fff-layer3-vxmesh: join multple client nets with vxlan

Easily span a layer 2 network over a small group of, not necessarily
adjacent, routers.

This patch introduces a new `vxmesh` configuration section. It takes
care of setting up a shared client network using vxlan among all
configured routers.

As a result, clients can finally roam between the routers of the mesh.
It integrates well with the underlying layer 3 routing to make best use
of the infrastructure available. This way the network is not depending
on a contiguous layer 2 spanning tree topology and can make use of all
fallback mechanisms of the layer 3 underlay.

This example config ...
```
config gateway
	option peer_ip6 '2001:0db8::1' # required

...

config vxmesh
	option proto 'vxlan|vxlan6' # required
	option vid   '42'           # required

	# ...
	# any vxlan options can be included
	# ...

	# list of peers for headend replication
	list peer '2001:0db8::1'    # list can include the ip of the router
	list peer '2001:0db8::2'    # this way the complete config section
	list peer '2001:0db8::3'    # can be copied to all routers in the
	list peer '2001:0db8::4'    # group
	...
```

... will generate ...

```
config interface client
	...
	# append and remove the vxmesh0 entry
	# depending on whether a vxmesh is configured
	ifname '... vxmesh0'
	...

...

config interface 'vxmesh0'
	option proto 'vxlan6'
	option vid '42'

config vxlan_peer
	option vxlan 'vxmesh0'
	option dst '2001:0db8::2'

config vxlan_peer
	option vxlan 'vxmesh0'
	option dst '2001:0db8::3'

config vxlan_peer
	option vxlan 'vxmesh0'
	option dst '2001:0db8::4'
```

It will also take care and configure the
`dhcp.@dnsmasq[0].authoritative` setting depending on whether a vxmesh
is enabled or not.

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

src/packages/fff/fff-layer3-vxmesh/Makefile

@@ -0,0 +1,29 @@
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=fff-layer3-vxmesh
+PKG_RELEASE:=1
+
+include $(INCLUDE_DIR)/package.mk
+
+define Package/fff-layer3-vxmesh
+	SECTION:=base
+	CATEGORY:=Freifunk
+	TITLE:=Freifunk-Franken layer3 configuration for mesh via vxlan
+	URL:=http://www.freifunk-franken.de
+	DEPENDS:=+vxlan
+endef
+
+define Package/fff-layer3-vxmesh/description
+	Adds a simple configuration to connect multple routers into one layer 2
+	network via vxlan.
+endef
+
+define Build/Compile
+	# nothing
+endef
+
+define Package/fff-layer3-vxmesh/install
+	$(CP) ./files/* $(1)/
+endef
+
+$(eval $(call BuildPackage,fff-layer3-vxmesh))

src/packages/fff/fff-layer3-vxmesh/files/etc/layer3.d/60-vxmesh

@@ -0,0 +1,111 @@
+#!/bin/sh
+
+configure() {
+	local proto
+	local peerip
+	local otherpeers
+	local fields="
+		proto
+		port
+		vid
+		ttl
+		tos
+		mtu
+		macaddr
+		zone
+		rxcsum
+		txcsum
+		srcportmin
+		srcportmax
+		ageing
+		maxaddress
+		learning
+		rsc
+		proxy
+		l2miss
+		l3miss
+		gbp
+		tunlink
+		ipaddr
+		ip6addr
+	"
+
+	# cleanup old vxmesh and peer entries
+	uci -q delete network.vxmesh0
+	while uci -q delete network.@vxlan_peer[-1]; do :; done
+
+	# remove vxmesh0 entry from the client bridge and remove extra whitespaces
+	uci set network.client.ifname="$(uci -q get network.client.ifname | sed s/vxmesh0// | xargs)"
+
+	# reset dns to authorative
+	uci set dhcp.@dnsmasq[0].authoritative="1"
+
+	# check if a vxmesh config is available, otherwise quit
+	uci -q get gateway.@vxmesh[0] > /dev/null || return 0
+
+	# check if proto is set and probe for the correct peer ip
+	proto="$(uci -q get gateway.@vxmesh[0].proto)"
+	case "$proto" in
+		vxlan6)
+			peerip="$(uci -q get gateway.@gateway[0].peer_ip6)"
+			;;
+		vxlan)
+			peerip="$(uci -q get gateway.@gateway[0].peer_ip)"
+			;;
+		*)
+			echo "FATAL: vxmesh: option proto 'vxlan|vxlan6' required!"
+			return 1
+			;;
+	esac
+
+	# vxmesh needs a separate peer ip as the ip on the client interface ip
+	# might be shared over multiple devices
+	[ -z "$peerip" ] && {
+		echo "FATAL: vxmesh: peer_ip|peer_ip6 required!"
+		return 1
+	}
+
+	uci -q get gateway.@vxmesh[0].vid > /dev/null || {
+		echo "FATAL: vxmesh: missing vid!"
+		return 1
+	}
+
+	# copy main options over
+	uci set network.vxmesh0="interface"
+	for option in $fields; do
+		uci set network.vxmesh0."$option"="$(uci -q get gateway.@vxmesh[0]."$option")"
+	done
+
+	# exclude peerip from the local router, so packets aren't sent to itself
+	otherpeers=$(uci -q get gateway.@vxmesh[0].peer | xargs -n1 | grep -v -e "$peerip")
+
+	for peer in $otherpeers; do
+		# create peer sections
+		if ! uci -q batch > /dev/null; then
+			echo "FATAL: vxmesh: error setting up peer!"
+			echo "       peer: \"$peer\""
+			return 1
+		fi <<- EOF
+			add network vxlan_peer
+			set network.@vxlan_peer[-1].vxlan="vxmesh0"
+			set network.@vxlan_peer[-1].dst="$peer"
+		EOF
+	done
+
+	# with multiple routers in the network, there shouldn't be an authoritative
+	# dhcp server
+	uci set dhcp.@dnsmasq[0].authoritative="0"
+
+	# add the vxlan interface to the client bridge
+	uci set network.client.ifname="$(uci -q get network.client.ifname) vxmesh0"
+}
+
+apply() {
+	uci commit network
+	uci commit dhcp
+}
+
+revert() {
+	uci revert network
+	uci revert dhcp
+}

src/packages/fff/fff-layer3/Makefile

@@ -1,7 +1,7 @@
 include $(TOPDIR)/rules.mk
 
 PKG_NAME:=fff-layer3
-PKG_RELEASE:=8
+PKG_RELEASE:=9
 
 include $(INCLUDE_DIR)/package.mk
 
@@ -36,7 +36,7 @@ define Package/fff-layer3
 	         +mtr \
 	         +tc \
 	         +tcpdump \
-	         +vxlan
+	         +fff-layer3-vxmesh
 endef
 
 define Package/fff-layer3/description