Netlink: File exists

[Ondrej Zajicek]

On Mon, Sep 13, 2010 at 08:48:50PM +0200, Timo Weingärtner wrote:
> Hi,
> 
> Am Dienstag, 2. Februar 2010 schrieb Ondrej Zajicek:
> > On Tue, Feb 02, 2010 at 06:57:14PM +0000, Chris Webb wrote:
> > > This seems to work fine, apart from the message "bird: Netlink: File
> > > exists" appearing in syslog every minute.
> 
> > > in case this is related to bird being unable to overwrite the existing
> > > static routes?
> > 
> > Yes, the behavior is that BIRD will ignore existing 'alien' routes and
> > can't overwrite them. As routes in kernel routing table have protocol tag
> > specifying who added such route, we remove 'our' unexpected routes (for
> > example, if BIRD is killed and restarted), but ignore 'alien' routes.
>  
> I also ran into that bug with six equal routers doing OSPF and one default 
> router not doing OSPF. Each of the OSPF routers has a default route and two 
> unreachable routes (ip r a ... proto static), that were tried to be 
> overwritten by BIRD, because BIRD liked the same route via OSPF better.

Yes, currently BIRD does not purge any user route. Therefore the
preference for kernel routes should be probably higher than the
preference of most dynamic protocols.

> From what I read in ip(8) (search for "rt_protos") the correct behaviour would 
> be:
>  * On start up purge all routes with protocol boot
>  * Respect routes with protocol static and give them higher precedence than
>    dynamic routes.

I thought about using this behavior, but it has one big problem -
although user-configured routes should be protocol static, 'ip' tool
sets protocol boot by default and most users don't know about protocol
field so they don't change it. Therefore routes of protocol static are
practically nonexistent and purging most user routes by default seems to
me as unexpected behavior for users. I am planning to implement some
config option that enables the behavior suggested by ip(8).

-- 
Elen sila lumenn' omentielvo

Ondrej 'SanTiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
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