cls_cgroup: factor out classid retrieval

Split out retrieving the cgroups net_cls classid retrieval into its
own function, so that it can be reused later on from other parts of
the traffic control subsystem. If there's no skb->sk, then the small
helper returns 0 as well, which in cls_cgroup terms means 'could not
classify'.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Cc: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 21 deletions

diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c
index ea611b216412..4c85bd3a750c 100644
--- a/net/sched/cls_cgroup.c
+++ b/net/sched/cls_cgroup.c
@@ -30,35 +30,16 @@ static int cls_cgroup_classify(struct sk_buff *skb, const struct tcf_proto *tp,
                                struct tcf_result *res)
 {
         struct cls_cgroup_head *head = rcu_dereference_bh(tp->root);
-        u32 classid;
-
-        classid = task_cls_state(current)->classid;
-
-        /*
-         * Due to the nature of the classifier it is required to ignore all
-         * packets originating from softirq context as accessing `current'
-         * would lead to false results.
-         *
-         * This test assumes that all callers of dev_queue_xmit() explicitely
-         * disable bh. Knowing this, it is possible to detect softirq based
-         * calls by looking at the number of nested bh disable calls because
-         * softirqs always disables bh.
-         */
-        if (in_serving_softirq()) {
-                /* If there is an sk_classid we'll use that. */
-                if (!skb->sk)
-                        return -1;
-                classid = skb->sk->sk_classid;
-        }
+        u32 classid = task_get_classid(skb);
 
         if (!classid)
                 return -1;
-
         if (!tcf_em_tree_match(skb, &head->ematches, NULL))
                 return -1;
 
         res->classid = classid;
         res->class = 0;
+
         return tcf_exts_exec(skb, &head->exts, res);
 }