next_head
while (next_head(arcn) == 0) {
static int next_head(ARCHD *);
while (next_head(arcn) == 0) {
while (next_head(arcn) == 0) {
int next_head = rxring->head;
struct netmap_slot *next_slot = &rxring->slot[next_head];
next_head = nm_ring_next(rxring, next_head);
next_slot = &rxring->slot[next_head];
rxring->head = rxring->cur = next_head;