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Diffstat (limited to 'doc/user/kernel.rst')
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diff --git a/doc/user/kernel.rst b/doc/user/kernel.rst new file mode 100644 index 0000000..210ede7 --- /dev/null +++ b/doc/user/kernel.rst @@ -0,0 +1,36 @@ +.. _kernel-interface: + +**************** +Kernel Interface +**************** + +There are several different methods for reading kernel routing table +information, updating kernel routing tables, and for looking up interfaces. +FRR relies heavily on the Netlink (``man 7 netlink``) interface to +communicate with the Kernel. However, other interfaces are still used +in some parts of the code. + +- ioctl + This method is a very traditional way for reading or writing kernel + information. `ioctl` can be used for looking up interfaces and for + modifying interface addresses, flags, mtu settings and other types of + information. Also, `ioctl` can insert and delete kernel routing table + entries. It will soon be available on almost any platform which zebra + supports, but it is a little bit ugly thus far, so if a better method is + supported by the kernel, zebra will use that. + +- sysctl + This is a program that can lookup kernel information using MIB (Management + Information Base) syntax. Normally, it only provides a way of getting + information from the kernel. So one would usually want to change kernel + information using another method such as `ioctl`. + +- proc filesystem + This is a special filesystem mount that provides an easy way of getting + kernel information. + +- routing socket / Netlink + Netlink first appeard in Linux kernel 2.0. It makes asynchronous + communication between the kernel and FRR possible, similar to a routing + socket on BSD systems. Netlink communication is done by reading/writing + over Netlink socket. |