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gluon-radv-filterd: improve documentation of selected router

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lemoer 2018-01-06 00:18:39 +01:00 committed by Jan-Philipp Litza
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docs/package/gluon-radv-filterd.rst
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@ -7,22 +7,29 @@ default router with the best metric according to B.A.T.M.A.N. advanced.
Note that advertisements originating from the node itself (for example
via gluon-radvd) are not affected and considered at all.
"Best" router
Selected router
-------------
The best router is determined by the TQ that is reported for its originator by
B.A.T.M.A.N. advanced. If, for some reason, another gateway with a better TQ
appears or an existing gateway increases its TQ above that of the chosen
gateway, the chosen gateway will remain selected until the better gateway has a
TQ value at least X higher than the selected gateway. This is called
hysteresis, and X can be specified on the commandline/via UCI/the site.conf and
defaults to 20 (just as for the IPv4 gateway selection feature built into
B.A.T.M.A.N. advanced).
The router selection mechanism is independent from the batman-adv gateway mode.
In contrast, the device originating the router advertisment could be any router
or client connected to the mesh, as radv-filterd captures all router
advertisements originating from it. All nodes announcing router advertisement
**with** a default lifetime greater than 0 are being considered as candidates.
In case a router is not a batman-adv originator itself, its TQ is defined by
the originator it is connected to. This lookup uses the batman-adv global
translation table.
Initially the router is the selected by choosing the candidate with the
strongest TQ. When another candidate can provide a better TQ metric it is not
picked up as the selected router until it will outperform the currently
selected router by X metric units. The hysteresis threshold is configurable
and prevents excessive flapping of the gateway.
"Local" routers
---------------
The package has functionality to assign "local" routers, i.e. those connected
The package has functionality to select "local" routers, i.e. those connected
via cable or WLAN instead of via the mesh (technically: appearing in the
``transtable_local``), a fake TQ of 512 so that they are always preferred.
However, if used together with the :doc:`package/gluon-ebtables-filter-ra-dhcp`