52 Commits

Author	SHA1	Message	Date
Martin Hundebøll	d56b1705e2	batman-adv: network coding - detect coding nodes and remove these after timeout ... To use network coding efficiently, a relay must know when neighbor nodes are likely to have enough information to be able to decode a network coded packet. This is detected by using OGMs from batman-adv to discover when one neighbor is in range of another neighbor. The relay check the TLL to detect when an OGM is forwarded from one neighbor by another neighbor, and thereby knows that the two neighbors are in range and thus overhear packets sent by each other. This information is saved in the orig_node struct to be used when searching for coding opportunities. Two lists are added to the orig_node struct: One for neighbors that can hear the orig_node (outgoing nc_nodes) and one for neighbors that the orig_node can hear (incoming nc_nodes). Information about nc_nodes is kept for 10 seconds and is available through debugfs in batman_adv/nc_nodes to use when debugging network coding. Signed-off-by: Martin Hundebøll <martin@hundeboll.net> Signed-off-by: Marek Lindner <lindner_marek@yahoo.de> Signed-off-by: Antonio Quartulli <ordex@autistici.org>	2013-03-13 22:53:49 +01:00
Martin Hundebøll	d353d8d4d9	batman-adv: network coding - add the initial infrastructure code ... Network coding exploits the 802.11 shared medium to allow multiple packets to be sent in a single transmission. In brief, a relay can XOR two packets, and send the coded packet to two destinations. The receivers can decode one of the original packets by XOR'ing the coded packet with the other original packet. This will lead to increased throughput in topologies where two packets cross one relay. In a simple topology with three nodes, it takes four transmissions without network coding to get one packet from Node A to Node B and one from Node B to Node A: 1. Node A ---- p1 ---> Node R Node B 2. Node A Node R <--- p2 ---- Node B 3. Node A <--- p2 ---- Node R Node B 4. Node A Node R ---- p1 ---> Node B With network coding, the relay only needs one transmission, which saves us one slot of valuable airtime: 1. Node A ---- p1 ---> Node R Node B 2. Node A Node R <--- p2 ---- Node B 3. Node A <- p1 x p2 - Node R - p1 x p2 -> Node B The same principle holds for a topology including five nodes. Here the packets from Node A and Node B are overheard by Node C and Node D, respectively. This allows Node R to send a network coded packet to save one transmission: Node A Node B | \ / | | p1 p2 | | \ / | p1 > Node R < p2 | | | / \ | | p1 x p2 p1 x p2 | v / \ v / \ Node C < > Node D More information is available on the open-mesh.org wiki[1]. This patch adds the initial code to support network coding in batman-adv. It sets up a worker thread to do house keeping and adds a sysfs file to enable/disable network coding. The feature is disabled by default, as it requires a wifi-driver with working promiscuous mode, and also because it adds a small delay at each hop. [1] http://www.open-mesh.org/projects/batman-adv/wiki/Catwoman Signed-off-by: Martin Hundebøll <martin@hundeboll.net> Signed-off-by: Marek Lindner <lindner_marek@yahoo.de> Signed-off-by: Antonio Quartulli <ordex@autistici.org>	2013-03-13 22:53:48 +01:00