Before detach the prog, we should check detach prog exist or not.
Signed-off-by: Zhengchao Shao <shaozhengchao@xxxxxxxxxx>
---
samples/bpf/xdp_fwd_user.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/samples/bpf/xdp_fwd_user.c b/samples/bpf/xdp_fwd_user.c
index 1828487bae9a..a273ede3fd73 100644
--- a/samples/bpf/xdp_fwd_user.c
+++ b/samples/bpf/xdp_fwd_user.c
@@ -49,7 +49,18 @@ static int do_attach(int idx, int prog_fd, int map_fd, const char *name)
static int do_detach(int idx, const char *name)
{
- int err;
+ int err = 1;
+ __u32 curr_prog_id;
+
+ if (bpf_xdp_query_id(idx, xdp_flags, &curr_prog_id)) {
+ printf("ERROR: bpf_xdp_query_id failed\n");
+ return err;
+ }
+
+ if (!curr_prog_id) {
+ printf("ERROR: flags(0x%x) xdp prog is not attached to %s\n", xdp_flags, name);
+ return err;
+ }
err = bpf_xdp_detach(idx, xdp_flags, NULL);
if (err < 0)
--
2.17.1
