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>

diff --git a/include/net/cls_cgroup.h b/include/net/cls_cgroup.h
index c15d394..ccd6d8b 100644 (file)
--- a/include/net/cls_cgroup.h
+++ b/include/net/cls_cgroup.h
@@ -49,9 +49,38 @@ static inline void sock_update_classid(struct sock *sk)
        if (classid != sk->sk_classid)
                sk->sk_classid = classid;
 }
+
+static inline u32 task_get_classid(const struct sk_buff *skb)
+{
+       u32 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() explicitly
+        * 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 0;
+
+               classid = skb->sk->sk_classid;
+       }
+
+       return classid;
+}
 #else /* !CONFIG_CGROUP_NET_CLASSID */
 static inline void sock_update_classid(struct sock *sk)
 {
 }
+
+static inline u32 task_get_classid(const struct sk_buff *skb)
+{
+       return 0;
+}
 #endif /* CONFIG_CGROUP_NET_CLASSID */
 #endif  /* _NET_CLS_CGROUP_H */

diff --git a/net/sched/cls_cgroup.c b/net/sched/cls_cgroup.c
index ea611b2..4c85bd3 100644 (file)
--- 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);
 }