Glossary

• domain  

  A complete protocol family.



• driver layer  

  I/O Kit Drivers for various networking types.



• extension  

  A general term for an object module that can be dynamically added to a running system; often used as a synonym for kernel extension.



• global socket filter  

  A socket filter that is automatically enabled for sockets of the type specified.



• ifnet structure  

  A data structure containing function pointers and data related to a particular network interface.



• in-band  

  Communication on a socket or interface that contains actual data destined for the endpoint (for example, send and recv calls). See also: out-of-band.



• interface filter  

  A filter that attached to a particular interface. An interface filter alters in-band and out-of-band communication specific to a given interface.



• interface layer  

  A layer above the driver layer containing interface KEXTs, interface filters, and protocol plumbers.



• interface KEXT  

  A network kernel extension that provides routines specific to a particular family of interfaces, such as ARP equivalence routines.



• IP filter  

  A filter that alters IP traffic each time it enters the protocol stack. By its very nature, an IP filter can only filter in-band communication.



• KEXT  

  Short for kernel extension; a plug-in for the OS X kernel (xnu).



• KPI  

  Short for kernel programming interface; a group of opaque data types and accessor functions designed to maintain binary compatibility across OS releases.



• mbuf  

  A data structure containing data about a network packet.



• network kernel extension (NKE)  

  1) The architecture that allows modules to be added to the OS X networking subsystem while the system is running. 2) A module that can be added to a running system.



• out-of-band  

  Communication on a socket or interface that relates to the operation of the socket or interface rather than data destined for the endpoint (for example, ioctl and getsockopt calls). See also: in-band.



• plug-in  

  A general term for an object module that can be dynamically added to a running system.



• programmatic socket filter  

  A socket filter that is enabled only under program control by calling setsockopt on a specific socket.



• protocol plumber  

  A network kernel extension that routes data between an interface and a network protocol stack.



• protocol stack  

  A layer of the kernel network architecture containing the core functionality for a protocol family such as TCP/IP.



• protosw structure  

  A data structure containing function pointers and data associated with a protocol family.



• socket structure  

  A data structure containing data associated with a network socket.



• socket filter  

  A filter that is associated with a particular socket or class of sockets, filtering in-band and out-of-band operations on the socket. A socket filter resides between a socket and the protocol layer.