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:

quoted

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 <redacted>
Cc: Alexei Starovoitov <redacted>
Cc: Daniel Borkmann <daniel@iogearbox.net>
Cc: Tejun Heo <tj@kernel.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,

...

quoted

+static u64 bpf_skb_in_cgroup(u64 r1, u64 r2, u64 r3, u64 r4, u64 r5)
+{

...

quoted

+	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.