[OpenWrt-Devel] watchping

[Juliusz Chroboczek]

Hi Bruno,

> Sometimes it's necessary to re-configure an OpenWRT system based on the
> fact wether Internet connectivity is available on a certain interface.
[...]
> One example where this is useful is: When Internet is available, we
> configure BATMAN to act as a gateway 'server', if not as a gateway
> 'client'.

I think that a solution that relies on distribution scripts is inherently
brittle.  The routing daemon should be able to detect the current
configuration, in a distribution-independent manner, and automatically
adapt to the current situation.  This is what happens with babeld -- it is
able to automatically redistribute a kernel route (typically the default
route, but not necessarily) into the routing protocol.

I know of three ways of automatically obtaining a default route, in
descending order of preference:

  - if the other end of the Internet connection speaks RIP, RIPng or OSPF,
    we run Quagga on the gateway and redistribute into Babel;

  - if DHCPv4 is reliable (it usually is), then we simply redistribute the
    DHCP-provided route into the routing protocol;

  - if DHCPv4 is unreliable, we use the "babel-pinger" utility which
    pings a remote host and installs a route depending on its availability.

Additionally, there is some very promising but still experimental work to
provide a fully general and highly integrated solution in the "hnetd-full"
package.

-- Juliusz
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