Re: [PATCH v17 0/3] BPF: New helper to obtain namespace data from current task

From: Quentin Monnet <quentin@isovalent.com>
To: Alexei Starovoitov <alexei.starovoitov@gmail.com>,
	Carlos Neira <cneirabustos@gmail.com>
Cc: Network Development <netdev@vger.kernel.org>,
	Yonghong Song <yhs@fb.com>,
	"Eric W. Biederman" <ebiederm@xmission.com>,
	Jesper Dangaard Brouer <brouer@redhat.com>,
	bpf <bpf@vger.kernel.org>
Subject: Re: [PATCH v17 0/3] BPF: New helper to obtain namespace data from current task
Date: Fri, 13 Mar 2020 10:39:41 +0000	[thread overview]
Message-ID: <33447490-7fa2-f56d-3622-d61c9c2046e5@isovalent.com> (raw)
In-Reply-To: <CAADnVQL4GR2kOoiLE0aTorvYzTPWrOCV4yKMh1BasYTVHkKxcg@mail.gmail.com>

2020-03-12 17:45 UTC-0700 ~ Alexei Starovoitov <alexei.starovoitov@gmail.com>
> On Wed, Mar 4, 2020 at 12:42 PM Carlos Neira <cneirabustos@gmail.com> wrote:
>>
>> Currently bpf_get_current_pid_tgid(), is used to do pid filtering in bcc's
>> scripts but this helper returns the pid as seen by the root namespace which is
>> fine when a bcc script is not executed inside a container.
>> When the process of interest is inside a container, pid filtering will not work
>> if bpf_get_current_pid_tgid() is used.
>> This helper addresses this limitation returning the pid as it's seen by the current
>> namespace where the script is executing.
>>
>> In the future different pid_ns files may belong to different devices, according to the
>> discussion between Eric Biederman and Yonghong in 2017 Linux plumbers conference.
>> To address that situation the helper requires inum and dev_t from /proc/self/ns/pid.
>> This helper has the same use cases as bpf_get_current_pid_tgid() as it can be
>> used to do pid filtering even inside a container.
> 
> Applied. Thanks.
> There was one spurious trailing whitespace that I fixed in patch 3
> and missing .gitignore update for test_current_pid_tgid_new_ns.
> Could you please follow up with another patch to fold
> test_current_pid_tgid_new_ns into test_progs.
> I'd really like to consolidate all tests into single binary.
> 

Compiling bpftool (with libbpf now relying on bpf_helper_defs.h
generated from helpers documentation), I observe the following
warning:

    .output/bpf_helper_defs.h:2834:72: warning: declaration of 'struct bpf_pidns_info' will not be visible outside of this function [-Wvisibility]
    static int (*bpf_get_ns_current_pid_tgid)(__u64 dev, __u64 ino, struct bpf_pidns_info *nsdata, __u32 size) = (void *) 120;

Would it be possible to address this as part of the follow-up too,
please? I think the fix would be to add "struct bpf_pidns_info"
to type_fds (I see it was added to known_types already) in
scripts/bpf_helpers_doc.py.

Thanks,
Quentin