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

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Message-ID: <CAEA6p_B5zzgUPL=aXyZs2yTdYiSeKpyGpjT7qRQQyAryKNVOiA@mail.gmail.com>
Date:   Fri, 26 Jan 2018 12:31:53 -0800
From:   Wei Wang <weiwan@...gle.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     David Miller <davem@...emloft.net>,
        Linux Kernel Network Developers <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 12:05 PM, Martin KaFai Lau <kafai@...com> wrote:
> 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?
>
Yes. NTF_ROUTER flag. Sorry...

>> 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
>>