This is an old revision of the document!
The MAC (Mandatory Access Control) framework provides an intuitive API to managing access control to kernel objects. Through the use of MAC entry points littered through-out the system, composition of kernel discretionary access control decisions may be modified and/or monitored through MAC modules. The MAC framework also facilitates inter-communication between MAC modules and the rest of the system (including user-space) through MAC labels (covering file descriptors to individual mbuf's) and other entry points (such as mac_syscall, a multiplexed system call of sorts). More information can be found in the FreeBSD Architecture Handbook.