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bpf: Allow selecting reuseport socket from a SOCKMAP/SOCKHASH 

SOCKMAP & SOCKHASH now support storing references to listening
sockets. Nothing keeps us from using these map types a collection of
sockets to select from in BPF reuseport programs. Whitelist the map types
with the bpf_sk_select_reuseport helper.

The restriction that the socket has to be a member of a reuseport group
still applies. Sockets in SOCKMAP/SOCKHASH that don't have sk_reuseport_cb
set are not a valid target and we signal it with -EINVAL.

The main benefit from this change is that, in contrast to
REUSEPORT_SOCKARRAY, SOCK{MAP,HASH} don't impose a restriction that a
listening socket can be just one BPF map at the same time.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Link: https://lore.kernel.org/bpf/20200218171023.844439-9-jakub@cloudflare.com
This commit is contained in:
Jakub Sitnicki 2020-02-18 17:10:20 +00:00 committed by Daniel Borkmann
parent 1d59f3bcee
commit 9fed9000c5
2 changed files with 17 additions and 8 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
kernel/bpf/verifier.c
View File

@ -3693,14 +3693,16 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
if (func_id != BPF_FUNC_sk_redirect_map &&
func_id != BPF_FUNC_sock_map_update &&
func_id != BPF_FUNC_map_delete_elem &&
func_id != BPF_FUNC_msg_redirect_map)
func_id != BPF_FUNC_msg_redirect_map &&
func_id != BPF_FUNC_sk_select_reuseport)
goto error;
break;
case BPF_MAP_TYPE_SOCKHASH:
if (func_id != BPF_FUNC_sk_redirect_hash &&
func_id != BPF_FUNC_sock_hash_update &&
func_id != BPF_FUNC_map_delete_elem &&
func_id != BPF_FUNC_msg_redirect_hash)
func_id != BPF_FUNC_msg_redirect_hash &&
func_id != BPF_FUNC_sk_select_reuseport)
goto error;
break;
case BPF_MAP_TYPE_REUSEPORT_SOCKARRAY:
@ -3774,7 +3776,9 @@ static int check_map_func_compatibility(struct bpf_verifier_env *env,
goto error;
break;
case BPF_FUNC_sk_select_reuseport:
if (map->map_type != BPF_MAP_TYPE_REUSEPORT_SOCKARRAY)
if (map->map_type != BPF_MAP_TYPE_REUSEPORT_SOCKARRAY &&
map->map_type != BPF_MAP_TYPE_SOCKMAP &&
map->map_type != BPF_MAP_TYPE_SOCKHASH)
goto error;
break;
case BPF_FUNC_map_peek_elem:

15
net/core/filter.c
View File

@ -8620,6 +8620,7 @@ struct sock *bpf_run_sk_reuseport(struct sock_reuseport *reuse, struct sock *sk,
BPF_CALL_4(sk_select_reuseport, struct sk_reuseport_kern *, reuse_kern,
struct bpf_map *, map, void *, key, u32, flags)
{
bool is_sockarray = map->map_type == BPF_MAP_TYPE_REUSEPORT_SOCKARRAY;
struct sock_reuseport *reuse;
struct sock *selected_sk;
@ -8628,12 +8629,16 @@ BPF_CALL_4(sk_select_reuseport, struct sk_reuseport_kern *, reuse_kern,
return -ENOENT;
reuse = rcu_dereference(selected_sk->sk_reuseport_cb);
if (!reuse)
/* selected_sk is unhashed (e.g. by close()) after the
* above map_lookup_elem(). Treat selected_sk has already
* been removed from the map.
if (!reuse) {
/* reuseport_array has only sk with non NULL sk_reuseport_cb.
* The only (!reuse) case here is - the sk has already been
* unhashed (e.g. by close()), so treat it as -ENOENT.
*
* Other maps (e.g. sock_map) do not provide this guarantee and
* the sk may never be in the reuseport group to begin with.
*/
return -ENOENT;
return is_sockarray ? -ENOENT : -EINVAL;
}
if (unlikely(reuse->reuseport_id != reuse_kern->reuseport_id)) {
struct sock *sk;