Re: [PATCH net-next v3 2/9] selftests: net: add helpers for running a command on other targets

[Ioana Ciornei]

On Fri, Mar 20, 2026 at 11:58:42AM +0100, Petr Machata wrote:
> 
> Ioana Ciornei <ioana.ciornei@xxxxxxx> writes:
> 
> > Add a couple of helpers which can be used by tests which need to run a
> > specific bash command on a different target than the local system, be it
> > either another netns or a remote system accessible through ssh.
> >
> > The run_cmd() function decides where to execute the command passed
> > through $@ based on the env variable TARGET value while run_on() will
> > receive the target through its first argument.
> >
> > Signed-off-by: Ioana Ciornei <ioana.ciornei@xxxxxxx>
> > ---
> > Changes in v3:
> > - s/TARGET/CUR_TARGET
> > - always fallback on running a command locally when either TARGETS is
> >   not declared or there is no entry for a specific interface
> > Changes in v2:
> > - patch is new
> >
> >  tools/testing/selftests/net/lib.sh | 39 ++++++++++++++++++++++++++++++
> >  1 file changed, 39 insertions(+)
> >
> > diff --git a/tools/testing/selftests/net/lib.sh b/tools/testing/selftests/net/lib.sh
> > index b40694573f4c..f7c54d05758e 100644
> > --- a/tools/testing/selftests/net/lib.sh
> > +++ b/tools/testing/selftests/net/lib.sh
> > @@ -28,6 +28,10 @@ EXIT_STATUS=0
> >  # Per-test return value. Clear at the beginning of each test.
> >  RET=0
> >  
> > +# If a specific command needs to be executed on another target than local, set
> > +# this appropriately before calling run_cmd
> > +CUR_TARGET="local:"
> > +
> 
> These are new functions, they should just expose these parameters as
> actual function parameters, not as hidden environment. If it is
> desirable that run_cmd() can run local commands, maybe it makes sense to
> make the current run_cmd() a helper like __run_cmd(), which takes the
> remote-config parameter, and have run_cmd() be a wrapper:
> 
> run_cmd()
> {
> 	__run_cmd local: "$@"
> }

Why I chose to also add a function like run_cmd that makes use of an
environment variable is to support cases such as the following.

get_ifname_by_ip()
{
	local ip_addr=$1; shift

	run_cmd ip -j addr show to "$ip_addr" | jq -r '.[].ifname'
}

Helpers such as get_ifname_by_ip() (added in patch #3) that don't have
access to an interface name so that they can directly call run_on.

Do you mean that for any helpers such as the one above that need to be
run both on the local system and the remote it's better just to add a
new parameter to it that it's indeed the target on which it should be
run and get rid of the run_cmd all together?

get_ifname_by_ip()
{
	local target=$1; shift
	local ip_addr=$1; shift

	run_on "$target" ip -j addr show to "$ip_addr" | jq -r '.[].ifname'
}

Ioana