net sched: skbedit action fix late binding

The process below was broken and is fixed with this patch.

//add a skbedit action and give it an instance id of 1
sudo tc actions add action skbedit mark 10 index 1
//create a filter which binds to skbedit action id 1
sudo tc filter add dev $DEV parent ffff: protocol ip prio 1 u32\
match ip dst 17.0.0.1/32 flowid 1:10 action skbedit index 1

Message before fix was:
RTNETLINK answers: Invalid argument
We have an error talking to the kernel

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

net/sched/act_skbedit.c

@@ -69,7 +69,7 @@ static int tcf_skbedit_init(struct net *net, struct nlattr *nla,
  struct tcf_skbedit *d;
  u32 flags = 0, *priority = NULL, *mark = NULL;
  u16 *queue_mapping = NULL;
- int ret = 0, err;
+ int ret = 0, err, exists = 0;
 
  if (nla == NULL)
  return -EINVAL;
@@ -96,12 +96,18 @@ static int tcf_skbedit_init(struct net *net, struct nlattr *nla,
  mark = nla_data(tb[TCA_SKBEDIT_MARK]);
  }
 
- if (!flags)
- return -EINVAL;
-
  parm = nla_data(tb[TCA_SKBEDIT_PARMS]);
 
- if (!tcf_hash_check(tn, parm->index, a, bind)) {
+ exists = tcf_hash_check(tn, parm->index, a, bind);
+ if (exists && bind)
+ return 0;
+
+ if (!flags) {
+ tcf_hash_release(a, bind);
+ return -EINVAL;
+ }
+
+ if (!exists) {
  ret = tcf_hash_create(tn, parm->index, est, a,
  sizeof(*d), bind, false);
  if (ret)
@@ -111,8 +117,6 @@ static int tcf_skbedit_init(struct net *net, struct nlattr *nla,
  ret = ACT_P_CREATED;
  } else {
  d = to_skbedit(a);
- if (bind)
- return 0;
  tcf_hash_release(a, bind);
  if (!ovr)
  return -EEXIST;