[Xorp-hackers] Some thoughts

[Patrick Preuss]

Hello,

> Now, suppose I configure the IP address of an interface through the
> rtrmgr.  The FEA will set this interface address.  And now someone
> changes it through ifconfig or whatever.  What is the correct action
> for XORP to do?

> The IP address has been configured in XORP, so XORP should in
> principle believe this is still what is wanted.  If it observes the
> change, then it should re-configure it back, as XORP is still
> configured to set this particular address.

> An alternative is for XORP to monitor the machine state, and consider
> the rest of the machine is in charge.  In which case it would then
> change it's running config automatically.  But the general idea is the
> running config is set by a human, so having this change under you
> isn't principle of least surprise.

> The end result is that there is no good answer to this.  As XORP is
> intended not as just a routing daemon, but as the entire router
> control plane (yes, long-term plan), then the most sensible (and
> certainly simplest) answer is "XORP is in charge".

Yes the answer is not simple, but on thought may be there could be an
option, compile time or in the configuration as global and or per interface
variable, where you can specify how xorp should deal with this, something
like an enforce the value configured in xorp or not.

> We discussed this ad-nauseum in the early days of XORP, and ended up
> with this decision.  There is simply no good solution to this that
> everyone would be happy with - you have to decide who is in charge.


> Now, the IPv6 link-local address issue is one where the kernel should
> be in charge.  Not any other user-space daemon.  Thus this is
> obviously one we should handle better than we do.

> And issues such as CARP/VRRP should be handled in a what that the user
> specifies somehow that this address is to be set automatically, and so
> can change under you.  We don't have the hooks for this right now, and
> should have.  But there's only so much time, and so many things to do.

Maybe such things like CARP/VRRP should be an integrated part of xorp,
because such things are primary defined/developed for Routers, so why not
integrate them in a later stage. 


> Cheers,
> Mark

Patrick

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