Re: [PATCH net] ipv6: Do not consider linkdown nexthops during multipath

[Andy Gospodarek <andy@greyhouse.net>]

On Tue, Nov 21, 2017 at 09:50:12AM +0200, Ido Schimmel wrote:
> When the 'ignore_routes_with_linkdown' sysctl is set, we should not
> consider linkdown nexthops during route lookup.
> 
> While the code correctly verifies that the initially selected route
> ('match') has a carrier, it does not perform the same check in the
> subsequent multipath selection, resulting in a potential packet loss.
> 
> In case the chosen route does not have a carrier and the sysctl is set,
> choose the initially selected route.
> 
> Fixes: 35103d11173b ("net: ipv6 sysctl option to ignore routes when nexthop link is down")
> Signed-off-by: Ido Schimmel <idosch@mellanox.com>

Nice find.  Looks good to me, as well.

Acked-by: Andy Gospodarek <andy@greyhouse.net>

> ---
>  net/ipv6/route.c | 5 +++++
>  1 file changed, 5 insertions(+)
> 
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 05eb7bc36156..0363db914c7a 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -472,6 +472,11 @@ static struct rt6_info *rt6_multipath_select(struct rt6_info *match,
>  				&match->rt6i_siblings, rt6i_siblings) {
>  			route_choosen--;
>  			if (route_choosen == 0) {
> +				struct inet6_dev *idev = sibling->rt6i_idev;
> +
> +				if (!netif_carrier_ok(sibling->dst.dev) &&
> +				    idev->cnf.ignore_routes_with_linkdown)
> +					break;
>  				if (rt6_score_route(sibling, oif, strict) < 0)
>  					break;
>  				match = sibling;
> -- 
> 2.14.3
>