Subject: Re: [PATCH net-next 1/2] net: mpls: Don't show nexthop if device has been deleted

From: Roopa Prabhu <[email-masked]>
Date: Sun, 26 Mar 2017 10:20:50 -0700

On 3/24/17, 3:21 PM, David Ahern wrote:
> If the device for a nexthop in a multipath route is deleted, the nexthop
> is effectively removed from the route. Currently, a route dump still
> returns the nexhop though without the device set:
>
> $ ip -f mpls ro ls
> 100
> 	nexthopvia inet 10.11.1.2  dev br0
> 	nexthopvia inet 10.100.3.1  dev eth3
> $ ip li del br0
> $ ip -f mpls ro ls
> 100
> 	nexthopvia inet 10.11.1.2  dev * dead linkdown
> 	nexthopvia inet 10.100.3.1  dev eth3
>
> Since the nexthop is effectively deleted, drop the hop from the route
> dump.
>
> Signed-off-by: David Ahern <[email-masked]>
> ---
>  net/mpls/af_mpls.c | 8 +++++---
>  1 file changed, 5 insertions(+), 3 deletions(-)
>
> diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
> index cd8be8d5e4ad..3861f8dfa9c1 100644
> --- a/net/mpls/af_mpls.c
> +++ b/net/mpls/af_mpls.c
> @@ -1769,13 +1769,15 @@ static int mpls_dump_route(struct sk_buff *skb, u32 portid, u32 seq, int event,
>  			goto nla_put_failure;
>  
>  		for_nexthops(rt) {
> +			dev = rtnl_dereference(nh->nh_dev);
> +			if (!dev)
> +				continue;
> +

size calculation may have to account for this too ?.
>  			rtnh = nla_reserve_nohdr(skb, sizeof(*rtnh));
>  			if (!rtnh)
>  				goto nla_put_failure;
>  
> -			dev = rtnl_dereference(nh->nh_dev);
> -			if (dev)
> -				rtnh->rtnh_ifindex = dev->ifindex;
> +			rtnh->rtnh_ifindex = dev->ifindex;
>  			if (nh->nh_flags & RTNH_F_LINKDOWN) {
>  				rtnh->rtnh_flags |= RTNH_F_LINKDOWN;
>  				linkdown++;

Acked-by: Roopa Prabhu <[email-masked]>