fff-layer3-config: add router_ip option

For some purposes (e.g. SNAT, vxlan) it might be necessary to have an
additional address just for the router which is not attached to any
interfaces. Addresses like this are typically added to the loopback
interface.

The new options "router_ip" and "router_ip6" are added to the gateway
config to allow the user to configure such addresses. It is possible to
both specify the address with or without a subnet size.

The default configuration contains the IPv4 loopback address
(127.0.0.1/8) explicitly, but this is not necessary. These addresses are
configured automatically, even if they are not present in the
configuration, so they can safely be removed, if present.

The filters of our routing daemon babeld are adjusted accordingly, so
the newly added addresses are announced correctly.

Signed-off-by: Fabian Bläse <fabian@blaese.de>
Reviewed-by: Christian Dresel <freifunk@dresel.systems>
Reviewed-by: Johannes Kimmel <fff@bareminimum.eu>

src/packages/fff/fff-babeld/files/etc/config/babeld

@@ -21,6 +21,11 @@ config filter
 	option local 'true'
 	option ip 'fd43:5602:29bd::/48'
 
+config filter
+	option type 'redistribute'
+	option local 'true'
+	option if 'lo'
+
 config filter
 	option type 'redistribute'
 	option local 'true'

src/packages/fff/fff-babeld/files/lib/functions/fff/babel

@@ -36,11 +36,14 @@ babel_add_peeraddr() {
 
 	if peer_ip=$(uci -q get gateway.@gateway[0].peer_ip); then
 		uci add_list "$option"="$peer_ip"
+	elif router_ip=$(uci -q get gateway.meta.router_ip); then
+		# use router_ip if no peer_ip is set
+		uci add_list "$option"="$router_ip"
 	elif ipaddr=$(uci -q get gateway.@client[0].ipaddr); then
-		# use ipaddr (without subnet) if no peer_ip set
+		# use client interface address (without subnet) if no router_ip is set
 		uci add_list "$option"=$(echo $ipaddr | cut -d / -f1)
 	else
-		echo "WARNING: Neither peer_ip nor ipaddr set! IPv4 routing is not possible."
+		echo "WARNING: No peer_ip, router_ip or client interface ipaddr set! IPv4 routing is not possible."
 		return 1
 	fi
 

src/packages/fff/fff-layer3-config/files/etc/layer3.d/30-network-routerip

@@ -0,0 +1,31 @@
+configure() {
+	local router_ip
+	local router_ip6
+
+	# clean old addresses
+	uci -q del network.loopback.ipaddr
+	uci -q del network.loopback.ip6addr
+
+	# remove netmask entry that ships by default
+	uci -q del network.loopback.netmask
+
+	# add router_ip
+	router_ip=$(uci -q get gateway.meta.router_ip)
+	for ip in $router_ip; do
+		uci -q add_list network.loopback.ipaddr="$ip"
+	done
+
+	# add router_ip6
+	router_ip6=$(uci -q get gateway.meta.router_ip6)
+	for ip in $router_ip6; do
+		uci -q add_list network.loopback.ip6addr="$ip"
+	done
+}
+
+apply() {
+	uci commit network
+}
+
+revert() {
+	uci revert network
+}