gluon-hoodselector

This package provides an automated way to continuously select the correct domain based on the geolocation of a node. The purpose of Hoodselector is to automatically detect in which domain the node is located based on its geolocation settings. Therefore domains are required to have bounding boxes, defined as polygons or rectangles. Based on this information Hoodselector will select a domain from the list of known domains and migrate towards it without requiring a reboot. This package therefore provides a scalable and decentralized approach to automatic domain selection.

Background information

The main problem of the Nordwest Freifunk community was the quickly rising number of nodes in the network. This indirectly affected the stability of the network, because the noise inside the network, e.g. management traffic from the batman-adv protocol, was rising, too. Inside the community there were some ideas like building separate firmwares for each region. This solution would cause issues with splitting regions again and nodes scattered among regions which belong to a different region. Therefore we decided to develop a dynamic and decentralized management of regions called domains. The Hoodselector’s task is to choose the “right” domains in an intelligent way and to hold the network together and accessible.

A domain is defined by geostationary fixed shapes by using longitude & latitude in combination with the domain configuration system. Below you can see a visual example of a regional domain:

../_images/gluon-hoodselector-domainmap.jpeg

Behaviour

The following is an abstract state diagramm which gives an overview of the process:

../_images/gluon-hoodselector.svg

The sequence of this diagram reflects the priority of its running modes. Each mode will be explained separately below.

geolocation mode

This mode will only be entered when a node has location coordinates set. Nodes with a position will set their domain based on it. The node will skip to the next mode when the node (a) has no position or (b) its position is not within any of the defined bounding boxes.

default domain mode

This mode will be entered if no other mode before fits. It provides a fallback to the default domain.

Domain shapes

There are two types of domains: the unique dehault one without a defined shape and others which contain shapes.

  • default domain

The default domain doesn’t hold any shapes and represents the inverted area of all other shapes held by other domains with geo coordinates. It will only be entered if a node could not be matched to a geo domain. A suggested approach is to define the “old” network as default domain and gradually migrate nodes from there to geo domains.

  • geo domains

A geo domain contains shapes, which are described by three dimensional arrays and represents the geographical size of the domain. There are two possible definitions of these shapes. The first one is using rectangles so that only two coordinates per box are needed to define it (see below for an example). The second one uses polygons which can have multiple edges. Each domain can hold multiple shapes.

../_images/gluon-hoodselector-rectangle-example.svg

site.conf

The designer of the shapes must always ensure that no overlapping polygons between domains will be created or else the order in the domain list will become relevant. If for example domain A and B overlap, Hoodselector would, for that overlapping area, only ever reach domain A, but never domain B. Here is an example of a rectangular definition of a shape: Example:

hoodselector = {
  shapes = {
    {
      {
        lat = 53.128,
        lon = 8.187
      },
      {
        lat = 53.163,
        lon = 8.216
      },
    },
  },
},

Here is an example of a shape defined by a triangle: Example:

hoodselector = {
  shapes = {
    {
      {
        lat = 53.128,
        lon = 8.187
      },
      {
        lat = 53.163,
        lon = 8.216
      },
      {
        lat = 53.196,
        lon = 8.194
      },
    },
  },
},

This package is incompatible with gluon-config-mode-domain-select.