Subject: Re: [patch net-next v2 5/6] selftests: forwarding: add wait_for_dev() helper

From: Benjamin Poirier <[email-masked]>
Date: Mon, 15 Apr 2024 17:39:42 -0400

On 2024-04-15 18:25 +0200, Jiri Pirko wrote:
> From: Jiri Pirko <[email-masked]>
> 
> The existing setup_wait*() helper family check the status of the
> interface to be up. Introduce wait_for_dev() to wait for the netdevice
> to appear, for example after test script does manual device bind.
> 
> Signed-off-by: Jiri Pirko <[email-masked]>
> ---
> v1->v2:
> - reworked wait_for_dev() helper to use slowwait() helper
> ---
>  tools/testing/selftests/net/forwarding/lib.sh | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/tools/testing/selftests/net/forwarding/lib.sh b/tools/testing/selftests/net/forwarding/lib.sh
> index 254698c6ba56..e85b361dc85d 100644
> --- a/tools/testing/selftests/net/forwarding/lib.sh
> +++ b/tools/testing/selftests/net/forwarding/lib.sh
> @@ -746,6 +746,19 @@ setup_wait()
>  	sleep $WAIT_TIME
>  }
>  
> +wait_for_dev()
> +{
> +        local dev=$1; shift
> +        local timeout=${1:-$WAIT_TIMEOUT}; shift
> +
> +        slowwait $timeout ip link show dev $dev up &> /dev/null

Sorry, I just noticed that this includes the "up" flag. I was confused
for a while until I realized that `ip` returns success even if the
interface is not up:

# ip link set dev eth1 down
# ip link show dev eth1 up
# echo $?
0

So wait_for_dev() really does just wait for the device to appear, not
for it to be up. If you agree, please remove the 'up' keyword to avoid
confusion.