[PATCH bpf-next v2 09/11] bpf: Allow selecting reuseport socket from a SOCKMAP
From: Jakub Sitnicki <jakub@cloudflare.com>
Date: 2020-01-10 10:50:45
Also in:
bpf
Subsystem:
bpf [core], bpf [general] (safe dynamic programs and tools), bpf [networking] (tcx & tc bpf, sock_addr), networking [general], the rest · Maintainers:
Alexei Starovoitov, Daniel Borkmann, Andrii Nakryiko, Eduard Zingerman, Kumar Kartikeya Dwivedi, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
SOCKMAP now supports storing references to listening sockets. Nothing keeps us from using it as an array of sockets to select from in SK_REUSEPORT programs. Whitelist the map type with the BPF helper for selecting socket. The restriction that the socket has to be a member of a reuseport group still applies. Socket from a SOCKMAP that does not have sk_reuseport_cb set is not a valid target and we signal it with -EINVAL. Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com> --- kernel/bpf/verifier.c | 6 ++++-- net/core/filter.c | 15 ++++++++++----- 2 files changed, 14 insertions(+), 7 deletions(-)
diff --git a/kernel/bpf/verifier.c b/kernel/bpf/verifier.c
index f5af759a8a5f..0ee5f1594b5c 100644
--- a/kernel/bpf/verifier.c
+++ b/kernel/bpf/verifier.c@@ -3697,7 +3697,8 @@ 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:
@@ -3778,7 +3779,8 @@ 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) goto error; break; case BPF_FUNC_map_peek_elem:
diff --git a/net/core/filter.c b/net/core/filter.c
index a702761ef369..c79c62a54167 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c@@ -8677,6 +8677,7 @@ 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;
@@ -8685,12 +8686,16 @@ 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;
--
2.24.1