@@ -41,6 +41,8 @@ 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
+ * @bind: called when family multicast group is added to a netlink socket
+ * @unbind: called when family multicast group is removed from a netlink socket
* @module: pointer to the owning module (set to THIS_MODULE)
* @mcgrps: multicast groups used by this family
* @n_mcgrps: number of multicast groups
@@ -84,6 +86,8 @@ struct genl_family {
void (*post_doit)(const struct genl_split_ops *ops,
struct sk_buff *skb,
struct genl_info *info);
+ int (*bind)(int mcgrp);
+ void (*unbind)(int mcgrp);
const struct genl_ops * ops;
const struct genl_small_ops *small_ops;
const struct genl_split_ops *split_ops;
@@ -1836,6 +1836,9 @@ static int genl_bind(struct net *net, int group)
!ns_capable(net->user_ns, CAP_SYS_ADMIN))
ret = -EPERM;
+ if (family->bind)
+ family->bind(i);
+
break;
}
@@ -1843,12 +1846,39 @@ static int genl_bind(struct net *net, int group)
return ret;
}
+static void genl_unbind(struct net *net, int group)
+{
+ const struct genl_family *family;
+ unsigned int id;
+
+ down_read(&cb_lock);
+
+ idr_for_each_entry(&genl_fam_idr, family, id) {
+ int i;
+
+ if (family->n_mcgrps == 0)
+ continue;
+
+ i = group - family->mcgrp_offset;
+ if (i < 0 || i >= family->n_mcgrps)
+ continue;
+
+ if (family->unbind)
+ family->unbind(i);
+
+ break;
+ }
+
+ up_read(&cb_lock);
+}
+
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,
.release = genl_release,
};
Add genetlink family bind()/unbind() callbacks when adding/removing multicast group to/from netlink client socket via setsockopt() or bind() syscall. They can be used to track if consumers of netlink multicast messages emerge or disappear. Thus, a client implementing callbacks, can now send events only when there are active consumers, preventing unnecessary work when none exist. Suggested-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Stanislaw Gruszka <stanislaw.gruszka@linux.intel.com> --- include/net/genetlink.h | 4 ++++ net/netlink/genetlink.c | 30 ++++++++++++++++++++++++++++++ 2 files changed, 34 insertions(+)