selftests: mptcp: lib: use setup/cleanup_ns helpers

This patch includes lib.sh into mptcp_lib.sh, uses setup_ns helper
defined in lib.sh to set up namespaces in mptcp_lib_ns_init(), and
uses cleanup_ns to delete namespaces in mptcp_lib_ns_exit().
Signed-off-by: Geliang Tang <tanggeliang@kylinos.cn>
Reviewed-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Signed-off-by: Matthieu Baerts (NGI0) <matttbe@kernel.org>
Link: https://lore.kernel.org/r/20240607-upstream-net-next-20240607-selftests-mptcp-net-lib-v1-5-e36986faac94@kernel.orgSigned-off-by: Jakub Kicinski <kuba@kernel.org>

tools/testing/selftests/net/mptcp/mptcp_lib.sh

 #! /bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
+. "$(dirname "${0}")/../lib.sh"
+
 readonly KSFT_PASS=0
 readonly KSFT_FAIL=1
 readonly KSFT_SKIP=4
@@ -438,17 +440,13 @@ mptcp_lib_check_tools() {
 }
 
 mptcp_lib_ns_init() {
-	local sec rndh
-
-	sec=$(date +%s)
-	rndh=$(printf %x "${sec}")-$(mktemp -u XXXXXX)
+	if ! setup_ns ${@}; then
+		mptcp_lib_pr_fail "Failed to setup namespace ${@}"
+		exit ${KSFT_FAIL}
+	fi
 
 	local netns
 	for netns in "${@}"; do
-		eval "${netns}=${netns}-${rndh}"
-
-		ip netns add "${!netns}" || exit ${KSFT_SKIP}
-		ip -net "${!netns}" link set lo up
 		ip netns exec "${!netns}" sysctl -q net.mptcp.enabled=1
 		ip netns exec "${!netns}" sysctl -q net.ipv4.conf.all.rp_filter=0
 		ip netns exec "${!netns}" sysctl -q net.ipv4.conf.default.rp_filter=0
@@ -456,9 +454,10 @@ mptcp_lib_ns_init() {
 }
 
 mptcp_lib_ns_exit() {
+	cleanup_ns "${@}"
+
 	local netns
 	for netns in "${@}"; do
-		ip netns del "${netns}"
 		rm -f /tmp/"${netns}".{nstat,out}
 	done
 }