Commit ab53cad9 authored by Jakub Sitnicki's avatar Jakub Sitnicki Committed by Alexei Starovoitov
Browse files

bpf, netns: Keep a list of attached bpf_link's 



To support multi-prog link-based attachments for new netns attach types, we
need to keep track of more than one bpf_link per attach type. Hence,
convert net->bpf.links into a list, that currently can be either empty or
have just one item.

Instead of reusing bpf_prog_list from bpf-cgroup, we link together
bpf_netns_link's themselves. This makes list management simpler as we don't
have to allocate, initialize, and later release list elements. We can do
this because multi-prog attachment will be available only for bpf_link, and
we don't need to build a list of programs attached directly and indirectly
via links.

No functional changes intended.

Signed-off-by: default avatarJakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Acked-by: default avatarAndrii Nakryiko <andriin@fb.com>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200625141357.910330-4-jakub@cloudflare.com
parent 695c1214

include/net/netns/bpf.h

+1 −1
Original line number Diff line number Diff line
@@ -15,7 +15,7 @@ struct netns_bpf { 
	/* Array of programs to run compiled from progs or links */

	struct bpf_prog_array __rcu *run_array[MAX_NETNS_BPF_ATTACH_TYPE];

	struct bpf_prog *progs[MAX_NETNS_BPF_ATTACH_TYPE];

	struct bpf_link *links[MAX_NETNS_BPF_ATTACH_TYPE];

	struct list_head links[MAX_NETNS_BPF_ATTACH_TYPE];

};



#endif /* __NETNS_BPF_H__ */

kernel/bpf/net_namespace.c

+23 −19
Original line number Diff line number Diff line
@@ -19,20 +19,12 @@ struct bpf_netns_link { 
	 * with netns_bpf_mutex held.

	 */

	struct net *net;

	struct list_head node; /* node in list of links attached to net */

};



/* Protects updates to netns_bpf */

DEFINE_MUTEX(netns_bpf_mutex);



/* Must be called with netns_bpf_mutex held. */

static void __net_exit bpf_netns_link_auto_detach(struct bpf_link *link)

{

	struct bpf_netns_link *net_link =

		container_of(link, struct bpf_netns_link, link);



	net_link->net = NULL;

}



/* Must be called with netns_bpf_mutex held. */

static void netns_bpf_run_array_detach(struct net *net,

				       enum netns_bpf_attach_type type)
@@ -66,7 +58,7 @@ static void bpf_netns_link_release(struct bpf_link *link) 
		goto out_unlock;



	netns_bpf_run_array_detach(net, type);

	net->bpf.links[type] = NULL;

	list_del(&net_link->node);



out_unlock:

	mutex_unlock(&netns_bpf_mutex);
@@ -225,7 +217,7 @@ int netns_bpf_prog_attach(const union bpf_attr *attr, struct bpf_prog *prog) 
	mutex_lock(&netns_bpf_mutex);



	/* Attaching prog directly is not compatible with links */

	if (net->bpf.links[type]) {

	if (!list_empty(&net->bpf.links[type])) {

		ret = -EEXIST;

		goto out_unlock;

	}
@@ -279,7 +271,7 @@ static int __netns_bpf_prog_detach(struct net *net, 
	struct bpf_prog *attached;



	/* Progs attached via links cannot be detached */

	if (net->bpf.links[type])

	if (!list_empty(&net->bpf.links[type]))

		return -EINVAL;



	attached = net->bpf.progs[type];
@@ -310,13 +302,15 @@ int netns_bpf_prog_detach(const union bpf_attr *attr) 
static int netns_bpf_link_attach(struct net *net, struct bpf_link *link,

				 enum netns_bpf_attach_type type)

{

	struct bpf_netns_link *net_link =

		container_of(link, struct bpf_netns_link, link);

	struct bpf_prog_array *run_array;

	int err;



	mutex_lock(&netns_bpf_mutex);



	/* Allow attaching only one prog or link for now */

	if (net->bpf.links[type]) {

	if (!list_empty(&net->bpf.links[type])) {

		err = -E2BIG;

		goto out_unlock;

	}
@@ -345,7 +339,7 @@ static int netns_bpf_link_attach(struct net *net, struct bpf_link *link, 
	run_array->items[0].prog = link->prog;

	rcu_assign_pointer(net->bpf.run_array[type], run_array);



	net->bpf.links[type] = link;

	list_add_tail(&net_link->node, &net->bpf.links[type]);



out_unlock:

	mutex_unlock(&netns_bpf_mutex);
@@ -404,24 +398,34 @@ out_put_net: 
	return err;

}



static int __net_init netns_bpf_pernet_init(struct net *net)

{

	int type;



	for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++)

		INIT_LIST_HEAD(&net->bpf.links[type]);



	return 0;

}



static void __net_exit netns_bpf_pernet_pre_exit(struct net *net)

{

	enum netns_bpf_attach_type type;

	struct bpf_link *link;

	struct bpf_netns_link *net_link;



	mutex_lock(&netns_bpf_mutex);

	for (type = 0; type < MAX_NETNS_BPF_ATTACH_TYPE; type++) {

		netns_bpf_run_array_detach(net, type);

		link = net->bpf.links[type];

		if (link)

			bpf_netns_link_auto_detach(link);

		else if (net->bpf.progs[type])

		list_for_each_entry(net_link, &net->bpf.links[type], node)

			net_link->net = NULL; /* auto-detach link */

		if (net->bpf.progs[type])

			bpf_prog_put(net->bpf.progs[type]);

	}

	mutex_unlock(&netns_bpf_mutex);

}



static struct pernet_operations netns_bpf_pernet_ops __net_initdata = {

	.init = netns_bpf_pernet_init,

	.pre_exit = netns_bpf_pernet_pre_exit,

};

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