On 04/23, Jakub Kicinski wrote:
> 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.
Ack, initialization didn't let me do that. But I think I can drop it, I
don't look prog_cnt in the syscall, maybe I should :-/
> > + 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.
Yes, its either attached or not; there is nothing like prog_array.
> > + return 0;
> > +}
