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genetlink: Add per family bind/unbind callbacks

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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>
Reviewed-by: Jiri Pirko <jiri@nvidia.com>
Link: https://lore.kernel.org/r/20240212161615.161935-2-stanislaw.gruszka@linux.intel.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Stanislaw Gruszka 2024-02-12 17:16:13 +01:00 committed by Jakub Kicinski
parent 841c351693
commit 3de21a8990
2 changed files with 34 additions and 0 deletions
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4
include/net/genetlink.h
View File

@ -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;

30
net/netlink/genetlink.c
View File

@ -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,
};