linux-kernel - Re: [PATCH -next 3/4] cgroup: bpf: Add bpf_skb_in_cgroup

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Date:	Tue, 21 Jun 2016 23:19:26 -0700
From:	Martin KaFai Lau <kafai@...com>
To:	Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:	<cgroups@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
	<netdev@...r.kernel.org>, Alexei Starovoitov <ast@...com>,
	Daniel Borkmann <daniel@...earbox.net>,
	Tejun Heo <tj@...nel.org>, <kernel-team@...com>
Subject: Re: [PATCH -next 3/4] cgroup: bpf: Add bpf_skb_in_cgroup_proto

On Tue, Jun 21, 2016 at 06:15:13PM -0700, Alexei Starovoitov wrote:
> On Tue, Jun 21, 2016 at 05:23:21PM -0700, Martin KaFai Lau wrote:
> > Adds a bpf helper, bpf_skb_in_cgroup, to decide if a skb->sk
> > belongs to a descendant of a cgroup2.  It is similar to the
> > feature added in netfilter:
> > commit c38c4597e4bf ("netfilter: implement xt_cgroup cgroup2 path match")
> >
> > The user is expected to populate a BPF_MAP_TYPE_CGROUP_ARRAY
> > which will be used by the bpf_skb_in_cgroup.
> >
> > Modifications to the bpf verifier is to ensure BPF_MAP_TYPE_CGROUP_ARRAY
> > and bpf_skb_in_cgroup() are always used together.
> >
> > Signed-off-by: Martin KaFai Lau <kafai@...com>
> > Cc: Alexei Starovoitov <ast@...com>
> > Cc: Daniel Borkmann <daniel@...earbox.net>
> > Cc: Tejun Heo <tj@...nel.org>
> > ---
> >  include/uapi/linux/bpf.h |  1 +
> >  kernel/bpf/verifier.c    |  8 ++++++++
> >  net/core/filter.c        | 36 ++++++++++++++++++++++++++++++++++++
> >  3 files changed, 45 insertions(+)
> >
> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index ef4e386..a91714bd 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -314,6 +314,7 @@ enum bpf_func_id {
> >  	 */
> >  	BPF_FUNC_skb_get_tunnel_opt,
> >  	BPF_FUNC_skb_set_tunnel_opt,
> > +	BPF_FUNC_skb_in_cgroup,
> ...
> > +static u64 bpf_skb_in_cgroup(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
> > +{
> ...
> > +	if (unlikely(!cgrp))
> > +		return -ENOENT;
> > +
> > +	return cgroup_is_descendant(sock_cgroup_ptr(&sk->sk_cgrp_data), cgrp);
>
> if you'd need to respin the patch for other reasons please add kdoc
> to bpf.h for this new helper similar to other helpers.
> To say that 0 or 1 return values is indication of cg2 descendant relation
> and < 0 in case of error.
Will do.

I will also address the '#ifndef CONFIG_CGROUPS' case in v2, as reported
by the kbuild test.