doc/user/kernel.rst

   1 .. _kernel-interface:
   2
   3 ****************
   4 Kernel Interface
   5 ****************
   6
   7 There are several different methods for reading kernel routing table
   8 information, updating kernel routing tables, and for looking up interfaces.
   9 FRR relies heavily on the Netlink (``man 7 netlink``) interface to
  10 communicate with the Kernel. However, other interfaces are still used
  11 in some parts of the code.
  12
  13 - ioctl
  14      This method is a very traditional way for reading or writing kernel
  15      information. `ioctl` can be used for looking up interfaces and for
  16      modifying interface addresses, flags, mtu settings and other types of
  17      information. Also, `ioctl` can insert and delete kernel routing table
  18      entries. It will soon be available on almost any platform which zebra
  19      supports, but it is a little bit ugly thus far, so if a better method is
  20      supported by the kernel, zebra will use that.
  21
  22 - sysctl
  23      This is a program that can lookup kernel information using MIB (Management
  24      Information Base) syntax. Normally, it only provides a way of getting
  25      information from the kernel. So one would usually want to change kernel
  26      information using another method such as `ioctl`.
  27
  28 - proc filesystem
  29      This is a special filesystem mount that provides an easy way of getting
  30      kernel information.
  31
  32 - routing socket / Netlink
  33      Netlink first appeard in Linux kernel 2.0. It makes asynchronous
  34      communication between the kernel and FRR possible, similar to a routing
  35      socket on BSD systems. Netlink communication is done by reading/writing
  36      over Netlink socket.