netdev - Re: [PATCH bpf-next 3/7] bpf: add netns cookie and enable it for bpf cgroup hooks

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Date:   Fri, 27 Mar 2020 18:48:44 -0700
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     m@...bda.lt, joe@...d.net.nz, bpf@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH bpf-next 3/7] bpf: add netns cookie and enable it for bpf
 cgroup hooks

On Fri, Mar 27, 2020 at 04:58:52PM +0100, Daniel Borkmann wrote:
> + *
> + * u64 bpf_get_netns_cookie(void *ctx)
> + * 	Description
> + * 		Retrieve the cookie (generated by the kernel) of the network
> + * 		namespace the input *ctx* is associated with. The network
> + * 		namespace cookie remains stable for its lifetime and provides
> + * 		a global identifier that can be assumed unique. If *ctx* is
> + * 		NULL, then the helper returns the cookie for the initial
> + * 		network namespace. The cookie itself is very similar to that
> + * 		of bpf_get_socket_cookie() helper, but for network namespaces
> + * 		instead of sockets.

All new helpers in this patch and few others are missing 'flags' argument.
Yes. It's kinda hard right now to come up with a use case for the flags,
since all helpers look kinda trivial, simple, and single purpose.
But the same thing happened with bpf_send_signal(). It felt that there is no
way to extend it. Yet later we had to add bpf_send_signal_thread() which could
have been handled with flags if they were there. So please add flags to all new
helpers though it might seem redundant.