header to a reply message
 202  * @skb: socket buffer holding the message
 203  * @info: receiver info
 204  * @family: generic netlink family
 205  * @flags: netlink message flags
 206  * @cmd: generic netlink command
 207  *
 208  * Returns pointer to user specific header
 209  */
 210 static inline void *genlmsg_put_reply(struct sk_buff *skb,
 211                                       struct genl_info *info,
 212                                       const struct genl_family *family,
 213                                       int flags, u8 cmd)
 214 {
 215         return genlmsg_put(skb, info->snd_portid, info->snd_seq, family,
 216                            flags, cmd);
 217 }
 218
 219 /**
 220  * genlmsg_end - Finalize a generic netlink message
 221  * @skb: socket buffer the message is stored in
 222  * @hdr: user specific header
 223  */
 224 static inline void genlmsg_end(struct sk_buff *skb, void *hdr)
 225 {
 226         nlmsg_end(skb, hdr - GENL_HDRLEN - NLMSG_HDRLEN);
 227 }
 228
 229 /**
 230  * genlmsg_cancel - Cancel construction of a generic netlink message
 231  * @skb: socket buffer the message is stored in
 232  * @hdr: generic netlink message header
 233  */
 234 static inline void genlmsg_cancel(struct sk_buff *skb, void *hdr)
 235 {
 236         if (hdr)
 237                 nlmsg_cancel(skb, hdr - GENL_HDRLEN - NLMSG_HDRLEN);
 238 }
 239
 240 /**
 241  * genlmsg_multicast_netns - multicast a netlink message to a specific netns
 242  * @family: the generic netlink family
 243  * @net: the net namespace
 244  * @skb: netlink message as socket buffer
 245  * @portid: own netlink portid to avoid sending to yourself
 246  * @group: offset of multicast group in groups array
 247  * @flags: allocation flags
 248  */
 249 static inline int genlmsg_multicast_netns(const struct genl_family *family,
 250                                           struct net *net, struct sk_buff *skb,
 251                                           u32 portid, unsigned int group, gfp_t flags)
 252 {
 253         if (WARN_ON_ONCE(group >= family->n_mcgrps))
 254                 return -EINVAL;
 255         group = family->mcgrp_offset + group;
 256         return nlmsg_multicast(net->genl_sock, skb, portid, group, flags);
 257 }
 258
 259 /**
 260  * genlmsg_multicast - multicast a netlink message to the default netns
 261  * @family: the generic netlink family
 262  * @skb: netlink message as socket buffer
 263  * @portid: own netlink portid to avoid sending to yourself
 264  * @group: offset of multicast group in groups array
 265  * @flags: allocation flags
 266  */
 267 static inline int genlmsg_multicast(const struct genl_family *family,
 268                                     struct sk_buff *skb, u32 portid,
 269                                     unsigned int group, gfp_t flags)
 270 {
 271         return genlmsg_multicast_netns(family, &init_net, skb,
 272                                        portid, group, flags);
 273 }
 274
 275 /**
 276  * genlmsg_multicast_allns - multicast a netlink message to all net namespaces
 277  * @family: the generic netlink family
 278  * @skb: netlink message as socket buffer
 279  * @portid: own netlink portid to avoid sending to yourself
 280  * @group: offset of multicast group in groups array
 281  * @flags: allocation flags
 282  *
 283  * This function must hold the RTNL or rcu_read_lock().
 284  */
 285 int genlmsg_multicast_allns(const struct genl_family *family,
 286                             struct sk_buff *skb, u32 portid,
 287                             unsigned int group, gfp_t flags);
 288
 289 /**
 290  * genlmsg_unicast - unicast a netlink message
 291  * @skb: netlink message as socket buffer
 292  * @portid: netlink portid of the destination socket
 293  */
 294 static inline int genlmsg_unicast(struct net *net, struct sk_buff *skb, u32 portid)
 295 {
 296         return nlmsg_unicast(net->genl_sock, skb, portid);
 297 }
 298
 299 /**
 300  * genlmsg_reply - reply to a request
 301  * @skb: netlink message to be sent back
 302  * @info: receiver information
 303  */
 304 static inline int genlmsg_reply(struct sk_buff *skb, struct genl_info *info)
 305 {
 306         return genlmsg_unicast(genl_info_net(info), skb, info->snd_portid);
 307 }
 308
 309 /**
 310  * gennlmsg_data - head of message payload
 311  * @gnlh: genetlink message header
 312  */
 313 static inline void *genlmsg_data(const struct genlmsghdr *gnlh)
 314 {
 315         return ((unsigned char *) gnlh + GENL_HDRLEN);
 316 }
 317
 318 /**
 319  * genlmsg_len - length of message payload
 320  * @gnlh: genetlink message header
 321  */
 322 static inline int genlmsg_len(const struct genlmsghdr *gnlh)
 323 {
 324         struct nlmsghdr *nlh = (struct nlmsghdr *)((unsigned char *)gnlh -
 325                                                         NLMSG_HDRLEN);
 326         return (nlh->nlmsg_len - GENL_HDRLEN - NLMSG_HDRLEN);
 327 }
 328
 329 /**
 330  * genlmsg_msg_size - length of genetlink message not including padding
 331  * @payload: length of message payload
 332  */
 333 static inline int genlmsg_msg_size(int payload)
 334 {
 335         return GENL_HDRLEN + payload;
 336 }
 337
 338 /**
 339  * genlmsg_total_size - length of genetlink message including padding
 340  * @payload: length of message payload
 341  */
 342 static inline int genlmsg_total_size(int payload)
 343 {
 344         return NLMSG_ALIGN(genlmsg_msg_size(payload));
 345 }
 346
 347 /**
 348  * genlmsg_new - Allocate a new generic netlink message
 349  * @payload: size of the message payload
 350  * @flags: the type of memory to allocate.
 351  */
 352 static inline struct sk_buff *genlmsg_new(size_t payload, gfp_t flags)
 353 {
 354         return nlmsg_new(genlmsg_total_size(payload), flags);
 355 }
 356
 357 /**
 358  * genl_set_err - report error to genetlink broadcast listeners
 359  * @family: the generic netlink family
 360  * @net: the network namespace to report the error to
 361  * @portid: the PORTID of a process that we want to skip (if any)
 362  * @group: the broadcast group that will notice the error
 363  *      (this is the offset of the multicast group in the groups array)
 364  * @code: error code, must be negative (as usual in kernelspace)
 365  *
 366  * This function returns the number of broadcast listeners that have set the
 367  * NETLINK_RECV_NO_ENOBUFS socket option.
 368  */
 369 static inline int genl_set_err(const struct genl_family *family,
 370                                struct net *net, u32 portid,
 371                                u32 group, int code)
 372 {
 373         if (WARN_ON_ONCE(group >= family->n_mcgrps))
 374                 return -EINVAL;
 375         group = family->mcgrp_offset + group;
 376         return netlink_set_err(net->genl_sock, portid, group, code);
 377 }
 378
 379 static inline int genl_has_listeners(const struct genl_family *family,
 380                                      struct net *net, unsigned int group)
 381 {
 382         if (WARN_ON_ONCE(group >= family->n_mcgrps))
 383                 return -EINVAL;
 384         group = family->mcgrp_offset + group;
 385         return netlink_has_listeners(net->genl_sock, group);
 386 }
 387 #endif  /* __NET_GENERIC_NETLINK_H */