On Thu, Oct 13, 2022 at 2:01 PM Gerhard Engleder
<gerhard@xxxxxxxxxxxxxxxxxxxxx> wrote:
>
> BPF map iteration in xdp1_user results in endless loop without any
> output, because the return value of bpf_map_get_next_key() is checked
> against the wrong value.
>
> Other call locations of bpf_map_get_next_key() check for equal 0 for
> continuing the iteration. xdp1_user checks against unequal -1. This is
> wrong for a function which can return arbitrary negative errno values,
> because a return value of e.g. -2 results in an endless loop.
>
> With this fix xdp1_user is printing statistics again:
> proto 0: 1 pkt/s
> proto 0: 1 pkt/s
> proto 17: 107383 pkt/s
> proto 17: 881655 pkt/s
> proto 17: 882083 pkt/s
> proto 17: 881758 pkt/s
>
> Signed-off-by: Gerhard Engleder <gerhard@xxxxxxxxxxxxxxxxxxxxx>
Acked-by: Song Liu <song@xxxxxxxxxx>
> ---
> samples/bpf/xdp1_user.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/samples/bpf/xdp1_user.c b/samples/bpf/xdp1_user.c
> index ac370e638fa3..281dc964de8d 100644
> --- a/samples/bpf/xdp1_user.c
> +++ b/samples/bpf/xdp1_user.c
> @@ -51,7 +51,7 @@ static void poll_stats(int map_fd, int interval)
>
> sleep(interval);
>
> - while (bpf_map_get_next_key(map_fd, &key, &key) != -1) {
> + while (bpf_map_get_next_key(map_fd, &key, &key) == 0) {
> __u64 sum = 0;
>
> assert(bpf_map_lookup_elem(map_fd, &key, values) == 0);
> --
> 2.30.2
>
