Re: [PATCH bpf-next v2] selftests/bpf: Properly enable hwtstamp in xdp_hw_metadata

[Jesper Dangaard Brouer <jbrouer@redhat.com>]

On 26/01/2023 23.50, Stanislav Fomichev wrote:
> The existing timestamping_enable() is a no-op because it applies
> to the socket-related path that we are not verifying here
> anymore. (but still leaving the code around hoping we can
> have xdp->skb path verified here as well)
> 
>    poll: 1 (0)
>    xsk_ring_cons__peek: 1
>    0xf64788: rx_desc[0]->addr=100000000008000 addr=8100 comp_addr=8000
>    rx_hash: 3697961069
>    rx_timestamp:  1674657672142214773 (sec:1674657672.1422)
>    XDP RX-time:   1674657709561774876 (sec:1674657709.5618) delta sec:37.4196
>    AF_XDP time:   1674657709561871034 (sec:1674657709.5619) delta
> sec:0.0001 (96.158 usec)
>    0xf64788: complete idx=8 addr=8000
> 

Again for the record, this output is from my devel version of
xdp_hw_metadata and not what is currently upstream.

Small nit below, which is too late as this is already applied.

> Also, maybe something to archive here, see [0] for Jesper's note
> about NIC vs host clock delta.
> 
> 0: https://lore.kernel.org/bpf/f3a116dc-1b14-3432-ad20-a36179ef0608@redhat.com/
> 
> v2:
> - Restore original value (Martin)
> 
> Fixes: 297a3f124155 ("selftests/bpf: Simple program to dump XDP RX metadata")
> Reported-by: Jesper Dangaard Brouer <jbrouer@redhat.com>
> Tested-by: Jesper Dangaard Brouer <jbrouer@redhat.com>
> Signed-off-by: Stanislav Fomichev <sdf@google.com>
> ---
>   tools/testing/selftests/bpf/xdp_hw_metadata.c | 45 ++++++++++++++++++-
>   1 file changed, 44 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c
> index 0008f0f239e8..3823b1c499cc 100644
> --- a/tools/testing/selftests/bpf/xdp_hw_metadata.c
> +++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
> @@ -24,6 +24,7 @@
>   #include <linux/net_tstamp.h>
>   #include <linux/udp.h>
>   #include <linux/sockios.h>
> +#include <linux/net_tstamp.h>
>   #include <sys/mman.h>
>   #include <net/if.h>
>   #include <poll.h>
> @@ -278,13 +279,53 @@ static int rxq_num(const char *ifname)
>   
>   	ret = ioctl(fd, SIOCETHTOOL, &ifr);
>   	if (ret < 0)
> -		error(-1, errno, "socket");
> +		error(-1, errno, "ioctl(SIOCETHTOOL)");
>   
>   	close(fd);
>   
>   	return ch.rx_count + ch.combined_count;
>   }
>   
> +static void hwtstamp_ioctl(int op, const char *ifname, struct hwtstamp_config *cfg)
> +{
> +	struct ifreq ifr = {
> +		.ifr_data = (void *)cfg,
> +	};
> +	strcpy(ifr.ifr_name, ifname);

I would use strncpy like:

  strncpy(ifr.ifr_name, ifname, IFNAMSIZ - 1);

> +	int fd, ret;
> +
> +	fd = socket(AF_UNIX, SOCK_DGRAM, 0);
> +	if (fd < 0)
> +		error(-1, errno, "socket");
> +
> +	ret = ioctl(fd, op, &ifr);
> +	if (ret < 0)
> +		error(-1, errno, "ioctl(%d)", op);
> +
> +	close(fd);
> +}
> +
> +static struct hwtstamp_config saved_hwtstamp_cfg;
> +static const char *saved_hwtstamp_ifname;
> +
> +static void hwtstamp_restore(void)
> +{
> +	hwtstamp_ioctl(SIOCSHWTSTAMP, saved_hwtstamp_ifname, &saved_hwtstamp_cfg);
> +}
> +
> +static void hwtstamp_enable(const char *ifname)
> +{
> +	struct hwtstamp_config cfg = {
> +		.rx_filter = HWTSTAMP_FILTER_ALL,
> +	};
> +
> +	hwtstamp_ioctl(SIOCGHWTSTAMP, ifname, &saved_hwtstamp_cfg);
> +	saved_hwtstamp_ifname = strdup(ifname);
> +	atexit(hwtstamp_restore);
> +
> +	hwtstamp_ioctl(SIOCSHWTSTAMP, ifname, &cfg);
> +}
> +
>   static void cleanup(void)
>   {
>   	LIBBPF_OPTS(bpf_xdp_attach_opts, opts);
> @@ -341,6 +382,8 @@ int main(int argc, char *argv[])
>   
>   	printf("rxq: %d\n", rxq);
>   
> +	hwtstamp_enable(ifname);
> +
>   	rx_xsk = malloc(sizeof(struct xsk) * rxq);
>   	if (!rx_xsk)
>   		error(-1, ENOMEM, "malloc");