used_len = DTLS1_RT_HEADER_LENGTH + mac_size + blocksize;
if (s->d1->mtu > used_len + DTLS1_HM_HEADER_LENGTH) {
curr_mtu = s->d1->mtu - used_len;
used_len = DTLS1_RT_HEADER_LENGTH + mac_size + blocksize;
if (s->d1->mtu > used_len + DTLS1_HM_HEADER_LENGTH) {
curr_mtu = s->d1->mtu - used_len;