doc: Add a man page for B.A.T.M.A.N. adv. interfaces

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

doc/interfaces-batman.scd

@@ -0,0 +1,87 @@
+interfaces-batman(5)
+
+# NAME
+
+*interfaces-batman* - B.A.T.M.A.N. adv. extensions for the interfaces(5)
+file format
+
+# DESCRIPTION
+
+Better Approach To Mobile Ad-Hoc Networking (B.A.T.M.A.N.) advanced is
+a mesh protocol which provides an Ethernet overlay network over an
+Ethernet underlay. The overlay interface is called _meshif_ whereas
+underlay interfaces are called _hardif_.
+
+It's supported in the Linux kernel and thus available in many Linux
+environments. The ifupdown-ng exectuor relies on the *batctl* tool
+being installed. Support for setting interface based hop-penalties
+required Linux Kernel 5.8 or later.
+
+B.A.T.M.A.N. adv. adds 30-60 bytes of encapsulation overhead depending
+on wether netword coding is activated or not. This should be taken into
+consideration when setting up overlay networks, particularly on underlay
+networks with a conventional 1500 byte MTU.
+
+See https://www.open-mesh.org/projects/open-mesh/wiki for more details
+and updates.
+
+The following options allow to set up B.A.T.M.A.N. adv. interfaces.
+
+# BATMAN-RELATED OPTIONS
+
+*batman-ifaces* _list of interfaces_
+	Specifies the underlay interfaces (hardifs) which should be
+	configured for the B.A.T.M.A.N. adv. meshif defined within
+	the iface stanza.
+
+*batman-hop-penalty* _hop-penalty_
+	The _hop-penalty_ defines the cost of traversing a node or an
+	interface. The _hop-penalty_ is a numeric value between 0 and
+	255. Historically a _hop-penalty_ could only be set on a meshif,
+	since B.A.T.M.A.N adv. v2020.3 (included in Kernel 5.8) it can
+	also be set on a per-interfaces (hardif) basis.
+
+*batman-gw-mode* _gw-mode_
+	Denotes the gateway mode which controls the role this node will
+	play within this B.A.T.M.A.N. adv. instance. The mode can be
+	_off_, _client_, or _server_.
+
+*batman-distributed-arp-table* _mode_
+	Activates or deactivates the Distributed ARP table (DAT) within
+	this B.A.T.M.A.N. adv. instance. Valid values are _enable_ and
+	_disable_.
+
+*batman-multicast-mode* _mode_
+	Activates or deactivates the multicast mode of this B.A.T.M.A.N.
+	adv. instance. Valid values are _enable_ and _disable_.
+
+# EXAMPLES
+
+A B.A.T.M.A.N. adv. _meshif_:
+
+```
+auto bat-pad-cty
+iface bat-pad-cty
+	batman-ifaces dummy-pad-cty vlan1234
+	batman-hop-penalty 5
+	#
+	hwaddress f2:00:c1:01:00:00
+	mtu 1500
+```
+
+A B.A.T.M.A.N. adv. member interfaces (_hardif_):
+
+```
+auto vlan1234
+iface vlan1234
+	mtu 1560
+	batman-hop-penalty 10
+```
+
+# SEE ALSO
+
+*batctl*(8)
+
+# AUTHORS
+
+Maximilian Wilhelm <max@sdn.clinic>

doc/interfaces.scd

@@ -126,6 +126,11 @@ The *use* keyword designates that an _option_ should be used.
 This system is extendable by additional packages, but the
 most common options are:
 
+*batman*
+	The interface is a B.A.T.M.A.N. adv. mesh interface.
+	Configuration of B.A.T.M.A.N. adv. interfaces requires the
+	*batctl* untiliy to be installed.
+
 *bond*
 	The interface is a bonded interface.  Configuration
 	of bonded interfaces requires the *bonding* package
@@ -191,6 +196,7 @@ iface eth0
 # SEE ALSO
 
 *interfaces-bond*(5)
+*interfaces-batman*(5)
 *interfaces-vrf*(5)
 *interfaces-vxlan*(5)