doc: Add man page for VRF related parameters

Signed-off-by: Maximilian Wilhelm <max@sdn.clinic>

doc/interfaces-vrf.scd

@@ -0,0 +1,58 @@
+interfaces-vrf(5)
+
+# NAME
+
+*interfaces-vrf* - VRF extensions for the interfaces(5) file format
+
+# DESCRIPTION
+
+Linux has support for Virtual Routing and Forwarding (VRF) instances
+since Kernel >= 4.4. The following options allow to set up VRFs and
+adding configured interfaces to VRFs.
+
+Note that in the Linux Kernel VRFs are represented as network interfaces,
+too. See https://www.kernel.org/doc/Documentation/networking/vrf.rst for
+more details.
+
+# VRF-RELATED OPTIONS
+
+*vrf-table* _table id_
+	The _id_ of the kernel routing table associated with this
+	VRF interface. This parameter indicates that the interface
+	where it is specified shall be a VRF.
+
+*vrf* _vrf interface_
+	The _vrf_ the interface should be assigned to. This parameter
+	is specified on regular interfaces which should be within the
+	given _vrf_.
+
+# EXAMPLES
+
+A VRF interface:
+
+```
+auto vrf_external
+iface vrf_external
+	vrf-table 1023
+```
+
+A regular interface which should be within a VRF:
+
+```
+auto eth0
+iface eth0
+	address 192.2.0.42/24
+	address 2001:db8::42/64
+	gateway 192.2.0.1
+	gateway 2001:db::1
+	vrf vrf_external
+```
+
+# SEE ALSO
+
+*ip-vrf*(8)
+*ip-link*(8)
+
+# AUTHORS
+
+Maximilian Wilhelm <max@sdn.clinic>

doc/interfaces.scd

@@ -155,6 +155,9 @@ most common options are:
 	The interface is a Virtual Extensible LAN (VXLAN) tunnel
 	endpoint.
 
+Check *interfaces-<option>(5)* for further informaton about a given
+option and available configuration parameters.
+
 # EXAMPLES
 
 Configure a bridge interface *br0* with *bond0* attached to it,
@@ -188,9 +191,10 @@ iface eth0
 # SEE ALSO
 
 *interfaces-bond*(5)
+*interfaces-vrf*(5)
 *interfaces-vxlan*(5)
 
 # AUTHORS
 
-Ariadne Conill <ariadne@dereferenced.org>
+Ariadne Conill <ariadne@dereferenced.org>++
 Maximilian Wilhelm <max@sdn.clinic>