[PATCH bpf-next v1 07/13] bpf: net_sched: Add a qdisc watchdog timer

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Add a watchdog timer to bpf qdisc. The watchdog can be used to schedule
the execution of qdisc through kfunc, bpf_qdisc_schedule(). It can be
useful for building traffic shaping scheduling algorithm, where the time
the next packet will be dequeued is known.

Signed-off-by: Amery Hung <amery.hung@xxxxxxxxxxxxx>
---
 include/net/sch_generic.h |  4 +++
 net/sched/bpf_qdisc.c     | 51 ++++++++++++++++++++++++++++++++++++++-
 net/sched/sch_api.c       | 11 +++++++++
 net/sched/sch_generic.c   |  8 ++++++
 4 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/include/net/sch_generic.h b/include/net/sch_generic.h
index 5d74fa7e694c..6a252b1b0680 100644
--- a/include/net/sch_generic.h
+++ b/include/net/sch_generic.h
@@ -1357,4 +1357,8 @@ static inline void qdisc_synchronize(const struct Qdisc *q)
 		msleep(1);
 }
 
+int bpf_qdisc_init_pre_op(struct Qdisc *sch, struct nlattr *opt, struct netlink_ext_ack *extack);
+void bpf_qdisc_destroy_post_op(struct Qdisc *sch);
+void bpf_qdisc_reset_post_op(struct Qdisc *sch);
+
 #endif
diff --git a/net/sched/bpf_qdisc.c b/net/sched/bpf_qdisc.c
index 28959424eab0..7c155207fe1e 100644
--- a/net/sched/bpf_qdisc.c
+++ b/net/sched/bpf_qdisc.c
@@ -8,6 +8,10 @@
 
 static struct bpf_struct_ops bpf_Qdisc_ops;
 
+struct bpf_sched_data {
+	struct qdisc_watchdog watchdog;
+};
+
 struct bpf_sk_buff_ptr {
 	struct sk_buff *skb;
 };
@@ -17,6 +21,32 @@ static int bpf_qdisc_init(struct btf *btf)
 	return 0;
 }
 
+int bpf_qdisc_init_pre_op(struct Qdisc *sch, struct nlattr *opt,
+			  struct netlink_ext_ack *extack)
+{
+	struct bpf_sched_data *q = qdisc_priv(sch);
+
+	qdisc_watchdog_init(&q->watchdog, sch);
+	return 0;
+}
+EXPORT_SYMBOL(bpf_qdisc_init_pre_op);
+
+void bpf_qdisc_reset_post_op(struct Qdisc *sch)
+{
+	struct bpf_sched_data *q = qdisc_priv(sch);
+
+	qdisc_watchdog_cancel(&q->watchdog);
+}
+EXPORT_SYMBOL(bpf_qdisc_reset_post_op);
+
+void bpf_qdisc_destroy_post_op(struct Qdisc *sch)
+{
+	struct bpf_sched_data *q = qdisc_priv(sch);
+
+	qdisc_watchdog_cancel(&q->watchdog);
+}
+EXPORT_SYMBOL(bpf_qdisc_destroy_post_op);
+
 static const struct bpf_func_proto *
 bpf_qdisc_get_func_proto(enum bpf_func_id func_id,
 			 const struct bpf_prog *prog)
@@ -134,12 +164,25 @@ __bpf_kfunc void bpf_qdisc_skb_drop(struct sk_buff *skb,
 	__qdisc_drop(skb, (struct sk_buff **)to_free_list);
 }
 
+/* bpf_qdisc_watchdog_schedule - Schedule a qdisc to a later time using a timer.
+ * @sch: The qdisc to be scheduled.
+ * @expire: The expiry time of the timer.
+ * @delta_ns: The slack range of the timer.
+ */
+__bpf_kfunc void bpf_qdisc_watchdog_schedule(struct Qdisc *sch, u64 expire, u64 delta_ns)
+{
+	struct bpf_sched_data *q = qdisc_priv(sch);
+
+	qdisc_watchdog_schedule_range_ns(&q->watchdog, expire, delta_ns);
+}
+
 __bpf_kfunc_end_defs();
 
 #define BPF_QDISC_KFUNC_xxx \
 	BPF_QDISC_KFUNC(bpf_skb_get_hash, KF_TRUSTED_ARGS) \
 	BPF_QDISC_KFUNC(bpf_kfree_skb, KF_RELEASE) \
 	BPF_QDISC_KFUNC(bpf_qdisc_skb_drop, KF_RELEASE) \
+	BPF_QDISC_KFUNC(bpf_qdisc_watchdog_schedule, KF_TRUSTED_ARGS) \
 
 BTF_KFUNCS_START(bpf_qdisc_kfunc_ids)
 #define BPF_QDISC_KFUNC(name, flag) BTF_ID_FLAGS(func, name, flag)
@@ -154,9 +197,14 @@ BPF_QDISC_KFUNC_xxx
 
 static int bpf_qdisc_kfunc_filter(const struct bpf_prog *prog, u32 kfunc_id)
 {
-	if (kfunc_id == bpf_qdisc_skb_drop_ids[0])
+	if (kfunc_id == bpf_qdisc_skb_drop_ids[0]) {
 		if (strcmp(prog->aux->attach_func_name, "enqueue"))
 			return -EACCES;
+	} else if (kfunc_id == bpf_qdisc_watchdog_schedule_ids[0]) {
+		if (strcmp(prog->aux->attach_func_name, "enqueue") &&
+		    strcmp(prog->aux->attach_func_name, "dequeue"))
+			return -EACCES;
+	}
 
 	return 0;
 }
@@ -189,6 +237,7 @@ static int bpf_qdisc_init_member(const struct btf_type *t,
 	case offsetof(struct Qdisc_ops, priv_size):
 		if (uqdisc_ops->priv_size)
 			return -EINVAL;
+		qdisc_ops->priv_size = sizeof(struct bpf_sched_data);
 		return 1;
 	case offsetof(struct Qdisc_ops, static_flags):
 		if (uqdisc_ops->static_flags)
diff --git a/net/sched/sch_api.c b/net/sched/sch_api.c
index f074053c4232..507abddcdafd 100644
--- a/net/sched/sch_api.c
+++ b/net/sched/sch_api.c
@@ -1357,6 +1357,13 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 		rcu_assign_pointer(sch->stab, stab);
 	}
 
+#ifdef CONFIG_NET_SCH_BPF
+	if (ops->owner == BPF_MODULE_OWNER) {
+		err = bpf_qdisc_init_pre_op(sch, tca[TCA_OPTIONS], extack);
+		if (err != 0)
+			goto err_out4;
+	}
+#endif
 	if (ops->init) {
 		err = ops->init(sch, tca[TCA_OPTIONS], extack);
 		if (err != 0)
@@ -1393,6 +1400,10 @@ static struct Qdisc *qdisc_create(struct net_device *dev,
 	 */
 	if (ops->destroy)
 		ops->destroy(sch);
+#ifdef CONFIG_NET_SCH_BPF
+	if (ops->owner == BPF_MODULE_OWNER)
+		bpf_qdisc_destroy_post_op(sch);
+#endif
 	qdisc_put_stab(rtnl_dereference(sch->stab));
 err_out3:
 	lockdep_unregister_key(&sch->root_lock_key);
diff --git a/net/sched/sch_generic.c b/net/sched/sch_generic.c
index 1e770ec251a0..ea4ee7f914be 100644
--- a/net/sched/sch_generic.c
+++ b/net/sched/sch_generic.c
@@ -1039,6 +1039,10 @@ void qdisc_reset(struct Qdisc *qdisc)
 
 	if (ops->reset)
 		ops->reset(qdisc);
+#ifdef CONFIG_NET_SCH_BPF
+	if (ops->owner == BPF_MODULE_OWNER)
+		bpf_qdisc_reset_post_op(qdisc);
+#endif
 
 	__skb_queue_purge(&qdisc->gso_skb);
 	__skb_queue_purge(&qdisc->skb_bad_txq);
@@ -1082,6 +1086,10 @@ static void __qdisc_destroy(struct Qdisc *qdisc)
 
 	if (ops->destroy)
 		ops->destroy(qdisc);
+#ifdef CONFIG_NET_SCH_BPF
+	if (ops->owner == BPF_MODULE_OWNER)
+		bpf_qdisc_destroy_post_op(qdisc);
+#endif
 
 	lockdep_unregister_key(&qdisc->root_lock_key);
 	bpf_module_put(ops, ops->owner);
-- 
2.20.1





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