WRITE_ONCE(msk->rcv_wnd_sent, ack_seq);
 }
 
-static u16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __sum16 sum)
+u16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum)
 {
        struct csum_pseudo_header header;
        __wsum csum;
        header.data_len = htons(data_len);
        header.csum = 0;
 
-       csum = csum_partial(&header, sizeof(header), ~csum_unfold(sum));
+       csum = csum_partial(&header, sizeof(header), sum);
        return (__force u16)csum_fold(csum);
 }
 
 static u16 mptcp_make_csum(const struct mptcp_ext *mpext)
 {
        return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
-                                mpext->csum);
+                                ~csum_unfold(mpext->csum));
 }
 
 void mptcp_write_options(__be32 *ptr, const struct tcp_sock *tp,
                                           __mptcp_make_csum(opts->data_seq,
                                                             opts->subflow_seq,
                                                             opts->data_len,
-                                                            opts->csum), ptr);
+                                                            ~csum_unfold(opts->csum)), ptr);
                } else {
                        put_unaligned_be32(opts->data_len << 16 |
                                           TCPOPT_NOP << 8 | TCPOPT_NOP, ptr);
 
 void mptcp_crypto_key_sha(u64 key, u32 *token, u64 *idsn);
 
 void mptcp_crypto_hmac_sha(u64 key1, u64 key2, u8 *msg, int len, void *hmac);
+u16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum);
 
 void __init mptcp_pm_init(void);
 void mptcp_pm_data_init(struct mptcp_sock *msk);