selftests: forwarding: lib: Split sysctl_save() out of sysctl_set()

JIRA: https://issues.redhat.com/browse/RHEL-59087

commit 6f51aed
Author: Petr Machata <petrm@nvidia.com>
Date:   Fri Jun 7 17:13:56 2024 +0200

    selftests: forwarding: lib: Split sysctl_save() out of sysctl_set()

    In order to be able to save the current value of a sysctl without changing
    it, split the relevant bit out of sysctl_set() into a new helper.

    Signed-off-by: Petr Machata <petrm@nvidia.com>
    Reviewed-by: Ido Schimmel <idosch@nvidia.com>
    Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
    Reviewed-by: David Ahern <dsahern@kernel.org>
    Link: https://lore.kernel.org/r/20240607151357.421181-5-petrm@nvidia.com
    Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Signed-off-by: CKI Backport Bot <cki-ci-bot+cki-gitlab-backport-bot@redhat.com>
Signed-off-by: Ivan Vecera <ivecera@redhat.com>

Author: ivecera

tools/testing/selftests/net/forwarding/lib.sh

@@ -943,12 +943,19 @@ bridge_ageing_time_get()
 }
 
 declare -A SYSCTL_ORIG
+sysctl_save()
+{
+	local key=$1; shift
+
+	SYSCTL_ORIG[$key]=$(sysctl -n $key)
+}
+
 sysctl_set()
 {
 	local key=$1; shift
 	local value=$1; shift
 
-	SYSCTL_ORIG[$key]=$(sysctl -n $key)
+	sysctl_save "$key"
 	sysctl -qw $key="$value"
 }