wmgwd

wmgwd is a distributed gateway daemon for WiMoVE. I wrote this daemon as part of my bachelor's thesis.

Architecture

The idea is to run an instance of etcd on every gateway. wmgwd connects to the local database instance. The daemon uses the database for three things:

Peer discovery: Every instance of wmgwd writes its name to a key, notifying all other instances.
Failure detection: wmgwd uses time-bound leases. When a lease expires, all other instances recognize the failure.
Virtual gateway management: The state of each overlay network is stored in the database. The daemon implements a state machine for each overlay network on top of the database.

To assign overlay networks to gateways, wmgwd uses consistent hashing to randomly assign overlay networks to physical gateways.

Host System Interaction

wmgwd enables and disables ARP on selected interfaces via the /proc filesystem. The daemon also reconfigures FRR via its command-line interface vtysh. Advertising and withdrawing BGP EVPN routes is done by configuring route-maps at runtime. Advertising and withdrawing OSPF routes is done by setting link costs to 100 or 65535.

Build

git clone https://github.com/rgwohlbold/wmgwd
cd wmgwd
go build

This creates an executable wmgwd.

Configuration

Name	Default	Explanation
name		Node name in etcd
minvni	1	Minimum VXLAN Network Identifier
maxvni	100	Maximum VXLAN Network Identifier
mock	false	Do not interact with host network configuration and FRR
uids		Comma-separated list of UIDs used for consistent hashing (default: random)
debug	false	Enable debug logging
etcd	http://localhost:2379	Etcd endpoint

Network Configuration

For each VNI i, wmgwd assumes two interfaces: vxlan$i and br$i where the vxlan$i has br$i as its master. br$i is assigned the IP addresses that all devices in that overlay network use as their default gateway.

wmgwd assumes that FRR is run on the gateway and announces routes with BGP EVPN into WiMoVE and with OSPF into the rest of the network. The daemon restricts which BGP EVPN routes are advertised by FRR using route maps.

There, a route map called filter-vni that permits all BGP EVPN routes that are not of type 2 (MAC/IP advertisement route) or type 5 (IP prefix route) is required. This is an example configuration file of FRR that works with wmgwd:

ip forwarding
ip nht resolve-via-default
ip6 nht resolve-via-default
router bgp 65000
  bgp router-id 10.0.1.11
  no bgp default ipv4-unicast
  neighbor fabric peer-group
  neighbor fabric remote-as 65000
  neighbor fabric capability extended-nexthop
  neighbor fabric ebgp-multihop 5
  neighbor fabric timers 1 3
  neighbor 10.0.1.17 peer-group fabric
  address-family l2vpn evpn
   neighbor fabric activate
   neighbor fabric route-map filter-vni out
   advertise-all-vni
   advertise-svi-ip
  exit-address-family
  !
!
router ospf
 ospf router-id 1.1.1.1
 network 0.0.0.0/0 area 0.0.0.0
!
route-map filter-vni permit 1
 match evpn route-type 2
 on-match goto 4
!
route-map filter-vni permit 2
 match evpn route-type 5
 on-match goto 4
!
route-map filter-vni permit 3
!