Re: [PATCH bpf-next 2/2] bpftool: show flow_dissector attachment status

[Jakub Kicinski]

On Tue, 23 Apr 2019 16:22:00 -0700, Stanislav Fomichev wrote:
> +static int query_flow_dissector(struct bpf_attach_info *attach_info)
> +{
> +     __u32 prog_ids[1] = {0};
> +     __u32 prog_cnt = ARRAY_SIZE(prog_ids);
> +     __u32 attach_flags;
> +     int fd;
> +     int err;

reverse christmas tree, please :)

Move the init into the code if necessary.

> +     fd = open("/proc/self/ns/net", O_RDONLY);
> +     if (fd < 0) {
> +             p_err("can't open /proc/self/ns/net: %d",
> +                   strerror(errno));
> +             return -1;
> +     }
> +     err = bpf_prog_query(fd, BPF_FLOW_DISSECTOR, 0,
> +                          &attach_flags, prog_ids, &prog_cnt);
> +     close(fd);
> +     if (err) {
> +             if (errno == EINVAL) {
> +                     /* Older kernel's don't support querying
> +                      * flow dissector programs.
> +                      */
> +                     return 0;
> +             }
> +             p_err("can't query prog: %s", strerror(errno));
> +             return -1;
> +     }
> +
> +     if (prog_cnt == 1)
> +             attach_info->flow_dissector_id = prog_ids[0];

So the count can only be 0 or 1?  Hm.

> +     return 0;
> +}