certreq_decode
rc = handler->certreq_decode(&aca.data, data, datalen);
int (*certreq_decode)(void **, u_int8_t *, u_int32_t);
struct certreq_aca *certreq_decode(u_int16_t, u_int8_t *, u_int32_t);
aca = certreq_decode(GET_ISAKMP_CERTREQ_TYPE(cp->p), cp->p +