ar_spa
((struct in_addr *)ar_spa(ah))->s_addr = pcb->dp_client;
memcpy(&isaddr, ar_spa(ah), sizeof(isaddr));
memcpy(ar_tpa(ah), ar_spa(ah), ah->ar_pln);
memcpy(ar_spa(ah), &itaddr, ah->ar_pln);
u_char ar_spa[]; /* sender protocol address */
(void)memcpy(ar_tpa(ah), ar_spa(ah), ah->ar_pln);
(void)memcpy(ar_spa(ah), &itaddr, ah->ar_pln);
bcopy(sip, ar_spa(ah), ah->ar_pln);
(void)memcpy(&isaddr, ar_spa(ah), sizeof (isaddr));