selftests: net: lib: Add several autodefer helpers

Add ip_link_set_addr(), ip_link_set_up(), ip_addr_add() and ip_route_add()
to the suite of helpers that automatically schedule a corresponding
cleanup.

When setting a new MAC, one needs to remember the old address first. Move
mac_get() from forwarding/ to that end.

Signed-off-by: Petr Machata <petrm@nvidia.com>
Reviewed-by: Ido Schimmel <idosch@nvidia.com>
Reviewed-by: Nikolay Aleksandrov <razor@blackwall.org>
Link: https://patch.msgid.link/add6bcbe30828fd01363266df20c338cf13aaf25.1733412063.git.petrm@nvidia.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

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

@@ -932,13 +932,6 @@ packets_rate()
 	echo $(((t1 - t0) / interval))
 }
 
-mac_get()
-{
-	local if_name=$1
-
-	ip -j link show dev $if_name | jq -r '.[]["address"]'
-}
-
 ether_addr_to_u64()
 {
 	local addr="$1"

tools/testing/selftests/net/lib.sh

@@ -435,6 +435,13 @@ xfail_on_veth()
 	fi
 }
 
+mac_get()
+{
+	local if_name=$1
+
+	ip -j link show dev $if_name | jq -r '.[]["address"]'
+}
+
 kill_process()
 {
 	local pid=$1; shift
@@ -459,3 +466,35 @@ ip_link_set_master()
 	ip link set dev "$member" master "$master"
 	defer ip link set dev "$member" nomaster
 }
+
+ip_link_set_addr()
+{
+	local name=$1; shift
+	local addr=$1; shift
+
+	local old_addr=$(mac_get "$name")
+	ip link set dev "$name" address "$addr"
+	defer ip link set dev "$name" address "$old_addr"
+}
+
+ip_link_set_up()
+{
+	local name=$1; shift
+
+	ip link set dev "$name" up
+	defer ip link set dev "$name" down
+}
+
+ip_addr_add()
+{
+	local name=$1; shift
+
+	ip addr add dev "$name" "$@"
+	defer ip addr del dev "$name" "$@"
+}
+
+ip_route_add()
+{
+	ip route add "$@"
+	defer ip route del "$@"
+}