net_sched: destroy proto tp when all filters are gone

Kernel automatically creates a tp for each
(kind, protocol, priority) tuple, which has handle 0,
when we add a new filter, but it still is left there
after we remove our own, unless we don't specify the
handle (literally means all the filters under
the tuple). For example this one is left:

  # tc filter show dev eth0
  filter parent 8001: protocol arp pref 49152 basic

The user-space is hard to clean up these for kernel
because filters like u32 are organized in a complex way.
So kernel is responsible to remove it after all filters
are gone.  Each type of filter has its own way to
store the filters, so each type has to provide its
way to check if all filters are gone.

Cc: Jamal Hadi Salim <jhs@mojatatu.com>
Signed-off-by: Cong Wang <cwang@twopensource.com>
Signed-off-by: Cong Wang <xiyou.wangcong@gmail.com>
Acked-by: Jamal Hadi Salim<jhs@mojatatu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 9 insertions, 5 deletions

diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index 243b7d1..ad9eed7 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1858,11 +1858,15 @@ reclassify:
 }
 EXPORT_SYMBOL(tc_classify);
 
-void tcf_destroy(struct tcf_proto *tp)
+bool tcf_destroy(struct tcf_proto *tp, bool force)
 {
-	tp->ops->destroy(tp);
-	module_put(tp->ops->owner);
-	kfree_rcu(tp, rcu);
+	if (tp->ops->destroy(tp, force)) {
+		module_put(tp->ops->owner);
+		kfree_rcu(tp, rcu);
+		return true;
+	}
+
+	return false;
 }
 
 void tcf_destroy_chain(struct tcf_proto __rcu **fl)
@@ -1871,7 +1875,7 @@ void tcf_destroy_chain(struct tcf_proto __rcu **fl)
 
 	while ((tp = rtnl_dereference(*fl)) != NULL) {
 		RCU_INIT_POINTER(*fl, tp->next);
-		tcf_destroy(tp);
+		tcf_destroy(tp, true);
 	}
 }
 EXPORT_SYMBOL(tcf_destroy_chain);