This PR proposes an approach to reduce the thread count of RPL.
The current RPL/Trickle stack needs about 5 threads to handle tasks
like updating the trickle timer, routing entries and the transmission of
DAOs.
This PR modifies RPL to use only one thread with a looped `msg_recv()` call.
The message is then multiplexed to the right task.
This PR removes code depending on a routing table with an entries
size > 0. Currently, all those functions and symbols are compiled into the binary,
even when there is no effective space in the routing table (as it is the
case for normal nodes in non-storing mode)
The dicision to drop a packet if no next hop exists is made by the
`rpl_get_next_hop` function, which is initialized as the routing
provider for rpl applications. Hence, it seems needless to do this in the
`rpl_send` function.
This implementation is based on RFC 6550 with addition of RFC 6554 (Source Routing Header for RPL). Both can be found under the following links:
- http://tools.ietf.org/html/rfc6550
- http://tools.ietf.org/html/rfc6554
The PR provides basic functionality for handling and forwarding packages in non-storing mode. In addition the structure of the previous implemented RPL storing mode is now revised, so that readability and modularity is increased. The following features are implemented:
- building function for a SRH and integration in common packets
- source-route build algorithm based on the structure of the DODAG
- an RPL-based interpretation of the SRH and removal at destination
- new structure for RPl-module with extracted beaconing-functionality
- leaf nodes are now supported
There are some missed goals and should be included in future updates:
- building a common routing table structure for different types of routing protocols
- routing tables are statically assigned via source code, future update should have an optional variable at build-time, which sets the size of the routing table depending on the desired functionality of a node in the network (root, node, leaf)
