diff --git a/tools/testing/selftests/net/mptcp/diag.sh b/tools/testing/selftests/net/mptcp/diag.sh
index cc8bdf95b104..afe862895946 100755
--- a/tools/testing/selftests/net/mptcp/diag.sh
+++ b/tools/testing/selftests/net/mptcp/diag.sh
@@ -1,12 +1,14 @@
 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
+# Double quotes to prevent globbing and word splitting is recommended in new
+# code but we accept it, especially because there were too many before having
+# address all other issues detected by shellcheck.
+#shellcheck disable=SC2086
+
 . "$(dirname "${0}")/mptcp_lib.sh"
 
-sec=$(date +%s)
-rndh=$(printf %x $sec)-$(mktemp -u XXXXXX)
-ns="ns1-$rndh"
-ksft_skip=4
+ns=""
 test_cnt=1
 timeout_poll=30
 timeout_test=$((timeout_poll * 2 + 1))
@@ -26,25 +28,17 @@ flush_pids()
 	done
 }
 
+# This function is used in the cleanup trap
+#shellcheck disable=SC2317
 cleanup()
 {
 	ip netns pids "${ns}" | xargs --no-run-if-empty kill -SIGKILL &>/dev/null
 
-	ip netns del $ns
+	mptcp_lib_ns_exit "${ns}"
 }
 
 mptcp_lib_check_mptcp
-
-ip -Version > /dev/null 2>&1
-if [ $? -ne 0 ];then
-	echo "SKIP: Could not run test without ip tool"
-	exit $ksft_skip
-fi
-ss -h | grep -q MPTCP
-if [ $? -ne 0 ];then
-	echo "SKIP: ss tool does not support MPTCP"
-	exit $ksft_skip
-fi
+mptcp_lib_check_tools ip ss
 
 get_msk_inuse()
 {
@@ -186,7 +180,7 @@ chk_msk_inuse()
 	expected=$((expected + listen_nr))
 
 	for _ in $(seq 10); do
-		if [ $(get_msk_inuse) -eq $expected ];then
+		if [ "$(get_msk_inuse)" -eq $expected ]; then
 			break
 		fi
 		sleep 0.1
@@ -224,8 +218,7 @@ wait_connected()
 }
 
 trap cleanup EXIT
-ip netns add $ns
-ip -n $ns link set dev lo up
+mptcp_lib_ns_init ns
 
 echo "a" | \
 	timeout ${timeout_test} \
@@ -273,7 +266,7 @@ chk_msk_inuse 0 "1->0"
 chk_msk_cestab 0 "1->0"
 
 NR_CLIENTS=100
-for I in `seq 1 $NR_CLIENTS`; do
+for I in $(seq 1 $NR_CLIENTS); do
 	echo "a" | \
 		timeout ${timeout_test} \
 			ip netns exec $ns \
@@ -282,7 +275,7 @@ for I in `seq 1 $NR_CLIENTS`; do
 done
 mptcp_lib_wait_local_port_listen $ns $((NR_CLIENTS + 10001))
 
-for I in `seq 1 $NR_CLIENTS`; do
+for I in $(seq 1 $NR_CLIENTS); do
 	echo "b" | \
 		timeout ${timeout_test} \
 			ip netns exec $ns \
diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.sh b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
index 7898d62fce0b..0ca2960c9099 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_connect.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
@@ -1,6 +1,11 @@
 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
+# Double quotes to prevent globbing and word splitting is recommended in new
+# code but we accept it, especially because there were too many before having
+# address all other issues detected by shellcheck.
+#shellcheck disable=SC2086
+
 . "$(dirname "${0}")/mptcp_lib.sh"
 
 time_start=$(date +%s)
@@ -13,7 +18,6 @@ sout=""
 cin_disconnect=""
 cin=""
 cout=""
-ksft_skip=4
 capture=false
 timeout_poll=30
 timeout_test=$((timeout_poll * 2 + 1))
@@ -121,16 +125,16 @@ while getopts "$optstring" option;do
 	esac
 done
 
-sec=$(date +%s)
-rndh=$(printf %x $sec)-$(mktemp -u XXXXXX)
-ns1="ns1-$rndh"
-ns2="ns2-$rndh"
-ns3="ns3-$rndh"
-ns4="ns4-$rndh"
+ns1=""
+ns2=""
+ns3=""
+ns4=""
 
 TEST_COUNT=0
 TEST_GROUP=""
 
+# This function is used in the cleanup trap
+#shellcheck disable=SC2317
 cleanup()
 {
 	rm -f "$cin_disconnect" "$cout_disconnect"
@@ -138,21 +142,12 @@ cleanup()
 	rm -f "$sin" "$sout"
 	rm -f "$capout"
 
-	local netns
-	for netns in "$ns1" "$ns2" "$ns3" "$ns4";do
-		ip netns del $netns
-		rm -f /tmp/$netns.{nstat,out}
-	done
+	mptcp_lib_ns_exit "${ns1}" "${ns2}" "${ns3}" "${ns4}"
 }
 
 mptcp_lib_check_mptcp
 mptcp_lib_check_kallsyms
-
-ip -Version > /dev/null 2>&1
-if [ $? -ne 0 ];then
-	echo "SKIP: Could not run test without ip tool"
-	exit $ksft_skip
-fi
+mptcp_lib_check_tools ip
 
 sin=$(mktemp)
 sout=$(mktemp)
@@ -163,10 +158,7 @@ cin_disconnect="$cin".disconnect
 cout_disconnect="$cout".disconnect
 trap cleanup EXIT
 
-for i in "$ns1" "$ns2" "$ns3" "$ns4";do
-	ip netns add $i || exit $ksft_skip
-	ip -net $i link set lo up
-done
+mptcp_lib_ns_init ns1 ns2 ns3 ns4
 
 #  "$ns1"              ns2                    ns3                     ns4
 # ns1eth2    ns2eth1   ns2eth3      ns3eth2   ns3eth4       ns4eth3
@@ -225,8 +217,9 @@ set_ethtool_flags() {
 	local dev="$2"
 	local flags="$3"
 
-	ip netns exec $ns ethtool -K $dev $flags 2>/dev/null
-	[ $? -eq 0 ] && echo "INFO: set $ns dev $dev: ethtool -K $flags"
+	if ip netns exec $ns ethtool -K $dev $flags 2>/dev/null; then
+		echo "INFO: set $ns dev $dev: ethtool -K $flags"
+	fi
 }
 
 set_random_ethtool_flags() {
@@ -256,8 +249,8 @@ fi
 
 check_mptcp_disabled()
 {
-	local disabled_ns="ns_disabled-$rndh"
-	ip netns add ${disabled_ns} || exit $ksft_skip
+	local disabled_ns
+	mptcp_lib_ns_init disabled_ns
 
 	# net.mptcp.enabled should be enabled by default
 	if [ "$(ip netns exec ${disabled_ns} sysctl net.mptcp.enabled | awk '{ print $3 }')" -ne 1 ]; then
@@ -271,7 +264,7 @@ check_mptcp_disabled()
 	local err=0
 	LC_ALL=C ip netns exec ${disabled_ns} ./mptcp_connect -p 10000 -s MPTCP 127.0.0.1 < "$cin" 2>&1 | \
 		grep -q "^socket: Protocol not available$" && err=1
-	ip netns delete ${disabled_ns}
+	mptcp_lib_ns_exit "${disabled_ns}"
 
 	if [ ${err} -eq 0 ]; then
 		echo -e "New MPTCP socket cannot be blocked via sysctl\t\t[ FAIL ]"
@@ -321,7 +314,7 @@ do_transfer()
 	local extra_args="$7"
 
 	local port
-	port=$((10000+$TEST_COUNT))
+	port=$((10000+TEST_COUNT))
 	TEST_COUNT=$((TEST_COUNT+1))
 
 	if [ "$rcvbuf" -gt 0 ]; then
@@ -353,6 +346,7 @@ do_transfer()
 
 	if $capture; then
 		local capuser
+		local rndh="${connector_ns:4}"
 		if [ -z $SUDO_USER ] ; then
 			capuser=""
 		else
@@ -378,12 +372,18 @@ do_transfer()
 			nstat -n
 	fi
 
-	local stat_synrx_last_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableSYNRX")
-	local stat_ackrx_last_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableACKRX")
-	local stat_cookietx_last=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtSyncookiesSent")
-	local stat_cookierx_last=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtSyncookiesRecv")
-	local stat_csum_err_s=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtDataCsumErr")
-	local stat_csum_err_c=$(mptcp_lib_get_counter "${connector_ns}" "MPTcpExtDataCsumErr")
+	local stat_synrx_last_l
+	local stat_ackrx_last_l
+	local stat_cookietx_last
+	local stat_cookierx_last
+	local stat_csum_err_s
+	local stat_csum_err_c
+	stat_synrx_last_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableSYNRX")
+	stat_ackrx_last_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableACKRX")
+	stat_cookietx_last=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtSyncookiesSent")
+	stat_cookierx_last=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtSyncookiesRecv")
+	stat_csum_err_s=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtDataCsumErr")
+	stat_csum_err_c=$(mptcp_lib_get_counter "${connector_ns}" "MPTcpExtDataCsumErr")
 
 	timeout ${timeout_test} \
 		ip netns exec ${listener_ns} \
@@ -446,11 +446,16 @@ do_transfer()
 	mptcp_lib_check_transfer $cin $sout "file received by server"
 	rets=$?
 
-	local stat_synrx_now_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableSYNRX")
-	local stat_ackrx_now_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableACKRX")
-	local stat_cookietx_now=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtSyncookiesSent")
-	local stat_cookierx_now=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtSyncookiesRecv")
-	local stat_ooo_now=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtTCPOFOQueue")
+	local stat_synrx_now_l
+	local stat_ackrx_now_l
+	local stat_cookietx_now
+	local stat_cookierx_now
+	local stat_ooo_now
+	stat_synrx_now_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableSYNRX")
+	stat_ackrx_now_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableACKRX")
+	stat_cookietx_now=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtSyncookiesSent")
+	stat_cookierx_now=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtSyncookiesRecv")
+	stat_ooo_now=$(mptcp_lib_get_counter "${listener_ns}" "TcpExtTCPOFOQueue")
 
 	expect_synrx=$((stat_synrx_last_l))
 	expect_ackrx=$((stat_ackrx_last_l))
@@ -459,8 +464,8 @@ do_transfer()
 	cookies=${cookies##*=}
 
 	if [ ${cl_proto} = "MPTCP" ] && [ ${srv_proto} = "MPTCP" ]; then
-		expect_synrx=$((stat_synrx_last_l+$connect_per_transfer))
-		expect_ackrx=$((stat_ackrx_last_l+$connect_per_transfer))
+		expect_synrx=$((stat_synrx_last_l+connect_per_transfer))
+		expect_ackrx=$((stat_ackrx_last_l+connect_per_transfer))
 	fi
 
 	if [ ${stat_synrx_now_l} -lt ${expect_synrx} ]; then
@@ -468,7 +473,7 @@ do_transfer()
 			"${stat_synrx_now_l}" "${expect_synrx}" 1>&2
 		retc=1
 	fi
-	if [ ${stat_ackrx_now_l} -lt ${expect_ackrx} -a ${stat_ooo_now} -eq 0 ]; then
+	if [ ${stat_ackrx_now_l} -lt ${expect_ackrx} ] && [ ${stat_ooo_now} -eq 0 ]; then
 		if [ ${stat_ooo_now} -eq 0 ]; then
 			printf "[ FAIL ] lower MPC ACK rx (%d) than expected (%d)\n" \
 				"${stat_ackrx_now_l}" "${expect_ackrx}" 1>&2
@@ -479,18 +484,20 @@ do_transfer()
 	fi
 
 	if $checksum; then
-		local csum_err_s=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtDataCsumErr")
-		local csum_err_c=$(mptcp_lib_get_counter "${connector_ns}" "MPTcpExtDataCsumErr")
+		local csum_err_s
+		local csum_err_c
+		csum_err_s=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtDataCsumErr")
+		csum_err_c=$(mptcp_lib_get_counter "${connector_ns}" "MPTcpExtDataCsumErr")
 
 		local csum_err_s_nr=$((csum_err_s - stat_csum_err_s))
 		if [ $csum_err_s_nr -gt 0 ]; then
-			printf "[ FAIL ]\nserver got $csum_err_s_nr data checksum error[s]"
+			printf "[ FAIL ]\nserver got %d data checksum error[s]" ${csum_err_s_nr}
 			rets=1
 		fi
 
 		local csum_err_c_nr=$((csum_err_c - stat_csum_err_c))
 		if [ $csum_err_c_nr -gt 0 ]; then
-			printf "[ FAIL ]\nclient got $csum_err_c_nr data checksum error[s]"
+			printf "[ FAIL ]\nclient got %d data checksum error[s]" ${csum_err_c_nr}
 			retc=1
 		fi
 	fi
@@ -658,7 +665,7 @@ run_test_transparent()
 		return
 	fi
 
-ip netns exec "$listener_ns" nft -f /dev/stdin <<"EOF"
+	if ! ip netns exec "$listener_ns" nft -f /dev/stdin <<"EOF"
 flush ruleset
 table inet mangle {
 	chain divert {
@@ -669,7 +676,7 @@ table inet mangle {
 	}
 }
 EOF
-	if [ $? -ne 0 ]; then
+	then
 		echo "SKIP: $msg, could not load nft ruleset"
 		mptcp_lib_fail_if_expected_feature "nft rules"
 		mptcp_lib_result_skip "${TEST_GROUP}"
@@ -684,8 +691,7 @@ EOF
 		local_addr="0.0.0.0"
 	fi
 
-	ip -net "$listener_ns" $r6flag rule add fwmark 1 lookup 100
-	if [ $? -ne 0 ]; then
+	if ! ip -net "$listener_ns" $r6flag rule add fwmark 1 lookup 100; then
 		ip netns exec "$listener_ns" nft flush ruleset
 		echo "SKIP: $msg, ip $r6flag rule failed"
 		mptcp_lib_fail_if_expected_feature "ip rule"
@@ -693,8 +699,7 @@ EOF
 		return
 	fi
 
-	ip -net "$listener_ns" route add local $local_addr/0 dev lo table 100
-	if [ $? -ne 0 ]; then
+	if ! ip -net "$listener_ns" route add local $local_addr/0 dev lo table 100; then
 		ip netns exec "$listener_ns" nft flush ruleset
 		ip -net "$listener_ns" $r6flag rule del fwmark 1 lookup 100
 		echo "SKIP: $msg, ip route add local $local_addr failed"
@@ -857,7 +862,7 @@ stop_if_error "Could not even run ping tests"
 echo -n "INFO: Using loss of $tc_loss "
 test "$tc_delay" -gt 0 && echo -n "delay $tc_delay ms "
 
-reorder_delay=$(($tc_delay / 4))
+reorder_delay=$((tc_delay / 4))
 
 if [ -z "${tc_reorder}" ]; then
 	reorder1=$((RANDOM%10))
diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 955ee651dcd5..1df2d24979a0 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -86,21 +86,11 @@ init_partial()
 {
 	capout=$(mktemp)
 
-	local sec rndh
-	sec=$(date +%s)
-	rndh=$(printf %x $sec)-$(mktemp -u XXXXXX)
-
-	ns1="ns1-$rndh"
-	ns2="ns2-$rndh"
+	mptcp_lib_ns_init ns1 ns2
 
 	local netns
 	for netns in "$ns1" "$ns2"; do
-		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.mptcp.pm_type=0 2>/dev/null || true
-		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
 		if $checksum; then
 			ip netns exec $netns sysctl -q net.mptcp.checksum_enabled=1
 		fi
@@ -145,45 +135,15 @@ cleanup_partial()
 {
 	rm -f "$capout"
 
-	local netns
-	for netns in "$ns1" "$ns2"; do
-		ip netns del $netns
-		rm -f /tmp/$netns.{nstat,out}
-	done
-}
-
-check_tools()
-{
-	mptcp_lib_check_mptcp
-	mptcp_lib_check_kallsyms
-
-	if ! ip -Version &> /dev/null; then
-		echo "SKIP: Could not run test without ip tool"
-		exit $ksft_skip
-	fi
-
-	if ! ss -h | grep -q MPTCP; then
-		echo "SKIP: ss tool does not support MPTCP"
-		exit $ksft_skip
-	fi
-
-	# Use the legacy version if available to support old kernel versions
-	if iptables-legacy -V &> /dev/null; then
-		iptables="iptables-legacy"
-		ip6tables="ip6tables-legacy"
-	elif ! iptables -V &> /dev/null; then
-		echo "SKIP: Could not run all tests without iptables tool"
-		exit $ksft_skip
-	elif ! ip6tables -V &> /dev/null; then
-		echo "SKIP: Could not run all tests without ip6tables tool"
-		exit $ksft_skip
-	fi
+	mptcp_lib_ns_exit "${ns1}" "${ns2}"
 }
 
 init() {
 	init=1
 
-	check_tools
+	mptcp_lib_check_mptcp
+	mptcp_lib_check_kallsyms
+	mptcp_lib_check_tools ip ss "${iptables}" "${ip6tables}"
 
 	sin=$(mktemp)
 	sout=$(mktemp)
@@ -470,12 +430,8 @@ reset_with_events()
 {
 	reset "${1}" || return 1
 
-	:> "$evts_ns1"
-	:> "$evts_ns2"
-	ip netns exec $ns1 ./pm_nl_ctl events >> "$evts_ns1" 2>&1 &
-	evts_ns1_pid=$!
-	ip netns exec $ns2 ./pm_nl_ctl events >> "$evts_ns2" 2>&1 &
-	evts_ns2_pid=$!
+	mptcp_lib_events "${ns1}" "${evts_ns1}" evts_ns1_pid
+	mptcp_lib_events "${ns2}" "${evts_ns2}" evts_ns2_pid
 }
 
 reset_with_tcp_filter()
@@ -648,7 +604,9 @@ wait_mpj()
 kill_events_pids()
 {
 	mptcp_lib_kill_wait $evts_ns1_pid
+	evts_ns1_pid=0
 	mptcp_lib_kill_wait $evts_ns2_pid
+	evts_ns2_pid=0
 }
 
 pm_nl_set_limits()
diff --git a/tools/testing/selftests/net/mptcp/mptcp_lib.sh b/tools/testing/selftests/net/mptcp/mptcp_lib.sh
index 438f557aac90..5d071b6eb780 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_lib.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_lib.sh
@@ -342,3 +342,71 @@ mptcp_lib_check_output() {
 		return 1
 	fi
 }
+
+mptcp_lib_check_tools() {
+	local tool
+
+	for tool in "${@}"; do
+		case "${tool}" in
+		"ip")
+			if ! ip -Version &> /dev/null; then
+				mptcp_lib_print_warn "SKIP: Could not run test without ip tool"
+				exit ${KSFT_SKIP}
+			fi
+			;;
+		"ss")
+			if ! ss -h | grep -q MPTCP; then
+				mptcp_lib_print_warn "SKIP: ss tool does not support MPTCP"
+				exit ${KSFT_SKIP}
+			fi
+			;;
+		"iptables"* | "ip6tables"*)
+			if ! "${tool}" -V &> /dev/null; then
+				mptcp_lib_print_warn "SKIP: Could not run all tests without ${tool}"
+				exit ${KSFT_SKIP}
+			fi
+			;;
+		*)
+			mptcp_lib_print_err "Internal error: unsupported tool: ${tool}"
+			exit ${KSFT_FAIL}
+			;;
+		esac
+	done
+}
+mptcp_lib_ns_init() {
+	local sec rndh
+
+	sec=$(date +%s)
+	rndh=$(printf %x "${sec}")-$(mktemp -u XXXXXX)
+
+	local netns
+	for netns in "${@}"; 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 "${!netns}" sysctl -q net.ipv4.conf.default.rp_filter=0
+	done
+}
+
+mptcp_lib_ns_exit() {
+	local netns
+	for netns in "${@}"; do
+		ip netns del "${netns}"
+		rm -f /tmp/"${netns}".{nstat,out}
+	done
+}
+
+mptcp_lib_events() {
+	local ns="${1}"
+	local evts="${2}"
+	declare -n pid="${3}"
+
+	:>"${evts}"
+
+	mptcp_lib_kill_wait "${pid:-0}"
+	ip netns exec "${ns}" ./pm_nl_ctl events >> "${evts}" 2>&1 &
+	pid=$!
+}
diff --git a/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh b/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
index c643872ddf47..6ed4aa32222f 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
@@ -1,6 +1,11 @@
 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
+# Double quotes to prevent globbing and word splitting is recommended in new
+# code but we accept it, especially because there were too many before having
+# address all other issues detected by shellcheck.
+#shellcheck disable=SC2086
+
 . "$(dirname "${0}")/mptcp_lib.sh"
 
 ret=0
@@ -8,17 +13,14 @@ sin=""
 sout=""
 cin=""
 cout=""
-ksft_skip=4
 timeout_poll=30
 timeout_test=$((timeout_poll * 2 + 1))
 iptables="iptables"
 ip6tables="ip6tables"
 
-sec=$(date +%s)
-rndh=$(printf %x $sec)-$(mktemp -u XXXXXX)
-ns1="ns1-$rndh"
-ns2="ns2-$rndh"
-ns_sbox="ns_sbox-$rndh"
+ns1=""
+ns2=""
+ns_sbox=""
 
 add_mark_rules()
 {
@@ -40,17 +42,10 @@ add_mark_rules()
 
 init()
 {
-	local netns
-	for netns in "$ns1" "$ns2" "$ns_sbox";do
-		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
-	done
+	mptcp_lib_ns_init ns1 ns2 ns_sbox
 
 	local i
-	for i in `seq 1 4`; do
+	for i in $(seq 1 4); do
 		ip link add ns1eth$i netns "$ns1" type veth peer name ns2eth$i netns "$ns2"
 		ip -net "$ns1" addr add 10.0.$i.1/24 dev ns1eth$i
 		ip -net "$ns1" addr add dead:beef:$i::1/64 dev ns1eth$i nodad
@@ -77,36 +72,18 @@ init()
 	add_mark_rules $ns2 2
 }
 
+# This function is used in the cleanup trap
+#shellcheck disable=SC2317
 cleanup()
 {
-	local netns
-	for netns in "$ns1" "$ns2" "$ns_sbox"; do
-		ip netns del $netns
-	done
+	mptcp_lib_ns_exit "${ns1}" "${ns2}" "${ns_sbox}"
 	rm -f "$cin" "$cout"
 	rm -f "$sin" "$sout"
 }
 
 mptcp_lib_check_mptcp
 mptcp_lib_check_kallsyms
-
-ip -Version > /dev/null 2>&1
-if [ $? -ne 0 ];then
-	echo "SKIP: Could not run test without ip tool"
-	exit $ksft_skip
-fi
-
-# Use the legacy version if available to support old kernel versions
-if iptables-legacy -V &> /dev/null; then
-	iptables="iptables-legacy"
-	ip6tables="ip6tables-legacy"
-elif ! iptables -V &> /dev/null; then
-	echo "SKIP: Could not run all tests without iptables tool"
-	exit $ksft_skip
-elif ! ip6tables -V &> /dev/null; then
-	echo "SKIP: Could not run all tests without ip6tables tool"
-	exit $ksft_skip
-fi
+mptcp_lib_check_tools ip "${iptables}" "${ip6tables}"
 
 check_mark()
 {
@@ -286,12 +263,12 @@ do_tcpinq_test()
 	local lret=$?
 	if [ $lret -ne 0 ];then
 		ret=$lret
-		echo "FAIL: mptcp_inq $@" 1>&2
+		echo "FAIL: mptcp_inq $*" 1>&2
 		mptcp_lib_result_fail "TCP_INQ: $*"
 		return $lret
 	fi
 
-	echo "PASS: TCP_INQ cmsg/ioctl $@"
+	echo "PASS: TCP_INQ cmsg/ioctl $*"
 	mptcp_lib_result_pass "TCP_INQ: $*"
 	return $lret
 }
diff --git a/tools/testing/selftests/net/mptcp/pm_netlink.sh b/tools/testing/selftests/net/mptcp/pm_netlink.sh
index 705106d60db5..427fc5c70b3c 100755
--- a/tools/testing/selftests/net/mptcp/pm_netlink.sh
+++ b/tools/testing/selftests/net/mptcp/pm_netlink.sh
@@ -1,16 +1,20 @@
 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
+# Double quotes to prevent globbing and word splitting is recommended in new
+# code but we accept it, especially because there were too many before having
+# address all other issues detected by shellcheck.
+#shellcheck disable=SC2086
+
 . "$(dirname "${0}")/mptcp_lib.sh"
 
-ksft_skip=4
 ret=0
 
 usage() {
 	echo "Usage: $0 [ -h ]"
 }
 
-
+optstring=h
 while getopts "$optstring" option;do
 	case "$option" in
 	"h")
@@ -24,30 +28,23 @@ while getopts "$optstring" option;do
 	esac
 done
 
-sec=$(date +%s)
-rndh=$(printf %x $sec)-$(mktemp -u XXXXXX)
-ns1="ns1-$rndh"
+ns1=""
 err=$(mktemp)
 
+# This function is used in the cleanup trap
+#shellcheck disable=SC2317
 cleanup()
 {
 	rm -f $err
-	ip netns del $ns1
+	mptcp_lib_ns_exit "${ns1}"
 }
 
 mptcp_lib_check_mptcp
-
-ip -Version > /dev/null 2>&1
-if [ $? -ne 0 ];then
-	echo "SKIP: Could not run test without ip tool"
-	exit $ksft_skip
-fi
+mptcp_lib_check_tools ip
 
 trap cleanup EXIT
 
-ip netns add $ns1 || exit $ksft_skip
-ip -net $ns1 link set lo up
-ip netns exec $ns1 sysctl -q net.mptcp.enabled=1
+mptcp_lib_ns_init ns1
 
 check()
 {
@@ -100,14 +97,14 @@ check "ip netns exec $ns1 ./pm_nl_ctl get 4" "" "duplicate addr"
 ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.4 flags signal
 check "ip netns exec $ns1 ./pm_nl_ctl get 4" "id 4 flags signal 10.0.1.4" "id addr increment"
 
-for i in `seq 5 9`; do
+for i in $(seq 5 9); do
 	ip netns exec $ns1 ./pm_nl_ctl add 10.0.1.$i flags signal >/dev/null 2>&1
 done
 check "ip netns exec $ns1 ./pm_nl_ctl get 9" "id 9 flags signal 10.0.1.9" "hard addr limit"
 check "ip netns exec $ns1 ./pm_nl_ctl get 10" "" "above hard addr limit"
 
 ip netns exec $ns1 ./pm_nl_ctl del 9
-for i in `seq 10 255`; do
+for i in $(seq 10 255); do
 	ip netns exec $ns1 ./pm_nl_ctl add 10.0.0.9 id $i
 	ip netns exec $ns1 ./pm_nl_ctl del $i
 done
diff --git a/tools/testing/selftests/net/mptcp/simult_flows.sh b/tools/testing/selftests/net/mptcp/simult_flows.sh
index ed0165c15a24..365fb3d6ef55 100755
--- a/tools/testing/selftests/net/mptcp/simult_flows.sh
+++ b/tools/testing/selftests/net/mptcp/simult_flows.sh
@@ -1,15 +1,17 @@
 #!/bin/bash
 # SPDX-License-Identifier: GPL-2.0
 
+# Double quotes to prevent globbing and word splitting is recommended in new
+# code but we accept it, especially because there were too many before having
+# address all other issues detected by shellcheck.
+#shellcheck disable=SC2086
+
 . "$(dirname "${0}")/mptcp_lib.sh"
 
-sec=$(date +%s)
-rndh=$(printf %x $sec)-$(mktemp -u XXXXXX)
-ns1="ns1-$rndh"
-ns2="ns2-$rndh"
-ns3="ns3-$rndh"
+ns1=""
+ns2=""
+ns3=""
 capture=false
-ksft_skip=4
 timeout_poll=30
 timeout_test=$((timeout_poll * 2 + 1))
 test_cnt=1
@@ -30,25 +32,19 @@ usage() {
 	echo -e "\t-d: debug this script"
 }
 
+# This function is used in the cleanup trap
+#shellcheck disable=SC2317
 cleanup()
 {
 	rm -f "$cout" "$sout"
 	rm -f "$large" "$small"
 	rm -f "$capout"
 
-	local netns
-	for netns in "$ns1" "$ns2" "$ns3";do
-		ip netns del $netns
-	done
+	mptcp_lib_ns_exit "${ns1}" "${ns2}" "${ns3}"
 }
 
 mptcp_lib_check_mptcp
-
-ip -Version > /dev/null 2>&1
-if [ $? -ne 0 ];then
-	echo "SKIP: Could not run test without ip tool"
-	exit $ksft_skip
-fi
+mptcp_lib_check_tools ip
 
 #  "$ns1"              ns2                    ns3
 #     ns1eth1    ns2eth1   ns2eth3      ns3eth1
@@ -70,12 +66,7 @@ setup()
 
 	trap cleanup EXIT
 
-	for i in "$ns1" "$ns2" "$ns3";do
-		ip netns add $i || exit $ksft_skip
-		ip -net $i link set lo up
-		ip netns exec $i sysctl -q net.ipv4.conf.all.rp_filter=0
-		ip netns exec $i sysctl -q net.ipv4.conf.default.rp_filter=0
-	done
+	mptcp_lib_ns_init ns1 ns2 ns3
 
 	ip link add ns1eth1 netns "$ns1" type veth peer name ns2eth1 netns "$ns2"
 	ip link add ns1eth2 netns "$ns1" type veth peer name ns2eth2 netns "$ns2"
@@ -135,7 +126,7 @@ do_transfer()
 	local sin=$2
 	local max_time=$3
 	local port
-	port=$((10000+$test_cnt))
+	port=$((10000+test_cnt))
 	test_cnt=$((test_cnt+1))
 
 	:> "$cout"
@@ -144,6 +135,7 @@ do_transfer()
 
 	if $capture; then
 		local capuser
+		local rndh="${ns1:4}"
 		if [ -z $SUDO_USER ] ; then
 			capuser=""
 		else
diff --git a/tools/testing/selftests/net/mptcp/userspace_pm.sh b/tools/testing/selftests/net/mptcp/userspace_pm.sh
index 1b94a75604fe..b0cce8f065d8 100755
--- a/tools/testing/selftests/net/mptcp/userspace_pm.sh
+++ b/tools/testing/selftests/net/mptcp/userspace_pm.sh
@@ -17,11 +17,7 @@ if ! mptcp_lib_has_file '/proc/sys/net/mptcp/pm_type'; then
 	echo "userspace pm tests are not supported by the kernel: SKIP"
 	exit ${KSFT_SKIP}
 fi
-
-if ! ip -Version &> /dev/null; then
-	echo "SKIP: Cannot not run test without ip tool"
-	exit ${KSFT_SKIP}
-fi
+mptcp_lib_check_tools ip
 
 ANNOUNCED=6        # MPTCP_EVENT_ANNOUNCED
 REMOVED=7          # MPTCP_EVENT_REMOVED
@@ -54,10 +50,8 @@ app6_port=50004
 client_addr_id=${RANDOM:0:2}
 server_addr_id=${RANDOM:0:2}
 
-sec=$(date +%s)
-rndh=$(printf %x "$sec")-$(mktemp -u XXXXXX)
-ns1="ns1-$rndh"
-ns2="ns2-$rndh"
+ns1=""
+ns2=""
 ret=0
 test_name=""
 
@@ -122,10 +116,7 @@ cleanup()
 		mptcp_lib_kill_wait $pid
 	done
 
-	local netns
-	for netns in "$ns1" "$ns2" ;do
-		ip netns del "$netns"
-	done
+	mptcp_lib_ns_exit "${ns1}" "${ns2}"
 
 	rm -rf $file $client_evts $server_evts
 
@@ -135,10 +126,8 @@ cleanup()
 trap cleanup EXIT
 
 # Create and configure network namespaces for testing
+mptcp_lib_ns_init ns1 ns2
 for i in "$ns1" "$ns2" ;do
-	ip netns add "$i" || exit 1
-	ip -net "$i" link set lo up
-	ip netns exec "$i" sysctl -q net.mptcp.enabled=1
 	ip netns exec "$i" sysctl -q net.mptcp.pm_type=1
 done
 
@@ -160,17 +149,23 @@ ip -net "$ns2" addr add dead:beef:1::2/64 dev ns2eth1 nodad
 ip -net "$ns2" addr add dead:beef:2::2/64 dev ns2eth1 nodad
 ip -net "$ns2" link set ns2eth1 up
 
+file=$(mktemp)
+mptcp_lib_make_file "$file" 2 1
+
+# Capture netlink events over the two network namespaces running
+# the MPTCP client and server
+client_evts=$(mktemp)
+mptcp_lib_events "${ns2}" "${client_evts}" client_evts_pid
+server_evts=$(mktemp)
+mptcp_lib_events "${ns1}" "${server_evts}" server_evts_pid
+sleep 0.5
+
 print_title "Init"
 print_test "Created network namespaces ns1, ns2"
 test_pass
 
 make_connection()
 {
-	if [ -z "$file" ]; then
-		file=$(mktemp)
-	fi
-	mptcp_lib_make_file "$file" 2 1
-
 	local is_v6=$1
 	local app_port=$app4_port
 	local connect_addr="10.0.1.1"
@@ -184,27 +179,8 @@ make_connection()
 		is_v6="v4"
 	fi
 
-	# Capture netlink events over the two network namespaces running
-	# the MPTCP client and server
-	if [ -z "$client_evts" ]; then
-		client_evts=$(mktemp)
-	fi
 	:>"$client_evts"
-	if [ $client_evts_pid -ne 0 ]; then
-		mptcp_lib_kill_wait $client_evts_pid
-	fi
-	ip netns exec "$ns2" ./pm_nl_ctl events >> "$client_evts" 2>&1 &
-	client_evts_pid=$!
-	if [ -z "$server_evts" ]; then
-		server_evts=$(mktemp)
-	fi
 	:>"$server_evts"
-	if [ $server_evts_pid -ne 0 ]; then
-		mptcp_lib_kill_wait $server_evts_pid
-	fi
-	ip netns exec "$ns1" ./pm_nl_ctl events >> "$server_evts" 2>&1 &
-	server_evts_pid=$!
-	sleep 0.5
 
 	# Run the server
 	ip netns exec "$ns1" \