pduq
typedef TAILQ_HEAD(, pduq) queue_t;
TAILQ_ENTRY(pduq) pq_link;
queue_t *pduq;
TAILQ_HEAD(,pduq) freepdu;
pq->pduq = &sp->isnd; // remember where you came from
pq->pduq = &sp->wsnd; // remember where you came from
pq->pduq = &sp->csnd; // remember where you came from
KASSERT(pq->pduq != NULL, ("pq->pduq is NULL"));
TAILQ_INSERT_TAIL(pq->pduq, pq, pq_link);