diff --git a/tools/testing/selftests/net/mptcp/mptcp_connect.sh b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
index c4f08976c418..d20e278480fb 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_connect.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_connect.sh
@@ -592,9 +592,8 @@ make_file()
 	ksize=$((SIZE / 1024))
 	rem=$((SIZE - (ksize * 1024)))
 
-	dd if=/dev/urandom of="$name" bs=1024 count=$ksize 2> /dev/null
+	mptcp_lib_make_file $name 1024 $ksize
 	dd if=/dev/urandom conv=notrunc of="$name" oflag=append bs=1 count=$rem 2> /dev/null
-	echo -e "\nMPTCP_TEST_FILE_END_MARKER" >> "$name"
 
 	echo "Created $name (size $(du -b "$name")) containing data sent by $who"
 }
diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index a5d66d1bfeb4..37f434cbfa44 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -1171,8 +1171,7 @@ make_file()
 	local who=$2
 	local size=$3
 
-	dd if=/dev/urandom of="$name" bs=1024 count=$size 2> /dev/null
-	echo -e "\nMPTCP_TEST_FILE_END_MARKER" >> "$name"
+	mptcp_lib_make_file $name 1024 $size
 
 	print_info "Test file (size $size KB) for $who"
 }
diff --git a/tools/testing/selftests/net/mptcp/mptcp_lib.sh b/tools/testing/selftests/net/mptcp/mptcp_lib.sh
index 718c79dda2b3..61be4f29a69a 100644
--- a/tools/testing/selftests/net/mptcp/mptcp_lib.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_lib.sh
@@ -247,3 +247,12 @@ mptcp_lib_get_counter() {
 
 	echo "${count}"
 }
+
+mptcp_lib_make_file() {
+	local name="${1}"
+	local bs="${2}"
+	local size="${3}"
+
+	dd if=/dev/urandom of="${name}" bs="${bs}" count="${size}" 2> /dev/null
+	echo -e "\nMPTCP_TEST_FILE_END_MARKER" >> "${name}"
+}
diff --git a/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh b/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
index bfa744e350ef..96dc46eda133 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_sockopt.sh
@@ -251,8 +251,7 @@ make_file()
 	local who=$2
 	local size=$3
 
-	dd if=/dev/urandom of="$name" bs=1024 count=$size 2> /dev/null
-	echo -e "\nMPTCP_TEST_FILE_END_MARKER" >> "$name"
+	mptcp_lib_make_file $name 1024 $size
 
 	echo "Created $name (size $size KB) containing data sent by $who"
 }
diff --git a/tools/testing/selftests/net/mptcp/userspace_pm.sh b/tools/testing/selftests/net/mptcp/userspace_pm.sh
index f136956f6c95..6167837f48e1 100755
--- a/tools/testing/selftests/net/mptcp/userspace_pm.sh
+++ b/tools/testing/selftests/net/mptcp/userspace_pm.sh
@@ -164,22 +164,12 @@ print_title "Init"
 print_test "Created network namespaces ns1, ns2"
 test_pass
 
-make_file()
-{
-	# Store a chunk of data in a file to transmit over an MPTCP connection
-	local name=$1
-	local ksize=1
-
-	dd if=/dev/urandom of="$name" bs=2 count=$ksize 2> /dev/null
-	echo -e "\nMPTCP_TEST_FILE_END_MARKER" >> "$name"
-}
-
 make_connection()
 {
 	if [ -z "$file" ]; then
 		file=$(mktemp)
 	fi
-	make_file "$file" "client"
+	mptcp_lib_make_file "$file" 2 1
 
 	local is_v6=$1
 	local app_port=$app4_port