Re: [PATCH bpf-next 4/5] tools/bpftool: add `link detach` subcommand

On Thu, Jul 30, 2020 at 2:02 PM Song Liu [off-list ref] wrote:

quoted

On Jul 29, 2020, at 4:05 PM, Andrii Nakryiko [off-list ref] wrote:

Add ability to force-detach BPF link. Also add missing error message, if
specified link ID is wrong.

Signed-off-by: Andrii Nakryiko <redacted>

Acked-by: Song Liu <redacted>

With two nitpicks below.

[...]

quoted

static int link_parse_fd(int *argc, char ***argv)
{
+     int fd;
+
      if (is_prefix(**argv, "id")) {
              unsigned int id;
              char *endptr;

@@ -35,7 +37,10 @@ static int link_parse_fd(int *argc, char ***argv)
              }
              NEXT_ARGP();

-             return bpf_link_get_fd_by_id(id);
+             fd = bpf_link_get_fd_by_id(id);
+             if (fd < 0)
+                     p_err("failed to get link with ID %d: %d", id, -errno);

How about we print strerror(errno) to match the rest of link.c?

sure, will do, was lazy :)

[...]

quoted

+static int do_detach(int argc, char **argv)
+{
+     int err, fd;
+
+     if (argc != 2)
+             return BAD_ARG();
+
+     fd = link_parse_fd(&argc, &argv);
+     if (fd < 0)
+             return 1;
+
+     err = bpf_link_detach(fd);
+     if (err)
+             err = -errno;
+     close(fd);
+     if (err) {
+             p_err("failed link detach: %d", err);

And strerror(err) here.