syncache_respond
static int syncache_respond(struct syncache *, int);
if (syncache_respond(sc, TH_SYN|TH_ACK) == 0) {
if (syncache_respond(sc, TH_SYN|TH_ACK) == 0) {
if (syncache_respond(sc, TH_ACK) == 0) {
if (syncache_respond(sc, TH_SYN|TH_ACK) == 0) {