mptcp: reuse __mptcp_make_csum in validate_data_csum

This patch reused __mptcp_make_csum() in validate_data_csum() instead of
open-coding.
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
Signed-off-by: Mat Martineau <mathew.j.martineau@linux.intel.com>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

net/mptcp/subflow.c

@@ -845,9 +845,8 @@ static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *
 					      bool csum_reqd)
 {
 	struct mptcp_subflow_context *subflow = mptcp_subflow_ctx(ssk);
-	struct csum_pseudo_header header;
 	u32 offset, seq, delta;
-	__wsum csum;
+	u16 csum;
 	int len;
 
 	if (!csum_reqd)
@@ -908,13 +907,11 @@ static enum mapping_status validate_data_csum(struct sock *ssk, struct sk_buff *
 	 * while the pseudo header requires the original DSS data len,
 	 * including that
 	 */
-	header.data_seq = cpu_to_be64(subflow->map_seq);
-	header.subflow_seq = htonl(subflow->map_subflow_seq);
-	header.data_len = htons(subflow->map_data_len + subflow->map_data_fin);
-	header.csum = 0;
-
-	csum = csum_partial(&header, sizeof(header), subflow->map_data_csum);
-	if (unlikely(csum_fold(csum))) {
+	csum = __mptcp_make_csum(subflow->map_seq,
+				 subflow->map_subflow_seq,
+				 subflow->map_data_len + subflow->map_data_fin,
+				 subflow->map_data_csum);
+	if (unlikely(csum)) {
 		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_DATACSUMERR);
 		subflow->send_mp_fail = 1;
 		MPTCP_INC_STATS(sock_net(ssk), MPTCP_MIB_MPFAILTX);