netdev - Re: [PATCH bpf-next 1/2] bpf: expose __sk_buff wire_len/gso_segs to BPF_PROG_TEST

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Message-ID: <20191213220600.GQ3105713@mini-arch>
Date:   Fri, 13 Dec 2019 14:06:00 -0800
From:   Stanislav Fomichev <sdf@...ichev.me>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Stanislav Fomichev <sdf@...gle.com>,
        Network Development <netdev@...r.kernel.org>,
        bpf <bpf@...r.kernel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [PATCH bpf-next 1/2] bpf: expose __sk_buff wire_len/gso_segs to
 BPF_PROG_TEST_RUN

On 12/13, Alexei Starovoitov wrote:
> On Fri, Dec 13, 2019 at 1:23 PM Stanislav Fomichev <sdf@...ichev.me> wrote:
> >
> > On 12/13, Alexei Starovoitov wrote:
> > > On Wed, Dec 11, 2019 at 9:53 AM Stanislav Fomichev <sdf@...gle.com> wrote:
> > > >
> > > > wire_len should not be less than real len and is capped by GSO_MAX_SIZE.
> > > > gso_segs is capped by GSO_MAX_SEGS.
> > > >
> > > > Signed-off-by: Stanislav Fomichev <sdf@...gle.com>
> > >
> > > This change breaks tests:
> > > ./test_progs -n 16
> > > test_kfree_skb:PASS:prog_load sched cls 0 nsec
> > > test_kfree_skb:PASS:prog_load raw tp 0 nsec
> > > test_kfree_skb:PASS:find_prog 0 nsec
> > > test_kfree_skb:PASS:find_prog 0 nsec
> > > test_kfree_skb:PASS:find_prog 0 nsec
> > > test_kfree_skb:PASS:find global data 0 nsec
> > > test_kfree_skb:PASS:attach_raw_tp 0 nsec
> > > test_kfree_skb:PASS:attach fentry 0 nsec
> > > test_kfree_skb:PASS:attach fexit 0 nsec
> > > test_kfree_skb:PASS:find_perf_buf_map 0 nsec
> > > test_kfree_skb:PASS:perf_buf__new 0 nsec
> > > test_kfree_skb:FAIL:ipv6 err -1 errno 22 retval 0 duration 0
> > > on_sample:PASS:check_size 0 nsec
> > > on_sample:PASS:check_meta_ifindex 0 nsec
> > > on_sample:PASS:check_cb8_0 0 nsec
> > > on_sample:PASS:check_cb32_0 0 nsec
> > > on_sample:PASS:check_eth 0 nsec
> > > on_sample:PASS:check_ip 0 nsec
> > > on_sample:PASS:check_tcp 0 nsec
> > > test_kfree_skb:PASS:perf_buffer__poll 0 nsec
> > > test_kfree_skb:PASS:get_result 0 nsec
> > > #16 kfree_skb:FAIL
> > > Summary: 0/0 PASSED, 0 SKIPPED, 1 FAILED
> > Ugh, it's probably because of '__skb->wire_len < skb->len' check.
> > Let me take a look.
> >
> > (sorry, I'm still not running/looking at full test_progs because BTF support
> > is WIP in our toolchain and some subtests fail because of that,
> > generating a bunch of noise).
> 
> I thought all bpf-next developers are developing against that tree ?
I am developing against that tree, but I have a wrapper around
make that points it to the proper version of cc/tools that we
use for prod builds (for consistency).

> Are you saying you cannot install the latest clang/pahole on your
> development system?
> git pull llvm;ninja;ninja install;
> git pull pahole; cmake;make
> why is it not possible?
Yeah, I'll do that now, it just requires some manual movements :-)

> Now your complains about skeleton make more sense,
> but it's an issue with your particular setup.
> 
> Anyway I'm not sure that this test issue is actually an issue with your patch.
> It could be that this test is flaky in a weird way. Just with and without your
> kernel patch it's 100% reproducible for me and I need to keep the rest
> of the patches
> moving without introducing failures in my test setup.
> All that will get resolved when we have kernel CI.
No, I'm pretty sure that's that wire_len check. I think I need to add
a special case to set it to skb->len if it's zero.
Will follow up with a v2!