selftests: forwarding: lib: Extract trap_{, un}install()

A mirror-to-vlan test that's coming next needs to install the trap
unconditionally. Therefore extract from slow_path_trap_{,un}install()
a more generic functions trap_install() and trap_uninstall(), and covert
the former two to conditional wrappers around these.
Signed-off-by: Petr Machata <petrm@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

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

@@ -448,26 +448,35 @@ tc_offload_check()
 	return 0
 }
 
-slow_path_trap_install()
+trap_install()
 {
 	local dev=$1; shift
 	local direction=$1; shift
 
-	if [ "${tcflags/skip_hw}" != "$tcflags" ]; then
-		# For slow-path testing, we need to install a trap to get to
-		# slow path the packets that would otherwise be switched in HW.
-		tc filter add dev $dev $direction pref 1 \
-		   flower skip_sw action trap
-	fi
+	# For slow-path testing, we need to install a trap to get to
+	# slow path the packets that would otherwise be switched in HW.
+	tc filter add dev $dev $direction pref 1 flower skip_sw action trap
 }
 
-slow_path_trap_uninstall()
+trap_uninstall()
 {
 	local dev=$1; shift
 	local direction=$1; shift
 
+	tc filter del dev $dev $direction pref 1 flower skip_sw
+}
+
+slow_path_trap_install()
+{
+	if [ "${tcflags/skip_hw}" != "$tcflags" ]; then
+		trap_install "$@"
+	fi
+}
+
+slow_path_trap_uninstall()
+{
 	if [ "${tcflags/skip_hw}" != "$tcflags" ]; then
-		tc filter del dev $dev $direction pref 1 flower skip_sw
+		trap_uninstall "$@"
 	fi
 }