Merge branch 'bpf_cgroup_classid'

Daniel Borkmann says:

====================
BPF update

This small helper allows for accessing net_cls cgroups classid. Please
see individual patches for more details.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 36 insertions, 0 deletions

diff --git a/include/net/cls_cgroup.h b/include/net/cls_cgroup.h
index c15d39456e14..ccd6d8bffa4d 100644
--- 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/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 29ef6f99e43d..2de87e58b12b 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -249,6 +249,13 @@ enum bpf_func_id {
 	 * Return: 0 on success
 	 */
 	BPF_FUNC_get_current_comm,
+
+	/**
+	 * bpf_get_cgroup_classid(skb) - retrieve a proc's classid
+	 * @skb: pointer to skb
+	 * Return: classid if != 0
+	 */
+	BPF_FUNC_get_cgroup_classid,
 	__BPF_FUNC_MAX_ID,
 };