On Tue, Oct 17, 2017 at 10:40 AM, Paolo Abeni <pab...@redhat.com> wrote:
> The commit 2b760fcf5cfb ("ipv6: hook up exception table to store
> dst cache") partially reverted 1e2ea8ad37be ("ipv6: set
> dst.obsolete when a cached route has expired").
>
> This change brings back the dst obsoleting and push it a step
> farther: cached dst are always obsoleted when removed from the
> fib tree, and removal by time expiration is now performed
> regardless of dst->__refcnt, to be consistent with what we
> already do for RTF_GATEWAY dst.
>
> Fixes: 2b760fcf5cfb ("ipv6: hook up exception table to store dst cache")
> Signed-off-by: Paolo Abeni <pab...@redhat.com>
> ---
> net/ipv6/route.c | 13 +++++++++++--
> 1 file changed, 11 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv6/route.c b/net/ipv6/route.c
> index 8b25a31b6b03..fce740049e3e 100644
> --- a/net/ipv6/route.c
> +++ b/net/ipv6/route.c
> @@ -1147,6 +1147,12 @@ static void rt6_remove_exception(struct
> rt6_exception_bucket *bucket,
> if (!bucket || !rt6_ex)
> return;
>
> + /* sockets, flow cache, etc. can hold a refence to this dst, be sure
> + * they will drop it.
> + */
> + if (rt6_ex->rt6i)
> + rt6_ex->rt6i->dst.obsolete = DST_OBSOLETE_FORCE_CHK;
> +
Hmm... I don't really think it is needed. rt6 is created with
rt6->dst.obsolete set to DST_OBSOLETE_FORCE_CHK. And by the time the
above function is called, it should still be that value.
Furthermore, the later call rt6_release() calls dst_dev_put() which
sets rt6->dst.obsolete to DST_OBSOLETE_DEAD to indicate this route has
been removed from the tree.
> net = dev_net(rt6_ex->rt6i->dst.dev);
> rt6_ex->rt6i->rt6i_node = NULL;
> hlist_del_rcu(&rt6_ex->hlist);
> @@ -1575,8 +1581,11 @@ 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 &&
> - time_after_eq(now, rt->dst.lastuse + gc_args->timeout)) {
> + /* we are pruning and obsoleting the exception route even if others
> + * have still reference to it, so that on next dst_check() such
> + * reference can be dropped
> + */
> + if (time_after_eq(now, rt->dst.lastuse + gc_args->timeout)) {
Why do we want to change this behavior? Before my patch series, cached
routes were only deleted from the tree in fib6_age() when
rt->dst.__refcnt == 1, isn't it?
> RT6_TRACE("aging clone %p\n", rt);
> rt6_remove_exception(bucket, rt6_ex);
> return;
> --
> 2.13.6
>
