selftests: mptcp: add mptcp_lib_check_transfer

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

check_transfer() and print_file_err() helpers are defined both in
mptcp_connect.sh and mptcp_sockopt.sh, export them into mptcp_lib.sh
and rename them with mptcp_lib_ prefix. And use them in all scripts.

Note: In mptcp_sockopt.sh it is OK to drop 'ret=1' in check_transfer()
because it will be set in run_tests() anyway.

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

···
 	set_ethtool_flags "$ns4" ns4eth3 "$ethtool_args"
 fi
 
-print_file_err()
-{
-	ls -l "$1" 1>&2
-	echo "Trailing bytes are: "
-	tail -c 27 "$1"
-}
-
-check_transfer()
-{
-	local in=$1
-	local out=$2
-	local what=$3
-
-	cmp "$in" "$out" > /dev/null 2>&1
-	if [ $? -ne 0 ] ;then
-		echo "[ FAIL ] $what does not match (in, out):"
-		print_file_err "$in"
-		print_file_err "$out"
-
-		return 1
-	fi
-
-	return 0
-}
-
 check_mptcp_disabled()
 {
 	local disabled_ns="ns_disabled-$rndh"
···
 		return 1
 	fi
 
-	check_transfer $sin $cout "file received by client"
+	mptcp_lib_check_transfer $sin $cout "file received by client"
 	retc=$?
-	check_transfer $cin $sout "file received by server"
+	mptcp_lib_check_transfer $cin $sout "file received by server"
 	rets=$?
 
 	local stat_synrx_now_l=$(mptcp_lib_get_counter "${listener_ns}" "MPTcpExtMPCapableSYNRX")

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

···
 	done | sort -n
 }
 
-print_file_err()
-{
-	ls -l "$1" 1>&2
-	echo -n "Trailing bytes are: "
-	tail -c 27 "$1"
-}
-
 check_transfer()
 {
 	local in=$1
···
 		local sum=$((0${a} + 0${b}))
 		if [ $check_invert -eq 0 ] || [ $sum -ne $((0xff)) ]; then
 			fail_test "$what does not match (in, out):"
-			print_file_err "$in"
-			print_file_err "$out"
+			mptcp_lib_print_file_err "$in"
+			mptcp_lib_print_file_err "$out"
 
 			return 1
 		else

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

···
 	dd if=/dev/urandom of="${name}" bs="${bs}" count="${size}" 2> /dev/null
 	echo -e "\nMPTCP_TEST_FILE_END_MARKER" >> "${name}"
 }
+
+# $1: file
+mptcp_lib_print_file_err() {
+	ls -l "${1}" 1>&2
+	echo "Trailing bytes are: "
+	tail -c 27 "${1}"
+}
+
+# $1: input file ; $2: output file ; $3: what kind of file
+mptcp_lib_check_transfer() {
+	local in="${1}"
+	local out="${2}"
+	local what="${3}"
+
+	if ! cmp "$in" "$out" > /dev/null 2>&1; then
+		echo "[ FAIL ] $what does not match (in, out):"
+		mptcp_lib_print_file_err "$in"
+		mptcp_lib_print_file_err "$out"
+
+		return 1
+	fi
+
+	return 0
+}

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

···
 	return 0
 }
 
-print_file_err()
-{
-	ls -l "$1" 1>&2
-	echo "Trailing bytes are: "
-	tail -c 27 "$1"
-}
-
-check_transfer()
-{
-	local in=$1
-	local out=$2
-	local what=$3
-
-	cmp "$in" "$out" > /dev/null 2>&1
-	if [ $? -ne 0 ] ;then
-		echo "[ FAIL ] $what does not match (in, out):"
-		print_file_err "$in"
-		print_file_err "$out"
-		ret=1
-
-		return 1
-	fi
-
-	return 0
-}
-
 do_transfer()
 {
 	local listener_ns="$1"
···
 		check_mark $connector_ns 4 || retc=1
 	fi
 
-	check_transfer $cin $sout "file received by server"
+	mptcp_lib_check_transfer $cin $sout "file received by server"
 	rets=$?
 
 	mptcp_lib_result_code "${retc}" "mark ${ip}"