Olsrd linux nl80211_extension

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Olsrd linux nl80211_extension

  1. 1. Abstract==========================================================================This document describes the OLSRd link quality extension that utilizeslinux NL80211 to apply wireless link information in the link qualitycalculation.Design==========================================================================Each second the latest information is gathered from linux NL80211. Thisdata contains the MAC addresses of the neighbor stations. To match thisMAC address with the neighbors IP, the linux ARP cache is queried.Implementation==========================================================================The extension adds an external dependency to build the code namely libnl.This library is used to simplify the IPC communication with linux kernel.The files src/linux/nl80211_link_info.* are doing the actual wireless linkstatus gathering. A modified link ffeth quality plugin will use the newlink status information for link quality calculations. This link qualityplugin is using #ifdef LINUX_NL80211 statements as much as possible tomake it easy to merge the code back into the original ffeth plugin. Thebenefit of merging those link quality plugins will be less duplicate codeand less code to maintain.Cost calculation==========================================================================A penalty is added to the old cost from the ffeth plugin, depending on thesignal strength and the link bandwidth. Both penalties can have a maximumvalue of 1.0.Costs = EXT + BandwidthPenalty + SignalPenaltyBandwidthPenalty = 1 - ( ActualBandwidth / ReferenceBandwidth)SignalPenalty = LookupSignalPenaltyTable(SignalStrenghtOfNeighbor)Both penalties are added into the two unused bytes of LQ_HELLO messages.Currently the nodes wont use this value when received from their neighborand only use their own NL80211 information.Considerations==========================================================================It is designed mainly for IPv4, but should work with minimal effort onIPv6 as well. Majority of that work will be actually testing it on IPv6.The netlink code is blocking, this shouldnt cause major problems but amore ideal design would be non-blocking.Current version does not use the NL80211 data received from its neighbors.A discussion is needed to find out if this is required or not.Currently both penalties have a maximum of 1.0, which might not be enough.If thats the case, a configurable multiplier for both penalties might beinteresting to add.The value for ReferenceBandwidth is hardcoded to 54 MBit.The values in the signal strength penalty table are hardcoded.Its desirable to have them configurable through the configuration file.Add configuration option to completely disable the use of NL80211 data, incase the plugin is merged with the existing ff_eth link quality plugin.

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