From 9fed9000c5c6cacfcaaa48aff74818072ae294cc Mon Sep 17 00:00:00 2001
From: Jakub Sitnicki <jakub@cloudflare.com>
Date: Tue, 18 Feb 2020 17:10:20 +0000
Subject: 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
---
net/core/filter.c | 15 ++++++++++-----
1 file changed, 10 insertions(+), 5 deletions(-)
(limited to 'net')
diff --git a/net/core/filter.c b/net/core/filter.c
index c180871e606d..77d2f471b3bb 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -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;
--
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