CONST_HDRLEN_V4
.tlen = ETH_MAX_MTU - CONST_HDRLEN_V4,
.r_len_last = ETH_MAX_MTU - CONST_HDRLEN_V4 -
.tlen = ETH_MAX_MTU - CONST_HDRLEN_V4 + 1,
#define CONST_MSS_V4 (CONST_MTU_TEST - CONST_HDRLEN_V4)