2 files changed, 51 insertions, 46 deletions

diff --git a/include/linux/genl_magic_func.h b/include/linux/genl_magic_func.h
index 5b9b8ae6748b..c0894dd8827b 100644
--- a/include/linux/genl_magic_func.h
+++ b/include/linux/genl_magic_func.h
@@ -273,49 +273,40 @@ static struct genl_family ZZZ_genl_family __read_mostly = {
  * Magic: define multicast groups
  * Magic: define multicast group registration helper
  */
+#define ZZZ_genl_mcgrps         CONCAT_(GENL_MAGIC_FAMILY, _genl_mcgrps)
+static const struct genl_multicast_group ZZZ_genl_mcgrps[] = {
+#undef GENL_mc_group
+#define GENL_mc_group(group) { .name = #group, },
+#include GENL_MAGIC_INCLUDE_FILE
+};
+
+enum CONCAT_(GENL_MAGIC_FAMILY, group_ids) {
+#undef GENL_mc_group
+#define GENL_mc_group(group) CONCAT_(GENL_MAGIC_FAMILY, _group_ ## group),
+#include GENL_MAGIC_INCLUDE_FILE
+};
+
 #undef GENL_mc_group
 #define GENL_mc_group(group)                                            \
-static struct genl_multicast_group                                      \
-CONCAT_(GENL_MAGIC_FAMILY, _mcg_ ## group) __read_mostly = {            \
-        .name = #group,                                                 \
-};                                                                      \
 static int CONCAT_(GENL_MAGIC_FAMILY, _genl_multicast_ ## group)(       \
         struct sk_buff *skb, gfp_t flags)                               \
 {                                                                       \
         unsigned int group_id =                                         \
-                CONCAT_(GENL_MAGIC_FAMILY, _mcg_ ## group).id;  \
-        if (!group_id)                                                  \
-                return -EINVAL;                                         \
+                CONCAT_(GENL_MAGIC_FAMILY, _group_ ## group);           \
         return genlmsg_multicast(&ZZZ_genl_family, skb, 0,              \
                                  group_id, flags);                      \
 }
 
 #include GENL_MAGIC_INCLUDE_FILE
 
-int CONCAT_(GENL_MAGIC_FAMILY, _genl_register)(void)
-{
-        int err = genl_register_family_with_ops(&ZZZ_genl_family, ZZZ_genl_ops);
-        if (err)
-                return err;
-#undef GENL_mc_group
-#define GENL_mc_group(group)                                            \
-        err = genl_register_mc_group(&ZZZ_genl_family,                  \
-                &CONCAT_(GENL_MAGIC_FAMILY, _mcg_ ## group));           \
-        if (err)                                                        \
-                goto fail;                                              \
-        else                                                            \
-                pr_info("%s: mcg %s: %u\n", #group,                     \
-                        __stringify(GENL_MAGIC_FAMILY),                 \
-                        CONCAT_(GENL_MAGIC_FAMILY, _mcg_ ## group).id);
-
-#include GENL_MAGIC_INCLUDE_FILE
-
 #undef GENL_mc_group
 #define GENL_mc_group(group)
-        return 0;
-fail:
-        genl_unregister_family(&ZZZ_genl_family);
-        return err;
+
+int CONCAT_(GENL_MAGIC_FAMILY, _genl_register)(void)
+{
+        return genl_register_family_with_ops_groups(&ZZZ_genl_family,   \
+                                                    ZZZ_genl_ops,       \
+                                                    ZZZ_genl_mcgrps);
 }
 
 void CONCAT_(GENL_MAGIC_FAMILY, _genl_unregister)(void)
diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index 60aef0df386b..ace4abf118d7 100644
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -10,14 +10,9 @@
 /**
  * struct genl_multicast_group - generic netlink multicast group
  * @name: name of the multicast group, names are per-family
- * @id: multicast group ID, assigned by the core, to use with
- *      genlmsg_multicast().
- * @list: list entry for linking
  */
 struct genl_multicast_group {
-        struct list_head        list;           /* private */
         char                    name[GENL_NAMSIZ];
-        u32                     id;
 };
 
 struct genl_ops;
@@ -38,7 +33,9 @@ struct genl_info;
  *      undo operations done by pre_doit, for example release locks
  * @attrbuf: buffer to store parsed attributes
  * @family_list: family list
- * @mcast_groups: multicast groups list
+ * @mcgrps: multicast groups used by this family (private)
+ * @n_mcgrps: number of multicast groups (private)
+ * @mcgrp_offset: starting number of multicast group IDs in this family
  * @ops: the operations supported by this family (private)
  * @n_ops: number of operations supported by this family (private)
  */
@@ -58,9 +55,11 @@ struct genl_family {
                                              struct genl_info *info);
         struct nlattr **        attrbuf;        /* private */
         const struct genl_ops * ops;            /* private */
+        const struct genl_multicast_group *mcgrps; /* private */
         unsigned int            n_ops;          /* private */
+        unsigned int            n_mcgrps;       /* private */
+        unsigned int            mcgrp_offset;   /* private */
         struct list_head        family_list;    /* private */
-        struct list_head        mcast_groups;   /* private */
         struct module           *module;
 };
 
@@ -150,22 +149,30 @@ static inline int genl_register_family(struct genl_family *family)
  *
  * Return 0 on success or a negative error code.
  */
-static inline int _genl_register_family_with_ops(struct genl_family *family,
-                                                 const struct genl_ops *ops,
-                                                 size_t n_ops)
+static inline int
+_genl_register_family_with_ops_grps(struct genl_family *family,
+                                    const struct genl_ops *ops, size_t n_ops,
+                                    const struct genl_multicast_group *mcgrps,
+                                    size_t n_mcgrps)
 {
         family->module = THIS_MODULE;
         family->ops = ops;
         family->n_ops = n_ops;
+        family->mcgrps = mcgrps;
+        family->n_mcgrps = n_mcgrps;
         return __genl_register_family(family);
 }
 
-#define genl_register_family_with_ops(family, ops)      \
-        _genl_register_family_with_ops((family), (ops), ARRAY_SIZE(ops))
+#define genl_register_family_with_ops(family, ops)                      \
+        _genl_register_family_with_ops_grps((family),                   \
+                                            (ops), ARRAY_SIZE(ops),     \
+                                            NULL, 0)
+#define genl_register_family_with_ops_groups(family, ops, grps) \
+        _genl_register_family_with_ops_grps((family),                   \
+                                            (ops), ARRAY_SIZE(ops),     \
+                                            (grps), ARRAY_SIZE(grps))
 
 int genl_unregister_family(struct genl_family *family);
-int genl_register_mc_group(struct genl_family *family,
-                           struct genl_multicast_group *grp);
 void genl_notify(struct genl_family *family,
                  struct sk_buff *skb, struct net *net, u32 portid,
                  u32 group, struct nlmsghdr *nlh, gfp_t flags);
@@ -251,13 +258,16 @@ static inline void genlmsg_cancel(struct sk_buff *skb, void *hdr)
  * @net: the net namespace
  * @skb: netlink message as socket buffer
  * @portid: own netlink portid to avoid sending to yourself
- * @group: multicast group id
+ * @group: offset of multicast group in groups array
  * @flags: allocation flags
  */
 static inline int genlmsg_multicast_netns(struct genl_family *family,
                                           struct net *net, struct sk_buff *skb,
                                           u32 portid, unsigned int group, gfp_t flags)
 {
+        if (group >= family->n_mcgrps)
+                return -EINVAL;
+        group = family->mcgrp_offset + group;
         return nlmsg_multicast(net->genl_sock, skb, portid, group, flags);
 }
 
@@ -266,13 +276,16 @@ static inline int genlmsg_multicast_netns(struct genl_family *family,
  * @family: the generic netlink family
  * @skb: netlink message as socket buffer
  * @portid: own netlink portid to avoid sending to yourself
- * @group: multicast group id
+ * @group: offset of multicast group in groups array
  * @flags: allocation flags
  */
 static inline int genlmsg_multicast(struct genl_family *family,
                                     struct sk_buff *skb, u32 portid,
                                     unsigned int group, gfp_t flags)
 {
+        if (group >= family->n_mcgrps)
+                return -EINVAL;
+        group = family->mcgrp_offset + group;
         return genlmsg_multicast_netns(family, &init_net, skb,
                                        portid, group, flags);
 }
@@ -282,7 +295,7 @@ static inline int genlmsg_multicast(struct genl_family *family,
  * @family: the generic netlink family
  * @skb: netlink message as socket buffer
  * @portid: own netlink portid to avoid sending to yourself
- * @group: multicast group id
+ * @group: offset of multicast group in groups array
  * @flags: allocation flags
  *
  * This function must hold the RTNL or rcu_read_lock().
@@ -365,6 +378,7 @@ static inline struct sk_buff *genlmsg_new(size_t payload, gfp_t flags)
  * @net: the network namespace to report the error to
  * @portid: the PORTID of a process that we want to skip (if any)
  * @group: the broadcast group that will notice the error
+ *      (this is the offset of the multicast group in the groups array)
  * @code: error code, must be negative (as usual in kernelspace)
  *
  * This function returns the number of broadcast listeners that have set the