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