CONST_HDRLEN_V6
.tlen = IP6_MAX_MTU - CONST_HDRLEN_V6,
.r_len_last = IP6_MAX_MTU - CONST_HDRLEN_V6 -
.tlen = IP6_MAX_MTU - CONST_HDRLEN_V6 + 1,
#define CONST_MSS_V6 (CONST_MTU_TEST - CONST_HDRLEN_V6)