IPTUN_UPCALL_PENDING
while (iptun->iptun_flags & IPTUN_UPCALL_PENDING)
iptun->iptun_flags |= IPTUN_UPCALL_PENDING;
iptun->iptun_flags &= ~IPTUN_UPCALL_PENDING;
IPTUN_MAC_STARTED|IPTUN_HASH_INSERTED|IPTUN_UPCALL_PENDING)));