Commit 3de21a89 authored by Stanislaw Gruszka's avatar Stanislaw Gruszka Committed by Jakub Kicinski
Browse files

genetlink: Add per family bind/unbind callbacks 



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: default avatarJakub Kicinski <kuba@kernel.org>
Signed-off-by: default avatarStanislaw Gruszka <stanislaw.gruszka@linux.intel.com>
Reviewed-by: default avatarJiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20240212161615.161935-2-stanislaw.gruszka@linux.intel.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 841c3516

include/net/genetlink.h

+4 −0
Original line number Diff line number Diff line
@@ -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;

net/netlink/genetlink.c

+30 −0
Original line number Diff line number Diff line
@@ -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,

	};