Subject: Re: [PATCH bpf-next v2 2/3] bpf: add BPF_PROG_TEST_RUN support for flow dissector

From: Stanislav Fomichev <[email-masked]>
Date: Fri, 25 Jan 2019 16:56:13 -0800

On 01/25, Song Liu wrote:
> On Thu, Jan 24, 2019 at 8:53 AM Stanislav Fomichev <[email-masked]> wrote:
> >
> > The input is packet data, the output is struct bpf_flow_key. This should
> > make it easy to test flow dissector programs without elaborate
> > setup.
> >
> > Signed-off-by: Stanislav Fomichev <[email-masked]>
> > ---
> >  include/linux/bpf.h |  3 ++
> >  net/bpf/test_run.c  | 82 +++++++++++++++++++++++++++++++++++++++++++++
> >  net/core/filter.c   |  1 +
> >  3 files changed, 86 insertions(+)
> >
> > diff --git a/include/linux/bpf.h b/include/linux/bpf.h
> > index e734f163bd0b..701ef954a258 100644
> > --- a/include/linux/bpf.h
> > +++ b/include/linux/bpf.h
> > @@ -397,6 +397,9 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
> >                           union bpf_attr __user *uattr);
> >  int bpf_prog_test_run_skb(struct bpf_prog *prog, const union bpf_attr *kattr,
> >                           union bpf_attr __user *uattr);
> > +int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
> > +                                    const union bpf_attr *kattr,
> > +                                    union bpf_attr __user *uattr);
> >
> >  /* an array of programs to be executed under rcu_lock.
> >   *
> > diff --git a/net/bpf/test_run.c b/net/bpf/test_run.c
> > index fa2644d276ef..2c5172b33209 100644
> > --- a/net/bpf/test_run.c
> > +++ b/net/bpf/test_run.c
> > @@ -240,3 +240,85 @@ int bpf_prog_test_run_xdp(struct bpf_prog *prog, const union bpf_attr *kattr,
> >         kfree(data);
> >         return ret;
> >  }
> > +
> > +int bpf_prog_test_run_flow_dissector(struct bpf_prog *prog,
> > +                                    const union bpf_attr *kattr,
> > +                                    union bpf_attr __user *uattr)
> 
> I think this function duplicates a lot of logic from bpf_prog_test_run_skb().
> Can we somehow reuse bpf_prog_test_run_skb()?
I did that initially
(https://marc.info/?l=linux-netdev&m=154830227529929&w=2), but then
Alexey suggested that there is not much to reuse (plus can hinder the
test performance of the existing types).
> 
> Thanks,
> Song
> 
> 
> > +{
> > +       u32 size = kattr->test.data_size_in;
> > +       u32 repeat = kattr->test.repeat;
> > +       struct bpf_flow_keys flow_keys;
> > +       u64 time_start, time_spent = 0;
> > +       struct bpf_skb_data_end *cb;
> > +       u32 retval, duration;
> > +       struct sk_buff *skb;
> > +       struct sock *sk;
> > +       void *data;
> > +       int ret;
> > +       u32 i;
> > +
> > +       if (prog->type != BPF_PROG_TYPE_FLOW_DISSECTOR)
> > +               return -EINVAL;
> > +
> > +       data = bpf_test_init(kattr, size, NET_SKB_PAD + NET_IP_ALIGN,
> > +                            SKB_DATA_ALIGN(sizeof(struct skb_shared_info)));
> > +       if (IS_ERR(data))
> > +               return PTR_ERR(data);
> > +
> > +       sk = kzalloc(sizeof(*sk), GFP_USER);
> > +       if (!sk) {
> > +               kfree(data);
> > +               return -ENOMEM;
> > +       }
> > +       sock_net_set(sk, current->nsproxy->net_ns);
> > +       sock_init_data(NULL, sk);
> > +
> > +       skb = build_skb(data, 0);
> > +       if (!skb) {
> > +               kfree(data);
> > +               kfree(sk);
> > +               return -ENOMEM;
> > +       }
> > +       skb->sk = sk;
> > +
> > +       skb_reserve(skb, NET_SKB_PAD + NET_IP_ALIGN);
> > +       __skb_put(skb, size);
> > +       skb->protocol = eth_type_trans(skb,
> > +                                      current->nsproxy->net_ns->loopback_dev);
> > +       skb_reset_network_header(skb);
> > +
> > +       cb = (struct bpf_skb_data_end *)skb->cb;
> > +       cb->qdisc_cb.flow_keys = &flow_keys;
> > +
> > +       if (!repeat)
> > +               repeat = 1;
> > +
> > +       time_start = ktime_get_ns();
> > +       for (i = 0; i < repeat; i++) {
> > +               preempt_disable();
> > +               rcu_read_lock();
> > +               retval = __skb_flow_bpf_dissect(prog, skb,
> > +                                               &flow_keys_dissector,
> > +                                               &flow_keys);
> > +               rcu_read_unlock();
> > +               preempt_enable();
> > +
> > +               if (need_resched()) {
> > +                       if (signal_pending(current))
> > +                               break;
> > +                       time_spent += ktime_get_ns() - time_start;
> > +                       cond_resched();
> > +                       time_start = ktime_get_ns();
> > +               }
> > +       }
> > +       time_spent += ktime_get_ns() - time_start;
> > +       do_div(time_spent, repeat);
> > +       duration = time_spent > U32_MAX ? U32_MAX : (u32)time_spent;
> > +
> > +       ret = bpf_test_finish(kattr, uattr, &flow_keys, sizeof(flow_keys),
> > +                             retval, duration);
> > +
> > +       kfree_skb(skb);
> > +       kfree(sk);
> > +       return ret;
> > +}
> > diff --git a/net/core/filter.c b/net/core/filter.c
> > index 2b3b436ef545..ff4641dae2be 100644
> > --- a/net/core/filter.c
> > +++ b/net/core/filter.c
> > @@ -7690,6 +7690,7 @@ const struct bpf_verifier_ops flow_dissector_verifier_ops = {
> >  };
> >
> >  const struct bpf_prog_ops flow_dissector_prog_ops = {
> > +       .test_run               = bpf_prog_test_run_flow_dissector,
> >  };
> >
> >  int sk_detach_filter(struct sock *sk)
> > --
> > 2.20.1.321.g9e740568ce-goog
> >