Re: [PATCH v2 bpf-next 3/5] bpf: Introduce bpf_sk_{,ancestor_}cgroup_id helpers

[Andrey Ignatov <rdna@fb.com>]

Yonghong Song <yhs@fb.com> [Thu, 2020-05-14 08:16 -0700]:
> On 5/13/20 2:38 PM, Andrey Ignatov wrote:

> > diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
> > index bfb31c1be219..e3cbc2790cdf 100644
> > --- a/include/uapi/linux/bpf.h
> > +++ b/include/uapi/linux/bpf.h
> > @@ -3121,6 +3121,37 @@ union bpf_attr {
> >    * 		0 on success, or a negative error in case of failure:
> >    *
> >    *		**-EOVERFLOW** if an overflow happened: The same object will be tried again.
> > + *
> > + * u64 bpf_sk_cgroup_id(struct bpf_sock *sk)
> > + *	Description
> > + *		Return the cgroup v2 id of the socket *sk*.
> > + *
> > + *		*sk* must be a non-**NULL** pointer that was returned from
> > + *		**bpf_sk_lookup_xxx**\ (). The format of returned id is same
> 
> It should also include bpf_skc_lookup_tcp(), right?

From what I see it should not.

cgroup id is available from sk->sk_cgrp_data that is a field of `struct
sock', i.e. `struct sock_common' doesn't have this field.

bpf_skc_lookup_tcp() returns RET_PTR_TO_SOCK_COMMON_OR_NULL and it can
be for example `struct request_sock` that has only `struct sock_common`
member, i.e. it doesn't have cgroup id.

-- 
Andrey Ignatov