sock: make cookie generation global instead of per netns

Generating and retrieving socket cookies are a useful feature that is
exposed to BPF for various program types through bpf_get_socket_cookie()
helper.

The fact that the cookie counter is per netns is quite a limitation
for BPF in practice in particular for programs in host namespace that
use socket cookies as part of a map lookup key since they will be
causing socket cookie collisions e.g. when attached to BPF cgroup hooks
or cls_bpf on tc egress in host namespace handling container traffic
from veth or ipvlan devices with peer in different netns. Change the
counter to be global instead.

Socket cookie consumers must assume the value as opqaue in any case.
Not every socket must have a cookie generated and knowledge of the
counter value itself does not provide much value either way hence
conversion to global is fine.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Eric Dumazet <edumazet@google.com>
Cc: Alexei Starovoitov <ast@kernel.org>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Martynas Pumputis <m@lambda.lt>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/core/sock_diag.c b/net/core/sock_diag.c
index 3312a5849a97..c13ffbd33d8d 100644
--- a/net/core/sock_diag.c
+++ b/net/core/sock_diag.c
@@ -19,6 +19,7 @@ static const struct sock_diag_handler *sock_diag_handlers[AF_MAX];
 static int (*inet_rcv_compat)(struct sk_buff *skb, struct nlmsghdr *nlh);
 static DEFINE_MUTEX(sock_diag_table_mutex);
 static struct workqueue_struct *broadcast_wq;
+static atomic64_t cookie_gen;
 
 u64 sock_gen_cookie(struct sock *sk)
 {
@@ -27,7 +28,7 @@ u64 sock_gen_cookie(struct sock *sk)
 
 		if (res)
 			return res;
-		res = atomic64_inc_return(&sock_net(sk)->cookie_gen);
+		res = atomic64_inc_return(&cookie_gen);
 		atomic64_cmpxchg(&sk->sk_cookie, 0, res);
 	}
 }