RELAY2: asymmetric routing

Currently, RELAY2 only supports routing to sites which are directly accessible from the current site (by registering via a bridge and adding their entries to the routing table).

Asymmetric routing should support sending messages to sites which are only indirectly connected. The attached Network.pdf is used as example.

• We have sites HF, Net1, Net2 and Net3
• HF is connected to Net1 only
• Net1 is connected to HF and Net2
• Net2 is connected to Net1 and Net3
• Net3 is connected to Net2 only

When a message is sent from HF to Net3, it has to be forwarded to Net1 -> Net2 -> Net3.

To implement this, we need the following things:

The routing tables of SiteMasters need to have specific routes for sites, and/or default routes, e.g. for HF:

Net1 -> Routes to Net1 // list of SiteMasters of Net1
DEFAULT -> Net1 // all other sites (e.g. Net3) -> forward to Net1

For Net2:

Net1 -> Routes to Net1 
Net3 -> Routes to Net3
HF -> Net1

This could also be written as:

Net3 -> Routes to Net3
DEFAULT -> Net1 // includes Net1 and HF

Required changes

• The routing tables need to be configured dynamically. This could be done by sending 'site-advertisement' (multicast) messages. Also when a site disappears, a message may need to be sent
• The SiteMasters for a given site currently overwrite each others' entries. This is not an issue, as there is only a single bridge channel, but when we have multiple channels, this will become an issue

Goals

• No change to existing configuration would be nice!
• However, can we do with small semantic changes, or does that requires a RELAY3?