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

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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: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Andrii Nakryiko <andriin@fb.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/bpf/20200625141357.910330-4-jakub@cloudflare.com
This commit is contained in:
Jakub Sitnicki 2020-06-25 16:13:56 +02:00 committed by Alexei Starovoitov
parent 695c12147a
commit ab53cad90e
2 changed files with 24 additions and 20 deletions
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2
include/net/netns/bpf.h
View File

@ -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__ */

42
kernel/bpf/net_namespace.c
View File

@ -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 @@ int netns_bpf_link_create(const union bpf_attr *attr, struct bpf_prog *prog)
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,
};