[OpenWrt-Devel] watchping

[Bruno Randolf]

Hi Juliusz and all,

Exporting a route to a routing protocol was just one example of what
could be done based on the fact that internet connectivity is available
on an interface. There are other uses one could imagine:
 - Activate a backup interface, say a 3G connection
 - Announce a default GW or not (routing proto or DHCP).
 - Check for firmware upgrades on a public server
 - Start or reconfigure a service

Second, a default route is not enough: what counts is wether inernet
connectivity is available thru that route. Sometimes a router announces
a default route but is not connected itself, or problems exist
"upstream". In that sense it's probably like your "babel-pinger" but
more generic.

The mwan3 package seems do do a similar thing in a script. Do you think
it could profit from a C-based ubus service? Would it make sense?

bruno



On 07/03/2015 09:19 PM, Juliusz Chroboczek wrote:
> 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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