__mptcp_make_csum
return __mptcp_make_csum(mpext->data_seq, mpext->subflow_seq, mpext->data_len,
__mptcp_make_csum(opts->data_seq,
__sum16 __mptcp_make_csum(u64 data_seq, u32 subflow_seq, u16 data_len, __wsum sum);
csum = __mptcp_make_csum(subflow->map_seq,