netdev - Re: BUG - routes not correctly deleted when address is deleted

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Message-ID: <20101201123426.082f224f@nehalam>
Date:	Wed, 1 Dec 2010 12:34:26 -0800
From:	Stephen Hemminger <shemminger@...tta.com>
To:	Julian Anastasov <ja@....bg>
Cc:	David Miller <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: BUG - routes not correctly deleted when address is deleted

On Wed, 1 Dec 2010 12:08:42 +0200 (EET)
Julian Anastasov <ja@....bg> wrote:

> 
>  	Hello,
> 
> On Tue, 30 Nov 2010, Stephen Hemminger wrote:
> 
> > If multiple addresses are assigned to an interface, and
> > a route is created that uses that address.  The route is not
> > deleted when the address is deleted.  Linux does cleanup properly
> > when the last address is deleted; it seems the FIB lacks the callback
> > to cleanup routes referencing an address.
> >
> > Simple example:
> >
> > # modprobe dummy
> > # ip li set dev dummy0 up
> > # ip addr add 192.168.74.160/24 dev dummy0
> > # ip addr add 192.168.18.11/24 dev dummy0
> > # ip ro add 74.11.49.0/24 via 192.168.74.160
> 
>  	Such routes look as old way to create direct
> routes over some device, used by "route" tool.
> Device is inherited from the local IP used as gateway.
> Such local gateways IPs are not used, see rt_set_nexthop()
> where nh_scope is checked. FIB removes routes only when
> the deleted IP is a prefsrc for this route, so may be
> it is a good idea to use prefsrc.

These are the kind of routes routing daemons like Quagga
create.

> > # ip addr del 192.168.74.160/24 dev dummy0
> > # ip ro show dev dummy0
> > 74.11.49.0/24 via 192.168.74.160
> > 192.168.18.0/24  proto kernel  scope link  src 192.168.18.11
> >
> > Before I go off and either brute force it (add another call back
> > into fib_hash and fib_trie), is there a better way?
> 
>  	Adding prefsrc is recommended. For me, it is not fatal
> such routes to stay because nh_gw is not used. It is a
> way to say at configuration time:

This isn't done by routing daemons.


> ip ro add 74.11.49.0/24 dev eth0
> 
>  	If you need such route to depend on the lifetime
> of some local IP then you need to specify prefsrc.
> 
>  	If you go ahead with changes may be you should call 
> fib_sync_down_dev from fib_del_ifaddr by providing the IP
> as new argument. While fib_sync_down_addr is called when this
> IP is removed from the last device where it was configured,
> now for nh_gw fib_sync_down_dev should be called for every
> fib_del_ifaddr call. For me, it is a complication, not sure
> what others think.

Probably just going to make the existing fib_sync_down_dev
take an optional address.

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