[xdp-hints] Re: [PATCH bpf-next v8 17/17] selftests/bpf: Simple program to dump XDP RX metadata

[Stanislav Fomichev <sdf@google.com>]

On Tue, Jan 24, 2023 at 7:26 AM Jesper Dangaard Brouer
<jbrouer@redhat.com> wrote:
>
>
> Testing this on mlx5 and I'm not getting the RX-timestamp.
> See command details below.

CC'ed Toke since I've never tested mlx5 myself.
I was pretty close to getting the setup late last week, let me try to
see whether it's ready or not.

> On 19/01/2023 23.15, Stanislav Fomichev wrote:
> > To be used for verification of driver implementations. Note that
> > the skb path is gone from the series, but I'm still keeping the
> > implementation for any possible future work.
> >
> > $ xdp_hw_metadata <ifname>
>
> sudo ./xdp_hw_metadata mlx5p1
>
> Output:
> [...cut ...]
> open bpf program...
> load bpf program...
> prepare skb endpoint...
> XXX timestamping_enable(): setsockopt(SO_TIMESTAMPING) ret:0
> prepare xsk map...
> map[0] = 3
> map[1] = 4
> map[2] = 5
> map[3] = 6
> map[4] = 7
> map[5] = 8
> attach bpf program...
> poll: 0 (0)
> poll: 0 (0)
> poll: 0 (0)
> poll: 1 (0)
> xsk_ring_cons__peek: 1
> 0x1821788: rx_desc[0]->addr=100000000008000 addr=8100 comp_addr=8000
> rx_timestamp: 0
> rx_hash: 2773355807
> 0x1821788: complete idx=8 addr=8000
> poll: 0 (0)
>
> The trace_pipe:
>
> $ sudo cat /sys/kernel/debug/tracing/trace_pipe
>            <idle>-0       [005] ..s2.  2722.884762: bpf_trace_printk:
> forwarding UDP:9091 to AF_XDP
>            <idle>-0       [005] ..s2.  2722.884771: bpf_trace_printk:
> populated rx_hash with 2773355807
>
>
> > On the other machine:
> >
> > $ echo -n xdp | nc -u -q1 <target> 9091 # for AF_XDP
>
> Fixing the source-port to see if RX-hash remains the same.
>
>   $ echo xdp | nc --source-port=2000 --udp 198.18.1.1 9091
>
> > $ echo -n skb | nc -u -q1 <target> 9092 # for skb
> >
> > Sample output:
> >
> >    # xdp
> >    xsk_ring_cons__peek: 1
> >    0x19f9090: rx_desc[0]->addr=100000000008000 addr=8100 comp_addr=8000
> >    rx_timestamp_supported: 1
> >    rx_timestamp: 1667850075063948829
> >    0x19f9090: complete idx=8 addr=8000
>
> xsk_ring_cons__peek: 1
> 0x1821788: rx_desc[0]->addr=100000000008000 addr=8100 comp_addr=8000
> rx_timestamp: 0
> rx_hash: 2773355807
> 0x1821788: complete idx=8 addr=8000
>
> It doesn't look like hardware RX-timestamps are getting enabled.
>
> [... cut to relevant code ...]
>
> > diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c
> > new file mode 100644
> > index 000000000000..0008f0f239e8
> > --- /dev/null
> > +++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
> > @@ -0,0 +1,403 @@
> [...]
>
> > +static void timestamping_enable(int fd, int val)
> > +{
> > +     int ret;
> > +
> > +     ret = setsockopt(fd, SOL_SOCKET, SO_TIMESTAMPING, &val, sizeof(val));
> > +     if (ret < 0)
> > +             error(-1, errno, "setsockopt(SO_TIMESTAMPING)");
> > +}
> > +
> > +int main(int argc, char *argv[])
> > +{
> [...]
>
> > +     printf("prepare skb endpoint...\n");
> > +     server_fd = start_server(AF_INET6, SOCK_DGRAM, NULL, 9092, 1000);
> > +     if (server_fd < 0)
> > +             error(-1, errno, "start_server");
> > +     timestamping_enable(server_fd,
> > +                         SOF_TIMESTAMPING_SOFTWARE |
> > +                         SOF_TIMESTAMPING_RAW_HARDWARE);
> > +
>
> I don't think this timestamping_enable() with these flags are enough to
> enable hardware timestamping.
>
> --Jesper
>