[PATCH bpf] samples/bpf: xdp_redirect, correctly get dummy program id

[PATCH bpf] samples/bpf: xdp_redirect, correctly get dummy program id

[Prashant Bhole]

When we terminate xdp_redirect, it ends up with following message:
"Program on iface OUT changed, not removing"
This results in dummy prog still attached to OUT interface.
It is because signal handler checks if the programs are the same that
we had attached. But while fetching dummy_prog_id, current code uses
prog_fd instead of dummy_prog_fd. This patch passes the correct fd.

Fixes: 3b7a8ec2dec3 ("samples/bpf: Check the prog id before exiting")
Signed-off-by: Prashant Bhole <prashantbhole.linux@gmail.com>
---
 samples/bpf/xdp_redirect_user.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/samples/bpf/xdp_redirect_user.c b/samples/bpf/xdp_redirect_user.c
index e9054c0269ff..1299e0f61dad 100644
--- a/samples/bpf/xdp_redirect_user.c
+++ b/samples/bpf/xdp_redirect_user.c
@@ -197,7 +197,7 @@ int main(int argc, char **argv)
 	}
 
 	memset(&info, 0, sizeof(info));
-	ret = bpf_obj_get_info_by_fd(prog_fd, &info, &info_len);
+	ret = bpf_obj_get_info_by_fd(dummy_prog_fd, &info, &info_len);
 	if (ret) {
 		printf("can't get prog info - %s\n", strerror(errno));
 		return ret;
-- 
2.20.1

Re: [PATCH bpf] samples/bpf: xdp_redirect, correctly get dummy program id

[Toke Høiland-Jørgensen]

Prashant Bhole <prashantbhole.linux@gmail.com> writes:

> When we terminate xdp_redirect, it ends up with following message:
> "Program on iface OUT changed, not removing"
> This results in dummy prog still attached to OUT interface.
> It is because signal handler checks if the programs are the same that
> we had attached. But while fetching dummy_prog_id, current code uses
> prog_fd instead of dummy_prog_fd. This patch passes the correct fd.
>
> Fixes: 3b7a8ec2dec3 ("samples/bpf: Check the prog id before exiting")
> Signed-off-by: Prashant Bhole <prashantbhole.linux@gmail.com>

Huh, I seem to recall fixing this for the other example program, but
guess I missed this one.

Acked-by: Toke Høiland-Jørgensen <toke@redhat.com>

Re: [PATCH bpf] samples/bpf: xdp_redirect, correctly get dummy program id

[Daniel Borkmann]

On 06/20/2019 08:58 AM, Prashant Bhole wrote:
> When we terminate xdp_redirect, it ends up with following message:
> "Program on iface OUT changed, not removing"
> This results in dummy prog still attached to OUT interface.
> It is because signal handler checks if the programs are the same that
> we had attached. But while fetching dummy_prog_id, current code uses
> prog_fd instead of dummy_prog_fd. This patch passes the correct fd.
> 
> Fixes: 3b7a8ec2dec3 ("samples/bpf: Check the prog id before exiting")
> Signed-off-by: Prashant Bhole <prashantbhole.linux@gmail.com>

Applied, thanks!