Re: suggestion for routing code improvement

[Andi Kleen <ak@suse.de>]

On Wed, Apr 10, 2002 at 01:51:12PM -0400, Chris Friesen wrote:
> 
> Well, we're into a new experimental branch, so I figured the time had come to
> bring back an idea that didn't make it in a year ago.
> 
> Currently, if you add custom routes and then down the device that the routes are
> associated with, the routes are then removed.  This is entirely understandable.
> 
> However, when you then up the interface, the routes do not come back up
> automatically.  This is the part that I don't agree with.
> 
> Addresses, automatic routes, and custom rules either stay in effect or are
> brought back up by the system when an interface is downed and then upped.  The
> only exception to this is custom routes.
> 
> I propose that these custom routes be stored in some fashion, and then be
> brought back up when the device is brought back up.  This would make certain
> types of link management much simpler.  Custom routes, once added, would stay in
> effect until explicitly removed.  As it stands now, any time you down/up a link
> you have to then go back and add all the custom routes again.  This can be a
> pain in the butt.
> 
> So, what do you guys think?  Is this a reasonable thing to do?  I think that it
> makes the system nicely symmetrical, as opposed to the asymmetrical handling of
> current kernels.
> 
> I don't have a really good grasp of what data structures are avialable to us in
> the routing code, so could someone with a better understanding of the code
> comment as to how hard this would be to implement?


I don't think it would be very hard. Internally device up/down state 
and the IP address lists and IP state are separated. The routes and addresses
are currently removed triggered by the NETDEV_DOWN event on the netdev_chain.
There is no fundamental reason AFAIK that needs to be done, you could
not react to the DOWN event in IP in some circumstances. the upper layer
should handle down devices already because that can always happen even now
due to races at shutdown.


-Andi