2 files changed, 64 insertions, 0 deletions

diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index 38620da4aa7a..3ed31e5a445b 100644
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -31,6 +31,9 @@ struct genl_info;
  *      do additional, common, filtering and return an error
  * @post_doit: called after an operation's doit callback, it may
  *      undo operations done by pre_doit, for example release locks
+ * @mcast_bind: a socket bound to the given multicast group (which
+ *      is given as the offset into the groups array)
+ * @mcast_unbind: a socket was unbound from the given multicast group
  * @attrbuf: buffer to store parsed attributes
  * @family_list: family list
  * @mcgrps: multicast groups used by this family (private)
@@ -53,6 +56,8 @@ struct genl_family {
         void                    (*post_doit)(const struct genl_ops *ops,
                                              struct sk_buff *skb,
                                              struct genl_info *info);
+        int                     (*mcast_bind)(int group);
+        void                    (*mcast_unbind)(int group);
         struct nlattr **        attrbuf;        /* private */
         const struct genl_ops * ops;            /* private */
         const struct genl_multicast_group *mcgrps; /* private */
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 76393f2f4b22..05bf40bbd189 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -983,11 +983,70 @@ static struct genl_multicast_group genl_ctrl_groups[] = {
         { .name = "notify", },
 };
 
+static int genl_bind(int group)
+{
+        int i, err;
+        bool found = false;
+
+        down_read(&cb_lock);
+        for (i = 0; i < GENL_FAM_TAB_SIZE; i++) {
+                struct genl_family *f;
+
+                list_for_each_entry(f, genl_family_chain(i), family_list) {
+                        if (group >= f->mcgrp_offset &&
+                            group < f->mcgrp_offset + f->n_mcgrps) {
+                                int fam_grp = group - f->mcgrp_offset;
+
+                                if (f->mcast_bind)
+                                        err = f->mcast_bind(fam_grp);
+                                else
+                                        err = 0;
+                                found = true;
+                                break;
+                        }
+                }
+        }
+        up_read(&cb_lock);
+
+        if (WARN_ON(!found))
+                err = 0;
+
+        return err;
+}
+
+static void genl_unbind(int group)
+{
+        int i;
+        bool found = false;
+
+        down_read(&cb_lock);
+        for (i = 0; i < GENL_FAM_TAB_SIZE; i++) {
+                struct genl_family *f;
+
+                list_for_each_entry(f, genl_family_chain(i), family_list) {
+                        if (group >= f->mcgrp_offset &&
+                            group < f->mcgrp_offset + f->n_mcgrps) {
+                                int fam_grp = group - f->mcgrp_offset;
+
+                                if (f->mcast_unbind)
+                                        f->mcast_unbind(fam_grp);
+                                found = true;
+                                break;
+                        }
+                }
+        }
+        up_read(&cb_lock);
+
+        WARN_ON(!found);
+}
+
 static int __net_init genl_pernet_init(struct net *net)
 {
         struct netlink_kernel_cfg cfg = {
                 .input          = genl_rcv,
                 .flags          = NL_CFG_F_NONROOT_RECV,
+                .bind           = genl_bind,
+                .unbind         = genl_unbind,
         };
 
         /* we'll bump the group number right afterwards */