Initial revision

1 files changed, 48 insertions, 0 deletions

diff --git a/doc/kernel.texi b/doc/kernel.texi
new file mode 100644
index 00000000..b863a1f6
--- /dev/null
+++ b/doc/kernel.texi
@@ -0,0 +1,48 @@
+@node Kernel Interface, SNMP Support, IPv6 Support, Top
+@comment  node-name,  next,  previous,  up
+@chapter Kernel Interface
+
+There are several different methods for reading kernel routing table
+information, updating kernel routing tables, and for looking up
+interfaces.
+
+@table @samp
+
+@item ioctl
+The @samp{ioctl} method is a very traditional way for reading or writing
+kernel information.  @samp{ioctl} can be used for looking up interfaces
+and for modifying interface addresses, flags, mtu settings and other
+types of information.  Also, @samp{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.
+
+@item sysctl
+@samp{sysctl} 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 @samp{ioctl}.
+
+@item proc filesystem
+@samp{proc filesystem} provides an easy way of getting kernel
+information.
+
+@item routing socket
+
+@item netlink
+On recent Linux kernels (2.0.x and 2.2.x), there is a kernel/user
+communication support called @code{netlink}.  It makes asynchronous
+communication between kernel and Zebra possible, similar to a routing
+socket on BSD systems.
+
+Before you use this feature, be sure to select (in kernel configuration) 
+the kernel/netlink support option 'Kernel/User network link driver' and 
+'Routing messages'.
+
+Today, the /dev/route special device file is obsolete.  Netlink
+communication is done by reading/writing over netlink socket.
+
+After the kernel configuration, please reconfigure and rebuild Zebra.
+You can use netlink as a dynamic routing update channel between Zebra
+and the kernel.
+@end table