netdev - Re: [PATCH bpf-next] bpf: add read/write access to skb->tstamp from tc clsact progs

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Message-ID: <20181121224613.ttksowflvlpuuv2l@ast-mbp>
Date:   Wed, 21 Nov 2018 14:46:15 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     Vlad Dumitrescu <vlad@...itrescu.ro>
Cc:     eric.dumazet@...il.com, Vlad Dumitrescu <vladum@...gle.com>,
        ast@...nel.org, Daniel Borkmann <daniel@...earbox.net>,
        netdev@...r.kernel.org, edumazet@...gle.com, willemb@...gle.com
Subject: Re: [PATCH bpf-next] bpf: add read/write access to skb->tstamp from
 tc clsact progs

On Wed, Nov 21, 2018 at 10:48:21AM -0800, Vlad Dumitrescu wrote:
> On Wed, Nov 21, 2018 at 5:08 AM Eric Dumazet <eric.dumazet@...il.com> wrote:
> >
> >
> >
> > On 11/20/2018 06:40 PM, Alexei Starovoitov wrote:
> >
> > >
> > > looks good to me.
> > >
> > > Any particular reason you decided to disable it for cg_skb ?
> > > It seems to me the same EDT approach will work from
> > > cgroup-bpf skb hooks just as well and then we can have neat
> > > way of controlling traffic per-container instead of tc-clsbpf global.
> > > If you're already on cgroup v2 it will save you a lot of classifier
> > > cycles, since you'd be able to group apps by cgroup
> > > instead of relying on ip only.
> >
> > Vlad first wrote a complete version, but we felt explaining the _why_
> > was probably harder.
> >
> > No particular reason, other than having to write more tests perhaps.
> 
> This sounds reasonable to me. I can prepare a v2.

thank you

> Any concerns regarding capabilities? For example data and data_end are
> only available to CAP_SYS_ADMIN. Note that enforcement of this would
> be done by a global component later in the pipeline (e.g., FQ qdisc).

I'd do cap_sys_admin for now, since i'm not sure whether any tstamp
values will be acceptable to fq.

> Any opinions on sk_filter, lwt, and sk_skb before I send v2?

sk_filter not appealing, since it's too late in the stack.
lwt could be interesting, but I'd wait until first user appears.
sk_skb - useful, but it requires more work.
We'll follow up to that sk_skb with our own patches.

Thanks!