netdev - Re: [PATCH v2 net] bpf: add bpf_sk_netns

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Date:   Sat, 4 Feb 2017 09:15:10 -0800
From:   Andy Lutomirski <luto@...capital.net>
To:     Alexei Starovoitov <ast@...com>
Cc:     "David S . Miller" <davem@...emloft.net>,
        Daniel Borkmann <daniel@...earbox.net>,
        David Ahern <dsa@...ulusnetworks.com>,
        Tejun Heo <tj@...nel.org>,
        "Eric W . Biederman" <ebiederm@...ssion.com>,
        Network Development <netdev@...r.kernel.org>
Subject: Re: [PATCH v2 net] bpf: add bpf_sk_netns_id() helper

On Fri, Feb 3, 2017 at 5:22 PM, Alexei Starovoitov <ast@...com> wrote:
> Note that all bpf programs types are global.

I don't think this has a clear enough meaning to work with.  In
particular, I think that, if you have some software that installs
cgroup+bpf programs and you run it in a container, then I have no idea
what "global" means in this context, and you may run into trouble with
this patch once namespace ids become migratable because the cgroup+bpf
program in the container would potentially see dev+ino numbers from
*outside* the container.  What happens when you migrate it?

I think that this patch plus a minor change to prevent installing
cgroup+bpf programs if the installer isn't in the init netns + fs ns
would work because it would allow new, migratable semantics to be
added down the road to relax the restriction.

Eric, what do you think?