selftests: mptcp: add mptcp_lib_make_file

To avoid duplicated code in different MPTCP selftests, we can add
and use helpers defined in mptcp_lib.sh.

make_file() helper in mptcp_sockopt.sh and userspace_pm.sh are the same.
Export it into mptcp_lib.sh and rename it as mptcp_lib_kill_wait(). Use
it in both mptcp_connect.sh and mptcp_join.sh.

Reviewed-by: Matthieu Baerts <[e-mail]>
Signed-off-by: Geliang Tang <[e-mail]>
Signed-off-by: Mat Martineau <[e-mail]>
Link: https://lore.kernel.org/r/[e-mail]
Signed-off-by: Jakub Kicinski <[e-mail]>

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

···
 	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"
 }

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

···
 	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"
 }

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

···
 
 	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}"
+}

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

···
 	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"
 }

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

···
 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