TCPOLEN_MPTCP_MPC_ACK_DATA
if (opsize >= TCPOLEN_MPTCP_MPC_ACK_DATA) {
len = TCPOLEN_MPTCP_MPC_ACK_DATA;
expected_opsize = TCPOLEN_MPTCP_MPC_ACK_DATA;
len = TCPOLEN_MPTCP_MPC_ACK_DATA;
(expected_opsize != TCPOLEN_MPTCP_MPC_ACK_DATA ||
#define TCPOLEN_MPTCP_MPC_ACK_DATA_CSUM (TCPOLEN_MPTCP_DSS_CHECKSUM + TCPOLEN_MPTCP_MPC_ACK_DATA)