Mailing List Archive: Re: [Spread-users] unconfigured interfaces

Hi,

There is a Wackamole list, wackamole-users@lists.backhand.org . I know
this Linux issue comes up from time to time, but I'm not sure if anyone
has solved it (except using the work-arounds you mentioned). Be aware
that running Spread on a different physical interface than Wackamole
might cause some issues, because the two interfaces can fail independently.

Cheers,
Ryan

Kieren Hynd wrote:

> Hi,
>
> More of a linux networking / Wackamole question really (is there a
> mailing list for Wackamole?), but maybe someone here has the answer :)
>
> We'd like to let Wackamole have its Virtual IP's on an interface by
> itself (eth0), with Spread messages going over another interface (eth1)
> on a private network.
>
> This works ok if we assign an address to eth0 in /etc/network/interfaces
> on the linux servers, but it also means that we have to statically bind
> one of the VIP's to each machine, or give it another address outside of
> the VIP range.
>
> So, the question is: Does anyone know of a way to get Wackamole to
> manage its virtual interfaces on a 'real' interface under linux that has
> no address assigned to it (ie; down)?
> If we try to run Wackamole on an interface that isn't up, it has
> problems bringing up its virtual interfaces because the interface eth0
> wasn't up, and therefore had no routes in place.
>
> I'd like not to have to assign one of the VIPs to eth0 to just get it
> configured (and also not to have to set preferred VIPs in wackamole).
> I'd also not like to assign other addresses outside of the VIP range to
> eth0 just to get the interface up.
>
> Is it possible to get Wackamole to create a default route when it brings
> up its virtual interfaces, or is this something that should be achieved
> in linux's IP functions (if so, could someone give me a clue how?).
>
> Thanks,
> Kieren
>
> _______________________________________________
> Spread-users mailing list
> Spread-users@lists.spread.org
> http://lists.spread.org/mailman/listinfo/spread-users
>

--
Ryan W. Caudy
Center for Networking and Distributed Systems
Department of Computer Science
Johns Hopkins University

> Kieren Hynd wrote:
>> So, the question is: Does anyone know of a way to get Wackamole to
>> manage its virtual interfaces on a 'real' interface under linux that
>> has
>> no address assigned to it (ie; down)?
>> If we try to run Wackamole on an interface that isn't up, it has
>> problems bringing up its virtual interfaces because the interface eth0
>> wasn't up, and therefore had no routes in place.

The problem is unclear to me. Is it that the IP address cannot be
added, or that it is added successfully but does not work because it is
lacking a route? The first would be a bug, while the second would be
an unimplemented feature. The CVS version of wackamole does have the
ability to run arbitrary C code and perl code when an interface goes up
or down -- so it could be done that way.

Honestly, adding routes is different (and complicated) enough on each
platform that it might be best to _not_ do this inside wackamole, but
have wackamole run a script to set the routes when an IP address is
added.

>> I'd like not to have to assign one of the VIPs to eth0 to just get it
>> configured (and also not to have to set preferred VIPs in wackamole).
>> I'd also not like to assign other addresses outside of the VIP range
>> to
>> eth0 just to get the interface up.
>> Is it possible to get Wackamole to create a default route when it
>> brings
>> up its virtual interfaces, or is this something that should be
>> achieved
>> in linux's IP functions (if so, could someone give me a clue how?).

On linux, it doesn't matter so much, but on FreeBSD and Solaris, this
poses a problem. The first IP address in a subnet should have that
subnet's netmask. All additional aliases should have a netmask of
0xffffffff (as stated in the ifconfig man page on FreeBSD). I suppose
that is pretty trivial logic to add into the ife*.c code. This is why
the examples have a real address in the subnet already plumbed on the
interfaces that _is not_ managed by Wackamole.

I supposed that ife could be modified to see if the IP address about to
be added exists in any of the subnets already configured and UP and if
so alter its netmask to 0xffffffff. We still have the problem of
loosing the "main" IP address, but I suppose that could be solved with
a "Prefer" statement on each machine.

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