gluon-client-bridge: add default next-node MAC address

The next-node MAC address doesn't need to be unique in different
communities, so we can as well add a default value.

docs/site-example/site.conf

@@ -80,9 +80,6 @@
     -- anycast IPs of all nodes
     ip4 = '10.xxx.0.xxx',
     ip6 = 'fdxx:xxxx:xxxx::xxxx',
-
-    -- anycast MAC of all nodes
-    mac = 'xe:xx:xx:xx:xx:xx',
   },
 
   -- Options specific to routing protocols (optional)

docs/user/site.rst

@@ -154,10 +154,14 @@ next_node \: package
       next_node = {
         ip4 = '10.23.42.1',
         ip6 = 'fdca:ffee:babe:1::1',
-        mac = 'ca:ff:ee:ba:be:00'
+        mac = '16:41:95:40:f7:dc'
       }
 
-    The IPv4 next-node address is optional.
+    All values of this section are optional. If the IPv4 or IPv6 address is
+    omitted, there will be no IPv4 or IPv6 anycast address. The MAC address
+    defaults to ``16:41:95:40:f7:dc``; this value usually doesn't need to be
+    changed, but it can be adjusted to match existing deployments that use a
+    different value.
 
 mesh \: optional
     Options specific to routing protocols.

package/gluon-client-bridge/check_site.lua

-need_string_match('next_node.mac', '^%x[02468aAcCeE]:%x%x:%x%x:%x%x:%x%x:%x%x$')
+need_string_match('next_node.mac', '^%x[02468aAcCeE]:%x%x:%x%x:%x%x:%x%x:%x%x$', false)
 
 if need_string_match('next_node.ip4', '^%d+.%d+.%d+.%d+$', false) then
 	need_string_match('prefix4', '^%d+.%d+.%d+.%d+/%d+$')

package/gluon-client-bridge/luasrc/lib/gluon/upgrade/310-gluon-client-bridge-local-node

 #!/usr/bin/lua
 
+local client_bridge = require 'gluon.client_bridge'
 local site = require 'gluon.site_config'
 local sysconfig = require 'gluon.sysconfig'
 
 local uci = require('simple-uci').cursor()
 
 
+local next_node = site.next_node or {}
+
+
 uci:delete('network', 'local_node_dev')
 uci:section('network', 'device', 'local_node_dev', {
 	type = 'veth',
 	name = 'local-node',
-	macaddr = site.next_node.mac,
+	macaddr = client_bridge.next_node_macaddr(),
 	peer_name = 'local-port',
 	peer_macaddr = sysconfig.primary_mac,
 })
@@ -18,13 +22,13 @@ uci:section('network', 'device', 'local_node_dev', {
 
 local ip4, ip6
 
-if site.next_node.ip4 then
+if next_node.ip4 then
 	local plen = site.prefix4:match('/%d+$')
-	ip4 = site.next_node.ip4 .. plen
+	ip4 = next_node.ip4 .. plen
 end
 
-if site.next_node.ip6 then
-	ip6 = site.next_node.ip6 .. '/128'
+if next_node.ip6 then
+	ip6 = next_node.ip6 .. '/128'
 end
 
 uci:delete('network', 'local_node')

package/gluon-client-bridge/luasrc/usr/lib/lua/gluon/client_bridge.lua

+local site = require 'gluon.site_config'
+
+
+module 'gluon.client_bridge'
+
+function next_node_macaddr()
+	return (site.next_node or {}).mac or '16:41:95:40:f7:dc'
+end

package/gluon-mesh-batman-adv/files/lib/gluon/ebtables/250-next-node

+local client_bridge = require 'gluon.client_bridge'
 local site = require 'gluon.site_config'
-local next_node = site.next_node
+local next_node = site.next_node or {}
 
-rule('FORWARD --logical-out br-client -o bat0 -d ' .. next_node.mac .. ' -j DROP')
-rule('OUTPUT --logical-out br-client -o bat0 -d ' .. next_node.mac .. ' -j DROP')
-rule('FORWARD --logical-out br-client -o bat0 -s ' .. next_node.mac .. ' -j DROP')
-rule('OUTPUT --logical-out br-client -o bat0 -s ' .. next_node.mac .. ' -j DROP')
+local macaddr = client_bridge.next_node_macaddr()
+
+rule('FORWARD --logical-out br-client -o bat0 -d ' .. macaddr .. ' -j DROP')
+rule('OUTPUT --logical-out br-client -o bat0 -d ' .. macaddr .. ' -j DROP')
+rule('FORWARD --logical-out br-client -o bat0 -s ' .. macaddr .. ' -j DROP')
+rule('OUTPUT --logical-out br-client -o bat0 -s ' .. macaddr .. ' -j DROP')
 
 if next_node.ip4 then
 	rule('FORWARD --logical-out br-client -o bat0 -p ARP --arp-ip-src ' .. next_node.ip4 .. ' -j DROP')