netdev - Re: [PATCH net] ipv6: change route cache aging logic

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Message-ID: <20180126200453.e64w2hlqinlyldkb@kafai-mbp.dhcp.thefacebook.com>
Date:   Fri, 26 Jan 2018 12:05:08 -0800
From:   Martin KaFai Lau <kafai@...com>
To:     Wei Wang <weiwan@...gle.com>
CC:     David Miller <davem@...emloft.net>, <netdev@...r.kernel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net] ipv6: change route cache aging logic

On Fri, Jan 26, 2018 at 11:40:17AM -0800, Wei Wang wrote:
> From: Wei Wang <weiwan@...gle.com>
> 
> In current route cache aging logic, if a route has both RTF_EXPIRE and
> RTF_GATEWAY set, the route will only be removed if the neighbor cache
> has no RTN_ROUTE flag. Otherwise, even if the route has expired, it
You meant NTF_ROUTER instead of RTN_ROUTE?

> won't get deleted.
> Fix this logic to always check if the route has expired first and then
> do the gateway neighbor cache check if previous check decide to not
> remove the exception entry.
> 
> Fixes: 1859bac04fb6 ("ipv6: remove from fib tree aged out RTF_CACHE dst")
> Signed-off-by: Wei Wang <weiwan@...gle.com>
> Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Nice catch!

Acked-by: Martin KaFai Lau <kafai@...com>

> ---
>  net/ipv6/route.c | 20 ++++++++++++--------
>  1 file changed, 12 insertions(+), 8 deletions(-)
> 
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 0458b761f3c5..a560fb1d0230 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -1586,12 +1586,19 @@ static void rt6_age_examine_exception(struct rt6_exception_bucket *bucket,
>  	 * EXPIRES exceptions - e.g. pmtu-generated ones are pruned when
>  	 * expired, independently from their aging, as per RFC 8201 section 4
>  	 */
> -	if (!(rt->rt6i_flags & RTF_EXPIRES) &&
> -	    time_after_eq(now, rt->dst.lastuse + gc_args->timeout)) {
> -		RT6_TRACE("aging clone %p\n", rt);
> +	if (!(rt->rt6i_flags & RTF_EXPIRES)) {
> +		if (time_after_eq(now, rt->dst.lastuse + gc_args->timeout)) {
> +			RT6_TRACE("aging clone %p\n", rt);
> +			rt6_remove_exception(bucket, rt6_ex);
> +			return;
> +		}
> +	} else if (time_after(jiffies, rt->dst.expires)) {
> +		RT6_TRACE("purging expired route %p\n", rt);
>  		rt6_remove_exception(bucket, rt6_ex);
>  		return;
> -	} else if (rt->rt6i_flags & RTF_GATEWAY) {
> +	}
> +
> +	if (rt->rt6i_flags & RTF_GATEWAY) {
>  		struct neighbour *neigh;
>  		__u8 neigh_flags = 0;
>  
> @@ -1606,11 +1613,8 @@ static void rt6_age_examine_exception(struct rt6_exception_bucket *bucket,
>  			rt6_remove_exception(bucket, rt6_ex);
>  			return;
>  		}
> -	} else if (__rt6_check_expired(rt)) {
> -		RT6_TRACE("purging expired route %p\n", rt);
> -		rt6_remove_exception(bucket, rt6_ex);
> -		return;
>  	}
> +
>  	gc_args->more++;
>  }
>  
> -- 
> 2.16.0.rc1.238.g530d649a79-goog
>