Re: [PATCH net 1/2] ipv6: do not delete previously existing ECMP routes if add fails

[roopa]

On 5/13/15, 5:49 AM, Michal Kubecek wrote:
> On Wed, May 13, 2015 at 02:28:57PM +0200, Nicolas Dichtel wrote:
> > Le 13/05/2015 11:50, Michal Kubecek a écrit :
> > > If adding a nexthop of an IPv6 multipath route fails, comment in
> > > ip6_route_multipath() says we are going to delete all nexthops already
> > > added. However, current implementation deletes even the routes it
> > > hasn't even tried to add yet. For example, running
> > >
> > >    ip route add 1234:5678::/64 \
> > >        nexthop via fe80::aa dev dummy1 \
> > >        nexthop via fe80::bb dev dummy1 \
> > >        nexthop via fe80::cc dev dummy1
> > >
> > > twice results in removing all routes first command added.
> > >
> > > Limit the second (delete) run to nexthops that succeeded in the first
> > > (add) run.
> > >
> > > Fixes: 51ebd3181572 ("ipv6: add support of equal cost multipath (ECMP)")
> > > Signed-off-by: Michal Kubecek <mkubecek@xxxxxxx>
> > > ---
> > >   net/ipv6/route.c | 1 +
> > >   1 file changed, 1 insertion(+)
> > >
> > > diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> > > index d3588885f097..18b92c05b541 100644
> > > --- a/net/ipv6/route.c
> > > +++ b/net/ipv6/route.c
> > > @@ -2536,6 +2536,7 @@ beginning:
> > >   				 * next hops that have been already added.
> > >   				 */
> > >   				add = 0;
> > > +				remaining = cfg->fc_mp_len - remaining;
> > >   				goto beginning;
> > Not sure to understand your fix. At the label beginning, the code is:
> >
> > beginning:
> >          rtnh = (struct rtnexthop *)cfg->fc_mp;
> >          remaining = cfg->fc_mp_len;
> >
> > Hence, 'remaining' will be overridden. How does your patch work?
> It does not, sorry. I'm still trying to find out what did I wrong while
> testing. I'll need to move the initialization of remaining above the
> label.
This looks like a similar bug i was trying to fix some time back:
http://patchwork.ozlabs.org/patch/362296/

(I am not sure if my full patch is still valid. I was thinking of 
re-spining it sometime soon. If you are interested in trying it out, 
please do)
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