Re: [PATCH bpf-next v2 1/2] bpf: Allow bpf_get_netns_cookie in BPF_PROG_TYPE_CGROUP_SOCKOPT

On 08/13, Martin KaFai Lau wrote:

On Thu, Aug 12, 2021 at 08:30:10AM -0700, Stanislav Fomichev wrote:

quoted

This is similar to existing BPF_PROG_TYPE_CGROUP_SOCK
and BPF_PROG_TYPE_CGROUP_SOCK_ADDR.

Signed-off-by: Stanislav Fomichev <redacted>
---
 kernel/bpf/cgroup.c | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index b567ca46555c..ca5af8852260 100644
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c

@@ -1846,11 +1846,30 @@ const struct bpf_verifier_ops  

cg_sysctl_verifier_ops = {

quoted

 const struct bpf_prog_ops cg_sysctl_prog_ops = {
 };

+#ifdef CONFIG_NET
+BPF_CALL_1(bpf_get_netns_cookie_sockopt, struct bpf_sockopt_kern *,  

ctx)

quoted

+{
+	struct sock *sk = ctx ? ctx->sk : NULL;
+	const struct net *net = sk ? sock_net(sk) : &init_net;

A nit.

ctx->sk can not be NULL here, so it only depends on ctx is NULL or not.

If I read it correctly, would it be less convoluted to directly test ctx
and use ctx->sk here, like:

	const struct net *net = ctx ? sock_net(ctx->sk) : &init_net;

and the previous "struct sock *sk = ctx ? ctx->sk : NULL;" statement
can also be removed.

Agreed, makes sense. Let me also add bpf_get_netns_cookie to some
existing BPF prog to make sure it's executed. That ctx.c isn't
really running the prog..