fff-babeld: redistribute all peer_ip and peer_ip6 addresses

So far peer ips were only distributed via babel if they happened to fall
into the predefined network ranges. Currently, these only contain the
prefixes from the private and ULA ranges. Specifying any other address,
e.g. a globally routed one, will not result in the router being
reachable via that address.

Now peer ips are added to the `loopback` interface and babel is
instructed to redistribute addresses from `lo`, so any peer ip is
redistributed and therefore the router is now reachable via these
addresses.

Another option could have been to dynamically add a redistribute filter
for the peer ips before this section:

```
config filter
    option type 'redistribute'
    option local 'true'
    option action 'deny'
```

Sadly it almost impossible to do this in a reasonable manner with uci,
that doesn't involve iterating over all filter options or requiring this
specific section to be always named.

Adding the peer ips to `lo` is also the more conventional way to
configure an address "owned" by a router.

Signed-off-by: Johannes Kimmel <fff@bareminimum.eu>

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

@@ -22,6 +22,11 @@ config filter
 	option local 'true'
 	option ip 'fd43:5602:29bd::/48'
 
+config filter
+	option type 'redistribute'
+	option local 'true'
+	option interface 'lo'
+
 config filter
 	option type 'redistribute'
 	option local 'true'

src/packages/fff/fff-babeld/files/etc/layer3.d/40-babel

@@ -90,6 +90,21 @@ configure() {
 	for prefix in $(uci -q get gateway.@client[0].ip6addr); do
 		babel_add_redistribute_filter "$prefix"
 	done
+
+	# clean up old peer ips
+	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
+
+	# re-add loopback addresses
+	uci -q add_list network.loopback.ipaddr="127.0.0.1/8"
+	uci -q add_list network.loopback.ip6addr="::1/128"
+
+	# add peer ips to lo to be redistributed
+	peerip=$(uci -q get gateway.@gateway[0].peer_ip) && uci -q add_list network.loopback.ipaddr="${peerip}/32"
+	peerip6=$(uci -q get gateway.@gateway[0].peer_ip6) && uci -q add_list network.loopback.ip6addr="${peerip6}/128"
 }
 
 apply() {