On 2/10/21 1:04 PM, Lorenz Bauer wrote:

We need to distinguish which network namespace a socket belongs to.
BPF has the useful bpf_get_netns_cookie helper for this, but accessing
it from user space isn't possible. Add a read-only socket option that
returns the netns cookie, similar to SO_COOKIE. If network namespaces
are disabled, SO_NETNS_COOKIE returns the cookie of init_net.

The BPF helpers change slightly: instead of returning 0 when network
namespaces are disabled we return the init_net cookie as for the
socket option.

Cc: linux-api@vger.kernel.org
Signed-off-by: Lorenz Bauer <redacted>
---

...

 
+static inline u64 __sock_gen_netns_cookie(struct sock *sk)
+{
+#ifdef CONFIG_NET_NS
+	return __net_gen_cookie(sk->sk_net.net);
+#else
+	return __net_gen_cookie(&init_net);
+#endif
+}
+
+static inline u64 sock_gen_netns_cookie(struct sock *sk)
+{
+	u64 cookie;
+
+	preempt_disable();
+	cookie = __sock_gen_netns_cookie(sk);
+	preempt_enable();
+
+	return cookie;
+}
+

I suggest we make net->net_cookie a mere u64 initialized in setup_net(),
instead of having to preempt_disable() around reading it.

(Here and in your patch 2/4)

Your patches would be much simpler.

Cleanup patch :

https://patchwork.kernel.org/project/netdevbpf/patch/20210210144144.24284-1-eric.dumazet@gmail.com/