On Thu, Oct 19, 2017 at 7:07 AM, Paolo Abeni <pab...@redhat.com> wrote:
> The commit 2b760fcf5cfb ("ipv6: hook up exception table to store
> dst cache") partially reverted the commit 1e2ea8ad37be ("ipv6: set
> dst.obsolete when a cached route has expired").
>
> As a result, RTF_CACHE dst referenced outside the fib tree will
> not be removed until the next sernum change; dst_check() does not
> fail on aged-out dst, and dst->__refcnt can't decrease: the aged
> out dst will stay valid for a potentially unlimited time after the
> timeout expiration.
>
> This change explicitly removes RTF_CACHE dst from the fib tree when
> aged out. The rt6_remove_exception() logic will then obsolete the
> dst and other entities will drop the related reference on next
> dst_check().
>
> pMTU exceptions are not aged-out, and are removed from the exception
> table only when the - usually considerably longer - ip6_rt_mtu_expires
> timeout expires.
>
> v1 -> v2:
> - do not touch dst.obsolete in rt6_remove_exception(), not needed
> v2 -> v3:
> - take care of pMTU exceptions, too
>
> Fixes: 2b760fcf5cfb ("ipv6: hook up exception table to store dst cache")
> Signed-off-by: Paolo Abeni <pab...@redhat.com>
> ---
Acked-by: Wei Wang <wei...@google.com>
> net/ipv6/route.c | 12 +++++++++++-
> 1 file changed, 11 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 5c27313803d2..87a15cbd0e8b 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -1575,7 +1575,13 @@ static void rt6_age_examine_exception(struct
> rt6_exception_bucket *bucket,
> {
> struct rt6_info *rt = rt6_ex->rt6i;
>
> - if (atomic_read(&rt->dst.__refcnt) == 1 &&
> + /* we are pruning and obsoleting aged-out and non gateway exceptions
> + * even if others have still references to them, so that on next
> + * dst_check() such references can be dropped.
> + * 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);
> rt6_remove_exception(bucket, rt6_ex);
> @@ -1595,6 +1601,10 @@ 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++;
> }
> --
> 2.13.6
>
